Constructing a 3D Interconnected Carbon Network for Mg-Doped Porous LiMn_0.85Fe_0.15PO₄/C Cathode Materials

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Lithium manganese iron phosphate (LiMnFePO4) cathode materials offer a theoretical specific energy advantage over LiFePO4.
• Low electronic conductivity and sluggish ion diffusion kinetics hinder the practical application of LiMnFePO4/C.
• Enhancing conductivity and ion transport is crucial for improving cathode material performance in batteries.

Purpose of the Study:

• To develop a simple solid-state synthesis method for porous LiMnFePO4/C cathode materials.
• To improve the electronic conductivity and lithium-ion diffusion kinetics of LiMnFePO4/C.
• To enhance the electrochemical performance and cycling stability of phosphate cathode materials for energy storage applications.

Main Methods:

• Solid-state synthesis of porous LiMn0.85Fe0.15PO4/C (LMFM0.01P-2C4P) doped with Mg and coated with composite carbon.
• Utilized citric acid and polyethylene glycol 400 as composite carbon sources to create a 3D conductive network.
• Characterized material properties including electronic conductivity and lithium-ion diffusion coefficients.
• Performed electrochemical studies to evaluate specific capacity, rate capability, and cycling stability.

Main Results:

• Mg substitution shortened lithium ion transport paths, enhanced intrinsic conductivity, and improved structural stability.
• The composite carbon coating formed a 3D conductive network, significantly boosting electronic conductivity (7.22 × 10⁻³ S cm⁻¹) and reducing internal resistance.
• The modified LMFM0.01P-2C4P material exhibited a superior specific capacity (152.1 mAh g⁻¹ at 0.1C, 124.9 mAh g⁻¹ at 1C) and excellent capacity retention (80.8% after 500 cycles at 1C) compared to unmodified LMFP-4C.

Conclusions:

• The developed Mg-doped and carbon-coated LiMnFePO4 material demonstrates significantly enhanced electronic conductivity and lithium-ion diffusion.
• This approach effectively overcomes the limitations of low conductivity in phosphate cathode materials.
• The findings present a viable strategy for developing high-performance cathode materials for advanced lithium-ion and sodium-ion batteries.