Inside-dense and outside-loose type small-particle-size high-nickel ternary positive electrode material precursor, preparation method thereof, high-nickel ternary positive electrode material and lithium ion battery

Abstract

The invention belongs to the field of lithium ion battery materials, and discloses a dense-inside loose-outside small-particle-size high-nickel ternary positive electrode material precursor, which is spherical or sphere-like secondary particles formed by agglomerating primary particles, and has a dense inner core and a shell which wraps the surface of the inner core and is of a loose structure, the inner core and the outer shell have the same chemical composition, the porosity of the inner core is 4-17%, the porosity of the outer shell is 7-28%, and the porosity of the inner core is smaller than that of the outer shell. The invention also discloses a preparation method of the precursor, and a high-nickel ternary positive electrode material and a lithium ion battery prepared from the precursor. The compact inner core of the precursor provides a firm structural framework for secondary particles, and high tap density and excellent mechanical stability are ensured; the loose and porous shell provides a huge specific surface area and abundant ion transmission channels, active sites are greatly increased, and infiltration of an electrolyte and rapid de-intercalation of lithium ions are facilitated.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery materials, and particularly relates to a high-nickel ternary cathode material precursor with a dense inner and loose outer particle size and small particle size, its preparation method, the high-nickel ternary cathode material, and the lithium-ion battery. Background Technology

[0002] High-nickel ternary cathode materials are considered key materials for next-generation power batteries due to their high energy density, and their performance largely depends on the microstructure of the precursor. An ideal precursor microstructure needs to balance several properties: a dense structure is beneficial for providing high tap density and good mechanical stability; while a porous structure facilitates the sintering and infiltration of lithium salts and provides abundant ion transport channels, thereby improving electrochemical performance.

[0003] To achieve this performance balance, existing technologies have proposed constructing a gradient structure precursor with a "dense core, loose middle, and dense outer shell." For example, patent application CN114014375A discloses a method for preparing a high-nickel quaternary precursor with a gradient structure by using cyclodextrin as an additive to refine primary particles. However, this method relies on the introduction of organic additives, which not only increases production costs but also may cause additives to decompose and remain during subsequent sintering, affecting material purity. Furthermore, its process sensitivity poses challenges to batch stability during large-scale production.

[0004] Another approach involves stabilizing the structure through elemental doping. For example, patent application CN120389014A discloses a lanthanum-titanium dual-doped core-shell high-nickel precursor, which improves electrochemical performance through the synergistic effect of lanthanum doping in the core and titanium doping in the outer shell. Patent application CN115180659A also discloses a similar core-shell structure with a coating layer of doped elements on the outermost layer. While these methods improve material properties to some extent, the introduction of doping elements (especially rare earth elements such as lanthanum) significantly increases raw material costs, and the preparation process is complex. Furthermore, the preparation process carries the risk of generating harmful byproducts, which can cause environmental pollution during industrial post-processing, contradicting the concept of green manufacturing.

[0005] In summary, existing methods for constructing high-nickel precursor gradient structures generally suffer from the following drawbacks: (1) they rely on additives or dopants, resulting in high costs and complex processes; (2) they may introduce impurities or cause environmental pollution. Therefore, developing a method for preparing small-particle-size precursor porosity gradient structures that does not require the addition of additives and dopants, is simple in process, environmentally friendly, and can precisely control the porosity gradient structure of small-particle-size precursors has become an urgent technical problem to be solved in this field. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a high-nickel ternary cathode material precursor with a dense inner and loose outer particle size and a preparation method thereof, as well as a high-nickel ternary cathode material and a lithium-ion battery.

[0007] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows: A high-nickel ternary cathode material precursor with a dense inner core and a loose outer shell, comprising small particle size, is disclosed. The precursor consists of spherical or near-spherical secondary particles formed by the aggregation of primary particles. The precursor has a dense core and a loosely structured outer shell surrounding the core. The core and the outer shell have the same chemical composition, both being Ni. x Co y Mn z (OH)₂, wherein 0.90≤x≤0.96, 0.03≤y≤0.06, 0.01≤z≤0.05, and x+y+z=1; the porosity of the core is 4%~17%, and the porosity of the shell is 7%~28%, with the porosity of the core being less than that of the shell. If the porosity of the core is too high, the core is not dense; if it is too low, ion transport is restricted. If the porosity of the shell is too high, there are more active sites that come into excessive contact with the electrolyte, leading to excessive interfacial side reactions; if it is too low, it is not porous. In the precursor of this invention, the dense core suppresses volume expansion and reduces grain boundary cracking. The dense core can also suppress the degradation of high-nickel materials during charge-discharge cycles due to the presence of Li. + The volume expansion (lattice distortion) caused by "intercalation / deintercalation" reduces the risk of grain boundary cracking and lowers the probability of "oxygen release" at high temperatures, thus improving the problems of "rapid cycle decay and poor thermal stability" in high-nickel materials. The porous outer shell has a higher specific surface area and abundant mesoporous / microporous channels, which on the one hand improves the mixing uniformity with the lithium source (such as LiOH / Li2CO3) and reduces sintering difficulty (reducing cathode material agglomeration); on the other hand, it can shorten the Li... + The diffusion path within the particles reduces charge transfer resistance and improves the rate performance of the battery.

