A review on research progress in electrolytes for sodium-ion batteries

Recently, sodium-ion batteries have attracted great attention due to extensive sodium resources and low-cost. The sodium-ion batteries are composed of a cathode, anode, electrolyte, and current collectors. In comparison to the number of studies on electrodes, a number of studies on electrolytes have been still rare. However, the electrolytes can balance and transfer charges, so they play an important role in batteries; the energy levels of frontier molecular orbitals of electrolyte components determine the electrochemical windows and affect the thermostability of batteries. Thus, the stability and ionic conductivity of electrolytes are critical factors that define battery performances. In this paper, according to the type of electrolytes, the structural characteristics, properties, and improved methods of the common liquid and solid electrolytes are reviewed. © 2020, Science Press. All right reserved.