A cobalt-free nickel-manganese binary precursor material, its preparation method and application

Abstract

The present invention provides a cobalt-free nickel-manganese binary precursor material, a preparation method thereof and an application. The preparation method comprises the following steps: mixing a nickel-manganese metal source solution, a precipitant solution and a first complexing agent solution to carry out the nucleation stage of the coprecipitation reaction; after the end of the nucleation stage, adjusting the pH of the coprecipitation reaction, and replacing the first complexing agent solution with a second complexing agent solution containing an additive to carry out the growth stage of the coprecipitation reaction to obtain a precursor slurry; washing and drying the precursor slurry to obtain the cobalt-free nickel-manganese binary precursor material; the washing liquid used for washing comprises a reducing agent. In the preparation method of the present invention, the growth of crystals is controlled by adding an additive in the growth stage of the coprecipitation reaction, and a reducing agent is added in the washing stage of the post-treatment to inhibit the precipitation of manganese oxides, so that the obtained precursor has better crystallinity and a lower amount of manganese oxide precipitation.

Description

Technical Field

[0001] The invention belongs to the technical field of batteries and relates to a cobalt-free nickel-manganese binary precursor material and a preparation method and application thereof. Background Art

[0002] The rapid development of electric vehicles has increased the demand for high-performance, high-safety and long-life lithium-ion batteries. Ternary cathode materials have become a research hotspot in the current power battery field due to their high energy density and good electrochemical properties. However, due to the scarcity and high price of metal cobalt resources, current research on cathode materials has gradually shifted to cobalt-free nickel-manganese binary material systems to avoid the limitations of cobalt resource shortages on the development of cathode materials. Nickel and manganese resources are relatively abundant, and nickel-manganese binary materials also have the advantages of high capacity, good capacity retention, low toxicity and low cost, making cobalt-free nickel-manganese binary materials a research hotspot for cathode materials.

[0003] However, the traditional cobalt-free nickel-manganese binary precursor often has problems such as poor crystallinity and easy precipitation of manganese oxide during the preparation process. These problems not only affect the electrochemical performance of the positive electrode material, but also reduce its cycle stability and safety. In the prior art, additives are usually added during the coprecipitation of the precursor to improve the above problems. For example, CN 116216796A adds ethylene glycol as a modifier to the reaction bottom liquid, which properly controls the crystallinity of the nickel-manganese binary precursor, inhibits the precipitation of manganese tetraoxide, and improves the material morphology. However, ethylene glycol may be mixed in the precursor particles, and for nickel-manganese binary materials with high manganese content, it may still be difficult to avoid manganese being oxidized in the post-processing link, thereby affecting the quality of the precursor product.

[0004] Therefore, it is necessary to develop a method for preparing a cobalt-free nickel-manganese binary precursor without introducing new impurities and ensuring that the precursor product has good crystallinity and no manganese oxide precipitation. Summary of the invention

[0005] The object of the present invention is to provide a cobalt-free nickel-manganese binary precursor material and a preparation method and application thereof. The preparation method controls crystal growth by adding an additive in the growth stage of the coprecipitation reaction, and adds a reducing agent in the washing stage of the post-treatment to inhibit the precipitation of manganese oxide, so that the obtained precursor has better crystallinity and lower manganese oxide precipitation, thereby improving the product quality of the precursor.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing a cobalt-free nickel-manganese binary precursor material, the preparation method comprising the following steps:

[0008] (1) Mix the nickel-manganese metal source solution, the precipitant solution, and the first complexing agent solution to carry out the nucleation stage of the coprecipitation reaction;

[0009] (2) After the nucleation stage described in step (1) ends, adjust the pH of the coprecipitation reaction, and replace the first complexing agent solution with a second complexing agent solution containing an additive to carry out the growth stage of the coprecipitation reaction to obtain a precursor slurry;

[0010] (3) Wash and dry the precursor slurry described in step (2) to obtain the cobalt-free nickel-manganese binary precursor material;

[0011] The washing liquid used for the washing includes a reducing agent.

[0012] In the present invention, a small amount of additive that can affect the crystal plane growth of the precursor is added in the growth stage of the coprecipitation reaction, which regulates the crystallinity and crystal structure of the precursor, and avoids the additive being wrapped inside the particles during the rapid nucleation stage of the precursor, introducing more impurities; moreover, in the washing step of the post-treatment in the present invention, a reducing agent is added to wash the precursor slurry, which inhibits the precipitation of manganese oxide on the surface of the particles, further ensures the high crystallinity and structural uniformity of the precursor, improves the surface morphology of the precursor, and prepares a cobalt-free nickel-manganese binary precursor with good crystallinity and no precipitation of manganese oxide.

