WO2020135766A1 - 正极活性材料、正极极片、电化学储能装置及装置 - Google Patents

正极活性材料、正极极片、电化学储能装置及装置 Download PDF

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WO2020135766A1
WO2020135766A1 PCT/CN2019/129365 CN2019129365W WO2020135766A1 WO 2020135766 A1 WO2020135766 A1 WO 2020135766A1 CN 2019129365 W CN2019129365 W CN 2019129365W WO 2020135766 A1 WO2020135766 A1 WO 2020135766A1
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positive electrode
active material
electrode active
energy storage
electrochemical energy
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French (fr)
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杜锐
柳娜
刘勇超
王嗣慧
赵德宇
冷雪
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宁德时代新能源科技股份有限公司
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Priority to EP19904411.6A priority Critical patent/EP3796433A4/en
Publication of WO2020135766A1 publication Critical patent/WO2020135766A1/zh
Priority to US17/132,567 priority patent/US11949093B2/en

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    • H—ELECTRICITY
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
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    • 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
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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    • C01G53/00—Compounds of nickel
    • C01G53/40—Nickelates
    • C01G53/42—Nickelates containing alkali metals, e.g. LiNiO2
    • C01G53/44—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese
    • C01G53/50—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese of the type [MnO2]n-, e.g. Li(NixMn1-x)O2, Li(MyNixMn1-x-y)O2
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    • 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
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    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
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    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • 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 application relates to the field of electrochemical technology, in particular to a positive electrode active material, a positive pole piece, an electrochemical energy storage device and device.
  • Lithium ion batteries have been widely used in various fields due to their advantages such as high specific energy, wide application temperature range, low self-discharge rate, long cycle life, good safety performance, and no pollution. At the same time, lithium ion batteries are used as energy systems New energy vehicles have gradually been tried to replace traditional diesel locomotives around the world.
  • cathode active materials such as: lithium iron phosphate (LiFePO 4 ), low nickel ternary materials (LiNi 1/3 Co 1/3 Mn 1/3 O 2 ), etc.
  • lithium iron phosphate LiFePO 4
  • low nickel ternary materials LiNi 1/3 Co 1/3 Mn 1/3 O 2
  • high-nickel ternary materials are currently one of the main research objects of positive active materials for lithium-ion batteries.
  • the side reaction between the ternary material and the electrolyte is also significantly intensified, which will lead to serious gas production in lithium-ion batteries. This is one of the biggest bottlenecks in the commercialization of high-nickel ternary materials.
  • the means to improve the gas production problem of lithium-ion batteries mainly include reducing the content of nickel in ternary materials or water washing to reduce the residual lithium content on the surface of the positive electrode active material.
  • the above methods will lead to the performance of lithium-ion batteries. Different degrees of damage, for example, the reversible gram capacity of lithium-ion batteries is reduced, and the cycle performance is deteriorated.
  • the purpose of the present application is to provide a positive electrode active material, a positive electrode sheet, an electrochemical energy storage device and a device.
  • the present application can effectively reduce the side reaction of the positive electrode active material and the electrolyte and reduce the electrochemical
  • the energy storage device produces gas, and can improve the storage performance of the electrochemical energy storage device without deteriorating the energy density, cycle performance, and rate performance of the electrochemical energy storage device.
  • the present application provides a positive electrode active material
  • the positive electrode active material is Li x Ni y Co z M k Me p O r A m or the surface is provided with a coating layer Li x Ni y Co z M k Me p O r A m , where 0.85 ⁇ x ⁇ 1.15, 0 ⁇ y ⁇ 1, 0 ⁇ z ⁇ 1, 0 ⁇ k ⁇ 1, 0 ⁇ p ⁇ 0.1, 1 ⁇ r ⁇ 2, 0 ⁇ m ⁇ 1, m+r ⁇ 2, M is selected from one or two of Mn and Al, Me is selected from Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, One or more of Sb, Y, W, and Nb, and A is one or more of N, F, S, and Cl.
  • the positive electrode active material secondary particles, and the particle diameter of the positive electrode active material satisfies D n 10: 0.5 ⁇ m ⁇ D n 10 ⁇ 3 ⁇ m.
  • the present application provides a positive electrode sheet including the positive electrode active material described in one aspect of the present application.
  • the present application provides an electrochemical energy storage device including the positive electrode active material described in another aspect of the present application.
  • the present application provides a device that is a vehicle and includes the electrochemical energy storage device described in yet another aspect of the present application.
  • This application effectively reduces the side reaction between the positive electrode active material and the electrolyte by reasonably controlling the particle morphology of the positive electrode active material and the amount of fine powder in the positive electrode active material, reduces the gas production of the electrochemical energy storage device, and can improve the electrochemical
  • the storage performance of the energy storage device does not deteriorate the energy density, cycle performance and rate performance of the electrochemical energy storage device.
  • the device of the present application includes the electrochemical energy storage device, and therefore has at least the same advantages as the electrochemical energy storage device.
  • Example 3 is a differential distribution curve of volume and particle size of the positive electrode active material of Example 3 of the present application;
  • Example 4 is a differential distribution curve of the number and particle size of the positive electrode active material of Example 3 of the present application.
  • FIG. 5 is a perspective view of an embodiment of an electrochemical energy storage device.
  • FIG. 6 is a perspective view of an embodiment of a battery module.
  • FIG. 7 is a perspective view of an embodiment of a battery pack.
  • Fig. 8 is an exploded view of Fig. 7.
  • FIG. 9 is a schematic diagram of an embodiment of a device in which an electrochemical energy storage device is used as a power source.
  • cathode active material according to the present application and its preparation method, cathode pole piece, electrochemical energy storage device and device are described in detail below.
  • lithium salt used may have problems of impureness and low melting point, it will melt, decompose and volatile loss at lower temperatures, so in the preparation of ternary materials An excessive amount of lithium salt is added during the process to make up for the lithium loss caused by the sintering process.
  • lithium ions will migrate from the body to the surface and form Li 2 CO 3 on the surface of the ternary material.
  • the process is accompanied by deoxidation of the surface of the ternary material to form a surface oxide layer with a distorted structure.
  • the excess lithium salt in the synthesis of ternary materials makes the product of excess lithium salt calcined at high temperature mainly Li oxide, which reacts with CO 2 and H 2 O in the air to form LiOH and Li 2 CO 3 again , Remaining on the surface of the ternary material, making the ternary material's pH higher.
  • Li 2 CO 3 remaining on the surface of the ternary material will decompose to produce CO 2 , because the CO 2 gas will cause a pressure difference with the temperature difference (especially when the reaction process is accompanied by thermal reaction When it occurs), thus exacerbating the flattening of the electrochemical energy storage device and deteriorating the storage performance of the electrochemical energy storage device.
  • Providing a coating layer on the surface of Li x Ni y Co z M k Me p O r A m can reduce the content of residual lithium (such as LiOH, Li 2 CO 3, etc.) on the surface of the positive electrode active material to a certain extent, and improve the electrochemical storage.
  • the purpose of the storage performance can be set.
  • providing a coating layer on the surface of Li x Ni y Co z M k Me p O r A m can also reduce the probability of side reactions between Li x Ni y Co z M k Me p O r A m and the electrolyte due to direct contact
  • the amount of oxygen released by the positive electrode active material in order to balance the charge during the charge and discharge process and the risk of crystal structure collapse can be reduced.
  • the content of Li 2 CO 3 on the surface of the positive electrode active material obtained by providing a coating layer on the surface of Li x Ni y Co z M k Me p O r A m is lower than that of LiOH.
  • the content of Li 2 CO 3 is less than 3000 ppm, and the content of LiOH is less than 5000 ppm.
  • a first aspect of the present disclosure of the positive active material of the secondary particle morphology, and particle size of the positive electrode active material satisfies D n 10: 0.5 ⁇ m ⁇ D n 10 ⁇ 3 ⁇ m.
  • the particle diameter of the positive electrode active material satisfies D n 10: 1 ⁇ m ⁇ D n 10 ⁇ 2 ⁇ m.
  • the energy density, storage performance, cycle performance and rate performance of the electrochemical energy storage device are closely related to the physical and chemical properties of the cathode active material.
  • the ternary material is a positive electrode active material mainly including transition metal elements Ni and Co adjacent to the same period, and achieving charge balance through the change of the valence state of Ni and Co.
  • Ni is one of the main active metal components, mainly exists in the form of +2 valence, Ni 2+ will be oxidized to Ni 3+ and Ni 4+ in the process of lithium deintercalation, and Co is also one of the active metal components , Mainly exists in the form of +3 valence, and Co 3+ will be oxidized to Co 4+ in the process of deintercalating lithium.
  • the ternary material mainly achieves charge balance through the change of the valence state of Ni and Co, and with the change of the ratio of Ni and Co, the energy density, storage performance, cycle of the electrochemical energy storage device Performance and rate performance will change to varying degrees.
  • the Ni content in the ternary material increases, the content of Ni 4+ with strong oxidizability will also increase.
  • the electrolyte contacts the ternary material, the electrolyte will have more side reactions with the ternary material, and In order to maintain the charge balance, the ternary material will release oxygen, which will not only destroy the crystal structure of the ternary material, but also exacerbate the gas expansion of the electrochemical energy storage device and deteriorate the storage performance of the electrochemical energy storage device.
  • the specific surface area of the small-diameter cathode active material is larger, the contact area with the electrolyte is increased, and more side reactions occur when contacted with the electrolyte, and
  • the positive electrode active material of small particle size will release more oxygen, which will not only destroy the crystal structure of the positive electrode active material of small particle size, but also aggravate the gas expansion of the electrochemical energy storage device and deteriorate the electrochemical energy storage device Storage performance.
  • the small particle size positive electrode active material has a weaker pressure resistance, and it is easier to break and produce more primary particles during the cold pressing of the pole piece, and some of these primary particles will be collected from the positive electrode because they do not contact the binder If it falls off, a part of the performance of the positive electrode sheet will locally deteriorate due to no contact with the conductive agent.
