Positive electrode material precursor and preparation method thereof, positive electrode material, battery and power-related equipment

Abstract

The invention provides a positive electrode material precursor and a preparation method thereof, a positive electrode material, a battery and electric equipment, and belongs to the field of batteries. The positive electrode material precursor provided by the invention comprises secondary particles formed by primary particles, and the particle size D50 of the secondary particles is 2.00 [mu] m-5. 00 [mu] m; the average value M of the length-width ratio a / b of the secondary particles is greater than or equal to 1.70, a is the length value of the long axis of the secondary particles, and b is the length value of the wide axis of the secondary particles. The positive electrode material precursor provided by the invention is relatively low in sintering energy consumption and easy to sinter into a single crystal, and after the positive electrode material is prepared into a battery, the increasing cycle performance requirement of an electric vehicle can be met.

Description

Technical Field

[0001] The present application belongs to the field of batteries, and in particular relates to a positive electrode material precursor and a preparation method thereof, a positive electrode material, a battery and electrical equipment. Background Art

[0002] Cathode materials are an important component of lithium batteries and play a key role in battery performance. Among them, nickel-containing cathode materials are widely used, making them a focus of attention in battery preparation.

[0003] However, the precursor of nickel-containing positive electrode materials still has high energy consumption during the single crystal sintering process and is not easy to sinter into single crystals. After the positive electrode materials are prepared to make batteries, the cycle life is difficult to meet the growing demand of electric vehicles.

[0004] In view of this, this application is hereby filed. Summary of the Invention

[0005] The present application provides a positive electrode material precursor and a preparation method thereof, a positive electrode material and a battery, aiming to solve or alleviate at least one problem existing in the above-mentioned prior art.

[0006] The first aspect of the present application provides a positive electrode material precursor, the positive electrode material precursor includes secondary particles composed of primary particles, the particle size D50 of the secondary particles is 2.00 μm-5.00 μm; the average value of the aspect ratio a / b of the secondary particles is Wherein, a is the length of the major axis of the secondary particle, and b is the length of the broad axis of the secondary particle.

[0007] The cathode material precursor provided in this application has secondary particles with a particle size D50 in the range of 2.00 μm-5.00 μm, and an average value of the aspect ratio a / b of the secondary particles Average value of aspect ratio a / b Compared to spherical secondary particles, secondary particles with larger aspect ratios require less time to sinter into single crystals due to their geometric anisotropy, requiring lower sintering temperatures. This reduces energy consumption and prevents lattice defects caused by over-sintering of small single crystals. Furthermore, during mixed lithium sintering, secondary particles with large aspect ratios have shorter lithium ion diffusion paths, and the grain boundary migration rate is better matched to the lithium source activity, reducing lithium-nickel mixing and resulting in better cycling performance.

[0008] Therefore, the positive electrode material precursor single crystal provided in this application has low energy consumption during sintering and is easy to sinter into a single crystal. After the positive electrode material is made into a battery, the cycle life can be significantly improved compared with traditional technology to meet the growing cycle performance requirements of electric vehicles.

[0009] In some embodiments, the cathode material precursor satisfies at least one of the following conditions:

[0010] A. Primary particles are in the form of flakes and / or plates;

[0011] B. At least some of the primary particles in the secondary particles are stacked along the long axis direction.

[0012] In some embodiments, the cathode material precursor satisfies at least one of the following conditions:

[0013] D. The number of primary particles stacked in a direction along the long axis accounts for more than 50% of the total number of primary particles; alternatively, the number of primary particles stacked in a direction along the long axis accounts for more than 80% of the total number of primary particles;

[0014] E. Average value of secondary particle aspect ratio a / b 1.70-2.50;

[0015] F. Average length of the major axis of secondary particles 3.60μm-5.00μm;

[0016] G. Average length of the broad axis b of the secondary particles 1.50μm-2.70μm;

[0017] H. The specific surface area of ​​secondary particles is 4.00 m 2 / g-9.00m 2 / g;

[0018] I. The tap density TD of the secondary particles is 1.70 g / cm 3 -2.10g / cm 3 ;

[0019] J. The particle size distribution K90 of secondary particles is 0.50-1.20;

[0020] K, average length of primary particles 400nm-1500nm;

[0021] L, average thickness of primary particles 80nm-200nm.

[0022] In some embodiments, the chemical formula of the cathode material precursor is: Ni x Co y Mn z M t (OH) 2+δ , wherein 0.60≤x<1.00, 0≤t≤0.10, -0.12≤δ≤0.20, x+y+z+t=1, and M is a doping element; optionally, the doping element M includes at least one of Al, Ti, Zr, Mo, Mg, Ba, Nb or Sr.

[0023] A second aspect of the present application provides a method for preparing a cathode material precursor, comprising:

[0024] The first synthesis stage: a metal salt solution, a precipitant solution, and a complexing agent solution are introduced into a first base liquid containing a precipitant and a complexing agent to carry out a first synthesis reaction to obtain a material obtained by the first synthesis reaction, and the material obtained by the first synthesis reaction is refined to obtain a seed slurry having a first target particle size;

[0025] The second synthesis stage: a seed slurry of the first target particle size is introduced into the raw materials of the first base liquid to prepare a second base liquid, and a metal salt solution, a precipitant solution, and a complexing agent solution are introduced into the second base liquid to carry out a second synthesis reaction to obtain a slurry having the second target particle size;

[0026] Post-processing stage: The slurry is post-processed to obtain the positive electrode material precursor.

[0027] In some embodiments, the first synthesis reaction process includes: after the first synthesis reaction begins, controlling the first initial pH value of the reaction system to drop to a first target pH value, then increasing the pH value of the reaction system to a second target pH value, then increasing the pH value of the reaction system to a third target pH value, and continuing the reaction until the first target particle size reaches 3.00 μm-4.00 μm;

[0028] The second synthesis reaction process includes: controlling the reaction system to gradually decrease from a second initial pH value to a fourth target pH value, and then continuing the reaction until the particle size reaches 2.00 μm-5.00 μm.

[0029] The pH value of the first base liquid is consistent with the first initial pH value, and the pH value of the second base liquid is consistent with the second initial pH value.

[0030] By controlling the parameters during the reaction, the average value of the aspect ratio a / b is obtained cathode material precursor.

[0031] In some embodiments, the preparation method satisfies at least one of the following conditions:

[0032] a. The metal salt in the metal salt solution includes nickel salt, cobalt salt, manganese salt and / or a combination of doped metal salts containing at least nickel salt; the nickel salt includes one or more of nickel sulfate, nickel nitrate and nickel chloride; the cobalt salt includes one or more of cobalt sulfate, cobalt nitrate and cobalt chloride; the manganese salt includes one or more of manganese sulfate, manganese nitrate and manganese chloride;

[0033] b. The precipitant includes one or more of sodium carbonate, sodium hydroxide or potassium hydroxide;

[0034] c. The complexing agent includes one or more of ammonia water, ammonium carbonate, oxalic acid, citric acid, sodium citrate, ammonium citrate or ammonium oxalate;

[0035] d. The metal salt concentration in the metal salt solution is 0.5 mol / L-3 mol / L;

[0036] e. The concentration of the precipitant solution is 25wt%-45wt%;

[0037] f. The concentration of the complexing agent solution is 10wt%-30wt%;

[0038] g. The pH value of the second base liquid is lower than the pH value of the first base liquid;

[0039] h. The complexing agent concentration of the second base solution is less than the complexing agent concentration of the first base solution;

[0040] i. The pH value of the first base solution is 11.0-11.6;

[0041] j. The complexing agent concentration of the first base solution is 4g / L-8g / L;

[0042] k. The pH value of the second base solution is 10.6-11.4;

[0043] 1. The concentration of the complexing agent in the second base solution is 4g / L-7g / L;

[0044] m. In the first synthesis reaction, the temperature of the reaction system is controlled to be 55°C-65°C, the stirring speed is 600rpm-1200rpm; the pH value of the reaction system is controlled to be in the range of 11.0-11.6, and the concentration of the complexing agent is controlled to be in the range of 4g / L-8g / L;

[0045] n. In the second synthesis reaction, the temperature of the reaction system is controlled to be 55°C-65°C, the stirring speed is 600rpm-1500rpm; the concentration of the complexing agent is controlled to be in the range of 3g / L-6g / L;

[0046] o, the first initial pH value, the first target pH value, the second target pH value, the third target pH value, the second initial pH value, and the fourth target pH value are independently controlled within the range of 10.0-12.0;

[0047] p. The first synthesis reaction and the second synthesis reaction are carried out entirely under an inert atmosphere, wherein the oxygen content of the gas in the first synthesis reaction vessel and the second synthesis reaction vessel is independently controlled to be less than 2.5%;

[0048] q. starting a second synthesis reaction under an inert atmosphere with the oxygen content of the gas in the reaction vessel controlled to be less than 5%, and raising the oxygen content of the gas in the reaction vessel to 5%-21% after the pH value drops to a fourth target pH value;

[0049] r. In the first synthesis stage, the flow rate of the metal salt solution is 6.0% / h-9.0% / h of the available volume of the reaction vessel;

[0050] s. In the first synthesis stage, the flow ratio of the metal salt solution, the precipitant solution, and the complexing agent solution is 1:(0.30-0.50):(0.03-0.06);

[0051] t. The particle size of the seed slurry is 0.50 μm-1.50 μm;

[0052] u. The refinement treatment is sand grinding, wherein the speed of the sand grinding treatment is 1800-4200 rpm and the sand grinding time is 3-5 hours;

[0053] v. The solid content of the second base liquid is 6.0%-9.0%;

[0054] w. In the second synthesis stage, the flow rate of the metal salt solution is 4.0% / h-8.0% / h of the available volume of the reaction vessel;

[0055] x. In the second synthesis stage, the flow ratio of the metal salt solution, the precipitant solution and the complexing agent solution is 1:(0.3-0.4):(0.025-0.065).

