Optimizing Electron Spin-Polarized States of MoSe/CrSe Heterojunction-Embedded Carbon Nanospheres for Superior Sodium/Potassium-Ion Battery Performances.

The principal challenges faced by sodium-ion batteries (SIBs) and potassium-ion batteries (KIBs) revolve around identifying suitable host materials capable of accommodating metal ions with larger dimensions and addressing the issue of sluggish chemical kinetics. Herein, a MoSe/CrSe heterojunction uniformly embedded is fabricated in nitrogen-doped hollow carbon nanospheres (MoSe/CrSe@N-HCSs) as an electrode material for SIBs and KIBs. CrSe exhibits spontaneous antiparallel alignment of magnetic moments. Mo doping is employed to regulate the electron spin states of CrSe. Moreover, the MoSe and CrSe heterojunctions induce a lattice mismatch at the heterostructure interface, resulting in spin-polarized states or localized magnetic moments at the interface, potentially contributing to spin-polarized surface capacitance. MoSe/CrSe@N-HCSs demonstrate a high capacity of 498 mAh g at 0.1 A g with good cycling stability (capacity of 405 mAh g and a coulombic efficiency of 99.8% after 1000 cycles). Additionally, density functional theory (DFT) calculations simulate the accumulation of spin-polarized charges at the MoSe/CrSe@N-HCSs heterojunction interface, dependent on the surface electron density of the antiferromagnetic CrSe and the surface spin polarization near the Fermi level. After regulating the electron spin states through Mo-doping, the band gap of the material decreases. These significant findings provide novel insights into the design and synthesis of electrode materials with exceptional performance characteristics for batteries.