JP2003017126A - Solid electrolyte cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid electrolyte cell with improved charging and discharging efficiency and cycle property by selecting solid electrolyte and proper electrode binding agent. SOLUTION: The solid electrolyte comprises a positive electrode having positive electrode activator dispersed in a binding agent, a negative electrode having negative electrode activator dispersed in a binding agent, and a solid electrolyte interposed between the positive electrode and the negative electrode. The positive electrode binding agent contains one or more of polymer compound chosen from ethylene tetrafluoride, polyamideimide, and poly(meta)acrylate, or co-polymer of them. The negative electrode binding agent contains one or more of polymer compound chosen from styrene-butadiene rubber, polyacrylic acid, polyamideimide, and polyether, or co-polymer of them. The solid electrolyte contains a polymer compound obtained by polymerizing and bridging a first compound having at least two or more of α,β-unsaturated carbonyl groups in a molecule.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a solid electrolyte battery in which reaction between a solid electrolyte and an electrode binder is suppressed.

[0002]

2. Description of the Related Art Recently, a VTR with a built-in camera, a mobile phone,
Many portable electronic devices such as portable computers have appeared, and their size and weight have been reduced. And as a portable power source for these electronic devices, batteries, especially secondary batteries,
Among them, with regard to lithium-ion batteries, research and development of thin and bendable batteries have been actively reversed. Solid electrolytes have been actively researched as electrolytes for batteries with flexible shapes, especially gel electrolytes, which are solid electrolytes containing a plasticizer, and polymer solid electrolytes in which a lithium salt is dissolved in a polymer. Is in the spotlight.

In particular, there are many research examples of a gel electrolyte or a solid electrolyte obtained by gelling or solidifying a liquid (containing) liquid monomer solution by a chemical reaction by a simple method.

For example, Japanese Patent Laid-Open No. 2000-1076,
In JP-A-2000-21446, an electrolytic solution,
Electrophilic α, β-unsaturated carbonyl groups and nucleophilic amino groups react with each other in the electrolyte and chemically bond to form gel,
Methods that can be solidified have been reported.

[0005]

However, the nucleophilic amino group used as a material for the gel-like solid electrolyte prepared by such a method is used as a binder for dispersing the active material in each electrode of the battery. It reacts with the commonly used polyvinylidene fluoride (PVdF) to deteriorate charging / discharging efficiency and cycle characteristics.

The present invention has been proposed in view of such conventional circumstances, and provides a solid electrolyte battery having good charge / discharge efficiency and cycle characteristics by selecting a solid electrolyte and an appropriate electrode binder. With the goal.

[0007]

The solid electrolyte battery of the present invention comprises a positive electrode having a positive electrode active material dispersed in a binder,
A negative electrode having a negative electrode active material dispersed in a binder,
And a solid electrolyte interposed between the positive electrode and the negative electrode.
The solid electrolyte battery of the present invention contains, as a binder for the positive electrode, one or more polymer compounds selected from tetrafluoroethylene, polyamideimide, poly (meth) acrylates, or copolymers thereof. , Containing one or more polymer compounds selected from styrene-butadiene rubber, polyacrylic acid, polyamide-imide, and polyether as a binder for the negative electrode, or a copolymer thereof, and as the solid electrolyte, α in the molecule Containing a polymer compound obtained by polymerizing and crosslinking a first compound having at least two β-unsaturated carbonyl groups and a second compound having two or more secondary amino groups in the molecule. It is characterized by being

In the solid electrolyte battery according to the present invention as described above, the first compound having at least two α, β-unsaturated carbonyl groups and the second compound having two or more secondary amino groups are used. It includes a solid electrolyte containing a polymer compound obtained by polymerizing and cross-linking the The reaction between the amino group and the binder is suppressed, and adverse effects on the battery characteristics are prevented.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A solid electrolyte battery to which the present invention is applied will be described below with reference to the drawings.

