WO2024037143A1 - 一种外涂层包覆的高镍三元正极材料及其制备方法 - Google Patents

一种外涂层包覆的高镍三元正极材料及其制备方法 Download PDF

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WO2024037143A1
WO2024037143A1 PCT/CN2023/099153 CN2023099153W WO2024037143A1 WO 2024037143 A1 WO2024037143 A1 WO 2024037143A1 CN 2023099153 W CN2023099153 W CN 2023099153W WO 2024037143 A1 WO2024037143 A1 WO 2024037143A1
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nickel ternary
cathode material
ternary cathode
outer coating
solution
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PCT/CN2023/099153
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English (en)
French (fr)
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袁玲
刘伟健
阮丁山
李长东
黄龙胜
亓黎越
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广东邦普循环科技有限公司
湖南邦普循环科技有限公司
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Priority to CN202380009606.9A priority Critical patent/CN117043975A/zh
Priority to PCT/CN2023/099153 priority patent/WO2024037143A1/zh
Publication of WO2024037143A1 publication Critical patent/WO2024037143A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present disclosure relates to the technical field of lithium-ion battery cathode materials, and in particular to an outer coating-coated high-nickel ternary cathode material and a preparation method thereof.
  • High-nickel layered oxide materials are considered ideal cathode materials for high-energy-density lithium-ion batteries due to their high reversible capacity.
  • this kind of material especially a material with a high specific surface area, porous structure and strong chemical hydrophilicity, will absorb water when exposed to the atmospheric environment, resulting in the formation of residual lithium compounds on the surface of the material, resulting in the problem of residual lithium, and this damage It will further absorb more moisture during subsequent storage, which will seriously corrode the cathode oxide.
  • Residual lithium compounds inevitably exist in high-nickel ternary cathode materials. They are usually detected in the form of Li2O , LiOH and Li2CO3 mixtures, and their proportions change with changes in storage conditions such as humidity and time . And its quantity increases with the increase of nickel content in high-nickel ternary cathode materials. During the synthesis process of most high-nickel ternary cathode materials, a small amount of lithium salt will inevitably remain on the surface of the high-nickel ternary cathode material. When the high-nickel ternary cathode material is exposed to the air, it will react with H 2 O and CO 2 reaction and gradually converted into LiOH and Li 2 CO 3 .
  • the problem of residual lithium on the surface of high-nickel ternary cathode materials will cause many problems such as capacity fading, low lithium ion diffusion performance, and poor cycle performance.
  • high residual alkali content on the surface of high-nickel ternary cathode materials will cause the slurry to gel during the preparation of cathode slurry, which will seriously affect the battery coating manufacturing process; it will also react with LiPF6 in the electrolyte to generate HF and CO 2 causes the battery to bloat and brings great safety risks to the battery.
  • a common method to remove residual alkali is water washing, but the water washing step not only increases the cost but also makes it difficult to control the operating steps.
  • the structure of the washed high-nickel ternary cathode material deteriorates and the performance attenuation is serious, resulting in a reduction in the washing effect. Therefore, reducing the residual alkali content on the surface of high-nickel ternary cathode materials and improving the surface moisture resistance are the keys to solving the processing performance and safety performance of high-nickel ternary cathode materials.
  • CN105336927A discloses a modified superhydrophobic material , it is coated in the form of a three-dimensional network on the particle surface of high-nickel cathode materials and filled between particles. It can effectively achieve hydrophobic conductive treatment on the surface of high-nickel cathode materials, reduce sensitivity to environmental moisture, and reduce trace amounts of water and Side reactions occur in the electrolyte to improve the safety, cycleability and storage performance of the high-nickel cathode material in the lithium-ion battery.
  • the particles of the high-nickel cathode material are only made of the modified superhydrophobic material. Bridging, rather than forming a strong chemical bond, this combination method is difficult to ensure that the hydrophobic material will not fall off during the subsequent battery manufacturing process, thus limiting the hydrophobicity between the active materials.
  • the purpose of the present disclosure is to provide a method for preparing a high-nickel ternary cathode material covered with an outer coating, by By adding lithium polyacrylate and silane coupling agent to the surface of the high-nickel ternary cathode material, the residual alkali content on the surface of the high-nickel ternary cathode material can be effectively reduced; at the same time, the added lithium polyacrylate has a bonding effect and can strengthen the outer coating.
  • the combination of the high-nickel ternary cathode material layer with the surface of the high-nickel ternary cathode material enables the surface of the high-nickel ternary cathode material to exhibit an outer coating structure with stable lipophilic and hydrophobic functional groups, thereby greatly improving the performance of the high-nickel ternary cathode material for lithium-ion batteries.
  • Storage, safety and processing performance provide help for the industrial application of high-nickel ternary cathode materials for lithium-ion batteries.
  • the prepared outer-coating-coated high-nickel ternary cathode material can effectively solve the problem of residual alkali on the surface of the high-nickel ternary cathode material. Air sensitivity issues.
  • a method for preparing an outer coating-coated high-nickel ternary cathode material including the following steps:
  • the high-nickel ternary cathode material Dry the high-nickel ternary cathode material, and then put it into a mixer for premixing; after the premixing, spray the silane coupling agent solution and the lithium polyacrylate solution at different nozzles at the same time.
  • the high-nickel ternary cathode material in the mixer is sprayed and stirred, and then subjected to drying and heat treatment to obtain a high-nickel ternary cathode material covered with an outer coating.
  • the preparation method of the silane coupling agent is: dissolving the silane coupling agent into a first solvent to obtain the silane coupling agent solution.
  • the chemical expression of the silane coupling agent is YSiX 3 , where Y is a hydrophobic functional group, which is one of a hydrocarbon group, an ester group, a phenyl group, and a fluorophenyl group; X is a hydrolyzable group, It is one of methoxy, halogen, ethoxy and acetoxy.
  • Y can also be a hydrocarbon group containing fluorine/double bond/aryl/ester/ether/amine/amide and other groups.
  • Y is one of methyl, propyl, phenyl, butyl, octyl, and vinyl.
  • the amount of the silane coupling agent is 0.5% to 5% of the mass of the high-nickel ternary cathode material.
  • the first solvent is a volatile organic solvent, which is one or more of anhydrous ethanol, anhydrous methanol, and acetone.
  • the preparation method of the lithium polyacrylate solution is: dissolving polyacrylic acid and lithium hydroxide into a second solvent to obtain a lithium polyacrylate solution, and the pH of the lithium polyacrylate solution is 5 to 9.
  • the amount of polyacrylic acid used is 0.5% to 3% of the mass of the high-nickel ternary cathode material, and the molecular weight of the polyacrylic acid is 250,000 to 500,000.
  • the second solvent is one or more of water, absolute ethanol, and isopropyl alcohol.
  • the volume concentration of the silane coupling agent solution is 10-100%; the volume concentration of the lithium polyacrylate solution is 10-100%.
  • the dissolution method during the preparation of the silane coupling agent solution and the lithium polyacrylate solution is selected from the group consisting of: One of stirring dissolution, oscillation dissolution, ultrasonic dissolution, and microwave-assisted dissolution, the temperature is normal temperature.
  • the drying conditions for drying the high-nickel ternary cathode material are: drying in a vacuum oven at a temperature of 90°C to 180°C and keeping the temperature for 0.5 to 3 hours.
  • the silane coupling agent solution and the lithium polyacrylate solution are first put into different spray equipment containers, and then after the premixing of the high-nickel ternary cathode material is completed, the The silane coupling agent solution and the lithium polyacrylate solution are simultaneously sprayed onto the high-nickel ternary cathode material in the mixer at different nozzles.
  • step (3) the rotation speed of the mixer is 300 to 1200 rpm, and the premixing time is 1 to 10 minutes.
  • step (3) the spray conditions of the silane coupling agent solution and the lithium polyacrylate solution on the spray equipment are both, the spray speed is 5 to 50 ml/min, and the spray time is 2 to 15 minutes.
  • step (3) the stirring time is 1 to 10 minutes.
  • step (3) the drying heat treatment conditions are oven drying, the temperature is 90-150°C, and the time is 2-24 hours.
