Atomic-scale characterization of tin-based intermetallic anodes

Electrochemical reactions of lithium with Ni₃Sn₄- and CoSn₂-based anodes for Li-ion batteries are analysed from a combined experimental and theoretical approach. We have found that the first discharge consists in the nanostructuration of the pristine materials into metallic and Li₇Sn₂ nanoparticles. Then, the basic mechanism of the charge and discharge cycles is the reversible transformation of Li₇Sn₂ into Ni₃Sn₄ or CoSn₂ particles. Finally, the large irreversible capacity loss observed at the beginning of the first discharge is explained from interfacial reactions.