Preparation method of high-nickel single-crystal cathode material for lithium-ion battery

Abstract

The present invention belongs to the technical field of cathode materials, and particularly relates to a preparation method of a high-nickel single-crystal cathode material for lithium-ion batteries. In the present invention, the precursor, the modifier and the flocculant are first subjected to a primary sintering, and then the modified precursor is mixed with a lithium source for a secondary sintering to obtain the high-nickel single-crystal cathode material. The method of the present invention retains the polycrystalline morphology of the precursor during the primary sintering, and at the same time, the formed fast ion conductor can also greatly improve the ion diffusion rate in the solid-phase reaction, significantly reducing the sintering temperature and time of the high-nickel single crystal. In addition, due to its large molecular weight and stable structure, the fast ion conductor is distributed on the particle surface, which can prevent the surface structure degradation of the single-crystal particles at high temperature, and simultaneously complete the concentration gradient doping and surface coating of the particles during the sintering process, effectively improving the electrochemical performance of the material.

Description

Technical Field

[0001] The invention belongs to the technical field of positive electrode materials, and specifically relates to a method for preparing a high-nickel single crystal positive electrode material for a lithium ion battery. Background Art

[0002] In recent years, with the promotion of green economic models and the increasing environmental pressure, the new energy industry has been booming. Taking the field of travel and transportation as an example, various industries have formed a trend of electrification as the main development direction, and the large-scale application of lithium-ion batteries has followed. With the widespread popularization of lithium-ion batteries, the market demand for lithium-ion batteries with high energy density, good cycle stability and excellent safety performance has become increasingly strong. As the core material of the lithium-ion battery system, the properties of the positive electrode material directly determine the working performance of the battery and even the car. The traditional positive electrode material is a polycrystalline secondary spherical particle composed of sintered and stacked primary particles and containing countless grain boundaries, which has isotropic characteristics. During the lithium ion deintercalation process, the lattice of the primary particles will expand and contract periodically, so the polycrystalline material will continue to accumulate structural stress generated by lattice changes at the grain boundaries, which will lead to the pulverization and breakage of the particles. This phenomenon will lead to the intensification of side reactions between the material surface and the electrolyte (such as gas production and heat generation), and on the other hand, it will cause some particles to be unable to contact the conductive network, and the capacity will drop. These problems will directly affect the safety and cycle performance of the battery.

[0003] In order to solve these problems of polycrystalline secondary spherical materials, the study found that by increasing the sintering temperature and extending the sintering time, promoting the secondary recrystallization between the primary particles, anisotropic single crystal materials can be obtained. Compared with polycrystalline materials, single crystal materials have many significant advantages, such as: small contact area with the electrolyte, fewer side reactions; the absence of grain boundaries, good stress release, and good particle integrity. These advantages can effectively avoid the safety and cycle stability problems of polycrystalline materials. However, the preparation process is different from that of secondary spherical polycrystalline materials. Single crystal materials usually need to be sintered at a higher temperature for a longer time to accelerate the diffusion rate of ions and promote the fusion between primary particles. Such process conditions are very effective in preparing single crystal positive electrode materials with low nickel content (such as LiNi 0.5 Co 0.2 Mn 0.3 O2), it will not have much impact on the performance of the material itself. However, when preparing high nickel content, especially high nickel single crystal materials with nickel content greater than 0.75 (such as LiNi 0.8 Co 0.1 Mn 0.1 O2), due to the low sintering temperature of the material itself and Ni 3+The content of ions is relatively high, and the structure of the material is extremely unstable at high temperatures. Although single-crystal materials can be prepared by the sintering method at high temperatures for a long time, the surface structure of the high-nickel single-crystal cathode material will degenerate, resulting in oxygen evolution and phase separation, leading to the formation of a large amount of impurities in the rock salt phase or spinel phase. At the same time, the cation mixing in the layered material will be more serious. These factors make it difficult to achieve by simply increasing the calcination temperature or extending the sintering time when preparing the high-nickel single-crystal cathode material.

[0004] Due to the limitations of such problems, there are currently mainly two types of methods to prepare the high-nickel single-crystal cathode material. One is to use the high-temperature molten salt method, and the other is to use a flux (which is also a dopant) to adjust the sintering temperature.

[0005] The high-temperature molten salt method refers to a method in which a precursor, a lithium salt, and one or several molten salts are mixed, and the sintering temperature is reduced by mixing a large amount of molten salts, so that the reaction between the precursor and the lithium salt proceeds in a molten state, and then a high-nickel single-crystal cathode material with good crystallinity is obtained. For example, Chinese invention patents CN 111200129 A and CN109879333A both use the high-temperature molten salt method to prepare the high-nickel single-crystal cathode material. However, the molten salts used in the high-temperature molten salt method are generally halides or sulfates, which cause serious corrosion to the equipment during the actual production process. In addition, due to the large amount of molten salts used, the by-products are all agglomerated with the cathode material after sintering, and a large amount of solvents are required for cleaning and environmental protection treatment, increasing the production cost.

[0006] The flux-assisted sintering method generally refers to mixing a precursor, a lithium source, and a small amount of flux, and using the fluxing effect to reduce the sintering temperature. For example, Chinese invention patent CN 110867580 A proposes to use a strontium-containing compound as a flux and a dopant to prepare a single-crystal cathode material. Such a flux needs to be limited to a dopant because the fluxing element will be doped into the lattice of the material during high-temperature calcination, and the dosage is not easy to be too much and it is difficult to enrich on the surface. Therefore, the fluxing and protection effects are limited. When preparing a high-nickel single-crystal material with a nickel content greater than 0.75 and a relatively low sintering temperature itself, it is difficult to maintain the surface stability of the material at high temperatures, and there are still problems of surface degradation and low capacity during the sintering process. Therefore, the main function of this method is still to improve the electrochemical performance of the material after sintering, and it cannot well solve the essential defects in the sintering process of the high-nickel single-crystal material.

