Hollow-Carbon-Templated Few-Layered VS Nanosheets Enabling Ultrafast Potassium Storage and Long-Term Cycling.

Due to the abundant potassium resource on the Earth's crust, researchers now have become interested in exploring high-performance potassium-ion batteries (KIBs). However, the large size of K would hinder the diffusion of K ions into electrode materials, thus leading to poor energy/power density and cycling performance during the depotassiation/potassiation process. So, few-layered VS nanosheets wrapping a hollow carbon sphere fabricated a facile hollow carbon template induced method could reversibly accommodate K storage and maintain the structure stability. Hence, the as-obtained VS@C electrode enables rapid and reversible storage of K with a high specific capacity of 645 mAh/g at 50 mA/g, a high rate capability, and long cycling stability, with 360 and 190 mAh/g achieved after 500 and 1000 cycles at 500 and 2000 mA/g, respectively. The excellent electrochemical performance is superior to the most existing electrode materials. The DFT calculations reveal that VS nanosheets have high electrical conductivity and low energy barriers for K intercalation. Furthermore, the reaction mechanism of the VS@C electrode in KIBs is probed the synchrotron X-ray diffraction technique, and it indicates that the VS@C electrode undergoes a sequential intercalation (KVS) and conversion reactions (KS) reversibly during the potassiation process.