Harvesting Mn 2+ by Encapsulated MnO x With sp 2 ‐Carbon to Enhance the Mn 2+ /MnO 2 Conversion for High‐Capacity Zn‐Ion Batteries

ABSTRACT Manganese oxide is a promising cathode material for aqueous Zn‐ion batteries (AZIBs), of which the key is to inhibit the dissolution of Mn 2+ and harvest Mn 2+ to achieve high‐capacity and long‐life. Herein, MnO x cathode is encapsulated into in situ formed sp 2 ‐carbon shell (denoted as CMC) via coating Mn‐based metal organic framework by coal tar pitch for Zn 2+ storage. Thanks to the in situ formed sp 2 ‐carbon shell in CMC, the formation energy of Mn vacancy is significantly increased, thus effectively inhibiting the dissolution of Mn 2+ . Meanwhile, a reversible Mn 2+ /MnO 2 conversion is achieved by harvesting Mn 2+ via electrostatic attraction, and preventing the formation of massive zinc hydroxide sulfate via repelling SO 4 2− and OH − . Moreover, the sp 2 ‐carbon shell with excellent conductivity enables effective re‐deposition of Mn 2+ to MnO 2 . As expected, the novel CMC cathode delivers an exceptional capacity of 438.2 mAh g −1 (889.5 mAh g −1 based on the mass of MnO x ) at 0.2 A g −1 with a capacity retention up to 91.1% over 5000 cycles at 2 A g −1 . This work proposes an effective strategy to synthesize advanced Mn‐based cathode materials to harvest Mn 2+ through interface engineering for AZIBs.