Synthesis And Characterization Of Lithium Ion Battery Cathode Materials

Lithium ion batteries are attracting more attentions for their superior properties like high voltage,high energy density,high-speed discharge,low self-discharge,low toxicity, etc. Since the electrochemical properties of the electrode materials mainly depend on the physical and chemical properties like particle size, stoichiometry, homogeneity, etc., the synthetic process plays a major role in improving the physical and chemical properties of the electrode materials. In conventional synthetic processes such as solid-state reactions, the main difficulty is to make the atomic level of mixing of the ingredients, thereby hardly completely eliminating the possible impure phase contamination. These disadvantages are partially overcome by using the wet chemistry methods such as sol–gel, hydrothermal, and soft combustion.(1),The thesis is started with the optimization of methods of preparing cathode materials. A newly developed molten salt method was successfully applied to synthesize high-voltage LiNiVO4 cathode materials. Pure phase inverse spinel LiNiVO4 powders with perfect crystallization and average particle sizes of about 80 nm were easily synthesized at a temperature as low as 350oC for 2 h, and the advantage of our method was discussed in detail, comparing with precursor calcined directly in preparing cathode material. The flexibility of the method has paved the way to make use of the low-temperature synthesis technology toward the synthesis of promising cathode materials.(2),The pure-phase LiNi0.5Mn1.5O4 cathode powders with nanometer size were successfully synthesized by the soft combustion reaction method. At the calcined temperature of 450oC,"nano-needle"crystallites of LiNi0.5Mn1.5O4 could be readily obtained, and no other impurities could be found. Both increasing calcined temperature and time would favor the growth of nano-crystalline LiNi0.5Mn1.5O4.