Solid polymer electrolytes

Details Solid polymer electrolytes Solid polymer electrolytes

1994-02-15

1996-12-03

Hindi, Nabil Z.

Optical: systems and elements

Optical modulator

Light wave temporal modulation

G02F 1153

Patent

active

055813941

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

(1) Field of the Invention
The present invention relates to solid polymer electrolytes processes for producing solid polymer electrolytes and precursors for solid polymer electrolytes. It relates also to electrical devices such as electrochromic devices incorporating such solid polymer electroclytes.
(2) Description of the Related Art
The formulation of polymer electrolytes for use in electrochromic devices is a long-standing problem. Attention has principally been concentrated on the use of polyethylene oxide containing lithium perchlorate as a conductive salt. Propylene carbonate has been used as a solvent in combination with polyethylene oxide.
Japanese Patent Specification No. 60037530 discloses a polymer electrolyte comprising polymethylmethacrylate, propylene carbonate and lithium perchlorate. The contents of polymethylmethacrylate is such that the electrolyte is gelatinous, having a consistency such that it is capable of being injected into an electrochromic cell.
Japanese Patent Specification No. 55-86070 discloses a battery electrolyte comprising polymethylmethacrylate, propylene carbonate and lithium fluoroborate in the form of a gel possessing elasticity produced by cooling a sol formed from the above materials. Battery electrolytes are not generally suitable for use in electrochromic devices and such suitability is not indicated in this specification. No conductivity figures are disclosed, nor are any fabrication methods which would lend themselves to the production of electrochromic devices.


SUMMARY OF THE INVENTION

We have sought to produce an electrolyte which is solid, stable on storage, electrically stable in use in electrochromic devices and preferably capable of being fabricated using a process of screen printing or of casting to form a film or sheet.
The present invention provides a solid polymer electrolyte for an electrochromic device comprising an alkylene carbonate, a polymer in a quantity sufficient to render the electrolyte solid and a conductive salt, preferably a lithium salt, said electrolyte containing no more than 500 ppm water.


DESCRIPTION OF THE PREFERRED EMBODIMENTS

The polymer is preferably an acrylic polymer such as a polyacrylic acid ester. Suitably the polymer is polyalkyl methacrylate, for instance polymethylmethacrylate.
The alkylene carbonate is preferably propylene carbonate.
The lithium salt is preferably lithium perchlorate.
The content of the polymer is sufficient to render the electrolyte solid. Preferably the polymer content is from 35 to 60 percent by weight based upon the combined weight of said polymer and said alkylene carbonate, e.g. 35 to 45 percent. More preferably, said percentage is about 40 percent, e.g. from 38 to 42 percent.
The electrolyte may further comprise an opacifying and reflecting material or pigment such as titanium dioxide. The object of this material is optically to isolate the front from the rear electrode in a display electrochromic cell and to reflect ambient light which has passed through the front electrode material. Suitably, the electrolyte contains from 10 to 30 percent of the opacifying material by weight based upon the weight of the electrolyte, e.g. from 15 to 25 percent.
The electrolyte preferably also comprises a resin modifier such as ethylacrylate, 2-ethylhexylacrylate copolymer. The purpose of the resin modifier will be described below in connection with the fabrication of the electrolyte.
The invention includes a process for making a solid polymer electrolyte comprising forming a precursor solution by dissolving a salt and a polymer in an alkylene carbonate, forming a thin layer of said solution and thereafter removing sufficient of the alkylene carbonate to solidify the electrolyte.
The alkylene carbonate can be removed to solidify the electrolyte by heating the solution.
The solution may he formed into a thin layer or thick film prior to said solidification by casting or by screen printing on to a substrate or support. Multiple layers of the polymer electrolyte may be built-up by seq

REFERENCES:
patent: 4009936 (1977-03-01), Kasai
patent: 4728117 (1988-03-01), Stepanek
patent: 4750817 (1988-06-01), Sammells
patent: 4792504 (1988-12-01), Schwb et al.
patent: 4798773 (1989-01-01), Yasukawa et al.
patent: 4824222 (1989-04-01), Green
patent: 4842381 (1989-06-01), Green
patent: 4902110 (1990-02-01), Green
patent: 5035965 (1991-07-01), Sangyoji et al.
patent: 5202009 (1993-04-01), Andrieu
Mizuno "Electrochromic Display Device" Feb. 1985, Re JP-A 60-37530.
"Antistatic acrylic resin compsn.- comprises methyl methacrylate polymer, lithium perchlorate, ethylene- and/or propylene-carbonate", Kyowa Gas Chem Ind., Jul. 1988, p. 3.
Database WPIL, Derwent Publication Ltd., London, GB; AN 91-041083 & JP,A,2 308 819 (Sanyo Chem. Ind.) 21 Dec. 1990 see abstract.
Database WPIL, Derwent Publication Ltd., London, GB; AN 91-320228 & JP, A,3 212 416 (Yuasa Battery) 18 Sep. 1991, see abstract.
Database WPIL, Derwent Publications Ltd., London, GB; & JP,A,4 145 143 (Tokuyama Soda) 19 May 1992, see abstract.

Affiliated with

Also associated with

Rating

Solid polymer electrolytes does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Solid polymer electrolytes, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Solid polymer electrolytes will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-790142