Small-particle-size positive electrode material precursor and preparation method thereof, positive electrode material, secondary battery and electric equipment

Abstract

The invention provides a small-particle-size positive electrode material precursor and a preparation method thereof, a positive electrode material, a secondary battery and electrical equipment, the precursor comprises secondary particles composed of primary particles, the particle size D50 of the small-particle-size positive electrode material precursor is 2.0 [mu] m or less, and the sphericity Rq of the secondary particles is 90%-100%. The small-particle-size positive electrode material precursor provided by the invention has relatively small particle size and high sphericity, and is beneficial to improving the cycling stability and safety performance of the small-particle-size positive electrode material while improving the capacity.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and in particular to a small-particle cathode material precursor and a preparation method thereof, a cathode material, a secondary battery and electrical equipment. Background Art

[0002] Lithium-ion batteries are currently widely used in power batteries, small power sources and other fields. As the core component of lithium-ion batteries, the performance of cathode materials will directly affect the battery's cycle life, safety performance, stability performance, etc. Therefore, the development of high-capacity, long-cycle, low-cost cathode material precursors is the future trend of lithium-ion battery cathode materials.

[0003] At present, the particle size of the nickel-cobalt-manganese cathode material precursor prepared by the coprecipitation method in industry is generally greater than 3.5μm, and most of them are 7-15μm. As the particle size increases, although the resistivity of the cathode material precursor powder is reduced to a certain extent, the migration path of lithium ions is increased, and the electrochemical performance is poor. Summary of the invention

[0004] The present application provides a small-particle cathode material precursor and a preparation method thereof, cathode material, secondary battery and electrical equipment, which are at least used to solve the above-mentioned technical problems existing in existing cathode materials.

[0005] According to a first aspect of the present invention, a small-particle cathode material precursor is provided, the small-particle cathode material precursor comprises secondary particles composed of primary particles, the particle size D50 of the small-particle cathode material precursor is less than 2.0 μm, and the sphericity R q It is 90%-100%.

[0006] Since the small-particle positive electrode material precursor provided by the present application has a smaller particle size, after the positive electrode material is prepared therefrom, it is beneficial to shorten the migration path of lithium ions in the positive electrode material, improve the migration rate of lithium ions, give full play to the activity of the internal substances of the positive electrode material, thereby improving the capacity performance of the positive electrode material, and at the same time reduce the concentration polarization phenomenon; in addition, the small-particle positive electrode material precursor provided by the present application has a high sphericity, which can ensure that the small-particle positive electrode material precursor particles have better overall structural consistency, so that the positive electrode material prepared therefrom has higher compressive strength and stronger anti-rupture ability during the charge and discharge cycle, which is beneficial to improving the cycle stability and safety performance of the positive electrode material.

[0007] In some embodiments of the present application, the BET range of the specific surface area of ​​the small-particle cathode material precursor is: 5m 2 / g-60m 2 / g, optional 20m 2 / g-40m2 / g.

[0008] In some embodiments of the present application, the average pore diameter of the small-particle cathode material precursor is 2-50 nm, and can be 5-30 nm.

[0009] In some embodiments of the present application, the adhesion coefficient k of the secondary particles is less than 10%.

[0010] In some embodiments of the present application, the particle size D50 of the small-particle cathode material precursor is less than 1.9 μm, and can be optionally less than 1.8 μm.

[0011] In some embodiments of the present application, the particle size D50 of the small-particle cathode material precursor is less than 1.9 μm, and the sphericity is greater than 94%.

[0012] In some embodiments of the present application, the small-particle cathode material precursor satisfies at least one of the following conditions:

[0013] a. The FWHM (001) in the XRD spectrum of the small-particle cathode material precursor is 0.210-0.690°, optionally 0.210-0.480°;

[0014] b. The peak intensity ratio I(101) / I(001) in the XRD spectrum of the small-particle cathode material precursor is 0.70-1.50, and can be 0.85-1.37;

[0015] c. The grain size D(001) of the small-particle cathode material precursor is 5.1-25.8 nm, optionally 7.3-22.4 nm;

[0016] d. The grain size D(100) of the small-particle cathode material precursor is 21.5-65.8 nm, optionally 30.5-55.0 nm;

[0017] e. The grain size D(100) / D(001) of the small-particle cathode material precursor is 1.01-10.46, and can be optionally 2.36-8.23.

[0018] In some embodiments of the present application, the secondary particles are formed by cross-arrangement of primary particles. Optionally, the primary particles meet one of the following conditions:

[0019] f. The primary particles are in the form of vertical sheets, and optionally, the edges of the primary particles are in the form of irregular teeth. Optionally, the average aspect ratio x / y of the primary particles is 1.0-58.9, and optionally 20.0-45.0;

[0020] g. The primary particles are composed of a plurality of thin sheet units vertically stacked and aggregated. Optionally, the average aspect ratio x / y of the primary particles is 10.0-20.0.

[0021] In some embodiments of the present application, the chemical formula of the small-particle cathode material precursor is

[0022] Ni a Co b Mn c M (1-a-b-c) (OH)2, wherein a, b, and c represent molar ratios, wherein 0.50≤a≤1.00 (optionally 0.90≤a≤1.00), 0≤b≤0.50, 0≤c≤0.50, and 0.80≤a+b+c≤1.00; and the doping element M is one or more of B, P, Ca, Ta, Nb, Sr, Ba, Mg, Al, Ti, Y, Zr, W, and La.

[0023] According to a second aspect of the present invention, there is provided a method for preparing the above-mentioned small-particle cathode material precursor, comprising:

[0024] A preparation step, preparing a base solution comprising a precipitant and a complexing agent, wherein the pH of the base solution is 11.8-12.2;

[0025] A synthesis reaction step, wherein a metal salt solution, a precipitant solution and a complexing agent solution are simultaneously introduced into the base liquid, and a synthesis reaction is performed under an atmosphere of protective gas, and the reaction temperature is maintained at 55 to 80° C. to obtain a mixed solution;

[0026] The separation step is to separate the mixed liquid into solid and liquid to obtain the small-particle cathode material precursor.