  • the volume percentage of small particle size powders, especially fine powder in the positive electrode active material is insignificant, so the conventional volume particle size is used to characterize the positive electrode active material
  • the content of micropowder cannot accurately reflect the relative content of small-sized particles in powder materials, and it is more accurate and intuitive to use quantitative particle size to characterize the content of micropowder in positive electrode active materials, which is beneficial to the reasonable control of gas expansion in electrochemical energy storage devices.
  • the cathode active material in the first aspect of the present application has a particle size D n 10 satisfying 0.5 ⁇ m ⁇ D n 10 secondary particle morphology ⁇ 3 ⁇ m ternary material Li x Ni y Co z m k Me p O r a m or a surface provided with a coating layer of ternary material Li x Ni y Co z m k Me p O r a m , by reasonably controlling the particle morphology of the positive electrode active material and the amount of fine powder in the positive electrode active material, the side reaction of the positive electrode active material and the electrolyte is effectively reduced, the gas production of the electrochemical energy storage device is reduced, and the electrochemical can be improved The storage performance of the energy storage device does not deteriorate the energy density, cycle performance and rate performance of the electrochemical energy storage device.
  • Li x Ni y Co z M k Me p O r A m 0.50 ⁇ y ⁇ 0.90, 0.05 ⁇ z ⁇ 0.2, 0.05 ⁇ k ⁇ 0.4, 0 ⁇ p ⁇ 0.05.
  • Li x Ni y Co z M k Me p O r A m 0.70 ⁇ y ⁇ 0.90, 0.05 ⁇ z ⁇ 0.2, 0.05 ⁇ k ⁇ 0.2, 0 ⁇ p ⁇ 0.05.
  • the relative amount of fine particles with small particle size has a more significant effect on the residual lithium content and gas production of the positive electrode active material.
  • the ternary material Li x Ni y Co z M k Me p O r A m that controls the morphology of high nickel secondary particles or the surface of the Li x Ni y Co z M k Me p O r A m D n 10 is in the range of 0.5 ⁇ m to 3 ⁇ m, which is an effective method to solve the gas production problem.
  • Li x Ni y Co z M k Me p O r A m may be LiNi 1/3 Co 1/3 Mn 1/3 O 2 , LiNi 0.5 Co 0.2 Mn 0.3 O 2 , LiNi 0.5 Co 0.25 Mn 0.25 O 2 , LiNi 0.55 Co 0.15 Mn 0.3 O 2 , LiNi 0.55 Co 0.1 Mn 0.35 O 2 , LiNi 0.55 Co 0.05 Mn 0.4 O 2 , LiNi 0.6 Co 0.2 Mn 0.2 O 2 , LiNi 0.75 Co 0.1 Mn 0.15 O 2 , LiNi 0.8 Co 0.1 Mn 0.1 O 2 , LiNi 0.85 Co 0.05 Mn 0.1 O 2 , LiNi 0.88 Co 0.05 Mn 0.07 O 2 , LiNi 0.9 Co 0.05 Mn 0.05 O 2 , also can be doped element Me and/or doped element A for the above substances Partially replace the modified substance.
  • the coating element in the coating layer is selected from one or more combinations of Al, Ba, Zn, Ti, Co, W, Y, Si, Sn, B, P. More preferably, the coating element in the coating layer is selected from a combination of two or more of Al, Ba, Zn, Ti, Co, W, Y, Si, Sn, B, and P.
  • the coating layer includes the oxide of the coating element. More preferably, the coating layer includes oxides formed by two or more of the foregoing coating elements.
  • the coating layer contains at least two oxides formed by the above coating elements, the stability of the coating layer's adhesion on the surface of Li x Ni y Co z M k Me p O r A m can be improved to make the coating layer It has certain ion conductivity and conductivity, which can reduce the influence of the coating layer on the polarization of the positive electrode active material.
  • the particle size D n 10 of the positive electrode active material in ⁇ m as the unit of measurement and the particle size D v 10 of the positive electrode active material in ⁇ m as the unit of measurement satisfy: 1 ⁇ D n 10 ⁇ D v 10 ⁇ 20. More preferably, the particle size D n 10 of the positive electrode active material in ⁇ m as the measurement unit and the particle size D v 10 of the positive electrode active material in ⁇ m as the measurement unit satisfy: 2 ⁇ D n 10 ⁇ D v 10 ⁇ 18 .
  • D v 10 is the particle size corresponding to the cumulative volume distribution percentage of the positive electrode active material reaching 10%
  • D n 10 is the particle size corresponding to the cumulative distribution percentage of the positive electrode active material reaching 10%.
  • the particle size D v 10 of the positive electrode active material is 2 ⁇ m to 8 ⁇ m. More preferably, the particle diameter D v 10 of the positive electrode active material is 3 ⁇ m to 6 ⁇ m.
  • the theoretical specific surface area BET 1 of the cathode active material and the true specific surface area BET 2 of the cathode active material satisfy: 0.8 ⁇ (BET 2 -BET 1 )/ BET 1 ⁇ 5.5.
  • the theoretical specific surface area of the positive electrode active material BET 1 6/( ⁇ D v 50).
  • ⁇ is the true density of the positive electrode active material, and the unit of measurement is g/cm 3 ;
  • D v 50 is the corresponding particle diameter when the cumulative volume distribution percentage of the positive electrode active material reaches 50%, and the unit of measurement is ⁇ m.
  • the true specific surface area BET 2 of the positive electrode active material can be determined by the N 2 adsorption method, for details, refer to GB/T19587-2004.
  • (BET 2 -BET 1 )/BET 1 represents the degree of deviation of the theoretical specific surface area of the positive electrode active material from the true specific surface area, which can measure the degree of unevenness of the surface of the positive electrode active material.
  • the positive electrode active material the true specific surface area BET 2 to 0.1m 2 /g ⁇ 0.8m 2 / g.
  • the positive specific surface area of the positive electrode active material is within the above range, and the contact area of the electrolyte and the positive electrode active material is small, which is beneficial to inhibit side reactions, avoid corrosion of the electrolyte, and damage the crystal structure of the positive electrode active material, resulting in increased gas inflation of the electrochemical energy storage device The problem.
  • the true specific surface area of the positive electrode active material in the above range is also conducive to the use of less auxiliary materials to meet the relatively strong adsorption performance of the positive electrode active material, the binder, and the conductive agent when mixing to form the positive electrode slurry. It is beneficial to increase the energy density of the electrochemical energy storage device.
  • the particle size D v 50 of the positive electrode active material is 5 ⁇ m to 18 ⁇ m. More preferably, the particle diameter D v 50 of the positive electrode active material is 8 ⁇ m to 15 ⁇ m.
  • the particle size D v 90 of the positive electrode active material is 10 ⁇ m to 30 ⁇ m. More preferably, the particle size D v 90 of the positive electrode active material is 12 ⁇ m to 25 ⁇ m.
  • the particle size differential distribution curve of the cathode active material has one and only one peak.
  • the particle size differential distribution curve includes both the volume particle size differential distribution curve and the quantity particle size differential distribution curve.
  • a method for preparing a positive electrode active material according to the second aspect of the present application is described, which is used to prepare the positive electrode active material according to the first aspect of the present application, which includes the steps of: converting a ternary material precursor (containing Ni, Co, and M) Compounds), compounds containing Li, compounds containing doping element Me, and compounds containing doping element A are placed in the mixing equipment for mixing, and then placed in an atmosphere furnace for sintering, and after sintering, the classification screening is obtained to obtain Positive active material.
  • converting a ternary material precursor containing Ni, Co, and M
  • compounds containing Li compounds containing doping element Me
  • compounds containing doping element A are placed in the mixing equipment for mixing, and then placed in an atmosphere furnace for sintering, and after sintering, the classification screening is obtained to obtain Positive active material.
  • the classification screening may be selected from air classification screening or screen screening.
  • the specific process of the air flow classification screening is as follows: the material after the sintering is put into the air flow classifier, and then it is sprayed together with the air flow of a certain pressure from the nozzle, and the size of the particles with different particle sizes is inconsistent Separation of particles. Among them, the particles with small weight are lighter and the flying distance is relatively short, while the particles with heavy weight are heavier and the flying distance is relatively long; adjust the distance between the collector and the nozzle to select the appropriate one Particle size to obtain a positive electrode active material.
  • the specific process of sieving through the sieve is as follows: after the sintering, the material is put into a 200-1000 mesh sieve for sieving. Due to the different particle size of the particles, the particles with small particle size will be screened out by the sieve. On the screen, the required particle size can be retained to obtain the positive electrode active material.
  • the mesh number of the screen is 500 mesh to 800 mesh.
  • the ternary material precursor may include but not limited to Ni 1/3 Co 1/3 Mn 1/3 (OH) 2 , Ni 0.5 Co 0.2 Mn 0.3 (OH) 2 , Ni 0.5 Co 0.25 Mn 0.25 (OH) 2 , Ni 0.55 Co 0.15 Mn 0.3 (OH) 2 , Ni 0.55 Co 0.1 Mn 0.35 (OH) 2 , Ni 0.55 Co 0.05 Mn 0.4 (OH) 2 , Ni 0.6 Co 0.2 Mn 0.2 (OH) 2 , Ni 0.75 Co 0.1 Mn 0.15 (OH) 2 , Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 , Ni 0.88 Co 0.05 Mn 0.07 (OH) 2 , 0.9Ni 0.8 Co 0.2 (OH) 2 ⁇ 0.1Al 2 (OH) 3 , 0.9Ni 0.9 Co 0.05 Mn 0.05 (OH) 2 ⁇ 0.1Al 2 (OH) 3 .
  • the Li-containing compound may be one or a combination of one or more of LiOH ⁇ H 2 O, LiOH, Li 2 CO 3 , and Li 2 O, including but not limited to.
  • the compound containing the doping element Me may be an oxide, nitrate, carbon containing at least one element of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, Nb A combination of one or more of the acid salts.
  • the compound containing the doping element A may include, but is not limited to, one or a combination of LiF, NaCl, Na 2 S, and Li 3 N.
  • the sintering conditions may be 700°C to 800°C, and the oxygen concentration ⁇ 20%.
