The author would like to point out that because American 3M Company applied for the patent related to ternary materials earlier, 3M Company named ternary materials in the order of nickel, manganese and cobalt (NMC), which is also commonly known as ternary materials NMC.
In pronunciation habit, it is called the misunderstanding between nickel cobalt manganese (NCM) and ternary material model. The name ratios of ternary materials are 333,442,532,622,811and so on. BASF is named by NMC in sequence, and the related patents of Argonne Laboratories (ANL) in the United States show that it is different from 3M, and it is deliberately called ternary material NCM when expanding the market.
Ternary material (NMC) actually combines the advantages of LiCoO2 and LiNiO2LiMnO2, because Ni.
There is an obvious synergistic effect between the properties of CoMn and NMC, and the single-component layered polar materials recognize the application prospect of new polar materials.
Generally speaking, the electrochemical properties of the three simple materials affect the layered structure of ternary materials with stable energy efficiency of Co, inhibit cation mixing, improve the conductivity of the materials and improve the cycle performance. The increase of Co ratio leads to the decrease of battery parameters ac, and the increase of c/a leads to the decrease of battery capacity.
Manganese storage will reduce the structural stability and safety of improved materials. High manganese content reduces the gram capacity of the material and is easy to produce spinel phase. The layered structure of the material increases the battery parameter ca and decreases the c/a, which leads to the deterioration of cycle performance and rate performance. The high pH value of high nickel material affects the practical use.
According to the proportion of each element, ternary materials are the same as Ni+2+3 valence Co, and trivalent Mn +4 valence ternary materials play the same role. The charging voltage is lower than 4.4V (relative to lithium metal cathode), and it is generally believed that Ni2+ participates in the electrochemical reaction in the form of Ni4+. Co3+ charged with higher voltage continues to participate in the reaction and Co4+Mn oxidized is generally considered to participate in the electrochemical reaction.
Ternary materials are divided into two basic series: low cobalt symmetric ternary material LiNixMnxCo 1-2xO2 high nickel ternary material LiNi 1-2yMnyCoyO2, and other ternary materials have their composition ratios of 353, 530 and 532. As shown in the figure.
The molar ratio of Ni/Mn of two metal elements in symmetric ternary materials is fixed at 1 to maintain the equilibrium of oxidation valence states of ternary metals. The representative product 333442 series ternary material group series is within the protection scope of American 3M patent.
Because of the low Ni content and high Mn content, the material has a relatively complete crystal structure and has the potential to develop to high voltage. The industrialization development of electrode materials for consumer lithium ion batteries is discussed in detail.
From the NMC formula of high nickel ternary, the equilibrium valence of Ni on the surface of high nickel ternary is the same as that of +2+3. The higher the nickel content, the higher the trivalent Ni, the higher the crystal structure of nickel ternary and the stability of asymmetric ternary materials. Except for two series, other groups generally avoid the patents of 3M or ANL, Umicore and Nichia, and there are more than 532 original groups in Bisogni.
Pine circumvents the patent right of 3M, but NMC532 is the best-selling ternary material in the world.
Ternary materials have higher specific capacity, and the energy density of single cell is similar to that of LFPLMO.
In recent years, the industrialization research of ternary battery has made progress in Korea, and NMC battery is generally considered as the mainstream choice for electric vehicles.
Generally speaking, based on the consideration of safety cycle, ternary batteries mainly adopt 333 and 442532 series with relatively low Ni content. Due to the increasing demand for energy density of PHEV/ electric vehicles, 622 John has been paid more and more attention.
The nuclear patent of ternary materials is mainly held by Argonne Laboratory (ANL) of American 3M Company. Some ternary materials (some of which are contained in lithium-rich manganese-based solid solutions) have been patented, which is generally considered to be of practical significance in the industry and related to 3M.
International ternary materials export Billy Umicore and Umicore3M to form Industry-University-Research League, foreign Korea L&; F benriya
De BASF, the main manufacturer of ternary materials in Dongda Industry (Yahua), has also joined the ranks of ternary upstarts.
