A ternary cathode material, its preparation method and application

Abstract

This invention discloses a ternary cathode material, its preparation method, and its applications, relating to the field of lithium battery technology. The ternary cathode material provided by this invention has the following characteristics: the proportion of secondary particles in particles with a longest Freret diameter of Dv90 or greater is greater than or equal to 30%; the cumulative volume percentage corresponding to the most frequent particle size Dm is less than 70%; the powder flow rate S is 4s / 50g~20s / 50g; and after 3T pressing, Dv5 / Dm... 3T The value range is 0.2~0.6. Ternary cathode materials that meet the above characteristics not only have high compaction density, but also have small particles of powder that deviate from the most frequent particles after being rolled, making them less prone to contact failure and pulverization, thus improving the cycle stability of the battery.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and more specifically, to a ternary cathode material, its preparation method, and its application. Background Technology

[0002] Lithium nickel cobalt manganese oxide (NCM) ternary cathode materials have become one of the mainstream power battery cathode materials due to their advantages such as high specific capacity, high discharge voltage, high energy density, and good rate performance. They can provide new energy vehicles with longer driving range and faster charging speeds, occupying a significant market share. Compared to secondary spherical ternary cathode materials, single-crystal ternary cathode materials have higher compressive strength, which prevents intergranular cracks caused by long-cycle strain accumulation, thereby improving cycle performance.

[0003] Currently, ternary single crystal materials have poor particle uniformity, and the particles have many edges and low sphericity, which makes them easy to break during the rolling preparation of electrodes, or the edges and corners are stress concentration points that are prone to cracking during cycling, thereby reducing cycling performance.

[0004] Therefore, there is an urgent need to provide ternary cathode materials with high compaction density and good cycle performance.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a ternary cathode material, its preparation method and application, aiming to simultaneously improve the compaction density and cycle stability of the ternary cathode material, thereby improving the volumetric capacity and cycle stability.

[0007] This invention is implemented as follows:

[0008] In a first aspect, the present invention provides a ternary cathode material comprising primary particles and secondary particles formed by the agglomeration of primary particles, and simultaneously satisfying conditions (1)-(4):

[0009] Condition (1): The ratio of secondary particles to the total number of particles in particles with the longest Freette diameter of Dv90 or more is 30% to 100%; Dv90 refers to the particle size value corresponding to when the cumulative volume distribution of particles in the particle size distribution curve reaches 90%.

[0010] Condition (2): In the particle size distribution curve, the cumulative volume percentage corresponding to the most frequent particle size Dm is less than 70%. The most frequent particle size Dm refers to the particle size value corresponding to the largest volume percentage in the particle size distribution curve.

[0011] Condition (3): Powder flow rate S is 4s / 50g~20s / 50g;

[0012] Condition (4): The most frequent particle size after 3T suppression is Dm 3TAfter 3T compression, Dv5 / Dm 3T The value range is 0.2 to 0.6.

[0013] In an optional implementation, the ternary single-crystal cathode material satisfies at least one of the following characteristics A1-D1:

[0014] Feature A1: Particle size distribution width span is 1.05~1.40;

[0015] Feature B1: Dv5 after 3T compression is 1μm~3μm;

[0016] Feature C1: Dm after 3T suppression 3T The thickness ranges from 3μm to 8μm.

[0017] Feature D1: Compacted density is 2.7 g / cm³ 3 ~3.5g / cm 3 .

[0018] Secondly, the present invention provides a method for preparing the ternary cathode material according to the aforementioned embodiments, comprising:

[0019] Nickel source, cobalt source, manganese source and solvent are mixed and dissolved to obtain metal mixture liquid; the metal mixture liquid is sprayed and pyrolyzed in a spray pyrolysis device equipped with a gas-solid separation device, a first metal oxide solid solution is obtained at the bottom of the gas-solid separation device, and a second metal oxide solid solution is obtained at the top of the gas-solid separation device.

[0020] A carbonate precursor was prepared by using a second metal oxide solid solution as a seed crystal for precipitation reaction.

[0021] A first metal oxide solid solution is mixed with a first lithium source and subjected to a first sintering to obtain a first particle; a carbonate precursor is mixed with a second lithium source and subjected to a second sintering to obtain a second particle.

[0022] The first particle is mixed with the second particle to prepare the cathode material.

[0023] In an optional embodiment, the metal mixture is sprayed from the atomizer of the spray pyrolysis apparatus into the reactor, and then enters the gas-solid separation device. The large particles output from the bottom of the gas-solid separation device are crushed and dried to obtain the first metal oxide solid solution. The small particles collected after the gas flow output from the top of the gas-solid separation device are the second metal oxide solid solution.

[0024] In an optional embodiment, the process for preparing the first metal oxide solid solution and the second metal oxide solid solution has at least one of the following features A2-G2:

[0025] Feature A2: The spray pyrolysis temperature is 600℃~1000℃, and the spray pyrolysis time is 4h~8h;

[0026] Feature B2: The particle size of the first metal oxide solid solution is 200 nm to 3000 nm, and the distribution width is 2.4 to 3.8.

[0027] Characteristic C2: The particle size Dv50 of the second metal oxide solid solution is 1000nm~2000nm, and the distribution width span is 1.2~2.0;

[0028] Feature D2: Large particles output from the bottom of the gas-solid separation device are immersed in water below 60°C for water-cooled crushing;

[0029] Feature E2: By adjusting the amounts of nickel, cobalt, and manganese sources, the molar ratio of nickel, cobalt, and manganese is made to be (0.35~0.8):(0.1~0.35):(0.1~0.35).

[0030] Feature F2: When preparing the metal mixture, a doped metal salt is also added. The doped metal is selected from at least one of Y, Ln, V, Re, Zr, Ti, Ca, Mg, W and Al. The amount of doped metal salt added is based on the content of the doped element in the cathode material being 0~1000ppm.

[0031] Feature G2: The nickel source, cobalt source, manganese source, and doped metal salt are all soluble salts, and the solvent is water.

