Positive electrode material precursor, preparation method thereof and positive electrode material

Abstract

The invention discloses a positive electrode material precursor, a preparation method thereof and a positive electrode material, the positive electrode material precursor provided by the invention comprises a secondary particle formed by aggregating a plurality of primary particles, and the secondary particle comprises a loose core and a compact shell formed on the surface of the loose core; in an XRD pattern of the positive electrode material precursor, the 001 peak half width FWHM (001) is less than or equal to 0.7, the 101 peak half width FWHM (101) is less than or equal to 0.7, the deformation fault rate fD is 1-10%, fD = 0.19 FWHM (101)-0.055 FWHM (102)-0.5 / D (001), in the formula, FWHM (101) is the 101 peak half width, FWHM (102) is the 102 peak half width, and D (001) is the grain size corresponding to a 001 crystal plane. In the XRD spectrum of the positive electrode material precursor, the half-peak widths of the 001 peak and the 101 peak are obviously narrower, which indicates that the microcrystals are less, the deformation fault rate fD is smaller, the crystal defects are less, and the sintering activity of the precursor is improved, so that the positive electrode material with obvious advantages in capacity and stability is obtained.

Description

Technical Field

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

[0002] With the rapid development of the power battery and energy storage battery market, ternary lithium-ion batteries have become the mainstay due to their significant advantages in energy density and cycle life. In recent years, the rapid development of applications such as intelligent robots and low-altitude aircraft has placed higher demands on the performance of lithium batteries.

[0003] Traditional ternary materials mostly use hydroxide precursors prepared by co-precipitation as raw materials. Most of their physical properties are inherited from the precursors. Therefore, the performance of the precursors can greatly affect the electrical performance and safety of the cathode materials. Optimizing the co-precipitation process and improving the performance of ternary precursors are also important means to improve the performance of lithium-ion batteries.

[0004] To facilitate lithium-ion transport and ensure strong physical and chemical stability, the ternary precursor must have a certain amount of interconnected pores, and the internal and external crystal structure of the particles must be as uniform and ordered as possible to avoid the generation of too many microcrystals or crystal defects during growth, which could lead to the deterioration of the cathode material's performance.

[0005] Patent CN114590846 increases internal porosity by using a nickel-cobalt-manganese oxide core to precipitate nickel-cobalt-manganese hydroxide, but this requires core synthesis and sintering, making the production process complex. In addition, the lattice parameters of the internal oxide and the external hydroxide are quite different, which can easily lead to mismatch during growth and abnormal precipitation, resulting in micro powder.

[0006] Patent CN117836245A modifies the morphology of the precursor product by adding an organic complexing agent, which can produce a precursor that is compact inside and loose outside. However, due to the use of an organic complexing agent, the mother liquor of the reaction needs to be recycled, which increases the production cost.

[0007] The above-mentioned solutions involve complex production processes, high production costs, or introduce impurities such as organic solvents into the production system that require additional treatment, making them unsuitable for actual production. Summary of the Invention

[0008] The purpose of this invention is to overcome the above-mentioned deficiencies of the prior art and provide a cathode material precursor, its preparation method, and the cathode material.

[0009] The technical problem solved by this invention is achieved by the following technical solution.

[0010] This invention provides a cathode material precursor, comprising secondary particles formed by the aggregation of multiple primary particles, wherein each secondary particle includes a loose core and a dense shell formed on the surface of the loose core; the XRD pattern of the cathode material precursor shows a 001 peak with a full width at half maximum (FWHM). （001） ≤0.7, 101 peak half-width (FWHM) （101） ≤0.7, deformation layer fault rate f D It is 1-10%, of which: f D =0.19FWHM (101) -0.055FWHM (102) –0.5 / D (001) In the formula, FWHM (101) With a peak half-peak width of 101, FWHM (102) The half-peak width is 102, D (001) This represents the grain size corresponding to the 001 crystal plane.

