JPH01319268A - Secondary battery - Google Patents

Abstract

PURPOSE:To keep energy density of a secondary battery by employing high molecular solid electrolyte composed by combining predetermined electrolyte solt in high density. CONSTITUTION:Electrolyte solt composing high molecular solid electrolyte includes solt composed of anion expressed by BR (R is alkyl, phenyl and halogen) whose lattice energy is less than 750KJ/mol and cation which forms a pair with the anion. The solt density is 0.04 or more than that per 1 unit of ion dissociation group. By employing the solt composed of the anion expressed by BR4 as the solt to be dissolved in high molecular solid electrolyte, a secondary battery is obtained, which has excellent characteristics of repeating doping and dedoping and is capable of keeping high energy density even by repeating charging/discharging.

Description

[Detailed description of the invention] [Technical field] The present invention relates to a secondary battery.

[Prior Art] An organic polymer compound having a conjugated double bond can be electrochemically doped with an anion such as ClO4-, BR4-, PF6-1^S dolo'' or a cation such as L11 ammonium, It is known that it becomes a p-type or n-type conductive polymer, [J, CJ, Chem
, Coma, (1979) P594-595], various electrochemical functional devices using these polymer compounds have been studied.

In particular, the development of batteries using conductive polymers as electrode active materials is progressing. Batteries using these conductive polymers as electrodes utilize a reaction in which ions in the electrolyte dope and undope the electrodes, so battery characteristics vary greatly depending on the type and concentration of the electrolyte salt.

Regarding the electrolyte concentration, for example, JP-A-62-195861
In the issue, the salt concentration of the electrolyte is 1 mol/I ~ [1 mol/I]
1 has been proposed to improve the cycling characteristics of polymer batteries. However, since the electrolytic solution of the above-mentioned battery is a liquid, this electrolytic solution is used in a state in which it is impregnated into a separator or the like disposed between the two electrodes.

Generally, the positive electrode, negative electrode, and separator are in contact simply by external pressure, so when creating a thin battery, especially a wide-area thin battery, it is difficult to maintain uniform contact between the electrode and the separator, especially during charging and discharging. As the process is repeated, a gap is formed between the electrode and the separator, which tends to cause some areas to lack electrolyte. Therefore, it has been difficult to obtain a battery that can stably maintain a high energy density.

[Objective] An object of the present invention is to provide a secondary battery that does not have these drawbacks and can maintain a high energy density even after repeated charging and discharging.

[Structure] The present inventors have conventionally developed a battery that can be made thinner in place of the electrolyte and separator in order to improve the thickness of the battery and to improve the partial lack of electrolyte inside the battery, which has excellent adhesion to the electrodes. As a result of various studies on all-solid polymer batteries using polymer electrolytes, we have found that the energy density of secondary batteries can be maintained at a high level by using a polymer solid electrolyte that is a complex of specific electrolyte salts at high concentrations. This discovery led to the present invention.

That is, the present invention provides a secondary battery comprising a solid polymer electrolyte and an electrode in which at least one of the electrodes uses a conductive polymer as an active material, in which the electrolyte salt constituting the solid polymer electrolyte is
BR4- with lattice energy of 750 kJ/mol or less
Contains a salt formed from an anion represented by (R represents alkyl, phenyl, halogen) and its counter cation, the salt concentration is per unit of ion dissociative group of the electrolyte,
The secondary battery is characterized in that the number of cells is 0.04 or more.

In batteries using conductive polymers as electrodes, doping and dedoping occur during charging and discharging, and ions in the electrolyte act not only as carriers for the electrolyte but also as dopants for the electrode. Therefore, the electrolyte of the battery is
Good battery characteristics cannot be obtained even if the composition is selected by considering only the composition that gives the maximum ionic conductivity. The conductivity of a conductive polymer increases as the amount of dopant increases. Therefore, in order to maintain high energy capacity, it is necessary to use anions that can be easily doped and undoped, and to always use a high concentration of dopant. A supplyable salt concentration is required. We have found an electrolyte composition that fully satisfies the above conditions.

In solid secondary batteries using conductive polymer electrodes, we used the formula BR4-
It has been found that when a salt consisting of an anion formed by (R-alkyl group, phenyl group, halogen) is used, the repeatability of doping and dedoping is excellent.

