In situ reflectance spectroscopy for state-of-lithiation mapping of porous silicon anodes

초록

Silicon is a promising candidate for next-generation lithium-ion battery anodes due to its superior gravimetric capacity, derived from its alloying reaction with lithium. Given the correlation between electrochemical and optical properties, optical inspection provides a non-invasive method for probing lithiation dynamics. In this study, the state of lithiation (SoL) was systematically linked with optical response through both ex situ and in situ measurements. Reflectance consistently decreased as lithium content increased within the silicon lattice, a trend validated across multiple experimental setups. For instance, a spatial lithium gradient, introduced by varying electrode sizes in coin cells, was successfully visualized via reflectance mapping. This approach also suggests a scalable quality-control strategy for prelithiation, the process of alloying silicon with lithium. The areal lithiation uniformity of prelithiated silicon anodes was evaluated, demonstrating the potential of this spectroscopic method for real-time inspection in roll-to-roll manufacturing. Additionally, the physical mechanism of reflectance changes was explored. Surface roughness measurements and density functional theory (DFT) calculations indicate that reduced reflectance at higher SoL is due to increased light scattering from particle expansion and bandgap narrowing. Overall, this spectroscopic method enables both a fundamental understanding of silicon lithiation and a practical framework for industrial-scale quality control.

키워드