A cobalt-free precursor material, a cobalt-free positive electrode material, and a preparation method and application thereof

Abstract

The application provides a cobalt-free precursor material, a cobalt-free positive electrode material and a preparation method and application thereof. The preparation method comprises the following steps: introducing a manganese-containing solution into a nickel-containing solution; while the manganese-containing solution is being introduced, the mixed solution obtained by introducing the manganese-containing solution into the nickel-containing solution, a precipitant solution and a complexing agent solution are introduced into a coprecipitation system together to perform a coprecipitation reaction, so that the cobalt-free precursor material is obtained. The preparation method of the cobalt-free precursor material can obtain a material with gradient distribution of nickel and manganese by improving the feeding mode, wherein the manganese content gradually increases from the inside to the outside, and the presence of a heterogeneous phase due to the incomplete burning of manganese in the material can be reduced, so that the electrochemical performance of the material is improved.

Description

Technical Field

[0001] This invention belongs to the field of battery technology and relates to a cobalt-free precursor material, a cobalt-free cathode material, and their preparation methods and applications. Background Technology

[0002] Traditional ternary cathode materials NCM (nickel-cobalt-manganese) or NCA (nickel-cobalt-aluminum) both contain cobalt, an element that is scarce and whose price is extremely volatile. Fluctuations in cobalt prices significantly impact its application, necessitating the "cobalt-free" transformation of batteries. Therefore, existing technologies disclose cobalt-free NM materials to reduce battery costs.

[0003] Existing cobalt-free materials mainly focus on products with a nickel content of 60 mol% or more. However, with the decline in cobalt prices, the price advantage of high-nickel cobalt-free materials is no longer obvious. Nevertheless, the market still demands cobalt-free materials and further cost reductions. Therefore, existing technologies disclose low-cost cobalt-free materials with a nickel content between 50-60 mol%.

[0004] However, when the nickel content is around 40 mol%, the precursor material can be sintered into a lithium-rich manganese-based material. However, when the nickel content is between 50-60 mol%, the material is prone to the formation of Li2MnO3 impurity phase due to the excessive manganese content, which is difficult to eliminate by simply optimizing the sintering process.

[0005] Based on the above research, there is a need to provide a method for preparing cobalt-free precursor materials to avoid the appearance of impurity phases during subsequent sintering. Summary of the Invention

[0006] The purpose of this invention is to provide a cobalt-free precursor material, a cobalt-free cathode material, a preparation method thereon, and an application thereof. The preparation method of the cobalt-free precursor material, by improving the feeding method, can obtain a material with a gradient distribution of nickel and manganese, wherein the manganese content gradually increases from the inside to the outside, which can reduce the occurrence of impurity phases due to incomplete burning of manganese inside the material, thereby improving the performance of the material.

[0007] To achieve this objective, the present invention employs the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing a cobalt-free precursor material, the method comprising the following steps:

[0009] A manganese-containing solution is passed into a nickel-containing solution. Simultaneously, the mixed solution obtained by passing the manganese-containing solution into the nickel-containing solution, the precipitant solution, and the complexing agent solution are all passed into the coprecipitation system to carry out the coprecipitation reaction and obtain the cobalt-free precursor material.

[0010] This invention obtains a mixed solution by passing a manganese-containing solution into a nickel-containing solution. Simultaneously, the mixed solution undergoes a co-precipitation reaction with a precipitant solution and a complexing agent solution. Therefore, the nickel and manganese content in the mixed solution changes dynamically. In the initial stage of the co-precipitation reaction, the manganese-containing solution is initially introduced into the nickel-containing solution, resulting in a lower manganese content and a higher nickel content in the mixed solution. In the later stage of the reaction, the manganese content is higher and the nickel content is lower, thus obtaining a cobalt-free precursor material with a gradient distribution of nickel and manganese. In this cobalt-free precursor material, the nickel content gradually decreases from the inside out, while the manganese content gradually increases from the inside out, reducing the possibility of incomplete sintering of manganese and the formation of impurity phases within the material.

