LMFP (LiMnₓFe₁₋ₓPO₄) is a promising cathode material due to its high energy density, cost efficiency, and safety. However, its inherent dual-voltage plateau causes abrupt voltage drops during discharge, complicating battery management. To address this issue, blending electrodes containing layered oxides NMC and LMFP is proposed for offering unique synergies. While blending LMFP with NMC cathodes can alleviate this issue, the material still exhibits significant voltage fade during cycling. In view of the different types of NCM batteries have different operating voltage intervals, to make the mixed electrode material have the best electrochemical performance, it is essential to figure out the working state and performance degradation mechanism of LMFP under different voltage intervals.
Researchers at Huazhong University of Science and Technology have identified the fundamental mechanism behind voltage decay in lithium manganese iron phosphate (LMFP) cathodes. The study clarifies how operational voltage windows critically influence material degradation during cycling. They found that wider voltage windows exacerbate voltage decay specifically at the Mn³⁺/Mn²⁺ redox plateau. What is crucial is that the capacity loss of this plateau is disproportionately greater than the overall capacity decay, which might be an unconventional Jahn-Teller effect. Structural analysis and density functional theory (DFT) calculations confirmed that the decay primarily originates from irreversible lattice distortion along the b-axis, which deteriorates lithium-ion diffusion kinetics. "Voltage decay is fundamentally linked to bulk structure degradation," stated Professor Li. "Stabilizing the crystal lattice presents a direct pathway to enhance cyclability." The work establishes a critical foundation for optimizing LMFP batteries by clarifying degradation mechanisms under practical operating conditions.
Science China Chemistry
Experimental study