Abstract:

Because of its high theoretical capacity, MnSe has been identified as a promising candidate as the anode material for sodium-ion batteries. However, its fast capacity deterioration due to the huge volume change during the intercalation/deintercalation of sodium ions severely hinders its practical application. Moreover, the sodium storage mechanism of MnSe is still under discussion and requires in-depth investigations. Herein, the unique thorn ball-like α-MnSe/C nanospheres have been prepared using manganese-containing metal organic framework (Mn-MOF) as a precursor followed by in situ gas-phase selenization at an elevated temperature. When serving as the anode material for sodium-ion battery, the as-prepared α-MnSe/C exhibits enhanced sodium storage capabilities of 416 and 405 mAh g^-1 at 0.2 and 0.5 A g^-1 after 100 cycles, respectively. It also shows a superior capacity retention of 275 mA h g^-1 at 10 A g^-1 after 2000 cycles, and a rate performance of 279 mA h g^-1 at 20 A g^-1. Such sodium storage properties could be attributed to the unique structure offering a highly efficient Na⁺ diffusion kinetics with a diffusion coefficient between 1 × 10^-11 and 3 × 10^-10 cm² s^-1. The density functional theory calculation indicates that the fast Na⁺ diffusion mainly takes place on the (100) plane of MnSe along a V-shaped path because of a relatively low diffusion energy barrier of 0.15 eV.

Key words: MnSe, Sodium storage mechanism, High-rate performance, Long-term stability, Uniform nanospheres