Double ionic-electronic transfer interface layers for all solid-state lithium batteries.

The interface between electrode and solid electrolyte concerning the high resistance and poor stability as well as poor compatibility against the Li+ migration is impeding the large-scale employment of all solid-state lithium batteries. Here, we report double ionic-electronic transfer interface layers 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 conductive polythiophene (PT) layer at cathode-electrolyte interface resulted in at least 7-fold decrease in interface resistance, and realized capacity retention of about 94% after 1000 cycles along with lower polarization voltage under 2 C rate. The mixed ionic-electronic conductive layers imparted superior interface stability and contact while keeping good compatibility with Li anode.