Broadly distributed cobalt-free lithium-rich manganese-based precursor and preparation method thereof

Abstract

The present application relates to the field of battery materials, and in particular to a widely distributed cobalt-free lithium-rich manganese-based precursor and a preparation method thereof. The preparation method comprises the following steps: preparing a precipitant solution, a complexing agent solution and a metal salt solution; preparing a reaction base liquid, wherein the pH value of the reaction base liquid is m0; under an inert atmosphere, the metal salt solution, the precipitant solution and the complexing agent solution are introduced into the reaction base liquid placed in a reactor to form a mixed reaction liquid, reacting for a time of t0 to obtain material particles with an initial median particle size and reducing the pH value of the mixed reaction liquid to m1 to allow the material particles to continue to grow; detecting the real-time median particle size of the material particles, and adjusting the pH value of the mixed reaction liquid according to the real-time median particle size. The method of the present application can be used to obtain a precursor material with a wide particle size range and a large specific surface area.

Description

Technical Field

[0001] The present application relates to the field of battery materials, and in particular to a broadly distributed cobalt-free lithium-rich manganese-based precursor and a preparation method thereof. Background Art

[0002] In recent years, lithium-rich manganese-based cathode materials have attracted widespread attention due to their advantages such as high operating voltage, high heat release capacity, and high thermal stability. Among them, cobalt-free lithium-rich manganese-based precursors reduce material costs with their high manganese content while improving the structural stability of the material. This type of cobalt-free material has a high market competitiveness due to its unique price advantage.

[0003] However, the current production of cobalt-free lithium-rich manganese-based precursors is mainly based on the intermittent method, which mainly adds metal salts, precipitants, and complexing agents into the reactor at a certain flow rate, performs co-precipitation under certain reaction conditions, and stops feeding after the particle size reaches the qualified particle size. Although the intermittent production process is conducive to obtaining materials with uniform morphology and particle size, the process is not conducive to improving the compaction density of the material, and the production capacity is low, which is not conducive to large-scale production of enterprises. Summary of the invention

[0004] The present application discloses a broadly distributed cobalt-free lithium-rich manganese-based precursor and a preparation method thereof, so as to obtain a precursor material with a wide particle size distribution range while realizing continuous production.

[0005] In order to achieve the above objectives, this application provides the following technical solutions:

[0006] In a first aspect, the present application provides a method for preparing a broadly distributed cobalt-free lithium-rich manganese-based precursor, the preparation method comprising the following steps:

[0007] Preparing a precipitant solution, a complexing agent solution and a metal salt solution for forming a cobalt-free lithium-rich manganese-based precursor; preparing a reaction base solution, wherein the pH value of the reaction base solution is m0;

[0008] Under an inert atmosphere, the metal salt solution, the precipitant solution and the complexing agent solution are introduced into the reaction base solution placed in the reaction kettle to form a mixed reaction solution, react for a time of t0 to obtain material particles with an initial median particle size, and reduce the pH value of the mixed reaction solution to m1 to allow the material particles to continue to grow;

[0009] The real-time median particle size of the material particles is detected, and the pH value of the mixed reaction liquid is adjusted according to the real-time median particle size, and the adjustment method is as follows:

[0010] Method 1), the real-time median particle size = target median particle size ± D1, increase the pH value of the mixed reaction liquid to m2 and maintain t 1+ or 1-After the reaction time, the pH value of the mixed reaction solution is reduced to m1 and the reaction is continued. 1+ >t 1- ;

[0011] Method 2), the real-time median particle size = target median particle size ± D2, increase the pH value of the mixed reaction liquid to m2 and maintain t 2+ or 2- After the reaction time, the pH value of the mixed reaction solution is reduced to m1 and the reaction is continued. 2+ >t 2- ;

[0012] Mode 3), the real-time median particle size = target median particle size ± D3, increase the pH value of the mixed reaction liquid to m2 and maintain t 3+ or 3- After the reaction time, the pH value of the mixed reaction solution is reduced to m1 and the reaction is continued. 3+ ≥t 3- ;

[0013] Mode 4), the real-time median particle size = target median particle size ± D4, increase the pH value of the mixed reaction liquid to m2 and maintain t 4+ or 4- After the reaction time, the pH value of the mixed reaction solution is reduced to m1 and the reaction is continued. 4+ ≈t 4- ;

[0014] Cycle the process of the method 1) to the method 4), collect the overflow slurry when the real-time median particle size meets the target median particle size ±0.1 μm, and post-treat the overflow slurry to obtain the broad distribution cobalt-free lithium-rich manganese-based precursor;

[0015] Among them, 10.7>m2>m1>10, and m0≥10.7; 1.2μm≥D1>D2>D3>D4≥0.2μm, 60min≥t 1+ >t 2+ >t 3+ >t 4+ ≥20min, 60min≥t 3- >t 2- >t 1- >t 4- ≥20min.

[0016] Further, the value of D1 is 0.90-1.1, the value of D2 is 0.7-0.89, the value of D3 is 0.4-0.69, and the value of D4 is 0.2-0.39. Exemplarily, the value of D1 is 1, the value of D2 is 0.8, the value of D3 is 0.5, and the value of D1 is 0.3.

