JPS6240175A - Secondary battery - Google Patents

Abstract

PURPOSE:To make a secondary cell good in long-period preservation and in high-temperature preservation and operation, by making at least one electrode of an electroconductive polymer having no conjugate double bond in the main chain, and by providing a solid electrolyte. CONSTITUTION:At least one electrode is made of an erlectroconductive polymer having no conjugate double bond in the main chain. A solid electrolyte is provided. The electroconductive polymer has a molecular weight of about 10,000 to 500,000 in general. For example, the polymer is an acenaphthylene polymer having a constituting unit represented by a formula 1. To be concrete, the electroconductive polymer is polyacenaphthylene or the like. A negative electrode is made of a polymer obtained through the radical polymerization of an acenaphthylene compound represented by a formula 2 or through the like. In the formulae 1 and 2, R<1> and R<2> denote hydrogen atoms or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a secondary battery, and more particularly to a solid electrolyte secondary battery using a conductive polymer as an electrode material.

<Conventional technology> Conventionally, non-aqueous electrolyte secondary batteries have used lithium titanate disulfide (L) as a negative electrode made of a light metal such as lithium.
i C, +204 > , Houf, lithium tsunide (Li
Battery systems constructed using non-aqueous electrolytes in which salts such as BF4) are dissolved have been studied.

Furthermore, in recent years, secondary batteries (so-called polymer batteries) using conductive polymers such as polyacetylene as electrode materials have been proposed.

The conductive polymer that serves as the electrode material for this type of secondary battery is
Normally, the conductivity is slight, but it is possible to dope or undope with various dopants 1 to 1, and the conductivity is dramatically increased by doping. Then, the anion-doped conductive polymer compound is used as the positive electrode I.
The conductive raw polymer compound doped with cations is used as the A material and as the negative electrode material, and it is possible to construct a chargeable and dischargeable battery by performing doping and undoping electrochemically and reversibly, for example. A
, G., MaCDiarmids: J.E.
Ielectrochem: Soc, 128165
1 (198t) or JP-A-56-138469
It has been proposed in the monthly bulletin, etc.

On the other hand, many studies have been conducted on batteries using solid electrolytes as non-aqueous electrolytes. These solid electrolyte batteries have the following advantages: they have excellent storage characteristics because they do not leak, they can be used over a wide temperature range, and they do not require a separator, making it easy to make the batteries extremely thin. Currently, various electrode materials are being considered. Among these, among the above-mentioned conductive polymers, those using polyacetylene etc. as electrode materials are disclosed in, for example, JP-A-58-128677.
It has been proposed as disclosed in the No.

<Problems to be solved by the invention> However, polyacetylene and other materials proposed as electrode materials for this type of polymer battery are conductive polymers that have military double bonds in their main chains; It has drawbacks such as being unstable and being oxidized very easily by oxygen in the air, and being susceptible to thermal transformation and thermal decomposition at temperatures above 300'C. For this reason, when manufacturing batteries using this type of polymer, it is important and extremely difficult to control the electrode manufacturing environment, making the electrode manufacturing work complicated.
There are drawbacks such as poor storage stability of the electrode itself. In addition, battery characteristics are easily deteriorated by small amounts of oxygen and water, and are also easily affected by temperature, so when used in polymer batteries using solid electrolytes, there may be difficulties in long-term storage or storage and operation at high temperatures. Currently, the features of solid electrolyte batteries cannot be fully utilized.

<Means for Solving the Problems> The secondary battery of the present invention uses a conductive polymer that does not have a conjugated double bond in its main chain as at least one electrode, and
The gist thereof is to include a solid electrolyte.

The molecular weight of a conductive polymer that does not have a conjugated double bond in its main chain is generally about 10,000 to 500,000,
Examples include 7-cenaphthylene-based polymers having an incidental unit represented by the following formula.

In the formula, R1 and R2 are a hydrogen atom; a halogen atom, such as chlorine, bromine, and iodine; an alkyl group, such as a carbon number of 1 to
6, preferably an alkyl group having 1 to 3 carbon atoms; an alkoxy group, for example, 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms;
3 alkoxy group; aryl group, for example, phenyl group,
1-ruyl group; aryloxy group, e.g. phenoxy group,
Methylphenoxy group: Represents a nitro group or a diano group.

Specifically, for example, polyacenaphthylene.

Polybromoacenaphthylene, polychloroacenaphthylene, polyethylacenaphthylene, polydimethylacenaphthylene, polymethoxyacenaphthylene, polydiphenylacenaphthylene, polyphenoxyacenaphthylene, polyethylacenaphthylene, poly Examples include cyanoacenaphthylene.