[0011] The present invention provides a method for preparing the above-mentioned cathode material precursor, which includes: adding metal sulfate solution, ammonia solution and sodium hydroxide solution in parallel to carry out a co-precipitation reaction, and controlling the temperature during the reaction process to regulate the crystallization-dissolution reaction of by-products to obtain a cathode material precursor with loose and porous interior and tightly packed exterior.

[0012] The present invention provides a cathode material, which is formed by sintering the above-mentioned cathode material precursor with lithium salt.

[0013] The present invention has the following beneficial effects: This invention provides a cathode material precursor, its preparation method, and the cathode material itself. In the XRD pattern of the cathode material precursor provided by this invention, the full width at half maximum (FWHM) of the 001 and 101 peaks is significantly narrower, indicating fewer crystallites and a lower deformation stacking fault rate f. D Smaller size and fewer crystal defects are beneficial for improving the sintering activity of the precursor, thus obtaining a cathode material with significant advantages in capacity and stability. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 The solubility curve of sodium sulfate; Figure 2 This is a cross-sectional view of the precursor obtained in Example 1; Figure 3 This is a cross-sectional view of the precursor prepared in Comparative Example 1. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0017] The following is a detailed description of a cathode material precursor, its preparation method, and the cathode material provided by embodiments of the present invention.

[0018] In a first aspect, embodiments of the present invention provide a cathode material precursor, the cathode material precursor comprising secondary particles formed by the aggregation of multiple primary particles, the secondary particles comprising a loose core and a dense shell formed on the surface of the loose core; the XRD pattern of the cathode material precursor shows a 001 peak full width at half maximum (FWHM). （001） ≤0.7, 101 peak half-width (FWHM) （101） ≤0.7, deformation layer fault rate f D It is 1-10%, of which: f D =0.19FWHM (101) -0.055FWHM (102) –0.5 / D (001) In the formula, FWHM (101) With a peak half-peak width of 101, FWHM (102) The half-peak width is 102, D (001) This represents the grain size corresponding to the 001 crystal plane.

[0019] This invention provides a cathode material precursor, wherein the XRD pattern of the cathode material precursor shows the full width at half maximum (FWHM) of the 001 and 101 peaks. （101） ≤0.7, deformation layer fault rate f D The half-widths (WHMs) of the 001 and 101 peaks in the cathode material precursor are significantly narrower, indicating fewer crystallites and a lower deformation stacking fault rate (f). D The significantly smaller size indicates fewer crystal defects, which is beneficial for improving the sintering activity of the precursor, thus obtaining a cathode material with significant advantages in capacity and stability.

[0020] In some alternative embodiments, the cathode material precursor satisfies one or more of the following conditions: a. The primary particles include sheet-like primary particles and strip-like primary particles. The sheet-like primary particles are interlaced to form the honeycomb structure, and the strip-like primary particles form the radial structure. b. The loose core has a honeycomb structure, and the dense outer shell has a radial structure; c. The porosity of the loose core is 5-15%, and the porosity of the dense shell is 1-5%. d. The tap density of the cathode material precursor is 1.3-2.2 g / cm³. 3 ; e. The specific surface area of ​​the cathode material precursor is 5-30 m². 2 / g; f. The particle size D50 of the cathode material precursor is 6-15 μm; g. The span value of the cathode material precursor is ≥1.1; h, The chemical formula of the cathode material precursor is Ni x Co y Mn (1-x-y) (OH)2, where 0≤x≤1, 0≤y<1.

[0021] Secondly, embodiments of the present invention provide a method for preparing the above-mentioned cathode material precursor, which includes: adding a metal sulfate solution, an ammonia solution, and a sodium hydroxide solution in parallel flow, carrying out a co-precipitation reaction under a protective atmosphere, and controlling the temperature during the reaction process to regulate the crystallization-dissolution reaction of the by-products to obtain a cathode material precursor with a loose and porous interior and a tightly packed exterior.