[0032] In an optional embodiment, the process of preparing the carbonate precursor includes: mixing a second metal oxide solid solution, a precipitant solution, and a complexing agent solution to obtain a base liquid; passing a salt solution, a precipitant solution, and a complexing agent solution into the base liquid to carry out a precipitation reaction; reacting until the particle Dv50 reaches 3μm~8μm, and then stopping the feed; wherein the salt solution contains nickel salt, cobalt salt, and manganese salt.

[0033] In an optional embodiment, the process for preparing the carbonate precursor has at least one of the following features A3-J3:

[0034] Feature A3: By adjusting the flow rate of the precipitant solution, the reaction pH is maintained at 10-12; by controlling the flow rate of the complexing agent solution, the ammonia concentration is maintained at 6g / L-10g / L.

[0035] Feature B3: Control the precipitation reaction temperature to 70℃~90℃;

[0036] Feature C3: In the base solution, the concentration of the second metal oxide solid solution is 50 g / L to 70 g / L, the pH value of the base solution is 10 to 12, and the ammonia concentration is 6 g / L to 10 g / L;

[0037] Feature D3: The flow rate of the salt solution is 1 L / h to 5 L / h;

[0038] Feature E3: The molar ratio of Ni, Co, and Mn in the salt solution is (0.35~0.8):(0.1~0.35):(0.1~0.35).

[0039] Characteristic F3: The total concentration of metal ions in the salt solution is 1.5 mol / L to 2.5 mol / L;

[0040] Feature G3: During the sedimentation process, the stirring rate is controlled at 500 rpm to 800 rpm;

[0041] Characteristic H3: The precipitant solution is a carbonate solution, and the carbonate is selected from at least one of sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate; the concentration of the precipitant solution is 1.5 mol / L to 3 mol / L;

[0042] Feature I3: The complexing agent solution is an ammonia solution;

[0043] Feature J3: After stopping the feeding, solid-liquid separation is performed, and the obtained solid material is washed and dried.

[0044] In an optional embodiment, the sintering temperature of the first sintering is 800℃~1000℃, and the time is 8h~12h;

[0045] And / or, the second sintering includes: first sintering at 600℃~800℃ for 4h~6h, and then sintering at 800℃~1000℃ for 2h~4h;

[0046] And / or, the molar ratio of lithium in the first lithium source to the total amount of metal in the first metal oxide solid solution is (1.05~1.10):1;

[0047] And / or, the first lithium source and the first metal oxide solid solution are mixed using a wet method;

[0048] And / or, the molar ratio of lithium in the second lithium source to the total amount of metal in the carbonate precursor is (1.05~1.10):1;

[0049] And / or, the first lithium source is selected from at least one of lithium hydroxide, lithium oxalate and lithium acetate;

[0050] And / or, the second lithium source is selected from at least one of lithium carbonate, lithium hydroxide and lithium acetate;

[0051] And / or, in the total amount of the first particle and the second particle, the mass percentage of the first particle is 20%-80%;

[0052] And / or, the first and second particles are mixed and then crushed, sieved and demagnetized to obtain the positive electrode material.

[0053] Thirdly, the present invention provides a positive electrode sheet, comprising any of the ternary positive electrode materials in the foregoing embodiments or ternary positive electrode materials prepared by any of the preparation methods in the foregoing embodiments.

[0054] Fourthly, the present invention provides a lithium battery including the positive electrode sheet of the aforementioned embodiments.

[0055] The present invention has the following beneficial effects: The ternary cathode material provided by the present invention has the following characteristics: the proportion of secondary particles in particles with the longest Freret diameter of Dv90 or more is greater than or equal to 30%; the cumulative volume percentage corresponding to the most frequent particle size Dm is less than 70%; the powder flow rate S is 4s / 50g~20s / 50g; and the Dv5 / Dm ratio after 3T pressing is... 3T The value range is 0.2~0.6. Ternary cathode materials that meet the above characteristics not only have high compaction density, but also have a small degree of deviation of small powder particles from the most frequent particles after the cathode material particles are rolled, and are not prone to contact failure or pulverization and detachment, which is conducive to improving cycle stability. Attached Figure Description

[0056] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0057] Figure 1 SEM image of the cathode material prepared in Example 1;

[0058] Figure 2 This is a SEM image of the cathode material prepared in Example 7. Detailed Implementation

[0059] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0060] Theoretically, to maximize the energy density of a battery, a high compaction density positive electrode sheet can be fabricated. Therefore, increasing the rolling pressure and the content of the positive electrode material in the positive electrode film can achieve this goal. However, under high rolling pressure, the positive electrode material may fracture, potentially leading to contact failure. Furthermore, the fractured coating may cause intensified reaction with the electrolyte, resulting in battery failure and reduced cycle stability. Therefore, simultaneously improving the compaction density and cycle stability of ternary positive electrode materials requires optimized design of the material's structure and morphology.

[0061] Therefore, this invention provides a ternary cathode material comprising primary particles and secondary particles formed by the agglomeration of primary particles, and simultaneously satisfying conditions (1)-(4):

[0062] Condition (1): The ratio of secondary particles to the total number of particles in particles with a longest Feret diameter of Dv90 or greater is 30% to 100%, such as 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, etc. Dv90 refers to the particle size value corresponding to 90% of the cumulative volume distribution of particles in the particle size distribution curve, typically obtained by laser diffraction. Particles with a longest Feret diameter greater than Dv90 include secondary particles and primary particles. Secondary particles are formed by partial grain boundary fusion of primary particles or agglomeration through van der Waals forces. The compactness of the primary particles in the secondary particles is usually greater than the packing density of these primary particles individually. Such secondary particles are generally beneficial to improving the compaction density of the material. The inventors found that when the proportion of secondary particles is greater than or equal to 30%, the compaction density of the cathode material can be effectively improved.

[0063] Condition (2): In the particle size distribution curve, the cumulative volume percentage corresponding to the most frequent particle size Dm is less than 70%. The most frequent particle size Dm refers to the particle size corresponding to the point with the highest volume percentage in the particle size distribution curve. The cumulative volume percentage corresponding to the most frequent particle size Dm can be 69%, 65%, 60%, 50%, 40%, 30%, 20%, 10%, etc.

