Diagnostic technology assesses Li-ion battery degradation

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With regard to all modern electronics, lithium-ion batteries play a central role and are currently increasingly being implemented in electric vehicles.

Scientists are developing an alternative diagnostic technology to rapidly assess the degradation mechanism of Li-ion batteries. Image credit: Gwangju Institute of Science and Technology.

As a result, there has been a rapid increase in its use and with it a growing demand for tools to reliably test the “state of health” (SOH) of these batteries. This is considered important because understanding the symptoms of battery degradation is crucial to improving maintenance and preventing accidents due to malfunctions.

Degradation of Li-ion batteries occurs in three different modes: loss of conductivity (CL), loss of active materials (LAM), and loss of lithium inventory (LLI). In recent years, many methods have been developed by researchers to non-invasively analyze these modes.

The most widely used of these is incremental capacitance differential voltage (IC-DV) analysis due to its good correlation with degradation modes. But IC-DV analysis is extremely laborious and cannot infer complicated mechanisms related to battery deterioration.

In a recent study led by Professor Jaeyoung Lee of Gwangju Institute of Science and Technology (GIST), the scientists have now developed an alternative method to the cumbersome IC-DV technique and have characterized the degradation modes by graphite/LiNi cycling0.5min0.3Co0.2O2 (NMC532) pocket cells having two different capacities at low and high C-rate (charging and discharging rate of a battery).

While many studies have been conducted to investigate the degradation symptoms of fatigued lithium-ion batteries with charge and discharge cycle data, rapid diagnostic technology is not yet sufficiently developed.

Jaeyoung Lee, Professor, Gwangju Institute of Science and Technology

We believe that a rapid degradation diagnostic technology using high C-rate could enable real-time detection of degradation modes and its use to effectively monitor the health status of individual cells.adds Lee detailing the motivation behind this study.

This study is published in the Energetic Chemistry Journal.

Initially, the researchers collected low C-rate data every 100 cycles of high C-rate analysis, then transformed the data into IC-DV curves using differential equations to evaluate the LAM and LLI modes of battery degradation.

The former was evaluated as a sum of the IC peak intensities due to its non-linear relationship with C-rates, while the latter was estimated by extrapolation given its good linearity with C-rates. In return, this has allowed rapid detection of LLI degradation.

The insights offered in current research could help in the rapid and elaborate analysis of SOH, which could prove useful in the evaluation of on-board battery systems.

The aim of our study was to help establish an easy diagnostic protocol for the maintenance of lithium-ion batteries. Our proposed mechanism not only makes the process cost effective but also environmentally friendly by providing a faster and more reliable selection process for battery reuse..

Jaeyoung Lee, Professor, Gwangju Institute of Science and Technology

Journal reference:

Seo, G. et al. (2022) Rapid determination of lithium-ion battery degradation: high C-rate LAM and calculated limit LLI. Energetic Chemistry Journal. doi.org/10.1016/j.jechem.2021.11.009.

Source: https://www.gist.ac.kr/en/main.html

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