Synergistically enhancing interface stability with soft gel and garnet-type Li6.4La3Zr1.4Ta0.6O12 bi-functional composite electrolyte of lithium metal batteries

Abstract

Solid electrolytes are expected to fundamentally replace liquid electrolytes due to their high safety and energy density. Solid inorganic electrolytes have excellent ionic conductivity and ion mobility; however, they easily induce lithium dendrites without the modification of the soft interface layer. Although they have excellent interfacial properties, they have low ionic conductivity at room temperature and poor mechanical strength. Therefore, a composite electrolyte was prepared by combining a polymer electrolyte with an inorganic electrolyte, and then asymmetric composite electrolytes were designed based on the selective adsorption of glass fibers to further improve the long cycle performance of a battery. In particular, SEI rich in inorganic components can be formed on the surface of lithium metal through the synergistic effect of lithium metal pretreatment and asymmetric structural design. The assembled lithium symmetrical cell was stably cycled for 500 h at a current density of 0.5 mA cm⁻². Matched with the LFP cathode electrode, it showed outstanding rate performance at 25 °C, and the initial discharge capacity of LFP‖As-THCE-10%LLZTO‖Li-FEC was 111.6 mA h g⁻¹ at 2C and 25 °C, while the capacity retention rate was 84.73% after 500 cycles. This work provides a new idea for the preparation of lithium metal solid-state batteries with high safety and stability through the rational structural design of composite electrolytes.