The first lecture is from Dr. Arief S Budiman. Silicon is a promising material for lithium-ion batteries. It expands by 300% on lithiation, leading to fracture. Nanostructuring of silicon is expected to be a promising method to improve the mechanical strength of the silicon electrodes. In this presentation, a unique battery test cell was designed to study the in situ stress evolution in the silicon nanowire (SiNW) electrode during electrochemical lithiation using synchrotron X-ray microdiffraction. Synchrotron X-ray microdiffraction (lSXRD) is effective for revealing insights of mechanical stress states and other mechanics considerations (such as plasticity, mechanisms preceding fracture events, or final catastrophic failure) in small-scale crystalline structures in many important technological applications, such as microelectronics, nanotechnology, and photovoltaics. Crystalline SiNWs and nanospheres on progressive lithiation form a core shell structure, where the outer shell transforms from crystalline silicon (c-Si) to amorphous lithiated silicon (LixSi) upon reaction with Li metal and the inner crystalline core remains same. The boundary between the crystalline core and the lithiated silicon shell is characterized by a sharp lithiation. All these models are based on SEM/TEM observations of the lithiation process and lithiated silicon particles/wires. Studies using this technique with advanced instrumentation would allow comprehensive experimental examination of the stress evolution in the SiNW electrodes during electrochemical lithiation. This research also improve the understanding of the stress states in the SiNWs and could help to the design of fracture-free silicon nanostructures for next-generation LIBs.
|Date||:||16 February 2021|