(Digital Presentation) Advanced Intercalation Electrode Materials for Calcium Rechargeable Batteries

Abstract

The growing demand for electric vehicles and stationary energy storage systems calls for developing next-generation batteries that combine high energy, high power and low cost. Among many post lithium-ion batteries, calcium rechargeable batteries utilizing divalent Ca2+ ion charge carriers are expected to offer clear benefits in affordability of batteries along with the potentially high energy density, due to the abundance of calcium in earth crust (46600 ppm versus 20 ppm for lithium) and the low redox potential of Ca/Ca2+ (-2.9 V vs. standard hydrogen electrode). Recent efforts on the development of negative electrodes, such as elemental calcium metal and natural graphite, has brought the rechargeable calcium chemistries a step closer to a practically feasible battery system. However, the lack of suitable cathode is the Achille’s heal of the calcium rechargeable battery technology.[1] The relatively large ionic radius and divalent nature of Ca ions make the intercalation kinetics generally sluggish in intercalation hosts. Moreover, a large Ca2+ intercalation is supposed to cause extended volume changes of the host, triggering a premature degradation of the electrode structure. In this talk, I would like to present our recent findings in graphite anode and polyanionic cathode materials as intercalation electrodes in high performance non-aqueous calcium rechargeable batteries. We demonstrated that a large amount of Ca ions can be reversibly (de)intercalation in graphite for Ca ion batteries by identifying a proper electrolyte to promote the solvated-ion co-intercalation reactions.[2] The solvated-Ca-ion co-intercalation chemistry is comprehensively investigated by combining first principle calculations and synchrotron in-situ X-ray diffraction. For cathodes, we find that the open-framework sodium vanadium fluorophosphate can function as a stable and fast-kinetic Ca2+ intercalation host with an extremely low capacity degradation rate of 0.02% per cycle over 500 cycles.[3] This value records the best stability reported for Ca ion battery cathodes so far. Through this talk, it is believed that the new findings in discovering novel materials or intercalation chemistries will be of great interest of the community working on multivalent ion batteries and other energy storage technologies.Reference:[1] C Chen, F Shi, ZL Xu, Advanced electrode materials for nonaqueous calcium rechargeable batteries, J. Mater. Chem. A, 2021, 9, 11908-11930[2] Z.L. Xu, J. Park, J. Wang, H. Moon, G. Yoon, J. Lim, Y.J. Ko, S.P. Cho, S.Y. Lee and K. Kang, A new high-voltage calcium intercalation host for ultra-stable and high-power calcium rechargeable batteries, Nat. Commun. 2021, doi:10.1038/s41467-021-23703-x.[3] J. Park,† Z.L. Xu,† G. Yoon,† S.K. Park, J. Wang, H. Hyun, H. Park, J. Lim, Y.J. Ko and K. Kang, Stable and High power calcium ion batteries enabled by calcium intercalation in graphite, Adv. Mater. 2020, 32.4: 1904411.