What are the key equipment for the industrialization of ternary cathode material for lithium batteries?
Common lithium-ion battery cathode material are cobalt acid lithium, manganese acid lithium, lithium iron phosphate and ternary cathode material, ternary cathode material has more balance cost, energy density, cycle and the safety performance advantages, and become the main choice for electric cars, electric bicycles, and other products selection, especially in the field of passenger cars.
The performance and cost of ternary cathode material mainly depend on the selection of production technology and key equipment. Compared with first-class lithium-ion battery manufacturers in Japan and South Korea, China’s production technology and equipment level is far from that of Japan and South Korea, which is in urgent need of transformation and upgrading. So, what are the key equipment used in the production of ternary cathode material?
Industrial production of ternary cathode material
At present, the mainstream production technology used in industrial production of ternary cathode material is: coprecipitation method to prepare the precursor, and then mixed with lithium source solid-phase sintering ternary cathode material.
Preparation of precursor key equipment
- The reaction kettle
The reactor is the core equipment of precursor reaction. The structure characteristics of the reactor body size, stirrer form, baffle number and size, whether or not there is a diversion tube, feeding position, whether or not there is a strengthening device will affect the density, morphology, specific surface area, crystallization degree, particle size and distribution of the precursor.
- Filtration and washing equipment
The function of filtration and washing equipment is to achieve solid-liquid separation of the precursor slurry obtained by the reaction, and then the washing liquid is used to wash the precursor filter cake, and remove the sulfate, chloride and sodium ions remaining in the filter cake.
At present, most of the precursor manufacturers use filtration and washing integrated equipment, mainly including filter press, centrifuge, microporous filter, filtration and washing “two-in-one” equipment, etc.
- Drying equipment
Drying process determines the moisture content of precursor products, and has a certain impact on crystal structure. So it is an important process. Whether drying equipment can be correctly selected directly related to product quality, operating environment and production cost. The drying temperature of precursor filter cake in air should be less than 150℃. When the temperature reaches 400℃, the precursor is oxidized to trivalent oxide.
At present, the commonly used precursor drying equipment includes hot air circulation oven, disc dryer, flash dryer, rotary drum dryer and so on.
Key equipment for ternary cathode material production
- Mixing equipment
In ternary cathode material production, mixing is to add stoichiometric ratio of lithium salts, precursors and additives into the mixing equipment for uniform mixing. The uniformity will affect the uniformity of lithium and additives in the sintering process, directly affect the degree of crystallization and residual alkali of ternary cathode material, which is finally reflected in the electrical properties.
The stability of the final lithium ratio of ternary cathode material depend on the accuracy of raw material weighing and the uniformity depends on the mixing effect of the mixer.
Mixing is generally divided into wet mixing and dry mixing, ternary cathode material usually adopt dry mixing. At present, the commonly used ternary cathode material mixing equipment is inclined mixer, high-speed mixer, V-type mixer, plough knife flying mixer and so on.
- Sintering equipment
Sintering equipment is the core equipment for the preparation of ternary cathode material, mainly referring to the kiln. Its structure has a great influence on the physical and electrochemical properties of ternary cathode material. At present, the industrial production of ternary cathode material mainly adopts push-plate kiln and roller kiln, among which roller kiln is the most widely used.
The sintering temperature of ternary cathode material is the most important process parameter, which can affect most of the properties of material. Therefore, ternary cathode material has high requirements on the stability and accuracy of kiln temperature, and the temperature control system is crucial to the sintering of ternary cathode material.
- Crushing equipment
In ternary cathode material production, due to agglomeration and adhesion between sintered material particles, it is necessary to use crushing equipment to dissociate sintered material, so as to control the particle size and distribution of powder. Particle size and its distribution affect the specific surface area, vibration density, compaction density, machining performance and electrochemical performance of ternary cathode material, which are very important for the quality of finished products.
ternary cathode material crushing is usually the sintering material for coarse crushing, and then grinding. Coarse crushing equipment generally uses jaw crusher or roller crusher; Grinding equipment generally adopts air mill, mechanical mill, colloid mill, which directly determines the degree of crushing of ternary cathode material.
- Iron removal equipment
Metal foreign bodies in terpolymer materials should be controlled at the level of tens of PPB (1ppb=1×10-9m). Excessive metal foreign bodies will lead to high self-discharge rate of batteries and even affect the lithium-ion battery safety.
The metal foreign bodies of ternary cathode material mainly come from raw materials and equipment wear in the production process, and are mainly magnetic metal impurities, especially metal iron. Therefore, the production process needs to remove iron once or even many times for finished products. The commonly used iron removal equipment is electromagnetic iron remover and permanent magnet iron remover.