[0027] In some embodiments of the present application, the preparation method satisfies at least one of the following conditions:

[0028] a. The metal salt is a combination of nickel salt, cobalt salt, manganese salt and doping element salt containing at least nickel salt; optionally, the sum of the mass concentrations of metal ions in the metal salt solution is 50-200 g / L, optionally 80-150 g / L;

[0029] b. The precipitant includes one or more of sodium carbonate, sodium hydroxide, and potassium hydroxide; optionally, the mass percentage concentration of the precipitant solution is 5.0%-50.0%, optionally 10.0%-30.0%;

[0030] c. The complexing agent includes one or more of ammonia, ammonium carbonate, oxalic acid, citric acid, sodium citrate, ammonium citrate, and ammonium oxalate; optionally, the mass percentage concentration of the complexing agent solution is 1.0%-40.5%, optionally 10.0%-20.0%;

[0031] d. In the preparation step, the base liquid is heated to 55 to 80 ° C;

[0032] e. In the synthesis reaction step, the pH of the synthesis reaction is maintained at 9.5-11.5, optionally 10.0-10.8;

[0033] f. In the synthesis reaction step, the mass concentration of the complexing agent is maintained at 2-8.0 g / L, optionally 3.0-5.0 g / L;

[0034] g. In the synthesis reaction step, the reaction speed is 300-800r / min, optionally 400-600r / min;

[0035] h. In the synthesis reaction step, the metal salt solution is introduced at a rate of 5 to 10% of the available volume of the reaction vessel / h;

[0036] i. In the synthesis reaction step, the precipitant solution is introduced at a rate of 1.8 to 2.5% / h of the available volume of the reaction vessel;

[0037] j. In the synthesis reaction step, the introduction rate of the complexing agent solution is 0.10-0.40% / h of the available volume of the reaction container, and can be 0.12-0.20% / h.

[0038] According to a third aspect of the present invention, a positive electrode material is provided. The positive electrode material is prepared by the above-mentioned small-particle-size positive electrode material precursor or the preparation method of the above-mentioned small-particle-size positive electrode material precursor.

[0039] According to a fourth aspect of the present invention, there is provided a secondary battery comprising a positive electrode plate, wherein the positive electrode plate is made of the positive electrode material mentioned above.

[0040] According to a fifth aspect of the present invention, there is provided an electrical device comprising the above-mentioned secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0042] Figure 1 This is the SEM image (3000 times) of the small-particle cathode material precursor prepared in Example 1.

[0043] Figure 2This is the SEM image (50,000 times) of the small-particle cathode material precursor prepared in Example 1.

[0044] Figure 3 This is the SEM image (10,000 times) of the small-particle cathode material precursor prepared in Example 1.

[0045] Figure 4 This is the CP diagram of the small-particle positive electrode material precursor prepared in Example 1.

[0046] Figure 5 This is the SEM image (3000 times) of the small-particle cathode material precursor prepared in Example 4.

[0047] Figure 6 This is the SEM image (50,000 times) of the small-particle cathode material precursor prepared in Example 4.

[0048] Figure 7 This is the CP diagram of the small-particle positive electrode material precursor prepared in Example 4.

[0049] Figure 8 This is the SEM image (3000 times) of the small-particle cathode material precursor prepared in Comparative Example 1.

[0050] Fig. 9 This is the SEM image (50,000 times) of the small-particle cathode material precursor prepared in Comparative Example 1.

[0051] Fig.10 This is the SEM image (3000 times) of the small-particle cathode material precursor prepared in Comparative Example 2.

[0052] Fig.11 This is the SEM image (50,000 times) of the small-particle cathode material precursor prepared in Comparative Example 2. DETAILED DESCRIPTION

[0053] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a 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 a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present 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 real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it 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.

[0054] If not otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0055] 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.

[0056] If not otherwise specified, all steps of the present application may be performed sequentially or randomly, and may be performed sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which 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 may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0057] If there is no special explanation, the "include" and "comprising" mentioned in this application represent open-ended or closed-ended expressions. For example, the "include" and "comprising" may also include or contain other components not listed, or may only include or contain the listed components.

[0058] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": 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).

[0059] The present application provides a small-particle cathode material precursor, which includes secondary particles composed of primary particles. The particle size D50 of the small-particle cathode material precursor is less than 2.0 μm, and the sphericity R q It is 90%-100%.

[0060] Small-particle precursor materials have smaller particle sizes and better stability, and can have both good rate performance and discharge specific capacity. Currently, the small-particle precursor materials prepared in industry have relatively poor primary particle morphology consistency, secondary particle sphericity, and dispersibility, resulting in poor overall performance of batteries made from small-particle precursor materials.

[0061] The small-particle cathode material precursor provided in the present application has a relatively small particle size D50≤2.0μm, and D50≤1.9μm can be selected, such as 0.9μm, 1.2μm, 1.5μm, 1.8μm, etc. After the cathode material is prepared therefrom, it is beneficial to shorten the migration path of lithium ions in the cathode material, increase the migration rate of lithium ions, give full play to the activity of the internal substances of the cathode material, thereby improving the capacity performance of the cathode material, and at the same time reduce the concentration polarization phenomenon; in addition, the small-particle cathode material precursor provided in the present application has a high sphericity R q 90%-100%, optionally 92%-100%, such as 93%, 95%, 98%, etc., can ensure that the small-size positive electrode material precursor particles have better overall structural consistency, so that the positive electrode material prepared therefrom has higher compressive strength and stronger resistance to rupture during the charge and discharge cycle, which is beneficial to improving the cycle stability and safety performance of the positive electrode material.

[0062] In some embodiments of the present application, the particle size D50 of the small-particle cathode material precursor is less than 1.9 μm, and can be optionally less than 1.8 μm.

[0063] In some embodiments of the present application, the particle size D50 of the small-particle cathode material precursor is less than 1.9 μm, and the sphericity is greater than 94%.

[0064] In some embodiments of the present application, the BET range of the specific surface area of ​​the small-particle cathode material precursor is: 5m 2 / g-60m 2 / g, optional 20m 2 / g-40m 2 / g.

[0065] In this application, the small-particle cathode material precursor has a large specific surface area of ​​5m 2 / g-60m 2 / g, optional 20m 2 / g-40m 2 / g, such as 25m 2 / g, 28m 2 / g, 33m 2 / g, 37m 2 / g, 39m 2 / g, etc., indicating that it has a porous structure, which is conducive to the electrolyte in the battery to fully infiltrate the positive electrode material prepared by it, improve the diffusion capacity of the electrolyte, promote the rapid transmission of electrons and ions, and effectively improve the charge and discharge performance of the battery.

