Harnessing Electronic-Structural Advantages from Amorphization and Synergistic Doping for MnO2 Cathodes in Zinc-Ion Batteries

Abstract

Conventional view holds that amorphization enhances cycling stability solely through a passive mechanical buffer that accommodates electrode volume changes. Here, we present a more complete picture by demonstrating that structural disorder in MnO2, a leading cathode candidate for aqueous zinc-ion batteries, operates at a fundamentally deeper, electronic level. Combined magnetic, synchrotron, and theoretical analyses reveal that amorphization in MnO2 pre-emptively lifts the d-orbital degeneracy and disrupts the uniformity of the magnetic exchange network. This stands in stark contrast to crystalline MnO2, where the Jahn–Teller effect and superexchange interactions induce cooperative distortions that cause structural instability. Instead, the dual electronic effect in amorphous MnO2 eliminates the driving force for dynamic distortion and halts their long-range coherent transmission, thereby eliminating progressive structural collapse. Moreover, to overcome MnO2’s inherent conductivity limitations, we further introduce Co doping to precisely tailor the electronic states near the Fermi level. The synergy is clear: amorphization suppresses the root cause of degradation, while Co doping restores efficient charge transport. As a result, the cathode retains 107 mAh g–1 after 6000 cycles at 2 A g–1─a 256% improvement over pristine crystalline MnO2. Its practical relevance is further confirmed in an Ah-level pouch cell and a hybrid capacitor stable for over 3000 cycles. This work not only redefines the functional role of amorphization as an active electronic regulator that resolves the long-standing degradation puzzle of MnO2 at its quantum mechanical origin, but also establishes an integrated amorphization-doping strategy for designing electrode materials with high stability and high rate capability.