An example of the structure of the gel electrolyte battery 1 according to this embodiment is shown in FIGS. 1 and 2. This gel electrolyte battery 1 includes a belt-shaped positive electrode 2, a belt-shaped negative electrode 3 arranged to face the positive electrode 2, a gel-shaped electrolyte layer 4 formed on the positive electrode 2 and the negative electrode 3, and a gel-shaped electrolyte layer. The separator 5 is provided between the positive electrode 2 having the electrode 4 formed thereon and the negative electrode 3 having the gel electrolyte layer 4 formed thereon.

In this gel electrolyte battery 1, a positive electrode 2 having a gel electrolyte layer 4 formed thereon and a negative electrode 3 having a gel electrolyte layer 4 formed thereon are laminated with a separator 5 in between and a longitudinal direction thereof is provided. The electrode winding body 6 shown in FIG. 3, which has been wound around, is covered and sealed with an exterior film 7 made of an insulating material. Then, the positive electrode 2 has a positive electrode terminal 8,
A negative electrode terminal 9 is connected to the negative electrode 3, and the positive electrode terminal 8 and the negative electrode terminal 9 are sandwiched by a sealing portion which is a peripheral edge portion of the exterior film 7. Further, in the portion where the positive electrode terminal 8 and the negative electrode terminal 9 are in contact with the exterior film 7,
The resin film 10 is arranged.

As shown in FIG. 4, the positive electrode 2 has a positive electrode active material layer 2a containing a positive electrode active material formed on both surfaces of a positive electrode current collector 2b. As the positive electrode current collector 2b, for example, a metal foil such as an aluminum foil is used.

As the positive electrode active material, a metal oxide, a metal sulfide or a specific polymer can be used depending on the type of the intended battery.

For example, when a lithium ion battery is constructed, the positive electrode active material may be TiS ₂ , MoS ₂ , NbS.
Metal sulfides or oxides such as e ₂ and V ₂ O ₅ can be used. Further, a lithium composite mainly composed of LiM _x O ₂ (wherein, M represents one or more kinds of transition metals, x varies depending on the charge / discharge state of the battery, and is usually 0.05 or more and 1.10 or less). Oxides and the like can be used. As the transition metal M constituting the lithium composite oxide, Co, Ni, Mn and the like are preferable. Specific examples of such a lithium composite oxide include LiCoO ₂ and LiN.
iO ₂ , LiNi _y Co _1-y O ₂ (wherein 0 <y <1
Is. ), LiMn ₂ O ₄ , Li _x MPO ₄ (in the formula,
M represents one or more kinds of transition metals, x varies depending on the charge / discharge state of the battery, and is usually 0.05 or more and 1.10 or less. ) Etc. can be mentioned. These lithium composite oxides can generate a high voltage and become a positive electrode active material excellent in energy density. For the positive electrode 2, plural kinds of these positive electrode active materials may be used together.

As the binder of the positive electrode mixture, a polymer compound having a low reactivity with amino groups contained in the matrix polymer constituting the gel electrolyte described later, specifically, oxidation resistance / From the viewpoint of resistance to reduction, one or more polymer compounds selected from tetrafluoroethylene, polyamide imide, and poly (meth) acrylic acid may be mentioned. Also,
It is also possible to use a copolymer of the above constituents.

By using a polymer compound having a low reactivity with an amino group as the binder of the positive electrode mixture, the reaction between the amino group contained in the gel electrolyte and the binder can be suppressed. This prevents deterioration of charge / discharge efficiency and cycle characteristics caused by the reaction between the gel electrolyte and the binder.

As shown in FIG. 5, the negative electrode 3 has a negative electrode active material layer 3a containing a negative electrode active material, and a negative electrode current collector 3b.
Are formed on both sides of. As the negative electrode current collector 3b, a metal foil such as a copper foil is used.