[0064] Condition (3): The powder flow rate S is 4s / 50g~20s / 50g, such as 4s / 50g, 5s / 50g, 8s / 50g, 10s / 50g, 13s / 50g, 15s / 50g, 18s / 50g, 20s / 50g, etc. The contact mode of the cathode material particles has an important influence on its compaction density. The contact mode of the particles is closely related to their roundness, surface roughness, particle size and distribution. The cathode material particle flow rate S provided by this invention is 4s / 50g~20s / 50g. When it is higher than 20s / 50g, the rolling resistance of the powder is too large, indicating that the roundness of the powder is poor, and / or the particle surface is relatively rough, and / or there is too much fine powder. All of the above are not conducive to improving the degree of contact. When it is lower than 4s / 50g, it indicates that the particle size of the powder is large, and the reduced specific surface area is not conducive to improving the rate performance of the material. Therefore, the powder flow rate S of the ternary cathode material provided by this invention is 4s / 50g to 20s / 50g, which is beneficial to balance the compaction density and rate performance of the ternary cathode material.

[0065] Condition (4): The most frequent particle size after 3T suppression is Dm 3T After 3T compression, Dv5 / Dm 3T The value range is 0.2~0.6, such as 0.2, 0.3, 0.4, 0.5, 0.6, etc. Specifically, the particle size distribution curves of the cathode material after 3T pressing are analyzed to obtain Dv5 and Dm. 3T Compressed Dv5 / Dm 3T This reflects the degree to which the small particles in the electrode deviate from the particles with the highest volume percentage content, and meets the Dv5 / Dm requirement after pressing. 3T A value of 0.2 to 0.6 indicates that after the cathode material particles are rolled, the small particles deviate little from the most frequent particles, making it less prone to contact failure and pulverization, thus improving cycle stability.

[0066] In some embodiments, the particle size distribution width of the ternary cathode material is 1.05~1.40, such as 1.05, 1.10, 1.20, 1.30, 1.40, etc. The particle size distribution width within this range indicates that the particle size of the cathode material is relatively uniform.

[0067] In some embodiments, the Dv5 after 3T pressing is 1μm~3μm, such as 1.0μm, 1.5μm, 2.0μm, 2.5μm, 3.0μm, etc.; the Dm after 3T pressing 3T The thickness ranges from 3μm to 8μm, and can be 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, etc. After 3T pressing, Dv5 and Dm... 3T Within the above range, the degree to which the small particles of the cathode material deviate from the most frequent particles after being rolled is smaller, which is beneficial to further improve cycle stability.

[0068] In some embodiments, the compaction density of the ternary cathode material is 2.7 g / cm³. 3 ~3.5g / cm 3 For example, it can be 2.7g / cm 3 3.0g / cm 3 3.2g / cm 3 3.5g / cm 3 It has a high compaction density.

[0069] This invention provides a method for preparing a ternary cathode material, comprising the following steps:

[0070] S1, spray pyrolysis

[0071] Nickel, cobalt, and manganese sources are dissolved in a solvent and stirred until homogeneous to obtain a metal mixture. Spray pyrolysis is performed using a spray pyrolysis apparatus equipped with a gas-solid separation device. The metal mixture is sprayed from the atomizer of the spray pyrolysis apparatus into the reaction furnace, and then enters the gas-solid separation device. Large particles are output from the bottom of the gas-solid separation device, and after crushing and drying, a first metal oxide solid solution is obtained. The gas flow output from the top of the gas-solid separation device is filtered, and the small particles collected are the second metal oxide solid solution.

[0072] Specifically, the gas-solid separation device can be a cyclone separator, but is not limited to this. The specific model of the spray pyrolysis apparatus equipped with the gas-solid separation device is not limited; it can be a commercially available spray pyrolysis apparatus.

[0073] In some embodiments, the spray pyrolysis temperature is 600℃~1000℃ (e.g., 600℃, 700℃, 800℃, 900℃, 1000℃, etc.), and the spray pyrolysis time is 4h~8h (e.g., 4h, 5h, 6h, 7h, 8h, etc.). At this pyrolysis temperature, it is beneficial to prepare hollow spheres of metal oxides.

[0074] In some embodiments, large particles output from the bottom of the gas-solid separator can be crushed using water-cooled crushing. Large particles at the bottom of the cyclone separator are then water-cooled while still hot (above 300°C) and subsequently dried to obtain a first metal oxide solid solution. Water-cooled crushing can involve transferring the large particles to deionized water below 60°C; alternatively, high-pressure water (deionized water below 60°C) can be applied to wash the powder as it falls under its own gravity.

[0075] It should be noted that oxides, as precursors, do not require dehydroxylation and decarburization, thus exhibiting high sintering activity and readily yielding large particles. Furthermore, grain boundary fusion easily occurs between particles, and controlled conditions are beneficial for preparing secondary particles with partial grain boundary fusion. However, spray pyrolysis preparation of metal oxides tends to produce hollow spheres (especially large particles), thus requiring improvement. This invention utilizes water-cooled crushing to break down large particles, washing away elements such as sulfur, chlorine, or nitrogen, while simultaneously disrupting the hollow structure of the large particles. This results in particles broken into a first metal oxide solid solution with a smaller particle size and wider distribution, facilitating grain boundary fusion during sintering to obtain the first particles.

[0076] In some embodiments, the particle size of the first metal oxide solid solution is 200 nm to 3000 nm, such as 200 nm, 500 nm, 800 nm, 1000 nm, 1500 nm, 2000 nm, 2500 nm, 3000 nm, etc.; the distribution width of the first metal oxide solid solution is 2.4 to 3.8, such as 2.4, 2.8, 3.0, 3.5, 3.8, etc. The particle size Dv50 of the second metal oxide solid solution is 1000 nm to 2000 nm, such as 1000 nm, 1300 nm, 1500 nm, 1800 nm, 2000 nm, etc.; the distribution width of the second metal oxide solid solution is 1.2 to 2.0, such as 1.2, 1.5, 1.8, 2.0, etc.