  • another method for preparing the cathode active material according to the third aspect of the present application is used to prepare the cathode active material according to the first aspect of the present application, which includes the step: S1, a ternary material precursor (containing Ni, Co and M compounds), compounds containing Li, compounds containing doping element Me, and compounds containing doping element A are placed in the mixing equipment for mixing, and then placed in an atmosphere furnace for sintering; S2, once The material after the sintering and the compound containing the coating element are placed in the mixing equipment for mixing, and then placed in the atmosphere furnace for the second sintering; S3, the materials after the second sintering are graded and screened to obtain the positive electrode Active materials.
  • a ternary material precursor containing Ni, Co and M compounds
  • compounds containing Li compounds containing doping element Me
  • compounds containing doping element A are placed in the mixing equipment for mixing, and then placed in an atmosphere furnace for sintering
  • S2 once The material after the sintering and the compound containing
  • the classification screening may be selected from air classification screening or screen screening.
  • the specific process of the air flow classification screening is as follows: the material after the second sintering is put into the air flow classifier, and then sprayed together with the air flow of a certain pressure from the nozzle, using the principle of inconsistent weight of particles of different particle sizes Separation of large and small particles. Among them, the particles with smaller weight are lighter and the flying distance is closer, while the particles with heavier weight are heavier and the flying distance is farther; adjust the distance between the collector and the nozzle to filter out Appropriate particle size to obtain positive electrode active material.
  • the specific process of sieving through the sieve is as follows: the material after the second sintering is put into a 200-1000 mesh sieve for sieving. Due to the different particle size of the particles, the particles with small particle size will be screened Out, and the required particle size can be retained on the screen to obtain the positive electrode active material.
  • the mesh number of the screen is 500 mesh to 800 mesh.
  • the ternary material precursor may include but not limited to Ni 1/3 Co 1/3 Mn 1/3 (OH) 2 , Ni 0.5 Co 0.2 Mn 0.3 (OH) 2 , Ni 0.5 Co 0.25 Mn 0.25 (OH) 2 , Ni 0.55 Co 0.15 Mn 0.3 (OH) 2 , Ni 0.55 Co 0.1 Mn 0.35 (OH) 2 , Ni 0.55 Co 0.05 Mn 0.4 (OH) 2 , Ni 0.6 Co 0.2 Mn 0.2 (OH) 2 , Ni 0.75 Co 0.1 Mn 0.15 (OH) 2 , Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 , Ni 0.88 Co 0.05 Mn 0.07 (OH) 2 , 0.9Ni 0.8 Co 0.2 (OH) 2 ⁇ 0.1Al 2 (OH) 3 , 0.9Ni 0.9 Co 0.05 Mn 0.05 (OH) 2 ⁇ 0.1Al 2 (OH) 3 .
  • the Li-containing compound may be one or a combination of one or more of LiOH ⁇ H 2 O, LiOH, Li 2 CO 3 , and Li 2 O, including but not limited to.
  • the doping element-containing Me compound may be an oxide, nitrate, carbonic acid containing at least one element of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, Nb A combination of one or more of the salts.
  • the compound containing the doping element A may include, but is not limited to, one or a combination of LiF, NaCl, Na 2 S, and Li 3 N.
  • the compound containing the coating element may be an oxide, nitrate, or phosphate containing one or more elements of Al, Ba, Zn, Ti, Co, W, Y, Si, Sn, B, P. A combination of one or more of carbonates.
  • the amount of the compound containing the coating element may be 0.01% to 0.5% of the total mass of the positive electrode active material.
  • the conditions of the primary sintering may be 700°C to 800°C, and the oxygen concentration ⁇ 20%.
  • the condition of the second sintering may be 200°C to 700°C.
  • a positive electrode sheet according to the fourth aspect of the present application which includes a positive electrode current collector and a positive electrode membrane provided on at least one surface of the positive electrode current collector and including the positive electrode active material according to the first aspect of the present application.
  • the positive electrode diaphragm may be provided on one surface of the positive electrode current collector or on both surfaces of the positive electrode current collector.
  • the positive electrode membrane may further include a conductive agent and a binder, wherein the types and contents of the conductive agent and the binder are not specifically limited, and may be based on actual conditions Need to choose.
  • the binder generally includes a fluorine-containing polyolefin-based binder. Compared with the fluorine-containing polyolefin-based binder, water is usually a good solvent, that is, the fluorine-containing polyolefin-based binder is usually in It has good solubility in water.
  • the fluorine-containing polyolefin binder may include but not limited to polyvinylidene fluoride (PVDF), vinylidene fluoride copolymer or their modification (for example, carboxylic acid, acrylic acid) , Acrylonitrile and other modified) derivatives.
  • PVDF polyvinylidene fluoride
  • the conductive agent may be various conductive agents suitable for electrochemical energy storage devices in the art, for example, it may be one of but not limited to acetylene black, conductive carbon black, carbon fiber, carbon nanotube, Ketjen black or Various combinations.
  • the type of the positive electrode current collector is also not specifically limited, and can be selected according to actual needs.
  • the positive electrode current collector may generally be a layered body, the positive electrode current collector is usually a structure or part capable of collecting current, and the positive electrode current collector may be various materials suitable for use as a positive electrode current collector of an electrochemical energy storage device in the art
  • the positive electrode current collector may include but not limited to metal foil, and more specifically may include but not limited to nickel foil and aluminum foil.
  • an electrochemical energy storage device which includes the positive electrode active material described in the first aspect of the present application.
  • the electrochemical energy storage device may be a supercapacitor, a lithium ion battery, a lithium metal battery, or a sodium ion battery.
  • the electrochemical energy storage device is a lithium ion battery are shown, but the present application is not limited thereto.
  • the electrochemical energy storage device may include a positive pole piece, a negative pole piece, a separator and an electrolyte spaced between the positive pole piece and the negative pole piece.
  • the positive pole piece is the positive pole piece described in the fourth aspect of the present application, and the positive pole piece comprises the positive electrode active material of the first aspect of the present application.
  • the positive electrode tab, the separator, and the negative electrode tab can each be a layered body, which can be cut to a target size After being stacked sequentially, it can also be wound to the target size for forming the electrode assembly, and can be further combined with the electrolyte to form an electrochemical energy storage device.
  • the negative electrode tab usually includes a negative electrode current collector and a negative electrode active material layer on the surface of the negative electrode current collector, and the negative electrode active material layer usually includes a negative electrode active material.
  • the negative electrode active material may be various materials suitable for the negative electrode active material of the electrochemical energy storage device in the art, for example, may include but not limited to graphite, soft carbon, hard carbon, carbon fiber, mesophase carbon microspheres, silicon A combination of one or more of a base material, a tin-based material, lithium titanate, or other metals capable of alloying with lithium.
  • the graphite may be selected from one or more of artificial graphite, natural graphite and modified graphite;
  • the silicon-based material may be selected from elemental silicon, silicon oxide compound, silicon carbon composite, silicon alloy One or more combinations of the above;
  • the tin-based material may be selected from one or more combinations of elemental tin, tin oxide compounds, and tin alloys.
  • the negative electrode current collector is generally a structure or part that collects current.
  • the negative electrode current collector may be various materials suitable for use as a negative electrode current collector of an electrochemical energy storage device in the art.
  • the negative electrode current collector may include but It is not limited to metal foil, and more specifically may include but not limited to copper foil.
  • the negative pole piece may also be a lithium piece.
  • the separator may be various materials suitable for the separator of the electrochemical energy storage device in the art, for example, may include but not limited to polyethylene, polypropylene, polyvinylidene fluoride, aromatic One or more combinations of nylon, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester and natural fibers.
  • the electrolyte may be various electrolytes suitable for electrochemical energy storage devices in the art.
  • the electrolyte generally includes an electrolyte and a solvent, and the electrolyte may generally include a lithium salt.
  • the lithium salt may be an inorganic lithium salt and/or an organic lithium salt, and may specifically include but not limited to LiPF 6 , LiBF 4 , LiN(SO 2 F) 2 (abbreviated as LiFSI), LiN(CF 3 SO 2 ) 2 (abbreviated as LiTFSI), LiClO 4 , LiAsF 6 , LiB(C 2 O 4 ) 2 (abbreviated as LiBOB), LiBF 2 C 2 O 4 (abbreviated as LiDFOB) one or more combinations .
  • the concentration of the electrolyte may be 0.8 mol/L to 1.5 mol/L.
  • the solvent may be a solvent of various electrolytes suitable for electrochemical energy storage devices in the art.
  • the solvent of the electrolyte is usually a non-aqueous solvent, preferably an organic solvent, and may specifically include but not limited to ethylene carbonate , Propylene carbonate, butylene carbonate, pentenyl carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate or a combination of one or more of their halogenated derivatives .
  • the electrochemical energy storage device may include an outer package for encapsulating the positive pole piece, the negative pole piece, and the electrolyte.
  • the positive pole piece, the negative pole piece and the separator can be laminated or wound to form a laminated structure electrode assembly or a wound structure electrode assembly, and the electrode assembly is encapsulated in an outer package;
  • the electrolyte can be an electrolyte, which is infiltrated by the electrolyte In the electrode assembly.
  • the number of electrode assemblies in the electrochemical energy storage device can be one or several, which can be adjusted according to requirements.
  • the outer packaging of the electrochemical energy storage device may be a soft bag, such as a pouch type soft bag.
  • the material of the soft bag may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.
  • the outer packaging of the electrochemical energy storage device may also be a hard shell, such as an aluminum shell.
  • the present application has no particular limitation on the shape of the electrochemical energy storage device, which may be cylindrical, square, or any other shape. As shown in FIG. 5, a square-structured electrochemical energy storage device 5 is used as an example.
  • the electrochemical energy storage device may be assembled into a battery module, and the number of electrochemical energy storage devices contained in the battery module may be multiple, and the specific number may be adjusted according to the application and capacity of the battery module.
  • FIG. 6 is a battery module 4 as an example.
  • a plurality of electrochemical energy storage devices 5 may be arranged in sequence along the length direction of the battery module 4. Of course, it can also be arranged in any other way. Further, the plurality of electrochemical energy storage devices 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing with an accommodation space, and a plurality of electrochemical energy storage devices 5 are accommodated in the accommodation space.
  • the above battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 provided in the battery box.
