JP2002042874A - Polymer secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the load characteristic and cycle characteristic of a polymer secondary battery. SOLUTION: This polymer secondary battery is provided with a negative electrode layer having at least a carbon material as an active material: a positive electrode layer having a chalcogen material containing at least lithium, as an active material: and a polymer solid electrolyte layer interposed between the positive and negative electrode layers. At least one of the positive electrode layer and negative electrode layer includes the same solid electrolyte as or a different solid electrolyte from a solid electrolyte included in the polymer solid electrolyte layer. The solid electrolyte is constituted by previously impregnating its precursor as a solution in the positive electrode layer or negative electrode layer and cross-linking after placing the polymer solid electrolyte layer on the positive electrode layer or negative electrode layer. Resistance inside the battery can thereby be reduced to provide the polymer secondary battery with excellent high load characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer secondary battery, and more particularly, to a polymer secondary battery using an ion conductive compound (solid electrolyte) that operates reversibly at ambient temperature. And a negative electrode using a carbon material having amorphous carbon attached to the surface thereof as an active material.

[0002]

2. Description of the Related Art As an electrolyte of a nonaqueous electrolyte battery such as a lithium primary battery or a lithium secondary battery currently on the market, an organic electrolyte obtained by dissolving an electrolyte salt in an organic solvent is generally used. However, this organic electrolyte is liable to leak out of components, elute and volatilize the electrolyte, and has problems such as long-term reliability, and the scattering of electrolyte during the sealing process. Was a problem.

[0003] In recent years, instead of using metallic lithium or its alloy for the negative electrode, matrix materials such as carbon materials and conductive polymers utilizing the occlusion-release process of lithium ions have been developed. As a result, the generation of dendrite, which occurs when metal lithium or its alloy is used, does not occur in principle, and the problem of a short circuit inside the battery has been drastically reduced. In particular, it is known that a carbon material has a lithium absorption-release potential closer to lithium extraction-dissolution potential than other materials. Above all, a graphite material is a carbon material having a high capacity per unit weight and unit volume because lithium can be theoretically taken into the crystal lattice at a ratio of one lithium atom to six carbon atoms. Further, the potential for lithium insertion and removal is flat, chemically stable, and greatly contributes to the cycle stability of the battery.

[0004] For example, in J. Electrochem. So
c. , Vol. 137, 2009 (1990), JP-A-4-115457, JP-A-4-115458, JP-A-4-237791, and the like, wherein a graphite-based carbon material is used as a negative electrode active material. 4-
JP-A-368778, JP-A-5-28996, JP-A-5-114421 and the like use a surface-treated graphite-based carbon material as a negative electrode active material.

[0005] A graphite-based carbon material can have a discharge capacity close to the theoretical capacity by using an organic electrolyte mainly composed of ethylene carbonate (EC). In addition, since the charge / discharge potential is slightly higher than the potential of lithium dissolution-extrusion and extremely flat, when a battery is manufactured using a graphite-based carbon material as a negative electrode active material, a high capacity and A secondary battery having high flatness of battery voltage can be realized, and high capacity of the battery can be achieved.

However, graphite-based carbon materials have a problem that they cause decomposition of the organic electrolyte because of their high crystallinity. For example, propylene carbonate (PC), which is a solvent for an organic electrolyte, has a wide potential window, a low freezing point (−70 ° C.), or a high chemical stability. Widely used.

However, when a graphite-based carbon material is used as the negative electrode active material, the decomposition reaction of PC occurs remarkably, and
% Of PC cannot be charged / discharged in a negative electrode made of a graphite-based carbon material only in the electrolyte. Ele
trochm. Soc. , Vol. 142,1746
(1995).

In recent years, there have been reports on organic electrolytes in which EC is mixed with various low-viscosity solvents in order to improve ionic conductivity at low temperatures. However, there remains a problem of its volatility and a problem of liquid leakage.

In recent years, ion conductive polymers having high ionic conductivity have been reported for the purpose of improving liquid leakage resistance, high safety, and long-term storage properties. One of the means for solving the above problems is as follows. Various studies are underway. As one of the ion conductive polymers currently being studied, a homopolymer or copolymer linear polymer, a crosslinked polymer or a comb polymer having ethylene oxide as a basic unit has been proposed, and is being practically used. is there. Batteries using the above-described ion-conductive polymer are widely described in patent documents and the like. For example, U.S. Pat. No. 4,3030 to Armand et al.
No. 3,748 (1981); U.S. Pat. No. 4,589,197 to North (1986); and U.S. Pat. No. 4,547,44 to Hooper et al.
No. 0 (1985). One of these features is that an ion conductive polymer obtained by dissolving an electrolyte salt in a polymer material having a polyether structure is used. These proposed ion-conductive polymers have been studied and developed as electrolytes for large lithium secondary batteries to be used as electric vehicle power supplies, but the above-mentioned ion-conductive polymers have low ionic conductivity at room temperature or lower. Therefore, it is difficult to achieve a small size, light weight, and high energy density required for a battery for a driving power supply or a memory backup power supply of a portable electronic device.

On the other hand, as a method for further improving the ion conductivity as compared with the above-mentioned ion conductive polymer, for example, JP-A-59-149601 and JP-A-58-7577.
No. 9 and US Pat. No. 4,792,504, etc., an organic solvent (particularly preferably a high dielectric constant organic solvent such as EC or PC) in an ion conductive polymer.
Is also proposed to maintain the solid state. However, when using these proposed methods, the ionic conductivity is definitely improved, but the film strength is significantly reduced. That is, even in the case of using the above-described method, when the ion-conductive polymer thin film is actually laminated between the electrodes and a battery or an electrochromic element is assembled, the electrolyte layer is damaged by compressive deformation,
There was a possibility of causing a slight short circuit.

