A lithium-rich manganese-based precursor with a porous aluminum gradient and its preparation method and application

Abstract

The present invention provides a lithium-rich manganese-based precursor with a porous aluminum gradient, and a preparation method and application thereof. The preparation method adopts a two-step co-precipitation reaction to prepare lithium-rich manganese-based precursor particles with a porous aluminum gradient, including a dense nickel-cobalt-manganese core and a loose porous aluminum concentration gradient shell coated on the surface. The precursor particles are dense inside and have a high tap density and energy density. The porous aluminum-containing shell formed on the surface enhances the transmission and diffusion of lithium ions, thereby improving the rate performance of the positive electrode material. The porous surface structure 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

Technical Field

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

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

[0003] Currently, the most common approach to optimizing the performance of lithium-rich manganese cathode materials is to adjust the precursor grain boundary structure and chemical structure during the precursor synthesis stage. Studies have shown that while element doping, morphology control, and surface coating can stabilize the structure and inhibit harmful phase changes to a certain extent, thereby improving the capacity retention of the cathode material during cycling, these improvements in cycling performance also reduce the initial capacity, which is detrimental to improving the electrochemical performance of the cathode material and prevents both cycling and rate performance from being balanced.

[0004] CN111628149A discloses a gradient-doped high-nickel ternary cathode material and its preparation method, comprising: first preparing the core of a nickel-cobalt-manganese ternary precursor; when the particles grow to 85%-95% of the target particle size, gradiently adding a doping solution to the reactor; adjusting the feed flow rate to gradually increase; obtaining particles of the ternary precursor of the target particle size; and achieving a "shell"-like doping by doping in the middle of the reaction. The positive electrode material cycle retention rate corresponding to the ternary precursor prepared by this process is improved, but there is still the problem of low material specific capacity, which cannot take into account both high cycle retention rate and specific capacity.

[0005] CN107968202A discloses a positive electrode material with an aluminum-containing nickel-cobalt-manganese core-shell structure and a preparation method thereof, comprising: feeding a mixed solution of a nickel source and a cobalt source together with a manganese source solution, and mixing with a precipitant and a complexing agent to cause a coprecipitation reaction; stopping the 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, alternately doping manganese and aluminum by coprecipitation to obtain a ternary precursor of an aluminum-containing nickel-cobalt-manganese core-shell structure. The positive electrode material corresponding to the ternary precursor prepared by this process has a high cycle retention rate, but there is still a problem of low material specific capacity. As the number of cycles increases, the material charge and discharge specific capacity decreases significantly, and it is still impossible to take into account both a high cycle retention rate and specific capacity.

[0006] Therefore, how to provide a preparation method for lithium-rich manganese-based precursors that can effectively improve the cycle performance while maintaining the original high-rate performance, while being simple to operate and applicable on a large scale, is a technical problem that needs to be solved urgently. Summary of the Invention

[0007] In view of the problems existing in the prior art, the present invention provides a lithium-rich manganese-based precursor with a porous aluminum gradient, and a preparation method and application thereof. The preparation method is a two-step co-precipitation reaction, and the obtained lithium-rich manganese-based precursor particles with a porous aluminum gradient include a dense nickel-cobalt-manganese core and a loose porous aluminum concentration gradient shell coated on the surface. The interior is dense, with high tap density and energy density. The porous aluminum-containing shell formed on the surface enhances the transmission and diffusion of lithium ions, thereby improving the rate performance of the positive electrode material; and the porous surface structure can also alleviate the stress changes during the charge and discharge process, reduce the generation of microcracks induced by lithium ion deintercalation, and improve the structural stability of the positive electrode material.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] One of the objectives of the present invention is to provide a method for preparing a lithium-rich manganese-based precursor having a porous aluminum gradient, the preparation method comprising the following steps:

[0010] A nickel-cobalt-manganese ternary salt solution, an alkali solution, and a complexing agent solution are injected into the reaction base liquid in parallel 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 base liquid in parallel 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 lithium-rich manganese-based precursor with a porous aluminum gradient;

[0011] Among them, 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.

