STADIES FOR SYNTHESIS OF LAYERED SOLIDE SOLUTION TYPE CATHODE MATERIALS AND ITS ELECTROCHEMICAL LITHIUM INTERCLATION BEHAVIOR.

发现层状LiNiO_2与层状Li_2MnO_3在所有组成范围内形成电活性固溶体。低温相Li_2TiO_3虽然与Li_2MnO_3具有相同的结构，但随着Ti含量的增加，阳离子混合增强，Li_2TiO_3与Li_2TiO_3之间的固溶体结构由层状结构转变为岩盐结构。另一方面，LiCrO_2与Li_2TiO_3形成层状固溶体。Ni/Ti=1的固溶体容量最大，可达170 mAh/g以上。最后证实LiCrO_2-Li_2MnO_3和LiCrO_2-Li_2TiO_3固溶体具有相似的电化学和晶体学性质，但LiNiO_2-Li_2MnO_3体系与LiNiO_2-Li_2TiO_3体系在这两个性质上有所不同。LiNiXMn_yCo_<1-x-y>O_2， Mn含量较低，y<0.5为电活性材料。LiNi_<1/3>Mn_<1/3>Co_<1/3>O_2是LiNi_xMn_yCo_<1-x-y>O_2中具有高容量的典型化合物，可视为LiNi_<1/2>Mn_<1/2>O_2与LiCoO_2之间的固溶体。LiNi_<1/3>Mn_<1/3>Co_<1/3>O_2的电化学性能很大程度上取决于制备工艺，我们发现可以通过初始充电曲线的形状来预测电池的性能。性能下降的根本原因是杂质NiO的存在，从而形成Li_2MnO_3的电活性固溶体，其性能低于纯LiNi_<1/3>Mn_<1/3>Co_<1/3>O_2。本文对LiNi_<1/2>Mn_<1/2-x>Ti_xO_2进行了研究，以阐明Mn和Ti在固溶体形成过程中的差异。在研究过程中，具有岩盐结构的完全Ti取代物LiNi_<1/2>Mn_<1/2-x>Ti_xO_2在50℃下输出大于150 mAh/g。这一事实表明，由于Li扩散困难而被认为不合适的岩盐结构阴极材料是可能存在的。这一发现将导致岩盐型电极材料的发展。新材料在室温下电化学性能的再现性较低，但与Li_2TiO_3形成固溶体证实了其性能的增强。少

It is found that layered LiNiO_2 forms electroactive solid solution with similar layered Li_2MnO_3 in the all composition range. Though low temperature phase Li_2TiO_3 has same structure with Li_2MnO_3, the structure of solid solution between LiNiO_2 and Li_2TiO_3 changes from layered structure to rock salt structure as the increase in Ti content because of enhanced cation mixing. On the other hand, LiCrO_2 forms layered solid solution with Li_2TiO_3. The solid solution with Ni/Ti=1 shows largest capacity of more than 170 mAh/g. It is finally confirmed that LiCrO_2-Li_2MnO_3 and LiCrO_2-Li_2TiO_3 solid solutions have similar electrochemical and crystallographic properties, however, LiNiO_2-Li_2MnO_3 system is different from LiNiO_2-Li_2TiO_3 system in both character.LiNiXMn_yCo_<1-x-y>O_2 with lower Mn content of y<0.5 is electroactive material. LiNi_<1/3>Mn_<1/3>Co_<1/3>O_2 with high capacity is a typical compound among LiNi_xMn_yCo_<1-x-y>O_2 and it will be considered as a solid solu … More tion between LiNi_<1/2>Mn_<1/2>O_2 and LiCoO_2. Electrochemical property of LiNi_<1/3>Mn_<1/3>Co_<1/3>O_2 extremely depends on preparation process, and we have found that the battery performance can be predicted from the shape of initial charge curve. The essential reason for lower performance would be due to the presence of impurity, NiO, as a result, electroactive solid solution with Li_2MnO_3, which shows lower performance than pure LiNi_<1/3>Mn_<1/3>Co_<1/3>O_2, is formed.The research for LiNi_<1/2>Mn_<1/2-x>Ti_xO_2 has been carried out in order to clarify the difference between Mn and Ti in the formation of solid solution. In the course of study, complete Ti substituted compound, LiNi_<1/2>Mn_<1/2-x>Ti_xO_2 with rock salt structure, delivers more than 150 mAh/g at 50 ℃. This fact indicates the possibility of excellent cathode materials with rock salt structure, which has been considered unsuitable because of difficulty in Li diffusion. This finding would lead to the development of rock salt type electrode materials. The new material shows low reproducibility in electrochemical property at room temperature, however, enhanced properties are confirmed by the formation of solid solution with Li_2TiO_3. Less