In a secondary battery, the electrolyte layer also receives a force of compression / relaxation against volume expansion / contraction of the electrode active material during charging or discharging. Therefore, in order to improve the performance of the ion-conductive polymer, it is necessary to consider not only the improvement in the ion conductivity but also the improvement in the mechanical properties.

[0012] In order to solve the above-mentioned problems, an attempt has been made to increase both the ionic conductivity and the mechanical strength of the electrolyte layer, but they have not been sufficiently satisfactory yet. It is very difficult to obtain a solid electrolyte that satisfies all of the handling of the solid electrolyte layer in consideration of the improvement of the mechanical properties and the productivity.

[0013]

Means for Solving the Problems As a result of intensive studies in view of the above problems, the present inventors have found that the negative electrode active material has
By using a carbon material, especially by using graphite particles with amorphous carbon attached to the surface, the decomposition of the ion conductive compound contained in the ion conductor is suppressed, and the mechanical properties of the electrolyte layer during the charge / discharge cycle are further reduced. It has been found that the reduction in strength can be improved, and the performance of a battery using the ion conductive compound can be improved.

That is, the present invention provides a negative electrode layer containing at least a carbon material as an active material, a positive electrode layer containing at least a lithium-containing chalcogenide as an active material, and a polymer solid electrolyte layer interposed between the positive and negative electrode layers. A polymer secondary battery comprising: at least one of the positive electrode layer or the negative electrode layer contains a solid electrolyte that is the same as or different from the solid electrolyte contained in the polymer solid electrolyte layer, and the solid electrolyte forms a precursor for the positive electrode layer. Alternatively, there is provided a polymer secondary battery characterized in that it is impregnated as a solution in the negative electrode layer in advance, and the polymer solid electrolyte layer is placed on the positive electrode layer or the negative electrode layer and then crosslinked. It is.

Further, the present invention is characterized in that the solid electrolyte crosslinked inside the electrode and the solid electrolyte constituting the polymer solid electrolyte layer interposed between the positive and negative electrodes are different.

With the above configuration, a polymer secondary battery which is extremely excellent in the following points as compared with a conventional battery, particularly a polymer secondary battery suitable as a small and lightweight battery is provided.

1) At least one of the electrodes is formed by mounting the polymer solid electrolyte layer on the electrode and then cross-linking a solid electrolyte precursor which has been impregnated in the electrode in advance, thereby forming an electrode structure inside the electrode. Resistance at the interface between the anode and the solid electrolyte, and at least one of the two contact interfaces existing between the positive electrode / polymer solid electrolyte layer / negative electrode can be reduced. Deterioration can be suppressed.

2) To have high performance and high energy density. In particular, in the present invention, by reducing the contact resistance at the electrode / solid electrolyte interface and improving the mechanical properties of the polymer solid electrolyte layer, the thickness of the polymer solid electrolyte layer can be reduced, thereby reducing the internal resistance of the battery. And the filling rate of the electrode active material can be reduced, and the above object can be achieved.

3) Have very high workability. In particular, the present invention is to reduce the number of steps of a positive electrode / polymer solid electrolyte layer / negative electrode bonding step by cross-linking the polymer solid electrolyte layer with a solid electrolyte precursor and an electrolyte solution previously contained inside the electrode. Thereby, the above object can be achieved.

4) The solid electrolyte cross-linked inside the electrode is
The characteristics required for the solid electrolyte in the electrode (such as adhesion to the active material) and the polymer solid electrolyte layer interposed between the positive and negative electrodes are different from those constituting the solid polymer electrolyte layer interposed between the positive and negative electrodes. Properties (mechanical strength,
When a film is covered during film formation, the peelability from the film can be considered separately, and a polymer secondary battery with high reliability and excellent productivity can be manufactured.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, since the negative electrode active material is a carbon material utilizing the process of inserting and extracting lithium ions, there is no precipitation of dendritic lithium during charging, and the short circuit of the battery is greatly reduced. , Safety is improved. As the carbon material, well-known materials that have been conventionally used can be used, for example, natural graphite, petroleum coke, cresol resin fired carbon, furan resin fired carbon, polyacrylonitrile fired carbon, vapor-grown carbon, mesophase pitch fired Examples of the material include carbon and a graphite material having an amorphous carbon layer formed on the surface of graphite having high crystallinity. Among these carbon materials, graphite materials having improved crystallinity are preferable because the voltage of the battery is flat and the energy density is large. Further, among the graphite materials, in particular, since the negative electrode active material is graphite particles having amorphous carbon adhered to the surface, it is possible to prevent the decomposition of the polymer solid electrolyte layer made of the ion conductive compound. The liquid disappears and the long-term reliability is improved.

Here, the graphite particles having amorphous carbon adhered to the surface thereof are made of a particulate carbon material (hereinafter referred to as “core carbon material” to “core carbon material”) or simply “core material”.
Is sometimes immersed in a raw material for a carbon material for forming a coating (for example, a coal-based heavy oil such as tar or pitch or a petroleum-based heavy oil; hereinafter, also simply referred to as “heavy oil or the like”), It has been found that, when this is separated from heavy oil or the like, when a specific means is adopted, a carbon material having a core material surface uniformly covered with a pitch can be produced. And the carbon material particles of the two-layer structure obtained in this way are:
It has been found that the carbon crystal has a spherical or ellipsoidal shape or a shape similar thereto, and that the edge portion of the carbon crystal has a round shape. Further, as a result of the measurement by the BET method, the value of the specific surface area of the particles is smaller than that of the core carbon material before the treatment, and the pores related to the specific surface area by the BET method are blocked in some manner. It became clear that it was.

