Ternary precursor, preparation method thereof, cathode material and application thereof

Abstract

This invention relates to the field of battery material preparation technology, and discloses a ternary precursor and its preparation method, a cathode material and its application. The ternary precursor has the chemical formula Ni. x Co y Mn z M a+b (OH)₂, where 0.80≤x<1, 0≤y<0.1, 0≤z<0.1, 0≤a+b<0.01, x+y+z+a+b=1; M includes Pb and Sr; the ternary precursor particles are secondary particles formed by the stacking of strip-shaped primary particles, which include an internal core and a shell surrounding the core; the porosity of the core is 5~12%, and Pb is doped in the core; the porosity of the shell is 12~30%, and Sr is doped in the shell; the D50 of the ternary precursor is 8~11 μm. This precursor has good electrochemical performance.

Description

Technical Field

[0001] The present invention relates to the technical field of battery materials, and in particular, to a ternary precursor, a preparation method thereof, a cathode material, and an application thereof. Background Art

[0002] As an important component of the cathode material of lithium batteries, ternary precursor materials have always been the core of technology. The indicators of ternary precursor materials directly restrict the performance of lithium-ion batteries. Manganese in ternary materials is a variable-valence metal, containing multiple valence states such as +1 to +7, and is extremely easy to react with oxygen to cause oxidation and valence change, thus affecting indicators such as SEM, TD, and BET of ternary precursors. Therefore, the control of oxygen content in the reaction synthesis stage during the production of precursors is of utmost importance. Providing a ternary precursor that only needs to be filled with inert gas throughout the process to prevent oxidation and its preparation method is beneficial to improving the consistency and stability of precursor performance, reducing process variation factors, and reducing the difficulty of synthesis control.

[0003] Generally, the secondary particles of ternary precursor materials are spherical-like, usually with a multi-core shell structure. The arrangement and porosity of primary particles between different shells restrict the performance of lithium-ion batteries. Specifically: <00th="0000060">During the charge and discharge process of the battery, the electrolyte penetrates into the spherical core through the pores on the surface of the secondary particle sphere. If the porosity is low or the arrangement of primary particles is disordered, it will lead to difficult electrolyte penetration or slow penetration rate. In addition, the disordered arrangement of primary particles will ultimately form holes of different sizes and a hollow structure of irregular multi-layer hollow circles inside the cathode material, resulting in low compaction ability, insufficient compressive resistance, and insufficient particle structure strength of the cathode material, and being prone to structural peeling, cracking or collapse between grain boundaries under high voltage or large current charge and discharge conditions, causing a large attenuation of the battery capacity during high-temperature cycling and shortening the battery life.

[0004] In view of this, the present invention is specifically proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide a ternary precursor, a preparation method thereof, a cathode material, and an application thereof.

[0006] The present invention is implemented as follows: In the first aspect, the present invention provides a ternary precursor with the chemical formula Ni z , , a+b , x , y Co y Mn z M a+b (OH)2, where 0.80 ≤ x < 1, 0 ≤ y < 0.1, 0 ≤ z < 0.1, 0 < a + b < 0.01, and x + y + z + a + b = 1; M includes Pb and Sr; The ternary precursor particles are secondary particles formed by the accumulation of strip-shaped primary particles, which include a core part located inside and a shell part wrapped outside the core part; the D50 of the core part of the ternary precursor is 5.0 - 7.0 μm, the porosity of the core part is 5 - 12%, Pb is doped in the core part; the porosity of the shell part is 12 - 30%, Sr is doped in the shell part; the D50 of the ternary precursor is 8 - 11 μm.

[0007] In an optional embodiment, it includes at least one of the following features (1) - (4): (1) The D50 of the core part of the ternary precursor is 5.0 - 7.0 μm; <0​​​​​​​​​​​​​​​​​​​​​​​​The first mixed metal salt solution and the second mixed metal salt solution are different solutions. The metal ions in the first mixed metal salt solution include Ni, Co, Mn, and Pb with a molar ratio of x:y:z:a, where 0.80 ≤ x < 1, 0 ≤ y < 0.1, 0 ≤ z < 0.1, and 0 < a < 0.01. The metal ions in the second mixed metal salt solution include Ni, Co, Mn, and Sr with a molar ratio of x:y:z:b, where 0.80 ≤ x < 1, 0 ≤ y < 0.1, 0 ≤ z < 0.1, and 0 < b < 0.01.

