Double Ionic–Electronic Transfer Interface Layers for All‐Solid‐State Lithium Batteries.

Large‐scale implementation of all‐solid‐state lithium batteries is impeded by the physical limitations of the interface between the electrode and solid electrolyte; specifically, high resistance and poor stability, as well as poor compatibility with Li+ migration. We report double ionic–electronic transfer interface layers grown at electrode–electrolyte interfaces by in situ polymerization of 2,2′‐bithiophene in polyethylene oxide (PEO) electrolyte. For all‐solid‐state LiFePO4∥PT‐PEO‐PT∥Li cells, the formation of a conductive polythiophene (PT) layer at the cathode–electrolyte interface resulted in an at least sevenfold decrease in interface resistance, and realized a capacity retention of about 94 % after 1000 cycles along with a lower polarization voltage under a rate of 2 C. The mixed ionic–electronic conductive layers imparted superior interface stability and contact while keeping good compatibility with the Li anode. [ABSTRACT FROM AUTHOR]