Tracking Lithium Intercalation in Battery Electrodes via Their Electrochromic Properties Using Operando Ellipsometry

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Understanding charge storage in lithium-ion battery electrodes is crucial for developing materials for fast charging and high power density.
• Disentangling complex charge storage mechanisms, especially in thin-film and nano-sized materials, remains a challenge.
• The electrochromic properties of battery electrodes are intrinsically linked to their charge storage behavior.

Purpose of the Study:

• To demonstrate how operando ellipsometry can provide detailed insights into charge storage kinetics in battery electrodes.
• To establish spectroscopic ellipsometry as a valuable tool for optimizing materials for energy storage.
• To explore the relationship between electrochromic properties and charge storage mechanisms.

Main Methods:

• Utilized operando ellipsometry to study charge storage in battery electrodes.
• Employed a model TiO2-anatase thin film for validation.
• Derived and analyzed the energy loss function (ELF) from the complex dielectric constant.
• Investigated the derivative of the energy loss function with respect to voltage (d(ELF)/dV).

Main Results:

• Validated the energy loss function (ELF) as a key indicator for tracking the lithiation state and state of charge in TiO2-anatase thin films.
• Demonstrated that d(ELF)/dV functions as an "opto-voltammogram" for probing and deconvoluting redox reactions.
• Showcased the capability of operando ellipsometry to provide detailed insights into charge storage kinetics.

Conclusions:

• Spectroscopic ellipsometry is a powerful technique for understanding charge storage in battery electrodes.
• The energy loss function and its voltage derivative offer new avenues for analyzing electrochemical processes.
• This approach can significantly aid in the optimization of materials for advanced energy storage applications.