[0013] Preferably, the total metal ion concentration of the nickel-manganese metal source solution described in step (1) is 1.0 - 3.0 mol / L, for example, it can be 1.0 mol / L, 2.0 mol / L, or 3.0 mol / L. Among them, the molar ratio of nickel ions to manganese ions is (1 - x):x, where x is 0.1 - 0.95, for example, it can be 0.1, 0.3, 0.5, 0.7, 0.9, or 0.95, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0014] Preferably, the concentration of the precipitant solution described in step (1) is 20 - 40 wt%, for example, it can be 20 wt%, 30 wt%, or 40 wt%, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0015] Preferably, the concentration of the first complexing agent solution described in step (1) is 10 - 25 wt%, for example, it can be 10 wt%, 20 wt%, or 25 wt%, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0016] Preferably, the mixing described in step (1) includes co-flowing the nickel-manganese metal source solution, the precipitant solution, and the first complexing agent solution into the bottom liquid.

[0017] Preferably, the bottom solution comprises water, a precipitant solution and a first complexing agent solution.

[0018] Preferably, the pH of the bottom solution is 11.2 - 12.5, for example, it can be 11.2, 11.5, 12.0 or 12.5, the concentration of the complexing agent is 2 - 12 g / L, for example, it can be 2 g / L, 5 g / L, 10 g / L or 12 g / L, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0019] Preferably, the temperatures of the nucleation stage in step (1) and the growth stage in step (2) are independently 40 - 80 °C, for example, it can be 40 °C, 60 °C or 80 °C, the concentration of the complexing agent in the reaction system is maintained within the range of 2 - 12 g / L, for example, it can be 2 g / L, 5 g / L, 10 g / L or 12 g / L, and it is carried out in nitrogen and / or argon.

[0020] Preferably, the pH of the nucleation stage in step (1) is 11.3 - 12.5, for example, it can be 11.3, 11.5, 12.0 or 12.5, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0021] Preferably, in the second complexing agent solution in step (2), the content of the additive is 0.1 - 10 wt%, for example, it can be 0.1 wt%, 1 wt%, 3 wt%, 5 wt%, 7 wt%, 9 wt% or 10 wt%, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0022] The content of the additive added in the growth stage of the present invention will affect crystal growth. If the addition amount of the additive is too small, it cannot play a role in regulating the growth of granular crystals. If the addition amount of the additive is too large, it is likely to remain in the sample, affecting the quality of the precursor, and will also increase the material cost.

[0023] Preferably, the additive in step (2) comprises any one or a combination of at least two of polyvinylpyrrolidone, polyethylene glycol, tetramethylammonium hydroxide, cetyltrimethylammonium bromide or triethanolamine.

[0024] Preferably, in the second complexing agent solution in step (2), the content of the complexing agent is 10 - 25 wt%, for example, it can be 10 wt%, 15 wt%, 20 wt% or 25 wt%, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0025] Preferably, the pH of the co-precipitation reaction in step (2) is adjusted to 9.6 - 11.3. For example, it can be 9.6, 10, 10.5, 11, or 11.3, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0026] Preferably, in the growth stage of step (2), the reaction proceeds until the D50 of the precursor particles is 2 - 20 μm. For example, it can be 2 μm, 5 μm, 10 μm, 15 μm, or 20 μm, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable, and preferably it is 4 - 12 μm.

[0027] Preferably, after the precursor slurry in step (2) is aged, the washing in step (3) is carried out.

[0028] Preferably, the pH of the aging is 9 - 11. For example, it can be 9, 10, or 11, and the aging time is 6 - 12 h. For example, it can be 6 h, 8 h, 10 h, or 12 h, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0029] The precursor slurry of the present invention is allowed to stand, and after the supernatant is drawn off, alkali solution and pure water are added to adjust the pH of the aging to 9 - 11 for aging.

[0030] Preferably, in the washing solution of step (3), the content of the reducing agent is 0.1 - 10 wt%. For example, it can be 0.1 wt%, 1 wt%, 3 wt%, 5 wt%, 7 wt%, 9 wt%, or 10 wt%, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0031] In the washing process of the present invention, the content of the reducing agent will affect the washing effect. If the amount of the reducing agent added is too small, the precipitation of manganese oxide cannot be effectively inhibited. If the amount of the reducing agent added is too large, it may remain in the sample, affecting the quality of the precursor and increasing the cost appropriately.

