Dual Anions Doping Enhanced Conductivity and Stability of Layered δ-MnO2 Cathode for Aqueous Zinc-Ion Battery

Manganese-based oxides have been identified as promising cathodes for aqueous zinc-ion batteries (AZIBs) due to their high theoretical energy density and cost-effectiveness. However, their low electronic conductivity and tendency to dissolve during cycling have limited their applications in AZIBs. Herein, a one-step calcination method is proposed to incorporate sulfur and nitrogen anions into the MnO2 structure (referred to as NS-MnO2). Characterizations and theoretical calculations confirm that the sulfur and nitrogen dopants improve the intrinsic electronic conductivity and structural stability of MnO2. Specifically, sulfur doping accelerates the diffusion of Zn2+, while the formation of Mn & horbar;N bonds strengthens the Mn & horbar;O bonds, thereby stabilizing the structure of MnO2 during cycling. In addition, the doping process creates oxygen vacancies that facilitate Zn2+ diffusion kinetics. As a result, the NS-MnO2 demonstrates a specific capacity of 295 mAh g-1 at a current density of 0.2 A g-1 and exhibits high cycling stability of 120 mAh g-1 at 1 A g-1 over 1500 cycles. This study highlights the effectiveness of dual anions doping in modifying the structure of transition metal oxides and suggests its potential application in designing other materials for energy storage.