Lithium-ion batteries are used in electric vehicles and grid storage applications. The electric motors run by these batteries are about twice as fuel efficient as gas combustion engines found in many cars. This makes them an important technology for resolving energy and environmental issues, so optimizing their operation is critical.
In order to charge quickly and store as much energy as possible, the batteries need both a high power density and a high energy density. Balancing both aspects is challenging, as it requires understanding the underlying mechanisms of battery operation. Lee et al. reviewed the electrochemical polarization that arises during the charging and discharging process.
Electrochemical polarization is associated with the internal resistance of a battery. Minimizing the polarization increases the power density and decreases charging times.
However, measuring electrochemical polarization is complex and made more difficult because established protocols do not currently exist. To address this problem, the researchers described each component of electrochemical polarization, its measurement technique, and its relative contribution to the resistance.
“My intention was to assist with setting the correct research and design targets and serve as a useful reference for researchers working in this field,” said author Hochun Lee.
Many Li-ion batteries achieve high power densities corresponding to short charging times, but these batteries often have low energy densities. The team identified some scenarios where this results in unrealistic high-power performances.
Lee said realistic goals for battery performance depend on a fundamental understanding of the electrochemical polarization, which this paper aims to provide.
Source: “Physicochemical nature of polarization components limiting the fast operation of Li-ion batteries,” by Junsik Kang, Bonhyeop Koo, Seokbum Kang, and Hochun Lee, Chemical Physics Reviews (2021). The article can be accessed at https://doi.org/10.1063/5.0068493.
