Nanostructured intermetallic InSb as a high-capacity and high-performance negative electrode for sodium-ion batteries

Following the trends of alloys as negative electrodes for Na-ion batteries, the sodiation of a nanostructured InSb intermetallic compound was investigated. The benefit of coupling Sb with In was evaluated through the chemical reduction synthesis of InSb in the form of nanostructured particles assembled in micrometric aggregates. After full structural, morphological and surface characterizations, the electrochemical performance of the nanostructured InSb compound was examined in a carbonated electrolyte with fluoroethylene carbonate (FEC) as the additive. Its performance turns out to be remarkable with a capacity of around 450 mA h g−1 after 50 cycles at C/5. In terms of cyclability, the capacity of InSb is impressively stable at 1C with a capacity retention of 96% up to 100 cycles, in contrast to the strong capacity decay observed for a nanostructured Sb electrode. A good high-rate behavior is also observed with a capacity of 310 mA h g−1 at 5C. The better stability of the InSb compound compared to pure Sb suggests that combining In with Sb improves the ability of the material to alleviate volume expansion and mechanical stress during the repeated sodiation/desodiation processes. X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy studies on cycled electrodes were finally implemented to shed light, respectively, on the surface chemistry and electrochemical stability behavior of the promising InSb compound.