Improvement of Rate Performance for All-Solid-State Na15Sn4 / Amorphous TiS3 Cells Using 94Na3PS4･6Na4SiS4 Glass-Ceramic Electrolytes

All-solid-state batteries have been attracting attention because they do not suffer from leakage, volatilization, and flammability of electrolytes. Sodium-ion batteries are considered to be a promising low-cost alternative to common lithium-ion batteries because of the abundance of sodium sources. All-solid-state sodium rechargeable batteries are expected to be highly safe and low-cost. We have found that all-solid-state sodium batteries with a Na₃PS₄ glass-ceramic electrolyte successfully operated as a rechargeable battery at 25^oC [1]. The Na₃PS₄ glass-ceramic exhibited a high conductivity of 4.6 x 10^-4 S cm^-1 at room temperature. The all-solid-state Na₁₅Sn₄ / amorphous TiS₃ (a-TiS₃) cell using Na₃PS₄ glass-ceramic showed a high capacity of about 300 mAh g^-1 and good cycle performance [2]. Development of rate performance of the cell is next issue to be solved. We have recently found that 94Na₃PS₄･6Na₄SiS₄ (mol%) glass-ceramic showed a higher conductivity of 7.4 x 10^-4 s cm^-1 at room temperature than the Na₃PS₄ glass-ceramic [3]. In this study, the addition of acetylene black (AB) as a conductive additive to Na₁₅Sn₄ negative electrode and the application of 94Na₃PS₄･6Na₄SiS₄ glass-ceramic as a solid electrode were conducted to improve the rate performance of the all-solid-state Na₁₅Sn₄ / a-TiS₃ cells.