High power performance by defect introduction into spinel oxides for the usage of large-scale lithium ion battery

锂离子电池正极材料的开发对于满足便携式设备、未来电动汽车的使用等方面的需求至关重要。在正极材料中，LiMn2O4及相关氧化物因其成本低、毒性低、能量密度较高而备受关注。特别是LiNi_lt；0.5&gt；Mn_(&lt)；1.5&gt；O_4由于其高的放电容量、良好的循环性能和4.7V左右的优势平台而备受关注，而其他材料在~4V和5V时表现出两个平台期。此外，还从缺陷化学的角度揭示了影响率性能的因素。在不同温度下合成了尖晶石型氧化物LiNi；lt；0.5&gt；Mn；lt；1.5&gt；O4，研究了它们的化学计量、晶体结构和电化学性质。在氧气气氛下，非化学计量比突然增加，吸热在760℃左右。此外，红外光谱研究表明，随着非化学计量比的增加，镍和锰在八面体位置上的有序排列部分崩溃。对高于760℃和低于760℃的样品在氧气气氛中的电化学性能进行了研究，发现高于760℃的样品比低于760 min的样品具有更好的倍率性能。因此，LiNi_&lt；0.5&gt；Mn_&lt；1.5&gt；O_4的合成温度是控制Ni和Mn的排列、非化学计量比和电化学性能的关键因素。

Development of the cathode materials for Li ion battery is vital to meet the demands of portable devices, future usages of electric vehicles and so on. Among the cathodes, LiMn_2O_4 and related oxides has gained much attention because of its low cost, low toxicity, and relatively high energy density. Especially, LiNi_<0.5>Mn_<1.5>O_4 has received much attention because of its high discharge capacity, good cyclability, and dominant plateau at around 4.7 V, whereas other materials showed two plateaus at 〜4 and 5 V. In this study, the improvement of rate performance was attempted by introducing defects into spinel oxides. In addition, it was aimed to reveal the factors affecting rate performance from the viewpoint of defect chemistry. Spinel type oxide, LiNi_<0.5>Mn_<1.5>O_4 was synthesized with various temperatures and investigated their stoichiometry, crystal structures and electrochemical properties. Under oxygen atmosphere, a sudden increase of nonstoichiometry occurred with endothermes at around 760℃. In addition, infrared spectroscopic study revealed that ordered arrangement of Ni and Mn in octahedral sites was partially collapsed by the increase of nonstoichiometry. The electrochemical performance for the samples quenched from above and below 760℃ in oxygen atmosphere were investigated, and the samples quenched above 760℃ showed better rate-performance than those quenched below 760℃ Accordingly, the synthesis temperature of LiNi_<0.5>Mn_<1.5>O_4 was the key factor for controlling the arrangement of Ni and Mn, nonstoichiometry and electrochemical properties.