JP2000164205A - Full solid secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a full solid secondary battery having excellent rate characteristic and cycle lifetime characteristic, especially a full solid Li secondary battery. SOLUTION: A film material of the high molecular solid electrolyte mainly composed of acrylonitrile-butadien copolymer having the bridge structure, ethylene carbonate, chain carbonate and alkali metal salt is interposed between a positive electrode carrying the positive mix in a positive electrode collector and a negative electrode so as to form a full solid secondary battery having a power generating element. Porosity of the positive electrode mix is set at 32-39%. As the alkali metal salt, Li salt is used and the negative electrode carries the negative electrode mix mainly composed of the carbonaceous material in a negative electrode collector, and porosity of the negative electrode mix is desirably set at 3-37%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an all-solid-state secondary battery using a polymer solid electrolyte, and more particularly to an all-solid-state secondary battery having excellent rate characteristics and cycle life characteristics. It relates to a Li secondary battery.

[0002]

2. Description of the Related Art In recent years, electronic devices such as mobile phones, video cameras, and personal computers have been reduced in size and weight, and lightweight and high-energy-density Li secondary batteries have been used as driving power supplies for such devices. In this Li secondary battery, a power generating element is configured by arranging a negative electrode, which will be described later, similarly to a positive electrode, which is described later, with a separator having electrical insulation and liquid retaining properties facing each other. And a non-aqueous electrolyte solution in which the Li salt is dissolved is injected, and the whole structure is closed.

[0003] Here, the positive electrode is usually manufactured as follows. First, for example, LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , V ₂
A non-aqueous solvent such as 1-methyl-2-pyrrolidone was added to a mixture of powders such as O ₅ and TiO ₂ , a conductive material powder such as carbon black, and a binder such as polyvinylidene fluoride. Thereafter, the mixture is kneaded to prepare a paste of the positive electrode mixture. Then, paste this paste into stainless steel foil, Al
After uniformly applying to a positive electrode current collector such as a foil, a Ni foil, or a Ti foil, drying is performed to evaporate the nonaqueous solvent, and then compression molding or roll molding is performed to obtain a positive electrode having a desired shape and size. I do.

Therefore, in this positive electrode, the positive electrode mixture is dried and hardened, and the powder of the positive electrode active material and the powder of the conductive material are bound with a binder to form a porous structure. Is carried on the surface of the positive electrode current collector. on the other hand,
As the negative electrode, a metal Li or Li alloy foil has been used as it is, but recently, although its energy density is lower than that of a battery using the above-described foil,
The following negative electrodes are mainly used because of their high safety.

That is, a mixture of a powder of a carbonaceous material such as amorphous carbon or artificial graphite and a powder of a binder such as polyvinylidene fluoride is mixed with a non-aqueous solvent such as 1-methyl-2-pyrrolidone. And then kneading to prepare a paste of the negative electrode mixture. Then, paste this paste into Cu foil,
The coating is uniformly applied to a negative electrode current collector such as a stainless steel foil, a Ni foil, or a Ti foil, and then dried to volatilize the non-aqueous solvent, and further subjected to compression molding or roll molding to obtain a desired shape and size. Make it a negative electrode.

Therefore, also in the case of the negative electrode, the negative electrode mixture, which is hardened by drying, has a porous structure in which the above-mentioned powder of the carbonaceous material is bound by the binder, is used as the negative electrode current collector. Carried on the surface of By the way, a Li secondary battery using a non-aqueous electrolyte always has a possibility of liquid leakage. Since this is a factor that causes a decrease in charge / discharge cycle life characteristics due to liquid leakage, a failure of mounted equipment, and the like, this problem lowers the long-term reliability of the Li secondary battery.

