球磨烧结对锰系混合正极材料性能的影响

Influence of ball milling and sintering on performance of manganese-based hybrid cathode materials

采用高温固相法合成尖晶石LiMn2O4（LMO）,采用共沉淀法合成层状三元正极材料LiNi1/3Co1/3Mn1/3O2（NCM）,将这两个材料按（比例7∶3）混合烧结,通过X射线衍射光谱法（×RD）、粒径测试、循环伏安和充放电测试,考察球磨和研磨工艺对材料粒径、结构和电化学性能的影响.研究发现,球磨烧结使得混合材料粒径明显减小,球磨混合样的氏为0.279 μm,而研磨混合样的d50为3.674 μm;两种方法混合的材料其XRD衍射峰强度减弱、峰型宽化,其中球磨混合样中应有的三元层状结构衍射峰已经消失,而研磨样品仍部分保留三元层状结构衍射峰;CV图显示球磨混合样在4.15V附近出现单一的尖晶石结构的氧化还原峰,表明在球磨烧结过程中LMO与NCM之间发生化学反应;充放电测试显示球磨烧结混合样在4.0～4.3V之间出现单一的充放电平台,循环性能十分稳定,50次循环后放电容量基本保持不变.

Spinel LiMn204 （LMO） was prepared via solid state method, and the ternary cathode materials LiNil/3ColaMn1/3O2 （NCM） was synthesized via co-precipitation method. The two materials were mixed and sintered with mole ratio of 7 ： 3. X-ray powder diffraction, laser diffraction particle size analyzer, cyclic voltammetry and charge-discharge tests were used to study the particle diameter distribution, structure and electrochemical performance of ball milling and grinding materials. The result shows that the particle diameter of the ball milled sample is significantly declined with d50 of 0.279 μm, compared to the grinded one with d50 of 3.674 μm.The diffraction peaks of both materials were weakened and broadened; the peaks of ternary layered structure were partially remained after grinding but not exited in ball milling materials. Only one pair of redox peaks was appeared in CV curves after ball milling, which can be inferred as chemical reaction between LMO and NCM during the milling and sintering process. Single platform in the voltage range of 4.0-4.3 V and a stable cycling performance with unchanged discharge capacity was obtained.