Lithium-rich manganese-based cathode precursor materials and their preparation methods, cathode materials and batteries

Abstract

This application belongs to the field of lithium-ion battery material technology, specifically relating to a lithium-rich manganese-based cathode precursor material, its preparation method, cathode material, and battery. The lithium-rich manganese-based cathode precursor material includes a core and a shell layer on the surface of the core. The core is formed by alternating layers of plate-like primary particles, and the shell layer is formed by radially arranged plate-like primary particles perpendicular to the surface of the core, thus forming a loose inner and tight outer structure. This structure results in a precursor material with good stability, and the lithium-rich manganese-based cathode material prepared from it also exhibits good cycle stability. This lithium-rich manganese-based cathode precursor material is prepared by a two-step co-precipitation method, which is simple and controllable.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery material technology, specifically relating to a lithium-rich manganese-based cathode precursor material and its preparation method, cathode material, and battery. Background Technology

[0002] Lithium-rich manganese-based cathode materials have promising market prospects due to their advantages such as high specific capacity, good thermal stability and cycle performance, wide charge / discharge voltage range, and low cost. However, in practical applications, lithium-rich manganese-based cathode materials suffer from problems such as low initial charge / discharge efficiency, significant voltage and capacity decay during cycling, and easy structural damage, which has prevented their widespread application.

[0003] In the fabrication of lithium-ion batteries, the process conditions and physicochemical properties of the precursor significantly influence the performance of the cathode material. The physical properties of lithium-rich manganese-based cathode precursors, such as their structure and morphology, are inherited by the lithium-rich manganese-based cathode material and greatly affect its electrochemical performance. Typically, lithium-rich manganese-based precursors are synthesized using a co-precipitation method. However, precursors prepared using this method have thin primary particles and poor mechanical strength. Under high-voltage charge-discharge conditions, lithium-rich manganese-based cathode materials prepared from these precursors are prone to structural collapse and deactivation, leading to increased impedance and deteriorated cycle and rate performance in the assembled lithium-ion battery.

[0004] Therefore, this invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a lithium-rich manganese-based cathode precursor material and its preparation method, cathode material and battery, aiming to improve the particle morphology of the lithium-rich manganese-based precursor material and increase its structural strength, thereby improving the electrochemical performance of the lithium-rich manganese-based cathode material.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a lithium-rich manganese-based cathode precursor material, the lithium-rich manganese-based cathode precursor material comprising a core and a shell layer on the surface of the core; the core is formed by alternating arrangement of plate-shaped primary particles, and the shell layer is formed by radially arranged plate-shaped primary particles perpendicular to the surface of the core along the radial plane.

[0008] In an optional embodiment, the core of the lithium-rich manganese-based cathode precursor material is nickel manganese hydroxide with the chemical formula Ni. x Mn y (OH)₂, wherein the shell is a complex of nickel manganese hydroxide and nickel manganese borate, and the chemical formula of the nickel manganese borate is (Ni x Mn y)3(BO3)2, where 0.2≤x≤0.4, 0.6≤y≤0.8, x+y=1.

[0009] In an optional embodiment, the porosity of the core of the lithium-rich manganese-based cathode precursor material is greater than the porosity of the shell.

[0010] In an optional embodiment, the thickness of the sheet-like primary particles in the lithium-rich manganese-based cathode precursor material is 0.04-0.11 μm, and the thickness of the plate-like primary particles is 0.1-0.3 μm.

[0011] In an optional embodiment, the core of the lithium-rich manganese-based cathode precursor material has a porosity of 8%-13%, and the shell has a porosity of 1%-5%.

[0012] In an optional embodiment, the diameter of the core in the lithium-rich manganese-based cathode precursor material is 1.5-4 μm, and the thickness of the shell layer is 1-3 μm.

[0013] In an optional embodiment, the median particle size Dv50 of the lithium-rich manganese-based cathode precursor material is 3-7 μm.

[0014] In an optional embodiment, the mass percentage of boron in the lithium-rich manganese-based cathode precursor material is 0.03%-0.2%.

[0015] In an optional embodiment, the tap density of the lithium-rich manganese-based cathode precursor material is 1.5-2.0 g / cm³. 3 .

[0016] In an optional embodiment, the specific surface area of ​​the lithium-rich manganese-based cathode precursor material is 12-20 m². 2 / g.

[0017] Secondly, the present invention provides a method for preparing a lithium-rich manganese-based cathode precursor material, the method comprising the following steps:

[0018] Prepare a first slurry containing nickel-manganese hydroxide particles; prepare a mixed solution containing nickel, manganese and boron;

[0019] The mixed solution, the first precipitant solution, and the first ammonia solution were added in parallel to the reactor containing the first slurry to carry out the first coprecipitation reaction. The concentrate was turned on to concentrate the solution. When the particle size Dv50 of the particles in the reactor reached 3-7 μm, the liquid feeding was stopped to obtain the second slurry. The second slurry was subjected to solid-liquid separation, washing, drying, and sieving to obtain the lithium-rich manganese-based cathode precursor material.

[0020] In an optional embodiment, the mixed solution is obtained by mixing a first nickel-manganese mixed salt solution with a boron source solution, wherein the concentration of the boron source solution is 0.1-2 mol / L; the boron source includes at least one of boric acid, sodium borate and ammonium borate.

[0021] In an optional embodiment, the mass of the boron source in the mixed solution is 0.2%-1% of the theoretical yield of nickel-manganese hydroxide in the lithium-rich manganese-based cathode precursor material.

[0022] In an optional embodiment, the reaction temperature of the first coprecipitation reaction is 45-60°C, the reaction pH is 9.5-10.5, and the ammonia concentration during the reaction is 1.5-4.5 g / L.

[0023] In an optional implementation, the first coprecipitation reaction requires continuous stirring at a speed of 300-450 r / min.

[0024] In an optional embodiment, the flow rate of the mixed solution added to the reactor is 2-4 L / h.

[0025] In an optional embodiment, the preparation step of the first slurry includes introducing an inert gas into a reaction vessel containing pure water and starting stirring, adding a second nickel-manganese mixed salt solution, a second precipitant solution, and a second ammonia water in parallel to the reaction vessel to carry out a second co-precipitation reaction, stopping the liquid feeding when the particle size Dv50 of the particles in the vessel reaches 1.5-4μm, and obtaining a first slurry containing nickel-manganese hydroxide particles.

[0026] In an optional embodiment, the nickel salt in the first nickel-manganese mixed salt solution and the second nickel-manganese mixed salt solution includes at least one of nickel sulfate, nickel chloride and nickel nitrate, and the manganese salt includes at least one of manganese sulfate, manganese chloride and manganese nitrate.

