Promising VO<sub>2</sub>(B)/rGO Heterojunction Cathode for Building High‐Capacity and Long‐Lifespan Ca‐Ion Batteries
Yu Wang, Junjun Wang, Wenwei Zhang, Feiyang Chao, Jinghao Li, Qinghong Kong, Fan Qiao, Lei Zhang, Meng Huang, Qinyou An
Abstract
Abstract Calciumion batteries (CIBs) are an appealing energy storage technology owing to the low redox potential of Ca 2+ /Ca and the abundant Ca reserves in the earth's crust. However, suitable cathode materials with high capacity and long lifespan are scarce. Herein, VO 2 (B)/reduced graphene oxide (rGO) heterojunction formed by interfacial V─O─C bonds is constructed and first reported as a cathode material for CIBs, which exhibits an ultrahigh discharge capacity of 319.2 mAh g −1 and exceptional long lifespan (3000 cycles at 500 mA g −1 with capacity retention of 85%). In addition, VO 2 (B)/rGO heterojunction also shows an outstanding rate capability at 50 °C (127.1 mAh g −1 at 1000 mA g −1 ). The remarkable electrochemical performance is attributed to the big tunnel structures of VO 2 (B) and the role of rGO in enhancing electronic conductivity. Density functional theory calculations reveal a feasible Ca 2+ diffusion path at the interface. Furthermore, a reversible single‐phase insertion/extraction reaction is revealed by in situ X‐ray diffraction, ex situ Raman, and ex situ X‐ray photoelectron spectroscopy. This work demonstrates that VO 2 (B)/rGO holds great potential for building high‐capacity and long‐lifespan CIBs.