JP2934450B2 - Polymer solid electrolyte and secondary battery using the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a solid polymer electrolyte and a secondary battery using the same.

[Prior Art] Conventionally, electrochemical elements such as batteries, capacitors, and sensors use an electrolyte solution, and thus have been problematic in that their reliability is reduced due to liquid leakage and that they are difficult to process during mounting.

In order to solve these problems, studies on solid electrolytes have been activated.

Among solid electrolytes, polymer solid electrolytes have attracted attention because they are lighter and more flexible than inorganic solid electrolytes and are excellent in moldability and processability.

Polyethylene oxide (PE) is used as the polymer solid electrolyte.
O) has been discovered to form a complex with an alkali metal [Polym. 14 , 586 (1973)], and studies have been focused on materials having PEO chains as alkali metal ion conductors. Of about 10 ^-5 S / cm, but it is still not enough.

Regarding application of these polymer solid electrolytes to devices,
For example, MnO ₂ / Li secondary batteries and the like in which lithium causes a redox reaction between positive and negative electrodes by charge and discharge have been studied.

On the other hand, various electrochemical devices have been proposed by utilizing doping and undoping of an anion by oxidation and reduction of a conductive polymer.

[Problems to be Solved by the Invention] However, when the present inventors applied a polyether-based solid electrolyte to an element using a conductive polymer as an electrode active material,
Anion doping and undoping hardly occurred, and good device characteristics could not be obtained.

The present invention has been made in view of the above circumstances, and has as its object to provide a polymer solid electrolyte having a high ionic conductivity. Further, the present invention provides a polymer solid electrolyte and a conductive or semiconductive polymer material which is an active material. It is an object of the present invention to provide a secondary battery in which an anion in an electrolyte is easily moved and anion injection (doping) and elution (de-doping) are rapidly performed by a redox reaction of an electrode. Is what you do.

Means for Solving the Problems The inventors of the present invention have been studying in order to solve the above-mentioned problems, and as a result, as a polymer matrix constituting a polymer solid electrolyte, a specific selected high polymer is used. The inventors have found that a combination of molecules is effective, and have reached the present invention.

That is, the present invention provides (1) a polymer solid electrolyte comprising at least a polymer matrix and an electrolyte salt, wherein the polymer matrix comprises (A) a polymer comprising a polyether chain and (B) a carbonate-based polymer as main components. And (2) a secondary battery using a conductive or semiconductive polymer material as an active material and using the polymer solid electrolyte described in (1) above as an electrolyte.

 Hereinafter, the present invention will be described in detail.

The solid polymer electrolyte of the present invention comprises at least a polymer serving as a matrix and an electrolyte salt serving as a carrier. Ionic conduction is achieved by the electrolyte salt solvated into the polymer matrix dissociating and diffusing through the matrix along the electric field.

The polymer matrix used in the present invention is mainly composed of a polymer comprising a polyether chain and a carbonate-based polymer.

Polyether polymers are known as alkali metal ion conductors. However, the behavior of anions has not yet been clarified despite studies of the measurement of transport numbers and the like.

In order to further improve the ionic conductivity of the polymer solid electrolyte, and to promote the ingress and egress of anions into and from the conductive polymer, the present inventors need to improve the ionic conductivity of the solid electrolyte only. Therefore, it was considered necessary to select a system in which anion transfer easily occurred.

That is, the above conditions could be satisfied by the solid electrolyte mainly composed of the polymer composed of the polyether chain and the carbonate-based polymer.

Examples of the polyether polymer include polyethylene oxide (PEO) and polypropylene oxide (PPO).

Ionic conductivity in the amorphous state is higher for PEO. However, since the PEO is crystallized near room temperature, the ionic conductivity decreases. To suppress crystallization of PEO and maintain high ionic conductivity, PEO is an amorphous polymer, PPO
Is preferably copolymerized. The copolymerization may be random copolymerization or block copolymerization. The copolymer structure preferably has a minimum amount of PPO necessary for maintaining the PEO in an amorphous state. That is, EO / PO = 30/1 to 8/5 is good.

