JP2013235653A - Sealed nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealed nonaqueous electrolyte secondary battery combining reliability during overcharge and high battery performance (excellent output characteristics in low SOC region).SOLUTION: The sealed nonaqueous electrolyte secondary battery comprises: a negative electrode including a negative electrode mixture layer, a positive electrode including a positive electrode mixture layer, and a nonaqueous electrolyte added with a gas generating agent, which are housed in a battery case; and a current interruption mechanism operating when the pressure in the battery case increases due to generation of the gas. In such a sealed nonaqueous electrolyte secondary battery, the negative electrode mixture layer contains a negative electrode active material which can occlude and release charge carriers reversibly, and a compound which can occlude the charge carriers at a potential higher than that of the negative electrode active material.

Description

  The present invention relates to a non-aqueous electrolyte secondary battery. More specifically, the present invention relates to a sealed nonaqueous electrolyte secondary battery provided with a current interruption mechanism that operates by increasing internal pressure.

Lithium secondary batteries and other non-aqueous electrolyte secondary batteries are preferably used as power sources for consumer electronic devices and vehicles because they are smaller, lighter, and have higher energy density and output density than existing batteries.
An example of such a battery is a sealed nonaqueous electrolyte secondary battery. The battery typically has a configuration in which an electrode body including a positive electrode and a negative electrode and a non-aqueous electrolyte (typically a non-aqueous electrolyte) are housed in a battery case and sealed (sealed). . The electrode (positive electrode and negative electrode) includes an electrode mixture mainly composed of an active material capable of reversibly occluding and releasing charge carriers (typically lithium ions) on corresponding positive and negative current collectors. Layers (specifically, a positive electrode mixture layer and a negative electrode mixture layer) are provided.

  This type of battery is generally used in a state where the voltage is controlled so as to be within a predetermined region (for example, 3.0 V or more and 4.2 V or less). However, if a current exceeding the normal level is supplied to the battery due to an erroneous operation or the like. In some cases, the battery may be overcharged by exceeding a predetermined voltage. Therefore, a current interruption device (CID) is widely used for the battery as a safety mechanism for stopping the progress of overcharge. Generally, when the battery is overcharged, the nonaqueous solvent of the electrolyte is electrolyzed and gas is generated. When the pressure in the battery case exceeds a predetermined value due to the gas generation, the current interruption mechanism can cut off the charging path of the battery and prevent further overcharge.

When using the current interruption mechanism, a compound that can be decomposed at a lower potential than the electrolyte (nonaqueous solvent) to generate gas (hereinafter referred to as “gas generating agent”) is previously contained in the electrolyte. The method of putting is known. The gas generating agent is rapidly oxidatively decomposed on the surface of the positive electrode when the battery is overcharged, and typically generates hydrogen ions (H ⁺ ). The hydrogen ions diffuse into the electrolyte and are reduced on the negative electrode, thereby generating hydrogen gas (H ₂ ). As a result, the pressure in the battery case rises quickly, so that the current interruption mechanism can be operated at an earlier stage.

JP 2008-084832 A Japanese Patent Application Laid-Open No. 11-073965 JP 2006-351306 A JP 2001-351640 A

  By the way, a plug-in hybrid vehicle in which a sealed nonaqueous electrolyte secondary battery (lithium secondary battery) is mounted as a power source for driving a motor in a vehicle that is being developed and put into practical use in recent years. PHV (hereinafter abbreviated as “PHV”). In PHV, an onboard battery is connected to an external power source such as a household power source and charged in advance, and the vehicle is driven using such charging. When the charge capacity of the battery is exhausted, the same mode as that of a conventional hybrid vehicle (HV) (that is, the engine (internal combustion engine) and the battery are used together as a power source, and the charge capacity of the battery is It is designed to be able to run by switching to a mode in which the battery is charged by automatically driving the engine when the number is reduced. Therefore, a battery for PHV requires a higher energy density (rated capacity) than a conventional battery.

  Further, such a battery is not automatically charged unlike a battery for HV even when the charging capacity is reduced. For this reason, it is assumed that rapid discharge (that is, acceleration of the automobile) is frequently performed even in a region where the state of charge (SOC) is low (hereinafter referred to as “low SOC region”). However, it is generally known that a nonaqueous electrolyte secondary battery has a high internal resistance in a region where the SOC is low, and the battery performance deteriorates. As a technique for coping with this problem, for example, Patent Document 1 discloses a technique of mixing polyimide into the negative electrode mixture layer.

  However, according to the inventor's investigation, it has been found that polyimide has low electron conductivity, so that addition of this suppresses the reduction reaction of hydrogen ions necessary for gas generation. In particular, in a battery for PHV, in order to realize a high energy density, the density of the electrode mixture layer is higher than in other applications, and the reaction field for gas generation is reduced. Therefore, the amount of gas generated during overcharging is greatly reduced, so that the pressure in the battery case does not rise rapidly, and the operation of the current interrupt mechanism may be delayed.

  The present invention has been made in view of the above points, and is a sealed nonaqueous electrolyte secondary battery provided with a current interrupting mechanism that operates due to an increase in pressure in a battery case, and reliability during overcharging, An object of the present invention is to provide a battery having high battery performance (excellent output characteristics in a low SOC region).

  As a result of various studies, the inventor has found that the increase in internal resistance in the low SOC region is mainly caused by the positive electrode, and more specifically, because the potential of the positive electrode is decreased in the low SOC region. Has been found to increase. Therefore, it was considered to shift the potential range (operating voltage) of the positive electrode used for charging / discharging to a higher potential side. FIG. 1 is a diagram showing the concept of the present invention, wherein the vertical axis represents potential and the horizontal axis represents SOC. That is, the present inventor can maintain the positive electrode potential in a relatively high state even in the low SOC region by shifting the negative electrode potential from (1) to (2). We thought that the internal resistance in the layer could be reduced. And the technique which can solve this was found and the present invention was completed.

  According to the present invention, a nonaqueous electrolyte to which a negative electrode including a negative electrode mixture layer, a positive electrode including a positive electrode mixture layer, and a gas generating agent capable of generating a gas when a predetermined battery voltage is exceeded is added. Is provided in a battery case, and a sealed nonaqueous electrolyte secondary battery provided with a current interrupting mechanism that operates when the pressure in the battery case increases as the gas is generated is provided. . The negative electrode mixture layer includes a negative electrode active material capable of reversibly occluding and releasing charge carriers and a charge storage material capable of occluding the charge carriers at a higher potential than the negative electrode active material. ing.

In the battery having the above configuration, the charge storage material contained in the negative electrode mixture layer stores charge carriers (for example, lithium ions) during the first charge / discharge. The charge once occluded becomes an irreversible capacity without being released thereafter, so that the potential of the negative electrode (vs. Li ^/ Li ⁺ ) can be relatively increased. Therefore, if the operating voltages of the batteries are the same, the operating potential range of the positive electrode can be shifted to a higher potential side than before. For this reason, even in the low SOC region where the increase in internal resistance due to the potential decrease of the positive electrode is remarkable, the resistance can be suitably suppressed. Moreover, as shown in the Example mentioned later, in the battery of the said structure, the gas amount required in order to operate a current interruption mechanism at the time of overcharge can be generated stably. Therefore, according to the said structure, the battery which has the reliability at the time of overcharge and high battery performance (the outstanding output characteristic in a low SOC area | region) can be provided.

In a preferred embodiment of the sealed nonaqueous electrolyte secondary battery disclosed herein, vanadium pentoxide (V ₂ O ₅ ), manganese dioxide (MnO ₂ ), niobium pentoxide (Nb ₂ O) is used as the charge storage material. ₅ ), including one or more selected from the group consisting of tungsten dioxide (WO ₂ ), titanium disulfide (TiS ₂ ), molybdenum disulfide (MoS ₂ ) and carbon tetrafluoride (CF ₄ ). Yes.
The charge storage material can suitably store charge carriers when the negative electrode reaches a charge storage start potential during the first charge / discharge. In addition, since the occluded charge carriers are held without being released, the potential of the negative electrode can be suitably increased. Therefore, the operating voltage of the positive electrode can be increased compared to the conventional case, and the internal resistance in the low SOC region can be effectively reduced.

Patent Document 2 discloses a non-aqueous electrolyte secondary battery containing carbon fluoride in the negative electrode. The conventional technology aims to improve the cycle characteristics of the battery, and by containing carbon fluoride in the negative electrode, the expansion and contraction of the negative electrode mixture layer associated with charge and discharge can be suppressed, and further the conductivity of the negative electrode can be improved. It is described that it can be improved. Patent Document 3 can use niobium pentoxide as the negative electrode active material of the nonaqueous electrolyte secondary battery, and Patent Document 4 can use manganese dioxide or the like as the positive electrode active material of the nonaqueous electrolyte battery. Are described respectively.
However, these conventional techniques do not have the problem of increasing the internal resistance in the low SOC region, and can increase the negative electrode potential to maintain the positive electrode potential in a relatively high state. There is no disclosure or suggestion that an increase in internal resistance in the SOC region can be suppressed. Therefore, these prior arts are different from the present application in the problem and usage of the charge storage material.

In a preferred aspect of the sealed nonaqueous electrolyte secondary battery disclosed herein, the density of the negative electrode mixture layer is 1.2 g / cm ³ or more and 1.6 g / cm ³ or less.
When satisfy | filling the said range, a high energy density is realizable compared with the past. Moreover, since the reaction field (namely, contact area with a nonaqueous electrolyte) required in order to generate gas at the time of overcharge is also ensured, the amount of gas required in order to operate an electric current interruption mechanism can be obtained. Therefore, high battery performance can be realized while maintaining reliability during overcharge.

In a preferred embodiment of the sealed nonaqueous electrolyte secondary battery disclosed herein, the negative electrode mixture layer has a thickness of 50 μm or more and 100 μm or less.
A higher energy density can be realized by making the negative electrode composite material layer 50 μm or thicker than in the past. Therefore, higher battery performance can be realized.

In a preferred embodiment of the sealed nonaqueous electrolyte secondary battery disclosed herein, the negative electrode active material is in the form of particles, and the volume-based measurement of the particles measured by particle size distribution measurement based on a laser diffraction / light scattering method. The average particle size is 20 μm or more and 50 μm or less.
When the particle size of the negative electrode active material is in the above range, a negative electrode mixture layer having high conductivity can be produced. Moreover, since a moderate space | gap can be hold | maintained in this negative electrode compound-material layer, a non-aqueous electrolyte is easy to be immersed and battery resistance can be reduced further.