[0007] In addition, there are also some studies that first mix and sinter the precursor and the flux (which is also a dopant), form a quasi-single crystal precursor, and then mix and sinter it with the lithium source to obtain a high-nickel single crystal material. For example, Chinese invention patent CN107768619 A proposes to mix and sinter a hydroxide precursor with a zirconium source, a dopant, and a wetting agent to form a quasi-single crystal oxide precursor, and then mix and sinter it with the lithium source to obtain a high-nickel single crystal cathode material. The advantage of this method is that through the dispersion of the wetting agent and a single high-temperature calcination, the zirconium source and the dopant can be uniformly doped into the dehydrated precursor, enabling the precursor to form element-doped quasi-single crystal oxide particles, and then mixing and sintering with the lithium source to form a single crystal cathode material while maintaining the single crystal morphology. The disadvantage is that this method will cause the precursor to become single crystal particles after the first sintering. Although uniform element doping is achieved in advance, the single crystal morphology will greatly limit the diffusion of lithium ions during the second sintering process. There is no grain boundary diffusion and only some crystal planes (such as the (111) crystal plane of the oxide) can provide diffusion channels. In addition, the single crystal precursor obtained by this method has very poor processability and requires an additional crushing and screening process before lithium matching. Therefore, although this type of method better solves the problems of multi-element doping and the difficulty of polycrystalline secondary recrystallization during the sintering process and can effectively improve the electrochemical performance of the material, it sacrifices the diffusion rate of ions during the solid-state reaction process and cannot solve the surface degradation problem.

[0008] Therefore, how to accelerate the diffusion rate of ions in the solid-state reaction and the recrystallization reaction rate of polycrystalline fusion into single crystals, effectively reduce the sintering temperature of the high-nickel single crystal cathode material, while ensuring the stability of the surface structure of the material during the sintering process, and optimizing the single crystal preparation process are urgent problems to be solved in the industry to obtain a high-nickel single crystal cathode material with good crystallinity and excellent electrochemical performance. Summary of the Invention

[0009] In this context, the present invention provides a method for preparing a high-nickel single crystal cathode material for a lithium-ion battery. The method of the present invention retains the polycrystalline morphology of the precursor, and at the same time, the formed fast ion conductor can greatly increase the ion diffusion rate in the solid-phase reaction, accelerate the secondary recrystallization of the polycrystalline precursor, and significantly reduce the sintering temperature and time of the high-nickel single crystal. In addition, due to its large molecular weight and stable structure, the fast ion conductor is distributed on the particle surface and can prevent the surface structure degradation of the single crystal particles during the sintering process, and simultaneously complete the concentration gradient doping and surface coating of the particles with the sintering process, effectively improving the electrochemical performance of the material.

[0010] To achieve the above object, the present invention proposes a method for preparing a high-nickel single crystal cathode material for a lithium-ion battery, comprising the following steps:

[0011] (1)Disperse the hydroxide precursor and the flocculant in water, add the modifier thereto, and stir the mixed slurry evenly;

[0012] (2)Stir and heat the evenly mixed slurry at a certain temperature, then evaporate the slurry to dryness, and perform high-temperature sintering on the obtained powder to obtain the modified polycrystalline precursor material;

[0013] (3)Mix the modified precursor material and the lithium source, and perform secondary sintering in an oxygen-containing atmosphere to obtain the high-nickel single-crystal cathode material.

[0014] Preferably, the hydroxide precursor in step (1) is Ni x Co y M z (OH)2, where x≥0.75, 0≤y≤0.25, 0≤z≤0.25, and x + y + z = 1, and the M element is one or more of Mn, Al, and Ti.

[0015] Preferably, the precursor in step (1) is polycrystalline secondary spherical particles formed by aggregation of primary particles, and its BET is preferably 4-10m 2 / g, more preferably 6-8m 2 / g.

[0016] Preferably, the particle size D of the precursor in step (1) 50 is preferably 3-8um, more preferably 4-6um.

[0017] Preferably, the modifier in step (1) is a compound comprising the elements Li, O, and element A, and the element A is one or more of Zr, Ti, Al, La, Ba, Ga, Ta, and Nb.

[0018] The modifier can be a single compound or a combination of multiple compounds, preferably a combination of multiple compounds, such as oxides, hydroxides, or inorganic salts of lithium or element A.

[0019] Preferably, the modifier will generate a fast ion conductor that allows lithium to pass through quickly after sintering.

[0020] In some preferred embodiments of the present invention, the structural general formula of the fast ion conductor is Li t La u B w O p , where 0.3≤t≤7, 0.5≤u≤5, 1≤w≤3, 2≤p≤12, and the B element is one or more of Zr, Ti, Al, Ba, Ga, and Nb.

[0021] The fast ion conductor can be Li7La3Zr2O 12, Li6BaLa2Ta2O 12 , Li5La3Nb2O 12 , Li5La3Ta2O 12 , Li 0.34 La 0.51 TiO 2.94 or a fast ion conductor containing other A elements as doping elements.

[0022] For example, if the compound is Li7La3Zr2O 12 , some elements such as Al and Ga can be doped to form a fast ion conductor Li 6.25 Al 0.3 La3Zr2O 12 , Li 6.5 Al 0.3 La3Zr 1.9 O 12 , Li 6.55 La3Zr2Ga 0.15 O 12 .

[0023] The fast ion conductor is preferably Li7La3Zr2O 12 , Li 6.25 Al 0.3 La3Zr2O 12 , Li 6.5 Al 0.3 La3Zr 1.9 O 12 , Li 6.55 La3Zr2Ga 0.15 O 12 , Li6BaLa2Ta2O 12 , Li5La3Nb2O 12 , Li5La3Ta2O 12 , Li 0.34 La 0.51 TiO 2.94 or one or more of them.

[0024] The addition amounts of each A element and lithium element in the modifier are added according to the molar ratio of each element in the target fast ion conductor.