In a device in which the reaction of the electrode is a doping, undoping, intercalation, or deintercalation reaction, the concentration of the electrolyte salt near the electrode changes during the reaction. For this reason, a polymer matrix having a small salt concentration dependence of ionic conductivity is required. Further, since electrolyte ions are also used in an electrode reaction, an electrolyte capable of maintaining high ion conductivity even at a high concentration is required.

In order to satisfy such a condition, particularly, the EO-PO copolymer is a block type, and every 8 to 30 EO repeating units.
It is preferable to introduce 1 to 5, especially 1 to 8, repeating units of PO. Further, the PEO-PPO block copolymer unit is made of PE
There are three or more O units, that is, [PEOPPO-PEO _X ] (X
≧ 2). Also,
In any case, it is preferable that the terminal of the side chain polyether chain is substituted with an alkoxy group such as a methoxy group or an ethoxy group, except for a chain used for cross-linking described later, to have a structure having no active hydrogen.

As the carbonate-based polymer used in the present invention, aliphatic carbonates and aromatic carbonates are not taken, but the structure in which the carbonate structure is introduced into the side chain from that forming the polymer main chain, particularly Those having a ring structure are preferred.

 An example is polyvinylene carbonate.

In the present invention, (A) a polymer comprising a polyether chain and (B) a carbonate-based polymer may be copolymerized or used as a mixture. Alternatively, they may be used after being crosslinked after mixing.

Crosslinking may be between polyether chains or between a polyether chain and a carbonate polymer.

The cross-linking site is selected from, but not limited to, a urethane bond, a urea bond, an ester bond, an amide bond, an ether bond, or a bond via a metal or a semimetal. These bonds can be, for example, urethane, urea, ester, and EO-PO copolymer, respectively, by using an isocyanate, an amine, a carboxylic acid or an acid chloride, and an epoxy as a crosslinking agent at the terminal of the EO-PO copolymer.
An ether bond can be formed. Also, by using a silyl halide, alkyl aluminum, etc.,
Bonds can be generated through metals and semi-metals.

As a crosslinking method, a reaction by light irradiation is also used. In the same manner as in the above reaction examples, a photosensitive group is introduced into the terminal of the side chain polyether chain, and a crosslinking reaction is performed. Here, the mixing or copolymerization ratio of (A) the polyether-based polymer and (B) the carbonate-based polymer and / or the lactone-based polymer is such that a carbonate ring or lactone ring unit is 0.5 to 1 oxygen atom in the ether chain. It is preferably set to 2.0.

Examples of the electrolyte salt serving as a carrier of the polymer solid electrolyte include SCN ⁻ , Cl ⁻ , Br ⁻ , I ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , CF ₃ SO ₃ ⁻ , and Sb ^{−
_{F 6 -, AsF 6 -,}} ClO 4 -, B (C 6 H 5) 4 - and an anion such as, L
alkali metal cations such as i ⁺ , Na ⁺ , K ⁺ , (C ₄ H ₉ ) ₄ N ⁺ ,
An electrolyte salt composed of a cation such as an organic cation such as (C ₂ H ₅ ) ⁴ N ⁺ is exemplified.

A solid polymer electrolyte, that is, a composite of a polymer matrix and an electrolyte salt can be prepared by dissolving the polymer matrix and the electrolyte salt in a solvent and casting from the solution. Alternatively, it can be produced by immersing a polymer matrix film in a solution in which a polymer is insoluble, in which an electrolyte salt is dissolved, and allowing the salt to be contained in the film.

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

In the battery of the present invention, the conductive polymer is doped with anions to store energy, and energy is released through an external circuit by undoping. Further, in the battery of the present invention, since the doping and undoping are performed reversibly, the battery can be used as a secondary battery.

The conductive polymer used in the present invention is a conductive or semiconductive polymer obtained by polymerizing pyrrole, thiophene, furan, benzene, azulene, aniline, diphenylbenzine, diphenylamine, triphenylamine or a derivative thereof, and particularly polyaniline. Is preferred.
These polymers form a complex with an anion by oxidation, and the anion is eliminated by reduction.

