Mechanochemistry of advanced anode designs in Li-ion batteries

• Applicant: Professor Dr. Wolfgang H. Müller
• Subject Area: Mechanics
• Term: from 2017 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 386355213

This proposal is a contribution toward improving the performance of Lithium-Ion Batteries (LIBs) by quantitative modeling based on fundamental principles of continuum physics. LIBs are important energy storage devices. They are required in various technological applications, such as portable electronics or for the powering of vehicles. The incorporation and removal of Li in the anode material during charging and discharging, which must be considered as a chemical reaction, is accompanied by a considerable increase in volume giving rise to a build-up of huge mechanical stresses and strains. These have an impact on the principal rechargeability of LIBs because they eventually block the reaction. Moreover, they might result in physical damage of the battery material. Of course, empirical measures have been taken in order to prevent this from happening, one based on choosing different designs of the to-be-charged silicon structure in terms of spheres, rods, honeycombs, etc., and the other consisting of turning to other host materials less brittle than Si. However, a thorough physically-based understanding of the mechano-chemically coupled process in terms of quantitative modeling is still at its infancy. Surely, there have been attempts at modeling the phenomenon. However, it is fair to say that joining the mechanical and thermochemical aspects has been accomplished on a rather phenomenological basis. In short: The corresponding theory was not built on solid ground by using fundamental thermodynamics principles. This is why we present this proposal. We shall, first, establish a consistent mechano-chemical theory. Second, this theory will be exploited analytically as well as numerically while being sure why and from where each term in the equations originates and how it contributes to the observed micromorphological changes in various anode materials of different structural design. Third, we shall compare and link our models to real custom-made experiments in order to improve its applicability not by adjusting coefficients but always by basing it on first principles. In the end we will possess a reliable tool to-be-used during the design process of future LIBs. Both research teams have many years of experience in these fields and complement each other both from the theoretical as well as from the experimental point-of-view. So far the Russian team has focused on, first, setting up thermodynamically consistent singular interface theories and, second, on applying them, for example, to the (qualitative) modeling of silicon oxidation. The German team contributes with expertise in, first, multi-component diffusion and phase-field modeling of the spinodal decomposition of eutectic tin-lead and silver copper solders, and, second, a strong experimentally as well as industrially based background to quantitative modeling in this field of continuum modeling.

• DFG Programme: Research Grants
• International Connection: Russia
• Partner Organisation: Russian Foundation for Basic Research
• Cooperation Partner: Professor Dr. Alexander B. Freidin