Charge-transfer reaction rate at the LiMn₂O₄ spinel oxide cathode/polymer electrolyte interface

Charge-transfer resistance at the LiMn₂O₄ thin film cathode/polyether based electrolyte interfaces was investigated. The thin film cathodes were prepared by electrostatic spray deposition (ESD) method, and charge-transfer resistances at the cathode/polymer electrolyte interfaces were measured by electrochemical impedance spectroscopy in the poly(ethylene glycol) dimethyl ether (PEGDME) whose average molecular weight is 500 (PEGDME500) dissolving LiCF₃SO₃ by adding various amounts of polyether having higher average molecular weight of 1000 (PEGDME1000). It was found that the charge-transfer resistance increased with increasing amounts of PEGDME1000. The Gibbs activation energies and the solvation state of lithium ions were almost constant with the amounts of PEGDME1000. On the other hand, the charge-transfer resistance was proportional to the viscosity of the electrolyte. It was suggested that the viscosity of the electrolyte was one of the important factors for the charge-transfer reaction rate at the LiMn₂O ₄ cathode/polyether based electrolytes interfaces.