In-situ modified lithium-rich manganese-based precursor as well as preparation method and application thereof

Abstract

The invention provides an in-situ modified lithium-rich manganese-based precursor and a preparation method and application thereof.The preparation method comprises the following steps that a nickel-cobalt-manganese mixed metal salt solution, a precipitator solution and a complexing agent solution are introduced into a base solution for a first coprecipitation reaction, and after the first coprecipitation reaction is finished, feeding is stopped; and introducing a doped nickel-cobalt-manganese mixed metal salt solution, a precipitant solution, a complexing agent solution and a carbon source solution into a system after the first coprecipitation reaction is finished, and carrying out a second coprecipitation reaction to obtain the in-situ modified lithium-rich manganese-based precursor. According to the preparation method, doping elements and a carbon source are introduced when the lithium-rich manganese-based precursor is prepared through the coprecipitation reaction, in-situ uniform construction of oxygen vacancies and a carbon coating layer on the surface of the material is synchronously achieved, the in-situ modified lithium-rich manganese-based precursor is obtained, the treatment step of subsequent secondary coating can be reduced, the production cost can be reduced, and the method is suitable for industrial production. The technological process is shortened.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and relates to a lithium-rich manganese-based precursor with in-situ modification, its preparation method and application. Background Art

[0002] Lithium-ion batteries have an important application position in consumer electronics and power batteries due to their advantages such as high energy density, portability, and high stability. However, limited by the development of positive and negative electrode materials, their actual energy density is limited. Among them, the problems of lower capacity and energy density of the positive electrode material are more prominent than those of the negative electrode material and other components, which are the key factors restricting the development of lithium-ion batteries. Lithium-rich manganese-based positive electrode materials are considered to be one of the most promising positive electrode materials for lithium-ion batteries due to their advantages of high capacity (>200 mAh g -1 ).

[0003] However, this over-lithiated layered lithium-rich manganese-based material inevitably undergoes an oxygen evolution process of the Li2MnO3 component during the initial cycle, an irreversible phase transition to an inactive phase after long-term cycling, and electrolyte decomposition, which subsequently accelerates surface degradation. Therefore, lithium-rich manganese-based materials will face problems such as "oxygen loss", irreversible transformation of the crystal phase structure, dissolution of transition metal ions, decomposition of the electrolyte, and gas evolution during the charge-discharge reaction process. The resulting poor cycle capacity and voltage stability are important factors restricting their practical application. In addition, lithium-rich manganese-based positive electrode materials also face problems of poor rate performance and low Coulomb efficiency.

[0004] In the prior art, doping and coating are used to improve the stability of lithium-rich manganese-based materials and solve the above problems faced by lithium-rich manganese-based positive electrode materials. For example, CN115986070A discloses a modified lithium-rich manganese-based layered oxide positive electrode material and its preparation method. The preparation method includes: (1) mixing ammonium fluoride particles, biomass carbon source and lithium-rich manganese-based layered oxide positive electrode material in a mass ratio of 0.001-0.1:0.01-0.30:1 and grinding; (2) pressing the ground mixture into tablets and sintering in a closed environment, the sintering temperature is 180°C - 400°C, the sintering time is 1h - 3h, and after sintering, it is naturally cooled to room temperature to obtain a sintered product; (3) grinding, washing and drying the sintered product, and then grinding and sieving again to obtain the final product.

[0005] It can be seen that in the prior art, doping elements or carbon layers are usually introduced in the post-treatment of lithium-rich manganese-based materials, which is prone to the problem of uneven coating, resulting in an increase in interfacial impedance, and the physical combination of the carbon layer and the material body may fall off at high voltage or during long cycling. In addition, the process complexity in the prior art increases, and additional steps (such as ball milling, sintering) are required, which will increase energy consumption and time costs.

[0006] Based on the above research, it is necessary to provide a preparation method of an in-situ modified lithium-rich manganese-based precursor. The preparation method has a simple process, can reduce subsequent treatment steps (such as secondary coating), lower production costs, and realize industrial application. Summary of the Invention

[0007] The purpose of the present invention is to provide an in-situ modified lithium-rich manganese-based precursor, its preparation method and application. By introducing a doping element and a carbon source during the co-precipitation reaction for preparing the lithium-rich manganese-based precursor, the in-situ and uniform construction of oxygen vacancies and a carbon coating layer on the material surface is synchronously achieved, obtaining an in-situ modified lithium-rich manganese-based precursor, which can reduce subsequent secondary coating treatment steps, lower production costs, and shorten the process flow.

