In‐Situ Intermolecular Interaction in Composite Polymer Electrolyte for Ultralong Life Quasi‐Solid‐State Lithium Metal Batteries

Abstract Solid‐state lithium metal batteries built with composite polymer electrolytes using cubic garnets as active fillers are particularly attractive owing to their high energy density, easy manufacturing and inherent safety. However, the uncontrollable formation of intractable contaminant on garnet surface usually aggravates poor interfacial contact with polymer matrix and deteriorates Li + pathways. Here we report a rational designed intermolecular interaction in composite electrolytes that utilizing contaminants as reaction initiator to generate Li + conducting ether oligomers, which further emerge as molecular cross‐linkers between inorganic fillers and polymer matrix, creating dense and homogeneous interfacial Li + immigration channels in the composite electrolytes. The delicate design results in a remarkable ionic conductivity of 1.43×10 −3 S cm −1 and an unprecedented 1000 cycles with 90 % capacity retention at room temperature is achieved for the assembled solid‐state batteries.