  • the battery case includes an upper case 2 and a lower case 3.
  • the upper case 2 can be covered on the lower case 3 and forms an enclosed space for accommodating the battery module 4.
  • the plurality of battery modules 4 can be arranged in the battery box in any manner.
  • the electrochemical device may be used as a power source for the device or as an energy storage unit of the device.
  • the device includes, but is not limited to, electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships And satellites.
  • electric trains, ships and satellites are vehicles, which belong to vehicles in a broad sense.
  • the device can select an electrochemical energy storage device, a battery module or a battery pack according to its use requirements.
  • Fig. 9 is a device as an example.
  • the device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • a battery pack or battery module may be used.
  • the lithium ion batteries of Examples 1-8 and Comparative Examples 1-2 were prepared according to the following methods.
  • the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 , the binder polyvinylidene fluoride, and the conductive agent acetylene black are mixed according to a mass ratio of 98:1:1, and then N-methylpyrrolidone is added to act as a vacuum mixer Stir uniformly to obtain a positive electrode slurry; uniformly apply the positive electrode slurry to a positive electrode current collector aluminum foil with a thickness of 12 ⁇ m, dry it at room temperature, and then transfer it to an oven at 100° C. to 130° C. for drying, and then perform cold pressing and slitting A positive pole piece is obtained.
  • the organic solvent is a mixed liquid containing ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC), wherein the volume ratio of EC, EMC and DEC is 20:20:60.
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • the sufficiently dried lithium salt LiPF 6 is dissolved in an organic solvent and mixed uniformly to obtain an electrolyte.
  • the concentration of the lithium salt is 1 mol/L.
  • a polypropylene film with a thickness of 12 ⁇ m is selected as the separation film.
  • the positive pole piece, separator, and negative pole piece in order, so that the separator is placed between the positive and negative pole pieces to play the role of isolation, and then wound into a square electrode assembly, put in aluminum plastic film, and then After baking and removing water at 80°C, the electrolyte is injected and sealed, and after a process of standing, hot and cold pressing, formation, jig, and volume division, a lithium ion battery is obtained.
  • the lithium ion battery of Example 9 was prepared according to the following method.
  • the positive electrode active material, the binder polyvinylidene fluoride, and the conductive agent acetylene black are mixed according to a mass ratio of 98:1:1, and then N-methylpyrrolidone is added, and stirred uniformly under the action of a vacuum mixer to obtain a positive electrode slurry ; Evenly coat the positive electrode slurry on the positive electrode current collector aluminum foil with a thickness of 12 ⁇ m, dry it at room temperature and transfer it to an oven at 100° C. to 130° C. for drying, and then cold-press and cut to obtain the positive pole piece.
  • the organic solvent is a mixed liquid containing ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC), wherein the volume ratio of EC, EMC and DEC is 20:20:60.
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • the sufficiently dried lithium salt LiPF 6 is dissolved in an organic solvent and mixed uniformly to obtain an electrolyte.
  • the concentration of the lithium salt is 1 mol/L.
  • a polypropylene film with a thickness of 12 ⁇ m is selected as the separation film.
  • the positive pole piece, separator, and negative pole piece in order, so that the separator is placed between the positive and negative pole pieces to play the role of isolation, and then wound into a square electrode assembly, put in aluminum plastic film, and then After baking and removing water at 80°C, the electrolyte is injected and sealed, and after a process of standing, hot and cold pressing, formation, jig, and volume division, a lithium ion battery is obtained.
  • the lithium ion battery of Example 10 was prepared in a similar manner to the lithium ion battery of Example 9, except that 0.5 wt% of Al 2 O 3 was replaced with 0.5 wt% of B 2 O 3 .
  • the lithium-ion battery At 25°C, first charge the lithium-ion battery to 4.2V with a constant current of 1C, and then charge it to a current of 0.05C with a constant voltage of 4.2V, and then use the drainage method to measure the volume of the lithium-ion battery and record it as the lithium-ion battery. Initial volume; The lithium ion battery is then stored at 80°C for 10 days. After the storage is completed, the volume of the lithium ion battery is measured again by the drainage method, which is recorded as the volume of the lithium ion battery after storage at 80°C for 10 days.
  • volume expansion rate (%) of lithium-ion battery after storage at 80°C for 10 days [Volume of lithium-ion battery after storage for 10 days at 80°C/initial volume of lithium-ion battery-1] ⁇ 100%.
  • Lithium-ion battery was allowed to stand for 2h at a constant temperature of 25°C, then charged at 1/3V to 4.2V at 2.8V ⁇ 4.2V, then charged at 4.2V under constant voltage to current ⁇ 0.05mA, and left for 5min Then, discharge to 2.8V at 1C, record the capacity of the lithium-ion battery, and divide the tested capacity value by the mass of the positive electrode active material in the battery, which is the capacity of the positive electrode active material in the lithium-ion battery.
  • test results of Examples 1-8 can also find that by controlling the degree of deviation of the theoretical specific surface area BET 1 of the positive electrode active material from the true specific surface area BET 2 , the microstructure of the positive electrode active material can be further optimized to ensure Its flat surface and less concave-convex structures are beneficial to reduce the polarization of the positive electrode active material and improve the ion transmission performance, thereby further reducing the gas production of the lithium ion battery and optimizing the dynamic performance of the lithium ion battery.
  • the positive electrode active materials in Example 9 and Example 10 are positive electrode active materials coated on the surface of Li(Ni 0.8 Co 0.1 Mn 0.1 ) 0.997 Zr 0.003 O 2.
  • 0.8 Co 0.1 Mn 0.1 ) 0.997 Zr 0.003 O 2 surface is coated to avoid the direct contact of Li(Ni 0.8 Co 0.1 Mn 0.1 ) 0.997 Zr 0.003 O 2 with the electrolyte, which can reduce the occurrence of negative electrode active material and electrolyte Probability of reaction.
  • the Al 2 O 3 and B 2 O 3 coatings also have good ion conductivity and conductivity, which can optimize the gas production problem and minimize the impact of the coating on the polarization of the positive electrode active material.
  • the D n 10 of the positive electrode active material is further reduced. From the volume particle size differential distribution curve and the number particle size differential distribution curve of FIGS. 1 and 2, it can be found that two of the particle size distribution curves of the positive electrode active material appear The possible reason is that the relative amount of fine powder in the positive electrode active material is too much. As can be seen with reference to FIGS. 3 and 4, the volume particle size differential distribution curve and the number particle size differential distribution curve of the positive electrode active material of the present application are single peaks, which further indicates that the relative amount of fine powder in the positive electrode active material is relatively small.
  • the micropowder cathode active material will release more oxygen, which will not only destroy the crystal structure of the cathode active material, but also aggravate the inflation of the lithium ion battery and deteriorate the storage performance of the lithium ion battery.
  • D n 10 is 4 ⁇ m.
  • the D v 50 needs to be kept within a certain range to meet the higher ion transmission, which results in positive electrode activity.
  • the particle size distribution of the material is too narrow, the pores between the positive electrode active material particles in the positive electrode sheet are too large, it is difficult to achieve high-pressure solid density, and the positive electrode active material is more prone to particle breakage during the cold pressing process of the positive electrode sheet On the one hand, it will affect the energy density of the lithium ion battery, on the other hand, it will aggravate the flatulence of the lithium ion battery.

