JPH05298915A - Electrolyte composite body - Google Patents

Abstract

PURPOSE:To provide an electrolyte composite body suitable for solid electrochemical elemental devices, especially, lithium batteries and provide a solid-electrolyte battery having high processability and productivity, cation transporting ratio near 1, and high energy density. CONSTITUTION:An inorganic solid electrolyte powder containing lithium ion as a main charge carrier is dispersed in a lithium ion conductive polymer in 5-95% volume ratio. Consequently ion conductivity and cation transporting ratio of the resulting solid electrolyte are improved and high processibility and productivity is obtained and it becomes easy to make the solid electrolyte thin and give it with a wide surface area. Furthermore, no electric charge transporting reaction occurs in the interfaces of the solid polymer and the inorganic solid and the drastic decrease of conductivity due to polarization of the interfaces following the reaction does not occur, either. Using the composite body, a primary or a secondary solid electrolyte battery can have a large capacity and charge-discharge cycle properties of it is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolyte composite, and more particularly to an electrolyte composite suitable for a solid-state electrochemical device, particularly a lithium battery.

[0002]

2. Description of the Related Art Conventionally, solid electrolytes for batteries have been made of inorganic materials such as LiI, polymers such as polyethylene oxide containing lithium salt, or composites of inorganic solid electrolyte powder dispersed in an insulating polymer. Came. However, all of these electrolytes have serious problems as battery electrolytes.

The inorganic solid electrolyte needs to be blocked by sintering or the like in order to increase the density, which is a major obstacle in obtaining productivity and uniformity. Furthermore, since the obtained block is hard and brittle, there is a limit to thinning it, and it is difficult to obtain a large current.

The solid polymer electrolyte developed to solve this problem has good mechanical properties and can be made thin, but the selectivity of mobile ions is poor, and the desired cation (eg,

[Outer 1] It

Therefore, attempts have been made to disperse an inorganic solid electrolyte having excellent ion selectivity in an insulating polymer to improve workability and enable thinning. Inorganic solids in an insulator matrix have been tried. Electrolyte powders have very small mutual electrical contact areas and

[Outside 2]

Even if the insulating polymer has a slight electron conductivity, a charge transfer reaction occurs at the interface of the insulating polymer / inorganic solid electrolyte, which may be a great obstacle to ionic conduction.

[0007]

The object of the present invention is to solve the above-mentioned problems of the prior art, to have excellent mechanical properties and processability, a cation transport number close to 1, and a high energy-density solid. An object is to provide an electrolyte composite capable of obtaining a battery.

Therefore, the present inventors have made it possible to disperse the inorganic solid electrolyte powder in the polymer solid electrolyte instead of the conventional insulating polymer, whereby the workability is excellent and the cation transport number is 1 In addition, an electrolyte composite was obtained which was close to that of the polymer matrix and had no hindrance of cation conduction at the polymer matrix or the polymer / inorganic powder interface.

[0009]

That is, according to the present invention, an inorganic solid electrolyte powder whose intended ions are the main charged bodies is added to a polymer solid electrolyte whose similar ions are the main charged bodies in an amount of 5 to 95% by volume. The present invention relates to an electrolyte composite characterized by being dispersed at a rate.

[0010]

DETAILED DESCRIPTION OF THE INVENTION Specific and detailed description will be given to facilitate understanding of the present invention. The composite of the present invention is basically composed of a matrix of polymer solid electrolyte and inorganic solid electrolyte powder dispersed therein.

The dispersion method is not particularly limited, but for example, an acetonitrile solution of a polymer solid electrolyte is prepared, and 5 to 95% by volume of an inorganic solid electrolyte powder is dispersed in this solution, and a doctor blade method is used. After casting on release paper and removing the solvent, the release paper is removed to obtain an electrolyte composite film.

When the volume fraction of this inorganic solid electrolyte is less than 5%, almost no effect on the cation transport number is observed, and when it is more than 95%, the composite becomes brittle and it becomes difficult to process it into a film. The electrolyte composite thus obtained does not have a charge transfer reaction at the polymer / inorganic powder interface because both constituent materials are conductors of the same ion.
It is possible to suppress a decrease in electrical conductivity due to interfacial polarization accompanying this.

The inorganic solid electrolyte used in the present invention is a lithium superionic conductor such as LiTi ₂ (PO ₄ ) containing a metal salt.
₃ , Li ₃ N, Li-β Al ₂ O ₃ , LiI, LiI-Li ₂ S-P ₂ O ₅ , LiI-L
There are i ₂ S-B ₂ S ₃ , Li ₃ N-LiI-LiOH and the like, but inorganic solid electrolyte powders other than these can be used together. As the other solid electrolyte powder, for example, silver ion conductors such as αAgI and AgI-Ag ₂ O-MoO ₃ glass and cation conductors such as sodium ion conductor of Na-βAl ₂ O ₃ are used.

