NCA material industrialization and production technology development status

NCA material industrialization and production technology development status

Power battery performance is a limiting factor in determining the development of electric vehicles. At present, due to insufficient power battery life, slow charging speed and high cost, the development of electric vehicles is restricted. This is the main reason why many consumers are discouraged. The price/performance ratio has greatly affected the market penetration of electric vehicles. The positive electrode material is the core key material of the power lithium battery. The energy density of the positive electrode material is closely related to the cruising range of the electric vehicle, and its cost accounts for about 1/3 of the cost of the lithium battery cell, so the development of high energy density, long life and high Safe, low-cost cathode materials are essential for large-scale commercial use of power lithium batteries and electric vehicles.
At present, there are three main schools in the domestic and international power lithium battery cathode material technology routes: lithium iron phosphate, lithium manganate, and three yuan (NCA/NCM). Among them, lithium iron phosphate as a positive electrode material has a long charge and discharge cycle life, but its disadvantages are that there are large gaps in energy density, high and low temperature performance, charge and discharge rate characteristics, and high production cost. Lithium iron phosphate battery technology and application have been The bottleneck of development; the lithium manganese oxide battery has low energy density, low cycle stability at high temperature and poor storage performance, so lithium manganate is only used as the cathode material of the international first-generation power lithium battery; and the multi-material has comprehensive performance and The dual advantages of cost are increasingly concerned and recognized by the industry, gradually surpassing the technical route of lithium iron phosphate and lithium manganate.
The ternary materials are mainly NCM ternary and NCA ternary. In the ternary material, as the content of nickel increases, the specific capacity of the positive electrode material gradually increases, as shown in the figure. With the increasing demand for electric vehicle mileage, the development of NCM811 and NCA materials for high-nickel systems is becoming more and more urgent. So what is the current status of NCA materials industrialization?
I. Current status of NCA material industrialization application
The NCA material (typically composed of LiNi0.8Co0.15Al0.05O2) combines the advantages of LiNiO2 and LiCoO2, which not only has high reversible specific capacity, but also low material cost. At the same time, aluminum (Al) is added to enhance the structural stability and safety of the material. In turn, the cycle stability of the material is improved, so NCA material is one of the most popular materials in commercial cathode materials.
In 2014, the global sales of NCA was about 6,000 tons, accounting for about 5% of the total sales of cathode materials (about 125,000 tons). Japan Chemical Industry Co., Ltd., Toda Chemical (Suda) and Sumitomo Metal (Sumitomo) are major suppliers of NCA materials. Korea's Ecopro and GSEM also sell products. Toda mainly supplies Japanese AESC and South Korea LGC. Sumitomo mainly supplies Panasonic and PEVE. South Korea's Ecopro counterpart is SDI. At present, the main application areas of NCA products are electric vehicles and small batteries. For example, AESC is a power battery for Nissan (Leaf), Panasonic for Tesla, and PEVE for Toyota (Pruis α). The small batteries are mainly power tools and charging treasures. A cylindrical battery used. Tesla sold 31,000 pure electric vehicles with NCA power batteries in 2014, and is currently working with Panasonic to build a battery plant in Nevada. Its 2015 car sales target is no less than 50,000, and strives to achieve by 2020. With an annual sales volume of 500,000 units, it is estimated that the amount of NCA used for the positive electrode material is 62,500 tons. Driven by the Tesla effect, many companies in China have started pilot and small-scale trial production, such as Dangsheng Technology, Hunan Shanshan New Materials Co., Ltd., Shenzhen Tianjiao Technology Development Co., Ltd. ("Shenzhen Tianjiao"), Ningbo Jinhe New Materials Co., Ltd., etc. Its precursor manufacturers include Dangsheng Technology, Jinrui New Material Technology Co., Ltd., Hunan Bangpu Cycle Technology Co., Ltd., Shenzhen Tianjiao and so on.
Compared with foreign counterparts, domestic manufacturers have completed the preliminary exploration of related technologies, but they have been continuously lower in price of conventional nickel-manganese-cobalt multi-materials (NMC) in domestic and foreign markets, and still rely on small consumer batteries for market demand. The combined impact of factors. NCA materials have not been mass-produced and sold in China, and there are still some technical problems to be solved. It is foreseeable that with the rise of the electric vehicle and energy storage market, the market demand for NCA materials will increase significantly. Domestic enterprises need to take this opportunity to increase investment and carry out localized development of NCA materials in advance. Although some performance indicators of NCA materials are excellent, the scale of commercialization is long and tortuous. NCA lithium-ion batteries have to face a large number of technical challenges to achieve large-scale industrial applications.
1. NCA material preparation technology is more difficult
Firstly, the preparation process of NCA precursor LiNi0.8Co0.15Al0.05(OH)2 is technically difficult. The sedimentation pH of Ni and Co elements is quite different. The solubility product constants are nickel hydroxide 10-16, cobalt hydroxide 10-14.9, and aluminum hydroxide 10-33. It is difficult for aluminum ions to complex with ammonia. In the conventional coprecipitation method, aluminum ions are extremely easy to form flocculent products. And Al(OH)3 is an amphoteric hydroxide, which decomposes into AlO2-1 at a higher pH value, resulting in uneven distribution of nickel-cobalt-aluminum precipitation product elements, difficulty in growing the particle size, low bulk density, and sodium at the same time. The problem that impurities such as sulfur are difficult to handle until the sodium aluminate process is used to solve the problem of coprecipitation of aluminum.
Due to the thermodynamic instability of Ni3+, the sintering temperature of NCA should not be too low or too high. Too low Ni2+ is difficult to oxidize to Ni3+, and too high Ni3+ will decompose into Ni2+. Therefore, the optimum sintering temperature conditions are generally 750 to 800 °C.
2. Production equipment requires special