[0056] A third aspect of the present application provides a positive electrode material, which is prepared using the positive electrode material precursor as described above or the positive electrode material precursor prepared by the above preparation method.

[0057] A fourth aspect of the present application provides a battery, wherein the positive electrode of the battery is made of the positive electrode material as described above.

[0058] A fifth aspect of the present application provides an electrical device comprising the battery as described above.

[0059] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the specific implementation methods or the description of the prior art. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0061] Figure 1 This is a surface SEM image of the cathode material precursor prepared in Example 2 of the present application (magnification 10,000 times);

[0062] Figure 2 Schematic diagram of the size measurement of the length a of the long axis and the length b of the wide axis of the positive electrode material precursor secondary particles prepared in Example 2 of the present application (magnification 30,000 times);

[0063] Figure 3 This is a surface SEM image of the positive electrode material precursor prepared in Comparative Example 1 of the present application (magnification 30,000 times);

[0064] Figure 4 Schematic diagram of secondary particles with primary particles stacked in a directional manner along the long axis. DETAILED DESCRIPTION

[0065] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0066] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0067] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0068] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, "the method includes steps a and b" means that the method may include steps a and b performed sequentially, or steps b and a performed sequentially. For example, "the method may further include step c" means that step c may be added to the method in any order, for example, the method may include steps a, b, and c, or steps a, c, and b, or steps c, a, and b, etc.

[0069] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0070] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0071] In view of the high energy consumption during the single crystal sintering process of nickel-cobalt-manganese positive electrode materials, the cycle life of the battery after the positive electrode materials are prepared is difficult to meet the application requirements of electric vehicles. In this embodiment of the present application, a positive electrode material precursor is provided. The positive electrode material precursor includes secondary particles composed of primary particles. The particle size D50 of the secondary particles is 2.00μm-5.00μm; the average value of the aspect ratio a / b of the secondary particles is Wherein, a is the length of the major axis of the secondary particle, and b is the length of the broad axis of the secondary particle.

[0072] It is understood that the particle size D50 of the secondary particles provided in the embodiments of the present application is 2.00 μm-5.00 μm, and the average value of the aspect ratio a / b of the secondary particles is Compared to the average value of aspect ratio a / b The traditional spherical secondary particles approaching 1 have a smaller particle size and a larger size in the long axis direction. When the secondary particles of the positive electrode material precursor are mixed with lithium and sintered, the diffusion path of lithium ions is shorter, and the grain boundary migration rate is better matched with the lithium source activity, so as to reduce the mixing of lithium and nickel, and promote the significant improvement of the cycle performance; and, during the sintering process of single crystals of secondary particles, due to the influence of their geometric anisotropy, their lattice distortion can be significantly lower than that of spherical precursors, which can have a shorter single crystal sintering time and a lower sintering temperature, so as to reduce energy consumption while avoiding lattice defects caused by over-burning of small particle single crystals.

[0073] It should be noted that this application involves the average value of the aspect ratio a / b of the secondary particles The calculation method is as follows: adjust the magnification of the scanning electron microscope (SEM) until about 10 complete images of the secondary particles of the cathode material precursor appear in the view and take a photo to obtain an SEM image (e.g. Figure 1 As shown in the figure, the magnification of the SEM image is 10,000 times), the longest axis of a secondary particle in the SEM image is defined as the long axis, and the longest axis perpendicular to the long axis is defined as the wide axis. The length a of the long axis and the length b of the wide axis of the secondary particle are measured to calculate the aspect ratio a / b of the secondary particle.

[0074] Select multiple secondary particles and repeat the above operation. Measure the length a and width axis length b of the multiple secondary particles respectively. Then calculate the aspect ratio a / b corresponding to each secondary particle. Finally, calculate the arithmetic mean of the aspect ratios a / b of the multiple secondary particles.

[0075] Count the length values ​​a of multiple secondary particles, and calculate the arithmetic mean of the length values ​​a of multiple secondary particles, that is, the average length value of the secondary particles.

[0076] Count the length values ​​b of multiple secondary particles, and calculate the arithmetic mean of the length values ​​b of multiple secondary particles, that is, the average width value of the secondary particles.

[0077] The embodiment of the present application can also use artificial intelligence software to automatically identify the outline of secondary particles according to the color depth of the pixels of the secondary particles and the surrounding area in the SEM electron microscope image, and then draw the major axis and minor axis, and then measure the length value a of the major axis and the length value b of the width axis of a certain secondary particle respectively, and then repeat the above operation to measure and calculate the length value a of the major axis and the length value b of the width axis of multiple secondary particles, and finally calculate the average length value of the secondary particles. and average width

[0078] The positive electrode material precursor provided in the present application has a particle size D50 of the secondary particles of 2.00μm-5.00μm. For example, the particle size D50 of the secondary particles can be 2.00μm, 2.25μm, 2.50μm, 2.75μm, 3.00μm, 3.25μm, 3.50μm, 3.75μm, 4.00μm, 4.25μm, 4.50μm, 4.75μm, 5.00μm or any particle size D50 range value or size value within the range of 2.00μm-5.00μm, 2.00μm-2.50μm, 2.50μm-3.00μm, 3.00μm-5.00μm, 2.00μm-4.00μm.

[0079] Average value of secondary particle aspect ratio a / b For example, It can be any value within the range of ≥1.7, ≥1.8, ≥1.9, ≥2.0, ≥2.1, ≥2.2, ≥2.3, ≥2.4 or ≥1.7.

[0080] To further improve the stability of the positive electrode material, in some embodiments, the average value of the aspect ratio a / b of the secondary particles is The average value of the aspect ratio a / b of the secondary particles is 1.70-2.50, which is more conducive to giving full play to the geometric anisotropy of the secondary particles, shortening the single crystal sintering time, reducing energy consumption, and improving the cycle performance. It is also beneficial to avoid the non-uniform fracture caused by compression or sintering caused by an excessively large average aspect ratio, thereby improving the consistency of the single crystal particle size and further improving the cycle performance. The average aspect ratio of the secondary particles may be 1.70-2.50, for example, the average aspect ratio of the secondary particles may be 1.70, 1.75, 1.80, 1.85, 1.90, 1.95, 2.00, 2.10, 2.15, 2.20, 2.25, 2.30, 2.35, 2.40, 2.45, 2.50 or an average aspect ratio in the range of 1.70-2.50, 1.70-2.30, 1.70-2.00, 2.00-2.30.

[0081] It should be understood that the particle size D50 of the secondary particles is in the range of 2.00μm-5.00μm. When the average aspect ratio of the secondary particles of the positive electrode material is too small, such as when the average aspect ratio is less than 1.70, the secondary particles are more spherical, it is difficult to obtain geometric anisotropy, the time for the precursor to be sintered into a single crystal is longer and the sintering temperature is higher, the energy consumption is larger, and during mixed lithium sintering, the diffusion path of lithium ions is longer, the grain boundary migration rate is weaker than the lithium source activity, small-particle single crystals are prone to overburning and cause lattice defects, and the cycle performance is difficult to effectively improve; and when the average aspect ratio of the secondary particles is too large, the secondary particles are more rod-shaped, and the secondary particles are prone to non-uniform fracture during compression or sintering. The primary particles are broken on the fracture surface, reducing the consistency of the single crystal particle size after sintering, and some particles that are too small will aggravate electrode polarization, and the cycle performance is slightly reduced.

[0082] In some embodiments, the primary particles are in the form of flakes or plates, and the primary particles have a thin thickness dimension and a large length dimension. Compared with block-shaped primary particles, the flake-shaped or plate-shaped primary particles in the embodiments of the present application can have a higher surface area and high surface energy, which significantly enhances the driving force ΔG (ΔG∝γ / r, where γ is the surface tension and r is the particle curvature radius) for sintering of the secondary particles, thereby accelerating atomic diffusion and being more conducive to the infiltration of lithium salts to form single crystals during sintering. Within this range, the primary particles match an appropriate thickness and their morphology is flake-shaped or plate-shaped to obtain a larger surface area, which makes it easier for lithium salts to infiltrate and form single crystals during sintering of the positive electrode material precursor.

