非化学计量比调控高电压尖晶石正极材料电化学性能研究  

Tuning Electrochemical Performance through Non-stoichiometric Compositions in High-voltage Spinel Cathode Materials

作　　者：赛喜雅勒图 王雪莹[2] 顾庆文 夏永高 刘兆平[2] 何杰[1] LEE Sai-Xi;WANG Xue-Yin;GU Qing-Wen;XIA Yong-Gao;LIU Zhao-Ping;HE Jie(School of Chemical Engineering,Anhui University of Science and Technology,Huainan 232001,China;Ningbo Institute of Materials Technology ＆ Engineering,Chinese Academy of Sciences,Ningbo 315201,China)

机构地区：[1]安徽理工大学化学工程学院,淮南232001 [2]中国科学院宁波材料技术与工程研究所,宁波315201

出　　处：《无机材料学报》2018年第9期993-1000,共8页Journal of Inorganic Materials

摘　　要：用一种简单的方法制备了高性能的高电压尖晶石正极材料,主要是调控正极材料中锂与过渡金属的摩尔比,即通过Ni_(0.25)Mn_(0.75)(OH)_2与Li_2CO_3进行高温固相反应制备了非化学计量比的Li_(1.05)Ni_(0.5)Mn_(1.5)O_4和化学计量比的LiNi_(0.5)Mn_(1.5)O_4尖晶石型高电压正极材料。用扫描电子显微镜、X射线衍射、中子衍射、拉曼光谱、X射线光电子能谱以及循环伏安曲线对其形貌、晶体结构及元素价态和电化学性能进行了表征。研究发现,非化学计量比的Li_(1.05)Ni_(0.5)Mn_(1.5)O_4中由于金属离子随机分布于16 d位置,所以Ni/Mn阳离子无序化程度更高。非化学计量比的高电压正极材料具有更为优异的倍率性能,并且在400次循环后比容量保持率高达91.2%。同时,原位X射线衍射测试结果表明,在充放电过程中非化学计量比的高电压正极材料发生连续单一的相转变,可以提高晶体结构的稳定性。因此,非计量比的尖晶石Li_(1.05)Ni_(0.5)Mn_(1.5)O_4正极材料在高能量密度的锂离子电池中具有更广阔的应用前景。In this study, a simple method to prepare high-voltage spinel cathode materials though controlling stoichiometric ratio in their compositions was reported. Non-stoichiometric and stoichiometric high-voltage spinel LiNi（0.5）Mn（1.5） O4 cathode materials were prepared by solid-state reaction between Li2 CO3 and Ni（0.25） Mn（0.75）（OH）2 prcursor. Their morphologies, structures and electrochemical performance were characterized by scanning electron microscopy, X-ray diffraction, neutron diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, as well as electrochemical curves. The second particles occupied the similar sizes ~8 μm, which were composed of nanoparticles. Compared to stoichiometric LiNi（0.5）Mn（1.5） O4, Ni/Mn cations in non-stoichiometric LiNi（0.5）Mn（1.5） O4 sample distributed randomly, resulting in structure disorder demonstrated by the analysis of X-ray diffraction, neutron diffration and Raman spectroscopy. Less Mn^（3＋） content in stoichiometric LiNi（0.5）Mn（1.5） O4 sample was detected though X-ray photoelectron spectroscopy. It is believed that more Mn^（3＋） content and Ni/Mn cation disorder would benefit rate cpability and cycling performance. As a result, non-stoichiometric LiNi（0.5）Mn（1.5） O4 sample delivers superior dicharge capacity at higher rates, even though it shows relatively minor discharge capacity at low rates. What＇s more, higher capacity retention for the non-stoichiometric LiNi（0.5）Mn（1.5） O4 sample was found, which was promoted to 91.2% at 1.0 C rate after 400 cycles. At the same time, in situ X-ray diffraction measurements revealed that single-step phase transformation for non-stoichiometric LiNi（0.5）Mn（1.5） O4 sample significantly enhanced structural stability during the electrochemical process. Spinel LiNi（0.5）Mn（1.5） O4 with non-stoichiometric composition provides a promising solution for their potential application in high-energy-density lithium-ion batteries.

关 键 词：高电压 尖晶石 正极材料 非化学计量比 循环稳定性 

分 类 号：TQ174[化学工程—陶瓷工业]