Oxygen-Deficient α-MnO Nanotube/Graphene/N, P Codoped Porous Carbon Composite Cathode To Achieve High-Performing Zinc-Ion Batteries.

A major drawback of α-MnO-based zinc-ion batteries (ZIBs) is the poor rate performance and short cycle life. Herein, an oxygen-deficient α-MnO nanotube (V-α-MnO)-integrated graphene (G) and N, P codoped cross-linked porous carbon nanosheet (CNPK) composite (V-α-MnO/CNPK/G) has been prepared for advanced ZIBs. The introduction of V in MnO can decrease the value of the Gibbs free energy of Zn adsorption near V (ca. -0.73 eV) to the thermal neutral value. The thermal neutral value demonstrates that the Zn adsorption/desorption process on V-α-MnO is more reversible than that on α-MnO. The as-made Zn/V-α-MnO battery is able to deliver a large capacity of 305.0 mAh g and high energy density up to 408.5 Wh kg. The good energy storage properties can be attributed to V. Additionally, the V-α-MnO/CNPK/G composite possesses the structure of nanotube arrays, which results from the vertical growth of α-MnO nanotubes on CNPK. This unique array structure helps to realize fast ion/electron transfer and stable microstructure. The electrochemical performance of V-α-MnO has been comprehensively improved by compositing with G and CNPK. The V-α-MnO/CNPK/G can achieve capacity up to 405.2 mAh g, energy density of 542.2 Wh kg, and long cycle life (80% capacity retention after 2000 cycles).