[0083] In some embodiments, the average length of the primary particles is The average length of the primary particles may be 400 nm-1500 nm. For example, the average length of the primary particles may be 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, 850 nm, 900 nm, 950 nm, 1000 nm, 1050 nm, 1100 nm, 1150 nm, 1200 nm, 1250 nm, 1300 nm, 1350 nm, 1400 nm, 1450 nm, or any average length value within the range of 400 nm-1500 nm, or 400 nm-600 nm.

[0084] Average length of primary particles Within the appropriate range, sintering into single crystals with consistent particle size is beneficial. If the primary particles are too long, uneven crystallinity and crystal deformities are likely to occur during the sintering process. For example, insufficient (003) crystal plane orientation growth affects the efficiency of lithium ion interlayer migration. Pores may also appear within the particles, affecting the cycle. In addition, the (003) crystal plane formation temperature of large particles is higher, requiring a higher sintering temperature. If the primary particles are too short, the possibility of forming micropowders is higher. At the same time, the particle structure strength decreases, affecting the cycle performance.

[0085] Average thickness of primary particles The average thickness of the primary particles can be 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm or any thickness value within the range of 80 nm to 200 nm, 80 nm to 150 nm.

[0086] In order to shorten the single crystal sintering time and improve the uniformity of the sintered single crystal, in some embodiments, the average thickness of the primary particles is The average thickness of primary particles is 80nm-200nm. When the thickness is less than 80nm, the primary particles are too thin, and there is a risk of secondary recrystallization during the secondary particle forming process. Large grains swallow small grains, resulting in pore wrapping and the need to fuse more grain boundaries. The particles are prone to adhesion, which is not conducive to sintering into uniform single crystals. The average thickness of the primary particles is When the thickness is greater than 200nm, the primary particles are too thick, the atomic diffusion distance in the secondary particles is long, higher temperature or longer sintering time is required for single crystal sintering, and abnormal grain growth is likely to occur. Therefore, the average thickness of the primary particles is The range of 80nm-200nm can shorten the single crystal sintering time and improve the uniformity of the sintered single crystal, which is more conducive to the infiltration of lithium salt to form single crystal during sintering, thereby improving the cycle performance of the positive electrode material.

[0087] It should be noted that this application involves the average length of the primary particles Average thickness value The calculation method is as follows: adjust the magnification of the scanning electron microscope (SEM) until 1-3 complete secondary particle images of the cathode material precursor appear in the view and take a photo to obtain an SEM image (e.g. Figure 2 As shown in the figure, the magnification of the SEM image is 30,000 times), the longest axis of a primary particle in the SEM image is defined as the long axis, and the longest axis perpendicular to the long axis is defined as the short axis. The length a' of the long axis and the length b' of the short axis of the primary particle are measured.

[0088] Select multiple primary particles and repeat the above operation to measure the length values ​​a' of the major axis and b' of the minor axis of the multiple primary particles respectively; calculate the arithmetic mean of the length values ​​a' of the major axis of the multiple primary particles to obtain the average length value of the primary particles. Calculate the arithmetic mean of the lengths b' of the minor axes of multiple primary particles to obtain the average thickness of the primary particles.

[0089] The embodiment of the present application can also use artificial intelligence software to automatically identify the length and width range of the primary particles according to the color depth of the pixels of the primary particles and the surrounding area in the SEM electron microscope image, and respectively measure the length value a' of the major axis and the length value b' of the minor axis of a certain primary particle, and then repeat the above operation to measure and calculate the length value a' and the length value b' of the minor axis of multiple primary particles, and finally calculate the average length value of the primary particles. and average thickness

[0090] In some embodiments, at least some of the primary particles in the secondary particles are stacked in a directional manner along the long axis (e.g. Figure 4 (as shown in the schematic diagram); compared with the directional stacking of primary particles along the width axis direction, the geometric anisotropy of the positive electrode material precursor is more obvious when the primary particles are directional stacked along the long axis direction, the stress is more concentrated during sintering, and it is easier to sinter into a single crystal, which is conducive to reducing the single crystal sintering temperature and time, reducing sintering energy consumption, and improving the cycle performance of the positive electrode material.

[0091] In some embodiments, the number of primary particles stacked in a direction along the long axis accounts for more than 50% of the total number of primary particles, indicating that most of the primary particles in a single secondary particle are stacked in a direction along the long axis, so as to improve the geometric anisotropy of the positive electrode material precursor, and the stress is more concentrated during sintering, so as to reduce the single crystal sintering temperature and time, reduce sintering energy consumption, and improve the cycle performance of the positive electrode material.

[0092] In some embodiments, the number of primary particles stacked in a direction along the long axis direction accounts for more than 80% of the total number of primary particles, so as to further improve the geometric anisotropy of the positive electrode material precursor, make the geometric anisotropy of the positive electrode material precursor more obvious, make single crystals easier to sinter and form, and significantly improve the cycle performance of the positive electrode material.

[0093] For example, the number of primary particles stacked in a direction along the long axis may account for more than 50%, more than 60%, more than 70%, more than 80%, or more than 90% of the total number of primary particles.

[0094] It should be noted that the test method for the proportion of oriented stacking in the long axis direction is based on the positive electrode material precursor prepared in Example 1. Figure 2 ) Randomly select multiple primary particles (for example, 20, selected from 4 different secondary particles), draw the long axis and wide axis on each secondary particle, and if the angle between the length direction of a single primary particle and the long axis is less than 40°, the primary particles are stacked along the long axis; if the angle between the length direction of a single primary particle and the wide axis is less than 40°, the primary particles are stacked along the wide axis.

[0095] In some embodiments, the average length of the major axis of the secondary particles is The average aspect ratio of the superimposed secondary particles is 1.7 or more when the particle size D50 is in the range of 3.60μm-5.00μm and the particle size D50 is in the range of 2.00μm-5.00μm. This makes it easier for secondary particles to sinter into single crystals and effectively improves the cycle performance of the positive electrode material. 3.60μm-8.00μm, for example, the average length of the major axis of the secondary particles is The average major axis length may be 3.60 μm, 3.80 μm, 4.20 μm, 4.40 μm, 4.60 μm, 4.80 μm, 5.00 μm, or any value within the range of 3.60 μm-8.00 μm, or 4.00 μm-5.00 μm.

[0096] In some embodiments, the average length of the broad axis of the secondary particles is The average value of the aspect ratio of the superimposed secondary particles obtained under the condition of particle size D50 being 1.50μm-2.70μm and being 1.7 or more is This makes it easier for secondary particles to sinter into single crystals and effectively improves the cycle performance of the positive electrode material. 1.50 μm-2.70 μm, for example, the average length of the broad axis of the secondary particles is The average broad axis length may be 1.50 μm, 1.60 μm, 1.70 μm, 1.80 μm, 1.90 μm, 2.00 μm, 2.10 μm, 2.20 μm, 2.30 μm, 2.40 μm, 2.50 μm, 2.60 μm, 2.70 μm, or any value within the range of 1.50 μm-2.70 μm, 2.00 μm-3.00 μm.

[0097] In some embodiments, the secondary particles have a BET specific surface area of ​​4.00 m 2 / g-9.00m 2 / g. Within this range, the secondary particles have a larger specific surface area. When the secondary particles of the positive electrode material precursor are mixed with lithium and sintered, the diffusion path of lithium ions is shorter, and the grain boundary migration rate is better matched with the lithium source activity, thereby reducing lithium and nickel mixing and significantly improving the cycle performance. The specific surface area of ​​the secondary particles is 4.00m 2 / g-8.00m 2 / g, for example, the specific surface area of ​​the secondary particles can be 4.00m 2 / g, 4.25m 2 / g, 4.50m 2 / g, 4.75m 2 / g, 5.00m 2 / g, 5.25m 2 / g, 5.50m 2 / g, 5.75m 2 / g, 6.00m 2 / g, 6.25m 2 / g, 6.50m 2 / g, 6.75m 2 / g, 7.00m 2 / g, 7.25m 2 / g, 7.50m 2 / g, 7.75m 2 / g、8.00m 2 / g or 4.00m 2 / g-8.00m 2 / g, 6.00m 2 / g-7.50m 2Any specific surface area BET value in the range of / g.

[0098] In some embodiments, the tap density TD of the secondary particles is 1.70 g / cm 3 -2.10g / cm 3 For example, the tap density TD of the secondary particles can be 1.70 g / cm 3 , 1.75g / cm 3 , 1.80g / cm 3 , 1.85g / cm 3 、1.90g / cm 3 , 1.95g / cm 3 , 2.00g / cm 3 , 2.05g / cm 3 , 2.10g / cm 3 or 1.70g / cm 3 -2.10g / cm 3 , 1.75g / cm 3 -1.90g / cm 3 Any tap density TD value within the range.