According to the present invention, the carbon material derived from heavy oil or the like adheres to part or all of the edge and base surface of the carbon material serving as the core material, or part or all of the edge and base surface. Is coated with the carbon material, and has a substantially spherical or ellipsoidal shape. In this carbon material, pores related to the specific surface area measured by the BET method are closed by the adhesion or coating of carbon derived from heavy oil or the like, and the specific surface area is 5 m ² / g or less (preferably). Is about 1 to 5 m ² / g). If the specific surface area is more than 5 m ² / g, the contact area with the electrolyte becomes large, and a side reaction with the ion-conductive compound tends to occur, which is not preferable.

In the present invention, as a carbon material serving as a core material, an average spacing (d ₀₀₂ ) of (002) planes by X-ray wide-angle diffraction method is 0.335 to 0.340 nm, and (00)
2) The crystallite thickness (Lc) in the plane direction is 10 nm or more (more preferably, 40 nm or more), and the crystallite thickness (La) in the (110) plane direction is 10 nm or more (more preferably, 50 nm).
nm or more) is used.
If (d ₀₀₂ ) is larger than 0.340 nm and (Lc) and (La) are 10 nm or less, the crystallinity of the carbon material is low and the discharge capacity is low, which is not preferable.

In the carbon material according to the present invention, as compared with the crystallinity of the core material, the carbon material adheres to the core material surface or covers the core material surface. ) Is characterized by low crystallinity.

The true specific gravity of the carbon material according to the present invention is
The value is 1.50 to 2.26 g / cm ^ThreeRange. true
Specific gravity is 1.50 g / cm^ThreeIf lower, the negative electrode active material in the battery
Low filling rate and low energy density of the battery
Not good. The true specific gravity is 2.26 g / cm^ThreeHigher
It becomes a graphite single crystal and has poor moldability as a battery material.

As the solid electrolyte contained in the positive electrode layer or the negative electrode layer, any known compounds referred to in the art as ion-conductive compounds can be used. Examples of the polymer solid electrolyte include a substance composed of an electrolyte and a polymer that dissociates the electrolyte, a substance having an ionic dissociating group in the polymer, and the like. Examples of the polymer that dissociates the electrolyte include a polyethylene oxide derivative or a polymer containing the derivative, a polypropylene oxide derivative, a polymer containing the derivative, and a phosphate ester polymer. The gel solid electrolyte using the polymer and the organic solvent as described above is very promising because it has the characteristics of a solid electrolyte free from liquid leakage and the ionic conductivity close to that of a liquid.

The organic compound serving as the skeleton of the gel electrolyte is not particularly limited as long as it has affinity with the solvent of the electrolyte and has a polymerizable functional group. For example, those having a polyether structure and an unsaturated double bond group, oligoester acrylates, polyesters, polyimines, polythioethers, polysulfans, etc., alone or in combination of two or more may be mentioned. Incidentally, those having a polyether structure and an unsaturated double bond group are preferred from the viewpoint of affinity with a solvent. Examples of the polyether structural unit include ethylene oxide, propylene oxide, butylene oxide, glycidyl ethers and the like, and a single or a combination of two or more thereof is suitably used. In the case of a combination of two or more, the form can be appropriately selected irrespective of block or random. Furthermore, examples of the unsaturated double bond group include allyl, methallyl, acroyl, and metalloyl groups.

Examples of the organic solvent used for the gel electrolyte include propylene carbonate (PC), cyclic carbonates such as ethylene carbonate (EC) and butylene carbonate, and dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dipropyl carbonate and the like. Chain carbonates, γ-butyrolactone, γ
Lactones such as valerolactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, ethers such as dioxane, dimethyl sulfoxide, sulfolane, methyl sulfolane, acetonitrile, methyl formate, methyl acetate, etc. And these can be used.

As an electrolyte salt, lithium perchlorate (Li
ClO _4), lithium borofluoride (LiBF _4), Rinfu' lithium (LiPF _{6), 6} fluoride arsenate lithium (LiAsF _{6), 6} lithium fluoride antimonate (L
iSbF ₆ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), lithium trifluoroacetate (Li
Lithium salts such as CF ₃ COO), lithium halide, lithium chloride aluminate (LiAiCl ₄ ), and lithium imide imide trifluoromethanesulfonate (LiN (CF ₃ SO ₂ ) ₂ ). Can be used.

The gel electrolyte is obtained by adjusting the electrolyte by dissolving the electrolyte salt in the solvent selected above, mixing with the organic compound, and polymerizing.

In particular, PC, GB
L, EMC, DMC or DEC is a gel containing an organic electrolyte solution in which a Li salt is dissolved in a mixed organic solvent obtained by mixing one or more solvents selected from the group consisting of graphite and amorphous carbon. It is preferable because decomposition at a negative electrode using a carbon material as an active material is small.

