MSE Seminar: “When ions meet electrons — Modeling the interfaces in Solid-State Batteries”

With the rapid development of fast Li-ion conductors, the major bottleneck for all-solid-state Li-ion batteries lies at the high interfacial resistance and Li dendrite growth. These problems require a fundamental understanding of the interfaces, where charge transfer reactions occur and electrochemistry, physics, and solid mechanics are coupled. This talk will focus on the new mechanistic understanding obtained by the recently developed multi-scale modeling approaches.

One challenge for solid-state batteries is the high interfacial resistance, due to two main factors: physical contact and chemical effect. The chemical effect was captured by a density functional theory (DFT)-informed theoretical model, which predicts the potential map inside a solid-state battery and determines the potential drop, electrostatic dipole, and space-charge layer at the electrode/solid-electrolyte interface. This new physics insight unified the seemingly contradictory experimental observations and led to new device design rules to promote interfacial ion transport in future solid-state batteries. The physical contact was described by combining contact mechanics and the 1D Newman battery model. The model suggested how much pressure should be applied to recover the capacity drop due to contact area loss.
Another challenge for high energy density solid-state barriers using Li-metal electrodes is the soft Li dendrite growth inside the hard solid electrolytes. A DFT-informed phase-field method was developed and successfully explained the experimentally observed dendrite intergranular growth and revealed that the trapped electrons at grain boundaries and surfaces may be the main reason to reduce Li-ion and nucleate metallic Li. A new dendrite resistant criterion is therefore proposed.

These modeling advancements will be integrated into a new framework to guide the development of all-solid-state Li-ion batteries.