A joint time-frequency analysis of the mechanical-electrochemical coupling mechanism from particles to electrodes for the Li-ion battery

Diffusion-induced stress (DIS) originates from the shrinkage/expand during Li extraction/insertion from/into the active particle for the Li-ion battery (LIB). Till today, the two-way coupled mechanical-electrochemical mechanism is still unclear. The above challenge can be decomposed into 2W+lH as follows: (i) Why need to reveal the two-way coupled mechanical-electrochemical mechanism? (ii) What is the two-way coupled mechanical-electrochemical mechanism? (iii) How to reveal the two-way coupled mechanical-electrochemical mechanism. In the process of answering the above 2W+lH, the following contributions have been made in this work: (i) An electro-chem-mechanical (ECM) model is established for the LIB, in which the mechanical-electrochemical coupling is two-way; (ii) The mechanical-electrochemical responses are solved for the ECM model in the time/frequency domain, respectively; (iii) The time-domain analysis shows that DIS enhances Li diffusion at the early and middle stages of discharge, while DIS inhibits Li diffusion at the end of discharge; (iv) The frequency-domain analysis shows that stress mainly affects solid-phase diffusion instead of electrolyte-phase diffusion. In a word, the multi-scale analysis quantitatively analyzes the impact of DIS on Li diffusion on the particle scale and reveals the two-way coupled mechanical-electrochemical mechanism on the electrode scale. The above results provide theoretical support for the battery manufacture and stress monitoring. The coupling mechanism is revealed on multiple scales by the joint time-frequency response analysis based on the mechanical-electrochemical coupling model for LIBs. • Establish two-way coupled electro-chemo-mechanical models for LIBs on multiple scales. • Deduce numerical solutions for electro-chemo-mechanical models in the time/frequency domain. • Reveal the two-way coupling mechanism between the stress and diffusion for LIBs.