A Statistical Mechanical Model Incorporating Coupled Concentration-Strain Effects in Lithium Ion Battery Electrode

Thursday, 1 June 2017: 11:24
Grand Salon C - Section 13 (Hilton New Orleans Riverside)
H. Chen and H. Y. S. Huang (North Carolina State University)
Electrochemical storage system such as Lithium-ion batteries have been widely used from power tools and portable electronics to recent PHEV/EV. However, Li-ion batteries’ low power density and cycling capability have limited many potential applications. Many studies have shown that mechanical deformation plays a significant role in these drawbacks. To understand the influence of mechanical deformation on electrochemical reactions and phase transition in electrodes, studies have used the phase field method to model the mechanical stresses/strains or Li-ion concentration profiles. Yet few of them have considered “coupling effects” of these two factors, and resulting in inaccurate simulation results. In this study, we use statistical mechanics and transition state theory to develop constitutive equations of electrodes that include the concentration-strain coupling effects. Specifically, we relate the activation energy change of microscopic particles of electrode components with materials’ strain energy density. Further, we model microscopic processes of electrodes’ deformation by describing the behavior of activated particles and their probability relationship with all local particles in electrodes. By combining the phase field method, our generalized constitutive equations could provide much more accurate simulation results of the concentration field and/or phases distributions, which could be used to design better electrodes structure and improve batteries’ power/cycling performance.