JP6184552B2 - Current collector, electrode structure, non-aqueous electrolyte battery, and power storage component - Google Patents

Description

  The present invention relates to a current collector, an electrode structure, a nonaqueous electrolyte battery, and a power storage component (such as an electric double layer capacitor and a lithium ion capacitor) suitable for charging and discharging at a large current density.

  Conventionally, non-aqueous electrolyte batteries typified by lithium ion batteries have been required to shorten the charging time, and for this purpose, they must be charged at a high current density. In particular, non-aqueous electrolyte batteries for automobiles are required to be able to discharge at a high current density in order to obtain sufficient acceleration performance. Thus, in order to improve the characteristic (high rate characteristic) in which the battery capacity does not decrease when charging / discharging at a large current density, it is important to reduce the internal resistance of the battery. The internal resistance includes interfacial resistance between constituent elements and resistance to movement of ions as charged particles in the electrolyte, and these must be reduced. Of these, one of the important internal resistances is the interface resistance, and it is known that improving the adhesion between the components is effective as one of the methods for reducing the interface resistance.

  For example, as a method for improving the adhesion between the current collector and the active material layer, a current collector in which a metal foil is coated with a conductive resin has been proposed. Patent Document 1 discloses a metal foil made of hydroxyalkyl chitosan. Techniques for coating are disclosed.

Japanese Patent Laid-Open No. 2008-60060

  However, as a result of experiments conducted by the present inventors, the technique described in Patent Document 1 may not always provide sufficient high rate characteristics.

  The present invention has been made in view of such circumstances, and can reduce the internal resistance of a nonaqueous electrolyte battery, such as a nonaqueous electrolyte battery such as a lithium ion secondary battery, a capacitor for an electric double layer, a lithium ion capacitor, etc. It is an object of the present invention to provide a current collector that can be suitably used for such power storage components and can improve high-rate characteristics.

  By using the following current collector, it is possible to obtain a non-aqueous electrolyte battery excellent in high-rate characteristics, a charged component such as an electric double layer capacitor or a lithium ion capacitor.

That is, according to the present invention,
(1) A current collector having a conductive resin layer on at least one surface of a conductive substrate, the resin layer containing a chitosan-based resin and a conductive material, and in a thermostatic chamber at 23 ° C. on the surface of the resin layer a current collector having a contact angle of 15 to 50 degrees as measured by the θ / 2 method;
(2) A current collector having a conductive resin layer on at least one surface of a conductive substrate, the resin layer containing a chitosan-based resin and a conductive material in a thermostatic chamber at 23 ° C. on the surface of the resin layer. a current collector characterized in that the contact angle of the aqueous model active material paste measured by the θ / 2 method is 10 degrees or more and 50 degrees or less;
(3) A current collector having a conductive resin layer on at least one surface of a conductive substrate, the resin layer containing a chitosan-based resin and a conductive material in a thermostatic chamber at 23 ° C. on the surface of the resin layer. The contact angle of the solvent-based model active material paste measured by the θ / 2 method is 15 degrees or more and 50 degrees or less, and the contact angle of the aqueous model active material paste is 10 degrees or more and 50 degrees or less And an electrode structure including the current collector, a nonaqueous electrolyte battery, and a power storage component (eg, an electric double layer capacitor or a lithium ion capacitor) are provided.

