Medium-low nickel precursor material coated with lithium super-ion conductor and preparation method and application of medium-low nickel precursor material

Abstract

The invention provides a lithium super ion conductor coated medium-low nickel precursor material and a preparation method and application thereof, and the preparation method comprises the following steps: mixing an organic metal salt solution and a mixed metal salt solution to obtain a first mixture; adding a lithium super-ion conductor, a precipitant solution and a complexing agent solution into the first mixture, and carrying out a co-precipitation reaction to obtain a second mixture; and continuously heating the second mixture for reaction to obtain the medium-low nickel precursor material coated with the lithium super-ion conductor. According to the preparation method disclosed by the invention, a lithium ion deintercalation rapid channel is effectively widened by adopting a lithium super-ion conductor coating method, the direct contact between the positive electrode material and an electrolyte is avoided, in addition, the problem of peroxidation for refining the primary particle morphology in the reaction process of a medium-low nickel precursor material is avoided by utilizing organic metal salt, and the preparation method has the advantages that the preparation process is simple, the cost is low, and the application prospect is wide. And the cycling stability and the conductivity of the battery are effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of batteries and relates to a medium-low nickel precursor material coated with a lithium superion conductor and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries are widely used because of their excellent electrochemical properties, low price, safety and environmental protection. With the rapid development of the new energy vehicle industry, people have higher and higher requirements for the performance of lithium-ion batteries. Therefore, how to improve the performance of ternary precursors has become a research hotspot. At present, the ternary precursors prepared by traditional processes have problems such as lattice mutation and poor stability, which lead to the inability to effectively guarantee the safety and life of the battery. In this regard, the prior art generally adopts methods such as doping and coating to improve the performance of the precursor. Among them, coating can not only avoid the contact between the positive electrode material and the electrolyte, avoid the generation of interfacial reactions and damage the internal structure, but also improve the structural stability, thereby improving the thermal stability of the positive electrode material, and improving the cycle stability and capacity retention rate during the battery charging and discharging process. In addition, for the widely used medium and low nickel precursor products, it is necessary to further effectively improve the problems such as the difficulty in refining the medium and low nickel primary particles and the few lithium ion channels while coating and modifying. It is necessary to improve the electrochemical performance of the medium and low nickel precursor products and improve the quality of the medium and low nickel positive electrode materials.

[0003] With regard to the commonly used oxide coatings, which have poor coating conductivity and cannot provide more sufficient fast channels for lithium ions, studies have found that the use of fast ion conductors to coat precursors can effectively improve the above problems. For example, in CN 109879331A, a nickel-cobalt-manganese hydroxide precursor is mechanically mixed with a lithium source and a compound containing M, and oxidized and calcined to obtain a substrate. After the fast ion conductor is ball-milled into powder, mixed and coated with the substrate, it is sintered to obtain a high-nickel ternary positive electrode material coated with a fast ion conductor. In CN110690435A, the raw materials for synthesizing fast ion conductors are weighed in proportion, evenly dispersed in a solvent, to obtain a mixed solution, and a high-nickel ternary precursor is added thereto, and a high-nickel ternary precursor powder coated with a fast ion conductor is obtained by stirring, drying and grinding.

[0004] However, the surface coating of the ternary precursor is prone to uneven coating. Mechanical mixing of the fast ion conductor and the positive electrode material cannot effectively promote the uniform coating of the fast ion conductor on the precursor, and it is easy to destroy the internal structure of the precursor, reducing the stability of the battery. In addition, in order to meet the high-quality and high-demand battery performance of medium and low nickel precursor positive electrode materials, and to further improve the electrochemical performance on the basis of coating modification, the micro-oxidation method is currently used to refine the primary particles, thereby increasing the specific surface area and enhancing the battery's conductivity. However, the micro-oxidation process is difficult to control, and it is easy to destroy the grain structure and produce small particles, thereby reducing the stability of the battery.