[0008] In the precursor of this invention, the dense core provides solid support for the entire precursor structure, enabling the material to better resist the stress caused by volume changes during charging and discharging. During the cycling of lithium batteries, the electrode material undergoes multiple volume expansions and contractions, which can easily lead to structural damage. The structure combining a dense core and a porous outer shell can buffer these stress changes to a certain extent, reducing structural damage and improving the cycling stability of the material. The porous outer shell has a larger specific surface area, providing more active sites for the reaction. More active sites mean that more lithium ions can participate in the reaction during battery operation, thereby increasing the battery's discharge specific capacity.

[0009] In the precursor of this invention, the core and shell are homogeneous high-nickel components, free from heterogeneous interfacial stress, which can prevent "core-shell peeling" during cycling and further improve structural stability. Based on "small particle size" (meeting the requirements of high specific surface area and high reactivity), a "dense inside and loose outside" structure is superimposed, with the dense core providing "structural support" and the loose shell retaining "active sites".

[0010] Preferably, in the above-mentioned high-nickel ternary cathode material precursor, the porosity of the core is 5%-7%, and the porosity of the outer shell is 17%-23%. Preferably, in the above-mentioned high-nickel ternary cathode material precursor, the diameter of the core is 0.90μm - 1.70μm, and the thickness of the outer shell is 0.40μm - 0.90μm.

[0011] If the diameter of the core is too small or too large, the dense core portion of the precursor will be either too small or too large. If it is too small, the overall structure of the material will be weak and prone to collapse or deformation during subsequent processing. If it is too large, the outer shell will not have enough reactive areas, and densification may not be complete, affecting electrical performance. If the thickness of the outer shell is too large, the outer shell structure may dominate, and there will be a lack of tightly connected skeletons inside, resulting in poor overall uniformity. If the thickness of the outer shell is too small, the open structure of the outer shell or the reaction channels will be insufficient, which is not conducive to the uniform penetration and binding of substances. Preferably, in the above-mentioned high-nickel ternary cathode material precursor, the primary particles have an elongated morphology with an aspect ratio of 3-5. Preferably, in the above-mentioned high-nickel ternary cathode material precursor, the secondary particles have a particle size D50 of 1.6μm-2.5μm, and the particle size distribution satisfies: 0.8<(D90-D10) / D50<1.5. Preferably, the high-nickel ternary cathode material precursor has a specific surface area of ​​16-30 m². 2 / g, tap density is 1.0-1.8 g / cm³ 3 More preferably, the specific surface area of ​​the high-nickel ternary cathode material precursor is 25-30 m². 2 / g, tap density is 1.0-1.4 g / cm³ 3 When the specific surface area is too large, the fluidity is usually poor, particles are prone to agglomeration and adhesion, and "bridging" phenomenon is easily generated, affecting the homogenization and electrode quality. When it is too small, there are insufficient active sites, the reaction rate is slow, and the chemical reaction is incomplete. When the tap density is too large, the electrode may be over-compacted, the ion migration channel is blocked, and the rate performance and cycle life may decrease. When it is too small, the volumetric energy density is low, and the amount of active material filled in a limited space (such as the battery case) is small, resulting in a decrease in overall capacity.

[0012] Based on a general inventive concept, the present invention also provides a method for preparing the above-described dense-inner-loose-outer-outer-small-particle-size high-nickel ternary cathode precursor, comprising the following steps: (1) Prepare a mixed metal salt solution containing nickel, cobalt, and manganese, a sodium hydroxide solution, and an ammonia solution; (2) Under nitrogen atmosphere, temperature of 60-70℃ and stirring speed of 4.5-8.2 m / s, a mixed metal salt solution, sodium hydroxide solution and ammonia solution are continuously injected into the reactor for co-precipitation reaction. During the co-precipitation reaction, the concentration of ammonium ions in the reactor is controlled to be 8-12 g / L. After the generated core particles D50 reaches 0.90-1.30 μm, they are washed and dried to obtain the core filter cake. (3) Add pure water and ammonia solution as base liquid to another reactor, and add the core filter cake. Under the conditions of air atmosphere, temperature of 40-45℃, ammonium ion concentration of 1-5 g / L, and stirring speed of 5.5-8.0 m / s, inject metal salt solution, sodium hydroxide solution and ammonia solution into the reactor in an intermittent manner to carry out co-precipitation reaction, so that the shell material grows on the core. After the overall particle D50 reaches 1.6-2.3μm, stop the reaction to obtain slurry; (4) The slurry is aged, washed, dried and sieved to obtain the high-nickel ternary cathode material precursor with small particle size, dense inside and loose outside. In the above preparation method, preferably, in step (2), the pH value in the reaction vessel is controlled to be 11.60-12.20 during the coprecipitation reaction.

[0013] In the above preparation method, preferably, in step (3), the pH of the reaction system is maintained at 10.10-11.40 by adjusting the sodium hydroxide solution during the co-precipitation process. Based on a general inventive concept, the present invention also provides a high-nickel ternary cathode material, which is formed by lithium-ion sintering from the above-mentioned high-nickel ternary cathode material precursor or the high-nickel ternary cathode material precursor prepared by the above-mentioned preparation method.

