Advances in Zn-ion batteries via regulating liquid electrolyte

Abstract With distinct advantages like high gravimetric and volumetric capacity, low redox potential, a natural abundance of zinc, and compatibility with water, Zn-ion batteries have become a potential alternative to Li-ion batteries. However, several challenges still need to be addressed prior to the practical applications of Zn-ion batteries, such as their narrow electrochemical window, irreversibility, unstable anode, sluggish kinetics and difficulties regarding the insertion of Zn2+ into the host material for the cathode. Such issues can be addressed by regulating the components and structures of the electrolyte which connects the cathode and anode parts. In this mini review, we systematically describe the compositions and structures of the electrolyte and then discuss the core issues faced by the batteries, particularly their mechanism and affected factors. Furthermore, a relatively comprehensive overview is presented of the strategies being utilized to improve Zn-ion batteries via regulating liquid electrolyte, mainly including the optimization of solvents and salts, adjustment of electrolyte concentration, introduction of additives into the electrolyte, and the fabrication of a hybrid-ion battery. In the final section, we offer insights into the development of liquid electrolytes for Zn-ion batteries.