[0077] In some embodiments, when preparing the metal mixture, the molar ratio of nickel, cobalt, and manganese is adjusted to (0.35~0.8):(0.1~0.35):(0.1~0.35) by controlling the amount of nickel source, cobalt source, and manganese source. The molar ratio of nickel, cobalt, and manganese can be taken in a wide range and can be adjusted according to the product model.

[0078] In some embodiments, a doped metal salt is added during the preparation of the metal mixture. The doped metal is selected from at least one of Y, Ln, V, Re, Zr, Ti, Ca, Mg, W, and Al, and can be any one or more of these. The doping amount of the doped metal is not limited; for example, the amount of doped metal salt added can be based on the doping element content in the cathode material being 0~1000 ppm. The nickel source, cobalt source, manganese source, and doped metal salt can all be soluble salts, the anion can be sulfate, chloride, nitrate, etc., and the solvent can be water.

[0079] S2. Preparation of core-shell structured carbonate precursors (MO2@MCO3)

[0080] A second metal oxide solid solution was used as a seed crystal in a precipitation reaction to prepare a carbonate precursor. In this embodiment of the invention, particles with different sizes collected at different locations in the product collection system of the spray pyrolysis apparatus were processed separately. Using the smaller particles as seed crystals to prepare the carbonate precursor helps improve the uniformity of the carbonate precursor's particle size distribution and sphericity.

[0081] It should be noted that carbonate precursors exhibit faster thermal shrinkage and greater shrinkage compared to hydroxide precursors, which is beneficial for obtaining particles with high sphericity. However, since the direct preparation of carbonate precursors via precipitation results in a wide particle size distribution and difficult morphology control, the addition of metal oxide solid solutions as seed crystals is beneficial for obtaining precursor particles with high sphericity and a lower particle size distribution.

[0082] In an optional embodiment, the process of preparing the carbonate precursor includes: adding a second metal oxide solid solution, a precipitant solution, and a complexing agent solution to a reaction vessel and mixing them evenly to obtain a bottom liquid; then, using a metering pump, introducing a salt solution containing nickel salt, cobalt salt, and manganese salt, the precipitant solution, and the complexing agent solution into the reaction vessel to carry out a precipitation reaction until the particle Dv50 reaches 3μm~8μm (e.g., 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, etc.); stopping the feed; separating the solid and liquid; and washing, drying, and sieving the obtained solid to obtain the precursor. The method of solid-liquid separation is not limited, and filtration may be used.

[0083] In some embodiments, the reaction pH is maintained at 10-12 (e.g., 10, 11, 12) by adjusting the flow rate of the precipitant solution; and the ammonia concentration is maintained at 6-10 g / L (e.g., 6 g / L, 7 g / L, 8 g / L, 9 g / L, 10 g / L) by controlling the flow rate of the complexing agent solution. By adjusting the pH and ammonia concentration, the particle growth rate is better controlled, resulting in uniform precursor particles.

[0084] In some embodiments, during the reaction process, the precipitation reaction temperature is controlled at 70℃~90℃, such as 70℃, 80℃, 90℃, etc. The total concentration of metal ions in the salt solution is 1.5mol / L~2.5mol / L, such as 1.5mol / L, 2.0mol / L, 2.5mol / L, etc., and the molar ratio of Ni, Co, and Mn in the salt solution is (0.35~0.8):(0.1~0.35):(0.1~0.35). The flow rate of the salt solution is 1L / h~5L / h, such as 1L / h, 2L / h, 3L / h, 4L / h, 5L / h, etc. The stirring rate is controlled at 500rpm~800rpm during precipitation, such as 500rpm, 600rpm, 700rpm, 800rpm, etc. By adjusting the above reaction conditions, the particle growth rate is prevented from being too fast, and the particle size of the precursor is better controlled.

[0085] In some embodiments, the concentration of the second metal oxide solid solution in the substrate is 50 g / L to 70 g / L, the pH value of the substrate is 10 to 12, and the ammonia concentration is 6 g / L to 10 g / L. The concentration of the second metal oxide solid solution, the pH value of the substrate, and the ammonia concentration are controlled to meet the reaction conditions for particle deposition. Specifically, the concentration of the second metal oxide solid solution in the substrate can be 50 g / L, 55 g / L, 60 g / L, 65 g / L, 70 g / L, etc.; the pH value of the substrate can be 10, 11, 12, etc.; and the ammonia concentration can be 6 g / L, 7 g / L, 8 g / L, 9 g / L, 10 g / L, etc.

[0086] In some embodiments, the precipitant solution is a carbonate solution, and the carbonate is selected from at least one of sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate; the carbonate can be any one or more of the above. The concentration of the precipitant solution is 1.5 mol / L to 3 mol / L, such as 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, 3.0 mol / L, etc. The complexing agent solution can be an ammonia solution, but is not limited thereto. The anions of the nickel salt, cobalt salt, and manganese salt are any one of sulfate, chloride, and nitrate.

[0087] S3, sinter separately

[0088] A first metal oxide solid solution is mixed with a first lithium source and subjected to a first sintering to obtain first particles; a carbonate precursor is mixed with a second lithium source and subjected to a second sintering to obtain second particles. Since the first metal oxide solid solution and the carbonate precursor require different sintering conditions, they are sintered separately.

[0089] In some embodiments, the sintering temperature of the first sintering is 800℃~1000℃, such as 800℃, 850℃, 900℃, 950℃, 1000℃, etc.; the sintering time is 8h~12h, such as 8h, 10h, 12h, etc. The molar ratio of lithium in the first lithium source to the total amount of metal in the first metal oxide solid solution is (1.05~1.10):1, such as 1.05:1, 1.06:1, 1.07:1, 1.08:1, 1.09:1, 1.10:1, etc. The first lithium source and the first metal oxide solid solution can be wet-mixed (i.e., mixed in a fluid medium) to improve the mixing uniformity of each phase.

