Quantifying the factors limiting rate performance in battery electrodes.

Area of Science:

• Materials Science
• Electrochemistry
• Chemical Engineering

Background:

• Battery charge-storage capacity rapidly decreases at higher charge/discharge rates.
• Existing models lack a general, fittable approach to connect capacity-rate data with electrode/electrolyte properties.

Purpose of the Study:

• To develop a general, fittable model for battery capacity versus rate data.
• To link battery rate performance to fundamental electrode and electrolyte properties.

Main Methods:

• Developed a novel equation to fit capacity-rate data, yielding three key performance parameters.
• Introduced a second equation to correlate characteristic charge/discharge time with physical electrode/electrolyte parameters.
• Validated the model against approximately 200 experimental datasets.

Main Results:

• The model successfully fits capacity-rate data and quantifies battery rate performance.
• Derived physical parameters like diffusion coefficients and electrolyte conductivities from the model.
• Identified dominant rate-limiting processes for specific battery systems.

Conclusions:

• The model provides a framework for understanding and optimizing battery rate performance.
• Enables rational design and cell optimization by identifying rate-limiting factors.
• Predicts upper speed limits for lithium-ion and sodium-ion batteries, consistent with state-of-the-art electrodes.