Cathode Material
In the preparation of inorganic electrode materials for lithium ion batteries, high temperature solid state reaction is the most commonly used. High temperature solid-phase reaction: refers to the process that the reactants including solid-phase substances react for a period of time at a certain temperature and produce chemical reactions through the mutual diffusion between various elements to produce the most stable compounds at a certain temperature, including solid-solid reaction, solid-gas reaction and solid-liquid reaction.
Even if sol-gel method, coprecipitation method, hydrothermal method and solvothermal method are used, solid-phase reaction or solid-phase sintering at high temperature is usually required. This is because the working principle of lithium-ion battery requires that its electrode material can repeatedly insert and remove li+, so its lattice structure must have sufficient stability, which requires that the crystallinity of active materials should be high and the crystal structure should be regular. This is difficult to achieve under low temperature conditions, so the electrode materials of lithium-ion batteries actually used at present are basically obtained through high-temperature solid-state reaction.
The cathode material processing production line mainly includes mixing system, sintering system, crushing system, water washing system (only high nickel), packaging system, powder conveying system and intelligent control system.
When the wet mixing process is used in the production of cathode materials for lithium-ion batteries, drying problems are often encountered. Different solvents used in the wet mixing process will lead to different drying processes and equipment. At present, there are mainly two kinds of solvents used in the wet mixing process: non-aqueous solvents, namely organic solvents such as ethanol, acetone, etc; Water solvent. The drying equipment for wet mixing of lithium-ion battery cathode materials mainly includes: vacuum rotary dryer, vacuum rake dryer, spray dryer, vacuum belt dryer.
The industrial production of cathode materials for lithium-ion batteries usually adopts high-temperature solid-state sintering synthesis process, and its core and key equipment is sintering kiln. The raw materials for the production of lithium-ion battery cathode materials are uniformly mixed and dried, then loaded into the kiln for sintering, and then unloaded from the kiln into the crushing and classification process. For the production of cathode materials, the technical and economic indicators such as temperature control temperature, temperature uniformity, atmosphere control and uniformity, continuity, production capacity, energy consumption and automation degree of the kiln are very important. At present, the main sintering equipment used in the production of cathode materials are pusher kiln, roller kiln and bell jar furnace.
◼ Roller kiln is a medium-sized tunnel kiln with continuous heating and sintering.
◼ According to the furnace atmosphere, like the pusher kiln, the roller kiln is also divided into air kiln and atmosphere kiln.
- Air kiln: mainly used for sintering materials requiring oxidizing atmosphere, such as lithium manganate materials, lithium cobalt oxide materials, ternary materials, etc;
- Atmosphere kiln: mainly used for NCA ternary materials, lithium iron phosphate (LFP) materials, graphite anode materials and other sintering materials that need atmosphere (such as N2 or O2) gas protection.
◼ The roller kiln adopts rolling friction process, so the length of the kiln will not be affected by the propulsion force. Theoretically, it can be infinite. The characteristics of the kiln cavity structure, better consistency when firing products, and the large kiln cavity structure is more conducive to the movement of air flow in the furnace and the drainage and rubber discharge of products. It is the preferred equipment to replace the pusher kiln to truly realize large-scale production.
◼ At present, lithium cobalt oxide, ternary, lithium manganate and other cathode materials of lithium-ion batteries are sintered in an air roller kiln, while lithium iron phosphate is sintered in a roller kiln protected by nitrogen, and NCA is sintered in a roller kiln protected by oxygen.
Negative Electrode Material
The main steps of the basic process flow of artificial graphite include pretreatment, pyrolysis, grinding ball, graphitization (that is, heat treatment, so that the originally disordered carbon atoms are arranged neatly, and the key technical links), mixing, coating, mixing screening, weighing, packaging and warehousing. All operations are fine and complex.
◼ Granulation is divided into pyrolysis process and ball milling screening process.
In the pyrolysis process, put intermediate material 1 into the reactor, replace the air in the reactor with N2, seal the reactor, electrically heat it according to the temperature curve, stir it at 200 ~ 300 ℃ for 1~3h, and then continue to heat it to 400 ~ 500 ℃, stir it to get material with particle size of 10 ~ 20mm, lower the temperature and discharge it to get intermediate material 2. There are two kinds of equipment used in the pyrolysis process, vertical reactor and continuous granulation equipment, both of which have the same principle. They both stir or move under a certain temperature curve to change the material composition and physical and chemical properties in the reactor. The difference is that the vertical kettle is a combination mode of hot kettle and cold kettle. The material components in the kettle are changed by stirring according to the temperature curve in the hot kettle. After completion, it is put into the cooling kettle for cooling, and the hot kettle can be fed. Continuous granulation equipment realizes continuous operation, with low energy consumption and high output.
◼ Carbonization and graphitization are an indispensable part. The carbonization furnace carbonizes the materials at medium and low temperatures. The temperature of the carbonization furnace can reach 1600 degrees Celsius, which can meet the needs of carbonization. The high-precision intelligent temperature controller and automatic PLC monitoring system will make the data generated in the carbonization process accurately controlled.
Graphitization furnace, including horizontal high-temperature, lower discharge, vertical, etc., places graphite in graphite hot zone (carbon containing environment) for sintering and smelting, and the temperature during this period can reach 3200 ℃.
◼ Coating
The intermediate material 4 is transported to the silo through the automatic conveying system, and the material is automatically filled into the box promethium by the manipulator. The automatic conveying system transports the box promethium to the continuous reactor (roller kiln) for coating, Get the intermediate material 5 (under the protection of nitrogen, the material is heated to 1150 ℃ according to a certain temperature rise curve for 8~10h. The heating process is to heat the equipment through electricity, and the heating method is indirect. The heating turns the high-quality asphalt on the surface of graphite particles into pyrolytic carbon coating. During the heating process, the resins in the high-quality asphalt condense, and the crystal morphology is transformed (amorphous state is transformed into crystalline state), An ordered microcrystalline carbon layer is formed on the surface of natural spherical graphite particles, and finally a coated graphite like material with a "core-shell" structure is obtained