[0090] In some embodiments, the second sintering includes: first sintering at 600℃~800℃ for 4h~6h, then sintering at 800℃~1000℃ for 2h~4h. The carbonate precursor and the second lithium source are first sintered at a low temperature, and then the temperature is increased to continue sintering at a high temperature to prevent particle breakage due to excessively high initial sintering temperature. Specifically, the temperature of the first stage sintering can be 600℃, 650℃, 700℃, 750℃, 800℃, etc., and the sintering time of the first stage can be 4h, 5h, 6h, etc.; the temperature of the second stage sintering can be 800℃, 850℃, 900℃, 950℃, 1000℃, etc., and the sintering time of the second stage can be 2h, 3h, 4h, etc. The molar ratio of lithium in the second lithium source to the total amount of metal in the carbonate precursor is (1.05~1.10):1, such as 1.05:1, 1.06:1, 1.07:1, 1.08:1, 1.09:1, 1.10:1, etc.

[0091] Furthermore, the first lithium source is selected from at least one of lithium hydroxide, lithium oxalate, and lithium acetate, and the first lithium source can be any one or more of the above. The second lithium source is selected from at least one of lithium carbonate, lithium hydroxide, and lithium acetate, and the second lithium source can be any one or more of the above.

[0092] S4, graded

[0093] The first and second particles are mixed, and particle size distribution is achieved using the first and second particles to obtain the target ternary cathode material. This ternary cathode material has a high compaction density of 2.7 g / cm³. 3 ~3.5g / cm 3 In actual operation, the first and second particles are mixed, crushed, sieved, and demagnetized to obtain ternary cathode material.

[0094] In some embodiments, the mass percentage of the first particle in the total amount of the first particle and the second particle is 20%-80%, such as 20%, 30%, 40%, 50%, 60%, 70%, 80%, etc.

[0095] This invention also provides a positive electrode sheet, including the ternary positive electrode material provided in this invention, and may further include a positive current collector, with a positive active coating formed on at least one surface of the positive current collector, wherein the ternary positive electrode material exists as a positive active material in the positive active coating.

[0096] This invention also provides a lithium battery, including the positive electrode provided in this invention, and may further include a negative electrode, electrolyte, separator, etc. to form a complete battery structure with good cycle performance.

[0097] This invention provides a device including the aforementioned lithium battery. The lithium battery can serve as a power source for the device or as an energy storage unit. This device can be, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0098] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0099] The present invention provides Examples 1-12 and Comparative Examples 1-2 to characterize the cathode materials obtained in each example and comparative example and to test their performance parameters.

[0100] (1) SEM: The morphology of the ternary cathode material particles was characterized using a Nova NanoSEM 450 scanning electron microscope and SEM images were obtained. Then, the SEM images of the material particles were analyzed using ImageJ software to identify all particles with a maximum Feretta diameter greater than Dv90 (obtained by the laser particle size analyzer in test (2)) (sample size of at least 20 particles). The particles were classified into primary particles and secondary particles, and the proportion of secondary particles was calculated. Secondary particles are particles formed by the partial fusion of primary particles. Grain boundary fusion refers to the fusion of the boundaries of primary particles, which makes the boundaries blurred, smooth, dense, or even disappear. The "partial" in partial grain boundary fusion describes the degree of boundary fusion, which means that some clear boundaries can still be observed between primary particles. Feretta diameter refers to the distance between the parallel lines of the two boundaries of the particle projection profile measured along a certain direction. The maximum Feretta diameter refers to the distance between the largest parallel lines.

[0101] (2) Particle size: The particle size was determined in accordance with GB / T 19077-2016, including Dv90 before pressing and Dv5 and Dm after pressing.

[0102] (3) Compacted density: The test was conducted in accordance with GB / T 24533-2009, with a load of 3 tons (3T) and an applied pressure of 200MPa calculated based on the mold size. The particle size was then tested.

[0103] (4) Flow rate: Place the glass tube (60cm long, 1cm inner diameter) vertically to the ground, then seal the lower end of the glass tube with a coverslip. Load 50±0.01g of sample into the glass tube (60cm long, 1cm inner diameter) through a funnel. Remove the coverslip from the lower end of the glass tube to allow the powder to flow down naturally (if it does not fall naturally when the coverslip is removed, tap the area near the upper end 1-2 times). Record the time required for the powder to start falling and fall completely. Repeat the test 3 times for each sample and take the average value. The powder needs to be dried at 120℃ for 24h before the test.

[0104] (5) Electrochemical performance:

[0105] Battery assembly was performed according to GB / T 37207-2018, with some conditions selected as follows: positive electrode active material: carbon black conductive agent: graphite conductive agent: PVDF = 95:2:1:2; solid content of positive electrode slurry was 40%; and the designed compaction density of the electrode sheet was 4.2 g / cm³. 3 Unless otherwise specified, conditions shall be set in accordance with the general provisions of GB / T 37207-2018.

[0106] ① The assembled battery was subjected to cycle stability test according to GB / T 37207-2018. The cycle stability was evaluated by the discharge plateau capacity ratio (discharge capacity at potential U (3.6V) in the nth cycle ÷ discharge capacity at the end voltage (3V) in the nth cycle × 100%). The discharge rate was 0.2C and the test temperature was 25℃.

[0107] ② After the assembled battery is formed according to the method of GB / T 37207-2018, the constant current charge ratio at different rates is tested (= the amount of charge in the constant current stage ÷ the rated capacity of the battery × 100%), and the test temperature is 25℃.

[0108] Table 1 Summary of parameters of the cathode materials provided in the examples and comparative examples

[0109]

[0110] Note: "Agglomerate percentage" refers to the ratio of secondary particles to the total number of particles in particles with a longest Freette diameter of Dv90 or greater.

[0111] Table 2 Summary of performance data of the cathode materials provided in the examples and comparative examples

[0112]

[0113] The test results in Tables 1 and 2 show that the percentage of agglomerates in the cathode material, the cumulative volume percentage corresponding to Dm, the powder flow rate, and the Dv5 / Dm ratio after 3T pressing all contribute to the overall performance. 3T If any parameter exceeds the range defined in this invention, it may affect the cycle performance or compaction density of the cathode material.

