Mechano-Electrochemical Stochastics in High-Capacity Electrodes for Energy Storage

Abstract

High-capacity anode materials (such as, silicon) are of critical importance for lithium-ion batteries aimed at achieving longer drive range for electric vehicles. Large lithium retention in these alloying materials is, however, accompanied by high volume expansion, which results in severe mechanical degradation and capacity decay. The inherently coupled mechano-electrochemical stochastics is elucidated in this work. A stochastic computational methodology has been developed to capture the large deformation and mechanical degradation in high-capacity anode materials. Lithiation and delithiation in such active particles follow a two-phase diffusive interface formation and propagation. Mechano-electrochemical interactions lead to different tensile forces acting on the active particle that may lead to microcrack formation. In this study, we have demonstrated that: (a) concentration gradient induced stress at the two-phase interface does not lead to severe mechanical degradation; and (b) large volume expansion induced tensile force at the particle surface actually gives rise to multiple spanning crack formation and further propagation during delithiation. Anode materials with higher partial molar volume of the lithiated phase can lead to enhanced mechanical degradation. Functionally graded materials, with reduced elastic modulus near the surface, hold potential for significant reduction in crack formation.