[0099] In some embodiments, the particle size distribution K90 of the secondary particles is 0.50-1.20, where K90 = (D90-D10) / D50. Within this range, the positive electrode material precursor has a uniform particle size, which is more conducive to sintering into single crystals and effectively improving the cycle performance of the positive electrode material. The particle size distribution K90 of the secondary particles is 0.50-1.20. For example, the particle size distribution K90 of the secondary particles can be 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1.00, 1.05, 1.10, 1.15, 1.20, or any particle size distribution K90 value within the range of 0.50-1.20, 0.70-0.90.

[0100] In some embodiments, the cathode material precursor is a nickel-containing hydroxide, for example, nickel-cobalt-manganese hydroxide, nickel-cobalt-manganese-aluminum hydroxide, or nickel-cobalt-aluminum hydroxide. The introduction of nickel into the nickel-containing hydroxide helps improve the electrochemical performance of the cathode material, leading to a higher energy density for the battery and thus improved cycling performance.

[0101] In some embodiments, the cathode material precursor is a hydroxide containing nickel, cobalt, and manganese, for example, nickel, cobalt, and manganese hydroxide, nickel, cobalt, and manganese aluminum hydroxide, nickel, cobalt, and manganese, and doped metal hydroxides.

[0102] In some embodiments, the chemical formula of the cathode material precursor is: Ni x Coy Mn z M t (OH) 2+δ , wherein 0.60≤x<1.00, 0≤t≤0.10, -0.12≤δ≤0.20, x+y+z+t=1, and M is a doping element; optionally, the doping element M includes at least one of Al, Ti, Zr, Mo, Mg, Ba, Nb or Sr.

[0103] It should be understood that the percentage of the molar content of nickel in the positive electrode material precursor in the embodiment of the present application accounts for more than 60% of the molar content of the total metal elements, which enables the positive electrode material to have a higher energy density and discharge capacity while having better cycle performance. The molar content of manganese and cobalt accounts for 5-30% of the molar content of the total metal elements, respectively. In addition, the positive electrode material precursor in the embodiment of the present application can be an undoped nickel-cobalt-manganese precursor, or a doped nickel-cobalt-manganese precursor having at least one doping element of Al, Ti, Zr, Mo, Mg, Ba, Nb or Sr. By appropriately doping with the above elements, the crystal structure stability of the positive electrode material can be enhanced, thereby improving the cycle performance of the battery.

[0104] Therefore, the positive electrode material precursor single crystal provided in the embodiment of the present application has low energy consumption during sintering and is easy to sinter into a single crystal. After the positive electrode material is made into a battery, the cycle life can be significantly improved compared with traditional technology to meet the growing cycle performance requirements of electric vehicles.

[0105] It should be understood that, based on the structural characteristics of the above-mentioned positive electrode material precursor, the positive electrode material precursor in the embodiment of the present application can be prepared by a co-precipitation method, a sol-gel method or a hydrothermal method. The following example illustrates a feasible method for preparing the positive electrode material.

[0106] To prepare the above-mentioned cathode material precursor, another embodiment of the present application provides a method for preparing the cathode material precursor, comprising:

[0107] The first synthesis stage: a metal salt solution, a precipitant solution, and a complexing agent solution are introduced into a first base liquid containing a precipitant and a complexing agent to carry out a first synthesis reaction to obtain a material obtained by the first synthesis reaction, and the material obtained by the first synthesis reaction is refined to obtain a seed slurry having a first target particle size;

[0108] The second synthesis stage: a seed slurry of the first target particle size is introduced into the raw materials of the first base liquid to prepare a second base liquid, and a metal salt solution, a precipitant solution, and a complexing agent solution are introduced into the second base liquid to carry out a second synthesis reaction to obtain a slurry having the second target particle size;

[0109] Post-processing stage: The slurry is post-processed to obtain the positive electrode material precursor.

[0110] It should be noted that by refining the material obtained by the first synthesis reaction, a flaky seed crystal of the first target particle size can be obtained, so that the primary particles can be stacked and grown in the second synthesis reaction. In this way, the embodiment of the present application adopts an intermittent coprecipitation synthesis reaction to prepare the positive electrode material precursor, so as to facilitate the fine control of various reaction parameters in the reaction process, realize the targeted regulation of the morphology of the positive electrode material precursor, and thus obtain a positive electrode material precursor with a particle size of 2.00μm-5.00μm and an average value of the aspect ratio a / b of the secondary particles. Can meet ≥1.7.

[0111] In some embodiments, post-processing includes washing, centrifuging, drying, and screening for demagnetization of the intermediate slurry in sequence; washing, centrifuging, drying, and screening for demagnetization of the hydroxide slurry in sequence helps to remove impurities and volatile solvents, making the positive electrode material precursor purer and the particle size distribution more uniform.

[0112] In some embodiments, the first synthesis reaction process includes: after the first synthesis reaction starts, controlling the first initial pH value of the reaction system to drop to the first target pH value, then increasing the pH value of the reaction system to the second target pH value, and then increasing the pH value of the reaction system to the third target pH value, and continuing the reaction until the first target particle size reaches 3.00μm-4.00μm; the second synthesis reaction process includes: controlling the pH value of the reaction system to gradually drop from the second initial pH value to the fourth target pH value, and then continuing the reaction until the second target particle size reaches 2.00μm-5.00μm.

[0113] In some embodiments, the metal salt in the metal salt solution includes a nickel salt, a cobalt salt, a manganese salt and / or a combination of doped metal salts containing at least a nickel salt; the nickel salt includes one or more of nickel sulfate, nickel nitrate and nickel chloride; the cobalt salt includes one or more of cobalt sulfate, cobalt nitrate and cobalt chloride; and the manganese salt includes one or more of manganese sulfate, manganese nitrate and manganese chloride.

[0114] In some embodiments, the precipitant includes one or more of sodium carbonate, sodium hydroxide, or potassium hydroxide.

[0115] In some embodiments, the complexing agent includes one or more of ammonia, ammonium carbonate, oxalic acid, citric acid, sodium citrate, ammonium citrate, or ammonium oxalate.

[0116] In some embodiments, the metal salt concentration in the metal salt solution is 0.5 mol / L-3 mol / L; illustratively, the metal salt concentration in the metal salt solution can be 0.5 mol / L, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, 3.0 mol / L or any value between 0.5 mol / L and 3 mol / L.

[0117] In some embodiments, the concentration of the precipitant solution is 25 wt%-45 wt%; illustratively, the concentration of the precipitant solution can be 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt% or any value therebetween.

[0118] In some embodiments, the concentration of the complexing agent solution is 10 wt%-30 wt%; illustratively, the concentration of the complexing agent solution can be 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt% or any value between 10 wt% and 30 wt%.

[0119] In some embodiments, the pH value of the second base liquid is lower than the pH value of the first base liquid.

[0120] In some embodiments, the concentration of the complexing agent in the second base solution is less than the concentration of the complexing agent in the first base solution.

[0121] In some embodiments, the pH value of the first base liquid is 11.0-11.6; illustratively, the pH value of the first base liquid can be 11.0, 11.1, 11.2, 11.3, 11.4, 11.5, 11.6 or any value between 11.0 and 11.6.

[0122] In some embodiments, the complexing agent concentration of the first base solution is 4 g / L-8 g / L; illustratively, the complexing agent concentration of the first base solution can be 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L or any value between 4 g / L and 8 g / L.

[0123] In some embodiments, the pH value of the second base liquid is 10.6-11.4; illustratively, the pH value of the second base liquid can be 10.6, 10.7, 10.8, 10.9, 11.0, 11.1, 11.2, 11.3, 11.4 or any value between 10.6 and 11.4.

[0124] In some embodiments, the complexing agent concentration of the second base solution is 4 g / L-7 g / L; illustratively, the complexing agent concentration of the second base solution can be 4 g / L, 5 g / L, 6 g / L, 7 g / L or any value between 4 g / L and 7 g / L.

[0125] In some embodiments, in the first synthesis reaction, the temperature of the reaction system is controlled to be 55°C-65°C, the stirring speed is 600rpm-1200rpm; the complexing agent concentration is controlled to be in the range of 4g / L-8g / L. For example, in the first synthesis reaction, the temperature of the reaction system can be controlled to be 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, 61°C, 62°C, 63°C, 64°C, 65°C or any value between 55°C and 65°C; the stirring speed can be 600rpm, 700rpm, 800rpm, 900rpm, 1000rpm, 1100rpm, 1200rpm or any value between 600rpm and 1200rpm; the complexing agent concentration can be controlled to be 4g / L, 5g / L, 6g / L, 7g / L, 8g / L or any value between 4g / L and 8g / L.

[0126] In some embodiments, the first synthesis reaction produces a material with a larger particle size, which is then refined to produce flake seed crystals meeting the first target particle size.

