Porous aluminum gradient lithium-rich manganese-based precursor, preparation method therefor and use thereof

Abstract

The present application provides a porous aluminum gradient lithium-rich manganese-based precursor, a preparation method therefor, and a use thereof. In the preparation method, a porous aluminum gradient lithium-rich manganese-based precursor particle prepared by means of a two-step co-precipitation reaction comprises a dense nickel-cobalt-manganese core and a loose porous aluminum concentration gradient shell layer coated on the surface of the core, so that the particle has a dense interior, providing relatively high tap density and energy density; the porous aluminum-containing shell layer formed on the surface enhances the transmission and diffusion of lithium ions, thereby improving the rate performance of a positive electrode material; in addition, the porous structure on the surface can also alleviate stress changes during charging and discharging, reduce the generation of microcracks induced by lithium ion deintercalation, and improve the structural stability of the positive electrode material.

Description

A porous aluminum gradient lithium-rich manganese-based precursor and a preparation method and application thereof TECHNICAL FIELD

[0001] The present application relates to the technical field of new energy battery material precursor synthesis, in particular to a porous aluminum gradient lithium-rich manganese-based precursor and a preparation method and application thereof. BACKGROUND

[0002] Lithium ion batteries (LIBs) have become an indispensable part of our daily life, which are widely used in portable devices, electric vehicles and renewable energy storage. Lithium-rich manganese-based layered oxides are considered to be one of the most promising lithium ion batteries due to their high specific capacity (>250mAhg -1 ), low cost and environmental friendliness. However, lithium-rich manganese-based layered oxides still have some major defects, especially poor cycle stability, such as irreversible phase transition and severe capacity and voltage decay during cycling.

[0003] The most common way to optimize the performance of lithium-rich manganese cathode materials at present is to adjust the grain boundary structure and chemical structure of the precursor during the synthesis of the precursor. Studies have shown that although element doping, morphology control and surface coating can stabilize the structure and inhibit harmful phase transition to some extent, thereby improving the capacity retention rate of the cathode material during cycling, but at the same time, it also reduces the initial capacity, which is not conducive to the improvement of the electrochemical performance of the cathode material, and cannot balance the cycle and rate performance.

[0004] CN111628149A discloses a gradient-doped high-nickel ternary cathode material and a preparation method thereof, which comprises: first preparing the inner core of a nickel-cobalt-manganese ternary precursor, and then adding a doping solution to the reaction kettle when the particle growth reaches 85%-95% of the target particle size, and adjusting the feeding flow to gradually increase, to obtain ternary precursor particles with target particle size, and achieve a "shell"-like doping through doping in the middle of the reaction. The ternary precursor prepared by this process has improved cycle retention rate of the corresponding cathode material, but still has the problem of low specific capacity of the material, and cannot balance high cycle retention rate and specific capacity.

[0005] CN107968202A discloses an aluminum-containing nickel-cobalt-manganese core-shell structure positive electrode material and a preparation method thereof, the preparation method comprising: feeding a mixed solution of a nickel source and a cobalt source and a manganese source solution together, and mixing with a precipitant and a complexing agent to cause a coprecipitation reaction; stopping feeding of the manganese source solution, feeding an aluminum source solution together with the mixed solution of the nickel source and the cobalt source, and causing a coprecipitation reaction; repeating the above steps to alternately dope manganese and aluminum by a coprecipitation method to obtain a ternary precursor with an aluminum-containing nickel-cobalt-manganese core-shell structure. The positive electrode material corresponding to the ternary precursor prepared by the process has a high cycle retention rate, but still has the problems of low specific capacity of the material and significant reduction in the charge-discharge specific capacity of the material with an increase in the number of cycles, and still cannot balance high cycle retention rate and specific capacity.

[0006] Therefore, how to provide a preparation method of a lithium-rich manganese-based precursor which can effectively improve the cycle performance, maintain the original high rate performance, is simple to operate, and can be applied on a large scale, is a technical problem to be solved at present. SUMMARY

[0007] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0008] The present application provides a porous aluminum gradient lithium-rich manganese-based precursor and a preparation method and application thereof. The preparation method is prepared by two-step coprecipitation reaction. The prepared porous aluminum gradient lithium-rich manganese-based precursor particle includes a dense nickel-cobalt-manganese inner core and a surface-coated loose porous aluminum concentration gradient shell. The inside is dense, has high tap density and energy density, the porous aluminum shell formed on the surface enhances the transmission and diffusion of lithium ions, thereby improving the rate performance of the positive electrode material. The surface porous structure can also relieve the stress change in the charge and discharge process, reduce the generation of lithium ion deintercalation-induced microcracks, and improve the structural stability of the positive electrode material.

