The mechanical stability of many advanced materials, such as battery materials, is highly determined by their local mechanical properties. However, experimental quantification for these properties is usually challenging, partially because of their highly air-sensitive nature and partially because of their heterogeneity at the micron- or even nanoscale. Nanoindentation is well suited as a tool for measuring the local mechanical properties of these materials as it can probe the mechanical response of small volumes on the samples at micro- or nanoscale. In the past few years, we customized the lab-based nanoindentation platform (instrumented indentation and AFM-based indentation) with delicate environmental and electrochemical loading controls to capture the topographical and mechanical responses of battery materials with high spatial resolution.

Ongoing projects:

-Mechanical degradation of NMC cathode in Li-ion batteries;
-Probe the mechanical strength of SEI in Li-metal batteries;
-Operando nanoindentation to measure the mechanical properties of electrodes during electrochemical reactions.

Representative publications:

1. Grid indentation analysis of mechanical properties of composite electrodes in Li-ion batteries
2. Mechanical degradation of LiNi_xMn_yCo_zO₂ cathode in Li-ion batteries: An experimental study
3. Quantitative spatiotemporal Li profiling using nanoindentation
4. Capture the swelling of solid-electrolyte interphase in lithium-metal batteries

With tremendous efforts being devoted to developing experimental techniques, researchers keep revealing new multi-physical phenomena in Li metal batteries. However, theoretical/numerical development to understand these multi-physical phenomena are relatively lagging due to the complexity of Li deposition/dissolution. Mechanical effects are not as instinctive and thus the coupled electro-chemo-mechanical phenomena in Li batteries are often concealed. We developed a theoretical framework that fully couples the electrochemistry (ion transport and reactions) and mechanics (deformation, stresses, and fracture) in Li-ion and Li metal batteries, and implemented this theory into the numerical problem to model the complex electro-chemo-mechanical interplay.

Ongoing projects:

-Heterogeneous electrochemistry and mechanics in electrodes;
-Fracture in electrochemical systems;
-Morphological evolution of Li metal anode during plating/striping.

Representative publications:

1. Heterogeneous damage in Li-ion batteries: Experimental analysis and theoretical modeling
2. Corrosive fracture of electrodes in Li-ion batteries
3. Mechanical interactions regulated kinetics and morphology of composite electrodes in Li-ion batteries
4. Dynamic polarization and spatial progression of isolated lithium metal during battery operations