Temperature-Dependent Fracture Resistance of Silicon Nanopillars during Electrochemical Lithiation.

During the lithation of silicon anodes, the solid-state diffusion of lithium into Li x Si follows the Arrhenius law, the resulting morphology and fracture behavior are determined by the silicon anode operation temperature. Here, we reveal the temperature dependence of the lithiation mechanics of crystalline silicon nanopillars (SiNPs) via microscopic observations of the anisotropic growth and fracture behavior. We fabricated 1D SiNP structures with various orientations (⟨100⟩, ⟨110⟩, and ⟨111⟩) as working electrodes and operated them at temperatures ranging from -20 to 40 °C. The lithiation of crystalline silicon at low temperatures exhibited preferential volume expansion along ⟨110⟩ and decreased fracture resistance. Furthermore, low temperatures caused the catastrophic fracture of amorphous silicon after the second lithiation. Our findings demonstrate the importance of silicon anode temperature control to prevent mechanical fracture during the cycle of lithium-ion batteries in harsh environments (e.g., electric vehicles in winter).