Here, the weight ratio of the ion conductive compound to the organic electrolyte is preferably in the range of 30:70 to 2:98. If the weight ratio of the ion conductive compound is higher than 30, the ion conductivity is not sufficient, and if the weight ratio of the ion conductive compound is lower than 2, sufficient mechanical strength cannot be obtained. Further, the EC component in the organic electrolytic solution is 2 to 5
It is preferable that the content is 5% by weight and the Li salt content is 3 to 35% by weight, since the ionic conductivity is sufficiently satisfactory. Further, when the EC component is 2 to 35% by weight, a decrease in ionic conductivity at a low temperature can be reduced.

In the present invention, the low-boiling solvent means a solvent having a boiling point of less than 100 ° C., and among the above-mentioned electrolytes, for example, a chain ester such as methyl propionate and ethyl propionate; (DEC),
Chain carbonates such as dimethyl carbonate (DMC) and methyl ethyl carbonate (EMC); tetrahydrofuran or derivatives thereof. A low-viscosity solvent can lower the viscosity of the entire electrolyte, improve ionic conductivity, and improve characteristics at low temperatures, but because of its high volatility, a method of bonding electrodes must be used. When it is taken, the low boiling point solvent on the surface volatilizes,
The interface resistance at the bonding interface may increase. However, by adopting the configuration of the present invention, a layer containing no low-boiling solvent can be placed on the outermost surface, so that a solid electrolyte mixed with a low-boiling solvent is used as an electrolyte inside the electrode. This makes it possible to sufficiently bring out its characteristics.

The solid electrolyte constituting the polymer solid electrolyte layer is not particularly limited, and any solid electrolyte known in the art can be used. Specifically, any of the same cross-linked solid electrolytes as those contained in the electrodes can be used. Further, it may contain the Li salt and the organic solvent exemplified above.

When the solid electrolyte contained in the polymer solid electrolyte layer is different from the solid electrolyte contained in the electrode, physical properties of the solid electrolyte include adhesive strength to a certain material. In the battery system according to the present invention, the volume of the active material changes with charge and discharge. Thus, the solid electrolyte in contact with the active material (ie, the solid electrolyte contained in the electrode)
By using a material having a strong adhesive strength to the active material, it is possible to follow a volume change and obtain long-term reliability.

On the other hand, in the production process, when the solid electrolyte for the polymer solid electrolyte layer is cured, when a releasable film or the like is used on the surface, if the adhesive strength with the film is high, it is difficult to remove the solid electrolyte. This can cause problems and significantly reduce productivity. In the present invention, by adopting a solid electrolyte that satisfies the relationship of “the adhesive strength of the solid electrolyte inside the electrode> the adhesive strength of the solid electrolyte used for the polymer solid electrolyte layer interposed between the positive electrode and the negative electrode” for a certain substance. , And a battery with high long-term reliability can be obtained.

That is, the solid electrolyte in the electrode has a strong adhesiveness to the active material and follows the volume change due to charge and discharge.
The solid electrolyte used for the polymer solid electrolyte layer interposed between the positive and negative electrodes, by using a material with low adhesive strength,
Productivity can be increased by improving the releasability of a film or the like over the surface. Here, a certain substance means a polyethylene film or the like for convenience.

The polymer solid electrolyte layer may contain a fibrous (woven or non-woven) organic compound. When this compound is at least one of a polypropylene fiber, a polyethylene fiber and a polyester fiber, the stability to an organic solvent is increased. These fibrous organic compounds are nonwoven fabrics having physical properties of air permeability of 1 to 500 sec / cm ³ . If the air permeability is lower than 1 sec / cm ³ , sufficient ionic conductivity cannot be obtained, and 500 sec / cm ³
If it is higher than cm ³ , the mechanical strength is not sufficient and a short circuit of the battery is easily caused, which is not preferable. Further, the weight ratio of the ion conductive compound and the fibrous organic compound constituting the electrolyte layer is suitably in the range of 91: 9 to 50:50. If the weight ratio of the ion conductive compound is higher than 91, sufficient mechanical strength cannot be obtained, and if it is lower than 50, sufficient ion conductivity cannot be obtained, which is not preferable.

As a method for crosslinking the solid electrolyte precursor in the polymer solid electrolyte layer and the electrode, a method using light energy such as ultraviolet rays, an electron beam, and visible light, and a method using heating can be used. It is also important to use a polymerization initiator if necessary. In particular, in a crosslinking method using ultraviolet light or heating, it is preferable to add a few percent or less of a polymerization initiator. As the polymerization initiator, commercially available products such as 2,2-dimethoxy-2-phenylacetophenone (DMPA) and benzoyl peroxide (BPO) can be used. The wavelength of the ultraviolet light is suitably from 250 to 360 nm.

After the polymer solid electrolyte layer is formed by the above-mentioned method, the polymer solid electrolyte layer is placed on the positive electrode layer and / or the negative electrode layer containing a solid electrolyte precursor and, if necessary, an electrolytic solution inside the electrode. It is preferable to crosslink. In this way,
Even if a low-viscosity solvent having high ionic conductivity is contained in the electrode, the polymer solid electrolyte layer will cover the electrode from above, so that volatilization of the low-viscosity solvent can be suppressed. Therefore, it is possible to manufacture a polymer secondary battery in which the resistance inside the electrode is reduced and which has excellent characteristics even under a high load. Also, even if the polymer concentration inside the electrode is lower than that of the polymer solid electrolyte layer, no liquid leakage occurs, and a polymer secondary battery with low internal resistance can be manufactured.