[0066] In some embodiments of the present application, the average pore diameter of the small-particle positive electrode material precursor is 2-50nm, and can be 5-30nm, such as 13nm, 15nm, 18nm, 22nm, 26nm, etc.

[0067] In some embodiments of the present application, the adhesion coefficient k of the secondary particles is less than 10%.

[0068] In the present application, the secondary particles constituting the small-particle positive electrode material precursor have high dispersibility (having a small adhesion coefficient k-10% or less), and k≤9% can be selected, such as 2%, 4%, 5%, 6%, 8%, etc., indicating that a single secondary particle has higher structural integrity and consistency and is not easy to agglomerate. At the same time, the secondary particles also have higher compressive strength, which is beneficial to improving the cycle performance of the positive electrode material prepared therefrom. In addition, it is also beneficial to improve the compaction density of the positive electrode material, that is, it is beneficial to improve the charge and discharge specific capacity of the positive electrode material.

[0069] In some embodiments of the present application, the FWHM (001) in the XRD spectrum of the small-particle cathode material precursor is 0.210-0.690°, and can be optionally 0.210-0.480°, such as 0.250-0.600°, 0.280-0.550°, 0.310-0.430°, etc. The small-particle cathode material precursor has a smaller half-peak width, which is beneficial to improving the cycle performance of the material.

[0070] In some embodiments of the present application, the peak intensity ratio I(101) / I(001) in the XRD spectrum of the small-particle positive electrode material precursor is 0.70-1.50, and can be optionally 0.85-1.37, such as 0.90-1.20, 0.95-1.10, etc. The small-particle positive electrode material precursor has a higher peak intensity ratio, indicating that the small-particle positive electrode material precursor has a higher degree of crystallinity, so that the positive electrode material prepared therefrom has better stability during the charge and discharge process, which is beneficial to improving the cycle performance of the positive electrode material and extending the service life of the battery.

[0071] In some embodiments of the present application, the grain size D(001) of the small-particle cathode material precursor is 5.1-25.8 nm, and optionally 7.3-22.4 nm.

[0072] In some embodiments of the present application, the grain size D(100) of the small-particle cathode material precursor is 21.5-65.8 nm, and may be 30.5-55.0 nm.

[0073] In some embodiments of the present application, the grain size D(100) / D(001) of the small-particle cathode material precursor is 1.01-10.46, and can be optionally 2.36-8.23.

[0074] In the present application, the grain size D value or D value ratio of the (001) crystal plane and (100) crystal plane of the secondary particles of the small-particle positive electrode material precursor are both large, indicating that the overall grain size is large, which is conducive to the formation of a uniform single crystal structure of the small-particle positive electrode material precursor during the sintering process of the positive electrode material, effectively solving the problem of inconsistent lithium ion deintercalation depth caused by different grain sizes in the positive electrode material, and improving the cycle stability performance of the positive electrode material.

[0075] In some embodiments of the present application, the secondary particles are formed by cross-arrangement of the primary particles.

[0076] In some embodiments of the present application, the secondary particles are formed by cross-arranged primary particles, the primary particles are in the shape of vertical sheets, optionally, the edges of the primary particles are in the shape of irregular teeth, optionally, the average aspect ratio x / y of the primary particles is 1.0-58.9, optionally 20.0-45.0.

[0077] In some embodiments of the present application, the secondary particles are formed by cross-arranged primary particles, and the primary particles are composed of a plurality of vertically stacked sheet units. Optionally, the average aspect ratio x / y of the primary particles is 10.0-20.0.

[0078] This shows that the primary particles that make up the secondary particles are in the shape of elongated flakes or strips, arranged vertically and crosswise, which is beneficial for the positive electrode material prepared therefrom to expose more reactive areas, promote the infiltration and diffusion of the electrolyte, and enhance the charge and discharge performance of the positive electrode material.

[0079] In some embodiments of the present application, the chemical formula of the small-particle cathode material precursor is

[0080] Ni a Co b Mn c M (1-a-b-c) (OH)2, wherein a, b, and c represent molar ratios, wherein 0.50≤a≤1.00 (optionally 0.90≤a≤1.00), 0≤b≤0.50, 0≤c≤0.50, and 0.80≤a+b+c≤1.00; the doping element M is one or more of B, P, Ca, Ta, Nb, Sr, Ba, Mg, Al, Ti, Y, Zr, W, and La. A variety of elements can be doped according to actual needs to improve the structural characteristics or electrochemical properties of the positive electrode material prepared therefrom.

[0081] The present application also provides a method for preparing the above-mentioned small-particle cathode material precursor, comprising:

[0082] A preparation step, preparing a base solution containing a precipitant and a complexing agent, wherein the pH of the base solution is 11.8-12.2;

[0083] The synthesis reaction step comprises introducing a metal salt solution, a precipitant solution and a complexing agent solution into the base liquid at the same time, carrying out a synthesis reaction under a protective gas atmosphere, and maintaining the reaction temperature at 55 to 80° C. to obtain a mixed solution;

[0084] In the separation step, the mixed liquid is subjected to solid-liquid separation to obtain a small-particle-size positive electrode material precursor.

[0085] In the preparation method provided by the present application, by preparing a base solution containing a precipitant and a complexing agent in advance, crystal nuclei of uniform size can be formed when a metal solution is subsequently introduced. Then, by adjusting the amount of the precipitant and the complexing agent added, the crystallization rate and the dispersibility of the small-sized positive electrode material precursor particles are effectively controlled, and a synthesis reaction is performed to prepare a positive electrode material precursor with high sphericity and small particle size.

[0086] In some embodiments of the present application, the selection of reagents, and the control of the sum of the mass concentrations of metal ions in the metal salt solution, the concentration of the precipitant, and the concentration of the complexing agent within a certain range are all beneficial to controlling the progress of the synthesis reaction.

