One-Step Low-Temperature N2 Plasma for Enhancing Electrochemical Performance of Lithium Iron Phosphate Cathodes

Abstract

Interface modulation on lithium iron phosphate (LiFePO₄) cathodes is highly important for enhancing their high-rate capability and discharge capacities at high current densities. In order to further improve the ionic/electronic conductivity and reaction kinetics of LiFePO₄ cathodes, in this work, we report a facile one-step low-temperature N₂ plasma technology to modify the LiFePO₄/C cathodes. During the plasma process, the LiFePO₄/C (LFP/C) particles are rotated in the N₂ plasma atmosphere, where numerous N-containing radicals can be induced into the outer carbon layer, leading to N-doped carbon (NC) and surface modification. The low-temperature N₂ plasma will create more active sites and defects to reinforce capacity and reaction kinetics by providing creative transportation channels for lithium ions on the cathode/electrolyte interface, thus accelerating the electrochemical kinetics and reaction reversibility. Electrochemical impedance spectroscopy and simulated distribution of relaxation times further confirm the reduced interface resistance and enhanced electrochemical kinetics. Accordingly, the well-designed plasma treated LFP@C electrode shows a higher discharge capacity of 134.8 mAh g^–1 at a high current density of 5 C, much better than the unmodified counterpart (109.8 mAh g^–1). This facile plasma strategy effectively unlocks its viability for next-generation high-rate energy storage systems.