[0007] For these reasons, recently, there has been no fear of causing liquid leakage, and an all-solid-state Li using a polymer solid electrolyte in which a polymer material is impregnated with an electrolytic solution and swollen.
Attention has been paid to secondary batteries, and research on their development is being vigorously pursued. As this all-solid-state Li secondary battery, for example, a polymer solid electrolyte film that conducts Li ions is interposed between the positive electrode and the negative electrode to form a power generation element, and this power generation element is hermetically sealed, for example, an aluminum laminate sheet. A typical example is a sheet or film type having a sealed structure using an exterior material as described above. In the case of this battery, not only is there no fear of liquid leakage, but also the whole is a thin film, and it has a suitable flexibility, so that a battery with a high degree of freedom in shape can be designed. There are advantages.

[0008]

However, the solid polymer electrolyte has a lower ionic conductivity than the non-aqueous electrolyte, and is interposed between the positive and negative electrodes in a solid state in the form of a film. There is a problem that the contact state between the active material in the positive electrode mixture carried on the positive electrode and the negative electrode becomes insufficient and the interface resistance is large.

Therefore, in the case of a battery using a solid polymer electrolyte, there is a problem that the rate characteristics and cycle life characteristics are greatly reduced as compared with a battery using a non-aqueous electrolyte. To solve such a problem, it has been proposed to form a composite electrode by mixing a polymer solid electrolyte and an active material. According to this method, although the area of the contact interface between the solid polymer electrolyte and the active material is increased, the interface resistance between the positive electrode and the negative electrode is reduced as compared with the case of a film, although the improvement is performed. However, the rate characteristics and the cycle life characteristics are still significantly inferior to the case where a non-aqueous electrolyte is used.

The present invention solves the above-mentioned problems in an all-solid-state secondary battery using a polymer solid electrolyte, and improves the rate characteristics and cycle life characteristics of the all-solid-state secondary battery. The purpose is to provide a secondary battery.

[0011]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, while using a specific polymer solid electrolyte described later as a polymer solid electrolyte, When the porous structure of the positive electrode mixture is brought to the state described below, the fact that the rate characteristics and cycle life characteristics are dramatically improved as compared with conventionally known all-solid-state secondary batteries has been found. This led to the development of the all-solid-state secondary battery of the present invention.

That is, the all-solid-state secondary battery of the present invention comprises:
Acrylonitrile-butadiene copolymer having a crosslinked structure, ethylene carbonate, and a chain carbonate,
An all-solid-state power generation element comprising a polymer solid electrolyte film containing an alkali metal salt as a main component and a positive electrode current collector carrying a positive electrode mixture interposed between a positive electrode and a negative electrode. Type secondary battery, wherein the porosity of the positive electrode mixture is 32 to
It is characterized by being 39%.

More specifically, an all-solid Li secondary battery (hereinafter referred to as battery I) in which the alkali metal salt is a Li salt and the negative electrode is made of a metal Li or Li alloy foil;
And the negative electrode is formed by supporting a negative electrode mixture mainly composed of a carbonaceous material on a negative electrode current collector, wherein the alkali metal salt is a Li salt, and the porosity of the negative electrode mixture is 3 to 37.
% Of an all-solid-state Li secondary battery (hereinafter, referred to as Den II).

In the latter battery, the carbonaceous material is made of amorphous carbon, and the porosity of the negative electrode mixture is 26%.
-37% all solid-state Li secondary battery (hereinafter referred to as Battery II-
1), wherein the carbonaceous material is made of artificial graphite and the porosity of the negative electrode mixture is 7 to 18%. (Hereinafter referred to as battery II-2), wherein the carbonaceous material is made of carbon fiber, and the porosity of the negative electrode mixture is 3 to 1
A 3% all-solid-state secondary battery (hereinafter referred to as Battery II-3) is provided.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In each of the above-mentioned batteries of the present invention, a power generating element is formed by interposing a film-like material of a polymer solid electrolyte described later between a positive electrode and a negative electrode. The solid polymer electrolyte used is described below. That is, in a polymer matrix having an acrylonitrile-butadiene copolymer having a crosslinked structure described later as a skeleton, a non-aqueous solvent composed of ethylene carbonate and a chain carbonate, and functions as an electrolyte by being dissolved in the non-aqueous solvent. An alkali metal salt is retained.