[0127] In some embodiments, in the second synthesis reaction, the temperature of the reaction system is controlled to be 55°C-65°C, the stirring speed is 600rpm-1500rpm; the complexing agent concentration is controlled to be in the range of 3g / L-6g / L. For example, in the second synthesis reaction, the temperature of the reaction system can be controlled to be 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, 61°C, 62°C, 63°C, 64°C, 65°C or any value between 55°C and 65°C; the stirring speed can be 600rpm, 700rpm, 800rpm, 900rpm, 1000rpm, 1100rpm, 1200rpm, 1300rpm, 1400rpm, 1500rpm or any value between 600rpm-1500rpm; the complexing agent concentration can be controlled to be 3g / L, 4g / L, 5g / L, 6g / L or any value between 3g / L-6g / L.

[0128] In some embodiments, the first initial pH value, the first target pH value, the second target pH value, the third target pH value, the second initial pH value, and the fourth target pH value are independently controlled within the range of 10.0-12.0, for example, they can be 10.0, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9, 11.0, 11.1, 11.2, 11.3, 11.4, 11.5, 11.6, 11.7, 11.8, 11.9, 12.0 or any value between 10.0 and 12.0.

[0129] The pH value can affect the nucleation and growth of primary particles. In the first synthesis reaction, a higher pH value facilitates nucleation, resulting in finer primary particles and less regular arrangement of primary particles. In the second synthesis reaction, a lower pH value inhibits nucleation, allowing primary particles to grow larger and more regularly.

[0130] In some embodiments, the second synthesis reaction produces a cathode material precursor having a secondary particle size D50 of 2.00 μm-5.00 μm.

[0131] It should be noted that in the preparation method of the embodiment of the present application, the different pH values ​​of the reaction system and the concentration of the complexing agent affect the morphology of the secondary particles of the cathode material precursor obtained. The pH value and the concentration of the complexing agent designed within the above range are conducive to promoting the particle size D50 of the secondary particles of the cathode material precursor to be 2.00 μm-5.00 μm and the average value of the aspect ratio a / b This results in lower energy consumption during the sintering process of the single crystal of the positive electrode material precursor, making it easier to sinter into a single crystal. After the positive electrode material is made into a battery, the cycle life can be significantly improved.

[0132] In some embodiments, in the second synthesis stage, cation exchange resin microspheres are further introduced into the second base liquid; for example, the cation exchange resin microspheres can be polystyrene-divinylbenzene microspheres with a particle size of 580 μm-700 μm and a density of 1.27 g / mL.

[0133] In some embodiments, the first and second synthesis reactions are conducted entirely under an inert atmosphere, wherein the oxygen content of the gases within the first and second synthesis reaction vessels is independently controlled to be less than 2.5%. It should be understood that the thickness of the primary particles in the present embodiments can be adjusted by the degree of oxidation of the reaction system; stronger oxidation results in thinner primary particles, while weaker oxidation results in thicker primary particles. Designing an oxygen content within the aforementioned range is more conducive to obtaining primary particles with an average thickness of 80 nm to 200 nm. For example, the oxygen content of the gases within the first and second synthesis reaction vessels can be independently controlled to any value between <2.5%, <2.0%, <1.5%, <1.0%, <0.5%, or <2.5%.

[0134] In some embodiments, the second synthesis reaction is initiated under an inert atmosphere and the oxygen content of the gas in the reaction vessel is controlled to be less than 5%. After the pH value drops to a fourth target pH value, the oxygen content of the gas in the reaction vessel is increased to 5%-21%, and the reaction is continued until the second target particle size of the slurry reaches 2.00 μm-5.00 μm. Exemplarily, the second synthesis reaction is initiated and the oxygen content of the gas in the reaction vessel is increased to 5%-21% after the pH value drops to the fourth target pH value, or any value between 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, and 21%.

[0135] By controlling the oxygen content of the gas in the reactor, the morphology and size of the primary particles can be coordinated and regulated.

[0136] In some embodiments, during the first synthesis stage, the flow rate of the metal salt solution is 6.0% / h-9.0% / h of the available volume of the reaction vessel. Exemplarily, during the first synthesis stage, the flow rate of the metal salt solution can be 6.0% / h, 7.0% / h, 8.0% / h, 9.0% / h, or any value between 6% / h and 9.0% / h of the available volume of the reaction vessel.

[0137] In some embodiments, in the first synthesis stage, the flow ratio of the metal salt solution, the precipitant solution, and the complexing agent solution is 1:(0.30-0.50):(0.03-0.06). Exemplarily, in the first synthesis stage, the flow ratio of the metal salt solution, the precipitant solution, and the complexing agent solution is any value between 1:0.30:0.03, 1:0.4:0.04, 1:0.50:0.06, 1:(0.35-0.37):(0.04-0.05), or 1:(0.30-0.50):(0.03-0.06).

[0138] In some embodiments, the particle size of the seed slurry is 0.50 μm-1.50 μm. For example, the particle size of the seed slurry can be 0.50 μm, 0.55 μm, 0.60 μm, 0.75 μm, 0.80 μm, 0.85 μm, 0.90 μm, 0.95 μm, 1.00 μm, 1.05 μm, 1.10 μm, 1.15 μm, 1.20 μm, 1.25 μm, 1.30 μm, 1.35 μm, 1.40 μm, 1.45 μm, 1.50 μm, or any value between 0.50 μm and 1.50 μm.

[0139] In some embodiments, the thinning treatment is a sanding treatment, wherein the rotation speed of the sanding treatment is 1800-4200 rpm and the sanding time is 3h-5h.

[0140] In some embodiments, the solid content of the second base liquid is 6.0%-9.0%. By adding an appropriate amount of seed crystals, the solid content of the second base liquid is adjusted to 6.0%-9.0%, which is conducive to controlling the growth rate, and the particle size D50 of the secondary particles is 2.00μm-5.00μm, and the average value of the aspect ratio a / b is cathode material precursor.

[0141] In some embodiments, during the second synthesis stage, the flow rate of the metal salt solution is 4.0% / h-8.0% / h of the available volume of the reaction vessel. Exemplarily, during the second synthesis stage, the flow rate of the metal salt solution can be 4.0%, 5.0%, 6.0%, 7.0%, 8.0% / h, or any value between 4.0% / h and 8.0% / h of the available volume of the reaction vessel.

[0142] In some embodiments, in the second synthesis stage, the flow ratio of the metal salt solution, the precipitant solution, and the complexing agent solution is 1:(0.3-0.4):(0.025-0.065). Exemplarily, in the second synthesis stage, the flow ratio of the metal salt solution, the precipitant solution, and the complexing agent solution can be any value between 1:0.3:0.03, 1:0.4:0.05, 1:(0.32-0.34):(0.04-0.05), or 1:(0.3-0.4):(0.025-0.065).

[0143] Another embodiment of the application provides a positive electrode material, which is prepared using the positive electrode material precursor as described above or the positive electrode material precursor prepared by the preparation method as described above. For example, the positive electrode material precursor is mixed with lithium hydroxide, and then the lithium-mixed material is sintered at a sintering temperature of 850°C-950°C in oxygen for 12h-18h to obtain the positive electrode material. Exemplarily, the sintering temperature can be 850°C, 870°C, 900°C, 920°C, 950°C, or any value between 850°C and 950°C.

[0144] Another embodiment of the present application provides a battery, wherein the positive electrode of the battery is made of the positive electrode material as described above. Another embodiment of the present application provides an electrical device, including the battery as described above.

[0145] The following examples further describe the present disclosure. These examples are intended for illustrative purposes only, as various modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise indicated, all reagents and starting materials used in the examples are commercially available or synthesized according to conventional methods, and all instruments used in the examples are commercially available.

[0146] Example 1:

[0147] Provide a positive electrode material precursor (Ni 0.65 Co 0.07 Mn 0.28 )(OH)2, the preparation method thereof comprises:

[0148] Battery-grade nickel sulfate, cobalt sulfate, and manganese sulfate were weighed according to a molar ratio of Ni:Co:Mn = 65:7:28, and water was added to prepare a 2 mol / L mixed metal salt solution; sodium hydroxide solution with a solute mass fraction of 32.5 wt% and ammonia water with a solute mass fraction of 20 wt% were prepared.

[0149] Pure water, sodium hydroxide solution and ammonia water were added to the reactor as the first bottom liquid. The pH value of the first bottom liquid was 11.6, the ammonia concentration was 6 g / L, and the temperature was 60°C.

