Positive electrode material precursor and preparation method and application thereof

Abstract

The invention relates to the technical field of batteries, in particular to a positive electrode material precursor and a preparation method and application thereof. The positive electrode material precursor comprises: an inner core; the transition layer is arranged on at least part of the surface of the inner core; the shell layer is arranged on at least part of the surface, far away from the inner core, of the transition layer. Compared with the prior art, the high-nickel inner core is protected through the outermost manganese-rich shell layer, the cycle performance and the thermal stability of the material are improved, meanwhile, the transition layer is arranged, it is ensured that all the layers make close contact, elements of all the layers are the same, the interface layering problem caused by the difference of the elements of the inner layer and the outer layer is avoided, and the high-capacity characteristic of the positive electrode material is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and more specifically, to a precursor of a cathode material, a preparation method thereof, and an application thereof. Background Art

[0002] With the continuous increase in the demand for battery energy density in fields such as electric vehicles, nickel-rich layered cathode materials have received extensive attention as high-voltage layered cathode materials. However, conventional nickel-rich layered cathode materials usually exhibit severe structural collapse and poor thermal stability under electrochemical cycling conditions.

[0003] Currently, the modification methods of nickel-rich layered cathode material precursors mainly involve core-shell structures, element coating, etc.; among them, the core-shell structure usually adopts composite configurations such as NCM-NCA, NCM-SiO2, etc. However, the volume change rates of the NCM core and the NCA shell layer during charge and discharge are significantly different, which easily leads to the generation of interface delamination or cracks; at the same time, aluminum elements are easily precipitated in the form of amorphous Al(OH)3, which destroys the compactness of the shell layer, thereby affecting the electrochemical performance and structural stability of the material; while SiO2 as the material shell supports the NCM core, although it can prevent the pulverization of the cathode material, the core and the shell materials are inconsistent, reducing the discharge capacity of the cathode material. Summary of the Invention

[0004] In view of this, an object of the present invention is to solve at least one of the technical problems in the related art to some extent. To this end, the present invention provides a precursor of a cathode material, a preparation method thereof, and an application thereof, which protect the high-nickel core through the outermost manganese-rich shell layer, improve the cycling performance and thermal stability of the material, and at the same time, by setting a transition layer, ensure that the structures of each layer are in close contact, and the elements of each layer are the same, avoiding the interface delamination problem caused by the element difference between the inner and outer layers, and realizing the high-capacity characteristics of the cathode material.

[0005] To solve the above technical problems, the present invention is implemented as follows: According to one aspect of the present invention, the present invention provides a precursor of a cathode material, including: A core, the core satisfying the chemical general formula Ni a1 Co b1 Mn c1 (OH)2, wherein, 0.7 < a1 ≤ 0.9, 0.05 ≤ b1 < 0.1, 0 < c1 ≤ 0.25, and a1 + b1 + c1 = 1; A transition layer, provided on at least part of the surface of the core, the transition layer satisfying the chemical general formula Ni a2 Co b2 Mn c2(OH)2, where 0.7 < a2 < 0.85, 0.05 < b2 < 0.1, 0.05 < c2 < 0.25, and a2 + b2 + c2 = 1; An outer shell layer is provided on at least part of the surface of the transition layer away from the inner core, and the outer shell layer satisfies the chemical general formula Ni a3 Co b3 Mn c3 (OH)2, where 0.2 < a3 ≤ 0.4, 0.1 ≤ b3 < 0.2, 0.4 ≤ c3 < 0.7, and a3 + b3 + c3 = 1.

[0006] In some of these embodiments, a1 > a2 > a3, b1 < b2 < b3, c1 < c2 < c3.

[0007] In some of these embodiments, the particle size D V 50 of the inner core is 3 μm to 4 μm.

[0008] In some of these embodiments, the thickness of the transition layer is 3 μm to 6 μm.

[0009] In some of these embodiments, the particle size D V 50 of the positive electrode material precursor is 7 μm to 13 μm.

[0010] In some of these embodiments, the outer shell layer includes a primary particle close-packed structure; the particle size D V 50 of the primary particles is 0.5 μm to 2 μm.

[0011] In some of these embodiments, the thickness of the outer shell layer is 1 μm to 3 μm.

[0012] According to another aspect of the present invention, the present invention provides a method for preparing a positive electrode material precursor, comprising the following steps: a) Adding solution A, a complexing agent solution, and a precipitating agent solution to a synthesis bottom liquid, performing a first-stage coprecipitation reaction to form an inner core, and obtaining a first reaction system; b) Mixing solution A and solution B to obtain solution AB; then adding solution AB, a complexing agent solution, and a precipitating agent solution to the first reaction system obtained in step a), performing a second-stage coprecipitation reaction to form a transition layer, and obtaining a second reaction system; c) Adding solution B, a surfactant, a complexing agent solution, and a precipitating agent solution to the second reaction system obtained in step b), performing a third-stage coprecipitation reaction to form an outer shell layer, and obtaining a positive electrode material precursor; The solution A is a mixed solution of nickel salt, cobalt salt and manganese salt with a molar ratio of Ni:Co:Mn of x1:y1:z1, where 0.7 < x1 ≤ 0.9, 0.05 ≤ y1 < 0.1, 0 < z1 ≤ 0.25, and x1 + y1 + z1 = 1; The solution B is a mixed solution of nickel salt, cobalt salt and manganese salt with a molar ratio of Ni:Co:Mn of x2:y2:z2, where 0.2 < x2 ≤ 0.4, 0.1 ≤ y2 < 0.2, 0.4 ≤ z2 < 0.7, and x2 + y2 + z2 = 1.

[0013] In some of these embodiments, the complexing agent includes one or more of ammonia water, ammonium sulfate, oxalic acid, ammonium bicarbonate.

[0014] In some of these embodiments, the precipitating agent includes one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, ammonium bicarbonate.

[0015] In some of these embodiments, the synthetic bottom liquid in step a) includes water, a precipitating agent and a complexing agent.

[0016] In some of these embodiments, the temperature of the synthetic bottom liquid in step a) is 50°C to 70°C, and the pH value is 11 to 13.

[0017] In some of these embodiments, step a) is carried out under the condition of continuously introducing an inert gas.

[0018] In some of these embodiments, the flow rate of the solution A added in step a) is 2 L / h to 4 L / h, the flow rate of the complexing agent solution added is 200 mL / h to 400 mL / h, and the flow rate of the precipitating agent solution added is 1.2 L / h to 2.6 L / h.

[0019] In some of these embodiments, step b) is first carried out under the condition of introducing an inert gas until the particle size D V 50 of the precipitated product increases by 1 μm to 3 μm compared to the core particle size D V 50, and then a mixed gas of inert gas and air is introduced to continue coprecipitation.

[0020] In some of these embodiments, the flow rate of the solution AB added in step b) is 5 L / h to 8 L / h, the flow rate of the complexing agent solution added is 300 mL / h to 600 mL / h, and the flow rate of the precipitating agent solution added is 2 L / h to 4.5 L / h.

[0021] In some of these embodiments, the surfactant includes one or more of cocamidopropyl betaine, sodium dodecylbenzenesulfonate, polyvinylpyrrolidone.

[0022] In some of these embodiments, the mass ratio of solution B to surfactant in step c) is 100:(0.1~1).

[0023] In some of these embodiments, step c) is performed under conditions of a continuous flow of a mixture of inert gas and air.

