3D morphological evolution of Li-ion battery negative electrode LiVO2 during oxidation using X-ray nano-tomography

Lithium vanadium oxide (LiVO21) holds the potential promise to replace graphite as an anode material in commercial Li-ion batteries as it doubles the volumetric energy density compared to graphite but can still operate at low voltage (~ 0.1 V vs. Li/Li+). Its degradation mechanism was investigated using a synchrotron X-ray nano-tomography technique to image the LiVO2 in three dimensions (3D). In particular an oxidation effect is discussed by a direct visualization and quantification of the 3D microstructure of the LiVO2 before and after being exposed to the air, which results in the oxidation of the LiVO2. After being exposed to air, an oxidation layer with thickness ~ 120–240 nm was observed at the interface of the LiVO2 particles and the binders/pores. While the total volume of LiVO2 remains relatively constant before and after oxidation, the particle size reduces, which is consistent with crack growth possibly due to the local exothermal oxidation reactions, accompanied by phase transition at an elevated temperature. The findings confirm the air-sensitivity of LiVO2 observed indirectly in the literature.

► 3D morphological evolution of LiVO2 due to oxidation was imaged at sub-30 nm.
► Critical 3D morphology parameters of LiVO2 were quantified before/after oxidation.
► Cracks with size in tens of nanometers were presented before oxidation.
► Oxidation layers formed on the surface of LiVO2 particles after oxidation.
► Further fracture and LiVO2 volume reduction occurred due to oxidation.