Introducing PANI into a Manganese-Based Cathode Material to Improve the Energy Storage Performance of Aqueous Zinc-Ion Batteries by Generating Dual Redox Reactions

Rechargeable manganese dioxide (MnO2)-based aqueous zinc-ion batteries (AZIBs) have emerged as potential next-generation large-scale energy storage devices due to their high theoretical specific capacity, low cost, intrinsic safety, and environmental friendliness. However, the practical application of manganese-based cathodes is limited by the insufficient utilization of the voltage window, resulting in a negligible capacity contribution in the voltage range of 0.8–1.2 V. Herein, the CNs/PANI/MnO2 cathode is rationally designed and synthesized by combining two redox active materials (PANI and MnO2) with complementary voltage windows using highly conductive and low-cost carbon nanospheres (CNs) as the substrate. The redox reactions of polyaniline (PANI) in the voltage range of 0.8–1.2 V strengthen the diffusion-controlled process and make up the capacity contribution to further improve the energy storage efficiency of AZIBs over the entire voltage window. After controllable structural and composition optimization, the CNs/PANI/MnO2 cathode delivered a maximum specific capacity of 363.4 mAh g–1 at 0.2 A g–1. Moreover, the presence of PANI protected MnO2 from degradation during the charge–discharge process to achieve excellent cycling stability with 99.6% capacity retention after 10,000 cycles. This study provides a feasible approach for designing high-performance AZIB electrodes by generating dual redox reactions.