WO2020134781A1 - 一种高压实密度正极材料及电化学储能装置 - Google Patents

一种高压实密度正极材料及电化学储能装置 Download PDF

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WO2020134781A1
WO2020134781A1 PCT/CN2019/120591 CN2019120591W WO2020134781A1 WO 2020134781 A1 WO2020134781 A1 WO 2020134781A1 CN 2019120591 W CN2019120591 W CN 2019120591W WO 2020134781 A1 WO2020134781 A1 WO 2020134781A1
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transition metal
metal oxide
positive electrode
lithium nickel
electrode material
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PCT/CN2019/120591
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French (fr)
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杜锐
刘勇超
赵德宇
柳娜
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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 EP19905262.2A priority Critical patent/EP3800710B1/en
Publication of WO2020134781A1 publication Critical patent/WO2020134781A1/zh
Priority to US17/135,552 priority patent/US11177468B2/en

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Definitions

  • the invention relates to the technical field of batteries, in particular to a high-pressure solid density cathode material and an electrochemical energy storage device.
  • cathode materials are generally optimized from two aspects.
  • the nickel content of the positive electrode material is increased to increase its reversible gram capacity; on the other hand, the size of the particles is matched to increase the compaction density of the powder.
  • the high-nickel ternary material has a high reversible gram capacity, but does not have a high powder compaction density.
  • the object of the present invention is to provide a high-pressure solid density cathode material and an electrochemical energy storage device using the cathode material.
  • the positive electrode material of the present invention can improve the gas generation performance problem of particle crushing during cold pressing.
  • one aspect of the present invention provides a positive electrode material
  • the positive electrode material includes lithium nickel transition metal oxide A and lithium nickel transition metal oxide B
  • the lithium nickel transition metal oxide A is two Secondary particles
  • the chemical formula of the lithium nickel transition metal oxide A is shown in formula I:
  • the lithium nickel transition metal oxide B is single crystal or single crystal-like morphology particles, and the chemical formula of the lithium nickel transition metal oxide B is shown in Formula II:
  • M' is selected from Al, Ti, Zr, A combination of one or more of Nb, Sr, Sc, Sb, Y, Ba, B, C, Co, Mn, X′ is selected from F and/or Cl;
  • Another aspect of the present invention provides an electrochemical energy storage device including the cathode material of the present invention.
  • the positive electrode material in the present invention includes large particles of lithium nickel transition metal oxide A (large particle high nickel ternary polycrystalline positive electrode material) and small particles of lithium nickel transition metal oxide B (small particle high nickel ternary single crystal or similar Single crystal cathode material), due to the high nickel content of cathode material A and cathode material B, it can improve the energy density of the battery; at the same time, by adjusting the crystallinity and particle size distribution of the cathode material after mixing, effectively improve the high nickel active material
  • the problem of particle crushing during cold pressing and circulation improves the compaction density of the powder of high-nickel active materials to ensure low gas production and excellent cycle performance.
  • FIG. 1 Electron micrograph of the positive electrode material prepared in Example 1 of the present invention.
  • FIG. 1 Electron micrograph of the positive electrode material prepared in Comparative Example 1 of the present invention.
  • the high-pressure solid-density positive electrode material and the electrochemical energy storage device using the positive electrode material according to the present invention will be described in detail below.
  • a first aspect of the present invention provides a cathode material including lithium nickel transition metal oxide A and lithium nickel transition metal oxide B, the lithium nickel transition metal oxide A being secondary particles, the lithium
  • the chemical formula of nickel transition metal oxide A is shown in formula I:
  • the lithium nickel transition metal oxide B is single crystal or single crystal-like morphology particles, and the chemical formula of the lithium nickel transition metal oxide B is shown in Formula II:
  • M' is selected from Al, Ti, Zr, A combination of one or more of Nb, Sr, Sc, Sb, Y, Ba, B, C, Co, Mn, X′ is selected from F and/or Cl;
  • the positive electrode material provided by the present invention uses lithium nickel transition metal oxide A (large particle high nickel ternary polycrystalline positive electrode material) containing large particles and small particle lithium nickel transition metal oxide B (small particle high nickel ternary single crystal Positive electrode material), by controlling the crystallinity and particle size distribution of the high nickel active material after mixing, it can effectively improve the problem of particle crushing during cold pressing and circulation, increase the compaction density of high nickel powder, and ensure production The gas volume is low and the cycle performance is excellent.
  • lithium nickel transition metal oxide A large particle high nickel ternary polycrystalline positive electrode material
  • B small particle high nickel ternary single crystal Positive electrode material
  • the single-crystal-like means that the size of the primary particles is greater than 1 ⁇ m, but the primary particles are agglomerated.
  • the single crystal means that the size of the primary particles is greater than 1 ⁇ m, and there is no obvious agglomeration.
