Micro-scale modeling of Lithium-ion battery

Good energy density, long lifetime, high capacity and high voltage make Lithiumion batteries the most widespread energy storage systems, suitable for several fields of application. Nevertheless, usage leads to cell degradation which mainly results in capacity and power fade. Degradation phenomena are the result of the interaction between mechanical and electro-chemical mechanisms, which are reviewed in this paper. Lithium-ion batteries store and deliver electric energy by means of ions transport between anode and cathode through the electrolyte. The active material of the electrodes consists of micrometer particles which can host lithium ions through insertion/extraction processes. These processes are modelled as diffusion-mechanical problem, since the lithium concentration gradient within the particle due to ions diffusion generates internal stresses in analogy with a temperature gradient. The model in this work, usually referred as diffusion induced stress (DIS), can predict the stresses in the active material particles which are the driving force for damage, pulverization, exfoliation and crack propagation. Indeed, the damage induced by the insertion/extraction processes explains the capacity reduction over charge/discharge cycles: a critical issue for batteries lifetime.