Four-cell battery manufacturer
O N Y, Panasonic, Samsung SDI LG) ternary material.
The average proportion of lithium cobaltate electrode material in internal production capacity is an important embodiment of its battery manufacturer's leading technology in the world.
Main problems and modification methods of 1 and ternary materials
At present, the main problems of NMC applied to battery energy storage include:
(1) The first charge-discharge efficiency of NMC is generally 90% due to the cation mixing effect and the change of the first charge range of the material surface microstructure.
(2) Ternary material battery cells have serious gas production and high safety, and the high-temperature storage period needs to be improved;
(3) The low conductivity lithium ion diffusion coefficient makes the rate performance of the material ideal;
(4) Ternary material particles are agglomerated into two spherical particles. Because the two particles are crushed under high pressure, the compaction of the ternary material electrode is limited and the energy density of the battery is improved. At present, the modification measures widely used in industry include:
Impurity doping can improve the related surface properties (thermal stability, cycle performance or rate performance, etc.). ) material requirements. Doping modification can often improve the electrochemical properties of a certain surface or part of the material, and at the same time, it is accompanied by the decrease of specific capacity of a certain surface of the material.
NMC studies cation doping according to the same doping elements: cation doping, anion doping and composite doping. The actual effect is limited to magnesium, aluminum, titanium, zirconium, chromium, yttrium and zinc. NMC is doped with cations to inhibit Li/Ni.
The mixed discharge of cations helps to reduce the first and second volumes.
Cation doping makes the layered structure more complete, which is helpful to improve the NMC rate, the stability of crystal structure and the cycle performance of materials. The thermal stability effect is obvious.
Anion doping mainly means that the doping radius is close to the radius of oxygen source. Proper F doping promotes the sintering of materials and makes the structure of polar materials more stable. F doping can stabilize the interface between substances and electrolytes in circulation and improve the cycling performance of polar materials.
Mixed doping, such as substance F or several cations, is widely used to dope NMC. The cycle rate performance of NMC doped with Mg-F, Al-F, Ti-F, Mg-Al-F and Mg-Ti-F is obviously improved, and the thermal stability of the material will also be improved. At present, mainstream manufacturers adopt major modifications.
The doping modification of NMC depends on the doping of doping elements, and the doping amount is small, which requires manufacturers to have certain R&D strength. NMC impurity is doped in precipitation stage, wet doping in sintering stage and dry doping in sintering stage. Manufacturers need to choose the appropriate technology route according to the economic situation of their own technology accumulation. The so-called all roads lead to Rome, which suits your own route technology.
Surface coating NMC surface coating oxide Non-oxide Two visible oxides include MgO, Al2O3, ZrO _ 2 TiO _ 2, and several visible non-oxides mainly include AlPO4 _ 4, AlF3 _ 3, LiAlO2 _ 2, LiTiO2 _ 2, etc. The surface coating of organic materials is mainly to reduce the mechanical side reaction between materials and electrolyte, inhibit metal dissociation and optimize the cycle performance of materials.
The coating on the same machine reduces the material circulation caused by the collapse of material structure during repeated charging and discharging.
The author discusses the comparative effect of NMC surface coating on reducing the residual alkali content on the surface of high nickel ternary materials.
The difficulty of coating the same surface lies in the problem that the coating is selected first and then coated, and the coating amount is small. Whether it is dry coating precursor stage or wet coating, manufacturers need to choose the appropriate process route according to their own conditions.
The optimization and improvement of production process are mainly to improve the quality of NMC products, reduce the residual alkali content on the surface, improve the integrity of crystal structure and reduce the fine powder content of materials. The electrochemical properties of Sudu materials are more affected. Adjusting the Li/M ratio, improving the rate performance of NMC and increasing the thermal stability of materials require manufacturers to understand the crystal structure of ternary materials.
