JPH02247979A - All-solid secondary battery and manufacture thereof - Google Patents

Abstract

PURPOSE:To achieve flexibility for this type of battery through its stabilized cycle charge/discharge performance by utilizing a sheet-like material consisting of carbon dispersed over a fibrous base structure as an electricity collector CONSTITUTION:A sheet-like material made up of carbon dispersed over a fibrous skeleton is used to form electricity collectors on both other sides of a component battery 5 having electrode layers on both surfaces of its electrolyte layer 1. The fiber is made of fluorine resin, and carbon consisting of fine carbon black is blended in a ratio is 30 to 80 weight percent ratio. The electrode material is a copper chevrel compound, while the electrolyte is made of a copper ion conductive material, and adhesive agent for the electrodes and electrolyte is made of resin. RbCu4I1.5Cl3.5 is used as the solid electrolyte. It is dissolved in toluene to, for example, 15wt. percent to produce the sheet 1 using a binding agent. Both positive pole sheet 2 and negative pole sheet 3, are, for example, 150mm in thickness and the sheet has the same thickness. Positive and negative sheets are arranged on both sides of the sheet/while sandwiching at in center.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an all-solid-state secondary battery in which the electrolyte is solidified and all constituent materials are solid, and a method for manufacturing the same.

Conventional Technology Until now, there has been a desire to realize all-solid-state secondary batteries using solid electrolytes in anticipation of new functions such as high reliability and thinning of batteries. Recently, in response to these trends, there has been active research into new inorganic or polymer solid electrolyte materials and all-solid-state secondary batteries using these materials. The main application of this battery is for memory backup, etc., and copper-based, silver-based, lithium-based, etc. are being used as solid electrolytes. Furthermore, many materials have been proposed for electrode materials. As a well-known system, the electrolyte is a copper ion conductor, especially RbCu4IIlCI, a system solid electrolyte, and the electrode is a copper Chevrehl compound as an electrode active material and Rb
There is a mixed material of CL1 a I x Cl y based solid electrolyte. In this case, it is known that the electrode material and electrolyte material are processed into, for example, Sea NJe using a binder such as resin.

The normal structure of this all-solid-state secondary battery is, like other batteries that use electrolytes as electrolytes, to have an electrolyte layer at the center, with positive and negative electrodes on both sides of this layer. Furthermore, it is common to arrange current collectors such as metal foil on both outer surfaces.

In this case, the current collector should have strong adhesion with the electrode layer;
In order to prevent the electrolyte in the electrode from deteriorating due to direct contact with metal, it is often used to construct the electrode with a conductive polymer film interposed therebetween.

This is further sealed with a metal laminate, resin, etc. to prevent direct contact with the outside air, and used as a battery. Furthermore, a technique for increasing the battery voltage by stacking this battery structure is also used as necessary.

Problems to be Solved by the Invention Until now, all-solid-state secondary batteries with such a configuration have been found to gradually decrease in discharge capacity when they are repeatedly charged and discharged, depending on the charging and discharging conditions. It was done. When we investigated the cause of this problem, we found that there were various problems with the current collector material.

In other words, due to repeated charging and discharging, partial peeling was observed in the contact between the electrode layer and the current collector layer, abnormalities were observed at the bonding interface compared to the initial stage, and when metal foil was used as the current collector. Corrosion of metal foil is observed.

In addition to the above-mentioned problems, this all-solid-state secondary battery has a very simple battery structure unlike batteries that use other electrolytes, so it is possible to create a thin battery, and it has a new function that allows it to be flexible. is required. For this purpose, the current collector material used must also be highly flexible while maintaining good contact with the electrode layer.

Therefore, the current collector material used in this battery must not only have excellent electrical conductivity, but also (1) strong contact with the electrode layer, (2) electrical conductivity, and (3) high flexibility. etc. are required.

The purpose of the present invention is to stabilize the charging and discharging performance and to make this battery flexible by using a current collector with excellent performance.