[0009] In a first aspect, the present application provides a preparation method of a porous aluminum gradient lithium-rich manganese-based precursor, the preparation method comprising the following steps:

[0010] The nickel-cobalt-manganese ternary salt solution, the alkali solution and the complexing agent solution are injected into the reaction bottom solution in parallel flow to perform a first coprecipitation reaction. After reaching a first target particle size D501, the nickel-cobalt-manganese ternary salt solution is replaced with a nickel-cobalt-manganese-aluminum quaternary salt solution, which is continuously injected into the reaction bottom solution in parallel flow with the alkali solution and the complexing agent solution to perform a second coprecipitation reaction. After reaching a second target particle size D502, solid-liquid separation is performed to obtain a porous aluminum gradient lithium-rich manganese-based precursor.

[0011] The molar ratio of Ni:Co:Mn in the nickel-cobalt-manganese ternary salt solution is x1:y1:z1; x1+y1+z1=1, and z1≥0.6; the molar ratio of Ni:Co:Mn:Al in the nickel-cobalt-manganese-aluminum quaternary salt solution is x2:y2:z2:w; x2+y2+z2=1, z2≥0.6, and 0.002≤w≤0.05.

[0012] The preparation method described in the present application is a conventional two-step co-precipitation reaction. On the basis of the original first co-precipitation reaction, the nickel-cobalt-manganese ternary salt solution is replaced with a nickel-cobalt-manganese-aluminum quaternary salt solution to perform a second co-precipitation reaction, and then the process parameters are adjusted to prepare an aluminum gradient lithium-rich manganese-based precursor. Moreover, the preparation method described in the present application does not need to change the process and equipment, is simple to operate, and is conducive to industrial application.

[0013] As an optional technical solution of the present application, the molar ratio of Ni:Co:Mn in the nickel-cobalt-manganese ternary salt solution is consistent with the molar ratio of Ni:Co:Mn in the nickel-cobalt-manganese-aluminum quaternary salt solution, that is, x1:y1:z1=x2:y2:z2.

[0014] In the preparation method described in the present application, the nickel-cobalt-manganese molar ratio of the nickel-cobalt-manganese ternary salt solution in the first co-precipitation reaction is consistent with the nickel-cobalt-manganese molar ratio of the nickel-cobalt-manganese-aluminum quaternary salt solution in the second co-precipitation reaction, and only the aluminum concentration is different, which can highlight the performance improvement caused by the aluminum gradient.

[0015] In one embodiment, the total mass concentration of metal ions in the nickel-cobalt-manganese ternary salt solution is consistent with the total mass concentration of metal ions in the nickel-cobalt-manganese-aluminum quaternary salt solution, both of which are 85-115 g / L, such as 85 g / L, 90 g / L, 95 g / L, 100 g / L, 105 g / L, 110 g / L, or 115 g / L, etc., but not limited to the listed values, and other values not listed in the above value range are also applicable.

[0016] In one embodiment, the alkali solution includes a sodium hydroxide solution and / or a potassium hydroxide solution.

[0017] In one embodiment, the mass concentration of the alkali solution is 30-35 wt%, such as 30 wt%, 31 wt%, 32 wt%, 33 wt%, 34 wt%, or 35 wt%, etc., but not limited to the listed values, and other values not listed in the above value range are also applicable.

[0018] In one embodiment, the complexing agent in the complexing agent solution includes any one or a combination of at least two of ammonia, sodium acetate, ammonium oxalate, or EDTA.

[0019] In one embodiment, the mass concentration of the complexing agent solution is 5-40 g / L, such as 5 g / L, 10 g / L, 15 g / L, 20 g / L, 25 g / L, 30 g / L, 35 g / L, or 40 g / L, etc., but not limited to the listed values, and other values not listed in the above numerical range are also applicable.

[0020] As an optional technical solution of the present application, the reaction base solution comprises pure water, lye, and a complexing agent.

[0021] In one embodiment, the pH value of the reaction base solution is 11.0-12.5, such as 11.0, 11.1, 11.2, 11.3, 11.4, 11.5, 11.6, 11.7, 11.8, 11.9, 12.0, 12.1, 12.2, 12.3, 12.4, or 12.5, etc., but not limited to the listed values, and other values not listed in the above numerical range are also applicable.

[0022] In one embodiment, the concentration of the complexing agent in the reaction base solution is 2-10 g / L, such as 2 g / L, 4 g / L, 6 g / L, 8 g / L, or 10 g / L, etc., but not limited to the listed values, and other values not listed in the above numerical range are also applicable.

[0023] As an optional technical solution of the present application, the stirring speed of the first coprecipitation reaction is 400-800 rpm, such as 400 rpm, 450 rpm, 500 rpm, 550 rpm, 600 rpm, 650 rpm, 700 rpm, 750 rpm, or 800 rpm, etc., but not limited to the listed values, and other values not listed in the above numerical range are also applicable.

