High Performance Flexible Lithium‐Ion Battery Electrodes: Ion Exchange Assisted Fabrication of Carbon Coated Nickel Oxide Nanosheet Arrays on Carbon Cloth

Abstract Transition metal oxides (TMOs)‐based anode materials of high theoretical capacities have been intensively studied for lithium‐ion storage. However, their poor high‐rate capability and cycling stability remain to be effectively resolved. Herein, a novel ion exchange (IE)‐assisted indirect carbon coating strategy is proposed to realize high performance freestanding TMO‐based anodes for flexible lithium‐ion batteries (FLIBs). This approach effectively avoids the possible side reaction of oxide reduction, enhances degrees of graphitization of the carbon coating, and preserves advantageous nanostructure of the starting template, leading to enhanced electrical conductivities, alleviated volume variation induced structural instability, fast lithium‐ion diffusion pathways and enhanced electron transfer kinetics. As a proof of concept, IE‐prepared carbon coated NiO nanosheet arrays with excellent structural and electrochemical stability are developed as freestanding anodes for LIBs and FLIBs, which exhibit outstanding electrochemical performances superior to most state‐of‐the‐art NiO‐based anodes reported in recent years. The product anode delivers a high areal capacity (3.08 mAh cm −2 at 0.25 mA cm −2 ), outstanding high‐rate capability (1.78 mAh cm −2 at 8 mA cm −2 ) and excellent cycling stability (over 300 cycles). Further pouch cell tests confirm the excellent flexibility of the freestanding electrode against mechanical deformation with well‐maintained electrochemical performance under folding.