[0027] In an optional embodiment, the molar concentration of the metal element in the first nickel-manganese mixed salt solution and the second nickel-manganese mixed salt solution is 0.5-2.5 mol / L.

[0028] In an optional embodiment, the molar ratio of nickel to manganese in the first nickel-manganese mixed salt solution and the second nickel-manganese mixed salt solution is (0.2-0.4):(0.6-0.8).

[0029] In an optional embodiment, the first precipitant solution and the second precipitant solution are sodium hydroxide solutions or potassium hydroxide solutions with a molar concentration of 6-12 mol / L.

[0030] In an optional embodiment, the molar concentrations of the first ammonia solution and the second ammonia solution are 0.5-2 mol / L.

[0031] In an optional embodiment, the inert gas is nitrogen, and the nitrogen flow rate is 5-30 L / min.

[0032] In an optional embodiment, the stirring speed is 450-600 r / min.

[0033] In an optional embodiment, the reaction temperature of the second coprecipitation reaction is 35-45°C, the reaction pH is 10.5-11.5, and the ammonia concentration during the reaction is 0.5-2 g / L.

[0034] In an optional embodiment, the flow rate of the second nickel-manganese mixed salt solution added to the reactor is 4-8 L / h.

[0035] Thirdly, the present invention provides a lithium-rich manganese-based cathode material, which is prepared by mixing and sintering the lithium-rich manganese-based cathode precursor material described in the first aspect with a lithium source.

[0036] Fourthly, the present invention provides a lithium-ion battery, the lithium-ion battery comprising a positive electrode sheet, the positive electrode sheet comprising the lithium-rich manganese-based positive electrode material as described in the third aspect.

[0037] The present invention has the following beneficial effects:

[0038] (1) The lithium-rich manganese-based cathode precursor material provided by the present invention is a secondary particle formed by the agglomeration of primary particles, and has a stable "loose inside and tight outside" structure, that is, the core of the material is loose and the shell is dense. At the same time, the cathode material prepared from it can also inherit the structural characteristics of the precursor. The loose core has a porous structure formed by the interlacing of plate-like primary particles. This structure has a high porosity, which is conducive to the diffusion of lithium ions. The shell is relatively dense and doped with boron. The introduction of borate can change the growth orientation of the precursor material grains, thereby improving the morphology of the shell primary particles. During the reaction, the shell primary particles will gradually thicken into plates and be radially distributed along the radial plane perpendicular to the core surface to form a dense shell. This shell structure can not only strengthen the core of the precursor material and increase the mechanical strength and structural stability of the precursor material, but also suppress the generation of side reactions between the cathode material prepared from it and the electrolyte, thereby improving the cycle life and charge-discharge performance of the lithium battery.

[0039] (2) The preparation method provided by the present invention combines a continuous method and a batch method. When preparing the loose core, a continuous method is used, in which feeding and discharging are carried out simultaneously during the reaction process, and the liquid level in the reactor is kept stable by overflow. When coating the core surface with a dense shell, a batch method is used, in which a concentrator is used to concentrate the liquid in the reactor during the reaction process to remove the clear liquid in the reactor, thereby increasing the solid content in the reactor. The combination of the continuous method and the batch method can effectively control the crystal morphology of the lithium-rich manganese-based precursor material. The resulting precursor material has good particle uniformity and batch stability. Moreover, the process is simple, the synthesis is highly controllable, and it is easy to achieve large-scale production.

[0040] After reading and understanding the accompanying diagrams and detailed descriptions, the other aspects can be understood. Attached Figure Description

[0041] The accompanying drawings are used to provide a further understanding of the technical solutions in this paper and form part of the specification. They are used together with the embodiments of this application to explain the technical solutions in this paper and do not constitute a limitation on the technical solutions in this paper.

[0042] Figure 1 SEM image (a) and SEM cross-sectional view (b) of the lithium-rich manganese-based cathode precursor material prepared in Example 5;

[0043] Figure 2 SEM image of the lithium-rich manganese-based cathode precursor material prepared in Comparative Example 1;

[0044] Figure 3 SEM image of the lithium-rich manganese-based cathode precursor material prepared in Comparative Example 2. Detailed Implementation

[0045] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of this disclosure and should not be construed as limiting the scope of the invention.

[0046] It should be noted that, unless otherwise specified in the examples, the conditions should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0047] The technical terms "first" and "second" in this invention are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features.

[0048] In this invention, the reference to "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments.

[0049] The technical term "and / or" in this invention is only a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.

[0050] In this invention, the character " / " generally indicates that the objects before and after it are in an "or" relationship, and "at least one" means one or more.

[0051] In a first aspect, the present invention provides a lithium-rich manganese-based cathode precursor material, the lithium-rich manganese-based cathode precursor material comprising a core and a shell layer on the surface of the core; the core is formed by alternating arrangement of plate-shaped primary particles, and the shell layer is formed by radially arranged plate-shaped primary particles perpendicular to the surface of the core along the radial plane.

[0052] The morphology and structure of the lithium-rich manganese-based cathode precursor material of the present invention are shown in the appendix to the specification. Figure 1 As shown in (b), the plate-like primary particles are randomly distributed and interleaved to form a loose core. The radial plane of the plate-like primary particles is perpendicular to the surface of the core sphere and is distributed radially to form a dense shell. The precursor material as a whole has a core-shell structure with a loose core and a dense shell. The loose core structure is conducive to the diffusion and migration of lithium ions, and the dense shell can act as a protective layer to increase the structural stability of the precursor material. This avoids the structural collapse of the cathode material prepared from it due to volume expansion during charging and discharging, which is beneficial to improving the cycle stability of the cathode material.

[0053] In some embodiments, the core of the lithium-rich manganese-based cathode precursor material is nickel manganese hydroxide with the chemical formula Ni. x Mn y (OH)₂, wherein the shell is a complex of nickel manganese hydroxide and nickel manganese borate, and the chemical formula of the nickel manganese borate is (Ni x Mn y )3(BO3)2, where 0.2≤x≤0.4, 0.6≤y≤0.8, x+y=1.

[0054] In some embodiments, the porosity of the core of the lithium-rich manganese-based cathode precursor material is greater than the porosity of the shell.

[0055] In some embodiments, the thickness of the sheet-like primary particles in the lithium-rich manganese-based cathode precursor material is 0.04-0.11 μm, and the thickness of the plate-like primary particles is 0.1-0.3 μm.

[0056] In some embodiments, the core porosity of the lithium-rich manganese-based cathode precursor material is 8%-13%, and the shell porosity is 1%-5%.