[0005] Based on the above research, it is necessary to provide a method for preparing a medium-low nickel precursor material. The medium-low nickel precursor material obtained by the preparation method can not only effectively improve the deintercalation of lithium ions, but also improve the porosity between primary particles and stabilize the internal structure. Summary of the invention

[0006] The purpose of the present invention is to provide a medium-low nickel precursor material coated with a lithium superion conductor, a preparation method and an application thereof. The preparation method adopts a lithium superion conductor coating method to effectively broaden the lithium ion fast insertion and extraction channel and avoid direct contact between the positive electrode material and the electrolyte. In addition, organic metal salts are used to avoid the problem of overoxidation in the reaction process of the medium-low nickel precursor material in order to refine the primary particle morphology, thereby effectively improving the cycle stability and conductivity of the battery.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a method for preparing a medium-low nickel precursor material coated with a lithium superion conductor, the preparation method comprising the following steps:

[0009] (1) mixing an organic metal salt solution and a mixed metal salt solution to obtain a first mixture;

[0010] (2) adding a lithium superion conductor, a precipitant solution and a complexing agent solution to the first mixture in step (1) to carry out a coprecipitation reaction to obtain a second mixture;

[0011] (3) The second mixture in step (2) is further heated to react to obtain the low-nickel precursor material coated with the lithium superion conductor.

[0012] The present invention not only broadens the lithium ion fast channel by coating the lithium superion conductor when preparing the precursor material by coprecipitation, which is beneficial to the deintercalation of lithium ions during the charge and discharge process, and improves the conductivity and rate performance of the ternary precursor material, but also effectively avoids the situation where the positive electrode material is in direct contact with the electrolyte and causes side reactions, thereby improving the cycle stability of the ternary precursor material and the battery life; at the same time, the present invention also adds an organic metal salt when preparing the precursor material, and continues to heat the reaction after the coprecipitation reaction. The characteristics of the organic metal salt are used to cause a sublimation reaction, thereby reducing the surface cavities of the ternary precursor, and promoting the separation of the primary particles of the precursor, thereby improving the morphology looseness and the phenomenon of the primary particles being too coarse, and avoiding the problem of overoxidation in order to refine the primary particle morphology during the reaction of the medium and low nickel ternary precursor.

[0013] Preferably, the organic metal salt solution in step (1) comprises diphenylchromium and / or cyclooctatetraene sandwich compound.

[0014] Preferably, in the first mixture of step (1), the molar ratio of the organic metal salt to the total metal ions in the mixed metal salt solution is 1:(5-10), for example, it can be 1:5, 1:7, 1:9 or 1:10, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0015] The molar ratio of the organic metal salt to the total metal ions in the mixed metal salt solution of the present invention will affect the performance of the organic metal salt. If the organic metal salt is too little, the effect of improving the peroxidation of the medium and low nickel precursor materials will be reduced. If the organic metal salt is too much, the organic metal salt will occupy a large amount of vacancies in the elements inside the crystal, resulting in a disordered arrangement of the elements inside the crystal and an unstable lattice structure.

[0016] Preferably, the concentration of the organic metal salt solution in step (1) is 3-5 mol / L, for example, 3 mol / L, 4 mol / L or 5 mol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0017] Preferably, a dispersant is also added when the organic metal salt solution and the mixed metal salt solution are mixed in step (1).

[0018] In the present invention, a dispersant is added when preparing the first mixture, which is beneficial to uniform mixing of the lithium superion conductor and the mixed salt solution and to uniform coating of the lithium superion conductor on the precursor.

[0019] Preferably, the molar ratio of the dispersant to the total metal ions in the mixed metal salt solution is 1:(4-8), for example, 1:4, 1:5, 1:6, 1:7 or 1:8, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0020] Preferably, the dispersant includes any one of sodium lauryl sulfate, coconut oil diethanolamide, methyl high hydrogen silicone oil emulsion or hydroxy silicone oil emulsion, or a combination of at least two of them.

[0021] Preferably, the rotation speed of mixing the organic metal salt solution and the mixed metal salt solution in step (1) is 10-20 r / min, for example, it can be 10 r / min, 15 r / min or 20 r / min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0022] Preferably, the solute in the mixed metal salt solution in step (1) comprises nickel salt, cobalt salt or manganese salt.

[0023] Preferably, the nickel salt includes any one of nickel chloride, nickel nitrate or nickel sulfate, or a combination of at least two of them.

[0024] Preferably, the cobalt salt includes any one or a combination of at least two of cobalt nitrate, cobalt chloride or cobalt sulfate.

[0025] Preferably, the manganese salt includes any one or a combination of at least two of manganese chloride, manganese nitrate or manganese sulfate.

