Cobalt-free nickel-manganese binary precursor material, and preparation method therefor and use thereof

Abstract

Provided in the present application are a cobalt-free nickel-manganese binary precursor material, and a preparation method therefor and the use thereof. The preparation method comprises the following steps: mixing a nickel-manganese metal source solution, a precipitant solution and a first complexing agent solution, and carrying out a nucleation stage of a coprecipitation reaction; after the nucleation stage is finished, adjusting the pH value of the coprecipitation reaction, replacing the first complexing agent solution with a second complexing agent solution containing an additive, and carrying out a growth stage of the coprecipitation reaction, so as to obtain a precursor slurry; and washing and drying the precursor slurry, so as to obtain the cobalt-free nickel manganese binary precursor material, wherein a washing solution used in washing comprises a reducing agent. In the preparation method of the present application, the additive is added in the growth stage of the coprecipitation reaction to control the growth of crystals, and the reducing agent is added in the washing stage of the post-treatment to inhibit the precipitation of a manganese oxide, thereby enabling the obtained precursor to have a better crystallinity and a lower precipitation amount of the manganese oxide.

Description

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

[0001] This application belongs to the field of battery technology and relates to a cobalt-free nickel-manganese binary precursor material, its preparation method and application. Background Technology

[0002] The rapid development of electric vehicles has led to an increasing demand for high-performance, high-safety, and long-life lithium-ion batteries. Ternary cathode materials have become a research hotspot in the field of power batteries due to their high energy density and excellent electrochemical performance. However, due to the scarcity and high price of cobalt resources, current research on cathode materials is gradually shifting towards cobalt-free nickel-manganese binary material systems to avoid the limitations imposed by cobalt resource scarcity on cathode material development. Nickel and manganese resources are relatively abundant, and nickel-manganese binary materials also possess advantages such as 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, traditional cobalt-free nickel-manganese binary precursors often suffer from poor crystallinity and easy precipitation of manganese oxides during preparation. These problems not only affect the electrochemical performance of the cathode material but also reduce its cycle stability and safety. Related technologies typically involve adding additives during precursor co-precipitation to mitigate these issues. For example, CN 116216796A adds ethylene glycol as a modifier to the reaction substrate, appropriately controlling the crystallinity of the nickel-manganese binary precursor and inhibiting the precipitation of manganese tetroxide, thus improving the material morphology. However, ethylene glycol may become trapped within the precursor particles, and for nickel-manganese binary materials with high manganese content, it may still be difficult to prevent manganese oxidation during post-processing, thereby affecting the quality of the precursor product.

[0004] Therefore, there is a need to develop a method for preparing a cobalt-free nickel-manganese binary precursor that does not introduce new impurities, ensures good crystallinity of the precursor product, and prevents manganese oxide precipitation. Summary of the Invention

[0005] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0006] This application provides a cobalt-free nickel-manganese binary precursor material, its preparation method, and its application. The preparation method controls crystal growth by adding additives during the growth stage of the co-precipitation reaction and adds a reducing agent during the washing stage of the post-treatment to inhibit the precipitation of manganese oxides, thereby giving the precursor better crystallinity and lower manganese oxide precipitation, thus improving the product quality of the precursor.

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

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

[0009] (2) After the nucleation stage described in 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 additives to carry out the growth stage of the coprecipitation reaction, thereby obtaining the precursor slurry.

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

[0011] The washing solution used in the washing process includes a reducing agent.

[0012] In this application, a small amount of additives that can affect the crystal growth of the precursor are added during the growth stage of the coprecipitation reaction. This controls the crystallinity and crystal structure of the precursor and avoids the additives being encapsulated inside the particles during the rapid nucleation stage of the precursor, thus introducing more impurities. Furthermore, in the washing stage of the post-treatment, a reducing agent is added to wash the precursor slurry, which inhibits the precipitation of manganese oxides on the particle surface. This further ensures the high crystallinity and structural uniformity of the precursor, improves the surface morphology of the precursor, and prepares a cobalt-nickel-manganese binary precursor with good crystallinity and no manganese oxide precipitation.

[0013] In one embodiment, the total metal ion concentration of the nickel-manganese metal source solution 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, wherein the molar ratio of nickel ions to manganese ions is (1-x):x, wherein 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 range are also applicable.

