Progress and future prospects of high-voltage and high-safety electrolytes in advanced lithium batteries: from liquid to solid electrolytes

Developing the next generation high energy density and safe batteries is of prime importance to meet the emerging challenges in electronics, automobile industries and various energy storage systems. High voltage lithium ion batteries (LIBs) and solid state batteries (SSBs) are two main directions gaining increasing interests in recent years, due to their visible applications in the near future. In both of the two kinds of batteries, the electrolytes play a pivotal role but also create several bottle-neck problems. In this review, recent progress in designing electrolytes for high voltage LIBs and SSBs is summarized. First, the solvents, additives, ionic liquids and super-concentrated salts strategy for constructing the high voltage liquid electrolytes are reviwed, and then the applications of inorganic solids, solid polymers, gel and ionic liquids in solid state electrolytes are presented. Finally, the general design rules of the electrolytes and their current limitations and future prospects are briefly discussed