Because NCA requires a pure oxygen atmosphere, the sealing requirements of the production equipment are high, and the oxidation resistance of the internal components of the furnace equipment is very high. The furnace for producing ordinary multi-materials fails to meet the requirements, and domestic equipment manufacturers are suitable for high nickel. The design and manufacturing experience of the professional kiln for the positive electrode material is insufficient, and the quality reliability is not high.
3. High material production costs
For ordinary ternary materials, only the air atmosphere is needed in the production process, while NCA requires a pure oxygen atmosphere. The cost of pure oxygen is high, and the requirements for manufacturing oxygen supply equipment are extremely high. At the same time, NCA is sensitive to temperature and humidity and needs to be The production environment humidity is controlled below 10%, which increases the cost of production and management.
4. NCA battery design and manufacturing is more difficult
The high thermal stability of the high-nickel material under the state of charge leads to a decrease in the safety of the battery. It is necessary to carry out systematic and reliable safety design from the aspects of battery design, power supply system design, power supply, etc., so that the battery manufacturer and the terminal product user NCA battery safety concerns; on the other hand, serious gas production during charging and discharging, resulting in battery bulging deformation, cycle and shelf life decreased, posing a safety hazard to the battery, so usually use NCA cathode material to make 18650 cylinder Battery to alleviate battery bulging deformation problems. Tesla ModelS uses a high-capacity 3.1AhNCA lithium battery pack jointly developed with Panasonic and consists of 7000 18650 cylindrical batteries.
The surface of the NCA material is highly alkaline, the viscosity of the electrode slurry is unstable, and the viscosity increase or even the jelly phenomenon is likely to occur, resulting in poor coating performance during the production of the battery plate; the NCA material is sensitive to humidity and is easy to absorb moisture, and Li2O in the material continues to react with CO2, resulting in deterioration or even failure of material properties. Therefore, in the battery production process, the electrode slurry, the plate, the core, etc. are very sensitive to moisture, and the humidity of the entire production environment is demanding, resulting in equipment. Higher input and production costs. Therefore, domestic battery manufacturers are actively developing NCA battery systems, most of which are in the stage of tracking research and technology exploration, and there is still a certain gap from the requirements of industrial applications.
Second, the status quo of industrialization technology research of NCA materials
1. NCA precursor production process route
At present, the main technical routes adopted by major NCA manufacturers at home and abroad are as follows:
Among the above three processes, the first and third alternatives of the Al element are added in the subsequent sintering or coating process. The Al element distribution is uneven, the surface Al content is high, the inert layer is formed, and the final product capacity is reduced. Complex, increasing production costs. In the second scheme, the Al element can be evenly distributed, the product performance is more excellent, the production process is simple, and the cost is low, but the preparation technique of the precursor is more difficult.
At present, the most mainstream technical route is the Ni1-x-yCoxAly (OH)2 preparation process route, such as Sumitomo, Japan, Toda, Japan, has entered the mass production stage. The method generally uses a sulfate as a raw material, and forms a precursor Ni1-xy CoxAly(OH)2 which is coprecipitated by Ni, Co and Al through sodium hydroxide and a complexing agent, and then forms a product by filtration, washing and drying. . The advantage of this process is that the production cost is low, the process is simple, and it is more suitable for large-scale industrial production.
2. NCA sintering process route
NCA's raw material lithium source usually uses lithium hydroxide. Because the NCA sintering temperature can't be too high, generally it does not exceed 800 °C. When using lithium carbonate as raw material, the thermal decomposition of lithium carbonate is incomplete, resulting in too much residual lithium carbonate on the surface of NCA, making NCA The surface is too alkaline and sensitive to humidity. At the same time, lithium hydroxide has a lower melting point than lithium carbonate, which is more favorable for low temperature sintering of NCA. However, due to the high volatility of lithium hydroxide and the high irritating odor, a well-ventilated production environment is required. The sintering atmosphere of NCA needs to be in a pure oxygen atmosphere to ensure the oxidation of Ni2+ to Ni3+. At the same time, due to the thermodynamic instability of Ni3+, the sintering temperature of NCA should not be too low or too high. At present, the optimum sintering temperature of NCA is 700-800 °C.
3. Research status of NCA material modification technology
With the increase of Ni% content in multi-materials, the material specific capacity increases, and it brings more technical problems: cycle performance, especially high-temperature cycle performance problems, rate problems, safety problems, basic impurity content and thus The problem of strong water absorption (high moisture). In response to these problems, in recent years, researchers have used a variety of anion, cation or multi-body doping to stabilize the structure of high-nickel materials to achieve improved cycle and storage performance. In addition, the coating is also an effective method to prevent the electrolyte from corroding the positive electrode material and improve material circulation and storage stability. However, these methods cannot solve the problem of residual impurities of high nickel materials, which is a key bottleneck for the industrialization and large-scale application of high-nickel materials.
Third, the conclusion
NCA has the characteristics of high energy density, good rate characteristics and good low temperature performance. It is one of the most promising high energy density lithium battery cathode materials. Internationally, from the development of electric vehicles, batteries, NCA cathode materials, to precursors, the technology is more mature and advanced, and the upstream and downstream industries have formed a complementary industrial chain and a relatively stable and mature supply chain; It is still in the initial stage of development. Apart from the precursors, there is a certain gap in the whole industry chain technology, and the industrial chain has not yet been formed. It is foreseeable that domestic precursor companies and cathode material manufacturers will increase investment in research and development, speed up the technical level and production capacity in high-end lithium battery cathode materials, and quickly enter the supply system of foreign advanced battery manufacturers to form materials.

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