Analysis of Aging, Electrochemical Performance and Physics-Based Models of a Commercial Na₄Fe₃(PO₄)₂P₂O₇ Sodium-Ion Battery

ECS Meeting Abstracts, vol. MA2026-01, pp. 540

Abstract

Sodium-ion battery cells represent a promising and increasingly viable alternative to conventional lithium-ion technology, particularly when critical raw materials such as nickel or cobalt are eliminated from the cell chemistry. Na₄Fe₃(PO₄)₂P₂O₇ (NFPP)-based sodium-ion cells are rapidly entering the commercial market, driven by the promise of high cycle stability, significantly reduced material costs, and inherently sustainable, nickel-free composition. While these cells exhibit lower energy density compared to state-of-the-art layered oxide sodium-ion and lithium iron phosphate systems, their resource efficiency could position the technology as an attractive option for stationary energy storage, grid stabilization, starter batteries and emerging applications where cost and longevity are prioritized over gravimetric energy density. Despite the growing commercial interest in this innovative cell chemistry, comprehensive aging analyses and systematic electrochemical characterization studies of commercial cell formats remain limited in the scientific literature. This work addresses this gap by presenting the first extensive aging analysis of a commercial NFPP sodium-ion cell. Initial investigations include a detailed teardown and chemical post-mortem analysis of the pristine commercial cell to establish baseline material and component specifications. The aging analysis is conducted through comprehensive electrical benchmarking protocols, encompassing systematic cyclic aging studies at multiple temperatures (10 °C, 25 °C, and 40 °C) to elucidate temperature-dependent degradation mechanisms, alongside accelerated calendar aging experiments at elevated temperatures to assess long-term stability. Post-mortem analysis is performed on aged cells utilizing X-ray computed tomography and scanning electron microscopy combined with energy dispersive X-ray spectroscopy to elucidate the physical and chemical processes governing cell performance degradation at the microstructural level and to correlate aging mechanisms observed electrochemically with structural and compositional changes in cell components. Furthermore, this study focuses on the development and parameterization of a physics-based electrochemical model for NFPP sodium-ion cells. Such advanced Doyle-Fuller-Newman based models are essential for predicting cell behavior across diverse operating scenarios, optimizing cell designs, and enabling rapid prototyping of battery management and fast charging strategies. The existing physicochemical framework is systematically parameterized using comprehensive electrical and chemical measurement data acquired during extensive characterization campaigns across the full temperature range investigated. Different simulations are employed to validate model predictions against experimental observations and to perform parameter optimization across multiple operating windows. A key innovation within this work is the extension of the model parameterization methodology to explicitly account for temperature-dependent effects, which significantly influence ionic transport, interfacial kinetics, and overall cell performance. Temperature represents one of the most critical variables affecting battery behavior. Yet accurate temperature-dependent modeling of emerging cell chemistries remains a substantial challenge. The parameterization methods developed here try to enable realistic representation of temperature influences across a relevant operating range, from low-temperature cold-start scenarios to regular thermal stress conditions. This enhanced temperature dependency is validated rigorously by comparing model predictions with experimental data collected at multiple temperatures and under various electrochemical protocols. This research contributes significantly to the scientific and engineering understanding of this emerging sodium-ion battery technology at a critical juncture in its commercialization. By combining experimental aging analysis, electrochemical modeling, and microstructural characterization, a foundation is established for the practical application of sodium-ion cells in energy storage. The insights gained from this comprehensive characterization and modeling effort will support continued innovation in cell chemistry optimization and system-level battery management, ultimately advancing the transition toward sustainable, cost-effective, and resource-efficient energy storage solutions for electromobility and grid applications.

Authors 11

1. Moritz Schütte Aachen

   RWTH Aachen University

   Affiliation as printed

   ISEA, RWTH Aachen University

2. Katharina Lillith Quade Aachen

   RWTH Aachen University

   Affiliation as printed

   ISEA, RWTH Aachen University

3. Caroline Kümmel Aachen

   RWTH Aachen University

   Affiliation as printed

   ISEA, RWTH Aachen University

4. Jonas Rinner Aachen

   RWTH Aachen University

   Affiliation as printed

   ISEA, RWTH Aachen University

5. Luís Gouveia Aachen

   RWTH Aachen University

   Affiliation as printed

   ISEA, RWTH Aachen University

6. Patrick Hoffmann Aachen

   RWTH Aachen University

   Affiliation as printed

   ISEA, RWTH Aachen University

7. Gereon Karsten Stahl Aachen

   RWTH Aachen University

   Affiliation as printed

   ISEA, RWTH Aachen University

8. Runyang Lian Aachen

   RWTH Aachen University

   Affiliation as printed

   ISEA, RWTH Aachen University

9. Heinrich Ditler Aachen

   RWTH Aachen University

   Affiliation as printed

   ISEA, RWTH Aachen University

10. Christiane Rahe Aachen

    RWTH Aachen University

    Affiliation as printed

    ISEA, RWTH Aachen University

11. Dirk Uwe Sauer Aachen

    RWTH Aachen University

    Affiliation as printed

    ISEA, RWTH Aachen University