[0024] In some of these embodiments, the flow rate of solution B and surfactant added in step c) is 6 L / h to 9 L / h, the flow rate of complexing agent solution added is 200 mL / h to 400 mL / h, and the flow rate of precipitant solution added is 2 L / h to 5 L / h.

[0025] In some embodiments, after forming the outer shell layer in step c), the reaction product is further washed with water and then filtered and dried to obtain the cathode material precursor.

[0026] In some embodiments, the concentration of the complexing agent in the synthetic substrate is 4 g / L to 8 g / L.

[0027] In some embodiments, the inert gas includes one or more of nitrogen, argon, and helium.

[0028] In some embodiments, the rate at which the inert gas is introduced in step a) is 0.5 m / s. 3 / h~3m 3 / h.

[0029] In some of these embodiments, the volume fraction of air in the mixture of inert gas and air introduced in step b) is 4% to 12%.

[0030] In some of these embodiments, the volume fraction of air in the mixture of inert gas and air introduced in step c) is 4% to 12%.

[0031] In some of these embodiments, the number of times the water is washed in step c) is 2 to 4, and the drying temperature is 90°C to 120°C.

[0032] According to another aspect of the present invention, a cathode material is provided, which is obtained by reacting raw materials including a cathode material precursor and a lithium source; the cathode material precursor includes the cathode material precursor described in the above-described technical solution or the cathode material precursor prepared by the preparation method described in the above-described technical solution.

[0033] In some of these embodiments, the cathode material satisfies the general chemical formula LiNi. α Co β Mn γO2, where 0.75≤α≤0.9, 0.05≤β<0.15, 0.05<γ≤0.2, and α+β+γ=1.

[0034] In some of these embodiments, the particle size D of the positive electrode material V 50 has a thickness of 7μm to 13μm.

[0035] In some embodiments, the reaction process includes: mixing the cathode material precursor and the lithium source uniformly and then sintering to obtain the cathode material; preferably, the sintering process includes: heating to 500°C to 700°C at a heating rate of 2°C / min to 6°C / min for a first sintering of 4h to 8h, and then heating to 700°C to 900°C at a heating rate of 2°C / min to 6°C / min for a second sintering of 12h to 24h.

[0036] According to another aspect of the present invention, a battery is provided, comprising the positive electrode material described in the above technical solution.

[0037] Implementing the technical solution of the present invention has at least the following beneficial effects: 1. The cathode material precursor provided by this invention protects the sensitive high-nickel core from directly penetrating into the electrolyte by setting a manganese-rich outer shell layer, suppressing unnecessary structural transformation and loss of nickel-rich active components, and improving the cycle performance and thermal stability of the cathode material. At the same time, by setting a transition layer with a gradient of elements, the outer shell layer and the transition layer are ensured to be in close contact. Meanwhile, the core, transition layer and outer shell layer are of the same element, avoiding the interface delamination problem caused by the difference in elements between the inner and outer layers, and realizing the high capacity characteristics of the cathode material.

[0038] 2. The method for preparing the cathode material precursor provided by the present invention not only utilizes the high capacity characteristics of high-nickel materials, but also improves thermal stability and cycle performance through the manganese-rich outer shell, and is more suitable for large-scale production, thereby promoting the practical application of high-energy nickel-rich layered cathodes.

[0039] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0040] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0041] Figure 1 This is a schematic diagram of the structure of the cathode material precursor provided in an embodiment of the present invention.

[0042] Figure 2This is a scanning electron microscope image of the cathode material precursor prepared in Example 1 of the present invention.

[0043] Explanation of reference numerals in the attached figures: 1 is the kernel, 2 is the transition layer, and 3 is the outer shell layer.

[0044] The accompanying drawings have illustrated specific embodiments of the invention, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0045] The present application will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0046] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges or individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0047] In the description of this application, "same chemical composition" should be interpreted broadly, that is, the main components of the two have the same chemical composition, or the two have substantially the same chemical composition, but may have errors or impurities within the acceptable range that can be understood by those skilled in the art.

[0048] In the description of this application, "A and / or B" can include any of the cases of A alone, B alone, or A and B, where A and B are merely examples and can be any technical feature connected by "and / or" in this application.

[0049] Unless otherwise specified, the terms "comprising" and "including" as used in this invention can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0050] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0051] Unless otherwise specified, all technical features and optional technical features of this invention can be combined to form new technical solutions.

[0052] Unless otherwise specified, all steps of the present invention can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) carried out sequentially, or may also include steps (b) and (a) carried out sequentially. For example, when it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may also include steps (a), (c) and (b), or may also include steps (c), (a) and (b), etc.

[0053] Currently, the modification methods of nickel-rich layered cathode material precursors mainly involve core-shell structures, element coating, etc.; among them, core-shell structures usually adopt composite configurations such as NCM-NCA, NCM-SiO2, etc. However, the volume change rates of the NCM core and the NCA shell layer during charge and discharge are significantly different, which easily leads to the generation of interface delamination or cracks; at the same time, aluminum elements are easily precipitated in the form of amorphous Al(OH)3, destroying the compactness of the shell layer, thereby affecting the electrochemical performance and structural stability of the material; while SiO2 as the material shell supporting the NCM core can prevent the pulverization of the cathode material, but the materials of the core and the shell are inconsistent, reducing the discharge capacity of the cathode material.

[0054] On this basis, the present invention provides a cathode material precursor. By setting a manganese-rich outer shell layer, it protects the sensitive inner core from directly penetrating into the electrolyte, inhibits unnecessary structural transformation and the loss of nickel-rich active components, and improves the cycling performance and thermal stability of the cathode material. And by setting a transition layer with a gradually changing element gradient, it ensures the close contact between the outer shell layer and the transition layer. At the same time, the elements of the inner core, the transition layer, and the outer shell layer are the same, avoiding the interface delamination problem caused by the element difference between the inner and outer layers, and realizing the high-capacity characteristics of the cathode material.

[0055] Specifically, the present invention adopts the following technical solutions: According to one aspect of the present invention, the present invention provides a cathode material precursor, comprising: An inner core, the inner core satisfying the chemical general formula Ni a1 Co b1 Mn c1 (OH)2, where 0.7 < a1 ≤ 0.9, 0.05 ≤ b1 < 0.1, 0 < c1 ≤ 0.25, and a1 + b1 + c1 = 1; A transition layer, provided on at least part of the surface of the inner core, the transition layer satisfying the chemical general formula Ni a2 Co b2 Mn c2(OH)₂, where 0.7 < a₂ < 0.85, 0.05 < b₂ < 0.1, 0.05 < c₂ < 0.25, and a₂ + b₂ + c₂ = 1; The outer shell layer is disposed on at least part of the surface of the transition layer away from the kernel, and the outer shell layer satisfies the chemical general formula Ni a3 Co b3 Mn c3 (OH)₂, where 0.2 < a₃ ≤ 0.4, 0.1 ≤ b₃ < 0.2, 0.4 ≤ c₃ < 0.7, and a₃ + b₃ + c₃ = 1. For details, see Figure 1 as shown, where 1 is the kernel, 2 is the transition layer, and 3 is the outer shell layer.

[0056] In a specific embodiment of the present invention, a₁ > a₂ > a₃, b₁ < b₂ < b₃, c₁ < c₂ < c₃. On this basis, the nickel content decreases from the kernel to the outer shell layer, and the cobalt content and manganese content increase from the kernel to the outer shell layer. By selecting the above suitable parameter limits, the high-capacity characteristics of the high-nickel material are utilized, and the thermal stability and cycling performance are improved by the manganese-rich outer shell, ensuring that a cathode material precursor meeting the performance requirements of the present invention can be obtained.