[0011] Preferably, the nickel-containing solution further includes a first dopant source.

[0012] Preferably, the first doping source includes a Ce source.

[0013] Preferably, the manganese-containing solution further includes a second dopant source.

[0014] Preferably, the second doping source includes a Bi source.

[0015] The nickel-containing solution of the present invention contains a Ce source, and the manganese-containing solution also contains a Bi source, so that the doping elements can be distributed in a gradient. In this invention, the Ce source is added to the nickel-containing solution and the Bi source is added to the manganese-containing solution, so that Ce is matched with Ni and Bi is matched with Mn, thereby promoting the doping elements to play an optimal fluxing role in the later sintering process of the cathode material, making it easier to sinter into single crystals and reducing the appearance of impurity phases.

[0016] Preferably, in the nickel-containing solution, the molar ratio of nickel to Ce is (0.5-0.55):(0.001-0.01), for example, 0.5:0.003, 0.52:0.006, 0.54:0.008 or 0.55:0.01, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0017] Preferably, in the manganese-containing solution, the molar ratio of manganese to Bi is (0.45-0.5):(0.001-0.01), for example, it can be 0.45:0.003, 0.47:0.005, 0.49:0.007 or 0.5:0.01, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] Preferably, the concentration of nickel ions in the nickel-containing solution is 1-3 mol / L, for example, it can be 1 mol / L, 2 mol / L or 3 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] Preferably, the concentration of manganese ions in the manganese-containing solution is 1-3 mol / L, for example, it can be 1 mol / L, 2 mol / L or 3 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] Preferably, the concentration of the precipitant solution is 2-10 mol / L, for example, it can be 2 mol / L, 4 mol / L, 6 mol / L, 8 mol / L or 10 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] Preferably, the concentration of the complexing agent solution is 1-5 mol / L, for example, it can be 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L or 5 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] Preferably, the precipitant solution comprises a sodium hydroxide solution, and the complexing agent solution comprises ammonia.

[0023] Preferably, the temperature of the coprecipitation reaction is 60-70°C, for example, 60°C, 65°C or 70°C, and the pH is 11.5-12, for example, 11.5, 11.7, 11.9 or 12, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] Preferably, the concentration of the complexing agent during the coprecipitation reaction is 1-2 g / L, for example, it can be 1 g / L, 1.5 g / L or 2 g / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] Preferably, the stirring speed of the coprecipitation reaction is 400-500 rpm, for example, 450 rpm, 475 rpm or 500 rpm, and the reaction time is 60-100 h, for example, 60 h, 80 h or 100 h, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] In a second aspect, the present invention provides a cobalt-free precursor material, which is prepared by the preparation method described in the first aspect.

[0027] Preferably, the general chemical formula of the cobalt-free precursor material is Ni. x Mn y Ce a Bi b(OH)2, where 0.50≤x≤0.55, for example, can be 0.50, 0.52, 0.54 or 0.55; 0.45≤y≤0.5, for example, can be 0.45, 0.47, 0.49 or 0.5; 0.001≤a≤0.01, for example, can be 0.001, 0.003, 0.005, 0.007, 0.009 or 0.01; 0.001≤b≤0.01, for example, can be 0.001, 0.003, 0.005, 0.007, 0.009 or 0.01, but not limited to the listed values, other unlisted values ​​within the range also apply.

[0028] Preferably, the particle size D50 of the cobalt-free precursor material is 2-3 μm, for example, it can be 2 μm, 2.5 μm or 3 μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] The particle size D50 of the cobalt-free precursor material described in this invention is controlled within the range of 2-3 μm, which is beneficial for the sintering of single crystals.

[0030] Thirdly, the present invention provides a method for preparing a cobalt-free cathode material, the method comprising the following steps:

[0031] The lithium source and the cobalt-free precursor material as described in the second aspect are mixed and sintered to obtain the cobalt-free cathode material.