[0024] In one embodiment, the temperature of the first coprecipitation reaction is 50-60°C, such as 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C, or 60°C, etc., but not limited to the listed values, and other values not listed in the above numerical range are also applicable.

[0025] In one embodiment, the pH value of the first coprecipitation reaction is 10.0-12.0, such as 10.0, 10.2, 10.4, 10.6, 10.8, 11.0, 11.2, 11.4, 11.6, 11.8, or 12.0, etc., but not limited to the listed values, and other values not listed in the above numerical range are also applicable.

[0026] In an embodiment, the first target particle size D501 of the first co-precipitation reaction is 5-10 μm, for example 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, or 10 μm, etc., but not only limited to the listed values, other values not listed in the above numerical range are also applicable.

[0027] As an optional technical solution of the present application, the stirring speed of the second co-precipitation reaction is 400-800 rpm, for example 400 rpm, 450 rpm, 500 rpm, 550 rpm, 600 rpm, 650 rpm, 700 rpm, 750 rpm, or 800 rpm, etc., but not only limited to the listed values, other values not listed in the above numerical range are also applicable.

[0028] In an embodiment, the temperature of the second co-precipitation reaction is 50-60℃, for example 50℃, 51℃, 52℃, 53℃, 54℃, 55℃, 56℃, 57℃, 58℃, 59℃, or 60℃, etc., but not only limited to the listed values, other values not listed in the above numerical range are also applicable.

[0029] In an embodiment, the pH value of the second co-precipitation reaction is 8.0-10.0, for example 8.0, 8.2, 8.4, 8.6, 8.8, 9.0, 9.2, 9.4, 9.6, 9.8, or 10.0, etc., but not only limited to the listed values, other values not listed in the above numerical range are also applicable.

[0030] In an embodiment, the difference between the second target particle size D502 and the first target particle size D501 is 0.5-3 μm, for example 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, or 3 μm, etc., but not only limited to the listed values, other values not listed in the above numerical range are also applicable.

[0031] In the present application, the difference between the second target particle size D502 and the first target particle size D501 is 0.5-3 μm, if the difference between the two is too small, i.e. the porous aluminum gradient shell is too thin, it is not conducive to the formation of the porous structure on the surface, and cannot effectively alleviate the stress change during charging and discharging, resulting in that the cycle stability of the positive electrode material is not obviously improved; if the difference between the two is too large, i.e. the porous aluminum gradient shell is too thick, too much aluminum element is introduced, resulting in that the charge and discharge capacity of the positive electrode material is significantly decreased, and the loose porous shell with a thick surface greatly reduces the tap density and energy density, resulting in that the electrochemical performance is significantly deteriorated.

[0032] As an optional technical solution of the present application, the solid-liquid separation includes suction filtration.

[0033] In one embodiment, the solid-liquid separation is followed by washing and drying in sequence.

[0034] In one embodiment, the washing comprises washing 3-5 times with alkaline solution and washing 3-5 times with pure water.

[0035] In one embodiment, the drying is performed at a temperature of 80-130℃, such as 80℃, 90℃, 100℃, 110℃, 120℃ or 130℃, but not limited to the listed values, and other values within the above range are also applicable.

[0036] As an optional technical solution of the present application, the preparation method comprises the following steps:

[0037] A nickel-cobalt-manganese ternary salt solution, a nickel-cobalt-manganese-aluminum quaternary salt solution, an alkaline solution and a complexing agent solution are prepared; the molar ratio of Ni:Co:Mn in the nickel-cobalt-manganese ternary salt solution is x1:y1:z1; x1+y1+z1=1, and z1≥0.6; the molar ratio of Ni:Co:Mn:Al in the nickel-cobalt-manganese-aluminum quaternary salt solution is x2:y2:z2:w; x2+y2+z2=1, z2≥0.6, and 0.002≤w≤0.05; and x1:y1:z1=x2:y2:z2; the total mass concentration of metal ions in the nickel-cobalt-manganese ternary salt solution is consistent with the total mass concentration of metal ions in the nickel-cobalt-manganese-aluminum quaternary salt solution, both being 85-115g / L; the alkaline solution comprises a sodium hydroxide solution and / or a potassium hydroxide solution; the mass concentration of the alkaline solution is 30-35wt%; the complexing agent in the complexing agent solution comprises any one or a combination of at least two of ammonia, sodium acetate, ammonium oxalate or EDTA; and the mass concentration of the complexing agent solution is 5-40g / L.

[0038] Pure water, alkaline solution and complexing agent are added to a reaction kettle as a reaction bottom solution, and the pH value of the reaction bottom solution is 11.0-12.5; the concentration of the complexing agent in the reaction bottom solution is 2-10g / L.