[0025] Specifically, if the chemical composition after sintering the modifier is selected as Li7La3Zr2O 12 , then the modifier adds nano-oxides, hydroxides or inorganic salts of the corresponding elements according to the molar ratio of 7:3:2 of the three elements Li, La, and Zr in the chemical formula, such as LiOH·H2O, nano-scale La2O3 and ZrO2.

[0026] Based on the molar amount of the hydroxide precursor, the molar fraction of the generated amount of the target compound in the modifier is 0.0001 to 0.005. If its content is too small, it cannot play the role of accelerating the ion transport rate and improving the surface structure stability of the material. If it is too much, it will limit the electrochemical performance of the material.

[0027] Preferably, the flocculant in step (1) is one or more of citric acid, glucose, maleic acid, oxalic acid, and sucrose. Its function is to enable the modifier to be evenly distributed on the surface and in the pores of the precursor during the heating and flocculation process, preventing the aggregation of nanoparticles. In addition, the flocculant will undergo a self-propagating combustion decomposition reaction during the first sintering process, which can instantly increase the local temperature, promote the reaction between nanoparticles to form lithium-containing oxide nanoclusters, and its decomposition products are carbon dioxide and water, which will not affect the elemental content of the main material.

[0028] Preferably, the addition amount of the flocculant in step (1) is 1% to 5% of the mass of the hydroxide precursor.

[0029] Preferably, the mixed slurry of the precursor, modifier, and flocculant in step (2) is heated to 50 to 80 °C for flocculation, and after the slurry becomes gel-like, it is dried.

[0030] Preferably, in step (2), the dried powder after flocculation is rapidly heated for sintering. Preferably, the sintering temperature in step (2) is 700 to 1000 °C, preferably 800 to 900 °C, and the sintering time is 2 to 5 h, preferably 2.5 to 4 h. Then it is cooled to room temperature, and the sintering atmosphere is an oxygen-containing atmosphere, such as air or oxygen.

[0031] Preferably, in step (2), the dried powder after flocculation is heated at a heating rate of 8 °C / min or more, preferably 8 to 20 °C / min. Preferably, the maximum heating rate does not exceed 25 °C / min.

[0032] The rapid heating sintering in this step can cause the flocculant to rapidly undergo a self-propagating combustion reaction, increasing the local temperature, and then enabling the modifier nanoparticles to form nanoclusters in a short time. At the same time, the rapid heating sintering and short sintering time can enable the nanoclusters to have a certain growth, improving the crystallinity. At the same time, the nanoclusters will not undergo grain fusion due to too long sintering time, reducing the dispersion degree. In addition, it can also reduce the residue of the flocculant.

[0033] Preferably, the modified precursor material obtained after the modified sintering in step (2) is Ni x Co y M z O2 oxide, and still maintains the morphology of polycrystalline secondary spheres. Among them, Ni x Coy M z The O2 oxide is the hydroxide precursor Ni x Co y M z (OH)2 is formed by dehydration at high temperature, characterized by polycrystalline secondary spherical particles with more grain boundaries and more pores; the fast ion conductor nanoclusters are compounds containing Li, O, and A elements formed by the rapid crystallization of the added modifier during the primary sintering process, such as Li7La3Zr2O 12 、Li 6.25 Al 0.3 La3Zr2O 12 、Li 6.5 Al 0.3 La3Zr 1.9 O 12 、Li 6.55 La3Zr2Ga 0.15 O 12 、Li6BaLa2Ta2O 12 、Li5La3Nb2O 12 、Li5La3Ta2O 12 、Li 0.34 La 0.51 TiO 2.94 One or several of them. After sintering, the modifier compound can be partially doped into the lattice of the host material in the form of a concentration gradient and partially coated on the surface of the host material in the form of chemical bonding, but its chemical composition remains unchanged, with excellent ionic conductivity and evenly distributed on the surface and grain boundaries of the Ni x Co y M z O2 oxide polycrystalline particles.

[0034] Compared with the existing dopant-assisted sintering scheme, the method of the present invention greatly accelerates the ion diffusion rate in the solid-phase reaction by generating fast ion conductor nanoclusters on the surface of the modified precursor material, rather than simply a fluxing effect. Therefore, while ensuring crystallinity, the sintering temperature and time of the high-nickel single crystal can be reduced by a greater margin. At the same time, the fast ion conductor on the surface can also protect the surface of the high-nickel single crystal and prevent its degradation of the structure at high temperature. In addition, due to the lower temperature and shorter time during the calcination of the method of the present invention, the fast ion conductor metal elements on the surface can be partially doped into the lattice of the host material in the form of a concentration gradient and partially coated on the surface of the host material in the form of chemical bonding, that is, the coating modification is completed synchronously.

[0035] In the step (3), the lithium source is selected from lithium carbonate, lithium hydroxide, and lithium hydroxide monohydrate, preferably lithium hydroxide monohydrate.

[0036] Preferably, the addition amount of the lithium source in step (3) is added according to the molar ratio of Li / (Ni+Co+M) = 1.005 to 1.05 to the metal elements in the precursor.

[0037] Preferably, the oxygen-containing atmosphere in step (3) is an oxygen-containing atmosphere such as air or oxygen, and preferably an atmosphere with an oxygen content of 95% or more.

[0038] Preferably, the sintering temperature in step (3) is not higher than the sintering temperature in step (2). Specifically: first, keep it at 300 - 500 °C for 1 - 3 h, then raise the temperature to 600 - 800 °C, preferably sinter at 650 - 800 °C for 6 - 10 h, and finally cool naturally to room temperature to obtain the high-nickel single-crystal cathode material.

[0039] The present invention also provides a high-nickel single-crystal cathode material prepared by the above method, and the chemical formula of this material is LiNi x Co y M z (Li α A β O γ ) ζ O2, where x≥0.75, 0≤y≤0.25, 0≤z≤0.25, 0.3≤α≤7, 1.5≤β≤6, 2≤γ≤12, 0.0001≤ζ≤0.005, and x + y + z = 1. Further, the M element is one or more of Mn, Al, and Ti, and the A element is a combination of one or more elements of Zr, Ti, Al, La, Ba, Ga, Ta, and Nb.

