Abstract
Renewable energy sources and reliable energy storage technologies are becoming increasingly crucial as climate change presents more urgent challenges. Although lithium-ion batteries currently dominate electrochemical energy storage, the scarcity and geographical confinement of lithium and associated cathode materials, such as cobalt and nickel, has motivated the development of sodium-ion batteries (NIBs). Among emerging NIB cathodes, polyanionic materials are particularly attractive for grid-level energy storage due to their high-rate capability, excellent low-temperature performance, and long cycle life. However, significant challenges remain in the development of scalable synthesis methods and the understanding of transient kinetic processes governing their electrochemical behavior. The first part of this dissertation develops a sustainable and scalable spray-drying synthesis method for sodium vanadium phosphate (Na3V2(PO4)3, NVP). Through an appropriate choice of carbon source precursor, this method produces commercially relevant NVP without expensive nanocarbon additives or hazardous organic solvents. Sucrose and L-ascorbic acid are compared as representative carbon sources. Comprehensive characterization reveals that the reducing and acidic nature of L-ascorbic acid fundamentally alters precursor chemistry, producing an amorphous precursor with accelerated calcination dynamics, more uniform secondary particles, and a more continuous graphitic carbon coating than the sucrose-derived material. Despite these conventionally desirable characteristics, the sucrose-derived material exhibits superior electrochemical performance. Potentiostatic intermittent titration technique (PITT) measurements reveal that this disparity is due to substantially faster activation-filling kinetics within the phase-transformation region surrounding the nominal 3.38 V plateau, demonstrating that traditional structural descriptors alone are insufficient to predict long-term performance. Building upon these observations, the second part of this work develops a coupled Population Dynamics (cPD) model which self-consistently and quantitatively describes the complex transient current responses observed during NVP PITT experiments. The proposed framework accurately reproduces the non-monotonic and shoulder-like features of the current transients, which are attributed to the sequential nucleation and propagation of intermediate phases. Furthermore, the extracted filling-rate constants follow Marcus-Hush-Chidsey kinetics, enabling the determination of electron-transfer reorganization energies directly from electrochemical measurements. More broadly, the cPD model decouples phase-transformation kinetics from intrinsic electron-transfer kinetics, providing a general approach for analyzing intercalation materials which proceed through multiple phase transformations. Finally, the synthesis methodology and electrochemical framework are applied to the more economically attractive sodium iron pyrophosphate (Na4Fe3(PO4)2P2O7, NFPP) cathode material. Through careful optimization of stoichiometry, precursor selection, and synthesis parameters, a high-performance phase-pure NFPP material is obtained. PITT measurements further reveal activation-filling kinetics surrounding the 2.9 V plateau, providing new insight into the imperfect solid-solution intercalation mechanism. This synthesis strategy is also successfully applied to manganese-substituted NFPP, establishing a foundation for further investigation of low-cost mixed-polyanionic cathode materials. Collectively, the results presented in this dissertation demonstrate that the practical development of high-performance sodium-ion cathodes requires integrated consideration of scalable synthesis, precursor chemistry, material structure, and electrochemical phase-transformation kinetics. By establishing relationships between these factors and the resulting electrochemical performance, this work provides new insights into the design and scalable manufacturing of sustainable polyanionic cathode materials for sodium-ion batteries.
Committee Chair
Peng Bai
Committee Members
Peng Bai; Richard Axelbaum; Rohan Mishra; Xinhua Liang; Young-Shin Jun
Degree
Doctor of Philosophy (PhD)
Author's Department
Energy, Environmental & Chemical Engineering
Document Type
Dissertation
Date of Award
8-31-2026
Language
English (en)
DOI
https://doi.org/10.7936/7m7s-3x98
Recommended Citation
Boutelle, Ethan, "Scalable Synthesis and Electrochemical Kinetics of Polyanion Cathode Materials for Sodium-based Batteries" (2026). McKelvey School of Engineering Graduate Student Theses & Dissertations. 1430.
The definitive version is available at https://doi.org/10.7936/7m7s-3x98