Towards high-rate lithium metal anodes with electrochemically inert and catalytic COF separators

Future high energy-density rechargeable batteries with Li metal anodes (LMAs) require a rational design of separators to stabilize Li plating/stripping and accommodate cathode with high mass loadings. Herein, we develop an electrochemically inert and catalytic sp2c-COF separator to address this challenge. Based on electrochemical analysis and ab-initio molecule dynamics (AIMD) calculation, it is found that nano-pores of sp2c-COF enables homogenous Li+ flux; electrochemical inertness of sp2c-COF fundamentally avert side reactions. Cyano-groups on sp2c-COF are critical for generating an inorganic-rich solid electrolyte interphase. Therefore, Li symmetrical cells demonstrate excellent Li plating/stripping behaviors for 3300 and 1100 h under 0.5 and 40 mA cm−2, respectively. Additionally, full batteries assembled with LiCoO2 and LiNi0.8Co0.1Mn0.1O2 cathodes (178 and 174.6 mg cm−2 for LCO and NCM811 loadings) demonstrate impressive areal capacity of 18.5 and 35.0 mAh cm−2, respectively. This work demonstrates an important strategy toward the stabilization of LMA for practical use in rechargeable batteries.