[0040] Preferably, Li α A β O γ is Li7La3Zr2O 12 、Li 6.25 Al 0.3 La3Zr2O 12 、Li 6.5 Al 0.3 La3Zr 1.9 O 12 、Li 6.55 La3Zr2Ga 0.15 O 12 、Li6BaLa2Ta2O 12 、Li5La3Nb2O 12 、Li5La3Ta2O 12 、Li 0.34 La 0.51 TiO 2.94 or several of them.

[0041] The preparation method for preparing a high-nickel single-crystal cathode material for lithium-ion batteries provided by the present invention mainly has the following advantages:

[0042] 1. The sintering temperature of the high-nickel single-crystal cathode material is effectively reduced. The method of the present invention retains the polycrystalline morphology of the precursor through high-temperature rapid modification sintering. The grain boundaries and widely exposed crystal planes inside it are beneficial to the diffusion of lithium ions during the secondary sintering process. In addition, with the self-propagating combustion reaction of the flocculant, the modifier forms fast-ion conductor nanoclusters at its grain boundaries and surfaces. These nanoclusters can reduce the overall specific surface energy of the particles, promote the mass transfer rate during recrystallization, greatly improve the ion diffusion rate in the solid-state reaction, and thus significantly reduce the sintering temperature and sintering time of the high-nickel single-crystal cathode material.

[0043] 2. The surface stability of the high-nickel single-crystal cathode material during the sintering process is improved. The fast-ion conductor formed in the primary sintering by the method of the present invention is a lithium-containing oxide, which will bind to the host material through metal-oxygen bonds. Due to its good thermal stability, it will exist relatively stably on the surface of the host material during the secondary sintering process, reducing the concentration and activity of Ni 3+ and thus stabilizing the surface structure and preventing the formation of spinel phase or rock salt phase impurities.

[0044] 3. The electrochemical performance of the material is improved. The long-time high-temperature secondary sintering process will inevitably lead to the complete doping of the modifier elements into the lattice of the host material. However, the low-temperature and short-time scheme provided by the method of the present invention can make some modifier elements diffuse into the lattice of the host material in the form of a concentration gradient. Such element doping can increase the entropy value of the material and further improve the cycle stability of the material. At the same time, due to its good stability, part of the fast-ion conductor will remain on the surface of the host material in the form of a coating. As a fast-ion conductor, it can accelerate the deintercalation and intercalation rate of lithium ions during the charge and discharge process, effectively improving the rate performance and safety performance of the material. Description of the Drawings

[0045] Figure 1 It is the SEM image of the cathode material obtained in Example 1 of the present invention.

[0046] Figure 2 It is the SEM image of the cathode material obtained in Comparative Example 1.

[0047] Figure 3 It is the SEM image of the cathode material obtained in Comparative Example 2.

[0048] It can be seen that at the same sintering time and temperature, through the method provided by the present invention, a high-nickel single-crystal material with distinct particles and D 50 of about 4-5 μm can be obtained. However, directly mixing the precursor and the lithium source for calcination or adding a flux for calcination cannot obtain a high-nickel single-crystal cathode material.

[0049] Figure 4 This is the HR-TEM image of the high-nickel single-crystal material in Example 1 of the present invention. It can be seen that the metal elements on the (003) plane of the layered material are arranged neatly, showing a typical O3 phase. There are no other types of element arrangements caused by the presence of rock salt phase or spinel phase impurities on the crystal surface and in the bulk phase, indicating that the method provided by the present invention can effectively prevent the surface degradation of the high-nickel single-crystal cathode material during the sintering process.

[0050] Figure 5 This is the XRD pattern of the cathode materials obtained in Example 1, Comparative Example 3, and Comparative Example 4 of the present invention. It can be seen that the XRD spectrum of the single-crystal material obtained by the method of Example 1 has good crystallinity and no impurity phase is generated, while obvious NiO impurity peaks exist in the XRD spectra of the single-crystal materials obtained by the methods of Comparative Example 3 and Comparative Example 4.

[0051] Figure 6 This is the comparison chart of the cycle performance of the cathode materials obtained in Example 1, Comparative Example 3, and Comparative Example 4 of the present invention. The test conditions are a half-cell, a voltage window of 3.0 - 4.3V, a temperature of 25°C, a nominal current of 190 mA / g at 1C, and after charging and discharging at 0.2C for two weeks, cycling at 1C for 48 cycles. It can be seen that the single-crystal cathode material prepared by the method provided by the present invention has been significantly improved in both capacity and cycle stability. This is because compared with directly mixing the precursor and lithium source for high-temperature sintering or directly performing high-temperature sintering after adding a dopant, the modified process provided by the present invention accelerates the rate of recrystallization, can greatly reduce the sintering temperature and time of the high-nickel single-crystal cathode material, and thus enables the material to complete sintering at a lower temperature and at a faster rate. Such a process minimizes the surface degradation and lithium-nickel mixing of the material at high temperatures, improves the crystallinity, and at the same time the surface coating and gradient doping significantly improve the electrochemical performance of the material.

[0052] Figure 7 This is the SEM image of the cathode material of Comparative Example 5 of the present invention. It can be seen that after reducing the heating rate of the modification step, due to the uneven dispersion of the nanocrystalline clusters of the fast ion conductor, some particles still have a polycrystalline secondary spherical morphology. Detailed implementation mode

[0053] The present invention will be further described below in conjunction with examples, but the present invention is not limited to the following examples.

[0054] Source of raw materials: Ni 0.83 Co 0.12 Mn 0.05 (OH)2, Ni 0.75 Co 0.15 Mn 0.10 (OH)2, Ni 0.80 Co0.10 Mn 0.10 (OH)2 was purchased from Zhongwei New Materials Co., Ltd., Ni 0.90 Co 0.05 Mn 0.05 (OH)2, Ni 0.95 Co 0.02 Mn 0.03 (OH)2 was purchased from GEM Co., Ltd.