[0014] Based on a general inventive concept, the present invention also provides a lithium-ion battery comprising the above-mentioned high-nickel ternary cathode material.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The high-nickel ternary cathode material precursor constructed in this invention has a dense core and a porous shell. The dense core provides a solid structural framework for the secondary particles, ensuring high tap density and excellent mechanical stability, making it less prone to breakage and collapse during subsequent processing and battery cycling. The porous shell provides a huge specific surface area and abundant ion transport channels, greatly increasing the active sites, which is beneficial for electrolyte wetting and rapid lithium ion insertion / extraction, thereby significantly improving the rate performance and charge / discharge capacity of the final cathode material. More importantly, the precursor core and shell of this invention have the same chemical composition, which fundamentally eliminates lattice mismatch and interfacial stress caused by component differences or doping elements, effectively preventing the "core-shell peeling" phenomenon that occurs during long-term battery cycling, and greatly improving the structural stability and cycle life of the material.

[0016] (2) The high-nickel ternary cathode material precursor of the present invention has a small particle size and a larger specific surface area, which can increase the contact area between the cathode material and the electrolyte, thereby promoting the improvement of the first discharge specific capacity. The small particle size of the high-nickel material shortens the ion migration path, which is conducive to the diffusion of lithium ions, so that it can maintain high energy density while having excellent rate performance, which well meets the urgent needs of cathode materials for specific application scenarios such as high-power power batteries and fast charging batteries.

[0017] (3) This invention completely eliminates organic additives such as cyclodextrin and precious metals or rare earth dopants such as lanthanum and titanium used in the prior art. It can achieve differentiated growth of the core and the outer layer by simply adjusting the co-precipitation process parameters of the reaction system. This greatly simplifies the process, reduces the dependence on special raw materials, and effectively controls the production cost.

[0018] (4) Since no external additives or dopants are introduced during the preparation process of this invention, the impurities that may be generated by the decomposition of these substances during the subsequent sintering process are avoided from the source. The generation of harmful by-products such as wastewater containing heavy metals is also eliminated, making the entire production process cleaner and more environmentally friendly, which is in line with the development concept of green manufacturing. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the structure of the high-nickel ternary cathode material precursor provided in an embodiment of the present invention; Figure 2This is a cross-sectional electron microscope image of the ternary precursor prepared in Example 1 of the present invention; Figure 3 This is a scanning electron microscope image of the ternary precursor prepared in Example 1 of the present invention; Figure 4 This is a cross-sectional electron microscope image of the ternary precursor prepared in Comparative Example 1 of the present invention; Figure 5 This is a cross-sectional electron microscope image of the ternary precursor prepared in Comparative Example 2 of this invention; Figure 6 This is a cross-sectional electron microscope image of the ternary precursor prepared in Comparative Example 3 of the present invention. Detailed Implementation

[0021] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0022] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0023] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0024] The structural schematic diagram of the internally dense and externally loose small-particle-size high-nickel ternary cathode material precursor of the present invention is shown below. Figure 1 As shown, the precursor is a spherical or near-spherical secondary particle formed by the aggregation of primary particles. The precursor has a dense core and a loosely structured shell that surrounds the surface of the core, and the core and shell have the same chemical composition.

[0025] The porosity of the following examples and comparative examples was measured using MIPAR software, while the length and width of the primary particles and the core-shell diameter were measured using Nano Measurer software.

[0026] Example 1: The preparation method of the high-nickel ternary cathode material precursor with dense inner and loose outer particles and small particle size in this embodiment includes the following steps: (1) Solution preparation: Prepare a mixed metal salt solution containing nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of 92:6:2, with a total molar concentration of 2 mol / L for the three metal ions in the mixed salt solution; prepare a 10 mol / L sodium hydroxide solution; and prepare a 6.7 mol / L ammonia solution.

[0027] (2) Continuous method for preparing dense kernels: (a) Add pure water, sodium hydroxide solution and ammonia solution as base liquid to a 300L reactor. Adjust the linear velocity of the stirring speed to 8.10m / s. Add pure water to the overflow port of the reactor. Adjust the temperature of the reactor to 65℃. Adjust the ammonium ion concentration in the reactor to 11g / L with ammonia solution. Adjust the pH value to 12.00 with sodium hydroxide solution. At the same time, introduce nitrogen into the reactor for 2 hours at a flow rate of 15L / min. (b) After the reaction vessel system stabilizes, the mixed metal salt solution, sodium hydroxide solution and ammonia solution are simultaneously injected into the reaction vessel through a peristaltic pump to carry out the co-precipitation reaction. During the reaction, the temperature is maintained at 65°C, the mixed metal salt is fed at a flow rate of 120 mL / min, and the flow rate of sodium hydroxide solution is adjusted to maintain the pH of the reaction system between 12.00 and 12.20. After the liquid level in the reaction vessel reaches the overflow port, the overflow valve is opened to allow the solution to slowly flow into the slurry tank. During the reaction, nitrogen gas is continuously introduced into the reaction vessel for protection, and the ammonium ion concentration in the vessel is controlled at 11 g / L. (c) Stop the reaction when the particle size D50 of the reaction slurry reaches 1.08 μm. Pump the reacted core slurry into a centrifuge for washing with water for 100 minutes at a temperature of 80°C. Then spin dry until the moisture content of the filter cake is 35% to obtain the core filter cake.

