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.
A well-designed solvothermal approach has been employed to synthesize olivine LiMn 0.5 Fe 0.5 PO 4 (LMFP) cathode material with a nanoplate configuration. This method precisely controls crystal growth to achieve a high proportion of (010) facets while minimizing intrinsic defects. These modifications significantly enhance lithium-ion diffusion kinetics and optimize the electrochemical performance of LMFP. The nanoscale of the (010) facets and the reduced anti-site defect concentration in the MP-PRO sample functionalize jointly to promote lithium-ion transport during the long-cycle. Furthermore, the superior electrochemical performance is closely linked with significantly reduced impedance and enhanced Mn redox kinetics. Both theoretical calculations and experimental results indicate that the confinement effect induced by 1,3-propanediol directs facet orientation and confines nanoplate growth. Compared to the product synthesized using water (MP-H 2 O), the 1,3-propanediol-based sample (MP-PRO) delivers a high specific capacity of 130.7 mAh g −1 at 5C and demonstrates excellent cycling stability, with an 84.6% capacity retention after 1000 cycles. This study provides new insights into the kinetics of Mn redox in LMFP electrodes and reveals an effective electrode structure design to realize long-life high rate batteries.
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