[0032] Preferably, the sintering is carried out in an air atmosphere.

[0033] Preferably, the sintering includes first performing a sintering to obtain a sintering material, and then performing a second sintering on the sintering material.

[0034] Preferably, the temperature of the first sintering is 900-1100℃, for example, 900℃, 1000℃ or 1100℃, and the time is 10-20h, for example, 10h, 15h or 20h, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] Preferably, the temperature of the secondary sintering is 700-900℃, for example, 700℃, 800℃ or 900℃, and the time is 5-10h, for example, 5h, 7h, 9h or 10h, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] Preferably, the sintering material is crushed to a particle size D50 of 3-5 μm, for example, 3 μm, 4 μm or 5 μm, and then subjected to secondary sintering.

[0037] Preferably, the lithium source and the cobalt-free precursor material are mixed and sintered in a metal ratio of (1.03-1.08):1, for example, it can be 1.03:1, 1.05:1, 1.07:1 or 1.08:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0038] Fourthly, the present invention provides a cobalt-free cathode material, which is prepared by the preparation method described in the third aspect.

[0039] Preferably, the general chemical formula of the cobalt-free cathode material is LiNi. x Mn y Ce a Bi b O2, where 0.50≤x≤0.55, for example, can be 0.50, 0.52, 0.54 or 0.55; 0.45≤y≤0.5, for example, can be 0.45, 0.47, 0.49 or 0.5; 0.001≤a≤0.01, for example, can be 0.001, 0.003, 0.005, 0.007, 0.009 or 0.01; 0.001≤b≤0.01, for example, can be 0.001, 0.003, 0.005, 0.007, 0.009 or 0.01, but not limited to the listed values, other unlisted values ​​within the range also apply.

[0040] Fifthly, the present invention provides a lithium-ion battery comprising the cobalt-free cathode material as described in the fourth aspect.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] This invention obtains a cobalt-free precursor material by passing a manganese-containing solution into a nickel-containing solution to obtain a mixed solution. Simultaneously, the mixed solution is co-precipitated with a precipitant solution and a complexing agent solution to obtain a cobalt-free precursor material with a nickel-manganese gradient distribution. In the cobalt-free precursor material, the nickel content gradually decreases from the inside to the outside, while the manganese content gradually increases from the inside to the outside, which can reduce the occurrence of impurities due to incomplete burning of manganese inside the material. Detailed Implementation

[0043] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0044] Example 1

[0045] This embodiment provides a method for preparing a cobalt-free precursor material, the method comprising the following steps:

[0046] According to Ni 0.52 Mn 0.48 Ce 0.005 Bi 0.005 The formula amount of (OH)2 was used to pass a manganese-containing solution into a nickel-containing solution. At the same time, a mixed solution obtained by passing the manganese-containing solution into the nickel-containing solution, a sodium hydroxide solution, and an ammonia solution were added to the reactor in parallel to carry out a co-precipitation reaction. The temperature of the co-precipitation reaction was 65℃, the pH was 11.8, the ammonia concentration was 1.5g / L, the stirring speed was 450rpm, and the feed was stopped after 80h of reaction to obtain a cobalt-free precursor material with a particle size D50 of 2.5μm.

[0047] The manganese-containing solution is a mixed MnBi solution in the prescribed amount, and the nickel-containing solution is a mixed NiCe solution in the prescribed amount; the nickel-containing solution has a nickel ion concentration of 2 mol / L, the manganese-containing solution has a manganese ion concentration of 2 mol / L, the sodium hydroxide solution has a concentration of 6 mol / L, and the ammonia solution has a concentration of 3 mol / L.

[0048] This embodiment also provides a method for preparing a single-crystal cobalt-free cathode material, the method comprising the following steps:

[0049] Lithium hydroxide and the cobalt-free precursor material obtained in this embodiment were mixed evenly at a lithium ratio of 1.05 and sintered at 1000°C in air for 15 hours to obtain a sintered product of single-crystal cathode material. The sintered product was crushed to 4 μm and then sintered at 800°C in air for 8 hours to obtain a single-crystal cobalt-free cathode material.