[0022] This invention provides a method for preparing the aforementioned cathode material precursor. The first stage of precipitation employs a continuous precipitation process, utilizing the rapid change in solubility of byproduct crystals between 10-40°C. By controlling the reaction temperature, sodium sulfate crystallization is controlled, providing nuclei for the precursor precipitation. This avoids the generation of numerous microcrystals with incomplete crystal structures that occur when controlling the precursor's own nucleation via pH in traditional continuous precipitation. This can improve the particle size distribution of the finished precursor to a certain extent, resulting in a higher tap density. In the second stage of precipitation, the sodium sulfate crystals are gradually dissolved, forming a precursor core framework with larger internal pores. This in-situ pore-forming effect facilitates the sintering of the cathode material and lithium-ion transport during battery cycling, thereby improving capacity and cycle performance.

[0023] In some alternative implementations, the following steps are included: S1. The metal sulfate solution, ammonia solution, and sodium hydroxide solution are fed into the first reactor in a parallel flow. The temperature, pH and stirring rate are adjusted to carry out the first stage of precipitation. The sodium sulfate crystals generated in the system are used to provide crystal nuclei for the growth of the precursor core, and the first precursor slurry is obtained. S2. Transfer the first precursor slurry to the second reactor, and continue to introduce the metal sulfate solution, ammonia solution, and sodium hydroxide solution into the second reactor in parallel. Adjust the temperature, pH, and stirring rate to carry out the second stage precipitation. While the precursor shell is generated on the surface of the precursor core, the sodium sulfate crystals are slowly dissolved to form a loose and porous structure in the precursor core, and the second precursor slurry is obtained. S3. The second precursor slurry is aged, washed, and dried to obtain the cathode material precursor.

[0024] This invention provides a method for preparing the above-mentioned cathode material precursor. The method mainly involves controlling the reaction equilibrium through temperature regulation, causing the byproduct sodium sulfate to undergo a crystallization-dissolution reaction during the reaction process, thereby obtaining a cathode material precursor with a loose and porous interior and a tightly packed exterior. Specifically: The first stage of precipitation uses continuous precipitation, where temperature control promotes the precipitation of sodium sulfate crystals. These sodium sulfate crystals provide nuclei for the precursor, inducing precipitation and avoiding the formation of excessive precursor microcrystals. This method avoids the generation of a large number of microcrystals with incomplete crystal structures during the nucleation of the precursor itself through pH control in traditional continuous precipitation, thus improving the particle size distribution of the finished precursor and giving it a higher tap density. In the second stage of precipitation, temperature control promotes the slow dissolution of sodium sulfate crystals in the core, forming a precursor core framework with larger internal pores. In this process, sodium sulfate plays a role in in-situ pore creation. The solubility curves of sodium sulfate at different temperatures are shown below. Figure 1 As shown.

[0025] After the second precipitation reaction is completed, the primary particles continue to grow along the morphology of the core during the subsequent growth process. The crystal structure is uniform inside and out, and by controlling the slow dissolution of sodium sulfate crystals in the core, the internal-to-outside connectivity pathway is preserved, which is beneficial to improving the sintering activity of the precursor and obtaining a cathode material with significant advantages in capacity and stability. The above preparation method does not change the existing production process, does not introduce harmful substances that cannot be treated by existing wastewater treatment systems, and the prepared cathode material has good electrochemical performance.

[0026] It is worth noting that the first-stage precipitation is a continuous precipitation process with simultaneous input and output; as long as the feed is continuous, there is a continuous product output. The second-stage precipitation is an intermittent precipitation process. After the seed crystals (the product of the first precipitation) are added, the product is continuously concentrated in the reactor until it grows to a certain particle size. Once the particle size is reached, the entire product is discharged, and then the seed crystals are added again for the next round of reaction. Therefore, after the first-stage precipitation is completed in the first reactor, the product of the first precipitation is used as the seed crystals to carry out the second-stage precipitation reaction in the second reactor. Furthermore, the above preparation method mainly utilizes the crystallization-dissolution process of sodium sulfate to prepare a cathode material precursor with a loose core and a dense outer shell. The solubility of sodium sulfate changes significantly with temperature within a certain temperature range, and crystallization can be controlled by temperature changes. However, the solubility of other sulfates such as potassium sulfate does not change significantly with temperature, and crystallization cannot be controlled by temperature. Therefore, the byproduct potassium sulfate cannot be used to prepare the cathode material precursor with the described morphology.

