The research objective of this grant is to fundamentally understand the thermodynamic driving forces and kinetic mechanisms leading to the formation of lithium metal dendrites in Li-batteries. One of the most significant challenges for Li-ion battery design is the prevention of Li-dendrite growth, which would allow faster charging for current Li-ion battery technology and the use of Li metal anodes for future "beyond Li-ion batteries." A computational model based on the phase-field method will be developed to predict the conditions for dendrite growth and morphological changes with input thermodynamic, mechanical and kinetic parameters from atomistic/first principles calculations and experimental measurements. The proposed model will be based on a nonlinear kinetics in which the dependence of the rate of changes of a phase-field parameter is nonlinear with respect to the thermodynamic driving force, and hence it is applicable to modeling the microstructure evolution under large overpotentials or high charging rates. One of the key parameters is the Li metal/electrolyte interface energy, which will be directly computed by connecting DFT calculations and liquid thermodynamic data. This three-year grant will lead to (1) fundamental understanding of the transport and chemical kinetics of dendrite formation and growth and their relationships to their solid electrolyte interphase (SEI) film properties and (2) the development of a physics-based microstructure evolution model that does not rely on non-transferable fitting parameters to predict the conditions for dendrite formation and growth morphology. The ultimate goal for this work is to eliminate the formation-- or at least to limit the growth-- of dendrites on Li metal electrodes.
Dendrite formation is the primary degradation and failure mechanism and a safety concern in Li batteries, either because dendrite pieces lose electrical contact with the rest of the Li electrode or because growing dendrites penetrate the separator and lead to short circuits. The fundamental understanding achieved from this research program is expected to contribute to the Li ion battery safety improvement, a critical need for the near-term development of hybrid and electric vehicles. The planned research, both the methodology and the actual results, are designed to make significant contributions to new battery technology by providing important fundamental information about electrode materials behavior under various electrochemical conditions. The direct involvement of GM scientists provides an important avenue for disseminating the knowledge generated from this project. The primary research results will be shared with the public on-line to the public at http://lithiumbatteryresearch.com/ in addition to peer-reviewed publication and conference proceedings. The graduate student and postdoc supported by this project will spend extended periods of time in an industrial environment, which will provide an important added dimension to their education. Both of these individuals will thus be very well positioned for future work in battery-related fields. In addition, undergraduate students will be integral to the program via Penn State's MURE (Minority Undergraduate Research Experience) programs and senior thesis projects in the Department of Materials Science and Engineering at Penn State.