[0010] In an optional embodiment, the pH regulator is selected from a solution of at least one of sodium hydroxide, potassium hydroxide, sodium bicarbonate, and sodium carbonate.

[0011] In an optional embodiment, the pH regulator is a sodium hydroxide solution with a concentration of 20% to 40%; Optionally, the complexing agent is selected from at least one of ammonia water, EDTA, ethylenediamine, sodium citrate, and urea; Optionally, the complexing agent is ammonia water with a mass concentration of 10% to 30%.

[0012] In an optional embodiment, the total concentration of metal ions in the mixed metal salt solution is 90 to 110 g / L, and the injection rate of the mixed metal salt solution is 3 - 6 L / h.

[0013] In an optional embodiment, during the first-stage reaction process, the stirring speed is 200 to 300 r / min; during the second-stage reaction process, the stirring speed is lower than that in the first-stage reaction process, the stirring speed is 100 to 220 r / min, and it gradually decreases; the stirring speed at the end of the second-stage reaction drops to 100 to 150 r / min.

[0014] In a third aspect, the present invention provides a cathode material obtained by mixing and sintering a ternary precursor according to any one of the foregoing embodiments or a ternary precursor prepared by the preparation method according to any one of the foregoing embodiments with a lithium source.

[0015] In a fourth aspect, the present invention provides an application of the cathode material according to the foregoing embodiment in a cathode or a battery.

[0016] The present invention has the following beneficial effects: [[ID=??]] The ternary precursor provided in this invention has a dense core structure, resulting in excellent compressive strength and high stability. The cathode material prepared from this precursor exhibits high energy density. Due to the porous shell structure, when used as a cathode material in a battery, it helps buffer volumetric strain during battery cycling, reducing resistance and improving battery cycle performance and safety. In this invention, lead doping in the core reduces lattice defects in the core layer, enhancing material stability, while strontium doping in the shell strengthens ion channel formation during preparation. Therefore, the cathode material prepared from the precursor provided by this invention exhibits superior electrochemical performance. Attached Figure Description

[0017] 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.

[0018] Figure 1 This is a SEM image of the precursor obtained in Example 2. Detailed Implementation

[0019] 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.

[0020] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0021] This invention provides a ternary precursor with the chemical formula Ni. x Co y Mn z M a+b (OH)2, where 0.80≤x<1, 0≤y<0.1, 0≤z<0.1, 0≤a+b<0.01, x+y+z+a+b=1; M includes Pb and Sr; Ternary precursor particles are secondary particles formed by the stacking of strip-shaped primary particles, including an inner core and a shell surrounding the core. The D50 of the core of the ternary precursor is 5.0~7.0 μm, the porosity of the core is 5~12%, and Pb is doped in the core. The porosity of the shell is 12~30%, the length of the primary particles constituting the shell is 1.5~2.5 μm, and Sr is doped in the shell.

[0022] The ternary precursor provided in this invention has a dense core structure, giving it excellent compressive strength and high stability. The cathode material made from this precursor has a high energy density. Because the shell has a porous structure, when the cathode material is used in a battery, it helps to buffer the volumetric strain during battery cycling, reducing resistance and improving battery cycle performance and safety. Within the porosity range of the core and shell in this solution, the density and consistency of the particles are ensured, and the impact on lithium-ion conductivity is minimized, thus ensuring that the battery has superior cycle performance after the cathode material is applied. A core that is too small is not conducive to buffering the stress caused by volume changes during charging and discharging. In this design, the core size of the ternary precursor particles is moderate, which helps to buffer volumetric strain during cyclic charging and discharging, reduce resistance, and improve rate performance. The specific dimensions of the core and shell facilitate the control of their thickness during fabrication, ensuring uniform and seamless growth of the ternary precursor particles and further enhancing structural stability. The ternary precursor particles are secondary particles formed by the stacking of strip-shaped primary particles. The gaps between the primary particles provide lithium-ion insertion / extraction channels, improving rate performance and lithium-ion conductivity, thereby enhancing battery performance. The appropriate length of the primary particles constituting the secondary particles reduces lithium-ion diffusion resistance, which is beneficial for lithium-ion conduction. Most importantly, in this invention, lead is doped into the core, which reduces lattice defects in the core layer and improves material stability, while strontium is doped into the shell, which enhances the formation of ion channels during fabrication.

