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Synthesis of MnSe@C yolk‐shell nanospheres via a water vapor‐assisted strategy for use as anode in sodium‐ion batteries

This study introduces a simple and eco‐friendly synthetic strategy for yolk‐shell nanospheres that consist of manganese selenide yolks and carbon shells (MnSe@C) by reacting manganese salt impregnated in the porous hollow carbon nanospheres (HCNS) with H2O vapor. First, manganese salt dissolved in ethanol was impregnated into the spacious pores of the HCNS by capillary force. Then, heat treatment of the powder in the presence of H2O triggered the nucleation and crystal growth of manganese hydroxide, resulting in the formation of HCNS whose central voids are filled with multiple nanoparticles. Subsequent selenization yielded yolk‐shell nanospheres with MnSe@void@carbon configuration. MnSe@C was applied as the anode for sodium‐ion batteries (SIBs), and the following electrochemical reaction was confirmed from various analytical techniques: MnSe +2Na+ + 2e− ↔ Mn + Na2Se. MnSe@C nanospheres exhibited stable cycle performance up to 1000 cycles at 0.5 A g−1, wherein a reversible capacity of 222 mA h g−1 was delivered in the 1000th cycle. Furthermore, MnSe@C nanospheres exhibited a fair rate performance (209 mA h g−1 at 2.0 A g−1).