Enhanced Na‐Ion Electrochemical Performance through Cu Doping‐Mediated Sb2Se3 Phase Transformation into CuSbSe2 with Improved Kinetics

Abstract This work investigates the influence of structural and electronic modification on the electrochemical performance of conversion and alloying materials. The CuSbSe 2 , a promising 2D layered conversion, and alloying material is being investigated with references to parent pristine Sb 2 Se 3 and a doped version of later Sn 0.2 Sb 1.8 Se 3 for their sodium‐ion battery performance. The CuSbSe 2 with layered structure is well known to accommodate lattice distortions via inter‐layer movement, potentially mitigating distortions brought about by the Alkali ion (Na in this case) insertion. In contrast, the parent conversion‐cum‐alloying material Sb 2 Se 3 with its one‐dimensional crystal structure leads to structural disintegration during battery operation. The Sn‐doped analog, Sn 0.2 Sb 1.8 Se 3 , comparatively exhibits enhanced kinetics owing to the reduced long‐range order. The 2D layered, CuSbSe 2 despite exhibiting 2D long‐range order exhibits superior electrochemical performance owing to the favorable electronic and structural features. The CuSbSe 2 exhibits a reversible capacity of 881 mAh g −1 compared to 516 mAh g −1 for Sn 0.2 Sb 1.8 Se 3 and 429 mAh g −1 for Sb 2 Se 3 , with an improved Coulombic efficiency as well. The transient electrochemical investigations of Electrochemical Impedance Spectroscopy (EIS) and Galvanostatic intermittent titration techniques (GITT) reveal that better performance exhibited by CuSbSe 2 may well be attributed to kinetics owing to enhanced diffusion coefficients in the intercalation and conversion regime.