Charactering and optimizing cathode electrolytes interface for advanced rechargeable batteries: Promises and challenges

With the advancement of secondary batteries, interfacial properties of electrode materials have been recognized as essential factors to their electrochemical performance. However, the majority of investigations are devoted into advanced electrode materials synthesis, while there is insufficient attention paid to regulate their interfaces. In this regard, the solid electrolyte interphase (SEI) at anode part has been studied for 40 years, already achieving remarkable outcomes on improving the stability of anode candidates. Unfortunately, the study on the cathode electrolyte interfaces (CEI) remains in infancy, which constitutes a potential restriction to the capacity contribution, stability and safety of cathodes. In fact, the native CEI generally possesses unfavorable characteristics against structural and compositional stability that requires demanding optimization strategies. Meanwhile, an in–depth understanding of the CEI is of great significance to guide the optimization principles in terms of composition, structure, growth mechanism, and electrochemical properties. In this literature, recent progress and advances of the CEI characterization methods and optimization protocols are summarized, and meanwhile the mutually–reinforced mechanisms between detection and modification are explained. The criteria and the potential development of the CEI characterization are proposed with insights of novel optimization directions.