不同预氧化方式合成LiNi_(0.8)Co_(0.15)Al_(0.05)O_2正极材料

Synthesis of LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 Cathode Materials by Different Pre-oxidation Methods

以不同预氧化方式制备的前驱体合成了锂离子电池正极材料LiNi0.8Co0.15Al0.05O2（LNCAO）。采用扫描电子显微镜、X射线衍射和化学滴定对样品及其前驱体的形貌、晶相结构和Ni的平均氧化态进行表征，并采用恒电流充放电方法对样品进行充放电性能测试。结果表明：预氧化方式不影响前驱体或样品的形貌，但对晶相结构、Ni的平均氧化态及样品的电化学性能有很大的影响，且前驱体中Ni的平均氧化态越高，相应样品的电化学性能越好。其中，“液-液预氧化”方式制备的前驱体为Ni0.8Co0.15Al0.05OOH，Ni的平均氧化态为＋3．000；该前驱体在氧气气氛下750℃焙烧10h得到的LNCAO正极材料，阳离子混排程度最小，结构最有序，Ni的平均氧化态最高，电化学性能最好：在2．8～4.3V（vs．Li／Li＋）电压，0．2C倍率时的首次放电比容量达192．1mA·h／g，循环50次后容量保持率为94．8％。

LiNi0.8Co0.15Al0.05O2（LNCAO） cathode materials were synthesized with different precursors prepared by different pre-oxidation methods. The microstructure and properties of precursors and cathode materials were characterized by scanning electron microscopy, X-ray diffraction, chemical titration and galvanostatic charge-discharge tests, respectively. The results show that the pre-oxidation routines affect the structure, average oxidation state of Ni, and electrochemical properties except the morphology. The precursors with a greater average oxidation state of Ni give the corresponding materials with the better electrochemical performance. Especially, the precursor prepared by the ＂liquid-liquid pre-oxidation＂ method is LiNi0.8Co0.15Al0.05OOH, and LNCAO synthesized under flowing oxygen at 750 ℃ for 10 h with the precursor LiNi0.8Co0.15Al0.05OOH has the minimum cation mixing degree, the most ordered structure, the maximum oxidation state of Ni, and the optimum electrochemical performance. According to the results of galvanostatic charge-discharge tests, the initial discharge specific capacity of these cathode powders is 192.1 mA.h/g at 0.2C in the voltage range of 2.8-4.3 V （vs. Li/Li^＋）, and the initial discharge capacity after 50 cycles is 94.8%.