Friday, Sep 23, 2016 - 2:00pm - Allen 411
A nonlinear electrochemical phase-field model and its applications to Li-ion batteries
Dr. Lei Chen, Mechanical Engineering, Msstate
Title: A nonlinear electrochemical phase-field model and its applications to Li-ion batteries
Abstract: The success of electric vehicles (EVs) requires a significant increase in the energy storage density of lithium (Li)-ion batteries. Remarkable efforts have been recently devoted to high-capacity electrode materials such as Li metal, silicon (Si) and germanium (Ge) as anodes, and Sulphur (S) and oxygen (O2) as cathodes. However, such high-capacity anodes form dendritic and mossy deposits, leading to serious safety concerns and degraded efficiency over recharging cycles. These high-capacity anodes also inherently suffer from their large volume change (e.g., ~300% for Si) when alloyed with Li, which induces plastic flow, fracture and pulverization in the electrodes. Although intensive experimental attempts have helped shed light on understanding the degradation processes, effective strategies to improve the cycling of alloy or metal anodes remain elusive. In this talk, I will present an innovative nonlinear phase-field model to fundamentally understand these degradation mechanisms. To accomplish this, the proposed model, for the first time, accounts for both nonlinear Butler-Volmer electrochemical reaction kinetics and large elasto-plastic deformation for modelling the co-evolution of microstructure and stress. The model is further validated utilizing both theoretical solutions and experimental observations. In particular, the retardation effect of elasto-plasticity on the lithiation kinetics is identified and discussed. A design map is proposed to tailor cell parameters and operating conditions to avoid undesired dendritic degradation. Finally, our recent attempts on phase-field model of microstructure evolution for additive manufacturing alloys, e.g., Ti-6Al-4V and IN718 are presented.