Means for Solving the Problems The all-solid-state secondary battery of the present invention has a cell with electrode layers formed on both sides of an electrolyte layer, and carbon dispersed in a fibrous skeleton on both outer surfaces of the unit cell to form a sheet. It is characterized by having a current collector made of a material made of In particular, it is preferable that the fibers be a fluororesin, the carbon be fine carbon black, and the blending ratio of the two be 30 to 80% by weight. In addition, the electrode material is a copper Sheprel compound,
The electrolyte material is a copper ion conductor, especially Rb Cu a I
It is suitable to use an all-solid-state secondary battery in which the x C1, system solid electrolyte and the binder between the electrode and the electrolyte are resin.

The method for manufacturing an all-solid-state secondary battery of the present invention involves kneading fluororesin and fine carbon powder, forming a sheet into a current collector,
It is characterized by directly adhering this to both outer surfaces of a unit cell formed by forming electrode layers on both sides of an electrolyte layer by a hot press method.

Operation The present invention, with the above-described configuration, can stabilize the charging and discharging performance, which has been a problem hitherto, and can also make the battery more flexible.

The current collector of this battery has a structure in which carbon, which has excellent electrical conductivity and is inert to the electrolyte material, is dispersed in a fibrous skeleton such as fluororesin, so that the current collector fibers are used as the electrode layer. This is thought to be due to the fact that the bonded state of the interface does not change even after repeated charging and discharging.

In addition, by employing a sheet having a fibrous skeleton as such a current collector, it is possible to make the battery bendable and flexible.

Already, the current collector of this battery has been constructed from a mixed material of, for example, styrene-butadiene rubber cane polymer and carbon, but these materials do not have a fibrous skeleton, so although carbon is used, it is insufficient. performance cannot be obtained.

According to the method of the present invention, an all-solid-state secondary battery having the above characteristics can be efficiently manufactured.

EXAMPLE Hereinafter, an example of the present invention will be described based on the accompanying drawings.

Copper Chebrel (Cu*
MOsSs) was used, and Rbcu4I was used as an electrolyte.
35 wt% of +, scl*, and s and 5 wt% of styrene-butadiene resin as a binder are dissolved in toluene, the whole is uniformly mixed, and a sheet is prepared by the usual doctor blade method. On the other hand, a sheet for the negative electrode was created with exactly the same configuration as that for the positive electrode.

As a solid electrolyte, Rb Cua I +, se l*
, s, the same binder was dissolved in toluene to a concentration of 15 wt %, the whole was mixed uniformly, and a sheet was also prepared by the doctor blade method. Among these, the electrode sheets were approximately 150 μm thick for both the positive electrode 2 and the negative electrode 3, and the solid electrolyte sheet 1 was similarly 150 μm thick.

Cut these sheets into an appropriate shape and make electrolyte sheet 1.
Centered on both sides of the positive electrode sheet 2. The negative electrode sheet 3 was arranged and pressurized at 180°C and 500 kg/cm''.The unit cell 6, in which the three layers were integrated in this way,
Furthermore, a current collector 4 with a thickness of 80 μm made of a sheet-like material with carbon dispersed in a fibrous skeleton is arranged on both sides.
The material with the fibrous skeleton in this case was polytetrafluoroethylene, which is a typical fluororesin, and the carbon was carbon black. The weight percent of carbon in the sheet was 60%. The figure is a cross-sectional view of the structure of the battery in this state. This battery of the present invention is designated as A.

Next, as a comparative battery, the unit cell was constructed in the same way as before, up to the integration of the three layers of electrode and electrolyte, but only the current collector was changed.

That is, B1 is a battery constructed by press-bonding a sheet made of styrene-butadiene rubber cane polymer and carbon black as a current collector, and the contact surface with the electrode is formed with a conductive polymer film. A battery having a structure in which a copper foil was pressure-bonded to the battery was designated as C.