[0023] Optionally, the D50 of the ternary precursor is 8~11 μm, and the particle size distribution (D90-D10) / D50 is 1.2~1.5. When the particle size and particle size distribution of the precursor are within the above range, the wider particle size distribution of the larger particles increases the compaction density of the battery, ensuring that the cathode has better energy density when used in the battery.

[0024] Optionally, the D50 of the core portion of the ternary precursor is 5.0~7.0 μm.

[0025] Optionally, the length of the primary particles constituting the core is shorter than the length of the primary particles constituting the shell. This facilitates the radial extension of the primary particles in the shell along the core, thereby improving lithium-ion conductivity.

[0026] Optionally, the specific surface area of ​​the ternary precursor is 8~16m². 2 / g, tap density is 1.8~2.4g / cm³ 3 Specific surface area and tap density within this range result in better battery conductivity.

[0027] Optionally, x + y + z = 0.99, a + b = 0.01, 0 < a < 0.01, 0 < b < 0.01, where a and b are the doping amounts of Pb and Sr respectively. When the doped metal elements are within this range, it is beneficial to buffer the volume strain force during the charge and discharge cycles of the battery, reduce the resistance, and improve the battery cycle performance and safety performance.

[0028] The preparation method of the above ternary precursor provided by the embodiments of the present invention includes: The first-stage reaction: A first mixed metal salt solution, a pH regulator, and a complexing agent are injected into a reaction kettle with water as the bottom liquid in a co-current manner, and a protective gas is introduced for precipitation reaction. During the reaction process, the pH value in the reaction kettle is gradually reduced within the range of 10.0 - 12.5. After the D50 of the particles generated in the reaction kettle is measured to reach 5.0 - 7.0 μm, the next-stage reaction is carried out; The second-stage reaction: The precipitate generated in the first-stage reaction is extracted and placed in another reaction kettle, water is supplemented, a second mixed metal salt solution, a pH regulator, and a complexing agent are injected in a co-current manner, the pH value in the reaction kettle is gradually increased within the range of 10.0 - 12.5, and the pH value at the end point of the second-stage reaction is 0.3 - 0.8 higher than the pH value at the end point of the first-stage reaction until the particles in the reaction kettle grow to the target size; In both the first-stage reaction and the second-stage reaction, the free complexing agent in the reaction kettle is controlled within the range of 4.5 - 10.5 g / L in terms of equivalent ammonia value, and the end point of the second-stage reaction is controlled to be 1 - 4 g / L higher than the end point of the first-stage reaction; The temperature of the whole reaction process is 50 - 70 °C; The first mixed metal salt solution and the second mixed metal salt solution are different solutions. The metal ions in the first mixed metal salt solution include Ni, Co, Mn, and Pb with a molar ratio of x:y:z:a, where 0.80 ≤ x < 1, 0 ≤ y < 0.1, 0 ≤ z < 0.1, 0 < a < 0.01, and the metal ions in the second mixed metal salt solution include Ni, Co, Mn, and Sr with a molar ratio of x:y:z:b, where 0.80 ≤ x < 1, 0 ≤ y < 0.1, 0 ≤ z < 0.1, 0 < b < 0.01.