[0050] Example 2

[0051] This embodiment provides a method for preparing a cobalt-free precursor material, the method comprising the following steps:

[0052] According to Ni 0.5 Mn 0.5 Ce 0.01 Bi 0.01 The formula amount of (OH)2 was used to pass a manganese-containing solution into a nickel-containing solution. At the same time, the mixed solution obtained by passing the manganese-containing solution into the nickel-containing solution, sodium hydroxide solution, and ammonia solution were added to the reactor in parallel to carry out a co-precipitation reaction. The temperature of the co-precipitation reaction was 70℃, the pH was 11.5, the ammonia concentration was 2g / L, the stirring speed was 500rpm, and the feed was stopped after 100h of reaction to obtain a cobalt-free precursor material with a particle size D50 of 3μm.

[0053] The manganese-containing solution is a mixed MnBi solution in the prescribed amount, and the nickel-containing solution is a mixed NiCe solution in the prescribed amount; the nickel-containing solution has a nickel ion concentration of 3 mol / L, the manganese-containing solution has a manganese ion concentration of 3 mol / L, the sodium hydroxide solution has a concentration of 10 mol / L, and the ammonia solution has a concentration of 5 mol / L.

[0054] This embodiment also provides a method for preparing a single-crystal cobalt-free cathode material, the method comprising the following steps:

[0055] Lithium hydroxide and the cobalt-free precursor material obtained in this embodiment were mixed evenly at a lithium ratio of 1.03 and sintered at 1100°C in air for 10 hours to obtain a sintered product of single-crystal cathode material. The sintered product was crushed to 5 μm and then sintered at 700°C in air for 10 hours to obtain a single-crystal cobalt-free cathode material.

[0056] Example 3

[0057] This embodiment provides a method for preparing a cobalt-free precursor material, the method comprising the following steps:

[0058] According to Ni 0.55 Mn 0.45 Ce 0.001 Bi 0.001 The formula amount of (OH)2 was used to pass a manganese-containing solution into a nickel-containing solution. At the same time, the mixed solution obtained by passing the manganese-containing solution into the nickel-containing solution, sodium hydroxide solution, and ammonia solution were added to the reactor in parallel to carry out a co-precipitation reaction. The temperature of the co-precipitation reaction was 60℃, the pH was 12, the ammonia concentration was 1g / L, the stirring speed was 400rpm, and the feed was stopped after 60h of reaction to obtain a cobalt-free precursor material with a particle size D50 of 2μm.

[0059] The manganese-containing solution is a mixed MnBi solution in the prescribed amount, and the nickel-containing solution is a mixed NiCe solution in the prescribed amount; in the nickel-containing solution, the concentration of nickel ions is 1 mol / L, in the manganese-containing solution, the concentration of manganese ions is 1-3 mol / L, the concentration of sodium hydroxide solution is 2 mol / L, and the concentration of ammonia solution is 1 mol / L.

[0060] This embodiment also provides a method for preparing a single-crystal cobalt-free cathode material, the method comprising the following steps:

[0061] Lithium hydroxide and the cobalt-free precursor material obtained in this embodiment were mixed evenly at a lithium ratio of 1.08 and sintered at 900°C in air for 20 hours to obtain a sintered product of single-crystal cathode material. The sintered product was crushed to 3 μm and then sintered at 900°C in air for another 5 hours to obtain a single-crystal cobalt-free cathode material.

[0062] Example 4

[0063] This embodiment provides a method for preparing a cobalt-free precursor material. The preparation method is the same as in Example 1, except that the manganese-containing solution is a MnCe mixed solution and the nickel-containing solution is a NiBi mixed solution.

