Synthesization And Optimization Of Spinel LiMn₂O₄ Cathode Material

Spinel LiMn₂O₄ as one of the most promising alternative cathode materiales because it has the advantages of high vlatage, naturally abundant, low cost, simple in preparation, structure stability, no toxicity, good safety and environmentally benign nature. we carried out a series of studies in order to resolve the present remaining problems of spinel LiMn₂O₄. And we obtained some meaningful results. Main points of these are listed as below:1. Synthesis of spinel LiMn₂O₄ precursor with high density: The precursor of spinel LiMn₂O₄ cathode material with high density was synthesized by co-precipitation and two-dryness method. we studied the relationship between the density of precursor and remaining water in filter cake, manner of dryness, manner of adding agglomerating agent. Our results provide an important reference on synthesis of high density spinel LiMn₂O₄ cathode material.2. Effects of the precursor treated on the structure and electrochemical properties of spinel LiMn₂O₄ cathode: The precursor of spinel LiMn₂O₄ cathode material was synthesized by co-precipitation and two-dryness method. In this paper, based on our previous studies, we via a two-step drying method to pretreat the precursor of LiMn₂O₄ in different methods. Effects of N2, hydrazine, H2O2 on the structure of LiMn₂O₄ and discharge capacity at room temperature and elevated temperature are researched in detail. Experiments show that with the precursor treated by adding hydrazine and puring N2 to synthesize LiMn₂O₄ with complete lattice, uniform paricle size, a very pure spinel phase with an ordered octahedron crystal morphology and a large tap density.The electrochemical results show that it has higher specific capacity and higher cyclic lif than other samples, especially at elevated temperature and high discharge current.3. Effects of the preparation process on the electrochemical properties of spinel LiMn₂O₄ cathode : The precursor and lithium salt were fully grinded with anhydrous alcohol as dispersant. The mixture was heated to 900oC for 15h, we improved the details in assembling batteries such as: prolong the time of spreating the mixture in an ultrasound, leave the pulp standing for a long time to layer, roller way and manner of dryness, et al. These measures can improve the cycle performance of cathode material. 4. Effects of the raw materials on the electrochemical properties of spinel LiMn₂O₄ cathode : we accurately tested the MnO₂ content in EMD bought by using Na2C₂O₄, and using EDTA direct titrimetric method to measure the content of Mn2+. We use Mn and sulphuric acid to synthesis the solution of MnSO4 and measure it's concentration of the solution.This not only cut the cost but also provide correct data to the experiment hereafter. We studied the effect on the electrochemical properties of spinel LiMn₂O₄ cathode of refluxed EMD, EMD, self-made MnSO4 and Na2C₂O₄. Accordingly we choosed the self-made MnSO₄ as the most suitable manganese source.5. The doping modification of LiMn₂O₄: Nitrogen, a certain amount of hydrazine and aluminum ions were added in while synthesizing LiAl_xMn_2-xO₄ precursor by co-precipitation and two-dryness method.The sintered product spinel LiAl_xMn_2-xO₄ with the increase of content of aluminum ions the lattice parameters get smaller enhance the crystal lattices. Although the discharge capacity decrease and plateau fall and become narrow with the increasing content of Al, these improve the cycle performance of cathode.