Examples of ions that form a complex with the conductive polymer include ClO ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , BF ₄ ⁻ , paratoluenesulfonic acid anion, nitrobenzenesulfonic acid anion, and Fe
^{_{(CN) 6 -, CP (}} CN) 6 - complex anion or AlC, such as
Examples thereof include Lewis acids such as l ₃ , FeCl ₃ , and GaCl ₃ .

These conductive polymers are obtained by chemical polymerization or electrolytic polymerization, and either method may be used.

Electropolymerization methods are generally described, for example, in J. Electrochem, Soc., V.
ol. 130, No. 7, 1506-1509 (1983), Electrochem. Acta.,
Vol. 27, No. 1, 61-65 (1982), J. Chem. Soc., Chem. Commu
n., 1199- (1984), etc., a solution prepared by dissolving a monomer and an electrolyte salt in a solvent is placed in a predetermined electrolytic bath, and the electrode is immersed in the electrolytic polymerization reaction by anodic oxidation or cathodic reduction. Can be carried out.

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 the electrolyte and the solvent.

In the present invention, as the dopant of the conductive polymer constituting the device, the same kind as the ion in the polymer solid electrolyte is desirable. Therefore, it is necessary to synthesize a conductive polymer using the same kind of dopant as the ions in the solid electrolyte and use it as it is for the device, or once polymerize it using different types of ions and perform de-doping treatment before assembling the device. Is preferred. Further, it is preferable that the same kind of ions as those in the solid electrolyte are doped after the dedoping treatment and used in the device.

The de-doping treatment includes chemical de-doping and electrochemical de-doping. In the present invention, the polymer film is immersed in an electrolytic solution, and a lower potential is applied to the extent that the film is not broken, thereby performing electrochemical de-doping. The doping treatment is performed by immersing the film in an electrolyte solution containing ions used as dopants and applying a noble potential at which doping starts. In the electrode using electrolytic polymerization, since a conductive polymer is formed on the electrode and then used as it is as a battery electrode, it is better to improve the adhesion between the two. For example, the surface of the electrode can be increased by roughening the electrode by a chemical method or an electrochemical method using a polishing material, a polishing machine, or the like, and the adhesion between the electrode and the conductive polymer can be improved. Improving the adhesion between the electrode and the conductive polymer by providing holes in the electrode by mechanical, chemical or electrochemical methods and integrating the conductive polymer grown from both sides of the electrode through the hole Can be. By these methods, the conductive polymer was hardly detached from the electrode or dropped, and the current collection efficiency was increased.

Examples of the material constituting the electrode include alloys such as metal stainless steel such as Ni, Pt, Au, Al, and Cu; metal oxides such as SnO ₂ and In ₂ O ₃ ; and carbon materials such as plastics such as polyester and polyvinyl chloride. A conductive coating electrode or a composite thereof, which has been deposited or coated thereon, is used.

The electrode is preferably in the form of a sheet and preferably has an area of 1 cm ² or more and a thickness of 5 μm to 300 μm.

As the negative electrode, cation-doped polyacetylene, polythiophene, polyparaphenylene, conductive polymers such as polyphenylenevinylene, polyphenylenexylylene, and metals such as Li, Na, K, Ag, Zn, Al, and Cu are used. Alternatively, a lithium alloy of Li with Al, Mg, Si, Pb, Ga, and In can be used.

FIG. 1 shows an example of the configuration of a secondary battery according to the present invention. 1 is a positive electrode current collector, 2 is a positive electrode active material, 3 is a negative electrode current collector, 4 is a negative electrode active material, 5 is a solid polymer electrolyte, and 6 is an exterior.

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

Example 1 0.15 g of benzoyl peroxide was added to 50 g of vinylene carbonate, degassed, sealed, and reacted at 75 ° C. for 20 hours to obtain polyvinylene carbonate.

10 g of the above polyvinylene carbonate, 5.1 g of dimethoxy polyethylene glycol (MW = 400), and 2.2 g of LiBF ₄ were cast from methyl ethyl ketone to produce a polymer solid electrolyte film. The ionic conductivity of the membrane was measured by a chemical impedance method and is shown in Table 1.