[0026] Preferably, in the mixed metal salt solution in step (1), the molar ratio of nickel ions, cobalt ions and manganese ions is x:y:z, where 0.4 < x < 0.8, for example, it can be 0.41, 0.45, 0.5, 0.55, 0.6, 0.7 or 0.79, 0 < y < 0.2, for example, it can be 0.1, 0.15 or 0.2, 0 < z < 0.3, for example, it can be 0.1, 0.2 or 0.3, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0027] Preferably, step (1) is carried out in a mixed atmosphere of air and nitrogen, then the air supply is stopped for step (2), and nitrogen is continuously supplied for step (2).

[0028] In the present invention, an organometallic salt solution, a mixed metal salt solution and a dispersant are added into a reaction kettle, stirred and air and nitrogen are introduced to obtain a first mixture, then the air is stopped, a lithium superionic conductor, a precipitant solution and a complexing agent solution are added, and step (2) is carried out in a nitrogen atmosphere, which can further avoid the problem that the medium and low nickel precursor materials are peroxidized due to the relatively fine primary particles.

[0029] Preferably, the volume ratio of the air to the nitrogen is (0.3 - 0.5):1, for example, it can be 0.3:1, 0.4:1 or 0.5:1, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0030] Preferably, the lithium superionic conductor in step (2) includes Li a M1 b M2 c Cl 3 , where 0.3 < a < 0.5, for example, it can be 0.31, 0.35, 0.4, 0.45 or 0.49, 0.2 < b < 0.3, for example, it can be 0.21, 0.25 or 0.29, 0.45 < c < 0.50, for example, it can be 0.46, 0.48 or 0.49, and both M1 and M2 are selected from transition elements and / or rare earth elements.

[0031] Preferably, M1 and M2 each independently include any one or a combination of at least two of La, Ta, Zr, Nb, V or Ti.

[0032] Preferably, the molar ratio of the lithium superion conductor to the total metal ions in the mixed metal salt solution in step (2) is 1:(50-150), for example, it can be 1:50, 1:100 or 1:150, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0033] Preferably, the precipitant solution in step (2) comprises a sodium hydroxide solution having a concentration of 7-12 g / L, for example, 7 g / L, 9 g / L, 11 g / L or 12 g / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0034] Preferably, the complexing agent solution in step (2) comprises aqueous ammonia at a concentration of 2-7 g / L, for example, 2 g / L, 4 g / L, 6 g / L or 7 g / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0035] Preferably, the rotation speed during the coprecipitation reaction in step (2) is 40-60 r / min, for example, 40 r / min, 50 r / min or 60 r / min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0036] Preferably, the temperature of the coprecipitation reaction in step (2) is 30-55°C, for example, 30°C, 40°C, 45°C, 50°C or 55°C, the heating rate is 1-1.5°C / min, for example, 1°C / min, 1.2°C / min, 1.4°C / min or 1.5°C / min, and the pH is 8-12, for example, 8, 9, 10, 11 or 12, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0037] Preferably, the temperature of the temperature rising reaction in step (3) is 120-140°C, for example, 120°C, 130°C or 140°C, and the heating rate is 0.5-1°C / min, for example, 0.5°C / min, 0.7°C / min, 0.9°C / min or 1°C / min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0038] Preferably, the pH of the temperature increase reaction in step (3) is 5-5.5, for example, 5, 5.2, 5.4 or 5.5, and the reaction time is 1-3h, for example, 1h, 2h or 3h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0039] In step (3) of the present invention, the pH is lowered to carry out the reaction, which can reduce the alkali content on the surface of the precursor, thereby reducing the influence of residual alkali on battery performance.

[0040] Preferably, an acidic substance is used to adjust the pH of the temperature-raising reaction in step (3).

[0041] Preferably, the acidic substance comprises an organic acid, and the organic acid comprises any one of citric acid, oxalic acid or acetic acid, or a combination of at least two of them.

[0042] Preferably, the rotation speed of the temperature rising reaction in step (3) is 300-380 r / min, for example, it can be 300 r / min, 320 r / min, 340 r / min, 360 r / min or 380 r / min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0043] In a second aspect, the present invention provides a medium-low nickel precursor material coated with a lithium superion conductor, wherein the medium-low nickel precursor material coated with a lithium superion conductor is prepared by the preparation method described in the first aspect.