[0017] Furthermore, the total molar concentration of the metal salt solution is 1.5-2 mol / L, and the molar ratio of nickel to manganese in the metal salt solution is n1:n2, wherein 0.2≤n1≤0.5, 0.5≤n2≤0.8.

[0018] Furthermore, the reaction temperature of the mixed reaction liquid is 45-65° C., and the stirring rate is 600-800 rpm.

[0019] Furthermore, the flow rate of the metal salt solution is 2 to 10 L / h, the flow rate of the precipitant solution is 1 to 5 L / h, and the flow rate of the complexing agent solution is 0.5 to 5 L / h.

[0020] Furthermore, the initial median particle size D500 satisfies 2≤D500≤3 μm.

[0021] Furthermore, the target median particle size D50 satisfies 4≤D50≤10 μm.

[0022] In a second aspect, the present application provides a broadly distributed cobalt-free lithium-rich manganese-based precursor, and the broadly distributed cobalt-free lithium-rich manganese-based precursor is prepared using the preparation method of the present application.

[0023] Furthermore, the median particle size of the broadly distributed cobalt-free lithium-rich manganese-based precursor is 4 to 10 μm, and the particle size distribution (D90-D10) / D50>1.5.

[0024] The technical solution of this application produces the following beneficial effects:

[0025] The preparation method of the wide distribution cobalt-free lithium-rich manganese-based precursor of the present application is to repeatedly increase and decrease the pH of the mixed reaction solution so that the surface of the obtained material particles is in different growth states, thereby playing a role in adjusting the surface morphology of the material. Under high pH conditions, the particles tend to grow in the direction of reduced surface energy, and the crystal grains agglomerated on the surface are easily peeled off for a nucleation growth, so that more small-sized particles can be obtained, the particle size distribution range of the material is widened, and the tap density of the material is improved. At the same time, after the pH value is increased, due to the increase in the concentration of alkaline anions, the particles are refined under the trend of grain orientation accumulation, resulting in thinning of the whiskers on the particle surface, thereby increasing the specific surface area of ​​the material. The low pH value condition is conducive to the growth of particles, and the grains peeled off from the particle surface can continue to grow, the whiskers continue to thicken, and the gaps between the particles are filled with new whiskers due to the precipitation of metal ions, thereby increasing the specific surface area of ​​the material. In addition, the preparation method of the present application can achieve continuous production and improve production efficiency by continuously passing the reaction raw materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a 1000-fold SEM image of the cobalt-free lithium-rich manganese-based precursor of Example 1;

[0027] Figure 2 This is a 50,000-fold SEM image of the cobalt-free lithium-rich manganese-based precursor of Example 1;

[0028] Figure 3 This is a 1000-fold SEM image of the cobalt-free lithium-rich manganese-based precursor of Comparative Example 1;

[0029] Figure 4 This is a 50,000-fold SEM image of the cobalt-free lithium-rich manganese-based precursor of Comparative Example 1. DETAILED DESCRIPTION

[0030] The following will be combined with the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0031] It should be noted that: in this application, if there is no special description, all the embodiments and preferred implementation methods mentioned herein can be combined with each other to form a new technical solution. In this application, if there is no special description, all the technical features and preferred features mentioned herein can be combined with each other to form a new technical solution. In this application, if there is no special description, percentage (%) or part refers to the weight percentage or weight part relative to the composition. In this application, if there is no special description, the components or their preferred components involved can be combined with each other to form a new technical solution. In this application, unless otherwise specified, the numerical range "a-b" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "6-22" means that all real numbers between "6-22" have been listed in this article, and "6-22" is just an abbreviation of these numerical combinations. The "range" disclosed in this application can be one or more lower limits and one or more upper limits in the form of lower limits and upper limits. In this application, unless otherwise specified, each reaction or operation step can be carried out sequentially or in sequence. Preferably, the reaction method in this article is carried out sequentially.

[0032] Unless otherwise specified, the professional and scientific terms used herein are the same as those familiar to those skilled in the art. In addition, any method or material similar or equivalent to the described content may also be applied to the present application.

[0033] In order to obtain a cobalt-free lithium-rich manganese-based precursor with a wide particle size distribution, the present application embodiment provides a method for preparing a cobalt-free lithium-rich manganese-based precursor. The preparation method comprises the following steps:

[0034] S11, preparing a precipitant solution, a complexing agent solution and a metal salt solution for forming a cobalt-free lithium-rich manganese-based precursor; preparing a reaction base solution, wherein the pH value of the reaction base solution is m0;

[0035] S12, under an inert atmosphere, introducing the metal salt solution, the precipitant solution and the complexing agent solution into the reaction base solution placed in the reactor to form a mixed reaction solution, reacting for t0 time to obtain material particles with an initial median particle size and reducing the pH value of the mixed reaction solution to m1 to allow the material particles to continue to grow;

[0036] S13, detecting the real-time median particle size of the material particles, and adjusting the pH value of the mixed reaction liquid according to the real-time median particle size, the adjustment method is as follows:

[0037] Method 1), the real-time median particle size = target median particle size ± D1, increase the pH value of the mixed reaction liquid to m2 and maintain t 1+ or 1- After the reaction time, the pH value of the mixed reaction solution is reduced to m1 and the reaction is continued. 1+ >t 1- ; Among them, when the real-time median particle size = target median particle size + D1, the reaction time is t 1+ ; When the real-time median particle size = target median particle size - D1, the reaction time is t 1- ;

[0038] Method 2), the real-time median particle size = target median particle size ± D2, increase the pH value of the mixed reaction liquid to m2 and maintain t 2+ or 2- After the reaction time, the pH value of the mixed reaction solution is reduced to m1 and the reaction is continued. 2+ >t 2- ; Among them, when the real-time median particle size = target median particle size + D2, the reaction time is t 2+ ; When the real-time median particle size = target median particle size - D2, the reaction time is t 2- ;

[0039] Mode 3), the real-time median particle size = target median particle size ± D3, increase the pH value of the mixed reaction liquid to m2 and maintain t 3+ or 3- After the reaction time, the pH value of the mixed reaction solution is reduced to m1 and the reaction is continued. 3+ >t 3- ; Among them, when the real-time median particle size = target median particle size + D3, the reaction time is t3+ ; When the real-time median particle size = target median particle size - D3, the reaction time is t 3- ;

[0040] Mode 4), the real-time median particle size = target median particle size ± D4, increase the pH value of the mixed reaction liquid to m2 and maintain t 4+ or 4- After the reaction time, the pH value of the mixed reaction solution is reduced to m1 and the reaction is continued. 4+ ≈t 4- ; Among them, when the real-time median particle size = target median particle size + D4, the reaction time is t 4+ ; When the real-time median particle size = target median particle size - D4, the reaction time is t 4- ;t 4+ and t 4- The difference may be Δt, and Δt may be, for example, ≤5 min.

[0041] The process from the method 1) to the method 4) is repeated, and when the real-time median particle size meets the target median particle size ±0.1 μm, the overflow slurry is collected, and the overflow slurry is post-processed to obtain the broadly distributed cobalt-free lithium-rich manganese-based precursor.

[0042] Among them, 10.7>m2>m1>10, and m0≥10.7; 1.2μm≥D1>D2>D3>D4≥0.2μm, 60min≥t 1+ >t 2+ >t 3+ >t 4+ ≥20min, 60min≥t 3- >t 2- >t 1- >t 4- ≥20min.

[0043] In one embodiment, in step S11, the precipitant in the precipitant solution includes but is not limited to at least one of sodium hydroxide and potassium hydroxide. The concentration of the precipitant solution is 10-11 mol / L. The complexing agent solution includes but is not limited to one of ammonia water, EDTA, and citric acid, and its concentration is 0.5-5 g / L.

[0044] The total molar concentration of the metal salt solution is 1.5-2 mol / L. The metal salt solution contains nickel salt and manganese salt. The nickel salt is one of nickel chloride, nickel sulfate and nickel nitrate; the manganese salt is one of manganese chloride, manganese sulfate and manganese nitrate; in the metal salt solution, the molar ratio of nickel to manganese is n1:n2, 0.2≤n1≤0.5, 0.5≤n2≤0.8.

[0045] The reaction base liquid is alkaline, so that the metal salt solution can quickly nucleate when entering the reaction system, accelerating the nucleation rate in the early stage. Exemplarily, the preparation process of the reaction base liquid is as follows: 100L of clean water is injected into the reactor, and the stirring speed and temperature parameters of the reactor are set; a certain amount of precipitant and complexing agent are added to configure a high pH reaction base liquid. The pH value of the reaction base liquid is m0, and the value range of m0 is 10.7 to 11.2.

[0046] In one embodiment, in step S12, the process of forming a mixed reaction liquid is as follows: nitrogen gas is introduced; after the reaction system is stable, a metal salt solution, a precipitant and a complexing agent are introduced into the reactor, and the startup particle size is monitored after the reaction for 1 hour, and after the startup particle size reaches the initial median particle size, the pH is slowly reduced to m1 to allow the material particles to continue to grow. The initial median particle size D500 satisfies 2μm≤D500≤3μm.

[0047] In the process of forming the mixed reaction liquid, the stirring rate in the reactor is 600-800 rpm, and the reaction temperature in the reactor is 45-65° C. The flow rate of the metal salt solution is 2-10 L / h, the flow rate of the precipitant solution is 1-5 L / h, and the flow rate of the complexing agent solution is 0.5-5 L / h.

[0048] In an optional embodiment, in step S13, the target median particle size is 4-10 μm.

[0049] In an optional embodiment, the value of D1 is 0.90-1.1, the value of D2 is 0.7-0.89, the value of D3 is 0.4-0.69, and the value of D1 is 0.2-0.39. As an exemplary explanation, the value of D1 is 1, the value of D2 is 0.8, the value of D3 is 0.5, and the value of D4 is 0.3.