First, an acrylonitrile-butadiene copolymer having a crosslinked structure, which is a skeleton component, cleaves a double bond present in a main chain or a side chain of the acrylonitrile-butadiene copolymer, and performs an addition reaction or a cyclization reaction. A crosslinked structure is formed within a molecule or between molecules by, for example, the above. As described above, in the case of this polymer solid electrolyte, since the skeleton component has a crosslinked structure, the mechanical strength is unlikely to decrease even if the electrolyte is finally impregnated with the electrolyte. .

This crosslinked structure is usually formed by adding acrylonitrile-butadiene copolymer to dicumyl peroxide,
organic peroxides such as tert-butylcumyl peroxide; organic sulfur compounds such as sulfur and thiuram;
It can be formed by adding a crosslinking agent such as quinone dioxium; and performing a heat treatment. The main chain or side chain of the acrylonitrile-butadiene copolymer has a methylolamide group, a hydroxyl group, a carboxyl group, an amino group,
When a reactive functional group such as an epoxy group or a carbonyl group is present, it is possible to form a crosslinked structure simply by heating without adding the above-mentioned crosslinking agent.

Further, as the acrylonitrile-butadiene copolymer, those obtained by carboxyl modification by directly introducing a carboxyl group into the main chain or side chain thereof may be used. Specifically, it is obtained by copolymerizing an acrylonitrile-butadiene copolymer with an unsaturated carboxylic acid such as acrylic acid, methacrylic acid, maleic acid, and itaconic acid.

Both ethylene carbonate and chain carbonate function as non-aqueous solvents for dissolving the alkali metal salt, which is another essential component, and both are used as a mixture. The chain carbonate is not particularly limited as long as it can dissolve the alkali metal salt, and dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate are preferred. These may be used alone or as a mixture of two or more.

The mixing ratio of ethylene carbonate and chain carbonate in the above non-aqueous solvent is such that when the proportion of ethylene carbonate exceeds 90% by weight, ion migration is reduced and ionic conductivity is significantly reduced. 90% by weight, chain carbonate 90-1
It is preferably set to 0% by weight. The ratio of the non-aqueous solvent in the polymer solid electrolyte is determined by the acrylonitrile-butadiene copolymer 10 having the crosslinked structure.
It is preferable to set 50 to 95 parts by weight with respect to 0 parts by weight. If the amount is less than 50 parts by weight, sufficient ionic conductivity cannot be obtained, and if the amount is more than 95 parts by weight, the mechanical strength tends to decrease.

Incidentally, a small amount of other non-aqueous solvents such as propylene carbonate, γ-butyrolactone, tetrahydrofuran and dimethoxyethane may be added to the non-aqueous solvent. The alkali metal salt that functions as an electrolyte is not particularly limited, but includes Li ⁺ , N
alkali metal cations such as a ⁺ and K ⁺ , and ClO ₄ ⁻ and B
An alkali metal salt comprising a combination with an anion such as F ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , and CF ₃ SO ₃ ⁻ can be given.

When the battery to be manufactured is a Li secondary battery, the alkali metal salt used is LiClO ₄ , Li
Needless to say, it must be a Li salt such as BF ₄ , LiPF ₆ , LiAsF ₆ , LiCF ₃ SO ₃ .
The content of the alkali metal salt in the solid electrolyte is preferably such that when the alkali metal salt is dissolved in the non-aqueous solvent, the concentration is 0.3 to 2 mol / L. If the concentration is lower than 0.3 mol / L, it is difficult to obtain a high ionic conductivity, and if the concentration is higher than 2 mol / L, it will not be sufficiently dissolved.

This polymer solid electrolyte can be produced, for example, as follows. First, an acrylonitrile-butadiene copolymer or a carboxyl-modified acrylonitrile-butadiene copolymer is dissolved in an organic solvent such as methyl ethyl ketone, toluene, and acetone. After dissolving the crosslinking agent in the obtained solution, the solution is cast, and the organic solvent is further volatilized to produce a film.