[0027] In some optional embodiments, the metal sulfate solution is a sulfate of nickel, cobalt, or manganese, the total molar concentration of metal ions in the metal sulfate solution is 1.2-2.5 mol / L, the mass concentration of the ammonia solution is 10-20%, and the mass concentration of the sodium hydroxide solution is 20-40%.

[0028] In some optional embodiments, in step S1, the temperature is adjusted to 10-40℃, the pH to 9-13, the ammonia concentration to 0-17 g / L, and the stirring speed to 100-600 rpm. The reaction process is a continuous reaction with simultaneous input and output. In step 1, if the pH value of the system is higher than 13, no matter how the reaction temperature is adjusted, the product D50 cannot reach 3 μm, and the product morphology is amorphous debris. This is because if the pH value is too high, a large number of crystal nuclei will be generated in the system, but the growth rate of the crystal nuclei is slow, and they cannot aggregate to form secondary spheres of the target particle size. If the pH value of the system is lower than 9, the metal ions cannot be completely precipitated and enter the mother liquor, and the mother liquor is always blue, with a main element yield of <95%, which cannot meet the needs of large-scale production. In addition, if the ammonia concentration is too high, the metal ions cannot be completely precipitated and enter the mother liquor, which will also make the mother liquor blue and reduce the main element yield.

[0029] In some optional embodiments, in step S2, the temperature is adjusted to 40-80℃, the pH to 9-12, the ammonia concentration to 0-17g / L, and the stirring speed to 100-600rpm. During the reaction, the second reaction vessel is connected to a thickener, and the material in the second reaction vessel is solidified by the thickener.

[0030] In some optional embodiments, in step S3, the aging temperature of the second precursor slurry is 30-80°C, and the time is 2-12 hours; the detergent used for washing is a sodium hydroxide aqueous solution with a mass fraction of 3-5% at 50-80°C and pure water at 50-80°C; the drying temperature is 80-200°C.

[0031] Thirdly, embodiments of the present invention provide a cathode material, characterized in that the cathode material is formed by sintering a mixture of the above-mentioned cathode material precursor and a lithium salt.

[0032] In some alternative embodiments, the cathode material precursor is mixed with a lithium salt at a molar ratio of 1:(1.01-1.10) and sintered at 650-980°C for 6-20 hours to produce the cathode material.

[0033] The following detailed description, in conjunction with embodiments, illustrates a cathode material precursor, its preparation method, and the cathode material provided by the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0034] Example 1 A cathode material precursor with the molecular formula Ni 0.8 Co 0.1 Mn 0.1 (OH)2, its preparation method includes the following steps: Step 1: Dissolve nickel sulfate, cobalt sulfate, and manganese sulfate in pure water at a ratio of 8:1:1 to prepare a 2 mol / L mixed metal sulfate solution. Simultaneously introduce the mixed metal sulfate solution, 16% ammonia, and 32% sodium hydroxide solution into the reactor using a metering pump. Start stirring at 300 rpm, maintain pH 12, ammonia concentration of 3 g / L, and set the initial reaction temperature to 30℃. Once the median particle size of the precursor grows to 3.0 ± 0.3 μm, begin adjusting the temperature. When D50 > 3.3 μm, lower the temperature to 20℃; when D50 > 3.5 μm, lower the temperature to 10℃; when D50 < 2.7 μm, raise the temperature to 30℃; and when D50 < 2.5 μm, raise the temperature to 35℃. Nitrogen gas is introduced for protection during the process, and material collection continues.

[0035] Step 2, transfer 1m 3 The precursor slurry collected in the previous step is placed into an empty reactor. At the same time, a mixed metal sulfate solution, 16% ammonia water, and 32% sodium hydroxide solution are introduced into the reactor using a metering pump. The temperature is adjusted to 60°C, the pH is maintained at 12, and the ammonia concentration is 3g / L. Nitrogen gas is introduced for protection during the process. A thickener is used for consolidation until the particles grow to a D50 of 7.0μm.

