A single-element heterovalent doping strategy stabilizing the cathode structure for reversible zinc-ion storage to...

Zinc-ion batteries (ZIBs), recognized for their safe aqueous electrolyte and low-cost, abundant zinc resources, offer significant promise for applications in energy storage. MnO₂ is a promising cathode material due to its environmental friendliness and low cost, but it faces challenges related to low conductivity and structural instability. Herein, a single-element (Ce) heterovalent doping strategy is proposed to boost the capacity and structural stability of δ-MnO₂ (Ce-MnO₂). Ce⁴⁺ can preferentially occupy the Mn sites due to its same and stable valence state as Mn⁴⁺, effectively suppressing structural collapse during charge and discharge processes. Ce³⁺ could contribute to improved electronic conductivity through aliovalent substitution, leading to charge compensation and altering the local chemical environment by creating oxygen vacancies and optimizing Mn-O interactions. Moreover, it can improve the specific surface area and provide active sites, thereby promoting electrochemical activity and facilitating superior ion transport. Consequently, the Ce-MnO₂ cathode achieved a high specific capacity of 374.5 mAh g^-1, with 90% capacity retention after 1000 cycles. When further applied to power a PNIPAM hydrogel actuator, Zn//MnO₂ ion batteries exhibited potential for actuator-driven technologies.