  • the present disclosure also provides an outer coating-coated high-nickel ternary cathode material, which is obtained by any of the above-mentioned preparation methods of an outer coating-coated high-nickel ternary cathode material.
  • the silane coupling agent solution and the lithium polyacrylate solution are sprayed on the surface of the high-nickel ternary cathode material, Forming an outer coating and covering the surface of the high-nickel ternary cathode material can significantly reduce the sensitivity of the high-nickel ternary cathode material to air moisture and improve its storage performance and electrochemical performance in the air.
  • the outer coating includes organic lithium silicate and lithium polyacrylate; by adding the silane coupling agent, it can react with the residual alkali on the surface of the high-nickel ternary cathode material to obtain organic lithium silicate with lipophilic and hydrophobic functional groups.
  • the silane coupling agent can be chemically bonded with Si-O on the surface of the high-nickel ternary cathode material to form a strong chemical bond, making it difficult to fall off.
  • the present disclosure further uses lithium polyacrylate, which itself has a certain adhesiveness, to strengthen the bond with the material surface.
  • lithium polyacrylate By adding the lithium polyacrylate, on the one hand, in order to more firmly stabilize the organic lithium silicate with hydrophobic functional groups and the high-nickel ternary cathode
  • lithium polyacrylate can also be used as an ion conductor, which can additionally compensate for the loss of lithium ions in high-nickel ternary cathode materials and reduce the impact of the inactive material such as the silane coupling agent on high-nickel ternary cathode materials. influence on the electrochemical properties of materials.
  • the present disclosure can significantly reduce the residual alkali on the surface of the high-nickel ternary cathode material and inhibit the substantial transformation of LiOH into Li 2 CO 3 , rationally utilizing residual alkali to convert it into an efficient outer coating to coat the surface of the high-nickel ternary cathode material, effectively improving the material's Processing performance and safety performance.
  • the outer coating coated on the surface of the high-nickel ternary cathode material includes two effective substances that exist simultaneously.
  • the organic lithium silicate generated on the surface of the high-nickel ternary cathode material provides a hydrophobic effect, and the high-nickel ternary cathode material has a hydrophobic effect.
  • Lithium polyacrylate on the surface of the nickel ternary cathode material provides binding and ionic conductor functions.
  • the high-nickel ternary cathode material with outer coating prepared by the present disclosure can significantly reduce the surface moisture and residual Li of the high-nickel ternary cathode material. + amount, especially improving the first-cycle capacity retention rate of high-nickel ternary cathode materials.
  • the silane coupling agent By reacting the silane coupling agent with the residual alkali on the surface of the high-nickel ternary cathode material, the amount of residual Li + is reduced.
  • the high-nickel ternary cathode material covered with the outer coating of the present disclosure has a significant effect of reducing residual alkali, and does not affect the first cycle capacity of the material, nor does it change the The internal structure of the high-nickel ternary cathode material.
  • the synthesized lithium polyacrylate is a conductive binder that can be used as an additional lithium salt to compensate for the loss of lithium ions, which can reduce the impact of the hydrophobic coating on the high-nickel ternary cathode.
  • the influence of the electrochemical properties of the material can also effectively improve the bonding force between the hydrophobic coating and the material surface, prevent the shedding of active substances during the subsequent coating process, firmly form a dense protective layer to isolate air and moisture, and significantly improve the air sensitivity of the material;
  • the solvent used in the preparation method of the high-nickel ternary cathode material covered with the outer coating of the present disclosure is less toxic, and compared with the water washing solution in the related technology, the high-nickel ternary cathode material covered with the outer coating of the present disclosure is less toxic.
  • the preparation method saves the washing step and reduces the cost.
  • the preparation method of the high-nickel ternary cathode material covered with the outer coating of the present disclosure is simple, easy to operate, has obvious effects, has little impact on the environment, and has considerable industrial application value.
  • the dosage of the silane coupling agent is 0.5% to 5% of the mass of the high-nickel ternary cathode material. If the amount of the silane coupling agent is too low, the content of the synthesized hydrophobic lithium organosilicate in the outer coating will be too low, resulting in poor surface hydrophobicity of the high-nickel ternary cathode material covered by the outer coating. If the dosage of the silane coupling agent is too high, since the siloxane coupling agent is an inactive non-conductive substance, it will adversely affect the electrochemical performance of the high-nickel ternary cathode material covered by the outer coating.
  • the amount of polyacrylic acid used is 0.5% to 3% of the mass of the high-nickel ternary cathode material. If the dosage of polyacrylic acid is too high, it will mask the hydrophobicity of the material and affect the electrochemical performance; if the dosage of polyacrylic acid is too low, it will reduce the bonding effect and the effect of compensating for lithium loss, which will also affect the electrochemical performance.
  • Figure 1 is a cycle data diagram of the high-nickel ternary cathode materials of Examples 1 to 3 and Comparative Example 1;
  • Figure 2 shows the changes in the discharge specific capacity of the high-nickel ternary cathode materials of Example 3 and Comparative Example 1 in the first cycle of each day in the air exposure experiment;
  • Figure 3 is a schematic diagram of the combination of mixer and spray device.
  • This embodiment provides a method for preparing an outer coating-coated high-nickel ternary cathode material, which includes the following steps:
  • the high-nickel ternary cathode material is mixed evenly and fully contacted, and finally placed in a vacuum drying oven at 110°C for drying for 2 hours to obtain a high-nickel ternary cathode material covered with an outer coating, which has a hydrophobic function.
  • Figure 3 is a schematic diagram of the mixer and spray equipment used during the experiment.
  • Marks 1 and 3 in the figure both refer to the air inlet pipe of the spray equipment, and marks 2 and 4 both refer to It is the liquid inlet pipe of the spray equipment, mark 5 refers to the degassing port of the mixer, and mark 6 refers to the stirring paddle of the mixer.
  • the outer coating-coated high-nickel ternary cathode material obtained in this example was subjected to a storage test experiment: an air exposure experiment was conducted in a conventional atmospheric environment, and a portion of the sample was taken every day to detect water content, residual lithium content, and first cycle capacity. Test results show that the smaller the increase in water content and residual lithium content, the better the moisture resistance of the high-nickel ternary cathode material after coating. The higher the first cycle capacity retention rate, the more proof that the moisture resistance improves the electrochemistry of the high-nickel ternary cathode material. Performance is more stable.
  • the outer coating-coated high-nickel ternary cathode material obtained in Example 1, before being placed in air, has a water content of 0.0195%, a LiOH content of 0.3094%, and a Li 2 CO 3 content of 0.1321%.
  • the first cycle of charging The specific capacity is 244.6mAh/g, the specific discharge capacity is 228.3mAh/g, and the first efficiency is 93.4%.
  • the water content was 0.4012%
  • the LiOH content was 0.44232%
  • the Li 2 CO 3 content was 0.5678%
  • the first cycle charge specific capacity was 244.0mAh/g
  • the discharge specific capacity was 227.8mAh/g
  • the first effect is 93.4%.
  • This embodiment provides a method for preparing an outer coating-coated high-nickel ternary cathode material, which includes the following steps:
  • the outer coating-coated high-nickel ternary cathode material obtained in this example was subjected to a storage test experiment: an air exposure experiment was conducted in a conventional atmospheric environment, and a portion of the sample was taken every day to detect water content, residual lithium content, and first cycle capacity. Test results show that the smaller the increase in water content and residual lithium content, the better the moisture resistance of the high-nickel ternary cathode material after coating. The higher the first cycle capacity retention rate, the more proof that the moisture resistance improves the electrochemistry of the high-nickel ternary cathode material. Performance is more stable.
  • the outer coating-coated high-nickel ternary cathode material obtained in Example 2 before being placed in air, has a water content of 0.0178%, a LiOH content of 0.2430%, and a Li 2 CO 3 content of 0.1046%.
  • the first cycle of charging The specific capacity is 244.6mAh/g, the specific discharge capacity is 227.3mAh/g, and the first efficiency is 92.9%.
  • the water content was 0.3345%
  • the LiOH content was 0.4161%
  • the Li 2 CO 3 content was 0.5018%
  • the first cycle charge specific capacity was 248.7mAh/g
  • the discharge specific capacity was 227.3mAh/g
  • the first effect is 91.4%.
