LiMn0.6Fe0.4PO4 (LMFP) cathodes possess high operating voltages, yet their application is severely hindered by sluggish electron/lithium-ion transport kinetics and interfacial instability during cycling. To address these challenges, this work proposes a surface engineering strategy utilizing a boron-doped carbon coating to modulate the interfacial kinetics of LMFP. The introduction of boron modifies the local electronic structure, inducing defects and holes that facilitate Li-ion migration, while simultaneously maintaining the layer’s physical continuity and protective function against manganese dissolution. Within the investigated doping range, the 2% B-doped sample exhibits the best equilibrium between rate performance and cyclability, retaining 95.66% capacity after 100 cycles at 1 C and 93.20% after 300 cycles at 5 C, significantly outperforming the pristine sample (82% and 74%, respectively). In situ electrochemical impedance spectroscopy (EIS) combined with distribution of relaxation times (DRT) analysis reveals that the coating synergistically reduces interfacial charge-transfer resistance throughout the charge–discharge process. Consequently, this study defines an optimal boron-doping window to successfully navigate the trade-off between achieving rapid Li-ion kinetics and ensuring robust interfacial stability in olivine cathodes.
Haifeng Yu,Erdong Zhang,Jinxun Yu,Songmin Yu,Yaoguo Fang,Ling Chen,Hao Jiang,Chunzhong Li
Olivine-type LiMnxFe1−xPO4 (LMFP, 0 < x < 1) is poised to supplant LiFePO4 cathode materials with a ∼20% energy-density increase for Li-ion batteries (LIBs). However, its intrinsic low conductivities and MnO6 octahedral unit-cell Jahn–Teller distortion limit its power capability and cycling life. Herein, we report a Mg/Ni dual-doped and carbon-coated LMFP micro-sized secondary sphere with greatly enhanced reaction kinetics and superior structure stability. Ni2+ reduces the average valence state of Mn ions to alleviate Jahn–Teller distortion by participating in charge compensation during charging while improving electronic conductivity together with carbon coating. Mg2+ with a smaller ion radius (65 pm) significantly widens the Li-ion transfer channel by extending Li–O bonds. The as-obtained LMFP cathodes increase reversible specific capacity by about 2.4 times at 5C compared with a pristine sample, reaching 115 mA h g−1. In a pouch-type full cell, 92% of its initial capacity is still maintained after 2000 cycles at 1C, demonstrating its attractive potential for practical application in high-power and long-life LIBs.
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