Evaluation of Commercial Sodium-Ion Batteries by State-of-the-Art Lithium-Ion Battery Configurations

Sodium-ion batteries (SIBs) are gaining attention in research and industry as a sustainable alternative to lithium-ion batteries (LIBs). However, the advantages of sodium over lithium in terms of accessibility, price, and environmental impact are currently not fully exploited because of inexperience in production, leading to inhomogeneities in their behavior. Using electrical (e.g., open-circuit voltage curve (OCV), electrochemical impedance spectroscopy) and non-electrical measurement methods (e.g., laser scanning microscopy, computed tomography), three widely used LIB technologies and one SIB technology, all with the same rated capacity (1500 mAh) and format (18650), are compared in this article. The study reveals significant differences, such as a 12% lower cell weight at the same rated capacity of the SIB using less windings in the jelly roll, as well as a high energy density cell configuration and a much more severe dependency of the discharge capacity on temperature, exceeding the LIBs by at least a factor of 5. Additionally, the impedance of the SIB differs due to slower ion kinetics on the electrodes, showing relevant differences in both the frequency behavior and the pulse relaxation to the LIBs. An OCV reconstruction indicates the sparsity in the available literature data and the necessity to further investigate the characteristics of the SIB to validate it as a drop-in technology on the market.