The present invention is characterized in that the state of the resin layer is defined by the contact angle of the model active material paste (hereinafter referred to as “paste contact angle”). The “model active material paste” is a model of an active material paste used when an active material layer is actually formed. There are two types of active material pastes: a solvent-based active material paste in which an active material is pasted using a solvent and a water-based active material paste in which an active material is pasted using water. There are active material paste and water-based model active material paste. Specifically, the solvent-based active material paste includes “LiMn ₂ O ₄ powder (manufactured by Yunan Yuxihuilong technology) 17.9 parts by mass, PVDF (Kishida Chemical # 1100) 1.1 parts by mass (solid) As a result, 1.0 parts by mass of acetylene black (Denka Black HS-100 manufactured by Electrochemical Co., Ltd.) as the conductive material and 20 parts by mass of NMP as the solvent were obtained by stirring for 3 minutes with a defoaming stirrer. It is defined as “paste”. Specifically, the water-based model active material paste is “LiMn ₂ O ₄ powder (manufactured by Yunan Yuxihuilong technology) as the active material and 24 parts by mass of water-dispersed PTFE (polyflon D-1E from Daikin) as the binder resin. 28 parts by mass (as solid content), 2.5 parts by mass of acetylene black (Denka Black HS-100 manufactured by Electrochemical Co., Ltd.) and 33 parts by mass of water as a conductive material, stirred at 2000 rpm for 1 minute in a disperser, and stirred It is defined as “a paste obtained by stirring for 30 seconds in a machine (Primics Filmmix 40-40, peripheral speed 30 m / s)”.

  The inventors of the present invention have found that the paste contact angle on the surface of the resin layer is strongly correlated with the high-rate characteristics when intensive studies were conducted to improve the high-rate characteristics of nonaqueous electrolyte batteries and the like. It has also been found that whether the high-rate characteristics are improved depends on whether the active material paste used is solvent-based or water-based. If the paste contact angle of the solvent-based active material paste (hereinafter referred to as “solvent-based paste contact angle”) is 15 degrees or more and 50 degrees or less, the high rate is obtained when the active material paste used is solvent-based. When the properties are good and the paste contact angle of the aqueous active material paste (hereinafter referred to as “aqueous paste contact angle”) is 10 degrees or more and 50 degrees or less, the active material paste used is aqueous. It has been found that the high rate characteristics are improved. In addition, based on this finding, when both the solvent-based paste contact angle and the water-based paste contact angle are within the above range, it is excellent regardless of whether the active material paste actually used is solvent-based or water-based. It was found that the high rate characteristics were improved. Conventionally, it has been difficult to form a resin layer that exhibits excellent characteristics regardless of whether the active material paste is solvent-based or water-based. It has become possible to form a resin layer capable of improving the characteristics.

  The present invention is based on two findings. The first finding is that the high rate characteristic is good when the paste contact angle is below a specific upper limit value. The contact angle is one of indexes indicating whether different materials are likely to adhere to each other. The smaller the contact angle, the higher the adhesion between different materials. Therefore, when the contact angle is less than or equal to the above upper limit value, the adhesiveness between the conductive substrate and the resin layer, and between the resin layer and the active material layer is increased, and the high rate characteristic is improved.

  Another finding is that the high rate characteristics are good when the paste contact angle is greater than or equal to a specific lower limit. As described above, the contact angle is one of the indexes indicating whether different materials are likely to adhere to each other. Therefore, the smaller the contact angle, the higher the adhesion between different materials. The inventors initially thought that there was no lower limit to the range of the preferred paste contact angle, and that the smaller the paste contact angle, the better the adhesion between different materials and the higher the high rate characteristics. However, it was surprisingly found that the high rate characteristics deteriorate when the paste contact angle is less than the lower limit. The reason why such a result was obtained is currently under investigation and is not necessarily clear, but if the paste contact angle is too small, the adhesion between the conductive substrate and the resin layer is deteriorated. I guess that.

  By the way, the paste contact angle of the resin layer is not uniquely determined by the material composition of the resin layer, and changes greatly when the method of forming the resin layer changes. When the inventors actually conducted an experiment, even when the resin material has the same composition, the paste contact angle of the resin layer changes greatly by changing the drying temperature, drying time, and drying method. Even if the composition and the drying temperature are known, the paste contact angle changes only by changing the production conditions such as the drying time. Therefore, it was found that it is extremely important to determine the paste contact angle in the present invention.

FIG. 1 is a cross-sectional view illustrating a configuration of a current collector according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a configuration of an electrode structure formed using the current collector of one embodiment of the present invention.