[0087] Specifically, the metal salt is a combination of nickel salt, cobalt salt, manganese salt and doping element salt containing at least nickel salt; optionally, the sum of the mass concentrations of metal ions in the metal salt solution is 50-200 g / L, optionally 80-150 g / L, such as 75 g / L, 87 g / L, 98 g / L, 110 g / L, 124 g / L, 132 g / L, 147 g / L, etc.

[0088] The precipitant includes one or more of sodium carbonate, sodium hydroxide, and potassium hydroxide; optionally, the mass percentage concentration of the precipitant solution is 5.0%-50.0%, optionally 10.0%-30.0%, such as 6.5%, 8.4%, 15.3%, 22.2%, 29.5%, etc.

[0089] The complexing agent includes one or more of ammonia water, ammonium carbonate, oxalic acid, citric acid, sodium citrate, ammonium citrate, and ammonium oxalate; optionally, the mass percentage concentration of the complexing agent solution is 1.0%-40.5%, optionally 10.0%-20.0%, such as 12.4%, 16.3%, 18.7%, etc.

[0090] In some embodiments of the present application, during the preparation step, the pH and temperature of the base solution are maintained within a suitable range, which can provide suitable reaction conditions for subsequent synthesis reactions. At the same time, the concentration of the complexing agent in the base solution is within a suitable range to facilitate controlling the reaction rate of the synthesis reaction.

[0091] Specifically, the pH of the base solution is 11.8-12.2, such as 11.9, 12.0, 12.1, 12.2, etc. The base solution is heated to 55-80°C; 60-75°C may be selected, such as 65°C, 69°C, 73°C, etc.

[0092] In some embodiments of the present application, in the synthesis reaction step, the pH of the synthesis reaction is maintained at 9.5-11.5, and can be 10.0-10.8, such as 10.2, 10.3, 10.5, 10.7, etc. The mass concentration of the complexing agent is maintained at 2-8.0 g / L, and can be 3.0-5.0 g / L, such as 2.6 g / L, 3.5 g / L, 4.3 g / L, etc. The temperature of the synthesis reaction is maintained at 55-80°C, and can be 60-75°C, such as 65°C, 69°C, 73°C, etc.

[0093] In some embodiments of the present application, in the synthesis reaction step, the stirring speed is 300-800 r / min, optionally 400-600 r / min, such as 420 r / min, 450 r / min, 500 r / min, 550 r / min, etc.

[0094] In some embodiments of the present application, in the synthesis reaction step, the introduction rate of the metal salt solution is 5-10% / h of the available volume of the reaction container, such as 6% / h, 7.5% / h, 9% / h, etc.

[0095] In some embodiments of the present application, in the synthesis reaction step, the introduction rate of the precipitant solution is 1.8-2.5% / h of the available volume of the reaction container, such as 1.4% / h, 1.8% / h, 2.2% / h, etc.

[0096] In some embodiments of the present application, in the synthesis reaction step, the introduction rate of the complexing agent solution is 0.10-0.40% / h of the available volume of the reaction container, and 0.12-0.20% / h can be selected, such as 0.13% / h, 0.15% / h, 0.18% / h, etc.

[0097] Sphericity is one of the key indicators for evaluating precursor performance. Small particle precursors with high sphericity are of great significance for improving the cycle performance and capacity performance of cathode materials. According to the current precursor synthesis technology, when the particle size is greater than 3.5-4.0μm, it is easier to obtain a precursor product with higher sphericity due to the relatively long reaction cycle and sufficient particle growth time. When the particle size is less than 3.5-4μm, the sphericity of the particles is relatively poor.

[0098] When D50 is less than 2 μm, it is more difficult to obtain secondary particles with high sphericity. The present application adopts a complexation controlled crystallization coprecipitation method. By optimizing the pH value, reaction temperature, stirring and other process parameters in the nucleation period, the crystallization nucleation rate in the nucleation period is controlled. At the same time, the ammonia concentration, pH, reaction temperature and other conditions of the growth period reaction are adjusted. As the reaction proceeds, at a continuously increasing solid-liquid ratio, the metal salt aqueous solution and the sodium hydroxide aqueous solution are coprecipitated under the complexation of ammonia water and the like to obtain a small-sized precursor particle precipitate with uniform element distribution, good sphericity, uniform particle size distribution and good dispersibility. The present invention solves the problems of poor sphericity, difficult particle size control, easy agglomeration and poor dispersibility of small-sized precursor particles prepared by the existing method.

[0099] The present application provides a positive electrode material, which is made from the above-mentioned small-particle positive electrode material precursor, and is made by mixing and sintering the above-mentioned small-particle positive electrode material precursor and a lithium source as raw materials.

[0100] The present application provides a secondary battery, including a positive electrode plate, wherein the positive electrode plate is made of the above-mentioned positive electrode material, so that the secondary battery has higher cycle capacity, stability and safety.

[0101] The present application provides an electrical device, which includes the secondary battery mentioned above.

[0102] In order to fully demonstrate the advantages of the small-particle cathode material precursor provided by the present application, a description will be given below in conjunction with specific embodiments.

[0103] Example 1

[0104] (1) Preparation of small-particle cathode material precursors

[0105] ① Prepare a metal salt solution with a metal ion mass concentration of 115 g / L as solution A, wherein the metal salts are nickel sulfate and cobalt sulfate, and the molar ratio of nickel to cobalt is Ni:Co=95:5; a sodium hydroxide solution with a mass percentage concentration of 18.9% as solution B; and an ammonia solution with a mass percentage concentration of 11.8% as solution C;

[0106] ② Add pure water, solution B and solution C into the reaction vessel to prepare the base solution, control the pH value of the base solution to 11.95, the mass concentration of ammonia water to 3.0 g / L, introduce nitrogen as a protective gas, and heat the base solution to 60°C.

[0107] ③ Solution A, solution B and solution C were introduced into the reaction vessel at the same time. The flow rates of solution A, solution B and solution C were 5% / h, 2.3% / h and 0.12% / h of the available volume of the reaction vessel, respectively. The reaction was carried out under a protective gas atmosphere. During the reaction, the pH of the mixed solution was controlled to be maintained at 10.20, and the stirring device was controlled to stir at a speed of 400.35 r / min.

[0108] ④ The reaction is continued until the particle size D50 of the synthesized particles reaches 1.8 μm, and the solid-liquid separation is performed to obtain a precipitate. After washing, drying and sieving the precipitate, a product with the chemical formula Ni 0.95 Co 0.05 Small particle size positive electrode material precursor of (OH)2.