[0055] Example 1:

[0056] The preparation process of the materials in this example includes the following steps:

[0057] 1. Take 10 mol, with a BET of 7 m 2 / g, D 50 being 5 um of Ni 0.83 Co 0.12 Mn 0.05 (OH)2 was dissolved in water, and 30 g of citric acid, 1.3735 g of LiOH·H2O, 2.4435 g of La2O3, 1.2322 g of ZrO2, and 0.0703 g of Ga2O3 were added thereto, and stirred evenly;

[0058] 2. The uniformly mixed slurry in step 1 was heated and stirred at 65 °C, and after the slurry became gel-like, it was evaporated to dryness;

[0059] 3. The powder material obtained in step 2 was sintered in a muffle furnace at an average heating rate of 11 °C / min to 850 °C for 3.5 h, the sintering atmosphere was air, then it was naturally cooled to room temperature, and after pulverization, the modified precursor material was obtained;

[0060] 4. The modified precursor material was mixed with 10.35 mol of LiOH·H2O;

[0061] 5. The mixed powder in step 4 was kept at 450 °C for 2 h in an atmosphere of 98% oxygen, then heated to 750 °C and sintered for 8 h, then naturally cooled to room temperature, and after pulverization, the high-nickel single-crystal cathode material LiNi 0.83 Co 0.12 Mn 0.05 (Li 6.55 La3Zr2Ga 0.15 O 12 ) 0.0005 O2.

[0062] Example 2:

[0063] The preparation process of the materials in this example includes the following steps:

[0064] 1. Take 10 mol of NiCoMn(OH)₂ with a BET of 6 m² / g and a D of 6 μm and dissolve it in water. Then add 10 g of glucose, 0.5494 g of LiOH·H₂O, 0.9774 g of La₂O₃, 0.4929 g of ZrO₂, and 0.0282 g of Ga₂O₃, and stir well. 2 / g, D 50 being 6 μm of Ni 0.75 Co 0.15 Mn 0.10 (OH)₂ is dissolved in water, and 10 g of glucose, 0.5494 g of LiOH·H₂O, 0.9774 g of La₂O₃, 0.4929 g of ZrO₂, and 0.0282 g of Ga₂O₃ are added thereto, and stirred well;

[0065] 2. Heat and stir the uniformly mixed slurry in step 1 at 80 °C, and evaporate to dryness after the slurry becomes gel-like.

[0066] 3. Sinter the powder material obtained in step 2 in a muffle furnace at an average heating rate of 15 °C / min to 850 °C for 2.5 h, with the sintering atmosphere being air, then cool naturally to room temperature, and pulverize to obtain the modified precursor material.

[0067] 4. Mix the modified precursor material with 10.15 mol of LiOH·H₂O.

[0068] 5. Keep the mixed powder in step 4 at 500 °C for 3 h in a 96% oxygen atmosphere, then heat up to 800 °C and sinter for 10 h, then cool naturally to room temperature, and pulverize to obtain the high-nickel single-crystal cathode material LiNiCoMn(LiLa₃Zr₂GaO). 0.75 Co 0.15 Mn 0.10 (Li 6.55 La₃Zr₂Ga 0.15 O 12 ) 0.0002 O₂.

[0069] Example 3:

[0070] The preparation process of the material in this example includes the following steps:

[0071] 1. Take 10 mol of NiCoMn(OH)₂ with a BET of 6 m² / g and a D of 5 μm and dissolve it in water. Then add 10 g of oxalic acid, 2.9358 g of LiOH·H₂O, 4.8870 g of La₂O₃, and 2.4644 g of ZrO₂, and stir well. 2 / g, D 50 being 5 μm of Ni 0.75 Co 0.15 Mn 0.10 (OH)₂ is dissolved in water, and 10 g of oxalic acid, 2.9358 g of LiOH·H₂O, 4.8870 g of La₂O₃, and 2.4644 g of ZrO₂ are added thereto, and stirred well;

[0072] 2. Heat and stir the uniformly mixed slurry in step 1 at 80 °C, and evaporate to dryness after the slurry becomes gel-like.

[0073] 3. The powder material obtained in Step 2 is sintered in a muffle furnace at an average heating rate of 18 °C / min to 900 °C for 2.5 h. The sintering atmosphere is air, and then it is naturally cooled to room temperature. After pulverization, the modified precursor material is obtained;

[0074] 4. The modified precursor material is mixed with 10.10 mol of LiOH·H2O;

[0075] 5. The mixed powder in Step 4 is kept at 500 °C for 3 h in an atmosphere of 96% oxygen, then heated to 800 °C and sintered for 10 h, and then naturally cooled to room temperature. After pulverization, the high-nickel single-crystal cathode material LiNi 0.75 Co 0.15 Mn 0.10 (Li7La3Zr2O 12 ) 0.001 O2 can be obtained.

[0076] Example 4:

[0077] The preparation process of the material in this example includes the following steps:

[0078] 1. Take 10 mol, with a BET of 6.5 m 2 / g and a D 50 of 5 μm of Ni 0.80 Co 0.10 Mn 0.10 (OH)2 is dissolved in water, and 20 g of citric acid, 3.1455 g of LiOH·H2O, 5.8644 g of La2O3, 2.9573 g of ZrO2 and 0.1835 g of Al2O3 are added thereto, and stirred well;

[0079] 2. The uniformly mixed slurry in Step 1 is heated and stirred at 75 °C. After the slurry becomes gel-like, it is evaporated to dryness;

[0080] 3. The powder material obtained in Step 2 is sintered in a muffle furnace at an average heating rate of 12 °C / min to 900 °C for 3 h. The sintering atmosphere is air, and then it is naturally cooled to room temperature. After pulverization, the modified precursor material is obtained;

[0081] 4. The modified precursor material is mixed with 10.30 mol of LiOH·H2O;