Improving the quality of the lithium ion battery industry development cannot leave the material, on the whole the ternary cathode material to develop in the direction of high nickel.The high nickel ternary material has higher requirements on the environment, atmosphere of the process equipment.
The production line must achieve a higher level of automation, especially in the production workshop temperature and humidity atmosphere control needs to be strengthened. The industrialization equipment of ternary cathode material will gradually develop to the direction of intelligence, large capacity, low energy consumption and environmental friendliness, in order to meet the requirements of high performance and low cost of ternary cathode material for power batteries.
Compare the differences between ternary cathode material companies
In the following part, we will talk about the differences between ternary cathode material companies from the perspective of patent research and development.
The cathode modification process has strong non-standard properties
Due to the structural characteristics of ternary cathode material, the energy density increases with the increase of nickel content, but the cycling stability and thermal stability become worse.
How to achieve the balance of energy density, cycling performance and thermal stability has always been the subject of exploration in the industry. Surface coating, doping, single crystal and structure control (core-shell structure, gradient concentration) make up the shortcomings of ternary cathode material to a certain extent.
The combination and application of each modification process reflects the non-standard attributes of the industry products, and each cathode manufacturer has its own unique solutions. The accumulation of special benefits of the modification process will eventually be reflected in the difference of product quality, which constitutes the competition barrier of leading companies.
Among them, the most commonly used ternary cathode modification process is the coating and doping process, and its principle and function are briefly introduced:
Surface coating can effectively stabilize the structure of high nickel material. By reducing the contact area between the electrode material and the electrolyte, the surface coating technology can reduce the side reaction between the impurity on the material surface and the electrolyte, improve the electronic conductivity of the ternary cathode material surface, and improve the cyclic stability of the material. Common surface coating materials include metal oxide, phosphate and other stable electrode materials.
According to the experimental analysis, the cyclic stability and thermal stability of high Ni materials are improved significantly by surface coating. The chemical properties of uncoated NCM811 and coated NCM811 by Li2MnO3 nanolayer were compared and analyzed :
(1) the lithium ion diffusion rate of coated NCM811 was higher, so it showed higher multiplicity; (2) The thermal decomposition temperature of the modified NCM811 is 256.2 degrees, higher than that of the pure NCM811 242.6 degrees, indicating that the modified NCM811 is beneficial to enhance the thermal stability of the material; (3) The cyclic stability of NCM811 was significantly enhanced after coating because the coating process effectively reduced the reaction between NCM811 surface impurities and electrolyte.
The improved doping process can significantly improve the cyclic stability of high Ni materials. The electronic conductivity and cyclic stability of ternary cathode material can be improved by mixing some metal ions or non-metal ions into the lattice of ternary cathode material. The common doping elements are Al, Mg, Ti, Zr and so on.
The particle size of ternary cathode material doped with copper ions decreases significantly. Experiments show that the cycling and doubling properties of NCM811 are significantly improved by doping appropriate amount of copper ions: the discharge specific capacity increases from 129.1mah /g to 157.29mAh/g after 100 cycles at 1C rate, and the capacity retention rate increases from 64.6% to 84.9%.
Ternary cathode material represent companies
In this part we will introduce the ternary cathode material represent companies by comparing their R&D ability and patent.
From the perspective of the cumulative number of patent of the cathode companies, Easpring Technology and B & M Technology have accumulated profound accumulation in the total number of patent applications and invention patent applications, while Ronbay New Energy, founded in 2014, lags behind in the number of patents due to its short history. However, Ronbay has already surpassed the established earlier Changyuan Lico and Zhenhua E-chem, and is fast catching up with Easpring Technology and B & M Technology.
XTC New Energy has also been established for a short time. Most of its existing patents have been granted to Xiamen Tungsten, but it has also shown a good momentum of patent growth in the past 20 years.
From the perspective of R & D investment of each cathode material company, the total investment level of Ronbay, Easpring and Changyuan Lico is similar, and Xiamen Tungsten is higher than its rivals. The main company is also in the two fields of lithium cobalt acid and ternary materials, in which the unit cost of lithium cobalt acid is given priority to, resulting in higher R & D material consumption costs.
In terms of the number of R&D staff, Ronbay technology has more than 300 people, leading other competitors. In terms of average salary of R&D personnel, Ronbay, Easpring and Changyuan Lico are all at about 200,000 rmb/year, which is ahead of Zhenhua New Material and Xia-Tungsten New Energy.