[0057] In some embodiments, the diameter of the core in the lithium-rich manganese-based cathode precursor material is 1.5-4 μm, and the thickness of the shell layer is 1-3 μm.

[0058] In some embodiments, the median particle size Dv50 of the lithium-rich manganese-based cathode precursor material is 3-7 μm.

[0059] In some embodiments, the mass percentage of boron in the lithium-rich manganese-based cathode precursor material is 0.03%-0.2%.

[0060] In some embodiments, the tap density of the lithium-rich manganese-based cathode precursor material is 1.5-2.0 g / cm³. 3 .

[0061] In some embodiments, the specific surface area of ​​the lithium-rich manganese-based cathode precursor material is 12-20 m². 2 / g.

[0062] The primary particle thickness, porosity, median particle size, boron content, tap density, and specific surface area of ​​the lithium-rich manganese-based cathode precursor material of the present invention are within a suitable range, which can enable the lithium-rich manganese-based cathode material to obtain superior electrochemical performance.

[0063] Secondly, the present invention provides a method for preparing a lithium-rich manganese-based cathode precursor material, the method comprising: preparing a first slurry containing nickel-manganese hydroxide particles; and preparing a mixed solution containing nickel, manganese and boron.

[0064] The mixed solution, the first precipitant solution, and the first ammonia solution were added in parallel to the reactor containing the first slurry to carry out the first coprecipitation reaction. The concentrate was then turned on to concentrate the solution. When the particle size Dv50 of the particles in the reactor reached 3-7 μm, the liquid feeding was stopped to obtain the second slurry. The second slurry was then subjected to solid-liquid separation, washing, drying, and sieving to obtain the lithium-rich manganese-based cathode precursor material.

[0065] In some embodiments, the mixed solution is obtained by mixing a first nickel-manganese mixed salt solution with a boron source solution, wherein the concentration of the boron source solution is 0.1-2 mol / L, for example, 0.1 mol / L, 0.8 mol / L, or 2 mol / L, but is not limited to the listed values; other unlisted values ​​within the above range are also applicable.

[0066] In some embodiments, the mass of the boron source in the mixed solution is 0.2%-1% of the theoretical yield of nickel manganese hydroxide in the lithium-rich manganese-based cathode precursor material, for example, it can be 0.2%, 0.4% or 1%, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0067] In some embodiments, before the first coprecipitation reaction is carried out, a sulfuric acid solution (1 mol / L) and a first ammonia solution are added to a reaction vessel containing a first slurry for adjustment, thereby controlling the pH value and ammonia concentration of the slurry in the vessel to reach the target values.

[0068] In some embodiments, the temperature of the first coprecipitation reaction is 45-60°C, for example, 45°C, 50°C or 60°C; the reaction pH is 9.5-10.5, for example, 9.5, 10 or 10.5; and the ammonia concentration during the reaction is 1.5-4.5 g / L, for example, 1.5 g / L, 3.0 g / L or 4.5 g / L, but not limited to the values ​​listed above. Other unlisted values ​​within the above range are also applicable.

[0069] In some embodiments, the first coprecipitation reaction requires continuous stirring at a speed of 300-450 r / min, such as 300 r / min, 420 r / min or 450 r / min, but not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0070] In this invention, during the first coprecipitation reaction, i.e., the shell growth stage, the ammonia concentration and reaction temperature are relatively high. The high ammonia concentration reduces the saturation of metal ions in the reaction solution, decreasing the number of free metal ions in the reaction system and slowing the growth rate of the primary shell particles. With the introduction of borate ions, the orientation of the primary particle growth changes, ultimately resulting in thicker, plate-like primary particles. The higher reaction temperature not only ensures stable operation of the coprecipitation reaction but also allows the primary particles to be orderly embedded within the secondary particles, thereby forming uniformly morphological lithium-rich manganese-based cathode precursor particles. If the reaction temperature and ammonia concentration in the reaction solution are too low during the first coprecipitation reaction, the primary shell particles will become thinner and more loosely distributed, making it difficult to form a dense outer shell.

[0071] In some embodiments, the flow rate of the mixed solution added to the reactor is 2-4 L / h, for example, 2 L / h, 3 L / h or 4 L / h, but not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0072] In some embodiments, the first coprecipitation reaction process includes maintaining the pH of the reaction system by adjusting the flow rate of the first precipitant solution and maintaining the ammonia concentration of the reaction system by adjusting the flow rate of the first ammonia solution.

[0073] In some embodiments, the preparation steps of the first slurry include introducing an inert gas into a reaction vessel containing pure water and starting stirring, adding a second nickel-manganese mixed salt solution, a second precipitant solution, and a second ammonia solution in parallel to the reaction vessel to carry out a second co-precipitation reaction, stopping the liquid feeding when the particle size Dv50 of the slurry particles in the vessel reaches 1.5-4 μm, and obtaining a first slurry containing nickel-manganese hydroxide particles.

[0074] In some embodiments, the molar concentration of the metal element in the first nickel-manganese mixed salt solution and the second nickel-manganese mixed salt solution is 0.5-2.5 mol / L, for example, it can be 0.5 mol / L, 2.0 mol / L or 2.5 mol / L, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0075] In some embodiments, the molar ratio of nickel to manganese in the first nickel-manganese mixed salt solution and the second nickel-manganese mixed salt solution is (0.2-0.4):(0.6-0.8), for example, it can be 0.2:0.8, 0.35:0.65 or 0.4:0.6, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0076] In some embodiments, the molar concentrations of the first precipitant solution and the second precipitant solution are 6-12 mol / L, for example, 6 mol / L, 10 mol / L and 12 mol / L, but not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0077] In some embodiments, the molar concentrations of the first ammonia solution and the second ammonia solution are 0.5-2 mol / L, for example, 0.5 mol / L, 1.5 mol / L or 2 mol / L, but not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0078] In some embodiments, the inert gas is nitrogen, and the nitrogen flow rate is 5-30 L / min, for example, 5 L / min, 10 L / min or 30 L / min. The stirring speed is 450-600 r / min, for example, 450 r / min, 550 r / min or 600 r / min, but not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0079] In some embodiments, the second coprecipitation reaction is carried out by adding a second precipitant solution and a second ammonia solution to a reaction vessel containing pure water for adjustment, thereby controlling the pH value and ammonia concentration of the bottom liquid in the vessel to reach the target value.

[0080] In some embodiments, the reaction temperature of the second coprecipitation reaction is 35-45°C, for example, 35°C, 40°C or 45°C; the reaction pH is 10.5-11.5, for example, 10.5, 11.0 or 11.5; and the ammonia concentration during the reaction is 0.5-2 g / L, for example, 0.5 g / L, 1 g / L or 2 g / L, but not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0081] In some embodiments, the feeding and discharging processes in the second coprecipitation reaction need to be carried out simultaneously, and the liquid level in the reactor is kept constant by overflow.

