Performance Limitations of CaCoSO as a Positive Electrode Material for Calcium Storage
(2025) ACS Applied Energy Materials — Vol. 8, n° 6, p. 3688-3697 (2025)
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Pal, Shubhadeep 
Kachmar, Andrii
- Abstract
- Calcium metal batteries (CMBs) are promising candidates for next-generation electrochemical energy storage systems due to their high volumetric capacity, abundance, sustainability, and safety. Recent DFT predictions suggested that the layered CaCoSO phase can enable sequential Co2+/Co3+ and Co3+/Co4+ redox activity at an average potential of 2.8 V vs Ca2+/Ca, making it a promising candidate for high-energy-density CMBs [Torres, A. Chem. Mater. 2021, 33(7), 2488–2497]. Inspired by these metrics, in this work, we present the synthesis and electrochemical analysis of the CaCoSO phase. Theoretical capacity can be extracted through galvanostatic cycling, albeit accompanied by high polarization. In situ XRD and DEMS analyses, however, reveal that the capacity arises primarily from a combination of material decomposition and electrolyte degradation rather than reversible Ca2+ ion storage. The apparent discharge capacity is attributed to the cathodic decomposition of generated water during the subsequent anodic step, making the overall electrochemical process appear as reversible. This work underscores the complexity of achieving stable calcium-ion storage and aligns with similar challenges reported for other systems, highlighting the need for realistic testing conditions and providing critical insights to guide the development of advanced electrode materials and electrolytes for CMBs.
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Citations
Tie, D., Apostol, P., Du, M., Li, Z., Lin, X., Pal, S., Markowski, R., Guo, X., Xu, H., Kachmar, A., Bakuru, V. R., Darsi Rambabu, Zhang, Y., Xia, F., Filinchuk, Y., Gohy, J.-F., & Vlad, A. (2025). Performance Limitations of CaCoSO as a Positive Electrode Material for Calcium Storage. ACS Applied Energy Materials, 8(6), 3688-3697. https://doi.org/10.1021/acsaem.4c03288 (Original work published 2025)