Hereinafter, the current collector of one embodiment of the present invention will be described with reference to FIG.
As shown in FIG. 1, a current collector 1 of the present invention is a current collector 1 having a conductive resin layer (current collector resin layer) 5 on at least one surface of a conductive base material 3. The conductive resin layer 5 includes a chitosan-based resin and a conductive material, and the solvent-based paste contact angle measured by the θ / 2 method in a thermostatic chamber at 23 ° C. on the surface of the resin layer 5 is 15 ° to 50 °, and / or Alternatively, the contact angle of the aqueous model active material paste is 10 degrees or more and 50 degrees or less.
Further, as shown in FIG. 2, by forming an active material layer or an electrode material layer 9 on the resin layer 5 of the current collector 1, it is used for a non-aqueous electrolyte battery, an electric double layer capacitor, or a lithium ion capacitor. As a result, a suitable electrode structure 7 can be formed.
Hereinafter, each component will be described in detail.

(1) Conductive base material As the conductive base material of the present invention, various metal foils for non-aqueous electrolyte batteries, electric double layer capacitors, or lithium ion capacitors can be used. Specifically, aluminum, aluminum alloy, copper, stainless steel, nickel, etc. can be used. Among these, aluminum, an aluminum alloy, and copper are preferable from the balance between high conductivity and cost. When an aluminum foil is used as the positive electrode, the present invention aims at improving high rate characteristics, and therefore, it is preferable to use a pure aluminum system such as JIS A1085 having high conductivity. The thickness of the conductive substrate is not particularly limited, but is preferably 0.5 μm or more and 50 μm or less. If the thickness is less than 0.5 μm, the strength of the foil is insufficient and it may be difficult to form a resin layer or the like. On the other hand, if it exceeds 50 μm, other components, particularly the active material layer or the electrode material layer, must be thinned. Especially, non-aqueous electrolyte batteries, electric double layer capacitors, lithium ion capacitors and other power storage components In such a case, a sufficient capacity may not be obtained.

(2) Conductive resin layer In this invention, the resin layer which added the electrically conductive material on the conductive base material is formed. Although the formation method of a conductive resin layer is not specifically limited, It is preferable to apply | coat the solution, dispersion liquid, paste, etc. of resin on the said conductive base material. As a coating method, a roll coater, a gravure coater, a slit die coater or the like can be used, but is not particularly limited. The conductive resin layer used in the present invention must be a chitosan resin. As a result of investigating the volume resistivity of the resin layer by adding a conductive material to various resins, the inventors have surprisingly found that a sufficiently low resistance can be obtained by using these resins with a defined paste contact angle. Based on knowledge. Note that this difference in resistance is presumed to be because the distribution state in the resin layer differs depending on the resin even if the same conductive material is added, and the resistance is different in combination with the specification of the paste contact angle described later.

<Chitosan resin>
In the present invention, the chitosan resin is a resin containing a chitosan derivative as a resin component. As the chitosan-based resin, one having a chitosan derivative of 100% by mass can be used, but it can also be used in combination with other resin components. When used in combination, at least the chitosan derivative is 50% by mass with respect to the total resin components. % Or more, and particularly preferably 80% by mass or more. The chitosan derivative is, for example, hydroxyalkyl chitosan, and specific examples include hydroxyethyl chitosan, hydroxypropyl chitosan, hydroxybutyl chitosan, glycerylated chitosan, glycerylated chitosan and the like.
The chitosan resin preferably contains an organic acid. Examples of organic acids include pyromellitic acid and terephthalic acid. The addition amount of the organic acid is preferably 20 to 300% by mass and more preferably 50 to 150% by mass with respect to 100% by mass of the chitosan derivative. This is because if the addition amount of the organic acid is too small, the chitosan derivative is not sufficiently cured, and if the addition amount of the organic acid is too large, the flexibility of the resin layer is lowered.
The weight average molecular weight of the chitosan derivative is, for example, 30,000 to 500,000, specifically, for example, 30,000, 40,000, 50,000, 60,000, 80,000, 90,000, 100,000, 150,000, It may be 200,000 or 500,000, and may be within a range between any two of the numerical values exemplified here. The weight average molecular weight means that measured by GPC (gel exclusion chromatograph).