[0036] Step 3: Wash the precursor slurry in a centrifuge, using a 3% sodium hydroxide solution at 70℃ and pure water at 70℃, and then spin dry; put the filter cake into an oven and dry it at 120℃ for 8 hours to obtain the finished precursor product.

[0037] The preparation process of a positive electrode material includes the following steps: Lithium carbonate was mixed with the above precursor at a molar ratio of 1.05:1 and sintered in a muffle furnace at 860°C for 12 hours in an air atmosphere. The sintered material was then crushed and sieved to obtain the finished cathode material.

[0038] Example 2 A cathode material precursor with the molecular formula Ni 0.6 Co 0.2 Mn 0.2 (OH)2, its preparation method includes the following steps: Step 1: Dissolve nickel sulfate, cobalt sulfate, and manganese sulfate in pure water at a ratio of 6:2:2 to prepare a 2 mol / L mixed metal sulfate solution. Simultaneously introduce the mixed metal sulfate solution, 16% ammonia, and 32% sodium hydroxide solution into the reactor using a metering pump. Start stirring at 300 rpm, maintain pH 12, ammonia concentration of 8 g / L, and set the initial reaction temperature to 30℃. Once the median particle size of the precursor grows to 3.0 ± 0.3 μm, begin adjusting the temperature. When D50 > 3.3 μm, lower the temperature to 20℃; when D50 > 3.5 μm, lower the temperature to 10℃; when D50 < 2.7 μm, raise the temperature to 30℃; and when D50 < 2.5 μm, raise the temperature to 35℃. Nitrogen gas is introduced for protection during the process, and material collection continues.

[0039] Step 2, transfer 1m 3 The precursor slurry collected in the previous step is placed into an empty reactor. At the same time, a mixed metal sulfate solution, 16% ammonia water, and 32% sodium hydroxide solution are introduced into the reactor using a metering pump. The temperature is adjusted to 65°C, the pH is maintained at 12, and the ammonia concentration is 8 g / L. Nitrogen gas is introduced for protection during the process. A thickener is used for consolidation until the particles grow to a D50 of 10.0 μm.

[0040] Step 3: Wash the precursor slurry in a centrifuge, using a 3% sodium hydroxide solution at 70℃ and pure water at 70℃, and then spin dry; put the filter cake into an oven and dry it at 120℃ for 8 hours to obtain the finished precursor product.

[0041] The preparation process of a positive electrode material includes the following steps: Lithium carbonate was mixed with the above precursor at a molar ratio of 1.05:1 and sintered in a muffle furnace at 860°C for 12 hours in an air atmosphere. The sintered material was then crushed and sieved to obtain the finished cathode material.

[0042] Comparative Example 1 A cathode material precursor with the molecular formula Ni 0.8 Co 0.1 Mn 0.1 (OH)2, its preparation method includes the following steps: Step 1: Dissolve nickel sulfate, cobalt sulfate, and manganese sulfate in pure water at a ratio of 8:1:1 to prepare a 2 mol / L mixed metal sulfate solution. Simultaneously introduce the mixed metal sulfate solution, 16% ammonia solution, and 32% sodium hydroxide solution into the reaction vessel using a metering pump. Start the stirrer at 300 rpm, maintain the temperature at 60℃, and keep the ammonia concentration at 3 g / L. Control the product D50 to 3.0 ± 0.5 μm by adjusting the pH. Nitrogen gas is introduced for protection during the process, and the material is continuously collected.

[0043] Step 2, transfer 1m 3 The precursor slurry collected in the previous step is placed into an empty reactor. At the same time, a mixed metal sulfate solution, 16% ammonia water, and 32% sodium hydroxide solution are introduced into the reactor using a metering pump. The temperature is controlled at 60°C, the pH is maintained at 12, and the ammonia concentration is 3g / L. Nitrogen gas is introduced for protection during the process. A thickener is used for consolidation until the particles grow to a D50 of 7.0μm.

