Modified ternary positive electrode material and preparation method and application thereof

Abstract

The application provides a modified ternary positive electrode material and a preparation method and application thereof, and the preparation method comprises the following steps: (1) a ternary salt solution, a niobium source solution, oxalic acid and ammonia water are added into a reaction container in parallel flow to react; (2) the solid-phase material obtained through the reaction is subjected to aging treatment to obtain a ternary precursor; and (3) the ternary precursor obtained through the step (2) is mixed with a lithium source, and the mixture is subjected to calcination treatment to obtain the modified ternary positive electrode material. The co-precipitation method of the application adopts oxalic acid as a precipitant, and the structural stability and safety of the high-voltage high-nickel ternary positive electrode material in the charging and discharging process are improved through Nb doping. The doping step is simple and suitable for large-scale production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium ion batteries, and relates to a modified ternary positive electrode material and a preparation method and application thereof. BACKGROUND

[0002] High-nickel ternary materials (Ni >= 60%) have the characteristics of high energy density and high endurance, meet the increasing demand of people for battery endurance, and are expected to gradually occupy most of the consumer lithium battery and power battery markets and become the mainstream positive electrode material in the lithium battery field. With the increase of nickel content, the voltage platform and capacity of the high-nickel ternary material increase, but the structural stability and safety in the charging and discharging process have always been a problem affecting its development in lithium ion batteries.

[0003] CN111377487A discloses a preparation method of an Al, F co-doped high-nickel ternary positive electrode material. A metal ion salt solution A of nickel sulfate, cobalt sulfate and manganese sulfate, a precipitant sodium hydroxide solution B and a complexing agent ammonia water solution C are used as raw materials to prepare a high-nickel ternary positive electrode material precursor in a nitrogen atmosphere. The high-nickel ternary positive electrode material precursor, a lithium source, an Al-containing additive and an F-containing additive are ball milled according to a certain stoichiometric ratio, and an Al, F co-doped high-nickel ternary positive electrode material is obtained by calcination.

[0004] CN111244419A discloses a high-nickel ternary positive electrode material, a preparation method and application thereof. The preparation method of the high-nickel ternary positive electrode material includes the following steps: S1. uniformly mixing a high-nickel ternary precursor, a lithium source and a dopant 1; S2. performing first sintering on the mixed raw materials to obtain a first sintering product; S3. uniformly mixing the first sintering product with a dopant 2 and performing second sintering to obtain a second sintering product; S4. uniformly mixing the second sintering product, a coating agent 1 and a coating agent 2 after water washing and drying, and performing third sintering to obtain a third sintering product; and S5. obtaining the high-nickel ternary positive electrode material through screening, batch mixing, magnetic removal and packaging.

[0005] In the high-nickel ternary positive electrode material prepared by the above scheme, the local element composition suddenly changes and the structure does not match, thereby causing deterioration of the use performance and failing to achieve the expected target. SUMMARY

[0006] The application aims to provide a modified ternary positive electrode material and a preparation method and application thereof. The application uses a co-precipitation method with oxalic acid as a precipitant, and improves the structural stability and safety of the high-nickel ternary positive electrode material in the charging and discharging process at high voltage by doping Nb. The doping step is simple and suitable for large-scale production.

[0007] To achieve the application purpose, the following technical scheme is adopted:

[0008] In a first aspect, the present application provides a preparation method of a modified ternary positive electrode material, comprising the following steps:

[0009] (1) adding a ternary salt solution, a niobium source solution, oxalic acid and ammonia water into a reaction container in parallel flow to perform a reaction;

[0010] (2) performing aging treatment on the solid-phase material obtained by the reaction to obtain a ternary precursor;

[0011] (3) mixing the ternary precursor obtained in step (2) and a lithium source, and performing a calcination treatment to obtain the modified ternary positive electrode material.

[0012] The doped niobium high-nickel positive electrode material obtained by using oxalic acid as a precipitant has no significant influence on the overall structure, but has a significant improvement in structural stability, which is manifested as enhanced electrochemical performance. The doped ternary positive electrode material synthesized by the method has a simple process, and the doped niobium element can be uniformly distributed in the interior of the ternary precursor crystal. After the calcination treatment, the spherical morphology of the secondary particles can be improved, so that the internal structure of the doped high-nickel ternary precursor particles is intact and is more tightly packed, which is conducive to improving the performance of the high-nickel positive electrode material at high voltage.

[0013] Preferably, the solute of the ternary salt solution in step (1) comprises nickel salt, cobalt salt and manganese salt.

[0014] Preferably, the solute of the niobium source solution comprises niobium oxalate.

[0015] Preferably, the mass concentration of the ternary salt solution in step (1) is 80-120 g / L, for example, 80 g / L, 90 g / L, 100 g / L, 110 g / L or 120 g / L, etc.