<Conductive material>
The conductive resin layer of the present invention is provided between the conductive base material and the active material layer or the electrode material layer, and serves as a passage for electrons moving between them. Therefore, the resin layer also needs to have electronic conductivity. is there. Since the resin is highly insulating, a conductive material must be blended in order to impart electronic conductivity. As the conductive material used in the present invention, known carbon powder, metal powder, and the like can be used. Among them, carbon powder is preferable. As the carbon powder, acetylene black, ketjen black, furnace black, carbon nanotubes and the like can be used. The added amount of the conductive material is preferably 30 to 100% by weight, and more preferably 50 to 80% by weight with respect to 100% by weight of the resin component of the resin layer. If the amount is less than 30% by mass, the volume resistivity of the resin layer is increased, and if it exceeds 100% by mass, the adhesion to the conductive substrate is lowered. A known method can be used for dispersing the conductive material in the resin component liquid. For example, the conductive material can be dispersed by using a planetary mixer, a ball mill, a homogenizer, or the like.

<Contact angle>
The paste contact angle on the surface of the resin layer of the present invention is such that the solvent-based paste contact angle is 15 degrees or more and 50 degrees or less, and / or the contact angle of the aqueous model active material paste is 10 degrees or more and 50 degrees or less. is necessary. Even if a resin layer is formed simply by adding a conductive material to the resin, sufficient adhesion is obtained at the interface between the conductive base material and the resin layer, the interface between the resin layer and the active material layer, or the interface between the resin layer and the electrode material layer. It may not be obtained. This is because even if it is a chitosan resin, the state of the resin layer changes depending on the type and forming conditions of the resin. In particular, there is a contact angle that indicates wettability of the liquid as a surface property that has a large effect on adhesion, and the contact angle of a model active material paste that models the active material paste that is actually used when forming the active material layer is measured. By doing so, the adhesiveness between the current collector and the active material layer or electrode material layer formed thereon can be evaluated. In this case, it seems that the resin layer and the paste contact angle seem to improve the adhesion as the paste contact angle is small and the discharge rate can be improved, but if the contact angle is too small, the adhesion to the conductive substrate In the present invention, it is necessary to define the paste contact angle. This point will be described later.

In this specification, the paste contact angle means a value obtained by measurement by the θ / 2 method in a constant temperature room at 23 ° C. The paste contact angle can be measured using a contact angle meter. After forming a resin layer on the current collector, several μl of model active material paste is adhered to the surface and the contact angle is measured. Since the surface tension of the model active material paste varies depending on the temperature, the paste contact angle is measured in a thermostatic chamber at 23 ° C.

As a result of forming the resin layer under various conditions and measuring the paste contact angle, it was found that sufficient adhesion to the active material layer and the electrode material layer can be obtained if it is not more than the above upper limit value. In addition, as a result of forming a resin layer having a different paste contact angle and investigating the adhesive relationship between the conductive substrate and the resin layer, the high rate characteristic is obtained when the paste contact angle on the surface of the resin layer is less than the lower limit. I found it inferior. Although the cause is not clear, it is presumed that a subtle difference in adhesion between the conductive substrate and the resin layer is detected. Therefore, the paste contact angle needs to be equal to or greater than the lower limit. Also, experiments have shown that the high-rate characteristics are particularly good when the solvent-based paste contact angle is 19 degrees or more and 42 degrees or less. Therefore, the paste contact angle is particularly preferably 19 degrees or more and 42 degrees or less.

  Thus, the regulation of the paste contact angle of the present invention is not only about the adhesion between the resin and the active material layer or the electrode material layer, but also considering the adhesion between the conductive substrate and the resin layer, As described above, the current collector of the present invention in which the contact angle of paste is defined can give a high rate characteristic satisfactorily when used for a battery or a charged part as an electrode structure.