[0032] Preferably, the reducing agent includes any one or a combination of at least two of glucose, citric acid, ascorbic acid, or oxalic acid.

[0033] Preferably, the washing solution of step (3) includes an alkali solution containing a reducing agent, and / or water containing a reducing agent.

[0034] The washing in step (3) of the present invention includes alkali washing more than twice first, and then water washing more than twice. Among them, alkali washing is carried out with an alkali solution containing a reducing agent, and water washing is carried out with water containing a reducing agent.

[0035] Preferably, in the alkaline solution containing a reducing agent, the content of the alkali is 1-10 wt%, for example, it can be 1 wt%, 5 wt% or 10 wt%, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0036] Preferably, the number of times of washing in step (3) is more than 2 times, for example, it can be 2 times, 4 times, 6 times or 8 times, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0037] Preferably, the drying temperature in step (3) is 80-150 °C, for example, it can be 80 °C, 100 °C, 130 °C or 150 °C, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0038] Preferably, the moisture content of the cobalt-free nickel-manganese binary precursor material in step (3) is below 0.8 wt%, for example, it can be 0.8 wt%, 0.6 wt%, 0.4 wt% or 0.2 wt%. The chemical general formula of the cobalt-free nickel-manganese binary precursor material is Ni 1-x Mn x (OH)2, where 0.10 ≤ x ≤ 0.95, for example, it can be 0.1, 0.3, 0.5, 0.7, 0.9 or 0.95, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0039] As a preferred technical solution of the preparation method of the present invention, the preparation method includes the following steps:

[0040] (1) A nickel-manganese metal source solution with a total metal ion concentration of 1.0-3.0 mol / L, a precipitant solution with a concentration of 20-40 wt%, and a first complexing agent solution with a concentration of 10-25 wt% are fed into the bottom liquid in parallel. In nitrogen and / or argon, at a temperature of 40-80 °C, a complexing agent concentration of 2-12 g / L, and a pH of 11.3-12.5, the nucleation stage of the coprecipitation reaction is carried out;

[0041] The bottom liquid includes water, a precipitant solution and a first complexing agent solution. The pH of the bottom liquid is 11.2-12.5, and the complexing agent concentration is 2-12 g / L;

[0042] (2) After the nucleation stage in step (1) ends, adjust the pH of the coprecipitation reaction to 9.6-11.3, and replace the first complexing agent solution with a second complexing agent solution containing an additive to carry out the growth stage of the coprecipitation reaction until the particle size D50 of the precursor particles is 2-20 μm, and then age at a pH of 9-11 for 6-12 h to obtain a precursor slurry;

[0043] In the second complexing agent solution, the content of the additive is 0.1-10 wt%, and the content of the complexing agent is 10-25 wt%.

[0044] (3) Wash the precursor slurry described in step (2), and then dry it at 80-150 °C to obtain the cobalt-free nickel manganese binary precursor material with a moisture content below 0.8 wt%.

[0045] The washing liquid used for the washing includes 0.1-10 wt% of a reducing agent, and the washing liquid includes an alkaline solution containing a reducing agent and / or water containing a reducing agent.

[0046] In a second aspect, the present invention provides a cobalt-free nickel manganese binary precursor material, which is prepared by using the preparation method described in the first aspect.

[0047] In a third aspect, the present invention provides a cobalt-free nickel manganese binary cathode material, which is obtained by mixing and sintering a lithium source and the cobalt-free nickel manganese binary precursor material described in the second aspect.

[0048] In a fourth aspect, the present invention provides a lithium-ion battery, which includes the cobalt-free nickel manganese binary cathode material described in the third aspect.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] By adding a small amount of additives that can affect the crystal plane growth of the precursor in the growth stage of the coprecipitation reaction, the present invention regulates the crystallinity and crystal structure of the precursor, and avoids the additives being wrapped inside the particles in the rapid nucleation stage of the precursor, introducing more impurities; moreover, in the washing step of the post-treatment, the present invention adds a reducing agent to wash the precursor slurry, inhibits the precipitation of manganese oxide on the particle surface, further ensures the high crystallinity and structural uniformity of the precursor, improves the surface morphology of the precursor, and prepares a cobalt-free nickel manganese binary precursor with good crystallinity and no precipitation of manganese oxide. Description of the Drawings

[0051] Figure 1 It is the SEM image of the cobalt-free nickel manganese binary precursor material obtained in Example 1 of the present invention;

[0052] Figure 2 It is the SEM image of the cobalt-free nickel manganese binary precursor material obtained in Comparative Example 1 of the present invention;