[0014] In one embodiment, the concentration of the precipitant solution 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. Other unlisted values ​​within the range are also applicable.

[0015] In one embodiment, the concentration of the first complexing agent solution 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. Other unlisted values ​​within the range are also applicable.

[0016] In one embodiment, the mixing in step (1) includes passing a nickel-manganese metal source solution, a precipitant solution, and a first complexing agent solution concurrently into a base liquid.

[0017] In one embodiment, the base liquid includes water, a precipitant solution, and a first complexing agent solution.

[0018] In one embodiment, the pH of the base solution is 11.2-12.5, for example, it can be 11.2, 11.5, 12.0 or 12.5, and 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. Other unlisted values ​​within the range are also applicable.

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

[0020] In one embodiment, 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. Other unlisted values ​​within the range are also applicable.

[0021] In one embodiment, in step (2), the content of the additive in the second complexing agent solution 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 range are also applicable.

[0022] The amount of additives added during the growth stage in this application affects crystal growth. If the amount of additives added is too small, it will not be able to regulate the growth of particle crystals. If the amount of additives added is too large, it will easily remain in the sample, affecting the quality of the precursor and increasing the material cost.

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

[0024] In one embodiment, in step (2), the content of the complexing agent in the second complexing agent solution 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. Other unlisted values ​​within the range are also applicable.

[0025] In one embodiment, step (2) involves adjusting the pH of the coprecipitation reaction to 9.6-11.3, for example, 9.6, 10, 10.5, 11 or 11.3, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] In one embodiment, the growth stage in step (2) reacts to a precursor particle size D50 of 2-20 μm, for example, 2 μm, 5 μm, 10 μm, 15 μm or 20 μm, but not limited to the listed values. Other unlisted values ​​within the range are also applicable, and can be selected as 4-12 μm.

[0027] In one embodiment, the precursor slurry described in step (2) is aged before the washing described in step (3).

[0028] In one embodiment, the aging pH is 9-11, for example, it can be 9, 10 or 11, and the aging time is 6-12h, for example, it can be 6h, 8h, 10h or 12h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

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

[0030] In one embodiment, the content of reducing agent in the washing liquid in step (3) 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 range are also applicable.

[0031] The content of reducing agent during the washing process of this application will affect the washing effect. If too little reducing agent is added, the precipitation of manganese oxides cannot be effectively inhibited. If too much reducing agent is added, it may remain in the sample, affecting the quality of the precursor and increasing the cost accordingly.

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

[0033] In one embodiment, the washing liquid in step (3) includes an alkaline solution containing a reducing agent and / or water containing a reducing agent.

[0034] The washing process described in step (3) of this application includes two or more alkaline washes followed by two or more water washes. The alkaline washes are performed using an alkaline solution containing a reducing agent, and the water washes are performed using water containing a reducing agent.

[0035] In one embodiment, the alkaline solution containing the reducing agent contains 1-10 wt% alkali, for example, 1 wt%, 5 wt%, or 10 wt%, but is not limited to the listed values; other unlisted values ​​within the range are also applicable.

[0036] In one embodiment, the number of times the washing is performed in step (3) is more than 2 times, for example, 2 times, 4 times, 6 times or 8 times, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0037] In one embodiment, 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. Other unlisted values ​​within the range are also applicable.

[0038] In one embodiment, the water 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%, and the general chemical 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, can be 0.1, 0.3, 0.5, 0.7, 0.9 or 0.95, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0039] As an optional technical solution for the preparation method described in this application, 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. The nucleation stage of the coprecipitation reaction is carried out in nitrogen and / or argon gas at a temperature of 40-80℃, a complexing agent concentration of 2-12 g / L, and a pH of 11.3-12.5.

[0041] The base solution comprises water, a precipitant solution, and a first complexing agent solution, wherein the pH of the base solution is 11.2-12.5, and the concentration of the complexing agent is 2-12 g / L;

[0042] (2) After the nucleation stage described in step (1) is completed, the pH of the coprecipitation reaction is adjusted to 9.6-11.3, and the first complexing agent solution is replaced with the second complexing agent solution containing additives to carry out the growth stage of the coprecipitation reaction until the precursor particle size D50 is 2-20μm. Then, it is aged at pH 9-11 for 6-12h to obtain the 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) The precursor slurry described in step (2) is washed and then dried at 80-150°C to obtain the cobalt-free nickel-manganese binary precursor material with a water content of less than 0.8wt%.