[0057] In a specific embodiment of the present invention, the particle size D of the kernel V is preferably 3 μm to 4 μm, and specifically can be 3 μm, 3.5 μm, 4 μm, etc. It should be noted that when the kernel particle size is too large, the kernel is prone to cracking; when the kernel particle size is too small, it affects the nickel content of the kernel. By selecting the above suitable kernel particle size, the high-capacity characteristics of the high-nickel kernel can be fully exerted, thereby further obtaining a cathode material meeting the performance requirements of the present invention.

[0058] In a specific embodiment of the present invention, the thickness of the transition layer is preferably 3 μm to 6 μm, and specifically can be 3 μm, 4 μm, 5 μm, 6 μm, etc. It should be noted that when the transition layer thickness is too large, it affects the main component nickel content and manganese content; when the transition layer thickness is too small, the component mutation between the kernel and the outer shell layer is likely to cause interfacial stress concentration, reduce the interfacial bonding property, and lead to the phenomenon of delamination between the outer shell layer and the kernel during the subsequent sintering process. By selecting the above suitable transition layer thickness, it can be ensured to be tightly combined with the kernel and the outer shell layer, thereby further increasing the discharge capacity of the cathode material.

[0059] In a specific embodiment of the present invention, the outer shell layer preferably includes a closely packed structure of primary particles; the particle size D of the primary particles VThe preferred particle size is 0.5 μm to 2 μm, specifically 0.5 μm, 1 μm, 1.5 μm, 2 μm, etc. It should be noted that if the primary particle size is too large, it disrupts the tightly packed structure, leading to a decrease in the mechanical strength of the outer shell layer; conversely, if the primary particle size is too small, the sintering process is prone to overgrowth or agglomeration, disrupting the uniform distribution of the primary particles. The present invention selects the aforementioned suitable primary particle size to ensure that the subsequently obtained cathode material precursor has good performance, thereby further obtaining a cathode material that meets the performance requirements of the present invention.

[0060] In a specific embodiment of the present invention, the thickness of the outer shell layer is preferably 1μm to 3μm, specifically 1μm, 2μm, 3μm, etc. It should be noted that if the outer shell layer thickness is too large, the transition effect of the transition layer decreases, and the large compositional difference causes delamination between the outer shell layer and the core during subsequent sintering; conversely, if the outer shell layer thickness is too small, it cannot protect the core, leading to the loss of nickel-rich active components and reducing the stability of the cathode material. The present invention selects the aforementioned suitable outer shell layer thickness to protect the sensitive core from direct penetration into the electrolyte, thereby improving the thermal stability and cycle life of the cathode material.

[0061] In a specific embodiment of the present invention, the particle size D of the positive electrode material precursor is... V The preferred particle size of 50 is 7μm to 13μm, specifically 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, etc. This invention selects the above-mentioned suitable cathode material precursor particle size to ensure a continuous spatial transition between the high-nickel core, transition layer, and high-manganese outer shell, avoiding interfacial stress concentration, thereby further obtaining a cathode material that meets the performance requirements of this invention.

[0062] The cathode material precursor provided by this invention protects the sensitive high-nickel core from directly penetrating into the electrolyte by setting a manganese-rich outer shell layer, suppressing unnecessary structural transformation and loss of nickel-rich active components, thereby improving the cycle performance and thermal stability of the cathode material. At the same time, by setting a transition layer with a gradient of elements, the outer shell layer and the transition layer are ensured to be in close contact. Meanwhile, the core, transition layer and outer shell layer are of the same element, avoiding the interface delamination problem caused by the difference in elements between the inner and outer layers, thus achieving the high capacity characteristics of the cathode material.

[0063] According to another aspect of the present invention, the present invention provides a method for preparing a cathode material precursor, comprising the following steps: a) Add solution A, complexing agent solution, and precipitant solution to the synthesis base liquid to carry out the first stage co-precipitation reaction, form the core, and obtain the first reaction system; b) Mix solution A and solution B to obtain solution AB; then add the solution AB, the complexing agent solution, and the precipitating agent solution to the first reaction system obtained in step a) to conduct a second-stage coprecipitation reaction to form a transition layer and obtain a second reaction system; c) Add solution B, the surfactant, the complexing agent solution, and the precipitating agent solution to the second reaction system obtained in step b) to conduct a third-stage coprecipitation reaction to form an outer shell layer and obtain a precursor of the cathode material; The solution A is a mixed solution of nickel salt, cobalt salt, and manganese salt with a molar ratio of Ni:Co:Mn of x1:y1:z1, where 0.7 < x1 ≤ 0.9, 0.05 ≤ y1 < 0.1, 0 < z1 ≤ 0.25, and x1 + y1 + z1 = 1; The solution B is a mixed solution of nickel salt, cobalt salt, and manganese salt with a molar ratio of Ni:Co:Mn of x2:y2:z2, where 0.2 < x2 ≤ 0.4, 0.1 ≤ y2 < 0.2, 0.4 ≤ z2 < 0.7, and x2 + y2 + z2 = 1.

[0064] The preparation method provided by the present invention adjusts the proportion of the three elements in the inner core, the transition layer, and the outer shell layer by changing the contents of Ni, Co, and Mn elements in solution A and solution B and the change of the gas atmosphere in the coprecipitation reaction. It not only utilizes the high-capacity characteristics of the high-nickel inner core but also improves the stability and cycling performance through the manganese-rich outer shell layer. At the same time, the elements in the inner core, the transition layer, and the outer shell layer are the same, and the formed gradient of the transition layer avoids the influence of the interfacial shell voids caused by the element differences between the inner and outer layers on the lithiation sintering of the cathode material.

[0065] In the present invention, first, solution A, the complexing agent solution, and the precipitating agent solution are added to the synthetic bottom liquid to conduct a first-stage coprecipitation reaction to form an inner core and obtain a first reaction system. The solution A is a mixed solution of nickel salt, cobalt salt, and manganese salt with a molar ratio of Ni:Co:Mn of x1:y1:z1, where 0.7 < x1 ≤ 0.9, 0.05 ≤ y1 < 0.1, 0 < z1 ≤ 0.25, and x1 + y1 + z1 = 1.

[0066] In the specific embodiment of the present invention, the nickel salt is preferably one or more of nickel sulfate, nickel nitrate, and nickel chloride; the cobalt salt is preferably one or more of cobalt sulfate, cobalt nitrate, and cobalt chloride; the manganese salt is preferably one or more of manganese sulfate, manganese nitrate, and manganese chloride. The present invention has no special limitation on the sources of the nickel salt, cobalt salt, and manganese salt, and commercially available products well-known to those skilled in the art can be used.

[0067] In specific embodiments of the present invention, the complexing agent preferably includes one or more of ammonia, ammonium sulfate, oxalic acid, and ammonium bicarbonate. The present invention does not impose any special restrictions on the source of the complexing agent; commercially available products well-known to those skilled in the art can be used. The complexing agent selected in the present invention can form coordination compounds with metal ions in solutions A and B, which, compared to free metal ions, is more conducive to the formation of uniform and stable metal deposition particles under the action of a precipitant.