In a preferred embodiment of the sealed nonaqueous electrolyte secondary battery disclosed herein, the negative electrode active material is in the form of particles, and the specific surface area of the particles based on the BET method using nitrogen gas is 1 m ² / g or more. 10 m ² / g or less.
When the specific surface area of the negative electrode active material is in the above range, the reaction field necessary for generating gas at the time of overcharge is secured, so that the reliability of the battery can be maintained. Therefore, reliability at the time of overcharge and high battery performance can be achieved at a high level.

In a preferred embodiment of the sealed nonaqueous electrolyte secondary battery disclosed herein, the charge storage material is added in an amount of 0.5 mg / cm ³ or more to 6.0 mg / cm ³ per unit volume of the negative electrode mixture layer. ³ or less.
When the above addition amount is satisfied, the irreversible capacity can be suppressed to the minimum necessary, so that the energy density of the battery can be maintained at a high value. Therefore, the object of the present application can be achieved at a higher level.

In a preferred embodiment of the sealed nonaqueous electrolyte secondary battery disclosed herein, the product of the theoretical capacity per unit mass (mAh / g) of the positive electrode active material and the mass (g) of the positive electrode active material. a positive electrode capacity is calculated _(C c (mAh)), negative electrode capacity is calculated by the product of the theoretical capacity per unit mass of the negative electrode active material (mAh / g) and the specific of the negative electrode active material weight (g) ( C _a (mAh)) and the ratio (C _a / C _c ) are 1.2 or more and 1.5 or less.
In applications requiring high energy density (typically for vehicle driving, for example, for PHV driving), the capacity ratio between the positive electrode and the negative electrode is smaller than that of the conventional case (typically C _a / C _c ≦ 1. 5, for example 1.2 ≦ C _a / C _c ≦ 1.5). However, if the capacity ratio is lowered, the irreversible capacity is reduced, and the operating voltage of the positive electrode tends to be high particularly in the low SOC region. For this reason, in such a configuration, the application effect of the present invention can be further exhibited.

In a preferred embodiment of the sealed nonaqueous electrolyte secondary battery disclosed herein, the positive electrode mixture layer includes a positive electrode active material capable of reversibly occluding and releasing charge carriers, and the positive electrode active material includes: General formula: Li _{1 + δ} (Ni _a Co _b Mn _c M _d ) O ₂ (where M is one or more selected from transition metal elements, typical metal elements and boron (B), and δ is , 0 ≦ δ ≦ 0.2, a value determined to satisfy the charge neutrality condition, a, b, c, d satisfy a + b + c + d≈1, and at least one of a, b, c is greater than 0 The lithium transition metal composite oxide represented by
A lithium transition metal composite oxide (lithium nickel cobalt manganese composite oxide) containing lithium element, nickel element, cobalt element and manganese element as a constituent element is excellent in thermal stability and can realize high energy density. However, on the other hand, the positive electrode using the oxide tends to have a low potential in a low SOC region (typically, a region of SOC of 25% or less), and the internal resistance tends to increase remarkably. According to the technique disclosed here, such an increase in resistance can be suitably suppressed, so that even higher battery performance can be exhibited.

In a preferred embodiment of the sealed nonaqueous electrolyte secondary battery disclosed herein, cyclohexylbenzene (CHB) and / or biphenyl (BP) is included as a gas generating agent.
Cyclohexylbenzene and biphenyl are easy to take a conjugated system and are easy to exchange electrons. For this reason, it is suitably oxidized and decomposed at the time of overcharging, and a large amount of hydrogen gas can be generated. Therefore, the current interruption mechanism can be operated more quickly, and the reliability of the battery can be improved.

In a preferred embodiment of the production method disclosed herein, the amount of the gas generating agent added is 0.5% by mass or more and 5% by mass or less with respect to 100% by mass of the electrolyte.
When the above range is satisfied, an increase in internal resistance (typically, an increase in charge transfer resistance) accompanying the addition of the gas generating agent can be suppressed to a lower level, so that the battery performance can be further improved.

In addition, according to the present invention, an assembled battery in which a plurality of sealed nonaqueous electrolyte secondary batteries (unit cells) disclosed herein are combined is provided.
The battery disclosed here can exhibit higher battery performance than conventional batteries. Therefore, an assembled battery formed by connecting a plurality of the batteries can exhibit performance (for example, energy density and output characteristics) superior to that of the conventional battery. In addition, since the current interruption mechanism can be stably operated during overcharge, the battery can be highly reliable.

Furthermore, according to the present invention, there is provided a vehicle including the assembled battery as a driving power source.
Although the battery disclosed here can be used for various purposes, the battery resistance is reduced as compared with the conventional battery, and the battery performance (for example, energy density and output characteristics) is excellent. Therefore, it can be suitably used in applications requiring such characteristics (for example, a power source (drive power source) for driving a motor mounted on a vehicle). Further, since the battery resistance is significantly reduced in the low SOC region, it can be suitably used particularly for PHV.

FIG. 1 is a graph showing the relationship between electrode potential (V) and SOC (%) for explaining the concept of the present invention. FIG. 2 is a perspective view schematically showing the outer shape of a sealed nonaqueous electrolyte secondary battery according to an embodiment of the present invention. 3 is a diagram schematically showing a cross-sectional structure taken along line III-III of the sealed nonaqueous electrolyte secondary battery of FIG. FIG. 4 is a schematic diagram illustrating a configuration of a wound electrode body of a sealed nonaqueous electrolyte secondary battery according to an embodiment of the present invention. FIG. 5 is a perspective view schematically showing an assembled battery in which a plurality of sealed nonaqueous electrolyte secondary batteries (unit cells) according to an embodiment of the present invention are combined. FIG. 6 is a side view showing a vehicle (automobile) provided with a sealed nonaqueous electrolyte secondary battery according to an embodiment of the present invention. FIG. 7 is a graph showing the relationship between the SOC (%) of the battery and the IV resistance. FIG. 8 is a graph showing the relationship between the charge storage material addition amount (mg / cm ³ ) and battery performance.

  Hereinafter, preferred embodiments of the sealed nonaqueous electrolyte secondary battery disclosed herein will be described. Matters necessary for implementation other than matters specifically mentioned in the present specification can be grasped as design matters of those skilled in the art based on the prior art in the field. The sealed nonaqueous electrolyte secondary battery having such a structure can be implemented based on the contents disclosed in the present specification and common technical knowledge in the field. Hereinafter, the case of a lithium secondary battery may be described in more detail as a typical example, but the application target of the present invention is not intended to be limited to such a battery.

In the present specification, the “non-aqueous electrolyte secondary battery” refers to a battery including a non-aqueous electrolyte (typically, an electrolytic solution containing a supporting salt in a non-aqueous solvent). The “lithium secondary battery” refers to a secondary battery that uses lithium ions as non-aqueous electrolyte ions and is charged and discharged by movement of lithium ions (transfer of charges) between positive and negative electrodes. A secondary battery generally referred to as a lithium ion battery, a lithium polymer battery, a lithium ion capacitor, or the like is a typical example included in the lithium secondary battery in this specification. In the present specification, the “active material” refers to a substance (compound) capable of reversibly occluding and releasing chemical species (lithium ions in a lithium secondary battery) serving as a charge carrier on the positive electrode side or the negative electrode side.
In the present specification, the “overcharge state” refers to a state where the depth of charge (SOC) exceeds 100%. Here, the SOC is a state of charge in which the upper limit voltage is obtained in the operating voltage range that can be reversibly charged and discharged (ie, the fully charged state) is 100%, and the lower limit voltage is obtained. It shows the state of charge when the value is 0%.

In this specification, “particle size” means a particle size (D ₅₀₎ corresponding to 50% cumulative from the fine particle side in a volume-based particle size distribution measured by particle size distribution measurement based on a general laser diffraction / light scattering method. It is also referred to as particle diameter or median diameter.) In the present specification, the “specific surface area” refers to a surface area (BET specific surface area) measured by a BET method (BET three-point method) using nitrogen gas. Further, in this specification, “tap density” indicates a value measured by a method defined in JIS K1469 using a general tapping type density measuring apparatus.

A configuration of a sealed nonaqueous electrolyte secondary battery (typically, a sealed lithium secondary battery) disclosed herein will be described. For example, as shown in FIG. 3, the battery 100 includes a battery case 50 including a positive electrode 10 having a positive electrode mixture layer 14, a negative electrode 20 having a negative electrode mixture layer 24, and a nonaqueous electrolyte (not shown). It is the structure accommodated in the inside. Here, a gas generating agent is added to the non-aqueous electrolyte, and the battery case 50 is provided with a current interruption mechanism 30. The negative electrode mixture layer 24 includes a negative electrode active material and a charge storage material.
In the battery having such a configuration, the charge storage material contained in the negative electrode mixture layer stores the charge carrier during the first charge / discharge. The charge once occluded becomes an irreversible capacity without being released thereafter, so that the potential of the negative electrode (vs. Li ^/ Li ⁺ ) can be relatively increased. Therefore, the operating potential range of the positive electrode can be shifted to a higher potential side than before, and an increase in internal resistance due to a decrease in the potential of the positive electrode can be suitably suppressed. Therefore, the battery having the above configuration has both reliability during overcharge and high battery performance (particularly, excellent output characteristics in a low SOC region).
Hereinafter, the components of the battery will be described in order.

  The positive electrode of the sealed nonaqueous electrolyte secondary battery disclosed herein includes a positive electrode current collector and a positive electrode mixture layer including at least a positive electrode active material formed on the positive electrode current collector. A method for manufacturing such a positive electrode is not particularly limited, and includes, for example, a positive electrode active material, a conductive material, a binder (binder), and the like mixed in a solvent to form a slurry (a paste or an ink). And the like) (hereinafter, referred to as “positive electrode mixture slurry”), and the slurry is applied onto the positive electrode current collector to form a positive electrode mixture layer (also referred to as a positive electrode active material layer). Can be made.

For the preparation of the positive electrode mixture slurry, various conventionally known stirring / mixing devices such as a ball mill, a mixer, a disper, and a kneader can be appropriately used. The solid content concentration (NV) of the slurry is not particularly limited, and can be, for example, 50% by mass to 80% by mass (preferably 55% by mass to 65% by mass, more preferably 55% by mass to 60% by mass). . In addition, the positive electrode mixture layer is formed by, for example, applying the positive electrode mixture slurry onto the positive electrode current collector using a known coating device such as a slit coater, a die coater, a comma coater, a gravure coater, or a dip coater. Can be done. Although not particularly limited, the mass of the positive electrode mixture layer provided per unit area of the positive electrode current collector (the mass of one surface in the configuration having the positive electrode mixture layer on both surfaces of the positive electrode current collector) is 5 mg / may be cm ² ~40mg / cm ² about (typically ^{10mg / cm 2 ~30mg / cm 2} , for example ^{10mg / cm 2 ~20mg / cm 2} ). In the manufacturing method, after the positive electrode mixture slurry is applied, the solvent contained in the positive electrode mixture slurry is removed by an appropriate drying method. As such a method, natural drying, hot air, low-humidity air, vacuum, infrared, far-infrared, electron beam, or the like can be used alone or in combination.