[0150] A mixed metal salt solution, a sodium hydroxide solution, and an aqueous ammonia solution are introduced into a reactor in parallel for a first synthesis reaction. During the reaction, the flow rate of the metal salt solution is controlled to be 7.5% / h of the reactor volume, and the flow ratio of the metal salt solution, the sodium hydroxide solution, and the aqueous ammonia solution is 1:0.37:0.045. The first initial pH value is 11.6, which is reduced to a first target pH value of 11.0 and maintained for reaction. The pH value is then increased to a second target pH value of 11.2, maintained for reaction, and increased to a third target pH value of 11.5. The third target pH value is then maintained unchanged until the reactor is stopped. During the reaction, the stirring speed is 900 rpm, the reaction temperature is 60°C, the free ammonia concentration is 4-5 g / L, nitrogen is passed through the reactor for protection, and the oxygen content is maintained at <1%. The total reaction time is 55 h, and an intermediate with an average particle size D50 of 3.5 μm is obtained. The intermediate is put into a sand mill for sand milling at a speed of 3000 rpm. After sand milling for 4 h, a seed slurry with a first target particle size of about 1.2 μm is obtained.

[0151] Pure water, seed slurry, sodium hydroxide solution and ammonia water were added to the reactor as the second bottom liquid. The pH value of the second bottom liquid was 11.0, the ammonia concentration was 5.0 g / L, the temperature was 60° C., and the solid content was 7.5%.

[0152] A mixed metal salt solution, a sodium hydroxide solution, and an ammonia solution are introduced into the reactor in parallel for a second synthesis reaction. During the reaction, the flow rate of the mixed metal salt solution is controlled to be 5.5% / h of the reactor volume, and the flow ratio of the metal salt solution, the sodium hydroxide solution, and the ammonia solution is 1:0.37:0.045. The second initial pH value is 11.0, which is gradually reduced to a fourth target pH value of 10.0, and then the pH value is maintained unchanged until the reactor is stopped. During the reaction, the stirring speed is 1000 rpm, the reaction temperature is 60°C, and the free ammonia concentration is 4-5 g / L; nitrogen is passed through the reactor for protection during the second bottom liquid and 3 hours before the reaction to maintain an oxygen content of <1%. After 3 hours of reaction, air is introduced below the liquid surface to increase the oxygen content of the gas in the reactor to 5% and maintain until the end of the reaction. The total reaction time is 55 hours, and an intermediate slurry with an average particle size D50 of 2.5 μm is obtained;

[0153] After washing, centrifugation, drying, sieving and demagnetizing the intermediate slurry, (Ni 0.65 Co 0.07 Mn 0.28 )(OH)2.

[0154] Example 2:

[0155] Provide a positive electrode material precursor (Ni 0.65 Co 0.07 Mn 0.28 )(OH)2, the difference between its preparation method and Example 1 is:

[0156] On the basis of Example 1, the pH value of the second base liquid was increased to 11.1, the solid content of the second base liquid was reduced to 6.0%, the fourth target pH value of the second synthesis reaction was increased to 10.2, the total reaction time of the second synthesis reaction was shortened to 45 h, and the other operations were consistent with Example 1 to obtain a positive electrode material precursor (Ni 0.65 Co 0.07 Mn 0.28 )(OH)2.

[0157] Example 3:

[0158] Provide a positive electrode material precursor (Ni 0.65 Co 0.07 Mn 0.28 )(OH)2, the difference between its preparation method and Example 1 is:

[0159] On the basis of Example 1, the pH value and solid content of the second base solution were increased to 11.2 and 9.0%, the fourth target pH value of the second synthesis reaction was increased to 10.3, the total reaction time of the second synthesis reaction was extended to 65 h, and other operations were consistent with Example 1 to obtain a positive electrode material precursor (Ni 0.65 Co 0.07 Mn0.28 )(OH)2.

[0160] Example 4:

[0161] Provide a positive electrode material precursor (Ni 0.75 Co 0.10 Mn 0.15 )(OH)2, the difference between its preparation method and Example 1 is:

[0162] On the basis of Example 1, the molar ratio of nickel, cobalt and manganese was adjusted to Ni:Co:Mn=75:10:15, the pH value of the first bottom solution was adjusted to 11.8, and the ammonia concentration was 5 g / L; in the first synthesis reaction, the first initial pH value was 11.8 after the reaction started, and it was reduced to the first target pH value of 11.4 to maintain the reaction, and then the pH value was increased to the second target pH value of 11.2, and after maintaining the reaction, it was increased to the third target pH value of 11.6, and then the third target pH value was maintained unchanged until the reactor was stopped, and the total reaction time was increased to 70 h; in addition, the pH of the second bottom solution was increased to 11.2, and the fourth target pH value in the second synthesis reaction was increased to 10.3. The other operations were consistent with Example 1 to obtain a positive electrode material precursor (Ni 0.75 Co 0.10 Mn 0.15 )(OH)2.

[0163] Example 5:

[0164] Provide a positive electrode material precursor (Ni 0.60 Co 0.10 Mn 0.29 Ti 0.01 )(OH) 2.02 , the difference between its preparation method and Example 1 is:

[0165] Based on Example 1, battery-grade nickel sulfate, cobalt sulfate, manganese sulfate, and titanium sulfate were weighed according to a molar ratio of Ni:Co:Mn:Ti=60:10:29:1, the pH value of the second base solution was increased to 11.3, and the fourth target pH value of the second synthesis reaction was increased to 10.4. The free ammonia concentration in the second synthesis reaction was increased to 5-6 g / L. Other operations were consistent with Example 1 to obtain a positive electrode material precursor (Ni 0.60 Co 0.10 Mn 0.29 Ti 0.01 )(OH) 2.02 .

[0166] Example 6:

[0167] Provide a positive electrode material precursor (Ni 0.65 Co 0.07 Mn 0.28)(OH)2, the difference between its preparation method and Example 1 is:

[0168] Based on Example 1, the first bottom liquid was adjusted to a pH value of 11.5 and an ammonia concentration of 7 g / L; in the first synthesis reaction, the first initial pH value was 11.5 after the reaction started, and after decreasing to a first target pH value of 10.9 and maintaining the reaction, the pH value was increased to a second target pH value of 11.1, and after maintaining the reaction, it was increased to a third target pH value of 11.4, and then the third target pH value was maintained unchanged until the reactor was stopped, and the total reaction time was reduced to 40 h; in addition, before the second synthesis reaction, 1 L of cation exchange resin microspheres (polystyrene-divinylbenzene microspheres, with a particle size of 580 to 700 μm and a density of 1.27 g / mL) was added to the second bottom liquid, and in the post-treatment, the intermediate slurry was filtered with a 200-mesh sieve to separate the cation exchange resin microspheres and the precursor slurry. The separated precursor slurry was then washed and dried, and the reaction cycle was extended to 60 h. The other operations were consistent with Example 1 to obtain a positive electrode material precursor (Ni 0.65 Co 0.07 Mn 0.28 )(OH)2.

[0169] Example 7:

[0170] Provide a positive electrode material precursor (Ni 0.65 Co 0.07 Mn 0.28 )(OH)2, the difference between its preparation method and Example 1 is:

[0171] On the basis of Example 1, the temperature of the second synthesis reaction was increased to 70° C. The second synthesis reaction was carried out under nitrogen protection throughout the entire process, without introducing air to control the oxygen content of the gas in the reactor to be less than 1%. Other operations were consistent with Example 1 to obtain a positive electrode material precursor (Ni 0.65 Co 0.07 Mn 0.28 )(OH)2.

[0172] Example 8:

[0173] Provide a positive electrode material precursor (Ni 0.65 Co 0.07 Mn 0.28 )(OH)2, the difference between its preparation method and Example 1 is:

[0174] On the basis of Example 1, the temperature of the second synthesis reaction was lowered to 50° C., air was introduced below the liquid level during the entire second synthesis reaction, and the oxygen content of the gas in the reactor was increased to 8%. Other operations were consistent with Example 1 to obtain a positive electrode material precursor (Ni 0.65 Co 0.07 Mn 0.28)(OH)2.

[0175] Example 9:

[0176] Provide a positive electrode material precursor (Ni 0.65 Co 0.07 Mn 0.28 )(OH)2, the difference between its preparation method and Example 1 is:

[0177] On the basis of Example 1, the solid content of the second base liquid was reduced to 3.0%, and the total reaction time of the second synthesis reaction was shortened to 25 h. Other operations were consistent with Example 1 to obtain a positive electrode material precursor (Ni 0.65 Co 0.07 Mn 0.28 )(OH)2.

[0178] Comparative Example 1:

[0179] Provide a spherical cathode material precursor (Ni 0.65 Co 0.07 Mn 0.28 )(OH)2, the preparation method thereof comprises:

[0180] Battery-grade nickel sulfate, cobalt sulfate, and manganese sulfate were weighed in a molar ratio of Ni:Co:Mn = 65:7:28, and water was added to prepare a 2 mol / L mixed metal salt solution; sodium hydroxide solution with a solute mass fraction of 32.5 wt.% and ammonia water with a solute mass fraction of 20 wt.% were prepared; pure water, sodium hydroxide solution, and ammonia water were added to a reactor as a base solution; the base solution had a pH of 11.5, an ammonia concentration of 6 g / L, and a temperature of 60°C;

[0181] A mixed metal salt solution, a sodium hydroxide solution and an ammonia solution are introduced into a reactor in parallel for a synthesis reaction. During the reaction, the flow rate of the mixed metal salt solution is controlled to be 5% / h of the volume of the reactor, the flow ratio of the mixed metal salt solution, the sodium hydroxide solution and the ammonia solution is 1:0.37:0.045, the initial pH value is 11.5, which is reduced to 11.3 after the reaction is maintained, and then the pH value is maintained stable until the end of the reaction. During the reaction, the stirring speed is 900 rpm, the reaction temperature is 60°C, the free ammonia concentration is 4-5 g / L, nitrogen protection is passed through the reactor to maintain the oxygen content <1%, and the total reaction time is 70 h. Then, after washing, drying, sieving, demagnetizing and packaging, a positive electrode material precursor (Ni) with an average particle size D50 of 3.04 μm is obtained. 0.65 Co 0.07 Mn 0.28 )(OH)2.