Since the dissociation properties of electrolyte salts vary greatly depending on the type of salt,
If the type of cation is changed, the carrier ion concentration will not be the same even if the salt concentration is the same, and the ionic conductivity will be different. In other words, BR4- maintains the ionic conductivity of the polymer solid electrolyte high in combinations where the lattice energy is 750 kJ/sol or less when forming a salt with a cation, and also reduces the dependence of ionic conductivity on salt concentration. I found out that it does.

In batteries using conductive polymer electrodes, doping and dedoping reactions cause local differences in salt concentration at the interface between the electrode and electrolyte. In particular, this phenomenon is considered to be significant in solid polymer electrolytes because the movement of ions is slower than in ordinary electrolytes.

In order to obtain stable battery characteristics, an electrolyte whose ionic conductivity is less dependent on salt concentration is desirable.

The present inventors believe that in order to obtain a battery with high energy density and excellent charge/discharge characteristics, as a combination of electrolyte salts,
We have found that a salt with an anion of BR4'' and a cation of BR4- has a lattice energy of 750 kJ/++ol or less, but it has also been found that the salt concentration of the electrolyte has a large effect on the energy capacity of the battery. I found it. That is, the electrolyte salt concentration at which a high concentration of dopant could always be supplied to the conductive polymer electrode was 0.04 or more per unit of ion dissociative groups of the polymer.

Further, even in elements such as chromic elements, when the salt concentration was lower than the above range, the response speed when the film thickness was increased was very low.

The present invention will be explained in detail below.

The polymer solid electrolyte used in the present invention, that is, the ion-conducting polymer, is composed of at least a polymer serving as a matrix and an electrolyte salt serving as a carrier. Ionic conduction occurs when an electrolyte solvated into a polymer matrix
This is achieved by dissociation and diffusion movement along the electric field in the matrix.

Polymer solid electrolytes can be classified into two-component systems consisting only of a polymer matrix and an electrolyte salt, and three-component systems in which a third component having a high boiling point is added to these systems. Examples of the former polymer matrix include polymers having 2 R2 (R+, R2 is polyalkylene oxide or polyethylene ysine) in the main chain or side chain. Further, it may be a block or random copolymerization product or a crosslinked product of these repeating units. In the present invention, among these two-component solid electrolytes, particularly when crosslinked polyalkylene oxide was used, good characteristics were obtained.

Examples of the polymer matrix of the three-component solid electrolyte include polyacrylonitrile, polyvinylidene fluoride, and the like, in addition to the above-mentioned polymers. Compounds with high boiling points and high dielectric constants to be added to these polymers include polyethylene glycol, monomethoxypolyethylene glycol, dimethoxypolyethylene glycol, polypropylene glycol, propylene carbonate, ethylene carbonate, dimethylformamide, dimethylacetamide, etc. By adding these compounds, the ionic conductivity was significantly increased.

As the anion of the electrolyte salt serving as a carrier, - Formula B
Ions formed by R4- (R+ alkyl group, phenyl group, halogen), such as BF2-1B(Ph) 4-
etc. When forming a salt with these anions, the cations that give the salt a lattice energy of 750 kJ/mol include alkali metal cations, Ll+, K+, N
Examples include a+.

To create a polymer solid electrolyte, that is, a composite of a polymer matrix and an electrolyte salt, a polymer matrix film is immersed in a polymer-insoluble solution in which an electrolyte is dissolved; Examples include a method in which an electrolyte salt is composited at the same time as a film is formed by a casting method from a dissolved solution.

The conductive polymers used in the present invention include pyrrole, thiophene, furan, benzene, azulene, aniline, diphenylbenzine, diphenylamine, triphenylamine, and conductive or semiconductive polymers obtained by polymerizing derivatives thereof. These polymers form a complex with an electrolyte anion at the same time as they are polymerized, and the anion moves in and out as a result of redox reactions.Polymers that form complexes with cations include polythiophene, polyphenylene, polyphenylene vinylene, polyphenylene xylylene, etc. can give.

Examples of ions that form complexes with conductive polymers include ClO4-, PF6'', ASF&-1BF4-
, paratoluenesulfonate anion, nitrobenzenesulfonate anion, Fe(CN)i-1CP(CN)S
complex anions such as - or AlCl3,) ccI
3, Lewis acids such as GaCl3, and the like.

