We develop a physical-statistical model of particle-based battery electrodes in Li ion batteries. Graphite particles and metal oxide crystallites are the active components in the battery electrodes. During charging/discharging cycles, electrodes experience reversible changes and they go through irreversible structural transformations. Our hierarchical approach employs a particle population balance model based on Fokker-Planck theory. It relates structure-transforming processes at the particle level to macroscopic changes in physicochemical properties and performance. At the particle level, the model accounts for particle activation or deactivation during charging or discharging. Moreover, at the negative electrode, it incorporates formation and growth of the solid electrolyte interphase (SEI), as well as the formation of cracks in the SEI and growth of the SEI area. At the positive electrode, it accounts for the kinetics of crystallite dissolution and isolation. These processes determine changes in the statistical particle density distribution function. So far, we have incorporated an SEI growth model into the population balance model. Our initial results show that the SEI thickness increases from 30 nm to 80 nm after 500 cycles. In a future step, we will include formation of cracks in the SEI and crack-initiated growth of the SEI surface and we will link these changes to the battery performance parameters e.g. capacity fade and power fade.