[0044] Step 3: Wash the precursor slurry in a centrifuge, using a 3% sodium hydroxide solution at 70℃ and pure water at 70℃, and then spin dry; put the filter cake into an oven and dry it at 120℃ for 8 hours to obtain the finished precursor product.

[0045] The preparation process of a positive electrode material includes the following steps: Lithium carbonate was mixed with the above precursor at a molar ratio of 1.05:1 and sintered in a muffle furnace at 860°C for 12 hours in an air atmosphere. The sintered material was then crushed and sieved to obtain the finished cathode material.

[0046] Comparative Example 2 A cathode material precursor with the molecular formula Ni 0.8 Co 0.1 Mn 0.1 (OH)2, its preparation method includes the following steps: Step 1: Dissolve nickel sulfate, cobalt sulfate, and manganese sulfate in pure water at a ratio of 8:1:1 to prepare a 2 mol / L mixed metal sulfate solution. Using a metering pump, introduce the mixed metal sulfate solution, 16% ammonia, and 32% sodium hydroxide solution into the reactor. Control the temperature at 60℃, maintain pH 12, and ammonia concentration at 3 g / L. Probe nitrogen gas for protection during the process. Use a thickener to solidify the particles until the D50 reaches 7.0 μm.

[0047] Step 2: Wash the precursor slurry in a centrifuge, using a 3% sodium hydroxide solution at 70℃ and pure water at 70℃, and then spin dry; put the filter cake into an oven and dry it at 120℃ for 8 hours to obtain the finished precursor product.

[0048] The preparation process of a positive electrode material includes the following steps: Lithium carbonate was mixed with the above precursor at a molar ratio of 1.05:1 and sintered in a muffle furnace at 860°C for 12 hours in an air atmosphere. The sintered material was then crushed and sieved to obtain the finished cathode material.

[0049] The tap density, specific surface area, and internal and external porosity of the precursors obtained from Examples 1-2 and Comparative Examples 1-2 are statistically analyzed and shown in the table below: Table 1 Physical properties of precursors prepared in the examples and comparative examples

[0050] As can be seen from the table above, compared with Comparative Example 1, the precursors prepared by the method of this embodiment have significantly narrower half-widths (WHMs) for the 001 and 101 peaks, indicating fewer crystallites and a lower deformation stacking fault rate (f). D The significantly smaller particle size indicates fewer crystal defects. Comparative Example 2, prepared by an intermittent method, showed a narrower particle size distribution and lower tap density.

[0051] The cathode materials obtained in Examples 1-2 and Comparative Examples 1-2 were subjected to electrochemical performance testing according to the following methods: The positive electrode material, conductive agent (acetylene black), and binder (PVDF) were mixed and dispersed in an organic solvent NMP at a ratio of 90:5:5. After stirring evenly, the mixture was coated onto aluminum foil to form a positive electrode sheet. A lithium sheet was used as the negative electrode. A button cell was fabricated in a glove box under a protective atmosphere. The electrical performance was tested on a battery testing system, and the test results are shown in Table 2. Table 2 Electrical properties of cathode materials

[0052] As can be seen from the table above, due to the fewer crystal defects in the precursor of the examples and the supportive effect of the core framework, the overall structural stability of the cathode material is improved, resulting in fewer side reactions during battery cycling. Therefore, it exhibits high capacity and good cycle performance. Comparative Example 2, prepared using an intermittent method, lacks internal and external interconnected channels, leading to relatively poor sinterability and thus limiting its capacity.

[0053] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A cathode material precursor, characterized in that, The cathode material precursor includes secondary particles formed by the aggregation of multiple primary particles. Each secondary particle comprises a loose core and a dense outer shell formed on the surface of the loose core. The XRD pattern of the cathode material precursor shows the full width at half maximum (FWHM) of the 001 peak. （001） ≤0.7, 101 peak half-width (FWHM) （101） ≤0.7, deformation layer fault rate f D It is 1-10%, of which: f D =0.19FWHM (101) -0.055FWHM (102) –0.5 / D (001) In the formula, FWHM (101) With a peak half-peak width of 101, FWHM (102) The half-peak width is 102, D (001) This represents the grain size corresponding to the 001 crystal plane.

