Interface Design Based on Gradual Synergy Between Groups for All‐Solid‐State Lithium Metal Batteries

Abstract Most of studies have exposed that a LiF‐rich solid electrolyte interface (SEI) layer can promote the stability of all‐solid‐state lithium metal batteries (ASSLMBs) because of high Young's modulus and low lithium‐ion diffusion barrier. Nevertheless, the low ionic conductivity caused by excess LiF content is always neglected. Herein, three kinds of porous organic polymers (POPs) attached by different polar functional groups (‐NH 2 group and ‐SH group) are synthesized to analyze the regulation mechanism of synergy between different groups on the component of LiF in SEI. Since the decomposition of bis(trifluoromethanesulfonyl)imide (TFSI − ) is considered to be a principal source of LiF, a “positive” group (‐NH 2 ) is introduced to promote the decomposition of TFSI − by prolonging the bond length of C─F bond while the “negative” group (‐SH) is introduced to attack the carbocation by lone‐pair electron to form a stable construct which means the decomposition of remnant has been inhibited. A “gradual synergy” between the groups has regulated the decomposition of TFSI − precisely and formed a proper LiF‐rich SEI. The experimental results show that the Li/CSE‐NH 2 ‐SH/Li battery can operate stably for over 4000 h. Meanwhile, the LiFePO 4 /CSE‐NH 2 ‐SH/Li battery shows an excellent cycling performance at 1 C (over 1500 cycles with 80% capacity retention) and 3 C (over 600 cycles with 80% capacity retention). The pouch cell also exhibits a stable performance in extreme conditions. This work provides a special perspective on designation of energy storage materials.