Activating Interfacial Ion Exchange in Composite Electrolyte to Realize High‐Rate and Long‐Cycling Solid‐State Lithium Batteries

Composite solid electrolytes (CSEs) are promising candidates for solid‐state lithium metal batteries. However, the poor cross‐phase Li+ transport restricts the rate performance and cycle life of the batteries. Herein, we revealed the Li+ percolation behavior in poly(vinylidene fluoride) (PVDF)‐based CSEs with Li6.4La3Zr1.4Ta0.6O12 filler. The de‐coordination barrier from Li+ clusters determines interfacial Li+ transport capability. We then employed a designed N‐methyl‐2,2,2‐trifluoroacetamide (NMTFA) ligand to lower the de‐coordination energy and activate interfacial Li+ exchange, The ionic conductivity is therefore increased from 3.32×10‐4 to 7.30×10‐4 S cm‐1. By tracking the 6Li and 7Li substitution process, it was identified that the proportion of interfacial Li+ transport increases from 11% to 26%. The NMTFA also contributes to the formation of inorganic‐rich interphases with electrodes. As a result, the Li||LiNi0.8Co0.1Mn0.1O2 solid‐state batteries exhibit ultra‐long lifespan of 2400, 3000 and 10000 times at 2, 5 and 10C, respectively, as well as achieve 1000 cycles at 50 °C and 300 cycles at ‐30 °C. This work highlights the critical role of interfacial Li+ transport for the CSEs with “polymer‐Li+ clusters‐filler” configuration to realize high‐rate and long‐cycling solid‐state lithium batteries.