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.
Currently, efforts to address the energy needs of large-scale power applications have expedited the development of sodium-ion (Na-ion) batteries. Transition-metal oxides, including Mn2O3, are promising for low-cost, eco-friendly energy storage/conversion. Due to its high theoretical capacity, Mn2O3 is worth exploring as an anode material for Na-ion batteries; however, its actual application is constrained by low electrical conductivity and capacity fading. Herein, we attempt to overcome the problems related to Mn2O3 with heteroatom-doped reduced graphene oxide (rGO) aerogels synthesised via the hydrothermal method with a subsequent freeze-drying process. The cubic Mn2O3 particles with an average size of 0.5-1.5 µm are distributed to both sides of heteroatom-doped rGO aerogels layers. Results indicate that heteroatom-doped rGO aerogels may serve as an efficient ion transport channel for electrolyte ion transport in Mn2O3. After 100 cycles, the electrodes retained their capacities of 242, 325, and 277 mAh g-1, for Mn2O3/rGO, Mn2O3/nitrogen-rGO, and Mn2O3/nitrogen, sulphur-rGO aerogels, respectively. Doping Mn2O3 with heteroatom-doped rGO aerogels increased its electrical conductivity and buffered volume change during charge/discharge, resulting in high capacity and stable cycling performance. The synergistic effects of heteroatom doping and the three-dimensional porous structure network of rGO aerogels are responsible for their excellent electrochemical performances.