A low-sulfur lithium-rich manganese-based precursor and its preparation method and application

Abstract

The present invention provides a low-sulfur lithium-rich manganese-based precursor and a preparation method and application thereof. The preparation method comprises the following steps: (1) injecting a ternary salt solution, a first alkali solution and a complexing agent into a bottom liquid in parallel, passing the solution into a concentration container, flowing a first clear liquid into a clear liquid tank for retention, and returning the slurry to a reaction container for co-precipitation reaction; (2) after reacting for 10 to 30 hours, injecting a second alkali solution alone for stirring, extracting the second clear liquid after sedimentation, injecting the clear liquid in the clear liquid tank into the reaction container, and continuing to inject a ternary salt solution, an alkali solution and a complexing agent solution for co-precipitation reaction; (3) repeating steps (1)-(2), injecting a second alkali solution alone after the particle size reaches an index, stopping the reaction after stirring, and obtaining the low-sulfur lithium-rich manganese-based precursor. The present invention removes sulfate radicals in the material in the precursor synthesis stage by a simple method, and can ensure that the sulfur content of the produced lithium-rich manganese-based precursor is less than 500ppm.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery materials and relates to a low-sulfur lithium-rich manganese-based precursor and a preparation method and application thereof. Background Art

[0002] With the continuous development of the new energy industry, the sales of lithium-ion batteries continue to increase. Different battery positive electrode materials are constantly applied to the market for different usage scenarios, and higher requirements are also put forward for battery materials. Lithium-rich manganese-based battery materials are gradually entering the market due to their higher specific capacity. However, in the production process of lithium-rich manganese-based precursors, due to their higher manganese content, their primary crystal form is coarser, resulting in tighter particle growth, causing the sulfate ions used in the reaction process to be easily wrapped inside the crystals, which are difficult to remove in the later washing process, resulting in excessive sulfur content in the later sintered positive electrode materials, affecting the safety of the battery.

[0003] CN103342395A discloses a method for preparing a low-sulfur ternary precursor, which is removed by washing with a certain concentration of alkali after the reaction is completed.

[0004] CN110817975A discloses a method for reducing the sulfur content of a ternary precursor, wherein sulfur is removed by intermittently adding water for washing during the reaction process.

[0005] CN107611383A discloses a method for preparing a nickel-cobalt-manganese ternary precursor with low sulfur and high tap density. During the reaction process, an intermittent process in which crystal nucleation and crystal growth are carried out in stages is adopted to prepare nickel-cobalt-manganese hydroxide, and PSP (stop reaction-sedimentation-remove supernatant-start reaction) is adopted in the crystal growth stage to remove the supernatant while reacting and settling to achieve the purpose of desulfurization.

[0006] CN207209982U discloses a nickel-cobalt-manganese ternary hydroxide washing system, which uses a new type of process washing equipment to remove sulfur.

[0007] The above scheme has the problem that the desulfurization effect is poor, the use of new washing equipment will increase the equipment cost or the washing effect needs to be improved. Summary of the invention

[0008] The purpose of the present invention is to provide a low-sulfur lithium-rich manganese-based precursor and a preparation method and application thereof. The present invention removes sulfate in the material in the precursor synthesis stage through a simple method, thereby ensuring that the sulfur content of the produced lithium-rich manganese-based precursor is less than 500ppm.

[0009] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a method for preparing a low-sulfur lithium-rich manganese-based precursor, the preparation method comprising the following steps:

[0011] (1) injecting the ternary salt solution, the first alkali solution and the complexing agent into the bottom liquid in parallel, passing the solution into a concentration container, the first clear liquid flowing into a clear liquid tank for retention, and returning the slurry to the reaction container for coprecipitation reaction;

[0012] (2) After reacting for 10 to 30 hours, inject the second alkali solution alone for stirring, and after settling, remove the second clear liquid, inject the clear liquid in the clear liquid tank into the reaction container, and continue to inject the ternary salt solution, alkali solution and complexing agent solution for coprecipitation reaction;

[0013] (3) Repeat steps (1)-(2), and inject a second alkali solution after the particle size reaches the target, and stop the reaction after stirring to obtain the low-sulfur lithium-rich manganese-based precursor.

[0014] In the preparation process of the low-sulfur lithium-rich manganese-based precursor of the present invention, a strong alkaline solution is used to remove sulfate ions adsorbed on the crystals for each layer of crystal growth, thereby ensuring that sulfate ions will not be wrapped inside the crystals as the crystals grow, thereby achieving the purpose of reducing the sulfur content of the lithium-rich manganese-based precursor. In addition, after the removal, the present invention passes the clear liquid in the reaction process into the reactor again, which can maintain the stability of the reaction, and the subsequent reaction will not cause excessive pH changes due to the addition of strong alkali, thereby causing the reaction to be unbalanced, regenerating small particles, changing the crystal form or other negative effects.