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

[0046] Secondly, this application provides a cobalt-free nickel-manganese binary precursor material, which is prepared by the preparation method described in the first aspect.

[0047] Thirdly, this application provides a cobalt-free nickel-manganese binary cathode material, which is obtained by mixing and sintering a lithium source with a cobalt-free nickel-manganese binary precursor material as described in the second aspect.

[0048] Fourthly, this application provides a lithium-ion battery comprising the cobalt-free nickel-manganese binary cathode material as described in the third aspect.

[0049] Compared with related technologies, this application has the following advantages:

[0050] This application regulates the crystallinity and crystal structure of the precursor by adding a small amount of additives that can affect the crystal face growth of the precursor during the growth stage of the coprecipitation reaction, and avoids the additives being encapsulated inside the particles and introducing more impurities during the rapid nucleation stage of the precursor. Furthermore, this application adds a reducing agent to wash the precursor slurry in the post-treatment washing stage, which inhibits the precipitation of manganese oxides on the particle surface, further ensuring the high crystallinity and structural uniformity of the precursor, improving the surface morphology of the precursor, and preparing a cobalt-nickel-manganese binary precursor with good crystallinity and no manganese oxide precipitation.

[0051] After reading and understanding the accompanying diagrams and detailed descriptions, the other aspects can be understood. Attached Figure Description

[0052] The accompanying drawings are used to provide a further understanding of the technical solutions in this paper and form part of the specification. They are used together with the embodiments of this application to explain the technical solutions in this paper and do not constitute a limitation on the technical solutions in this paper.

[0053] Figure 1 is a SEM image of the cobalt-free nickel-manganese binary precursor material obtained in Example 1 of this application;

[0054] Figure 2 is a SEM image of the cobalt-free nickel-manganese binary precursor material obtained in Comparative Example 1 of this application.

[0055] Figure 3 is a SEM image of the cobalt-free nickel-manganese binary precursor material obtained in Comparative Example 2 of this application;

[0056] Figure 4 is a SEM image of the cobalt-free nickel-manganese binary precursor material obtained in Comparative Example 3 of this application. Detailed Implementation

[0057] The technical solution of this application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely to help understand this application and should not be regarded as specific limitations on this application.

[0058] Example 1

[0059] This embodiment provides a method for preparing a cobalt-free nickel-manganese binary precursor material, the method comprising the following steps:

[0060] (1) According to the molecular formula Ni 0.25 Mn 0.75 (OH)2 was prepared by adding manganese sulfate, nickel sulfate and water to form a nickel-manganese metal source solution with a total metal ion concentration of 2 mol / L. 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 solution with a concentration of 16 wt% were added to a 50 L reactor containing the bottom liquid at flow rates of 1.86 kg / h, 0.78 kg / h and 0.24 kg / h, respectively, to carry out the nucleation stage of co-precipitation reaction. The pH of the nucleation stage was controlled at 12.0 and maintained for 6 h.

[0061] Throughout the coprecipitation reaction, the reaction was carried out under nitrogen atmosphere at 55°C with a stirring speed of 600 rpm and an ammonia concentration maintained at 5.5 g / L. The base solution consisted of water, sodium hydroxide solution, and ammonia solution, with a pH of 12.2 and an ammonia concentration of 5.5 g / L.

[0062] (2) After the nucleation stage described in step (1) is completed, the pH of the coprecipitation reaction is adjusted to 10.0, and the first ammonia solution is replaced with the second complexing agent solution containing additives to carry out the growth stage of the coprecipitation reaction until the precursor particle size D50 is 10 μm. Then the feed is stopped, and the mixture is allowed to stand. After the supernatant is drawn off, sodium hydroxide alkali solution and pure water are added to adjust the pH to 10 and aged for 8 hours to obtain the precursor slurry.

[0063] In the second complexing agent solution, the content of the additive is 4 wt%, the content of the complexing agent is 16 wt%, the additive is triethanolamine, and the complexing agent is ammonia.