  In order to obtain the current collector of the present invention, a resin layer can be obtained by a known method on at least one surface of the conductive base material such as the aluminum foil described above, but the paste contact angle described above is obtained. It is necessary to. For example, when a resin layer is formed by coating, the baking temperature and baking time affect the paste contact angle. The baking temperature is preferably 120 to 250 ° C. as the temperature reached by the conductive substrate, and the baking time is preferably 15 to 180 seconds. This is because when the resin layer is formed under such conditions, it contributes to adjusting the paste contact angle on the surface within the above range. However, since the paste contact angle is comprehensively determined by various factors such as the resin composition, the resin concentration in the resin liquid, the baking temperature, the baking time, and the baking method, the baking temperature and baking time are within the above range. Even within the range, the paste contact angle may be less than the lower limit value or may exceed the upper limit value. Conversely, even if the baking temperature and baking time are outside the above ranges, the paste contact angle may be within the above ranges.

  In general, the higher the baking temperature and the longer the baking time, the larger the paste contact angle. Therefore, in order to make the paste contact angle within the above range, first, a resin layer is formed under a certain condition, the paste contact angle is measured in the formed resin layer, and the measured paste contact angle is smaller than the lower limit value. If the baking temperature is increased or the baking time is increased, and the measured paste contact angle is larger than the upper limit, adjustments such as lowering the baking temperature or shortening the baking time are necessary. Therefore, the value of the paste contact angle is not determined only by the resin composition or baking temperature. However, if the above method is used, the paste contact angle can be set to a desired value with only a few trials and errors. It is.

  When the current collector of the present invention is used, even when an active material layer or an electrode material layer is formed and the electrolyte solution is infiltrated, sufficient adhesion is provided at the interface between the resin layer and the active material layer or the resin layer and the electrode material layer. In addition to ensuring, sufficient adhesion can also be secured at the interface with the conductive substrate. Further, even after repeated charge and discharge, no large peeling is observed, and sufficient adhesion and excellent discharge rate characteristics can be obtained.

  The thickness of the resin layer is preferably 0.1 μm or more and 5 μm or less. If the thickness is less than 0.1 μm, a portion that cannot be completely coated is generated, and sufficient battery characteristics may not be obtained. If the thickness exceeds 5 μm, when the battery or power storage component described later is used, the active material layer or the electrode material layer may have to be thinned, so that a sufficient capacity density may not be obtained. In addition, when used in a prismatic battery such as a lithium ion secondary battery, when the electrode structure is wound in combination with a separator, a relatively hard resin layer is cracked at the innermost winding portion with a very small radius of curvature. In some cases, a part peeled off from the active material layer or the like may occur. More preferably, it is 0.3 to 3 μm.

  Although the manufacturing method of the current collector of the present invention is not particularly limited, when the resin layer is formed on the conductive substrate, the conductive substrate is improved so that the adhesion of the surface of the conductive substrate is improved. It is also effective to perform a known pretreatment. In particular, when a metal foil produced by rolling is used, rolling oil or wear powder may remain, and adhesion can be improved by removing it by degreasing or the like. The adhesion can also be improved by a dry activation treatment such as a corona discharge treatment.

Electrode Structure The electrode structure of the present invention can be obtained by forming an active material layer or an electrode material layer on at least one surface of the current collector of the present invention. The electrode structure for an electrical storage component in which the electrode material layer is formed will be described later. First, in the case of an electrode structure in which an active material layer is formed, an electrode structure (battery component) for a non-aqueous electrolyte battery, for example, a lithium ion secondary battery, using the electrode structure, a separator, a non-aqueous electrolyte solution, etc. Can be manufactured). In the electrode structure for a nonaqueous electrolyte battery and the nonaqueous electrolyte battery of the present invention, a member other than the current collector can be a known nonaqueous battery member.
Here, the active material layer formed as an electrode structure in the present invention may be conventionally proposed for non-aqueous electrolyte batteries. For example, the current collector of the present invention using aluminum as the positive electrode, LiCoO ₂ , LiMnO ₂ , LiNiO ₂ or the like as the active material, carbon black such as acetylene black as the conductive material, and PVDF as a binder Alternatively, the positive electrode structure of the present invention can be obtained by applying and drying a paste dispersed in water-dispersed PTFE.
In the case of a negative electrode structure, for example, graphite, graphite, mesocarbon microbeads or the like are used as the active material for the current collector of the present invention using copper as the conductive substrate, and these are thickeners. After dispersion in CMC, the negative electrode structure of the present invention can be obtained by applying and drying a paste mixed with SBR as a binder as an active material layer forming material.

