Electrochemical Sodiation/Desodiation into Mn₃O₄ Nanoparticles

Mn₃O₄ is considered to be a promising anode material for sodium-ion batteries (SIBs) because of its low cost, high capacity, and enhanced safety. However, the inferior cyclic stability of the Mn₃O₄ anode is a major challenge for the development of SIBs. In this study, a one-step solvothermal method was established to produce nanostructured Mn₃O₄ with an average particle size of 21 nm and a crystal size of 11 nm. The Mn₃O₄ obtained exhibits a unique architecture, consisting of small clusters composed of numerous tiny nanoparticles. The Mn₃O₄ material could deliver high capacity (522 mAh g^-1 at 100 mA g^-1), reasonable cyclic stability (158 mAh g^-1 after 200 cycles), and good rate capability (73 mAh g^-1 at 1000 mA g^-1) even without further carbon coating, which is a common exercise for most anode materials so far. The sodium insertion/extraction was also confirmed by a reversible conversion reaction by adopting an ex situ X-ray diffraction technique. This simple, cost-effective, and environmentally friendly synthesis technique with good electrochemical performance shows that the Mn₃O₄ nanoparticle anode has the potential for SIB development.