Then, the film is heated in a non-oxidizing atmosphere to form a skeleton of a crosslinked structure. Then, the film-like substance having a cross-linked structure is immersed in a non-aqueous electrolytic solution obtained by dissolving an alkali metal salt in a non-aqueous solvent composed of a mixture of ethylene carbonate and a chain carbonate, and the non-aqueous electrolytic solution is What is necessary is just to impregnate into a bridge structure.

Next, the positive electrode of the present invention will be described. The positive electrode of the present invention has a positive electrode mixture having a porous structure in which a predetermined positive electrode active material powder and a conductive material powder are bound with a binder, and pores are present inside the positive electrode current collector. In this case, the porosity of the positive electrode mixture is 32 to 39.
%.

Here, the porosity referred to in the present invention is a ratio (percentage) of the total volume of the pores to the apparent volume of the positive electrode mixture including the pores.
This is a value calculated as follows. First, the apparent total volume V ₁ of the positive electrode mixture is represented by the following formula: V ₁ = A × (t−t ′) (1) (where A is the area of the positive electrode (cm ² ), and t is an optical microscope. The measured average thickness (cm) of the entire positive electrode and t ′ are calculated based on the average thickness (cm) of the positive electrode current collector measured with an optical microscope, respectively.

On the other hand, the actual volume V2 of the positive electrode mixture is calculated by the following equation: V2 = v1 + v2 + v3 (2) Here, v1, v2, v3, the actual volume of the positive electrode active materials occupied in the positive electrode mixture (cm ^3), the actual volume of the conductive material occupying the positive electrode mixture (cm ^3), and occupying in the positive electrode mixture The actual volume (cm ³ ) of the binder is shown.

These v1, v2, and v3 are calculated based on the following equations. That, v1 = m1 × (W- A × t '× d 0) / d 1 ... (3) v2 = m2 × (W-A × t' × d 0) / d 2 ... (4) v3 = m3 × (W−A × t ′ × d ₀ ) / d ₃ (5) (where m1, m2, and m3 are weight ratios of the positive electrode active material, the conductive material, and the binder in the positive electrode mixture, respectively) Is a value satisfying m1 + m2 + m3 = 1, and d ₀ is a specific gravity (g / cm ³ ) of the positive electrode current collector, and d ₁ , d ₂ , d
₃ represents the specific gravity (g / cm ³ ) of the positive electrode active material, the conductive material, and the binder, respectively, and W represents the weight (g) of the entire positive electrode. A and t ′ have the same meaning as in the case of the formula (1)).

Then, the porosity (%) is calculated based on the following equation: (V ₁ −V ₂ ) × 100 / V ₁ (6) When the positive electrode mixture has a porosity of less than 32%, it is difficult for the electrolyte in the solid polymer electrolyte to sufficiently penetrate into the inside of the positive electrode mixture. It becomes insufficient, and the rate characteristics and cycle life characteristics of the battery deteriorate.
Conversely, in the case of a positive electrode mixture having a porosity of more than 39%, the electrolyte solution in the solid polymer electrolyte is in a favorable state, but on the other hand, a structurally conductive network is not formed. Insufficiently, the electric resistance becomes large, and the problem that the positive electrode mixture is easily peeled off from the current collector occurs, so that the rate characteristics and the cycle life characteristics are reduced. The preferred porosity of the positive electrode mixture is from 32 to 39%.