[0028] (3) Preparation of loose shells by intermittent method: (a) Add pure water and ammonia solution as base liquid to a 300L reactor, and add 17kg of the core filter cake prepared in step (2). Adjust the linear velocity of the stirring speed to 7.70m / s, the volume of pure water to 265L, adjust the temperature of the reactor to 45℃, adjust the ammonium ion concentration in the reactor to 2g / L with ammonia solution, and simultaneously introduce air into the reactor for 2 hours at a flow rate of 7L / min. (b) After the reaction vessel system stabilizes, inject the mixed metal salt solution, sodium hydroxide solution, and ammonia solution simultaneously into the reaction vessel using a peristaltic pump. Maintain the temperature at 45°C during the reaction. The mixed metal salt is fed at a flow rate of 240 mL / min. Adjust the flow rate of sodium hydroxide to maintain the pH of the reaction system between 10.10 and 10.20. Once the liquid level in the reaction vessel reaches the overflow port, open the 0.25 m³ / min container. 3 The concentrator and the reactor are started and run in a cycle. During the reaction, air is continuously introduced into the reactor at a rate of 7L / min to control the ammonium ion concentration in the reactor to 2g / L. (c) After the D50 of the reaction product reaches 1.85 μm, proceed to the next stage; (4) Post-processing steps: The slurry prepared in step (3) is aged, washed, dried, and sieved to obtain Ni.0.92 Co 0.06 Mn 0.02 (OH )2 Precursor.

[0029] Testing revealed that the precursor particles prepared in this embodiment had a particle size D50 of 1.85 μm, a particle size distribution of 1.12, and a TD of 1.35 g / cm³. 3 BET is 27.65m 2 / g, the porosity of the prepared ternary precursor core is 5.21%, the porosity of the shell is 19.66%, the diameter of the core is 0.98μm, the thickness of the shell is 0.81μm, the primary particles have a slender morphology and an aspect ratio of 3.9.

[0030] The cross-sectional electron microscope image of the ternary cathode material precursor prepared in this embodiment is shown below. Figure 2 As shown, the scanning electron microscope image is as follows: Figure 3 As shown in the figure, the precursor has a dense core and a loose outer shell.

[0031] Example 2: The preparation method of the high-nickel ternary cathode material precursor with dense inner and loose outer particles and small particle size in this embodiment includes the following steps: (1) Solution preparation: Prepare a mixed metal salt solution containing nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of 96:3:1, with a total molar concentration of 2 mol / L for the three metal ions. Prepare a 10 mol / L sodium hydroxide solution and a 6.7 mol / L ammonia solution.

[0032] (2) Continuous method for preparing dense kernels: (a) Add pure water, sodium hydroxide solution and ammonia solution as base liquid to a 300L reactor. Adjust the linear velocity of the stirring speed to 7.70m / s. Add pure water to the overflow port of the reactor. Adjust the temperature of the reactor to 60℃. Adjust the ammonium ion concentration in the reactor to 9g / L with ammonia solution. Adjust the pH value to 11.80-11.90 with sodium hydroxide solution. At the same time, introduce nitrogen into the reactor for 2 hours at a flow rate of 15L / min. (b) After the reaction vessel system stabilizes, the mixed metal salt solution, sodium hydroxide solution and ammonia solution are simultaneously injected into the reaction vessel by a peristaltic pump to carry out the co-precipitation reaction. The temperature is maintained at 60°C during the reaction. The mixed metal salt is fed at a flow rate of 150 mL / min. The flow rate of the sodium hydroxide solution is adjusted to maintain the pH of the reaction system between 11.90 and 12.10. After the liquid level in the reaction vessel reaches the overflow port, the overflow valve is opened to allow the solution to slowly flow into the slurry tank. Nitrogen gas is continuously introduced into the reaction vessel for protection during the reaction, and the ammonium ion concentration in the vessel is controlled at 9 g / L. (c) Stop the reaction when the particle size D50 of the reaction slurry reaches 1.34 μm. Pump the reacted core slurry into a centrifuge for washing with water for 100 minutes at a temperature of 80°C. Then spin dry until the moisture content of the filter cake is 35% to obtain the core filter cake.

[0033] (3) Preparation of loose shells by intermittent method: (a) Add pure water and ammonia solution as base liquid to a 300L reactor, and add 20kg of the core filter cake prepared in step (2). Adjust the linear velocity of the stirring speed to 8.00m / s, the volume of pure water to 250L, adjust the temperature of the reactor to 45℃, adjust the ammonium ion concentration in the reactor to 2g / L with ammonia solution, and simultaneously introduce air into the reactor for 2 hours at a flow rate of 10L / min. (b) After the reaction vessel system stabilizes, inject the mixed metal salt solution, sodium hydroxide solution, and ammonia solution simultaneously into the reaction vessel using a peristaltic pump. Maintain the temperature at 45°C during the reaction. The mixed metal salt is fed at a flow rate of 300 mL / min. Adjust the flow rate of sodium hydroxide to maintain the pH of the reaction system between 10.20 and 10.30. Once the liquid level in the reaction vessel reaches the overflow port, open the 0.25 m³ / min container. 3 The concentrator and the reactor are started and run in a cycle. During the reaction, air is continuously introduced into the reactor at a rate of 10L / min to control the ammonium ion concentration in the reactor to 2g / L. (c) After the D50 of the reaction product reaches 1.90 μm, proceed to the next stage; (4) Post-processing steps: The slurry prepared in step (3) is aged, washed, dried, and sieved to obtain Ni. 0.96 Co 0.03 Mn 0.01 (OH )2 Precursor.

[0034] Testing revealed that the precursor particles prepared in this embodiment had a particle size D50 of 1.90 μm, a particle size distribution of 1.33, and a TD of 1.22 g / cm³. 3 BET is 28.65m 2 / g, the porosity of the prepared ternary precursor core is 6.36%, the porosity of the shell is 18.23%, the diameter of the core is 1.30μm, the thickness of the shell is 0.56μm, the primary particles have a slender morphology and an aspect ratio of 4.4.

