A coupled phase field formulation for modelling fatigue cracking in lithium-ion battery electrode particles

TL;DR

This study introduces a multi-physics phase field fatigue model for lithium-ion battery electrode particles, capturing crack growth over hundreds of cycles and highlighting the importance of fatigue damage in battery degradation.

Contribution

A novel coupled electrochemo-mechanical phase field fatigue model that simulates realistic crack propagation in battery particles over multiple cycles.

Findings

Crack area increases exponentially with cycle number.

Three crack growth stages: slow, accelerating, unstable.

Critical parameters are lower than static fracture models.

Abstract

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.