Troubleshooting Carbon Nanotube Bundling Using Electrostatic Energy-Driven Dispersion for LiFePO4 Bimodal Thick Electrode in Lithium-Ion Batteries

Abstract

Interest in using thick LiFePO4 cathodes to enhance lithium-ion battery energy density has recently been growing. To obtain thick cathodes with superior electrical conductivity throughout their depth, it is crucial to substitute conventional zero-dimensional conductive agents with one-dimensional carbon nanotubes (CNTs). Nevertheless, the inherent properties of CNT, including their high aspect ratio and strong van der Waals interaction, hinder uniform dispersion, causing poor performance in thick electrodes. In this work, we adopted an electrostatic energy-driven dispersion (EED) method to achieve a homogeneous distribution of multiwalled carbon nanotubes (MWCNTs) with LiFePO4 for thick cathodes. The EED process, guided by the charge residue model and ion evaporation model theories, facilitated the formation of a well-distributed LiFePO4-MWCNT composite. This method yielded e-LiFePO4/MWCNT composites with consistent morphology even at a high MWCNT concentration (5 wt %), as verified by cross-sectional scanning electron microscopy and a microcomputed tomography scan. The e-LiFePO4/MWCNT cathode exhibited reduced overpotential during the Li-ion redox process, along with enhanced areal capacity and capacity retention (7.27 mAh cm(-2) at 0.3 C and 80.74% after 90 cycles), outperforming the conventional mixing-only method. These results underline the importance of prioritizing the uniform distribution of active materials and conductive agents in future thick electrode research.