[0029] Specifically, the preparation method includes: S1. The first-stage reaction Inject 60 L of pure water into the reaction kettle as the bottom liquid, and raise the temperature of the reaction kettle to 50 - 70 °C; A first mixed metal salt solution, pH adjuster, and complexing agent are injected concurrently into the reactor, and a protective gas is introduced to carry out a precipitation reaction. During the reaction, the pH value in the reactor is controlled to gradually decrease within the range of 10.0 to 12.5. The free complexing agent in the reactor, calculated as ammonia, is in the range of 4.5 to 10.5 g / L. When the particle D50 generated in the reactor reaches 5.0 to 7.0 μm, the next stage of reaction is carried out.

[0030] The first mixed metal salt solution contains metal ions including Ni, Co, Mn and Pb in a molar ratio of x:y:z:a, where 0.80≤x<1, 0≤y<0.1, 0≤z<0.1 and 0≤a<0.01.

[0031] Optionally, the total concentration of metal ions in the first mixed metal salt solution is 90~110 g / L, and the injection rate of the first mixed metal salt solution is 3~6 L / h.

[0032] Optionally, the solute in the first mixed metal salt solution is at least one of sulfate, chloride, and nitrate.

[0033] In this step, lead is doped into the cathode material. Lead has a larger atomic radius than the main elements nickel, cobalt, and manganese, which can provide strong support for the internal structure, prevent lattice collapse, and improve the stability of the material, thereby improving the cycle performance of the cathode material.

[0034] Optionally, the pH adjuster is selected from a solution of at least one of sodium hydroxide, potassium hydroxide, sodium bicarbonate, and sodium carbonate. Preferably, a commonly used pH adjuster is a sodium hydroxide solution with a mass concentration of 20-40%.

[0035] Optionally, the complexing agent is selected from at least one of ammonia, EDTA, ethylenediamine, sodium citrate, and urea. Preferably, ammonia with a mass concentration of 10-30% is commonly used as the complexing agent.

[0036] Optionally, in this stage, the stirring speed is 200~300 r / min. This speed is conducive to the formation of a dense core layer.

[0037] During this stage of the reaction, controlling the pH within the range of 10.0–12.5 is beneficial for the rapid growth of core and shell particles, reducing interparticle porosity, increasing bonding strength, and thus improving the compressive strength and structural stability of the prepared ternary precursor. Lowering the pH during the reaction facilitates the gradual formation of a dense core, avoiding disordered connections between fine primary particles within the particles, reducing porous gaps in the particle arrangement, and forming a dense structure with ordered, low-porosity, seamless bonding layers. This ensures uninterrupted and tightly connected particle growth, improving the compressive strength and structural stability of the particles.

[0038] In this stage, a particle D50 of 5.0~7.0μm in the reactor means that the diameter of the core of the final precursor is 5.0~7.0μm. By controlling the size of the core, this stage controls the size of the central pore of the ternary precursor, preventing the structure from cracking and collapsing due to excessively large pores. This also helps to buffer the volumetric strain of the inner and outer layers during cyclic charging and discharging, thereby improving the structural strength of the material.

[0039] S2, Second Stage Reaction The precipitate obtained from the first stage reaction is extracted and placed in another reaction vessel. Pure water is added, and a mixed metal salt solution, pH adjuster, and complexing agent are injected. The pH value in the reaction vessel is controlled to gradually increase within the range of 10.0 to 12.5. The pH value at the end of the second stage reaction is controlled to be 0.3 to 0.8 higher than that at the end of the first stage reaction. The free complexing agent in the reaction vessel, calculated as ammonia, is in the range of 4.5 to 10.5 g / L, and the end of the second stage reaction is controlled to be 1 to 4 g / L higher than that at the end of the first stage reaction, until the particles in the reaction vessel grow to the target size.

[0040] The second mixed metal salt solution contains metal ions including Ni, Co, Mn, and Sr in a molar ratio of x:y:z:b, where 0.80 ≤ x < 1, 0 ≤ y < 0.1, 0 ≤ z < 0.1, and 0 ≤ b < 0.01.

[0041] This step involves doping with strontium. Strontium has an atomic radius similar to that of the main elements nickel, cobalt, and manganese, and can replace some of the main elements, thereby increasing the porosity of the shell and forming a loose and porous structure. This provides a transport path for lithium ions, thus improving the rate performance of the cathode material.