[0015] Preferably, the element composition of the ternary salt solution in step (1) is Ni:Co:Mn=x:y:z, x+y+z=1, z≥0.6.

[0016] Preferably, the concentration of the ternary salt solution is 0.5-1.5 mol / L, for example, 0.5 mol / L, 0.8 mol / L, 1 mol / L, 1.2 mol / L or 1.5 mol / L.

[0017] Preferably, the first alkali solution comprises sodium hydroxide solution and / or potassium hydroxide solution.

[0018] Preferably, the concentration of the first alkali solution is 6-9 mol / L, for example, 6 mol / L, 6.5 mol / L, 7 mol / L, 8 mol / L or 9 mol / L.

[0019] Preferably, the complexing agent includes any one of ammonia water, sulfosalicylic acid, oxalic acid, salicylic acid or acetylacetone, or a combination of at least two thereof.

[0020] Preferably, the concentration of the complexing agent is 0.1-0.5 mol / L, for example, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L or 0.5 mol / L.

[0021] Preferably, the base solution comprises a strong alkaline solution.

[0022] Preferably, the temperature of the coprecipitation reaction in step (1) is 40-70°C, for example, 40°C, 45°C, 50°C, 60°C or 70°C.

[0023] Preferably, the stirring speed of the coprecipitation reaction is 200-560 rpm, for example, 200 rpm, 300 rpm, 400 rpm, 500 rpm or 560 rpm.

[0024] Preferably, the pH of the coprecipitation reaction is 10-13, for example, 10, 10.5, 11, 12 or 13.

[0025] Preferably, the second alkali solution in step (2) comprises sodium hydroxide solution and / or potassium hydroxide solution.

[0026] Preferably, the mass concentration of the second alkali solution is 3-10%, for example: 3%, 4%, 5%, 8% or 10%.

[0027] The mass concentration of the second alkali solution is controlled at 3-10%, and the sulfur content of the low-sulfur lithium-rich manganese-based precursor is low. If the concentration of the second alkali solution is too low, the desulfurization effect is not obvious. If the concentration of the second alkali solution is too high, the desulfurization effect does not change significantly, but it will cause the Na content in the precursor to be too high, and at the same time, the liquid alkali is wasted, increasing the cost.

[0028] Preferably, the stirring time in step (2) is 1 to 5 hours, for example: 1 hour, 2 hours, 3 hours, 4 hours or 5 hours.

[0029] Preferably, the sedimentation time is 1 to 5 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours or 5 hours.

[0030] Preferably, the stirring time in step (3) is 1 to 5 hours, for example: 1 hour, 2 hours, 3 hours, 4 hours or 5 hours.

[0031] In a second aspect, the present invention provides a low-sulfur lithium-rich manganese-based precursor, which is prepared by the method described in the first aspect.

[0032] In a third aspect, the present invention provides a lithium-rich manganese-based positive electrode material, which is prepared by mixing and sintering the low-sulfur lithium-rich manganese-based precursor as described in the second aspect with a lithium source.

[0033] In a fourth aspect, the present invention provides a positive electrode plate, wherein the positive electrode plate comprises the lithium-rich manganese-based positive electrode material as described in the third aspect.

[0034] In a fifth aspect, the present invention provides a lithium-ion battery, wherein the lithium-ion battery comprises the positive electrode sheet as described in the fourth aspect.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) The method of the present invention reduces the sulfur content in the ternary positive electrode material, thereby reducing the impact on the electrode activity and avoiding the corrosion of the electrode by sulfur during the battery charging and discharging process.

[0037] (2) The sulfur content in the low-sulfur lithium-rich manganese-based precursor prepared by the method of the present invention can be controlled below 500 ppm, and in the process of reducing the sulfur content, no other adverse effects are caused on the precursor synthesis. DETAILED DESCRIPTION

[0038] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0039] Example 1

[0040] This embodiment provides a low-sulfur lithium-rich manganese-based precursor, and the preparation method of the low-sulfur lithium-rich manganese-based precursor is as follows:

[0041] (1) preparing a sulfate solution of about 0.8 mol / L with a molar ratio of Ni:Co:Mn=2:1:7, a sodium hydroxide solution of 6 mol / L, and an ammonia solution of about 0.1 mol / L;