In the present invention, the dopant for the conductive polymer constituting the device is preferably the same type of ion as the ion in the solid polymer electrolyte. Therefore, a conductive polymer can be synthesized using the same type of dopant as the ions in the solid electrolyte and used as it is in a device, or it can be polymerized first using a different type of ion and subjected to dedoping treatment before being assembled into a device. is preferable. Further, it is preferable to dope the solid electrolyte with ions of the same type as the ions in the solid electrolyte after dedoping treatment and use the same type of ions in the device.

Dedoping treatment includes chemical dedoping and electrochemical dedoping, and in the present invention, electrochemical dedoping is performed by immersing the polymer membrane in an electrolytic solution and applying a more base potential within a range that does not destroy the membrane. Further, doping treatment is performed by immersing the membrane in an electrolyte solution containing ions used as dopants, and applying a sufficient potential to initiate doping.

These conductive polymers can be obtained by chemical polymerization or electrolytic polymerization, and in particular, according to the electrolytic polymerization method, the conductive polymer is deposited in the form of a film on an electrode for electrolysis, so that it can serve as a current collector for electrolysis. The electrode on which the conductive polymer is deposited can be used as it is as a battery electrode, which is preferable.

Electrolytic polymerization methods are generally described, for example, in J. EIecLroches, Soc., Vol. 13.
0. No. 7, 1508-1509 (1983), E
! electrochem, AcLa,, Vol. 27
, No. 1.81-85 (1982), J. Chem.
Soc,, Ches, Comllun,, 1199 ~
(!H4) etc., a solution in which a monomer and an electrolyte salt are dissolved in a solvent is placed in a designated electrolytic bath, electrodes are immersed, and an electrolytic polymerization reaction is caused by anodic oxidation or cathodic reduction. This can be done by:

Furthermore, it is also possible to obtain a composite of a solid electrolyte and a conductive polymer by performing electrolytic polymerization in a solid electrolyte instead of an electrolyte and a solvent. Since the electrode used for electrolytic polymerization is used as a battery electrode after forming a conductive polymer on the electrode, it is better to improve the adhesion between the two.

For example, the surface of the electrode can be roughened by a mechanical method using an abrasive, a polisher, etc., or by a chemical or electrochemical method to increase the surface area and improve the adhesion between the electrode and the conductive polymer. Furthermore, holes are formed in the electrode by mechanical, chemical, or electrochemical methods, and the conductive polymer that has grown from both sides of the electrode is integrated through the hole, thereby improving the adhesion between the electrode and the conductive polymer. I can do it. With these methods, detachment or loss of the conductive polymer from the electrode is less likely to occur (and the current collection efficiency is increased).

The material constituting the electrode is Nl5Pts Aus A.
Metals such as T, Cu, alloys such as stainless steel, Sn02, I
A conductive coated electrode in which a metal oxide such as n2O3 or a carbon material is vapor-deposited or coated on a plastic such as polyester or polyvinyl chloride, or a composite thereof is used.

The electrode is preferably in the form of a sheet, with an area of 1 cj or more and a thickness of 5 μm to 300 μm.

The battery of the present invention basically comprises a positive electrode, a negative electrode, and a polymer solid electrolyte, and a conductive polymer material is used as the electrode active material for at least one of the electrodes.

In the battery of the present invention, a conductive polymer is doped with anions or cations to store energy, and the energy is released through an external circuit by dedoping. Furthermore, in the battery of the present invention, this doping-dedoping is performed reversibly, so it can be used as a secondary battery.

As a negative electrode, in addition to polyacetylene, polythiophene, and polyparaphenylene that can be doped with cations, conductive polymers such as polyphenylene vinylene and polyphenylene xylylene, LI% Nas K% Ags
Metals such as Zn5AISCu, or Li and AI,
Examples include a lithium alloy with Mg5Sis Pbq Gas In.

An example of the configuration of a secondary battery according to the present invention is shown in FIG.

l is a positive electrode current collector, 2 is a positive electrode active material, 3 is a negative electrode current collector, 4
5 is a negative electrode active material, 5 is a polymer solid electrolyte, and 6 is an exterior packaging.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example of creating a positive electrode 1 A 20 μm nickel sheet (reaction area 3x 3c
m) Nickel was similarly used for the counter electrode, and aniline was polymerized using a constant current of 1IIIAlc-. The amount of current is 3c/c
It was set as d. After thoroughly washing this nickel polyaniline electrode with running water, using nickel as a counter electrode and a saturated sweet tooth electrode (SCE) as a reference electrode in 0.2N sulfuric acid, -0
, 4V vs SCE was applied to perform a sufficient dedoping operation. After thorough washing with running water, the reference electrode was heated at 4.4 V against the reference electrode in a 7:3 propylene carbonate/1,2-dimethoxyethane solution containing 3.5 M electrolyte salt.
Doping was performed by applying a potential up to The electrolyte salt used was of the same type as the electrolyte salt in the solid electrolyte constituting the device. This was sufficiently dried to obtain a nickel polyaniline composite electrode.

