JPS61163562A - Secondary cell - Google Patents

Abstract

PURPOSE:To assure a high output and an excellent cycle life by employing a conductive high polymer material as a positive electrode and a noncrystalline carbon material as a negative electrode. CONSTITUTION:A material containing a conductive material capable of electrochemically doping an electrolyte negative ion and a noncrystalline carbon material are respectively employed, and furthermore a solution containing a compound dissolved in a nonaqueous solvent is employed, said compound ions, each of which can be doped into said positive and negative electrodes by electrolysis. Moreover, for the carbon material, any of materials can be employed each mainly comprising carbon atoms and having an interval of a graphitized portion in a direction of a C axis being 3.8Angstrom or more. Such arrangement of a secondary cell makes effective a combination of the positive and negative electrodes, whereby a high output can be assured while a cycle life, particularly a life of a cycle of the repetition of charge and discharge at higher capacity of the charge and discharge can be assured without allowing metal to be deposited.

Description

[Detailed Description of the Invention] Color! Yu!艷The present invention uses a conductive polymer material as a positive electrode and a carbon material whose graphitized portion has a plane spacing of 3.8 A or more in the C-axis direction as a negative electrode. The present invention relates to a non-aqueous solvent-based secondary battery that is free from precipitation and has a good cycle life.

BACKGROUND OF THE INVENTION In recent years, it has been revealed that conductive molecular substances such as polyacetylene are used as electrode materials for secondary batteries, and various secondary batteries using these substances have been proposed. These secondary batteries can be broadly classified into the following three types.

(1) A conductive polymer material such as polyacetylene is used for both electrodes.

(2) 1 for Seishin! It uses an electrically conductive molecular substance and uses a lithium electrode as the negative electrode.

(3) A conductive polymer material having a conjugated double bond is used for the positive electrode, and a carbon material containing many graphite rings, preferably graphite, is used for the negative electrode (Japanese Patent Application Laid-Open No. 143280/1983).

These batteries usually use an electrolytic solution containing lithium ions as a dopant in order to reduce the weight and stabilize the secondary battery.

However, the batteries (1) to (3) above each have the following drawbacks.

That is, although the battery (1) has excellent electrode characteristics on the positive electrode side, the negative electrode side doped with lithium is severely degraded, causing a shortened battery life.

In addition, in the battery using lithium for the negative electrode (2), when the 9 electrodes are doped with lithium through repeated charging and discharging,
This method has the disadvantage that dendritic precipitation of lithium occurs on the negative electrode, resulting in a short circuit between the electrodes, resulting in a significant reduction in service life.

Furthermore, (3) a battery using a graphite substance with a high degree of crystallinity for the negative electrode is good when repeated charging and discharging is performed at a low charge/discharge capacity, but a battery with a high charge/discharge capacity of 100 AH/ka or more is good. When charging and discharging are repeated in a place, dendritic precipitation of lithium occurs on graphite.
It has the disadvantage of reducing cycle life.

Go to 11"L The present invention was made in view of the above circumstances, and has a high output.
Moreover, it is an object of the present invention to provide a secondary battery that does not deposit metals such as lithium on the negative electrode and has a good cycle life, especially when repeated charging and discharging at a high charging and discharging capacity.

That is, in order to achieve the above object, the present invention uses a conductive polymer material that can electrochemically and reversibly dope electrolyte anions as a positive electrode, and electrolyte cations are doped electrochemically and reversibly. In a secondary battery, the obtained carbon material is used as a negative electrode, and a solution of a compound capable of producing ions that can be doped into the positive and negative electrodes by electrolysis in a non-aqueous solvent is used as an electrolyte. The carbon material used is one in which the distance between graphite parts in the C-axis direction is 3.8 or more, E.

To explain this point in more detail, in order to solve the above problem, the present inventors used an electrolytic solution containing lithium ions as a dopant, and as a result of intensive studies on various carbon materials with different structures as negative electrodes. Surprisingly, compared to carbon materials obtained by baking nitrogen-containing compounds such as polyacrylonitrile (PAN), carbon materials obtained by baking cellulose materials or phenolic resins do not precipitate lithium and exhibit much better performance. Furthermore, among the carbon raw materials obtained by sintering the same kind of raw materials, lower quality carbon raw materials are free from lithium precipitation compared to graphite carbon materials.
In addition, we found that the charge/discharge capacity and cycle life were large, and exhibited much better performance.As a result of the X1m analysis of the carbon material suitable as the negative electrode material mentioned above, we found that The interplanar spacing is 3.8 Å
We discovered that lithium precipitation does not occur in the above cases.
It has been found that a secondary battery in which a carbon material having a lattice spacing in the C-axis direction of 3.88 or more is used as a negative electrode and a conductive polymer substance is used as a positive electrode has excellent performance as described above.