2. Production of Ternary Material Precursors
Compared with other polar substances, NMC has its own unique precursor precipitation process. Although LCO and LMOLFP are both liquid phase precursors, high-end materials are produced more frequently than several enterprises, and solid phase is still the mainstream process of several materials.
Ternary materials (including NCAOLO) must adopt liquid phase to ensure uniform mixing of elements. The unique precipitation process of solid phase makes NMC modify several polar materials more easily and effectively.
At present, the mainstream NMC precursor production in the world adopts hydroxide precipitation method NaOH as precipitant and ammonia complexing agent to produce high-density spherical hydroxide precursor. The advantage of this method is that it is relatively easy to control the particle size, specific surface area and morphology tap density of the precursor. In actual production, the reactor operation is relatively easy to produce wastewater treatment problems (including sodium sulfate NH3), which may increase the overall production cost.
From the control point of view, the carbonate precipitation process has some advantages. Even if complexing agent is used, the main problems in the process of producing spherical granular carbonate are poor process stability and easy control of product particle size. The high content of impurities (NaS) in carbonate precursor phase affects the electrochemical performance of ternary materials. The tap density of carbonate precursor is lower than that of hydroxide precursor, which limits the energy density of NMC.
The author thinks that from the point of view of control and practical application of ternary battery with high specific surface area, carbonate method, as the main supplement of mainstream hydroxide precipitation method, needs to attract enough attention from domestic manufacturers.
At present, manufacturers of internal polar materials generally ignore the direct procurement of precursors for sintering by R&D ternary precursor production department. What I want to emphasize is the precursor quality (morphology, particle size, particle size distribution, specific surface area, impurity content, tap density, etc.). ) is very important for the production of ternary precursors, which directly determines the physical and chemical indexes of sintered products.
It is said that the precursor technology of ternary materials is 60%, and the sintering technology is basically transparent. From the point of view of quality control of this product, ternary manufacturers must produce their own precursors.
In fact, the mainstream manufacturers of ternary materials are Umicore, Nichia, L& etc. Fuda, Toda
Except Kogyo, only the self-produced precursors have enough production capacity to be suitable for outsourcing. Domestic electrode manufacturers must attach great importance to the research and development of precursors.
3. Control of residual alkali content on the surface of ternary materials
NMC (including NCA) has a high content of residual alkali on the surface, and its practical application is quite prominent. The alkaline substances on NMC surface mainly exist in the form of Li2SO4LiOH other than Li2CO3.
The alkaline compounds on the surface of polar materials mainly live in the actual production process of bimorphs, and lithium salts are calcined at high temperature. The volatile components in the Li/M ratio increased slightly (that is, the amount of lithium salt was appropriate) to make up for the loss during sintering, and a small amount of Li remained (in the form of high temperature Li2O). When cooling at room temperature, Li2O absorbs air, CO2, H2O, Li OH, Li2co3, etc.
The second elementary experiment has proved that the oxygen anion on the surface of polar material reacts with air CO2 water, and carbonate and lithium migrate from the body surface, and the surface of the material looks like Li2CO3, which distorts the surface oxide layer with deoxygenated structure. Any polar substance is less than carbonate exposed to air.
The surface shape of polar materials with surface alkalization shrinkage is as regular as NCA.
≈ high nickel NMC > low nickel NMC≈LCO > LMO>；; LFP said that the residual alkali content on the surface of ternary or binary materials is directly related to the nickel content.
The negative effect of high residual alkali content on the surface of polar materials is firstly to affect the electrochemical properties of surface alkaline compounds caused by high basic oxide content on the main surface of NCA nickel-rich ternary materials, which are easy to form and freeze. The impact is mainly reflected in the increase of reverse capacity loss and the deterioration of cycle performance.
In addition to NCA nickel-rich ternary materials, it is said that the high-pressure solution of Li2CO3 on the surface of the inflated battery mainly has potential safety hazards, and reducing the residual alkali content on the surface is of great significance in the practical application of ternary materials batteries.