[0082] In this invention, during the second coprecipitation reaction, i.e., the core growth stage, the reaction pH is controlled near the crystallization line of nickel-manganese hydroxide, which effectively inhibits the growth of primary core particles. Compared with the first coprecipitation reaction, the second coprecipitation reaction has a relatively lower ammonia concentration and reaction temperature, and the complexing effect of the complexing agent on metal ions is weaker. This provides better reaction conditions for homogeneous nucleation of nickel-manganese hydroxide crystals, which is conducive to the growth of crystal nuclei and can inhibit the continuous thickening of the formed crystal nuclei. Ultimately, a large number of thin, lamellar primary core particles are obtained, which are interleaved and randomly distributed, exhibiting a loose structure. If the reaction temperature and ammonia concentration in the second coprecipitation reaction are too high, the complexing effect of the complexing agent on metal ions is stronger, which will cause the crystal nucleation reaction rate to be too fast, resulting in thicker, less uniform primary core particles, which is not conducive to the formation of a loose core.

[0083] In some embodiments, the flow rate of the second nickel-manganese mixed salt solution added to the reactor is 4-8 L / h, for example, it can be 4 L / h, 6 L / h or 8 L / h, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0084] In some embodiments, the second coprecipitation reaction process includes maintaining the pH of the reaction system by adjusting the flow rate of the second precipitant solution and maintaining the ammonia concentration of the reaction system by adjusting the flow rate of the second ammonia solution.

[0085] Thirdly, the present invention provides a lithium-rich manganese-based cathode material, which is prepared by mixing and sintering the lithium-rich manganese-based cathode precursor material described in the first aspect with a lithium source.

[0086] Fourthly, the present invention provides a lithium-ion battery, comprising a positive electrode, a negative electrode, a separator spaced between the positive and negative electrodes, and an electrolyte. The positive electrode comprises a lithium-rich manganese-based positive electrode material as described in the third aspect. Methods for preparing the lithium-ion battery should be known to those skilled in the art. For example, the positive electrode, separator, and negative electrode can each be a sheet, which can be cut to a target size and stacked sequentially, or wound to a target size to form a cell, and further combined with an electrolyte to form a lithium-ion battery.

[0087] Specifically, the features and performance of the present invention will be further described in detail below with reference to the accompanying drawings, embodiments and comparative examples.

[0088] Example 1

[0089] This embodiment provides a lithium-rich manganese-based cathode precursor material, wherein the porosity of the core of the precursor material is 10.17%, and the porosity of the shell is 2.59%; the thickness of the plate-like primary particles in the core is 0.08 μm, and the thickness of the plate-like primary particles in the shell is 0.20 μm. The preparation method of the lithium-rich manganese-based cathode precursor material is as follows:

[0090] S1. Dissolve nickel sulfate and manganese sulfate in deionized water according to the molar ratio of Ni:Mn = 0.35:0.65 to prepare a first and second nickel-manganese mixed salt solution with a molar concentration of 2.0 mol / L; prepare a first and second sodium hydroxide solution with a molar concentration of 10 mol / L; prepare a first and second ammonia solution with a molar concentration of 2 mol / L.

[0091] S2. Add pure water to a 100L reactor equipped with a temperature-controlled water bath jacket, agitator, and pH probe until the pure water bottom solution completely submerges the agitator (the volume of pure water is approximately 40% of the reactor volume). After heating to 40℃, introduce nitrogen gas at a flow rate of 10L / min into the sealed reactor. Simultaneously, turn on the agitator and set its rotation speed to 600r / min. Introduce a second ammonia solution and a second sodium hydroxide solution into the reactor until the ammonia concentration in the bottom solution reaches 1.0g / L and the pH value reaches 11.0. Then, use a precision metering pump to introduce a 6L / min flow rate... The second nickel-manganese mixed salt solution, the second sodium hydroxide solution, and the second ammonia solution were added to the reactor in parallel to carry out the second coprecipitation reaction. During the reaction, the liquid level in the reactor was kept stable by overflow, and the ammonia concentration and pH of the reaction system were maintained at 1.0 g / L and 11.0 by controlling the flow rate of the second ammonia solution and the second sodium hydroxide solution. Every 1.5 h during the reaction, samples were taken from the reactor and the particle size of the sampled particles was measured by a laser particle size analyzer. When the particle size Dv50 of the slurry particles in the reactor reached 2.5 μm, the liquid feeding was stopped, and the first slurry containing nickel-manganese hydroxide particles was obtained.

[0092] S3. Mix 0.8 mol / L boric acid solution with the first nickel-manganese mixed salt solution to obtain a mixed solution (the mass of boron source in the mixed solution is 0.4% of the theoretical yield of nickel-manganese hydroxide); heat the reactor to 50℃, adjust the speed of the stirrer to 420 r / min, and introduce 1 mol / L sulfuric acid solution and the first ammonia solution into the reactor until the pH value of the slurry in the reactor reaches 9.5 and the ammonia concentration reaches 3.0 g / L; use a precision metering pump to add the mixed solution, the first sodium hydroxide solution, and the first ammonia solution in parallel to the reactor at a flow rate of 4 L / h to carry out the first coprecipitation reaction. During the reaction, samples are taken from the reactor every 1.5 h and analyzed using a laser particle size analyzer. The particle size of the sampled particles was tested. As the feed continued, the mixture was concentrated using a concentrator, and the liquid level was maintained near the overflow port. During the reaction, the ammonia concentration of the reaction system was maintained at 3.0 g / L and the pH at 9.5 by controlling the flow rates of the first ammonia solution and the first sodium hydroxide solution. When the particle size Dv50 of the particles in the reactor reached 4.5 μm, the feed was stopped, and the second slurry was obtained. The second slurry was centrifuged to dry, then washed with dilute sodium hydroxide solution (50 L, 0.8 mol / L) for alkaline washing and pure water (350 L) for water washing. The washed material was then placed in a 120°C forced-air oven for drying and then passed through a 300-mesh sieve to obtain lithium-rich manganese-based cathode precursor material.

[0093] Example 2

[0094] This embodiment provides a lithium-rich manganese-based cathode precursor material, wherein the porosity of the core of the precursor material is 11.55%, and the porosity of the shell is 3.91%; the thickness of the plate-like primary particles in the core is 0.07 μm, and the thickness of the plate-like primary particles in the shell is 0.17 μm. The preparation method of the lithium-rich manganese-based cathode precursor material is as follows:

[0095] S1. Dissolve nickel sulfate and manganese sulfate in deionized water according to the molar ratio of Ni:Mn=0.2:0.8 to prepare a first and second nickel-manganese mixed salt solution with a molar concentration of 0.5 mol / L; prepare a first and second sodium hydroxide solution with a molar concentration of 6 mol / L; prepare a first and second ammonia solution with a molar concentration of 0.5 mol / L.

