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 CuSbSe₂, a promising 2D layered conversion, and alloying material is being investigated with references to parent pristine Sb₂Se₃ and a doped version of later Sn_0.2Sb_1.8Se₃ for their sodium-ion battery performance. The CuSbSe₂ 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 Sb₂Se₃ with its one-dimensional crystal structure leads to structural disintegration during battery operation. The Sn-doped analog, Sn_0.2Sb_1.8Se₃, comparatively exhibits enhanced kinetics owing to the reduced long-range order. The 2D layered, CuSbSe₂ despite exhibiting 2D long-range order exhibits superior electrochemical performance owing to the favorable electronic and structural features. The CuSbSe₂ exhibits a reversible capacity of 881 mAh g^-1 compared to 516 mAh g^-1 for Sn_0.2Sb_1.8Se₃ and 429 mAh g^-1 for Sb₂Se₃, 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 CuSbSe₂ may well be attributed to kinetics owing to enhanced diffusion coefficients in the intercalation and conversion regime.