Vertically Aligned NiCo₂O₄ Nanosheet-Encapsulated Carbon Fibers as a Self-Supported Electrode for Superior Li⁺...

Binary transition metal oxides (BTMOs) have been explored as promising candidates in rechargeable lithium-ion battery (LIB) anodes due to their high specific capacity and environmental benignity. Herein, 2D ultrathin NiCo₂O₄ nanosheets vertically grown on a biomass-derived carbon fiber substrate (NCO NSs/BCFs) were obtained by a facile synthetic strategy. The BCF substrate has superior flexibility and mechanical strength and thus not only offers a good support to NCO NSs/BCFs composites, but also provides high-speed paths for electron transport. Furthermore, 2D NiCo₂O₄ nanosheets grown vertically present a large contact area between the electrode and the electrolyte, which shortens the ions/electrons transport distance. The nanosheets structure can effectively limit the volume change derived from Li⁺ insertion and extraction, thus improving the stability of the electrode material. Therefore, the synthesized self-supporting NCO NSs/BCFs electrode displays excellent electrochemical performance, such as a large reversible capacity of 1128 mA·h·g^-1 after 80 cycles at a current density of 100 mA·g^-1 and a good rate capability of 818.5 mA·h·g^-1 at 1000 mA·g^-1. Undoubtedly, the cheap biomass carbon source and facile synthesis strategy here described can be extended to other composite materials for high-performance energy-storage and conversion devices.