COMPARISON OF ORGANIC AND INORGANIC GELATION AGENTS IN ETHYLENE CARBONATE BASED ELECTROLYTES FOR LITHIUM-ION BATTERIES

Two types of electrolyte which are suitable for lithium-ion batteries are investigated. In both cases the basic electrolyte is a mixture of organic solvents such as ethylene carbonate (EC) and propylene carbona te (PC) or EC and dimethyl carbonate (DMC). The lithium salts applied are LiClO4, LiPF6, LiTFMSI and LiTFMS. Gel-type electrolytes were prep ared by adding a few wt.% of highly dispersed silica (HDS) to the liqu id electrolyte. If hydrophilic HDS is used, thixotropic gels are forme d. The second type of electrolytes an poly( acrylonitrile) (PAN) based . These electrolytes can be prepared as dimensionally stable films. Th e conductivity of the HDS gel electrolytes is very close to that of th e liquid electrolyte. PAN-based electrolytes exhibit lower conductivit ies than the comparable liquid electrolytes. If a lithium anode is use d in a rechargeable battery, PAN-based electrolytes offer significant advantages, since they are efficient to avoid internal short circuits due to lithium dendrite formation. A small test battery of the type li thium/PAN-based electrolyte/LiCoO2 was deep-cycled for about 450 times without any indication of internal shorts. (C) 1997 Published by Else vier Science S.A.