  • This embodiment provides a method for preparing an outer coating-coated high-nickel ternary cathode material, which includes the following steps:
  • the high-nickel ternary cathode material with hydrophobic function covered by the outer coating obtained in this example was subjected to a storage test experiment: an air exposure experiment was conducted in a conventional atmospheric environment, and a part of the sample was taken every day to detect water content and residual lithium. Quantity, first circle capacity. Test results show that the smaller the increase in water content and residual lithium content, the better the moisture resistance of the high-nickel ternary cathode material after coating. The higher the first cycle capacity retention rate, the more proof that the moisture resistance improves the electrochemistry of the high-nickel ternary cathode material. Performance is more stable.
  • the test results are as follows: before the outer coating-coated high-nickel ternary cathode material obtained in Example 3 was placed in the air, the water content was 0.0154%, the LiOH content was 0.2058%, and the Li 2 CO 3 content was 0.0963%.
  • the first cycle of charging The specific capacity is 244.5mAh/g, the specific discharge capacity is 228.9mAh/g, and the first efficiency is 93.6%.
  • the water content was 0.2896%
  • the LiOH content was 0.3871%
  • the Li 2 CO 3 content was 0.4526%
  • the first cycle charge specific capacity was 242.3mAh/g
  • the discharge specific capacity was 226.9mAh/g
  • the first effect is 93.6%.
  • This embodiment provides a method for preparing an outer coating-coated high-nickel ternary cathode material, which includes the following steps:
  • the outer coating-coated high-nickel ternary cathode material obtained in this example was subjected to a storage test experiment: an air exposure experiment was conducted in a conventional atmospheric environment, and a portion of the sample was taken every day to detect water content, residual lithium content, and first cycle capacity. Test results show that the smaller the increase in water content and residual lithium content, the better the moisture resistance of the high-nickel ternary cathode material after coating. The higher the first cycle capacity retention rate, the more proof that the moisture resistance improves the electrochemistry of the high-nickel ternary cathode material. Performance is more stable.
  • the outer coating-coated high-nickel ternary cathode material obtained in Example 4, before being placed in air, has a water content of 0.0126%, a LiOH content of 0.2728%, and a Li 2 CO 3 content of 0.1196%.
  • the first cycle of charging The specific capacity is 244.2mAh/g, the specific discharge capacity is 226.1mAh/g, and the first efficiency is 92.6%.
  • the water content was 0.2298%
  • the LiOH content was 0.3631%
  • the Li2CO3 content was 0.4028%
  • the first cycle charge specific capacity was 242.5mAh/g
  • the discharge specific capacity was 224.2mAh/g
  • the first efficiency was 92.5% .
  • This embodiment provides a method for preparing an outer coating-coated high-nickel ternary cathode material, which includes the following steps:
  • Spray onto the high-nickel ternary cathode material in the mixer at the same time Go control the spray speed to 12 mL/min so that the spray time is about 5 minutes, fully stir while spraying, continue to stir for 2 minutes after spraying, so that solution A and solution B and the high nickel ternary cathode material are evenly mixed and fully contacted, and finally put After drying for 2 hours in a vacuum drying oven at 110°C, a high-nickel ternary cathode material covered with an outer coating can be obtained, which has a hydrophobic function.
  • the outer coating-coated high-nickel ternary cathode material obtained in this example was subjected to a storage test experiment: an air exposure experiment was conducted in a conventional atmospheric environment, and a portion of the sample was taken every day to detect water content, residual lithium content, and first cycle capacity. Test results show that the smaller the increase in water content and residual lithium content, the better the moisture resistance of the high-nickel ternary cathode material after coating. The higher the first cycle capacity retention rate, the more proof that the moisture resistance improves the electrochemistry of the high-nickel ternary cathode material. Performance is more stable.
  • the outer coating-coated high-nickel ternary cathode material obtained in Example 5, before being placed in air, has a water content of 0.0165%, a LiOH content of 0.2458%, and a Li 2 CO 3 content of 0.1478%.
  • the first cycle of charging The specific capacity is 244.4mAh/g, the specific discharge capacity is 227.0mAh/g, and the first efficiency is 92.9%.
  • the water content was 0.2934%
  • the LiOH content was 0.3945%
  • the Li 2 CO 3 content was 0.4793%
  • the first cycle charge specific capacity was 243.9mAh/g
  • the discharge specific capacity was 226.4mAh/g
  • the first effect is 92.8%.
  • This embodiment provides a method for preparing an outer coating-coated high-nickel ternary cathode material, which includes the following steps:
  • the outer coating-coated high-nickel ternary cathode material obtained in this example was subjected to a storage test experiment: an air exposure experiment was conducted in a conventional atmospheric environment, and a portion of the sample was taken every day to detect water content, residual lithium content, and first cycle capacity. Test results show that the smaller the increase in water content and residual lithium content, the better the moisture resistance of the high-nickel ternary cathode material after coating. The higher the first cycle capacity retention rate, the more proof that the moisture resistance improves the electrochemistry of the high-nickel ternary cathode material. Performance is more stable.
  • the water content of the high-nickel ternary cathode material with hydrophobic function covered by the outer coating obtained in Example 6 before being placed in the air was 0.0187%
  • the LiOH content was 0.2379%
  • the Li 2 CO 3 content was 0.1102%
  • the first cycle charge specific capacity is 245.3mAh/g
  • the discharge specific capacity is 228.4mAh/g
  • the first efficiency is 93.1%.
  • the water content was 0.3086%
  • the LiOH content was 0.4125%
  • the Li 2 CO 3 content was 0.4533%
  • the first cycle charge specific capacity was 243.9mAh/g
  • the discharge specific capacity was 227.1mAh/g
  • the first effect is 93.1%.
  • This embodiment provides a method for preparing a high-nickel ternary cathode material without outer coating, which includes the following steps:
  • the storage performance test experiment was carried out on the high-nickel ternary cathode material without outer coating in Example 1: an air exposure experiment was carried out in a regular atmospheric environment, and a part of the sample was taken every day to test the water content, residual lithium content, first circle capacity.
  • Comparative Example 1 obtained a high-nickel ternary cathode material without outer coating.
  • the water content was 0.037%
  • the LiOH content was 0.5181%
  • the Li2CO3 content was 0.2306%
  • the first cycle charge specific capacity was 244.9 mAh/g
  • the specific discharge capacity is 228.6mAh/g
  • the first efficiency is 93.3%.
  • the water content was 0.6876%
  • the LiOH content was 0.3619%
  • the Li2CO3 content was 0.9304%
  • the first cycle charge specific capacity was 239.8mAh/g
  • the discharge specific capacity was 219.3mAh/g
  • the first efficiency was 91.5% .
  • the test results are compared with Examples 1 to 6.
  • Lithium-ion button cell batteries are assembled in an argon atmosphere glove box (H 2 O ⁇ 0.1ppm, O 2 ⁇ 0.1ppm).
  • the high-nickel ternary cathode materials, conductive agents, and binders prepared in Examples 1 to 6 and Comparative Example 1 were evenly mixed according to a mass ratio of 90:5:5, and then nitrogen-methylpyrrolidone solvent was added and stirred to form a slurry.
  • the button battery was assembled.
  • the electrolyte was LiPF6 dissolved in a mixed solvent of ethylene carbonate and diethyl carbonate.
  • the separator was made of glass fiber.
  • the negative electrode was made of lithium metal sheet. After assembly, let it stand for 3 hours for the first cycle test of the battery.
  • the cycle performance test uses an all-electric button battery, replaces the lithium metal negative electrode with a carbon material, and tests the battery cycle stability under 0.1C conditions.
  • the preparation method of the outer coating-coated high-nickel ternary cathode material provided in Examples 1 to 6 can synthesize the outer-coating-coated high-nickel ternary cathode material and significantly reduce the residual lithium content of the high-nickel ternary cathode material.
  • Surface water content, residual alkali content, and the high-nickel ternary cathode material covered with the outer coating still has a high first-cycle capacity retention rate after being exposed to air, which greatly improves the high-nickel ternary cathode material covered with the outer coating.
