JPS63298980A - Solid electrolyte battery - Google Patents

Abstract

PURPOSE:To increase reliability by forming a thin lithium nitride layer on the surface, facing a polymer solid electrolyte, of a lithium negative electrode. CONSTITUTION:A lithium nitride layer 1 is formed by exposing the one side of a lithium negative electrode 3 in N2 gas at room temperature before assembly. Paste prepared by dissolving 9 pts. PEO and 1 pt. LiClO4 in acetonitrile AN is applied to the negative electrode 3, and the acetonitrile is removed by vacuum drying to form polymer solid electrolyte layer 2. Paste containing 70 pts. TiS2, 10 pts. AB, 20 pts. LiClO4-PEO complex, and acetonitrile solvent is applied to the layer 2, and acetonitrile is removed by vacuum drying to form a positive electrode 4. A foil made of stainless steel or titanium is placed on the positive electrode 4 to use as a current collector 5. A plastic film 6 is used as insulator between the current collector 5 and a cover 8. A container 7 made of stainless steel or nickel is welded to the cover 8. A positive terminal 10 is connected to the current collector 5 with a lead wire 9 and sealed by hermetic seal. Internal short circuit is prevented and reliability is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is a solid-state electric film! *[Concerning the improvement of batteries, especially secondary batteries using lithium ion conductive polymer solid electrolytes.

BACKGROUND OF THE INVENTION In recent years, research and development efforts have been actively conducted on polymer solid electrolyte batteries using polyethylene oxide (PEO) and polyphonuphozene as electrolyte materials. This battery has the advantage of not leaking, can be easily formed into a stacked structure or flat type, and has a high energy density.

Furthermore, since the solid polymer electrolyte has elasticity, applying tight pressure can improve the adhesion between the electrolyte and the battery case.

Furthermore, it has advantages that inorganic solid electrolytes do not have, such as being flexible. On the other hand, solid polymer electrolytes have the drawbacks of low conductivity, plasticity, and deformation due to external pressure.

Batteries using conventional polymer solid electrolytes, for example, use an electrolyte film formed by the doctor grade method as a cathode active material layer/
[The configuration was such that the solute layer/negative electrode active material layer were laminated in this order.

Here, the polymer solid electrolyte is PEO and Li (JO4 and Li
It is a Li+ conductor made of a complex with 0F3SO3.

The positive electrode is a layer consisting of a mixture of a positive electrode active material such as TiS 2 or V6O13, a conductive agent such as acetylene black, and the above solid polymer electrolyte. Negative electrode is Li or Li-An
? It is made of L1 alloy foil.

The conductivity of solid polymer electrolytes is approximately 1O8-12- at room temperature.
1, and Li is added to an organic solvent such as propylene carbonate.
Conductivity of liquid electrolyte in which 0104 etc. is dissolved: approximately 10
-23-cm'.

Therefore, in polymer solid electrolyte batteries, in order to lower the electrical resistance of the electrolyte layer, it is required that the thickness of the electrolyte layer be made as thin as possible (preferably 30 μm or less).

On the other hand, in solid electrolyte batteries, it is necessary to constantly apply tension to the layered cells in order to maintain good contact between the electrolyte and the electrodes.

However, as mentioned above, solid polymer electrolytes such as PEO have plasticity, and under pressure conditions, ?
I! Even if there is a slight protrusion (protrusion) on the extreme surface, it will deform,
If the electrolyte layer was thin, the insulation would break at the convex portions of the electrode surface, resulting in a short circuit.

For the reasons mentioned above, in conventional polymer solid electrolyte batteries, the thickness of the electrolyte layer must be at least 80 to 100 μm, and the internal resistance is high, making it difficult to operate at room temperature. It was common to operate at high temperatures.

The purpose of the invention was made in view of the above-mentioned conventional problems,
An object of the present invention is to provide a highly reliable solid electrolyte battery that operates at room temperature, has an excellent active material utilization rate, and is free from internal short circuits.

Structure of the Invention In order to achieve the above object, the present invention provides a battery consisting of a positive electrode, a solid polymer electrolyte, and a lithium negative electrode, in which lithium nitride (
This is a solid electrolyte battery characterized by a thin layer of Li5N).

Example Hereinafter, one embodiment of the present invention will be explained.