[0064] (3) The precursor slurry described in step (2) is transferred to a washer and washed three times with alkali and three times with water using a dilute sodium hydroxide solution containing D-isoascorbic acid (reducing agent D-isoascorbic acid: sodium hydroxide: water = 1:4:95) and water (reducing agent D-isoascorbic acid: water = 2:98). After solid-liquid separation, it is dried at 120°C to obtain the cobalt-free nickel-manganese binary precursor material with a water 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;

[0065] The dilute sodium hydroxide solution containing D-isoascorbic acid has a D-isoascorbic acid content of 1 wt%, and the water containing D-isoascorbic acid has a D-isoascorbic acid content of 2 wt%.

[0066] The SEM image of the cobalt-free nickel-manganese binary precursor material obtained in this embodiment is shown in Figure 1.

[0067] Example 2

[0068] This embodiment provides a method for preparing a cobalt-free nickel-manganese binary precursor material, the method comprising the following steps:

[0069] (1) According to the molecular formula Ni 0.5 Mn 0.5 (OH)2, a nickel-manganese metal source solution with a total metal ion concentration of 3.0 mol / L was prepared by manganese sulfate, nickel sulfate and water. 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 solution with a concentration of 25 wt% were added to a 50 L reactor containing the bottom liquid to carry out the nucleation stage of coprecipitation reaction. The pH of the nucleation stage was controlled at 11.3 and maintained for 6 h.

[0070] The entire coprecipitation reaction was carried out in nitrogen atmosphere at 80°C with an ammonia concentration of 12 g / L; the base solution included water, sodium hydroxide solution and ammonia, the pH of the base solution was 11.2, and the complexing agent concentration was 12 g / L.

[0071] (2) After the nucleation stage described in step (1) is completed, the pH of the coprecipitation reaction is adjusted to 9.6, and the first ammonia solution is replaced with the second complexing agent solution containing additives to carry out the growth stage of the coprecipitation reaction until the precursor particle size D50 is 12μm. Then the feed is stopped, and the mixture is allowed to stand. After the supernatant is drawn off, sodium hydroxide alkali solution and pure water are added to adjust the pH to 9 and aged for 12h to obtain the precursor slurry.

[0072] 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 hexadecyltrimethylammonium bromide, and the complexing agent is ammonia.

[0073] (3) The precursor slurry described in step (2) is transferred to a washer and subjected to two alkaline washes and three water washes using a dilute sodium hydroxide solution containing citric acid (citric acid: sodium hydroxide: water = 10:4:86) and water (citric acid: water = 0.1:99.9). After solid-liquid separation, it is dried at 150°C to obtain the cobalt-free nickel-manganese binary precursor material with a water 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;

[0074] The dilute sodium hydroxide solution containing citric acid contains 10 wt% citric acid, and the water containing citric acid contains 0.1 wt% citric acid.

[0075] Example 3

[0076] This embodiment provides a method for preparing a cobalt-free nickel-manganese binary precursor material, the method comprising the following steps:

[0077] (1) According to the molecular formula Ni 0.25 Mn 0.75 (OH)2, a nickel-manganese metal source solution with a total metal ion concentration of 1.0 mol / L was prepared by manganese sulfate, nickel sulfate and water. 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 solution with a concentration of 10 wt% were added to a 50 L reactor containing the bottom liquid to carry out the nucleation stage of coprecipitation reaction. The pH of the nucleation stage was controlled at 12.5 and maintained for 6 h.

[0078] The entire coprecipitation reaction stage was carried out in nitrogen atmosphere at a temperature of 40°C and an ammonia concentration of 2 g / L; the base solution included water, a precipitant solution, and a first complexing agent solution, the pH of the base solution was 12.5, and the complexing agent concentration was 2 g / L;

[0079] (2) After the nucleation stage described in step (1) is completed, the pH of the coprecipitation reaction is adjusted to 11.3, and the first ammonia solution is replaced with the second complexing agent solution containing additives to carry out the growth stage of the coprecipitation reaction until the precursor particle size D50 is 4μm. Then the feed is stopped, and the mixture is allowed to stand. After the supernatant is drawn off, sodium hydroxide alkali solution and pure water are added to adjust the pH to 11 and aged for 6 hours to obtain the precursor slurry.