The thickness and density of the positive electrode mixture layer can be adjusted by appropriately pressing the positive electrode. For the press treatment, various conventionally known press methods such as a roll press method and a flat plate press method can be employed. The thickness of the positive electrode mixture layer after the press treatment (thickness per side in the structure having the positive electrode mixture layer on both surfaces of the positive electrode current collector) is, for example, 40 μm or more (typically 50 μm or more), and 100 μm or less. (Typically 80 μm or less). The density of the positive electrode mixture layer after the press treatment is not particularly limited, but is, for example, 2.0 g / cm ³ or more (typically 2.5 g / cm ³ or more) and 4.5 g / cm ³ or less. (Typically 4.2 g / cm ³ or less). A positive electrode mixture layer satisfying the above range is preferable because high battery performance (for example, high energy density and output density) can be realized.
Below, the material etc. which comprise a positive electrode are demonstrated.

  As the positive electrode current collector, a conductive member made of a metal having good conductivity (for example, aluminum, nickel, titanium, stainless steel, etc.) is preferably used. The shape of the current collector may be different depending on the shape of the battery to be constructed, and is not particularly limited. For example, a rod-like body, a plate-like body, a foil-like body, a net-like body, or the like can be used. In addition, in the battery provided with the winding electrode body mentioned later, a foil-like body is mainly used. The thickness of the foil-like current collector is not particularly limited, but a thickness of about 5 μm to 50 μm (more preferably 8 μm to 30 μm) can be used in consideration of the capacity density of the battery and the strength of the current collector.

As the positive electrode active material, one type or two or more types of materials conventionally used in non-aqueous electrolyte secondary batteries can be used without any particular limitation. For example, lithium element and at least one transition metal element (preferably nickel) such as lithium nickel oxide (eg LiNiO ₂ ), lithium cobalt oxide (eg LiCoO ₂ ), lithium manganese oxide (eg LiMn ₂ O ₄ ), etc. , An oxide containing at least one of cobalt and manganese as a constituent metal element (lithium transition metal oxide); lithium elements such as lithium manganese phosphate (LiMnPO ₄ ) and lithium iron phosphate (LiFePO ₄ ); And phosphates containing transition metal elements as constituent metal elements. Among them, the main component is a lithium nickel cobalt manganese composite oxide (for example, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ) having a layered structure containing lithium element, nickel element, cobalt element and manganese element as constituent elements. The positive electrode active material (typically, a positive electrode active material substantially composed of a lithium nickel cobalt manganese composite oxide) can be preferably used because it is excellent in thermal stability and can realize a high energy density. The positive electrode using the oxide tends to increase the internal resistance in the low SOC region, but according to the technique disclosed here, the increase in the resistance can be suitably suppressed. In addition, as such a lithium transition metal complex oxide, what was prepared by the conventionally well-known method (typically particulate form) can be used as it is, for example.

  Here, the lithium-nickel-cobalt-manganese composite oxide is an oxide containing lithium (Li), nickel (Ni), cobalt (Co), manganese (Mn) as a constituent metal element, Li, Ni, Co, Mn Is meant to include oxides substituted by at least one other metal element (transition metal elements other than Li, Ni, Co, and Mn and / or typical metal elements). Such metal elements include, for example, magnesium (Mg), calcium (Ca), strontium (Sr), titanium (Ti), zirconium (Zr), vanadium (V), niobium (Nb), chromium (Cr), molybdenum (Mo ), Tungsten (W), iron (Fe), rhodium (Rh), palladium (Pb), platinum (Pt), copper (Cu), zinc (Zn), boron (B), aluminum (Al), gallium (Ga) ), Indium (In), tin (Sn), lanthanum (La), and cerium (Ce). The same applies to lithium nickel oxide, lithium cobalt oxide, and lithium manganese oxide. The amount of the substitutional constituent element is not particularly limited. For example, it is 0.05% by mass or more (typically 0.1% by mass with respect to the total of 100% by mass of the substitution element, Ni, Co, and Mn. % Or more, for example, 0.2% by mass or more) and 5% by mass or less (typically 3% by mass or less, for example, 2.5% by mass or less).

For example, the general formula: xLi [Li _1/3 Mn _2/3 ] O _2. (1-x) LiMeO ₂ (wherein Me is one or more transition metals, and x is 0 It is also possible to use a so-called solid solution type lithium-excess transition metal oxide represented by <satisfying x ≦ 1.

The positive electrode active material used here is typically in the form of particles (powder). Although the properties of the particles are not particularly limited, for example, the particle size can be 20 μm or less (typically 0.1 μm to 20 μm, for example 0.5 μm to 15 μm, preferably 1 μm to 10 μm). For example, the specific surface area of the particles is 0.1 m ² / g or more (typically 0.5 m ² / g or more, preferably 1 m ² / g or more), and 30 m ² / g or less (typically May be 20 m ² / g or less, preferably 10 m ² / g or less. When the properties of the positive electrode active material particles are in the above range, a dense and highly conductive positive electrode mixture layer can be produced. Moreover, since a moderate space | gap can be hold | maintained in this positive electrode compound material layer, a non-aqueous electrolyte can be easily immersed and battery resistance can be reduced. Further, since a wide reaction field with the gas generating agent can be secured, reliability during overcharge can be secured.

  The proportion of the positive electrode active material in the entire positive electrode mixture layer is not particularly limited, but may be 50% by mass or more (typically 70% by mass or more and less than 100% by mass, for example, 80% by mass or more and 99% by mass or less). preferable.

As the conductive material, one kind or two or more kinds of substances conventionally used in non-aqueous electrolyte secondary batteries can be used without any particular limitation. For example, carbon black (for example, acetylene black, furnace black, ketjen black, channel black, lamp black, thermal black, etc.), coke, activated carbon, graphite (natural graphite and its modified products, artificial graphite), carbon fiber (PAN) Carbon fiber, pitch-based carbon fiber), carbon nanotubes, fullerenes, graphene, and other carbon materials. Or metal fibers (e.g. Al fibers, stainless steel (SUS) fibers), conductive metal powder (e.g. Ag, Ni, metal powder such as Cu), metal oxides (e.g. ZnO, SnO _2, etc.), metal surface coating Synthetic fibers and the like may be used. Among these, carbon black (typically acetylene black) having a relatively small particle size and a large specific surface area can be preferably used.
The proportion of the conductive material in the entire positive electrode mixture layer is not particularly limited, but is, for example, 0.1% by mass to 15% by mass (typically 1% by mass to 10% by mass, for example, 2% by mass to 7% by mass). Below).

As the binder, one kind or two or more kinds of substances conventionally used in non-aqueous electrolyte secondary batteries can be used without any particular limitation. For example, when the positive electrode mixture layer is formed using an organic solvent-based slurry (a solvent-based slurry in which the main component of the dispersion medium is an organic solvent), a polymer material that is dispersed or dissolved in the organic solvent can be preferably used. . Examples of such a polymer material include polyvinylidene fluoride (PVdF), polyvinylidene chloride (PVdC), and polyethylene oxide. Alternatively, when the positive electrode mixture layer is formed using an aqueous slurry, a polymer material that is dissolved or dispersed in water can be preferably used. Examples of water-soluble (water-soluble) polymer materials include cellulose polymers such as carboxymethyl cellulose (CMC), methyl cellulose (MC), cellulose acetate phthalate (CAP), and hydroxypropyl methyl cellulose (HPMC); polyvinyl alcohol (PVA) ), Acrylic polymers such as polymethyl methacrylate (PMMA); urethane polymers such as polyurethane; and the like. Examples of polymer materials that are dispersed in water (water-dispersible) include vinyl polymers such as polyethylene (PE) and polypropylene (PP); ethylene polymers such as polyethylene oxide (PEO) and polytetrafluoroethylene (PTFE). Polymers: Fluororesin such as tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA); vinyl acetate copolymer; styrene butadiene rubber (SBR), Rubbers such as acrylic acid-modified SBR resin (SBR latex); and the like.
The ratio of the binder in the entire positive electrode composite material layer is not particularly limited, but may be, for example, 0.1% by mass or more and 10% by mass or less (preferably 1% by mass or more and 7% by mass or less).

  The solvent is not particularly limited as long as the material used for forming the slurry can be uniformly dispersed or dissolved. For example, one or more of the solvents conventionally used in the production of non-aqueous electrolyte secondary batteries are used. Can be used. Such solvents are roughly classified into organic solvents and aqueous solvents. Examples of the organic solvent include amide solvents, alcohol solvents, ketone solvents, ester solvents, amine solvents, ether solvents, nitrile solvents, cyclic ether solvents, and aromatic hydrocarbon solvents. . More specifically, N-methyl-2-pyrrolidone (NMP), N, N-dimethylformamide, N, N-dimethylacetamide, 2-propanol, ethanol, methanol, acetone, methyl acetate, ethyl acetate, methyl acrylate , Diethyltriamine, N, N-dimethylaminopropylamine, acetonitrile, ethylene oxide, tetrahydrofuran, dioxane, benzene, toluene, ethylbenzene, xylene dimethyl sulfoxide, dichloromethane, trichloromethane, dichloroethane, etc., typically using NMP Can do. The aqueous solvent is preferably water or a mixed solvent mainly composed of water. As the solvent other than water constituting the mixed solvent, one or more organic solvents (lower alcohol, lower ketone, etc.) that can be uniformly mixed with water can be appropriately selected and used. For example, it is preferable to use an aqueous solvent in which 80% by mass or more (more preferably 90% by mass or more, more preferably 95% by mass or more) of the aqueous solvent is water. A particularly preferable example is an aqueous solvent (for example, water) substantially consisting of water.

In addition, the positive electrode mixture slurry prepared here has various additives (for example, an inorganic compound that generates gas during overcharge and a material that can function as a dispersant, as long as the effects of the present invention are not significantly impaired. ) Etc. can also be added.
Examples of the compound capable of generating gas during the overcharge include carbonate (for example, lithium carbonate) and oxalate (for example, lithium oxalate). Examples of the dispersant include a polymer compound having a hydrophobic chain and a hydrophilic group (for example, an alkali salt, typically a sodium salt); an anionic compound having a sulfate, a sulfonate, a phosphate, and the like; And cationic compounds such as amines. More specifically, carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, butyral, polyvinyl alcohol, modified polyvinyl alcohol, polyethylene oxide, polyvinyl pyrrolidone, polycarboxylic acid, oxidized starch, phosphoric acid starch and the like can be mentioned.

