NASICON-based solid state Li-Fe-F conversion batteries enabled by multi-interface-compatible sericin protein buffer layer

Abstract

Li1.3Al0.3Ti1.7(PO4)3 (LATP) electrolyte suffers from serious structure degradation owing to easy Ti4+ reduction by Li metal, which leads to interface collapse and hinders the development of NASICON-based solid-state batteries. Here, a multi-interface compatible buffer layer is proposed for the stabilization and endurance of Li-LATP interface via constructing conformal sericin protein film (SPF). This biomass derivative interlayer is electrochemically stable and electronically insulating, enabling an effective trapping and confining of ionic liquid (IL) as interfacial Li-ion wires via intermolecular force between sericin-chain and TFSI group. The homogenous dispersion and fluidity suppression of IL moieties mitigate the decomposition, passivation and cracking of IL@SPF buffered Li-LATP interface with the preservation of conformal and compact morphology even during long-term cycling. The suppression effects of LATP reduction and Li dendrite growth enable the reversible cycling of NASICON-based solid state Li-F conversion batteries based on FeF3 cathodes with initial capacity exceeding 500 mAh g−1 for the first time.