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Abstract

一种正极活性材料、正极极片、电化学储能装置及装置。所述正极活性材料为Li xNi yCo zM kMe pO rA m或表面设置有包覆层的Li xNi yCo zM kMe pO rA m，所述正极活性材料为二次颗粒，且所述正极活性材料的粒径D n10满足：0.5μm≤D n10≤3μm。通过合理控制正极活性材料的颗粒形貌以及正极活性材料中微粉的数量，有效减少了正极活性材料与电解液的副反应，降低了电化学储能装置产气量，且能在改善电化学储能装置存储性能的同时不恶化电化学储能装置的能量密度、循环性能和倍率性能。

Description

正极活性材料、正极极片、电化学储能装置及装置 技术领域
本申请涉及电化学技术领域，尤其涉及一种正极活性材料、正极极片、电化学储能装置及装置。
背景技术
随着能源危机以及环境问题的不断升级，开发新型绿色能源已迫在眉睫。锂离子电池由于具有比能量高、应用温度范围宽、自放电率低、循环寿命长、安全性能好、无污染等优点，已被广泛应用于各个领域中，同时以锂离子电池为能源系统的新能源汽车取代传统内燃机车也已在世界各地逐步得到尝试。然而目前常用的正极活性材料，例如：磷酸铁锂(LiFePO 4)、低镍三元材料(LiNi 1/3Co 1/3Mn 1/3O 2)等，由于受到材料本身的性质局限，不能完全满足锂离子电池对能量密度的需求，而提高三元材料的镍含量可以提升锂离子电池的能量密度，因此高镍三元材料是目前锂离子电池正极活性材料的主要研究对象之一。但是，随着镍含量的增加，三元材料与电解液的副反应也明显加剧，从而会导致锂离子电池产气严重，这是目前高镍三元材料量产商业化的最大瓶颈之一。
目前在材料层面，改善锂离子电池产气问题的手段主要包括降低三元材料中镍元素的含量或水洗等方式降低正极活性材料表面的残锂含量，然而上述方法均会导致对锂离子电池性能不同程度的破坏，例如，锂离子电池的可逆克容量降低、循环性能变差等。
因此需要有效的技术手段使锂离子电池具有较高的能量密度以满足越来越来越严格的应用需求，同时降低锂离子电池的产气量，改善锂离子电池的存储性能。
发明内容
鉴于背景技术中存在的问题，本申请的目的在于提供一种正极活性材 料、正极极片、电化学储能装置及装置，本申请能有效减少正极活性材料与电解液的副反应，降低电化学储能装置产气量，且能在改善电化学储能装置存储性能的同时不恶化电化学储能装置的能量密度、循环性能和倍率性能。
为了达到上述目的，在本申请的一方面，本申请提供了一种正极活性材料，所述正极活性材料为Li xNi yCo zM kMe pO rA m或表面设置有包覆层的Li xNi yCo zM kMe pO rA m，其中，0.85≤x≤1.15，0＜y＜1，0＜z＜1，0＜k＜1，0≤p≤0.1，1≤r≤2，0≤m≤1，m+r≤2，M选自Mn、Al中的一种或两种，Me选自Zr、Zn、Cu、Cr、Mg、Fe、V、Ti、Sr、Sb、Y、W、Nb中的一种或几种，A选自N、F、S、Cl中的一种或几种。所述正极活性材料为二次颗粒，且所述正极活性材料的粒径D n10满足：0.5μm≤D n10≤3μm。
在本申请的另一方面，本申请提供了一种正极极片，其包括本申请一方面所述的正极活性材料。
在本申请的又一方面，本申请提供了一种电化学储能装置，其包括本申请另一方面所述的正极活性材料。
在本申请的还一方面，本申请提供了一种装置，所述装置为车辆且包括本申请又一方面所述的电化学储能装置。
本申请的有益效果包括：
本申请通过合理控制正极活性材料的颗粒形貌以及正极活性材料中微粉的数量，有效减少了正极活性材料与电解液的副反应，降低了电化学储能装置产气量，且能在改善电化学储能装置存储性能的同时不恶化电化学储能装置的能量密度、循环性能和倍率性能。本申请的装置包括所述的电化学储能装置，因而至少具有与所述电化学储能装置相同的优势。
附图说明
图1为本申请的对比例1的正极活性材料的体积粒度微分分布曲线；
图2为本申请的对比例1的正极活性材料的数量粒度微分分布曲线；
图3为本申请的实施例3的正极活性材料的体积粒度微分分布曲线；
图4为本申请的实施例3的正极活性材料的数量粒度微分分布曲线。
图5是电化学储能装置的一实施方式的立体图。
图6是电池模块的一实施方式的立体图。
图7是电池包的一实施方式的立体图。
图8是图7的分解图。
图9是电化学储能装置作为电源的装置的一实施方式的示意图。
其中，附图标记说明如下：
1电池包
2上箱体
3下箱体
4电池模块
5电化学储能装置
具体实施方式
下面详细说明根据本申请的正极活性材料及其制备方法、正极极片、电化学储能装置及装置。
首先说明根据本申请第一方面的正极活性材料。
根据本申请第一方面的正极活性材料为Li xNi yCo zM kMe pO rA m或表面设置有包覆层的Li xNi yCo zM kMe pO rA m，其中，0.85≤x≤1.15，0＜y＜1，0＜z＜1，0＜k＜1，0≤p≤0.1，1≤r≤2，0≤m≤1，m+r≤2，M选自Mn、Al中的一种或两种，Me选自Zr、Zn、Cu、Cr、Mg、Fe、V、Ti、Sr、Sb、Y、W、Nb中的一种或几种，A选自N、F、S、Cl中的一种或几种。
在三元材料的实际生产过程中，由于所使用的原料锂盐可能存在不纯及熔点低的问题，其在较低温度下就会发生熔融、分解和挥发损失，因此在三元材料的制备过程中会加入过量的锂盐以弥补烧结过程中造成的锂损失。三元材料表面存在活性氧阴离子，其会和空气中的CO 2和H 2O反应而生成碳酸根，同时锂离子会从本体迁移到表面并在三元材料表面形成Li 2CO 3，这一过程同时伴随着三元材料表面脱氧而形成结构扭曲的表面氧化物层。另外，三元材料合成中锂盐过量的做法使得多余的锂盐在高温煅烧后的产物主要是Li的氧化物，其与空气中的CO 2和H 2O反应再次生成LiOH和Li 2CO 3，残留在三元材料表面，使三元材料的pH值较高。且在充放电过程中，残留在 三元材料表面的Li 2CO 3会发生分解产生CO 2，由于CO 2气体会随着温度的差异而造成气压差(特别是当反应过程中伴随着热反应发生的时候)，因此加剧了电化学储能装置胀气，恶化了电化学储能装置的存储性能。
在Li xNi yCo zM kMe pO rA m的表面设置包覆层可以在一定程度上降低正极活性材料表面残锂(例如LiOH、Li 2CO 3等)含量，达到改善电化学储能装置存储性能的目的。此外在Li xNi yCo zM kMe pO rA m表面设置包覆层还可以降低Li xNi yCo zM kMe pO rA m与电解液因直接接触而发生副反应的概率，进而可以减少正极活性材料在充放电过程中为了平衡电荷而释放出的氧气量以及由此带来晶体结构崩塌的风险。其中，在Li xNi yCo zM kMe pO rA m的表面设置包覆层而得到的正极活性材料表面上，Li 2CO 3的含量低于LiOH。优选地，在Li xNi yCo zM kMe pO rA m的表面设置包覆层而得到的正极活性材料表面上，Li 2CO 3的含量低于3000ppm，LiOH的含量低于5000ppm。
本申请第一方面所述的正极活性材料为二次颗粒形貌，且所述正极活性材料的粒径D n10满足：0.5μm≤D n10≤3μm。优选地，所述正极活性材料的粒径D n10满足：1μm≤D n10≤2μm。
电化学储能装置的能量密度、存储性能、循环性能以及倍率性能与正极活性材料的物理性质和化学性质密切相关。三元材料是一种主要包括同周期相邻的过渡金属元素Ni和Co，并通过Ni和Co的价态变化来达到电荷平衡的正极活性材料。其中，Ni是主要活性金属成分之一，主要以+2价的形式存在，在脱嵌锂的过程中Ni 2+会被氧化为Ni 3+、Ni 4+，而Co也是活性金属成分之一，主要以+3价的形式存在，在脱嵌锂的过程中Co 3+会被氧化为Co 4+。因此，在脱嵌锂的过程中，三元材料主要通过Ni和Co的价态变化来达到电荷平衡，而随着Ni、Co比例的变化，电化学储能装置的能量密度、存储性能、循环性能以及倍率性能会发生不同程度的变化。
在三元材料中，Ni的含量越高，三元材料的克容量通常就越大，也越有利于提升电化学储能装置的能量密度，但是当三元材料中Ni的含量较高时，三元材料的层状结构会因为Ni 2+与Li +的混排而崩塌，使得Li +在三元材料中的脱嵌越来越困难，最终导致电化学储能装置循环性能恶化。三元材料中Ni含量的增加还会降低三元材料的热分解温度，导致放热量增加，三元材料的热稳定性变差。三元材料中的Ni含量增加时，具有强氧化性的Ni 4+的含 量也会随之增加，当电解液与三元材料接触时，电解液会与三元材料发生更多副反应，而为了保持电荷平衡，三元材料会释放出氧气，这样不仅会破坏三元材料的晶体结构，而且会加剧电化学储能装置胀气，恶化电化学储能装置的存储性能。
相对于大粒径的正极活性材料而言，小粒径的正极活性材料的比表面积更大，与电解液之间的接触面积增大，与电解液接触时会发生更多的副反应，而为了保持电荷平衡，小粒径的正极活性材料会释放出更多的氧气，不仅会破坏小粒径的正极活性材料的晶体结构，而且会加剧电化学储能装置胀气，恶化电化学储能装置的存储性能。同时小粒径的正极活性材料的抗压能力更弱，在极片冷压过程中更加容易破碎并产生更多的一次颗粒，这些一次颗粒一部分会因为没有接触到粘结剂而从正极集流体上脱落，一部分会因为没有接触到导电剂而使正极极片的性能出现局部恶化。
此外，通常对于粒径分布范围较广的正极活性材料而言，小粒径的粉料，尤其是微粉在正极活性材料中的体积百分比微不足道，因此用常规的体积粒径来表征正极活性材料中微粉的含量无法准确反映粉体材料中小粒径颗粒的相对含量，而用数量粒径来表征正极活性材料中微粉的含量则更加精确和直观，进而对合理控制电化学储能装置胀气有利。
因此，综合考虑上述因素对电化学储能装置能量密度、存储性能、循环性能以及倍率性能的影响，本申请第一方面所述的正极活性材料为粒径D n10满足0.5μm≤D n10≤3μm的二次颗粒形貌的三元材料Li xNi yCo zM kMe pO rA m或表面设置有包覆层的三元材料Li xNi yCo zM kMe pO rA m，通过合理控制正极活性材料的颗粒形貌以及正极活性材料中微粉的数量，有效减少了正极活性材料与电解液的副反应，降低了电化学储能装置产气量，且能在改善电化学储能装置存储性能的同时不恶化电化学储能装置的能量密度、循环性能和倍率性能。
