Method for preparing composition for use as a polymer electrolyte

Abstract

A process for preparing a composition for use as a polymer electrolyte is provided which comprises mixing one or more polar materials and one or more polyesters of formula III,wherein y is from 1.5 to 80 and each unit A may be identical or different and is of the structure IV,wherein x is from 1 to 5 and each unit B may be identical or different and is of the structure V,wherein R and R1 are each, independently, hydrogen, optionally substituted hydrocarbyl or an inert functional group,wherein the mixture is prepared to contain from 1 to 50 wt. % of the one or more polar materials and from 50 to 99 wt. % of the one or more polyesters of formula III. A method for using such polymer electrolytes in cells, batteries, coulometers, displays, and smart windows is also provided.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]The present application is a divisional application claiming priority from U.S. patent application Ser. No. 10 / 343,804 filed Feb. 18, 2003 which claims priority from International Application No. PCT / EP01 / 08855 filed Jul. 31, 2001.FIELD OF THE INVENTION[0002]The present invention provides a process for preparing a composition for use as a polymer electrolyte, and a method for its use, particularly in coulometers, displays, smart windows, cells, and batteries.BACKGROUND OF THE INVENTION[0003]Liquid electrolytes tend to suffer from problems relating to the loss of electrolyte from the cell case and require the use of cell seals. Under extreme conditions, for example during short circuit abuse of cells, the local heating within the cell case can lead to seal rupture, even with the most sophisticated seal and cell case design.[0004]In general, solid electrolytes offer many advantages over liquid electrolytes such as more efficient use of spac...

AI Technical Summary

Benefits of technology

[0030]There has now been found a novel class of polymer electrolytes based on polymers that possess good ionic conductivity and excellent mechanical properties.

Problems solved by technology

Liquid electrolytes tend to suffer from problems relating to the loss of electrolyte from the cell case and require the use of cell seals.

Under extreme conditions, for example during short circuit abuse of cells, the local heating within the cell case can lead to seal rupture, even with the most sophisticated seal and cell case design.

Typical disadvantages of some solid electrolytes are that they tend to have a relatively low ionic conductivity and a poor mechanical compatibility with certain types of electrode materials.

However, whilst polymer electrolytes offer several important advantages over conventional liquid non-aqueous systems, the first generation of lithium ion conducting solvent-free polymer electrolytes also suffered from severe drawbacks.

However, in spite of the promise of initial results, systems based on poly(ethylene oxide) were found to crystallise as salt-polymer complexes or free polymer, resulting in a less favourable conductivity behaviour in certain ranges of salt concentrations and over a critical range of operating temperatures.

It has been found that ion conductivity is confined to the amorphous domains of a polymer electrolyte and that the tendency of the polymer electrolyte to crystallise results in difficulties in the reproducible preparation of electrolytes (G. G. Cameron, M. D. Ingram and K. Sarmouk, Eur. Polym. J. 26 (1990) 1097-1101).

Wei et al. hypothesise that this is due to the irregularity of the PVICOX system (II) which frustrates close packing, thereby increasing static free volume and conductivity.

However, surprisingly high conductivities have been reported.

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