Review on composite solid electrolytes for solid-state lithium-ion batteries

Lithium-ion batteries have become a promising energy storage device and power source, but the organic liquid electrolyte used in traditional lithium-ion batteries has a series of serious security risks such as decomposition, leakage, spontaneous combustion, and even explosion. Solid electrolytes have become a hot research topic to replace liquid electrolytes because of their high safety and excellent electrochemical properties. However, there are many types of solid electrolytes and each electrolyte has its advantages and disadvantages, so there are few solid electrolytes with comprehensive performance to meet the commercial application requirements. Composite solid electrolytes can make up for the disadvantages of each component and prepare solid electrolytes with comprehensive performance. This review first introduces the advantages and disadvantages of different types of electrolytes, and then, from the point of view of the influence of filler and film structure on composite electrolytes, the strategies for improving the ionic conductivity of composite electrolytes, broadening the electrochemical stability window, inhibiting the growth of lithium dendrite, and achieving good contact between electrode and electrolyte interface are analyzed. Then, the self-healing electrolytes which can repair the electrolyte damage caused by the external force and internal stress changes are reviewed. Finally, the future development and challenges of composite solid electrolytes are discussed.