[0044] In a third aspect, the present invention provides a positive electrode material, which is obtained by mixing and sintering a lithium source and a medium-low nickel precursor material coated with a lithium superion conductor as described in the second aspect.

[0045] Preferably, the sintering includes heating to 450-550°C, such as 450°C, 500°C or 550°C, at a rate of 2-2.5°C / min, such as 2.0°C / min, 2.2°C / min, 2.4°C / min or 2.5°C / min, keeping warm for 5-8h, such as 5h, 7h or 8h, and then continuing to heat to 800-850°C, such as 800°C, 820°C, 840°C or 850°C, at a rate of 4-6°C / min, such as 4°C / min, 5°C / min or 6°C / min, and keeping warm for 15-20h, such as 15h, 17h or 20h. However, the present invention is not limited to the values ​​listed, and other values ​​not listed within the numerical range are also applicable.

[0046] In a fourth aspect, the present invention provides a lithium-ion battery, wherein the lithium-ion battery comprises the positive electrode material as described in the third aspect.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] (1) The present application not only broadens the lithium ion fast channel by coating the surface of the medium-low nickel precursor material with a lithium superion conductor, which is beneficial to the deintercalation of lithium ions during the charge and discharge process, and improves the conductivity and rate performance of the medium-low nickel precursor material, but also effectively avoids the side reactions caused by direct contact between the positive electrode material and the electrolyte, thereby improving the cycle stability and battery life of the ternary precursor material.

[0049] (2) The present application adopts a uniform mixture of organic metal salt and mixed metal salt solution, and utilizes the characteristics of organic metal salt to reduce the surface voids of medium and low nickel precursor materials, promote the separation of precursor primary particles from each other, improve the looseness of the morphology and the phenomenon of primary particles being too coarse, and avoid the problem of overoxidation in the process of medium and low nickel ternary precursor reaction in order to refine the primary particle morphology.

[0050] (3) The present application adopts lithium superion conductor coating and reacts under low pH conditions to reduce the alkali content on the surface of the precursor, thereby reducing the impact of residual alkali on battery performance.

[0051] (4) The present application adds a dispersant to the solution, which is beneficial for uniform mixing of the lithium superion conductor and the mixed metal salt solution, and is beneficial for uniform coating of the lithium superion conductor on the precursor.

[0052] (5) The preparation method of the present application is simple, and the material prepared by the method has stronger cycle stability and higher electrical conductivity than the conventional process. DETAILED DESCRIPTION

[0053] 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.

[0054] Example 1

[0055] This embodiment provides a method for preparing a medium-low nickel precursor material coated with a lithium superion conductor, the preparation method comprising the following steps:

[0056] (1) mixing diphenyl chromium with tetrahydrofuran to prepare an organic metal salt solution with a concentration of 3 mol / L, adding the organic metal salt solution, the mixed metal salt solution and sodium dodecyl sulfate into a reaction kettle, introducing air and nitrogen with a volume ratio of 0.5:1, and mixing at a rotation speed of 20 r / min to obtain a first mixture;

[0057] In the first mixture, the molar ratio of the organic metal salt to the total metal ions in the mixed metal salt solution is 1:8, and the molar ratio of the sodium dodecyl sulfate to the total metal ions in the mixed metal salt solution is 1:6;

[0058] The mixed metal salt solution includes nickel ions, cobalt ions and manganese ions in a molar ratio of 0.7:0.1:0.3;

[0059] (2) Stop introducing air, continue introducing nitrogen, add a lithium superion conductor, a sodium hydroxide solution with a concentration of 10 g / L, and an ammonia solution with a concentration of 5 g / L to the first mixture in step (1), and carry out a coprecipitation reaction at 50° C., a heating rate of 1.2° C. / min, a rotation speed of 60 r / min, and a pH of 9.5 for 45 hours to obtain a second mixture;

[0060] The lithium superion conductor includes Li 0.365 Ta 0.239 La 0.478 Cl 3 , the molar ratio of the lithium superion conductor to the total metal ions in the mixed metal salt solution is 1:100;

[0061] (3) The second mixture is further heated to 130° C. at a heating rate of 0.8° C. / min, and oxalic acid is added to adjust the pH to 5, and the mixture is reacted at a speed of 380 r / min for 2 h, and then washed and dried to obtain the lithium superion conductor-coated medium-low nickel precursor material (precursor D50 is 8 μm, BET is 14 μm 2 / g, primary particles are in the form of thin strips).