[0080] In the second complexing agent solution, the content of the additive is 0.1 wt%, the content of the complexing agent is 25 wt%, the additive is triethanolamine, and the complexing agent is ammonia.

[0081] (3) The precursor slurry described in step (2) is transferred to a washer and washed three times with alkali and twice with water using a dilute sodium hydroxide solution containing D-isoascorbic acid (reducing agent D-isoascorbic acid: sodium hydroxide: water = 0.1:4:95.9) and water (reducing agent D-isoascorbic acid: water = 10:90). After solid-liquid separation, it is dried at 100°C to obtain the cobalt-free nickel-manganese binary precursor material with a water 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;

[0082] The dilute sodium hydroxide solution containing D-isoascorbic acid contains 0.1 wt% D-isoascorbic acid, and the water containing D-isoascorbic acid contains 10 wt% D-isoascorbic acid.

[0083] Example 4

[0084] This embodiment provides a method for preparing a cobalt-free nickel-manganese binary precursor material. Except for step (2), in which the content of the additive in the second complexing agent solution is 0.05 wt%, the preparation method is the same as in Example 1.

[0085] Example 5

[0086] This embodiment provides a method for preparing a cobalt-free nickel-manganese binary precursor material. Except for step (2), in which the content of the additive in the second complexing agent solution is 12 wt%, the preparation method is the same as in Example 1.

[0087] Example 6

[0088] This embodiment provides a method for preparing a cobalt-free nickel-manganese binary precursor material. The preparation method is the same as in Example 1, except that the content of D-isoascorbic acid in the dilute sodium hydroxide solution containing D-isoascorbic acid is 0.05 wt%.

[0089] Example 7

[0090] This embodiment provides a method for preparing a cobalt-free nickel-manganese binary precursor material. The preparation method is the same as in Example 1, except that the content of D-isoascorbic acid in the dilute sodium hydroxide solution containing D-isoascorbic acid is 12wt%.

[0091] Comparative Example 1

[0092] This comparative example provides a method for preparing a cobalt-free nickel-manganese binary precursor material. The preparation method is the same as in Example 1 except that the first ammonia solution is not replaced with a second complexing agent solution containing additives, and the washing solution used in step (3) does not contain a reducing agent. The method is to perform alkaline washing three times with a 4% sodium hydroxide solution and water washing three times with pure water.

[0093] Figure 2 shows the SEM image of the cobalt-free nickel-manganese binary precursor material obtained in this comparative example.

[0094] Comparative Example 2

[0095] This comparative example provides a method for preparing a cobalt-free nickel-manganese binary precursor material. Except for step (3), where the washing solution used for washing does not contain a reducing agent, and the washing is performed three times with an alkali solution of 4% sodium hydroxide and three times with pure water, the preparation method is the same as in Example 1.

[0096] The SEM image of the cobalt-free nickel-manganese binary precursor material obtained in this comparative example is shown in Figure 3.

[0097] Comparative Example 3

[0098] This comparative example provides a method for preparing a cobalt-free nickel-manganese binary precursor material. The preparation method is the same as in Example 1, except that the first ammonia solution is not replaced with a second complexing agent solution containing additives.

[0099] The SEM image of the cobalt-free nickel-manganese binary precursor material obtained in this comparative example is shown in Figure 4.

[0100] Comparative Example 4

[0101] This comparative example provides a method for preparing a cobalt-free nickel-manganese binary precursor material. The preparation method is the same as in Example 1, except that the first ammonia solution in step (1) is replaced with a second complexing agent solution containing additives, so that the second complexing agent solution containing additives is used throughout the coprecipitation reaction.

[0102] 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, and then sintered at 850°C for 18 hours to obtain lithium-rich manganese-based cathode materials. These materials were then assembled into coin cells for electrochemical performance testing. The specific experimental steps are as follows: First, the active material (the sintered lithium-rich manganese-based cathode material), conductive agent acetylene black, and binder polyvinylidene fluoride were dissolved in N-methylpyrrolidone at a mass ratio of 8:1:1. The slurry was homogenized at room temperature using a homogenizer in a multi-stage mode. Then, the ground slurry was uniformly coated onto aluminum foil using a coater and dried in a vacuum drying oven at 80°C for 12 hours. Finally, the aluminum foil was stamped into 1.13 cm diameter pieces. 2 Circular electrode plates.