[0042] Optionally, the target particle size is, for example, 8.0~11.0 μm. This is beneficial for obtaining ternary precursor materials with dense structure and strong compressive strength.

[0043] During this stage of the reaction, increasing the pH value and gradually increasing the concentration of the complexing agent is beneficial to the rapid growth of fine particles and the gradual formation of a shell structure with a more loose arrangement of particles relative to the core layer, thereby enhancing particle consistency and connectivity.

[0044] Optionally, the concentration of metal ions in the second doped metal salt solution is 90~110 g / L, and the addition rate is 3~6 L / h.

[0045] Optionally, the stirring speed in this stage of the reaction process is lower than that in the first stage of the reaction process, and the stirring speed is 100~220 r / min.

[0046] In the second stage of the reaction, the stirring speed is gradually reduced to decrease the supersaturation of the reaction solution, which is conducive to crystal growth at the interface, thereby rapidly forming a loose and diffuse shell and improving the compressive strength of the ternary precursor particles.

[0047] Throughout the reaction process, the protective atmosphere is controllable. The oxygen content is adjusted by regulating the flow rate of inert gas. The reaction is biased towards preventing oxidation, making it easy to control and ensuring good stability of the indicators.

[0048] The cathode material provided in this embodiment of the invention is obtained by mixing and sintering a ternary precursor provided in this embodiment of the invention or a ternary precursor prepared by the preparation method provided in this invention with a lithium source.

[0049] The embodiments of the present invention also provide the application of the above-mentioned cathode material in cathodes or batteries.

[0050] Example 1 Preparation of materials: The first mixed metal nitrate solution has a molar ratio of Ni, Co, Mn and Pb of 0.85:0.04:0.05:0.002 and a metal ion concentration of 90 g / L. The second mixed metal nitrate solution has a molar ratio of Ni, Co, Mn and Sr of 0.85:0.04:0.05:0.003 and a metal ion concentration of 90 g / L. Ammonia solution, concentration 10%; Sodium hydroxide solution, with a mass concentration of 20%; First-stage response: Inject 60L of pure water into a 100L reactor as the base liquid, raise the reactor temperature to 50℃, and set the stirrer speed to 200 r / min. A first mixed metal salt solution was injected into the reactor in a parallel flow at a rate of 3 L, along with an ammonia solution and a sodium hydroxide solution, until the particle size (D50) in the reactor reached 5.0 μm, at which point the next stage of the reaction could proceed. In this step, the ammonia concentration in the reactor was controlled at 4.5 g / L, and the pH was reduced from the initial 12.5 to 12.1.

[0051] The slurry obtained from the first stage reaction is dehydrated to obtain a dry base.

[0052] Second-stage response: The dry sample was placed in another reactor, and 40 L of pure water was added. A second mixed metal salt solution was then continuously injected at a flow rate of 3 L / L. Ammonia and sodium hydroxide solutions were also continuously injected until the particle size (D50) in the reactor reached 8.0 μm, at which point the reaction was considered complete. In this step, the ammonia value was controlled to continuously increase from an initial 5 g / L to a final value of 7.5 g / L, and the pH value continuously increased from an initial 11.9 to a final value of 12. The stirring speed was reduced from 220 r / min at the beginning of the second stage to 150 r / min.

[0053] The chemical formula of the obtained ternary precursor is Ni 0.85 Co 0.04 Mn 0.05 Pb 0.002 Sr 0.003 (OH)₂, D50 is 8.0 μm, particle size distribution (D90-D10) / D50 is 1.2, specific surface area is 8 m². 2 / g, tap density is 2.3g / cm³ 3 The core has a D50 of 5.0 μm.

