On the origin of the capacity fading for aluminium negative electrodes in Li-ion batteries

The origin of the capacity loss for aluminium negative electrodes in Li-ion batteries has been studied for electrodeposited aluminium nanorod electrodes coated with Al2O3 layers of different thicknesses (i.e. a native oxide layer, 30 and 60 nm) mainly employing pouch cell voltammetric cycling versus metallic lithium. Whereas the capacity decreased continuously during cycling between 0.1 and 3 V vs. Li+/Li, good cycling stability was obtained when the cycling was carried out between 0.1 and 1 V vs. Li+/Li. Since no significant dependence of the cycling stability on the thickness of the alumina layer was found in any of the experiments, the observed loss of capacity is unlikely to have been caused by volume expansion effects. The latter is further supported by the finding that the capacity (obtained when cycling between 0.1 and 3 V vs. Li+/Li) decreased linearly with the inverse of the square root of the cycling time, indicating that the capacity loss was due to the loss of lithium as a result of lithium diffusion into the bulk of the aluminium electrodes. The latter is explained based on a lithium-aluminium alloying and dealloying model which complements previously published models.