Synergistic Se-Doping and Accompanying S-Vacancies Drive Lattice Distortion and p-Band Modulation for Enhanced Sodium...

Metal sulfides, especially those containing alloying-capable metal elements, have shown great potential as sodium storage materials. However, the complex reaction process imposes more stringent requirements on the kinetic rate. A simple lattice distortion strategy is first proposed in this work to engineer the p-band center of S in Cu₃SbS₃ for enhanced Na⁺ storage. Though the co-doping of Se and accompanying S vacancies, the resultant lattice distortion elongated the bonds between metal and nonmetal elements to weaken their orbital hybridization and lift the p-band center for a high Na⁺ adsorption. The defects also increase the number of charge carriers for an improved conductivity. All those merits combined to contribute a superior electrochemical reaction kinetic in the Se-Cu₃SbS₃@rGO anode. It achieved a high capacity of 569.1 mAh g^-1 at 0.1 A g^-1, excellent rate capability of 273.6 mAh g^-1 at 50 A g^-1 and superior cycling stability of 387.4 mAh g^-1 (90%) after 1000 cycles at 5 A g^-1 as well as 92% after 150 cycles at 0.5 A g^-1 in the full cells. The insights into the function mechanism of Se-vacancies doping-induced lattice distortion offer valuable insights into the design and development of sulfide-based anode materials and sodium-ion batteries.