The positive electrode active material is preferable because the chalcogenide containing lithium has a lithium source for the lithium insertion reaction into the carbon negative electrode required for the first charge. In particular, since a metal oxide containing lithium has a high charge / discharge potential, a battery with high energy density can be formed. For example, LiCoO ₂ , LiNiO ₂ ,
LiMnO ₂ , LiMn ₂ O ₄ or LiCo _x Ni _1-x
O ₂ (0 <x <1), but is not limited thereto.

When producing the above-mentioned positive electrode layer and negative electrode layer,
For the purpose of obtaining a uniform mixed-dispersed coating solution (paste) and for the purpose of improving various characteristics (such as discharge characteristics and charge / discharge cycle characteristics) of the positive electrode layer and the negative electrode layer, a binder or a conductive material is appropriately added. be able to.

When a binder is used, an electrode active material and, in some cases, the above-mentioned ion-conductive compound are dispersed in a binder solution in which a thermoplastic resin and an elastic polymer are dissolved in a solvent. A method of using the composition as a coating liquid is exemplified.

Examples of the binder include the following. That is, acrylonitrile, methacrylonitrile, vinylidene fluoride, vinyl fluoride, chloroprene, vinylpyrrolidone, vinylpyridine, styrene and its derivatives, vinylidene chloride, ethylene, propylene, dienes (for example, cyclopentadiene, 1,
Examples thereof include polymers of compounds such as 3-cyclohexadiene and butadiene) and copolymers of the above compounds. Specific examples include polyacrylonitrile, polyvinylidene fluoride, polyvinylpyrrolidone, polyethylene,
Examples include polypropylene, ethylene-propylene-diene-polymer (EPDM), sulfonated EPDM, and styrene-butadiene rubber.

The conductive material does not inhibit the battery reaction of each electrode,
An electron conductive material that does not cause a chemical reaction is desirable. Generally, conductive materials such as artificial graphite, natural graphite (such as flaky graphite and flaky graphite), carbon black, acetylene black, ketjen black, carbon fiber, metal powder, and conductive metal oxide are used for the positive electrode and the negative electrode. It can be mixed in a mixture for formation to improve electron conductivity.

The amount of the binder added is not particularly limited, but the amount of the binder in the electrode is preferably in the range of 1 to 25% by weight. The amount of the conductive material is not particularly limited, but the amount of the conductive material in the electrode is preferably in the range of 2 to 15% by weight.

The method for forming the positive electrode layer and the negative electrode layer on the positive electrode current collector and the negative electrode current collector includes, for example, means such as roll coating using an applicator roll, a doctor blade method, spin coating, and a bar coder. It is desirable to apply a uniform thickness using
It is not limited to these. In addition, when these means are used, it is possible to increase the actual surface area of the electrode active material in contact with the electrolyte layer and the current collector. As a result, they can be arranged in a thickness and shape according to the application.

Materials such as aluminum, stainless steel, titanium, and copper are preferable for the positive electrode current collector plate, and materials such as stainless steel, iron, nickel, and copper are preferable for the negative electrode current collector plate. Not something. Also,
Examples of the form include, but are not limited to, foil, mesh, expanded metal, lath, porous body, and resin film coated with an electron conductive material.

The shape of the battery includes a cylindrical type, a coin type, a film type, a card type and the like, but is not limited thereto. Further, as the exterior material, metal, Al laminate resin, and the like can be given.

[0051]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto.

When the precursor of the ion-conductive compound used in all of the following Examples and Comparative Examples is crosslinked with ultraviolet light having a wavelength of 365 nm, the initiator DMPA is added to the precursor at 0.1.
1% by weight was used.

FIGS. 1 and 2 are schematic structural explanatory views of a battery manufactured according to the present invention.

First, in FIG. 1 and FIG. 2, the polymer secondary battery 8 mainly comprises a positive electrode 5, an electrolyte layer 6, a negative electrode 7, and these package members 4. 1 is the negative electrode 7
Reference numeral 2 denotes a terminal of the positive electrode 5, and 3 denotes a sealing portion of the exterior material 4. FIG. 3 is a schematic enlarged view of a cross section of the electrode and the solid polymer electrolyte layer. In the figure, 9 is a polymer solid electrolyte layer, 10 is a solid electrolyte in an electrode, 11 is an active material, and 12 is a current collector.

(Example 1) (d) Wide-angle X-ray diffraction method
₀₀₂ ) = 0.336 nm, (Lc) = 100 nm, (L
a) = 97 nm, BET specific surface area of 2 m ² /
g, powder of surface amorphous graphite having an average particle size of 10 μm,
A paste obtained by mixing 9 wt% of polyvinylidene fluoride (PVDF) as a binder, adding N-methyl-2-pyrrolidone (NMP) and mixing and dissolving is coated on a rolled copper foil having a thickness of 20 μm, and dried. After pressing and pressing, a negative electrode was obtained. The electrode area was 9 cm ² and the thickness was 85 μm.

7% by weight of PVDF as a binder and 5% by weight of acetylene black having an average particle size of 2 μm as a binder were mixed with LiCoO ₂ powder having an average particle size of 7 μm.
The paste obtained by mixing and dissolving MP is 20 μm thick.
, And dried and pressed to obtain a positive electrode. The area of the positive electrode is 9 cm ² and the thickness is 80 μm.
m.