[0082] 5. The mixed powder in Step 4 is kept at 450 °C for 2 h in an atmosphere of 97% oxygen, then heated to 780 °C and sintered for 9 h, and then naturally cooled to room temperature. After pulverization, the high-nickel single-crystal cathode material LiNi 0.80 Co 0.10 Mn 0.10 (Li 6.25Al 0.3 La3Zr2O 12 ) 0.0012 O2。

[0083] Example 5:

[0084] The preparation process of the material in this example includes the following steps:

[0085] 1. Take 10 mol of NiCoMn(OH)2 with a BET of 6.5 m 2 / g and a D 50 of 5 um, dissolve it in water, and add 20 g of citric acid, 0.2516 g of LiOH·H2O, 0.3258 g of La2O3, 0.1973 g of BaCO3, and 0.4418 g of Ta2O5 to it, and stir well; 0.80 Co 0.10 Mn 0.10 (OH)2 is dissolved in water, and 20 g of citric acid, 0.2516 g of LiOH·H2O, 0.3258 g of La2O3, 0.1973 g of BaCO3, and 0.4418 g of Ta2O5 are added to it, and stirred well;

[0086] 2. Heat and stir the uniformly mixed slurry in step 1 at 70 °C, and evaporate it to dryness after the slurry becomes gel-like;

[0087] 3. Sinter the powder material obtained in step 2 in a muffle furnace at an average heating rate of 12 °C / min to 900 °C for 2.5 h, with the sintering atmosphere being air, then naturally cool it to room temperature, and crush it to obtain the modified precursor material;

[0088] 4. Mix the modified precursor material with 10.25 mol of LiOH·H2O;

[0089] 5. Keep the mixed powder in step 4 at 450 °C for 2 h in a 97% oxygen atmosphere, then heat it to 780 °C and sinter for 9 h, then naturally cool it to room temperature, and crush it to obtain the high-nickel single-crystal cathode material LiNi 0.80 Co 0.10 Mn 0.10 (Li6BaLa2Ta2O 12 ) 0.0001 O2。

[0090] Example 6:

[0091] The preparation process of the material in this example includes the following steps:

[0092] 1. Take 10 mol of NiCoMn with a BET of 7.5 m 2 / g and a D 50 of 4 um, 0.90 Co 0.05 Mn 0.05(OH)2 is dissolved in water, and 40 g of maleic acid, 3.1455 g of LiOH·H2O, 7.3305 g of La2O3 and 3.9873 g of Nb2O5 are added thereto, and stirred evenly;

[0093] 2. Heat and stir the uniformly mixed slurry in step 1 at 55 °C, and evaporate to dryness after the slurry becomes gel-like;

[0094] 3. Sinter the powder material obtained in step 2 in a muffle furnace at an average heating rate of 10 °C / min to 850 °C for 4 h, the sintering atmosphere is air, then naturally cool to room temperature, and obtain the modified precursor material after pulverization;

[0095] 4. Mix the modified precursor material with 10.40 mol of LiOH·H2O;

[0096] 5. Keep the mixed powder in step 4 at 350 °C for 2 h in an atmosphere of 98% oxygen, then raise the temperature to 700 °C and sinter for 8 h, then naturally cool to room temperature, and obtain the high-nickel single-crystal cathode material LiNi 0.90 Co 0.05 Mn 0.05 (Li5La3Nb2O 12 ) 0.0015 O2.

[0097] Example 7:

[0098] The preparation process of the material in this example includes the following steps:

[0099] 1. Take 10 mol, BET is 8 m 2 / g, D 50 is 4 um of Ni 0.95 Co 0.02 Mn 0.03 (OH)2 is dissolved in water, and 45 g of citric acid, 0.7130 g of LiOH·H2O, 4.1540 g of La2O3 and 3.9935 g of TiO2 are added thereto, and stirred evenly;

[0100] 2. Heat and stir the uniformly mixed slurry in step 1 at 50 °C, and evaporate to dryness after the slurry becomes gel-like;

[0101] 3. Sinter the powder material obtained in step 2 in a muffle furnace at an average heating rate of 9 °C / min to 800 °C for 3.5 h, the sintering atmosphere is air, then naturally cool to room temperature, and obtain the modified precursor material after pulverization;

[0102] 4. Mix the modified precursor material with 10.45 mol of LiOH·H2O;

[0103] 5. Keep the mixed powder in step 4 under an atmosphere of 99% oxygen at 500 °C for 2 h, then raise the temperature to 650 °C and sinter for 10 h, and then naturally cool to room temperature. After pulverization, the high-nickel single-crystal cathode material LiNi 0.95 Co 0.02 Mn 0.03 (Li 0.34 La 0.51 TiO 2.94 ) 0.005 O2 can be obtained.

[0104] Example 8:

[0105] The preparation process of the material in this example includes the following steps:

[0106] 1. Take 10 mol of Ni 2 / g, D 50 with a BET of 8 m 0.95 Co 0.02 Al 0.03 (OH)2 and dissolve it in water. Then add 35 g of sucrose, 1.049 g of LiOH·H2O, 2.4435 g of La2O3, and 1.3291 g of Nb2O5 thereto, and stir well.

[0107] 2. Heat and stir the uniformly mixed slurry in step 1 at 60 °C until the slurry becomes gel-like, and then evaporate it to dryness.

[0108] 3. Sinter the powder material obtained in step 2 in a muffle furnace at an average heating rate of 8 °C / min to 800 °C for 4 h. The sintering atmosphere is air, and then naturally cool to room temperature. After pulverization, the modified precursor material is obtained.

[0109] 4. Mix the modified precursor material with 10.50 mol of LiOH·H2O.

[0110] 5. Keep the mixed powder in step 4 under an atmosphere of 99% oxygen at 500 °C for 2 h, then raise the temperature to 650 °C and sinter for 7 h, and then naturally cool to room temperature. After pulverization, the high-nickel single-crystal cathode material LiNi 0.95 Co 0.02 Al 0.03 (Li5La3Nb2O 12 ) 0.0005 O2 can be obtained.

