Electron-spin-resonance study of the reaction of electrolytic solutions on the positive electrode for lithium-ion secondary batteries

Electron spin resonance is used to investigate an intermediate cation radical structure in the reaction between a positive electrode and an electrolytic solution as well as one of the mechanisms for capacity fade of the positive electrode during storage. The intermediate cation radical structures of the oxidation reaction in carbonate group solvents have a delocalized radical on the OCO bond, and neighboring solvent molecules are coordinated with the cation radical species. We measure the radical quantity of nonaqueous solvents (ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate) in contact with the charged positive electrode. (C) 2000 The Electrochemical Society. S0013-4651(00)03-016-0. All rights reserved.