[0012] The preparation method of the present invention adopts a conventional two-step coprecipitation reaction. On the basis of the original first coprecipitation reaction, the nickel-cobalt-manganese ternary salt solution is replaced with a nickel-cobalt-manganese-aluminum quaternary salt solution, and a second coprecipitation reaction is carried out. Then, combined with the adjustment of process parameters, a lithium-rich manganese-based precursor with an aluminum gradient is prepared. Moreover, the preparation method of the present invention does not require additional changes to the process and equipment, is simple to operate, and is conducive to industrial application.

[0013] As a preferred technical solution of the present invention, 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 invention, the nickel-cobalt-manganese ternary salt solution in the first coprecipitation reaction and the nickel-cobalt-manganese-aluminum quaternary salt solution in the second coprecipitation reaction are required to have the same nickel-cobalt-manganese molar ratio, and only the aluminum concentration is different, which can highlight the performance improvement caused by the aluminum gradient.

[0015] Preferably, 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 are not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0016] Preferably, the alkali solution comprises sodium hydroxide solution and / or potassium hydroxide solution.

[0017] Preferably, the mass concentration of the alkali solution is 30-35wt%, such as 30wt%, 31wt%, 32wt%, 33wt%, 34wt% or 35wt%, etc., but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

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

[0019] Preferably, the mass concentration of the complexing agent solution is 5-40 g / L, for example, 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 is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0020] As a preferred technical solution of the present invention, the reaction base liquid includes pure water, alkaline solution and a complexing agent.

[0021] Preferably, the pH value of the reaction base solution is 11.0-12.5, for example, 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 is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0022] Preferably, the concentration of the complexing agent in the reaction base solution is 2-10 g / L, for example, 2 g / L, 4 g / L, 6 g / L, 8 g / L or 10 g / L, etc., but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0023] As a preferred technical solution of the present invention, the stirring speed of the first coprecipitation 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 is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0024] Preferably, the temperature of the first coprecipitation reaction is 50-60°C, for example, 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 is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0025] Preferably, the pH value of the first coprecipitation reaction is 10.0-12.0, for example, 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 is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0026] Preferably, the first target particle size D501 of the first coprecipitation 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 is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0027] As a preferred technical solution of the present invention, the stirring speed of the second coprecipitation 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 is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0028] Preferably, the temperature of the second coprecipitation reaction is 50-60°C, for example, 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 is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0029] Preferably, the pH value of the second coprecipitation 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 is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0030] Preferably, 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 is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0031] In the present invention, the difference between the second target particle size D502 and the first target particle size D501 is 0.5-3μm. If the difference between the two is too small, that is, the porous aluminum gradient shell is thin, it is not conducive to the formation of a porous structure on the surface, and the stress changes during the charge and discharge process cannot be effectively alleviated, resulting in the positive electrode material's cycle stability not being significantly improved; if the difference between the two is too large, that is, the porous aluminum gradient shell is thick, then too much aluminum element is introduced, resulting in a significant decrease in the charge and discharge capacity of the positive electrode material, and the thicker loose porous shell on the surface greatly reduces the tap density and energy density, resulting in a significant deterioration in the electrochemical performance.

[0032] As a preferred technical solution of the present invention, the solid-liquid separation includes suction filtration.

[0033] Preferably, after the solid-liquid separation, washing and drying are also performed in sequence.

[0034] Preferably, the washing comprises: first washing with alkaline solution for 3-5 times, and then washing with pure water for 3-5 times.

