Electrode materials based on antimony (Sb) are of growing interest because Sb achieves a balance between high capacity and good cycle performance in battery operation. The electrochemical performance of CoSb nanoparticles synthesized by a template-free assisted ball-milling method is reported for the first time. The first discharge (sodiation) profile is characterized by a gentle slope around 0.3 V. During subsequent electrochemical cycles, the reaction proceeds between 0.4 and 0.8 V. The obtained reversible capacity is 211 mAh/g. To get a mechanistic insight into the Na insertion into the CoSb lattice, suites of material analyses were performed in different stages of (dis)­charging. Upon sodiation, the formation of the Na3Sb phase was evidenced, which converts to elemental Na and Sb following a two-step alloying pathway upon desodiation. The local environment probed by various ex situ tools (diffraction, spectroscopy, microscopy, and electrochemical) hinted at the formation of an Sb-deficient CoSb1–x (Co4Sb) phase. The structural change was evident from the structural analysis, confirming the formation of Na metal. CoSb is by far the best among the most reported fluoroethylene-carbonate-free Sb intermetallic anodes for sodium-ion batteries.

Li-rich oxides, operating partially on high-voltage anionic redox, permit energy densities larger than electrode materials relying solely on transition-metal redox. On the contrary, Li-rich sulfides present a lower hysteresis but operate at a lower voltage. Oxysulfide electrodes, if adequately designed, can bridge this gap and offer high energy density with a minor penalty of hysteresis or capacity. Tetragonal-layered CuMOX (M = Bi/La, X = S/Se) chalcogenides are explored in this direction, and we found that Cu can be extracted at room temperature both electrochemically and chemically with different outcomes, some of which lead to new layered monoclinic bismuth “oxyperchalcogenide” oxidized phases, BiOX*, with dimerized S/Se. Moreover, we show that these new BiOX* phases can insert lithium to form new tetragonal-layered LiBiOX phases, isostructural to pristine CuBiOX. Both the CuBiOX and BiOX* phases are shown to insert four lithium ions via conversion and intercalation–conversion reactions, respectively. Further, we demonstrate the importance of the host cation on the above insertion reactivity by replacing Bi with La to produce a new layered tetragonal phase Cu1–x Li x LaOS. The encountered different reaction pathways are rationalized by theoretical calculations. This work shows that Cu-based layered oxychalcogenides can offer rich hunting grounds for new metastable electrochemically active layered materials.

No abstract

No abstract