[0035] Example 3: The preparation method of the high-nickel ternary cathode material precursor with dense inner and loose outer particles and small particle size in this embodiment includes the following steps: (1) Solution preparation: Prepare a mixed metal salt solution containing nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of 95:4:1, with a total molar concentration of 2 mol / L for the three metal ions in the mixed salt solution; prepare a 10 mol / L sodium hydroxide solution; and prepare a 6.7 mol / L ammonia solution.

[0036] (2) Continuous method for preparing dense kernels: (a) Add pure water, sodium hydroxide solution and ammonia solution as base liquid to a 300L reactor. Adjust the linear velocity of the stirring speed to 8.10m / s. Add pure water to the overflow port of the reactor. Adjust the temperature of the reactor to 70℃. Adjust the ammonium ion concentration in the reactor to 12g / L with ammonia solution. Adjust the pH value to 12.20 with sodium hydroxide solution. At the same time, introduce nitrogen into the reactor for 2 hours at a flow rate of 15L / min. (b) After the reaction vessel system stabilizes, the mixed metal salt solution, sodium hydroxide solution and ammonia solution are simultaneously injected into the reaction vessel through a peristaltic pump to carry out the co-precipitation reaction. During the reaction, the temperature is maintained at 70°C, the mixed metal salt is fed at a flow rate of 120 mL / min, and the flow rate of sodium hydroxide solution is adjusted to maintain the pH of the reaction system between 12.20 and 12.30. After the liquid level in the reaction vessel reaches the overflow port, the overflow valve is opened to allow the solution to slowly flow into the slurry tank. During the reaction, nitrogen gas is continuously introduced into the reaction vessel for protection, and the ammonium ion concentration in the vessel is controlled at 12 g / L. (c) Stop the reaction when the particle size D50 of the reaction slurry reaches 1.16μm. Pump the reacted core slurry into a centrifuge for washing with water for 100 minutes at a temperature of 80℃. Then spin dry until the moisture content of the filter cake is 35% to obtain the core filter cake.

[0037] (3) Preparation of loose shells by intermittent method: (a) Add pure water and ammonia solution as base liquid to a 300L reactor, and add 12kg of the core filter cake prepared in step (2). Adjust the linear velocity of the stirring speed to 7.70m / s, the volume of pure water to 265L, adjust the temperature of the reactor to 40℃, adjust the concentration of ammonium ions in the reactor to 1g / L with ammonia solution, and simultaneously introduce air into the reactor for 2 hours at a flow rate of 7L / min. (b) After the reaction vessel system stabilizes, inject the mixed metal salt solution, sodium hydroxide solution, and ammonia solution simultaneously into the reaction vessel using a peristaltic pump. Maintain the temperature at 40°C during the reaction. The mixed metal salt is fed at a flow rate of 240 mL / min. Adjust the flow rate of sodium hydroxide to maintain the pH of the reaction system between 10.10 and 10.20. When the liquid level in the reaction vessel reaches the overflow port, open the 0.25 m³ / min container. 3 The concentrator and the reactor are started and run in a cycle. During the reaction, air is continuously introduced into the reactor at a rate of 7L / min to control the concentration of ammonium ions in the reactor to 1g / L. (c) After the D50 of the reaction product reaches 1.96 μm, proceed to the next stage; (4) Post-processing steps: The slurry prepared in step (3) is aged, washed, dried, and sieved to obtain Ni. 0.95 Co 0.04 Mn 0.01 (OH )2 Precursor.

[0038] Testing revealed that the precursor particles prepared in this embodiment had a particle size D50 of 1.96 μm, a particle size distribution of 1.21, and a TD of 1.12 g / cm³. 3 BET is 29.66m 2 / g, the porosity of the prepared ternary precursor core is 5.89%, the porosity of the shell is 19.69%, the diameter of the core is 1.10μm, the thickness of the shell is 0.83μm, the primary particles have a slender morphology and an aspect ratio of 4.7.

[0039] Comparative Example 1: The preparation method of the high-nickel ternary cathode material precursor in this comparative example includes the following steps: (1) Prepare a mixed salt solution containing nickel sulfate, cobalt sulfate and manganese sulfate in a ratio of 92:6:2 for nickel, cobalt and manganese metal ions. The total molar concentration of the three metal ions in the mixed salt solution is 2 mol / L. Prepare a 10 mol / L sodium hydroxide solution. Prepare a 6.7 mol / L ammonia solution. (2) Continuous method for preparing loose kernels: (a) Add pure water, sodium hydroxide solution and ammonia solution to a 300L reactor as bottom liquid. Adjust the linear velocity of the stirring speed to 7.70m / s. Add pure water to the overflow port of the reactor. Adjust the temperature of the reactor to 45℃. Adjust the concentration of ammonium ions in the reactor to 2g / L with ammonia solution. Adjust the pH value to 11.50 with sodium hydroxide solution. At the same time, purge nitrogen into the reactor for 2 hours at a flow rate of 15L / min to prepare the bottom liquid of the reactor. (b) After the reaction vessel system stabilizes, the metal salt solution, alkali solution and ammonia solution are simultaneously injected into the reaction vessel using a peristaltic pump. The temperature is maintained at 45°C during the reaction. The metal salt is fed at a flow rate of 240 mL / min. The alkali flow rate is adjusted to maintain the pH of the reaction system between 11.50 and 11.60. After the liquid level in the reaction vessel reaches the overflow port, the overflow valve is opened to allow the solution to slowly flow into the slurry tank. Nitrogen gas is continuously introduced into the reaction vessel for protection during the reaction, and the ammonium ion concentration in the vessel is controlled at 2 g / L.