[0053] Figure 3 It is the SEM image of the cobalt-free nickel manganese binary precursor material obtained in Comparative Example 2 of the present invention;

[0054] Figure 4SEM image of the cobalt-free nickel-manganese binary precursor material obtained in Comparative Example 3 of the present invention. Detailed implementation mode

[0055] The technical solution of the present invention will be further described below through specific implementation modes. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0056] Example 1

[0057] This example provides a preparation method of a cobalt-free nickel-manganese binary precursor material. The preparation method includes the following steps:

[0058] (1) According to the molecular formula Ni 0.25 Mn 0.75 (OH)2, prepare a nickel-manganese metal source solution with a total metal ion concentration of 2 mol / L from manganese sulfate, nickel sulfate and water. Add the nickel-manganese metal source solution with a total metal ion concentration of 2 mol / L, a sodium hydroxide solution with a concentration of 32 wt%, and a first ammonia water solution with a concentration of 16 wt% to a 50 L reaction kettle containing bottom liquid at a flow rate of 1.86 kg / h, 0.78 kg / h and 0.24 kg / h respectively to carry out the nucleation stage of the coprecipitation reaction. The pH of the nucleation stage is controlled at 12.0 and maintained for 6 h;

[0059] During the entire coprecipitation reaction stage, it is carried out in nitrogen at a temperature of 55 °C and a stirring speed of 600 rpm, and the ammonia concentration is maintained at a concentration of 5.5 g / L; the bottom liquid includes water, sodium hydroxide solution and ammonia water solution, and the pH of the bottom liquid is 12.2 and the ammonia water concentration is 5.5 g / L;

[0060] (2) After the nucleation stage in step (1) ends, adjust the pH of the coprecipitation reaction to 10.0, and replace the first ammonia water solution with a second complexing agent solution containing an additive to carry out the growth stage of the coprecipitation reaction until the particle size D50 of the precursor particles is 10 μm, stop feeding, then let it stand, draw the supernatant, and add sodium hydroxide lye and pure water to adjust the pH to 10 for aging for 8 h to obtain a precursor slurry;

[0061] In the second complexing agent solution, the content of the additive is 4 wt%, and the content of the complexing agent is 16 wt%. The additive is triethanolamine and the complexing agent is ammonia water;

[0062] (3) Transfer the precursor slurry described in step (2) to a scrubber, and perform alkali washing 3 times and water washing 3 times with a dilute sodium hydroxide solution containing D-isoascorbic acid (reductant D-isoascorbic acid: sodium hydroxide: water = 1:4:95) and water (reductant D-isoascorbic acid: water = 2:98). Then, after solid-liquid separation, dry at 120 °C to obtain the cobalt-free nickel-manganese binary precursor material with a moisture content of 0.5 wt%. The molecular formula of the cobalt-free nickel-manganese binary precursor material is Ni 0.25 Mn 0.75 (OH)2;

[0063] In the dilute sodium hydroxide solution containing D-isoascorbic acid, the content of D-isoascorbic acid is 1 wt%. In the water containing D-isoascorbic acid, the content of D-isoascorbic acid is 2 wt%;

[0064] The SEM image of the cobalt-free nickel-manganese binary precursor material obtained in this example is as Figure 1 shown

[0065] Example 2

[0066] This example provides a preparation method of a cobalt-free nickel-manganese binary precursor material. The preparation method includes the following steps:

[0067] (1) According to the molecular formula Ni 0.5 Mn 0.5 (OH)2, prepare a nickel-manganese metal source solution with a total metal ion concentration of 3.0 mol / L from manganese sulfate, nickel sulfate and water. Add the nickel-manganese metal source solution with a total metal ion concentration of 3.0 mol / L, a sodium hydroxide solution with a concentration of 40 wt% and a first ammonia water solution with a concentration of 25 wt% to a 50 L reaction kettle containing a bottom solution for the nucleation stage of the co-precipitation reaction. Control the pH in the nucleation stage at 11.3 and maintain it for 6 h;

[0068] During the entire co-precipitation reaction stage, it is carried out in nitrogen at a temperature of 80 °C and an ammonia water concentration of 12 g / L; the bottom solution includes water, sodium hydroxide solution and ammonia water, the pH of the bottom solution is 11.2, and the complexing agent concentration is 12 g / L;

[0069] (2) After the nucleation stage described in step (1) ends, adjust the pH of the co-precipitation reaction to 9.6, and replace the first ammonia water solution with a second complexing agent solution containing an additive for the growth stage of the co-precipitation reaction until the precursor particle size D50 reaches 12 μm, stop feeding, then let it stand, draw the supernatant, and add sodium hydroxide alkali solution and pure water to adjust the pH to 9 for aging for 12 h to obtain a precursor slurry;