[0114] The preparation methods for the above embodiments and comparative examples are as follows:

[0115] Example 1

[0116] The preparation method of the ternary cathode material in this embodiment includes the following steps:

[0117] (1) Preparation of metal oxide solid solutions

[0118] Nickel, cobalt, and manganese salts were dissolved in deionized water to obtain a salt solution with a total metal element concentration of 2M (i.e., 2 mol / L). Spray pyrolysis was performed using a spray pyrolysis apparatus equipped with a cyclone separator. Large particles collected at the bottom of the cyclone separator were transferred to deionized water at 30°C while hot (400~500°C) and stirred for 30 minutes. After solid-liquid separation, the solution was dried at 120°C to obtain the first metal oxide solid solution. Small particles collected by the airflow at the top of the cyclone separator through a filter (dust collector bag) were the second metal oxide solid solution.

[0119] Nickel salts, cobalt salts, and manganese salts are mixed in a Ni:Co:Mn molar ratio of 8:1:1. All nickel salts, cobalt salts, and manganese salts are sulfates.

[0120] The spray pyrolysis conditions are as follows: the carrier gas is argon, and the atomized droplets are fed into the pyrolysis tower at a flow rate of 5 L / min, and pyrolysis is carried out at 800℃ for 6 h.

[0121] The first metal oxide solid solution has a particle size of 200 nm to 3000 nm (overall particle size range) and a span of 3.24; the second metal oxide solid solution has a Dv50 of 1322 nm and a span of 1.67.

[0122] (2) Preparation of core-shell carbonate precursor (MO2@MCO3)

[0123] The second metal oxide solid solution was added to the reactor as a seed crystal. The bottom liquid in the reactor was 130L, the initial pH was 11, the ammonia concentration was 8g / L, and the seed crystal concentration was 50g / L. The second salt solution containing nickel salt, cobalt salt, and manganese salt, sodium carbonate solution, and ammonia water were introduced into the reactor through a metering pump to carry out the precipitation reaction. The flow rate of the precipitant solution was controlled to maintain the pH at 11, and the flow rate of the complexing agent solution was controlled to maintain the ammonia concentration at 8g / L. When the slurry particle Dv50 reached 4.28μm, the feeding was stopped, and the mixture was filtered, washed, dried, and sieved to obtain the carbonate precursor.

[0124] The precipitation reaction was carried out at a temperature of 85°C, with the flow rate of the second salt solution at 4 L / h and the stirring speed at 700 rpm.

[0125] The anions of nickel, cobalt, and manganese salts are sulfate. In the second salt solution, the molar ratio of Ni, Co, and Mn is 0.6:0.2:0.2, and the total concentration of metal ions in the second salt solution is 2 mol / L.

[0126] The concentration of the precipitant solution is 1.8 mol / L.

[0127] (3) Sinter separately

[0128] The first metal oxide solid solution and lithium hydroxide were dispersed in deionized water, the solvent was evaporated by heating, and then a first sintering was performed to obtain the first particles. The first sintering temperature was 900℃ and the time was 9h. The amount of lithium hydroxide added was according to a molar ratio of n(Li):n(TM) = 1.08:1, where TM represents the total amount of metal elements in the first metal oxide solid solution.

[0129] The carbonate precursor was mixed with lithium carbonate and then subjected to a second sintering process to obtain the second particles. The second sintering process was two-stage: the first stage was sintered at 600℃ for 5 hours, and the second stage was sintered at 900℃ for 3 hours.

[0130] The amount of lithium carbonate added is based on a molar ratio of n(Li):n(TM) = 1.08:1, where TM represents the total amount of metal elements in the carbonate precursor.

[0131] (4) The first particle and the second particle are mixed and pulverized by airflow at a mass ratio of 60:40, and then sieved and demagnetized to obtain the positive electrode material.

[0132] SEM image of the cathode material prepared in Example 1 is shown below. Figure 1 As shown in the figure, the dashed lines represent secondary particles, and the solid lines represent primary particles.

[0133] Example 2

[0134] The difference from Example 1 is that the first sintering temperature is 1000°C and the time is 12 hours; the first particles and the second particles are mixed at a mass ratio of 20:80.

[0135] Example 3

[0136] The difference from Example 1 is that the first sintering temperature is 800°C and the time is 8 hours. When preparing the first particles, the amount of lithium hydroxide added is according to the molar ratio n(Li):n(TM) = 1.1:1. The first particles and the second particles are mixed at a mass ratio of 80:20.

[0137] Example 4

[0138] The difference from Example 1 is as follows:

[0139] In step (1), the spray pyrolysis temperature is 1000℃, the particle size of the first metal oxide solid solution is 200nm~3000nm, and the span is 2.48; the Dv50 of the second metal oxide solid solution is 1147nm, and the span is 1.52.

[0140] In step (2), Dv50 reaches 4.17μm, and feeding is stopped.

[0141] In step (3), the temperature of the first sintering is 1000℃ and the time is 12h.

[0142] In step (4), the first particle and the second particle are mixed at a mass ratio of 20:80.

[0143] Example 5

[0144] The difference from Example 1 is as follows:

[0145] In step (1), the total concentration of metal elements in the salt solution is 1.5M, the particle size of the first metal oxide solid solution is 200nm~3000nm, and the span is 3.57; the Dv50 of the second metal oxide solid solution is 1058nm, and the span is 1.88.

[0146] In step (2), the seed concentration is 70 g / L, the Dv50 reaches 3.95 μm, and the feeding is stopped.

[0147] In step (3), the difference from Example 1 is that the first sintering temperature is 800℃ and the time is 12h, and the amount of lithium hydroxide added is according to the molar ratio n(Li):n(TM) = 1.1:1; the second sintering is a two-stage process, the first stage is heated to 600℃ and sintered for 6h, and the second stage is heated to 1000℃ and sintered for 3h. The amount of lithium carbonate added is according to the molar ratio n(Li):n(TM) = 1.1:1.

