高容量梯度锂离子电池正极材料Li[Ni0.85Co0.08Mn0.07]O2的制备

Synthesis of High Capacity Gradient Cathode Material Li[Ni0.85Co0.08Mn0.07]O2 for Lithium Ion Battery

通过改变金属离子的浓度比例,采用连续控制结晶法制备出镍钴锰金属元素连续浓度梯度变化的前驱体[Ni0.85Co0.08Mn0.07](OH)2。再与LiOH·H2O混合,通过高温固相法得到全梯度材料Li[Ni0.85Co0.08Mn0.07]O2。XRD结果表明该梯度材料阳离子混排程度比纯相Li[Ni0.85Co0.08Mn0.07]O2更低,具有更好的层状结构。扫描电镜结果显示Li[Ni0.85Co0.08Mn0.07]O2具有球形形貌,粒径分布比较集中,颗粒平均粒径分布在11.5~12μm,切面元素扫描显示沿着球径方向从球心到外壳,镍含量越来越低,而钴锰的含量越来越高。越靠近颗粒表面,镍的含量越低,而钴锰的含量越高。电材料在0.1C放电倍率下首次放电比容量可达204.3mAh·g^-1,1C放电倍率的首次放电比容量为185.3mAh·g^-1,循环100次后,仍有164.7mAh·g^-1,容量保持率达89.17%。在高温55℃环境下,1C首次放电比容量可达202.7mAh·g^-1,容量保持率为85.84%,性能均好于纯相Li[Ni0.85Co0.08Mn0.07]O2。

Precursor [Ni0.85Co0.08Mn0.07](OH)2 with continuous concentration gradient change of metal elements were prepared by a continuous crystallization method. The new gradient composite Cathode material Li[Ni0.85Co0.08Mn0.07]O2 was synthesized by sintering the mixture of as-prepared precursor and LiOH·H2O in O2. X-ray diffraction results indicated a low degree of cationic miscibility and a better layered structure. Scanning electronic microscopy showed the gradient material had a perfect spherical morphology. Particle size distribution was relatively concentrated in 11.5~12 μm. The line scan test of elements on the cross section area of coating shell showed that the main elements of the materials changed gradiently. From the center to the outer surface, the content of nickel became lower, while that of cobalt and manganese were higher. The initial discharge capacity was 204.3 mAh·g^-1 at 0.1C rate between 2.8 and 4.3 V. At 1C rate, its capacity was 185.3 mAh·g^-1 and retained 164.7 mAh·g^-1 (89.17%) after 100 cycles. When cycled at 55 ℃, the capacity of 1C rate was 202.7 mAh·g^-1 and retained 85.84% after 100 cycles, indicating good electrochemical capacity and cycling stability.