[0035] Preferably, the drying temperature is 80-130°C, such as 80°C, 90°C, 100°C, 110°C, 120°C or 130°C, etc., but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0036] As a preferred technical solution of the present invention, the preparation method comprises the following steps:

[0037] Prepare a nickel-cobalt-manganese ternary salt solution, a nickel-cobalt-manganese-aluminum quaternary salt solution, an alkali 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 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; the alkali solution includes sodium hydroxide solution and / or potassium hydroxide solution; the mass concentration of the alkali solution is 30-35 wt%; the complexing agent in the complexing agent solution includes any one of ammonia, sodium acetate, ammonium oxalate or EDTA or a combination of at least two thereof; the mass concentration of the complexing agent solution is 5-40 g / L;

[0038] Pure water, alkali solution and complexing agent are added into the reaction kettle as a reaction base liquid, wherein the pH value of the reaction base liquid is 11.0-12.5; and the concentration of the complexing agent in the reaction base liquid is 2-10 g / L;

[0039] A nickel-cobalt-manganese ternary salt solution, an alkali solution, and a complexing agent solution are injected into the reaction base solution in parallel to carry out a first coprecipitation reaction, wherein the stirring speed of the first coprecipitation reaction is controlled to be 400-800 rpm, the temperature is controlled to be 50-60° C., and the pH value is controlled to be 10.0-12.0; a first target particle size D501 is set to 5-10 μm, and after the median particle size of the particles reaches 5-10 μm, feeding is stopped, and the nickel-cobalt-manganese ternary salt solution is replaced with a nickel-cobalt-manganese-aluminum quaternary salt solution, which is continued to be injected in parallel with the alkali solution and the complexing agent solution to carry out a second coprecipitation reaction, wherein the stirring speed of the second coprecipitation reaction is controlled to be 400-800 rpm, the temperature is controlled to be 50-60° C., and the pH value is controlled to be 8.0-10.0; feeding is stopped when the median particle size of the particles satisfies the difference between the second target particle size D502 and the first target particle size D501, which is 0.5-3 μm;

[0040] The slurry after the reaction is filtered, washed with alkaline solution for 3-5 times, and then washed with pure water for 3-5 times. The solid material obtained by filtration and washing is then transferred to an oven and dried at 100°C to finally obtain a lithium-rich manganese-based precursor with a porous aluminum gradient.

[0041] The second object of the present invention is to provide a lithium-rich manganese-based precursor with a porous aluminum gradient. The lithium-rich manganese-based precursor with a porous aluminum gradient is prepared by the preparation method as described in one of the objects. The lithium-rich manganese-based precursor with a porous aluminum gradient includes a dense nickel-cobalt-manganese core and a loose porous aluminum concentration gradient shell coated on the surface.

[0042] The interior of the lithium-rich manganese-based precursor particles with a porous aluminum gradient described in the present invention is dense and can provide a higher tap density and energy density. The porous aluminum gradient shell coated on the surface, the addition of aluminum ions occupies some manganese ion sites, and selectively combines with the primary particles, so that the secondary particles no longer tighten further, forming a surface porous structure that is conducive to electrolyte transport. This porous structure can alleviate stress changes during charging and discharging, reduce the generation of microcracks induced by lithium ion deintercalation, thereby improving the structural stability of the lithium-rich manganese-based positive electrode material, and at the same time can effectively enhance the transmission and diffusion of lithium ions, thereby improving the rate performance of the positive electrode material.

[0043] A third object of the present invention is to provide a lithium-rich manganese-based positive electrode material, wherein a lithium-rich manganese-based precursor having a porous aluminum gradient is uniformly mixed with a lithium salt, and the lithium-rich manganese-based positive electrode material is obtained by sintering;

[0044] Among them, the lithium-rich manganese-based precursor with a porous aluminum gradient is prepared by the preparation method described in purpose one, or the lithium-rich manganese-based precursor with a porous aluminum gradient is the lithium-rich manganese-based precursor with a porous aluminum gradient described in purpose two.

[0045] A fourth object of the present invention is to provide a lithium-ion battery, wherein the lithium-ion battery comprises the lithium-rich manganese-based positive electrode material as described in the third object.