[0096] S2. Add pure water to a 100L reactor equipped with a temperature-controlled water bath jacket, agitator, and pH probe until the pure water solution completely submerges the agitator (the volume of pure water is approximately 40% of the reactor volume). After heating to 35℃, introduce nitrogen gas at a flow rate of 5L / min into the sealed reactor. Simultaneously, turn on the agitator and set its rotation speed to 450r / min. Introduce a second ammonia solution and a second sodium hydroxide solution into the reactor until the ammonia concentration in the bottom solution reaches 0.5g / L and the pH value reaches 10.5. Then, use a precision metering pump to introduce a 4L / min flow rate... The second nickel-manganese mixed solution, the second sodium hydroxide solution, and the second ammonia solution were added to the reactor in parallel to carry out the second coprecipitation reaction. During the reaction, the liquid level in the reactor was kept stable by overflow, and the ammonia concentration and pH of the reaction system were maintained at 0.5 g / L and 10.5 by controlling the flow rate of the second ammonia solution and the second sodium hydroxide solution. Every 1.5 hours during the reaction, samples were taken from the reactor and the particle size of the sampled particles was measured by a laser particle size analyzer. When the particle size Dv50 of the slurry particles in the reactor reached 1.5 μm, the liquid feeding was stopped, and the first slurry containing nickel-manganese hydroxide particles was obtained.

[0097] S3. Mix 0.1 mol / L boric acid solution with the first nickel-manganese mixed salt solution to obtain a mixed solution (the mass of boron source in the mixed solution is 1.0% of the theoretical yield of nickel-manganese hydroxide); heat the reactor to 45°C, adjust the stirring speed to 300 r / min, and introduce 1 mol / L sulfuric acid solution and the first ammonia solution into the reactor until the pH value of the slurry in the reactor reaches 10 and the ammonia concentration reaches 1.5 g / L; use a precision metering pump to add the mixed solution, the first sodium hydroxide solution, and the first ammonia solution in parallel to the reactor at a flow rate of 4 L / h to carry out the first coprecipitation reaction. During the reaction, samples are taken from the reactor every 1.5 h and analyzed using a laser particle size analyzer. The particle size of the sampled particles was tested. As the feed continued, the mixture was concentrated using a concentrator, and the liquid level was maintained near the overflow port. During the reaction, the ammonia concentration of the reaction system was maintained at 1.5 g / L and the pH at 10 by controlling the flow rates of the first ammonia solution and the first sodium hydroxide solution. When the particle size Dv50 of the particles in the reactor reached 3.0 μm, the feed was stopped, and the second slurry was obtained. The second slurry was centrifuged to dry, then washed with dilute sodium hydroxide solution (50 L, 0.8 mol / L) for alkaline washing and pure water (350 L) for water washing. The washed material was then placed in a 120°C forced-air oven for drying and then passed through a 300-mesh sieve to obtain lithium-rich manganese-based cathode precursor material.

[0098] Example 3

[0099] This embodiment provides a lithium-rich manganese-based cathode precursor material, wherein the porosity of the core of the precursor material is 12.83%, and the porosity of the shell is 4.67%; the thickness of the plate-like primary particles in the core is 0.05 μm, and the thickness of the plate-like primary particles in the shell is 0.13 μm. The preparation method of the lithium-rich manganese-based cathode precursor material is as follows:

[0100] S1. Dissolve nickel sulfate and manganese sulfate in deionized water according to the molar ratio of Ni:Mn = 0.4:0.6 to prepare a first and second nickel-manganese mixed salt solution with a molar concentration of 2.5 mol / L; prepare a first and second sodium hydroxide solution with a molar concentration of 12 mol / L; prepare a first and second ammonia solution with a molar concentration of 1.5 mol / L.

[0101] S2. Add pure water to a 100L reactor equipped with a temperature-controlled water bath jacket, agitator, and pH probe until the pure water solution completely submerges the agitator (the volume of pure water is approximately 40% of the reactor volume). After heating to 45℃, introduce nitrogen gas at a flow rate of 30L / min into the sealed reactor. Simultaneously, turn on the agitator and set its rotation speed to 550r / min. Introduce a second ammonia solution and a second sodium hydroxide solution into the reactor until the ammonia concentration in the bottom solution reaches 2.0g / L and the pH value reaches 11.5. Then, use a precision metering pump to introduce a second ammonia solution at a flow rate of 8L / min. The second nickel-manganese mixed salt solution, the second sodium hydroxide solution, and the second ammonia solution were added to the reactor in parallel to carry out the second coprecipitation reaction. During the reaction, the liquid level in the reactor was kept stable by overflow, and the ammonia concentration of the reaction system was maintained at 2.0 g / L and the pH was maintained at 11.5 by controlling the flow rate of the second ammonia solution and the second sodium hydroxide solution. Every 1.5 hours during the reaction, samples were taken from the reactor and the particle size of the sampled particles was measured by a laser particle size analyzer. When the particle size Dv50 of the slurry particles in the reactor reached 4.0 μm, the liquid feeding was stopped, and the first slurry containing nickel-manganese hydroxide particles was obtained.

[0102] S3. Mix 2 mol / L boric acid solution with the first nickel-manganese mixed salt solution to obtain a mixed solution (the mass of boron source in the mixed solution is 0.2% of the theoretical yield of nickel-manganese hydroxide); heat the reactor to 60℃, adjust the stirring speed to 450 r / min, and introduce 1 mol / L sulfuric acid solution and the first ammonia solution into the reactor until the pH value of the slurry in the reactor reaches 10.5 and the ammonia concentration reaches 4.5 g / L; use a precision metering pump to add the mixed solution, the first sodium hydroxide solution, and the first ammonia solution in parallel to the reactor at a flow rate of 3 L / h to carry out the first coprecipitation reaction. During the reaction, samples are taken from the reactor every 1.5 h and measured with a laser particle size analyzer. The particle size of the sampled particles was determined. As the feed continued, the mixture was concentrated using a concentrator, and the liquid level was maintained near the overflow port. During the reaction, the ammonia concentration of the reaction system was maintained at 4.5 g / L and the pH at 10.5 by controlling the flow rates of the first ammonia solution and the first sodium hydroxide solution. When the particle size Dv50 of the particles in the reactor reached 7.0 μm, the feed was stopped, and the second slurry was obtained. The second slurry was centrifuged to dry, then washed with dilute sodium hydroxide solution (50 L, 0.8 mol / L) for alkaline washing and pure water (350 L) for water washing. The washed material was then placed in a 120°C forced-air oven for drying and then passed through a 300-mesh sieve to obtain lithium-rich manganese-based cathode precursor material.

