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.
Conventional LiFePO4 cathodes face limitations due to their low operating voltage (3.4 V) and discharge capacity. Partial Mn substitution in LiMn0.6Fe0.4PO4 (LMFP) elevates the discharge potential to 4.1 V, yet challenges such as Mn dissolution and structural degradation persist during charge/discharge cycling. Traditional solid-state approaches often produce inhomogeneous phases and impurities, while hydrated phosphate precursors synthesized via coprecipitation offer a promising alternative─though their thermal evolution remains poorly characterized. This study deciphers the phase transformation mechanisms during LMFP synthesis from Mn0.6Fe0.4PO4·0.25H2O precursors, employing in situ heating X-ray diffraction (XRD) to map structural evolution under thermal treatment. Carbon integration promotes structural decoupling, enabling efficient Li+ insertion into the olivine lattice. Contrasting with the conventional single-step process, the gradient-sintered (multistage heating) based on the phase transition mechanism enhances phase purity, suppresses impurities, and improves crystallinity by optimizing intermediate phase transitions. Electrochemical evaluations confirm that gradient-sintered LMFP delivers a higher specific capacity than the non-gradient counterparts. These findings establish a paradigm for controlled reaction pathways in LMFP synthesis, emphasizing the critical role of staged thermal treatment and carbon mediation in minimizing parasitic reactions. This work advances scalable strategies for high-performance manganese-stable lithium-ion battery cathodes.
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