Nonaqueous electrolyte battery The present invention may be a nonaqueous electrolyte battery. In this case, there is no particular limitation other than using the current collector of the present invention. For example, the non-aqueous electrolyte battery of the present invention is sandwiched between separators impregnated with an electrolyte for a non-aqueous electrolyte battery having a non-aqueous electrolyte between the positive electrode structure and the negative electrode structure having the current collector of the present invention as a constituent element. A water electrolyte battery can be constructed. As the nonaqueous electrolyte and the separator, those used for known nonaqueous electrolyte batteries can be used. As the electrolytic solution, carbonates or lactones can be used as a solvent. For example, a solution obtained by dissolving LiPF ₆ or LiBF ₄ as an electrolyte in a mixed solution of EC (ethylene carbonate) and EMC (ethyl methyl carbonate) is used. Can do. As the separator, for example, a film having a microporous made of polyolefin can be used.

Power storage components (electric double layer capacitors, lithium ion capacitors, etc.)
The electric double layer capacitor, lithium ion capacitor, etc. of the present invention can also be applied to power storage components such as electric double layer capacitors and lithium ion capacitors that require high-speed charge / discharge at a large current density. is there. The electrode structure for a power storage component of the present invention is obtained by forming an electrode material layer on the current collector of the present invention. By using this electrode structure and a separator, an electrolytic solution, etc., an electric double layer capacitor, a lithium ion capacitor, etc. A power storage component can be manufactured. In the electrode structure and power storage component of the present invention, members other than the current collector can be members for known electric double layer capacitors or lithium ion capacitors.

  The electrode material layer can be made of an electrode material, a conductive material, and a binder for both the positive electrode and the negative electrode. In the present invention, an electricity storage component can be obtained after forming the electrode material layer on at least one side of the current collector of the present invention to form an electrode structure. Here, as the electrode material, those conventionally used as electrode materials for electric double layer capacitors and lithium ion capacitors can be used. For example, carbon powder or carbon fiber such as activated carbon or graphite can be used. As the conductive material, carbon black such as acetylene black can be used. As the binder, for example, PVDF (polyvinylidene fluoride), SBR (styrene butadiene rubber), water-dispersed PTFE, or the like can be used. In addition, the electric storage component of the present invention can constitute an electric double layer capacitor or a lithium ion capacitor by fixing the electrode structure of the present invention with a separator interposed therebetween and allowing the electrolyte to penetrate into the separator. As the separator, for example, a polyolefin microporous film, an electric double layer capacitor nonwoven fabric, or the like can be used. For example, carbonates and lactones can be used as the solvent in the electrolyte, and the electrolyte includes tetraethylammonium salt and triethylmethylammonium salt as the cation, and hexafluorophosphate and tetrafluoroborate as the anion. Can be used. A lithium ion capacitor is a combination of a negative electrode of a lithium ion battery and a positive electrode of an electric double layer capacitor. These production methods can be carried out according to known methods, except that the current collector of the present invention is used, and are not particularly limited.

  EXAMPLES Hereinafter, although the Example and comparative example of this invention are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.

<1. Evaluation of current collector>
<Preparation of current collector>
The resin and organic acid shown in Table 1 are dissolved in normal methyl 2-pyrrolidone (NMP) in the amount shown in Table 1, acetylene black is mixed in the amount shown in Table 1, and dispersed in a ball mill for 8 hours. did. This paint was applied to one side of an aluminum foil (JIS A1085) having a thickness of 20 μm with a bar coater and baked under the conditions shown in Table 1. The temperatures in Table 1 are all substrate arrival temperatures.