[0054] Example 2 Preparation of materials: The first mixed metal nitrate solution has a molar ratio of Ni, Co, Mn and Pb of 0.85:0.04:0.05:0.005 and a metal ion concentration of 100 g / L. The second mixed metal nitrate solution has a molar ratio of Ni, Co, Mn and Sr of 0.85:0.04:0.05:0.005 and a metal ion concentration of 100 g / L. Ammonia solution, concentration 20%; Sodium hydroxide solution, with a mass concentration of 30%; First-stage response: Inject 60L of pure water into a 100L reactor as the base liquid, raise the reactor temperature to 60℃, and set the stirrer speed to 250 r / min. A first mixed metal salt solution was injected into the reactor in a parallel flow at a rate of 4.5 L, along with an ammonia solution and a sodium hydroxide solution, until the particle size (D50) in the reactor reached 6.0 μm, before proceeding to the next stage of the reaction. In this step, the ammonia concentration in the reactor was controlled at 6.5 g / L, and the pH value was reduced from the initial 12.3 to 11.8.

[0055] The slurry obtained from the first stage reaction is dehydrated to obtain a dry base.

[0056] Second-stage response: The dry sample was placed in another reactor, and 40 L of pure water was added. A second mixed metal salt solution was then continuously injected at a flow rate of 3 L / L. Ammonia and sodium hydroxide solutions were also continuously injected until the particle size (D50) in the reactor reached 10 μm, at which point the reaction was terminated. In this step, the ammonia value was controlled to continuously increase from an initial 6.5 g / L to a final value of 7.5 g / L, and the pH value continuously increased from an initial 11.8 to a final value of 12.1. The stirring speed was reduced from 220 r / min at the beginning of the second stage to 150 r / min.

[0057] The chemical formula of the obtained ternary precursor is Ni 0.85 Co 0.04 Mn 0.05 Pb 0.005 Sr 0.005 (OH)₂, D50 is 10 μm, particle size distribution (D90-D10) / D50 is 1.3, specific surface area is 12 m². 2 / g, tap density is 2g / cm³ 3 The D50 of the core is 6.0 μm.

[0058] Example 3 Preparation of materials: The first mixed metal nitrate solution has a molar ratio of Ni, Co, Mn and Pb of 0.85:0.04:0.05:0.003 and a metal ion concentration of 110 g / L. The second mixed metal nitrate solution has a molar ratio of Ni, Co, Mn and Sr of 0.85:0.04:0.05:0.002 and a metal ion concentration of 110 g / L. Ammonia solution, concentration 30%; Sodium hydroxide solution, with a mass concentration of 40%; First-stage response: Inject 60L of pure water into a 100L reactor as the base liquid, raise the reactor temperature to 70℃, and set the stirrer speed to 250 r / min. A first mixed metal salt solution was injected into the reactor in a parallel flow at a rate of 6 L / min. Ammonia and sodium hydroxide solutions were also injected until the particle size (D50) in the reactor reached 7.0 μm, at which point the next stage of the reaction could proceed. In this step, the ammonia concentration in the reactor was controlled at 9 g / L, and the pH was reduced from an initial 12 to 11.5.

[0059] The slurry obtained from the first stage reaction is dehydrated to obtain a dry base.

[0060] Second-stage response: The dry sample was placed in another reactor, and 40 L of pure water was added. A second mixed metal salt solution was then continuously injected at a flow rate of 6 L / min. Ammonia and sodium hydroxide solutions were also continuously injected until the particle size (D50) in the reactor reached 11 μm, at which point the reaction was terminated. In this step, the ammonia value was controlled to continuously increase from an initial 10.5 g / L to a final value of 9.5 g / L, and the pH value continuously increased from an initial 11.5 to a final value of 12. The stirring speed was reduced from 200 r / min at the beginning of the second stage to 130 r / min.

[0061] The chemical formula of the obtained ternary precursor is Ni 0.85 Co 0.04 Mn 0.05 Pb 0.003 Sr 0.002 (OH)₂, D50 is 11 μm, particle size distribution (D90-D10) / D50 is 1.4, specific surface area is 16 m². 2 / g, tap density is 1.8g / cm³ 3 The core has a D50 of 7.0 μm.

[0062] Comparative Example 1 This comparative example is basically the same as Example 1, except that the first doped metal Pb was not implanted in the first stage reaction compared to Example 1.

