The synthesis methods of lithium cobalt oxide mainly include high temperature solid phase method and low temperature liquid phase method. Traditional high-temperature solid-phase reactions use lithium and cobalt carbonates, nitrates, acetates, oxides or hydroxides as lithium and cobalt sources. After mixing and pressing the tablets, they are heated to 600 ~ 900 ℃ in the air. Higher temperature, heat preservation for a certain period of time. In order to obtain a product with a pure phase and uniform particles, it is necessary to combine roasting and ball milling techniques for long-term or multi-stage heating. The high-temperature solid-phase synthesis method has a simple process and is conducive to industrial production, but it has the following shortcomings: ①The reactants are difficult to mix uniformly, require a higher reaction temperature and a longer reaction time, and the energy consumption is huge; ②The product has a large particle size and With a wide range of particle size and irregular particle morphology, it is difficult to adjust the morphological characteristics of the product, which makes it difficult to control the electrochemical properties of the material.
The low-temperature liquid phase method mainly includes the co-precipitation method and the sol-gel method. The co-precipitation method is to disperse the components of the co-precipitation in the state of ions or molecules in the solution, add an appropriate precipitating agent to the solution to uniformly precipitate a variety of metal ions under the action of the precipitating agent, and then filter and wash the precipitate to obtain Powder precursor. For lithium cobaltate, since most lithium salts are highly soluble in water, generally speaking, the solvent is evaporated under appropriate conditions without filtering after adding the precipitant, so as to obtain an accurate ratio and uniform precipitation. Do not precipitate. Sometimes organics are also used as solvents. The sol-gel method is to mix organometallic salts and inorganic salts uniformly into a solution, control the process conditions to polymerize to form a sol, and then use temperature control, high-speed stirring and chemical reactions to make the sol lose its solvent, increase its viscosity, and change Into a gel. Then calcined at an appropriate temperature to obtain powder. The use of liquid phase synthesis technology realizes the mixing of raw materials at the molecular level, which is conducive to the formation and growth of LiCoO2 crystals, which can effectively reduce the reaction temperature, shorten the reaction time, and reduce energy consumption. Among them, the sol-gel method has the advantages of high product purity, good uniformity, small particles, and easy control of the reaction process. The key to this method is to select an appropriate precursor solution, control an appropriate pH range, and form a sol under certain temperature and humidity conditions.
Although the co-precipitation method and sol-gel method of the low-temperature liquid phase method can improve the performance of the material within a certain range, due to the complexity of the process and the difficulty of controlling the particle size of the synthetic material powder, high temperature is still the more mature method in large-scale industrial production. Solid-phase synthesis method, that is, lithium carbonate (Li2CO3) and cobalt oxides such as cobalt carbonate, cobalt oxide or cobalt tetroxide are mixed in the ratio of Li/Co=1, and they are prepared by high temperature heat treatment in the air.