(Invited, Digital Presentation) Understanding Interfacial Chemo-Mechanics of Two-Dimensional Materials-Based Heterogeneous Functional Materials for Energy Storage

Abstract

Two-dimensional (2D) materials and their heterostructures (2D + nD, n = 0,1,2,3) attracted enormous interest in wide range of applications including electrochemical systems, e.g., batteries. Electro-chemo-mechanics, the coupling of mechanics and electrochemistry, plays a crucial role in designing these systems. This talk considers battery as a model system and demonstrates the role of 2D materials in overcoming various interfacial electro-chemo-mechanical challenges. 2D materials are engineered as the van der Waals (vdW) “slippery” interface. For example, silicon (Si) electrodes can be placed over the graphene-coated current collector for Lithium-Ion Batteries (LIBs). This arrangement provides less stress build-up and less stress “cycling” on the vdW slippery substrate instead of a fixed interface. 2D materials such as MXenes can also be used to replace polymer binders, e.g., in Si-based LIBs. Our DFT studies show more stable performance and higher Coulombic efficiency for Si films deposited on graphene-coated nickel (i.e., slippery interface) than conventional nickel current collectors. The interface strength of monoclinic Se (selenium) is 0.43 J/m2, which is similar in magnitude in amorphous Si with graphene (0.41 J/m2). However, the interface strength of c-Se on a 3D aluminum (Al) current collector is higher (0.99 J/m2), suggesting a stronger adhesion for 3D/3D interface than 3D/2D interface. Furthermore, interface strength variation between a-Si and Ti3C2Tx MXenes are determined for various surface functional groups (Tx). The completely hydroxylated Ti3C2 has the highest interface strength of 0.60 J/m2 with a-Si. The talk also summarizes our recent efforts in developing High Dimensional Deep Learning Potential (HDDLP) to study interfacial electro-chemo-mechanics in 2D materials-based systems. Our computational results are in good agreement with experiments. Besides batteries, our comprehensive interface analyses are beneficial in advancing understanding of other 2D materials-based systems, e.g., sensors, fuel cells, solar cells, nanomedicine, soft-actuators, etc.