Modulating the interlayer H⁺ migration in MnO₂ via W and K co-doping engineering to high-capacity aqueous zinc-ion...

MnO₂ is a promising cathode material for high-energy-density aqueous zinc-ion batteries (AZIBs) due to its high voltage and abundance. However, its electrochemical activity is seriously damaged by the sediment of discharge by-product Zn₄SO₄(OH)₆·nH₂O (ZSH), which results from the pH change of electrolyte after "dead" H⁺ ions are trapped within the MnO₂ lattice. Herein, MnO₂ co-regulated by tungsten (W) and potassium (K) (denoted as WKMO) is proposed to address this issue. The addition of W and K significantly diminishes the resistance to H⁺ insertion/extraction and facilitates the migration of H⁺ within the MnO₂ lattice, relieving the heavy accumulation of ZSH during the long cycle. Meanwhile, stronger W-O and K-O bonds stabilize the layered structure of WKMO and moderate oxygen defects endow WKMO with high conductivity and increased active sites. Benefiting from the effect of W and K co-doping, exceptional rate performance (150 mAh g^-1 at 5 A g^-1) and long-term cycling stability (238 mAh g^-1 after 1000 cycles at 1 A g^-1) are exhibited by WKMO, which are 42 % and 209 % higher than the original material, respectively. The reaction mechanism of H⁺/Zn²⁺ stepwise insertion/extraction is elucidated through physical and chemical characterization. The strategy of strengthening H⁺ migration and mitigating ZSH deposition via multi-element modulation offers a novel approach for fostering long-life Zn//MnO₂ batteries.