[0008] To achieve the purpose of this invention, the following technical solutions are adopted:

[0009] In the first aspect, the present invention provides a preparation method of an in-situ modified lithium-rich manganese-based precursor, and the preparation method includes the following steps:

[0010] (1) Introduce a nickel-cobalt-manganese mixed metal salt solution, a precipitant solution, and a complexing agent solution into a bottom solution for a first co-precipitation reaction. After the first co-precipitation reaction ends, stop feeding;

[0011] (2) Introduce a doped nickel-cobalt-manganese mixed metal salt solution, a precipitant solution, a complexing agent solution, and a carbon source solution into the system after the end of the first co-precipitation reaction in step (1) for a second co-precipitation reaction to obtain the in-situ modified lithium-rich manganese-based precursor.

[0012] In the present invention, a doping element and a carbon source are introduced during the preparation stage of the lithium-rich manganese-based precursor. The doping element can be uniformly distributed in-situ in the precursor lattice, inducing the formation of oxygen vacancies, improving the initial Coulomb efficiency and cycle stability of the material. The carbon source can be uniformly dispersed inside the material by the co-precipitation method to form a three-dimensional conductive network, significantly improving the electronic conductivity and ion diffusion rate, thereby improving the rate performance and overall electrochemical performance of the material. Therefore, by combining the introduction of oxygen vacancies and carbon coating during the precursor synthesis stage, the present invention can achieve a synergistic effect, realizing in-situ modification during the precursor synthesis stage. The obtained material has high structural uniformity, strong intrinsic properties of the material, a simple process, can reduce production costs, and can also improve the electrochemical performance of the lithium-rich manganese-based material.

[0013] The in-situ modified lithium-rich manganese-based precursor obtained by the present invention includes a core and a shell on the surface of the core. The core includes a nickel-cobalt-manganese precursor material, and the shell includes a doped nickel-cobalt-manganese precursor material and a carbon material.

[0014] Preferably, the carbon source solution in step (2) includes a silane-modified carbon source.

[0015] The present invention preferably uses a silane-modified carbon source, which can introduce a carbon source into the precursor material by utilizing the Si-O-M bond (M is the metal in the system) after silane hydrolysis, improving the uniformity of carbon source distribution and the bonding strength with the precursor.

[0016] Preferably, the silane-modified carbon source includes amino-silane-modified carbon nanotubes and / or amino-silane-modified graphene.

[0017] Exemplarily, the preparation methods of the amino-silane-modified carbon nanotubes and the amino-silane-modified graphene include the following steps: First, acidify the carbon nanotubes or graphene with nitric acid and sulfuric acid, then disperse the acidified carbon nanotubes or the acidified graphene in water and ethanol to form a suspension, add an amino-silane coupling agent (such as kh550) for reaction and drying to obtain the amino-silane-modified carbon nanotubes or the amino-silane-modified graphene; wherein, the mass ratio of the acidified carbon nanotubes to the amino-silane coupling agent is (3-6):1, for example, it can be 3:1, 4:1, 5:1 or 6:1, and the mass ratio of the acidified graphene to the amino-silane coupling agent is (3-6):1, for example, it can be 3:1, 4:1, 5:1 or 6:1, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0018] Preferably, in the system of the second co-precipitation reaction in step (2), the concentration of the carbon source is 0.5-5 g / L, for example, it can be 0.5 g / L, 1.5 g / L, 2.5 g / L, 3.5 g / L, 4.5 g / L or 5 g / L, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0019] The concentration of the carbon source in the system of the second co-precipitation reaction of the present invention affects the amount of carbon source introduced and the dispersibility of the carbon source. If the carbon source concentration in the system is too small, the amount of carbon source introduced into the precursor is too small, thus affecting the electrochemical performance of the material. If the carbon source concentration in the system is too high, an overly thick carbon coating layer will be formed on the surface of the precursor, resulting in a decrease in the lithium ion diffusion rate and the coverage of electrochemically active sites, thus reducing the electrochemical performance of the material.