  • the range of D 104 ⁇ PSD is optionally 50 nm to 450 nm, 50 nm to 80 nm, 80 nm to 120 nm, 80 nm to 250 nm, 120 nm to 250 nm, 250 nm to 350 nm, 350 nm to 450 nm.
  • the range of D 104 ⁇ PSD is 80 nm to 250 nm.
  • the ⁇ PSD is 1.2 to 2.5, 1.5 to 2.2, 1.2 to 1.5, 1.5 to 2.1, 2.1 to 2.5, 2.5 to 3.1.
  • the particle size distribution of the positive electrode material is relatively concentrated.
  • the relative content of small-diameter particles can be reduced to avoid deterioration of the gas generation problem; at the same time, the compact density of the pole piece can be increased to meet the energy of high-capacity batteries At the same time, it reduces the probability that the positive electrode material particles are crushed under high pressure, and the particles are not easy to crack during the extrusion process.
  • the range of the ⁇ PSD is 1.5-2.2.
  • the positive electrode material has a D v 50 of 5 ⁇ m to 15 ⁇ m, 5 ⁇ m to 8 ⁇ m, 8 ⁇ m to 12 ⁇ m, 12 ⁇ m to 15 ⁇ m, and a D v 10 of 1 ⁇ m to 5 ⁇ m, 1 ⁇ m to 3 ⁇ m, and 3 ⁇ m to 5 ⁇ m.
  • D v 90 is 12 ⁇ m to 25 ⁇ m, 12 ⁇ m to 15 ⁇ m, 15 ⁇ m to 20 ⁇ m, and 20 ⁇ m to 25 ⁇ m.
  • D v 10 is the corresponding particle size when the cumulative volume distribution percentage of the sample reaches 10%
  • D v 50 is the corresponding particle size when the cumulative volume distribution percentage of the sample reaches 50%
  • D v 90 is the cumulative volume distribution percentage of the sample reaching 90 % Corresponds to the particle size.
  • the positive electrode material has a D v 50 of 8 ⁇ m to 12 ⁇ m, a D v 10 of 1 ⁇ m to 3 ⁇ m, and a D v 90 of 15 ⁇ m to 20 ⁇ m.
  • the D 104 is 40 nm to 200 nm, 40 nm to 50 nm, 50 nm to 100 nm, 100 nm to 150 nm, and 150 nm to 200 nm.
  • D 104 is a mixed system of secondary particle lithium nickel transition metal oxide A and single crystal/single crystal-like lithium nickel transition metal oxide B. After X-ray diffraction test, the peak intensity of the 104 crystal plane is fitted The calculation shows that when the mixed system is regarded as a whole, the average crystal grain size of the corresponding crystal.
  • D 104 is within the above range, the capacity of the positive electrode material is better, the polarization of the positive electrode material is smaller during the cycle, and the side reaction with the electrolyte is less.
  • the D 104 is 50nm-100nm.
  • the compact density of the positive electrode material is 3.3 g/cm 3 to 3.7 g/cm 3 .
  • the compacted density is less than 3.3g/cm 3 , the compacted density will be too small and the energy density will be too low.
  • the compacted density is greater than 3.7g/cm 3 , the compacted density will be too large, which will result in severe particle breakage and serious gas production.
  • specific surface area of the positive electrode material is 0.5m 2 /g ⁇ 1.5m 2 /g,0.5m 2 /g ⁇ 0.6m 2 /g,0.6m 2 /g ⁇ 1.0m 2 / g, 1m 2 /g ⁇ 1.5m 2 / g.
  • the true specific surface area of the positive electrode active material is within the above range, and the contact area between the electrolyte and the electrolyte is small, which is beneficial to suppress side reactions, avoid damage to the crystal structure of the positive electrode active material, and accelerate battery inflation.
  • the specific surface area of the positive electrode active material is within the above range, which is conducive to the use of less auxiliary materials when mixing to form the positive electrode slurry, which can meet the relatively strong adsorption performance of the positive electrode active material, the binder, and the conductive agent, and is conducive to improving the battery Energy density.
  • the specific surface area of the positive electrode material is 0.6m 2 /g ⁇ 1.0m 2 / g.
  • the positive electrode material provided by the present invention in the formula I of the chemical formula of the lithium nickel transition metal oxide A, 0.95 ⁇ a1 ⁇ 1, 1 ⁇ a1 ⁇ 1.05. Generally speaking, if a1 ⁇ 0.95, the material will be deficient in lithium and the gram capacity will be too low, while if a1>1.05, the lithium-rich will cause the residual lithium on the surface of the material to be too high, thereby deteriorating gas production.
  • the lithium-nickel transition metal oxide A in the present invention selects a layered lithium transition metal oxide with a high nickel content to increase the energy density of the battery; and if b1>0.98, it will lead to serious lithium-nickel mixed discharge, which will cause excessive gas production high.
