Addressing practical challenges of LiB cells in their pack applications

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Battery packs require multiple lithium-ion batteries (LiBs) in series/parallel for desired power output.
• Pack replacement is triggered if any LiB cell's State of Health (SoH) drops below 80%, necessitating uniform cell degradation.
• Current methods for screening LiB cells face practical challenges in predicting degradation rates before pack integration.

Purpose of the Study:

• To address practical challenges in estimating and predicting LiB cell degradation rates.
• To develop methods for screening weak LiB cells from production batches.
• To enable on-line, in-situ determination of SoH for individual cells within a battery pack.

Main Methods:

• Development of a screening technique utilizing data from the first discharge cycle of LiB cells.
• Implementation of a predictive model for the statistical distribution of LiB cell degradation rates.
• Design of an on-line, in-situ method for monitoring the SoH of individual LiB cells in a pack.

Main Results:

• Experimental validation confirms the ability to screen weak LiB cells from a production batch using only the first discharge cycle.
• The study successfully predicts the statistical distribution of degradation rates across LiB cells in a production batch.
• The proposed on-line, in-situ SoH determination method is verified across diverse LiB types from multiple manufacturers.

Conclusions:

• Effective screening of LiB cells is achievable early in the production process, minimizing premature pack failures.
• Predicting degradation rates enhances battery pack design and management strategies.
• The developed on-line SoH monitoring provides real-time health assessment for individual cells within LiB packs.