2. The cathode material precursor according to claim 1, characterized in that, The cathode material precursor satisfies one or more of the following conditions: a. The primary particles include sheet-like primary particles and strip-like primary particles. The sheet-like primary particles are interlaced to form the honeycomb structure, and the strip-like primary particles form the radial structure. b. The loose core has a honeycomb structure, and the dense outer shell has a radial structure; c. The porosity of the loose core is 5-15%, and the porosity of the dense shell is 1-5%. d. The tap density of the cathode material precursor is 1.3-2.2 g / cm³. 3 ; e. The specific surface area of ​​the cathode material precursor is 5-30 m². 2 / g; f. The particle size D50 of the cathode material precursor is 6-15 μm; g. The span value of the cathode material precursor is ≥1.1; h, The chemical formula of the cathode material precursor is Ni x Co y Mn (1-x-y) (OH)2, where 0≤x≤1, 0≤y<1.

3. A method for preparing a cathode material precursor according to claim 1 or 2, characterized in that, It includes: A metal sulfate solution, an ammonia solution, and a sodium hydroxide solution are added in parallel to carry out a co-precipitation reaction. The temperature during the reaction process is controlled to regulate the crystallization-dissolution reaction of the by-products, resulting in a positive electrode material precursor with a loose and porous interior and a tightly packed exterior.

4. The preparation method according to claim 3, characterized in that, Includes the following steps: S1. The metal sulfate solution, ammonia solution, and sodium hydroxide solution are fed into the first reaction vessel in a parallel flow. The temperature, pH and stirring rate are adjusted to carry out the first stage of precipitation. The sodium sulfate crystals in the system are used to provide crystal nuclei for the growth of the precursor core, and the first precursor slurry is obtained. S2. Transfer the first precursor slurry to the second reactor, and continue to introduce the metal sulfate solution, ammonia solution, and sodium hydroxide solution into the second reactor in parallel. Adjust the temperature, pH, and stirring rate to carry out the second stage precipitation. While the precursor shell is generated on the surface of the precursor core, the sodium sulfate crystals are slowly dissolved to form a loose and porous structure in the precursor core, and the second precursor slurry is obtained. S3. The second precursor slurry is aged, washed, and dried to obtain the cathode material precursor.

5. The preparation method according to claim 4, characterized in that, The metal sulfate solution is a sulfate of nickel, cobalt, or manganese, the total molar concentration of metal ions in the metal sulfate solution is 1.2-2.5 mol / L, the mass concentration of the ammonia solution is 10-20%, and the mass concentration of the sodium hydroxide solution is 20-40%.

6. The preparation method according to claim 4, characterized in that, In step S1, the temperature is adjusted to 10-40℃, the pH to 9-13, the ammonia concentration to 0-17g / L, the stirring speed to 100-600rpm, and the reaction process is a continuous reaction with simultaneous input and output.

7. The preparation method according to claim 4, characterized in that, In step S2, the temperature is adjusted to 40-80℃, the pH to 9-12, the ammonia concentration to 0-17g / L, and the stirring speed to 100-600rpm. During the reaction, the second reaction vessel is connected to a thickener, and the material in the second reaction vessel is solidified by the thickener.

8. The preparation method according to claim 4, characterized in that, In step S3, the aging temperature of the second precursor slurry is 30-80℃, and the time is 2-12h; the detergent used for washing is a sodium hydroxide aqueous solution with a mass fraction of 3-5% at 50-80℃ and pure water at 50-80℃; the drying temperature is 80-200℃.

9. A positive electrode material, characterized in that, The cathode material is formed by sintering a cathode material precursor with a lithium salt, wherein the cathode material precursor is prepared by the cathode material precursor according to any one of claims 1-2 or by the preparation method according to any one of claims 3-8.

10. The cathode material according to claim 9, characterized in that, The cathode material precursor is mixed with lithium salt at a molar ratio of 1:(1.01-1.10) and sintered at 650-980℃ for 6-20h to produce the cathode material.

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