[0042] (2) Using sodium hydroxide solution as the base liquid, sulfate solution, sodium hydroxide solution and ammonia water are injected into the reactor in parallel, and the stirring rate is controlled at 450 rpm, the temperature is 68°C, the ammonia concentration is 4 g / L, and the pH is 10.4-10.8; the reaction is started, and after the reaction container is full, the solution is passed into the concentration container, and the clear liquid flows into the clear liquid tank for retention, and the slurry is returned to the reaction container. After reacting for 20 hours, the feeding is stopped, and a sodium hydroxide solution with a mass concentration of 5% is passed. After stirring for 1 hour, the injection is stopped. After settling for 1 hour, the clear liquid is drawn off, and the clear liquid in the clear liquid tank in the previous reaction process is injected into the reaction container, so that the reaction environment returns to the state before the feeding is stopped, and the sulfate solution, sodium hydroxide solution and ammonia water are continuously injected into the reactor in parallel to start the reaction growth;

[0043] (3) When the particle size enters a stable period next time, repeat the steps of introducing a 5% sodium hydroxide solution - stirring - settling - pumping out the clear liquid - injecting the sulfate solution, sodium hydroxide solution and ammonia water into the reactor in parallel. After the particle size reaches the target, inject a 5% sodium hydroxide solution, stir for 1 hour and then stop the reaction. After centrifugation, washing and drying, the low-sulfur lithium-rich manganese-based precursor is obtained.

[0044] Example 2

[0045] This embodiment provides a low-sulfur lithium-rich manganese-based precursor, and the preparation method of the low-sulfur lithium-rich manganese-based precursor is as follows:

[0046] (1) preparing a sulfate solution of about 1 mol / L with a molar ratio of Ni:Co:Mn=2:1:7, a sodium hydroxide solution of 8 mol / L, and an ammonia solution of about 0.3 mol / L;

[0047] (2) Using sodium hydroxide solution as the base liquid, sulfate solution, sodium hydroxide solution and ammonia water are injected into the reactor in parallel, and the stirring rate is controlled at 400 rpm, the temperature is 65°C, the ammonia concentration is 4 g / L, and the pH is 11-11.4; the reaction is started, and after the reaction container is full, the solution is passed into the concentration container, and the clear liquid flows into the clear liquid tank for retention, and the slurry is returned to the reaction container. After reacting for 15 hours, the feeding is stopped, and a sodium hydroxide solution with a mass concentration of 4% is passed. After stirring for 1 hour, the injection is stopped. After settling for 1 hour, the clear liquid is drawn off, and the clear liquid in the clear liquid tank in the previous reaction process is injected into the reaction container, so that the reaction environment returns to the state before the feeding is stopped, and the sulfate solution, sodium hydroxide solution and ammonia water are continuously injected into the reactor in parallel to start the reaction growth;

[0048] (3) When the particle size enters a stable period next time, repeat the steps of introducing a sodium hydroxide solution with a mass concentration of 4% - stirring - settling - pumping out the clear liquid - injecting the sulfate solution, sodium hydroxide solution and ammonia water into the reactor in parallel. After the particle size reaches the target, inject a sodium hydroxide solution with a mass concentration of 4%, stir for 1 hour and then stop the reaction. After centrifugation, washing and drying, the low-sulfur lithium-rich manganese-based precursor is obtained.

[0049] Example 3

[0050] The only difference between this embodiment and embodiment 1 is that the concentration of the second alkali solution used is 2%, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0051] Example 4

[0052] The only difference between this embodiment and embodiment 1 is that the concentration of the second alkali solution used is 15%, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0053] Comparative Example 1

[0054] The only difference between this comparative example and Example 1 is that the second alkali solution is replaced with water, and the other conditions and parameters are exactly the same as those in Example 1.

[0055] Comparative Example 2

[0056] The only difference between this comparative example and Example 1 is that the second alkali solution is not added, and the coprecipitation reaction is directly carried out. The other conditions and parameters are exactly the same as those in Example 1.

[0057] Performance Testing:

[0058] The sulfur content of the obtained lithium-rich manganese-based precursor was tested, and the test results are shown in Table 1:

[0059] Table 1

[0060] Sulfur content in low-sulfur lithium-rich manganese-based precursor (ppm) Example 1 495 Example 2 498 Example 3 892 Example 4 505 Comparative Example 1 1350 Comparative Example 2 2120

[0061] As can be seen from Table 1, from Examples 1-2, the sulfur content in the low-sulfur lithium-rich manganese-based precursor prepared by the method of the present invention can be controlled below 500 ppm.