These A, B, and C batteries are 15mm x 30mm.
After that, the area around the battery was sealed with a metal laminate film composed of a polypropylene sheet and stainless steel foil, and the positive and negative electrode lead terminals were taken out from both stainless steel foils and the battery was subjected to a cycle charge/discharge test.

That is, charging to 0.55 V at 2 mA and discharging to 0.3 V at <2 mA were repeated at room temperature, and the discharge capacity for each cycle was examined. As a result, battery A has 500
It was found that the battery exhibited an almost constant capacity of 2.8 mAh during charging and discharging from the initial stage to 500 cycles, and had extremely stable performance.

On the other hand, in battery B, an initial discharge capacity of 2.7 mAh was obtained, but the performance was significantly degraded to 2.0 mAh after 200 cycles and 0.5 mAh after 1300 cycles. Battery C also had an initial discharge capacity of 2.6mAh, but
2.2mAh in cycles 0.7mA in 1200 cycles
Similar to battery B and battery B, there was a large decrease in performance.

A similar cycle charge/discharge test was also conducted at 70°C. In this case, for both batteries B1 and C, the decline in discharge capacity with each cycle was even more accelerated than in the previous test results at room temperature, whereas battery A showed similarly stable performance even after 500 cycles. Maintained.

From this, a current collector made of a sheet-like material with carbon dispersed in a fibrous skeleton is 1. It has been proven that the adhesive has excellent adhesion stability with the electrode layer and is chemically stable.

Further, these batteries A, B, and C were each subjected to a bending test of 50 times at 90 degrees left and right, and then their charging and discharging performance was examined. Battery A was stable with no change in performance observed before and after the bending test, but battery B1
In C, peeling of the current collector and electrode layer was observed in some cases, and the performance deteriorated significantly.

In addition, the ratio of fluororesin fiber and carbon, which was separately investigated, was 30~
It has been found that 80% by weight is appropriate, and that if it exceeds this range, the stability of charging and discharging deteriorates.

Effects of the Invention Since the all-solid-state secondary battery of the present invention uses a sheet-like material in which carbon is dispersed in a fibrous skeleton as a current collector, the cycle charge/discharge performance is stabilized and the battery becomes flexible. It is possible to realize this.

Further, the method for manufacturing an all-solid-state secondary battery of the present invention can efficiently manufacture a battery having the above-mentioned characteristics.

[Brief explanation of drawings]

The drawing is a cross-sectional view of the configuration of an all-solid-state secondary battery in one embodiment of the present invention. 1... Solid electrolyte sheet, 2... Positive electrode sheet, 3.
...Negative electrode sheet, 4... Current collector, 5... Unit cell. Name of agent: Patent attorney Shigetaka Awano and 1 other person 1-11 Kokutai Saikakuban Kasumi Shito 2-m-positive electrode sheet 3-1 member, tree 2 sheet 4--$Emushitai 5--Ichimoto Electricity beggar

Claims (5)

[Claims] (1) A current collector made of a sheet-like material in which carbon is dispersed in a fibrous skeleton is arranged on both outer surfaces of a cell formed by forming electrode layers on both sides of an electrolyte layer. All-solid-state secondary battery. (2) The fibers are fluororesin and the carbon is fine carbon black, and the blending ratio of the two is 30 to 8.
The all-solid-state secondary battery according to claim 1, which contains 0% by weight of the material. (3) The all-solid-state secondary battery according to claim 1, wherein the electrode material is a copper Chebrel compound, the electrolyte material is a copper ion conductor, and the electrode/electrolyte binder is a resin. (4) The all-solid-state secondary battery according to claim 3, wherein the copper ion conductor is an RbCu_4I_xCl_y solid electrolyte. (5) A hot pressing method in which a fluororesin and fine carbon powder are kneaded and made into a sheet shape, which is then used as a current collector, and this is directly applied to both outer surfaces of a unit cell, which is formed by forming electrode layers on both sides of an electrolyte layer. 1. A method for manufacturing an all-solid-state secondary battery, characterized by adhering the battery.