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

[0047] (1) The preparation method of the present invention adopts a conventional two-step coprecipitation reaction. On the basis of the original first coprecipitation reaction, the nickel-cobalt-manganese ternary salt solution is replaced with a nickel-cobalt-manganese-aluminum quaternary salt solution, and a second coprecipitation reaction is performed. Then, combined with the adjustment of process parameters, a lithium-rich manganese-based precursor with an aluminum gradient is prepared;

[0048] (2) The porous aluminum gradient lithium-rich manganese-based precursor particles of the present invention are densely packed and can provide higher tap density and energy density. The porous aluminum gradient shell layer coated on the surface of the precursor particles occupies some of the manganese ion sites and 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 electrolyte transport. This porous structure can alleviate stress changes during charging and discharging, reduce the generation of microcracks induced by lithium ion deintercalation, thereby improving the structural stability of the lithium-rich manganese-based positive electrode material, and can also effectively enhance the transmission and diffusion of lithium ions, thereby improving the rate performance of the positive electrode material;

[0049] (3) The preparation method of the present invention does not require additional changes to the process and equipment in the existing mature co-precipitation process, is simple to operate, and is conducive to industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is an SEM image of the lithium-rich manganese-based precursor with a porous aluminum gradient prepared in Example 1. DETAILED DESCRIPTION

[0051] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0052] To better illustrate the present invention and facilitate understanding of the technical solutions of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0053] Example 1

[0054] This embodiment provides a method for preparing a lithium-rich manganese-based precursor with a porous aluminum gradient, the preparation method comprising the following steps:

[0055] A nickel-cobalt-manganese ternary salt solution, a nickel-cobalt-manganese-aluminum quaternary salt solution, an alkali solution, and a 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 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 alkali solution 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;

[0056] Pure water, alkali solution and complexing agent were added to a 100 L reactor as a reaction base liquid, wherein the pH value of the reaction base liquid was 11.5 and the concentration of the complexing agent in the reaction base liquid was 8 g / L;

[0057] A nickel-cobalt-manganese ternary salt solution, an alkali solution, and a complexing agent solution are injected into the reaction base liquid in parallel through a metering pump to perform a first coprecipitation reaction, wherein the stirring speed of the first coprecipitation 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, and the nickel-cobalt-manganese ternary salt solution is replaced with a nickel-cobalt-manganese-aluminum quaternary salt solution through a metering pump, and the solution is continuously injected into the reaction base liquid in parallel with the alkali solution and the complexing agent solution to perform a second coprecipitation reaction, wherein the stirring speed of the second coprecipitation 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 after the median particle size of the particles reaches 9.0 μm, the feeding is stopped;

[0058] The slurry after the reaction was transferred to a suction filtration bottle for filtration, first washed with alkaline solution 3 times, then washed with pure water 3 times, and then the solid material obtained by filtration and washing was transferred to an oven and dried at 100°C to finally obtain a lithium-rich manganese-based precursor with a porous aluminum gradient.

[0059] Figure 1 The SEM image of the lithium-rich manganese-based precursor with a porous aluminum gradient prepared in this embodiment is shown. It can be seen that a loose porous aluminum-containing shell layer is formed on the surface of the obtained precursor.

[0060] Example 2

[0061] This embodiment provides a method for preparing a lithium-rich manganese-based precursor with a porous aluminum gradient, the preparation method comprising the following steps:

[0062] A nickel-cobalt-manganese ternary salt solution, a nickel-cobalt-manganese-aluminum quaternary salt solution, an alkali solution, 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 alkali solution is a sodium hydroxide solution with a mass concentration of 30 wt%; and the complexing agent solution is sodium acetate with a mass concentration of 12 g / L.

[0063] Pure water, alkali solution and complexing agent were added to a 100 L reactor as a reaction base liquid, wherein the pH value of the reaction base liquid was 12.0 and the concentration of the complexing agent in the reaction base liquid was 6 g / L;

