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Experimental Observations and Measurements of Stress and Damage Evolution During Initial Lithiation and Delithiation of Crystalline Silicon

Michael Chon (Brown University), Vijay Sethuraman (Brown University), Pradeep Guduru (Brown University), Allan Bower (Brown University)

Lithium ion batteries: When Chemistry meets Mechanics

Mon 4:20 - 5:40

Salomon 003

Silicon is a promising material for the next generation lithium-ion anode materials due to its high energy density and abundant supply. However, wider use of silicon-based anodes as viable electrodes is hindered by challenges involving rapid performance degradation due to large volumetric changes during cycling, resulting in high stresses and mechanical and chemical degradation. We report experimental observations and measurements on stress and damage evolution during the initial lithiation cycle of crystalline silicon. Stress and damage evolution during initial phase transformation of crystalline silicon (c-Si) to amorphous lithiated silicon (a-LixSi) during electrochemical lithiation is measured for the (100), (110) and (111) planes. We observe that the a-LixSi phase experiences compressive stress ~600 MPa and undergoes inelastic deformation. The phase transition is observed to occur across an atomistically sharp phase boundary, which is not always normal to the lithiation plane. Upon initial delitiation of a-LixSi, the stress in the amorphous region rapidly changes from ~600 MPa (compressive) to ~700 MPa (tensile), followed by inelastic deformation until the film fractures. Two distinct fracture patterns are observed: macroscopic ordered channel cracks - which appear to be influenced by the underlying crystallographic planes of the substrate - and microscopic, randomly oriented cracks. Real time stress measurements and concurrent microscopic observation of crack formation are reported, which allow for the measurement of fracture energy of lithiated amorphous silicon as a function of Li concentration.