[0109] (2) Preparation of positive electrode materials

[0110] The obtained small-particle cathode material precursor was uniformly mixed with lithium hydroxide in a ratio of 1:1.05, and sintered at 580° C. for 12 h to obtain the cathode material.

[0111] Example 2

[0112] (1) Preparation of small-particle cathode material precursors

[0113] ① Prepare a metal salt solution with a metal ion mass concentration of 115 g / L as solution A, wherein the metal salts are nickel sulfate and cobalt sulfate, and the molar ratio of nickel to cobalt is Ni:Co=95:5; a sodium hydroxide solution with a mass percentage concentration of 18.9% as solution B; and an ammonia solution with a mass percentage concentration of 11.8% as solution C;

[0114] ② Add pure water, solution B and solution C into the reaction vessel to prepare the base solution, control the pH value of the base solution to 11.95, the mass concentration of ammonia water to 7.0 g / L, introduce nitrogen as a protective gas, and heat the base solution to 60°C.

[0115] ③ Solution A, solution B and solution C were introduced into the reaction vessel at the same time. The flow rates of solution A, solution B and solution C were 5% / h, 2.3% / h and 0.28% / h of the available volume of the reaction vessel, respectively. The reaction was carried out under a protective gas atmosphere. During the reaction, the pH of the mixed solution was controlled to be maintained at 10.20, and the stirring device was controlled to stir at a speed of 400.35 r / min.

[0116] ④ The reaction is continued until the particle size D50 of the synthesized particles reaches 1.8 μm, and the solid-liquid separation is performed to obtain a precipitate. After washing, drying and sieving the precipitate, a product with the chemical formula Ni 0.95 Co 0.05 Small particle size positive electrode material precursor of (OH)2.

[0117] (2) Preparation of positive electrode materials

[0118] The obtained small-particle cathode material precursor was uniformly mixed with lithium hydroxide in a ratio of 1:1.05, and sintered at 580° C. for 12 h to obtain the cathode material.

[0119] Example 3

[0120] (1) Preparation of small-particle cathode material precursors

[0121] ① Prepare a metal salt solution with a metal ion mass concentration of 115 g / L as solution A, wherein the metal salts are nickel sulfate and cobalt sulfate, and the molar ratio of nickel to cobalt is Ni:Co=95:5; a sodium hydroxide solution with a mass percentage concentration of 18.9% as solution B; and an ammonia solution with a mass percentage concentration of 11.8% as solution C;

[0122] ② Add pure water, solution B and solution C into the reaction vessel to prepare the base solution, control the pH value of the base solution to 11.95, the mass concentration of ammonia water to 3.0 g / L, introduce nitrogen as a protective gas, and heat the base solution to 60°C.

[0123] ③ Solution A, solution B and solution C were introduced into the reaction vessel at the same time. The flow rates of solution A, solution B and solution C were 5% / h, 2.3% / h and 0.12% / h of the available volume of the reaction vessel, respectively. The reaction was carried out under a protective gas atmosphere. During the reaction, the pH of the mixed solution was controlled to be maintained at 10.20, and the stirring device was controlled to stir at a speed of 300.35 r / min.

[0124] ④ The reaction is continued until the particle size D50 of the synthesized particles reaches 1.8 μm, and the solid-liquid separation is performed to obtain a precipitate. After washing, drying and sieving the precipitate, a product with the chemical formula Ni 0.95 Co 0.05 Small particle size positive electrode material precursor of (OH)2.

[0125] (2) Preparation of positive electrode materials

[0126] The obtained small-particle cathode material precursor was uniformly mixed with lithium hydroxide in a ratio of 1:1.05, and sintered at 580° C. for 12 h to obtain the cathode material.

[0127] Example 4

[0128] (1) Preparation of small-particle cathode material precursors

[0129] ① Prepare a metal salt solution with a metal ion mass concentration of 115 g / L as solution A, wherein the metal salts are nickel sulfate and cobalt sulfate, and the molar ratio of nickel to cobalt is Ni:Co=95:5; a sodium hydroxide solution with a mass percentage concentration of 18.9% as solution B; and an ammonia solution with a mass percentage concentration of 11.8% as solution C;

[0130] ② Add pure water, solution B and solution C into the reaction vessel to prepare the base solution, control the pH value of the base solution to 11.95, the mass concentration of ammonia water to 3.0 g / L, introduce nitrogen as a protective gas, and heat the base solution to 60°C.

[0131] ③ Solution A, solution B and solution C were introduced into the reaction vessel at the same time. The flow rates of solution A, solution B and solution C were 5% / h, 2.3% / h and 0.12% / h of the available volume of the reaction vessel, respectively. The reaction was carried out under a protective gas atmosphere. During the reaction, the pH of the mixed solution was controlled to be maintained at 11.20, and the stirring device was controlled to stir at a speed of 400.35 r / min.

[0132] ④ The reaction is continued until the particle size D50 of the synthesized particles reaches 1.8 μm, and the solid-liquid separation is performed to obtain a precipitate. After washing, drying and sieving the precipitate, a product with the chemical formula Ni 0.95 Co 0.05 Small particle size positive electrode material precursor of (OH)2.

[0133] (2) Preparation of positive electrode materials

[0134] The obtained small-particle cathode material precursor was uniformly mixed with lithium hydroxide in a ratio of 1:1.05, and sintered at 580° C. for 12 h to obtain the cathode material.

[0135] Example 5

[0136] (1) Preparation of small-particle cathode material precursors

[0137] ① Prepare a metal salt solution with a metal ion mass concentration of 110 g / L as solution A, wherein the metal salts are nickel sulfate, cobalt sulfate and manganese sulfate, and the molar ratio of nickel, cobalt and manganese is Ni:Co:Mn=60:10:30; a sodium hydroxide solution with a mass percentage concentration of 18.9% as solution B; and an ammonia solution with a mass percentage concentration of 11.8% as solution C;

[0138] ② Add pure water, solution B and solution C into the reaction vessel to prepare the base solution, control the pH value of the base solution to 12.20, the mass concentration of ammonia water to 3.0 g / L, introduce nitrogen as a protective gas, and heat the base solution to 60°C.