[0103] The obtained electrode sheet was used as the positive electrode, the lithium metal sheet as the counter electrode, and a porous polypropylene membrane (Celgard 2400, USA) was used as the separator between the positive and counter electrodes. The CR-2032 battery was assembled in a glove box filled with Ar gas. The battery was tested using a battery testing system (Landian CT2001A, Wuhan, China). First, the battery was activated three times at 0.1C rate / 2.0–4.6V. Then, the activated coin cells were subjected to electrochemical performance testing at 2.0V–4.6V@0.1C / 0.1C conditions.

[0104] The test results are shown in Table 1:

[0105] Table 1

[0106] As can be seen from Table 1:

[0107] (1) As can be seen from Example 1 and Comparative Examples 1-3, the addition of additives during the precursor growth stage and the addition of reducing agent during the washing stage can ensure crystallinity and avoid the precipitation of small manganese oxide particles. According to the comparison of Figures 1-2, the addition of additives during the growth stage of the co-precipitation reaction and the addition of reducing agent during the alkaline washing and water washing process in the post-treatment stage resulted in no precipitation of small manganese oxide particles on the surface of the precursor particles, and the primary grains had clear boundaries, complete development, and good crystallinity. In contrast, Comparative Example 1, which did not add additives and reducing agents, showed more small particles precipitating on the surface of the precursor, and the primary grains had blurred boundaries, porous morphology, and poor crystallinity. Therefore, the battery obtained by Comparative Example 1 had a decreased first-cycle discharge specific capacity and cycle performance.

[0108] (2) As shown in Figures 1 and 3, in Comparative Example 2, an additive was added during the growth stage of the co-precipitation reaction, but no reducing agent was added in the post-treatment stage. The resulting precursor particles had small manganese oxide particles precipitated on their surface, but their primary grains were well-developed, pore-free, and had good crystallinity. This indicates that the addition of the additive plays an important role in improving its crystallinity, but its effect on inhibiting manganese oxide precipitation is not significant. The first-cycle discharge specific capacity and cycle performance of the battery obtained in Comparative Example 2 decreased compared to Example 1. As shown in Figures 1 and 4, in Comparative Example 3, no additive was added during the growth stage of the co-precipitation reaction, but a reducing agent was added in the post-treatment stage. The resulting... No obvious manganese oxide particles were precipitated on the surface of the precursor particles, but its primary grain development was poor, with pores and poor crystallinity. This verified that the reducing agent had a significant effect on inhibiting manganese oxide precipitation. The first-cycle discharge specific capacity and cycle performance of the battery obtained in Comparative Example 3 were lower than those of Example 1. Meanwhile, comparing Figures 2 and 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. This also shows that the addition of the reducing agent in the post-processing stage also has a certain effect on improving the crystallinity of the nickel-manganese precursor while inhibiting manganese oxide precipitation. Therefore, the first-cycle discharge specific capacity and cycle performance of the battery in Comparative Example 3 were improved compared with those in Comparative Example 1.

[0109] (3) As can be seen from Example 1 and Comparative Example 4, the present application also uses a complexing agent solution containing additives in the nucleation stage, which will encapsulate the additives inside the particles, introduce more impurities inside the particles, and make them difficult to wash away, thereby affecting the performance of the precursor; As can be seen from Example 1 and Examples 4-5, the content of additives will affect their function; As can be seen from Example 1 and Examples 6-7, the amount of reducing agent added during the washing process of the present application will affect its function of inhibiting the precipitation of manganese oxides, thereby affecting the performance of the obtained precursor.

[0110] In summary, this application provides a cobalt-free nickel-manganese binary precursor material, its preparation method, and its application. The preparation method controls crystal growth by adding additives during the growth stage of the co-precipitation reaction and adds a reducing agent during the washing stage of the post-treatment to inhibit the precipitation of manganese oxides, thereby giving the precursor better crystallinity and lower manganese oxide precipitation, thus improving the product quality of the precursor.

[0111] The above description is only a specific embodiment of this application, but the protection scope of this application is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application fall within the protection and disclosure scope of this application.

