Plasma‐Induced Oxygen‐Rich Vanadium Hexacyanoferrate Embedded in Hierarchical Porous Carbon Framework for Superior Aqueous Manganese‐Ion Storage

Abstract As a new energy storage device, manganese‐ion hybrid supercapacitor (Mn 2+ HSC) shows great potential due to the characteristics combined with high theoretical capacity, great safety, low cost and environmental friendliness. However, it remains a great challenge to develop electrode materials with fast manganese‐ion storage kinetics. Herein, a plasma‐induced oxygen‐rich vanadium hexacyanoferrate (VHCF) embedded in hierarchical porous carbon framework (HPCF) (denoted as VHCF/HPCF‐O) is reported, which serves as an outstanding manganese‐ion storage material for Mn 2+ HSCs. The VHCF/HPCF‐O composite shows high electrical conductivity, enhanced hydrophilicity, multiple active sites and electrochemical stability, resulting in a remarkable specific capacitance of 240 F g −1 with a low polarization of 142 mV at 5 mV s −1 and excellent cycling stability (102.1% after 10 000 cycles). Both experimental results and theoretical calculations verify that two redox‐active sites of V = O and Fe‐C≡N contribute to the high capacitance and the high‐rate storage benefiting from the interconnected conductive network. By pairing the VHCF/HPCF‐O cathode with the Ti 3 C 2 T x anode, the assembled Mn 2+ HSC delivers a remarkable energy density of 23.3 Wh kg −1 at 180 W kg −1 , superior to most recently reported HSCs. This work highlights the material design for manganese‐ion storage and its great potential for novel energy storage devices.