[0062] Example 2

[0063] This embodiment provides a method for preparing a medium-low nickel precursor material coated with a lithium superion conductor, the preparation method comprising the following steps:

[0064] (1) mixing diphenyl chromium with tetrahydrofuran to prepare an organic metal salt solution with a concentration of 4 mol / L, adding the organic metal salt solution, the mixed metal salt solution and sodium dodecyl sulfate into a reaction kettle, introducing air and nitrogen with a volume ratio of 0.4:1, and mixing at a rotation speed of 15 r / min to obtain a first mixture;

[0065] In the first mixture, the molar ratio of the organic metal salt to the total metal ions in the mixed metal salt solution is 1:10, and the molar ratio of the sodium dodecyl sulfate to the total metal ions in the mixed metal salt solution is 1:4;

[0066] The mixed metal salt solution includes nickel ions, cobalt ions and manganese ions in a molar ratio of 0.7:0.1:0.3;

[0067] (2) stopping the introduction of air and continuing the introduction of nitrogen, adding a lithium superion conductor, a sodium hydroxide solution with a concentration of 7 g / L, and an ammonia solution with a concentration of 2 g / L to the first mixture in step (1), and conducting a coprecipitation reaction at 45° C., a heating rate of 1° C. / min, a rotation speed of 50 r / min, and a pH of 12 to obtain a second mixture;

[0068] The lithium superion conductor includes Li 0.365 Ta 0.239 La 0.478 Cl 3 , the molar ratio of the lithium superion conductor to the total metal ions in the mixed metal salt solution is 1:50;

[0069] (3) The second mixture is further heated to 140° C. at a heating rate of 0.5-1° C. / min, and acetic acid is added to adjust the pH to 5.3, and the mixture is reacted at a rotation speed of 350 r / min for 1 hour, followed by washing and drying to obtain the low-nickel precursor material coated with the lithium superion conductor.

[0070] Example 3

[0071] This embodiment provides a method for preparing a medium-low nickel precursor material coated with a lithium superion conductor, the preparation method comprising the following steps:

[0072] (1) mixing diphenyl chromium with tetrahydrofuran to prepare an organic metal salt solution with a concentration of 5 mol / L, adding the organic metal salt solution, the mixed metal salt solution and sodium dodecyl sulfate into a reaction kettle, introducing air and nitrogen at a volume ratio of 0.3:1, and mixing at a rotation speed of 10 r / min to obtain a first mixture;

[0073] In the first mixture, the molar ratio of the organic metal salt to the total metal ions in the mixed metal salt solution is 1:5, and the molar ratio of the sodium dodecyl sulfate to the total metal ions in the mixed metal salt solution is 1:8;

[0074] The mixed metal salt solution includes nickel ions, cobalt ions and manganese ions in a molar ratio of 0.7:0.1:0.3;

[0075] (2) stopping the introduction of air and continuing the introduction of nitrogen, adding a lithium superion conductor, a sodium hydroxide solution with a concentration of 12 g / L, and an ammonia solution with a concentration of 7 g / L to the first mixture in step (1), and conducting a coprecipitation reaction at 55° C., a heating rate of 1.5° C. / min, a rotation speed of 40 r / min, and a pH of 9 to obtain a second mixture;

[0076] The lithium superion conductor includes Li 0.365 Ta 0.239 La 0.478 Cl 3 , the molar ratio of the lithium superion conductor to the total metal ions in the mixed metal salt solution is 1:150;

[0077] (3) The second mixture is further heated to 120° C. at a heating rate of 0.5-1° C. / min, and oxalic acid is added to adjust the pH to 5.5, and the mixture is reacted at a rotation speed of 300 / min for 3 hours, followed by washing and drying to obtain the low-nickel precursor material coated with the lithium superion conductor.

[0078] Example 4

[0079] This embodiment provides a method for preparing a medium-low nickel precursor material coated with a lithium superion conductor. The preparation method is the same as that of Example 1 except that the molar ratio of the organic metal salt to the total metal ions in the mixed metal salt solution in step (1) is 1:3.