[0064] A nickel-cobalt-manganese ternary salt solution, an alkali solution, and a complexing agent solution are injected into the reaction base liquid in parallel through a metering pump to perform a first coprecipitation reaction, wherein the stirring speed of the first coprecipitation reaction is controlled to be 500 rpm, the temperature is controlled to be 58° C., and the pH value is controlled to be 9.5-11.0; after the median particle size of the particles reaches 9.0 μm, the feeding is stopped, and the nickel-cobalt-manganese ternary salt solution is replaced with a nickel-cobalt-manganese-aluminum quaternary salt solution through a metering pump, and the solution is continuously injected into the reaction base liquid in parallel with the alkali solution and the complexing agent solution to perform a second coprecipitation reaction, wherein the stirring speed of the second coprecipitation reaction is controlled to be 500 rpm, the temperature is controlled to be 58° C., and the pH value is controlled to be 8.5-9.5; after the median particle size of the particles reaches 10.0 μm, the feeding is stopped;

[0065] The slurry after the reaction was transferred to a suction filtration bottle for filtration, first washed with alkaline solution 3 times, then washed with pure water 3 times, and then the solid material obtained by filtration and washing was transferred to an oven and dried at 100°C to finally obtain a lithium-rich manganese-based precursor with a porous aluminum gradient.

[0066] Example 3

[0067] This embodiment provides a method for preparing a lithium-rich manganese-based precursor with a porous aluminum gradient, the preparation method comprising the following steps:

[0068] A nickel-cobalt-manganese ternary salt solution, a nickel-cobalt-manganese-aluminum quaternary salt solution, an alkali solution, and a complexing agent solution are prepared; 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 alkali solution is a sodium hydroxide solution with a mass concentration of 34 wt%; and the complexing agent solution is ammonia water with a mass concentration of 16 g / L;

[0069] Pure water, alkali solution and complexing agent were added to a 100 L reactor as a reaction base liquid, wherein the pH value of the reaction base liquid was 11.5 and the concentration of the complexing agent in the reaction base liquid was 8 g / L;

[0070] A nickel-cobalt-manganese ternary salt solution, an alkali solution, and a complexing agent solution are injected into the reaction base liquid in parallel through a metering pump to perform a first coprecipitation reaction, wherein the stirring speed of the first coprecipitation reaction is controlled to be 600 rpm, the temperature is controlled to be 58° C., and the pH value is controlled to be 10.0-11.5; after the median particle size of the particles reaches 7.0 μm, the feeding is stopped, and the nickel-cobalt-manganese ternary salt solution is replaced with a nickel-cobalt-manganese-aluminum quaternary salt solution through a metering pump, and the solution is continuously injected into the reaction base liquid in parallel with the alkali solution and the complexing agent solution to perform a second coprecipitation reaction, wherein the stirring speed of the second coprecipitation reaction is controlled to be 600 rpm, the temperature is controlled to be 58° C., and the pH value is controlled to be 9.0-10.0; after the median particle size of the particles reaches 8.0 μm, the feeding is stopped;

[0071] The slurry after the reaction was transferred to a suction filtration bottle for filtration, first washed with alkaline solution 3 times, then washed with pure water 3 times, and then the solid material obtained by filtration and washing was transferred to an oven and dried at 100°C to finally obtain a lithium-rich manganese-based precursor with a porous aluminum gradient.

[0072] Example 4

[0073] This embodiment provides a preparation method of a lithium-rich manganese-based precursor with a porous aluminum gradient. Compared with Example 1, the only difference 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.

[0074] Example 5

[0075] This embodiment provides a preparation method of a lithium-rich manganese-based precursor with a porous aluminum gradient. Compared with Example 1, the only difference is that: in the second co-precipitation reaction, the feeding is stopped after the median particle size of the particles reaches 11 μm, that is, the difference between the second target particle size D502 and the first target particle size D501 is as high as 3.5 μm.

[0076] Comparative Example 1

[0077] This comparative example provides a method for preparing a lithium-rich manganese-based precursor. Compared with Example 1, the only difference is that only the first coprecipitation reaction is performed, and the nickel-cobalt-manganese ternary salt solution is no longer replaced with a nickel-cobalt-manganese-aluminum quaternary salt solution;

[0078] The specific contents are as follows:

[0079] A nickel-cobalt-manganese ternary salt solution, an alkali solution, and a 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 alkali solution 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;

[0080] Pure water, alkali solution and complexing agent were added to a 100 L reactor as a reaction base liquid, wherein the pH value of the reaction base liquid was 11.5 and the concentration of the complexing agent in the reaction base liquid was 8 g / L;

[0081] The nickel-cobalt-manganese ternary salt solution, the alkali solution, and the complexing agent solution were injected into the reaction base liquid in parallel by a metering pump to carry out a first coprecipitation reaction. The stirring speed of the first coprecipitation reaction was controlled at 500 rpm, the temperature was 55° C., and the pH value was 11.0-11.5. When the median particle size of the particles reached 9.0 μm, the feeding was stopped.