[0139] ③ Solution A, solution B and solution C were introduced into the reaction vessel at the same time. The flow rates of solution A, solution B and solution C were 5% / h, 2.3% / h and 0.12% / h of the available volume of the reaction vessel, respectively. The reaction was carried out under a protective gas atmosphere. During the reaction, the pH of the mixed solution was controlled to be maintained at 9.80, and the stirring device was controlled to stir at a speed of 400.35 r / min.

[0140] ④ The reaction is continued until the particle size D50 of the synthesized particles reaches 1.8 μm, and the solid-liquid separation is performed to obtain a precipitate. After washing, drying and sieving the precipitate, a product with the chemical formula Ni 0.60 Co 0.10 Mn 0.30 Small particle size positive electrode material precursor of (OH)2.

[0141] (2) Preparation of positive electrode materials

[0142] The obtained small-particle cathode material precursor was uniformly mixed with lithium hydroxide in a ratio of 1:1.05, and sintered at 580° C. for 12 h to obtain the cathode material.

[0143] Comparative Example 1

[0144] (1) Preparation of small-particle cathode material precursors

[0145] ① Prepare a metal salt solution with a metal ion mass concentration of 115 g / L as solution A, wherein the metal salts are nickel sulfate and cobalt sulfate, and the molar ratio of nickel to cobalt is Ni:Co=95:5; a sodium hydroxide solution with a mass percentage concentration of 18.9% as solution B; and an ammonia solution with a mass percentage concentration of 11.8% as solution C;

[0146] ② Add pure water, solution B and solution C into the reaction vessel to prepare the base solution, control the pH value of the base solution to 11.95, the mass concentration of ammonia water to 7.0 g / L, introduce nitrogen as a protective gas, and heat the base solution to 60°C.

[0147] ③ Solution A, solution B and solution C were introduced into the reaction vessel at the same time. The flow rates of solution A, solution B and solution C were 5% / h, 2.3% / h and 0.28% of the available volume of the reaction vessel, respectively. The reaction was carried out under a protective gas atmosphere. During the reaction, the pH of the mixed solution was controlled to be maintained at 10.20, and the stirring device was controlled to stir at a speed of 280.35 r / min.

[0148] ④ The reaction is continued until the particle size D50 of the synthesized particles reaches 2.0 μm, and the solid-liquid separation is performed to obtain a precipitate. After washing, drying and sieving the precipitate, a product with the chemical formula Ni 0.95 Co 0.05 Small particle size positive electrode material precursor of (OH)2.

[0149] (2) Preparation of positive electrode materials

[0150] The obtained small-particle cathode material precursor was uniformly mixed with lithium hydroxide in a ratio of 1:1.05, and sintered at 580° C. for 10 h to obtain the cathode material.

[0151] Comparative Example 2

[0152] (1) Preparation of small-particle cathode material precursors

[0153] ① Prepare a metal salt solution with a metal ion mass concentration of 115 g / L as solution A, wherein the metal salts are nickel sulfate and cobalt sulfate, and the molar ratio of nickel to cobalt is Ni:Co=95:5; a sodium hydroxide solution with a mass percentage concentration of 18.9% as solution B; and an ammonia solution with a mass percentage concentration of 11.8% as solution C;

[0154] ② Add pure water, solution B and solution C into the reaction vessel to prepare the base solution, control the pH value of the base solution to 11.95, the mass concentration of ammonia water to 3.0 g / L, introduce nitrogen as a protective gas, and heat the base solution to 60°C.

[0155] ③ Solution A, solution B and solution C were introduced into the reaction vessel at the same time. The flow rates of solution A, solution B and solution C were 5% / h, 2.3% / h and 0.12% / h of the available volume of the reaction vessel, respectively. The reaction was carried out under a protective gas atmosphere. During the reaction, the pH of the mixed solution was controlled to be maintained at 11.00, and the stirring device was controlled to stir at a speed of 400.35 r / min.

[0156] ④ The reaction is continued until the particle size D50 of the synthesized particles reaches 2.5 μm, and the solid-liquid separation is performed to obtain a precipitate. After washing, drying and sieving the precipitate, a precipitate with the chemical formula Ni is obtained. 0.95 Co 0.05 Small particle size positive electrode material precursor of (OH)2.

[0157] (2) Preparation of positive electrode materials

[0158] The obtained small-particle cathode material precursor was uniformly mixed with lithium hydroxide in a ratio of 1:1.05, and sintered at 580° C. for 12 h to obtain the cathode material.

[0159] Test Data

[0160] 1. Physical and chemical properties

[0161] In this application, the aspect ratio is a parameter that characterizes the morphology of primary particles. The longest axis of a single primary particle is regarded as its length, and the short axis measured perpendicular to the midpoint of the longest axis is regarded as its width. The specific calculation method is to use a field emission scanning electron microscope (HITACHI's SU8100 series) to take multiple (at least 5) SEM images (50000×) of the same small-particle cathode material precursor. For each SEM image, use Nano Measurer software to measure the length and width of the primary particles on the surface of the secondary particles in the SEM image. Take at least 10 groups of single primary particle data, and then take the average value to obtain the average width and average length of the primary particles, and calculate the average aspect ratio. Several (such as 5) SEM images can be taken for calculation, and then the average value is taken. The length and width of the primary particles in the article are obtained by this method.

[0162] In this application, in order to characterize the dispersibility of the secondary particles of the small-particle cathode material precursor, the adhesion coefficient of the secondary particles is used for evaluation. The specific calculation method is to take multiple (at least 5) SEM images (3000×) of the same small-particle cathode material precursor under a field emission scanning electron microscope (HITACHI's SU8100 series), count the total number of particles N0 in the SEM image, and then count the number of adhesion particles N1 in the SEM image, where adhesion particles refer to particles with a peanut-shaped structure formed by the mutual adhesion of adjacent secondary particles (such as Figure 1 The adhesion coefficient of the secondary particles in a SEM image is calculated using the formula: k = N1 / N0 × 100%. Several (e.g., 5) SEM images can be taken for calculation and then the average value can be taken.

