Porous Ga0.25Li6.25La3Zr2O12 frameworks by gelcasting–reaction sintering for high-performance hybrid quasi-solid lithium metal batteries

Abstract

The poor interface between Li/LLZO leads to the easy penetration of lithium metal into the garnet-type electrolyte, which limits its application. A hybrid quasi-solid electrolyte (HQSE) composed of porous LLZO and liquid electrolyte (LE) can effectively solve the interface problem. In practice, the implementation of HQSE-based batteries typically necessitates the use of porous LLZO scaffolds that possess sufficient mechanical strength. Herein, a novel method was developed to prepare porous LLZO scaffolds by combining gel casting and in situ reaction sintering. The enhanced mass transfer effect of the Li₂O liquid phase on the surface of LLZO particles in the early stages, as well as the LiGaO₂ liquid phase at the grain boundaries in the later stages, would result in the rapid densification of porous LLZO. By controlling the sintering temperature, the degree of densification can be controlled, thereby achieving a balance between porosity and mechanical strength in the porous LLZO scaffolds. When the solid phase content is 27.5 vol%, the porous LLZO scaffold obtained by heating at 1050 °C for 2 h exhibits a porosity of 32.7% and a flexural strength of up to 46.5 MP. In addition, the HQSE exhibits a high room-temperature ionic conductivity of up to 2.06 × 10⁻³ S cm⁻¹. The symmetric cells delivered high cycling stability of over 800 h for lithium plating and stripping at a current density of 0.5 mA cm⁻² with a small polarization voltage of about 0.05 V. This method offers a new route toward constructing a range of 3D scaffolds with SSEs for quasi-solid-state battery applications.