Design of Conductive Network through the Hybrid Application of Super P and Multi-Walled Carbon Nanotube in Thick LiFePO₄ Electrodes

Enhancing the energy density of electrodes by increasing thickness and mass loading is a technological challenge. Thick electrodes suffer from severe deterioration in electrochemical performance due to insufficient structural integrity and sluggish charge transport, particularly under high current density. Herein, we fabricated thick LiFePO₄ (LFP) electrodes with thicknesses ranging from 85.7 to 90.3 µm and an average mass loading of 17.68 mg/cm² by tailoring the ratio of zero-dimensional (Super P, SP) and one-dimensional (multi-walled carbon nanotube, MWCNT) conductive additives. The electrodes containing MWCNT exhibited crack-free structure and enhanced electrochemical performance with increasing MWCNT ratio because of the superior mechanical properties and electrical conductivity of MWCNT. However, the electrochemical performance of the electrode containing only MWCNT deteriorated due to aggregation of the MWCNT and poor point to point contact with the LFP particles. The multi-dimensional conductive additives improve the dispersion of components within the electrode and the structural stability of the electrode. As a result, the tailored electrode exhibited a lower degree of electrode thickness expansion (1.4 %), lower polarization (60.8 mV at 0.1 C), excellent high-rate capability (132.7 mAh/g at 2 C), superior capacity retention (27.5 % at 3 C), and lower electrical resistivity and interfacial resistance (14.9 Ω cm and 3.8 Ω cm², respectively) compared to other samples.