Next, the negative electrode of the sealed nonaqueous electrolyte secondary battery disclosed herein includes a negative electrode current collector and a negative electrode mixture layer formed on the negative electrode current collector. The negative electrode mixture layer includes at least a negative electrode active material and a charge storage material capable of storing charge carriers at a higher potential than the negative electrode active material. A method for producing such a negative electrode is not particularly limited. For example, a negative electrode active material, a charge storage material, a binder and the like are mixed in a suitable solvent to form a slurry composition (hereinafter referred to as “negative electrode mixture slurry”). And the slurry is applied onto a negative electrode current collector to form a negative electrode mixture layer (also referred to as a negative electrode active material layer). The method for preparing the negative electrode mixture slurry may be the same as that for the positive electrode described above. Although the solid content concentration (NV) of the slurry is not particularly limited, it can be, for example, 40% by mass to 65% by mass (preferably 45% by mass to 55% by mass, more preferably 45% by mass to 50% by mass). . The method for forming the negative electrode mixture layer and the drying method can be the same as those for the positive electrode described above. Although not particularly limited, the mass of the negative electrode mixture layer provided per unit area of the negative electrode current collector (the mass on one side in the configuration having the negative electrode mixture layer on both sides of the negative electrode current collector) is, for example, 5 mg. / Cm ^{2 to} about ²⁰ mg / cm ² (typically 5 mg / cm ^{2 to} 10 mg / cm ² ).

The thickness and density of the negative electrode mixture layer can be adjusted by appropriately pressing the negative electrode. The thickness of the negative electrode mixture layer after the press treatment (thickness per side in the configuration having the negative electrode mixture layer on both sides of the negative electrode current collector) is, for example, 40 μm or more (typically 50 μm or more), and 100 μm or less. (Typically 80 μm or less). Further, the density of the negative electrode mixture layer after the press treatment is not particularly limited, and is, for example, 1.1 g / cm ³ or more (typically 1.2 g / cm ³ or more, for example, 1.25 g / cm ³ or more). And 2.0 g / cm ³ or less (typically 1.6 g / cm ³ or less, for example, 1.5 g / cm ³ or less, 1.45 g / cm ³ or less). When satisfy | filling the said range, a high energy density is realizable compared with the past. Moreover, since the reaction field (namely, contact area with a nonaqueous electrolyte) required in order to generate gas at the time of overcharge is also ensured, the amount of gas required in order to operate an electric current interruption mechanism can be obtained.
Below, the material etc. which comprise a negative electrode are demonstrated.

  As the negative electrode current collector, a conductive material made of a metal having good conductivity (for example, copper, nickel, titanium, stainless steel, etc.) is preferably used. The shape of the negative electrode current collector can be the same as the shape of the positive electrode current collector.

As the negative electrode active material, one kind or two or more kinds of materials conventionally used in non-aqueous electrolyte secondary batteries can be used without any particular limitation. Specific materials include, but are not limited to, natural graphite (graphite), artificial graphite manufactured from petroleum or coal-based materials and modified products thereof, hard carbon (non-graphitizable carbon), soft Carbon materials such as carbon (easily graphitized carbon) and carbon nanotubes; silicon oxide (eg, SiO, SiO ₂ ), titanium oxide (eg, TiO, TiO ₂ ), vanadium oxide (eg, VO ₂ , V ₂ O ₅ ), iron oxide (Eg FeO, Fe ₂ O ₃ , Fe ₃ O ₄ ), cobalt oxide (eg CoO, Co ₂ O ₃ ), nickel oxide (eg NiO), niobium oxide (eg Nb ₂ O ₅ ), tin oxide (eg SnO, SnO _2), lithium-silicon composite oxide, a lithium titanium composite oxide (lithium titanium composite oxide: LTO, for example, _Li 4 _Ti 5 _{O 12, iTi 2 O 4, Li 2 Ti} 3 O 7), lithium vanadium composite oxide, lithium-manganese composite oxide, metal oxides such as lithium-tin composite oxide material; lithium nitride _(Li 3 N), lithium-cobalt composite nitride , Metal nitride materials such as lithium nickel composite nitride; metals such as tin (Sn), silicon (Si), aluminum (Al), zinc (Zn), lithium (Li), or metals mainly composed of these metal elements Metal materials made of alloys; and the like. Especially, since a high energy density is obtained, a graphite material (graphite) can be preferably used.
The proportion of the negative electrode active material in the entire negative electrode mixture layer is not particularly limited, but it is usually suitably about 50% by mass or more, and preferably 90% by mass or more and 99% by mass (eg, 95% by mass or more and 99% by mass). Mass% or less).

Although the charge storage start potential (vs. Li ^/ Li ⁺ ) of the negative electrode active material varies slightly depending on the non-aqueous solvent or the like, it is generally 0.01 V to 1.6 V. More specifically, for example, graphite material is 0.25 V, iron oxide (Fe ₂ O ₃ ) is about 0.8 V, and lithium titanium composite oxide (Li ₄ Ti ₅ O ₁₂ ) is about 1.5 V to 1.6 V. Silicon (Si) has a charge storage start potential (vs. Li ^/ Li ⁺ ) at 0.04 V to 0.33 V, respectively.
The charge carrier occlusion start potential (vs. Li ^/ Li ⁺ ) can be measured by a cyclic voltammetry (CV) method using, for example, a general electrochemical measurement device. More specifically, platinum as a working electrode and lithium metal as a counter electrode and a reference electrode are disposed in a cell (typically a tripolar cell) filled with a solution containing a measurement object, respectively. -It can be grasped by scanning the potential between the counter electrodes (vs. Li ^/ Li ⁺ ) at a predetermined speed. Here, a potential at which an oxidation current starts to be observed at a measurement temperature of 25 ° C. (typically, a current starts to flow at 0.2 mA / cm ² or more) is shown as a charge carrier storage start potential (charge carrier storage potential). More simply, a value based on a general quantum chemistry calculation result can be used.

The negative electrode active material used here is typically in the form of particles. The properties of the particles are not particularly limited. For example, the particle size can be 50 μm or less (typically 10 μm or more and 50 μm or less, for example, 20 μm or more and 50 μm or less). The specific surface area of the particles is, for example, 0.1 m ² / g or more (typically 0.5 m ² / g or more, preferably 1 m ² / g or more), and 30 m ² / g or less (typical 20 m ² / g or less, preferably 10 m ² / g or less. The tap density of the particles is, for example, 0.1 g / cm ³ or more (preferably 0.5 g / cm ³ or more), and 1.5 g / cm ³ or less (for example, 1.3 g / cm ³ or less). can do. When the properties of the negative electrode active material particles are in the above range, a negative electrode mixture layer having high conductivity can be produced. Moreover, since a moderate space | gap can be hold | maintained in this negative electrode compound-material layer, a non-aqueous electrolyte is easy to be immersed and battery resistance can be reduced further. At the same time, since a reaction field necessary for generating gas at the time of overcharging is secured, the reliability of the battery can be maintained. Suitable properties of the particles can be prepared, for example, according to firing conditions (such as firing temperature and temperature rise conditions) and pulverization conditions (such as pressure and number of times) of the raw material.

  The properties of the negative electrode active material used in the conventional HV battery are, for example, a particle size of 20 μm or less (typically 0.1 μm or more and 20 μm or less, for example, 1 μm or more and 10 μm or less). It is different from the range.

As the charge storage material, a compound that can store charge carriers at a higher potential than the negative electrode active material and retain (without releasing) the stored charge carriers can be used. Although it will not specifically limit if it is a compound which has such a property, For example, the oxide, sulfide, nitride, fluoride, etc. of a metal element can be used. More specific compounds include titanium oxide (TiO ₂ , Ti ₂ O ₃ ), vanadium oxide (VO, V ₂ O ₃ , V ₂ O ₅ ), chromium oxide (Cr ₂ O ₃ , Cr ₃ O ₄ ), Manganese oxide (Mn ₂ O, Mn ₂ O ₃ , MnO), iron oxide (FeO, Fe ₂ O ₃ , Fe ₃ O ₄ ), cobalt oxide (CoO, Co ₂ O ₃ , Co ₃ O ₄ ), nickel oxide ( NiO, Ni ₂ O ₃ , Ni ₃ O ₄ ), copper oxide (Cu ₂ O, CuO, ZnO), zinc oxide (ZnO), strontium oxide (SrO, SrO ₂ ), yttrium oxide (Y ₂ O ₃ ), oxidation Zirconium (ZrO ₂ ), niobium oxide (NbO, NbO ₂ , Nb ₂ O ₅ ), molybdenum oxide (MoO ₂ , MoO ₃ ), ruthenium oxide (RuO ₂ ), silver oxide (Ag ₂ O), Oxides such as tin oxide (SnO, SnO ₂ ), tungsten oxide (WO ₂ , WO ₃ ); aluminum sulfide (Al ₂ S ₃ ), titanium sulfide (TiS ₂ ), vanadium sulfide (VS, V ₂ S ₅ ), Chromium sulfide (CrS), manganese sulfide (MnS, MnS ₂ ), iron sulfide (FeS, FeS ₂ ), cobalt sulfide (CoS), nickel sulfide (NiS, Ni ₂ S ₃ ), copper sulfide (CuS), zinc sulfide ( Sulfidation of ZnS), zirconium sulfide (ZrS ₂ ), molybdenum sulfide (MoS ₂ ), silver sulfide (Ag ₂ S), tin sulfide (SnS, SnS ₂ ), tantalum sulfide (TaS ₂ ), tungsten sulfide (WS ₂ ), etc. Material: Titanium nitride (TiN), chromium nitride (Cr ₂ N), iron nitride (Fe ₃ N, Fe ₄ N), cobalt nitride (Co ₃ N), copper nitride (Cu ₃ N) , Nitrides such as zirconium nitride (ZrN), niobium nitride (NbN), molybdenum nitride (Mo ₂ N), tungsten nitride (WN ₂ ); titanium fluoride (TiF ₃ ), vanadium fluoride (VF ₃ ), fluoride Manganese (MnF ₂ ) iron fluoride (FeF ₂ , FeF ₃ ), cobalt fluoride (CoF ₂ , CoF ₃ ), copper fluoride (CuF ₂ ), zinc fluoride (ZnF ₂ ), silver fluoride (AgF), And fluorides such as tin fluoride (SnF ₂ ). Further, carbon fluoride (CFn (where n satisfies 1 ≦ n ≦ 8)) can also be used. Among these, vanadium pentoxide (V ₂ O ₅ ), manganese dioxide (MnO ₂ ), niobium pentoxide (Nb ₂ O ₅ ), tungsten dioxide (WO ₂ ), titanium disulfide (TiS ₂ ), molybdenum disulfide (MoS). ₂ ) and one or more selected from the group consisting of carbon tetrafluoride (CF ₄ ) can be preferably used.
The ratio of the charge storage material in the entire negative electrode mixture layer is not particularly limited, and may be, for example, 1% by mass to 10% by mass (preferably 2% by mass to 5% by mass). The ratio of the charge storage material can be the above negative per unit volume of the electrode mixture layers 0.5 mg / cm ³ or more 6.0 mg / cm ³ or less. When the above range is satisfied, the irreversible capacity can be suppressed to the minimum necessary, so that the energy density of the battery can be maintained at a high value.