[0062] By comparing Example 1 with Examples 3-4, it can be seen that in the preparation process of the low-sulfur lithium-rich manganese-based precursor described in the present invention, the concentration of the second alkali solution used will affect its sulfur content. The mass concentration of the second alkali solution is controlled at 3-10%, and the sulfur content of the low-sulfur lithium-rich manganese-based precursor is low. If the concentration of the second alkali solution is too low, the desulfurization effect is not obvious. If the concentration of the second alkali solution is too high, the desulfurization effect does not change significantly, but the Na content in the precursor will be high, and the liquid alkali will be wasted, increasing the cost.

[0063] By comparing Example 1 and Comparative Examples 1-2, it can be seen that in the preparation process of the low-sulfur lithium-rich manganese-based precursor of the present invention, replacing the second alkali solution with water can also remove a certain amount of sulfur, but the effect is not obvious. The strong alkaline solution can remove the sulfate ions adsorbed on the crystals, thereby ensuring that the sulfate ions will not be wrapped inside the crystals as the crystals grow, thereby achieving the purpose of reducing the sulfur content of the lithium-rich manganese-based precursor.

[0064] The applicant declares that the above is only a specific implementation mode 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 shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a low-sulfur lithium-rich manganese-based precursor, It is characterized in that The preparation method comprises the following steps: (1) injecting the ternary salt solution, the first alkali solution and the complexing agent into the bottom liquid in parallel, passing the solution into a concentration container, the first clear liquid flowing into a clear liquid tank for retention, and returning the slurry to the reaction container for coprecipitation reaction; (2) After reacting for 10 to 30 hours, inject the second alkali solution alone for stirring, and after settling, remove the second clear liquid, inject the clear liquid in the clear liquid tank into the reaction container, and continue to inject the ternary salt solution, alkali solution and complexing agent solution for coprecipitation reaction; (3) repeating steps (1)-(2), injecting a second alkali solution separately after the particle size reaches the target, stirring and stopping the reaction, and obtaining the low-sulfur lithium-rich manganese-based precursor; Wherein, the mass concentration of the second alkali solution is 5-10%.

2. The preparation method according to claim 1, It is characterized in that The element composition of the ternary salt solution in step (1) is Ni:Co:Mn=x:y:z, x+y+z=1, z≥0.

6.

3. The preparation method according to claim 1, It is characterized in that The concentration of the ternary salt solution in step (1) is 0.5 to 1.5 mol / L.

4. The preparation method according to claim 1, It is characterized in that In step (1), the first alkali solution comprises sodium hydroxide solution and / or potassium hydroxide solution.

5. The preparation method according to claim 1, It is characterized in that The concentration of the first alkali solution in step (1) is 6 to 9 mol / L.

6. The preparation method according to claim 1, It is characterized in that The complexing agent in step (1) includes any one of ammonia water, sulfosalicylic acid, oxalic acid, salicylic acid or acetylacetone, or a combination of at least two thereof.

7. The preparation method according to claim 1, It is characterized in that The concentration of the complexing agent in step (1) is 0.1-0.5 mol / L.

8. The preparation method according to claim 1, It is characterized in that The base solution in step (1) comprises a strong alkaline solution.

9. The preparation method according to claim 1, It is characterized in that The temperature of the coprecipitation reaction in step (1) is 40-70°C.

10. The preparation method according to claim 1, It is characterized in that The stirring speed of the coprecipitation reaction in step (1) is 200 to 560 rpm.

11. The preparation method according to claim 1, It is characterized in that The pH of the coprecipitation reaction in step (1) is 10-13.

12. The preparation method according to claim 1, It is characterized in that In step (2), the second alkaline solution comprises sodium hydroxide solution and / or potassium hydroxide solution.

13. The preparation method according to claim 1, It is characterized in that The stirring time in step (2) is 1 to 5 hours.

14. The preparation method according to claim 1, It is characterized in that The sedimentation time in step (2) is 1 to 5 hours.

15. The preparation method according to claim 1, It is characterized in that The stirring time in step (3) is 1 to 5 hours.

16. A low-sulfur lithium-rich manganese-based precursor, It is characterized in that The low-sulfur lithium-rich manganese-based precursor is prepared by the method according to any one of claims 1 to 15.

17. A lithium-rich manganese-based positive electrode material, It is characterized in that The lithium-rich manganese-based positive electrode material is obtained by mixing and sintering the low-sulfur lithium-rich manganese-based precursor as described in claim 16 with a lithium source.

18. A positive electrode sheet, It is characterized in that The positive electrode plate comprises the lithium-rich manganese-based positive electrode material as claimed in claim 17.

19. A lithium ion battery, It is characterized in that The lithium-ion battery comprises the positive electrode sheet as claimed in claim 18.