优选地，在Li xNi yCo zM kMe pO rA m中，0.50≤y≤0.90，0.05≤z≤0.2，0.05≤k≤0.4，0≤p≤0.05。
更优选地，在Li xNi yCo zM kMe pO rA m中，0.70≤y≤0.90，0.05≤z≤0.2，0.05≤k≤0.2，0≤p≤0.05。对于镍含量更高(0.70≤y≤0.90)的三元材料而言，小粒径微粉的相对数量对正极活性材料的残锂量、产气问题影响更加显 著。因此控制高镍二次颗粒形貌的三元材料Li xNi yCo zM kMe pO rA m或表面设置有包覆层的Li xNi yCo zM kMe pO rA m的D n10在0.5μm～3μm的范围内，是解决其产气问题的一种有效手段。
具体地，Li xNi yCo zM kMe pO rA m可以为LiNi 1/3Co 1/3Mn 1/3O 2、LiNi 0.5Co 0.2Mn 0.3O 2、LiNi 0.5Co 0.25Mn 0.25O 2、LiNi 0.55Co 0.15Mn 0.3O 2、LiNi 0.55Co 0.1Mn 0.35O 2、LiNi 0.55Co 0.05Mn 0.4O 2、LiNi 0.6Co 0.2Mn 0.2O 2、LiNi 0.75Co 0.1Mn 0.15O 2、LiNi 0.8Co 0.1Mn 0.1O 2、LiNi 0.85Co 0.05Mn 0.1O 2、LiNi 0.88Co 0.05Mn 0.07O 2、LiNi 0.9Co 0.05Mn 0.05O 2，也可以为上述物质经过掺杂元素Me和/或掺杂元素A进行部分取代改性后的物质。
在根据本申请第一方面的正极活性材料中，通过在Li xNi yCo zM kMe pO rA m表面进行包覆处理，可以避免Li xNi yCo zM kMe pO rA m与电解液的直接接触，降低正极活性材料与电解液的副反应。优选地，所述包覆层中的包覆元素选自Al、Ba、Zn、Ti、Co、W、Y、Si、Sn、B、P中的一种或多种的组合。更优选地，所述包覆层中的包覆元素选自Al、Ba、Zn、Ti、Co、W、Y、Si、Sn、B、P中的两种及以上的组合。
优选地，所述包覆层包括上述包覆元素的氧化物。更优选地，所述包覆层包括上述包覆元素中的两种及以上形成的氧化物。当包覆层中含有至少两种上述包覆元素形成的氧化物时，可以提高包覆层在Li xNi yCo zM kMe pO rA m表面附着的稳定性，使包覆层兼具一定的导离子性和导电子性，进而可以减少包覆层对正极活性材料极化的影响。
在根据本申请第一方面所述的正极活性材料中，所述正极活性材料以μm为计量单位的粒径D n10与所述正极活性材料以μm为计量单位的粒径D v10满足：1≤D n10×D v10≤20。更优选地，所述正极活性材料以μm为计量单位的粒径D n10与所述正极活性材料以μm为计量单位的粒径D v10满足：2≤D n10×D v10≤18。其中，D v10为所述正极活性材料的体积累计分布百分数达到10％时对应的粒径，D n10为所述正极活性材料的数量累计分布百分数达到10％时对应的粒径。当正极活性材料的D n10与D v10的乘积在上述范围内时，表明此时正极活性材料中粒径过小的微粉的相对数量较少、正极活性材料的容量较高，有利于改善正极活性材料的产气问题，同时保证电化学储能装置的体积能量密度较高。
优选地，所述正极活性材料的粒径D v10为2μm～8μm。更优选地，所述正极活性材料的粒径D v10为3μm～6μm。
在根据本申请第一方面所述的正极活性材料中，所述正极活性材料的理论比表面积BET 1与所述正极活性材料的真实比表面积BET 2满足：0.8≤(BET 2-BET 1)/BET 1≤5.5。
所述正极活性材料的理论比表面积BET 1＝6/(ρ×D v50)。ρ为所述正极活性材料的真实密度，计量单位为g/cm 3；D v50为所述正极活性材料的体积累计分布百分数达到50％时对应的粒径，计量单位为μm。
所述正极活性材料的真实比表面积BET 2可经N 2吸附法测定，具体可参考GB/T19587-2004。
本申请中，(BET 2-BET 1)/BET 1表示正极活性材料的理论比表面积与真实比表面积的偏离程度，其可以衡量正极活性材料表面的凹凸起伏程度。通过控制正极活性材料理论比表面积与真实比表面积的偏离程度在一定范围内，可以保证二次颗粒形貌的正极活性材料表面较平整、凹凸起伏结构较少，还表明形成上述二次颗粒的一次颗粒尺寸的均匀性较好，有利于降低正极活性材料的极化、提高离子传输性能，并进一步降低产气量、优化动力学性能。
优选地，所述正极活性材料的真实比表面积BET 2为0.1m 2/g～0.8m 2/g。正极活性材料的真实比表面积在上述范围内，电解液与正极活性材料的接触面积较少，有利于抑制副反应，避免电解液腐蚀并破坏正极活性材料的晶体结构导致加剧电化学储能装置胀气的问题。同时正极活性材料的真实比表面积在上述范围内还有利于在混合形成正极浆料时，使用较少的辅料即可以满足正极活性材料与粘结剂、导电剂的吸附性能相对较强，由此有利于提升电化学储能装置的能量密度。
优选地，所述正极活性材料的粒径D v50为5μm～18μm。更优选地，所述正极活性材料的粒径D v50为8μm～15μm。
优选地，所述正极活性材料的粒径D v90为10μm～30μm。更优选地，所述正极活性材料的粒径D v90为12μm～25μm。
在根据本申请第一方面所述的正极活性材料中，优选地，所述正极活性材料的粒度微分分布曲线有且仅有一个峰。所述粒度微分分布曲线既包括体积粒度微分分布曲线，也包括数量粒度微分分布曲线。
其次说明根据本申请第二方面的正极活性材料的一种制备方法，用于制备本申请第一方面所述的正极活性材料，其包括步骤：将三元材料前驱体(含Ni、Co和M的化合物)、含Li化合物、含掺杂元素Me的化合物、含掺杂元素A的化合物置于混料设备中进行混料，然后置于气氛炉中进行烧结，烧结结束后进行分级筛选，得到正极活性材料。
其中，所述分级筛选的方式没有特别的限制，可根据实际情况进行选择。优选地，所述分级筛分可选自气流分级筛选或筛网过筛筛选。
所述气流分级筛选的具体过程为：将烧结结束后的物料投入到气流分级机中，然后与一定气压的气流从喷嘴中一起喷出，利用不同粒径的颗粒重量不一致的原理对其进行大小颗粒分离，其中，重量小的颗粒比较轻，飞出的距离比较近，而重量大的颗粒比较重，飞出的距离比较远；调节收集器与喷嘴之间的距离，即可筛选出合适的粒径，得到正极活性材料。
所述筛网过筛筛选的具体过程为：将烧结结束后的物料投入200目～1000目筛网中进行过筛，由于颗粒的粒径不同，小粒径的颗粒会被筛网筛出，而筛网上可保留所需要的粒径，得到正极活性材料。优选地，所述筛网的目数为500目～800目。
所述三元材料前驱体可以是包括但不限于Ni 1/3Co 1/3Mn 1/3(OH) 2、Ni 0.5Co 0.2Mn 0.3(OH) 2、Ni 0.5Co 0.25Mn 0.25(OH) 2、Ni 0.55Co 0.15Mn 0.3(OH) 2、Ni 0.55Co 0.1Mn 0.35(OH) 2、Ni 0.55Co 0.05Mn 0.4(OH) 2、Ni 0.6Co 0.2Mn 0.2(OH) 2、Ni 0.75Co 0.1Mn 0.15(OH) 2、Ni 0.8Co 0.1Mn 0.1(OH) 2、Ni 0.88Co 0.05Mn 0.07(OH) 2、0.9Ni 0.8Co 0.2(OH) 2·0.1Al 2(OH) 3、0.9Ni 0.9Co 0.05Mn 0.05(OH) 2·0.1Al 2(OH) 3。
所述含Li的化合物可以是包括但不限于LiOH·H 2O、LiOH、Li 2CO 3、Li 2O中的一种或多种的组合。
所述含掺杂元素Me的化合物可以是含有Zr、Zn、Cu、Cr、Mg、Fe、V、Ti、Sr、Sb、Y、W、Nb中至少一种元素的氧化物、硝酸盐、碳酸盐中的一种或多种的组合。
所述含掺杂元素A的化合物可以是包括但不限于LiF、NaCl、Na 2S、Li 3N中的一种或多种的组合。
所述烧结的条件可以是700℃～800℃、氧气浓度≥20％。
再次说明根据本申请第三方面的正极活性材料的另一种制备方法，用于制备本申请第一方面所述的正极活性材料，其包括步骤：S1，将三元材料前驱体(含Ni、Co和M的化合物)、含Li化合物、含掺杂元素Me的化合物、含掺杂元素A的化合物置于混料设备中进行混料，然后置于气氛炉中进行一次烧结；S2，将一次烧结结束后的物料与含包覆元素的化合物置于混料设备中进行混料，然后置于气氛炉中进行二次烧结；S3，对二次烧结结束后的物料进行分级筛选，即得到正极活性材料。
其中，所述分级筛选的方式没有特别的限制，可根据实际情况进行选择。优选地，所述分级筛分可选自气流分级筛选或筛网过筛筛选。
所述气流分级筛选的具体过程为：将二次烧结结束后的物料投入到气流分级机中，然后与一定气压的气流从喷嘴中一起喷出，利用不同粒径的颗粒重量不一致的原理对其进行大小颗粒分离，其中，重量小的颗粒比较轻，飞出的距离比较近，而重量大的颗粒比较重，飞出的距离比较远；调节收集器与喷嘴之间的距离，即可筛选出合适的粒径，得到正极活性材料。
所述筛网过筛筛选的具体过程为：将二次烧结结束后的物料投入200目～1000目筛网中进行过筛，由于颗粒的粒径不同，小粒径的颗粒会被筛网筛出，而筛网上可保留所需要的粒径，得到正极活性材料。优选地，所述筛网的目数为500目～800目。
所述三元材料前驱体可以是包括但不限于Ni 1/3Co 1/3Mn 1/3(OH) 2、Ni 0.5Co 0.2Mn 0.3(OH) 2、Ni 0.5Co 0.25Mn 0.25(OH) 2、Ni 0.55Co 0.15Mn 0.3(OH) 2、Ni 0.55Co 0.1Mn 0.35(OH) 2、Ni 0.55Co 0.05Mn 0.4(OH) 2、Ni 0.6Co 0.2Mn 0.2(OH) 2、Ni 0.75Co 0.1Mn 0.15(OH) 2、Ni 0.8Co 0.1Mn 0.1(OH) 2、Ni 0.88Co 0.05Mn 0.07(OH) 2、0.9Ni 0.8Co 0.2(OH) 2·0.1Al 2(OH) 3、0.9Ni 0.9Co 0.05Mn 0.05(OH) 2·0.1Al 2(OH) 3。
