JPH03129603A - solid electrolyte - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to solid electrolytes used in solid electrochemical devices such as solid batteries.

Conventional technology Solid electrolyte batteries (above) whose constituent materials are all solid substances
Compared to batteries using liquid electrolytes that require a certain size
There is no need to worry about liquid leakage or gas generation, and high reliability can be expected.Also, since a container of a certain size is not required, the shape can be chosen arbitrarily. It has many advantages over conventional devices, such as being able to be integrated into the same package as electronic components such as a body.

In this way, solid electrolytes are used instead of liquid electrolytes (＼
Attempts have been made in various fields to solidify the device. For example, if a Li ion conductive solid electrolyte is used as the solid electrolyte,
＼ An example is a solid secondary battery that uses a reversible Ll electrode as an electrode.

Solid electrolytes (most often in powder form) are used either in the form of pellets by pressure molding or as thin films by methods such as vapor deposition. At present, solid electrochemical devices using solid electrolytes are hardly ever put into practical use because they are easily broken and difficult to process, and thinning them by vapor deposition complicates the manufacturing process. Therefore, solid electrochemical devices using polymer complex solid electrolytes with excellent flexibility and processability are being developed. In particular, Li ion conductive polymer complex solid electrolytes with high ionic conductivity (more flexible polymer complex solid electrolytes) are being developed. It is attracting attention in the field of solid-state electrochemical devices where performance is important, such as thin all-solid-state batteries.

As described above, for solid electrochemical devices using solid electrolytes, bonding between solid electrolytes and electrodes has become an important issue.In other words, due to changes in the volume of the electrodes due to electrochemical reactions such as charging and discharging, solid electrolyte This impairs the bonding properties of the electrodes.In the case of devices using the original liquid electrolyte,
Even if a volume change occurred in the electrode, the electrolyte was a liquid, so bonding properties were not impaired.This problem arose because the electrolyte was solid. In this respect, solid electrochemical devices that use soft polymer complex solid electrolytes as solid electrolytes are no exception.Therefore, electrodes and solid electrolytes are bonded together by applying pressure, and in some cases the device is operated under pressure. A method is being taken. However, since the polymer complex solid electrolyte has the drawback of low ionic conductivity, it is necessary to make the solid electrolyte a thin film and shorten the distance between the two electrodes arranged through the solid electrolyte in order to compensate for this drawback. It has become. In this case, when the solid electrolyte is made into a thin film and pressure is applied to bond them, due to problems such as the roughness of the surface of the electrode in contact with the solid electrolyte or the end surface of the electrode, depending on the bonding conditions, the electrodes may become partially short-circuited. 8. In particular, there arises a problem that self-discharge characteristics deteriorate. For this purpose, a structural wire made of an electronic insulating material, such as a woven fabric or non-woven fabric made of an organic or inorganic polymeric material, and a structural material having a granular shape, such as Al2O5, 5i02, etc., are added to the polymer complex solid electrolyte to connect the positive electrode and the negative electrode. act as a spacer for
Efforts are being made to prevent minute short circuits.

Problem to be Solved by the Invention When an electronically insulating material is mixed with a polymer complex solid electrolyte in this way, the electronically insulating material can prevent minute short circuits between the two electrodes.Q By blocking the conductive path of ions, the solid electrolyte This results in a substantial decrease in ionic conductivity. The problem is that the internal resistance of the coupling element increases and the output current decreases.

In view of the above problems, the present invention aims to improve self-discharge characteristics without increasing the internal resistance of the device by using a specific solid electrolyte.

Means for Solving the Problems A Li ion conductive inorganic solid electrolyte is added to the Li ion conductive polymer complex solid electrolyte. Here, Hiro Li ion conductive polymer complex solid electrolyte is polyethylene oxide,
Polyethylene glycol/lz.

A solid electrolyte is used in which Li salt is dissolved in at least one kind of polymeric material selected from polypropylene oxide and polypropylene glyco.As the Li ion conductive inorganic solid electrolyte, LiI or LiI in which high surface area Al2O3 is dispersed is used.

Function: The Li ion conductive inorganic solid electrolyte has approximately the same Li ion conductivity and electronic conductivity as the Li ion conductive polymer complex solid electrolyte. Therefore, by adding a Li ion conductive inorganic solid electrolyte to the Li ion conductive polymer complex solid electrolyte, the inorganic solid electrolyte acts as a spacer between the positive electrode and the negative electrode. Since it is possible to prevent minute short circuits between the two electrodes disposed at the same time, and the electronic insulation properties of the solid electrolyte are not deteriorated, the self-discharge characteristics of the device are improved.

However, compared to the case where an electronically insulating material is mixed with a polymer complex solid electrolyte, the Li ion conductivity of the solid electrolyte can be maintained, and the internal resistance of the element does not increase and a decrease in output current is prevented. I can do it.

As described above, according to the present invention, it is possible to prevent minute short circuits between both poles.
A solid electrolyte can be obtained that makes it possible to easily construct a solid electrochemical device with excellent self-discharge characteristics without reducing output current.

