Nondestructive Characterization of Na Ion Batteries at 0C and Below

As a promising alternative to Li-ion batteries, Na-ion batteries offer a potential alternative due to their better ion transfer efficiency and lower cost [1,2]. In this study, cycling tests were conducted on Li and Na ion cells at temperatures of -20°C and 0°C with varying charge and discharge rates. This revealed that Na-ion cells experience significant energy losses, or “hysteresis,” at a rate of 1C. The extent of hysteresis was quantified by calculating the ratio of charge capacity to discharge capacity, which revealed that Na-ion cells exhibit higher values of 3.45±0.4 at -20°C and 1.59±0.05 at 0°C, compared to 0.93±0.01 at room temperature. In contrast, Li-ion cells exhibited lower hysteresis ratios of 1.1±0.00 at -20°C, 1.09±0.02 at 0°C, and 1±0.00 at room temperature. These results demonstrate that Na-ion cells experience more pronounced hysteresis at lower temperatures, while their performance approaches that of Li-ion cells at room temperature. To further investigate, differential capacity (dQ/dV) analysis revealed shifting and broadening of peaks is more in Na-ion batteries compared to Li-ion, indicating degradation in the form of material aging and increased impedance over repeated cycles. Notably, during discharge, peak voltage shifts were higher for Na-ion cells, with 700 mV observed at 0°C and 760 mV at -20°C, compared to 350 mV at 0°C and 470 mV at -20°C for Li-ion cells. This suggests that lower temperatures lead to more pronounced impedance changes [3], particularly in Na-ion batteries. This behavior was especially prominent at higher C-rates, where Na-ion cells showed larger voltage shifts during both compared to Li-ion cells. As C-rates increased, the voltage shifts for Na-ion cells also increased significantly, while Li-ion cells exhibited smaller shifts at comparable C-rates. Additionally, as the temperature decreased, both types of cells experienced more prominent voltage shifts, though Na-ion cells were more affected. We observed peak shifts were linked to increased polarization resistance, a phenomenon that can be quantified using IR drop calculations (R = ΔV/I) [4]. Estimate shows more polarization resistance at -20°C than at 0°C for both the cells, particularly for Na-ion cells. The results highlight that this resistance growth is more due to kinetic factors than thermodynamic changes when using high C-rates at sub-zero temperatures. Ongoing work is being conducted to compare the same batteries at low C-rates (C/10). Additionally, CT scans of the cells before and after cycling showed that, unlike Li-ion cells, Na-ion batteries exhibited significantly less 'breathing'. Furthermore, core collapsing and buckling, commonly observed in Li-ion cells, were much less prominent in Na-ion cells, highlighting their structural stability and supporting their potential for use in low-temperature applications.


References:
1. Li, Peiyuan, et al. "Recent Progress and Perspective: Na Ion Batteries Used at Low Temperatures." Nanomaterials 12.19 (2022): 3529.
2. Ponrouch, Alexandre, et al. "Towards high energy density sodium ion batteries through electrolyte optimization." Energy & Environmental Science 6.8 (2013): 2361-2369.
3. Wu, Yujun, et al. "Recent Progress in Sodium-Ion Batteries: Advanced Materials, Reaction Mechanisms and Energy Applications." Electrochemical Energy Reviews 7.1 (2024): 17
4. Shu, X., Li, Y., Yang, B., Wei, K., Punyawudho, K. (2024). Electrochemical Impedance Spectroscopy Characterization of Sodium-Ion Batteries with Different Operating States. In: Chen, B., Liang, X., Lin, T.R., Chu, F., Ball, A.D. (eds) Proceedings of the TEPEN International Workshop on Fault Diagnostic and Prognostic. TEPEN 2024. Mechanisms and Machine Science, vol 170. Springer, Cham. https://doi.o