Furthermore, the present inventors found that among the above carbon materials, organic components,
In other words, when carboxyl groups, water am, hydrogen groups, etc. are small and the hydrogen atom/carbon atomic ratio becomes 0.25 or more, the *m ratio decreases, the overvoltage increases, and the performance as a negative electrode material decreases. Therefore, as a carbon material, the hydrogen atom/carbon atomic ratio is less than 0.25v4 (J [rate 10' S/cn+J
The inventors have discovered that the carbon material (X above) is more desirable and that by using this type of carbon material, a secondary battery with further improved performance can be obtained, leading to the present invention.

The present invention will be explained in more detail below.

11.11.1 Good As described above, the secondary battery according to the present invention uses a conductive polymer substance as a positive electrode, an amorphous carbon material as a negative electrode, and generates ions that can be doped into the positive and negative electrodes respectively by electrolysis. The electrolyte consists of a solution in which a compound capable of oxidation is dissolved in a non-aqueous solvent.

As the carbon material used in the present invention, any material mainly consisting of carbon atoms can be used as long as the graphite portion has a structure in which the spacing in the C-axis direction is 3.88 or more. In this case, there is no particular limitation on the upper limit of the distance between the graphite portions in the C-axis direction.

As such a carbon material, one obtained by firing a cellulose material or a phenol resin at a temperature below 1200° C. can be particularly preferably used.

In this case, the upper limit of the firing temperature is more preferably 1000°C.
The lower limit is preferably higher than 500°C.

Further, the carbon material used in the present invention preferably has a hydrogen atom/carbon atom ratio of less than 0.25, particularly less than 0.15. Moreover, it is preferable that the lower limit is 0.01. Furthermore, the carbon material preferably has an electrical conductivity of 10'S/am or more.

There is no particular restriction on the form of the carbon material used as the negative electrode, and it can be used in various forms, such as m-thread, cloth, nonwoven fabric, film, plate, and powder. Specifically, carbon fiber, carbon cloth, carbon nonwoven fabric, carbon vapor, carbon foil, carbon foam, carbon powder, etc. can be used.

Next, examples of >s-conductive polymeric substances used in the positive electrode include polyaniline, polythenylene, polyfuran, polypyrrole, polyphenylene sulfide, and polyphenylene oxide, among which polyaniline is most preferably used.

Note that these conductive polymer substances can be obtained by electrochemical methods, for example, by electrolytically synthesizing these conductive polymer substances directly on the electrode using a metal or carbon molded body, and then It can be used as is for positive electrode binding, and by adopting such a method, the manufacturing process of the conductive polymer material can be shortened.

The compound that is used in the electrolytic solution constituting this secondary battery and that generates ions that can be doped into the positive and negative electrodes is a compound consisting of a combination of an anion and a cation, and examples of the anion include PF6-. 5tlF6-, AS
Halide anions of group VA elements such as Fs-, 5tlCjs-.

Halide anions of mA group elements such as B F4- , Aj Cj 4-, I-([3-), Br-.

Halogen anions such as CJ-, perchlorate anions such as ClO4-* HFt-, CF350g-.

CN5-. 804-, H8O4-, etc. can be mentioned. Moreover, as a cation, L i +.

Examples include alkali metal ions such as Na'' and K''. Specific examples of compounds having these anions and cations include Li PFe, Li 81) F@, Li As F
s.

Shii CtOa, Li 1. Li Or, Li
Cj.

NaPFs, NaSbFa, NaAsF
s *Na ClO4, l'tla 1. KPFs.

KSb Fe, KAS Fn, KC, 104.

Li BF4, Li AJICj4,
LiHF7.

Examples include, but are not limited to, CNS, KSON, Li 301 CF3, etc.
From the point of view of weight reduction and stabilization of secondary batteries, lithium salts, especially Li ClO4, Li BF4゜Li PFs, Li
1. Li Br , Li C,1, etc. are preferably used.

Incidentally, the compound compound is usually dissolved in a solvent and used in a light state, and in this case, the solvent is not particularly limited, but a relatively polar solvent is preferably used. in particular,
Propylene carbonate, ethylene carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2
-Methyltetrahydrofuran, γ-butyO-lactone, dioxolane, methylene chloride, triethyl phosphate.

Triethyl phosphite, dimethyl sulfate, dimethyl formamide, dimethyl acetamide, dimethyl sulfoxide, dioxane, dimethoxyethane, polyethylene glycol, sulforane.

1 such as dichloroethane, chlorobenzene, nitropenzene! I or a mixture of 2 seconds or more.

