(603c) Effect of Transporting Enhancer in Fe3O4 Li-Ion Battery Anodes

Battery electrodes are complex mesoscale systems comprised of active material, conductive agents, current collector and binders [1]. For the improved design of a composite electrode, both electron and ion transport are critical factors to improve electrochemical performance. However, research rarely focuses on both factors.

The present work focuses on enhancing electron and ion transport in high capacity anode systems, by introducing a poly[3-(potassium-4-butanoate) thiophene] (PPBT) as a binder component and a polyethylene glycol (PEG) surface coating on Fe₃O₄ nanoparticles. PPBT is a water soluble carboxylate functionalized polythiophene, which seems favorable for forming porous structures. The PEG coating reduced the aggregate size and improved dispersion. Together the PPBT water system and PEG coating helped improve capacity retention by effectively decreasing charge-transfer resistance. PPBT and PPBT carbon composites also exhibited high electronic conductivity compared to PVDF, which was used as a reference due to its common use as a binder in Li-ion battery electrodes. SEM images illustrated that the PEG coating reduced the size of aggregates as compared to a Fe₃O₄/carbon/PPBT electrode from ~5mm to ~0.5-1mm. This improved dispersion, which positively contributed to battery performance. Furthermore, FT-IR and XPS provided evidence of chemical interaction between PPBT and Fe₃O₄ nanoparticles. Strong interactions between a binder and surface of active materials have been reported to improve stability [2]. The use of a PPBT binder and PEG surface coating improved both ion and electron transport, which provides a new approach for high-capacity energy materials [3].

An ongoing portion of this work takes a closer look at the active material, Fe₃O₄, and further studies the difference in particle sizes and PEG coating on battery performance. The PEG coating has already been shown to reduce aggregate size and improve dispersion [3]. Further testing is ongoing to study how crystallite size (10 nm vs. 20 nm) of nanoparticles affects battery properties. Preliminary SEM results indicate that at higher nanoparticle size (20nm), the aggregates from PEG are closer in size to the nanoparticles, which begs the question of how this impacts battery performance. Future testing is still needed to confirm this hypothesis and determine the â??criticalâ? nanoparticle size for greatest battery performance by enhancing the active material of the electrode.

[1] Y. H. Kwon, M. M. Huie, D. Choi, M. Chang, A. C. Marschilok, K. J. Takeuchi, E. S. Takeuchi, E. Reichmanis, ACS Appl. Mater. Interfaces, 2016, 8 (5), 3452â??3463.

[2] D. Mazouzi, B. Lestriez, L. Roué, D. Guyomard, Electrochem. Solid-State Lett. 2009, 12, A215.

[3] Y. H. Kwon, K. Minnici, M. M. Huie, A. C. Marschilok, K. J. Takeuchi, E. S. Takeuchi, E. Reichmanis. Electron/Ion Transport Enhancer in High Capacity Li-ion Battery Anodes, submitted.