[0039] The nickel-cobalt-manganese ternary salt solution, the lye and the complexing agent solution are injected into the reaction bottom solution in parallel flow to perform a first co-precipitation reaction, the stirring speed of the first co-precipitation reaction is controlled to be 400-800 rpm, the temperature is controlled to be 50-60℃, and the pH value is controlled to be 10.0-12.0; the first target particle size D501 is set to be 5-10 μm, after the median particle size of the particles reaches 5-10 μm, the feeding is stopped, the nickel-cobalt-manganese ternary salt solution is replaced by a nickel-cobalt-manganese-aluminum quaternary salt solution, and the second co-precipitation reaction is continued to be performed by injecting the lye and the complexing agent solution in parallel flow, the stirring speed of the second co-precipitation reaction is controlled to be 400-800 rpm, the temperature is controlled to be 50-60℃, and the pH value is controlled to be 8.0-10.0; after the median particle size of the particles meets the difference between the second target particle size D502 and the first target particle size D501 being 0.5-3 μm, the feeding is stopped.

[0040] The slurry after the reaction is subjected to suction filtration, is washed with the lye for 3-5 times, is washed with pure water for 3-5 times, and then the solid material obtained by the suction filtration and washing is transferred to an oven for drying at 100℃, and finally the porous aluminum gradient lithium-rich manganese-based precursor is obtained.

[0041] In the second aspect, the application provides a porous aluminum gradient lithium-rich manganese-based precursor, which is prepared by the preparation method in the first aspect.

[0042] The porous aluminum gradient lithium-rich manganese-based precursor particle has a compact internal structure, which can provide a high tap density and energy density, the porous aluminum gradient shell layer coated on the surface of the particle, the addition of aluminum ions occupies part of the sites of manganese ions, and the secondary particles are selectively combined with the primary particles, so that the secondary particles are no longer further tightened, a surface porous structure beneficial to electrolyte transport is formed, the stress change in the charging and discharging process can be relieved, the generation of lithium ion deintercalation-induced microcracks can be reduced, and thus the structural stability of the lithium-rich manganese-based positive electrode material is improved, and the lithium ion transport and diffusion can be effectively enhanced, and thus the rate performance of the positive electrode material is improved.

[0043] In the third aspect, the application provides a lithium-rich manganese-based positive electrode material, which is prepared by mixing the porous aluminum gradient lithium-rich manganese-based precursor with a lithium salt and then sintering.

[0044] The porous aluminum gradient lithium-rich manganese-based precursor is prepared by the preparation method in the first aspect or is the porous aluminum gradient lithium-rich manganese-based precursor in the second aspect.

[0045] In a fourth aspect, the present application provides a lithium ion battery, which comprises the lithium-rich manganese-based positive electrode material according to the third aspect.

[0046] Compared with the related technical solutions, the present application has at least the following beneficial effects:

[0047] (1) The preparation method according to the present application, by means of a conventional two-step co-precipitation reaction, on the basis of the original first co-precipitation reaction, replaces the nickel-cobalt-manganese ternary salt solution with a nickel-cobalt-manganese-aluminum quaternary salt solution to perform a second co-precipitation reaction, and then combines with process parameter adjustment to prepare an aluminum-gradient lithium-rich manganese-based precursor;

[0048] (2) The internal compactness of the porous aluminum-gradient lithium-rich manganese-based precursor particles according to the present application can provide a higher tap density and energy density, and the surface-coated porous aluminum-gradient shell layer occupies part of the sites of manganese ions, selectively combines with the primary particles, so that the secondary particles are no longer further tightened, forming a surface porous structure that is conducive to the transport of electrolyte. Such a porous structure can alleviate the stress change during the charging and discharging process, reduce the generation of lithium-ion deintercalation-induced microcracks, thereby improving the structural stability of the lithium-rich manganese-based positive electrode material, and also effectively enhance the transport and diffusion of lithium ions, thereby improving the rate performance of the positive electrode material;

[0049] (3) The preparation method according to the present application does not need to change the process and equipment additionally in the existing mature co-precipitation process, is simple to operate, and is conducive to industrial application.

[0050] Other aspects can be appreciated after reading and understanding the drawings and detailed description. BRIEF DESCRIPTION OF DRAWINGS

[0051] FIG. 1 is an SEM image of the porous aluminum-gradient lithium-rich manganese-based precursor prepared in Example 1. DETAILED DESCRIPTION

[0052] The technical solutions of the present application will be further described below in combination with the drawings and through specific embodiments.

