A Uniform Conductive Carbon Coating of Nitrogen-Doped Carbon Improves the Electrochemical Performance of LiMn0.7Fe0.3PO4 Cathode Material for Lithium-ion Batteries

Abstract

The practical application of LiMn_1−xFe_xPO₄ as a cathode material is hindered considerably by its poor electronic conductivity and slow lithium-ion diffusion. In the present study, a uniform nitrogen-doped carbon coating on LiMn_0.7Fe_0.3PO₄ (LiMn_0.7Fe_0.3PO₄@NC) was achieved using ethylene diamine tetraacetic acid (EDTA) as a chelating agent and carbon source. The nitrogen-doped carbon layer enhanced the electronic conductivity and ionic diffusion of the LiMn_0.7Fe_0.3PO₄ cathode. Furthermore, the uniform carbon layer prevented metal ion dissolution and stabilized the crystal structure. The resulting LiMn_0.7Fe_0.3PO₄@NC-2 sample demonstrated superior performance with a specific capacity of 152.5 mAh g⁻¹ at 0.1 C and preserved 93.7 % of this capacity over 200 cycles at 1 C. Meanwhile, the LiMn_0.7Fe_0.3PO₄@NC-2 sample demonstrated a high Li⁺ diffusion coefficient (3.98×10⁻¹¹ cm² s⁻¹) and electrical conductivity (1.47×10⁻² S cm⁻¹). This study presents a novel approach to designing high-performance cathode materials using a cost-effective and straightforward process.