Due to the increasing interest on the Li-ion battery aging studies among researchers, there are numerous battery degradation models presented in literature. However, they are either focused on a single technology, form factor or scale. This can be challenging for researchers that typically have to bridge multiple technologies and are interested in crossing multiple scales, from material-level, to cell and module/pack level. This paper explores the models presented for Li-ion battery degradation in different scales from the material level to the application level. In each scale, the main aging variables are summarized, the mathematical presentation of models are analyzed and the merits and disadvantages of each scale is discussed. This review aims at bringing together methods and results for multiple technologies, form factors for the most common Li-ion battery technologies.