Spin trapping study of gradual decomposition of electrolyte solutions for lithium secondary batteries

Spin trapping was used to study the gradual decomposition of electrolyte so lutions for lithium secondary batteries. After the reductive electrolysis o f ester-based electrolyte solutions, continuous production of active alkyl radicals was confirmed by spin trapping, which suggests the existence of a chain reaction initiated by cathodic polarization of the electrode. Liquid chromatography confirmed the existence of the produced polymer in electroly te solutions after 4 weeks of electrolysis. A gradual degradation mechanism of electrolyte solutions is proposed, in which the polymerization reaction initiating from the electron transfer equilibrium accompanies the continuo us production of active alkyl radicals. This is one mechanism for the gradu al decomposition of electrolyte solutions and could be a cause of the polym eric components in the surface film on the electrode. (C) 1999 The Electroc hemical Society. S0013-4651(98)04-078-6. All rights reserved.