  • the effects of the present disclosure will be described in detail below in conjunction with Comparative Example 1.
  • Example 1 is a data table of the LiOH content, Li 2 CO 3 content, and residual Li + content of the high-nickel ternary cathode materials obtained in Examples 1 to 6 and Comparative Example 1. From it, it can be seen that Example 1 Compared with Comparative Example 1, the high-nickel ternary cathode material coated with an outer coating of ⁇ 6 has significantly lower residual alkali on the material surface.
  • Table 2 is the first cycle charge and discharge capacity data table of the high-nickel ternary cathode material obtained in Examples 1 to 6 and Comparative Example 1 under the condition of 4.3V/0.1C. It can be seen that Examples 1 to 6 Compared with the high-nickel ternary cathode material obtained in Comparative Example 1, the discharge specific capacity decreased slightly, which is attributed to the introduction of a small amount of silane coupling agent and lithium polyacrylate.
  • Table 3 is a data table of the daily H 2 O content, LiOH content, and Li 2 CO 3 content of the high-nickel ternary cathode material obtained in Example 2 and Comparative Example 1 in the air exposure experiment. From it, you can see It is found that as the number of storage days increases, the rising trend of the H 2 O content in Example 2 is obviously lower than that in Comparative Example 1, and the transformation of LiOH to Li 2 CO 3 can be significantly inhibited in Example 2.
  • this disclosure uses a simple device to combine low-cost silane coupling agent and lithium polyacrylate with the surface of high-nickel ternary cathode material, significantly reducing the residual alkali on the surface of high-nickel ternary cathode material and inhibiting the large-scale transfer of LiOH to Li. 2 CO 3 conversion, rational use of residual alkali to convert into an efficient coating to coat the surface of the high-nickel ternary cathode material.
  • the outer coating includes hydrophobic coatings of organic lithium silicate and lithium polyacrylate, which effectively improves the processing of the material. Performance and security issues.

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Abstract

本公开涉及一种外涂层包覆的高镍三元正极材料及其制备方法，属于锂离子电池正极材料技术领域。本公开的外涂层包覆的高镍三元正极材料的制备方法中，通过在高镍三元正极材料的表面，分别喷洒硅烷偶联剂溶液和聚丙烯酸锂溶液，形成外涂层，包覆在高镍三元正极材料表面，可以显著降低高镍三元正极材料对空气水分的敏感度，提高其在空气中的存储性能以及电化学性能。其中，外涂层包括疏水涂层有机硅酸锂和聚丙烯酸锂；通过加入所述硅烷偶联剂，能够与高镍三元正极材料表面的残碱反应，得到具有亲油疏水官能团的有机硅酸锂，并与聚丙烯酸锂共同与高镍三元正极材料表面结合，显著降低高镍三元正极材料表面残碱并且抑制LiOH大幅度向Li2CO3转变。

Description

一种外涂层包覆的高镍三元正极材料及其制备方法 技术领域
本公开涉及锂离子电池正极材料技术领域，特别是涉及一种外涂层包覆的高镍三元正极材料及其制备方法。
背景技术
高镍层状氧化物材料因其具有高可逆容量而被认为是高能量密度锂离子电池的理想正极材料。但是这种材料，尤其是具有高比表面积、多孔结构和强化学亲水性的材料，暴露在大气环境中会吸水，导致在材料表面形成残余的锂化合物，出现残锂问题，并且这种损害会在后续储存过程中进一步吸收更多的水分，进而严重腐蚀阴极氧化物。
残余锂化合物不可避免地存在于高镍三元正极材料中，它们通常以Li2O、LiOH和Li2CO3混合物的形式检测到，它们的比例随湿度和时间等存储条件的变化而变化，且其数量随高镍三元正极材料中镍含量的增加而增加。大多数高镍三元正极材料在合成过程中，不可避免地会存在少量的锂盐留在高镍三元正极材料表面，当高镍三元正极材料暴露于空气时会与H2O和CO2反应，逐渐转化为LiOH和Li2CO3。高镍三元正极材料表面的残锂问题会带来容量衰减，低锂离子扩散性能，循环性能变差等诸多困扰。例如，高镍三元正极材料的表面残碱含量过高会导致制备阴极浆料过程中的浆料凝胶化，会严重影响电池涂布制作工艺；还会与电解液中LiPF6反应生成HF和CO2，导致电池胀气，给电池带来极大的安全隐患。常见的去除残碱的方法是水洗，但是水洗步骤不仅增加成本并且难以控制操作步骤，水洗后的高镍三元正极材料结构恶化，性能衰减严重，导致水洗效果降低。因此降低高镍三元正极材料表面的残碱含量以及提高表面抗湿性能是解决高镍三元正极材料加工性能和安全性能的关键。