[0163] In this application, in order to characterize the contour shape of the secondary particles, the sphericity of the secondary particles is evaluated, wherein the closer the shape of the secondary particles is to a circle, the closer its sphericity is to 100%. The specific calculation method is to take multiple (at least 5) SEM images (3000×) of the same small-particle cathode material precursor under a field emission scanning electron microscope (HITACHI's SU8100 series), and then use the sphericity analysis software (Avizo) to intelligently identify all small-particle cathode material precursor particles in the SEM image, and calculate the average sphericity in each SEM image by the calculation formula: Sphericity = (4π×area) / (perimeter×perimeter)×100%. Several (such as 5) SEM images can be taken for calculation, and then the average value is taken.

[0164] In the present application, the grain size D value of the (001) crystal plane and the (100) crystal plane is calculated using the Debye-Scherrer formula: D = (K × γ) / (B × cosθ). Wherein, K is the Scherrer constant, K = 0.89, γ is the wavelength of the x-ray, γ = 0.154nm, B represents the half-peak width of the corresponding peak of XRD, and θ is the angle corresponding to the half-peak width.

[0165] In this application, the specific surface area method is used to measure the average pore diameter. First, the small-particle cathode material precursor is subjected to nitrogen adsorption treatment to obtain its specific surface area data, and then the average pore diameter is calculated based on the size of the pores at each point on the specific surface area.

[0166] In the present application, in order to evaluate the cross-sectional structure (CP diagram) of the secondary particles, the prepared small-particle cathode material precursor particles are first vacuum embedded in a conductive adhesive, and then the particles are cut. Finally, the cut small-particle cathode material precursor powder is photographed under a field emission scanning electron microscope (HITACHI's SU8100 series) to obtain a CP diagram of the secondary particles.

[0167] Please refer to Table 1 and Table 2 for the physical and chemical data of the small-particle cathode material precursors prepared in the embodiments and comparative examples obtained in the above manner.

[0168] Table 1 Physical and chemical data of small-particle cathode material precursors prepared in various embodiments and comparative examples

[0169]

[0170] 2. Electrochemical performance

[0171] In this application, a button-type semi-electric battery is used for electrochemical performance testing. The positive electrode materials prepared in the above embodiments and comparative examples are mixed with conductive carbon black and binder PVDF (polyvinylidene fluoride) in a ratio of 8:1:1 to form a slurry, which is coated on aluminum foil to make a positive electrode sheet. The negative electrode sheet uses a metal lithium sheet, and the electrolyte uses 1 mol / L LiPF6 / EC:DMC (volume ratio 1:1). In a vacuum glove box, the battery shell, positive electrode sheet, negative electrode sheet, diaphragm, spring sheet, and gasket are assembled into a button battery. The electrochemical performance test is carried out using a blue electric test system.

[0172] At room temperature, a 0.3C charge-discharge test and a 1C (1C = 210 mA / g) cycle test for 100 cycles were performed at 3.0-4.3 V. Please refer to Table 2 for the electrochemical properties of the positive electrode materials prepared in each embodiment and comparative example.

[0173] Table 2 Electrochemical performance test data of the positive electrode materials prepared in each embodiment and comparative example

[0174]

[0175]

[0176] Please refer to Table 1~Table 2 and Figure 1-Figure 11 As shown, the small-particle cathode material precursors prepared in Examples 1 to 5 all have a relatively small particle size (below 1.87 μm). After the cathode material is prepared therefrom, it is beneficial to shorten the migration path of lithium ions in the cathode material, improve the migration rate of lithium ions, give full play to the activity of the internal substances of the cathode material, thereby improving the capacity performance of the cathode material, and at the same time reduce the concentration polarization phenomenon; and high sphericity (all above 90%), which can ensure that the small-particle cathode material precursor particles have better overall structural consistency, so that the cathode material prepared therefrom has higher compressive strength and stronger anti-rupture ability during the charge and discharge cycle, which is beneficial to improving the cycle stability and safety performance of the cathode material.

[0177] In Comparative Example 1, the sphericity R of the small-size cathode material precursor particles is q The value is smaller than that of Example 1, and the adhesion coefficient k value is larger than that of Example 1, and its cycle performance is obviously worse than that of Example 1, which further illustrates that the lower particle adhesion coefficient and higher sphericity can make the prepared positive electrode material have better compressive strength during the charge and discharge cycle process and the overall structure is more stable, which is beneficial to improving the cycle stability and safety performance of the positive electrode material.

[0178] In Comparative Example 2, the particle size of the small-diameter positive electrode material precursor particles is significantly higher than that of Example 1, and the other indicators are close to those of Example 1. Its discharge specific capacity performance is significantly lower than that of Example 1, indicating that a smaller particle size is more conducive to exerting the electrochemical activity of the internal material and improving its capacity performance.

[0179] Among them, relative to Example 1, in Example 2, the adhesion coefficient k value of the small-particle-size positive electrode material precursor particles is relatively large; in Example 3, the sphericity Rq value of the small-particle-size positive electrode material precursor particles is relatively small, indicating that the lower particle adhesion coefficient and higher sphericity can make the positive electrode material have better compressive strength and stronger particle rupture resistance during the cycle, and the overall structure is more stable, which is more conducive to improving the material's cycle stability and safety performance. In Example 4, the specific surface area and average pore diameter of the small-particle-size positive electrode material precursor are smaller than those of Examples 1 to 3, and its charge and discharge capacity performance is lower than that of Examples 1 to 3. It can be seen that with the increase of BET and the average pore diameter, the capacity shows an increasing trend. It shows that having a larger specific surface area and a larger pore diameter is conducive to promoting the active material inside the material to fully contact with the electrolyte, improving the diffusion capacity of the electrolyte, accelerating the rapid transmission of electrons and ions, and effectively improving the battery's charge and discharge capacity performance. In Example 5, the specific surface area and average pore diameter of the small-particle cathode material precursor are significantly larger than those of Examples 1 to 4. Due to its significantly lower Ni content, its charge and discharge capacity performance is significantly lower than that of Examples 1 to 4, indicating that the discharge specific capacity of the high-Ni product is relatively larger.