[0020] Preferably, the concentration of the carbon source solution in step (2) is 1-10 g / L, for example, it can be 1 g / L, 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L or 10 g / L, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0021] Preferably, the doped nickel-cobalt-manganese mixed metal salt solution in step (2) includes a doping element, and the doping element includes any one or a combination of at least two of aluminum, magnesium, titanium or iron.

[0022] Preferably, in the doped nickel-cobalt-manganese mixed metal salt solution described in step (2), the molar ratio of nickel element, cobalt element, manganese element and doping element is a:b:c:d, a + b + c + d = 1, 0.2 ≤ a ≤ 0.35, for example, it can be 0.2, 0.25, 0.30 or 0.35, 0.01 ≤ b ≤ 0.15, for example, it can be 0.01, 0.04, 0.10 or 0.15, c ≥ 0.6, for example, it can be 0.6, 0.62, 0.64, 0.66, 0.68 or 0.7, 0.002 ≤ d ≤ 0.05, for example, it can be 0.002, 0.01, 0.02, 0.03, 0.04 or 0.05. In the nickel-cobalt-manganese mixed metal salt solution described in step (1), the molar ratio of nickel element, cobalt element and manganese element is a':b':c', a' + b' + c' = 1, 0.2 ≤ a' ≤ 0.35, for example, it can be 0.2, 0.25, 0.30 or 0.35, 0.01 ≤ b' ≤ 0.15, for example, it can be 0.01, 0.04, 0.10 or 0.15, c' ≥ 0.6, for example, it can be 0.6, 0.62, 0.64, 0.66, 0.68 or 0.7. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0023] Preferably, the total metal ion concentrations of the doped nickel-cobalt-manganese mixed metal salt solution described in step (2) and the nickel-cobalt-manganese mixed metal salt solution described in step (1) are independently 85 - 115 g / L, for example, it can be 85 g / L, 95 g / L, 105 g / L or 115 g / L. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0024] Preferably, the pH of the second coprecipitation reaction described in step (2) is in the range of 8.0 - 10.0, for example, it can be 8.0, 8.5, 9, 9.5 or 10.0. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0025] Preferably, the temperatures of the second coprecipitation reaction described in step (2) and the first coprecipitation reaction described in step (1) are independently 50 - 60 °C, for example, it can be 50 °C, 55 °C or 60 °C, and the stirring speeds are independently 400 - 800 rpm, for example, it can be 400 rpm, 500 rpm, 600 rpm, 700 rpm or 800 rpm. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0026] Preferably, the particle size D50 at the end point of the second coprecipitation reaction in step (2) is D502 = D501 + (0.5 - 2 μm). For example, it can be D501 + 0.5 μm, D501 + 1 μm, D501 + 1.5 μm, or D501 + 2 μm, where D501 is the particle size D50 at the end point of the first coprecipitation reaction.

[0027] The particle size D50 at the end point of the second coprecipitation reaction in the present invention is obtained by adding 0.5 - 2 μm to the particle size D50 at the end point of the first coprecipitation reaction. Therefore, the particle size D50 at the end point of the second coprecipitation reaction determines the content of the doping element and the carbon source introduced into the precursor material, thereby affecting the performance of the lithium-rich manganese-based precursor material.

[0028] Preferably, after the second coprecipitation reaction in step (2), solid-liquid separation, washing, and drying steps are also carried out.

[0029] Preferably, the washing method includes washing 3 - 5 times successively with an alkali solution and pure water. For example, it can be 3 times, 4 times, or 5 times.

[0030] Preferably, the drying temperature is 80 - 130 °C. For example, it can be 80 °C, 90 °C, 100 °C, 110 °C, 120 °C, or 130 °C, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0031] Preferably, the precipitating agent solution in step (2) and the precipitating agent solution in step (1) include sodium hydroxide solution and / or potassium hydroxide solution.

[0032] Preferably, the mass fraction of the precipitating agent solution in step (2) and the precipitating agent solution in step (1) is 30 - 35%. For example, it can be 30%, 31%, 32%, 33%, 34%, or 35%, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0033] Preferably, the complexing agent solution in step (2) and the complexing agent solution in step (1) include ammonia water and / or EDTA.