目前采用到的能够有效改善高镍三元正极材料对水分敏感性问题的技术手段有掺杂、包覆及其它表面改性等手段，例如包覆方案，CN105336927A公开了一种改性超疏水材料，它是以三维网络形式包覆在高镍正极材料的颗粒表面以及填充到颗粒与颗粒之间，可有效实现高镍正极材料表面的疏水导电处理，减少对环境水分敏感性降低痕量水与电解液发生副反应，提高锂离子电池高镍正极材料在电池中的安全性、循环性和存储性能，但由于该方案中高镍正极材料的颗粒与颗粒之间仅由所述改性超疏水材料桥接，而不是形成强有力的化学键，这种结合方式很难保证后续制作电池工序中疏水材料不会脱落，而使此活性物质间的疏水性受到限制。
发明内容
基于此，本公开的目的在于，提供一种外涂层包覆的高镍三元正极材料的制备方法，通 过在高镍三元正极材料表面加入聚丙烯酸锂和硅烷偶联剂，可以有效降低高镍三元正极材料表面的残碱含量；同时加入的聚丙烯酸锂具有粘结的作用，能够加强外涂层与高镍三元正极材料表面的结合，使高镍三元正极材料的表面展示出具有稳固的亲油疏水官能团的外涂层结构形态，从而大大提升锂离子电池高镍三元正极材料的存储性、安全性和加工性能，为锂离子电池高镍三元正极材料的工业化应用提供帮助。本公开所述的外涂层包覆的高镍三元正极材料的制备方法，其制备得到的外涂层包覆的高镍三元正极材料能够有效解决高镍三元正极材料表面残碱以及对空气敏感的问题。
一种外涂层包覆的高镍三元正极材料的制备方法，包括以下步骤：
制备硅烷偶联剂溶液；
制备聚丙烯酸锂溶液；
将高镍三元正极材料进行干燥，然后放进混料机中进行预混；预混结束后，分别将所述硅烷偶联剂溶液和所述聚丙烯酸锂溶液在不同的喷口处同时喷洒到所述混料机中的所述高镍三元正极材料，边喷洒边搅拌，结束后进行干燥热处理，得到外涂层包覆的高镍三元正极材。
在一个方案中，所述硅烷偶联剂的制备方法为：将硅烷偶联剂溶解到第一溶剂中，得到所述硅烷偶联剂溶液。
在一个方案中，所述硅烷偶联剂的化学表达式为YSiX3，其中，Y为疏水官能团，为烃基、酯基、苯基、氟苯基中的一种；X为可水解基团，为甲氧基、卤素、乙氧基、乙酰氧基中的一种。在一个方案中，Y还可以采用含氟/双键/芳基/酯/醚/胺/酰胺等基团的烃基。
在一个方案中，Y为甲基、丙基、苯基、丁基、辛基、乙烯基的一种。
在一个方案中，所述硅烷偶联剂的用量为所述高镍三元正极材料质量的0.5％～5％。
在一个方案中，所述第一溶剂为易挥发的有机溶剂，为无水乙醇、无水甲醇、丙酮中的一种或几种。
在一个方案中，所述聚丙烯酸锂溶液的制备方法为：将聚丙烯酸与氢氧化锂溶解到第二溶剂中，得到聚丙烯酸锂溶液，所述聚丙烯酸锂溶液的pH为5～9。
在一个方案中，所述聚丙烯酸的用量为所述高镍三元正极材料质量的0.5％～3％，所述聚丙烯酸的分子量为25～50万。
在一个方案中，所述第二溶剂为水、无水乙醇、异丙醇中的一种或几种。
在一个方案中，所述硅烷偶联剂溶液的体积浓度为10～100％；所述聚丙烯酸锂溶液的体积浓度为10～100％。
在一个方案中，所述硅烷偶联剂溶液、所述聚丙烯酸锂溶液制备过程中的溶解方法选自 搅拌溶解、振荡溶解、超声溶解、微波辅助溶解中的一种，温度为常温。
在一个方案中，所述高镍三元正极材料的化学表达式为LiNixCoyMzO2，其中，M为元素Mn或元素Al；x的取值为0.7～1.0，y的取值为0～0.3，z的取值为0～0.3，且x+y+z＝1。
在一个方案中，所述高镍三元正极材料进行干燥的干燥条件为，在真空烘箱下进行干燥，温度为90℃～180℃，保温0.5～3小时。
在一个方案中，先将所述硅烷偶联剂溶液和所述聚丙烯酸锂溶液分别装入不同的喷雾设备容器罐中，然后在所述高镍三元正极材料预混结束后，将所述硅烷偶联剂溶液和所述聚丙烯酸锂溶液在不同的喷口处同时喷洒到所述混料机中的所述高镍三元正极材料。
在一个方案中，步骤(3)中，所述混料机的转速为300～1200转/分钟，预混时间为1～10分钟。
在一个方案中，步骤(3)中，所述硅烷偶联剂溶液和所述聚丙烯酸锂溶液在所述喷雾设备上的喷洒条件均为，喷速为5～50毫升/分钟，喷洒时间为2～15分钟。
在一个方案中，步骤(3)，搅拌时间为1～10分钟。
在一个方案中，步骤(3)中，所述干燥热处理的条件为烘箱干燥，温度为90～150℃，时间为2～24小时。
本公开还提供一种外涂层包覆的高镍三元正极材料，通过上述任一所述的外涂层包覆的高镍三元正极材料的制备方法得到。
本公开具有以下有益效果：
1、本公开的外涂层包覆的高镍三元正极材料的制备方法中，通过在高镍三元正极材料的表面，分别喷洒所述硅烷偶联剂溶液和所述聚丙烯酸锂溶液，形成外涂层，包覆在高镍三元正极材料表面，可以显著降低高镍三元正极材料对空气水分的敏感度，提高其在空气中的存储性能以及电化学性能。其中，外涂层包括有机硅酸锂和聚丙烯酸锂；通过加入所述硅烷偶联剂，能够与高镍三元正极材料表面的残碱反应，得到具有亲油疏水官能团的有机硅酸锂，另外，所述硅烷偶联剂可以与高镍三元正极材料表面进行Si-O化学键结合，形成强有力的化学键，使其不易脱落。本公开还进一步借助本身具有一定粘结性的聚丙烯酸锂来加强与材料表面的结合，通过加入所述聚丙烯酸锂，一方面为了更加稳固具有疏水官能团的有机硅酸锂与高镍三元正极材料表面的结合，另一方面，聚丙烯酸锂还可以作为离子导体，能够额外弥补高镍三元正极材料损失的锂离子，降低所述硅烷偶联剂这种非活性物质对高镍三元正极材料的电化学性能的影响。本公开通过所述聚丙烯酸锂和所述硅烷偶联剂协同与高镍三元正极材料表面结合，能够显著降低高镍三元正极材料表面残碱，并且抑制LiOH大幅度向Li2CO3转变，合理利用残碱转化成高效的外涂层包覆在高镍三元正极材料表面，有效改善了材料的 加工性能和安全性能。
2、本公开在在高镍三元正极材料表面包覆的外涂层，包括两种同时存在的有效物质，在高镍三元正极材料表面生成的有机硅酸锂提供疏水的作用，而高镍三元正极材料表面的聚丙烯酸锂提供粘结、离子导体的作用，这两种存在于高镍三元正极材料表面的有效物质共同构成外涂层形态。
3、相对于无外涂层包覆的高镍三元正极材料，本公开制备的具有外涂层包覆的高镍三元正极材料，能够显著降低高镍三元正极材料表面水分、残余Li+量，尤其提高了高镍三元正极材料的首圈容量保持率。通过所述硅烷偶联剂与高镍三元正极材料表面残碱反应，降低残余Li+量。
4.相对于相关技术中的单一涂层的包覆方案，本公开的外涂层包覆的高镍三元正极材料，其降低残碱效果显著，既不影响材料首圈容量，也不改变高镍三元正极材料的内部结构，合成的聚丙烯酸锂是一种导电的粘结剂，可作为一种额外的锂盐弥补损失的的锂离子，可以降低疏水涂层对高镍三元正极材料电化学性能的影响，还能有效提高疏水涂层与材料表面的结合力，防止后续涂布过程活性物质的脱落，稳固地形成致密的保护层隔绝空气与水分，明显改善材料空气敏感性；
5、本公开的外涂层包覆的高镍三元正极材料的制备方法中使用溶剂毒害小，且相对于相关技术采用水洗的方案，本公开外涂层包覆的高镍三元正极材料的制备方法省掉水洗步骤，降低成本，本公开的的外涂层包覆的高镍三元正极材料的制备方法简单，容易操作且效果明显，对环境影响小，有可观的工业应用价值。
6、所述硅烷偶联剂的用量为所述高镍三元正极材料质量的0.5％～5％。若所述硅烷偶联剂的用量太低，则外涂层中合成的疏水物质有机硅酸锂的含量太低，导致外涂层包覆的高镍三元正极材料的表面疏水性变差。若所述硅烷偶联剂的用量太高，由于硅氧烷偶联剂是一种非活性不导电物质，会对外涂层包覆的高镍三元正极材料的电化学性能造成不利影响。
7、所述聚丙烯酸的用量为所述高镍三元正极材料质量的0.5％～3％。若聚丙烯酸的用量太高，会掩盖材料疏水性，同时影响电化学性能；若聚丙烯酸的用量太低，会降低粘结效果以及降低弥补锂损失效果，进而也会影响电化学性能。
为了更好地理解和实施，下面结合附图详细说明本公开。
附图说明