[0111] Comparative Example 1:

[0112] The preparation process of the material in this comparative example includes the following steps:

[0113] 1. Take 10 mol of NiCoMn(OH)₂ with a BET of 7 m² / g and a D of 5 μm and mix it with 10.35 mol of LiOH·H₂O; 2 / g, D 50 being 5 μm of Ni 0.83 Co 0.12 Mn 0.05 (OH)₂ and mix it with 10.35 mol of LiOH·H₂O;

[0114] 2. Keep the mixed powder in step 1 at 450 °C for 2 h in an atmosphere of 98% oxygen, then raise the temperature to 750 °C and sinter for 8 h, and then naturally cool to room temperature. After pulverization, the cathode material LiNiCoMnO₂ can be obtained. 0.83 Co 0.12 Mn 0.05 O₂.

[0115] Comparative Example 2:

[0116] The preparation process of the material in this comparative example includes the following steps:

[0117] 1. Take 10 mol of NiCoMn(OH)₂ with a BET of 7 m² / g and a D of 5 μm, mix it with 10.35 mol of LiOH·H₂O, and then mix it with 1.3735 g of LiOH·H₂O, 2.4435 g of La₂O₃, 1.2322 g of ZrO₂ and 0.0703 g of Ga₂O₃; 2 / g, D 50 being 5 μm of Ni 0.83 Co 0.12 Mn 0.05 (OH)₂ and 10.35 mol of LiOH·H₂O, and then mix it with 1.3735 g of LiOH·H₂O, 2.4435 g of La₂O₃, 1.2322 g of ZrO₂ and 0.0703 g of Ga₂O₃;

[0118] 2. Keep the mixed powder in step 1 at 450 °C for 2 h in an atmosphere of 98% oxygen, then raise the temperature to 750 °C and sinter for 8 h, and then naturally cool to room temperature. After pulverization, the cathode material LiNiCoMn(La₃Zr₂Ga)O₂ doped with three elements of La, Zr and Ga can be obtained. 0.83 Co 0.12 Mn 0.05 (La₃Zr₂Ga 0.15 ) 0.0005 O₂.

[0119] Comparative Example 3:

[0120] The preparation process of the material in this comparative example includes the following steps:

[0121] 1. Take 10 mol of NiCoMn(OH)₂ with a BET of 7 m² / g and a D of 5 μm and mix it with 10.35 mol of LiOH·H₂O; 2 / g, D 50 being 5 μm of Ni 0.83 Co 0.12 Mn 0.05 (OH)₂ and mix it with 10.35 mol of LiOH·H₂O;

[0122] 2. Keep the mixed powder in step 1 under an oxygen atmosphere of 98% and heat it at 450 °C for 2 h, then raise the temperature to 8000 °C and sinter for 12 h, and then cool it naturally to room temperature. After pulverization, the high-nickel single-crystal cathode material LiNi 0.83 Co 0.12 Mn 0.05 O2 can be obtained.

[0123] Comparative Example 4:

[0124] The preparation process of the material in this comparative example includes the following steps:

[0125] 1. Take 10 mol, with a BET of 7 m 2 / g and a D 50 of 5 μm for Ni 0.83 Co 0.12 Mn 0.05 (OH)2 and 10.35 mol of LiOH·H2O are mixed, and then mixed with 1.3735 g of LiOH·H2O, 2.4435 g of La2O3, 1.2322 g of ZrO2, and 0.0703 g of Ga2O3;

[0126] 2. Keep the mixed powder in step 1 under an oxygen atmosphere of 98% and heat it at 450 °C for 2 h, then raise the temperature to 790 °C and sinter for 12 h, and then cool it naturally to room temperature. After pulverization, the high-nickel single-crystal cathode material LiNi 0.83 Co 0.12 Mn 0.05 (La3Zr2Ga 0.15 ) 0.0005 O2 can be obtained.

[0127] Comparative Example 5:

[0128] The preparation process of the material in this comparative example includes the following steps:

[0129] 1. Take 10 mol, with a BET of 7 m 2 / g and a D 50 of 5 μm for Ni 0.83 Co 0.12 Mn 0.05 (OH)2 is dissolved in water, and 30 g of citric acid, 1.3735 g of LiOH·H2O, 2.4435 g of La2O3, 1.2322 g of ZrO2, and 0.0703 g of Ga2O3 are added thereto, and stirred well;

[0130] 2. Heat and stir the uniformly mixed slurry in step 1 at 65 °C, and evaporate it to dryness after the slurry becomes gel-like;

[0131] 3. Heat the powder material obtained in step 2 in a muffle furnace at an average heating rate of 2 °C / min to 850 °C and sinter for 3.5 h. The sintering atmosphere is air, then naturally cool to room temperature, and obtain the modified precursor material after pulverization;

[0132] 4. Mix the modified precursor material with 10.35 mol of LiOH·H2O;

[0133] 5. Keep the mixed powder in step 4 at 450 °C for 2 h in an atmosphere of 98% oxygen, then heat up to 750 °C and sinter for 8 h, then naturally cool to room temperature, and obtain the high-nickel cathode material LiNi 0.83 Co 0.12 Mn 0.05 (Li 6.55 La3Zr2Ga 0.15 O 12 ) 0.0005 O2 after pulverization.