The polymer used as the negative electrode in the present invention can be obtained by preparing an acenaphthylene compound represented by the following general formula (2) (wherein R1 and R2 have the same meanings as in general formula (1)) by a known method.
That is, the method of radical polymerization (Chemical abstract rough 1~
Vol. 55, p. 12911 (1961)), Method of cationic polymerization (Kobunshi Kagaku Vol. 15, No. 158.368
Page (1958) ),? How to combine ions' J (Polymer Communication Vol. 25, 108i (19
84) ) etc.

Further, after obtaining a polymer in which R1 and/or R2 are hydrogen in the general formula (1) by the above polymerization method, the side chains of the polymer are prepared by a known method (Journal of Organic Chemistry Vol. 1-148, 2949 pages (198
3) A polymer having a channel unit represented by the general formula (1) in which R and/or R2 has a substituent other than hydrogen can be obtained by carrying out a polymer reaction according to (3)).

In the radical polymerization reaction of the acenaphthylene compound represented by the general formula (2) described above, an ordinary radical polymerization initiator is used as an initiator, preferably benzoyl peroxide, azobisisobutyro Nitrile, ammonium persulfate, potassium persulfate, etc. are used, and the amount of initiator used for the acenaphthylene compound is 1
The molar ratio is preferably 0 to 10<-1>. The reaction is carried out without solvent or with benzene.

The reaction is carried out in an organic solvent such as toluene or heptane, or in an aqueous solvent based on a water-emulsifier system. When a solvent is used, the acenaphthylene compound is preferably used in a concentration range of 1Q-2 to 102 molar. The reaction temperature ranges from 0 to 150°C, preferably from 10 to 100°C. In the cationic polymerization reaction, an ordinary cationic polymerization reaction initiator is used as an initiator, but preferably boron trifluoride etherate, aluminum chloride, aluminum bromide, phosphorus pentafluoride, 1-lifluoromethanesulfonic acid ester etc., and the use of initiator i to the acenaphthylene compound is preferably carried out in a molar ratio of 10@-6 to 10@-1. The reaction involves methylene chloride, carbon tetrachloride, and di(-lomethane).

10-2 to 10 in an organic solvent such as dichloroethane
Preferably, it is carried out within a 2 molar concentration range.

The reaction temperature is -78 to 100°C, preferably -78 to 50°C.
' It is done in C. In the anionic polymerization reaction, a normal anionic polymerization reaction initiator is used as an initiator, preferably n-butyllithium, 5ec-butyllithium, phenylmagnesium bromide, etc., and the amount of initiator used relative to the acenaphthylene compound is 10-6
The molar ratio is preferably 10-1. The reaction is carried out using an ether solvent, preferably diethyl ether, dibutyl ether, or tetrahydrofuran.

It is preferably carried out in dioxane, diphenyl ether, etc., and the acenaphthylene compound is preferably carried out at a concentration in the range of 10@-2 to 10@2 molar. The reaction temperature is -78~15°C
, preferably Shikuha-78-1o.

It is carried out at ℃.

Conductive polymers that do not have conjugated double bonds in their main chains are more stable in air than polyacetylene and do not oxidize, and do not undergo deterioration due to thermal decomposition even at temperatures above 300'C. There are some features such as:

Although this type of conductive polymer can be used alone as a battery electrode, it is necessary to add thermoplastic resin, conductive materials, etc. to increase mechanical strength and conductivity and improve battery characteristics. It is desirable to do so.

As an example of a battery that uses this type of polymer, the battery reaction at each electrode of a secondary battery that uses this type of polymer for the negative electrode, a metal sulfide for the positive electrode, and a lithium ion conductive solid electrolyte for the electrolyte is as follows. is expressed in

(Charge) (Negative electrode> P + Li+ =:= P (Li) (Discharge) (Discharge) However, P: Conductive polymer M: Metal atom In other words, in this battery system, when discharging, L1+ from the conductive polymer pinged and reacts with metal sulfides,
When charging, the opposite reaction occurs.

Examples of lithium conductive solid electrolytes used in this type of battery system include Li1. Lir-A, e203. Li
3N, LISICON, IJ-) Lamb ion conductive glass (e.g. L; 2S-P2S5-LiI system, etc.), γ1-
L! Lithium ion conductive materials having a 3PO4 type structure (e.g. L14S!04-L13PO4 type etc.), lithium ion conductive polymer electrolytes (e.g. polyethylene oxide LICJ204 type etc.) and additives added thereto etc.