[0182] Comparative Example 2:

[0183] Provide a positive electrode material precursor (Ni0.65 Co 0.07 Mn 0.28 )(OH)2, the difference between its preparation method and comparative example 1 is:

[0184] Based on Comparative Example 1, 1 L of cation exchange resin microspheres (polystyrene-divinylbenzene microspheres, particle size of 580-700 μm, density of 1.27 g / mL) was added to the bottom liquid before the synthesis reaction. The stirring speed during the synthesis reaction was adjusted to 1500 rpm. The other operations were consistent with Comparative Example 1 to obtain a positive electrode material precursor (Ni 0.60 Co 0.10 Mn 0.30 )(OH)2.

[0185] Comparative Example 3:

[0186] Provide a two-layer structure of positive electrode material precursor (Ni 0.65 Co 0.07 Mn 0.28 )(OH)2, the preparation method thereof comprises:

[0187] Battery-grade nickel sulfate, cobalt sulfate, and manganese sulfate were weighed in a molar ratio of Ni:Co:Mn = 65:7:28, and water was added to prepare a 2 mol / L mixed metal salt solution; sodium hydroxide solution with a solute mass fraction of 32.5 wt.% and ammonia water with a solute mass fraction of 20 wt.% were prepared; pure water, sodium hydroxide solution, and ammonia water were added to a reactor as a base solution; the base solution had a pH of 11.6, an ammonia concentration of 6 g / L, and a temperature of 60°C;

[0188] A mixed metal salt solution, a sodium hydroxide solution and an ammonia solution are introduced into a reactor in parallel for a synthesis reaction. During the reaction, the flow rate of the mixed metal salt solution is controlled to be 5% / h of the reactor volume, the flow ratio of the mixed metal salt solution, the sodium hydroxide solution and the ammonia solution is 1:0.37:0.045, the initial pH value is 11.6, which is reduced to 11.4 after the reaction is maintained, and then reduced to 11.2 after the reaction is continued, and then the pH value is maintained unchanged until the reactor is stopped. During the reaction, the stirring speed is 900 rpm, the reaction temperature is 60°C, the free ammonia concentration is 4-5 g / L, nitrogen protection is passed through the reactor to maintain the oxygen content <1%, the reaction time is 90 h, and then washed, dried, sieved, demagnetized and packaged to obtain a positive electrode material precursor (Ni) with an average particle size D50 of 14.15 μm. 0.63 Co 0.12 Mn 0.25 )(OH)2.

[0189] Physical and chemical analysis

[0190] The positive electrode material precursors prepared in each embodiment and comparative example were characterized and tested, and the physical and chemical data obtained from the test were as follows: Figures 1-2 As shown in Table 1 and Table 2 below, Figure 1 This is an SEM image of the cathode material precursor prepared in Example 1 of the present application (magnification 10,000 times); Figure 2 Schematic diagram of the size measurement of the length a of the long axis and the length b of the wide axis of the positive electrode material precursor secondary particles prepared in Example 1 of the present application (magnification 30,000 times); Figure 3 This is a surface SEM image of the positive electrode material precursor prepared in Comparative Example 1 of the present application (magnification 30,000 times).

[0191] Table 1. Statistics of physical and chemical data of cathode material precursors Table 1

[0192]

[0193] It should be noted that the test method of the secondary particles in Table 1 above is based on the positive electrode material precursor prepared in Example 1. Figure 1 ) Randomly select multiple secondary particles (for example, 40, selected from 5 different secondary particles) and measure them according to the test method described in the instructions.

[0194] Table 2. Statistics of physical and chemical data of cathode material precursors

[0195]

[0196]

[0197] It should be noted that the test method of primary particles in Table 2 above is based on the cathode material precursor prepared in Example 1. Figure 2 ) Randomly select multiple primary particles (for example, 20, selected from 4 different secondary particles) and measure them according to the test method described in the instructions.

[0198] refer to Figure 1 and Figure 2 It can be found that the primary particles on the surface of the secondary particles of the positive electrode material precursor prepared in Example 1 of the present application are flake-shaped or plate-shaped, the primary particles are stacked in layers on the secondary particles, and most of the primary particles are stacked in a direction along the long axis of the secondary particles, and the long axis size of the secondary particles is larger than the wide axis size.

[0199] On the other hand, comparative example 1, reference Figure 3 It can be found that the secondary particles of the positive electrode material precursor prepared in Comparative Example 1 are spherical.

[0200] In order to verify the performance advantages of the positive electrode material precursors prepared in each embodiment and comparative example, the positive electrode material precursors prepared in each embodiment and comparative example were used to prepare positive electrode materials. The preparation process of each positive electrode material is as follows:

[0201] The cathode material precursors prepared in each embodiment and comparative example were mixed with lithium hydroxide, and the molar ratio of Li:(Ni+Co+n) in the mixed lithium material was 1.05:1. The mixed lithium material was then sintered in oxygen to form a polycrystalline cathode material.

[0202] During the preparation process, the sintering temperature for Examples 1 to 8 was 850-950°C and the sintering time was 14-16 hours. The sintering temperature for Comparative Examples 1 and 2 was 1000°C and the sintering time was 18-22 hours, and crushing was required before sintering. Comparative Example 3 sintered to a polycrystalline structure, with a relatively short sintering temperature and sintering time of 800°C and 16 hours, respectively. The sintering parameters (sintering time and sintering temperature) during the preparation of the positive electrode material from the positive electrode material precursors of each Example and Comparative Example were statistically analyzed.

[0203] The positive electrode material precursors of each embodiment and comparative example were further used to prepare positive electrode material assemblies to form button-type half-cells for electrochemical performance testing. The preparation process of the button-type half-cells is as follows:

[0204] The positive electrode materials prepared from the positive electrode material precursors of the above-mentioned embodiments and comparative examples were respectively mixed with conductive acetylene black and a binder polytetrafluoroethylene PVDF (8 wt% PVDF / NMP solution) in a mass percentage of 8:1:1 to form a slurry, which was coated on aluminum foil to form a positive electrode sheet. The negative electrode sheet used a metal lithium sheet, and the electrolyte used 1 mol / L LiPF6 / EC:DMC (volume ratio 1:1). In a vacuum glove box, the battery case, positive and negative electrode sheets, diaphragm (Celgard-2325), springs, gaskets and electrolyte were assembled into a CR-2032 half-cell.

[0205] The electrochemical performance of each CR-2032 half-cell was tested using a blue electric test system. Specifically, the cycle capacity retention rate was tested at room temperature at 3.0-4.35V and 1C = 180mAh / g for 200 cycles at 1C current. The test results were statistically summarized together with the aforementioned sintering parameters as shown in Table 3 below:

[0206] Table 3. Sintering parameters and electrochemical test data statistics

[0207]

[0208] Performance Analysis:

[0209] Referring to Tables 1 to 3, the cathode material precursors prepared in Examples 1 to 9 of the present application include secondary particles composed of primary particles, the particle size D50 of the secondary particles is 2.00 μm-5.00 μm; the average value of the aspect ratio a / b of the secondary particles is The positive electrode material precursor single crystal provided in the embodiment of the present application has low sintering energy consumption during sintering and is easy to sinter into a single crystal. After the positive electrode material is made into a battery, it can meet the growing cycle performance requirements of electric vehicles.

[0210] Among them, the secondary particles of the positive electrode material precursor obtained in Examples 1-3 all present a small particle long strip structure, and the aspect ratio of the secondary particles is gradient distributed. As the aspect ratio increases, it is easier to sinter into a single crystal, but the cycle performance decreases. Compared with Example 1, Example 4 increases the Ni content of the positive electrode material precursor, and the first discharge capacity of the positive electrode material obtained increases; Example 5 The positive electrode material precursor is doped with Ti element to obtain a positive electrode material with improved cycle performance, but the first discharge capacity decreases; Example 6 The primary particles in the secondary particles of the positive electrode material precursor are stacked in a directional manner along the width axis, and the sintering temperature is high during the firing of the positive electrode material, which easily causes overburning and a decrease in cycle performance; Example 7 The primary particles in the secondary particles of the positive electrode material precursor are thicker, and the temperature is high during the firing of the positive electrode material; Example 8 The primary particles in the secondary particles of the positive electrode material precursor are thinner and easy to secondary crystallize, and the cycle performance of the positive electrode material obtained is slightly decreased; Example 9 The average value of the aspect ratio a / b of the secondary particles of the positive electrode material precursor If the particle size is too large, non-uniform fracture may occur during the sintering process of the positive electrode material, and the primary particles on the fracture surface will be broken, which will reduce the consistency of the single crystal particle size after sintering. In addition, some particles that are too small will aggravate the electrode polarization, and the cycle performance of the positive electrode material will be reduced.