[0016] Preferably, the molar ratio of nickel element, cobalt element and manganese element in the ternary salt solution is (0.6-0.95):(0.01-0.1):(0.01-0.30), for example, 0.6:0.1:0.3, 0.7:0.05:0.25, 0.8:0.1:0.1, 0.9:0.05:0.05, or 0.95:0.02:0.03, etc.

[0017] Preferably, the molar concentration of the niobium source solution is 0.001-3 mol / L, for example, 0.001 mol / L, 0.005 mol / L, 0.01 mol / L, 1 mol / L, 2 mol / L or 3 mol / L, etc., preferably 0.01-1.2 mol / L.

[0018] Preferably, the molar concentration of the oxalic acid is 1-7 mol / L, for example, 1 mol / L, 2 mol / L, 3 mol / L, 5 mol / L or 7 mol / L, etc.

[0019] Preferably, the molar concentration of the ammonia water is 7-11 mol / L, for example: 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L or 11 mol / L, etc.

[0020] Preferably, the flow rate of the ternary salt solution in step (1) is 9-20 L / h, for example: 9 L / h, 10 L / h, 12 L / h, 15 L / h or 20 L / h, etc.

[0021] Preferably, the flow rate of the niobium source solution is 1-4 L / h, for example: 1 L / h, 2 L / h, 3 L / h or 4 L / h, etc.

[0022] Preferably, the flow rate of the oxalic acid is 3-6 L / h, for example: 3 L / h, 4 L / h, 5 L / h or 6 L / h, etc.

[0023] Preferably, the flow rate of the ammonia water is 0.4-1.4 L / h, for example: 0.4 L / h, 0.6 L / h, 0.8 L / h, 1 L / h or 1.4 L / h, etc.

[0024] Preferably, the pH of the reaction in step (1) is 3.5-9, for example: 3.5, 4, 5, 6, 7 or 9, etc., preferably 6-7.

[0025] Preferably, stirring is performed during the reaction.

[0026] Preferably, the stirring speed is 180-450 rpm, for example: 180 rpm, 200 rpm, 250 rpm, 300 rpm or 450 rpm, etc.

[0027] Preferably, the temperature of the reaction is 30-80℃, for example: 30℃, 40℃, 50℃, 60℃, 70℃ or 80℃, etc.

[0028] Preferably, the median particle size D50 of the solid phase material in step (2) is 3-15 μm, for example: 3 μm, 4 μm, 5 μm, 8 μm, 10 μm or 15 μm, etc.

[0029] Preferably, washing and drying treatment are performed after the aging treatment.

[0030] Preferably, the lithium source in step (3) comprises lithium hydroxide and / or lithium carbonate.

[0031] Preferably, the molar ratio of lithium in the lithium source to nickel-cobalt-manganese in the precursor is 1.05-1.12:1, for example: 1.05:1, 1.06:1, 1.08:1, 1.1:1 or 1.2:1, etc.

[0032] Preferably, the temperature of the calcination treatment is 650-800℃, for example: 650℃, 680℃, 700℃, 750℃ or 800℃, etc.

[0033] Preferably, the time of the calcination treatment is 6-15h, for example: 6h, 8h, 10h, 12h or 15h, etc.

[0034] In a second aspect, the present application provides a modified ternary cathode material, which is prepared by the method of the first aspect.

[0035] The bond dissociation energy (ΔHf 298 (Nb-O) is stronger than that of M-O (ΔHf 298 (Ni-O) is 391.6 kJ / mol), ΔHf 298 (Co-O) is 368 kJ / mol, and ΔHf 298 (Mn-O) is 402 kJ / mol), the introduction of Nb in the high-nickel ternary material can effectively inhibit the structural degradation and enhance the final electrochemical performance.

[0036] In a third aspect, the present application provides a cathode sheet, which comprises the modified ternary cathode material of the second aspect.

[0037] In a fourth aspect, the present application provides a lithium ion battery, which comprises the cathode sheet of the third aspect.

[0038] Compared with the prior art, the present application has the following beneficial effects:

[0039] (1) The present application adopts the co-precipitation method with oxalic acid as the precipitant, and improves the structural stability and safety of the high-nickel ternary cathode material during the charging and discharging process at high voltage by doping Nb. The doping step is simple and suitable for large-scale production.

[0040] (2) The present application adopts the co-precipitation method with oxalic acid as the precipitant, and the distribution of niobium inside the cathode material is uniform, the structure is more stable, the primary particles are easy to control, and the sphericity is better. DETAILED DESCRIPTION

[0041] The technical solutions of the present application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only to help understand the present application and should not be regarded as specific limitations on the present application.

