Granular phase transformation of polycrystalline aluminum during electrochemical lithiation

Lithium storage in aluminum stems from a phase transformation from lithium-poor α phase (Al, face-centered cubic) to lithium-rich β phase (LiAl, cubic) at room temperature. We investigate the electrochemical lithiation of polycrystalline Al using operando light microscopy coupled with electron backscatter diffraction. The operando videos reveal that the β phase patches expand radially from discrete nuclei with inhibition observed for specific Al grains at the α/β interface. Statistical analyses indicate that these grains have a preferred out-of-plane <111> orientation. This study suggests that lithiation of Al is a whole-grain process that is influenced by grain textures rather than grain boundaries.