Enhanced Zn ion storage performance of polypyrrole coated Mn3O4 composites electrode

Aqueous zinc ion batteries (AZIBs) possess significant application potential in energy storage field due to their large capacity, low redox potential and high safety. Among various materials, Mn3O4 electrode has been widely investigated featuring its mixed Mn valence states (Mn2+, Mn3+ and Mn4+). However, it still suffers from the challenges of poor electrical conductivity and unstable structures. Herein, we coat a layer of polypyrrole (PPy) film on the surface of Mn3O4 microspheres by a simple one-step hydrothermal route. The assembled Zn//Mn3O4@PPy cells show a reversible capacity of 491.5 mAh/g at 0.1 A/g and a capacity retention of 96% at 2 A/g after 1200 times cycling. They also possess an energy density of 295 Wh/kg at a power density of 60 W/kg.