Positive electrode creation example 2 Same as creation example 1 except that in creation example 1, a 60 μm aluminum sheet was used as the reaction electrode, platinum was used as the counter electrode, SCE was used as the reference electrode, and aniline was polymerized at a potential of 0.8 V vs SCE. operated.

Example 1 A solid polymer electrolyte layer was coated on the nickel-polyaniline composite electrode shown in the positive electrode preparation example by a dipping method. The dipping liquid is polyethylene oxide triol (
PEO)loog, LIBF+8.5g (0.04 ionically dissociable groups per unit) dibutyltin dilaurate 0.08g, tolylene-2,4-diisocyanate (TDI) 8.5g, methyl ethyl ketone (ME)
K) Prepared by dissolving in 100g. Next, the composite electrode coated with the polymer solid electrolyte was heated at 70°C for 5 minutes, and the PEO
After immobilizing it on the electrode as a crosslinked body, (solid electrolyte layer one side approximately 30 μm) Ll-A1 of 60 μm
The alloy was crimped to create a battery as shown in Figure 1, and its charge and discharge characteristics were measured.

Example 2 In place of the dipping liquid in Example 1, 1. Propylene carbonate (PC) 100gl: Liar+ 4.7g
(0.04 per unit of ion-dissolving M group), and 15% polyvinylidene fluoride (PVDP) was added to the knee.
A solution obtained by mixing g and bringing the temperature to 80°C was used.

After allowing the electrode 2 coated with the solution to cool to room temperature (approximately 30 μm thick on one side of the solid electrolyte layer), 80 μm lithium aluminum alloy was bonded to both electrodes to create the battery shown in FIG. 1.
The charge and discharge characteristics were measured.

Example 3 A solid polymer electrolyte layer was coated on the aluminum-polyaniline composite electrode shown in Example 2 of positive electrode production by dipping. Using the same dipping solution as that shown in Example 1, the battery shown in FIG. 1 was prepared in the same manner, and its charge-discharge characteristics were measured.

Example 4 A solid polymer electrolyte layer was coated on the nickel-polyaniline composite electrode shown in Example 1 of positive electrode production by dipping. The dipping solution consists of 100g of PEO, LiB
F421g (0.1 per unit of ionolytic M group
) dibutyltin dilaurate 0.08g% TD18.
It was prepared by dissolving 5g in 100g of NEW. Next, the composite electrode coated with the solid polymer electrolyte was heated at 70°C for 5 minutes to fix PEO as a crosslinker on the electrode, and then 60 μm of Li-Al alloy was crimped onto both sides of the electrode. A battery as shown in Figure 1 was created and its charge/discharge characteristics were measured.

Example 5 A solid polymer electrolyte was coated on the nickel-polyaniline composite electrode shown in Example 1 of positive electrode production by dipping. Dipping solution is PE0100g, LiBF42
5g-dibutyltin dilaurate 0.0Bg, TD
I 8.5g, propylene carbonate (PC) 40g
was prepared by dissolving it in 100 g of MEK. Next, the composite electrode coated with a solid polymer electrolyte was heated at 70°C for 5 minutes.
After fixing the PEO cross-linked material on the electrode with an A of about 30 μs on one side, 60 μm of Ll-A1 alloy was crimped on both sides of the electrode to create a battery as shown in Figure 1, and the charge-discharge characteristics were measured. did.

Example 6 Creating a Positive Electrode On the nickel-polyaniline composite electrode shown in Example 1, a solid polymer polymer was coated by dipping. Dipping solution is PE0100g, Lil)F4
30g (0.1M per unit of ionic dissociative group)
Y), dibutyltin dilaurate 0.06g, T
It was prepared by dissolving 40 g of polyethylene glycol having a DI of 8.5 g and an average molecular weight of 800 in 100 g of 14HK. Next, 7 composite electrodes coated with polymer solid electrolyte were applied.
After heating at 0°C for 5 minutes and fixing it on the electrode as a PEO crosslinked body so that it has a thickness of 30 μm on one side, 6
A battery as shown in FIG. 1 was prepared by pressing a 0 μm Ll-A1 alloy, and its charge/discharge characteristics were measured.