[0053] In order to better illustrate the present application and facilitate the understanding of the technical solutions of the present application, the typical but non-limiting embodiments of the present application are as follows:

[0054] Example 1

[0055] The present embodiment provides a preparation method of a porous aluminum-gradient lithium-rich manganese-based precursor, which comprises the following steps:

[0056] Preparation of a nickel-cobalt-manganese ternary salt solution, a nickel-cobalt-manganese-aluminum quaternary salt solution, a lye, and a complexing agent solution; the molar ratio of Ni:Co:Mn in the nickel-cobalt-manganese ternary salt solution is 0.20:0.05:0.75; the total mass concentration of metal ions in the nickel-cobalt-manganese ternary salt solution is 90 g / L; the molar ratio of Ni:Co:Mn:Al in the nickel-cobalt-manganese-aluminum quaternary salt solution is 0.20:0.05:0.75:0.01; the total mass concentration of metal ions in the nickel-cobalt-manganese-aluminum quaternary salt solution is 90 g / L; the lye is a sodium hydroxide solution with a mass concentration of 32 wt%; and the complexing agent solution is an ammonia water solution with a mass concentration of 15 g / L;

[0057] A 100-L reaction kettle is charged with pure water, a lye, and a complexing agent as a reaction bottom solution; the pH value of the reaction bottom solution is 11.5; and the concentration of the complexing agent in the reaction bottom solution is 8 g / L.

[0058] The nickel-cobalt-manganese ternary salt solution, the lye, and the complexing agent solution are injected into the reaction bottom solution in parallel flow by a metering pump to perform a first co-precipitation reaction; the stirring speed of the first co-precipitation reaction is controlled to be 500 rpm, the temperature is controlled to be 55°C, and the pH value is controlled to be 10.0-11.5; after the median particle size of the particles reaches 7.5 μm, the feeding is stopped, the nickel-cobalt-manganese ternary salt solution is replaced with the nickel-cobalt-manganese-aluminum quaternary salt solution by a metering pump, and the second co-precipitation reaction is continued to be performed by injecting the lye and the complexing agent solution in parallel flow; the stirring speed of the second co-precipitation reaction is controlled to be 500 rpm, the temperature is controlled to be 55°C, and the pH value is controlled to be 8.5-10.0; and the feeding is stopped after the median particle size of the particles reaches 9.0 μm.

[0059] The slurry after the reaction is transferred to a suction filter bottle to perform suction filtration; the slurry is washed with the lye for 3 times and then washed with pure water for 3 times; and the solid material obtained after the suction filtration and washing is transferred to an oven to be dried at 100°C to finally obtain the porous aluminum gradient lithium-rich manganese-based precursor.

[0060] FIG. 1 shows an SEM image of the porous aluminum gradient lithium-rich manganese-based precursor prepared in this embodiment, and it can be seen that a loose porous aluminum-containing shell layer is formed on the surface of the obtained precursor.

[0061] Example 2

[0062] This embodiment provides a preparation method of a porous aluminum gradient lithium-rich manganese-based precursor, and the preparation method comprises the following steps:

[0063] A nickel-cobalt-manganese ternary salt solution, a nickel-cobalt-manganese-aluminum quaternary salt solution, a lye, and a complexing agent solution are prepared; the molar ratio of Ni:Co:Mn in the nickel-cobalt-manganese ternary salt solution is 0.30:0.05:0.65; the total mass concentration of metal ions in the nickel-cobalt-manganese ternary salt solution is 100 g / L; the molar ratio of Ni:Co:Mn:Al in the nickel-cobalt-manganese-aluminum quaternary salt solution is 0.30:0.05:0.65:0.005; the total mass concentration of metal ions in the nickel-cobalt-manganese-aluminum quaternary salt solution is 100 g / L; the lye is a sodium hydroxide solution with a mass concentration of 30 wt%; and the complexing agent solution is a sodium acetate solution with a mass concentration of 12 g / L.

[0064] A 100-L reaction kettle is charged with pure water, lye, and complexing agent as a reaction bottom liquid; the pH value of the reaction bottom liquid is 12.0; and the concentration of the complexing agent in the reaction bottom liquid is 6 g / L.

[0065] The nickel-cobalt-manganese ternary salt solution, the lye, and the complexing agent solution are injected into the reaction bottom liquid in parallel flow by a metering pump to perform a first co-precipitation reaction; the stirring speed of the first co-precipitation reaction is controlled to be 500 rpm, the temperature is 58°C, and the pH value is 9.5-11.0; after the median particle size of the particles reaches 9.0 μm, the feeding is stopped, the nickel-cobalt-manganese ternary salt solution is replaced with the nickel-cobalt-manganese-aluminum quaternary salt solution by a metering pump, and the second co-precipitation reaction is continued by injecting the lye and the complexing agent solution in parallel flow; the stirring speed of the second co-precipitation reaction is controlled to be 500 rpm, the temperature is 58°C, and the pH value is 8.5-9.5; and the feeding is stopped after the median particle size of the particles reaches 10.0 μm.

