High-performance lithium metal batteries based on composite solid-state electrolytes with high ceramic content

Abstract

The large scale application of solid state lithium metal batteries based on NASICON-type Li1+xAlxTi2-x(PO4)3 (LATP) electrolyte has been hindered by insufficient ion conductivity and interface instability due to the spontaneous Ti4+ reduction reaction between Li metal and LATP. To address these issues, Li1.7Al0.3-xBixTi1.7(PO4)3 (0 ≤ x ≤ 0.03) (LABTP) electrolytes were prepared, and the influence of Bi substitution on the microstructure and conductivity of LATP were investigated. Suitable amount of Bi substitution accelerates densification and improves the ionic conductivity. Furthermore, unlike commonly used polyethylene oxide (PEO) and polyvinylidene difluoride (PVDF), polyvinylbutyral (PVB)-based quasi-solid electrolytes with LABTP is first-time proposed to improve the compatibility and stability of the LATP/Li interface. The synergistic effect of Bi doping and PVB reduces the reduction reaction of Ti4+. Small voltage hysteresis is observed in the corresponding Li||Li symmetric cells. The solid-state Li|LABTP@PVB|LiFePO4 full cell can deliver a high capacity of 146.2 mAh g−1 and a stable cycling performance without reduction after 200 cycles.