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 or replacing graphite in Li-ion battery anodes. Li3Sb and Li3Bi have the same cubic structure (Fm (3) over barm), but the ternary Li-Sb-Bi system has not been studied. We synthesized Li-3(Sb-x Bi1-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 farovides 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 difhision in Li3Bi.

Automated summary

Antimony and bismuth are attractive candidates for replacing graphite in Li-ion battery anodes as they can alloy with lithium. The Li-Sb-Bi ternary system has been studied and ternary alloys with different Sb mole fractions were synthesized. These alloys exhibit cubic crystal structures but show a tendency towards phase segregation at certain mole fractions.