[0080] Example 5

[0081] This embodiment provides a method for preparing a medium-low nickel precursor material coated with a lithium superion conductor. The preparation method is the same as that of Example 1 except that the molar ratio of the organic metal salt to the total metal ions in the mixed metal salt solution in step (1) is 1:12.

[0082] Example 6

[0083] This embodiment provides a method for preparing a medium-low nickel precursor material coated with a lithium superion conductor. The preparation method is the same as that of Embodiment 1 except that pure nitrogen is introduced in step (1).

[0084] Example 7

[0085] This embodiment provides a method for preparing a low-nickel precursor material coated with a lithium superion conductor. The preparation method is the same as that of Embodiment 1 except that the introduction of air is not stopped in step (2) and step (2) is still carried out in an atmosphere of air and nitrogen at a ratio of 0.5:1.

[0086] Example 8

[0087] This embodiment provides a method for preparing a medium-low nickel precursor material coated with a lithium superion conductor. The preparation method is the same as that of Example 1, except that the pH is not adjusted in step (3) and is still performed at the pH of step (2).

[0088] Comparative Example 1

[0089] This comparative example provides a method for preparing a medium-low nickel precursor material. The preparation method is the same as Example 1 except that no lithium superion conductor is added in step (2).

[0090] Comparative Example 2

[0091] This comparative example provides a method for preparing a medium-low nickel precursor material. The preparation method is the same as Example 1 except that no organic metal salt solution is added in step (1).

[0092] Comparative Example 3

[0093] This comparative example provides a method for preparing a medium-low nickel precursor material. The preparation method is the same as Example 1 except that step (3) is not performed and washing and drying are performed directly after the reaction in step (2) is completed.

[0094] The low-nickel precursor material obtained in the above embodiments and comparative examples and lithium hydroxide were heated to 500°C at a rate of 2.5°C / min, kept warm for 8h, and then continued to be heated to 850°C at a rate of 5°C / min, and then calcined for 20h to obtain a positive electrode material; the prepared positive electrode material, conductive carbon black and polyvinylidene fluoride were mixed into a slurry in a mass ratio of 8:1:1, and coated on an aluminum foil to make a positive electrode sheet, a metal lithium sheet was used as a negative electrode sheet, and 1 mol / L LiPF 6 / EC:DMC (volume ratio 1:1) as the electrolyte, the battery shell, positive and negative electrode sheets, diaphragm, spring and gasket were assembled into button batteries in a vacuum glove box. The Blue Electric test system was used to perform a 0.5C cycle test for 100 weeks at 2.0-4.8V at a high temperature of 45°C. The test results are shown in Table 1:

[0095] Table 1

[0096]

[0097]

[0098] From the above table we can see that:

[0099] It can be seen from Example 1 and Comparative Example 1 that the present invention can improve the stability and conductivity of the precursor material by coating the surface with a lithium superion conductor, thereby effectively improving the performance of the precursor material; it can be seen from Example 1 and Comparative Example 2 that the addition of the organic metal salt of the present invention is aimed at the problem that the medium and low nickel precursor materials are easily overoxidized, and effectively improves the looseness of the material morphology and the phenomenon of excessive coarseness of the primary particles, thereby effectively improving the performance of the precursor material; it can be seen from Example 1 and Comparative Example 3 that if step (3) is not performed, the role of the organic metal salt cannot be effectively exerted, thereby affecting the performance of the precursor material; it can be seen from Example 1 and Examples 4-7 that the addition amount of the organic metal salt of the present invention and the atmosphere of the coprecipitation reaction will also affect the performance of the material; it can be seen from Example 1 and Example 8 that step (3) of the present invention is preferably carried out at a relatively low pH, which can not only promote the role of the organic metal salt, but also reduce the alkali content on the surface of the precursor, thereby effectively improving the performance of the precursor material.

[0100] In summary, the present invention provides a medium-low nickel precursor material coated with a lithium superion conductor, a preparation method and an application thereof. The preparation method effectively broadens the fast channel for lithium ion deintercalation and avoids direct contact between the positive electrode material and the electrolyte by adopting a lithium superion conductor coating method. In addition, organic metal salts are used to avoid the problem of overoxidation in the reaction process of the medium-low nickel precursor material in order to refine the primary particle morphology, thereby effectively improving the cycle stability and conductivity of the battery.

