Lithium Tracer Diffusion in Amorphous Li_xSi for Low Li Concentrations

Abstract

Li tracer self-diffusion was studied in amorphous lithium−silicon compounds which are important as negative electrodes in Li-ion batteries. Experiments were done on Li x Si/ 6 Li x Si (Li x Si, x ∼ 0.02 and x ∼ 0.06) thin-film heterostructures using secondary ion mass spectrometry. The diffusivities follow the Arrhenius law in the temperature range between 140 and 325 °C, both with an activation energy of (1.42 ± 0.03) eV, while the Li-richer samples show 1 order of magnitude higher diffusivities. A trap-limited diffusion mechanism is suggested, explaining this result with a lower concentration of unsaturated traps. A discussion against the literature suggests a strong lithium concentration dependence of diffusivities also for higher x.

Interplay between electrochemical reactions and mechanical responses in silicon–graphite anodes and its impact on degradation

“…There is the distinctive pathway for minimizing the concentration gradient, Li + mass transport from silicon to graphite due to the internal redox reaction. During CV charge, this pathway delays the end of CV charging time because Li + diffusivity in silicon is 2 orders lower than that in graphite [33,34]. Consequently, the time for CV charge increases, and then delithiated cathode experiences high cut-off voltage during extended CV charging time.…”

Neutron reflectometry to measure in situ the rate determining step of lithium ion transport through thin silicon layers and interfaces

“…51 Further, systematic diffusion studies in Li x Si revealed that Li diffusivities are significantly enhanced with increasing Li content. 50 Consequently, as a perspective, the application of the NR methodology to determine in situ the rate determining step of Li permeation through Li x Si alloys and their interfaces to, e.g., different oxide based solid electrolyte materials is desirable in the context of battery applications.…”

Machine learning-accelerated quantum mechanics-based atomistic simulations for industrial applications

“…[ 141 – 144 ]: − cm s 2019 [ 145 ] Activation energy ( ) 0.5 − 0.8 eV N/A 2019 [ 145 ] ( ) 1.21-1.46 eV Exp. [ 146 ]: 1.38 − 1.46 eV 2020 [ 147 ] Solid electrolytes Amorphous- 0.55 eV Exp. [ 148 ]: 0.58 eV 2017 [ 149 ] 0.16 eV Exp.…”