Study of lithium-ion battery state of charge based on propagation characteristics of guided waves

The swing process of lithium-ion results in dynamic electrode mechanics, which affects the propagation characteristics of acoustic wave in lithium-ion batteries. The robust state-vector formalism, the Legendre polynomial method, and the classical Biot theory are introduced for multilayer porous lithium-ion battery structures. Meanwhile, the chemo-mechanical coupling effects are considered simultaneously in the model, mainly due to the physical coupling effects caused by the interaction between the local current density of the particles, the lithium-ion diffusion process and the stresses. Finally, the relationship between the propagation characteristics of guided waves and the state of charge in lithium-ion batteries is interpreted in the form of eigenvalue-eigenvectors. An ultrasonic guided wave experimental detection system is built, and the experimental method of measuring and extracting the time- and frequency-domain characteristic parameters in customized batteries is studied. The time of flight and the theoretical calculation results are then verified against each other, indicating that the measurement and analysis method is feasible. Furthermore, the influence law of different discharge rates on the acoustic characteristic parameters of lithium-ion batteries is investigated to realize the acoustic analysis of potential factors of aging failure of lithium-ion batteries. This provides a research path for the non-destructive testing and evaluation of the operational status of lithium-ion batteries.