Example 2 10 g of the polyvinyl carbonate synthesized in Example 1 and E
O / PO random copolymer (EO / PO = 6/1, MW = 600) 5.3g and L
Cast 2.2 g of iBF ₄ from methyl ethyl ketone,
A polymer solid electrolyte film was prepared. The ionic conductivity of the membrane was measured by the chemical impedance method,
It was shown to.

Example 3 10 g of polyvinylene carbonate synthesized in Example 1 and E
O / PO block copolymer CH ₃ O ｛(EO) ₁₈ (PO) ₃ ｝ ₂ OC
5.3 g of H ₃ and 2.2 g of LiBF ₄ were cast from methyl ethyl ketone to produce a polymer solid electrolyte film. The ionic conductivity of the membrane was measured by a chemical impedance method and is shown in Table 1.

Example 4 10 g of polyvinylene carbonate synthesized in Example 1 and 5 g of a trifunctional polyether shown below, CH ₂ ｛(EO) _18. (PO) ₃ ｝ ₂ EOOH CH ｛(EO) _18. (PO) ₃ ｝ ₂ EOOH CH ₂ ｛(EO) ₁₈ · (PO) ₃ ｝ ₂ EOOH Tolylene-2,4-diisocyanate 0.165 as a crosslinking agent
g, 0.005 g of dibutyltin dilaurate and 2.2 g of LiBF ₄ were cast from methyl ethyl ketone and heated at 80 ° C. for 10 minutes to produce a crosslinked film. After the membrane was sufficiently dried, the ionic conductivity was measured by a chemical impedance method, and the results are shown in Table 1.

Preparation Example of Polyaniline Positive Electrode Dissolve aniline to 0.5M in 1.5NH ₂ SO ₄ aqueous solution,
Polyaniline was synthesized by potentiostatic polymerization of 7V vs SCE. At this time, a stainless steel foil subjected to a 10 μm blast treatment was used as an electrode for polymerization. Next, electrochemical dedoping was performed in a 0.2 NH ₂ SO ₄ aqueous solution, and the resultant was immersed in a 20% hydrazine methanol solution for 10 minutes. Then, it was electrochemically doped in a 1 M LiBF ₄ solution of propylene carbonate.

Example 5 The polymer solid electrolyte film shown in Example 1 was cast on the above-mentioned polyaniline positive electrode, and then a 50 μm lithium foil was pressed thereon to produce the battery shown in FIG.

The battery was subjected to a charge / discharge test, and the discharge amount was shown in Table-2.

Examples 6, 7, 8 In Example 5, the polymer solid electrolyte film was
In the same manner, the battery shown in FIG. 1 was produced.

The battery was subjected to a charge / discharge test, and the charge capacity was shown in Table-2.

Comparative Example 1 5.0 g of the trifunctional polyether used in Example 4, 0.165 g of tolylene-2,4-diisocyanate, 0.005 g of dibutyltin dilaurate and 2.2 g of LiBF ₄ were cast from methyl ethyl ketone and heated at 80 ° C. for 10 minutes. Thus, a crosslinked film was prepared. After the membrane was sufficiently dried, the ionic conductivity was measured by a chemical impedance method, and the results are shown in Table 1.

Comparative Example 2 The crosslinked film produced in Comparative Example 1 was cast on a polyaniline positive electrode in the same manner as in Example 5 to produce a battery shown in FIG. The battery was subjected to a charge / discharge test, and the discharge capacity was shown in Table-2.

[Effect of the Invention] As described above, according to the configuration of the present invention, a polymer solid electrolyte having high ionic conductivity can be obtained,
Further, doping and undoping are easily performed by using the polymer solid electrolyte, and a secondary battery having a large capacity can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram illustrating the configuration of batteries in Examples and Comparative Examples.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01M 10/36-10/40

Claims (2)

(57) [Claims] 1. A polymer solid electrolyte comprising at least a polymer matrix and an electrolyte salt, wherein the polymer matrix comprises (A) a polymer comprising a polyether chain and (B) a carbonate-based polymer as main components. Characterized polymer solid electrolyte. 2. A secondary battery using a conductive or semiconductive polymer material as an active material and using the polymer solid electrolyte according to claim 1 as an electrolyte.