[0068] In specific embodiments of the present invention, the precipitant preferably includes one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, and ammonium bicarbonate; the present invention does not have special restrictions on the source of the precipitant, and commercially available products well known to those skilled in the art can be used. The present invention selects the above-mentioned precipitant to create an alkaline environment, reduce free metal ions, promote the formation of coordination compounds, and is more conducive to the formation of metal particle deposits.

[0069] In a specific embodiment of the present invention, the synthesis substrate in step a) preferably includes water, a precipitant, and a complexing agent; the concentration of the complexing agent in the synthesis substrate is preferably 4 g / L to 8 g / L, specifically 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, etc.; the temperature of the synthesis substrate is preferably 50℃ to 70℃, specifically 50℃, 60℃, 70℃, etc.; the pH value of the synthesis substrate is preferably 11 to 13, specifically 11, 12, 13, etc. The present invention uses a synthesis substrate with the above-mentioned suitable components, temperature, and pH conditions, which is beneficial for the conversion of free metal ions into coordination compounds, ensuring the uniform and stable deposition of the coordination compounds, thereby obtaining uniform metal particles.

[0070] In a specific embodiment of the present invention, step a) is preferably carried out under conditions of continuous introduction of inert gas, wherein the inert gas preferably includes one or more of nitrogen, argon, and helium, and the rate of introduction of the inert gas is preferably 0.5 m / s. 3 / h~3m 3 / h, specifically 0.5m 3 / h、1m 3 / h, 1.5m 3 / h、2m 3 / h, 2.5m 3 / h、3m 3 / h etc. This invention selects the above-mentioned first-stage co-precipitation reaction conditions to isolate oxygen and prevent the formation of metal oxides, thereby obtaining a core that meets the performance requirements of this invention.

[0071] In a specific embodiment of the present invention, the preferred flow rate for adding solution A in step a) is 2 L / h to 4 L / h, specifically 2 L / h, 3 L / h, 4 L / h, etc.; the preferred flow rate for adding the complexing agent solution is 200 mL / h to 400 mL / h, specifically 200 mL / h, 300 mL / h, 400 mL / h, etc.; and the preferred flow rate for adding the precipitant solution is 1.2 L / h to 2.6 L / h, specifically 1.2 L / h, 1.9 L / h, 2.6 L / h, etc. The present invention selects the above-mentioned flow rates for adding solutions to ensure that the metal ions in solution A fully undergo coordination reactions with the complexing agent solution and fully undergo precipitation reactions with the precipitant, and ensures timely replenishment of the complexing agent solution and the precipitant solution, thereby obtaining a core that meets the performance requirements of the present invention.

[0072] After obtaining the first reaction system, the present invention mixes solution A and solution B to obtain solution AB; then, solution AB, complexing agent solution, and precipitant solution are added to the first reaction system obtained above to carry out a second-stage co-precipitation reaction, forming a transition layer to obtain the second reaction system.

[0073] In a specific embodiment of the present invention, step b) is first carried out under the condition of introducing an inert gas until the particle size of the precipitated product is D. V 50 compared to kernel particle size D V After increasing the particle size by 1-2 μm, a mixture of inert gas and air is introduced to continue co-precipitation. This invention uses air during the reaction process to form the transition layer, avoiding a decrease in radial porosity of the transition layer due to an increase in Mn content during the particle growth stage.

[0074] In a specific embodiment of the present invention, the volume fraction of air in the mixture of inert gas and air introduced in step b) is preferably 4% to 12%, specifically 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, etc. The present invention adjusts the air ratio according to the Mn element variation to avoid significant deposition of Mn-rich primary particles and ensure the sphericity of secondary particles, thereby obtaining a transition layer that meets the performance requirements of the present invention.

[0075] In a specific embodiment of the present invention, in the solution AB obtained after mixing solution A and solution B in step b), the proportion of Ni decreases and the proportion of Co and Mn increases. As the reaction atmosphere changes, the gradient of Ni proportion decreases and the gradient of Co and Mn proportion increases in the transition layer, thereby achieving seamless connection of element content in the core, transition layer and outer shell.

[0076] In a specific embodiment of the present invention, the preferred flow rate for adding solution AB in step b) is 5 L / h to 8 L / h, specifically 5 L / h, 6 L / h, 7 L / h, 8 L / h, etc.; the preferred flow rate for adding the complexing agent solution is 300 mL / h to 600 mL / h, specifically 300 mL / h, 400 mL / h, 500 mL / h, 600 mL / h, etc.; and the preferred flow rate for adding the precipitant solution is 2 L / h to 4.5 L / h, specifically 2 L / h, 2.5 L / h, 3 L / h, 3.5 L / h, 4 L / h, 4.5 L / h, etc. The present invention selects the above-mentioned solution addition flow rates to ensure that the metal ions in solution AB fully undergo coordination reactions with the complexing agent solution and fully undergo precipitation reactions with the precipitant, and to ensure timely replenishment of the complexing agent solution and the precipitant solution, thereby obtaining a transition layer that meets the performance requirements of the present invention.

[0077] After obtaining the second reaction system, the present invention adds solution B, surfactant, complexing agent solution, and precipitant solution to the second reaction system obtained in step b) to carry out a third-stage co-precipitation reaction to form an outer shell layer and obtain a positive electrode material precursor.

[0078] In a specific embodiment of the present invention, step c) is preferably carried out under the condition of continuously introducing a mixture of inert gas and air; the volume fraction of air in the introduced mixture of inert gas and air is preferably 4% to 12%, specifically 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, etc. The present invention selects the above-mentioned air-to-air mixture to avoid significant deposition of Mn-rich primary particles and ensure the sphericity of secondary particles, thereby obtaining an outer shell layer that meets the performance requirements of the present invention.

[0079] In specific embodiments of the present invention, the surfactant preferably includes one or more of cocamidopropyl betaine (CAB), sodium dodecylbenzene sulfonate (SDBS), and polyvinylpyrrolidone (PVP). The present invention does not impose any special restrictions on the source of the surfactant; commercially available products well-known to those skilled in the art can be used. The present invention selects the above-mentioned surfactant to adjust the primary particle stacking density of the manganese-rich outer shell layer, thereby obtaining an outer shell layer that meets the performance requirements of the present invention.

[0080] In a specific embodiment of the present invention, the mass ratio of solution B to surfactant in step c) is preferably 100:(0.1~1), specifically 100:0.1, 100:0.2, 100:0.3, 100:0.4, 100:0.5, 100:0.6, 100:0.7, 100:0.8, 100:0.9, 100:1, etc. The present invention selects the above-mentioned suitable mass ratio to adjust the primary particle stacking density of the manganese-rich outer shell layer, thereby obtaining an outer shell layer that meets the performance requirements of the present invention.

[0081] In a specific embodiment of the present invention, the preferred flow rate for adding solution B and surfactant in step c) is 6 L / h to 9 L / h, specifically 6 L / h, 7 L / h, 8 L / h, 8 L / h, etc.; the preferred flow rate for adding complexing agent solution is 200 mL / h to 400 mL / h, specifically 200 mL / h, 300 mL / h, 400 mL / h, etc.; and the preferred flow rate for adding precipitant solution is 2 L / h to 5 L / h, specifically 2 L / h, 3 L / h, 4 L / h, 5 L / h, etc. By selecting the above-mentioned solution addition flow rates, the present invention ensures that the subsequently obtained outer shell layer has good performance, thereby further obtaining a cathode material precursor that meets the performance requirements of the present invention.

