In Situ Hybrid Crosslinking Polymerization of Nanoparticles for Composite Polymer Electrolytes to Achieve Highly‐Stable Solid Lithium–Metal Batteries

Abstract The composite solid electrolyte, which combines the advantages of inorganic conductors and organic polymer electrolytes, has become a crucial strategy for the construction of solid‐state batteries. However, the physical deposition and agglomeration of traditional composite fillers seriously affect their structural uniformity and ion transport performance, and the construction of uniform and stable composite electrolytes is still an insurmountable challenge. Herein, a strategy of in situ hybrid crosslinking polymerization of TiO2 nanoparticles is proposed for highly stable polymer composite electrolytes (NHCPE) with an ultrahigh ionic conductivity of 1.74 × 10−3 S cm−1 at 25 °C, and a high lithium‐ion transference number of 0.725. These properties enable the composed lithium symmetric battery to be stably deposited/plating off at 0.5 mA cm−2 for more than 1000 h. Moreover, the assembled LFP|PDOL@nanoTiO2|Li battery exhibits a superior specific discharge capacity of 142.6 mAh g−1 at 1 C and 25 °C, and an ultrahigh capacity retention rate of 90% after 1000 cycles. The proposed PDOL@nanoTiO2 NHCPE greatly inhibits the defects of easy agglomeration of composite electrolytes, solves the problems of easy decomposition, low thermal stability, and poor safety of polyether electrolytes, and opens up a new way for the design and industrial application of high‐stability composite polymer electrolytes.