Lithiated polyanion supported Li1.5Al0.5Ge1.5(PO4)3 composite membrane as single-ion conducting electrolyte for security and stability advancement in lithium metal batteries

Abstract Polymer electrolytes with single ion conducting behavior, high ion conductivity and fire-resistant play a vital role in suppressing lithium dendrite growth for high security, stability and high energy density of rechargeable lithium metal batteries (LMBs). Herein, we develop a gel single-ion composite electrolyte (SICE) by incorporating Li1.5Al0.5Ge1.5(PO4)3 nanoparticles into alternating diblock lithiated bis(benzene sulfonyl)imide polyanion with repeating ether groups. Li1.5Al0.5Ge1.5(PO4)3 nanoparticles can significantly endow SICE membrane more Li+ transportation channels, which offers elevated ionic conductivity (8.3 × 10−4 S cm−1) and Li+ transference number (0.93) to promote homogenously Li+ deposition in lithium foil for dendrite suppression. As a result, a highly reversible Li plating/stripping in a Li symmetric cell enables to run stably for at least 1600 h at 0.5 mA cm−2. Furthermore, Li1.5Al0.5Ge1.5(PO4)3 nanoparticles increases the electrochemical window of SICE up to 4.6 V (vs. Li+/Li), meanwhile enhances the thermal stability and fire-resistance, and promotes fast electrolyte wetting. Accordingly, a single-ion conducting LiFePO4/Li cell assembled with optimized SICE membrane endowed a high capacity retention of 92.9% after 800 cycles at 1 C, superior to the commercial LiPF6/PP system. This work paves a scalable and deployable way for design of advanced single-ion conducting electrolyte membranes to develop secure and stable LMBs.