Synergistic Enhancement of Zinc‐Ion Hybrid Capacitors via Redox‐Active Doping and Sulfonated MXene‐Modified Polypyrrole Cathodes
Zhanhui Fan, Tao Xue, Yongbiao Mu, Lin Yang, Chao Yang, Limin Zang, Lin Zeng
Abstract
Abstract Polypyrrole (PPy) has emerged as a promising cathode material for zinc‐ion hybrid capacitors (ZIHCs) owing to its facile synthesis, high chemical stability, and reversible doping/dedoping behavior. Redox‐active dopants can provide additional capacity, thereby improving the electrochemical performance of PPy‐based electrodes. Meanwhile, sulfonic acid‐functionalized Ti 3 C 2 T x (S‐Ti 3 C 2 T x ) is introduced as a substrate for PPy. The excellent flexibility and electrical conductivity of S‐Ti 3 C 2 T x help to buffer the volume changes of PPy, enhancing its structural integrity. Moreover, the grafted −SO 3 H groups on Ti 3 C 2 T x serve as in situ proton reservoirs, maintaining a localized acidic microenvironment near the electrode surface. This feature is beneficial for suppressing the formation of zinc hydroxide sulfate byproducts to a certain extent. Density functional theory calculations reveal that the integration of redox‐active dopants and S‐Ti 3 C 2 T x optimizes the electronic structure, resulting in improved conductivity of the composite electrode. As a result, the ZIHCs employing sodium hydroquinone sulfonate‐doped PPy/S‐Ti 3 C 2 T x as the cathode delivers a high specific capacity of 192.4 mAh g −1 and an energy density of 153.9 Wh kg −1 at a scan rate of 2 mV s −1 . This work offers valuable insights into enhancing the electrochemical performance of conducting polymer‐based electrodes through the synergistic design of redox‐active dopants and functionalized MXene substrates.