At present, domestic manufacturers generally use ternary materials for water washing and low-temperature secondary sintering (water washing
+
The second sintering process reduced the residual alkali content on the surface of NMC. The surface residual alkali cleaning is more thorough, and the disadvantages are not obvious. The rate cycling performance of ternary materials is obviously reduced to meet the requirements of battery and water washing.
+second burn increases the author, recommended.
The author thinks it is necessary to take a series of measures to effectively reduce the alkali content on the surface of ternary materials. In the precursor stage, it is necessary to control the ammonia content and protective atmosphere to resist high nickel ternary materials, and even add appropriate additives to reduce the carbon and sulfur content.
Strictly control the Li/M ratio in the mixing stage, optimize the sintering temperature in the sintering stage, control the oxygen pressure and cooling rate in the annealing stage, and vacuum seal the packaging materials in the workshop humidity.
It is said that the initial packaging of precursors needs to strictly control the contact between materials and air, and the comprehensive effect of a series of technical measures is to reduce the amount of residual alkali on the surface of ternary materials. Even though the surface pH value of unmodified high nickel 622 is controlled around 1 1, and the surface coating is effective to reduce the residual alkali content on the surface of ternary materials, it is still necessary to modify the surface coating as a high nickel NMC.
The author emphasizes that the problem of residual alkali on the surface of polar materials, especially NMCNCA, must be paid great attention by polar material manufacturers, although the content must be as low as possible or controlled within a stable and reasonable range (generally 500- 1000).
PPM) The important technology of NCA direct energy mass production ignores the strict control of atmospheric and environmental temperature and humidity, and realizes closed production.
4. Production of NMC with high specific surface area and narrow particle size
For HEVPHEV batteries, the requirements for power and energy density need to be considered. The demand for mechanical ternary materials is the same as that of ordinary ternary materials used in consumer electronics. In order to meet the demand of high rate, the specific surface area of ternary materials must be increased, and the reactive area is opposite to that of ordinary ternary materials.
The specific surface area of ternary materials is determined by the precursor BET. How to improve the BET of precursor as much as possible while keeping the sphericity and tap density of precursor unchanged? Mechanical ternary materials must overcome technical problems.
Generally speaking, to improve the BET of precursors, it is necessary to adjust the concentration of complexing agent and change some parameters of the reactor, such as speed, temperature and flow rate. Some process parameters need to be optimized comprehensively to sacrifice the sphericity and tap density of the precursor to a greater extent and affect the energy density of the battery.
Ways to improve the BET efficiency of precursor preparation by carbonate precipitation method The author mentioned that there are some technical problems in carbonate precipitation method at present, and the author thought that carbonate precipitation method might be used to prepare ternary materials with high specific surface area, and made further research.
At present, the basic requirements for the cycle life of power batteries require at least matching the half-life of the whole vehicle (8- 10). 100% DOD period should reach 5000. At present, the cycle life of ternary materials can reach the target. At present, the reported cycle record of ternary materials is Samsung.
The cycle life of NMC532 ternary battery manufactured by SDI is close to 3000 times at 0.5C C.
The author thinks that besides impurity doping and surface coating, the cycle life improvement potential of ternary materials is an important way to control the particle size distribution of products. This is especially important for batteries. I know that the particle size distribution of ternary materials is very wide, such as 1.2- 1.8, and the content of Dooley metal is the same.
Fine element segregation shows that the Li-Ni content of particles is higher than the average (Li-Ni content) and the Li-Ni content of particles is lower than the average (Li-Ni feet). In the process of charging, the total lithium removal structure of polarized primary particles is destroyed, and the side reaction between charged high nickel particles and electrolyte is more intense, and the high temperature is more obvious, resulting in faster cycle life of particles, while the situation of decaying particles is the opposite.
