The effect of removing the native passivation film on the electrochemical performance of lithium metal electrodes

Abstract

Lithium metal is accepted as the promising anode for next-generation Li batteries such as solid-state, Li–S, and Li-air batteries, etc. Besides, it is commonly employed as the reference electrodes for evaluating the electrode materials of Li-ion batteries (LIBs) in a half-cell. However, native passivation film (NPF), which is inevitable on the surface, can change the topography and surface composition distribution, and thus deteriorate the performance stability of lithium metal electrodes. Unfortunately, these effects are always neglected during the evaluation of anode or cathode materials of LIBs. Here, we conduct a comprehensive study on the effects of NPF on the electrochemical performance of lithium metal electrodes. After the removal of NPF by polishing, both the interfacial impedance and electrode overpotential are significantly decreased, with a more homogeneous lithium deposition during the charge/discharge process. When it is employed as the reference electrode for characterizing the commercial LiFePO4 or graphite materials in a coin cell, the consistency of the results is remarkably improved. This work not only provides an insight for the interfacial electrochemistry of lithium metal electrodes, but also helps characterize electrode materials in a reliable way.