[0103] Example 4

[0104] This embodiment provides a lithium-rich manganese-based cathode precursor material, wherein the porosity of the core of the precursor material is 10.23%, and the porosity of the shell is 2.37%; the thickness of the plate-like primary particles in the core is 0.06 μm, and the thickness of the plate-like primary particles in the shell is 0.19 μm. The preparation method of the lithium-rich manganese-based cathode precursor material is as follows:

[0105] Compared with Example 1, the ammonia concentration of the bottom liquid in step S2 was changed to 0.5 g / L, and the liquid feeding was stopped when the particle size Dv50 of the slurry in the reactor reached 3 μm; the ammonia concentration of the slurry in step S3 was changed to 1.5 g / L, and the liquid feeding was stopped when the particle size Dv50 of the particles in the reactor reached 4.5 μm; the remaining steps remained unchanged.

[0106] Example 5

[0107] This embodiment provides a lithium-rich manganese-based cathode precursor material, wherein the porosity of the core of the precursor material is 10.51%, and the porosity of the shell is 3.34%; the thickness of the plate-like primary particles in the core is 0.09 μm, and the thickness of the plate-like primary particles in the shell is 0.18 μm. The preparation method of the lithium-rich manganese-based cathode precursor material is as follows:

[0108] Compared with Example 1, the ammonia concentration of the bottom liquid in the reactor in step S2 was changed to 2.0 g / L, and the liquid feeding was stopped when the particle size Dv50 of the slurry in the reactor reached 3 μm; the ammonia concentration of the slurry in step S3 was changed to 3.0 g / L, and the liquid feeding was stopped when the particle size Dv50 of the particles in the reactor reached 5 μm; the remaining steps remained unchanged.

[0109] Example 6

[0110] This embodiment provides a lithium-rich manganese-based cathode precursor material, wherein the porosity of the core of the precursor material is 8.37%, and the porosity of the shell is 1.97%; the thickness of the plate-like primary particles in the core is 0.10 μm, and the thickness of the plate-like primary particles in the shell is 0.23 μm. The preparation method of the lithium-rich manganese-based cathode precursor material is as follows:

[0111] Compared with Example 1, the temperature of the second coprecipitation reaction in step S2 was changed to 45°C, and the ammonia concentration in the bottom liquid of the reactor was changed to 2.0 g / L, while the other steps remained unchanged.

[0112] Example 7

[0113] This embodiment provides a lithium-rich manganese-based cathode precursor material, wherein the porosity of the core of the precursor material is 10.33%, and the porosity of the shell is 2.54%; the thickness of the plate-like primary particles in the core is 0.06 μm, and the thickness of the plate-like primary particles in the shell is 0.18 μm. The preparation method of the lithium-rich manganese-based cathode precursor material is as follows:

[0114] Compared with Example 1, the temperature of the second coprecipitation reaction in step S2 was changed to 35°C, and the ammonia concentration in the bottom liquid of the reactor was changed to 0.5 g / L, while the other steps remained unchanged.

[0115] Example 8

[0116] This embodiment provides a lithium-rich manganese-based cathode precursor material, wherein the porosity of the core of the precursor material is 9.85%, and the porosity of the shell is 3.05%; the thickness of the plate-like primary particles in the core is 0.07 μm, and the thickness of the plate-like primary particles in the shell is 0.14 μm. The preparation method of the lithium-rich manganese-based cathode precursor material is as follows:

[0117] Compared with Example 1, the temperature of the first coprecipitation reaction in step S3 was changed to 45°C, and the ammonia concentration in the bottom liquid of the reactor was changed to 1.5 g / L, while the other steps remained unchanged.

[0118] Example 9

[0119] This embodiment provides a lithium-rich manganese-based cathode precursor material, wherein the porosity of the core of the precursor material is 9.78%, and the porosity of the shell is 2.86%; the thickness of the plate-like primary particles in the core is 0.07 μm, and the thickness of the plate-like primary particles in the shell is 0.22 μm. The preparation method of the lithium-rich manganese-based cathode precursor material is as follows:

[0120] Compared with Example 1, the temperature of the first coprecipitation reaction in step S3 was changed to 60°C, and the ammonia concentration in the bottom liquid of the reactor was changed to 4.5 g / L, while the other steps remained unchanged.

[0121] Example 10

[0122] This embodiment provides a lithium-rich manganese-based cathode precursor material, wherein the porosity of the core of the precursor material is 9.68%, and the porosity of the shell is 3.07%; the thickness of the plate-like primary particles in the core is 0.08 μm, and the thickness of the plate-like primary particles in the shell is 0.17 μm. The preparation method of the lithium-rich manganese-based cathode precursor material is as follows:

[0123] Compared with Example 1, the mass of boron source in the mixed solution in step S3 was changed to 0.2% of the theoretical yield of nickel manganese hydroxide, while the other steps remained unchanged.

[0124] Example 11

[0125] This embodiment provides a lithium-rich manganese-based cathode precursor material, wherein the porosity of the core of the precursor material is 9.91%, and the porosity of the shell is 1.55%; the thickness of the plate-like primary particles in the core is 0.07 μm, and the thickness of the plate-like primary particles in the shell is 0.27 μm. The preparation method of the lithium-rich manganese-based cathode precursor material is as follows:

[0126] Compared with Example 1, the mass of boron source in the mixed solution in step S3 was changed to 1.0% of the theoretical yield of nickel manganese hydroxide, while the other steps remained unchanged.

[0127] Comparative Example 1

[0128] This comparative example provides a lithium-rich manganese-based cathode precursor material, wherein the porosity of the core of the precursor material is 12.77% and the porosity of the shell is 5.37%; the thickness of the plate-like primary particles in the core of the precursor material is 0.04 μm and the thickness of the plate-like primary particles in the shell is 0.09 μm.

[0129] Compared to Example 5, in step S3, sulfuric acid solution is not introduced into the reactor to adjust the pH of the slurry before the first coprecipitation reaction. Instead, the pH is maintained during the second coprecipitation reaction stage. During the first coprecipitation reaction, the pH of the slurry in the reactor is lowered by 0.1 every 1 hour until it reaches 9.5 and is maintained until the reaction ends. During the first coprecipitation reaction, the first nickel-manganese mixed salt solution, the first sodium hydroxide solution, and the first ammonia solution are added to the reactor in a parallel flow. The remaining steps remain unchanged. (No boron source is used.)

