Development of the cold sintering process and its application in solid-state lithium batteries

Solid-state batteries (SSBs) are developed with the use of inflammable solid-state electrolytes to realize higher energy density and improved safety. However, the densification temperature of solid electrolytes via conventional sintering methods is usually high, especially for oxide-type electrolytes. Advanced sintering techniques such as spark plasma sintering have been developed to decrease the heat-treatment temperature and time. Recently, a novel cold sintering process (CSP) has been developed, which offers an alternative route to the densification of many solid-state electrolyte materials below 300 °C. Generally, the CSP involves multi-stage non-equilibrium processes such as dissolution-precipitation under external stress, viscous flow of saturated solutions and diffusion of species. Herein, the CSP application in different solid electrolytes and electrodes are summarized. It is expected that the CSP has great potential in preparing solid-state batteries and solid electrolytes in the future.