Example 7 A solid polymer electrolyte was coated on the nickel-polyaniline composite electrode shown in Example 1 of positive electrode production by dipping. The dipping solution was PEO], 00g, LiB(P
h) 429g (0.04 pieces per unit of 11 groups of ionic molecules), dibutyltin dilaurate 0.0
6g of TDI and 8.5g of TDI were dissolved in 100g of MEK. Next, the composite electrode coated with the solid polymer electrolyte was heated at 70°C for 5 minutes, and the PEO crosslinked body was fixed on the electrode with a thickness of 30 μm on one side, and then 80 μm of Ll-A1 alloy was applied on both sides of the electrode. A battery as shown in FIG. 1 was prepared by crimping, and its charge/discharge characteristics were measured.

Example 8 A solid polymer electrolyte was coated on the nickel-polyaniline composite electrode shown in Example 1 of positive electrode production by dipping. The dipping solution is PE0100g, LIB(Ph
) 0.1 ion dissociative group per unit that dissolves 441g) , Koni l: Mix 15g of PVDP and make 8
A solution kept at 0°C was used. After applying the existing solution to a thickness of 30 μm on one side and allowing it to cool to room temperature, a 60 μm thick Ll-A1 alloy was bonded to both sides of the electrode to create a battery as shown in Figure 1, and the charge-discharge characteristics were determined. was measured.

Example 9 A solid polymer electrolyte was coated on the nickel-polyaniline composite electrode shown in Example 1 of positive electrode production by dipping. The dipping solution is PIFoloog, I, Ir3
(Ph) 472.5g (Ion solution AIM 1!
= 0.1 pieces per knit), dibutyltin dilaurate 0
．． 0(ig, TDl 8.58 to MEK 100g
It was prepared by dissolving it in Next, the composite electrode coated with the solid polymer electrolyte was heated at 70°C for 5 minutes, and a 1-sided lioμm Ll-A1 alloy was bonded onto the electrode as a PEO crosslinker to create a battery as shown in Figure 1. The charge and discharge characteristics were measured.

Comparative Example 1 In Example 1, the dipping solution was PEOlong,
LIBF44.2g (ion dissociation 2i!i 0.02 pieces per unit) dibutyltin dilaurate 0.0
6g.

A battery was prepared by dissolving TDI&g in MEKloog, and a battery was prepared in the same manner, and the charge/discharge characteristics were measured.

Comparative Example 2 In Example 1, the dipping solution was PEOlongS.
LICIO40.88g (0.04 ion dissociative groups per unit) dibutyl dilaurate o, oag
.

A battery was prepared by dissolving 8.5 g of TDl in 100 g of ME, and a battery was prepared in the same manner, and the charge/discharge characteristics were measured.

Comparative Example 3 In Example 1, the dipping solution was PE0100g,
LiBH42, g (0.04 ionically dissociable groups per unit) dibutyltin dilaurate 0.06 g.

A battery was prepared by dissolving 5 g of TD l 8 in MEKloog, and a battery was prepared in the same manner, and the charge/discharge characteristics were determined by CI.

[Effects] As explained above, the secondary battery according to the present invention has the following effects by selecting the electrolyte and its concentration in the solid polymer electrolyte.
Energy density can be significantly increased.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating the configuration of an example of a secondary battery of the present invention. l... Positive electrode current collector, 2... Positive electrode active material, 3... Negative electrode current collector, 4... Negative electrode active material, 5... Polymer solid electrolyte, 6... Exterior.

Claims (1)

[Claims] In a secondary battery consisting of a polymer solid electrolyte and an electrode in which at least one side uses a conductive polymer as an active material, the electrolyte salt constituting the polymer solid electrolyte has a lattice energy of 75
Contains a salt formed from an anion represented by BR_4^- (R represents alkyl, phenyl, or halogen) and its counter cation, and the salt concentration is 0 kJ/mol or less per unit of ion dissociative group of the electrolyte. .04 or more secondary batteries.