Facile template-free synthesis of yolk–shell MnO/C nanospheres for stable and high-rate aqueous zinc-ion batteries

Manganous oxide (MnO) is a promising high-capacity cathode for aqueous zinc-ion batteries (AZIBs), but its practical application is severely hindered by low intrinsic electronic conductivity and large volume fluctuations during cycling. Constructing yolk–shell architectures with conductive carbon matrices is an effective strategy, yet conventional templating methods usually involve sacrificial templates and multi-step procedures, limiting scalability and structural uniformity. Herein, we report a facile, template-free strategy to fabricate uniform yolk–shell MnO/C nanospheres. The synthesis involves a single-step solvothermal preparation of a Mn–glucose complex precursor, followed by controlled thermal annealing under argon. The resulting architecture features a well-defined internal void, a porous MnO/C composite shell, and a continuous three-dimensional carbon network. These structural attributes synergistically accommodate volume expansion, facilitate electron transport, and shorten ion diffusion pathways. When evaluated as a cathode for AZIBs, the yolk–shell MnO/C delivers a high reversible capacity of 290.0 mAh g⁻¹ at 0.2 A g⁻¹ and outstanding long-term cycling stability, retaining 191.2 mAh g⁻¹ at 1 A g⁻¹ and 146.5 mAh g⁻¹ at 2 A g⁻¹ each after 1000 cycles. Quantitative kinetic analysis reveals that the superior rate capability originates from a surface pseudocapacitance-dominated hybrid charge-storage mechanism, enabled by the high specific surface area and abundant mesoporous channels of the yolk-shell architecture. This work provides a straightforward and scalable pathway for fabricating advanced yolk–shell structured metal oxide/carbon composites for advanced energy storage.