It is said that the overall cycle performance of materials is actually determined by particles, which restricts the improvement of cycle performance of ternary materials. The important problem is that 3C battery embodies its cycle performance requirement of 500, and the cycle life of the battery is required to reach 5000. For unimportant problems, to improve the cycling performance of ternary materials, it is necessary to produce uniform particle size (particle size distribution is 0.8). Ternary materials try to avoid the challenge of particle storage in industrial production belt. The particle size distribution of NMC depends entirely on the precursor. Let me look at the importance of precursors to the production of ternary materials. The particle size distribution of 65438 0.0 can be produced by using ordinary reactors. Precursor particles need to adopt specially designed reactors or physical technology progress to reduce the size distribution of precursor particles. Using stage machine, the particle size distribution can reach 0.8, except for the particle size distribution, the precursor yield decreases, which actually increases the precursor production cost.
In order to realize the comprehensive utilization of raw materials and reduce the production cost, manufacturers must establish a precursor collection and reprocessing production line, and manufacturers need to comprehensively weigh the advantages and disadvantages and choose the appropriate technological process.
The practical application of narrow particle cloth ternary material obviously improves the coating performance of the pole piece, which not only increases the cycle life of the battery, but also reduces the polarization of the battery and improves the rate performance. Due to the limitation of technical level, domestic ternary manufacturers have not yet realized the importance of the problem. The author thinks that the important technical index hope of narrow-grained cloth ternary material has caused domestic manufacturers to attach great importance to the safety of 5 ternary material.
Compared with LFPLMO battery, ternary material battery has more serious safety problems, mainly because the needle filling condition is easy to be closed, the battery flattens more seriously, and the high temperature cycle is ideal. The author believes that the safety of ternary batteries needs to be done on both sides of the electrolyte of the material itself in order to achieve better results.
NMC material itself must first strictly control the residual alkali content on the surface of ternary materials. Except for the measures discussed by the author, the surface coating is ineffective. Generally speaking, alumina coating is effective. Alumina, that is, liquid coating in precursor stage and solid coating in sintering stage, is definitely ineffective.
In recent years, ALD technology has been developed to improve the electrochemical performance of several layers of Al2O3 on NMC surface. Obviously, the cost per ton of ALD coatings increased by 565.438 billion yuan. How to reduce the cost is the premise of practical ALD technology.
In order to improve the structural stability of NMC, impurity doping is mainly used. At present, more compounds of anions and cations are used to improve the thermal stability of the material structure. In addition, the content of Ni must be considered. With the increase of Ni content, its specific capacity increases. I want to realize that the negative effect caused by increasing Ni content is not obvious.
With the increase of nickel content, the mixed discharge effect of Li Ni layer is more obvious, which directly deteriorates its cycle rate performance. The increase of nickel content makes the stability of crystal structure worse. With the increase of some elements, the safety problem is more prominent, especially under the high temperature test conditions, the higher the nickel content of ternary material which does not produce serious gas in the battery, and the requirements of various indexes must be considered comprehensively.
The author thinks that the single use of high nickel ternary materials can limit the negative effects of 70% nickel content and high nickel belt to offset the loss of capacity improvement advantages.
In addition, the author wants to point out that the content of fine powder should be strictly controlled. Fine powder particles also have the same concept. The shape of fine powder is regular and the particle size is 0.5 micron. It is difficult to produce only regular particles except for the safety hazards left by the use of electrode materials. How to control and eliminate the important problems in the production of fine powder?
The safety of ternary battery needs to be improved by combining electrolyte, which can be solved by comparison. There are few reports on the technical secrets involved in electrolyte blocks. Generally speaking, adding PC to DEC will reduce the electrochemical performance of ternary material DMC system. For electrolyte salts, LIBOLIPF 6 should be added to improve the high-temperature cycle performance of ternary materials.
At present, the modification of electrolyte mainly adopts special functional additives, including VEC, DTA, LiDFOB, PS, etc. Apple is known to improve the electrochemical performance of ternary batteries, which requires the joint research of battery manufacturers and electrolyte manufacturers. It is suitable for the application of ternary materials in the electrolyte market of six ternary materials. It is widely expected that lithium cobaltate will replace dozens of fast ternary lithium cobaltate 3C batteries, and the sales volume of lithium cobaltate will still exceed 50%.