图1为实施例1～3与对比例1的高镍三元正极材料的循环数据图；
图2为实施例3与对比例1的高镍三元正极材料在空气暴露实验中每天首圈放电比容量变化；
图3为混料机与喷雾装置联用简示图。
具体实施方式
实施例1
本实施例提供一种外涂层包覆的高镍三元正极材料的制备方法，包括以下步骤：
(1)量取15mL的甲基三甲氧基硅烷偶联剂溶解到35mL的无水乙醇中，形成硅烷偶联剂溶液，记为溶液A；
(2)量取24mL质量分数为30％的聚丙烯酸溶液用去离子水稀释到质量分数为20％的聚丙烯酸溶液，然后将氢氧化锂放入到质量分数为20％的聚丙烯酸溶液中，待氢氧化锂完全溶解，测试溶液的pH为7，得到聚丙烯酸锂溶液，记为溶液B；
将溶液A、溶液B分别放到超声机下处理5min，分别使溶液A充分混合均匀、溶液B充分混合均匀；
(3)将3kg高镍三元正极材料LiNi0.92Co0.06Mn0.02O2先在90℃真空干燥箱中干燥0.5h，然后在800rpm的混料机里面先预混2min，然后将上述配置好的溶液A和溶液B分别装入不同的喷雾设备容器罐，将喷雾设备与混料机连接好，在预混结束后将已经装进喷雾设备容器罐里的溶液A和溶液B分别从不同的喷头处同时喷洒到混料机里的高镍三元正极材料上去，控制喷速10mL/min使喷雾时间在5min左右，一边喷同时一边充分搅拌，喷完之后继续搅拌2min使溶液A和溶液B与高镍三元正极材料混合均匀充分接触，结束后最后放到真空干燥箱110℃下进行干燥2h，即可得到外涂层包覆的高镍三元正极材料，其具有疏水功能。
请参阅图3，其为实验过程中使用的混料机与喷雾设备联用的简示图，图中标记1和标记3均指的是喷雾设备的进气管，标记2和标记4均指的是喷雾设备的进液管，标记5指的是混料机的脱气口，标记6指的是混料机的搅拌桨。
将本实施例得到的外涂层包覆的高镍三元正极材料进行存储测试实验：在常规大气环境中进行空气暴露实验，并且每天取一部分样品送样检测水含量、残锂量、首圈容量。测试结果水含量、残锂量上升越小说明包覆后高镍三元正极材料的抗湿性能越好，首圈容量保持率越高越证明抗湿作用让高镍三元正极材料的电化学性能更加稳定。
结果如下：实施例1得到的外涂层包覆的高镍三元正极材料，未放置空气之前，水含量为0.0195％，LiOH含量为0.3094％，Li2CO3含量为0.1321％，首圈充电比容量为244.6mAh/g，放电比容量为228.3mAh/g，首效为93.4％。在空气中放置7天后，水含量为0.4012％，LiOH含量为0.44232％，Li2CO3含量为0.5678％，首圈充电比容量为244.0mAh/g，放电比容量为227.8mAh/g，首效为93.4％。
实施例2
本实施例提供一种外涂层包覆的高镍三元正极材料的制备方法，包括以下步骤：
(1)量取30mL的甲基三甲氧基硅烷偶联剂溶解到30mL的无水乙醇中，形成硅烷偶联剂溶液，记为溶液A；
(2)量取24mL质量分数为30％的聚丙烯酸溶液用去离子水稀释到质量分数为20％的聚丙烯酸溶液，然后将氢氧化锂放入到质量分数为20％的聚丙烯酸溶液中，待氢氧化锂完全溶解，测试溶液的pH为7，得到聚丙烯酸锂溶液，记为溶液B；
将溶液A、溶液B分别放到超声机下处理5min，分别使溶液A充分混合均匀、溶液B充分混合均匀；
(3)将3kg高镍三元正极材料LiNi0.92Co0.06Mn0.02O2先在90℃真空干燥箱中干燥0.5h，然后在800rpm的混料机里面先预混2min，然后将上述配置好的溶液A和溶液B分别装入不同的喷雾设备容器罐，将喷雾设备与混料机连接好，在预混结束后将已经装进喷雾设备容器罐里的溶液A和溶液B分别从不同的喷头处同时喷洒到混料机里的高镍三元正极材料上去，控制喷速12mL/min使喷雾时间在5min左右，一边喷同时一边充分搅拌，喷完之后继续搅拌2min使溶液A和溶液B与高镍三元正极材料混合均匀充分接触，结束后最后放到真空干燥箱110℃下进行干燥2h，即可得到外涂层包覆的高镍三元正极材料，其具有疏水功能。
请参阅图3，本实施例实验过程中使用的混料机与喷雾设备联用，与实施例1相同。
将本实施例得到的外涂层包覆的高镍三元正极材料进行存储测试实验：在常规大气环境中进行空气暴露实验，并且每天取一部分样品送样检测水含量、残锂量、首圈容量。测试结果水含量、残锂量上升越小说明包覆后高镍三元正极材料的抗湿性能越好，首圈容量保持率越高越证明抗湿作用让高镍三元正极材料的电化学性能更加稳定。
结果如下：实施例2得到的外涂层包覆的高镍三元正极材料，未放置空气之前，水含量为0.0178％，LiOH含量为0.2430％，Li2CO3含量为0.1046％，首圈充电比容量为244.6mAh/g，放电比容量为227.3mAh/g，首效为92.9％。在空气中放置7天后，水含量为0.3345％，LiOH含量为0.4161％，Li2CO3含量为0.5018％，首圈充电比容量为248.7mAh/g，放电比容量为227.3mAh/g，首效为91.4％。
实施例3
本实施例提供一种外涂层包覆的高镍三元正极材料的制备方法，包括以下步骤：
(1)量取60mL的甲基三甲氧基硅烷偶联剂溶解到30mL的无水乙醇中，形成硅烷偶联剂溶液，记为溶液A；
(2)量取71mL质量分数为30％的聚丙烯酸溶液用去离子水稀释到质量分数为20％的聚丙烯酸溶液，然后将氢氧化锂放入到质量分数为20％的聚丙烯酸溶液中，待氢氧化锂完全溶解，测试溶液的pH为5，得到聚丙烯酸锂溶液，记为溶液B；
将溶液A、溶液B分别放到超声机下处理5min，分别使溶液A充分混合均匀、溶液B充分混合均匀；
(3)将3kg高镍三元正极材料LiNi0.92Co0.06Mn0.02O2先在90℃真空干燥箱中干燥0.5h，然后在800rpm的混料机里面先预混2min，然后将上述配置好的溶液A和溶液B分别装入不同的喷雾设备容器罐，将喷雾设备与混料机连接好，在预混结束后将已经装进喷雾设备容器罐里的溶液A和溶液B分别从不同的喷头处同时喷洒到混料机里的高镍三元正极材料上去，控制喷速18mL/min使喷雾时间在5min左右，一边喷同时一边充分搅拌，喷完之后继续搅拌2min使溶液A和溶液B与高镍三元正极材料混合均匀充分接触，结束后最后放到真空干燥箱110℃下进行干燥2h，即可得到外涂层包覆的高镍三元正极材料，其具有疏水功能。
请参阅图3，本实施例实验过程中使用的混料机与喷雾设备联用，与实施例1相同。
将本实施例得到的外涂层包覆的具有疏水功能的高镍三元正极材料进行存储测试实验：在常规大气环境中进行空气暴露实验，并且每天取一部分样品送样检测水含量、残锂量、首圈容量。测试结果水含量、残锂量上升越小说明包覆后高镍三元正极材料的抗湿性能越好，首圈容量保持率越高越证明抗湿作用让高镍三元正极材料的电化学性能更加稳定。
测试结果如下：实施例3得到的外涂层包覆的高镍三元正极材料未放置空气之前，水含量为0.0154％，LiOH含量为0.2058％，Li2CO3含量为0.0963％，首圈充电比容量为244.5mAh/g，放电比容量为228.9mAh/g，首效为93.6％。在空气中放置7天后，水含量为0.2896％，LiOH含量为0.3871％，Li2CO3含量为0.4526％，首圈充电比容量为242.3mAh/g，放电比容量为226.9mAh/g，首效为93.6％。
实施例4
本实施例提供一种外涂层包覆的高镍三元正极材料的制备方法，包括以下步骤：
(1)量取90mL的甲基三甲氧基硅烷偶联剂，记为溶液A；
(2)量取24mL质量分数为30％的聚丙烯酸溶液用去离子水稀释到质量分数为20％的聚丙烯酸溶液，然后将氢氧化锂放入到质量分数为20％的聚丙烯酸溶液中，待氢氧化锂完全溶解，测试溶液的pH为7，得到聚丙烯酸锂溶液，记为溶液B；
将溶液A、溶液B分别放到超声机下处理5min，分别使溶液A充分混合均匀、溶液B充分混合均匀；