<Measurement of resin layer thickness>
The thickness of the resin layer is calculated using the film thickness measuring instrument Keitaro G (manufactured by Seiko em) from the difference in thickness between the resin layer forming part and the unformed part (aluminum foil only part). did.

<Electric resistance of resin layer>
A cubic copper block with a side of 20 mm was placed on the resin layer (the surface in contact with the resin was mirror-finished), and a load of 700 gf was applied to measure the electrical resistance between the aluminum foil and the copper block.

<Measurement of paste contact angle>
Use a contact angle meter (Dropmaster DM-500, manufactured by Kyowa Interface Science Co., Ltd.) for the solvent or aqueous paste contact angle, and attach 2 μL of solvent or aqueous model active material paste to the resin layer surface in a constant temperature room at 23 ° C. The contact angle after 2 seconds was measured by the θ / 2 method.

<2. Lithium-ion battery discharge rate characteristics evaluation, electrode life evaluation>
As shown below, discharge rate characteristic evaluation and electrode life evaluation of a lithium ion battery formed by forming an active material layer using a solvent-based active material paste were measured.

<Method for producing lithium ion battery>
As the positive electrode, a paste obtained by dispersing a paste in which PVD (polyvinylidene fluoride) as a binder was dispersed in an active material of LiCoO ₂ and a conductive material of acetylene black at a thickness of 70 μm was used. For the negative electrode, an active material graphite dispersed in CMC (carboxymethylcellulose) and then a paste mixed with a binder SBR (styrene butadiene rubber) was applied to a 20 μm thick copper foil at a thickness of 70 μm. It was. A coin battery was manufactured by sandwiching a polypropylene microporous separator between these electrode structures in a battery case. As the electrolytic solution, an electrolytic solution obtained by adding 1M LiPF ₆ to a mixed solution of EC (ethylene carbonate) and EMC (ethyl methyl carbonate) was used.

<Discharge rate characteristics evaluation method>
The discharge capacities of these lithium ion batteries (0,0,5, 10 and 20 C) at a charge upper limit voltage of 4.2 V, a charge current of 0.2 C, a discharge end voltage of 2.8 V and a temperature of 25 ° C. 2C standard, unit%). (1C is the current value (A) when the current capacity (Ah) of the battery is taken out in one hour (h). At 20C, the current capacity of the battery can be taken out in 1 / 20h = 3 min. can do.)

<Evaluation method of electrode life>
After charging at an electrolyte temperature of 40 ° C. with an upper limit voltage of 4.2 V and a charging current of 20 C, the battery was discharged at an end voltage of 2.8 V and a discharging current of 20 C, and the discharge capacity was 60 with respect to the discharge capacity of the first cycle. The number of times of less than% (up to 500 times) was measured and evaluated according to the following criteria.
A: 500 times or more B: 450 times or more and less than 500 times C: 400 times or more and less than 450 times D: Less than 400 times

<3. Evaluation of discharge rate characteristics and electrode life of electric double layer capacitors>
As shown below, discharge rate characteristic evaluation and electrode life evaluation of an electric double layer capacitor formed by forming an active material layer using a solvent-based electrode material paste were measured.

<Method of manufacturing electric double layer capacitor>
A paste obtained by dispersing activated carbon as an electrode material and ketjen black as a conductive material in PVDF as a binder was applied to the current collector electrode at a thickness of 80 μm to form the same electrode structure for both the positive electrode and the negative electrode. The two electrode structures were fixed with an electric double layer capacitor non-woven fabric impregnated with an electrolytic solution therebetween, thereby constituting an electric double layer capacitor. The electrolytic solution used was propylene carbonate, which is a solvent, with 1.5 M TEMA (triethylmethylammonium) and tetrafluoroboric acid added.