[0064] This embodiment also provides a method for preparing a single-crystal cobalt-free cathode material. Except for using the cobalt-free precursor material obtained in this embodiment, the preparation method is the same as in Example 1.

[0065] Example 5

[0066] This embodiment provides a method for preparing a cobalt-free precursor material. The preparation method is the same as in Example 1, except that the manganese-containing solution does not contain Bi and the nickel-containing solution does not contain Ce. Instead, a mixed solution obtained by passing the manganese-containing solution through the nickel-containing solution, a sodium hydroxide solution, an ammonia solution, and a CeBi mixed solution of a certain amount are added to the reactor in parallel for co-precipitation reaction.

[0067] This embodiment also provides a method for preparing a single-crystal cobalt-free cathode material. Except for using the cobalt-free precursor material obtained in this embodiment, the preparation method is the same as in Example 1.

[0068] Example 6

[0069] This embodiment provides a method for preparing a cobalt-free precursor material. The preparation method is the same as in Example 1, except that the nickel-containing solution does not contain Ce.

[0070] This embodiment also provides a method for preparing a single-crystal cobalt-free cathode material. Except for using the cobalt-free precursor material obtained in this embodiment, the preparation method is the same as in Example 1.

[0071] Example 7

[0072] This embodiment provides a method for preparing a cobalt-free precursor material. The preparation method is the same as in Example 1, except that the manganese-containing solution does not contain Bi.

[0073] This embodiment also provides a method for preparing a single-crystal cobalt-free cathode material. Except for using the cobalt-free precursor material obtained in this embodiment, the preparation method is the same as in Example 1.

[0074] Comparative Example 1

[0075] This comparative example provides a method for preparing a cobalt-free precursor material. The preparation method is the same as in Example 1, except that the manganese-containing solution, nickel-containing solution, sodium hydroxide solution and ammonia solution are added to the reaction vessel in parallel for co-precipitation reaction.

[0076] This comparative example also provides a method for preparing a cobalt-free cathode material. Except for using the cobalt-free precursor material obtained in this comparative example, the preparation method is the same as in Example 1.

[0077] Comparative Example 2

[0078] This comparative example provides a method for preparing a cobalt-free precursor material. The preparation method is the same as in Example 1, except that a nickel-containing solution is passed into a manganese-containing solution, and at the same time, a mixed solution obtained by passing the nickel-containing solution into the manganese-containing solution, a sodium hydroxide solution, and an ammonia solution are added to the reactor in parallel for co-precipitation reaction.

[0079] This comparative example also provides a method for preparing a cobalt-free cathode material. Except for using the cobalt-free precursor material obtained in this comparative example, the preparation method is the same as in Example 1.

[0080] The cobalt-free cathode material obtained in the above examples and comparative examples was used to prepare a cathode sheet, which was then used to prepare a battery with lithium sheet, lithium hexafluorophosphate electrolyte and polyethylene separator. The battery performance was then tested under the following conditions: 0.1C for the first charge and discharge capacity at a voltage of 3.0-4.8V, and 1C for 1000 cycles to test the capacity retention rate.

[0081] The test results are shown in Table 1:

[0082] Table 1

[0083]

[0084]

[0085] As can be seen from Table 1:

[0086] As can be seen from Example 1 and Comparative Example 1, by improving the feeding method, the present invention can obtain a precursor material with nickel content gradually decreasing from the inside to the outside and manganese content gradually increasing from the inside to the outside, thus reducing the occurrence of impurity phases due to incomplete sintering of manganese inside the material. As can be seen from Example 1 and Comparative Example 2, in the material obtained in Comparative Example 2, the manganese content gradually decreases from the inside to the outside, resulting in incomplete sintering of manganese and the presence of Li2MnO3 impurity phase in the obtained cobalt-free cathode material. As can be seen from Example 1 and Examples 4-7, the present invention preferably adds Ce to the nickel-containing solution and preferably adds Bi to the manganese-containing solution to promote the optimal fluxing effect of the dopant element in the later sintering process of the cathode material, thereby making it easier to sinter into single crystals and reducing the formation of impurity phases.

