Editors’ Choice—Investigation of the Dynamic Evolution of the Cathode-Electrolyte Interphase Using Scanning Electrochemical Microscopy

Cathode-electrolyte interphase (CEI) is critical for inhibiting the cathode degradation to maintain cell life. However, the evolution of the CEI is still unclear due to its complex and slow dynamic process. Here we used scanning electrochemical microscopy (SECM) for in situ investigation of CEI formation process on LiFePO4 cathode. Feedback images and probe scan curves showed a heterogeneous passivation that was gently generated on the LiFePO4 particles during both charging and discharging. Besides, a LiFePO4 composited electrode was also used to investigate the CEI formation to simulate the condition of real battery system. The composited cathode does not show obvious CEI formation within first two cycles. The SECM results between the pristine LiFePO4 particles and the composited LiFePO4 indicated the dynamic accumulation of CEI, which is influenced by the ability to charge transfer kinetics of cathode materials. This approach provided a feasible consideration for the connections between the dynamic evolution of the CEI and changes in charge transfer capability of cathode during cycling.