[0050] In an optional embodiment, the pH value of the mixed reaction liquid is adjusted according to the real-time median particle size, and the adjustment method is as follows:

[0051] Method 1), the real-time median particle size = target median particle size + 1, increase the pH value of the mixed reaction liquid to m2 and maintain t 1+ After the reaction time, the pH value of the mixed reaction solution is reduced to m1 and the reaction is continued;

[0052] Method 2), the real-time median particle size = target median particle size + 0.8, increase the pH value of the mixed reaction liquid to m2 and maintain t 2+ After the reaction time, the pH value of the mixed reaction solution is reduced to m1 and the reaction is continued;

[0053] Method 3), the real-time median particle size = target median particle size + 0.5, increase the pH value of the mixed reaction liquid to m2 and maintain t3+ After the reaction time, the pH value of the mixed reaction solution is reduced to m1 and the reaction is continued;

[0054] Mode 4), the real-time median particle size = target median particle size + 0.3, raise the pH value of the mixed reaction liquid to m2 and maintain t 4+ After the reaction time, the pH value of the mixed reaction solution is reduced to m1 and the reaction is continued;

[0055] Mode 5), the real-time median particle size = target median particle size - 1, increase the pH value of the mixed reaction liquid to m2 and maintain t 1- After the reaction time, the pH value of the mixed reaction solution is reduced to m1 and the reaction is continued;

[0056] Mode 6), the real-time median particle size = target median particle size - 0.8, raise the pH value of the mixed reaction liquid to m2 and maintain t 2- After the reaction time, the pH value of the mixed reaction solution is reduced to m1 and the reaction is continued;

[0057] Method 7), the real-time median particle size = target median particle size - 0.5, increase the pH value of the mixed reaction liquid to m2 and maintain t 3- After the reaction time, the pH value of the mixed reaction solution is reduced to m1 and the reaction is continued;

[0058] Mode 8), the real-time median particle size = target median particle size - 0.3, increase the pH value of the mixed reaction liquid to m2 and maintain t 4- After the reaction time, the pH value of the mixed reaction solution is reduced to m1 and the reaction is continued.

[0059] Among them, when the real-time median particle size obtained by the test is one of the above-mentioned methods 1) to 8), the pH value of the mixed reaction liquid can be adjusted according to the corresponding method. After the pH value adjustment is completed and the reaction is carried out under high pH conditions for a certain period of time, the pH value is lowered to restore it to the original reaction conditions and continue the reaction. The overflow slurry is collected until the median particle size meets the requirements. For example, when the real-time median particle size of the tested material particles is the target median particle size + 1, the pH value of the mixed reaction liquid is increased to m2 and maintained at t 1+ After the reaction time, the pH value of the mixed reaction liquid is reduced to m1 and the reaction is continued. When the real-time median particle size of the tested material particles is the target median particle size -1, the pH value of the mixed reaction liquid is increased to m2 and maintained at t 1- After the reaction time, the pH value of the mixed reaction solution is reduced to m1 to continue the reaction. This cycle is repeated. The pH value of the mixed reaction solution is continuously adjusted according to the real-time median particle size until the particle size of the precursor meets the requirements. The pH value of the mixed reaction solution can be regulated by adjusting the amount of metal salt solution, the amount of precipitant solution, and the amount of complexing agent solution.

[0060] The preparation method of the cobalt-free lithium-rich manganese-based precursor of the embodiment of the present application is to repeatedly increase and decrease the pH of the mixed reaction solution so that the surface of the obtained material particles is in different growth states, thereby playing a role in adjusting the surface morphology of the material. Under high pH conditions, the particles tend to grow in the direction of reduced surface energy, and the crystal grains agglomerated on the surface are easily peeled off for a nucleation growth, so that more small-sized particles can be obtained, the particle size distribution range of the material is widened, and the tap density of the material is improved. At the same time, after the pH value is increased, due to the increase in the concentration of alkaline anions, under the trend of grain orientation accumulation, the particles are refined, resulting in thinning of the whiskers on the surface of the particles, thereby increasing the specific surface area of ​​the material. The low pH value condition is conducive to the growth of particles, and the grains peeled off from the surface of the particles can continue to grow, the whiskers continue to thicken, and the gaps between the particles are filled with new whiskers due to the precipitation of metal ions, thereby increasing the specific surface area of ​​the material. In addition, the preparation method of the present application can achieve continuous production and improve production efficiency by continuously passing the reaction raw materials.

[0061] The median particle size of the cobalt-free lithium-rich manganese-based precursor obtained by the preparation method of the present application is 4 to 10 μm, and the particle size distribution (D90-D10) / D50>1.5. The particle size distribution range of the precursor of the embodiment of the present application is wide, which is conducive to increasing the compaction density of the positive electrode material to increase the capacity of the battery.

[0062] The cobalt-free lithium-rich manganese-based precursor and the preparation method thereof of the present application will be further described in detail below in conjunction with specific embodiments.

[0063] Example 1

[0064] This embodiment is a cobalt-free lithium-rich manganese-based precursor, and its preparation method includes the following steps:

[0065] S11. Prepare a metal salt solution having a total molar concentration of 1.5 mol / L and not containing cobalt, wherein the molar ratio of nickel to manganese is 35:65; and prepare 10.5 mol / L of a precipitant.

