Investigation of Initial Lithiation of Silicon (100) Using Solid-State 7Li NMR

TL;DR

This study uses solid-state 7Li NMR spectroscopy to analyze how initial lithiation of silicon (100) wafers affects lithium distribution and structural changes, revealing that Li concentration remains constant at a given flux regardless of total charge.

Contribution

It provides new insights into the kinetics and reaction mechanisms of initial silicon lithiation by controlling Li flux and analyzing resulting structural changes with NMR.

Findings

Li peak shifts depend on flux during lithiation

Li concentration in LixSi remains constant at a given flux

Results improve understanding of lithiation kinetics and mechanisms

Abstract

Structural changes in amorphous LixSi during the initial lithiation of single crystal Si to amorphous LixSi were investigated as a function of Li flux and total charge using solid-state 7Li nuclear magnetic resonance (NMR) spectroscopy. Single crystal (100) Si wafers were used as a model system in this study, as the Li flux could be precisely controlled and uniformly distributed across the surface of the wafer. It was observed that peak shifts in solid-state 7Li NMR spectra varied as a function of the Li flux during the initial lithiation and stayed constant for samples of the same Li flux regardless of the total charge applied to the electrodes. We conclude from these results that the Li concentration in LixSi stays constant for a given flux regardless of the total coulombic charge applied to the electrode. The results from this study help better understand the kinetics, the reaction mechanisms, and the kinetic modeling of chemical reactions at the reaction front during the initial lithiation of Si (100).