The charge storage material is preferably appropriately selected according to the type of the negative electrode active material, the design of the battery (operation voltage), and the like. For example, 0.2 V (typically 0.3 V) from the charge storage potential of the negative electrode active material. For example, a material having a charge storage potential higher than 0.5 V) can be preferably selected. By making the difference in potential more than the above value, the charge carrier can be suitably occluded during the first charge / discharge. For this reason, the electric potential of a negative electrode can be raised relatively and the increase in internal resistance can be suppressed suitably. The charge carrier occlusion start potential (vs. Li ^/ Li ⁺ ) of each charge occlusion material can be measured in the same manner as the negative electrode active material by the CV method. According to this measurement, for example, vanadium pentoxide is 3.0V, manganese dioxide is 2.8V, niobium pentoxide is 2.0V, tungsten dioxide is 3.45V, titanium disulfide is 2.1V, and molybdenum disulfide is 1V. .8V, and carbon tetrafluoride has a charge storage start potential (vs. Li ^/ Li ⁺ ) at 2.8V, respectively.

  The charge storage material used here is typically in the form of particles. The properties of the particles are not particularly limited. For example, the particle size can be 100 μm or less (typically 10 μm to 100 μm, for example, 10 μm to 50 μm, preferably 20 μm to 40 μm). Preferably, the ratio (Da / Do) of the particle size (Do) of the charge storage material to the particle size (Da) of the negative electrode active material is 0.5 ≦ Da / Do ≦ 2. When satisfy | filling this range, the electroconductivity in a negative mix layer can improve, and the internal resistance of this battery can be reduced further.

As the binder, an appropriate material can be selected from the polymer materials exemplified as the binder for the positive electrode mixture layer. Specifically, styrene butadiene rubber (SBR), polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE) and the like are exemplified.
The ratio of the binder in the entire negative electrode composite material layer is not particularly limited, but may be, for example, 1% by mass or more and 10% by mass or less (preferably 2% by mass or more and 5% by mass or less).
In addition, the above-mentioned various additives (for example, carboxymethyl cellulose (CMC) as a dispersant), a conductive material, and the like can be used as appropriate.

  The positive electrode and the negative electrode are laminated to produce an electrode body. The shape of the electrode body is not particularly limited. For example, as shown in FIG. 4, a positive electrode mixture layer 14 having a predetermined width is formed on the long positive electrode current collector 12 along the longitudinal direction of the current collector. A long negative electrode mixture layer 24 having a predetermined width is formed on the long positive electrode 10 and the long negative electrode current collector 22 formed along the longitudinal direction of the current collector. The wound negative electrode 20 and the wound electrode body 80 formed by laminating and winding can be obtained.

  In a typical configuration of the sealed nonaqueous electrolyte secondary battery disclosed herein, a separator is interposed between the positive electrode and the negative electrode. As the separator, various porous sheets similar to those conventionally used in non-aqueous electrolyte secondary batteries can be used. For example, polyethylene (PE), polypropylene (polypropylene: PP), polyester, cellulose, Examples thereof include a porous resin sheet (film, nonwoven fabric, etc.) made of a resin such as polyamide. Such a porous resin sheet may have a single layer structure, or may have a two or more layers structure (for example, a three-layer structure in which a PP layer is laminated on both sides of a PE layer). In addition, in the secondary battery (lithium polymer battery) using a solid nonaqueous electrolyte, it is good also as a structure where the said nonaqueous electrolyte serves as a separator.

Although the thickness of a separator is not specifically limited, For example, it is 10 micrometers or more and 50 micrometers or less (typically 10 micrometers or more and 40 micrometers or less). Further, the properties of the separator (typically a porous resin sheet) are not particularly limited. For example, the pore diameter is about 0.001 μm to 30 μm (typically 0.01 μm to 20 μm, for example, 0.1 μm to 10 μm). Can be used. Further, for example, those having a porosity (porosity) of about 20% to 90% by volume (typically 30% to 80% by volume, for example, 35% to 70% by volume) can be used. . In the present specification, “pore diameter” refers to a value obtained based on general mercury porosimetry. The “porosity” is calculated by dividing the pore volume (Vb (cm ³ )) obtained by the mercury intrusion measurement by the apparent volume (Va (cm ³ )) and multiplying by 100. Means the value.

  And as shown in FIG. 3, the electrode body 80 and the nonaqueous electrolyte to which the gas generating agent (not shown) was added are accommodated in the battery case 50. A sealed nonaqueous electrolyte secondary battery 100 is constructed by installing the current interruption mechanism 30 in the battery case 50 and sealing it.

  As a battery case, the material and shape conventionally used for a nonaqueous electrolyte secondary battery can be used. Examples of the material of the case include metal materials such as aluminum and steel; resin materials such as polyphenylene sulfide resin and polyimide resin. Among these, a relatively light metal (for example, aluminum or aluminum alloy) can be preferably employed for the purpose of improving heat dissipation and increasing energy density. Further, the shape of the case (outer shape of the container) is not particularly limited. For example, the shape (cylindrical shape, coin shape, button shape), hexahedron shape (cuboid shape, cube shape), bag shape, and the like are processed and deformed. It can be a shape or the like.

  As the nonaqueous electrolyte, one containing at least a supporting salt and a gas generating agent is used. Such a non-aqueous electrolyte typically has a composition in which a supporting salt (typically a lithium salt) is contained in an appropriate non-aqueous solvent. For example, a polymer is added to a liquid non-aqueous electrolyte to form a solid. It may be in a shape (typically a so-called gel).

  As the non-aqueous solvent, one or two or more of those conventionally used in non-aqueous electrolyte secondary batteries can be used without particular limitation. Typically, aprotic solvents such as carbonates, esters, ethers, nitriles, sulfones and lactones can be mentioned. More specifically, ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), 1,2-dimethoxyethane, 1,2-diethoxy Examples include ethane, tetrahydrofuran, 2-methyltetrahydrofuran, dioxane, 1,3-dioxolane, diethylene glycol, dimethyl ether, ethylene glycol, acetonitrile, propionitrile, nitromethane, N, N-dimethylformamide, dimethyl sulfoxide, sulfolane, and γ-butyrolactone. It is done. For example, a non-aqueous solvent mainly composed of carbonates can be preferably used in the technique disclosed herein because a film can be suitably formed on the surface of the negative electrode active material in the initial charge treatment. Among them, it is more preferable to use EC having a high relative dielectric constant, DMC, EMC, or the like having a high standard oxidation potential (that is, a wide potential window). For example, the nonaqueous solvent contains one or more carbonates, and the total volume of these carbonates is 60% by volume or more (more preferably 75% by volume or more, and further preferably 90% by volume) of the total volume of the nonaqueous solvent. That is, it may be substantially 100% by volume.) A non-aqueous solvent can be preferably used.

As the supporting salt, various materials known to be able to function as a supporting electrolyte for nonaqueous electrolyte secondary batteries can be appropriately employed. For example, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiC (SO ₂ CF ₃ ) ₃ One or two or more selected from various lithium salts such as LiClO ₄ can be used, and among them, LiPF ₆ can be preferably used. The concentration of the supporting salt is not particularly limited, but if it is too low, the amount of charge carriers (typically lithium ions) contained in the electrolyte is insufficient, and the ionic conductivity tends to decrease. On the other hand, if it is too high, the viscosity of the electrolyte increases in a temperature range below room temperature (for example, 0 ° C. to 30 ° C.) and the internal resistance tends to increase. For this reason, it is preferable that the density | concentration of a support salt shall be 0.1 mol / L or more and 2 mol / L or less (preferably 0.8 mol / L or more and 1.5 mol / L or less), for example.

As the gas generating agent, a compound capable of decomposing and generating gas when a predetermined battery voltage is exceeded (that is, the oxidation potential is equal to or higher than the operating voltage of the nonaqueous electrolyte secondary battery, and the battery is in an overcharged state) If it is a compound that decomposes and generates a gas), one or two or more of those used in the same application can be used without any particular limitation. Specific examples include aromatic compounds such as biphenyl compounds, alkylbiphenyl compounds, cycloalkylbenzene compounds, alkylbenzene compounds, organic phosphorus compounds, fluorine atom-substituted aromatic compounds, carbonate compounds, cyclic carbamate compounds, and alicyclic hydrocarbons. . More specific compounds (and oxidation potential (vs. Li ^/ Li ⁺ ) of the compound) include biphenyl (4.5V), cyclohexylbenzene (4.6V), 1-fluoro-2-cyclohexylbenzene (4 .8V), 1-fluoro-3-cyclohexylbenzene (4.8V), 1-fluoro-4-cyclohexylbenzene (4.8V), 1-bromo-4-cyclohexylbenzene (4.8V), trans-butylcyclohexyl Benzene (4.6V), cyclopentylbenzene, tert-butylbenzene (4.9V), tert-pentylbenzene (4.8V), 1-fluoro-4-tert-butylbenzene (4.9V), 1-chloro- 4-tert-butylbenzene (4.9V), 1-bromo-4-tert-butylbenzene 4.9V), tert-pentylbenzene (4.8V), 1-fluoro-4-tert-pentylbenzene (4.8V), 1-chloro-4-tert-pentylbenzene (4.8V), 1-bromo -4-tert-pentylbenzene (4.8V), tert-aminobenzene, terphenyl, 2-fluorobiphenyl, 3-fluorobiphenyl, 4-fluorobiphenyl, 4,4′-difluorobiphenyl, o-cyclohexylfluorobenzene, p-cyclohexyl fluorobenzene, tris- (t-butylphenyl) phosphate (4.8V), phenyl fluoride (4.9V), 4-fluorophenyl acetate (4.7V), diphenyl carbonate (4.9V), methyl Phenyl carbonate (4.8V), Bicester Chill phenyl carbonate (4.7V), diphenyl ether, dibenzofuran, and the like. Of these, cyclohexylbenzene and biphenyl can be preferably used. These are easy to take a conjugated system and are easy to exchange electrons. For this reason, it is suitably oxidized and decomposed at the time of overcharging, and a large amount of hydrogen gas can be generated. Therefore, the current interruption mechanism can be operated more quickly, and the reliability of the battery can be further enhanced.