Claims

1. A preparation method of a high-nickel single-crystal cathode material for a lithium-ion battery, characterized in that, It includes the following steps: (1) Disperse the hydroxide precursor and the flocculant in water, add the modifier thereto, and stir the mixed slurry evenly; (2) Stir and heat the evenly mixed slurry at a certain temperature, then evaporate the slurry to dryness, and subject the obtained powder to high-temperature sintering to obtain the modified polycrystalline precursor material; in step (2), the powder after flocculation and drying is heated at a heating rate of 8 °C / min or more; (3) Mix the modified precursor material and the lithium source, and perform secondary sintering in an oxygen-containing atmosphere to obtain the high-nickel single-crystal cathode material; The modifier in step (1) is a compound comprising elements Li, O, La, and element B. After sintering, the modifier will generate a fast ion conductor that allows lithium to pass through quickly. The structural general formula of the fast ion conductor is Li t La u B w O p , where 0.3 ≤ t ≤ 7, 0.5 ≤ u ≤ 5, 1 ≤ w ≤ 3, 2 ≤ p ≤ 12, and element B is one or more of Zr, Ti, Al, Ba, Ga, Ta, and Nb; The hydroxide precursor in step (1) is Ni x Co y M z (OH)2, where x≥0.75, 0≤y≤0.25, 0≤z≤0.25, and x + y + z = 1, and the M element is one or more of Mn, Al, and Ti.

2. The preparation method according to claim 1, characterized in that, In step (1), the precursor is a polycrystalline secondary spherical particle formed by the agglomeration of primary particles, and its BET is 4-10 m 2 / g.

3. The preparation method according to claim 2, characterized in that, The precursor BET in step (1) is 6 - 8 m 2 / g.

4. The preparation method according to claim 1, characterized in that, The particle size D of the precursor in step (1) 50 is 3 to 8 μm.

5. The preparation method according to claim 4, characterized in that, The particle size D of the precursor in step (1) 50 is 4 to 6 μm.

6. The preparation method according to claim 1, wherein The modifier is a compound or a combination of compounds.

7. The preparation method according to claim 6, characterized in that, The modifier is a combination of compounds.

8. The preparation method according to claim 1, wherein The fast ion conductor is Li7La3Zr2O 12 , Li6BaLa2Ta2O 12 , Li5La3Nb2O 12 , Li5La3Ta2O 12 , Li 0.34 La 0.51 TiO 2.94 or a fast ion conductor containing other B elements as doping elements.

9. The preparation method according to claim 1, characterized in that, The fast ion conductor is Li7La3Zr2O 12 、Li 6.5 Al 0.3 La3Zr 1.9 O 12 、Li 6.55 La3Zr2Ga 0.15 O 12 、Li6BaLa2Ta2O 12 、Li5La3Nb2O 12 、Li5La3Ta2O 12 、Li 0.34 La 0.51 TiO 2.94 or one or more of the following 10. The preparation method according to claim 1, wherein, The addition amounts of each A element and lithium element in the modifier are added according to the molar ratio of each element in the target fast ion conductor.

11. The preparation method according to claim 1, wherein, Based on the molar amount of the hydroxide precursor, the molar fraction of the generated amount of the target compound in the modifier is 0.0001 to 0.

005.

12. The preparation method according to claim 1, characterized in that, In step (1), the addition amount of the flocculant is 1% to 5% of the mass of the hydroxide precursor.

13. According to the preparation method described in claim 1, it is characterized in that, The flocculant in step (1) is one or more of citric acid, glucose, maleic acid, oxalic acid, and sucrose.

14. The preparation method according to claim 1, wherein, In the step (2), the mixed slurry of the precursor, the modifier, and the flocculant is heated to 50 to 80 °C for flocculation, and after the slurry becomes gel-like, it is dried.

15. The preparation method according to claim 1, characterized in that, In step (2), the powder after flocculation and drying is rapidly heated for sintering.

16. The preparation method according to claim 1, wherein In the step (2), the sintering temperature is 700 to 1000 °C, and the sintering time is 2 to 5 h.

17. The preparation method according to claim 16, wherein, In the step (2), the sintering temperature is 800 to 900 °C, and the sintering time is 2.5 to 4 h.

18. The preparation method according to claim 1, characterized in that, In step (2), the sintering atmosphere is an oxygen-containing atmosphere.

19. The preparation method according to claim 1, wherein In step (2), the maximum heating rate of the powder after flocculation and drying does not exceed 25 °C / min.

20. The preparation method according to claim 19, wherein In step (2), the powder after flocculation and drying is heated at a heating rate of 8 to 20 °C / min.

21. The preparation method according to claim 1, characterized in that, In the step (3), the lithium source is selected from lithium carbonate, lithium hydroxide, and lithium hydroxide monohydrate.

22. The preparation method according to claim 21, wherein, In the step (3), the lithium source is selected from lithium hydroxide monohydrate.

23. The preparation method according to claim 1, characterized in that, In step (3), the addition amount of the lithium source is added according to the molar ratio Li / (Ni + Co + M) = 1.005 to 1.05 with the metal elements in the precursor.

24. The preparation method according to claim 1, characterized in that, In step (3), the oxygen-containing atmosphere is air or oxygen.

25. The preparation method according to claim 24, characterized in that, In step (3), the oxygen-containing atmosphere is an atmosphere with an oxygen content of 95% or more.

26. The preparation method according to claim 1, characterized in that, In step (3), the sintering temperature is not higher than the sintering temperature in step (2).

27. The preparation method according to claim 1, characterized in that, In the step (3), first keep it at 300 to 500 °C for 1 to 3 h, then raise the temperature to 600 to 800 °C for sintering for 6 to 10 h, and finally naturally cool to room temperature.

28. The preparation method according to claim 27, wherein In the step (3), first keep it at 300 to 500 °C for 1 to 3 h, then raise the temperature to 650 - 800 °C for sintering for 6 to 10 h, and finally naturally cool to room temperature.

29. A high-nickel single-crystal cathode material prepared by the preparation method according to any one of claims 1-28, the chemical formula of the material being LiNi x Co y M z (Li t La u B w O p ) ζ O2, wherein, x≥0.75, 0≤y≤0.25, 0≤z≤0.25, 0.3≤t≤7, 0.5≤u≤5, 1≤w≤3, 2≤p≤12, 0.0001≤ζ≤0.005, and x + y + z = 1; Element M is one or more of Mn, Al, and Ti, and element B is a combination of one or more elements among Zr, Ti, Al, Ba, Ga, Ta, and Nb.

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