[0082] In a specific embodiment of the present invention, after forming the outer shell layer in step c), the process further includes: washing the reaction product with water and then filtering and drying it sequentially to obtain the cathode material precursor. The washing with water is preferably performed 2 to 4 times, specifically 2, 3, or 4 times; the drying temperature is preferably 90℃ to 120℃, specifically 90℃, 100℃, 110℃, or 120℃. By employing the above processing method, the present invention ensures that the subsequently obtained cathode material precursor has good performance, thereby further obtaining a cathode material that meets the performance requirements of the present invention.

[0083] Compared with traditional methods for preparing nickel-rich layered cathode material precursors, the preparation method provided by this invention not only utilizes the high capacity characteristics of high-nickel materials, but also improves thermal stability and cycle performance through manganese enrichment of the outer shell, and is more suitable for large-scale production, thereby promoting the practical application of high-energy nickel-rich layered cathodes.

[0084] According to another aspect of the present invention, a cathode material is provided, which is obtained by reacting raw materials including a cathode material precursor and a lithium source; the cathode material precursor includes the cathode material precursor described in the above-described technical solution or the cathode material precursor prepared by the preparation method described in the above-described technical solution.

[0085] In a specific embodiment of the present invention, the ratio of the total molar amount of nickel, cobalt, and manganese in the cathode material precursor to the molar amount of lithium in the lithium source is preferably 1:(1~1.1), specifically 1:1, 1:1.05, 1:1.1, etc. By selecting raw materials with the above-mentioned ratio, the present invention ensures that the subsequently obtained cathode material has good performance, thereby further obtaining a cathode that meets the performance requirements of the present invention.

[0086] In a specific embodiment of the present invention, the cathode material satisfies the general chemical formula LiNi. α Co β Mn γO2, wherein 0.75≤α≤0.9, 0.05≤β<0.15, 0.05<γ≤0.2, and α+β+γ=1; the particle size D of the positive electrode material V 50 is 7μm~13μm; the above-mentioned cathode material is selected in this invention to ensure that the cathode obtained subsequently has good performance, thereby further obtaining a battery that meets the performance requirements of this invention.

[0087] In a specific embodiment of the present invention, the reaction process includes: uniformly mixing the cathode material precursor and the lithium source, followed by sintering to obtain the cathode material; wherein, the sintering process preferably includes: heating to 500℃~700℃ at a heating rate of 2℃ / min~6℃ / min for a first sintering of 4h~8h, and then heating to 700℃~900℃ at a heating rate of 2℃ / min~6℃ / min for a second sintering of 12h~24h. The above reaction conditions selected by the present invention ensure that the subsequently obtained cathode material has good performance, thereby further obtaining a cathode that meets the performance requirements of the present invention.

[0088] According to another aspect of the present invention, a battery is provided, comprising the positive electrode material described in the above-described technical solution. Specifically, the battery is assembled using a negative electrode, a separator, and a positive electrode comprising the positive electrode material described in the above-described technical solution, as well as those well known to those skilled in the art, in a conventional manner, and then with the addition of an electrolyte. In a preferred embodiment of the present invention, the battery preparation process includes: sequentially assembling the negative electrode, separator, and positive electrode, immersing them in an electrolyte, and then performing processes such as formation to form the battery. The specific conditions and parameters for each step in the above preparation process can be achieved using battery preparation techniques well known to those skilled in the art, and the present invention does not impose any special limitations on them.

[0089] In a specific embodiment of the present invention, the positive electrode may be a positive electrode sheet well known to those skilled in the art, which includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector along the thickness direction; wherein, the positive current collector has two surfaces opposite to each other in its own thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0090] In a specific embodiment of the present invention, the positive electrode active material layer includes the positive electrode material described in the above technical solution, and further includes a binder and a conductive agent; wherein, the binder includes, but is not limited to, one or more of polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS); the conductive agent includes, but is not limited to, one or more of conductive carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The present invention does not impose any special restrictions on the source of the above-mentioned binder and conductive agent; commercially available products well known to those skilled in the art can be used.

[0091] In a specific embodiment of the present invention, the method for preparing the positive electrode sheet includes: thoroughly mixing a positive electrode active material, a binder, and a conductive agent to prepare a slurry; coating the slurry onto a positive electrode current collector; and drying, cold pressing, and slitting to obtain the positive electrode. The positive electrode current collector can be a metal foil such as aluminum foil.

[0092] In specific embodiments of the present invention, the negative electrode can be a negative electrode sheet well known to those skilled in the art, preferably a copper sheet; the separator is preferably a glass fiber membrane; and the electrolyte can be any conventional electrolyte used in batteries well known to those skilled in the art. The present invention does not impose any special restrictions on the source of the above-mentioned negative electrode, separator, and electrolyte; commercially available products well known to those skilled in the art can be used.

[0093] The present application will be specifically described below with reference to the accompanying drawings and embodiments. However, the implementation and protection of the present invention are not limited thereto. The following embodiments are only some embodiments of the present application and are not intended to limit the present application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Where the manufacturers of the reagents or instruments used are not specified, they are all conventional products that can be obtained commercially. In addition, the synthesis base solution used is obtained according to the following preparation method: 200L of pure water, 12wt% ammonia water and 30wt% sodium hydroxide aqueous solution are added to a 500L reaction vessel, and then... 3 Nitrogen gas is introduced into the mixture at a rate of / h, and the mixture is stirred at a speed of 200r / min to ensure uniform mixing. The temperature is then raised to 50℃, and the pH of the synthesis solution is controlled at 11.5±0.05, with an ammonia concentration of 4g / L.

[0094] Example 1 (1) The first nickel-cobalt-manganese ternary solution, 12wt% ammonia water, and 30wt% sodium hydroxide aqueous solution were injected into the synthesis base solution at flow rates of 3L / h, 300mL / h, and 1.9L / h, respectively. The pH of the reaction system was stably controlled at 11.5±0.05, and the ammonia concentration was 4g / L. 3 Nitrogen gas is continuously introduced at a rate of / h to carry out the first stage co-precipitation reaction, forming a nucleus with a particle size D. V 50 is 4μm, thus obtaining the first reaction system.

[0095] The first nickel-cobalt-manganese ternary solution is a sulfate mixture with a Ni:Co:Mn molar ratio of 90:5:5 and a total Ni, Co, and Mn ion concentration of 50 g / L.

[0096] (2) The second nickel-cobalt-manganese ternary solution was pumped into the separately prepared first nickel-cobalt-manganese ternary solution at a flow rate of 7 L / h to obtain solution AB; then solution AB, 12 wt% ammonia water, and 30 wt% sodium hydroxide aqueous solution were injected into the first reaction system obtained in step (1) at flow rates of 5 L / h, 350 mL / h, and 2.6 L / h, respectively, to stabilize the pH value of the reaction system at 10.5 ± 0.05 and the ammonia concentration at 2.5 g / L, at a flow rate of 1 m 3 Nitrogen gas is continuously introduced at a rate of / h to carry out the second stage coprecipitation reaction until the particle size of the precipitate is D. V The thickness of the nitrogen gas is 5μm. Then, a mixture of nitrogen and air with a volume ratio of 4% is introduced to continue the second stage of co-precipitation reaction, forming a transition layer with a thickness of 5μm, thus obtaining the second reaction system.

[0097] The second nickel-cobalt-manganese ternary solution is a sulfate mixture with a Ni:Co:Mn molar ratio of 40:20:40 and a total Ni, Co, and Mn ion concentration of 50 g / L.

