Sustainable porous biochar coated MnO2 composites as the cathode in aqueous Zn/Mn batteries

Sustainable development is the theme of the current era, and the reutilization of resources and clean energy are the keys to achieve it. Zn/Mn batteries had become a research hotspot due to its advantages of safety and efficiency, but the poor conductivity and the dissolution of manganese oxides restrict the further development of the batteries. Herein, we put forward a strategy to form a uniform graphitized carbon layer with porous structure on the MnO2 by a simple hydrothermal reaction from pistachio shell, which immobilizes MnO2 and effectively inhibits its dissolution into the electrolyte. The electrochemical results shows that the specific capacity of biochar composites cathode reaches 292.9 mA h g−1 after 50 stable cycles at a current density of 100 mA g−1, which is three times higher than that of the non-coated MnO2 cathode (92.5 mA h g−1). This unique porous material with high conductivity provides some new ideas for the modification of Mn-based zinc ion batteries and the sustainable reuse of biological resources.