Anisotropic behavior in the lithiation of a silicon nanopillar

Kinetic analysis of silicon–lithium alloying reaction in silicon single crystal using soft X-ray absorption spectroscopy

“…11,12 The cracks are caused by anisotropic lithium diffusion, where inhomogeneous volume expansion and silicon compression cause enormous strain in the particles. [13][14][15][16] The scanning electron microscopic studies of electrochemical lithiation into silicon nanowires indicated that the Si-Li alloying reaction exhibits anisotropy properties based on the crystal plane. 13,[17][18][19][20][21][22] Nevertheless, the effect of the anisotropy of the lithiation with silicon of different orientations remains unclear.…”

“…Many ndings have reported energetically favourable Li-Si alloying reactions in the [110] direction of the Si crystal plane since it experiences less structural degradation and minimizes the amount of capacity lost during electrochemical cycling. 14,18,20,[23][24][25] Meanwhile, even though stresses are concentrated in the Si (100) crystal plane due to the tensile and compressive forces, 23,26,27 recent ndings also indicate that Si (100) has better cycle reversibility and faster Li diffusion compared to Si (111) and (110) due to its better interfacial reaction with lithium. 26,[28][29][30] The simulation study by the nite element method has also successfully demonstrated the crack formation in the (100) direction, 23 which leads to more exposure of the silicon surface to lithium.…”

“…26 To suppress degradation caused by anisotropy, morphology control such as nanowires and leaf shapes have been proposed. 14,[31][32][33] Moreover, Lau et al reported that the effect of highly doped n-type silicon single crystal seems to reduce surface fragmentation during initial lithiation. 30 Uncovering the anisotropy of the Si-Li alloy reaction will be valuable insight for improving the cycle properties of Si.…”

“…34,35 Theoretical studies have been carried out to analyze the anisotropy of alloying reactions, especially at the atomic level. 14 Similarly, the anisotropy of diffusion phenomena with surface reactions has also been analyzed. 36 Nonetheless, to the best of the authors' knowledge, experimental attempts to quantify the anisotropy of diffusion phenomena have not been successful.…”

Chemical stress in a largely deformed electrode: Effects of trapping lithium

“…Li et al. 35 developed an anisotropic chemo-mechanical model with anisotropic properties of crystalline silicon and analyzed deformation and stress fields in Li 15 Si 4 . Their results demonstrate that anisotropic expansion could potentially reduce von Mises stress in [110]-oriented silicon nanopillars, which could retard mechanical degradation of silicon-based electrodes.…”