[0040] (c) Stop the reaction when the precursor particle size D50 reaches 1.62 μm, pump the reacted core slurry into a centrifuge for washing with water for 60 minutes at a temperature of 80°C, and spin dry until the filter cake moisture content is 35% to obtain the core filter cake. (3) Preparation of a dense outer shell by intermittent method: (a) Add pure water and ammonia solution as bottom liquid and first-stage core filter cake to a 300L reactor. Adjust the linear velocity of the stirring speed to 8.10m / s, the volume of pure water to 200L, adjust the temperature of the reactor to 65℃, adjust the ammonium ion concentration in the reactor to 9g / L with ammonia solution, add 22kg of core filter cake, and simultaneously purge nitrogen into the reactor for 2 hours at a flow rate of 20L / min to prepare the bottom liquid of the reactor. (b) After the reaction system stabilizes, simultaneously inject the metal salt solution, alkali solution, and ammonia solution into the reaction vessel using a peristaltic pump, maintaining the temperature at 65°C throughout the reaction. Feed the metal salt at a flow rate of 320 mL / min, adjusting the alkali flow rate to maintain the pH of the reaction system between 11.60 and 11.70. Once the liquid level in the reaction vessel reaches the overflow port, open the 0.25 m³ / min container. 3 The concentrator and the reaction vessel are started and run in a cycle. During the reaction, nitrogen gas is continuously introduced into the reaction vessel at a rate of 20L / min to control the ammonium ion concentration in the vessel to 9g / L.

[0041] (c) After the D50 of the reaction product reaches 2.10 μm, the next stage is carried out. The prepared slurry is aged, washed, dried, and sieved to obtain Ni. 0.92 Co 0.06 Mn 0.02 (OH)2 precursor products.

[0042] Testing revealed that the precursor particles prepared in this embodiment had a particle size D50 of 2.10 μm, a particle size distribution of 1.21, and a TD of 1.64 g / cm³. 3 BET is 16.85m 2 / g, the porosity of the core of this ternary precursor is 16.96%, the porosity of the shell is 7.12%, the diameter of the core is 1.58μm, the thickness of the shell is 0.45μm, the primary particles have a slender morphology and an aspect ratio of 3.2.

[0043] A cross-sectional electron microscope image of the ternary precursor prepared in this comparative example is shown below. Figure 4 As shown in the figure, the obtained high-nickel small-particle precursor has a porous core and a dense outer shell.

[0044] Comparative Example 2: The preparation method of the high-nickel ternary cathode material precursor in this comparative example includes the following steps: (1) Prepare a mixed salt solution containing nickel sulfate, cobalt sulfate and manganese sulfate in a ratio of 92:6:2 for nickel, cobalt and manganese metal ions. The total molar concentration of the three metal ions in the mixed salt solution is 2 mol / L. Prepare a 10 mol / L sodium hydroxide solution. Prepare a 6.7 mol / L ammonia solution. (2) Continuous method for preparing loose kernels: (a) Add pure water, sodium hydroxide solution and ammonia solution to a 300L reactor as bottom liquid. Adjust the linear velocity of the stirring speed to 4.99m / s. Add pure water to the overflow port of the reactor. Adjust the temperature of the reactor to 40℃. Adjust the concentration of ammonium ions in the reactor to 3g / L with ammonia solution. Adjust the pH value to 11.60 with sodium hydroxide solution. At the same time, purge nitrogen into the reactor for 2 hours at a flow rate of 15L / min to prepare the bottom liquid of the reactor. (b) After the reaction vessel system stabilizes, the metal salt solution, alkali solution, and ammonia solution are simultaneously injected into the reaction vessel using a peristaltic pump. The temperature is maintained at 40°C during the reaction. The metal salt is fed at a flow rate of 280 mL / min, and the alkali flow rate is adjusted to maintain the pH of the reaction system between 11.60 and 11.70. After the liquid level in the reaction vessel reaches the overflow port, the overflow valve is opened to allow the solution to slowly flow into the slurry tank. Nitrogen gas is continuously introduced into the reaction vessel for protection during the reaction, and the ammonium ion concentration in the vessel is controlled at 3 g / L.

[0045] (c) Stop the reaction after the precursor particle size D50 reaches 1.50 μm, pump the reacted core slurry into a centrifuge for washing with water for 60 minutes at a temperature of 80°C, and spin dry until the filter cake moisture content is 35% to obtain the core filter cake. (3) Preparation of a dense outer shell by intermittent method: (a) Add pure water and ammonia solution as bottom liquid and first-stage core filter cake to a 300L reactor. Adjust the linear velocity of the stirring speed to 5.60m / s, the volume of pure water to 150L, ​​adjust the temperature of the reactor to 60℃, adjust the ammonium ion concentration in the reactor to 6g / L with ammonia solution, add 20kg of core filter cake, and simultaneously purge nitrogen into the reactor for 2 hours at a flow rate of 15L / min to prepare the bottom liquid of the reactor. (b) After the reaction system stabilizes, simultaneously inject the metal salt solution, alkali solution, and ammonia solution into the reaction vessel using a peristaltic pump, maintaining the temperature at 60°C throughout the reaction. Feed the metal salt at a flow rate of 240 mL / min, adjusting the alkali flow rate to maintain the pH of the reaction system between 11.10 and 11.30. Once the liquid level in the reaction vessel reaches the overflow port, open the 0.25 m³ / min container. 3 The concentrator and the reactor are started and run in a cycle. During the reaction, nitrogen gas is continuously introduced into the reactor at a rate of 15L / min to control the ammonium ion concentration in the reactor to 6g / L.

