Conductive Polymer Designed of Binder-Free Polypyrrole-MnO2/Ti3C2 for Oxidative Stable Aqueous Zinc-Ion Batteries

Abstract

Affordable and nontoxic manganese dioxide (MnO2) cathodes hold great promise for high-voltage and high-capacity rechargeable zinc-ion batteries (ZIBs). However, their low energy density and cycle lifespan remain a grand challenge. Limitations in typical aqueous electrolytes stem from insufficient electrical conductivity and failure in structural integrity due to manganese dissolution and H+/Zn2+ co-intercalation. This work shows the effectiveness of binder-free, heteronanosheets of polypyrrole-functionalized MnO2/MXene (PPy-MnO2/MXene) for high-performance ZIBs. Although conductive MXene nanosheets increased electron transport and structural stability, phase transitions caused by delaminated crystals and structural deterioration are shortcomings that should be addressed. With enhanced resistance to water-induced oxidation, PPy-MnO2/MXene retained its dispersity in aqueous solutions. The PPy-MnO2/MXene heterostructure exhibited outstanding high rate performance and consistent cycling behavior. It sustains 98% of its capacity after 1500 cycles, achieving a specific capacity of 198 mA h g–1 at a current density of 5 A g–1 and 148 mA h g–1 at a current density of 10 A g–1. The density of states calculations revealed the metallic property of PPy-MnO2/MXene and enhanced electronic conductivity compared to that of simple MnO2/MXene. Electrochemical studies revealed improved Zn2+/H+ mobility and pseudocapacitive behavior, indicating the potential of this binder-free heterostructure for strengthening the performance of ZIBs.