Operando Study of Divalent Cation Storage Mechanism in Poly(tetra-sulfonamide) based coordination polymers: Unveiling Structure-Performance Relationships via Synchrotron Techniques

The development of sustainable, high-energy-density battery chemistries is critical for the future of energy storage. Among the most promising alternatives to Li-ion batteries are multivalent systems based on magnesium (Mg), calcium (Ca), and other divalent cations. While significant progress has been made in developing Mg and Ca electrolytes, advances in positive electrode materials remain limited due to the strong interactions between divalent cations and rigid inorganic hosts. Recent studies have shown that organic coordination polymer electrodes, particularly those based on poly(tetra-sulfonamide) (PTtSA) chemistry, offer superior electrochemical performance in multivalent systems, including enhanced energy density, reversibility, and rate capability.
This proposal focuses on understanding the charge storage mechanisms of Ca-Zn-PTtSA, Sr-Zn-PTtSA, and Ba-Zn-PTtSA positive electrodes. Using operando X-ray absorption spectroscopy (XAS) at the S, Ca, Sr, Ba, and Zn K-edges, we will monitor the evolution of the electronic structure and local coordination environment of these systems during battery cycling. This investigation will allow us to explore the dynamic nature of divalent cation interactions with the PTtSA polymer backbone, as well as the role of transition metals like Zn in the redox process. Special attention will be given to the variations in local structure during charge/discharge cycles, particularly for Ca²⁺, Sr²⁺, and Ba²⁺, and how these affect the voltage profiles.
The insights gained from this study will improve our understanding of multivalent cation storage mechanisms in electrodes materials and contribute to the design of next-generation energy storage materials with enhanced performance and stability.