定-转子反应器制备LiFe1-xMxPO4 (M= Mn, Ni)粉体及其性能研究

Synthesis of LiFe1-xMxPO4 (M= Mn, Ni) in a rotor-stator reactor and study on its electrical performance

摘要:

采用具有高效传质和微观混合性能的定-转子反应器制备了LiFe_1-xMn_xPO₄ (x=0.0, 0.1, 0.2, 0.3)和LiFe_1-xNi_xPO₄ (x=0.00, 0.03, 0.05, 0.07)粉体,分别用作正极材料制成电池后,采用电池测试系统测定了电池的电化学性能随温度的变化规律。结果表明,粉体颗粒呈类球形,尺寸分布均匀,粒径范围为5~10 μm,Mn和Ni的掺杂没有改变粉体的晶体结构。以LiFe_0.8Mn_0.2PO₄和LiFe_0.95Ni_0.05PO₄两种组成的粉体性能最好,在倍率0.1 C下,所得电池的首次充放电比容量在室温和50 _oC时,分别为153.2和155.7 mAh/g,及156.4和160.4 mAh/g；100次充放电循环后电池的容量保持率分别为95.4和96.5%,及93.8和95.0%。借助具有过程强化作用的定-转子反应器制备的Mn和Ni掺杂LiFePO₄正极材料的电性能得到显著提高。原因是定-转子反应器一方面可以制备颗粒尺寸均匀的粉体,另一方面又可使掺杂的Mn和Ni在粉体颗粒中均匀分布,两者同时提高了电池中Li₊的扩散速率,进而提高了锂离子电池的电化学性能和高温电性能。

Abstract:

LiFe_1-xMn_xPO₄ (x=0.0, 0.1, 0.2, 0.3) and LiFe_1-xNi_xPO₄ (x=0.00, 0.03, 0.05, 0.07) powders were synthesized in a rotor-stator reactor and the reactor possesses high efficient performances of mass transfer and micro-mixing. The powders are used as cathode materials in the batteries and the battery test system is employed to explore the dependence of electrochemical property on temperature. The particle is in the shape of near-sphere, uniformly distributed and in the particle size of 5~10 μm. The crystallographic evidence demonstrates that the introduction of Mn and Ni does not change the host crystal structure. The powders have favorable electrochemical and high-temperature electrical properties. Particularly, LiFe_0.8Mn_0.2PO₄ and LiFe_0.95Ni_0.05PO₄ exhibit the best performance. At room temperature and 50 _oC, their first charge-discharge specific capacities are 153.2/155.7 mAh/g and 156.4/160.4 mAh/g separately with 0.1 C fixed. The capacity retention ratios are 95.4/96.5% and 93.8/95.0% separately after 100 cycles. On one hand, the rotor-stator reactor makes the obtained particle homogeneously dispersed. On the other hand, it also leads the doping Mn and Ni distributing uniformly in the particle. Both of the two advantages increase the Li₊ ionic diffusion rate and enhance the electrochemical and high-temperature electrical properties of the materials.