[0046] (c) After the D50 of the reaction product reaches 1.94 μm, the next stage is carried out. The prepared slurry is aged, washed, dried, and sieved to obtain Ni. 0.92 Co 0.06 Mn 0.02 (OH)2 precursor products.

[0047] Testing revealed that the precursor particles prepared in this comparative example had a particle size D50 of 1.94 μm, a particle size distribution of 1.34, and a TD of 1.45 g / cm³. 3 BET is 20.78m 2 / g, with a core porosity of 14.95% and a shell porosity of 8.63%, a core diameter of 1.45μm, a shell thickness of 0.46μm, and a primary particle with a slender morphology and an aspect ratio of 3.5.

[0048] A cross-sectional electron microscope image of the ternary precursor prepared in this comparative example is shown below. Figure 5 As shown in the figure, the obtained high-nickel small-particle precursor has a porous core and a dense outer shell.

[0049] Comparative Example 3: The preparation method of the high-nickel ternary cathode material precursor in this comparative example includes the following steps: (1) Prepare a mixed salt solution containing nickel sulfate, cobalt sulfate and manganese sulfate in a ratio of 96:3:1 for nickel, cobalt and manganese metal ions. The total molar concentration of nickel, cobalt and manganese metal ions in the mixed salt solution is 2 mol / L. Prepare a 10 mol / L sodium hydroxide solution. Prepare a 6.7 mol / L ammonia solution. (2) Continuous method for preparing loose kernels: (a) Add pure water, sodium hydroxide solution and ammonia solution to a 300L reactor as bottom liquid. Adjust the linear velocity of the stirring speed to 8.00m / s. Add pure water to the overflow port of the reactor. Adjust the temperature of the reactor to 45℃. Adjust the concentration of ammonium ions in the reactor to 1g / L with ammonia solution. Adjust the pH value to 10.90 with sodium hydroxide solution. At the same time, purge nitrogen into the reactor for 2 hours at a flow rate of 15L / min to prepare the bottom liquid of the reactor. (b) After the reaction vessel system stabilizes, the mixed metal salt solution, sodium hydroxide solution and ammonia solution are simultaneously injected into the reaction vessel using a peristaltic pump. The temperature is maintained at 45°C during the reaction. The mixed metal salt is fed at a flow rate of 300 mL / min. The flow rate of sodium hydroxide is adjusted to maintain the pH of the reaction system between 10.90 and 11.00. After the liquid level in the reaction vessel reaches the overflow port, the overflow valve is opened to allow the solution to slowly flow into the slurry tank. Nitrogen gas is continuously introduced into the reaction vessel for protection during the reaction, and the ammonium ion concentration in the vessel is controlled at 1 g / L. (c) Stop the reaction when the precursor particle size D50 reaches 1.72 μm, pump the reacted core slurry into a centrifuge for washing with water for 100 minutes at a water temperature of 80°C, and then spin dry until the filter cake moisture content is 35% to obtain the core filter cake. (3) Preparation of loose shells by intermittent method: (a) Add pure water and ammonia solution as bottom liquid and first-stage core filter cake to a 300L reactor. Adjust the linear velocity of the stirring speed to 7.70m / s, the volume of pure water to 120L, adjust the temperature of the reactor to 60℃, adjust the ammonium ion concentration in the reactor to 4g / L with ammonia solution, add 14kg of core filter cake, and simultaneously introduce air into the reactor for 2 hours at a flow rate of 7L / min to prepare the bottom liquid of the reactor. (b) After the reaction system stabilizes, simultaneously inject the metal salt solution, alkali solution, and ammonia solution into the reaction vessel using a peristaltic pump, maintaining the temperature at 60°C throughout the reaction. Feed the metal salt at a flow rate of 480 mL / min, adjusting the alkali flow rate to maintain the pH of the reaction system between 11.10 and 11.20. Once the liquid level in the reaction vessel reaches the overflow port, open the 0.25 m³ / min container. 3 The concentrator and the reaction vessel are started and run in a cycle. During the reaction, air is continuously introduced into the reaction vessel at a rate of 7L / min to control the concentration of ammonium ions in the vessel to 4g / L.

[0050] (c) After the D50 of the reaction product reaches 2.23 μm, the next stage is carried out. The prepared slurry is aged, washed, dried, and sieved to obtain Ni. 0.96 Co 0.03 Mn 0.01 (OH)2 Precursor.

[0051] The precursor particles prepared in this comparative example had a particle size D50 of 2.23 μm, a particle size distribution of 1.07, and a TD of 1.78 g / cm³. 3 BET is 16.44m 2 / g, the porosity of its precursor core is 15.73%, the porosity of its shell is 9.94%, the diameter of the core is 1.65μm, the thickness of the shell is 0.54μm, the primary particles have a slender morphology and an aspect ratio of 3.8.

[0052] A cross-sectional electron microscope image of the ternary precursor prepared in this comparative example is shown below. Figure 6 As shown in the figure, the obtained high-nickel small-particle precursor has a porous core and a loose outer shell.

