Safety regulation of gel electrolytes in electrochemical energy storage devices

Electrochemical energy storage devices, such as lithium ion batteries (LIBs), supercapacitors and fuel cells, have been vigorously developed and widely researched in past decades. However, their safety issues have appealed immense attention. Gel electrolytes (GEs), with a special state in-between liquid and solid electrolytes, are considered as the most promising candidates in electrochemical energy storage because of their high safety and stability. This review summarized the recent progresses made in the application of GEs in the safety regulation of the electrochemical energy storage devices. Special attention was paid to the gel polymer electrolytes, the organic low molecule-mass GEs, as well as the fumed silica-based and siloxane-based GEs. Finally, the current challenges and future directions were proposed in terms of the development of GEs.