This positive electrode can be manufactured as follows. That is, an alkali metal and CoO ₂ , Mn
Powders of a positive electrode active material such as a composite oxide with ₂ O ₄ and NiO ₂ , V ₂ O ₅ , TiS ₂ , polyaniline, polyacene, various organic sulfur compounds, and acetylene black, ketjen black, graphite, etc. A conductive material powder and a binder such as polytetrafluoroethylene, polyvinylidene fluoride, polystyrene, polyethylene, styrene butadiene rubber, acrylonitrile butadiene rubber, styrene butadiene ethylene styrene elastomer are combined with 1-methyl-
A paste is prepared by kneading using a non-aqueous solvent such as 2-pyrrolidone, and the paste is mixed with Al, N
i, Ti, and uniformly coated on a positive electrode current collector such as a foil or net made of stainless steel, dried and evaporated to evaporate the non-aqueous solvent, and then subjected to compression molding or roll molding to obtain a desired shape and size. Process into

At this time, the porosity of the positive electrode mixture in the finally obtained positive electrode is changed by changing the amount of the non-aqueous solvent used or changing the molding pressure applied during compression molding or roll molding. It can be adjusted within the above range.
The all-solid-state secondary battery of the present invention is assembled using the above-described solid polymer electrolyte and the above-described positive electrode, and using the negative electrode described below. This will be described for the case of an all solid-state Li secondary battery.

First, the battery I, the battery II, and the battery II-1, the battery II-2, and the battery II-, which are specific examples of the battery II, are described.
In any of 3, the alkali metal salt used for producing the solid polymer electrolyte is a Li salt. Specifically, L
iClO ₄ , LiBF ₄ , LiPF ₆ , LiAsF ₆ , Li
One or more of CF ₃ SO ₃ is used. Battery I
In this case, a metal Li or Li alloy foil is used as it is as the negative electrode. When the battery to be manufactured is not a Li secondary battery, the necessary alkali metal or alkali metal alloy foil is used as it is.

In the case of the battery II, a dried porous negative electrode mixture mainly composed of a carbonaceous material described later is supported on the surface of the negative electrode current collector. Specifically, a paste is prepared by kneading a powder of a carbonaceous material, a powder of a binder as used when producing the above-described positive electrode, and a non-aqueous solvent such as 1-methyl-2-pyrrolidone. This paste is uniformly applied to the surface of a negative electrode current collector such as a Cu foil, dried, and then the non-aqueous solvent is volatilized, followed by compression molding or roll molding.

In this case, the porosity of the negative electrode mixture carried on the negative electrode current collector is set to 3 to 37% by appropriately adjusting the molding pressure applied during compression molding or roll molding. When the porosity is smaller than 3%, as in the case of the above-described positive electrode, the electrolyte in the solid polymer electrolyte hardly penetrates into the inside of the negative electrode mixture. This is because disadvantages such as an increase in electric resistance and peeling of the negative electrode mixture from the current collector occur.

The porosity of the negative electrode mixture is a value calculated based on the equations (1) to (6) described for the positive electrode mixture. Battery II-
In the case of 1, amorphous carbon is selected as the carbon material. In that case, the porosity of the negative electrode mixture is preferably set to 26 to 37%. More preferably, 28 to 3
4%.

In the case of Battery II-2, artificial graphite is selected as the carbonaceous material. In that case, the porosity of the negative electrode mixture is preferably set to 7 to 18%. More preferably, it is 10 to 16%. In the case of battery II-3, carbon fiber is selected as the carbonaceous material. Specifically, a material obtained by cutting a long carbon fiber into a short one is used. In that case, the porosity of the negative electrode mixture is preferably set to 3 to 13%. More preferably, it is 5 to 11%.

The form and assembling method of the all-solid-state secondary battery of the present invention are not particularly limited. For example, various forms such as a coin type, a sheet or film type, a cylindrical type, and a square type are available. May be used.

[0038]

EXAMPLES Examples 1 to 20 and Comparative Examples 1 to 10 Production of Film-shaped Solid Polymer Electrolyte 1571 (trade name, carboxyl-modified acrylonitrile-butadiene copolymer latex manufactured by Zeon Corporation) was spread thinly and evenly on a Petri dish using a spin coater, and then at room temperature and normal pressure. For 24 hours, and further dried at room temperature under reduced pressure of 1 × 10 ⁻⁵ Mpa or less for 24 hours to form a film having a thickness of about 0.2 mm.