As the negative electrode active material, it is preferable to use lithium, a lithium alloy, or a material capable of doping and dedoping lithium. As a material that can be doped or dedoped with lithium, for example, a carbon material such as a non-graphitizable carbon-based material or a graphite-based material can be used. Specifically, carbon materials such as pyrolytic carbons, cokes, graphites, glassy carbon fibers, organic polymer compound fired bodies, carbon fibers, and activated carbon can be used. Examples of the above cokes include pitch coke, nice coke, petroleum coke, and the like. Further, the above-mentioned organic polymer compound fired body refers to one obtained by firing a phenol resin, a furan resin or the like at an appropriate temperature to carbonize.

In addition to the above-mentioned carbon material, a polymer such as polyacetylene or polypyrrole or an oxide such as SnO ₂ can be used as a material that can be doped or dedoped with lithium. Further, as the lithium alloy, a lithium-aluminum alloy or the like can be used.

Further, as the binder of the above-mentioned negative electrode mixture, a polymer compound having a low reactivity with amino groups contained in the matrix polymer constituting the gel electrolyte described later, specifically, oxidation resistance From the viewpoint of reduction resistance, one or more polymer compounds selected from styrene-butadiene rubber, polyacrylic acid, polyamideimide, and polyether can be mentioned. Further, a copolymer of the above constituents can also be used.

By using a polymer compound having a low reactivity with an amino group as the binder of the negative electrode mixture, the reaction between the amino group contained in the gel electrolyte and the binder can be suppressed. This prevents deterioration of charge / discharge efficiency and cycle characteristics caused by the reaction between the gel electrolyte and the binder.

The gel electrolyte layer 4 is composed of a gel electrolyte containing a plasticizer containing a lithium salt and a matrix polymer that gelates the plasticizer.

As the plasticizer, nonaqueous solvents such as esters, ethers and carbonates may be used alone or in combination of two or more.

As the lithium salt contained in the plasticizer, the lithium salt used in ordinary battery electrolytes can be used. Specifically, for example, LiPF ₆ , LiBF ₄ , L
iAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiN
(SO ₂ CF ₃ ) ₂ , LiC (SO ₂ CF ₃ ) ₃ , Li
Examples thereof include AlCl ₄ and LiSiF _6, and among them, LiPF ₆ and LiBF ₄ are particularly preferable from the viewpoint of oxidation stability.

The concentration for dissolving the lithium salt is 0.1 mol / L to 3.0 m in the plasticizer in the case of gel electrolyte.
It can be used in the range of ol / L. The range is more preferably 0.5 mol / L to 2.0 mol / L.

The matrix polymer that gels such a plasticizer comprises a first monomer having at least two α, β-unsaturated carbonyl groups in the molecule and a secondary amino group in the molecule. It is formed by cross-linking by a Michael reaction with the second monomer having one or more.

First having an α, β-unsaturated carbonyl group
Examples of the monomer include ethers, esters, carbonates, alkyls, perfluorocarbons, nitriles, various diacrylates having a main chain or side chains, and triacrylates, and the like.

As the second monomer having a secondary amino group, various secondary amine compounds having an ether, an ester, a carbonate, an alkyl, a perfluorocarbon, a nitrile or the like in a main chain type or a side chain type are also mentioned. .

Here, it is necessary that the second monomer has a secondary amino group. When the primary amino group is used instead of the secondary amino group, the reactivity is poor and the crosslinking reaction does not proceed and it is difficult to gel the plasticizer. Further, in the case of a tertiary amino group, since there is no reaction hand for the crosslinking reaction, the crosslinking reaction does not occur and the plasticizer cannot be gelled. By using a secondary amino group,
The cross-linking reaction can be favorably progressed and the plasticizer can be gelled.

The number of α, β-unsaturated carbonyl groups in the first monomer and the number of secondary amino groups in the second monomer must be 2 or more. α, β
-When the number of the unsaturated carbonyl group and the secondary amino group is 1, when the first monomer and the second monomer are polymerized, the polymerization proceeds only two-dimensionally, and the matrix polymer is three-dimensionally formed. Cannot have a standard mesh structure. α, β
-By setting the number of unsaturated carbonyl groups and secondary amino groups to be 2 or more, a three-dimensional network structure can be imparted to the matrix polymer, and the stability and mechanical strength of the gel can be enhanced.

