Highly Efficient Na+ Storage in Uniform Thorn Ball-Like α-MnSe/C Nanospheres

摘要

Because of its high theoretical capacity,MnSe has been identified as a promising candidate as the anode material for sodiumion 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-likeα-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-preparedα-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) cm^(2) 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.