The secondary battery of the present invention is usually constructed by interposing an electrolyte between the positive and negative electrodes, but in this case, a separator may be interposed between the positive and negative electrodes to prevent short circuits of current due to contact between the two electrodes. . As the separator, it is possible to use a material that is porous and can allow the electrolyte to pass through or contain it, such as synthetic resin fabrics, textiles, and nets made of polytetrafluoroethylene, polypropylene, polyethylene, and the like.

11 to 11 As explained above, in the secondary battery of the present invention, the positive electrode is formed of a lightning-resistant polymer material, the negative electrode is formed of a carbon material in which the distance between the graphitized portions in the C-axis direction is 3.8 or more, Since the combination of these positive and negative electrodes is effective, two outputs can be achieved, no metal is deposited on the negative electrode, and the cycle life is 1f, especially high charge/discharge I! It has a good cycle DI@ due to repeated charging and discharging while hanging, and is lightweight, so it is suitable for use in a wide variety of applications such as automobiles, airplanes, portable machines, and fully electric vehicles.

Below, in order to evaluate the negative electrode performance (electrochemical storage capacity of lithium) of carbon materials independently of the type II bulky polymer material cathode, we will construct a cell with a carbon material as a working electrode and a lithium fully exposed electrode as a counter electrode. An experimental example is shown in which electrochemical doping and undoping of lithium into an electrode was investigated.

[Experimental Example 11 8 pieces of cellulose m-thread (rayon woven fabric) subjected to non-combustible treatment
Carbon woven fabric obtained by firing at 00°C (C-axis direction spacing 3.95A, hydrogen atom/carbon atomic ratio 0.09) 50 m
is vacuum dried and attached to a nickel mesh East ffi electrode with a stainless steel stapler to form a positive electrode. A battery was constructed using lithium gold FA foil as the negative electrode and a solution of anhydrous lithium perchlorate dissolved in dehydrated propylene carbonate as the electrolyte. In this case, a battery was created by incorporating the positive electrode, negative electrode, and electrolyte into a test tube cell in an argon-substituted glove box.

After the battery was assembled, the voltage between both sides was 3.2■. This battery was operated at 1 mA for 10 hours (200 AI-1 per working electrode)
/ko) Hoi! (doping of lithium to the working electrode), and then charging (doping of lithium from the working electrode) at 11 mA until the terminal voltage reached 1.5 V. This charging and discharging process was repeated 50 times, but no lithium was deposited on the carbon clay. The Coulombic efficiency at this time was 85 to 95%.

[Experiment Example 21 Cellulose II, I (rayon woven fabric) subjected to nonflammable treatment
Gura 7? obtained by firing at 2000℃ Orisaku Ito (C
A battery was prepared in the same manner as in Experimental Example 1, except that the axial spacing was 3.6 and the hydrogen atom/carbon atomic ratio O) was used as the working electrode.

The voltage between the poles of the battery assembled hakama was 3.1v. This battery was operated at 11A for 10 hours (200AH/k per working electrode)
G) Discharge and then terminal voltage 1.5v at same <1mA
I charged it until it was. When this charging and discharging process was repeated five times, lithium precipitation on the graphite woven soil was observed. The coulombic efficiency at this time was 87 to 98%.

[Experimental Example 3J Carbon woven fabric obtained by firing a PAN woven fabric at 800°C (C-axis direction spacing 3.5 A1 hydrogen atoms 7' carbon atomic ratio 0
) was used as the working electrode, but the same battery as in Experimental Example 1 was prepared.

The voltage between the two poles after battery assembly was 3.3V. This battery was operated at 1 wA for 10 hours (200 A H per working electrode).
/ka) and then charged at the same voltage of 1111/1 until the terminal voltage reached 1.5V. When this charging and discharging process was repeated eight times, lithium was observed to be deposited on the carbon woven fabric. The coulomb efficiency at this time is 90~
It was 95%.

[Experimental Example 4] A carbon woven fabric obtained by firing the phenol resin side part at 800°C (C-axis direction face-to-face M3.95A).

Hydrogen atom/carbon atomic ratio 0.08, electrical conductivity 3.48/C
A battery similar to that in Experimental Example 1 was prepared except that 1l) was used as the working electrode.

The voltage between the poles during battery assembly was 3.2v. This battery was operated at 1111A for 1m at 10 hours (200m per working electrode)
The battery was discharged (A H/kg), and then charged in the same manner until the terminal voltage reached 1.5μ. This charging and discharging process was repeated 50 times, but no precipitation of lithium was observed on the carbon woven fabric. The coulombic efficiency at this time was 85 to 98% throughout.

[Experimental Example 5j Phenolic Resin I! A battery was made in the same manner as in Experimental Example 1, except that a graphite silk cloth obtained by firing the lI cloth at 2000°C (c-axis direction spacing 3.55, hydrogen atom/carbon atomic ratio 0) was used as the working electrode. .

The voltage between the two poles after battery assembly was 3.15V.

