Mixing, Domains, and Fast Li-Ion Dynamics in Ternary Li–Sb–Bi Battery Anode Alloys

Both antimony and bismuth can alloy with up to three molar equivalents of lithium and are therefore attractive candidates for replacing graphite in Li-ion battery anodes. Li3Sb and Li3Bi have the same cubic structure (Fm3̅m), but the ternary Li–Sb–Bi system has not been studied. We synthesized Li3(SbxBi1–x) with different Sb mole fractions at room temperature by ball milling. These ternary alloys all have cubic crystal structures, as determined by X-ray diffraction (XRD), but show a tendency toward phase segregation for x = 0.25 and 0.50. For x = 0.25, the lattice parameter presents a clear positive deviation from Vegard's law in XRD, while for x = 0.50, XRD reveals two phases after milling, with the Bi-rich minority phase diminishing after thermal annealing. Solid-state nuclear magnetic resonance spectroscopy provides evidence for a Sb-enriched environment around the Li atoms for Li3Sb0.25Bi0.75, and nuclear spin–lattice relaxation measurements of the binary and ternary alloy phases point to low activation energies and rapid Li-ion diffusion in Li3Bi.