Observation of morphological changes in silicon-based negative-electrode active materials during charging/discharging...

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Understanding morphological changes in silicon-based negative electrode materials during battery operation is crucial for material handling and electrode design.
• Direct observation of these dynamic processes is challenging yet vital for optimizing battery performance.

Purpose of the Study:

• To develop and apply an operando scanning electron microscopy (operando SEM) technique for quantitative evaluation of Si-based negative electrode material expansion and contraction.
• To observe the morphological behavior of silicon monosilicate (SiO)/graphite composite electrodes during lithium-ion battery cycling.

Main Methods:

• Development of a specialized operando SEM setup for observing a small all-solid-state lithium-ion battery.
• In-situ charging and discharging of the battery within the SEM to monitor particle volume changes.
• Quantitative analysis of expansion and contraction coefficients correlated with battery capacity.

Main Results:

• The operando SEM technique successfully visualized the dynamic morphological changes of Si-based electrode particles during battery cycling.
• In a SiO/graphite negative electrode, silicon monosilicate (SiO) was observed to expand initially during the charging process.
• Graphite components within the composite electrode were found to contract first during the discharging process.

Conclusions:

• The study demonstrates the utility of operando SEM for in-situ characterization of Si-based negative electrode materials.
• Insights into the distinct expansion/contraction behaviors of SiO and graphite components provide a basis for improved electrode design.
• The findings contribute to understanding the relationship between electrode material morphology, capacity, and expansion/contraction coefficients in advanced batteries.