Enhanced Zn ion storage performance of a polypyrrole-coated Mn3O4 composite electrode

Abstract

Aqueous zinc ion batteries (AZIBs) possess significant application potential in the energy storage field due to their high capacity, low redox potential and high safety. Among various materials, the 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 structure. 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 mA h g⁻¹ at 0.1 A g⁻¹ and a capacity retention of 96% at 2 A g⁻¹ after 1200 times cycling. They also possess an energy density of 295 W h kg⁻¹ at a power density of 60 W kg⁻¹.