[0070] In the second complexing agent solution, the content of the additive is 10 wt%, the content of the complexing agent is 10 wt%, the additive is cetyltrimethylammonium bromide, and the complexing agent is ammonia water;

[0071] (3) Transfer the precursor slurry described in step (2) to a scrubber, and perform alkali washing twice and water washing three times with a dilute sodium hydroxide solution containing citric acid (reductant citric acid:sodium hydroxide:water = 10:4:86) and water (reductant citric acid:water = 0.1:99.9). Then, after solid-liquid separation, dry at 150 °C to obtain the cobalt-free nickel-manganese binary precursor material with a moisture content of 0.8 wt%. The molecular formula of the cobalt-free nickel-manganese binary precursor material is Ni 0.5 Mn 0.5 (OH)2;

[0072] In the dilute sodium hydroxide solution containing citric acid, the content of citric acid is 10 wt%, and in the water containing citric acid, the content of citric acid is 0.1 wt%.

[0073] Example 3

[0074] This example provides a method for preparing a cobalt-free nickel-manganese binary precursor material, and the preparation method includes the following steps:

[0075] (1) According to the molecular formula Ni 0.25 Mn 0.75 (OH)2, prepare a nickel-manganese metal source solution with a total metal ion concentration of 1.0 mol / L from manganese sulfate, nickel sulfate and water. Add the nickel-manganese metal source solution with a total metal ion concentration of 1.0 mol / L, a sodium hydroxide solution with a concentration of 20 wt%, and a first ammonia water solution with a concentration of 10 wt% to a 50 L reaction kettle containing a bottom solution for the nucleation stage of the coprecipitation reaction. The pH of the nucleation stage is controlled at 12.5 and maintained for 6 h;

[0076] During the entire coprecipitation reaction stage, it is carried out in nitrogen, at a temperature of 40 °C and an ammonia water concentration of 2 g / L; the bottom solution includes water, a precipitant solution and a first complexing agent solution, the pH of the bottom solution is 12.5, and the complexing agent concentration is 2 g / L;

[0077] (2) After the nucleation stage described in step (1) ends, adjust the pH of the coprecipitation reaction to 11.3, and replace the first ammonia water solution with a second complexing agent solution containing an additive for the growth stage of the coprecipitation reaction until the particle size D50 of the precursor particles is 4 μm, then stop feeding, and then let it stand. After pumping out the supernatant, add sodium hydroxide alkali solution and pure water to adjust the pH to 11 for aging for 6 h to obtain a precursor slurry;

[0078] In the second complexing agent solution, the content of the additive is 0.1 wt%, and the content of the complexing agent is 25 wt%. The additive is triethanolamine, and the complexing agent is ammonia water;

[0079] (3) Transfer the precursor slurry described in step (2) to a scrubber, and perform alkali washing 3 times and water washing 2 times with a dilute sodium hydroxide solution containing D-isoascorbic acid (reductant D-isoascorbic acid: sodium hydroxide: water = 0.1:4:95.9) and water (reductant D-isoascorbic acid: water = 10:90). Then, after solid-liquid separation, dry at 100 °C to obtain the cobalt-free nickel-manganese binary precursor material with a moisture content of 0.8 wt%. The molecular formula of the cobalt-free nickel-manganese binary precursor material is Ni 0.25 Mn 0.75 (OH)2;

[0080] In the dilute sodium hydroxide solution containing D-isoascorbic acid, the content of D-isoascorbic acid is 0.1 wt%, and in the water containing D-isoascorbic acid, the content of D-isoascorbic acid is 10 wt%.

[0081] Example 4

[0082] This example provides a preparation method of a cobalt-free nickel-manganese binary precursor material. Except that the content of the additive in the second complexing agent solution described in step (2) is 0.05 wt%, the rest are the same as in Example 1.

[0083] Example 5

[0084] This example provides a preparation method of a cobalt-free nickel-manganese binary precursor material. Except that the content of the additive in the second complexing agent solution described in step (2) is 12 wt%, the rest are the same as in Example 1.

[0085] Example 6

[0086] This example provides a preparation method of a cobalt-free nickel-manganese binary precursor material. Except that the content of D-isoascorbic acid in the dilute sodium hydroxide solution containing D-isoascorbic acid is 0.05 wt%, the rest are the same as in Example 1.