In the above example, a lithium ion conductor is shown as the solid electrolyte, but when using lithium or potassium as the negative electrode active material, a solid electrolyte with sodium ion conductivity or potassium ion conductivity is used, respectively. Just use it.

<Function> Conductive polymers that do not have conjugated double bonds in their main chains and are used as electrodes are stable against oxygen, moisture, and heat, as shown in (e) above, so the characteristics of secondary batteries using solid electrolytes are Improvements can be made.

<Example> In a four-bottle round bottom flask with a capacity of 500 mg, 20.0 CI (0,131 mol) of acenaphthylene and 2. Take Oq, 100 mN of demineralized water, replace the system with nitrogen, and add 6.1111 ammonium perfiA acid.
Add g. While stirring these, the reaction temperature was 90'C.
After being held for 4 hours, the reaction solution was cooled and added to a saturated aqueous solution of sodium sulfate to precipitate the produced polyacenaphthylene. Next, after repeated washing with methanol and water and filtration, the obtained pale yellow solid was
Dissolved in luene, poured into methanol and reprecipitated.
A pale yellow polymer (polyacenaphthylene) of Wb4 L/, 12.9 CI was obtained. When this polymer was subjected to molecular weight measurement by GPC using TE (~rahydrofuran), the average molecular resistance of the polymer was found to be 1.5×105.

Next, n-butyllithium was added to the polyacenaphthylene thus obtained in -n-hexane to dope lithium into the polyacenaphthylene, and after drying, acetylene black ( AB), polytetrafluoroethylene (TFE) as a binder, weight ratio of polyacenaphthylene:AB:TFE=80:10:1
The mixture was mixed to a temperature of 0 and then molded under 110 pressure to form a negative sucrose. In addition, as a solid electrolyte, lithium iodide-alumina (
2:1) system, and as a positive electrode, the mixture ratio is T i 3
2:AB:TFE was mixed in a ratio of 80:10:10.

500mg of the positive electrode, 150mc+ solid electrolyte, and 300mg of the negative electrode made as above, in this order, in two layers mmφ.
After putting the three layers into a mold and pressing the three layers at the same time, the known insulating backing 4, positive electrode can 5, positive electrode current collector 6, negative electrode can 7, and negative electrode current collector 8 were combined, as shown in FIG. of the structure shown,
A battery according to the present invention was manufactured. Further, for comparison, Battery B was produced in exactly the same manner except that polyacetylene was used as the conductive polymer for the negative electrode.

These batteries △ and B were charged at 0.1 mA for 2 hours at an environmental temperature of 80'C, and the final voltage reached 0 at 0.1 mA.
．． When a charge/discharge test was performed in which the batteries were discharged to 5 ■, both batteries A and B showed a charge/discharge efficiency of 70% or more in the first cycle. Therefore, such a series of charge/discharge cycles was repeated to examine cycle changes in charge/discharge capacity efficiency. The results are as shown in FIG. 2, and the battery A of the present invention has 6
Even after 0 cycles, charging and discharging is almost the same as the first cycle @
While the volume efficiency was maintained, battery B showed a deterioration in charge/discharge capacity efficiency after 20 cycles.
At 60 cycles, a significant decrease in performance was observed compared to Battery A.

The reason for this is thought to be that the polymer used in Battery A of the present invention is hardly degraded by trace amounts of oxygen or moisture present in the battery system, and is stable for a long period of time even at high temperatures.

It is clear that similar effects can be obtained even when this invention is applied to a positive electrode.

<Effects of the Invention> The secondary battery of the present invention constructed as described above uses a conductive polymer that does not have a military double bond in its main chain as an electrode material. Since it is stable against water, moisture, and heat, it is suitable as an electrode material for batteries using solid electrolytes, and has the effect of significantly improving the characteristics of this type of solid electrolyte batteries.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the battery structure of an embodiment of the present invention;
FIG. 2 is a graph showing cycle characteristics such as charge/discharge capacity and effectiveness of various batteries. 1... Positive electrode, 2... Solid electrolyte, 3... Negative electrode, 5
...Positive electrode can, 7...Negative electrode can. Patent applicant Mitsubishi Chemical Industries, Ltd. Sanyo Electric Co., Ltd.

Claims (1)

[Claims] 1. A secondary battery comprising at least one electrode made of a conductive polymer that does not have a conjugated double bond in its main chain, and a solid electrolyte.