Next, the film-like material was heated at a temperature of 105
The mixture was heated at a temperature of 24 ° C. under a reduced pressure of 1 × 10 ⁻⁵ Mpa for 24 hours to form a crosslinked structure. A non-aqueous electrolyte solution obtained by dissolving this film in a non-aqueous mixed solvent of ethylene carbonate and dimethyl carbonate in a volume ratio of 1: 2 under an Ar atmosphere so that LiClO ₄ has a concentration of 1 mol / L. For 24 hours. Then, it was taken out and the liquid on the surface was wiped off. The obtained film is used as an example electrolyte.

On the other hand, the above-mentioned 1571 and 2507H (trade name, styrene-butadiene copolymer latex manufactured by Nippon Zeon Co., Ltd.) were mixed at a weight ratio of 50:50, and the mixed latex was placed on a petri dish using a spin coater. And then dried at room temperature under normal pressure for 5 hours, and then dried at a temperature of 105 ° C. and a reduced pressure of 1 × 10 ⁻⁵ Mpa or less.
After heating for 4 hours, a film having a thickness of about 0.2 mm was obtained.

Then, this film-like substance was dissolved in a non-aqueous mixed solvent consisting of γ-butyrolactone and dimethoxyethane in a volume ratio of 1: 1 under an Ar atmosphere so that the concentration of LiClO ₄ was 1 mol / L. For 24 hours. And take it out,
The liquid on the surface was wiped off. The obtained film-like material is used as a comparative example electrolyte.

2. Manufacture of positive electrode NC5N (trade name, LiCoO ₂ powder manufactured by NiKKO Rica), TB4300 (trade name, carbon black manufactured by Tokai Carbon Co., Ltd.), polyvinylidene fluoride powder (produced by Kureha Chemical Industry Co., Ltd.) Are mixed in a weight ratio of 87: 10: 3, in which 50% by weight of 1-methyl-
2-Pyrrolidone was added, and the whole was kneaded to prepare a paste of the positive electrode mixture.

Then, this paste was uniformly applied to both sides of an Al foil having a diameter of 16 mm and a thickness of 0.05 mm by a doctor blade method, and allowed to stand in the air at room temperature for 24 hours.
It was dried at a temperature of 105 ° C. under a reduced pressure of 1 × 10 ⁻⁵ Mpa for 24 hours. Subsequently, compression molding was performed using Riken Power (trade name, uniaxial press machine manufactured by Riken Seiki Co., Ltd.) to produce a positive electrode. At this time, various positive electrodes having the porosity shown in Tables 1 and 2 were obtained by adjusting the pressing pressure.

Since the structure of carbon black as a conductive material is complicated, it is difficult to accurately measure specific gravity. Therefore, when calculating the porosity of the positive electrode mixture, the value calculated by the benzene immersion replacement method described in “Carbon Black Handbook” of Tosho Publishing Co .: 1.83
g / cm ³ was employed. These positive electrodes are all designed to have a theoretical capacity of 5 mAh.

3. Production of Negative Electrode A metal Li foil having a thickness of 0.1 mm (manufactured by Honjo Metal Co., Ltd.) was punched into a disk having a diameter of 16 mm. This is designated as negative electrode A. The negative electrode A has a theoretical capacity of about 20 mAh.
Further, 95: 5% by weight of MBC-NC (trade name, amorphous carbon manufactured by Mitsubishi Chemical Corporation) powder (average particle size: 29 μm) and polyvinylidene fluoride powder (Kureha Chemical Industry Co., Ltd.) were used. The mixture was mixed in a ratio, and 100% by weight of 1-methyl-2-pyrrolidone was added thereto, and the whole was kneaded to prepare a negative electrode mixture paste.