[0066] The slurry after the reaction is transferred to a suction filter bottle for suction filtration; the solid material obtained by suction washing is transferred to an oven and dried at 100°C; and a porous aluminum gradient lithium-rich manganese-based precursor is finally obtained.

[0067] Example 3

[0068] The present embodiment provides a preparation method of a porous aluminum gradient lithium-rich manganese-based precursor, which comprises the following steps:

[0069] Preparation of a nickel-cobalt-manganese ternary salt solution, a nickel-cobalt-manganese-aluminum quaternary salt solution, a lye, and a complexing agent solution; the molar ratio of Ni:Co:Mn in the nickel-cobalt-manganese ternary salt solution is 0.25:0.05:0.70; the total mass concentration of metal ions in the nickel-cobalt-manganese ternary salt solution is 105 g / L; the molar ratio of Ni:Co:Mn:Al in the nickel-cobalt-manganese-aluminum quaternary salt solution is 0.25:0.05:0.70:0.013; the total mass concentration of metal ions in the nickel-cobalt-manganese-aluminum quaternary salt solution is 105 g / L; the lye is a sodium hydroxide solution with a mass concentration of 34 wt%; the complexing agent solution is ammonia water with a mass concentration of 16 g / L;

[0070] In a 100 L reaction kettle, pure water, lye, and complexing agent are added as a reaction bottom liquid; the pH value of the reaction bottom liquid is 11.5; the concentration of the complexing agent in the reaction bottom liquid is 8 g / L;

[0071] The nickel-cobalt-manganese ternary salt solution, lye, and complexing agent solution are injected into the reaction bottom liquid in parallel through a metering pump to perform a first co-precipitation reaction; the stirring speed of the first co-precipitation reaction is controlled to be 600 rpm, the temperature is 58℃, and the pH value is 10.0-11.5; after the median particle size of the particles reaches 7.0 μm, the feeding is stopped, the nickel-cobalt-manganese ternary salt solution is replaced with the nickel-cobalt-manganese-aluminum quaternary salt solution through a metering pump, and the second co-precipitation reaction is continued by injecting the lye and the complexing agent solution in parallel; the stirring speed of the second co-precipitation reaction is controlled to be 600 rpm, the temperature is 58℃, and the pH value is 9.0-10.0; after the median particle size of the particles reaches 8.0 μm, the feeding is stopped;

[0072] The slurry after the reaction is transferred to a suction filter bottle for suction filtration; the solid material obtained by suction washing is transferred to an oven for drying at 100℃, and a porous aluminum gradient lithium-rich manganese-based precursor is finally obtained.

[0073] Example 4

[0074] The embodiment provides a preparation method of a porous aluminum gradient lithium-rich manganese-based precursor, and the difference from the embodiment 1 is that, in the second co-precipitation reaction, the feeding is stopped after the median particle size of the particles reaches 7.8 μm, that is, the difference between the second target particle size D502 and the first target particle size D501 is only 0.3 μm.

[0075] Example 5

[0076] The embodiment provides a preparation method of a porous aluminum gradient lithium-rich manganese-based precursor, and the difference from the embodiment 1 is that, in the second coprecipitation reaction, feeding is stopped after the median particle size of the particles reaches 11 mu m, that is, the difference between the second target particle size D502 and the first target particle size D501 is up to 3.5 mu m.

[0077] Comparative example 1

[0078] The comparative example provides a preparation method of a lithium-rich manganese-based precursor, and the difference from the embodiment 1 is that only the first coprecipitation reaction is performed, and the nickel-cobalt-manganese ternary salt solution is not replaced by a nickel-cobalt-manganese-aluminum quaternary salt solution.

[0079] The specific content is as follows:

[0080] The nickel-cobalt-manganese ternary salt solution, the lye and the complexing agent solution are prepared, the molar ratio of Ni:Co:Mn in the nickel-cobalt-manganese ternary salt solution is 0.20:0.05:0.75, the total mass concentration of metal ions in the nickel-cobalt-manganese ternary salt solution is 90 g / L, the lye is a sodium hydroxide solution with a mass concentration of 32 wt%, and the complexing agent solution is ammonia water with a mass concentration of 15 g / L.

[0081] Pure water, lye and complexing agent are added into a 100 L reaction kettle as a reaction bottom liquid, the pH value of the reaction bottom liquid is 11.5, and the concentration of the complexing agent in the reaction bottom liquid is 8 g / L.

[0082] The nickel-cobalt-manganese ternary salt solution, the lye and the complexing agent solution are injected into the reaction bottom liquid in parallel through a metering pump to perform the first coprecipitation reaction, the stirring speed of the first coprecipitation reaction is controlled to be 500 rpm, the temperature is 55 DEG C, the pH value is 11.0-11.5, and feeding is stopped after the median particle size of the particles reaches 9.0 mu m.