[0148] Step (4) is the same as in Example 1.

[0149] Example 6

[0150] Step (1) is the same as in Example 1.

[0151] Step (2) differs from Example 1 in that the ammonia concentration is 6 g / L, the reaction temperature is 90°C, the stirring speed is 500 rpm, the precipitant concentration is 1.5 M, and the Dv50 reaches 4.43 μm before the feed is stopped.

[0152] Step (3) differs from Example 1 in that the first sintering temperature is 1000℃ and the time is 12h; the second sintering is a two-stage process, with the first stage heated to 600℃ and sintered for 4h, and the second stage heated to 1000℃ and sintered for 4h.

[0153] Step (4) differs from Example 1 in that the first particle and the second particle are mixed at a mass ratio of 20:80.

[0154] Example 7

[0155] Step (1) is the same as in Example 1.

[0156] Step (2) differs from Example 1 in that the pH is 12, the Dv50 reaches 4.26 μm, and the feeding is stopped.

[0157] Step (3) differs from Example 1 in that the temperature of the first sintering is 800℃ and the time is 8h; the amount of lithium hydroxide added is fed according to the molar ratio n(Li):n(TM) = 1.1:1; the second sintering is a two-stage process, the first stage is heated to 800℃ and sintered for 4h, and the second stage is heated to 900℃ and sintered for 4h.

[0158] Step (4) differs from Example 1 in that the first particle and the second particle are mixed at a mass ratio of 80:20.

[0159] SEM image of the cathode material prepared in Example 7 is shown below. Figure 2 As shown.

[0160] Example 8

[0161] Step (1) is the same as in Example 1.

[0162] Step (2) differs from Example 1 in that the ammonia concentration is 6 g / L, the reaction temperature is 90°C, the stirring speed is 500 rpm, the precipitant concentration is 1.5 M, the Dv50 reaches 4.29 μm, and the feeding is stopped.

[0163] Step (3) differs from Example 1 in that the second sintering is a two-stage process. The first stage is heated to 600°C and sintered for 4 hours, and the second stage is heated to 1000°C and sintered for 4 hours.

[0164] Step (4) is the same as in Example 1.

[0165] Example 9

[0166] Step (1) is the same as in Example 1.

[0167] Step (2) differs from Example 1 in that the pH is 12, the Dv50 reaches 4.32 μm, and the feeding is stopped.

[0168] Step (3) is the same as in Example 1.

[0169] Step (4) is the same as in Example 1.

[0170] Example 10

[0171] The difference between step (1) and Example 1 is that the spray pyrolysis temperature is 600℃ and the time is 4h; the particle size of the first metal oxide solid solution is 200nm~3000nm and the span is 2.52; the Dv50 of the second metal oxide solid solution is 1847nm and the span is 1.44.

[0172] Step (2) differs from Example 1 in that the seed concentration is 70 g / L, the Dv50 reaches 6.58 μm, and the feeding is stopped.

[0173] Step (3) is the same as in Example 1.

[0174] Step (4) is the same as in Example 1.

[0175] Example 11

[0176] The difference between step (1) and Example 1 is that the total concentration of metal elements in the salt solution is 2.5M; the spray pyrolysis flow rate is 3L / min; the particle size of the first metal oxide solid solution is 200nm~3000nm and the span is 3.14; the Dv50 of the second metal oxide solid solution is 1026nm and the span is 1.35.

[0177] Step (2) differs from Example 1 in that the seed concentration is 30 g / L, the pH is 11, the Dv50 reaches 3.58 μm, and the feeding is stopped.

[0178] Step (3) is the same as in Example 1.

[0179] Step (4) is the same as in Example 1.

[0180] Example 12

[0181] Step (1) is the same as in Example 1.

[0182] Step (2) is the same as in Example 1.

[0183] Step (3) differs from Example 1 in that the first metal oxide solid solution is dry-mixed with lithium carbonate, followed by a first sintering to obtain the first particles. The first sintering temperature is 800℃, and the time is 10h. The amount of lithium carbonate added is based on a molar ratio of n(Li):n(TM) = 1.1:1.

[0184] Step (4) is the same as in Example 1.

[0185] Comparative Example 1

[0186] Step (1) is the same as in Example 1.

[0187] Step (2) differs from Example 1 in that all the metal oxide solid solution is added to the reactor as seed crystals, and the Dv50 reaches 5.24 μm, at which point the feeding is stopped.

[0188] The sintering conditions for step (3) are the same as those for the second sintering.

[0189] Step (4) involves airflow pulverization, sieving, and demagnetization to obtain the positive electrode material.

[0190] Comparative Example 2

[0191] Step (1) is the same as in Example 1.

[0192] Step (2) is omitted.

[0193] Step (3) Disperse all metal oxide solid solutions and lithium hydroxide in deionized water, heat to evaporate the solvent, and then sinter. Sintering conditions: sintering temperature is 1000℃, time is 12h, molar ratio n(Li):n(TM) = 1.1:1.

[0194] Step (4) involves airflow pulverization, sieving, and demagnetization to obtain the positive electrode material.

[0195] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A ternary cathode material, characterized in that, It includes primary particles and secondary particles formed by the agglomeration of the primary particles, and simultaneously satisfies conditions (1)-(4): Condition (1): The ratio of secondary particles to the total number of particles in particles with the longest Freette diameter of Dv90 or more is 30% to 100%. Dv90 refers to the particle size value corresponding to the cumulative volume distribution of particles in the particle size distribution curve reaching 90%. Condition (2): In the particle size distribution curve, the cumulative volume percentage corresponding to the most frequent particle size Dm is less than 70%. The most frequent particle size Dm refers to the particle size value corresponding to the largest volume percentage in the particle size distribution curve. Condition (3): Powder flow rate S is 4s / 50g~20s / 50g; Condition (4): The most frequent particle size after 3T suppression is Dm 3T After 3T compression, Dv5 / Dm 3T The value range is 0.2~0.6; the Dv5 after 3T compression is 1.00μm~1.90μm, and the Dm after 3T compression is... 3T The range is 3μm to 4.72μm.