  The gas generating agent is preferably selected as appropriate according to the design (operating voltage) of the battery. For example, the gas generating agent is about 0.1 V (typically 0.2 V, for example 0.3 V) from the operating upper limit voltage of the battery. Those having a high oxidation potential can be preferably selected. The oxidation potential can be measured in the same manner as the charge carrier occlusion start potential by, for example, a cyclic voltammetry (CV) technique.

  The amount of the gas generating agent added is not particularly limited, but if it is too small, the amount of gas generated during overcharging decreases, and the current interrupt mechanism may not operate normally. Further, if an excessive amount is added to emphasize reliability, battery performance may be deteriorated. Therefore, the addition amount of the gas generating agent with respect to 100% by mass of the nonaqueous electrolyte is 0.1% by mass or more (typically 0.5% by mass or more, for example, 1% by mass or more), and 10% by mass or less ( Typically, it is preferably 5% by mass or less, for example, 4% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less. By making the addition amount of the gas generating agent within the above range, the increase in internal resistance (typically, increase in charge transfer resistance) accompanying the addition of the gas generating agent can be suppressed to a lower level, and high reliability and excellent The battery performance can be made compatible.

  The non-aqueous electrolyte in the technique disclosed herein can appropriately contain components other than the above-described supporting salt, gas generating agent, and non-aqueous solvent as long as the effects of the present invention are not significantly impaired. Examples of such optional components include various additives such as film forming agents such as vinylene carbonate (VC), vinyl ethylene carbonate (VEC), and fluoroethylene carbonate (FEC); dispersants; thickeners;

  The current interrupting mechanism is not particularly limited as long as the current can be interrupted according to the increase in pressure in the battery case (that is, using the increase in internal pressure as a trigger for operation), and the current provided in this type of battery. A mechanism similar to any conventionally known blocking mechanism can be appropriately employed. As an example, a configuration as shown in FIG. 3 to be described later can be employed. In such a configuration, when the internal pressure of the battery case rises, the member constituting the conductive path from the electrode terminal to the electrode body is deformed, and the conductive path is cut by being separated from the other.

The battery after the construction is typically subjected to charge / discharge treatment under predetermined conditions. By such charge / discharge treatment, charges are occluded in the charge occlusion material, and the potential of the negative electrode can be increased. The voltage between the positive and negative terminals (typically the highest potential) in the charging process varies depending on the electrode material (active material) and nonaqueous electrolyte used, but at least the charge storage start potential (vs. Li / Li ⁺ ) or higher is required. On the other hand, if the potential is too high, the battery performance may be adversely affected, for example, by promoting the decomposition reaction of the nonaqueous electrolyte. Therefore, it is preferable to set the potential so as not to greatly exceed the upper limit of the operating voltage of the battery. Therefore, for example, in a battery whose upper limit of the operating voltage is 4.1 V, it can be set to 1 V to 4.5 V (typically 1.5 V to 4.2 V, for example, 3 V to 4.2 V). .

When adjusting the voltage, for example, constant current charging (charging at a constant current of 0.1 C or higher (typically 0.1 C or higher and 1 C or lower) from the start of charging until the voltage between the positive and negative terminals reaches a predetermined value) CC charging). Alternatively, a constant current is charged at a constant current of 0.1 C or higher (typically 0.1 C or higher and 1 C or lower) from the start of charging until the voltage between the positive and negative terminals reaches a predetermined value, and further charged at a constant voltage for a predetermined time. You may carry out by constant voltage charge (CCCV charge). In addition, the said charge process may be performed once, for example, charging / discharging operation of 2 times or more can also be performed repeatedly. Furthermore, other operations (for example, pressure load due to restraint or irradiation of ultrasonic waves) can be used in combination as long as the battery performance is not greatly affected.

  The sealed non-aqueous electrolyte secondary battery disclosed here only needs to contain the charge storage material in the negative electrode mixture layer at least immediately after the battery construction, and after that, part or all of the charge storage material is altered. (Reaction, ionization, decomposition, etc.). As described above, most of the charge storage materials contained in the negative electrode mixture layer immediately after battery construction can store charge carriers by the first charge / discharge treatment. Therefore, in the present invention, in a battery (for example, a battery after charge / discharge treatment) that has passed since the construction of the battery, it is not always necessary to remain in the state (composition) when the charge storage material is added.

In a preferred embodiment of the sealed nonaqueous electrolyte secondary battery disclosed herein, the calculation is performed by the product of the theoretical capacity (mAh / g) per unit mass of the positive electrode active material and the mass (g) of the positive electrode active material. is the positive electrode capacity _(C c _(mAh)), negative electrode capacity is calculated by the product of the theoretical capacity per unit mass of the negative electrode active material (mAh / g) and the specific of the negative electrode active material weight (g) _{(C a} (MAh)) and the ratio (C _a / C _c ) is 1.2 or more and 1.5 or less. In applications requiring high energy density (typically for vehicle driving, for example, for PHV driving), the capacity ratio between the positive electrode and the negative electrode is smaller than that of the conventional one (typically 1.2 ≦ C _a / C _c ≦ 1.5). However, if the capacity ratio is reduced, the operating voltage of the positive electrode tends to be high especially in the low SOC region. For this reason, in such a configuration, the application effect of the present invention can be further exhibited.

  Although not intended to be particularly limited, as a schematic configuration of a sealed nonaqueous electrolyte secondary battery according to an embodiment of the present invention, a flatly wound electrode body (winding electrode body), and a nonaqueous electrolyte Are shown in a flat rectangular parallelepiped (box-shaped) container as an example of a sealed non-aqueous electrolyte secondary battery (unit cell), and FIGS. In the following drawings, members / parts having the same action are denoted by the same reference numerals, and redundant description may be omitted or simplified. The dimensional relationship (length, width, thickness, etc.) in each figure does not reflect the actual dimensional relationship.

FIG. 2 is a perspective view schematically showing the outer shape of the sealed nonaqueous electrolyte secondary battery 100 according to one embodiment of the present invention. FIG. 3 is a diagram schematically showing a cross-sectional structure taken along line III-III of the sealed nonaqueous electrolyte secondary battery shown in FIG.
As shown in FIGS. 2 and 3, the sealed nonaqueous electrolyte secondary battery 100 according to this embodiment includes a wound electrode body 80 and a hard case (outer container) 50. The hard case 50 includes a flat rectangular parallelepiped (square) hard case main body 52 having an open upper end, and a lid 54 that closes the opening. On the upper surface of the hard case 50 (that is, the lid body 54), a positive electrode terminal 70 that is electrically connected to the positive electrode sheet of the wound electrode body 80 and a negative electrode terminal 72 that is electrically connected to the negative electrode sheet of the electrode body are provided. ing. In addition, the lid 54 is provided with a safety valve 55 for discharging gas generated inside the battery case to the outside of the case, similarly to the hard case of the conventional nonaqueous electrolyte secondary battery.

  Inside the battery case 50, an electrode body (winding) in which a long positive electrode sheet 10 and a long negative electrode sheet 20 are wound flatly through long separator sheets 40A and 40B. Electrode body) 80 is accommodated together with a non-aqueous electrolyte (not shown) (typically including an aromatic compound and an oxalato complex compound). Further, the positive electrode sheet 10 is formed such that the positive electrode mixture layer 14 is not provided (or removed) at one end along the longitudinal direction, and the positive electrode current collector 12 is exposed. Similarly, the wound negative electrode sheet 20 is not provided with (or removed from) the negative electrode mixture layer 24 at one end along the longitudinal direction, so that the negative electrode current collector 22 is exposed. Is formed. A positive current collector 74 is attached to the exposed end of the positive current collector 12, and a negative current collector 76 is attached to the exposed end of the negative current collector 22. The positive terminal 70 and the negative terminal 72 are electrically connected to each other.

In addition, a current interrupt mechanism 30 that operates when the internal pressure of the battery case increases is provided inside the battery case 50. The current interruption mechanism 30 only needs to be configured to cut a conductive path (for example, a charging path) from at least one electrode terminal to the electrode body 80 when the internal pressure of the battery case 50 increases, and has a specific shape. It is not limited to. In the embodiment shown in FIG. 3, the current interrupt mechanism 30 is provided between the positive electrode terminal 70 fixed to the lid body 54 and the electrode body 80, and when the internal pressure of the battery case 50 rises, the positive electrode terminal 70 to the electrode body 80. It is configured to cut the conductive path leading to.
More specifically, the current interrupt mechanism 30 may include a first member 32 and a second member 34, for example. When the internal pressure of the battery case 50 rises, at least one of the first member 32 and the second member 34 is deformed and separated from the other, thereby cutting the conductive path. In the embodiment shown in FIG. 3, the first member 32 is a deformed metal plate, and the second member 34 is a connection metal plate joined to the deformed metal plate 32. The deformed metal plate (first member) 32 has an arch shape in which a central portion is curved downward, and a peripheral portion thereof is connected to the lower surface of the positive electrode terminal 70 via a current collecting lead terminal 35. Further, the tip of the curved portion 33 of the deformed metal plate 32 is joined to the upper surface of the connection metal plate 34. A positive current collector plate 74 is joined to the lower surface (back surface) of the connection metal plate 34, and the positive current collector plate 74 is connected to the positive electrode 10 of the electrode body 80. In this way, a conductive path from the positive electrode terminal 70 to the electrode body 80 is formed.

  The current interrupt mechanism 30 includes an insulating case 38 made of plastic or the like. The insulating case 38 is provided so as to surround the deformed metal plate 32 and hermetically seals the upper surface of the deformed metal plate 32. The internal pressure of the battery case 50 does not act on the upper surface of the hermetically sealed curved portion 33. The insulating case 38 has an opening into which the curved portion 33 of the deformed metal plate 32 is fitted, and the lower surface of the curved portion 33 is exposed from the opening to the inside of the battery case 50. The internal pressure of the battery case 50 acts on the lower surface of the curved portion 33 exposed inside the battery case 50. In the current interruption mechanism 30 having such a configuration, when the internal pressure of the battery case 50 increases, the internal pressure acts on the lower surface of the curved portion 33 of the deformed metal plate 32, and the curved portion 33 curved downward is pushed upward. The upward push of the curved portion 33 increases as the internal pressure of the battery case 50 increases. When the internal pressure of the battery case 50 exceeds the set pressure, the curved portion 33 is inverted so as to bend upside down and bend upward. Due to the deformation of the curved portion 33, the joint point 36 between the deformed metal plate 32 and the connection metal plate 34 is cut. As a result, the conductive path from the positive electrode terminal 70 to the electrode body 80 is cut, and the overcharge current is cut off.

