SnSe nanocomposite chemically-bonded with carbon-coating as an anode material for K-ion batteries with outstanding capacity and cyclability

Abstract

• A chemically bonded, nanosize SnSe@C composite is fabricated by a scalable method. • The chemically bonded SnSe@C nanocomposite anode is explored for use in K-ion batteries. • The use of amorphous carbon and selenium can significantly suppress the volume expansion of SnSe. • The chemically bonded SnSe@C nanocomposite exhibits excellent cyclability and rate capability. The use of SnSe alloys as anode materials in potassium-ion batteries (PIBs) has recently attracted considerable attention owing to the natural abundance of Sn and Se and the environmental friendliness, high theoretical capacity, and 2D layered structure of SnSe. However, due to the large volumetric change and severe pulverisation during potassiation and depotassiation, they exhibit poor cycling stability in PIBs. In this work, we fabricated a strongly chemically bonded SnSe@C nanocomposite using a simple two-step process consisting of a facile chemical reaction followed by high-energy ball milling. In addition, the introduction of amorphous carbon and selenium effectively suppressed the stress/strain originating from volume expansion during potassiation/depotassiation. The chemically bonded SnSe@C nanocomposite exhibited high initial discharge and charge capacities of 744.8 and 440.7 mAh g −1 , respectively. Even after 50 cycles, it retained a charge capacity of 401 mAh g −1 at 50 mA g −1 , with a coulombic efficiency (CE) of 99.6%. Even at high specific currents of 300 and 500 mA g −1 , the electrode maintained capacities of 270.7 and 203.4 mAh g −1 after 100 and 1000 cycles, respectively, and the CE was almost 100%. Furthermore, a SnSe@C/KFe[Fe(CN) 6 ·xH 2 O] full cell also showed superior cyclability and better rate capability. After 100 cycles, it retained a discharge capacity of 213.9 mAh g −1 at 200 mA g −1 . In addition, the phase transitions in the SnSe@C electrode during potassiation/depotassiation were investigated using ex-situ X-ray diffraction analysis. This work will provide an effective reference for Sn-Se alloy-based anodes for batteries to replace the lithium-ion batteries (LIBs).