Evaluation of the Impact of Conductive Additives on the EPR Spectra of Hard Carbon Anodes

Wang, W, Xu, Y, Li, Y, Sun, Y, Fielding, AJ ORCID: 0000-0002-4437-9791, Iamprasertkun, P, Yang, J, Wang, B ORCID: 0000-0002-0461-9199, Li, Q, Wu, M and Hu, H (2025) Evaluation of the Impact of Conductive Additives on the EPR Spectra of Hard Carbon Anodes. Small Methods.

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Abstract

Hard carbon (HC), a prime anode candidate for sodium-ion batteries, exhibits unresolved charge-state-microstructure debates reveal critical sodium storage mechanism gaps. This study employs electron paramagnetic resonance (EPR) spectroscopy as a principal characterization tool, capitalizing on its unique capability to probe electronic configurations and detect subtle structural transformations in carbon matrices. Through systematic EPR investigations of sodium storage dynamics in varied carbon architectures, the quasi-metallic state of sodium ions stored in closed pores exhibits distinct signal characteristics due to size effect-induced structural confinement, compared to surface storage mechanisms. Furthermore, the underappreciated influence of conductive carbon additives, a ubiquitous component in electrode formulations is specifically addressed, on spectroscopic interpretations. This findings reveal that sodium's distinctive storage states (ionic vs quasi-metallic) and their spatial distribution within carbon matrices induce quantifiable modifications in EPR spectral parameters, including characteristic linewidth broadening and lineshape evolution. The comparative analysis demonstrates that trace amounts (≤10 wt.%) of conductive additives can substantially distort ex situ EPR measurements, with interference patterns exhibiting strong material-dependent behavior. Therefore, the application of conductive additives demands rigorous consideration in EPR-based investigations of energy-storing carbon materials, given their methodological implications.

Item Type:	Article
Additional Information:	This is the peer reviewed version of the following article: W. Wang, Y. Xu, Y. Li, Y. Sun, A. J. Fielding, P. Iamprasertkun, J. Yang, B. Wang, Q. Li, M. Wu, H. Hu, Evaluation of the Impact of Conductive Additives on the EPR Spectra of Hard Carbon Anodes. Small Methods 2025, 2500786. https://doi.org/10.1002/smtd.202500786, which has been published in final form at https://doi.org/10.1002/smtd.202500786. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited.
Uncontrolled Keywords:	conductive additive; electron paramagnetic resonance; energy storage mechanisms; hard carbon; sodium‐ion batteries; 40 Engineering; 4016 Materials Engineering; 34 Chemical Sciences; 3406 Physical Chemistry; 7 Affordable and Clean Energy
Subjects:	Q Science > QD Chemistry R Medicine > RS Pharmacy and materia medica
Divisions:	Pharmacy and Biomolecular Sciences
Publisher:	Wiley
Date of acceptance:	2 June 2025
Date of first compliant Open Access:	1 September 2025
Date Deposited:	01 Sep 2025 10:22
Last Modified:	01 Sep 2025 10:30
DOI or ID number:	10.1002/smtd.202500786
URI:	https://researchonline.ljmu.ac.uk/id/eprint/27064

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