CuSbS2 as a negative electrode material for sodium ion batteries

CuSbS2 was tested as a negative electrode material for sodium-ion batteries. The material synthesized by ball milling offers a specific charge of 730 mAh g(-1), close to the theoretical value (751 mAh g(-1)), over a few cycles. The reaction mechanism was investigated by means of operando X-ray diffraction, (121)sb MOssbauer spectroscopy, and Cu k-edge X-ray absorption spectroscopy. These studies reveal a sodiation mechanism that involves an original conversion reaction in two steps, through the formation of a ternary phase, CuSb(1-x)S(2-y), as well as a NaxS alloy and Sb, followed by an lloying reaction involving the previously formed Sb. The desodiation process ends with the reformation of the ternary phase, CuSb(1-x')S(2-y'), deficient in Sb and S; this phase is responsible for the good reversibility observed upon cycling. (C) 2016 Published by Elsevier B.V.