Atomistically informed continuum model of energy-storage materials
The demand for high-capacity lithium-ion batteries for portable electronics, hybrid electric vehicles, and large-scale energy storage has stimulated a continuing search for new electrode materials with radically increased energy density. While there are logical and systematic approaches to identify high-capacity electrode materials (such as silicon, with the highest known theoretical capacity), the science behind battery lifetime extension is not on a solid footing. High-capacity electrode materials suffer from rapid, irreversible capacity decay and poor cyclability due to the Li-ion insertion/extraction induced huge volume changes and mechanical degradation, which presents a serious roadblock to the development of high-performance lithium ion batteries.
Zhang’s group has recently established an atomistically informed continuum model to account for the chemomechanical degradation in high-capacity electrode materials, including Si and Ge. The models bidirectionally couple the mechanics and chemistry: Li reaction and diffusion generate mechanical stress, and the stress in turn modulates reaction and diffusion kinetics. The model successfully predicted anisotropic swelling and surface fracture in crystalline Si upon lithiation, and bending induced symmetry breaking in lithiated Ge nanowires, etc. All these simulation results agree with the in-situ TEM observations. The modeling approach will pave the way toward the development of durable high-performance electrodes for the next-generation rechargeable batteries.