[0130] Comparative Example 2

[0131] This comparative example provides a lithium-rich manganese-based cathode precursor material, wherein the porosity of the core of the precursor material is 5.57% and the porosity of the shell is 2.97%; the thickness of the plate-like primary particles in the core of the precursor material is 0.12 μm and the thickness of the plate-like primary particles in the shell is 0.43 μm.

[0132] Compared with Example 5, the temperature of the second coprecipitation reaction in step S2 is 50°C and the ammonia concentration of the bottom liquid in the reactor is 4 g / L; the temperature of the first coprecipitation reaction in step S3 is 50°C and the ammonia concentration of the bottom liquid slurry in the reactor is 4 g / L; the mass of the boron source in the mixed solution is 0.4% of the theoretical yield of nickel manganese hydroxide; and the remaining steps remain unchanged.

[0133] The primary particle thickness and porosity of the lithium-rich manganese-based cathode precursor materials prepared in Examples 1-11 and Comparative Examples 1-2 were measured using the following methods: the primary particle thickness was measured by analyzing the SEM images of the corresponding samples using Nano Measurer software; the porosity was measured by analyzing the SEM images of the corresponding samples using ImageJ software.

[0134] The lithium-rich manganese-based cathode precursor materials prepared in Examples 1-11 and Comparative Examples 1-2 were tested for elemental content, specific surface area, tap density, and electrochemical performance, specifically including the following steps:

[0135] 1. Element content detection: Inductively coupled plasma atomic emission spectrometer.

[0136] 2. Specific Surface Area Test (BET): Specific surface area analyzer.

[0137] 3. Tap density test (TD): Riesler tap density meter.

[0138] 4. Electrochemical performance testing:

[0139] (1) Preparation of lithium-rich manganese-based cathode materials

[0140] The obtained lithium-rich manganese-based cathode precursor material was mechanically mixed with lithium hydroxide (the molar ratio of metal elements in the precursor material to lithium elements in lithium hydroxide was 1:1.05), and then placed in a muffle furnace for high-temperature sintering at 800-1100℃ for 15-30 hours to finally obtain the lithium-rich manganese-based cathode material.

[0141] (2) Preparation of button cells

[0142] The prepared lithium-rich manganese-based cathode material was mixed with conductive agent acetylene black (AB) and binder polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1. Using N-methylpyrrolidone (NMP) as solvent, the mixture was stirred in a small beaker at 800 r / min for 2 h to obtain a slurry. The slurry was coated onto current collector aluminum foil using an automatic coating machine, laid flat on tempered glass, and dried in a vacuum drying oven at 105℃ for 4 h. After being die-cut into 12 mm diameter electrode sheets, they were assembled into CR2032 coin cells in a glove box filled with argon atmosphere, where the water and oxygen content were both below 0.1 ppm. The battery uses a pure metallic lithium sheet with a diameter of 16 mm and a thickness of 0.5 mm as the negative electrode, a porous polyethylene membrane of model Celgard2300 with a diameter of 18 mm as the separator, and a 1 mol / L lithium hexafluorophosphate-ethylene carbonate:dimethyl carbonate (LiPF6-EC:DMC, with a volume ratio of EC to DMC of 1:1).

[0143] (3) Electrochemical performance testing

[0144] The assembled coin cells were subjected to electrochemical performance tests within a charge / discharge voltage range of 2.0-4.6V.

[0145] The test results are shown in Table 1-2.

[0146] Table 1

[0147]

[0148] Table 2

[0149]

[0150] In the attached image: Figure 1 This is a SEM image of the lithium-rich manganese-based cathode precursor material prepared in Example 5. The image shows that the plate-like primary particles are randomly distributed and interleaved, agglomerated to form a loose core. Figure 1 (b)), plate-like primary particles are radially distributed along the radial plane perpendicular to the surface of the inner sphere and aggregate to form a dense and compact shell. Figure 1 (a)-(b)). Figure 2 The image shows a SEM image of the lithium-rich manganese-based cathode precursor material prepared in Comparative Example 1. The primary particles in the shell are thin sheets, and after agglomeration, they are loosely distributed and not compact. There are also thin sheet-like primary particles that have detached from the shell surface. Figure 3 The image shows a SEM image of the lithium-rich manganese-based cathode precursor material prepared in Comparative Example 2. The primary particles in the shell are mostly blocky and of uneven thickness, and are relatively densely distributed after agglomeration.

[0151] Table 1-2: Analysis of Examples 1-11 shows that the lithium-rich manganese-based cathode precursor material of the present invention has relatively superior specific surface area and tap density. The cathode material prepared from it has high discharge specific capacity and cycle capacity retention rate, indicating that the cathode material has good electrochemical performance and maintains high structural stability during cycling. This may be due to the cathode material inheriting the excellent physicochemical properties and stable "loose inside and tight outside" morphological structure of the lithium-rich manganese-based cathode precursor material.

[0152] Analysis of Examples 1 and 6-7, and Comparative Example 2 reveals that, in the preparation process of the lithium-rich manganese-based cathode precursor material of the present invention, the lower reaction temperature and ammonia concentration in the second co-precipitation reaction provide better reaction conditions for the homogeneous nucleation of nickel-manganese hydroxide core crystals, resulting in uniform and thin primary core particles. During the subsequent mixing and sintering process with the lithium source, these primary core particles can be fully lithiated, which helps to enhance the electrochemical performance of the cathode material during charge and discharge. Furthermore, due to the good uniformity of the primary core particles, stress between particles is less likely to accumulate, resulting in high structural strength of the secondary particles. This gives the cathode material an advantage in cycle capacity retention. Conversely, higher reaction temperatures and ammonia concentrations lead to thicker primary core particles with deteriorated uniformity. The agglomerated secondary particles are prone to stress accumulation during charge and discharge, causing particle breakage, which is detrimental to improving the electrochemical performance and maintaining cycle stability of the cathode material.

[0153] Analysis of Examples 1 and 8-9 shows that in the preparation process of the lithium-rich manganese-based cathode precursor material of the present invention, a higher reaction temperature in the first coprecipitation reaction enables the reaction to run stably and promotes the orderly aggregation of primary particles. A higher ammonia concentration reduces the number of free metal ions in the reaction environment, slows down the growth rate of the primary particles in the shell, and thus forms precursor particles with uniform morphology. The cathode material prepared with this material has better electrochemical performance. On the other hand, a lower reaction temperature and ammonia concentration will result in thinner and more loosely distributed primary particles in the shell, which is not conducive to their aggregation into a dense shell, thereby affecting the structural stability of the cathode material prepared subsequently and reducing its cycle performance.