In my opinion, ternary materials can hardly replace lithium cobaltate in 3C field.
It is difficult to meet the rigid requirements of smart phone voltage platform by using ternary materials alone on the main surface; On the other hand, the two-particle structure of ternary material is difficult to make high voltage, which makes the volume energy density of ternary material battery still reach the high-end (high voltage and high voltage) lithium cobaltate level, and the 3C field of ternary material will still play an auxiliary role in the future.
Single crystal high-pressure ternary materials have been widely used in the field of high-pressure electrolyte curing energy 3C. Refer to the discussion published by the author on the development of pole materials for consumer-grade lithium-ion batteries. In fact, the author tends to think that ternary materials are more suitable for power tools and batteries. In recent years, the energy density requirements of electric vehicles have been significantly improved, and automobile manufacturers have begun to test ternary batteries in HEVPHEV.
Only in terms of energy density requirements, HEV energy density requirements are low, LMO and LFPNMC batteries meet the requirements, and PHEV energy density requirements are high. At present, NMC/NCA batteries meet the requirements of PHEV. Due to the technical route of Tesla batteries, NMC will expand its application trend.
At present, the trend of transferring LMO battery to NMC battery is not obvious. The Ministry of Industry and Information Technology has given three hard indicators to new energy vehicle battery enterprises: 20 15. The energy density of single battery is 180Wh/kg (the energy density of module is 150).
Wh/kg) cycle life exceeds 2000 or calendar life reaches 10, which is lower than 2 yuan /Wh. At present, NMC batteries meet the first three hard indicators.
The author thinks that the mainstream electrode material LFPLMO of NMC battery can play an auxiliary role because of its own shortcomings.
At present, the industry comparison shows the trend of NMC batteries, but the supply of high-end ternary lithium batteries is not prosperous in 3-5 years. In the short term, at present, lithium manganate is still the main internal lithium battery in lithium ferrous phosphate. As an auxiliary lithium battery, electric vehicle enterprises can master the technology of 2-3 internal molded mature batteries through lithium ferrous phosphate materials, improve their own technical level, and then cross the technical route of ternary materials.
Strengthening the layout of ternary materials is a strategic problem that material battery manufacturers urgently need to solve.
The author is talking about ternary materials. The price of NMC phase LMOLFP is higher. I strongly support the original intention of LFP. At present, compared with the high-end LMO price of ternary material15-180,000 yuan/ton, the price of internal substance is about 80,000 yuan. At present, the quality is lower than that of LFP 100000 yuan, and LMOLFP has been upgraded and compressed by 60 thousand yuan and 6-80 yuan.
This limits the scale of ternary materials for power batteries. I briefly analyzed the ratio of ternary material to metal, and found that the production process of single raw material reduced the space.
The author thinks that there are two realistic ways to improve the quality of NMC products and achieve the super-cycle life. Compared with the single cycle cost, it is doubtful to improve the cycle life and reduce the overall use of the battery during the whole life. This requires enterprises to have strong R&D technical strength and increase production costs.
Although the international polar material giants generally adopt this strategy, it is actually very difficult for domestic polar material manufacturers to make a profit rate on R&D level at present.
Another way to establish a complete battery collection system to charge and utilize metal resources is similar to Xijiatong's compulsory collection of waste lithium batteries. The author simply calculated that after deducting the collection process cost (CoNiMnFe is too cheap to confiscate the value), metal collection will almost make up for 20%-30% of the raw material cost and the final ternary material cost 10%-20% of the space reduction.
Considering the competitiveness of ternary battery with high energy density /Wh compared with LFPLMO battery, it is necessary for two leading domestic enterprises to integrate the industrial chain, namely, metal and mineral raw materials, ternary material production and battery production, to realize the optimal allocation of resources and reduce production costs.
The author thinks that the R&D technical strength of domestic former manufacturers is generally weak, and the resource utilization ratio (this) takes a relatively appropriate balance in product quality, so as to rapidly expand the market and compete with international industry giants.