Structure Engineering of Vanadium Tetrasulfides for High-Capacity and High-Rate Sodium Storage.

Structure engineering of electrode materials can significantly improve the life cycle and rate capability of the sodium-ion battery (SIB), yet remains a challenging task due to the lack of an effective synthetic strategy. Herein, the microstructure of VS 4 hollow spheres is successfully engineered through a facile hydrothermal method. The hollow VS 4 microspheres possess rich porosity and are covered with 2D ultrathin nanosheets on the surface. The finite element simulation (FES) reveals that such heterostructures can effectively relieve the stress induced by the sodiation and thereby enhance the structural integrity. The SIB with the hollow VS 4 microspheres as anode displays impressively high specific capacity, excellent stability upon ultra-long cycling, and extraordinary rate capacity, e.g., a reversible capacity of ≈378 mA h g -1 at ultra-high 10 A g -1 , while retaining 73.2% capacity after 1000 cycles. The Na storage mechanism is also elucidated through in situ/ex situ characterizations. Moreover, the hollow VS 4 microspheres demonstrate reliable rate performance at a low temperature of -40 °C (e.g., the capacity is ≈163 mA h g -1 at 2 A g -1 ). This work provides novel insights toward high-performance SIBs.