A design of MnO-CNT@C3N4 cathodes for high-performance aqueous zinc-ion batteries

Manganese oxides have been regarded as one of the most promising candidates in rechargeable aqueous zinc ion batteries due to their high specific capacity, high operating voltage, low cost and no-toxicity. Nevertheless, the grievous dissolution of manganese and the sluggish Zn2+ ions diffusion kinetics deteriorate the long cycling stability and the rate performance. Herein, we propose a combination of hydrothermal and thermal treatment strategy to design a MnO-CNT@C3N4 composite cathode material where MnO cubes are coated by carbon nanotubes (CNTs) and C3N4. Owing to the enhanced conductivity by CNTs and the alleviation of the dissolution of Mn2+ from the active material by C3N4, the optimized MnO-CNT@C3N4 exhibits an excellent rate performance (101 mAh g−1 at a large current density of 3 A g−1) and a high capacity (209 mAh g−1 at a current density of 0.8 A g−1), which is much better than its MnO counterpart. The energy storge mechanism of MnO-CNT@C3N4 is confirmed to be the co-insertion of H+/Zn2+. The present work provides a viable strategy for the design of advanced cathodes for high-performance zinc ion batteries.