[0101] The above description 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 are within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a medium-low nickel precursor material coated with a lithium superion conductor, characterized in that: The preparation method comprises the following steps: (1) mixing an organic metal salt solution and a mixed metal salt solution to obtain a first mixture; (2) adding a lithium superion conductor, a precipitant solution and a complexing agent solution to the first mixture in step (1) to carry out a coprecipitation reaction to obtain a second mixture; (3) The second mixture in step (2) is further heated to react to obtain the low-nickel precursor material coated with the lithium superion conductor.

2. The preparation method according to claim 1, characterized in that: The organic metal salt solution in step (1) comprises diphenylchromium and / or cyclooctatetraene sandwich compound; Preferably, in the first mixture of step (1), the molar ratio of the organic metal salt to the total metal ions in the mixed metal salt solution is 1:(5-10); Preferably, the concentration of the organic metal salt solution in step (1) is 3-5 mol / L.

3. The preparation method according to claim 1 or 2, characterized in that: When the organic metal salt solution and the mixed metal salt solution are mixed in step (1), a dispersant is also added; Preferably, the molar ratio of the dispersant to the total metal ions in the mixed metal salt solution is 1:(4-8); Preferably, the dispersant includes any one of sodium lauryl sulfate, coconut oil diethanolamide, methyl high hydrogen silicone oil emulsion or hydroxy silicone oil emulsion, or a combination of at least two of them.

4. The preparation method according to any one of claims 1 to 3, characterized in that In the mixed metal salt solution of step (1), the molar ratio of nickel ions, cobalt ions and manganese ions is x:y:z, wherein 0.4 <x<0.8,0<y<0.2,0<z<0.3; Preferably, step (1) is carried out in a mixed atmosphere of air and nitrogen, and then the introduction of air is stopped to carry out step (2), and the introduction of nitrogen continues to carry out step (2); Preferably, the volume ratio of air to nitrogen is (0.3-0.5):

1.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The lithium superionic conductor described in step (2) includes Li a M1 b M2 c Cl3, where 0.3 < a < 0.5, 0.2 < b < 0.3, 0.45 < c < 0.50, and both M1 and M2 are selected from transition elements and / or rare earth elements; Preferably, M1 and M2 independently include any one or a combination of at least two of La, Ta, Zr, Nb, V or Ti; Preferably, the molar ratio of the lithium superion conductor to the total metal ions in the mixed metal salt solution in step (2) is 1:(50-150); Preferably, the precipitant solution in step (2) comprises a sodium hydroxide solution having a concentration of 7-12 g / L; Preferably, the complexing agent solution in step (2) comprises aqueous ammonia at a concentration of 2-7 g / L; Preferably, the temperature of the coprecipitation reaction in step (2) is 30-55°C, the heating rate is 1-1.5°C / min, and the pH is 8-12.

6. The preparation method according to any one of claims 1 to 5, characterized in that the temperature of the temperature-raising reaction in step (3) is 120-140° C., and the heating rate is 0.5-1° C. / min; Preferably, the pH of the temperature-raising reaction in step (3) is 5-5.5, and the time is 1-3 hours; Preferably, an acidic substance is used to adjust the pH of the temperature-raising reaction in step (3); Preferably, the acidic substance includes any one of citric acid, oxalic acid or acetic acid, or a combination of at least two of them.

7. A medium-low nickel precursor material coated with a lithium superion conductor, characterized in that: The medium-low nickel precursor material coated with the lithium superion conductor is prepared by the preparation method according to any one of claims 1 to 6.

8. A positive electrode material, characterized in that The positive electrode material is obtained by mixing and sintering a lithium source and a medium-low nickel precursor material coated with a lithium superion conductor as claimed in claim 7.

9. The positive electrode material according to claim 8, characterized in that The sintering includes heating to 450-550° C. at a rate of 2-2.5° C. / min, keeping the temperature for 5-8 hours, and then continuing to heat to 800-850° C. at a rate of 4-6° C. / min, and keeping the temperature for 15-20 hours.

10. A lithium ion battery, characterized in that: The lithium-ion battery comprises the positive electrode material according to claim 8 or 9.

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