[0087] In summary, this invention provides a cobalt-free precursor material, a cobalt-free cathode material, a preparation method, and an application. The preparation method of the cobalt-free precursor material, by improving the feeding method, can obtain a material with a gradient distribution of nickel and manganese, wherein the manganese content gradually increases from the inside to the outside, which can reduce the occurrence of impurity phases due to incomplete burning of manganese inside the material, thereby improving the performance of the material.

[0088] The above description is only a specific embodiment 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 conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method of making a cobalt-free precursor material, characterized by, The preparation method comprises the following steps: The manganese-containing solution is introduced into the nickel-containing solution, and at the same time of the introduction, the mixed solution obtained by introducing the manganese-containing solution into the nickel-containing solution, the precipitant solution and the complexing agent solution are introduced into the co-precipitation system to perform a co-precipitation reaction to obtain the cobalt-free precursor material; The nickel-containing solution further comprises a first doping source; The first doping source comprises a Ce source; The manganese-containing solution further comprises a second doping source; The second doping source comprises a Bi source; In the nickel-containing solution, the molar ratio of nickel element to Ce element is (0.5-0.55):(0.001-0.01); In the manganese-containing solution, the molar ratio of manganese element to Bi element is (0.45-0.5):(0.001-0.01).

2. The production method according to claim 1, characterized by, In the nickel-containing solution, the concentration of nickel ions is 1-3 mol / L.

3. The preparation method according to claim 1, characterized in that, In the manganese-containing solution, the concentration of manganese ions is 1-3 mol / L.

4. The method of claim 1, wherein, The concentration of the precipitant solution is 2-10 mol / L.

5. The preparation method according to claim 1, characterized in that, The concentration of the complexing agent solution is 1-5 mol / L.

6. The method of claim 1, wherein, The temperature of the co-precipitation reaction is 60-70℃, and the pH is 11.5-12.

7. The preparation method according to claim 1, characterized in that, The concentration of the complexing agent during the co-precipitation reaction is 1-2 g / L.

8. The method of claim 1, wherein, The stirring speed of the co-precipitation reaction is 400-500 rpm, and the reaction time is 60-100 h.

9. A cobalt-free precursor material, characterized in that, The cobalt-free precursor material is prepared by the preparation method in any one of claims 1-8.

10. The cobalt-free precursor material of claim 9, wherein, The cobalt-free precursor material has a chemical formula of Ni x Mn y Ce a Bi b (OH)2, wherein 0.50≤x≤0.55, 0.45≤y≤0.5, 0.001≤a≤0.01, 0.001≤b≤0.

01.

11. The cobalt-free precursor material of claim 9, wherein, The particle size D50 of the cobalt-free precursor material is 2-3 μm.

12. A method of preparing a cobalt-free cathode material, characterized by, The preparation method comprises the following steps: The lithium source and the cobalt-free precursor material in any one of claims 9-11 are mixed and sintered to obtain the cobalt-free positive electrode material.

13. The method of claim 12, wherein, The sintering is performed in an air atmosphere.

14. The method of claim 12, wherein, The sintering comprises first performing primary sintering to obtain a sintered material, and then performing secondary sintering on the sintered material.

15. The method of claim 14, wherein, The temperature of the primary sintering is 900-1100℃, and the time is 10-20 h.

16. The method of claim 14, wherein, The temperature of the secondary sintering is 700-900℃, and the time is 5-10 h.

17. The preparation method according to claim 14, characterized in that, The sintered material is crushed to a particle size D50 of 3-5 μm before the secondary sintering.

18. A cobalt-free cathode material, characterized in that, The cobalt-free positive electrode material is prepared by the preparation method in any one of claims 12-17.

19. A lithium-ion battery, characterized by, The lithium ion battery comprises the cobalt-free positive electrode material in claim 18.

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