[0066] S12. Fill a 100L reactor with clean water, and set the stirring speed and temperature parameters of the reactor to 650rpm and 55°C respectively; add a certain amount of precipitant and complexing agent to prepare a reaction base liquid with a pH of 11.0, and introduce nitrogen gas; after the reaction system is stable, introduce a metal salt solution at a flow rate of 6L / h, a precipitant at a flow rate of 1.5L / h, and a complexing agent at a flow rate of 0.5L / h. After reacting for 1 hour, the startup particle size is monitored to be 2.6, which meets the initial median particle size requirement, and slowly reduce the pH to 10.2.

[0067] S13, when the measured median particle size of the particles is D50=5.5±0.1 μm, the pH is rapidly increased to 10.5 and maintained for 20 minutes, and then the pH is rapidly decreased to 10.2;

[0068] When the measured median particle size of the particles is D50=5.8±0.1 μm, the pH is rapidly increased to 10.5 and maintained for 25 minutes, and then the pH is rapidly decreased to 10.2;

[0069] When the measured median particle size of the particles is D50=6.0±0.1 μm, the pH is rapidly increased to 10.5 and maintained for 30 minutes, and then rapidly decreased to 10.2;

[0070] When the measured median particle size of the particles is D50=6.3±0.1 μm, the pH is rapidly raised to 10.5 and maintained for 15 minutes, and then rapidly lowered to 10.2;

[0071] When the measured median particle size of the particles is D50=6.8±0.1 μm, the pH is rapidly raised to 10.5 and maintained for 15 minutes, and then the pH is rapidly lowered to 10.2;

[0072] When the measured median particle size of the particles is D50=7.0±0.1 μm, the pH is rapidly increased to 10.5 and maintained for 35 minutes, and then the pH is rapidly decreased to 10.2;

[0073] When the measured median particle size of the particles is D50=7.3±0.1 μm, the pH is rapidly increased to 10.5 and maintained for 40 minutes, and then the pH is rapidly decreased to 10.2;

[0074] When the measured median particle size of the particles is D50=7.0±0.1 μm, the pH is rapidly increased to 10.5 and maintained for 50 minutes, and then the pH is rapidly decreased to 10.2;

[0075] The pH was controlled in this cycle, and the overflow slurry was collected when the measured median particle size D50 was 6.5±0.1 μm.

[0076] S14. The overflow slurry is subjected to aging, washing, centrifugation, drying and other treatments to obtain a cobalt-free lithium-rich manganese-based precursor having a widely distributed nickel-manganese ratio of 35:65.

[0077] Example 2

[0078] This embodiment is a cobalt-free lithium-rich manganese-based precursor, and its preparation method includes the following steps:

[0079] S11. Prepare a metal salt solution having a total molar concentration of 1.5 mol / L and not containing cobalt, wherein the molar ratio of nickel to manganese is 30:70; and prepare 11.0 mol / L of a precipitant.

[0080] S12. Fill a 100L reactor with clean water, and set the stirring speed and temperature parameters of the reactor to 650rpm and 60°C respectively; add a certain amount of precipitant and complexing agent to prepare a reaction base liquid with a pH of 11.0, and introduce nitrogen gas; after the reaction system is stable, introduce a metal salt solution at a flow rate of 6L / h, a precipitant at a flow rate of 1.8L / h, and a complexing agent at a flow rate of 0.8L / h. After reacting for 1 hour, the startup particle size is monitored to be 2.2, which meets the initial median particle size requirement, and slowly reduce the pH to 10.1.

[0081] S13, when the measured median particle size of the particles is D50=7±0.1 μm, the pH is rapidly increased to 10.4 and maintained for 15 minutes, and then the pH is rapidly decreased to 10.1;

[0082] When the measured median particle size of the particles is D50=7.3±0.1 μm, the pH is rapidly increased to 10.4 and maintained for 20 minutes, and then the pH is rapidly decreased to 10.1;

[0083] When the measured median particle size of the particles is D50=7.5±0.1 μm, the pH is rapidly increased to 10.4 and maintained for 25 minutes, and then rapidly decreased to 10.1;

[0084] When the measured median particle size of the particles is D50=7.8±0.1 μm, the pH is rapidly increased to 10.4 and maintained for 10 minutes, and then the pH is rapidly decreased to 10.1;

[0085] When the measured median particle size of the particles is D50=8.2±0.1 μm, the pH is rapidly increased to 10.4 and maintained for 10 minutes, and then the pH is rapidly decreased to 10.1;

[0086] When the measured median particle size of the particles is D50=8.5±0.1 μm, the pH is rapidly increased to 10.4 and maintained for 30 minutes, and then the pH is rapidly decreased to 10.1;

[0087] When the measured median particle size of the particles is D50=8.7±0.1 μm, the pH is rapidly increased to 10.4 and maintained for 35 minutes, and then the pH is rapidly decreased to 10.1;

[0088] When the measured median particle size of the particles is D50=9±0.1 μm, the pH is rapidly increased to 10.4 and maintained for 45 minutes, and then the pH is rapidly decreased to 10.1;

[0089] The pH was controlled in this cycle, and the overflow slurry was collected when the measured median particle size D50 was 8±0.1 μm.