[0098] (3) Add polyvinylpyrrolidone (PVP) to a separately prepared second nickel-cobalt-manganese ternary solution and stir until homogeneous to obtain a mixed solution with a PVP concentration of 0.5 wt%. Then, inject the mixed solution, 12 wt% ammonia, and 30 wt% sodium hydroxide aqueous solution into the second reaction system obtained in step (2) at flow rates of 6.5 L / h, 250 mL / h, and 2.9 L / h, respectively. Stabilize the pH of the reaction system to 9.5 ± 0.05 and the ammonia concentration to 1.5 g / L. 3 A mixture of nitrogen and air, comprising 4% of the air volume, is continuously introduced at a rate of / h to initiate the third-stage co-precipitation reaction, forming an outer shell layer with a thickness of 1μm. The reaction product is washed three times with water, filtered, and dried at 90℃ to obtain the cathode material precursor, denoted as Ni. 0.82 Co 0.08 Mn 0.10(OH)2 (total metal molar ratio of the precursor product with target particle size); the particle size D of the prepared cathode material precursor was tested. V 50 represents 10 μm; see SEM image. Figure 2 As shown.

[0099] (4) The cathode material precursor obtained in step (3) and lithium hydroxide are mixed evenly in a high-speed mixer. The molar ratio of the total molar amount of nickel, cobalt and manganese in the cathode material precursor to the molar amount of lithium in the lithium hydroxide is controlled to be 1:1.05. The resulting mixture is placed in a box furnace for sintering. The temperature is increased to 500°C at a heating rate of 3°C / min for the first sintering for 5 hours. Then the temperature is increased to 850°C at a heating rate of 3°C / min for the second sintering for 16 hours. After cooling, the cathode material is obtained, which satisfies the general chemical formula LiNi. 0.82 Co 0.08 Mn 0.10 O2.

[0100] Example 2 The cathode material precursor was prepared using the preparation method provided in Example 1, and the cathode material was further prepared. The difference is that in step (2), 1m 3 Nitrogen gas is continuously introduced at a rate of / h to carry out the second stage coprecipitation reaction until the particle size of the precipitate is D. V 50 is 7μm, and then a mixture of nitrogen and air with a volume ratio of 4% is introduced to continue the second stage co-precipitation reaction; in step (3), PVP is not added.

[0101] Example 3 The cathode material precursor was prepared by the preparation method provided in Example 1 and the cathode material was further prepared. The difference is that in step (2), nitrogen gas was always introduced to carry out the second stage co-precipitation reaction; in step (3), the PVP concentration in the mixed solution was 1 wt%.

[0102] Example 4 The cathode material precursor was prepared by the preparation method provided in Example 1 and the cathode material was further prepared. The difference is that in step (2), a mixture of nitrogen and air with an air volume ratio of 8% was used to replace the mixture of nitrogen and air with an air volume ratio of 4%; in step (3), a mixture of nitrogen and air with an air volume ratio of 12% was used to replace the mixture of nitrogen and air with an air volume ratio of 4%.

[0103] Comparative Example 1 (1) The third nickel-cobalt-manganese ternary solution, 12wt% ammonia water, and 30wt% sodium hydroxide aqueous solution were injected into the synthesis base solution at flow rates of 3L / h, 300mL / h, and 1.9L / h, respectively. The pH of the reaction system was stably controlled at 11.5±0.05, and the ammonia concentration was 4g / L. 3 Nitrogen gas is continuously introduced at a rate of / h to carry out the first stage co-precipitation reaction, forming a nucleus with a particle size D. V 50 is 4μm, thus obtaining the first reaction system.

[0104] The third nickel-cobalt-manganese ternary solution is a sulfate mixture with a Ni:Co:Mn molar ratio of 82:8:10 and a total Ni, Co, and Mn ion concentration of 50 g / L.

[0105] (2) The third nickel-cobalt-manganese ternary solution, 12wt% ammonia, and 30wt% sodium hydroxide aqueous solution were injected into the first reaction system obtained in step (1) at flow rates of 5L / h, 350mL / h, and 2.6L / h, respectively. The pH of the reaction system was stably controlled at 10.5±0.05 and the ammonia concentration at 2.5g / L. The flow rate was 1m 3 Nitrogen gas is continuously introduced at a rate of / h to carry out the second stage coprecipitation reaction until the particle size of the precipitate is D. V The thickness of the nitrogen gas is 5μm. Then, a mixture of nitrogen and air with a volume ratio of 4% is introduced to continue the second stage of co-precipitation reaction, forming a transition layer with a thickness of 5μm, thus obtaining the second reaction system.

[0106] (3) Add polyvinylpyrrolidone (PVP) to a separately prepared third nickel-cobalt-manganese ternary solution and stir until homogeneous to obtain a mixed solution with a PVP concentration of 0.5 wt%. Then, inject the mixed solution, 12 wt% ammonia, and 30 wt% sodium hydroxide aqueous solution into the second reaction system obtained in step (2) at flow rates of 6.5 L / h, 250 mL / h, and 2.9 L / h, respectively. Stable control of the pH value of the reaction system is maintained at 9.5 ± 0.05, and the ammonia concentration is 1.5 g / L. 3 A mixture of nitrogen and air, comprising 4% of the air volume, is continuously introduced at a rate of / h to initiate the third-stage co-precipitation reaction, forming an outer shell layer with a thickness of 1μm. The reaction product is washed three times with water, filtered, and dried at 90℃ to obtain the cathode material precursor, denoted as Ni. 0.82 Co 0.08 Mn 0.10 (OH)2; The particle size D of the prepared cathode material precursor was tested. V 50 represents 10μm.

[0107] (4) The cathode material precursor obtained in step (3) and lithium hydroxide are mixed evenly in a high-speed mixer. The molar ratio of the total molar amount of nickel, cobalt and manganese in the cathode material precursor to the molar amount of lithium in the lithium hydroxide is controlled to be 1:1.05. The resulting mixture is placed in a box furnace for sintering. The temperature is increased to 500°C at a heating rate of 3°C / min for the first sintering for 5 hours. Then the temperature is increased to 850°C at a heating rate of 3°C / min for the second sintering for 16 hours. After cooling, the cathode material is obtained, which satisfies the general chemical formula LiNi. 0.82 Co 0.08 Mn 0.10 O2.

[0108] Comparative Example 2 (1) The first nickel-cobalt-manganese ternary solution, 12wt% ammonia water, and 30wt% sodium hydroxide aqueous solution were injected into the synthesis base solution at flow rates of 3L / h, 300mL / h, and 1.9L / h, respectively. The pH of the reaction system was stably controlled at 11.5±0.05, and the ammonia concentration was 4g / L. 3 Nitrogen gas is continuously introduced at a rate of / h to carry out the first stage co-precipitation reaction, forming a nucleus with a particle size D. V 50 is 4μm, thus obtaining the first reaction system.

[0109] The first nickel-cobalt-manganese ternary solution is a sulfate mixture with a Ni:Co:Mn molar ratio of 90:5:5 and a total Ni, Co, and Mn ion concentration of 50 g / L.

[0110] (2) The second nickel-cobalt-manganese ternary solution, 12wt% ammonia water, and 30wt% sodium hydroxide aqueous solution were injected into the first reaction system obtained in step (1) at flow rates of 5L / h, 350mL / h, and 2.6L / h, respectively. The pH of the reaction system was stably controlled at 10.5±0.05, and the ammonia concentration was 2.5g / L. The flow rate was 1m 3 Nitrogen gas is continuously introduced at a rate of / h to carry out the second stage coprecipitation reaction until the particle size of the precipitate is D. V The thickness of the nitrogen gas is 5μm. Then, a mixture of nitrogen and air with a volume ratio of 4% is introduced to continue the second stage of co-precipitation reaction, forming a transition layer with a thickness of 5μm, thus obtaining the second reaction system.