所述含Li的化合物可以是包括但不限于LiOH·H 2O、LiOH、Li 2CO 3、Li 2O中的一种或多种的组合。
所述含掺杂元素Me化合物可以是含有Zr、Zn、Cu、Cr、Mg、Fe、V、Ti、Sr、Sb、Y、W、Nb中至少一种元素的氧化物、硝酸盐、碳酸盐中的一种或多种的组合。
所述含掺杂元素A的化合物可以是包括但不限于LiF、NaCl、Na 2S、Li 3N 中的一种或多种的组合。
所述含包覆元素的化合物可以是含有Al、Ba、Zn、Ti、Co、W、Y、Si、Sn、B、P中的一种或多种元素的氧化物、硝酸盐、磷酸盐、碳酸盐中的一种或多种的组合。所述含包覆元素的化合物的使用量可以是正极活性材料总质量的0.01％～0.5％。
所述一次烧结的条件可以是700℃～800℃、氧气浓度≥20％。
所述二次烧结的条件可以是200℃～700℃。
接下来说明根据本申请第四方面的正极极片，其包括正极集流体以及设置在正极集流体至少一个表面上且包括根据本申请第一方面所述的正极活性材料的正极膜片。
在根据本申请第四方面所述的正极极片中，所述正极膜片可设置在正极集流体的其中一个表面上也可以设置在正极集流体的两个表面上。
在根据本申请第四方面所述的正极极片中，所述正极膜片还可包括导电剂以及粘结剂，其中导电剂以及粘结剂的种类和含量不受具体的限制，可根据实际需求进行选择。所述粘结剂通常包括含氟聚烯烃类粘结剂，相对于所述含氟聚烯烃类粘结剂来说，水通常是良溶剂，即所述含氟聚烯烃类粘结剂通常在水中具有良好的溶解性，例如，所述含氟聚烯烃类粘结剂可以是包括但不限于聚偏氟乙烯(PVDF)、偏氟乙烯共聚物或它们的改性(例如，羧酸、丙烯酸、丙烯腈等改性)衍生物等。所述导电剂可以是本领域各种适用于电化学储能装置的导电剂，例如，可以是包括但不限于乙炔黑、导电炭黑、碳纤维、碳纳米管、科琴黑中的一种或多种的组合。
在根据本申请第四方面所述的正极极片中，所述正极集流体的种类也不受具体的限制，可根据实际需求进行选择。所述正极集流体通常可以为层体，所述正极集流体通常是可以汇集电流的结构或零件，所述正极集流体可以是本领域各种适用于作为电化学储能装置正极集流体的材料，例如，所述正极集流体可以是包括但不限于金属箔，更具体可以是包括但不限于镍箔、铝箔。
接下来说明根据本申请第五方面的电化学储能装置，其包括本申请第一方面所述的正极活性材料。
在本申请第五方面所述的电化学储能装置中，需要说明的是，所述电化学储能装置可为超级电容器、锂离子电池、锂金属电池或钠离子电池。在本申请的实施例中，仅示出电化学储能装置为锂离子电池的实施例，但本申请不限于此。
本申请第五方面所述的电化学储能装置可包括正极极片、负极极片、间隔于正极极片和负极极片之间的隔离膜、电解液。其中，所述正极极片为本申请第四方面所述的正极极片，所述正极极片包括本申请第一方面的正极活性材料。
制备所述电化学储能装置的方法对于本领域技术人员来说应该是已知的，例如，所述正极极片、隔离膜和负极极片各自都可以是层体，从而可以裁剪成目标尺寸后依次叠放，还可以卷绕至目标尺寸，以用于形成电极组件，并可以进一步与电解液结合以形成电化学储能装置。
在电化学储能装置中，所述负极极片通常包括负极集流体和位于负极集流体表面的负极活性材料层，所述负极活性材料层通常包括负极活性材料。所述负极活性材料可以是本领域各种适用于电化学储能装置的负极活性材料的材料，例如，可以是包括但不限于石墨、软碳、硬碳、碳纤维、中间相碳微球、硅基材料、锡基材料、钛酸锂或其他能与锂形成合金的金属中的一种或多种的组合。其中，所述石墨可选自人造石墨、天然石墨以及改性石墨中的一种或多种的组合；所述硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅合金中的一种或多种的组合；所述锡基材料可选自单质锡、锡氧化合物、锡合金中的一种或多种的组合。所述负极集流体通常是汇集电流的结构或零件，所述负极集流体可以是本领域各种适用于作为电化学储能装置负极集流体的材料，例如，所述负极集流体可以是包括但不限于金属箔，更具体可以是包括但不限于铜箔。
在电化学储能装置中，所述负极极片也可为锂片。
在电化学储能装置中，所述隔离膜可以是本领域各种适用于电化学储能装置隔离膜的材料，例如，可以是包括但不限于聚乙烯、聚丙烯、聚偏氟乙烯、芳纶、聚对苯二甲酸乙二醇酯、聚四氟乙烯、聚丙烯腈、聚酰亚胺，聚酰胺、聚酯和天然纤维中的一种或多种的组合。
在电化学储能装置中，所述电解液可以是本领域各种适用于电化学储能 装置的电解液，例如，所述电解液通常包括电解质和溶剂，所述电解质通常可以包括锂盐，更具体的，所述锂盐可以是无机锂盐和/或有机锂盐，具体可以是包括但不限于LiPF 6、LiBF 4、LiN(SO 2F) 2(简写为LiFSI)、LiN(CF 3SO 2) 2(简写为LiTFSI)、LiClO 4、LiAsF 6、LiB(C 2O 4) 2(简写为LiBOB)、LiBF 2C 2O 4(简写为LiDFOB)中的一种或多种的组合。再例如，所述电解质的浓度可以为0.8mol/L～1.5mol/L。所述溶剂可以是本领域各种适用于电化学储能装置的电解液的溶剂，所述电解液的溶剂通常为非水溶剂，优选可以为有机溶剂，具体可以是包括但不限于碳酸乙烯酯、碳酸丙烯酯、碳酸丁烯酯、碳酸戊烯酯、碳酸二甲酯、碳酸二乙酯、碳酸二丙酯、碳酸甲乙酯或它们的卤代衍生物中的一种或多种的组合。
在一些实施例中，电化学储能装置可以包括外包装，用于封装正极极片、负极极片和电解质。作为一个示例，正极极片、负极极片和隔离膜可经叠片或卷绕形成叠片结构电极组件或卷绕结构电极组件，电极组件封装在外包装内；电解质可采用电解液，电解液浸润于电极组件中。电化学储能装置中电极组件的数量可以为一个或几个，可以根据需求来调节。
在一些实施例中，电化学储能装置的外包装可以是软包，例如袋式软包。软包的材质可以是塑料，如可包括聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)、聚丁二酸丁二醇酯(PBS)等中的一种或几种。电化学储能装置的外包装也可以是硬壳，例如铝壳等。
本申请对电化学储能装置的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。如图5是作为一个示例的方形结构的电化学储能装置5。
在一些实施例中，电化学储能装置可以组装成电池模块，电池模块所含电化学储能装置的数量可以为多个，具体数量可根据电池模块的应用和容量来调节。
图6是作为一个示例的电池模块4。参照图6，在电池模块4中，多个电化学储能装置5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个电化学储能装置5进行固定。
可选地，电池模块4还可以包括具有容纳空间的壳体，多个电化学储能 装置5容纳于该容纳空间。
在一些实施例中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以根据电池包的应用和容量进行调节。
图7和图8是作为一个示例的电池包1。参照图7和图8，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
最后说明根据本申请第六方面的装置，其包括本申请第五方面所述的电化学装置，所述电化学装置可以用作所述装置的电源，也可以作为所述装置的能量存储单元。所述装置包括但不限于是电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星等。此外，电气列车、船舶及卫星均是运载工具，属于广义上的车辆(vehicle)。
所述装置可以根据其使用需求来选择电化学储能装置、电池模块或电池包。
图9是作为一个示例的装置。该装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该装置对电化学储能装置的高功率和高能量密度的需求，可以采用电池包或电池模块。
下面结合实施例，进一步阐述本申请。应理解，这些实施例仅用于说明本申请而不用于限制本申请的范围。
实施例1-8和对比例1-2的锂离子电池均按照下述方法进行制备。
(1)正极活性材料的制备
将三元材料前驱体Ni 0.8Co 0.1Mn 0.1(OH) 2、LiOH·H 2O、ZrO 2以摩尔比为0.997:1.05:0.003置于混料机中进行混料，然后置于充满氧气的气氛炉中进行烧结，烧结结束后进行分级筛分以选取合适的粒径，得到正极活性材料Li(Ni 0.8Co 0.1Mn 0.1) 0.997Zr 0.003O 2。
(2)正极极片的制备
将正极活性材料LiNi 0.8Co 0.1Mn 0.1O 2、粘结剂聚偏氟乙烯、导电剂乙炔黑按照质量比为98:1:1进行混合，然后加入N-甲基吡咯烷酮，在真空搅拌机的作用下搅拌均匀获得正极浆料；将正极浆料均匀涂覆于厚度为12μm的正极集流体铝箔上，在室温晒干后转移至100℃～130℃的烘箱中干燥，然后进行冷压、分切得到正极极片。
(3)负极极片的制备
将负极活性材料石墨、增稠剂羧甲基纤维素钠、粘接剂丁苯橡胶、导电剂乙炔黑按照质量比97:1:1:1进行混合，加入去离子水，在真空搅拌机作用下获得负极浆料；将负极浆料均匀涂覆在厚度为8μm的铜箔上，在室温晾干后转移至100℃～130℃烘箱干燥，然后经过冷压、分切得到负极极片。
(4)电解液的制备
有机溶剂为含有碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)和碳酸二乙酯(DEC)的混合液，其中，EC、EMC和DEC的体积比为20:20:60。在含水量<10ppm的氩气气氛手套箱中，将充分干燥的锂盐LiPF 6溶解于有机溶剂中，混合均匀，获得电解液。其中，锂盐的浓度为1mol/L。
(5)隔离膜的制备
选用12μm厚的聚丙烯膜作为隔离膜。
(6)锂离子电池的制备
将正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正、负极极片之间起到隔离的作用，再卷绕成方形的电极组件后，装入铝塑膜，然后在80℃下烘烤除水后，注入电解液、封口，经静置、热冷压、化成、夹具、分容等工序后，得到锂离子电池。