FIG. 1 is a sectional view of a coin-type solid electrolyte battery of the present invention.

Here, 1 is a layer of lithium nitride, 2 is a polymer solid electrolyte, 3 is a lithium negative electrode, 4 is a positive electrode, 5 is a positive electrode current collector, and 6
1 is a plastic film, 7 is a battery case, 8 is a lid, 9 is a lead wire, and 10 is a positive terminal.

The lithium nitride layer has a thickness of about 10 μm, and one side of the lithium negative electrode before assembly is coated with 100 to 200 pp of moisture #1.
It is produced by contacting the containing N2 gas for 15 to 20 minutes at room temperature. The solid polymer electrolyte is made of a Li0IO4-PEO composite with a thickness of approximately 20 μm, which is obtained by dissolving 5 to 10% Li0JO4 in PKO having a molecular weight of 500,000 to 2,000,000.

The layer of polymer solid electrolyte consists of 9 parts PKo, Li0IO4
Part 1 (A7 Toni)! Created by applying a paste dissolved in JA/(AN) to the lithium nitride-generating surface of the Li negative electrode described above using a doctor blade method, and then removing AN by drying under reduced pressure at 90°C for about 1 hour.
The positive electrode has a thickness of 50 to 200 μm and is made of TiS 2 as well as acetylene black and a Li0104-pgo composite mixture. 'r1s 270 parts, acetylene black (MuB) 1
A paste containing 0 parts of Li0104-PEO complex and 20 parts of Li0104-PEO complex as a solvent was coated on the solid electrolyte or on a flat plate to form a film by the doctor grade method, and then heated at 90°C. The AN is removed by vacuum drying for about 1 hour and laminated onto the solid electrolyte. The positive electrode current collector is made of SUS or Ti foil, and is brought into close contact with the positive electrode by roll pressing. The plastic film is made of polyethylene or other elastic material, and in addition to serving as an insulator between the positive fli current collector and the battery cover, the elasticity of the material itself allows it to maintain V!
Apply pressure to the stack of electrodes and electrolyte.

N3N is made of SUSwNi or the like and is welded to the pot.

The positive electrode terminal is electrically connected to the positive electrode current collector by a lead wire through a hermetic seam M.

Lithium nitride has the highest 4 conductivity (approximately 1"3B-cWV") among the L1+ conductive materials discovered to date.
It is attracting attention as a substance that has 1). The mechanical strength against pressurization is high, but the elasticity is low. In batteries using only Li3N as an electrolyte, it is difficult to maintain good contact with the electrolyte, and there is no flexibility and the shape of a spiral etc. Not suitable for curved cells.

However, in the present invention, a thin layer (5 to 10 μm thick) of lithium nitride is disposed on the surface of the negative electrode lithium facing the electrolyte, so PFO or polyphosphoric acid Li1X'0
4 The thickness of the polymer solid electrolyte made of a composite such as Li0F3SO3 is 10 to 30 μm, which is a fraction of the conventional thickness.
Since there is Li3N even if it is 1/10th of that, the insulation of the electrolyte layer will not be broken and short circuits will not occur, which was the case in the past.Also,
Due to the elasticity of the polymer solid electrolyte, the electrolyte and 1! Good contact between the poles is maintained.

Furthermore, since the thickness of Li3N is extremely thin, it is flexible when layered as a cell, and can be formed into a spiral shape. ~
However, in a battery in which the solid electrolyte is made only of lithium nitride, the active material utilization rate in room temperature discharge is as low as 5 to 10%, and the discharge performance is poor. This is because lithium nitride is inflexible and the contact between the electrolyte and the electrode is poor.

Note that the method for forming the thin layer of Li3N is not limited to the above method.

Effects of the Invention As mentioned above, the present invention can provide a highly reliable solid electrolyte battery that operates at room temperature, has an excellent active material utilization rate, and is free from internal short circuits, so its industrial value is extremely large. be.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a solid electrolyte battery that is an embodiment of the present invention. 1... Lithium nitride layer 2... Polymer solid electrolyte

Claims (1)

[Claims] A solid electrolyte battery consisting of a positive electrode, a solid polymer electrolyte, and a lithium negative electrode, characterized in that a thin layer of lithium nitride (Li_3N) is provided on the surface of the lithium negative electrode facing the solid polymer electrolyte.