As the solid polymer electrolyte used in the present invention, an amorphous non-crystalline polymer having a known typical material such as PEO (polyethylene oxide) or PPO (polypropylene oxide) in its main chain or side chain is used. Lithium salt of crystalline polymer (the anion of which is, for example, I ⁻ , Br ⁻ , ClO
₄ ^-, SCN ^- or F ₃ CSO ₃ ^- a. ) Is dissolved in the solid electrolyte.

Further, EC (ethylene carbonate) and PC
It is useful that a mixture of (propylene carbonate) is added and the molar ratio of the components is represented by the following general formula (1), which shows a high electric conductivity. [PEOa: [xEC: yPC] b] n: LiX (I) (However, PEO in the formula represents polyethylene oxide, and
Represents ethylene carbonate, PC represents propylene carbonate, a, b, x, y and n are finite and each represents a molar amount, and X is an anion. )

For example, an inorganic solid electrolyte is a lithium salt-added
LiTi ₂ (PO ₄ ) ₃ powder, polymer electrolyte is [PEO: [2EC: 2PC]] ₂₀ Li
When ClO ₄ is used, the starting materials are Li ₂ CO ₃ and Ti.
O ₂ , (NH ₄ ) ₂ · HPO ₄ are mixed, and the mixture is heated at 850 to 950 ° C. for 1 to 4
It is calcined for an hour and crushed in a ball mill for 3-9 hours. After mixing Li3PO4 with this powder and calcining again under the same conditions,
It is pulverized with a rumill for 3 to 9 hours to obtain an inorganic solid electrolyte powder.

This powder was dispersed in [PEO: [2EC: 2PC]] ₂₀ LiClO ₄ polymer electrolyte in an amount of 5 to 95% by volume, and was cast on a release paper in a film form by a doctor blade method or the like. After that, it is dried in a vacuum thermostat or a draft to obtain an intended electrolyte complex.

[0018]

[Outside 3] In addition, there is no charge transfer reaction at the polymer / inorganic solid interface, and therefore there is no significant decrease in conductivity due to interfacial polarization accompanying this reaction.

[0019]

EXAMPLES The present invention will be described below with reference to examples. A solution of polymer solid electrolytes PEO, LiClO ₄ , EC and PC in acetonitrile was prepared so that the composition complies with [PEO: [2EC: 2PC]] ₂₀ LiClO ₄ , and inorganic solid electrolyte Li 3 PO ₄ was added to the solution.
When 50% by volume of LiTi ₂ (PO ₄ ) ₃ powder added with mol% was dispersed, and the solvent was removed after casting on release paper, an electrolyte composite film (thickness 50 to 100 μm) was obtained.

The conductivity of this electrolyte composite at 25 ° C. was 5.5 × 10 ^-4 ohm ^-1 cm ^-1.

[Outside 4] It was.

[PEO: [2EC: 2PC]] ₂₀ L measured for comparison
The conductivity of iClO ₄ polymer electrolyte is 25

[Outside 5] It was. Therefore, the electrolyte composite according to the present invention dramatically improved the ionic transport number.

[0022]

INDUSTRIAL APPLICABILITY The electrolyte composite of the present invention is excellent in ionic conductivity and cation transport number, is excellent in processability and productivity, and can be easily thinned and made large in area. Furthermore, there is no charge transfer reaction at the solid polymer / inorganic solid interface, and there is no significant decrease in conductivity due to interfacial polarization. Therefore, by using this electrolyte composite, it is possible to increase the capacity of the primary or secondary solid electrolyte battery and improve the charge / discharge cycle characteristics.

Claims (3)

[Claims] 1. An electrolyte composite, wherein an inorganic solid electrolyte powder containing lithium ions as a main charged body is dispersed in a lithium ion conductive solid polymer at a volume fraction of 5 to 95%. 2. The inorganic solid electrolyte is LiTi ₂ (PO ₄ ) ₃ , L
i ₃ N, Li-β Al ₂ O ₃ , LiI, LiI-Li ₂ S-P ₂ O ₅ , LiI-Li ₂ S
The electrolyte composite according to claim 1, containing at least one of -B ₂ S ₃ and Li ₃ N-LiI-LiOH. 3. The lithium ion conductive solid polymer having a molar ratio of the following general formula (I): [PEOa: [xEC: yPC] b] n: LiX (I) (where PEO is a poly Represents ethylene oxide, EC represents ethylene carbonate, PC represents propylene carbonate, a, b, x, y and n are finite and each represent a molar amount, and X is an anion). The electrolyte composite according to claim 1, which is represented.