[0042] Example 1

[0043] This embodiment provides a modified ternary cathode material, and the preparation method of the modified ternary cathode material is as follows:

[0044] (1) ternary salt solution with mass concentration of 100 g / L (wherein the molar ratio of nickel, cobalt and manganese elements is 8:1:1), niobium oxalate solution with molar concentration of 1 mol / L, oxalic acid with molar concentration of 3 mol / L and ammonia water with molar concentration of 9 mol / L are added into a reaction kettle at a speed of 15 L / h, 2 L / h, 4 L / h and 1 L / h respectively, and the reaction is carried out at a pH of 6, an ammonia water concentration of 8 g / L, a stirring speed of 300 rpm and a reaction temperature of 50℃;

[0045] (2) when the median particle size D50 reaches 8 μm, the solid phase is separated, and the solid phase is aged, washed and dried to obtain a ternary precursor;

[0046] (3) the ternary precursor obtained in step (2) and lithium hydroxide are mixed in a planetary mixer at Li / M = 1.1 for 3 h, and then the powder is placed in a crucible and placed in a resistance furnace for calcination at 700℃, with a heating rate of 5℃ / min and a calcination time of 18 h to obtain the modified ternary positive electrode material.

[0047] Example 2

[0048] The present embodiment provides a modified ternary positive electrode material, and the preparation method thereof is as follows:

[0049] (1) ternary salt solution with mass concentration of 110 g / L (wherein the molar ratio of nickel, cobalt and manganese elements is 8:1:1), niobium oxalate solution with molar concentration of 1.2 mol / L, oxalic acid with molar concentration of 3.5 mol / L and ammonia water with molar concentration of 9.5 mol / L are added into a reaction kettle at a speed of 12 L / h, 1.8 L / h, 3.5 L / h and 0.8 L / h respectively, and the reaction is carried out at a pH of 6.5, an ammonia water concentration of 7.5 g / L, a stirring speed of 320 rpm and a reaction temperature of 55℃;

[0050] (2) when the median particle size D50 reaches 6 μm, the solid phase is separated, and the solid phase is aged, washed and dried to obtain a ternary precursor;

[0051] (3) the ternary precursor obtained in step (2) and lithium hydroxide are mixed in a planetary mixer at Li / M = 1.1 for 3 h, and then the powder is placed in a crucible and placed in a resistance furnace for calcination at 720℃, with a heating rate of 5℃ / min and a calcination time of 16 h to obtain the modified ternary positive electrode material.

[0052] Example 3

[0053] The present embodiment is only different from Example 1 in that the pH of the reaction in step (1) is 5, and other conditions and parameters are exactly the same as those in Example 1.

[0054] Example 4

[0055] The difference between this example and Example 1 is that the pH of the reaction in step (1) is 8, and other conditions and parameters are exactly the same as those in Example 1.

[0056] Example 5

[0057] The difference between this example and Example 1 is that the molar concentration of niobium oxalate in step (1) is 0.005 mol / L, and other conditions and parameters are exactly the same as those in Example 1.

[0058] Example 6

[0059] The difference between this example and Example 1 is that the molar concentration of niobium oxalate in step (1) is 1.5 mol / L, and other conditions and parameters are exactly the same as those in Example 1.

[0060] Comparative Example 1

[0061] The difference between this comparative example and Example 1 is that the modified ternary positive electrode material is prepared by using the traditional sodium hydroxide co-precipitation method, and other conditions and parameters are exactly the same as those in Example 1.

[0062] Comparative Example 2

[0063] The difference between this comparative example and Example 1 is that the modified ternary positive electrode material is prepared by calcining after fully ball-milling the ternary precursor, niobium source and lithium source, and other conditions and parameters are exactly the same as those in Example 1.

[0064] Comparative Example 3

[0065] The difference between this comparative example and Example 1 is that no niobium element is doped, and other conditions and parameters are exactly the same as those in Example 1.

[0066] Performance test:

[0067] The positive electrode materials prepared in the examples and comparative examples are assembled into full cells to test their electrochemical performance. The rate performance test is carried out at a voltage platform of 3.2-4.8 V, and different positive electrode materials are subjected to 300 times of charge-discharge test at a current density of 1.0 C, and the discharge specific capacity of different samples at a current density of 1.0 C is recorded. The cycle performance test method is that the capacity retention rate of different samples is cycled 300 times at 1.0 C, and the test results of Example 1 are taken as 100%, and the test results of other samples are relative to the relative percentage of Example 1. The test results of the above tests are shown in Table 1:

[0068] Table 1

[0069]

[0070]

[0071] As can be seen from Table 1, it can be obtained from Examples 1-2 that the discharge specific capacity of the battery made of the modified ternary positive electrode material according to the application can reach 178 mAh / g or more after 300 cycles.

[0072] As can be obtained from the comparison between Example 1 and Examples 3-4, in the preparation process of the modified ternary positive electrode material according to the application, the pH of the reaction will affect the performance of the prepared positive electrode material. If the pH of the reaction is too low, the discharge specific capacity and capacity retention rate of the prepared positive electrode material will decrease, and if the pH of the reaction is too high, it will affect the compactness of the secondary particle development of the material.

