Electrochemical Impedance Spectroscopy Sheds Light on Charge Transfer in Lithium-Ion Batteries

Lithium-ion batteries are a key source of power for many consumer electronics. The production of lithium-ion batteries is critical, and researchers are prioritizing studying and evaluating lithium-ion batteries to help improve their functionality (1).

A recent study from researchers at Bilkent University and Sabancı University in Turkey explored this topic. The team developed a novel approach using electrochemical impedance spectroscopy (EIS) (2), which uses an alternating current (AC) signal to an electrochemical system (1). EIS helps to measure the response over a frequency range, typically from 0.01 Hz to 100 kHz (1).

Lithium ion battery. Battery close-up. AA batteries. Battery fast charging concept. 3D rendering. | Image Credit: © Alexander - stock.adobe.com

EIS has been used to evaluate battery aging (1). In this study led by Burak Ülgüt, he and his team used EIS to better understand the mechanisms of charge transfer within secondary Li batteries (2). Analyzing the electrochemical level of these systems in lithium-ion batteries has been notoriously difficult because of their complexity and inherent inert properties (2). EIS, a powerful diagnostic tool, offers the potential to probe these systems, but its efficacy has been limited by the complexity of the data produced and the challenges associated with interpreting it accurately (2). This study addresses these issues head-on.

The researchers focused on simplifying EIS data interpretation by employing symmetric cell configurations, which allowed them to isolate and quantify the charge transfer resistance values for each electrode in a controlled manner (2). This step proved essential in distinguishing the different electrochemical processes contributing to the battery's overall performance. To expand on these findings, the team further explored how changes in electrolyte composition, temperature, and the state of health of the battery influenced charge transfer (2).

For their experimental setup, they paired a metallic lithium anode with a LiMn₂O₄ (LMO) cathode. Through this setup, Ülgüt and his colleagues were able to learn more about the cathodic and anodic limiting processes (2). Notably, the variation in the electrolyte type and operating temperature had significant impacts on the charge transfer resistance, ultimately affecting the battery’s overall efficiency (2).

The ability to identify and measure charge transfer processes accurately is fundamental for designing batteries with improved energy density, faster charging times, and longer cycle life (2). By elucidating how different electrolytes and temperatures affect these processes, Ülgüt's research provides a roadmap for tailoring battery components to specific performance needs (2).

The important takeaway from this study is that the researchers were able to show the correlation between charge transfer and mass transfer processes. This insight is important because it allows researchers to better understand the interplay between ion movement and electrochemical reactions (2). Such knowledge is invaluable for optimizing electrolyte formulations and adjusting battery operation parameters for maximum efficiency (2).

Therefore, this research can be applied toward solving some of the most pressing challenges in the electronics industry. The lithium battery industry is at the forefront of powering everything from consumer electronics to electric vehicles, and advancements in understanding their internal processes could significantly impact future energy storage solutions (2). Ülgüt’s approach highlights the potential of EIS as a versatile in situ technique that can be applied to various battery chemistries and configurations, extending its utility beyond just metallic Li anodes (2).

Lithium-ion batteries are expected to continue to receive an increased level of focus. In addition to lithium-ion batteries, lithium metal batteries are also being studied, as it is thought that they can improve on the limitations of lithium-ion batteries (3). Many more changes are expected, as this industry seeks on producing new batteries that are more sustainable and resolve the current limitations of current power sources.

References

1. Wetzel, W. Evaluating Battery Health for Electric Vehicles Using Electrochemical Impedance Spectroscopy Measurements. Spectroscopy. Available at: https://www.spectroscopyonline.com/view/evaluating-battery-health-for-electric-vehicles-using-electrochemical-impedance-spectroscopy-measurements (accessed 2024-11-06).
2. Zabara, M. A.; Katirci, G.; Civan, F. E.; et al. Insights into Charge Transfer Dynamics of Li Batteries through Temperature-dependent Electrochemical Impedance Spectroscopy (EIS) Utilizing Symmetric Cell Configuration. Electrochimica Acta 2024, 485, 144080. DOI: 10.1016/j.electacta.2024.144080
3. Wetzel, W. Lithium Metal Batteries and the Push for More Sustainable Electronics. Spectroscopy. Available at: https://www.spectroscopyonline.com/view/lithium-metal-batteries-and-the-push-for-more-sustainable-electronics (accessed 2024-11-06).