Investigation of lithium transport through LiMn2O4 film electrode in aqueous LiNO3 solution

Lithium transport through LiMn2O4 film electrode was investigated in aqueous saturated LiNO3 solution by analyses of the potentiostatic current transient and ac-impedance spectra. It was found that the current transient hardly shows the Cottrell behaviour, and the initial current is linearly proportional to the potential step. This strongly suggests that lithium transport through the film electrode proceeds in aqueous LiNO3 solution by the same mechanism involving the cell-impedance-controlled constraint, as does lithium transport in non-aqueous organic solution such as LiClO4 in propylene carbonate (PC). However, the cell-impedance in aqueous LiNO3 solution was determined to be much smaller by more than one order in value than that cell-impedance in non-aqueous LiClO4-PC solution over the whole potential range, indicating lithium transport is markedly enhanced in aqueous electrolyte. From the comparison between the ac-impedance spectra obtained in aqueous and non-aqueous electrolytes, the reduced cell-impedance in aqueous electrolyte can be accounted for by the kinetic facility for the interfacial charge-transfer reaction in the absence of the resistive surface film as well as by the high conductivity of the electrolyte itself. (C) 2003 Elsevier Ltd. All rights reserved.