[0083] The slurry after the reaction is transferred to a suction filter bottle for suction filtration, washed with the lye for three times and then washed with pure water for three times, and then the solid material obtained through the suction filtration and washing is transferred to an oven and dried at 100 DEG C, so that a lithium-rich manganese-based precursor is finally obtained.

[0084] The lithium-rich manganese-based precursors obtained through the above embodiment and the comparative example are uniformly mixed with lithium carbonate according to a molar ratio of 1:1.5, sintered at 900 DEG C in an air atmosphere for 12 h, the obtained lithium-rich manganese-based positive electrode materials are prepared into lithium ion button batteries, and the specific capacity and the cycle capacity retention rate are tested, and the test results are shown in Table 1.

[0085] Table 1

[0086] In summary, the preparation method described in the application is prepared by two-step co-precipitation reaction, and the porous aluminum gradient lithium-rich manganese-based precursor particles prepared by the method include a dense nickel-cobalt-manganese inner core and a surface-coated loose porous aluminum concentration gradient shell. The inner core is dense, has a high tap density and energy density, and the porous aluminum shell formed on the surface enhances the transmission and diffusion of lithium ions, thereby improving the rate performance of the positive electrode material. In addition, the surface porous structure can also relieve the stress change during charging and discharging, reduce the generation of lithium ion deintercalation-induced microcracks, and improve the structural stability of the positive electrode material.

[0087] The above embodiments are used to illustrate the detailed structural features of the application, but the application is not limited to the above detailed structural features, i.e., it does not mean that the application must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the application, equivalent replacement of the components selected by the application, addition of auxiliary components, selection of specific modes, etc., all fall within the protection scope and disclosure scope of the application.

[0088] The above describes the preferred embodiments of the application, but the application is not limited to the specific details in the above embodiments. Within the technical concept scope of the application, various simple modifications can be made to the technical solutions of the application, and these simple modifications all belong to the protection scope of the application.

[0089] In addition, it should be noted that each specific technical feature described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the application will not further describe various possible combination manners.

[0090] In addition, various different embodiments of the application can also be combined in any manner, as long as it does not deviate from the idea of the application, and it should also be considered as disclosed by the application.

Claims

1. A method for preparing a porous aluminum gradient lithium-rich manganese-based precursor, comprising the following steps: a first co-precipitation reaction is performed by injecting a nickel-cobalt-manganese ternary salt solution, an alkali solution and a complexing agent solution into a reaction bottom solution in a concurrent manner, after a first target particle size D501 is reached, the nickel-cobalt-manganese ternary salt solution is replaced by a nickel-cobalt-manganese-aluminum quaternary salt solution, and the injection of the alkali solution and the complexing agent solution is continued in a concurrent manner, a second co-precipitation reaction is performed, after a second target particle size D502 is reached, solid-liquid separation is performed to obtain a porous aluminum gradient lithium-rich manganese-based precursor; wherein the molar ratio of Ni:Co:Mn in the nickel-cobalt-manganese ternary salt solution is x1:y1:z1; x1+y1+z1=1, and z1≥0.6; the molar ratio of Ni:Co:Mn:Al in the nickel-cobalt-manganese-aluminum quaternary salt solution is x2:y2:z2:w; x2+y2+z2=1, z2≥0.6, and 0.002≤w≤0.

05.

2. The production method according to claim 1, wherein The molar ratio of Ni:Co:Mn in the nickel-cobalt-manganese ternary salt solution is consistent with the molar ratio of Ni:Co:Mn in the nickel-cobalt-manganese-aluminum quaternary salt solution, i.e., x1:y1:z1=x2:y2:z2; Optionally, the total mass concentration of metal ions in the nickel-cobalt-manganese ternary salt solution is consistent with the total mass concentration of metal ions in the nickel-cobalt-manganese-aluminum quaternary salt solution, both being 85-115 g / L.

3. The production method according to claim 1 or 2, wherein, The alkali solution comprises a sodium hydroxide solution and / or a potassium hydroxide solution; Optionally, the mass concentration of the alkali solution is 30-35 wt%.

4. The production process according to any one of claims 1 to 3, wherein The complexing agent in the complexing agent solution comprises any one or a combination of at least two of ammonia, sodium acetate, ammonium oxalate or EDTA; Optionally, the mass concentration of the complexing agent solution is 5-40 g / L.

5. The production process according to any one of claims 1 to 4, wherein The reaction bottom solution comprises pure water, an alkali solution and a complexing agent; Optionally, the pH value of the reaction bottom solution is 11.0-12.5; Optionally, the concentration of the complexing agent in the reaction bottom solution is 2-10 g / L.

