A Single‐Ion Conducting Network as Rationally Coordinating Polymer Electrolyte for Solid‐State Li Metal Batteries

Abstract Solid state single‐ion conducting polymer electrolytes (SSPEs) are one of the most promising candidates for long‐life lithium‐metal batteries. However, the traditional polyanion‐type structure of SSPEs inevitably gives rise to insufficient conductivity and inferior mechanical stability, which limits their practical application. Herein, an interpenetrating single‐ion network polymer (PTF‐4EO) is fabricated by crosslinking lithium tetrakis(4‐(chloromethyl)‐2,3,5,6‐tetrafluorophenyl)borate salt with tetraethylene glycol. The unique structure enables a PTF‐4EO with weakly interacting anions and coordinating ether oxygen segments that functions as a high‐performing SSPE, that delivers a high room‐temperature conductivity of 3.53 × 10 −4 S cm −1 , exceptional superior lithium‐ion transference number of 0.92, wide electrochemical window > 4.8 V, and good mechanical properties. Moreover, the resultant SSPE can directly participate in constructing a favorable Janus solid electrolyte interphase, which further enhances the interfacial stability of the metallic lithium anode. The as‐assembled LiFePO 4 ||Li solid batteries present prominent cycling stability, coulombic efficiency, and capacity retention over 200 cycles between 2.50 and 4.25 V. Furthermore, LiNi 0.7 Mn 0.2 Co 0.1 O 2 ||Li pouch cells exhibit remarkable safety even under harsh conditions. This study thereby offers a promising strategy for SSPE design to simultaneously achieve high ionic conductivity and good interfacial compatibility toward practical high‐energy‐density solid‐state lithium metal batteries.