[0087] Example 7

[0088] This example provides a preparation method of a cobalt-free nickel-manganese binary precursor material. Except that the content of D-isoascorbic acid in the dilute sodium hydroxide solution containing D-isoascorbic acid is 12 wt%, the rest are the same as in Example 1.

[0089] Comparative Example 1

[0090] This comparative example provides a method for preparing a cobalt-free nickel-manganese binary precursor material. Except that the first ammonia water solution is not replaced with a second complexing agent solution containing additives, and the washing liquid used in step (3) does not contain a reducing agent, and the material is alkali-washed 3 times with a 4% sodium hydroxide solution by mass fraction and washed 3 times with pure water, the rest are the same as in Example 1;

[0091] The SEM image of the cobalt-free nickel-manganese binary precursor material obtained in this comparative example is as Figure 2 shown.

[0092] Comparative Example 2

[0093] This comparative example provides a method for preparing a cobalt-free nickel-manganese binary precursor material. Except that the washing liquid used in step (3) does not contain a reducing agent, and the material is alkali-washed 3 times with a 4% sodium hydroxide solution by mass fraction and washed 3 times with pure water, the rest are the same as in Example 1;

[0094] The SEM image of the cobalt-free nickel-manganese binary precursor material obtained in this comparative example is as Figure 3 shown.

[0095] Comparative Example 3

[0096] This comparative example provides a method for preparing a cobalt-free nickel-manganese binary precursor material. Except that the first ammonia water solution is not replaced with a second complexing agent solution containing additives, the rest are the same as in Example 1;

[0097] The SEM image of the cobalt-free nickel-manganese binary precursor material obtained in this comparative example is as Figure 4 shown.

[0098] Comparative Example 4

[0099] This comparative example provides a method for preparing a cobalt-free nickel-manganese binary precursor material. Except that the first ammonia water solution in step (1) is replaced with a second complexing agent solution containing additives, and the entire coprecipitation reaction uses the second complexing agent solution containing additives, the rest are the same as in Example 1.

[0100] After the cobalt-free nickel-manganese binary precursor materials obtained in the above examples and comparative examples were uniformly mixed with lithium hydroxide at a lithium ratio of Li / TM = 1.55, they were sintered at 850 °C for 18 h to obtain a lithium-rich manganese-based cathode material, which was assembled into a coin cell for electrochemical performance testing. The specific experimental steps are as follows: First, the active material (the lithium-rich manganese-based cathode material obtained by sintering), the conductive agent acetylene black, and the binder polyvinylidene fluoride were dissolved in N-methylpyrrolidone at a mass ratio of 8:1:1, and the slurry was homogenized at room temperature using a homogenizer in multiple stages; then, the ground slurry was evenly coated on the aluminum foil with a coater and dried in a vacuum drying oven at 80 °C for 12 h; finally, the aluminum foil was stamped into a circular electrode sheet with a diameter of 1.13 cm 2 .

[0101] The obtained electrode sheet was used as the positive electrode, the lithium metal sheet was used as the counter electrode, and the porous polypropylene membrane (Celgard 2400, USA) was used as the separator for separating the positive electrode and the counter electrode. The CR-2032 battery was assembled in a glove box filled with Ar gas. The battery was tested using a battery testing system (BlueTEC CT2001A, Wuhan, China). First, it was activated 3 times at a rate of 0.1C / 2.0 - 4.6V, and then the activated coin cell was tested for electrochemical performance under the conditions of 2.0V - 4.6V @ 0.1C / 0.1C.

[0102] The test results are shown in Table 1:

[0103] Table 1

[0104] <![CDATA[Initial cycle discharge specific capacity / mAh·g -1 > Capacity retention rate / % after 100 cycles at 0.1C Example 1 255.78 93.22 Example 2 253.46 92.53 Example 3 252.98 92.18 Example 4 245.26 91.70 Example 5 247.33 91.39 Example 6 244.68 90.44 Example 7 249.49 91.06 Comparative Example 1 226.63 84.39 Comparative Example 2 240.97 87.95 Comparative Example 3 237.52 85.73 Comparative Example 4 242.85 88.21

[0105] It can be seen from Table 1 that:

[0106] (1) From Example 1 and Comparative Examples 1 - 3, it can be seen that by adding an additive in the precursor growth stage of the present invention and adding a reducing agent for washing in the washing stage, the crystallinity can be ensured and the precipitation of small particles of manganese oxide can be avoided. By comparison, adding an additive in the growth stage of the coprecipitation reaction and adding a reducing agent in the alkali washing and water washing processes in the post-treatment stage, no small particles of manganese oxide precipitate on the surface of the obtained precursor particles, and the boundaries of the primary grains are clear, well-developed, and have good crystallinity. In contrast, in Comparative Example 1 where no additive and reducing agent were added, more fine particles precipitated on the surface of the precursor, the boundaries of the primary grains were blurred, the morphology was porous, and the crystallinity was poor. Therefore, the initial discharge specific capacity and cycle performance of the battery obtained in Comparative Example 1 decreased. Figure 1 - Figure 2 (2) From