As a support for the solid polymer electrolyte layer, a nonwoven fabric made of polyester, having an air permeability of 380 sec / cm ³ ,
LiBF ₄ was used as a solid electrolyte precursor in an area of 10 cm ² and a thickness of 20 μm, in which 1: 1 ethylene carbonate (hereinafter referred to as EC) and diethyl carbonate (hereinafter referred to as DEC) were used.
In 50 g of an electrolytic solution dissolved in a solvent (volume ratio) to 13% by weight, polyethylene oxide / polypropylene oxide copolymer diacrylate (average molecular weight: 500
0) 10 g was dissolved, and the precursor was left under reduced pressure for 15 minutes to penetrate into the nonwoven fabric. And 38mW /
Ultraviolet rays were irradiated for 2 minutes at an intensity of cm ² . At this time, the weight ratio between the solid electrolyte and the fibrous organic compound was 90:10.

For the positive electrode layer, first, LiBF ₄ was added to PC
And an EMC solution prepared by dissolving 13% by weight in a mixed solvent of EMC (PC content: 35% by weight), the electrolyte solution, and polyethylene oxide / polypropylene oxide copolymer diacrylate (average molecular weight: 5000) An equal weight mixture of polyethylene oxide / polypropylene oxide copolymer acrylate (average molecular weight 500) was prepared so as to have a weight ratio of 95: 5. Thereafter, the positive electrode was allowed to stand under reduced pressure for 5 minutes, and a mixed solution of an electrolyte solution and a precursor mixture was poured therein, and the mixture was allowed to stand for another 15 minutes.

Then, a polymer solid electrolyte layer was placed on the positive electrode, and irradiated with ultraviolet rays at an intensity of 38 mW / cm ² for 2 minutes to obtain a positive electrode layer. At that time, the total thickness of the positive electrode layer and the solid polymer electrolyte layer was 100 μm.

As for the negative electrode layer, first, LiBF ₄ was subjected to EC
And a GBL mixed solvent (EC content 35% by weight) was dissolved to prepare 13% by weight of an electrolytic solution, and the electrolytic solution and a polyethylene oxide / polypropylene oxide copolymer diacrylate (average molecular weight 5000) were prepared. It was prepared so as to have a weight ratio of 90:10. Thereafter, the negative electrode was allowed to stand under reduced pressure for 5 minutes, and a mixed solution of an electrolytic solution and a precursor was poured into the negative electrode, and further allowed to stand for 15 minutes.

Then, 38 mW / cm from the top of the negative electrode
^A negative electrode layer was obtained by irradiating ultraviolet rays at an intensity of 2 for 2 minutes. At that time, the thickness of the negative electrode layer was 85 μm.

The thus obtained composite of the positive electrode layer and the solid polymer electrolyte layer was bonded to the negative electrode layer to produce a battery using the solid polymer electrolyte.

Comparative Example 1 The same positive electrode, negative electrode and polymer solid electrolyte layer as those used in Example 1 were used.

For the positive electrode layer, first, LiBF ₄ was added to PC
An electrolyte solution was prepared by dissolving the solution in an amount of 13% by weight in water, and the electrolyte solution was mixed with a polyethylene oxide / polypropylene oxide copolymer diacrylate (average molecular weight: 500
0) and an equal weight mixture of a polyethylene oxide / polypropylene oxide copolymer acrylate (average molecular weight 500) were prepared in a weight ratio of 90:10. Thereafter, the positive electrode was allowed to stand under reduced pressure for 5 minutes, and a mixed solution of an electrolyte solution and a precursor mixture was poured therein, and the mixture was allowed to stand for another 15 minutes.

Then, 38 mW / cm from the top of the positive electrode
^A positive electrode layer was obtained by irradiating ultraviolet rays at an intensity of 2 for 2 minutes. At that time, the thickness of the positive electrode layer was 80 μm.

For the negative electrode layer, first, LiBF ₄ was added to EC
And a GBL mixed solvent (EC content 35% by weight) dissolved in an amount of 13% by weight to prepare an electrolyte solution, and the electrolyte solution and a polyethylene oxide / polypropylene oxide copolymer, which is a precursor of a solid electrolyte. Acrylate (average molecular weight 5000) was prepared to be 90:10 by weight. Thereafter, the negative electrode was allowed to stand under reduced pressure for 5 minutes, and a mixed solution of an electrolytic solution and a precursor was poured therein, and the mixture was allowed to stand for another 15 minutes.

Then, 38 mW / cm from the top of the negative electrode.
^A negative electrode layer was obtained by irradiating ultraviolet rays at an intensity of 2 for 2 minutes. At that time, the thickness of the negative electrode layer was 85 μm.

The positive electrode layer, the solid polymer electrolyte layer, and the negative electrode layer thus obtained were successively bonded to each other to produce a battery using the solid polymer electrolyte.

(Example 2) The same positive and negative electrodes as those used in Example 1 were used.

Regarding the polymer solid electrolyte layer, first, Li
An electrolytic solution was prepared by dissolving PF ₆ in a mixed solvent of EC and GBL (EC content: 35% by weight) so as to have a concentration of 13% by weight. The electrolytic solution was mixed with polyethylene oxide / polypropylene oxide as a solid electrolyte precursor. The copolymer diacrylate (average molecular weight 5000) was added in a weight ratio of 90: 1.
It was adjusted to be 0. The mixed solution is allowed to have an air permeability of 38.
It was immersed in a non-woven fabric made of polyether having a thickness of 0 sec / cm ³ , an area of 10 cm ² and a thickness of 20 μm, and allowed to stand under reduced pressure for 15 minutes in order to allow the precursor to penetrate inside the non-woven fabric. And 38
Ultraviolet rays were irradiated at an intensity of mW / cm ² for 2 minutes. At this time, the weight ratio between the solid electrolyte and the fibrous organic compound is 90: 1.
It was 0.