EXAMPLE The following is an explanation using an example in which a solid-state battery is constructed as an example of a solid-state electrochemical device. It can also be applied to applications such as solidifying electric double layer capacitors and electrochromic displays.

(Example 1) LiCFsSOs as a salt for producing a polymer solid electrolyte
The lithium salt represented by and the polymer (CHa-C
H2-0) 500 g of polyethylene oxide (average molecular weight 2X10', hereinafter referred to as PE○) represented by [
LiCF-8ow] / [PE0unit]
800 cc of acetonitrile was added to this mixture and mixed and dissolved in dry nitrogen gas for 20 hours to obtain a solution of polymer complex solid electrolyte. Li as an electrolyte
Add 50 g of I powder and disperse and stir thoroughly to obtain a paste. This was applied onto a smooth substrate using a known doctor blade method, and vacuum dried at 60°C for 24 hours to evaporate the solvent and obtain a thin film of solid electrolyte. The thickness of this solid electrolyte was measured using a spring-type thickness gauge and was 110 μm.
Let this solid electrolyte be A.

As a first comparative example, a solid electrolyte without LiI powder was dried in vacuum at 60°C in the same manner to evaporate the solvent, and a solid electrolyte with a thickness of 110 μm was obtained f:o This solid electrolyte was designated as B. .

As a second comparative example, a solid electrolyte with 50 g of Al2O3 powder added as an electronic insulating material instead of LiI powder was vacuum-dried at 60°C in the same manner to evaporate the solvent, and a thin film of solid electrolyte with a thickness of 110 μm was prepared. Obtain 9 Let this solid electrolyte be C.

The positive electrode of a solid lithium secondary battery using the solid electrolyte obtained in this way is a 50 μm thick titanium foil and sulfur sealed in a quartz tube under vacuum and heated to coat the surface with titanium disulfide. Also, the thickness of the negative electrode is 30μ.
Using a metal lithium thin film vacuum-deposited on a stainless steel bath of 400 m, the negative electrodes of solid electrolytes A and B and C1 were each cut into pieces of 10 cm x 10 cm using a pressure machine, and then pressure-bonded at 3 tons/cm2 using a flat plate press and bonded using nine or more methods. The solid battery was cut into pieces of 1 cm x 1 am using a cutting machine to obtain solid batteries. Let C be the solid state battery.

A cross-sectional view of the structure of the solid battery A in this example is shown in Fig. 1. Figure + 1 is a Li ion-conducting polymer complex solid electrolyte, 2 is a Li ion-conducting inorganic solid electrolyte, 3 is a negative electrode Li, and 4 is a positive electrode Titanium disulfide, 5 is stainless steel breath as a negative electrode current collector, 6 is titanium breath as a positive electrode current collector, 7 is a negative electrode lead, 8 is a positive electrode lead, and 9 is a resin package.

For the output current, measure the external short circuit current and
The measurement temperature was 25°C, and the performance was 80 μA/am” for solid battery A and 80 μA/cm for solid battery B, while the performance was 30 μA/cm2 for solid battery C. Therefore, In terms of output current characteristics, solid battery A and solid battery B are superior.Next, we investigated the self-discharge characteristics of each battery.After charging to 2V, we left it at 60℃ for 10 days. Figure 2 shows the self-discharge characteristics of each solid-state battery in the example. For solid battery B, it is 26% fQ, and for solid battery C, it is 98%.
Based on the results of two types of tests, it is clear that the battery with excellent both self-discharge characteristics and output current characteristics is solid battery A. In addition to the above-mentioned polyethylene oxide as the polymer solid electrolyte, for example, polyethylene glycol, A similar effect was obtained when a solid electrolyte in which Li salt was dissolved in at least one kind of polymer material selected from polypropylene oxide and polypropylene glycol was used. CHs)-〇) n-H
500g of polypropylene glycol with an average molecular weight of 1000 (hereinafter referred to as PPG) IQ L
50g of Li1 powder as ion conductive inorganic solid electrolyte
Disperse and stir thoroughly. Furthermore, hexamethylene diisocyanate was added as a crosslinking agent, and this was applied onto a smooth substrate using a known doctor blade method.
React at 0°C for 2 hours, then polish at 60°C for 24 hours. Vacuum dry to obtain a PPG crosslinked product in which LiI is dispersed. It was immersed in an acetonitrile solution of a lithium salt represented by LiC1○4 and then dried [L
iC10i:] / [PP0un it]=0.0
A polymer complex solid electrolyte with a thickness of 110 μm, which is the ratio of 6, was obtained as a first comparative example. A 110 μm polymer complex solid electrolyte E was obtained. As a second comparative example, a solid electrolyte containing 50 g of 5102 powder as an electronic insulating material instead of LiI powder was vacuum-dried at 60° C. to remove the solvent. evaporate,
A thin film of solid electrolyte with a thickness of 110 μm is used as a battery. This solid electrolyte is designated as F.