Claims

1. A method for preparing a cobalt-free nickel-manganese binary precursor material, comprising 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, adjusting the pH of the coprecipitation reaction and replacing the first complexing agent solution with a second complexing agent solution containing an additive to perform a growth stage of the coprecipitation reaction to obtain a precursor slurry; (3) washing and drying the precursor slurry of step (2) to obtain the cobalt-free nickel-manganese binary precursor material; The washing liquid used in the washing includes a reducing agent.

2. The production method according to claim 1, wherein, The total metal ion concentration of the nickel-manganese metal source solution of 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; Optionally, the concentration of the precipitant solution of step (1) is 20-40 wt%; Optionally, the concentration of the first complexing agent solution of step (1) is 10-25 wt%.

3. The production method according to claim 1 or 2, wherein The mixing of step (1) includes passing the nickel-manganese metal source solution, the precipitant solution and the first complexing agent solution into a bottom liquid in parallel flow; Optionally, the bottom liquid includes water, the precipitant solution and the first complexing agent solution; Optionally, the pH of the bottom liquid is 11.2-12.5, and the complexing agent concentration is 2-12 g / L; Optionally, the temperature of the nucleation stage of step (1) and the growth stage of step (2) is independently 40-80℃, respectively, the complexing agent concentration of the reaction system is maintained within the range of 2-12 g / L, and the reaction is performed in nitrogen and / or argon; Optionally, the pH of the nucleation stage of step (1) is 11.3-12.

5.

4. The production process according to any one of claims 1 to 3, wherein The content of the additive in the second complexing agent solution of step (2) is 0.1-10 wt%; Optionally, the additive of step (2) includes any one or a combination of at least two of polyvinylpyrrolidone, polyethylene glycol, tetramethylammonium hydroxide, cetyltrimethylammonium bromide or triethanolamine; Optionally, the content of the complexing agent in the second complexing agent solution of step (2) is 10-25 wt%.

5. The production process according to any one of claims 1 to 4, wherein The pH of the coprecipitation reaction is adjusted to 9.6-11.3 in step (2); Optionally, the growth stage of step (2) is reacted until the precursor particle size D50 is 2-20 μm, and further optionally 4-12 μm; Optionally, the precursor slurry of step (2) is aged before the washing of step (3); Optionally, the pH of the aging is 9-11, and the aging time is 6-12 h.

6. The production process according to any one of claims 1 to 5, wherein The content of the reducing agent in the washing liquid of step (3) is 0.1-10 wt%; Optionally, the reducing agent includes any one or a combination of at least two of glucose, citric acid, ascorbic acid or oxalic acid; Optionally, the washing liquid of step (3) includes an alkali solution containing a reducing agent and / or water containing a reducing agent; Optionally, the drying temperature of step (3) is 80-150℃; Optionally, the water content of the cobalt-free nickel-manganese binary precursor material of step (3) is below 0.8 wt%.

7. The preparation method according to any one of claims 1-6, comprising the following steps: (1) passing 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% into a bottom liquid in parallel, and performing a nucleation stage of the coprecipitation reaction under nitrogen and / or argon, a temperature of 40-80 °C, a complexing agent concentration of 2-12 g / L, and a pH of 11.3-12.5; the bottom liquid comprises water, the precipitant solution, and the first complexing agent solution, and the pH of the bottom liquid is 11.2-12.5 and the complexing agent concentration is 2-12 g / L; (2) after the nucleation stage of step (1) is completed, adjusting the pH of the coprecipitation reaction to 9.6-11.3, and replacing the first complexing agent solution with a second complexing agent solution containing an additive to perform a growth stage of the coprecipitation reaction until the precursor particle size D50 is 2-20 μm, and then aging for 6-12 h at a pH of 9-11 to obtain a precursor slurry; 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%; (3) washing the precursor slurry of step (2), and then drying at 80-150 °C to obtain the cobalt-free nickel-manganese binary precursor material with a water 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 the reducing agent and / or water containing the reducing agent.

8. A cobalt-free nickel-manganese binary precursor material prepared by the preparation method according to any one of claims 1-7.

9. A cobalt-free nickel-manganese binary positive electrode material prepared by mixing and sintering a lithium source and the cobalt-free nickel-manganese binary precursor material according to claim 8.

10. A lithium ion battery comprising the cobalt-free nickel-manganese binary positive electrode material according to claim 9.

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