[0154] Analysis of Examples 1 and 10-11 shows that during the preparation of the lithium-rich manganese-based cathode precursor material of the present invention, appropriate boron doping increases the structural stability of the precursor material, thereby enhancing the cycle performance of the subsequently prepared cathode material; while excessive boron doping will occupy too many structural voids in the precursor material, thereby inhibiting the diffusion of lithium ions and reducing the electrochemical performance of the cathode material.

[0155] Analysis of Example 5 and Comparative Example 1 shows that the lithium-rich manganese-based cathode precursor material prepared by the present invention has boron added to the shell layer. Compared with Comparative Example 1, the introduction of borate can change the growth orientation of the precursor material grains, thereby improving the morphology of the primary particles in the shell layer. During the reaction, the primary particles in the shell layer gradually thicken into plates and are radially distributed along the radial plane perpendicular to the core surface, and agglomerate into a dense shell layer. This shell layer structure can not only strengthen the core of the precursor material and make the structure of the precursor material more stable, but also suppress the generation of side reactions between the cathode material prepared from it and the electrolyte, further improving the electrochemical performance of the material.

[0156] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A lithium-rich manganese-based cathode precursor material, characterized in that, The lithium-rich manganese-based cathode precursor material comprises a core and a shell layer on the surface of the core; the core is formed by alternating layers of plate-like primary particles, and the shell layer is formed by radially arranged plate-like primary particles perpendicular to the surface of the core; the core is nickel-manganese hydroxide with the chemical formula Ni. x Mn y (OH)₂, wherein the shell is a complex of nickel manganese hydroxide and nickel manganese borate, and the chemical formula of the nickel manganese borate is (Ni x Mn y )3(BO3)2, where 0.2≤x≤0.4, 0.6≤y≤0.8, x+y=1.

2. The lithium-rich manganese-based cathode precursor material according to claim 1, characterized in that, The porosity of the core of the lithium-rich manganese-based cathode precursor material is greater than that of the shell.

3. The lithium-rich manganese-based cathode precursor material according to claim 1 or 2, characterized in that, The thickness of the sheet-like primary particles is 0.04-0.11 μm, and the thickness of the plate-like primary particles is 0.1-0.3 μm; And / or, the porosity of the core is 8%-13%, and the porosity of the shell is 1%-5%; And / or, the diameter of the core is 1.5-4 μm, and the thickness of the shell is 1-3 μm; And / or, the median particle size Dv50 of the lithium-rich manganese-based cathode precursor material is 3-7 μm; And / or, the mass percentage of boron in the lithium-rich manganese-based cathode precursor material is 0.03%-0.2%; And / or, the tap density of the lithium-rich manganese-based cathode precursor material is 1.5-2.0 g / cm³. 3 ; And / or, the specific surface area of ​​the lithium-rich manganese-based cathode precursor material is 12-20 m². 2 / g.

4. A method for preparing the lithium-rich manganese-based cathode precursor material according to any one of claims 1 to 3, characterized in that, Includes the following steps: Prepare a first slurry containing nickel-manganese hydroxide particles; prepare a mixed solution containing nickel, manganese and boron; The mixed solution, the first precipitant solution, and the first ammonia solution were added in parallel to the reactor containing the first slurry to carry out the first coprecipitation reaction. The concentrate was turned on to concentrate the solution. When the particle size Dv50 of the particles in the reactor reached 3-7 μm, the liquid feeding was stopped to obtain the second slurry. The second slurry was subjected to solid-liquid separation, washing, drying, and sieving to obtain the lithium-rich manganese-based cathode precursor material.

5. The method for preparing the lithium-rich manganese-based cathode precursor material according to claim 4, characterized in that, The mixed solution is obtained by mixing a first nickel-manganese mixed salt solution with a boron source solution, wherein the concentration of the boron source solution is 0.1-2 mol / L; the boron source includes at least one of boric acid, sodium borate, and ammonium borate. And / or, the mass of the boron source in the mixed solution is 0.2%-1% of the theoretical yield of nickel-manganese hydroxide in the lithium-rich manganese-based cathode precursor material; And / or, the reaction temperature of the first coprecipitation reaction is 45-60℃, the reaction pH is 9.5-10.5, and the ammonia concentration during the reaction is 1.5-4.5 g / L; And / or, the flow rate of the mixed solution added to the reactor is 2-4 L / h.

6. The method for preparing the lithium-rich manganese-based cathode precursor material according to claim 4, characterized in that, The preparation steps of the first slurry include introducing an inert gas into a reaction vessel containing pure water and starting stirring, adding a second nickel-manganese mixed salt solution, a second precipitant solution, and a second ammonia water in parallel into the reaction vessel to carry out a second co-precipitation reaction, stopping the liquid feeding when the particle size Dv50 of the particles in the vessel reaches 1.5-4μm, and obtaining a first slurry containing nickel-manganese hydroxide particles.

7. The method for preparing the lithium-rich manganese-based cathode precursor material according to any one of claims 4 to 6, characterized in that, The nickel salt in the first nickel-manganese mixed salt solution and the second nickel-manganese mixed salt solution includes at least one of nickel sulfate, nickel chloride and nickel nitrate, and the manganese salt includes at least one of manganese sulfate, manganese chloride and manganese nitrate; And / or, the molar concentration of the metal element in the first nickel-manganese mixed salt solution and the second nickel-manganese mixed salt solution is 0.5-2.5 mol / L; And / or, the molar ratio of nickel to manganese in the first nickel-manganese mixed salt solution and the second nickel-manganese mixed salt solution is (0.2-0.4):(0.6-0.8); And / or, the first precipitant solution and the second precipitant solution are sodium hydroxide solution or potassium hydroxide solution with a molar concentration of 6-12 mol / L; And / or, the molar concentrations of the first ammonia solution and the second ammonia solution are 0.5-2 mol / L.

8. The method for preparing the lithium-rich manganese-based cathode precursor material according to claim 6, characterized in that, The inert gas is nitrogen, and the nitrogen flow rate is 5-30 L / min; And / or, the reaction temperature of the second coprecipitation reaction is 35-45℃, the reaction pH is 10.5-11.5, and the ammonia concentration during the reaction is 0.5-2g / L; And / or, the flow rate of the second nickel-manganese mixed salt solution added to the reactor is 4-8 L / h.

9. A lithium-rich manganese-based cathode material, characterized in that, The lithium-rich manganese-based cathode material is prepared by mixing and sintering the lithium-rich manganese-based cathode precursor material according to any one of claims 1 to 3 with a lithium source.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes a positive electrode sheet, which includes the lithium-rich manganese-based positive electrode material as described in claim 9.

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