[0211] In addition, compared with Example 1, the cathode material precursors prepared in Comparative Examples 1 and 2 are spherical secondary particles, and the average aspect ratio a / b is Less than 1.70, the sintering temperature is high and the sintering time is long during the sintering of the positive electrode material, and the particles need to be crushed before sintering, resulting in poor consistency of the crushed particles, and the first discharge capacity and cycle performance of the obtained positive electrode material are also poor; the positive electrode material precursor prepared in Comparative Example 3 is a spherical secondary particle with an average aspect ratio a / b of Less than 1.70, the secondary particle size D50 is 14.15μm, greater than 5μm, the sintering time is too long during the sintering of the positive electrode material, and it is sintered into polycrystalline, resulting in low cycle performance of the positive electrode material.

[0212] In summary, the positive electrode material precursor single crystal provided in the embodiment of the present application has low energy consumption and less lattice distortion during sintering. After the positive electrode material is made into a battery, the cycle life can be significantly improved to meet the growing cycle performance requirements of electric vehicles.

[0213] The various technical features described above can be combined arbitrarily. Although not all possible combinations of these technical features are described, any combination of these technical features should be considered to be covered by this specification as long as such combination does not conflict.

[0214] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A cathode material precursor, characterized in that: The positive electrode material precursor includes secondary particles composed of primary particles, and the particle size D50 of the secondary particles is 2.00 μm-5.00 μm; The average value of the aspect ratio a / b of the secondary particles Wherein, a is the length of the long axis of the secondary particle, and b is the length of the wide axis of the secondary particle.

2. The cathode material precursor according to claim 1, characterized in that The positive electrode material precursor satisfies at least one of the following conditions: A. The primary particles are in the form of flakes and / or plates; B. At least part of the primary particles in the secondary particles are stacked along the long axis direction.

3. The cathode material precursor according to any one of claims 1 or 2, characterized in that: The positive electrode material precursor satisfies at least one of the following conditions: D. The number of primary particles stacked in a direction along the long axis accounts for more than 50% of the total number of primary particles; optionally, the number of primary particles stacked in a direction along the long axis accounts for more than 80% of the total number of primary particles; E. Average value of aspect ratio a / b of the secondary particles 1.70-2.50; F, the average length of the major axis of the secondary particles 3.60μm-5.00μm; G. Average length of the width axis of the secondary particles 1.50μm-2.70μm; H. The specific surface area of ​​the secondary particles is 4.00 m 2 / g-9.00m 2 / g; I. The tap density TD of the secondary particles is 1.70 g / cm 3 -2.10g / cm 3 ; J. The particle size distribution K90 of the secondary particles is 0.50-1.20; K, the average length of the primary particles 400nm-1500nm; L, the average thickness of the primary particles 80nm-200nm.

4. The cathode material precursor according to any one of claims 1 to 3, characterized in that: The chemical formula of the positive electrode material precursor is: Ni x Co y Mn z M t (OH) 2+δ , where 0.60≤x<1.00, 0≤t≤0.10, -0.12≤δ≤0.20, x+y+z+t=1, M is a doping element; Optionally, the doping element M includes at least one of Al, Ti, Zr, Mo, Mg, Ba, Nb or Sr.

5. A method for preparing a cathode material precursor according to any one of claims 1 to 4, characterized in that: include: The first synthesis stage: a metal salt solution, a precipitant solution, and a complexing agent solution are introduced into a first base liquid containing a precipitant and a complexing agent to carry out a first synthesis reaction to obtain a material obtained by the first synthesis reaction, and the material obtained by the first synthesis reaction is refined to obtain a seed slurry having a first target particle size; The second synthesis stage: introducing the seed slurry of the first target particle size into the raw materials of the first base liquid to prepare a second base liquid, and introducing a metal salt solution, a precipitant solution, and a complexing agent solution into the second base liquid to carry out a second synthesis reaction to obtain a slurry having the second target particle size; Post-processing stage: post-processing the slurry to obtain the positive electrode material precursor.

6. The preparation method according to claim 5, characterized in that The first synthesis reaction process includes: after the first synthesis reaction starts, controlling the first initial pH value of the reaction system to drop to a first target pH value, then increasing the pH value of the reaction system to a second target pH value, and then increasing the pH value of the reaction system to a third target pH value, and continuing the reaction until the first target particle size reaches 3.00 μm-4.00 μm; The second synthesis reaction process includes: controlling the reaction system to gradually decrease from a second initial pH value to a fourth target pH value, and then continuing the reaction until the second target particle size reaches 2.00 μm-5.00 μm.

7. The preparation method according to claim 5 or 6, characterized in that: The preparation method satisfies at least one of the following conditions: a. The metal salt in the metal salt solution includes a nickel salt, a cobalt salt, a manganese salt and / or a combination of doped metal salts containing at least a nickel salt; the nickel salt includes one or more of nickel sulfate, nickel nitrate and nickel chloride; the cobalt salt includes one or more of cobalt sulfate, cobalt nitrate and cobalt chloride; the manganese salt includes one or more of manganese sulfate, manganese nitrate and manganese chloride; b. The precipitant comprises one or more of sodium carbonate, sodium hydroxide or potassium hydroxide; c. The complexing agent includes one or more of ammonia water, ammonium carbonate, oxalic acid, citric acid, sodium citrate, ammonium citrate or ammonium oxalate; d. The metal salt concentration in the metal salt solution is 0.5 mol / L-3 mol / L; e. The concentration of the precipitant solution is 25wt%-45wt%; f. The concentration of the complexing agent solution is 10wt%-30wt%; g. The pH value of the second base liquid is lower than the pH value of the first base liquid; h. The complexing agent concentration of the second base solution is less than the complexing agent concentration of the first base solution; i. The pH value of the first base solution is 11.0-11.6; j. The complexing agent concentration of the first base solution is 4g / L-8g / L; k. The pH value of the second base liquid is 10.6-11.4; 1. The complexing agent concentration of the second base solution is 4g / L-7g / L; m. In the first synthesis reaction, the temperature of the reaction system is controlled to be 55°C-65°C, the stirring speed is 600rpm-1200rpm; the concentration of the complexing agent is controlled in the range of 4g / L-8g / L; n. In the second synthesis reaction, the temperature of the reaction system is controlled to be 55° C.-65° C., the stirring speed is 600 rpm-1500 rpm; and the concentration of the complexing agent is controlled to be in the range of 3 g / L-6 g / L; o, the first initial pH value, the first target pH value, the second target pH value, the third target pH value, the second initial pH value, and the fourth target pH value are independently controlled within the range of 10.0-12.0; p. The first synthesis reaction and the second synthesis reaction are entirely carried out under an inert atmosphere, wherein the oxygen content of the gas in the first synthesis reaction vessel and the second synthesis reaction vessel is independently controlled to be less than 2.5%; q. starting the second synthesis reaction under an inert atmosphere with the oxygen content of the gas in the reaction vessel controlled to be less than 5%, and raising the oxygen content of the gas in the reaction vessel to 5%-21% after the pH value drops to the fourth target pH value; r. In the first synthesis stage, the flow rate of the metal salt solution is 6.0% / h-9.0% / h of the available volume of the reaction vessel; s. In the first synthesis stage, the flow ratio of the metal salt solution, the precipitant solution, and the complexing agent solution is 1:(0.30-0.50):(0.03-0.06); t. The particle size of the seed slurry is 0.50 μm-1.50 μm; u. The refinement treatment is a sanding treatment, wherein the rotation speed of the sanding treatment is 1800-4200 rpm and the sanding time is 3h-5h; v. The solid content of the second base liquid is 6.0%-9.0%; w. In the second synthesis stage, the flow rate of the metal salt solution is 4.0% / h-8.0% / h of the available volume of the reaction vessel; x. In the second synthesis stage, the flow ratio of the metal salt solution, the precipitant solution and the complexing agent solution is 1:(0.3-0.4):(0.025-0.065).

8. A positive electrode material, characterized in that The positive electrode material is prepared by using the positive electrode material precursor according to any one of claims 1 to 4 or the positive electrode material precursor according to any one of claims 5 to 7.

9. A battery, characterized in that: The positive electrode of the battery is made of the positive electrode material according to claim 8.

10. An electrical equipment, characterized in that: Comprising the battery of claim 9.

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