A Facile Method for Forming an Artificial CEI Layer Utilizing Residual Lithium Compounds on High-Ni Cathodes in All-Solid-State Batteries

All-solid-state batteries (ASSBs) are garnering considerable interest as potential successors to traditional lithium-ion batteries, attributed to their enhanced safety and superior energy density. However, the interaction between solid electrolytes and cathode materials often leads to a decline in the performance of these electrochemical cells. An alternative method involves the creation of an artificial cathode electrolyte interphase (CEI) layer formed through reactions within the electrode materials. This research presents a novel approach in ASSBs to boost electrochemical performance by introducing a spontaneously formed artificial CEI layer. This layer forms during thermal processing via chemical reactions between the solid electrolytes and residual lithium compounds on the LiNi_0.9Co_0.05Mn_0.05O₂ (NCM) cathode without causing degradation. During repetitive electrochemical cycling, the artificial CEI layer effectively minimizes side reactions between the solid electrolytes and high-Ni NCM. Consequently, the NCM full-cell with the artificial CEI layer demonstrates 141 mAh g^-1 after 300 cycles at a 0.2 C rate.