实施例9的锂离子电池按照下述方法进行制备。
(1)正极活性材料的制备
将三元材料前驱体Ni 0.8Co 0.1Mn 0.1(OH) 2、LiOH·H 2O、ZrO 2以摩尔比为0.997:1.05:0.003置于混料机中进行混料，然后置于充满氧气的气氛炉中进行一次烧结；将一次烧结结束后的物料与0.5wt％Al 2O 3置于混料设备中进行混料，然后置于气氛炉中进行二次烧结；接着将二次烧结结束后的物料进行分级筛分以选取合适的粒径，得到Li(Ni 0.8Co 0.1Mn 0.1) 0.997Zr 0.003O 2表面设置有 Al 2O 3的正极活性材料。
(2)正极极片的制备
将上述正极活性材料、粘结剂聚偏氟乙烯、导电剂乙炔黑按照质量比为98:1:1进行混合，然后加入N-甲基吡咯烷酮，在真空搅拌机的作用下搅拌均匀获得正极浆料；将正极浆料均匀涂覆于厚度为12μm的正极集流体铝箔上，在室温晒干后转移至100℃～130℃的烘箱中干燥，然后进行冷压、分切得到正极极片。
(3)负极极片的制备
将负极活性材料石墨、增稠剂羧甲基纤维素钠、粘接剂丁苯橡胶、导电剂乙炔黑按照质量比97:1:1:1进行混合，加入去离子水，在真空搅拌机作用下获得负极浆料；将负极浆料均匀涂覆在厚度为8μm的铜箔上，在室温晾干后转移至100℃～130℃烘箱干燥，然后经过冷压、分切得到负极极片。
(4)电解液的制备
有机溶剂为含有碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)和碳酸二乙酯(DEC)的混合液，其中，EC、EMC和DEC的体积比为20:20:60。在含水量<10ppm的氩气气氛手套箱中，将充分干燥的锂盐LiPF 6溶解于有机溶剂中，混合均匀，获得电解液。其中，锂盐的浓度为1mol/L。
(5)隔离膜的制备
选用12μm厚的聚丙烯膜作为隔离膜。
(6)锂离子电池的制备
将正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正、负极极片之间起到隔离的作用，再卷绕成方形的电极组件后，装入铝塑膜，然后在80℃下烘烤除水后，注入电解液、封口，经静置、热冷压、化成、夹具、分容等工序后，得到锂离子电池。
实施例10的锂离子电池按照与实施例9的锂离子电池类似的方法制备，区别在于将0.5wt％的Al 2O 3替换为0.5wt％的B 2O 3。
接下来说明锂离子电池的测试过程。
(1)正极活性材料表面残锂含量测定
取30g制备的正极活性材料粉料加入100mL水中并搅拌30min，用盐酸标准溶液滴定待测样品中残锂。以复合pH电极为指示电极，借助电位变化产生的突跃确定滴定终点。
(2)锂离子电池的高温循环性能测试
在45℃下，将锂离子电池以1C恒流充电至电压为4.2V，然后以4.2V恒压充电至电流为0.05C，接着以1C恒流放电，直到最终电压为2.8V，记录首次循环的放电容量。然后按照上述操作进行充电和放电循环，循环至初始容量的80％时，停止充放电，此时的循环圈数即为高温循环寿命。
(3)锂离子电池的高温存储性能测试
在25℃下，先以1C的恒定电流对锂离子电池充电至4.2V，进一步以4.2V恒定电压充电至电流为0.05C，然后用排水法测定锂离子电池的体积，记为锂离子电池的初始体积；然后将锂离子电池置于80℃下存储10天，待存储结束后，再次采用排水法测定锂离子电池的体积，记为锂离子电池80℃存储10天后的体积。
锂离子电池80℃存储10天后的体积膨胀率(％)＝[锂离子电池80℃存储10天后的体积/锂离子电池的初始体积-1]×100％。
(4)锂离子电池中正极活性材料的容量测试
将锂离子电池在25℃的恒温环境下静置2h，然后在2.8V～4.2V下，以1/3C充电至4.2V，然后在4.2V下恒压充电至电流≤0.05mA，静置5min，然后以1C放电至2.8V，记录该锂离子电池的容量，将测试的容量值除以该电池中正极活性材料的质量，即为该锂离子电池中正极活性材料的容量。
表1实施例1-10和对比例1-2的正极活性材料参数
Figure PCTCN2019129365-appb-000001
Figure PCTCN2019129365-appb-000002
表2实施例1-10和对比例1-2的性能测试结果
Figure PCTCN2019129365-appb-000003
从表2的测试结果分析可知，在实施例1～10的锂离子电池正极活性材料中，粒径小于1μm的细粉在正极活性材料中的相对数量较少，正极活性材料具有较高的容量，同时锂离子电池具有较高的高温循环寿命和较低的高温存储体积膨胀率。因此通过合理控制正极活性材料的颗粒形貌以及正极活性材料中微粉的数量，能够有效减少正极活性材料与电解液之间的副反应，降低锂离子电池产气量，还能在改善锂离子电池存储性能的同时不恶化锂离子电池的能量密度、循环性能和倍率性能。
其中，对实施例1～8的测试结果进行进一步分析还可以发现，通过控制正极活性材料的理论比表面积BET 1与真实比表面积BET 2的偏离程度，可以进一步优化正极活性材料的微观结构，保证其表面较平整、凹凸起伏结构较少，有利于降低正极活性材料的极化、提高离子传输性能，从而进一步降低锂离子电池的产气量、优化锂离子电池的动力学性能。
与实施例1相比，实施例9和实施例10中的正极活性材料为在Li(Ni 0.8Co 0.1Mn 0.1) 0.997Zr 0.003O 2表面进行了包覆处理的正极活性材料，在Li(Ni 0.8Co 0.1Mn 0.1) 0.997Zr 0.003O 2表面进行包覆处理，可以避免Li(Ni 0.8Co 0.1Mn 0.1) 0.997Zr 0.003O 2与电解液的直接接触，可以降低正极活性材料与电解液发生副反应的概率。同时Al 2O 3和B 2O 3包覆层还具有良好的导离子性和导电子性，可以在优化产气问题的同时，还能尽量减少包覆层对正极活性材料极化的影响。
在对比例1中，正极活性材料的D n10进一步降低，从图1和图2的体积粒度微分分布曲线和数量粒度微分分布曲线可以发现，其正极活性材料的粒度分布曲线均出现了两个峰，可能的原因在于正极活性材料中微粉的相对数量过多。而参考图3和图4可知，本申请的正极活性材料的体积粒度微分分布曲线和数量粒度微分分布曲线均为单峰，这进一步说明正极活性材料中的微粉相对数量较少。当正极活性材料中的微粉的相对数量过多时，由于微粉的比表面积更大、表面残锂量更高，与电解液之间的接触面积更大，因此其与电解液接触时会发生更多的副反应，而为了保持电荷平衡，微粉正极活性材料会释放出更多的氧气，不仅会破坏正极活性材料的晶体结构，而且会加剧锂离子电池胀气，恶化锂离子电池的存储性能。
在对比例2中，D n10为4μm，虽然此时正极活性材料中微粉的含量较低，但是由于D v50需要保持在一定范围内以满足较高的离子传输性，这导致了正极活性材料的粒径分布过窄，正极极片中正极活性材料颗粒间的孔隙过多、较难实现高压实密度，且在正极极片的冷压过程中正极活性材料更容易发生颗粒破碎的问题，一方面会影响锂离子电池的能量密度，另一方面还会加剧锂离子电池胀气。

Claims (11)

  1. 一种正极活性材料，其特征在于，
    所述正极活性材料为Li xNi yCo zM kMe pO rA m或表面设置有包覆层的Li xNi yCo zM kMe pO rA m，其中，0.85≤x≤1.15，0＜y＜1，0＜z＜1，0＜k＜1，0≤p≤0.1，1≤r≤2，0≤m≤1，m+r≤2，M选自Mn、Al中的一种或两种，Me选自Zr、Zn、Cu、Cr、Mg、Fe、V、Ti、Sr、Sb、Y、W、Nb中的一种或几种，A选自N、F、S、Cl中的一种或几种；
    所述正极活性材料为二次颗粒，且所述正极活性材料的粒径D n10满足：0.5μm≤D n10≤3μm，优选满足：1μm≤D n10≤2μm；
    其中，D n10为所述正极活性材料的数量累计分布百分数达到10％时对应的粒径。
  2. 根据权利要求1所述的正极活性材料，其特征在于，所述包覆层中的包覆元素选自Al、Ba、Zn、Ti、Co、W、Y、Si、Sn、B、P中的一种或几种。
  3. 根据权利要求1或2所述的正极活性材料，其特征在于，
    所述正极活性材料以μm为计量单位的粒径D n10与所述正极活性材料以μm为计量单位的粒径D v10满足：1≤D n10×D v10≤20，
    其中，D v10为所述正极活性材料的体积累计分布百分数达到10％时对应的粒径。
  4. 根据权利要求1或3所述的正极活性材料，其特征在于，所述正极活性材料的粒径D v10为2μm～8μm，优选为3μm～6μm。
  5. 根据权利要求1至4中任一项所述的正极活性材料，其特征在于，
    所述正极活性材料的理论比表面积BET 1与所述正极活性材料的真实比表面积BET 2满足：0.8≤(BET 2-BET 1)/BET 1≤5.5；
    其中，BET 1＝6/(ρ×D v50)；
    ρ为所述正极活性材料的真实密度，计量单位为g/cm 3；
    D v50为所述正极活性材料的体积累计分布百分数达到50％时对应的粒径，计量单位为μm。
  6. 根据权利要求5所述的正极活性材料，其特征在于，所述正极活性材料的真实比表面积BET 2为0.1m 2/g～0.8m 2/g。
  7. 根据权利要求5所述的正极活性材料，其特征在于，所述正极活性材料的粒径D v50为5μm～18μm，优选为8μm～15μm。
  8. 根据权利要求1至7中任一项所述的正极活性材料，其特征在于，所述正极活性材料的粒度微分分布曲线有且仅有一个峰。
  9. 一种正极极片，其特征在于，包括根据权利要求1至8中任一项所述的正极活性材料。
  10. 一种电化学储能装置，其特征在于，包括根据权利要求1至8中任一项所述的正极活性材料。
  11. 一种装置，其特征在于，所述装置为车辆且包括根据权利要求10所述的电化学储能装置。
PCT/CN2019/129365 2018-12-29 2019-12-27 正极活性材料、正极极片、电化学储能装置及装置 WO2020135766A1 (zh)

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