6. The method of making according to any one of claims 1-5, wherein, The stirring speed of the first co-precipitation reaction is 400-800 rpm; Optionally, the temperature of the first co-precipitation reaction is 50-60°C; Optionally, the pH value of the first co-precipitation reaction is 10.0-12.0; Optionally, the first target particle size D501 of the first co-precipitation reaction is 5-10 μm.

7. The method of making according to any one of claims 1-6, wherein, The stirring speed of the second co-precipitation reaction is 400-800 rpm; Optionally, the temperature of the second co-precipitation reaction is 50-60°C; Optionally, the pH value of the second co-precipitation reaction is 8.0-10.0; Optionally, the difference between the second target particle size D502 and the first target particle size D501 is 0.5-3 μm.

8. The method of making according to any one of claims 1-7, wherein, The solid-liquid separation comprises suction filtration.

9. The method of making according to any one of claims 1-8, wherein, After the solid-liquid separation, washing and drying are sequentially performed; Optionally, the washing comprises washing 3-5 times with an alkali solution first, and then washing 3-5 times with pure water; Optionally, the temperature of the drying is 80-130°C.

10. The production method according to claim 1, wherein, The method for preparing a porous aluminum gradient lithium-rich manganese-based precursor comprises the following steps: Preparation of a nickel-cobalt-manganese ternary salt solution, a nickel-cobalt-manganese-aluminum quaternary salt solution, a lye solution, and a complexing agent solution; the molar ratio of Ni:Co:Mn in the nickel-cobalt-manganese ternary salt solution is x1:y1:z1; x1+y1+z1=1, z1≥0.6; the molar ratio of Ni:Co:Mn:Al in the nickel-cobalt-manganese-aluminum quaternary salt solution is x2:y2:z2:w; x2+y2+z2=1, z2≥0.6, 0.002≤w≤0.05; and x1:y1:z1=x2:y2:z2; the total mass concentration of metal ions in the nickel-cobalt-manganese ternary salt solution and the total mass concentration of metal ions in the nickel-cobalt-manganese-aluminum quaternary salt solution are consistent, both being 85-115 g / L; the lye solution comprises a sodium hydroxide solution and / or a potassium hydroxide solution; the mass concentration of the lye solution is 30-35 wt%; the complexing agent in the complexing agent solution comprises any one or a combination of at least two of ammonia, sodium acetate, ammonium oxalate, or EDTA; and the mass concentration of the complexing agent solution is 5-40 g / L. In a reaction kettle, pure water, lye, and a complexing agent are added as a reaction bottom solution, the pH value of the reaction bottom solution is 11.0-12.5, and the concentration of the complexing agent in the reaction bottom solution is 2-10 g / L. The nickel-cobalt-manganese ternary salt solution, the lye solution, and the complexing agent solution are injected into the reaction bottom solution in parallel flow to perform a first co-precipitation reaction, the stirring speed of the first co-precipitation reaction is controlled to be 400-800 rpm, the temperature is controlled to be 50-60℃, and the pH value is controlled to be 10.0-12.0; the first target particle size D501 is set to be 5-10 μm, the feeding is stopped after the median particle size of the particles reaches 5-10 μm, the nickel-cobalt-manganese ternary salt solution is replaced with the nickel-cobalt-manganese-aluminum quaternary salt solution, and the lye solution and the complexing agent solution are continuously injected in parallel flow to perform a second co-precipitation reaction, the stirring speed of the second co-precipitation reaction is controlled to be 400-800 rpm, the temperature is controlled to be 50-60℃, and the pH value is controlled to be 8.0-10.0; the feeding is stopped after the median particle size of the particles meets the difference between the second target particle size D502 and the first target particle size D501, which is 0.5-3 μm. The slurry after the reaction is subjected to suction filtration, washed with the lye solution for 3-5 times, washed with pure water for 3-5 times, and then the solid material obtained by the suction filtration and washing is transferred to an oven for drying at 100℃, and finally a porous aluminum gradient lithium-rich manganese-based precursor is obtained.

11. A porous aluminum gradient lithium-rich manganese-based precursor prepared by the preparation method of any one of claims 1-10, the porous aluminum gradient lithium-rich manganese-based precursor comprising a compact nickel-cobalt-manganese inner core and a surface-coated loose porous aluminum concentration gradient shell layer.

12. A lithium-rich manganese-based positive electrode material obtained by uniformly mixing the porous aluminum gradient lithium-rich manganese-based precursor with a lithium salt and sintering. wherein, The porous aluminum gradient lithium-rich manganese-based precursor is prepared by the preparation method of any one of claims 1-10, or the porous aluminum gradient lithium-rich manganese-based precursor is the porous aluminum gradient lithium-rich manganese-based precursor of claim 11.

13. A lithium-ion battery comprising the lithium-rich manganese-based cathode material of claim 12.

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