  The current interrupt mechanism 30 is not limited to the positive terminal 70 side, and may be provided on the negative terminal 72 side. Further, the current interrupt mechanism 30 is not limited to the mechanical cutting accompanied by the deformation of the deformed metal plate 32 described above. For example, the internal pressure of the battery case 50 is detected by a sensor, and the internal pressure detected by the sensor sets the set pressure. An external circuit that cuts off the charging current when exceeded can be provided as a current cut-off mechanism.

  FIG. 4 is a diagram schematically showing a long sheet structure (electrode sheet) in a stage before assembling the wound electrode body 80. Of the positive electrode sheet 10 in which the positive electrode mixture layer 14 is formed along the longitudinal direction on one or both surfaces (typically both surfaces) of the long positive electrode current collector 12, and the long negative electrode current collector 22. The negative electrode sheet 20 on which the negative electrode mixture layer 24 is formed along the longitudinal direction on one side or both sides (typically both sides) is overlapped with the long separator sheets 40A and 40B and wound in the longitudinal direction. A wound electrode body is prepared. A flat wound electrode body 80 is obtained by squashing and winding the wound electrode body from the side surface direction.

  FIG. 5 shows an example of an assembled battery 200 in which sealed nonaqueous electrolyte secondary batteries (unit cells) 100 are connected in series and / or in parallel. In the form shown in FIG. 5, the assembled battery 200 includes a plurality of (typically 10 or more, preferably about 10 to 30, for example, 20) sealed nonaqueous electrolyte secondary batteries (unit cells) 100. The wide surfaces of the battery case 50 are arranged in the facing direction (stacking direction) while being reversed one by one so that the positive terminals 70 and the negative terminals 72 are alternately arranged. A cooling plate 110 having a predetermined shape is sandwiched between the arranged unit cells 100. The cooling plate 110 functions as a heat dissipating member for efficiently dissipating heat generated in each unit cell 100 during use, and preferably a cooling fluid (typically between the unit cells 100). Air) (for example, a shape in which a plurality of parallel grooves extending vertically from one side of the rectangular cooling plate to the opposite side are provided on the surface). A cooling plate made of metal having good thermal conductivity or lightweight and hard polypropylene or other synthetic resin is suitable.

  A pair of end plates (restraint plates) 120 are arranged at both ends of the unit cells 100 and the cooling plate 110 arranged as described above. One or a plurality of sheet-like spacer members 150 as length adjusting means may be sandwiched between the cooling plate 110 and the end plate 120. The unit cell 100, the cooling plate 110, and the spacer member 150 arranged in the above manner are applied with a predetermined restraining pressure in the stacking direction by a fastening restraint band 130 attached so as to bridge between both end plates. It is restrained. More specifically, by tightening and fixing the end portion of the restraining band 130 to the end plate 120 with screws 155, the unit cells and the like are restrained so that a predetermined restraining pressure is applied in the arrangement direction. Thereby, restraint pressure is also applied to the wound electrode body 80 housed in the battery case 50 of each unit cell 100. Then, between the adjacent unit cells 100, one positive terminal 70 and the other negative terminal 72 are electrically connected by a connecting member (bus bar) 140. Thus, the assembled battery 200 of the desired voltage is constructed | assembled by connecting each cell 100 in series.

  Further, the sealed nonaqueous electrolyte secondary battery (typically a lithium secondary battery) disclosed herein can be used for various applications, but is characterized by having both high battery performance and reliability. And Therefore, it can be preferably used in applications where high energy density and output density are required and applications where high reliability is required. As such an application, for example, a power source (drive power source) for a motor mounted on the vehicle 1 as shown in FIG. Although the kind of vehicle 1 is not specifically limited, For example, a plug-in hybrid vehicle (PHV), a hybrid vehicle (HV), an electric vehicle (EV), an electric truck, a motorbike, an electric assist bicycle, an electric wheelchair, an electric railway, etc. are mentioned. It is done. In addition, the battery disclosed here can exhibit excellent output characteristics particularly in a low SOC region (for example, a region of SOC of 25% or less), and thus rapid discharge frequently occurs even in a low SOC region such as PHV and EV. It is suitable as a power source for driving a vehicle. Here, the assembled battery 200 in which a plurality of unit cells 100 are connected in series and / or in parallel is used, but it is of course possible to use the unit cell 100 alone.

  Several examples relating to the present invention will be described below, but the present invention is not intended to be limited to the specific examples.

[Construction of sealed nonaqueous electrolyte secondary battery]
<Comparative Example 1>
LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (NCM) as a positive electrode active material powder, acetylene black (AB) as a conductive material, and polyvinylidene fluoride (PVdF) as a binder, these materials The mass ratio of NCM: AB: PVdF = 91: 6: 3 is charged into a kneader and the viscosity is adjusted with N-methylpyrrolidone (NMP) so that the solid content concentration (NV) is 50% by mass. While mixing, a positive electrode active material slurry was prepared. This slurry was applied to one side of an aluminum foil (positive electrode current collector) having a thickness of 15 μm and pressed after drying to produce a positive electrode having a positive electrode mixture layer on the positive electrode current collector. The thickness of the positive electrode after the press treatment was approximately 60 μm, and the density of the positive electrode mixture layer was 2.8 g / cm ³ .

Next, amorphous coated graphite (C, particle size 25 μm, specific surface area 2.5 m ² / g) as a negative electrode active material, styrene butadiene rubber (SBR) and carboxymethyl cellulose (CMC) as binders are used. The mass ratio is charged into a kneader so that C: SBR: CMC = 98: 1: 1, and kneading while adjusting the viscosity with ion-exchanged water so that the solid content concentration (NV) is 45% by mass, A negative electrode active material slurry was prepared. This slurry was applied to one side of a long copper foil (negative electrode current collector) having a thickness of 10 μm and dried and then pressed to prepare a negative electrode having a negative electrode mixture layer on the negative electrode current collector. Note that the thickness of the negative electrode after the press treatment was about 55 μm, and the density of the negative electrode mixture layer was 1.28 g / cm ³ .

The prepared positive electrode and negative electrode were wound facing each other through a separator (made of PE, thickness 20 μm), and then formed into a flat shape to produce a wound electrode body. A positive electrode terminal is provided at the positive electrode current collector end of the electrode body (uncoated portion of the positive electrode mixture layer), and a negative electrode terminal is provided at the end of the negative electrode current collector (uncoated portion of the negative electrode mixture layer). Joined by welding. Such an electrode body is accommodated in a battery case made of a laminate sheet, and a nonaqueous electrolyte (here, ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) is EC: DMC: EMC = 3: 4). : LiPF ₆ as a supporting salt is dissolved at a concentration of 1 mol / L in a mixed solvent containing a volume ratio of 3: 3, and cyclohexylbenzene (CHB) and biphenyl (BP) as gas generating agents are each 2% by mass. What was contained in a proportion was used.) Was injected. Then, the battery case was sealed (sealed) to construct a laminated cell type sealed nonaqueous electrolyte secondary battery (Comparative Example 1).

<Comparative example 2>
A sealed nonaqueous electrolyte secondary battery (Comparative Example 2) as in Comparative Example 1 except that LiNi _1/3 Co _1/3 Mn _1/3 W _1/200 O ₂ was used as the positive electrode active material powder. Built.

<Example 1>
Comparative Example 1 except that manganese dioxide (MnO ₂ , particle size 25 μm) as a charge storage material was charged into a kneader at a ratio of 2 parts by mass with respect to 100 parts by mass of the negative electrode active material when the negative electrode was produced. In the same manner as above, a sealed nonaqueous electrolyte secondary battery (Example 1) was constructed. The addition amount of manganese dioxide per unit volume of the negative electrode mixture layer was 2.31 mg / cm ³ .

<Example 2>
Comparison was made except that carbon tetrafluoride (CF ₄ , particle size 25 μm) as a charge storage material was charged into a kneader at a ratio of 5 parts by mass with respect to 100 parts by mass of the negative electrode active material and kneaded. In the same manner as in Example 1, a sealed nonaqueous electrolyte secondary battery (Example 2) was constructed. The amount of carbon tetrafluoride added per unit volume of the negative electrode mixture layer was 5.79 mg / cm ³ .

<Example 3>
Comparative Example, except that titanium disulfide (TiS ₂ , particle size 25 μm) as a charge storage material was charged into a kneader at a ratio of 5 parts by mass with respect to 100 parts by mass of the negative electrode active material when the negative electrode was produced. As in Example 1, a sealed non-aqueous electrolyte secondary battery (Example 3) was constructed. The amount of titanium disulfide added per unit volume of the negative electrode mixture layer was 5.79 mg / cm ³ .

<Example 4>
Comparative Example, except that molybdenum disulfide (MoS ₂ , particle size 25 μm) as a charge storage material was charged into a kneader at a ratio of 5 parts by mass with respect to 100 parts by mass of the negative electrode active material when the negative electrode was produced. As in Example 1, a sealed non-aqueous electrolyte secondary battery (Example 4) was constructed. The addition amount of molybdenum disulfide per unit volume of the negative electrode mixture layer was 5.79 mg / cm ³ .

<Example 5>
Comparative Example 1 except that tungsten dioxide (WO ₂ , particle size 25 μm) as a charge storage material was charged into a kneading machine at a ratio of 5 parts by mass with respect to 100 parts by mass of the negative electrode active material when the negative electrode was produced. In the same manner as described above, a sealed nonaqueous electrolyte secondary battery (Example 5) was constructed. The addition amount of tungsten dioxide per unit volume of the negative electrode mixture layer was 5.79 mg / cm ³ .

<Example 6>
Except that vanadium pentoxide (V ₂ O ₅ , particle size 25 μm) as a charge storage material was charged into a kneader at a ratio of 5 parts by mass with respect to 100 parts by mass of the negative electrode active material when kneading the negative electrode. As in Comparative Example 1, a sealed nonaqueous electrolyte secondary battery (Example 6) was constructed. The amount of vanadium pentoxide added per unit volume of the negative electrode mixture layer was 5.79 mg / cm ³ .

<Example 7>
Comparative Example, except that niobium pentoxide (NbO ₅ , particle size 25 μm) as a charge storage material was charged into a kneader at a ratio of 5 parts by mass with respect to 100 parts by mass of the negative electrode active material when the negative electrode was produced. In the same manner as in Example 1, a sealed nonaqueous electrolyte secondary battery (Example 7) was constructed. In addition, the addition amount of niobium pentoxide per unit volume of the negative electrode mixture layer was 5.79 mg / cm ³ .
Table 1 summarizes the characteristics of the battery constructed as described above.