1ml of this battery is 200A per 101011I working electrode.
H/lcc+) was discharged, and then charged at the same 11 IA until the terminal voltage reached 1.5 V. When this charging and discharging process was repeated five times, lithium was observed to be deposited on the graphite woven fabric. Coulomb 9 at this time! h band is 8
It was 8-98%.

EXAMPLES Hereinafter, the present invention will be specifically explained by showing examples and comparative examples, but the present invention is not limited to the following examples.

[Example 1] A perchloric acid aqueous solution containing aniline was used as a solution, and a platinum plate (2×21) was immersed therein as a working electrode and a counter electrode, and polyaniline was synthesized by low potential electrolysis. The obtained polyaniline (weight 6.4 Kl) was thoroughly washed with distilled water and then vacuum dried.

Next, while using this polyaniline as a positive electrode,
Carbon I miscellaneous (C-axis direction spacing 3.9
5A, a hydrogen atom/carbon atom ratio of 0.09>2.7 wa, and a solution of anhydrous lithium perchlorate dissolved in dehydrated propylene carbonate at 11111 mol/J as the electrolyte. In this case, a battery was constructed by incorporating the positive electrode, negative electrode, and electrolyte into a test IR type cell in an argon a-filled glove box.

The voltage between the two poles after battery assembly was 0.5V,
When charging with a constant current of 50 μA, the voltage between the two poles immediately increases to 2.
The voltage rose to 0.2 V, and as charging continued, the voltage gradually increased and when it reached 3.8 V, charging was terminated. The time required for charging at this time was 12.5 hours. That is, the charging capacity is 98 AH/kG per polyaniline, 233 AH/kG per carbon, and 70 AH/k per pole.
Corresponds to a. Next, the terminal voltage is 2 at the same 50 μA.
．． Discharge was performed until the voltage reached OV (average released ltI voltage 3.2V).

This charging and discharging process was repeated 50 times, but no precipitation of lithium on the carbon grains was observed.

The coulombic efficiency at this time was 86%.

[Comparative Example 1 7.0m of polyaniline synthesized in the same manner as in Example was used as the positive electrode, and 200m of rayon 1III subjected to nonflammable treatment was used as the positive electrode.
w121! Same as in Example except that graphite fiber M obtained by firing at 0°C (c-axis direction spacing 3.68, hydrogen atom/carbon atomic ratio O) was used as the negative electrode! ! It was created.

The voltage between the poles of the assembled battery was 0.6V. This 11F#1 was charged for 13.5 hours at a constant current of 50 μA (97 AH/9 per polyaniline, 233 AH/ka per graphite, 69 AH/kg per pole), and then the terminal voltage was -2 at the same 50 μA). Discharge was performed until the voltage reached OV (average discharge rate 3.2V). When this charging and discharging process was repeated five times, lithium precipitation was observed on the graphite fibers. The coulomb efficiency at this time is 86
%Met.

Applicant Brideston Co., Ltd. Agent Patent Attorney Takashi Kojima Procedural amendment (voluntary) September 12, 1985 1) Indication of the case 1985 Patent Application No. 3084 2) Name of the invention Secondary battery 3) Amendment Relationship with the case involving the applicant Patent applicant address: 10-1 Kyobashi-chome, Chuo-ku, Tokyo
Name (527) Representative of Brideston Co., Ltd.
House: 1924) Agent: 104 Address: 5th floor, Dapa Create Building, 3-11-14 Ginza, Chuo-ku, Tokyo Telephone: (545) 6454 "Detailed Description of the Invention" section of the specification.

6. In the 8th line of page 12 of the specification of amendments, next to ``indicates,'' [In this experiment, the interplane distance was determined by It was determined directly from 2θ which gives the value. ” is inserted.

that's all

Claims (1)

[Claims] 1) A positive electrode containing a conductive polymer substance that can electrochemically and reversibly dope the anions of the electrolyte, and a graphitization that can electrochemically and reversibly dope the cations of the electrolyte. A negative electrode containing a carbon material whose portions have a plane spacing in the C-axis direction of 3.8 Å or more, and a compound capable of generating ions that can be doped into the positive electrode and negative electrode by electrolysis, respectively, is dissolved in a non-aqueous solvent. A secondary battery characterized by using a solution as an electrolyte. 2) The carbon material is cellulose material or phenolic resin.
The secondary battery according to claim 1, which is obtained by firing at a temperature below 200°C. 3) The secondary battery according to claim 1 or 2, wherein the carbon material has a hydrogen atom/carbon atomic ratio of less than 0.25. 4) The secondary battery according to any one of claims 1 to 3, wherein the carbon material has an electrical conductivity of 10^-^4/cm or more. 5) The secondary battery according to any one of claims 1 to 4, wherein the conductive polymer material is polyaniline.