  Electrode particle cracking is one of the main phenomena driving battery
capacity degradation. Recent phase field fracture studies have investigated
particle cracking behaviour. However, only the beginning of life has been
considered and effects such as damage accumulation have been neglected. Here, a
multi-physics phase field fatigue model has been developed to study crack
propagation in battery electrode particles undergoing hundreds of cycles. In
addition, we couple our electrochemo-mechanical formulation with X-ray CT
imaging to simulate fatigue cracking of realistic particle microstructures.
Using this modelling framework, non-linear crack propagation behaviour is
predicted, leading to the observation of an exponential increase in cracked
area with cycle number. Three stages of crack growth (slow, accelerating and
unstable) are observed, with phenomena such as crack initialisation at concave
regions and crack coalescence having a significant contribution to the
resulting fatigue crack growth rates. The critical values of C-rate, particle
size and initial crack length are determined, and found to be lower than those
reported in the literature using static fracture models. Therefore, this work
demonstrates the importance of considering fatigue damage in battery
degradation models and provides insights on the control of fatigue crack
propagation to alleviate battery capacity degradation.