The solid electrolytes obtained in this way, E and F
, the pressurized negative electrode obtained in Example 1 was heated to 10 C each.
Cut into mX 15 cm solid electrolytes D, E and F
The positive and negative electrodes obtained in Example 1 were arranged, pressure bonded using a roller press, and pressure bonded using nine or more methods.
A solid battery was obtained by cutting it into pieces of 1 cm in size.Here, the solid battery using the solid electrolyte is referred to as E. The solid battery using the solid electrolyte E is designated as F. The solid battery using solid electrolyte F is designated as F.

First, regarding the output current, we investigated the external short-circuit current at 25°C.For the solid-state battery, it was 60μA/cm2.On the other hand, for the solid-state battery E, it was the same at 60μA/cm2, fQ.On the other hand, for the solid-state battery F, it was the same at 60μA/cm2. 28μA/Cm2
Therefore, in terms of output current characteristics, solid-state battery and solid-state battery E were superior.Next, we investigated the self-discharge characteristics of each battery.After charging to 2.2V, we left it at 60℃ for 10 days, and when it stopped, We measured the capacity and found that the capacity retention rate after 10 days was 99% for solid-state batteries, while it was 30% for solid-state batteries.
In addition, for solid battery F, it was 98% or more.From the two types of test results, the solid battery was the one with excellent both self-discharge characteristics and output current characteristics (Example 3). Using 500 g of PEG with an average molecular weight of 2000, as a Li ion conductive inorganic solid electrolyte,
1 LiI in which 25 mo1% of high surface area Al○2 is dispersed
00g Kamaru Furthermore, as a crosslinking agent, 4-methyl-1,3-
Phenyl diisocyanate was added and stirred thoroughly, and the other methods were the same as in Examples 1 and 2.
A PEG crosslinked body in which 3 was dispersed was obtained.L i BF=[L i BF4] / [PE0u
doped L,, L so that n i t] =0.03
A PEG solid electrolyte G with a thickness of 110 μm in which IL-Al2O3 was dispersed was obtained.9 As a first comparative example, a polymer complex solid electrolyte H with a thickness of 110 μm was obtained in the same manner as above except that LiI Al2O3 was not added. As a second comparative example, a solid electrolyte in which 50 g of Si○2 powder was added as an electronic insulating material instead of Lil-Al2O3 powder was vacuum-dried in the same manner at <60°C to evaporate the solvent, and the thickness was A thin film of solid electrolyte with a diameter of 110 μm was obtained. This solid electrolyte is designated as ■.

Solid electrolytes G, H and ■ obtained in this way
, the positive and negative electrodes obtained in Example 1 were each 10 cm thick.
, xlOcm, solid electrolyte G1 and the pressure plate obtained in Example 1 were placed on the negative electrode.
The pieces were pressure-bonded using a flat plate press at 3 ton/cm2 and then pressure-bonded using nine or more methods, and then cut into 1 cm
Cut the solid battery into 1.5 cm pieces to obtain a solid battery. Here, the solid battery using solid electrolyte G is G, the solid battery using solid electrolyte H is H1, the solid battery using solid electrolyte process is ■
First, regarding the output current, we measured the external short circuit current at 25°C, and its viscosity was 72μA/ for solid battery G.
cm2, while for solid battery H it is 74 μA/crn
It is almost the same for 2 and 20 μA for 9-6 solid battery ■.
/cm'' Therefore, in terms of output current characteristics, solid-state batteries G and solid-state batteries H are excellent. As a result of measuring the capacity from time to time, the capacity retention rate after 10 days is solid state battery G
In the case of the solid battery H, it was 100%, while in the case of the solid battery H, it was 35%, and in the case of the solid battery ■, it was 98%. A battery that is excellent in both is the solid battery G.Effects of the Invention According to the present invention, it is possible to prevent minute short circuits between the two electrodes arranged through the solid electrolyte even when pressurized.
Furthermore, a solid electrochemical device with excellent self-discharge characteristics can be easily constructed without reducing the output current of the device.

[Brief explanation of the drawing]

FIG. 1 shows the cross-sectional structure of a battery having a solid electrolyte as a component in one embodiment of the present invention. FIG. 2 shows the self-discharge characteristics of the same embodiment and a comparative example. l...Polymer solid electrolyte, 2...Inorganic solid electrolyte,...
・Negative electrode・Positive winding

Claims (3)

[Claims] (1) A solid electrolyte comprising at least a Li ion conductive polymer complex solid electrolyte and a Li ion conductive inorganic solid electrolyte. (2) The Li ion-conducting polymer complex solid electrolyte is characterized in that Li salt is dissolved in at least one polymeric material selected from polyethylene oxide, polyethylene glycol, polypropylene oxide, and polypropylene glycol. solid electrolyte. (3) The solid electrolyte according to claim 1, wherein the Li ion conductive inorganic solid electrolyte is LiI or LiI in which high surface area Al_2O_3 is dispersed.