For the positive electrode layer, first, LiPF ₆ was added to PC
An electrolyte solution was prepared by dissolving it in a concentration of 13% by weight, and the electrolyte solution and a precursor of the solid electrolyte, polyethylene oxide / polypropylene oxide copolymer diacrylate (average molecular weight: 5000), were added in a weight ratio of 90:10. Was prepared. Thereafter, the positive electrode was allowed to stand under reduced pressure for 5 minutes, and a mixed solution of an electrolyte solution and a precursor mixture was poured therein, and the mixture was allowed to stand for another 15 minutes.

Then, 38 mW / cm from the top of the positive electrode
^A positive electrode layer was obtained by irradiating ultraviolet rays at an intensity of 2 for 2 minutes. At that time, the thickness of the positive electrode layer was 80 μm.

For the negative electrode layer, first, LiPF ₆ was added to E
C, a mixed solvent of PC and EMC (EC: 35% by weight,
13% by weight in PC: 17% by weight, EMC: 35% by weight)
Prepare a dissolved electrolyte so as to become, and the electrolyte,
An equal weight mixture of polyethylene oxide / polypropylene oxide copolymer diacrylate (average molecular weight 7000) and polyethylene oxide / polypropylene oxide copolymer acrylate (average molecular weight 2000) was prepared in a weight ratio of 95: 5. Thereafter, the negative electrode was allowed to stand under reduced pressure for 5 minutes, and a mixed solution of an electrolytic solution and a precursor was poured therein, and the mixture was allowed to stand for another 15 minutes.

Then, a polymer solid electrolyte layer was placed on the negative electrode, and irradiated with ultraviolet rays at an intensity of 38 mW / cm ² for 2 minutes to obtain a negative electrode layer. At that time, the total thickness of the negative electrode layer and the solid polymer electrolyte layer was 105 μm.

The positive electrode layer thus obtained was bonded to a composite of the negative electrode layer and the solid polymer electrolyte layer to produce a battery using the solid polymer electrolyte.

Comparative Example 2 The same positive electrode, negative electrode and polymer solid electrolyte layer as those used in Example 2 were used.

For the positive electrode layer, first, LiPF ₆ was added to PC
An electrolyte solution was prepared by dissolving the solution in an amount of 13% by weight in water, and the electrolyte solution was mixed with a polyethylene oxide / polypropylene oxide copolymer diacrylate (average molecular weight: 500
0) was prepared in a weight ratio of 90:10. Thereafter, the positive electrode was allowed to stand under reduced pressure for 5 minutes, and a mixed solution of an electrolyte solution and a precursor mixture was poured therein, and the mixture was allowed to stand for another 15 minutes.

Then, 38 mW / cm from the top of the positive electrode
^A positive electrode layer was obtained by irradiating ultraviolet rays at an intensity of 2 for 2 minutes. At that time, the thickness of the positive electrode layer was 80 μm.

For the negative electrode layer, first, LiPF ₆ was
And a mixed solvent of PC (EC: 60% by weight, PC: 27
(% By weight) to prepare an electrolytic solution dissolved to 13% by weight, and the electrolytic solution, polyethylene oxide / polypropylene oxide copolymer diacrylate (average molecular weight: 7000) and polyethylene oxide / polypropylene oxide copolymer acrylate ( Average molecular weight 2000)
Was prepared in a weight ratio of 90:10. Thereafter, the negative electrode was allowed to stand under reduced pressure for 5 minutes, and a mixed solution of an electrolytic solution and a precursor was poured therein, and the mixture was allowed to stand for another 15 minutes.

Then, 38 mW / cm from the top of the negative electrode.
^A negative electrode layer was obtained by irradiating ultraviolet rays at an intensity of 2 for 2 minutes. At that time, the thickness of the negative electrode layer was 85 μm.

The positive electrode layer, the solid polymer electrolyte layer, and the negative electrode layer thus obtained were successively bonded to each other to produce a battery using the solid polymer electrolyte.

Example 3 (d) Wide-angle X-ray Diffraction
₀₀₂ ) = 0.337 nm, (Lc) = 100 nm, (L
a) = 100 nm, specific surface area by BET method is 10 m ²
/ G of artificial graphite powder with PVDF as binder
The paste obtained by mixing by weight%, adding NMP and mixing and dissolving was coated on a rolled copper foil having a thickness of 20 μm, dried and pressed to obtain a negative electrode. This electrode area is 9cm ² ,
The thickness was 85 μm.

A battery using a solid polymer electrolyte was prepared in the same manner as in Example 2 except that the above-mentioned negative electrode was used.

The batteries of Examples 1 to 3 and Comparative Examples 1 and 2 were charged at a constant current of 2.3 mA until the battery voltage reached 4.1 V.
After reaching 4.1 V, the battery was charged at a constant voltage for a precharge time of 12 hours. Discharge was performed at a constant current of 2.3 mA, 5 mA, 10 mA,
The battery was charged at 0 mA until the battery voltage reached 2.75 V. FIG. 4 shows the results of the discharge capacity for each discharge current value under this condition.

Example 1 and Comparative Example 1, Example 2 and Comparative Example 2
As is clear from the results of above, after placing the prepared polymer solid electrolyte layer on the positive electrode and / or the negative electrode, it is better to crosslink the solid electrolyte precursor in the electrode. It is possible to use a low-viscosity solvent, and
It has been found that the number of electrode / polymer solid electrolyte layer interfaces can be reduced, the internal resistance of the battery can be reduced, and the high load characteristics of the battery can be improved.