[0180] The adhesion coefficient k of the precursor of the small-particle positive electrode material is less than 10%, the primary particles all have a large aspect ratio, and the secondary particles all have a large pore diameter. After the positive electrode material is prepared from it, it is conducive to the infiltration and diffusion of the electrolyte during the charge and discharge process, and the charge and discharge capacity performance of the positive electrode material is improved; and the larger peak ratio I(101) / I(001) indicates that it has good crystallization performance, and the larger D(100) / D(001) indicates that its size is relatively uniform, which can keep the overall structure of the material stable, so that the positive electrode material prepared from it can have good cycle stability performance; in addition, the smaller half-peak width FWHM(001) value is conducive to improving the cycle performance of the positive electrode material prepared from it. Therefore, the positive electrode material prepared in some embodiments not only has a higher 0.3C first discharge capacity, but also has better rate performance and higher capacity retention rate.

[0181] Finally, it should be noted that the various technical features described above can be combined arbitrarily. Although all possible combinations of these technical features are not described, any combination of these technical features should be considered to be covered by this specification as long as there is no contradiction in such combination.

[0182] In addition, 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 above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein by 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 small-particle cathode material precursor, characterized in that: The small-particle cathode material precursor comprises secondary particles composed of primary particles, the particle size D50 of the small-particle cathode material precursor is less than 2.0 μm, and the sphericity R q It is 90%-100%.

2. The small-particle cathode material precursor according to claim 1, characterized in that: The BET range of the specific surface area of ​​the small-particle cathode material precursor is: 5m 2 / g-60m 2 / g, optional 20m 2 / g-40m 2 / g; And / or, the average pore diameter of the small-particle cathode material precursor is 2-50 nm, optionally 5-30 nm; and / or, the adhesion coefficient k of the secondary particles is less than 10%; And / or, the particle size D50 of the small-particle cathode material precursor is less than 1.9 μm, and optionally less than 1.8 μm.

3. The small-particle cathode material precursor according to claim 1, characterized in that: The small-particle cathode material precursor satisfies at least one of the following conditions: a. The FWHM (001) in the XRD spectrum of the small-particle cathode material precursor is 0.210-0.690°, optionally 0.210-0.480°; b. The peak intensity ratio I(101) / I(001) in the XRD spectrum of the small-particle cathode material precursor is 0.70-1.50, and can be 0.85-1.37; c. The grain size D(001) of the small-particle cathode material precursor is 5.1-25.8 nm, optionally 7.3-22.4 nm; d. The grain size D(100) of the small-particle cathode material precursor is 21.5-65.8 nm, optionally 30.5-55.0 nm; e. The grain size D(100) / D(001) of the small-particle cathode material precursor is 1.01-10.46, and can be optionally 2.36-8.

23.

4. The small-particle cathode material precursor according to claim 1, characterized in that: The secondary particles are formed by cross-arrangement of primary particles. Optionally, the primary particles meet one of the following conditions: f. The primary particles are in the form of vertical sheets, and optionally, the edges of the primary particles are in the form of irregular teeth. Optionally, the average aspect ratio x / y of the primary particles is 1.0-58.9, and optionally 20.0-45.0; g. The primary particles are composed of a plurality of thin sheet units vertically stacked and aggregated. Optionally, the average aspect ratio x / y of the primary particles is 10.0-20.

0.

5. The small-particle cathode material precursor according to any one of claims 1 to 4, characterized in that: The chemical formula of the small-particle cathode material precursor is Ni a Co b Mn c M (1-a-b-c) (OH)2, wherein a, b, and c represent molar ratios, 0.50≤a≤1.00, 0≤b≤0.50, 0≤c≤0.50, and 0.80≤a+b+c≤1.00; the doping element M is one or more of B, P, Ca, Ta, Nb, Sr, Ba, Mg, Al, Ti, Y, Zr, W, and La.

6. A method for preparing a small-particle cathode material precursor according to any one of claims 1 to 5, characterized in that: include: A preparation step, preparing a base solution comprising a precipitant and a complexing agent, wherein the pH of the base solution is 11.8-12.2; A synthesis reaction step, wherein a metal salt solution, a precipitant solution and a complexing agent solution are simultaneously introduced into the base liquid, and a synthesis reaction is performed under an atmosphere of protective gas, and the reaction temperature is maintained at 55 to 80° C. to obtain a mixed solution; The separation step is to separate the mixed liquid into solid and liquid to obtain the small-particle cathode material precursor.

7. The method for preparing a small-particle cathode material precursor according to claim 6, characterized in that: The preparation method satisfies at least one of the following conditions: a. The metal salt is a combination of nickel salt, cobalt salt, manganese salt and doping element salt containing at least nickel salt; optionally, the sum of the mass concentrations of metal ions in the metal salt solution is 50-200 g / L, optionally 80-150 g / L; b. The precipitant includes one or more of sodium carbonate, sodium hydroxide, and potassium hydroxide; optionally, the mass percentage concentration of the precipitant solution is 5.0%-50.0%, optionally 10.0%-30.0%; c. The complexing agent includes one or more of ammonia, ammonium carbonate, oxalic acid, citric acid, sodium citrate, ammonium citrate, and ammonium oxalate; optionally, the mass percentage concentration of the complexing agent solution is 1.0%-40.5%, optionally 10.0%-20.0%; d. In the preparation step, the base liquid is heated to 55 to 80 ° C; e. In the synthesis reaction step, the pH of the synthesis reaction is maintained at 9.5-11.5, optionally 10.0-10.8; f. In the synthesis reaction step, the mass concentration of the complexing agent is maintained at 2-8.0 g / L, optionally 3.0-5.0 g / L; g. In the synthesis reaction step, the stirring speed is 300-800r / min, optionally 400-600r / min; h. In the synthesis reaction step, the metal salt solution is introduced at a rate of 5-10% / h of the available volume of the reaction vessel; i. In the synthesis reaction step, the precipitant solution is introduced at a rate of 1.8-2.5% / h of the available volume of the reaction vessel; j. In the synthesis reaction step, the introduction rate of the complexing agent solution is 0.10-0.40% / h of the available volume of the reaction container, and can be 0.12-0.20% / h.

8. A positive electrode material, characterized in that The positive electrode material is prepared by the small-particle-size positive electrode material precursor described in any one of claims 1 to 5 or the preparation method of the small-particle-size positive electrode material precursor described in any one of claims 6 to 7.

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

10. An electrical equipment, characterized in that: A secondary battery comprising the secondary battery according to claim 9.

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