[0111] The second nickel-cobalt-manganese ternary solution is a sulfate mixture with a Ni:Co:Mn molar ratio of 40:20:40 and a total Ni, Co, and Mn ion concentration of 50 g / L.

[0112] (3) Add polyvinylpyrrolidone (PVP) to a separately prepared second nickel-cobalt-manganese ternary solution and stir until homogeneous to obtain a mixed solution with a PVP concentration of 0.5 wt%. Then, inject the mixed solution, 12 wt% ammonia, and 30 wt% sodium hydroxide aqueous solution into the second reaction system obtained in step (2) at flow rates of 6.5 L / h, 250 mL / h, and 2.9 L / h, respectively. Stabilize the pH of the reaction system to 9.5 ± 0.05 and the ammonia concentration to 1.5 g / L. 3 A mixture of nitrogen and air, comprising 4% of the air volume, is continuously introduced at a rate of / h to initiate the third-stage co-precipitation reaction, forming an outer shell layer with a thickness of 1μm. The reaction product is washed three times with water, filtered, and dried at 90℃ to obtain the cathode material precursor, denoted as Ni. 0.75 Co 0.09 Mn 0.16 (OH)2; The particle size D of the prepared cathode material precursor was tested. V 50 represents 10μm.

[0113] (4) The cathode material precursor obtained in step (3) and lithium hydroxide are mixed evenly in a high-speed mixer. The molar ratio of the total molar amount of nickel, cobalt and manganese in the cathode material precursor to the molar amount of lithium in the lithium hydroxide is controlled to be 1:1.05. The resulting mixture is placed in a box furnace for sintering. The temperature is increased to 500°C at a heating rate of 3°C / min for the first sintering for 5 hours. Then the temperature is increased to 850°C at a heating rate of 3°C / min for the second sintering for 16 hours. After cooling, the cathode material is obtained, which satisfies the general chemical formula LiNi. 0.75 Co 0.09 Mn 0.16 O2.

[0114] Comparative Example 3 (1) Polyvinylpyrrolidone (PVP) was added to the second nickel-cobalt-manganese ternary solution and stirred until homogeneous to obtain a mixed solution with a PVP concentration of 0.5 wt%. The mixed solution, along with 12 wt% ammonia and 30 wt% sodium hydroxide aqueous solution, were then injected into the synthesis substrate at flow rates of 6.5 L / h, 250 mL / h, and 2.9 L / h, respectively. The pH of the reaction system was stabilized at 9.5 ± 0.05, and the ammonia concentration was 1.5 g / L. The flow rate was 1 m 3 A mixture of nitrogen and air, comprising 4% of the air volume, is continuously introduced at a rate of / h to carry out a co-precipitation reaction until the particle size of the precipitate is D. V 50 represents 10 μm. The reaction product was washed three times with water, filtered, and dried at 90 °C to obtain the cathode material precursor, denoted as Ni. 0.4 Co 0.2 Mn 0.4 (OH)2, Ni 0.4 Co0.2 Mn 0.4 The particle size D of (OH)2 V 50 represents 10μm.

[0115] The second nickel-cobalt-manganese ternary solution is a sulfate mixture with a Ni:Co:Mn molar ratio of 40:20:40 and a total Ni, Co, and Mn ion concentration of 50 g / L.

[0116] (2) The cathode material precursor obtained in step (1) and lithium hydroxide are mixed evenly in a high-speed mixer. The molar ratio of the total molar amount of nickel, cobalt and manganese in the cathode material precursor to the molar amount of lithium in the lithium hydroxide is controlled to be 1:1.05. The resulting mixture is placed in a box furnace for sintering. The temperature is increased to 500℃ at a heating rate of 3℃ / min for the first sintering for 5h. Then the temperature is increased to 850℃ at a heating rate of 3℃ / min for the second sintering for 16h. After cooling, the cathode material is obtained, denoted as LiNi. 0.4 Co 0.2 Mn 0.4 O2.

[0117] Performance testing: The specific surface area and tap density of the cathode material precursors prepared in Examples 1-4 and Comparative Examples 1-3 were tested, and the results are shown in Table 1.

[0118] Table 1. Physicochemical data of cathode material precursors in the Examples and Comparative Examples As can be seen from Table 1, Examples 1-4 changed the process of using the mixed gas in the co-precipitation stage and the amount of additives (surfactants) in the outer shell solution, resulting in significant differences in the specific surface area and tap density of the cathode material precursor, leading to significant differences in the oxidation degree of the transition layer and the outer shell layer. Compared with Example 1, Comparative Examples 1-3 changed the metal molar ratio of the precursor in the co-precipitation stage, resulting in differences in the specific surface area and tap density of the cathode material precursor with different components.

[0119] The positive electrode materials obtained in Examples 1-4 and Comparative Examples 1-3 were used to prepare lithium-ion batteries: The obtained positive electrode materials, conductive carbon black SP (TIMCAL), and polyvinylidene fluoride PVDF (HSV900) were mixed at a mass ratio of 90:5:5, with N-methylpyrrolidone as the solvent. The mixture was stirred into a slurry, and the slurry was uniformly coated onto a 13μm aluminum foil with 100μm gaps using a scraper. After coating, the foil was first dried by blowing air, then rolled and cut into circular electrode sheets, and then vacuum dried at 120°C. The weight of the electrode sheets was then measured to obtain a positive electrode sheet with a diameter of 12mm. The negative electrode was a lithium metal sheet, the separator was a PP microporous membrane, and the electrolyte was a basic lithium battery electrolyte. The positive electrode sheet, lithium metal sheet, separator, and electrolyte were assembled to obtain a CR. 2032 coin cell; the battery was tested using a battery testing system (Landian CT2001A, Wuhan, China). First, it was activated 5 times at a 0.1C rate and 2.8V~4.4V. Then, the activated coin cells were tested for electrochemical performance at 0.1C / 1C conditions within the 2.8V~4.4V test range. The initial charge capacity C' and initial discharge capacity C1 were obtained. The initial efficiency was calculated as C1 / C'×100%. Subsequently, the cells were charged at 0.1C to 4.4V, allowed to stand for 5 minutes, and then discharged at 1C to 2.8V. This "charge-stand-discharge" process was repeated 100 times, and the discharge capacity C100 at the 100th time was recorded. The capacity retention rate was calculated as C100 / C1×100%. The results are shown in Table 2.

[0120] Table 2. Electrical performance test results of the batteries using the cathode materials in the application examples and comparative examples. As shown in Table 2, Example 1 exhibits high initial discharge capacity, initial coulombic efficiency, and capacity retention, at 207 mAh / g, 93.4%, and 89.8%, respectively. Comparisons of Examples 1-4 demonstrate that changing the reactive gas and surfactant dosage effectively improves discharge capacity. However, excessively high air content in the mixed gas and excessive surfactant both lead to a significant decrease in discharge capacity and reduced material cycle performance. Comparisons of Example 1 and Comparative Example 1 show that a manganese-rich outer shell effectively improves capacity retention, while a single homogenized cathode precursor results in poor capacity retention. Comparisons of Example 1 and Comparative Examples 2-3 indicate that a high-nickel core significantly impacts discharge capacity, and the use of a single transition layer and a manganese-rich cathode precursor significantly reduces capacity.

