Mechanochemical Synthesis of Pyrite Ni1−xFexS2 Electrode for All-solid-state Sodium Battery

Abstract

All-solid-state sodium secondary batteries are expected to be low-cost, next-generation batteries. NiS2 and FeS2 are potential candidates as positive electrode materials owing to their high theoretical capacities. However, it is difficult to achieve sufficient capacity with bulk FeS2. In this study, pyrite Ni1−xFexS2 (x = 0, 0.3, 0.5, 0.7, 0.9, and 1) electrodes are prepared by a mechanochemical process. The all-solid-state sodium cells with Ni1−xFexS2 show higher discharge–charge potentials than those with NiS2, and higher capacities than those with FeS2. In addition, Ni1−xFexS2 exhibits a higher rate performance than those of NiS2 and FeS2. The all-solid-state cells using Ni1−xFexS2 (x = 0.3, 0.5, and 0.7) are discharged and charged with a high capacity of approximately 390 mAh g−1, without significant capacity fading for at least 30 cycles. The solid-solution formation of NiS2 and FeS2 results in lower material cost, higher rate performance, higher discharge–charge potential than those of NiS2, and higher capacity than that of FeS2. Pyrite Ni1−xFexS2 is a promising positive electrode material for all-solid-state sodium secondary batteries.

Keywords

• all-solid state battery
• sodium battery
• positive electrode
• metal sulfide