The batteries of Examples 2 and 3 were charged at a constant current of 2.3 mA until the battery voltage reached 4.1 V.
After reaching 1 V, the battery was charged at a constant voltage for a precharge time of 12 hours.
The battery was discharged at a constant current of 2.3 mA until the battery voltage reached 2.75 V. The cycle characteristics were evaluated under these charge and discharge conditions. The result is shown in FIG.

From this result and FIG. 5, it can be seen that the battery using the surface amorphous carbon material for the negative electrode suppresses the decomposition of the ion conductive compound in the electrolyte layer and suppresses the destruction of the negative electrode / electrolyte layer interface. It has been found that a battery having excellent cycle characteristics can be manufactured.

[0088]

According to the present invention, there is provided a polymer comprising a negative electrode layer containing at least a carbon material as an active material, a positive electrode layer containing at least a lithium-containing chalcogenide as an active material, and a solid polymer electrolyte layer interposed between the positive and negative electrode layers. A secondary battery,
At least one of the positive electrode layer or the negative electrode layer contains the same or a different solid electrolyte as the solid electrolyte contained in the polymer solid electrolyte layer, and the solid electrolyte is impregnated with a precursor thereof as a solution in the positive electrode layer or the negative electrode layer in advance, After placing the polymer solid electrolyte layer on the positive electrode layer or the negative electrode layer,
By being crosslinked, the resistance inside the battery can be reduced, and a polymer secondary battery excellent in high load characteristics can be provided.

Further, according to the present invention, it is possible to use a gelled solid electrolyte containing a low-boiling-point solvent, to provide a polymer secondary battery which can reduce the internal resistance of the battery and have excellent high-load characteristics. be able to.

Further, according to the present invention, the polymer concentration of the solid electrolyte previously contained in the electrode can be made lower than the polymer concentration of the electrolyte layer, so that not only the resistance inside the battery but also the charge and discharge can be reduced. It is possible to configure a solid electrolyte that can follow the accompanying volume change of the electrode, and it is possible to provide a polymer secondary battery having excellent cycle characteristics.

According to the present invention, since the negative electrode active material is obtained by attaching amorphous carbon to the surface of graphite particles, it is possible to suppress decomposition of the polymer solid electrolyte or the solid electrolyte in the electrode during charging. As a result, the destruction of the interface and an increase in resistance due to reaction products at the interface are suppressed, and a polymer secondary battery having excellent long-term reliability can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic external view of a polymer secondary battery for evaluation used in Examples and Comparative Examples.

FIG. 2 is a schematic sectional view of a polymer secondary battery for evaluation used in Examples and Comparative Examples.

FIG. 3 is a schematic enlarged view of a cross section of an electrode and a polymer solid electrolyte layer of polymer secondary batteries of Examples and Comparative Examples.

FIG. 4 is a graph showing current load characteristics of the polymer secondary batteries of Examples and Comparative Examples.

FIG. 5 is a graph showing cycle characteristics of a polymer secondary battery of an example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Negative electrode terminal 2 Positive electrode terminal 3 Outer material seal part 4 Outer material 5 Positive electrode 6, 9 Polymer solid electrolyte layer 7 Negative electrode 8 Polymer secondary battery for evaluation 10 Solid electrolyte in electrode 11 Active material 12 Current collector

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Naoto Tora 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Yoshiaki Nishijima 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Takehito Mitate 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka Prefecture Inside Sharp Corporation (72) Masako Matsuda 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka Sharp stock Company F-term (reference) 5H029 AJ02 AJ05 AJ06 AK03 AK05 AL06 AL07 AL08 AM00 AM16 BJ03 BJ12 CJ11 CJ21 CJ22 CJ23 CJ28 DJ09 HJ10 5H050 AA02 AA07 AA12 BA17 CA08 CA09 CA11 CB07 CB08 GA23

Claims (5)

[Claims] 1. A polymer comprising a negative electrode layer containing at least a carbon material as an active material, a positive electrode layer containing at least a lithium-containing chalcogenide as an active material, and a polymer solid electrolyte layer interposed between the positive and negative electrode layers. A secondary battery,
At least one of the positive electrode layer or the negative electrode layer contains the same or different solid electrolyte as the solid electrolyte contained in the polymer solid electrolyte layer, and the solid electrolyte is impregnated with a precursor thereof as a solution in the positive electrode layer or the negative electrode layer in advance, After placing the polymer solid electrolyte layer on the positive electrode layer or the negative electrode layer,
A polymer secondary battery characterized by being crosslinked. 2. The polymer secondary battery according to claim 1, wherein the solid electrolyte contained in the positive electrode layer or the negative electrode layer is obtained by irradiating a precursor thereof with ultraviolet rays to crosslink the solid electrolyte. 3. The method according to claim 1, wherein the solid electrolyte in the positive electrode layer or the negative electrode layer is a gel electrolyte containing an organic electrolyte, and the organic electrolyte contains a low boiling point solvent. Polymer secondary battery. 4. The polymer secondary battery according to claim 1, wherein the solid electrolyte in the positive electrode layer or the negative electrode layer has a lower polymer concentration than the polymer solid electrolyte layer. 5. The polymer secondary battery according to claim 1, wherein the carbon material is obtained by attaching amorphous carbon to the surface of graphite particles.