Disorder-driven Sintering-free Garnet-type Solid Electrolytes

Abstract

Oxide ceramic electrolytes for realization of high-energy lithium metal batteries generally require a series of high-temperature processes for the formation of the desired phase and inter-particle sintering. The high-temperature processing can lead to compositional changes or mechanical deformation, consequently, resulting in serious issues with material reliabilities. Here, we introduce a disorder-driven sintering-free garnet-type solid electrolyte using a novel approach for creating an amorphous matrix followed by a single-step mild heat-treatment. The softened mechanical property (yield pressure, P_y = 359.8 MPa) of disordered base materials can achieve a facile formation of a dense amorphous matrix and contributes to maintaining inter-particle connectivity during crystallization. Remarkably, the formation of the highly conductive cubic-phase garnet is triggered at a drastically lowered temperature of 350°C, leading to high ionic conductivity (σ_Li+ = 1.8 × 10^–4 S/cm at 25°C) through a single-step mild heat treatment at 500°C. The disorder-driven garnet solid electrolyte exhibits electrochemical performance similar to that of the conventional garnet solid electrolyte sintered at > 1100°C. This electrolyte exhibits the lowest processing temperature ever reported for garnet-type solid electrolytes with a high lithium ionic conductivity of ~ 10^–4 S/cm. These findings will promote the fabrication of uniform, thin, and wide solid electrolyte membranes, which is a significant hurdle in the commercialization of oxide-based lithium metal batteries, and demonstrate the untapped capabilities of garnet-type oxide solid electrolytes.