(3)将3kg高镍三元正极材料LiNi0.92Co0.06Mn0.02O2先在90℃真空干燥箱中干燥0.5h，然后在800rpm的混料机里面先预混2min，然后将上述配置好的溶液A和溶液B分别装入不同的喷雾设备容器罐，将喷雾设备与混料机连接好，在预混结束后将已经装进喷雾设备容器罐里的溶液A和溶液B分别从不同的喷头处同时喷洒到混料机里的高镍三元正极材料上去，控制喷速18mL/min使喷雾时间在5min左右，一边喷同时一边充分搅拌，喷完之后继续搅拌2min使溶液A和溶液B与高镍三元正极材料混合均匀充分接触，结束后最后放到真空干燥箱110℃下进行干燥2h，即可得到外涂层包覆的高镍三元正极材料，其具有疏水功能。
请参阅图3，本实施例实验过程中使用的混料机与喷雾设备联用，与实施例1相同。
将本实施例得到的外涂层包覆的高镍三元正极材料进行存储测试实验：在常规大气环境中进行空气暴露实验，并且每天取一部分样品送样检测水含量、残锂量、首圈容量。测试结果水含量、残锂量上升越小说明包覆后高镍三元正极材料的抗湿性能越好，首圈容量保持率越高越证明抗湿作用让高镍三元正极材料的电化学性能更加稳定。
结果如下：实施例4得到的外涂层包覆的高镍三元正极材料，未放置空气之前，水含量为0.0126％，LiOH含量为0.2728％，Li2CO3含量为0.1196％，首圈充电比容量为244.2mAh/g，放电比容量为226.1mAh/g，首效为92.6％。在空气中放置7天后，水含量为0.2298％，LiOH含量为0.3631％，Li2CO3含量为0.4028％，首圈充电比容量为242.5mAh/g，放电比容量为224.2mAh/g，首效为92.5％。
实施例5
本实施例提供一种外涂层包覆的高镍三元正极材料的制备方法，包括以下步骤：
(1)量取30mL的丙基三甲氧基硅烷偶联剂溶解到30mL的无水乙醇中，形成硅烷偶联剂溶液，记为溶液A；
(2)量取24mL质量分数为30％的聚丙烯酸溶液用去离子水稀释到质量分数为20％的聚丙烯酸溶液，然后将氢氧化锂放入到质量分数为20％的聚丙烯酸溶液中，待氢氧化锂完全溶解，测试溶液的pH为7，得到聚丙烯酸锂溶液，记为溶液B；
将溶液A、溶液B分别放到超声机下处理5min，分别使溶液A充分混合均匀、溶液B充分混合均匀；
(3)将3kg高镍三元正极材料LiNi0.92Co0.06Mn0.02O2先在90℃真空干燥箱中干燥0.5h，然后在800rpm的混料机里面先预混2min，然后将上述配置好的溶液A和溶液B分别装入不同的喷雾设备容器罐，将喷雾设备与混料机连接好，在预混结束后将已经装进喷雾设备容器罐里的溶液A和溶液B分别从不同的喷头处同时喷洒到混料机里的高镍三元正极材料上 去，控制喷速12mL/min使喷雾时间在5min左右，一边喷同时一边充分搅拌，喷完之后继续搅拌2min使溶液A和溶液B与高镍三元正极材料混合均匀充分接触，结束后最后放到真空干燥箱110℃下进行干燥2h，即可得到外涂层包覆的高镍三元正极材料，其具有疏水功能。
请参阅图3，本实施例实验过程中使用的混料机与喷雾设备联用，与实施例1相同。
将本实施例得到的外涂层包覆的高镍三元正极材料进行存储测试实验：在常规大气环境中进行空气暴露实验，并且每天取一部分样品送样检测水含量、残锂量、首圈容量。测试结果水含量、残锂量上升越小说明包覆后高镍三元正极材料的抗湿性能越好，首圈容量保持率越高越证明抗湿作用让高镍三元正极材料的电化学性能更加稳定。
结果如下：实施例5得到的外涂层包覆的高镍三元正极材料，未放置空气之前，水含量为0.0165％，LiOH含量为0.2458％，Li2CO3含量为0.1478％，首圈充电比容量为244.4mAh/g，放电比容量为227.0mAh/g，首效为92.9％。在空气中放置7天后，水含量为0.2934％，LiOH含量为0.3945％，Li2CO3含量为0.4793％，首圈充电比容量为243.9mAh/g，放电比容量为226.4mAh/g，首效为92.8％。
实施例6
本实施例提供一种外涂层包覆的高镍三元正极材料的制备方法，包括以下步骤：
(1)量取30mL的苯基三甲氧基硅烷偶联剂溶解到30mL的无水乙醇中形成溶液，记为溶液A；
(2)量取471mL质量分数为30％的聚丙烯酸溶液用去离子水稀释到质量分数为20％的聚丙烯酸溶液，然后将氢氧化锂放入到质量分数为20％的聚丙烯酸溶液中，待氢氧化锂完全溶解，测试溶液的pH为5，得到聚丙烯酸锂溶液，记为溶液B；
将溶液A、溶液B分别放到超声机下处理5min，分别使溶液A充分混合均匀、溶液B充分混合均匀；
(3)将3kg高镍三元正极材料LiNi0.92Co0.06Mn0.02O2先在90℃真空干燥箱中干燥0.5h，然后在800rpm的混料机里面先预混2min，然后将上述配置好的溶液A和溶液B分别装入不同的喷雾设备容器罐，将喷雾设备与混料机连接好，在预混结束后将已经装进喷雾设备容器罐里的溶液A和溶液B分别从不同的喷头处同时喷洒到混料机里的高镍三元正极材料上去，控制喷速12mL/min使喷雾时间在5min左右，一边喷同时一边充分搅拌，喷完之后继续搅拌2min使溶液A和溶液B与高镍三元正极材料混合均匀充分接触，结束后最后放到真空干燥箱110℃下进行干燥2h，即可得到外涂层包覆的高镍三元正极材料，其具有疏水功能。
请参阅图3，本实施例实验过程中使用的混料机与喷雾设备联用，与实施例1相同。
将本实施例得到的外涂层包覆的高镍三元正极材料进行存储测试实验：在常规大气环境中进行空气暴露实验，并且每天取一部分样品送样检测水含量、残锂量、首圈容量。测试结果水含量、残锂量上升越小说明包覆后高镍三元正极材料的抗湿性能越好，首圈容量保持率越高越证明抗湿作用让高镍三元正极材料的电化学性能更加稳定。
结果如下：实施例6得到的外涂层包覆的具有疏水功能的高镍三元正极材料，未放置空气之前，水含量为0.0187％，LiOH含量为0.2379％，Li2CO3含量为0.1102％，首圈充电比容量为245.3mAh/g，放电比容量为228.4mAh/g，首效为93.1％。在空气中放置7天后，水含量为0.3086％，LiOH含量为0.4125％，Li2CO3含量为0.4533％，首圈充电比容量为243.9mAh/g，放电比容量为227.1mAh/g，首效为93.1％。
对比例1
本实施例提供一种无外涂层包覆的高镍三元正极材料的制备方法，包括以下步骤：
(1)将3kg高镍三元正极材料LiNi0.92Co0.06Mn0.02O2先在90℃真空干燥箱中干燥0.5h，然后在800rpm的混料机里面先预混2min，然后将30mL的溶剂无水乙醇装入喷雾设备容器罐，将喷雾设备与混料设备连接好，在预混结束后将已经装进喷雾设备容器罐里的溶剂无水乙醇从喷头处喷洒到混料机里的高镍三元正极材料上去，控制喷速6mL/min使喷雾时间在5min左右，一边喷同时一边充分搅拌，喷完之后继续搅拌2min使溶剂无水乙醇与高镍三元正极材料混合均匀充分接触，结束后最后放到真空干燥箱110℃下进行干燥2h，即可得到无外涂层包覆的高镍三元正极材料，其不具有疏水功能。
请参阅图3，本对比例实验过程中使用的混料机与喷雾设备联用，与实施例1相同。
将对比例1中无外涂层包覆的高镍三元正极材料进行存储性能测试实验：在常规大气环境中进行空气暴露实验，并且每天取一部分样品送样检测水含量、残锂量、首圈容量。
结果如下：对比例1得到无外涂层包覆高镍三元正极材料，未放置空气之前，水含量为0.037％，LiOH含量为0.5181％，Li2CO3含量为0.2306％，首圈充电比容量为244.9mAh/g，放电比容量为228.6mAh/g，首效为93.3％。在空气中放置7天后，水含量为0.6876％，LiOH含量为0.3619％，Li2CO3含量为0.9304％，首圈充电比容量为239.8mAh/g，放电比容量为219.3mAh/g，首效为91.5％。测试结果与实施例1～6进行比较。