In order to maintain the mechanical strength of the gel, the number of functional groups in one molecule of the first monomer and the number of functional groups in one molecule of the second monomer are preferably 5 or more. . Compounds having different skeletons can be used alone or in combination of two or more.

The gel electrolyte layer 4 is obtained by applying a solution prepared by mixing the above-mentioned plasticizer and the monomer constituting the matrix polymer onto the positive electrode active material layer and the negative electrode active material layer, and applying the solution to the positive electrode active material layer. Further, the negative electrode active material layer is impregnated, the solvent is removed, and then the monomers constituting the matrix polymer are polymerized to be solidified. A part of the gel electrolyte seeded on the positive electrode active material layer and the negative electrode active material layer is impregnated in the positive electrode active material layer and the negative electrode active material layer.

The temperature at which the plasticizer is gelled by the matrix polymer is less than 50 ° C. because the higher the temperature, the greater the damage to the battery and the lower the temperature, the smaller the diffusion of these compounds. Is preferred. Specifically, it is more preferable that the temperature is around 25 ° C.

Regarding the ratio of the plasticizer to the matrix polymer, the more the plasticizer is, the higher the ionic conductivity becomes, but the mechanical strength of the gel cannot be maintained. On the contrary, if the amount of the plasticizer is too small, the mechanical strength is high but the ionic conductivity is low. Therefore, 50% by weight of gel electrolyte as a plasticizer
The above range is preferably 95% by weight or less. Further, as the matrix polymer, 3% by weight or more of the gel electrolyte, 50
A range of less than or equal to wt% is preferred.

In the gel electrolyte battery 1 according to the present invention, the first monomer having at least two α, β-unsaturated carbonyl groups and the second monomer having two or more secondary amino groups are used. Since a solid electrolyte containing a polymer compound obtained by polymerizing and cross-linking is used, and a polymer compound having low reactivity with an amino group is used as a binder for the positive electrode and a binder for the negative electrode. The reaction between the amino group contained in the solid electrolyte and the binder is suppressed. As a result, in the gel electrolyte battery 1, deterioration of charge / discharge efficiency and cycle characteristics caused by the reaction between the solid electrolyte and the binder is prevented, and the charge / discharge efficiency and cycle characteristics are excellent.

In the above-described embodiment, the gel electrolyte battery using a gel electrolyte containing a plasticizer as a solid electrolyte is described as an example, but the present invention is not limited to this. However, it is also applicable to a solid electrolyte battery using a solid electrolyte containing no plasticizer. Furthermore, known additives such as a conductive agent can be added to the positive electrode mixture and the negative electrode mixture.

In the above-described embodiment, the case where the strip-shaped positive electrode 2 and the strip-shaped negative electrode 3 are laminated and further wound in the longitudinal direction to form the electrode winding body 6 has been described as an example.
The present invention is not limited to this, and is applicable to the case where the rectangular positive electrode 2 and the rectangular negative electrode 3 are laminated to form an electrode laminated body, or when the electrode laminated body is alternately folded. is there. The gel electrolyte battery 1 according to the present embodiment as described above is not particularly limited in its shape, and may be various sizes such as thin and large. Further, the present invention can be applied to both the primary battery and the secondary battery.

[0038]

[Examples] Next, to confirm the effects of the present invention,
Examples and comparative examples will be described. In the following description, specific numerical values are given as an example, but it goes without saying that the present invention is not limited to this.

<Example 1> First, a negative electrode was prepared as follows. 90 pieces of crushed graphite powder as a negative electrode active material
By weight, 10 parts by weight of polyacrylic acid as a binder was mixed to prepare a negative electrode mixture, which was further dispersed in N-methyl-2-pyrrolidone to form a slurry. Then, this slurry was uniformly applied to a copper foil having a thickness of 15 μm, which is a negative electrode current collector, dried, and compression-molded with a roll press machine to produce a negative electrode.