<Discharge rate characteristics evaluation method>
Under the conditions of an upper limit charging voltage of 2.8 V, a charging current of 1 C, a charging end condition of 2 h, a discharge end voltage of 0 V, a temperature of 25 ° C., a discharge current rate of 100 C, 300 C, and 500 C, the discharge capacity of these electric double layer capacitors (1 C reference, Unit%) was measured.

<Evaluation method of electrode life>
After charging at an electrolyte temperature of 40 ° C. with an upper limit voltage of 2.8 V and a charging current of 500 C, the discharging current is discharged to 500 V with a discharging current of 500 C and the discharging capacity is 80% of the discharging capacity of the first cycle. The number of times of being less than (maximum 5000 times) was measured and evaluated according to the following criteria.
A: 5000 times or more B: 4500 times or more and less than 5000 times C: 4000 times or more and less than 4500 times D: Less than 4000 times

  The evaluation results are shown in Table 1. According to Table 1, in all examples in which the resin of the resin layer is a chitosan derivative (hydroxyalkylchitosan) and the solvent-based paste contact angle on the surface of the resin layer is 15 degrees to 50 degrees, a solvent-based paste is used. Both the lithium ion battery and the electric double layer capacitor produced in this way showed excellent high-rate characteristics and battery life. On the other hand, in Comparative Example 1 where the solvent-based paste contact angle is too small and Comparative Example 2 which is too large, the high rate characteristics were not good. Further, even in Comparative Example 3 using ethyl cellulose as the resin of the resin layer, the high rate characteristics were not good.

  In addition, referring to Examples 1 to 5, it can be seen that particularly excellent high rate characteristics were exhibited when the paste contact angle was 19 degrees or more and 42 degrees or less. Furthermore, referring to Examples 6 to 9, it can be seen that when the content of the conductive material was 50 to 80 parts by mass with respect to 100 parts by mass of the resin, particularly excellent high rate characteristics were exhibited.

  Further, according to the results in Table 1, even when the contact angle of the aqueous model active material paste is 10 degrees or more and 50 degrees or less, in the lithium ion battery or electric double layer capacitor produced using the solvent-based paste, the discharge rate The characteristics may not be good. However, according to the results of preliminary experiments by the present inventors, when the contact angle of the aqueous model active material paste is 10 degrees or more and 50 degrees or less, a lithium ion battery or an electric double layer capacitor manufactured using the aqueous paste Especially good results have been obtained. In addition, when both the solvent-based paste contact angle and the water-based model active material paste contact angle are within the above ranges, even if the paste used for producing the lithium ion battery or the electric double layer capacitor is a solvent-based paste, Even so, good results were obtained.

1: Current collector
3: Conductive substrate 5: Resin layer (resin layer for current collector)
7: Electrode structure 9: Active material layer or electrode material layer

Claims (4)

  A current collector for an aqueous active material paste having an electrically conductive resin layer on at least one surface of an electrically conductive substrate for using an aqueous active material paste as an active material paste, wherein the resin layer is electrically conductive with a chitosan resin. The contact angle of the water-based model active material paste measured by the θ / 2 method in a constant temperature room at 23 ° C. on the surface of the resin layer is 10 degrees or more and 50 degrees or less. Electric body.   A current collector for an aqueous active material paste having an electrically conductive resin layer on at least one surface of an electrically conductive substrate for using an aqueous active material paste as an active material paste, wherein the resin layer is electrically conductive with a chitosan resin. The contact angle of the solvent-based model active material paste is 15 degrees or more and 50 degrees or less, and the contact angle of the water-based model active material paste is 15 degrees or less and 50 degrees or less as measured by the θ / 2 method in a constant temperature room of 23 ° C. on the surface of the resin layer. A current collector for an aqueous active material paste, wherein the current collector is at least 10 degrees and at most 50 degrees. An electrode structure comprising an active material layer or an electrode material layer on the resin layer of the current collector according to claim 1. A nonaqueous electrolyte battery or a power storage component comprising the electrode structure according to claim 3.