[0107] (2) From Figure 1 and Figure 3It can be found that in Comparative Example 2, an additive was added during the growth stage of the coprecipitation reaction, but no reducing agent was added during the post-treatment. Small particles of manganese oxide precipitated on the surface of the obtained precursor particles. However, its primary grains were well-developed, without pores, and had good crystallinity, indicating that the addition of this additive played an important role in improving its crystallinity, but the effect of inhibiting the precipitation of manganese oxide was not obvious. The initial discharge specific capacity and cycle performance of the battery obtained in Comparative Example 2 decreased compared with those in Example 1; from Figure 1 and Figure 4 It can be found that in Comparative Example 3, no additive was added during the growth stage of the coprecipitation reaction, but a reducing agent was added during the post-treatment. No obvious small particles of manganese oxide precipitated on the surface of the obtained precursor particles. However, its primary grains were poorly developed, with pores, and had poor crystallinity, verifying that the reducing agent had an obvious effect on inhibiting the precipitation of manganese oxide. The initial discharge specific capacity and cycle performance of the battery obtained in Comparative Example 3 decreased compared with those in Example 1; at the same time, comparing Figure 2 and Figure 4 it can be found that the crystallinity of the primary grains in Comparative Example 3 was still better than that in Comparative Example 1, which also indicates that adding a reducing agent during the post-treatment also had a certain effect on improving the crystallinity of the nickel-manganese precursor when inhibiting the precipitation of manganese oxide. Therefore, the initial discharge specific capacity and cycle performance of the battery in Comparative Example 3 were improved compared with those in Comparative Example 1.

[0108] (3) It can be seen from Example 1 and Comparative Example 4 that if the present invention also uses a complexing agent solution containing an additive in the nucleation stage, the additive will be wrapped inside the particles, introducing more impurities inside the particles and being difficult to wash away, thus affecting the performance of the precursor; it can be seen from Example 1 and Examples 4-5 that the content of the additive will affect the exertion of its function; it can be seen from Example 1 and Examples 6-7 that the addition amount of the reducing agent in the washing process of the present invention will affect the exertion of its function of inhibiting the precipitation of manganese oxide, thus affecting the performance of the obtained precursor.

[0109] In summary, the present invention provides a cobalt-free nickel-manganese binary precursor material, its preparation method and application. The preparation method controls crystal growth by adding an additive during the growth stage of the coprecipitation reaction, and adds a reducing agent during the washing stage of the post-treatment to inhibit the precipitation of manganese oxide, so that the obtained precursor has better crystallinity and a lower amount of manganese oxide precipitation, improving the product quality of the precursor.

[0110] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a cobalt-free nickel-manganese binary precursor material, characterized in that: The preparation method comprises the following steps: (1) mixing a nickel-manganese metal source solution, a precipitant solution and a first complexing agent solution to perform a nucleation stage of a coprecipitation reaction; (2) after the nucleation stage of step (1) is completed, the pH of the coprecipitation reaction is adjusted, and the first complexing agent solution is replaced with a second complexing agent solution containing an additive to carry out a growth stage of the coprecipitation reaction to obtain a precursor slurry; (3) washing and drying the precursor slurry in step (2) to obtain the cobalt-free nickel-manganese binary precursor material; The washing liquid used in the washing includes a reducing agent; The additive in step (2) comprises any one of polyvinyl pyrrolidone, polyethylene glycol, tetramethylammonium hydroxide, hexadecyltrimethylammonium bromide or triethanolamine, or a combination of at least two thereof; The reducing agent in step (3) includes any one of glucose, citric acid, ascorbic acid or oxalic acid, or a combination of at least two of them.

2. The preparation method according to claim 1, characterized in that: The total metal ion concentration of the nickel-manganese metal source solution in step (1) is 1.0-3.0 mol / L, wherein the molar ratio of nickel ions to manganese ions is (1-x):x, wherein x is 0.1-0.

95.

3. The preparation method according to claim 1, characterized in that: The concentration of the precipitant solution in step (1) is 20-40wt%.

4. The preparation method according to claim 1, characterized in that: Step (1) The concentration of the first complexing agent solution is 10-25 wt%.

