Template Synthysis Of Layed Lithium Manganese Materials And Their Dopped Research

Lithium manganese oxide material is considered as one of the most promising cathode material because of its abundant resources,low price,friendly environmental,durability to over-discharge and over-charge, discharge at high electric current, and super safety. And it is particularly suitable for future electric vehicle power battery cathode material. In the manganese oxides,spinel LiMn₂O₄ and layered LiMnO₂ can be used as cathode materials. However, the initial capacity of the spinel LiMn₂O₄ is low and the cycle performance is poor, while the layered LiMnO₂ theoretical capacity is up to 285mAh/g,which is almost twice of the LiMn₂O₄, the cycle performance of the LiMnO₂ is also very good ,and which has caused great interests of people. Layered LiMnO₂ has a broad prospects for development in the cathode materials.In this paper, commercial-grade silica with large hole was used as template,we used the porous structure of silica prepare nanosized layered LiMnO₂ cathode material. TEM transmission electron microscopy showed that the particle size of the material prepared by template method is about 30-50nm which is consistent with the pore size of silica gel. Then the micron LiMnO₂ material was prepared by general method. Charge-discharge cycle tests investigated the electrochemical properties of the product.Compared with micron-grade materials,template synthesis of nano-size LiMnO₂ showed better electrochemical performance and cycle stability,but both of them had a poor discharge capacity.In order to improve the discharge capacity and cycle performance of the material, we doped different proportions of rare earth elements Ce and La based on the template method. XRD results showed that the phase of the dopped materials all had a good degree of crystalbility and high purity. Particle size is between silica pore size range. Charge-discharge tests showed that the discharge capacity and cycling performance all have a greatly improved when the materials dopped La and Ce. The initial capacity of 2% Ce-doped LiMnO₂ material is 108.6mAh/g, after 30 cycles the storage capacity is 98.8 mAh/g,the rate of the capacity retention is 90.9%. The initial capacity of 4% La-doped LiMnO₂ materials is 113.5mAh/g, after 30 cycles the discharge capacity is 103mAh / g, the rate of the capacity retention is 90.7%.Based on the mono-doped of the template method,we tried the dual-doped method in order to further improve the electrochemical properties of the material.Based on 2%Ce and 4% La-doped respectively,we doped different proportions of Ni.Charge-discharge tests showed that the discharge capacity of the material had a steady increase in the process,and then stabilized.The initial capacity of LiMn_0.90Ni_0.08Ce_0.02O₂ is 87.8mAh/g,30 cycles later the discharge capacity is 132.4 mAh/g, the rate of the capacity retention is 150.7%. The initial capacity of LiMn_0.86Ni_0.10La_0.04O₂ is 106.1mAh/g, 30 cycles later the discharge capacity is 141.3mAh/g, the rate of the capacity retention is 133.2%. It illustrated that doped elements played a key role in the suppression phase transition and cycle stability.