试验：
电池组装与测试：在氩气气氛手套箱内(H2O＜0.1ppm，O2＜0.1ppm)进行锂离子扣式电池组装。将实施例1～6和对比例1制备的高镍三元正极材料、导电剂、粘结剂按照质量比为90：5：5混合均匀，加入氮-甲基吡咯烷酮溶剂搅拌形成浆料后进行涂布，110℃下烘2 小时后进行冲片，在105℃真空烘箱下再次干燥4小时，组装扣式电池，电解液采用LiPF6溶于碳酸乙烯酯和碳酸二乙酯混合溶剂，隔膜为玻璃纤维，负极采用锂金属片，组装好后静置3小时进行电池首圈测试，测试条件为25℃测试0.1C下的充放电容量及首效，1C＝210mAh/g。循环性能测试采用全电扣式电池，将锂金属负极更换为碳材料，在0.1C条件下测试电池循环稳定性。
实施例1～6提供的外涂层包覆的高镍三元正极材料制备方法，可以合成具有外涂层包覆的高镍三元正极材料，显著降低高镍三元正极材料残锂含量、表面水含量、残碱量，并且所述外涂层包覆的高镍三元正极材料暴露空气后仍有很高的首圈容量保持率，大大提高了所述外涂层包覆的高镍三元正极材料的空气存储性能以及电化学性能，下面结合对比例1，对本公开的效果进行具体说明。
请参阅表1，其为实施例1～6与对比例1中得到的高镍三元正极材料的LiOH含量和Li2CO3含量，残余Li+含量的数据表，从中可以看出实施例1～6的外涂层包覆的高镍三元正极材料较对比例1，其材料表面的残碱明显降低。
请参阅表2，其为实施例1～6与对比例1中得到的高镍三元正极材料在4.3V/0.1C条件下首圈充放电容量数据表，从中可以看出实施例1～6较对比例1得到的高镍三元正极材料的放电比容量略有下降，这归因于引入少量的硅烷偶联剂和聚丙烯酸锂。
请参阅图1，实施例1～3与对比例1中得到的高镍三元正极材料的循环性能比较，其中，实施例1、实施例2、实施例3在循环170圈后的容量保持率分别是83.7％、80.7％、80.5％，而对比例1循环170圈后容量保持率为76.6％，是低于实施例1～3的循环性能。
表1
表2
请参阅表3，其为实施例2与对比例1中得到的高镍三元正极材料在空气暴露实验中每天H2O含量、LiOH含量，和Li2CO3含量的数据表，从中可以看出随着放置天数的增加，实施例2的H2O含量上升趋势明显要低于对比例1，并且实施例2中可以显著抑制LiOH向Li2CO3转变。
表3
请参阅图2，实施例3与对比例1中得到的高镍三元正极材料在空气暴露实验中每天首圈放电比容量变化，可以看到实施例3在空气暴露8天后的放电比容量仍有225.9mAhg-1，容量保持率为98.43％，而对比例1在空气暴露8天后的放电比容量为213.2mAhg-1，容量保持率仅为93.14％，明显低于实施例3。
相对于相关技术，本公开通过简单的装置将低廉的硅烷偶联剂和聚丙烯酸锂与高镍三元正极材料表面结合，显著降低高镍三元正极材料表面残碱并且抑制LiOH大幅度向Li2CO3转变，合理利用残碱转化成高效的涂层包覆在高镍三元正极材料表面，其中，外涂层包括疏水涂层有机硅酸锂和聚丙烯酸锂，有效改善了材料的加工性能和安全性能问题。
以上所述实施例仅表达了本公开的几种实施方式，其描述较为具体和详细，但并不能因此而理解为对发明专利范围的限制。应当指出的是，对于本领域的普通技术人员来说，在不脱离本公开构思的前提下，还可以做出若干变形和改进，则本公开也意图包含这些改动和变形。

Claims (18)

  1. 一种外涂层包覆的高镍三元正极材料的制备方法，其特征在于：包括以下步骤：
    制备硅烷偶联剂溶液；
    制备聚丙烯酸锂溶液；
    将高镍三元正极材料进行干燥，然后放进混料机中进行预混；预混结束后，分别将所述硅烷偶联剂溶液和所述聚丙烯酸锂溶液在不同的喷口处同时喷洒到所述混料机中的所述高镍三元正极材料，边喷洒边搅拌，结束后进行干燥热处理，得到外涂层包覆的高镍三元正极材料。
  2. 根据权利要求1所述的外涂层包覆的高镍三元正极材料的制备方法，其特征在于：所述硅烷偶联剂的制备方法为：将硅烷偶联剂溶解到第一溶剂中，得到所述硅烷偶联剂溶液。
  3. 根据权利要求2所述的外涂层包覆的高镍三元正极材料的制备方法，其特征在于：所述硅烷偶联剂的化学表达式为YSiX3，其中，Y为疏水官能团，为烃基、酯基、苯基、氟苯基中的一种；X为可水解基团，为甲氧基、卤素、乙氧基、乙酰氧基中的一种。
  4. 根据权利要求3所述的外涂层包覆的高镍三元正极材料的制备方法，其特征在于：Y为甲基、丙基、苯基、丁基、辛基、乙烯基的一种。
  5. 根据权利要求2所述的外涂层包覆的高镍三元正极材料的制备方法，其特征在于：所述硅烷偶联剂的用量为所述高镍三元正极材料质量的0.5％～5％。
  6. 根据权利要求2所述的外涂层包覆的高镍三元正极材料的制备方法，其特征在于：所述第一溶剂为易挥发的有机溶剂，为无水乙醇、无水甲醇、丙酮中的一种或几种。
  7. 根据权利要求1所述的外涂层包覆的高镍三元正极材料的制备方法，其特征在于：所述聚丙烯酸锂溶液的制备方法为：将聚丙烯酸与氢氧化锂溶解到第二溶剂中，得到聚丙烯酸锂溶液，所述聚丙烯酸锂溶液的pH为5～9。
  8. 根据权利要求7所述的外涂层包覆的高镍三元正极材料的制备方法，其特征在于：所述聚丙烯酸的用量为所述高镍三元正极材料质量的0.5％～3％，所述聚丙烯酸的分子量为25～50万。
  9. 根据权利要求7所述的外涂层包覆的高镍三元正极材料的制备方法，其特征在于：所述第二溶剂为水、无水乙醇、异丙醇中的一种或几种。
  10. 根据权利要求1所述的外涂层包覆的高镍三元正极材料的制备方法，其特征在于：所述硅烷偶联剂溶液的体积浓度为10～100％；所述聚丙烯酸锂溶液的体积浓度为10～100％。
  11. 根据权利要求1所述的外涂层包覆的高镍三元正极材料的制备方法，其特征在于： 所述高镍三元正极材料的化学表达式为LiNixCoyMzO2，其中，M为元素Mn或元素Al；x的取值为0.7～1.0，y的取值为0～0.3，z的取值为0～0.3，且x+y+z＝1。
  12. 根据权利要求1所述的外涂层包覆的高镍三元正极材料的制备方法，其特征在于：所述高镍三元正极材料进行干燥的干燥条件为，在真空烘箱下进行干燥，温度为90℃～180℃，保温0.5～3小时。
  13. 根据权利要求1所述的外涂层包覆的高镍三元正极材料的制备方法，其特征在于：先将所述硅烷偶联剂溶液和所述聚丙烯酸锂溶液分别装入不同的喷雾设备容器罐中，然后在所述高镍三元正极材料预混结束后，将所述硅烷偶联剂溶液和所述聚丙烯酸锂溶液在不同的喷口处同时喷洒到所述混料机中的所述高镍三元正极材料。
  14. 根据权利要求1所述的外涂层包覆的高镍三元正极材料的制备方法，其特征在于：所述混料机的转速为300～1200转/分钟，预混时间为1～10分钟。
  15. 根据权利要求13所述的外涂层包覆的高镍三元正极材料的制备方法，其特征在于：所述硅烷偶联剂溶液和所述聚丙烯酸锂溶液在所述喷雾设备上的喷洒条件均为，喷速为5～50毫升/分钟，喷洒时间为2～15分钟。
  16. 根据权利要求1所述的外涂层包覆的高镍三元正极材料的制备方法，其特征在于：搅拌时间为1～10分钟。
  17. 根据权利要求1所述的外涂层包覆的高镍三元正极材料的制备方法，其特征在于：所述干燥热处理的条件为烘箱干燥，温度为90～150℃，时间为2～24小时。
  18. 一种外涂层包覆的高镍三元正极材料，其特征在于：通过1～17任一所述的外涂层包覆的高镍三元正极材料的制备方法得到。
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