Fast and stable Na insertion/deinsertion in double-shell hollow MnO nanospheres

MnO has received much attention at the anode material for sodium storage due to its low cost, environmental friendliness, and non-toxicity. However, many MnO-based electrodes exhibit poor cyclic stability, and very limited attention has been paid to the sodium storage mechanism of MnO. Herein, we report a self-templating method to synthesize uniform MnO double-shell hollow nanospheres. By thermally annealing the Mn-based metal organic framework precursor, Mn2O3 double-shell hollow nanospheres has been synthesized via a possible Ostwald ripening process and MnO double-shell hollow nanospheres is obtained by a subsequent thermal reduction of Mn2O3. When used as the anode material for sodium storage, the as-prepared MnO demonstrate a reversible capability of 261 mAh g-1 at 0.2Ag-1 after 200 cycles. Furthermore, compared with solid MnO without a hollow interior, the MnO double-shell hollow nanospheres exhibit a more stable retention of 81mAh g-1 at 5Ag-1 after 2000 cycles, and a better rate performance of 97mAh g-1 at 10Ag-1. Surprisingly, the ex-situ XRD results reveal that the sodium storage process of MnO is governed mainly by intercalation/deinsertion reactions, while the conversion between Mn and Na2O only takes place to a little extent. Such a hollow construction allows a more stable structural integrity granting enhanced long-term cycling stability. •A self-templated method was developed, using uniform Mn MOF as the precursor, to synthesize MnO double-shell hollow nanospheres (h-MnO).•The as-prepared h-MnO sample demonstrated enhanced high-rate performance and good cycle life upon extended cycling, significantly better compared to solid MnO nanoparticles.•Post-mortem analysis indicated that the spherical morphology of the sample could be perfectly retained after cycling test, showing excellent structural robustness.•Ex-situ XRD measurement revealed that the storage process mainly consisted of Na insertion/deinsertion, while conversion reaction took place only to a minor extent.