[0034] Preferably, the mass concentration of the complexing agent solution in step (2) and the complexing agent solution in step (1) is 5 - 40 g / L. For example, it can be 5 g / L, 10 g / L, 20 g / L, 30 g / L, or 40 g / L, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0035] Preferably, the particle size D50 at the end point of the first co-precipitation reaction in step (1) is D501, where D501 is 5-10 μm. For example, it can be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0036] Preferably, the pH of the bottom liquid in step (1) is 11.0-12.5. For example, it can be 11.0, 11.5, 12.0, or 12.5, and the complexing agent concentration is 2-10 g / L. For example, it can be 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L, or 10 g / L, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0037] In a second aspect, the present invention provides a lithium-rich manganese-based precursor with in-situ modification, and the lithium-rich manganese-based precursor with in-situ modification is prepared by the preparation method as described in the first aspect.

[0038] In a third aspect, the present invention provides a lithium-rich manganese-based cathode material, and the lithium-rich manganese-based cathode material is obtained by mixing and sintering a lithium source and the lithium-rich manganese-based precursor with in-situ modification as described in the second aspect.

[0039] In a fourth aspect, the present invention provides a lithium-ion battery, and the lithium-ion battery includes the lithium-rich manganese-based cathode material as described in the third aspect.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] (1) By in-situ modification, that is, modification during the precursor synthesis stage, the obtained material has high structural uniformity, can enhance the intrinsic properties of the material, and has a simple process, which can reduce production costs.

[0042] (2) By introducing doping elements (such as any one or a combination of at least two of Al, Mg, Ti, or Fe) in the second co-precipitation reaction, the doping elements can be uniformly distributed in-situ in the precursor lattice, which can induce the formation of oxygen vacancies and improve the first Coulomb efficiency and cycle stability of the material.

[0043] (3) By introducing a carbon source in the second co-precipitation reaction, it can be uniformly dispersed inside the material through the co-precipitation method to form a three-dimensional conductive network, significantly improving the electronic conductivity and ion diffusion rate, thereby improving the rate performance and overall electrochemical performance of the material.

[0044] (4) By combining the introduction of oxygen vacancies and carbon coating during the precursor synthesis stage, a synergistic effect can be achieved to further improve the performance of the lithium-rich manganese-based material. Detailed implementation manners

[0045] The technical solution of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0046] Example 1

[0047] This example provides a method for preparing an in-situ modified lithium-rich manganese-based precursor. The preparation method includes the following steps:

[0048] (1) Add pure water, a sodium hydroxide solution with a mass concentration of 32%, and ammonia water as the reaction bottom liquid into a 100L reaction kettle, control the initial pH value of the bottom liquid to be 11.5, and the ammonia concentration to be 5g / L;

[0049] (2) Simultaneously inject a nickel-cobalt-manganese ternary solution with a mass concentration of 90g / L (the molar ratio of Ni, Co, and Mn is 0.30:0.05:0.65), a sodium hydroxide solution with a mass concentration of 32%, and ammonia water with a concentration of 15g / L into the reaction kettle through a metering pump. Set the stirring speed of the reaction kettle to 500rpm, control the reaction temperature to 55°C, and control the pH to be between 10.0 - 11.0 for the first coprecipitation reaction. When the median particle size D501 of the precursor particles reaches 6.0μm, stop feeding;

[0050] (3) Introduce a nickel-cobalt-manganese-aluminum quaternary solution with a mass concentration of 90g / L (the molar ratio of Ni, Co, Mn, and Al is 0.30:0.05:0.64:0.01) into the reaction system of step (2), and simultaneously introduce a sodium hydroxide solution with a mass concentration of 32%, ammonia water with a concentration of 15g / L, and an amino-silane modified carbon nanotube solution (kh550 modified) with a concentration of 5g / L. Control the pH to be between 8.5 - 10.0 for the second coprecipitation reaction. In the second coprecipitation reaction system, the concentration of the amino-silane modified carbon nanotubes is 1.5g / L; when the median particle size D502 reaches 6.5μm (D501 + 0.5μm), stop feeding;

[0051] (4) Transfer the slurry after the reaction to a suction flask, and wash it three times with alkali solution and pure water respectively;

[0052] (5) Transfer the solid material obtained by suction filtration and washing to an oven, dry it at 100°C, and finally obtain the in-situ modified lithium-rich manganese-based precursor.

