Enhanced reversible conversion of Cu2S anodes for Na-ion batteries enabled by carbon nanotubes

Sodium-ion batteries (SIBs) with copper(I) sulfide (Cu2S) anodes has been gaining significant attention because of their relatively high capacity and inherent safety. The highly reversible conversion of Cu/Na2S in charging process to pristine Cu2S is essential for its electrochemical properties. Here, we have prepared Cu2S/carbon nanotube (CNT) anode for SIBs, in which highly-conductive CNTs are employed as a catalyst to promote the reversible reaction kinetics of Cu2S anode. By using a combination of electrochemical and ex-situ X-ray diffraction analysis, we demonstrate that Cu2S/CNT anodes can be converted efficiently and reversibly in comparison with a pure Cu2S anode. CNTs have superior electron conductivity and high surface area, and are therefore used for balancing the poor electronic conductivity of Cu2S and discharged products, as well as physically inhibition of the dissolution of sodium polysulfide. Consequently, a partially reversible conversion reaction is enabled during the charging process. In this study, we are contributing to the design of conversion-type materials that feature reversible mechanisms, opening up new possibilities for materials design. •CNTs are used to promote the reversible reaction kinetics of the Cu2S anode for SIBs.•CNTs with superior electron conductivity are used for balancing the poor conductivity of Cu2S and discharged products.•CNTs can physically inhibit the dissolution of sodium polysulfide.•Cu2S@CNT anode shows long-term cycling stability.