[0073] As can be obtained from the comparison between Example 1 and Examples 5-6, in the preparation process of the modified ternary positive electrode material according to the application, the molar concentration of the niobium source solution will affect the performance of the prepared positive electrode material. If the molar concentration of the niobium source solution is too low, the secondary particle development is poor, and if the molar concentration of the niobium source solution is too high, it will lead to uneven distribution of niobium elements.

[0074] As can be obtained from the comparison between Example 1 and Comparative Examples 1-2, the doped ternary precursor synthesized by the co-precipitation method according to the application has a simple process, the doped niobium elements can be uniformly distributed inside the ternary precursor crystal, and the spherical morphology of the secondary particles can be improved after calcination, so that the doped high-nickel ternary precursor particles have a perfect internal structure and are more tightly packed, which is conducive to improving the performance of the high-nickel positive electrode material at high voltage. The ternary precursor prepared by traditional co-precipitation or solid-state calcination method is prone to uneven distribution of niobium elements from the outside to the inside in the microstructure, which leads to local element composition mutation and structure mismatch, thereby causing deterioration of the performance and making it difficult to achieve the expected target.

[0075] As can be obtained from the comparison between Example 1 and Comparative Example 3, by doping Nb, the structural stability and safety of the high-nickel ternary positive electrode material during the charge and discharge process at high voltage are improved according to the application. The doping step is simple and suitable for large-scale production.

[0076] The applicant declares that the above is only a specific embodiment of the application, but the protection scope of the application is not limited thereto. It should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the application can be easily thought of by any person skilled in the art, and all fall within the protection scope and disclosure scope of the application.

Claims

1. A method for preparing a modified ternary cathode material, characterized in that, The preparation method includes the following steps: (1) The ternary salt solution, niobium source solution, oxalic acid and ammonia water are added to the reaction vessel in parallel to carry out the reaction; (2) The solid material obtained from the reaction is aged to obtain a ternary precursor; (3) The ternary precursor obtained in step (2) and the lithium source are mixed and calcined to obtain the modified ternary cathode material; The molar concentration of the niobium source solution is 1~1.2 mol / L; the molar concentration of the oxalic acid is 3~7 mol / L; In step (1), the flow rate of the ternary salt solution is 9~20 L / h; the flow rate of the niobium source solution is 1~4 L / h; the flow rate of the oxalic acid is 3~6 L / h; and the flow rate of the ammonia water is 0.4~1.4 L / h.

2. The preparation method according to claim 1, characterized in that, The solutes in the ternary salt solution in step (1) include nickel salt, cobalt salt and manganese salt.

3. The preparation method according to claim 1, characterized in that, The solute in the niobium source solution includes niobium oxalate.

4. The preparation method according to claim 1, characterized in that, The mass concentration of the ternary salt solution in step (1) is 80~120g / L.

5. The preparation method according to claim 2, characterized in that, The molar ratio of nickel, cobalt, and manganese in the ternary salt solution is (0.6~0.95):(0.01~0.1):(0.01~0.30).

6. The preparation method according to claim 1, characterized in that, The molar concentration of the ammonia water is 7~11 mol / L.

7. The preparation method according to claim 1, characterized in that, The pH of the reaction in step (1) is 3.5 to 9.

8. The preparation method according to claim 7, characterized in that, The pH of the reaction in step (1) is 6-7.

9. The preparation method according to claim 1, characterized in that, Stirring is performed during the reaction.

10. The preparation method according to claim 9, characterized in that, The stirring speed is 180~450 rpm.

11. The preparation method according to claim 9, characterized in that, The reaction temperature is 30~80℃.

12. The preparation method according to claim 1, characterized in that, The median particle size D50 of the solid material in step (2) is 3~15μm.

13. The preparation method according to claim 1, characterized in that, The aging process is followed by washing and drying.

14. The preparation method according to claim 1, characterized in that, The lithium source in step (3) includes lithium hydroxide and / or lithium carbonate.

15. The preparation method according to claim 1, characterized in that, The molar ratio of lithium in the lithium source to nickel, cobalt and manganese in the precursor is 1.05~1.12:

1.

16. The preparation method according to claim 1, characterized in that, The roasting temperature is 650~800℃.

17. The preparation method according to claim 1, characterized in that, The roasting process takes 6 to 15 hours.

18. A modified ternary cathode material, characterized in that, The modified ternary cathode material is prepared by the method described in any one of claims 1-17.

19. A positive electrode plate, characterized in that, The positive electrode sheet comprises the modified ternary positive electrode material as described in claim 18.

20. A lithium-ion battery, characterized in that, The lithium-ion battery includes the positive electrode as described in claim 19.

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