[0053] Example 2

[0054] This example provides a method for preparing an in-situ modified lithium-rich manganese-based precursor. The preparation method includes the following steps:

[0055] (1) Add pure water, a sodium hydroxide solution with a mass concentration of 32%, and EDTA into a 100 L reactor as the reaction bottom liquid, control the initial pH value of the bottom liquid to be 12.5, and the EDTA concentration to be 2 g / L;

[0056] (2) Simultaneously inject a nickel-cobalt-manganese ternary solution with a mass concentration of 90 g / L (the molar ratio of Ni, Co, and Mn is 0.25:0.05:0.70), a sodium hydroxide with a mass concentration of 30%, and an EDTA solution with a concentration of 11 g / L into the reactor through a metering pump. Set the stirring speed of the reactor to 500 rpm, control the reaction temperature to 58 °C, and control the pH between 9.5 - 11.0 to conduct the first coprecipitation reaction. When the median particle size D501 of the precursor particles reaches 7.0 μm, stop feeding;

[0057] (3) Introduce a nickel-cobalt-manganese-titanium quaternary solution with a mass concentration of 90 g / L (the molar ratio of Ni, Co, Mn, and Ti is 0.245:0.05:0.70:0.005) into the reaction system of step (2), and simultaneously introduce a sodium hydroxide solution with a mass concentration of 32%, an EDTA solution with a concentration of 12 g / L, and an amino-silane-modified graphene solution (modified with kh550) with a concentration of 6 g / L. Control the pH between 8.5 - 9.5 to conduct the second coprecipitation reaction. In the second coprecipitation reaction system, the concentration of amino-silane-modified carbon nanotubes is 2 g / L. When the median particle size D502 reaches 8 μm (D501 + 1 μm), stop feeding;

[0058] (4) Transfer the slurry after the reaction to a suction flask, and wash it three times with an alkali solution and pure water respectively;

[0059] (5) Transfer the solid material obtained by suction filtration and washing to an oven, dry it at 100 °C, and finally obtain the in-situ modified lithium-rich manganese-based precursor.

[0060] Example 3

[0061] This example provides a preparation method of an in-situ modified lithium-rich manganese-based precursor, and the preparation method includes the following steps:

[0062] (1) Add pure water, a sodium hydroxide solution with a mass concentration of 34%, and ammonia water into a 100 L reactor as the reaction bottom liquid, control the initial pH value of the bottom liquid to be 11.0, and the ammonia concentration to be 10 g / L;

[0063] (2) Simultaneously inject a ternary nickel-cobalt-manganese solution with a mass concentration of 105 g / L (molar ratio of Ni, Co, and Mn being 0.30:0.05:0.65), sodium hydroxide with a mass concentration of 34%, and ammonia water with a concentration of 16 g / L into the reaction kettle. Set the stirring speed of the reaction kettle to 600 rpm, control the reaction temperature at 58 °C, and control the pH between 10.0 - 11.5 for the first coprecipitation reaction. Stop feeding when the median particle size D501 of the precursor particles reaches 9 μm;

[0064] (3) Introduce a quaternary nickel-cobalt-manganese-magnesium solution with a mass concentration of 105 g / L (molar ratio of Ni, Co, Mn, and Mg being 0.30:0.037:0.65:0.013) into the reaction system of step (2), and simultaneously introduce a sodium hydroxide solution with a mass concentration of 34%, ammonia water with a concentration of 16 g / L, and an amino-silane modified carbon nanotube solution (kh550 modified) with a concentration of 10 g / L. Control the pH between 9.0 - 10.0 for the second coprecipitation reaction. In the second coprecipitation reaction system, the concentration of the amino-silane modified carbon nanotubes is 5 g / L. Stop feeding when the median particle size D502 reaches 10 μm (D501 + 1 μm);

[0065] (4) Transfer the slurry after the reaction to a suction flask and wash it three times with alkali solution and pure water respectively;

[0066] (5) Transfer the solid material obtained by suction filtration and washing to an oven and dry it at 100 °C to finally obtain the in-situ modified lithium-rich manganese-based precursor.

[0067] Example 4

[0068] This example provides a method for preparing an in-situ modified lithium-rich manganese-based precursor. Except that in step (3), feeding is stopped when D502 reaches 8.5 μm (D501 + 2 μm), the rest are the same as in Example 1.

[0069] Example 5

[0070] This example provides a method for preparing an in-situ modified lithium-rich manganese-based precursor. Except that in step (3), feeding is stopped when D502 reaches 9.5 μm (D501 + 3 μm), the rest are the same as in Example 1.