[0090] S14. The overflow slurry is subjected to aging, washing, centrifugation, drying and other treatments to obtain a cobalt-free lithium-rich manganese-based precursor having a widely distributed nickel-manganese ratio of 30:70.

[0091] Example 3

[0092] This embodiment is a cobalt-free lithium-rich manganese-based precursor, and its preparation method includes the following steps:

[0093] S11. Prepare a metal salt solution having a total molar concentration of 1.5 mol / L and not containing cobalt, wherein the molar ratio of nickel to manganese is 25:75; and prepare 10.8 mol / L of a precipitant.

[0094] S12. Fill a 100L reactor with clean water, and set the stirring speed and temperature parameters of the reactor to 600rpm and 50°C respectively; add a certain amount of precipitant and complexing agent to prepare a reaction base liquid with a pH of 11.0, and introduce nitrogen gas; after the reaction system is stable, introduce a metal salt solution at a flow rate of 5L / h, a precipitant at a flow rate of 1.4L / h, and a complexing agent at a flow rate of 0.3L / h. After reacting for 1 hour, the startup particle size is monitored to be 2.5, which meets the initial median particle size requirement, and slowly reduce the pH to 10.2.

[0095] S13, when the measured median particle size of the particles is D50=4±0.1 μm, the pH is rapidly increased to 10.5 and maintained for 15 minutes, and then the pH is rapidly decreased to 10.2;

[0096] When the measured median particle size of the particles is D50 = 4.3 ± 0.1 μm, the pH is rapidly increased to 10.5 and maintained for 20 minutes, and then the pH is rapidly decreased to 10.2;

[0097] When the measured median particle size of the particles is D50=4.5±0.1 μm, the pH is rapidly increased to 10.5 and maintained for 25 minutes, and then rapidly decreased to 10.2;

[0098] When the measured median particle size of the particles is D50 = 4.8 ± 0.1 μm, the pH is rapidly increased to 10.5 and maintained for 10 minutes, and then the pH is rapidly decreased to 10.2;

[0099] When the measured median particle size of the particles is D50=5.2±0.1 μm, the pH is rapidly increased to 10.5 and maintained for 10 minutes, and then the pH is rapidly decreased to 10.2;

[0100] When the measured median particle size of the particles is D50=5.5±0.1 μm, the pH is rapidly increased to 10.5 and maintained for 30 minutes, and then the pH is rapidly decreased to 10.2;

[0101] When the measured median particle size of the particles is D50=5.7±0.1 μm, the pH is rapidly increased to 10.5 and maintained for 35 minutes, and then the pH is rapidly decreased to 10.2;

[0102] When the measured median particle size of the particles is D50=6±0.1 μm, the pH is rapidly raised to 10.5 and maintained for 45 minutes, and then the pH is rapidly lowered to 10.2;

[0103] The pH was controlled in this cycle, and the overflow slurry was collected when the measured median particle size D50 was 5±0.1 μm.

[0104] S14. The overflow slurry is subjected to aging, washing, centrifugation, drying and other treatments to obtain a cobalt-free lithium-rich manganese-based precursor having a widely distributed nickel-manganese ratio of 25:75.

[0105] Comparative Example 1

[0106] This comparative example is a cobalt-free lithium-rich manganese-based precursor, and its preparation method comprises the following steps:

[0107] S11. Prepare a metal salt solution having a total molar concentration of 1.5 mol / L and not containing cobalt, wherein the molar ratio of nickel to manganese is 35:65; and prepare 10.5 mol / L of a precipitant.

[0108] S12. Fill a 100L reactor with clean water, and set the stirring speed and temperature parameters of the reactor to 650rpm and 55°C respectively; add a certain amount of precipitant and complexing agent to prepare a reaction base liquid with a pH of 11.0, and introduce nitrogen gas; after the reaction system is stable, introduce a metal salt solution at a flow rate of 6L / h, a precipitant at a flow rate of 1.5L / h, and a complexing agent at a flow rate of 0.5L / h. After reacting for 1 hour, the startup particle size is monitored to be 2.4, which meets the startup particle size requirement, and slowly reduce the pH to 10.2.

[0109] S13. When the measured median particle size of the particles reaches D50 = 6.5 ± 0.1 μm, the feeding is stopped, and the reaction kettle liquid is transported to the aging kettle.

[0110] S14, subjecting the slurry to aging, washing, centrifugation, drying and other treatments to obtain a lithium-rich manganese-based precursor with a nickel-manganese ratio of 35:65.

[0111] Comparative Example 2

[0112] This comparative example is a cobalt-free lithium-rich manganese-based precursor, and its preparation method comprises the following steps:

[0113] S11, preparing a metal salt solution containing no cobalt with a total molar ratio of 1.5 mol / L, wherein the molar ratio of nickel to manganese is 30:70; preparing 11.0 mol / L of a precipitant.

