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

Abstract

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-chemo-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.