2. The ternary cathode material according to claim 1, characterized in that, The ternary cathode material satisfies at least one of the following characteristics A1-B1: Feature A1: Particle size distribution width span is 1.05~1.40; Feature B1: Compacted density is 2.7 g / cm³ 3 ~3.5g / cm 3 .

3. A method for preparing the ternary cathode material according to claim 1 or 2, characterized in that, include: Nickel source, cobalt source, manganese source and solvent are mixed and dissolved to obtain metal mixture liquid; the metal mixture liquid is spray pyrolyzed in a spray pyrolysis device equipped with a gas-solid separation device, a first metal oxide solid solution is obtained at the bottom of the gas-solid separation device, and a second metal oxide solid solution is obtained at the top of the gas-solid separation device. The second metal oxide solid solution was used as a seed crystal to carry out a precipitation reaction to prepare a carbonate precursor. The first metal oxide solid solution is mixed with a first lithium source and subjected to a first sintering to obtain the first particles; the carbonate precursor is mixed with a second lithium source and subjected to a second sintering to obtain the second particles. The first particle and the second particle are mixed to prepare a positive electrode material.

4. The preparation method according to claim 3, characterized in that, The metal mixture is sprayed from the atomizer of the spray pyrolysis apparatus into the reaction furnace, and then enters the gas-solid separation device. The large particles output from the bottom of the gas-solid separation device are crushed and dried to obtain the first metal oxide solid solution. The small particles collected after the gas flow output from the top of the gas-solid separation device are the second metal oxide solid solution.

5. The preparation method according to claim 4, characterized in that, The process for preparing the first metal oxide solid solution and the second metal oxide solid solution has at least one of the following characteristics A2-G2: Feature A2: The spray pyrolysis temperature is 600℃~1000℃, and the spray pyrolysis time is 4h~8h; Feature B2: The particle size of the first metal oxide solid solution is 200nm~3000nm, and the distribution width is 2.4~3.

8. Feature C2: The particle size Dv50 of the second metal oxide solid solution is 1000nm~2000nm, and the distribution width span is 1.2~2.0; Feature D2: Large particles output from the bottom of the gas-solid separation device are immersed in water at a temperature below 60°C for water-cooled crushing; Feature E2: By adjusting the amounts of the nickel source, the cobalt source, and the manganese source, the molar ratio of nickel, cobalt, and manganese is made to be (0.35~0.8):(0.1~0.35):(0.1~0.35). Feature F2: When preparing the metal mixture, a doped metal salt is also added, wherein the doped metal is selected from at least one of Y, Ln, V, Re, Zr, Ti, Ca, Mg, W and Al; the amount of doped metal salt added is based on the content of the doped element in the cathode material being 0~1000ppm. Feature G2: The nickel source, the cobalt source, the manganese source and the doped metal salt are all soluble salts, and the solvent is water.

6. The preparation method according to claim 3, characterized in that, The process of preparing the carbonate precursor includes: mixing the second metal oxide solid solution, precipitant solution and complexing agent solution to obtain a base liquid; passing the salt solution, precipitant solution and complexing agent solution into the base liquid to carry out a precipitation reaction; stopping the feed when the particle Dv50 reaches 3μm~8μm; wherein the salt solution contains nickel salt, cobalt salt and manganese salt.

7. The preparation method according to claim 6, characterized in that, The process for preparing the carbonate precursor has at least one of the following characteristics A3-J3: Feature A3: By adjusting the flow rate of the precipitant solution, the reaction pH is maintained at 10-12; by controlling the flow rate of the complexing agent solution, the ammonia concentration is maintained at 6g / L-10g / L. feature B3: Control the precipitation reaction temperature to 70℃~90℃; Feature C3: In the bottom solution, the concentration of the second metal oxide solid solution is 50 g / L to 70 g / L, the pH value of the bottom solution is 10 to 12, and the ammonia concentration is 6 g / L to 10 g / L; Feature D3: The flow rate of the salt solution is 1 L / h to 5 L / h; Feature E3: The molar ratio of Ni, Co, and Mn in the salt solution is (0.35~0.8):(0.1~0.35):(0.1~0.35); feature F3: The total concentration of metal ions in the salt solution is 1.5 mol / L to 2.5 mol / L; feature G3: During the sedimentation process, control the stirring rate to 500 rpm to 800 rpm; Feature H3: The precipitant solution is a carbonate solution, and the carbonate is selected from at least one of sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate; the concentration of the precipitant solution is 1.5 mol / L to 3 mol / L; Feature I3: The complexing agent solution is an ammonia solution; Feature J3: After stopping the feeding, solid-liquid separation is performed, and the obtained solid material is washed and dried.

8. The preparation method according to claim 3, characterized in that, The sintering temperature of the first sintering is 800℃~1000℃, and the sintering time is 8h~12h; And / or, the second sintering includes: first sintering at 600℃~800℃ for 4h~6h, and then sintering at 800℃~1000℃ for 2h~4h; And / or, the molar ratio of lithium in the first lithium source to the total amount of metal in the first metal oxide solid solution is (1.05~1.10):1; And / or, the first lithium source and the first metal oxide solid solution are mixed using a wet method; And / or, the molar ratio of lithium in the second lithium source to the total amount of metal in the carbonate precursor is (1.05~1.10):1; And / or, the first lithium source is selected from at least one of lithium hydroxide, lithium oxalate and lithium acetate; And / or, the second lithium source is selected from at least one of lithium carbonate, lithium hydroxide, and lithium acetate; And / or, in the total amount of the first particle and the second particle, the mass percentage of the first particle is 20%-80%; And / or, the first particle and the second particle are mixed and then crushed, sieved and demagnetized to obtain the positive electrode material.

9. A positive electrode sheet, characterized in that, The ternary cathode material includes any one of the ternary cathode materials described in claims 1-2 or any one of the ternary cathode materials prepared by the preparation method described in claims 3-8.

10. A lithium battery, characterized in that, Includes the positive electrode sheet as described in claim 9.

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