[0114] S12. Fill a 100L reactor with clean water, and set the stirring speed and temperature parameters of the reactor to 650rpm and 60°C respectively; add a certain amount of precipitant and complexing agent to prepare a reaction base liquid with a pH of 11.0, and introduce nitrogen gas; after the reaction system is stable, introduce a metal salt solution at a flow rate of 6L / h, a precipitant at a flow rate of 1.8L / h, and a complexing agent at a flow rate of 0.8L / h. After reacting for 1 hour, the startup particle size is monitored to be 2.6, which meets the startup particle size requirement, and slowly reduce the pH to 10.1.

[0115] S13. When the measured median particle size of the particles reaches D50=8±0.1 μm, the feeding is stopped, and the reaction kettle feed liquid is transported to the aging kettle.

[0116] S14, subjecting the slurry to aging, washing, centrifuging, drying and other treatments to obtain a lithium-rich manganese-based precursor with a nickel-manganese ratio of 30:70.

[0117] Comparative Example 3

[0118] This comparative example is a cobalt-free lithium-rich manganese-based precursor, and its preparation method comprises the following steps:

[0119] S1. Prepare a metal salt solution containing no cobalt and having a total molar concentration of 1.5 mol / L, wherein the molar ratio of nickel to manganese is 25:75; and prepare 10.8 mol / L of a precipitant.

[0120] S2. Fill a 100L reactor with clean water, and set the stirring speed and temperature parameters of the reactor to 600rpm and 50°C respectively; add a certain amount of precipitant and complexing agent to prepare a reaction base liquid with a pH of 11.0, and introduce nitrogen gas; after the reaction system is stable, introduce a metal salt solution at a flow rate of 5L / h, a precipitant at a flow rate of 1.4L / h, and a complexing agent at a flow rate of 0.3L / h. After reacting for 1 hour, the startup particle size is monitored to be 2.4, which meets the startup particle size requirement, and slowly reduce the pH to 10.2.

[0121] S3. When the measured median particle size of the particles reaches D50 = 5±0.1 μm, the feeding is stopped and the reaction kettle feed liquid is transported to the aging kettle.

[0122] S4. The slurry is subjected to aging, washing, centrifugation, drying and other treatments to obtain a lithium-rich manganese-based precursor with a nickel-manganese ratio of 25:75.

[0123] The D10, D50 and D90, particle size distribution span and specific surface area of ​​each embodiment and comparative example sample were tested respectively, wherein span = (D90-D10) / D50. The test results are listed in Table 1.

[0124] Table 1

[0125] Serial number D10 D50 D90 span <![CDATA[Specific surface area / m 2 / g]]> Example 1 1.55 6.57 12.69 1.70 19.8 Example 2 3.86 8.02 16.42 1.57 21.5 Example 3 1.97 4.94 10.05 1.64 20.6 Comparative Example 1 4.84 6.53 9.13 0.66 12.4 Comparative Example 2 5.73 8.09 11.92 0.77 14.2 Comparative Example 3 2.56 4.59 6.32 0.82 13.8

[0126] It can be seen from the relevant test data in Table 1 that the particle size distribution span value of the cobalt-free lithium-rich manganese-based precursor of Examples 1-3 of the present application is significantly higher than that of Comparative Examples 1-3, and the specific surface area of ​​Examples 1-3 of the present application is also higher than that of Comparative Examples 1-3.

[0127] Figure 1 This is a 1000-fold SEM image of the cobalt-free lithium-rich manganese-based precursor of Example 1. Figure 2 This is a 50,000-fold SEM image of the cobalt-free lithium-rich manganese-based precursor of Example 1.

[0128] like Figure 1 As shown, the particles of the cobalt-free lithium-rich manganese-based precursor obtained in Example 1 of the present application are of different sizes and have a wide particle size distribution. After testing, the D10, D50 and D90 of the cobalt-free lithium-rich manganese-based precursor of this embodiment are 1.55, 6.74 and 12.69, respectively, and the particle size distribution (D90-D10) / D50 is 1.65. It can be seen that the cobalt-free lithium-rich manganese-based precursor obtained in Example 1 of the present application has a wide range of particle size distribution. This is mainly attributed to the acceleration of the primary nucleation process under high pH values.

[0129] like Figure 2 As shown in the figure, the particle surface whiskers of the cobalt-free lithium-rich manganese-based precursor of Example 1 have a relatively large aspect ratio, and its specific surface area is 19.8 m 2 / g. This is mainly attributed to the pH change during the continuous preparation process. Increasing the pH will refine the whiskers on the surface of the particles, resulting in thinner whiskers on the surface of the material; while rapidly decreasing the pH will promote the growth of the particles, the original whiskers will continue to grow and thicken, and new whiskers will grow and fill in the gaps between the original whiskers, thereby increasing the specific surface area of ​​the material.

[0130] Figure 3 This is a 1000-fold SEM image of the cobalt-free lithium-rich manganese-based precursor of Comparative Example 1. Figure 4 This is a 50,000-fold SEM image of the cobalt-free lithium-rich manganese-based precursor of Comparative Example 1.