[0071] Example 6

[0072] This example provides a method for preparing an in-situ modified lithium-rich manganese-based precursor. Except that in step (3), feeding is stopped when D502 reaches 6.7 μm (D501 + 0.2 μm), the rest are the same as in Example 1.

[0073] Example 7

[0074] This example provides a method for preparing an in-situ modified lithium-rich manganese-based precursor. Except that in the second co-precipitation reaction system described in step (3), the concentration of amino-silane modified carbon nanotubes is 0.3 g / L (achieved by changing the flow rate of the carbon source solution), the rest are the same as in Example 1.

[0075] Example 8

[0076] This example provides a method for preparing an in-situ modified lithium-rich manganese-based precursor. Except that in the second co-precipitation reaction system described in step (3), the concentration of amino-silane modified carbon nanotubes is 5.5 g / L (achieved by changing the flow rate of the carbon source solution), the rest are the same as in Example 1.

[0077] Example 9

[0078] This example provides a method for preparing an in-situ modified lithium-rich manganese-based precursor. Except that the amino-silane modified carbon nanotube solution described in step (3) is replaced with a carbon nanotube solution at the same concentration, the rest are the same as in Example 1.

[0079] Comparative Example 1

[0080] This comparative example provides a method for preparing a lithium-rich manganese-based precursor. Except that the nickel-cobalt-manganese-aluminum quaternary solution described in step (3) is replaced with the nickel-cobalt-manganese ternary solution in step (1), the rest are the same as in Example 1.

[0081] Comparative Example 2

[0082] This comparative example provides a method for preparing a lithium-rich manganese-based precursor. Except that the amino-silane modified carbon nanotube solution is not introduced in step (3), the rest are the same as in Example 1.

[0083] Comparative Example 3

[0084] This comparative example provides a method for preparing a lithium-rich manganese-based precursor. Except that step (3) is not carried out, the rest are the same as in Example 1.

[0085] The lithium-rich manganese-based precursor obtained in the above embodiments and comparative examples is evenly mixed with lithium carbonate in a molar ratio of 1:1.4, and sintered in an air atmosphere at 900°C for 12 hours to obtain the corresponding lithium-rich manganese-based positive electrode material. The lithium-rich manganese-based positive electrode material, polyvinylidene fluoride and Super P are added to N-methylpyrrolidone in a mass ratio of 80:5:5 and stirred into a positive electrode slurry. The positive electrode slurry is then evenly coated on the positive electrode collector aluminum foil, and after drying and rolling, a positive electrode sheet is obtained; the lithium sheet, diaphragm, electrolyte (the electrolyte is a 5V high-voltage electrolyte) and the positive electrode sheet obtained above are assembled in sequence. The battery model is a 2032 battery shell to obtain a lithium-ion button battery. The obtained lithium-ion button battery is tested for specific capacity and cycle capacity retention under 2.0V-4.6V@0.1C / 0.1C charge and discharge conditions. The test results are shown in Table 1:

[0086] Table 1

[0087]

[0088]

[0089] It can be seen from Example 1 and Comparative Examples 1-3 that the performance of Comparative Example 3 is greatly reduced, indicating that the present invention combines the introduction of oxygen vacancies and carbon coating in the precursor synthesis stage, which can achieve a synergistic effect and greatly improve the electrochemical properties of lithium-rich manganese-based materials; it can be seen from Example 1 and Examples 4-6 that the particle size D501 at the end point of the first coprecipitation reaction of the present invention and the particle size D502 at the end point of the second coprecipitation reaction satisfy a specific relationship, thereby introducing appropriate contents of doping elements and carbon sources into the precursor particles; it can be seen from Example 1 and Examples 7-8 that the present invention preferably introduces an appropriate amount of carbon source to promote the role of the carbon source and further improve the material performance; it can be seen from Example 1 and Example 9 that the carbon source of the present invention is preferably a silane-modified carbon source, which can improve the uniformity of carbon source distribution and the bonding strength with the precursor, thereby further improving the electrochemical properties of the material.

