LiFePO4 (LFP) is widely used as cathode material in Li-ion batteries in electric vehicles (EV’s). The theoretical capacity of LFP is 170 mAhg−1. It is difficult to achieve the theoretical capacity value, especially at high C-rates, mainly because of its poor ionic as well as electronic conductivity. Several doping strategies have been adopted of which Mn as well as V doping individually, show beneficial effect in improving the electrochemical performance. However, co-doping of these two ions and the synergistic effect, if any, on the electrochemical performance of LFP has not been explored hitherto. In the present study, Mn and V co-doped LFP cathode materials were synthesized by solvothermal method. Phase formation was confirmed by X-ray diffraction studies, while 7Li MAS NMR spectra revealed changes in isomeric shift (-18.03 ppm for pristine LFP, -1.01 ppm for Mn-doped, and -0.65 ppm for Mn, V co-doped LFP), confirming Mn and V are incorporated into the olivine lattice. The co-doped LFP exhibited a unique two-dimensional morphology with uniform, fluffy particles (~ 3 µm × 2 µm). X-ray photoelectron spectra confirmed the presence of Fe2+, Mn2+, and V4+ oxidation states. The Li-ion diffusion coefficient (DLi+) of Mn and V co-doped LFP (6.93 × 10−15 cm2s−1) was higher than that of pristine LFP (2.97 × 10−15 cm2s−1), indicating enhanced Li-ion diffusion in the co-doped sample. Electrochemical tests in half-cell mode showed that co-doped LFP achieved a 167, 153 and 145 mAhg−1 capacity at 0.1, 1.0, and 2.0 C-rates, respectively. Inaddition, the co-doped composition showed excellent capacity retention, even at high C-rates i.e., 135 mAhg−1 with 90% retention after 500 cycles at 1C and 101.3 mAhg-1 with 70% retention after 1000 cycles at 2C. Also, the co-doped phase exhibited lower polarization and charge transfer resistance, highlighting its potential for high-performance lithium-ion batteries. Graphical Abstract The graphical image illustrates the discharge capacity and coulombic efficiency over 1000 cycles at 2C-rate. The discharge capacity reaching 101.3 mAhg−1 (70% retention) after 1000 cycles, indicating decent long-term performance. Meanwhile, the coulombic efficiency remains consistent, close to 100%, demonstrating stable charge–discharge efficiency. Highlighting the optimal performance of the Co-doped LFP cathode at a 2C rate over 1000 cycles with consistent coulombic efficiency.

A dual-dopant strategy for enhancing the electrochemical performance of LiFePO₄ for high-performance lithium-ion batteries

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发表日期：

2025年10月6日

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Giridharan Balakrishnan,
Praneash Venkatachalam,
Sujith Kalluri,
Sambasivam Sangaraju,
U. V. Varadaraju,
Pardha Saradhi Maram

摘要

LiFePO₄ (LFP) is widely used as cathode material in Li-ion batteries in electric vehicles (EV’s). The theoretical capacity of LFP is 170 mAhg⁻¹. It is difficult to achieve the theoretical capacity value, especially at high C-rates, mainly because of its poor ionic as well as electronic conductivity. Several doping strategies have been adopted of which Mn as well as V doping individually, show beneficial effect in improving the electrochemical performance. However, co-doping of these two ions and the synergistic effect, if any, on the electrochemical performance of LFP has not been explored hitherto. In the present study, Mn and V co-doped LFP cathode materials were synthesized by solvothermal method. Phase formation was confirmed by X-ray diffraction studies, while ⁷Li MAS NMR spectra revealed changes in isomeric shift (-18.03 ppm for pristine LFP, -1.01 ppm for Mn-doped, and -0.65 ppm for Mn, V co-doped LFP), confirming Mn and V are incorporated into the olivine lattice. The co-doped LFP exhibited a unique two-dimensional morphology with uniform, fluffy particles (~ 3 µm × 2 µm). X-ray photoelectron spectra confirmed the presence of Fe²⁺, Mn²⁺, and V⁴⁺ oxidation states. The Li-ion diffusion coefficient (D_Li+) of Mn and V co-doped LFP (6.93 × 10⁻¹⁵ cm²s⁻¹) was higher than that of pristine LFP (2.97 × 10⁻¹⁵ cm²s⁻¹), indicating enhanced Li-ion diffusion in the co-doped sample. Electrochemical tests in half-cell mode showed that co-doped LFP achieved a 167, 153 and 145 mAhg⁻¹ capacity at 0.1, 1.0, and 2.0 C-rates, respectively. Inaddition, the co-doped composition showed excellent capacity retention, even at high C-rates i.e., 135 mAhg⁻¹ with 90% retention after 500 cycles at 1C and 101.3 mAhg-1 with 70% retention after 1000 cycles at 2C. Also, the co-doped phase exhibited lower polarization and charge transfer resistance, highlighting its potential for high-performance lithium-ion batteries.

Graphical Abstract

The graphical image illustrates the discharge capacity and coulombic efficiency over 1000 cycles at 2C-rate. The discharge capacity reaching 101.3 mAhg⁻¹ (70% retention) after 1000 cycles, indicating decent long-term performance. Meanwhile, the coulombic efficiency remains consistent, close to 100%, demonstrating stable charge–discharge efficiency.

Highlighting the optimal performance of the Co-doped LFP cathode at a 2C rate over 1000 cycles with consistent coulombic efficiency.

A dual-dopant strategy for enhancing the electrochemical performance of LiFePO4 for high-performance lithium-ion batteries

摘要

A dual-dopant strategy for enhancing the electrochemical performance of LiFePO₄ for high-performance lithium-ion batteries