Progress in the Development of Sodium-Ion Solid Electrolytes

The development of safe, reliable, yet economical energy storage has been reemphasized with recent incidents involving the explosion and subsequent recall of lithium-ion batteries. The organic liquid electrolyte used in the conventional lithium-ion battery can potentially act as a fuel for combustion in a thermal-runaway reaction, and hence an alternative with a significantly reduced flammability must be sought. All-solid-state batteries have the potential to meet safety and reliability requirements with the possibility of increasing the volumetric energy density of the system, making these a promising candidate for the development of the next generation of energy storage. Moreover, the sodium-ion battery exhibits a better cost-efficiency without significantly compromising the energy density, making the combination of the sodium chemistry with the solid electrolyte an attractive choice for safe and economical energy storage. Here, a general background on the recent development of ceramic and glass-ceramic sodium-ion-conducting electrolytes is provided with regard to oxide-,sulfide-, and hydride-based electrolytes. The ionic conductivity, chemical stability, and mechanical properties of the sodium-based solid electrolyte are discussed, which is followed by a perspective on future developments in the field.