[0090] 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 thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A preparation method of an in-situ modified lithium-rich manganese-based precursor, characterized in that, The preparation method comprises the following steps: (1) A nickel-cobalt-manganese mixed metal salt solution, a precipitant solution, and a complexing agent solution are introduced into a bottom solution for a first coprecipitation reaction. After the first coprecipitation reaction ends, the feeding is stopped; (2) A doped nickel-cobalt-manganese mixed metal salt solution, a precipitant solution, a complexing agent solution, and a carbon source solution are introduced into the system after the first coprecipitation reaction described in step (1) for a second coprecipitation reaction to obtain the in-situ modified lithium-rich manganese-based precursor.

2. The preparation method according to claim 1, characterized in that, The carbon source solution described in step (2) comprises a silane-modified carbon source; Preferably, the silane-modified carbon source comprises amino-silane-modified carbon nanotubes and / or amino-silane-modified graphene.

3. The preparation method according to claim 1 or 2, characterized in that, In the system of the second coprecipitation reaction described in step (2), the concentration of the carbon source is 0.5 - 5 g / L; Preferably, the concentration of the carbon source solution described in step (2) is 1 - 10 g / L.

4. The preparation method according to any one of claims 1-3, characterized in that, The doped nickel-cobalt-manganese mixed metal salt solution described in step (2) comprises a doping element, and the doping element comprises any one or a combination of at least two of aluminum, magnesium, titanium, or iron; Preferably, in the doped nickel-cobalt-manganese mixed metal salt solution described in step (2), the molar ratio of nickel element, cobalt element, manganese element, and doping element is a:b:c:d, a + b + c + d = 1, 0.2 ≤ a ≤ 0.35, 0.01 ≤ b ≤ 0.15, c ≥ 0.6, 0.002 ≤ d ≤ 0.05, and in the nickel-cobalt-manganese mixed metal salt solution described in step (1), the molar ratio of nickel element, cobalt element, and manganese element is a’:b’:c’, a’ + b’ + c’ = 1, 0.2 ≤ a’ ≤ 0.35, 0.01 ≤ b’ ≤ 0.15, c’ ≥ 0.6; Preferably, the total metal ion concentrations of the doped nickel-cobalt-manganese mixed metal salt solution described in step (2) and the nickel-cobalt-manganese mixed metal salt solution described in step (1) are independently 85 - 115 g / L.

5. The preparation method according to any one of claims 1-4, characterized in that, The pH of the second coprecipitation reaction described in step (2) is in the range of 8.0 - 10.0; Preferably, the temperatures of the second coprecipitation reaction described in step (2) and the first coprecipitation reaction described in step (1) are independently 50 - 60 °C, and the stirring speeds are independently 400 - 800 rpm; Preferably, the particle size D50 at the end point of the second coprecipitation reaction described in step (2) is D502 = D501 + (0.5 - 2 μm), where D501 is the particle size D50 at the end point of the first coprecipitation reaction; Preferably, after the second coprecipitation reaction described in step (2), solid-liquid separation, washing, and drying steps are also carried out.

6. The preparation method according to any one of claims 1-5, characterized in that, The precipitant solution described in step (2) and the precipitant solution described in step (1) comprise sodium hydroxide solution and / or potassium hydroxide solution; Preferably, the mass fraction of the precipitant solution described in step (2) and the precipitant solution described in step (1) is 30 - 35%; Preferably, the complexing agent solution described in step (2) and the complexing agent solution described in step (1) comprise ammonia water and / or EDTA; Preferably, the mass concentration of the complexing agent solution described in step (2) and the complexing agent solution described in step (1) is 5 - 40 g / L.

7. The preparation method according to any one of claims 1-6, characterized in that, The particle size D50 at the end point of the first coprecipitation reaction in step (1) is D501, and D501 is 5 to 10 μm; Preferably, the pH of the bottom liquid in step (1) is 11.0 to 12.5, and the complexing agent concentration is 2 - 10 g / L.

8. An in-situ modified lithium-rich manganese-based precursor, characterized in that, The in-situ modified lithium-rich manganese-based precursor is prepared by the preparation method according to any one of claims 1-7.

9. A lithium-rich manganese-based cathode material, characterized in that, The lithium-rich manganese-based cathode material is obtained by mixing and sintering a lithium source and the in-situ modified lithium-rich manganese-based precursor according to claim 8.

10. A lithium-ion battery, characterized in that, The lithium ion battery includes the lithium-rich manganese-based cathode material according to claim 9.

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