Then, the paste was uniformly applied to both sides of a Cu foil having a diameter of 16 mm and a thickness of 0.04 mm by a doctor blade method, and allowed to stand in the air at room temperature for 24 hours.
It was dried at a temperature of 180 ° C. under a reduced pressure of 1 × 10 ⁻⁵ Mpa for 24 hours. Next, compression molding was performed using the above-mentioned Riken power. At this time, various negative electrodes having the porosity shown in Tables 1 and 2 were obtained by adjusting the pressing pressure. These series using amorphous carbon are referred to as negative electrode B.

The carbonaceous material is MAG-B-30 (trade name,
Powder of Hitachi Chemical Co., Ltd. artificial graphite) (average particle size 27μ)
A negative electrode having a different porosity of the negative electrode mixture was manufactured in the same manner as in the case of the negative electrode A, except that m). These series using artificial graphite are referred to as negative electrode C. The carbonaceous material is B
L924 (trade name, carbon fiber manufactured by Lonza) with a particle size of 15
A negative electrode having a different porosity of the negative electrode mixture was produced in the same manner as in the case of the negative electrode A, except that the short fibers were cut into μm (average fiber diameter: 8.8 μm). These series using carbon fibers are referred to as a negative electrode D. In addition, these negative electrodes B ~
The theoretical capacity of D is designed to be 5 mAh.

4. Battery assembly A polymer solid electrolyte film was punched into a film foil having a diameter of 16 mm. Next, this film foil is sandwiched between the above-described positive electrode and negative electrode in a combination as shown in Tables 1 and 2 to form various power generating elements. A sealed coin-type Li secondary battery having a diameter of 20 mm and a height of 1.2 mm was assembled.

5. Measurement of battery characteristics (1) Measurement of rate characteristics Rate characteristics of each battery were examined as follows. That is, constant-current charging is performed at a constant current of 1 mA until the battery voltage reaches 4.15 V in the atmosphere at a temperature of 25 ° C. under normal pressure, and then the current value is 0.1 mA at a constant voltage of 4.15 V.
Charge and discharge until the battery voltage becomes 2.5 V at a constant current of 1 mA and then pause for 30 minutes again as one cycle. Was performed for 5 cycles, and in the sixth cycle, the charging conditions were the same as those in the first cycle, but the discharging was performed at a constant current of 5 mA until the battery voltage reached 2.5 V. The discharge capacities at the first cycle (1 mA discharge) and the sixth cycle (5 mA discharge) were determined and are shown in Tables 1 and 2. Further, the ratio (percentage) of the discharge capacity at the sixth cycle (5 mA discharge) to the discharge capacity at the fifth cycle (1 mA discharge) was determined, and the ratio was defined as a large current discharge capacity ratio. The larger the value, the better the rate characteristics.

(2) Measurement of cycle life characteristics The cycle life characteristics of each battery were examined as follows. That is, in the air at a temperature of 25 ° C. under normal pressure,
Constant current charging was performed at a constant current of 1 mA until the battery voltage reached 4.15 V, followed by constant voltage charging until the current value reached 0.1 mA at a constant voltage of 4.15 V, followed by a 30-minute pause. Thereafter, the battery was discharged at a constant current of 1 mA until the battery voltage reached 2.5 V, and charge / discharge was performed 100 cycles, with one cycle of resting for 30 minutes.

Then, the discharge capacity of the battery at the 100th cycle was determined, and the ratio (%) of the value to the discharge capacity at the first cycle was calculated to obtain the discharge capacity retention rate. A battery having a higher discharge capacity retention ratio has a smaller capacity decrease due to repetition of charge / discharge cycles, that is, it has better cycle life characteristics. The above results are collectively shown in Tables 1 and 2.

