Multi‐Cation Synergy in MnO 2 ‐Based Cathodes: Electronic Engineering for Ultra‐Stability and High‐Capacity Charge Storage

Abstract Transition metal oxide electrodes, while promising for high‐energy storage, suffer from rapid capacity fading and sluggish kinetics due to inherent structural and electronic limitations. Herein, a transformative heterovalent multi‐cation integration strategy is reported that redefines the electronic landscape of δ‐MnO 2 , overcoming longstanding barriers in stability and pseudocapacitance. By incorporating complementary high‐valent (Nb 5+ , Ce 4+ ) and low‐valent (Fe 3+ , Co 2+ , Ag + ) cations into distinct lattice sites of MnO 2 , dual optimization of structural robustness and surface electrochemistry is achieved. First, the reduced formation enthalpy mitigates Mn migration and the suppressed Jahn–Teller distortion alleviates Mn dissolution, guaranteeing the excellent structural stability. Second, the elevated d‐band center enhances ion adsorption kinetics and the narrowed bandgap facilitates charge transfer, contributing to the improved pseudocapacitive activity. The engineered MnO 2 cathode delivers a remarkable pseudocapacitance of 478.4 F g −1 (0.5 A g −1 ), outperforming most reported analogues. When configured into asymmetric device, the system attains an exceptional energy‐power balance (71.1 Wh kg −1 @447 W kg −1 ) with unprecedented cycling endurance (no capacity decay after 50 k cycles). Scalable pouch‐type cells demonstrate outstanding mechanical flexibility and performance retention, underscoring the practical viability. This synergistic electronic engineering paradigm establishes a universal design principle for addressing intrinsic material limitations in oxide electrodes.