Binary Metallic CuCo5S8 Anode for High Volumetric Sodium‐ion Storage

With the rapid improvement of compact smart devices, fabricating anode materials with high volumetric capacity has gained substantial interest for future sodium-ion batteries (SIBs) applications. Herein, a novel bimetal sulfide CuCo5 S8 material is proposed with enhanced volumetric capacity due to the intrinsic metallic electronic conductivity of the material and multi-electron transfer during electrochemical procedures. Due to the intrinsic metallic behavior, the conducting additive (CA) could be removed from the electrode fabrication without scarifying the high rate capability. The CA-free CuCo5 S8 electrode can achieve a high volumetric capacity of 1436.4 mA h cm-3 at a current density of 0.2 A g-1 and 100 % capacity retention over 2000 cycles in SIBs, outperforming most metal chalcogenides, owing to the enhanced electrode density. Reversible conversion reactions are revealed by combined measurements for sodium systems. The proposed new strategy offers a viable approach for developing innovative anode materials with high-volumetric capacity.