[0082] The slurry after the reaction was transferred to a suction filtration bottle for filtration, first washed with alkaline solution 3 times, then washed with pure water 3 times, and then the solid material obtained by filtration and washing was transferred to an oven and dried at 100°C to finally obtain a lithium-rich manganese-based precursor.

[0083] The lithium-rich manganese-based precursors prepared in the above examples and comparative examples were uniformly mixed with lithium carbonate at a molar ratio of 1:1.5, and sintered at 900°C in an air atmosphere for 12 hours. The obtained lithium-rich manganese-based positive electrode materials were prepared into lithium-ion button batteries, and the specific capacity and cycle capacity retention rate were tested respectively. The test results are shown in Table 1.

[0084] Table 1

[0085]

[0086]

[0087] In summary, the preparation method of the present invention adopts a two-step co-precipitation reaction to prepare porous aluminum gradient lithium-rich manganese-based precursor particles, which include a dense nickel-cobalt-manganese core and a loose porous aluminum concentration gradient shell coated on the surface. The interior is dense and has a high tap density and energy density. The porous aluminum-containing shell formed on the surface enhances the transmission and diffusion of lithium ions, thereby improving the rate performance of the positive electrode material; and the porous surface structure can also alleviate the stress changes during the charge and discharge process, reduce the generation of microcracks induced by lithium ion deintercalation, and improve the structural stability of the positive electrode material.

[0088] While the present invention is described through the above-described embodiments to illustrate the detailed structural features of the present invention, the present invention is not limited to these detailed structural features, nor does it necessarily rely on these detailed structural features for implementation. Those skilled in the art should understand that any improvements to the present invention, equivalent replacements for selected components, additions of auxiliary components, and selection of specific embodiments, etc., fall within the scope of protection and disclosure of the present invention.

[0089] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0090] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0091] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for preparing a lithium-rich manganese-based precursor with a porous aluminum gradient, characterized in that: The preparation method comprises the following steps: A nickel-cobalt-manganese ternary salt solution, an alkali solution, and a complexing agent solution are injected into the reaction base liquid in parallel 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 base liquid in parallel 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 lithium-rich manganese-based precursor with a porous aluminum gradient; 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; 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; The first target particle size D501 of the first coprecipitation reaction is 5-10 μm; the difference between the second target particle size D502 and the first target particle size D501 is 0.5-3 μm.

2. The preparation method according to claim 1, characterized in that 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.

3. The preparation method according to claim 1, characterized in that The alkali solution includes sodium hydroxide solution and / or potassium hydroxide solution; the mass concentration of the alkali solution is 30-35wt%.

4. The preparation method according to claim 1, characterized in that The complexing agent in the complexing agent solution includes any one of ammonia water, sodium acetate, ammonium oxalate or EDTA, or a combination of at least two thereof; the mass concentration of the complexing agent solution is 5-40 g / L.

5. The preparation method according to claim 1, characterized in that The reaction base liquid comprises pure water, alkali solution and a complexing agent.

6. The preparation method according to claim 5, characterized in that The pH value of the reaction bottom liquid is 11.0-12.

5.

7. The preparation method according to claim 5, characterized in that The concentration of the complexing agent in the reaction base liquid is 2-10 g / L.

8. The preparation method according to claim 1, characterized in that The stirring speed of the first coprecipitation reaction is 400-800 rpm.

9. The preparation method according to claim 1, characterized in that The temperature of the first coprecipitation reaction is 50-60°C.