[0121] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0122] The basic principles of the present invention have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in the present invention are merely examples and not limitations, and should not be considered as essential features of each embodiment of the present invention. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the present invention to the necessity of employing the aforementioned specific details.

[0123] In the foregoing description of this specification, references to terms such as "one embodiment," "another embodiment," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment is included in at least one embodiment of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples, without contradiction. Additionally, it should be noted that in this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0124] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cathode material precursor, characterized in that, Including: a core, the core satisfying the chemical general formula Ni a1 Co b1 Mn c1 (OH)2, where 0.7 < a1 ≤ 0.9, 0.05 ≤ b1 < 0.1, 0 < c1 ≤ 0.25, and a1 + b1 + c1 = 1; A transition layer is provided on at least a part of the surface of the core, and the transition layer satisfies the chemical general formula Ni a2 Co b2 Mn c2 (OH)2, where 0.7 < a2 < 0.85, 0.05 < b2 < 0.1, 0.05 < c2 < 0.25, and a2 + b2 + c2 = 1; The outer shell layer is disposed on at least a part of the surface of the transition layer away from the kernel, and the outer shell layer satisfies the chemical general formula Ni a3 Co b3 Mn c3 (OH)2, where 0.2 < a3 ≤ 0.4, 0.1 ≤ b3 < 0.2, 0.4 ≤ c3 < 0.7, and a3 + b3 + c3 = 1.

2. The cathode material precursor according to claim 1, characterized in that, a1 > a2 > a3, b1 < b2 < b3, c1 < c2 < c3.

3. The cathode material precursor according to claim 1, characterized in that, The particle size D of the kernel V 50 is 3μm~4μm; And / or, the thickness of the transition layer is 3 μm to 6 μm; And / or, the particle size D of the cathode material precursor V 50 has a thickness of 7μm to 13μm.

4. The cathode material precursor according to claim 1, characterized in that, The outer shell layer comprises a primary particle close-packed structure; the particle size D of the primary particles V 50 ranges from 0.5μm to 2μm; And / or, the thickness of the outer shell layer is 1 μm to 3 μm.

5. A method for preparing a cathode material precursor according to any one of claims 1 to 4, characterized in that, Including the following steps: a) Add solution A, complexing agent solution, and precipitating agent solution into the synthetic bottom solution, carry out the first-stage coprecipitation reaction to form a core, and obtain the first reaction system; b) Mix solution A and solution B to obtain solution AB; Then add the solution AB, complexing agent solution, and precipitating agent solution into the first reaction system obtained in step a) to carry out the second-stage coprecipitation reaction to form a transition layer, and obtain the second reaction system; c) Add solution B, surfactant, complexing agent solution, and precipitating agent solution into the second reaction system obtained in step b) to carry out the third-stage coprecipitation reaction to form an outer shell layer, and obtain the precursor of the positive electrode material; The solution A is a mixed solution of nickel salt, cobalt salt, and manganese salt with a molar ratio of Ni:Co:Mn of x1:y1:z1, where 0.7 < x1 ≤ 0.9, 0.05 ≤ y1 < 0.1, 0 < z1 ≤ 0.25, and x1 + y1 + z1 = 1; The solution B is a mixed solution of nickel salt, cobalt salt, and manganese salt with a molar ratio of Ni:Co:Mn of x2:y2:z2, where 0.2 < x2 ≤ 0.4, 0.1 ≤ y2 < 0.2, 0.4 ≤ z2 < 0.7, and x2 + y2 + z2 = 1.

6. The preparation method according to claim 5, characterized in that, The preparation method satisfies at least one of the following characteristics (1) to (13): (1) The complexing agent includes one or more of ammonia water, ammonium sulfate, oxalic acid, ammonium bicarbonate; (2) The precipitating agent includes one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, ammonium bicarbonate; (3) The synthetic bottom solution in step a) includes water, precipitating agent, and complexing agent; (4) The temperature of the synthetic bottom solution in step a) is 50°C to 70°C, and the pH value is 11 to 13; (5) Step a) is carried out under the condition of continuously introducing an inert gas; (6) The flow rate of adding solution A in step a) is 2 L / h to 4 L / h, the flow rate of adding the complexing agent solution is 200 mL / h to 400 mL / h, and the flow rate of adding the precipitating agent solution is 1.2 L / h to 2.6 L / h; (7) Step b) is first carried out under the condition of introducing an inert gas until the particle size of the precipitated product is D. V 50 compared to kernel particle size D V After increasing the size by 1μm to 3μm, a mixture of inert gas and air is introduced to continue co-precipitation. (8) The flow rate of adding solution AB in step b) is 5 L / h to 8 L / h, the flow rate of adding the complexing agent solution is 300 mL / h to 600 mL / h, and the flow rate of adding the precipitating agent solution is 2 L / h to 4.5 L / h; (9) The surfactant includes one or more of cocamidopropyl betaine, sodium dodecylbenzenesulfonate, polyvinylpyrrolidone; (10) The mass ratio of solution B to the surfactant in step c) is 100:(0.1 to 1); (11) Step c) is carried out under the condition of continuously introducing a mixture of inert gas and air; (12) In step c), the flow rate of adding solution B and surfactant is 6 L / h to 9 L / h, the flow rate of adding complexing agent solution is 200 mL / h to 400 mL / h, and the flow rate of adding precipitant solution is 2 L / h to 5 L / h. (13) After forming the outer shell layer as described in step c), the reaction product is washed with water and then filtered and dried to obtain the cathode material precursor.

7. The preparation method according to claim 6, characterized in that, The preparation method satisfies at least one of the following features (1) to (5): (1) The concentration of the complexing agent in the synthesis substrate is 4 g / L to 8 g / L; (2) The inert gas includes one or more of nitrogen, argon, and helium; (3) The rate at which the inert gas is introduced in step a) is 0.5 m / s. 3 / h~3m 3 / h; (3) The volume fraction of air in the mixture of inert gas and air introduced in step b) is 4%~12%; (4) The volume fraction of air in the mixture of inert gas and air introduced in step c) is 4%~12%; (5) The number of times the water is washed in step c) is 2 to 4 times, and the drying temperature is 90℃ to 120℃.

8. A positive electrode material, characterized in that, It is obtained by reacting raw materials including a cathode material precursor and a lithium source; the cathode material precursor includes the cathode material precursor according to any one of claims 1 to 4 or the cathode material precursor prepared by the preparation method according to any one of claims 5 to 7.

9. The cathode material according to claim 8, characterized in that, The cathode material satisfies the general chemical formula LiNi. α Co β Mn γ O2, among which, 0.75≤α≤0.9, 0.05≤β<0.15, 0.05<γ≤0.2, and α+β+γ=1; And / or, the particle size D of the positive electrode material V 50 has a thickness of 7μm to 13μm; And / or, the reaction process includes: mixing the cathode material precursor and the lithium source evenly and then sintering to obtain the cathode material; preferably, the sintering process includes: heating to 500℃~700℃ at a heating rate of 2℃ / min~6℃ / min for a first sintering of 4h~8h, and then heating to 700℃~900℃ at a heating rate of 2℃ / min~6℃ / min for a second sintering of 12h~24h.

10. A battery, characterized in that, Includes the cathode material as described in any one of claims 8 to 9.

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