[0131] like Figure 3 As shown, the particle size of the cobalt-free lithium-rich manganese-based precursor of Comparative Example 1 is relatively uniform. The particle size distribution range is narrow. After testing, the particle sizes D10, D50, and D90 of the cobalt-free lithium-rich manganese-based precursor of Comparative Example 1 are 4.84, 6.63, and 9.13, respectively, and the particle size distribution (D90-D10) / D50 is 0.65. The particle size distribution range of the obtained precursor is narrow, which is mainly attributed to the single change trend of pH.

[0132] like Figure 4As shown in Figure 1, the aspect ratio of the whiskers on the particle surface of the cobalt-free lithium-rich manganese-based precursor of Comparative Example 1 is basically the same, and there are no thin and short whiskers, which is attributed to the improvement of the uniformity of the precursor whiskers prepared by the intermittent method. The specific surface area of ​​the precursor prepared by this method is 12.4m 2 / g, which is lower than the specific surface area of ​​the precursor in the embodiment of the present application.

[0133] Obviously, those skilled in the art can make various changes and modifications to the embodiments of the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A method for preparing a broadly distributed cobalt-free lithium-rich manganese-based precursor, characterized in that: include: preparing a precipitant solution, a complexing agent solution and a metal salt solution for forming a cobalt-free lithium-rich manganese-based precursor; Preparing a reaction base liquid, wherein the pH value of the reaction base liquid is m0; Under an inert atmosphere, the metal salt solution, the precipitant solution and the complexing agent solution are introduced into the reaction base solution placed in the reaction kettle to form a mixed reaction solution, react for a time of t0 to obtain material particles with an initial median particle size, and reduce the pH value of the mixed reaction solution to m1 to allow the material particles to continue to grow; The real-time median particle size of the material particles is detected, and the pH value of the mixed reaction liquid is adjusted according to the real-time median particle size, and the adjustment method is as follows: Method 1), the real-time median particle size = target median particle size ± D1, increase the pH value of the mixed reaction liquid to m2 and maintain t 1+ or 1- After the reaction time, the pH value of the mixed reaction solution is reduced to m1 and the reaction is continued. 1+ >t 1- ; Method 2), the real-time median particle size = target median particle size ± D2, increase the pH value of the mixed reaction liquid to m2 and maintain t 2+ or 2- After the reaction time, the pH value of the mixed reaction solution is reduced to m1 and the reaction is continued. 2+ >t 2- ; Mode 3), the real-time median particle size = target median particle size ± D3, increase the pH value of the mixed reaction liquid to m2 and maintain t 3+ or 3- After the reaction time, the pH value of the mixed reaction solution is reduced to m1 and the reaction is continued. 3+ ≥t 3- ; Mode 4), the real-time median particle size = target median particle size ± D4, increase the pH value of the mixed reaction liquid to m2 and maintain t 4+ or 4- After the reaction time, the pH value of the mixed reaction solution is reduced to m1 and the reaction is continued. 4+ ≈t 4- ; Cycle the process of the method 1) to the method 4), collect the overflow slurry when the real-time median particle size meets the target median particle size ±0.1 μm, and post-treat the overflow slurry to obtain the broad distribution cobalt-free lithium-rich manganese-based precursor; Among them, 10.7>m2>m1>10, and m0≥10.7; 1.2μm≥D1>D2>D3>D4≥0.2μm, 60min≥t 1+ >t 2+ >t 3+ >t 4+ ≥20min, 60min≥t 3- >t 2- >t 1- >t 4- ≥20min.

2. The preparation method according to claim 1, characterized in that: The value of D1 is 0.90-1.1, the value of D2 is 0.7-0.89, the value of D3 is 0.4-0.69, and the value of D1 is 0.2-0.

39.

3. The preparation method according to claim 1, characterized in that: The total molar concentration of the metal salt solution is 1.5-2 mol / L, and the molar ratio of nickel and manganese in the metal salt solution is n1:n2, wherein 0.2≤n1≤0.5, 0.5≤n2≤0.

8.

4. The preparation method according to claim 1, characterized in that: The reaction temperature of the mixed reaction liquid is 45-65° C., and the stirring rate is 600-800 rpm.

5. The preparation method according to claim 1, characterized in that: The flow rate of the metal salt solution is 2 to 10 L / h, the flow rate of the precipitant solution is 1 to 5 L / h, and the flow rate of the complexing agent solution is 0.5 to 5 L / h.

6. The preparation method according to claim 1, characterized in that: The initial median particle size D500 satisfies 2 μm≤D500≤3 μm.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The target median particle size D50 satisfies 4 μm≤D50≤10 μm.

8. A broadly distributed cobalt-free lithium-rich manganese-based precursor, characterized in that: The broadly distributed cobalt-free lithium-rich manganese-based precursor is prepared by the preparation method according to any one of claims 1 to 7.

9. The broadly distributed cobalt-free lithium-rich manganese-based precursor according to claim 8, characterized in that: The median particle size of the broadly distributed cobalt-free lithium-rich manganese-based precursor is 4 to 10 μm, and the particle size distribution (D90-D10) / D50>1.5.

Images