Solid state cell electrolyte

• US 5,183,715 A
• Filed: 11/15/1991
• Issued: 02/02/1993
• Est. Priority Date: 02/18/1987
• Status: Expired due to Term

• Current Assignee: NGK Spark PLUG Company Limited (Niterra Co., Ltd.)
• Original Assignee: Dowty Electronic Components Limited, Gould Electronics Ltd (ENEOS Holdings, Inc.)
• Inventors: North, John M.
• Primary Examiner(s): KALAFUT, STEPHEN J
• Application Number:
  US07/792,691
• Time in Patent Office: 445 Days
• Field of Search: 429/192, 429/197
• US Class Current: 429/312
• CPC Class Codes: H01M 10/052 Li-accumulators
• CPC Class Codes: H01M 10/0565 Polymeric materials, e.g. gel-type or solid-type
• CPC Class Codes: H01M 6/164 by the solvent
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A solid polymer electrolyte for a solid state electrochemical cell comprises a complex of a solid polymer such as poly(ethene oxide) and an alkali metal salt such as LiClO₄, which polymer is capable of forming donor: acceptor type bonds with alkali metal ions and is capable of conducting alkali metal ions, the complex being associated with a mixture of more than one 1,3-dioxolane-2-ones, for example ethylene carbonate and propylene carbonate, such that the electrolyte possesses satisfactory ambient temperature ionic conductivity (e.g. 10^-3 to 10^-4 ohm^-1 cm^-1) and a cell including the electrolyte substantially maintains its discharge capacity at ambient temperature after repeated charge/discharge cycling.

Claims

1. A solid state electrochemical cell comprising a lithium-containing anode, a cathode, and a solid polymer electrolyte comprising a complex of poly(ethylene oxide) associated with a mixture consisting essentially of ethylene carbonate and propylene carbonate and a lithium salt which is capable of conducting lithium ions and wherein the solid polymer electrolyte remains in the amorphous form at a lower temperature than a solid polymer electrolyte containing the same components but without any propylene carbonate.

2. The solid state electrochemical cell of claim 1 wherein the molar ratios of the constituents of the solid polymer electrolyte are represented by the general formula (I) below:

space="preserve" listing-type="equation">PEO.sub.a ;

[xEC;

yPC].sub.b n;

LiX (I)

where PEO represents poly(ethylene oxide)

EC represents ethylene carbonate

PC represents propylene carbonate

and each of a, b, x, y and n is finite and represents a molar quantity, and X is an anion.

3. The solid electrochemical cell of claim 2 wherein the molar ratios of the constituents therein are represented by the formula (II) below:

space="preserve" listing-type="equation">PEO;

[2EC;

12PC]20;

LiClO.sub.4 (II)

where the number represent molar quantities.

4. The solid state electrochemical cell of claim 1 wherein the polymer electrolyte has an ionic conductivity of 10^-3 to 10^-4 ohms^-1 cm^-1 at temperatures between 15°

C. and 30°

C.

5. A solid state electrochemical cell of claim 1 wherein the ratio of ethylene carbonate to propylene carbonate is 3:

1 by weight.