[0063] The chemical formula of the obtained ternary precursor is Ni 0.85 Co 0.045 Mn 0.05 Sr 0.005 (OH)₂, D50 is 10 μm, particle size distribution (D90-D10) / D50 is 1.31, specific surface area is 11.8 m². 2 / g, tap density is 1.99g / cm³ 3 The D50 of the core is 6.0 μm.

[0064] Comparative Example 2 This comparative example is basically the same as Example 1, except that, compared with Example 2, this comparative example did not inject a second doped metal Sr during the second stage reaction.

[0065] The chemical formula of the obtained ternary precursor is Ni 0.85 Co 0.045 Mn 0.05 Pb 0.005 (OH)₂, D50 is 10 μm, particle size distribution (D90-D10) / D50 is 1.3, specific surface area is 12.1 m². 2 / g, tap density is 2.05g / cm³ 3 The D50 of the core is 6.0 μm.

[0066] Comparative Example 3 This comparative example is basically the same as Example 2, except that the doping order of the first doped metal salt Pb and the second doped metal Sr is replaced.

[0067] The chemical formula of the obtained ternary precursor is Ni 0.85 Co 0.04 Mn 0.05 Pb 0.005 Sr 0.005 (OH)₂, D50 is 10 μm, particle size distribution (D90-D10) / D50 is 1.33, specific surface area is 12.4 m². 2 / g, tap density is 2.11g / cm³ 3 The D50 of the core is 6.0 μm.

[0068] Experimental Example The precursors prepared in each embodiment and comparative example were mixed with lithium hydroxide at a metal element to lithium molar ratio of 1:1.05, sintered, and coin cells were prepared for electrical performance testing. The test results are recorded in Table 1. The positive electrode active material, conductive agent Super-P, and binder PVDF were uniformly dispersed in NMP at a mass ratio of 95:2.5:2.5 and then coated onto aluminum foil to form the positive electrode sheet. Lithium foil was used as the negative electrode, and Celgard 2400 separator was used. The electrolyte was 1 mol / L, with LiPF6 dissolved in a mixture of EC+DEC+EMC. CR2025 coin cells were assembled in a glove box filled with a protective atmosphere. Electrical performance tests were performed on a battery testing system under the following conditions: charge / discharge voltage range of 2.8-4.3V and temperature of 25℃.

[0069] Table 1 Electrochemical performance of precursors for each example and comparative example.

[0070] As can be seen from Table 1, the precursors prepared in each embodiment of the present invention exhibit good electrochemical performance when used as cathodes. Comparing Comparative Example 1 with Example 2, Comparative Example 1 shows significantly worse capacity and cycle life, indicating that Pb doping is beneficial for improving the capacity and cycle life of the precursor. Comparing Comparative Example 2 with Example 2, Comparative Example 2 shows significantly worse capacity and cycle life, indicating that Sr doping is beneficial for improving the capacity and cycle life of the precursor. Comparing Comparative Example 3 with Example 2, Comparative Example 3 shows even worse capacity and cycle life, indicating that although Pb and Sr are doped, if the doping positions are not in accordance with the requirements of the present invention, it will be difficult to obtain a precursor with better electrochemical performance.

[0071] In summary, the ternary precursor provided in this invention has a dense core structure, resulting in superior compressive strength and high stability. The cathode material prepared from this precursor exhibits high energy density. Furthermore, the porous shell structure helps buffer volumetric strain during battery cycling, reducing resistance and improving cycle performance and safety. In this invention, lead doping in the core reduces lattice defects in the core layer, enhancing material stability, while strontium doping in the shell strengthens ion channel formation during the preparation process.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A ternary precursor, characterized in that, Its chemical formula is Ni x Co y Mn z M a+b (OH)2, where \(0.80\leq x\lt1\), \(0\leq y\lt0.1\), \(0\leq z\lt0.1\), \(0\lt a + b\lt0.01\), and \(x + y+z + a + b = 1\); M includes Pb and Sr; The ternary precursor particles are secondary particles formed by the accumulation of strip-shaped primary particles, which include a core part located inside and a shell part wrapped outside the core part; the D50 of the core part of the ternary precursor is 5.0 - 7.0 μm, the porosity of the core part is 5 - 12%, and Pb is doped in the core part; the porosity of the shell part is 12 - 30%, and Sr is doped in the shell part; the D50 of the ternary precursor is 8 - 11 μm.

