Lithiation/delithiation kinetics in nano-, micro- and highly porous silicon

Abstract

Highly porous silicon microparticles were prepared by magnesiothermic reduction of silica. The properties of the prepared porous material, as well as commercial micro- and nanoparticles of silicon have been studied using XRD, Raman spectroscopy, SEM, BET and galvanostatic cycling. The kinetics of lithium diffusion have been studied by cyclic voltammetry. The diffusion coefficients of lithium cations during lithiation were (1.5 ± 0.3) × 10⁻¹¹, (1.2 ± 0.1) × 10⁻¹¹ and (2.3 ± 0.5) × 10⁻¹² cm²/s for nanoparticles, hierarchically porous and monolithic silicon microparticles, respectively. The diffusion coefficients during delithiation were (8.3 ± 1.3) × 10⁻¹², (6.7 ± 0.3) × 10⁻¹² and (2.5 ± 0.4) × 10⁻¹² cm²/s, respectively. The difference in the rates of lithiation and delithiation is most pronounced for nanoscale materials.