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

Electron spin resonance is used to investigate an intermediate cation radic al structure in the reaction between a positive electrode and an electrolyt ic solution as well as one of the mechanisms for capacity fade of the posit ive electrode during storage. The intermediate cation radical structures of the oxidation reaction in carbonate group solvents have a delocalized radi cal 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, ethy l methyl carbonate, and diethyl carbonate) in contact with the charged posi tive electrode. (C) 2000 The Electrochemical Society. S0013-4651(00)03-016- 0. All rights reserved.