Enhancing the mechanical stability of composite electrodes by regulating the volume of active material using a prelithiation strategy

Abstract

Significant volume variations in alloy-type and conversion-type anode materials during lithiation/delithiation cycling increase the challenge of assembling a composite electrode with high mechanical stability. This paper theoretically investigated the possibility of applying a prelithiation strategy to the assembly of a composite electrode to improve the mechanical stability of the composite electrode by controlling the pre-volume expansion of the active material. A chemo-mechanical coupled model containing an internal variable describing the irreversible volume dilation is developed to analyze a microunit of the composite electrode. Simulation results indicate that whereas a marginal prelithiation cannot effectively alleviate the high stress, and an excessive prelithiation increases the risk of damage. The optimal prelithiation range mainly depends on the irreversible volume dilation of the active material during cycling. For Si electrodes with the irreversible volume dilation of ~40%, the preferred prelithiation stoichiometric number is 0.3–0.6, the theoretical predictions are consistent with previous experimental results. The theoretical model and findings provide deeper insights on the prelithiation strategy based on the mechanical aspects.