The Progress in the Electrolytes for Solid State Sodium-Ion Battery

Sodium as the closest analogue of lithium in periodic table is attracting intense interest as a potential replacement, in the hope that Na⁺ offers similar intercalation chemistries in electrode hosts at much lower cost. Sodium-ion battery is an alternative choice to meet the large-scale electrical energy storage and also able to be used to store the electricity generated by solar cells and wind turbines as a green, renewable energy source. The use of solid electrolytes to replace the organic electrolyte is an alternative to improve the safety and avoid liquid leakage. The detailed and comprehensive research progress for sodium-ion battery solid electrolyte is summarized. The recent research reveals that the chemical composition and crystal structure of electrolytes profoundly affects the cell performance in many aspects. The room temperature ionic conductivity for solid polymer electrolytes (SPEs) is generally lower than ≈10⁻⁵ S cm⁻¹. Gel polymer electrolyte (GPE) yields acceptable ionic conductivity as the transition between liquid electrolyte and all-solid electrolyte. There also has groundbreaking progress of inorganic solid electrolyte chemistries exhibiting superionic Na⁺ conductivities. However, their interphasial chemistries are the emphasis to break through. In the future, exciting breakthroughs in solid electrolytes and interphasial chemistries should be made in those fields.