[0052]

[Table 1]

[0053]

[Table 2]

The following is clear from Tables 1 and 2. (1) First, the batteries of Comparative Examples 6 to 10 assembled using the comparative example electrolyte as the solid electrolyte have remarkably deteriorated cycle life characteristics as compared with the other batteries. For example, as is clear from comparison of Example 2 with Comparative Example 6, Example 6 with Comparative Example 8, and Example 12 with Comparative Example 9, although the positive electrode and the negative electrode of the power generation element are the same, ,
The cycle life characteristics of each comparative example in which the comparative example electrolyte was incorporated were significantly deteriorated. Thus, the usefulness of using the electrolytes of the examples is clear.

(2) Example Even in a battery using an electrolyte, the porosity of the positive electrode mixture in the positive electrode was 32 to 39%.
In all cases, the rate characteristics and the cycle life characteristics are reduced. For example, Examples 1-3
This is the case with Comparative Examples 1 and 2. Further, as is apparent from the comparison between Example 6, Comparative Example 3, Example 12, Comparative Example 4, Example 17, and Comparative Example 5, even though the negative electrodes of the respective batteries are the same, In the case of the comparative example in which the porosity of the positive electrode mixture is out of the range of 32 to 39%, the rate characteristics and the cycle life characteristics are deteriorated. From this, it is understood that the porosity of the positive electrode mixture in the positive electrode should be set to 32 to 39% regardless of the type of the negative electrode.

(3) In that case, it can be seen that the suitable porosity of the negative electrode mixture in the negative electrode should be changed according to the type of the carbonaceous material that is the main component. For example, negative electrode B
In the case of (amorphous carbon), the rate characteristics and the cycle life of Examples 4 and 9 are lower than those of Examples 5 to 8.
For this reason, when the negative electrode B is incorporated, the porosity of the negative electrode mixture is preferably set to 26 to 37%.

In the case of the negative electrode C (artificial graphite),
In Nos. 0 and 15, lower rate characteristics and lower cycle life are observed as compared with Examples 11 to 14. For this reason, when the negative electrode C is incorporated, the porosity of the negative electrode mixture is 7 to 18
% Is preferably set. Furthermore, in the case of the negative electrode D (carbon fiber), the rate characteristics and the cycle life of Example 20 are lower than those of Examples 16 to 19. For this reason, when the negative electrode D is incorporated, it is preferable to set the porosity of the negative electrode mixture to 3 to 13%.

[0058]

As is apparent from the above description, according to the present invention, it is possible to obtain an all solid-state secondary battery having excellent rate characteristics and cycle life characteristics, especially an all solid-state Li secondary battery. This is a polymer solid electrolyte having a crosslinked structure described above, a positive electrode of a positive electrode mixture having a porosity described above,
This is an effect based on combining the negative electrode and the power generating element.

Claims (6)

[Claims] 1. A positive electrode current collector comprising: a polymer solid electrolyte film mainly composed of an acrylonitrile-butadiene copolymer having a crosslinked structure, ethylene carbonate, a chain carbonate, and an alkali metal salt. An all-solid-state secondary battery having a power generating element interposed between a positive electrode carrying a positive electrode mixture and a negative electrode, wherein the porosity of the positive electrode mixture is 32 to 39%. Characteristic all-solid-state secondary battery. 2. The all-solid-state secondary battery according to claim 1, wherein the alkali metal salt is a Li salt, and the negative electrode is made of a metal Li or Li alloy foil. 3. The method according to claim 1, wherein the alkali metal salt is a Li salt, and the negative electrode is formed by supporting a negative electrode mixture containing a carbonaceous material as a main component on a negative electrode current collector, and has a porosity of 3%.
The all-solid-state secondary battery according to claim 1, wherein the content is about 37%. 4. The carbonaceous material comprises amorphous carbon,
The all-solid-state secondary battery according to claim 3, wherein the porosity of the negative electrode mixture is 26 to 37%. 5. The all-solid-state secondary battery according to claim 3, wherein the carbonaceous material is made of artificial graphite, and the porosity of the negative electrode mixture is 7 to 18%. 6. The all-solid-state secondary battery according to claim 3, wherein the carbonaceous material is made of carbon fiber, and the porosity of the negative electrode mixture is 3 to 13%.