锂离子电池正极材料层状LiNi1/2Mn1/2O2的制备与表征

用一种简单的共沉淀法制备出了层状LiNi_1/2Mn_1/2O₂材料，并且用XRD、SEM、循环充放电、循环伏安(CV)和电化学阻抗谱(EIS)等方法对材料进行了表征测试。首先，用共沉淀法制备氢氧化镍和氢氧化锰的混合物;然后，对共沉淀溶液进行预氧化来制备前驱体;最后，用预氧化的前驱体合成了LiNi_1/2Mn_1/2O₂材料。SEM和XRD测试结果分别表明:LiNi_1/2Mn_1/2O₂材料是粒径范围在100～200 nm之间的球形粒子，并且具有非常好的层状结构。循环充放电表明:在空气中900 ℃下合成时间为9 h的材料，在充放电截止电压为2.8～4.6 V的情况下，经过40次循环，材料的容量可以稳定地保持在140 mAh·g^-1左右。循环伏安曲线表明:在锂的初始脱嵌和入嵌过程中存在不可逆相变。电化学阻抗谱测试表明LiNi_1/2Mn_1/2O₂具有很好的锂离子扩散能力。

Synthesis and Characterization of Layered LiNi1/2Mn1/2O2 as Cathode Material for Lithium Ion Batteries

Layered LiNi1/2Mn1/2O2 was synthesized using a simplified co-precipitation method and characterized by XRD, SEM, charge discharge cycling, cyclic voltammetry (CV) and Electrochemistry impedance spectroscopy (EIS). Firstly, the mixture solution of the nickel hydroxide and manganese hydroxide was prepared by coprecipitation. Secondly, the precursor was prepared from the co-precipitated solution using a preoxidation method. Finally, the LiNi1/2Mn1/2O2 was synthesized from the as-prepared precursor. The SEM and XRD results indicate that the material is composed of spherical particles with size of 100～200 nm and has well-defined layered structure. The charge discharge cycling tests reveal that the material synthesized at 900 ℃ for 9 h in air atmosphere exhibits stable capacities of about 140 mAh·g-1 in the cutoff voltage of 2.8～4.6 V for charge and discharge at the end of 40th cycle. The CV curves show that the material has irreversible phase change at the initial state of lithium deintercalation and reintercalation processes. EIS tests show that the LiNi1/2Mn1/2O2 has good ability of Li-ion diffusion.