  The batteries of Comparative Examples 1 and 2 and Examples 1 to 7 constructed above were charged (CC charging) until the voltage between the positive and negative terminals reached 4.1 V at a constant current of 1 C. Thereafter, the operation was paused for 5 minutes, and an operation of charging for 2 hours by constant voltage charging (CV charging) was performed, and the initial charging capacity (mAh / g) was confirmed. Thereafter, the battery was discharged to 3 V at a constant current of 0.3 C, and the initial discharge capacity (mAh / g) was confirmed. And the battery performance (IV resistance) and the gas generation amount at the time of overcharge were evaluated using this battery. The C rate shown below was calculated using the measured initial discharge capacity as 100%.

[Measurement of IV resistance]
Under the temperature of 25 ° C., each battery constructed as described above was adjusted to a predetermined SOC, and IV resistance was measured. Specifically, first, the battery was charged (or discharged) at a constant current of 1 C until reaching a predetermined SOC, and then the SOC was adjusted by performing constant voltage charging (or constant voltage discharging) for 2 hours. The battery was then discharged at a discharge rate of 5C, and IV resistance was determined from the voltage drop after 10 seconds.
Here, 6 points (namely, SOC 10%, 20%, 25%, 30%, 35%, 40%) were measured in the range of SOC of 10% to 40%. As an example, the results of Comparative Example 1 and Example 1 are shown in FIG. In FIG. 7, the vertical axis represents IV resistance (relative value) based on the IV resistance value of Comparative Example 1 at SOC 20%. In addition, as a representative value, an IV resistance at 20% SOC (similarly, a relative value based on the IV resistance of Comparative Example 1 at 20% SOC) is shown in the corresponding column of Table 1.

  As is apparent from FIG. 7, in Comparative Example 1, a rapid increase in IV resistance is observed in a region where the SOC is 25% or less. This is presumably because the potential of the positive electrode decreased and the resistance in the positive electrode mixture layer increased. On the other hand, in Example 1 (battery in which manganese dioxide is added to the negative electrode as a charge storage material) according to the present invention, even in the region where the SOC is 20% or less, the resistance increases by about 1.3 times compared to the case where the SOC is 40%. It was suppressed. This is considered because the working potential range of the positive electrode can be shifted to the high potential side as compared with Comparative Example 1. In addition, as shown in Table 1, similar results were obtained in Examples 1 to 7 in which various charge storage materials were added. Such a result supports the technical significance of the present invention.

[Overcharge test (measurement of gas generation)]
The amount of gas generation was measured using the Archimedes method. The Archimedes method is a method in which a measurement object (in this example, a laminate sheet type battery) is immersed in a liquid medium (for example, distilled water or alcohol) and the buoyancy applied to the measurement object is measured. This is a method for obtaining the volume of an object. Here, first, the volume of the battery before the overcharge test was measured at a temperature of 25 ° C. Thereafter, the battery was charged with a constant current at a rate of 1 C until it was overcharged (in this example, SOC was 140%). And the volume of this battery was measured again.
By subtracting the volume (B (cm ³ )) of the cell after the conditioning treatment from the volume (A (cm ³ )) of the cell after overcharging, the amount of gas generated (AB) (Cm ³ )) was calculated. Values (relative values) obtained by dividing the obtained gas generation amount (absolute value) by the amount of gas necessary for operating the current interrupting mechanism are shown in the corresponding columns of Table 1.

  As shown in Table 1, in Comparative Example 1 and all Examples, a desired gas could be generated. On the other hand, in Comparative Example 2, only about half of the required amount of gas could be generated. From the above results, it was shown that the battery disclosed here can ensure reliability during overcharge.

Next, a suitable amount of charge storage material was examined. Here, a sealed nonaqueous electrolyte secondary battery was constructed in the same manner as in Example 1 except that the charge storage material was added in the ratio shown in Table 2, and the initial capacity was confirmed and the IV resistance was measured. . The results are shown in the corresponding column of Table 2. In addition, the addition amount of the charge storage material in Table 2 is the addition amount when the negative electrode active material is 100 parts by mass (mass part) and the addition amount per unit volume of the negative electrode mixture layer (mg / cm ³ ) , Respectively. The initial efficiency (%) is a value obtained by dividing the initial discharge capacity (mAh / g) obtained in the confirmation of the initial capacity by the initial charge capacity (mAh / g) and multiplying by 100. FIG. 8 shows the relationship between the charge storage material addition amount (mg / cm ³ ) and the battery performance.

As shown in Table 2, in all Examples, a desired gas could be generated. For this reason, it was shown that the reliability at the time of overcharge can be ensured with this battery.
Further, as shown in Table 2 and FIG. 8, the initial efficiency gradually decreased as the amount of the charge storage material added was increased. This indicates that the charge storage material of the negative electrode occludes charge carriers, and the irreversible capacity of the negative electrode is increased. Further, when the amount of the charge storage material added to the negative electrode active material exceeded 1 part by mass, the IV resistance at 20% SOC was greatly reduced. And IV resistance became substantially constant when the addition amount of the charge storage material was 2 parts by mass or more. From the above results, the amount of the charge storage material added per unit volume of the negative electrode mixture layer is 0.5 mg / cm ³ or more (typically 1.1 mg / cm ³ or more, for example 2.0 mg / cm ³ or more). It was shown that the IV resistance in the low SOC region can be reduced. In other words, by adding the charge storage material to the negative electrode active material in an amount of 0.5 parts by mass or more (typically 1 part by mass or more, for example, 2 parts by mass or more), the IV resistance in the low SOC region is effective. It was shown that it can be reduced. Further, from the viewpoint of energy density, the amount of the charge storage material per unit volume of the negative-electrode mixture layer 6.0 mg / cm ³ or less (typically 5.0 mg / cm ³ or less, for example 4.0 mg / with cm ^3), the initial efficiency of 87% or more (typically 88% or more, it was shown that may be, for example, more than 89%). Therefore, it was shown that by making the ratio of the charge storage material within such a range, the effects of the present invention can be exhibited more suitably and the battery performance can be further improved.

  As mentioned above, although the specific example of this invention was demonstrated in detail, these are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

1 Automobile (vehicle)
10 Positive electrode sheet (positive electrode)
12 Positive electrode current collector 14 Positive electrode mixture layer 20 Negative electrode sheet (negative electrode)
22 Negative electrode current collector 24 Negative electrode composite material layer 30 Current interruption mechanism 32 Deformed metal plate (first member)
34 Connection metal plate (second member)
38 Insulating cases 40A, 40B Separator sheet 50 Battery case 52 Case body 54 Lid 55 Safety valve 70 Positive electrode terminal 72 Negative electrode terminal 80 Winding electrode body 100 Sealed nonaqueous electrolyte secondary battery 110 Cooling plate 120 End plate 130 Restraint band 140 Connection Member 150 Spacer member 155 Screw 200 Battery assembly

Claims (13)

A negative electrode provided with a negative electrode mixture layer;
A positive electrode provided with a positive electrode mixture layer;
A non-aqueous electrolyte to which a gas generating agent capable of generating a gas when a predetermined battery voltage is exceeded is added;
Is housed in the battery case,
And a sealed non-aqueous electrolyte secondary battery provided with a current interruption mechanism that operates when the pressure in the battery case rises with the generation of the gas,
The negative electrode mixture layer includes a negative electrode active material capable of reversibly occluding and releasing charge carriers and a charge storage material capable of occluding the charge carriers at a higher potential than the negative electrode active material. A sealed nonaqueous electrolyte secondary battery characterized by the above. Examples of the charge storage material include vanadium pentoxide (V ₂ O ₅ ), manganese dioxide (MnO ₂ ), niobium pentoxide (Nb ₂ O ₅ ), tungsten dioxide (WO ₂ ), titanium disulfide (TiS ₂ ), and disulfide. The sealed nonaqueous electrolyte secondary battery according to claim 1, comprising one or more selected from the group consisting of molybdenum (MoS ₂ ) and carbon tetrafluoride (CF ₄ ). ^3. The sealed nonaqueous electrolyte secondary battery according to claim 1, wherein a density of the negative electrode mixture layer is 1.2 g / cm ³ or more and 1.6 g / cm ³ or less.   4. The sealed nonaqueous electrolyte secondary battery according to claim 1, wherein the negative electrode mixture layer has a thickness of 50 μm or more and 100 μm or less. 5.   The negative electrode active material is in the form of particles, and the volume-based average particle diameter of the particles measured by particle size distribution measurement based on a laser diffraction / light scattering method is 20 μm or more and 50 μm or less. The sealed nonaqueous electrolyte secondary battery according to Item. The negative electrode active material is in the form of particles, and the specific surface area of the particles based on the BET method using nitrogen gas is 1 m ² / g or more and 10 m ² / g or less. Sealed nonaqueous electrolyte secondary battery. The amount of the charge storage material, the negative electrode mixture layer per unit volume 0.5 mg / cm ³ or more 6.0 mg / cm ³ or less, sealed according to any one of claims 1 to 6 Non-aqueous electrolyte secondary battery. A positive electrode capacity (C _c ) calculated by a product of a theoretical capacity per unit mass of the positive electrode active material and a mass of the positive electrode active material;
The ratio (C _a / C _c ) of the negative electrode capacity (C _a ) calculated by the product of the theoretical capacity per unit mass of the negative electrode active material and the mass of the negative electrode active material is 1.2 or more and 1.5 The sealed nonaqueous electrolyte secondary battery according to any one of claims 1 to 7, which is: The positive electrode mixture layer includes a positive electrode active material capable of reversibly occluding and releasing charge carriers,
The positive electrode active material has the general formula (1):
Li _{1 + δ} (Ni _a Co _b Mn _c M _d ) O ₂ (1)
(Here, M is one or more selected from a transition metal element, a typical metal element, and boron (B), and δ satisfies the charge neutrality condition with 0 ≦ δ ≦ 0.2. A, b, c, d satisfy a + b + c + d≈1, and at least one of a, b, c is greater than 0);
The sealed nonaqueous electrolyte secondary battery according to any one of claims 1 to 8, comprising a lithium transition metal composite oxide represented by:   The sealed nonaqueous electrolyte secondary battery according to any one of claims 1 to 9, comprising cyclohexylbenzene and / or biphenyl as the gas generating agent.   The sealed nonaqueous electrolyte 2 according to any one of claims 1 to 10, wherein an addition amount of the gas generating agent is 0.5% by mass or more and 5% by mass or less with respect to 100% by mass of the electrolyte. Next battery.   An assembled battery in which a plurality of sealed nonaqueous electrolyte secondary batteries according to any one of claims 1 to 11 are combined.   A vehicle comprising the assembled battery according to claim 12 as a driving power source.

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