A positive electrode was prepared as follows.
In order to obtain the positive electrode active material (LiCoO ₂ ), lithium carbonate and cobalt carbonate were mixed at a ratio of 0.5 mol to 1 mol, and the mixture was baked in air at 900 ° C. for 5 hours. Next, 85 parts by weight of the obtained LiCoO ₂ , 5 parts by weight of graphite as a conductive agent, and 10 parts by weight of tetrafluoroethylene as a binder were mixed to prepare and disperse a positive electrode mixture. It was made into a slurry. Then, this slurry was used as a positive electrode current collector with a thickness of 20.
It was evenly applied to a strip-shaped aluminum foil having a thickness of μm, dried, and then compression-molded with a roll press to prepare a positive electrode.

The negative electrode and the positive electrode obtained as described above were brought into close contact with each other through a separator made of a microporous polyethylene film having a thickness of 25 μm, and further wound in the longitudinal direction to obtain an electrode wound body.

Further, 1.3% by weight of polyethyleneimine (Mw = 600) was used as the secondary amine, and poly (ethylene glycol) diacrylate (Mw was used as the acrylate).
w = 258) 3.7% by weight and propylene carbonate 20%
Wt%, 20 wt% of ethylene carbonate, and 50 wt% of diethyl carbonate are mixed in a mixed solvent of 0.1 mmol / dm ³ of caprylic acid as an additive and lithium hexafluorophosphate as an electrolyte salt. 0.5 mol / L
And 0.5 mol / L of lithium tetrafluoroborate were dissolved to prepare a monomer solution.

Then, the above electrode winding body was sealed in an exterior film made of an insulating material, and the above-mentioned monomer solution was injected into the exterior film. Then, the outer peripheral edge portion of the exterior film was sealed, the positive electrode terminal and the negative electrode terminal were sandwiched by the sealing portion of the exterior film, and the electrode winding body was sealed in the exterior film under reduced pressure. Finally, the monomer was crosslinked by leaving it at room temperature for 6 hours. The gel electrolyte battery was completed as described above.

<Examples 2 to 12 and Comparative Examples 1 to 8> The combinations of the binder used in the positive electrode mixture and the binder used in the negative electrode mixture were changed as shown in Table 1. except,
A gel electrolyte battery was produced in the same manner as in Example 1.

Regarding the batteries prepared in Examples 1 to 12 and Comparative Examples 1 to 8, the types of the binder used in the positive electrode mixture and the binder used in the negative electrode mixture are shown in Table 1. Are shown together.

[0046]

[Table 1]

Then, the battery characteristics of the battery manufactured as described above were evaluated.

First, for each battery, 23 ° C., 100 m
The constant-current constant-voltage charging of A was performed up to 4.2 V for 15 hours, and then discharge at 100 mA (5-hour rate discharge) was performed at a final voltage of 2.5 V.

Then, for each battery, 23 ° C., 500
Constant current constant voltage charging of mA is performed up to 4.2 V for 2 hours, and then 500 mA (1 hour rate discharge) is applied and the final voltage is 2.5.
Between V. This charging / discharging was carried out for 500 cycles, and the capacity retention rate at the 500th cycle was calculated when the discharge capacity at the 1st cycle was 100%.

Table 2 shows the evaluation results of the battery characteristics of the batteries of Examples 1 to 12 and Comparative Examples 1 to 8.

[0051]

[Table 2]

As is clear from Table 2, a comparative example in which polyvinylidene fluoride (PVdF) having high reactivity with amine contained in the gel electrolyte was used as a binder for the positive electrode mixture and / or the negative electrode mixture. In the batteries of 1 to Comparative Example 8,
It can be seen that PVdF reacts with the amine contained in the gel electrolyte, which inhibits charge and discharge and causes deterioration of cycle characteristics.

On the other hand, as the polymer compound having a low reactivity with amine, fluorinated ethylene, polyamideimide or polymethyl acrylate is used as the binder of the positive electrode mixture, and
Styrene butadiene rubber (SB
In the batteries of Examples 1 to 12 using R), polyacrylic acid, polyamide-imide, or polyether, since the reaction between the binder and the amine contained in the gel electrolyte does not occur, the charge / discharge efficiency is It can be seen that the deterioration of the cycle characteristics and the cycle characteristics are prevented and the capacity retention rate is high even after 500 cycles.

