Constructing Electronic and Ionic Dual Conductive Polymeric Interface in the Cathode for High‐Energy‐Density Solid‐State Batteries

Abstract Solid–solid interfaces in the composite cathode for solid‐state batteries face the thorny issues of poor physical contact, chemical side reaction, temporal separation, and sluggish Li + /e − transfer. Developing key material to achieve the composite cathode with efficient solid–solid interfaces is critical to improving the coulombic efficiency, cycling life, and energy density of solid‐state batteries. Herein, electronic and ionic dual conductive polymer (DCP) is prepared for the composite cathode via intermolecular interaction on the base of lithiated polyvinyl formal‐derived Li + single‐ion conductor (LiPVFM), lithium difluoro(oxalato)borate (LiODFB), and electronic conducting polymer. Crosslinking, coordination, and hydrogen‐bonding effect enable DCP with high electrical conductivity of 68.9 S cm −1 , Li + ionic conductivity (2.76 × 10 −4 S cm −1 ), large electrochemical window above 6 V and a high modulus of 6.8 GPa. Besides, DCP can form a coating layer on the active material powders to maintain structural integrity via buffering the internal stress during lithiation/delithiation, meanwhile, to construct long‐ and short‐range electronic/ionic conductive channel together with a small amount of CNTs. Rigid and flexible DCP‐based composite cathode enables the excellent cycling of solid‐state batteries with a high loading up to 11.7 mg cm −2 and high content of active materials close to 90 wt% without current collector.