  • the lithium nickel transition metal oxide A may be LiNi 0.7 Co 0.1 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 and LiNi 0.9 Co 0.05 Mn 0.05 O 2 may also be materials modified by M and/or X substitution of the above substances, where M is selected from Al, Ti, Zr, Nb, Sr , One or more of Sc, Sb, Y, Ba, B, C, Co, Mn, X is selected from F and/or Cl.
  • the lithium nickel transition metal oxide B selects a layered lithium transition metal oxide with a high nickel content to improve the energy density of the battery; and if b2>0.98, it will cause serious mixing of lithium nickel, resulting in excessive gas production high.
  • the lithium nickel transition metal oxide B may be LiNi 0.7 Co 0.1 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 and LiNi 0.9 Co 0.05 Mn 0.05 O 2 may also be materials modified by M′ and/or X′ substitution of the above substances, where M′ is selected from Al, Ti, Zr, A combination of one or more of Nb, Sr, Sc, Sb, Y, Ba, B, C, Co, Mn, X′ is selected from F and/or Cl.
  • the single-particle compressive strength of the lithium nickel transition metal oxide A is ⁇ 100 MPa
  • the single-particle compressive strength of the lithium nickel transition metal oxide B is ⁇ 50 MPa.
  • the above-mentioned two kinds of single-particle compressive strength lithium-nickel transition metal oxides are mixed to obtain a positive electrode material, which can improve the compressive performance of the overall positive electrode material.
  • single crystal/single crystal-like particles with small particle diameters are mainly used for filling the gap between secondary particles with larger particle size, the stress is relatively small, but when the compressive strength is too low, it may still be broken under the expansion of the pole piece or external force; while the larger particle size
  • the secondary particles bear most of the external force during the expansion or compression of the pole piece. Due to the large number of grain boundaries inside the secondary particles, external forces or micro-cracks are easily generated during the circulation process.
  • a mixed cathode material with a single particle compressive strength of lithium nickel transition metal oxide B ⁇ 50 MPa and a single particle compressive strength of lithium nickel transition metal oxide A ⁇ 100 MPa is selected to ensure the compressive performance of the mixed cathode material Satisfy the external force extrusion of pole piece preparation and circulation process.
  • the single particle compressive strength of the lithium nickel transition metal oxide A is higher than the single particle compressive strength of the lithium nickel transition metal oxide B.
  • the single particle compressive strength refers to "the particle size fluctuates by 10% in the average particle size D v 50, and a single secondary particle is used as a single particle under the action of external force. , The minimum pressure during crushing".
  • the lithium nickel transition metal oxide A has a D v 50 of 8 ⁇ m-15 ⁇ m, 8 ⁇ m-10 ⁇ m, 10 ⁇ m-12 ⁇ m, 12 ⁇ m-15 ⁇ m; a D v 10 of 3 ⁇ m-8 ⁇ m, 3 ⁇ m-5 ⁇ m , 5 ⁇ m ⁇ 8 ⁇ m; D v 90 is 15 ⁇ m ⁇ 25 ⁇ m, 15 ⁇ m ⁇ 18 ⁇ m, 18 ⁇ m ⁇ 20 ⁇ m, 20 ⁇ m ⁇ 25 ⁇ m.
  • the lithium nickel transition metal oxide A is secondary particles composed of primary particles, and the particle diameters of the primary particles are 30 nm to 800 nm, 30 nm to 100 m, 100 nm to 200 nm, and 200 nm to 500nm, 500nm ⁇ 800nm.
  • the particle size of the primary particles is too small, the capacity will increase, and the side reaction with the electrolyte will increase, and if the particle size of the primary particles is too large, the capacity will be too low.
  • the particle size of the primary particles is 200 nm to 500 nm.
  • the Dv 50 of the lithium nickel transition metal oxide B is 1 ⁇ m to 7 ⁇ m, 1 ⁇ m to 3 ⁇ m, 3 ⁇ m to 5 ⁇ m, 5 ⁇ m to 7 ⁇ m, D v 10 is 1 ⁇ m to 3 ⁇ m, D v 90 It is 5 ⁇ m to 10 ⁇ m, 5 ⁇ m to 8 ⁇ m, and 8 ⁇ m to 10 ⁇ m.
  • the lithium nickel transition metal oxide B has a D v 50 of 3 ⁇ m to 5 ⁇ m.
  • the mass ratio of the lithium nickel transition metal oxide A to the lithium nickel transition metal oxide B is 10:1 to 1:1, 10:1 to 4:1, 4: 1 ⁇ 2:1, 2:1 ⁇ 1:1.
  • the mass ratio of the lithium nickel transition metal oxide A to the lithium nickel transition metal oxide B is 4:1 to 2:1.