Further, Examples 1 to 12 and Comparative Examples 1 to 1
As can be seen by comparing Comparative Example 3 and Comparative Examples 5 to 8, the effect of the present invention can be obtained even if the binder having low reactivity with amine as described above is used only in one of the positive electrode and the negative electrode. It can be seen that it is necessary to use a binder having a low reactivity with an amine for both the positive electrode and the negative electrode, which is not obtained.

[0055]

In the solid electrolyte battery of the present invention, α, β-
A solid electrolyte containing a polymer compound obtained by polymerizing and cross-linking a first monomer having at least two unsaturated carbonyl groups and a second monomer having two or more secondary amino groups, and further comprising: Since a polymer compound having low reactivity with an amino group is used as the positive electrode binder and the negative electrode binder, the reaction between the amino group contained in the solid electrolyte and the binder can be suppressed. As a result, the solid electrolyte battery of the present invention is prevented from being deteriorated in charge / discharge efficiency and cycle characteristics caused by the reaction between the solid electrolyte and the binder, and has excellent charge / discharge efficiency and cycle characteristics.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration example of a gel electrolyte battery according to the present embodiment.

FIG. 2 is a cross-sectional view taken along line X ₁ -X ₂ in FIG.

FIG. 3 is a perspective view showing a state in which a positive electrode and a negative electrode are formed into an electrode winding body.

FIG. 4 is a perspective view showing a configuration example of a positive electrode.

FIG. 5 is a perspective view showing a configuration example of a negative electrode.

[Explanation of symbols]

1 gel electrolyte battery, 2 positive electrode, 3 negative electrode, 4
Gel electrolyte layer, 5 separator, 6 electrode winding body, 7 exterior film, 8 positive electrode terminal, 9 negative electrode terminal, 10 resin film

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01M 4/62 H01M 4/62 Z (72) Inventor Masahiro Morooka 6-735 Kitashinagawa, Shinagawa-ku, Tokyo No.Sony Co., Ltd. F-term (reference) 5H029 AJ03 AJ05 AK03 AK05 AK19 AL02 AL06 AL12 AL16 AM00 AM03 AM04 AM05 AM07 AM11 BJ02 BJ14 DJ08 EJ12 EJ14 HJ02 5H050 AA07 AA08 BA18 CA07 CA11 CA29 CB02 CB24 DA23 CB12 DA23 CB12 DA23 EA28 FA05 HA02

Claims (5)

[Claims] 1. A positive electrode having a positive electrode active material dispersed in a binder, a negative electrode having a negative electrode active material dispersed in the binder, and a solid electrolyte interposed between the positive electrode and the negative electrode. And one or more polymer compounds selected from tetrafluoroethylene, polyamideimide, poly (meth) acrylates, or copolymers thereof as a binder for the positive electrode, and a binder for the negative electrode. It contains, as an agent, one or more polymer compounds selected from styrene-butadiene rubber, polyacrylic acid, polyamideimide and polyether, or copolymers thereof, and as the solid electrolyte, α, β-unsaturated in the molecule. It is characterized by containing a polymer compound obtained by polymerizing and crosslinking a first compound having at least two carbonyl groups and a second compound having two or more secondary amino groups in the molecule. Solid electrolyte battery to collect. 2. The solid electrolyte battery according to claim 1, wherein the solid electrolyte contains a swelling solvent and is in a gel form. 3. The solid electrolyte battery according to claim 1, wherein the negative electrode active material contains lithium metal or a material capable of being doped / dedoped with lithium. 4. The solid electrolyte battery according to claim 3, wherein the material capable of being doped or dedoped with lithium is a carbon material. 5. The solid electrolyte battery according to claim 1, wherein the positive electrode active material contains a composite oxide of lithium and a transition metal.