5. The preparation method according to claim 1, characterized in that: The mixing in step (1) includes flowing the nickel-manganese metal source solution, the precipitant solution and the first complexing agent solution into the base solution in parallel.

6. The preparation method according to claim 5, characterized in that: The base solution comprises water, a precipitant solution and a first complexing agent solution.

7. The preparation method according to claim 5, characterized in that: The pH of the base solution is 11.2-12.5, and the concentration of the complexing agent is 2-12 g / L.

8. The preparation method according to claim 1, characterized in that: The temperature of the nucleation stage in step (1) and the growth stage in step (2) are independently 40-80° C., the concentration of the complexing agent in the reaction system is maintained in the range of 2-12 g / L, and the reaction is carried out in nitrogen and / or argon.

9. The preparation method according to claim 1, characterized in that: The pH of the nucleation stage in step (1) is 11.3-12.

5.

10. The preparation method according to claim 1, characterized in that: In step (2), the content of the additive in the second complexing agent solution is 0.1-10 wt%.

11. The preparation method according to claim 1, characterized in that: In step (2), the content of the complexing agent in the second complexing agent solution is 10-25wt%.

12. The preparation method according to claim 1, characterized in that: In step (2), the pH of the coprecipitation reaction is adjusted to 9.6-11.

3.

13. The preparation method according to claim 1, characterized in that: In step (2), the growth phase reacts until the precursor particles have a particle size D50 of 2-20 μm.

14. The preparation method according to claim 1, characterized in that: The growth phase of step (2) reacts until the precursor particles have a particle size D50 of 4-12 μm.

15. The preparation method according to claim 1, characterized in that: After the precursor slurry in step (2) is aged, the washing in step (3) is performed.

16. The preparation method according to claim 15, characterized in that: The pH of the aging is 9-11, and the aging time is 6-12 hours.

17. The preparation method according to claim 1, characterized in that: In the washing liquid of step (3), the content of reducing agent is 0.1-10wt%.

18. The preparation method according to claim 1, characterized in that: The washing liquid in step (3) includes an alkaline solution containing a reducing agent, and / or water containing a reducing agent.

19. The preparation method according to claim 1, characterized in that: The drying temperature in step (3) is 80-150°C.

20. The preparation method according to claim 1, characterized in that: The water content of the cobalt-free nickel-manganese binary precursor material in step (3) is below 0.8wt%.

21. The preparation method according to claim 1, characterized in that: The preparation method comprises the following steps: (1) a nickel-manganese metal source solution having a total metal ion concentration of 1.0-3.0 mol / L, a precipitant solution having a concentration of 20-40 wt % and a first complexing agent solution having a concentration of 10-25 wt % are introduced into the bottom liquid in parallel, and a nucleation stage of a coprecipitation reaction is performed in nitrogen and / or argon at a temperature of 40-80° C., a complexing agent concentration of 2-12 g / L and a pH of 11.3-12.5; The base solution includes water, a precipitant solution and a first complexing agent solution, the pH of the base solution is 11.2-12.5, and the concentration of the complexing agent is 2-12 g / L; (2) After the nucleation stage of step (1), the pH of the coprecipitation reaction is adjusted to 9.6-11.3, and the first complexing agent solution is replaced with a second complexing agent solution containing an additive to carry out the growth stage of the coprecipitation reaction until the particle size D50 of the precursor particles is 2-20 μm, and then aged at a pH of 9-11 for 6-12 hours to obtain a precursor slurry; In the second complexing agent solution, the content of the additive is 0.1-10wt%, and the content of the complexing agent is 10-25wt%; (3) washing the precursor slurry of step (2), and then drying it at 80-150° C. to obtain the cobalt-free nickel-manganese binary precursor material having a moisture content of less than 0.8 wt %; The washing liquid used in the washing comprises 0.1-10 wt % of a reducing agent, and the washing liquid comprises an alkali solution containing a reducing agent, and / or water containing a reducing agent.

22. A cobalt-free nickel-manganese binary precursor material, characterized in that: The cobalt-free nickel-manganese binary precursor material is prepared by the preparation method according to any one of claims 1 to 21.

23. A cobalt-free nickel-manganese binary positive electrode material, characterized in that: The cobalt-free nickel-manganese binary positive electrode material is obtained by mixing and sintering a lithium source and the cobalt-free nickel-manganese binary precursor material as claimed in claim 22.

24. A lithium ion battery, characterized in that: The lithium-ion battery comprises the cobalt-free nickel-manganese binary positive electrode material as described in claim 23.

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