10. The preparation method according to claim 1, characterized in that The pH value of the first coprecipitation reaction is 10.0-12.

0.

11. The preparation method according to claim 1, characterized in that The stirring speed of the second coprecipitation reaction is 400-800 rpm.

12. The preparation method according to claim 1, characterized in that The temperature of the second coprecipitation reaction is 50-60°C.

13. The preparation method according to claim 1, characterized in that The pH value of the second coprecipitation reaction is 8.0-10.

0.

14. The preparation method according to claim 1, characterized in that The solid-liquid separation includes suction filtration.

15. The preparation method according to claim 1, characterized in that After the solid-liquid separation, washing and drying are performed in sequence.

16. The preparation method according to claim 15, characterized in that The washing comprises: first washing with alkaline solution for 3-5 times, and then washing with pure water for 3-5 times.

17. The preparation method according to claim 15, characterized in that The drying temperature is 80-130°C.

18. The preparation method according to claim 1, characterized in that The preparation method comprises the following steps: Prepare a nickel-cobalt-manganese ternary salt solution, a nickel-cobalt-manganese-aluminum quaternary salt solution, an alkali 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 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; the alkali solution includes sodium hydroxide solution and / or potassium hydroxide solution; the mass concentration of the alkali solution is 30-35 wt%; the complexing agent in the complexing agent solution includes any one of ammonia, sodium acetate, ammonium oxalate or EDTA or a combination of at least two thereof; the mass concentration of the complexing agent solution is 5-40 g / L; Pure water, alkali solution and complexing agent are added into the reaction kettle as a reaction base liquid, wherein the pH value of the reaction base liquid is 11.0-12.5; and the concentration of the complexing agent in the reaction base liquid is 2-10 g / L; A nickel-cobalt-manganese ternary salt solution, an alkali solution, and a complexing agent solution are injected into the reaction base solution in parallel to carry out a first coprecipitation reaction, wherein the stirring speed of the first coprecipitation reaction is controlled to be 400-800 rpm, the temperature is controlled to be 50-60° C., and the pH value is controlled to be 10.0-12.0; a first target particle size D501 is set to 5-10 μm, and after the median particle size of the particles reaches 5-10 μm, feeding is stopped, and the nickel-cobalt-manganese ternary salt solution is replaced with a nickel-cobalt-manganese-aluminum quaternary salt solution, which is continued to be injected in parallel with the alkali solution and the complexing agent solution to carry out a second coprecipitation reaction, wherein the stirring speed of the second coprecipitation reaction is controlled to be 400-800 rpm, the temperature is controlled to be 50-60° C., and the pH value is controlled to be 8.0-10.0; feeding is stopped when the median particle size of the particles satisfies 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 filtered, washed with alkaline solution for 3-5 times, and then washed with pure water for 3-5 times. The solid material obtained by filtration and washing is then transferred to an oven and dried at 100°C to finally obtain a lithium-rich manganese-based precursor with a porous aluminum gradient.

19. A lithium-rich manganese-based precursor with a porous aluminum gradient, characterized in that: The lithium-rich manganese-based precursor with a porous aluminum gradient is prepared by the preparation method as described in any one of claims 1 to 18. The lithium-rich manganese-based precursor with a porous aluminum gradient includes a dense nickel-cobalt-manganese core and a loose porous aluminum concentration gradient shell coated on the surface.

20. A lithium-rich manganese-based positive electrode material, characterized in that The lithium-rich manganese-based precursor with a porous aluminum gradient is mixed evenly with a lithium salt, and the mixture is sintered to obtain a lithium-rich manganese-based positive electrode material; Wherein, the lithium-rich manganese-based precursor with a porous aluminum gradient is prepared by the preparation method described in any one of claims 1 to 18, or the lithium-rich manganese-based precursor with a porous aluminum gradient is the lithium-rich manganese-based precursor with a porous aluminum gradient described in claim 19.

21. A lithium ion battery, characterized in that: The lithium-ion battery comprises the lithium-rich manganese-based positive electrode material according to claim 20.

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