[0053] Battery performance test: To evaluate the electrochemical performance of the prepared dense-inner-loose-outer-outer-small-particle-size high-nickel ternary precursor, the following steps were used to assemble the precursor into a coin cell and perform charge-discharge cycle characteristics tests: A. Preparation of cathode material: The precursor samples prepared in the examples and comparative examples were taken and mixed with lithium hydroxide (LiOH·H2O) at a molar ratio of 1:1.08. The mixture was placed in a muffle furnace and sintered at 800°C for 12 hours (oxygen atmosphere). After cooling, the cathode material was obtained.

[0054] B. Electrode preparation: The obtained positive electrode material is mixed with conductive agent (acetylene black) and binder (PVDF) at a mass ratio of 90:5:5. An appropriate amount of NMP solvent is added to make a uniform slurry, which is uniformly coated on aluminum foil current collector. After drying and rolling, it is punched into round sheets as positive electrode sheets.

[0055] C. Button cell assembly: In an argon atmosphere glove box, using the above-mentioned positive electrode as the positive electrode and the lithium sheet as the negative electrode, a polypropylene separator (Celgard2400) and liquid electrolyte (1MLiPF6 / EC+DMC=1:1, volume ratio) are used to assemble CR2032 button cells.

[0056] At 25°C, the charge-discharge cycle characteristics of the coin cells prepared in each experimental group were tested using a blue electric test cabinet. Charge and discharge were performed at a rate of 0.1C within a voltage range of 2.8V to 4.3V. The charge-discharge capacity after the first cycle was recorded.

[0057] Table 1 Electrochemical performance of precursors for each example and comparative example

Claims

1. A high-nickel ternary cathode material precursor with a dense inner and loose outer particle size, characterized in that, The precursor is a spherical or near-spherical secondary particle formed by the aggregation of primary particles. The precursor has a dense core and a loosely structured outer shell surrounding the surface of the core. The core and the outer shell have the same chemical composition, both being Ni. x Co y Mn z (OH)2, wherein 0.90≤x≤0.96, 0.03≤y≤0.06, 0.01≤z≤0.05, and x+y+z=1; the porosity of the core is 4%-17%, the porosity of the shell is 7%-28%, and the porosity of the core is less than that of the shell.

2. The high-nickel ternary cathode material precursor as described in claim 1, characterized in that, The porosity of the core is 5%-7%, and the porosity of the outer shell is 17%-23%.

3. The high-nickel ternary cathode material precursor as described in claim 1, characterized in that, The core has a diameter of 0.9μm - 1.7μm, and the outer shell has a thickness of 0.40μm - 0.90μm.

4. The high-nickel ternary cathode material precursor as described in claim 1, characterized in that, The primary particles have a slender shape with an aspect ratio of 3-5.

5. The high-nickel ternary cathode material precursor as described in claim 1, characterized in that, The secondary particles have a particle size D50 of 1.6μm-2.5μm, and the particle size distribution satisfies: 0.8 < (D90-D10) / D50 < 1.

5.

6. The high-nickel ternary cathode material precursor as described in claim 1, characterized in that, The specific surface area of ​​the high-nickel ternary cathode material precursor is 16-30 m². 2 / g, tap density is 1.0-1.8 g / cm³ 3 .

7. A method for preparing a dense-inner-density, loose-inner-outer-loose-inner-particle-size, high-nickel ternary cathode precursor as described in any one of claims 1-6, characterized in that, Includes the following steps: (1) Prepare a mixed metal salt solution containing nickel, cobalt, and manganese, a sodium hydroxide solution, and an ammonia solution; (2) Under nitrogen atmosphere, temperature of 60-70℃ and stirring speed of 4.5-8.2 m / s, a mixed metal salt solution, sodium hydroxide solution and ammonia solution are continuously injected into the reactor for co-precipitation reaction. During the co-precipitation reaction, the concentration of ammonium ions in the reactor is controlled to be 8-12 g / L. After the generated core particles D50 reaches 0.90-1.30 μm, they are washed and dried to obtain the core filter cake. (3) Add pure water and ammonia solution as base liquid to another reactor, and add the core filter cake. Under the conditions of air atmosphere, temperature of 40-45℃, ammonium ion concentration of 1-5 g / L, and stirring speed of 5.5-8.0 m / s, inject the mixed metal salt solution, sodium hydroxide solution and ammonia solution into the reactor in an intermittent manner to carry out co-precipitation reaction, so that the shell material grows on the core. After the overall particle D50 reaches 1.6-2.3μm, stop the reaction to obtain slurry; (4) The slurry is aged, washed, dried and sieved to obtain the high-nickel ternary cathode material precursor with small particle size, dense inside and loose outside.

8. The preparation method according to claim 7, characterized in that, In step (2), the pH value inside the reactor is controlled to be 11.60-12.20 during the coprecipitation reaction.

9. The preparation method according to claim 7, characterized in that, In step (3), the pH of the reaction system is maintained at 10.10-11.40 by adjusting the sodium hydroxide solution during the co-precipitation process.

10. A high-nickel ternary cathode material, characterized in that, The high-nickel ternary cathode material precursor prepared by any one of claims 1 to 6 or by any one of the preparation methods of claims 7 to 9 is sintered with lithium.

11. A lithium-ion battery, characterized in that, Including the high-nickel ternary cathode material as described in claim 10.

Images