2. The ternary precursor of claim 1, wherein, It includes at least one of the following features (2) - (4): (2) The D50 of the ternary precursor is 8 - 11 μm, and the particle size distribution (D90 - D10) / D50 is 1.2 - 1.5; (3) The specific surface area of ​​the ternary precursor is 8~16m². 2 / g, tap density is 1.8~2.4g / cm³ 3 ; (4) The length of the primary particles constituting the core part is less than the length of the primary particles constituting the shell part.

3. A method of producing a ternary precursor as claimed in claim 1 or 2, characterized in that It includes: The first-stage reaction: A first mixed metal salt solution, a pH regulator, and a complexing agent are injected into a reaction kettle with water as the bottom liquid in a co-current manner, and a protective gas is introduced for precipitation reaction. During the reaction process, the pH value in the reaction kettle is gradually decreased within the range of 10.0 - 12.

5. After measuring that the D50 of the particles generated in the reaction kettle reaches 5.0 - 7.0 μm, the next-stage reaction is carried out; The second-stage reaction: The precipitate generated in the first-stage reaction is extracted and placed in another reaction kettle, water is added, a second mixed metal salt solution, a pH regulator, and a complexing agent are injected in a co-current manner, the pH value in the reaction kettle is gradually increased within the range of 10.0 - 12.5, and the pH value at the end of the second-stage reaction is 0.3 - 0.8 higher than the pH value at the end of the first-stage reaction until the particles in the reaction kettle grow to the target size; In both the first-stage reaction and the second-stage reaction, the free complexing agent in the reaction kettle is controlled within the range of 4.5 - 10.5 g / L in terms of ammonia value, and the end of the second-stage reaction is controlled to be 1 - 4 g / L higher than the end of the first-stage reaction; The temperature of the whole reaction process is 50 - 70 °C; The first mixed metal salt solution and the second mixed metal salt solution are different solutions. The metal ions in the first mixed metal salt solution include Ni, Co, Mn, and Pb with a molar ratio of x:y:z:a, where 0.80 ≤ x < 1, 0 ≤ y < 0.1, 0 ≤ z < 0.1, 0 < a < 0.

01. The metal ions in the second mixed metal salt solution include Ni, Co, Mn, and Sr with a molar ratio of x:y:z:b, where 0.80 ≤ x < 1, 0 ≤ y < 0.1, 0 ≤ z < 0.1, 0 < b < 0.

01.

4. The method of preparing a ternary precursor according to claim 3, wherein The pH regulator is selected from the solution of at least one of sodium hydroxide, potassium hydroxide, sodium bicarbonate, and sodium carbonate.

5. The method of claim 3, wherein the method further comprises, The pH regulator is a sodium hydroxide solution with a concentration of 20 - 40%; The complexing agent is selected from at least one of ammonia water, EDTA, ethylenediamine, sodium citrate, and urea.

6. The method for preparing the ternary precursor according to claim 5, characterized in that, The complexing agent is ammonia water with a mass concentration of 10 - 30%.

7. The method for preparing the ternary precursor according to claim 3, characterized in that, The total concentration of metal ions in the mixed metal salt solution is 90 - 110 g / L, and the injection rate of the mixed metal salt solution is 3 - 6 L / h.

8. The method for preparing the ternary precursor according to claim 3, characterized in that, During the first stage of the reaction, the stirring speed is 200~300 r / min; during the second stage of the reaction, the stirring speed is lower than that during the first stage of the reaction, the stirring speed is 100~220 r / min, and gradually decreases; at the end of the second stage of the reaction, the stirring speed drops to 100~150 r / min.

9. A positive electrode material, characterized by, The ternary precursor prepared by the method described in claim 1 or 2 or the method described in any one of claims 3 to 8 is mixed with a lithium source and sintered.

10. The application of the cathode material as described in claim 9 in a cathode or battery.

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