  • the surface of at least one active material in the lithium nickel transition metal oxide A and the lithium nickel transition metal oxide B is surface-modified, and the surface modification method includes at least One or more combinations of particle surface doping, coating oxide on particle surface, and coating carbon on particle surface, the doping and coating elements are selected from Mg, Al, Ti, Co, Fe, Cd , Zr, Mo, Zn, B, P, Cu, V, Ag one or more combinations.
  • a surface-modified layer on the surface of at least one active material in the lithium nickel transition metal oxide A and the lithium nickel transition metal oxide B is a surface modification layer, and the surface modification layer
  • the weight is 0.01wt% ⁇ 0.5wt% of the weight of the positive electrode material.
  • a second aspect of the present invention provides a method for preparing a cathode material according to the first aspect of the present invention, including:
  • the lithium nickel transition metal oxide A and the lithium nickel transition metal oxide B are mixed.
  • the lithium nickel transition metal oxide A and/or lithium nickel transition metal oxide B may be surface-modified, for example, the lithium nickel transition metal oxide A and/or Or lithium nickel transition metal oxide B is surface-modified separately and then mixed, wherein the surface modification methods of lithium nickel transition metal oxide A and lithium nickel transition metal oxide B may be the same or different; The transition metal oxide A and the lithium nickel transition metal oxide B are mixed first, and then the surface modification process is performed together.
  • the preparation method of the cathode material provided by the present invention may include: providing lithium nickel transition metal oxide A.
  • the method for providing the lithium nickel transition metal oxide A should be known to those skilled in the art, for example, it may include: mixing and sintering the raw materials of the lithium nickel transition metal oxide A to provide the lithium nickel transition Metal oxide A.
  • a person skilled in the art may select an appropriate raw material and a ratio according to the elemental composition of lithium nickel transition metal oxide A.
  • the raw materials of the lithium-nickel transition metal oxide A may include a precursor of the lithium-nickel transition metal oxide A, a lithium source, an M source, an X source, etc.
  • the ratio between the raw materials is generally referred to the lithium nickel transition metal oxide
  • the proportion of each element in A is matched.
  • the precursor of the lithium nickel transition metal oxide A may include, but is not limited to, Ni 0.7 Co 0.1 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 lithium source may be a lithium-containing compound, and the lithium-containing compound may be one or more of LiOH ⁇ H 2 O, LiOH, Li 2 CO 3 , Li 2 O, etc.
  • the M source may generally be a compound containing M elements
  • the compound containing M elements may be Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W,
  • the X source may be a compound containing X element
  • the compound containing X element may include but not limited to LiF , NaCl, etc. one or more combinations.
  • the sintering conditions may be 800° C. and the oxygen concentration ⁇ 20%.
  • the preparation method of the positive electrode material provided by the present invention may include: providing lithium nickel transition metal oxide B.
  • the method for providing the lithium nickel transition metal oxide B should be known to those skilled in the art, for example, it may include: mixing and sintering the raw materials of the lithium nickel transition metal oxide B to provide the lithium nickel transition Metal oxide B.
  • a person skilled in the art may select an appropriate raw material and a ratio according to the elemental composition of lithium nickel transition metal oxide B.
  • the raw materials of the lithium-nickel transition metal oxide B may include a precursor of the lithium-nickel transition metal oxide B, a lithium source, an M'source, an X'source, etc.
  • the ratio between the raw materials is generally referred to as lithium nickel transition metal oxide
  • the proportion of each element in B is matched.
  • the precursor of the lithium nickel transition metal oxide B may include, but not limited to, Ni 0.7 Co 0.1 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 lithium source may be a lithium-containing compound, and the lithium-containing compound may be one or more of LiOH ⁇ H 2 O, LiOH, Li 2 CO 3 , Li 2 O, etc.
  • the M'source can usually be a compound containing an M'element
  • the compound containing an M'element can be a compound containing Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y ,
  • the source of X′ may be a compound containing element X′
  • the compound containing element X′ may be It includes but is not limited to one or a combination of LiF, NaCl, etc.
  • the sintering conditions may be 700°C to 900°C, and the oxygen concentration ⁇ 15%.
  • the preparation method of the cathode material provided by the present invention may further include: modifying the surface of the lithium nickel transition metal oxide A and/or the lithium nickel transition metal oxide B.
  • the method of surface modification on the surface of lithium nickel transition metal oxide A and/or lithium nickel transition metal oxide B should be known to those skilled in the art, for example, it may include: converting lithium nickel transition metal oxide A And/or lithium nickel transition metal oxide B is sintered in the presence of a compound containing a doping element, a compound containing a coating element, or a carbon-coated precursor to convert lithium nickel transition metal oxide A and/or lithium
  • the surface of the nickel transition metal oxide B is surface-modified.
  • a person skilled in the art can select a suitable compound containing a doping element, a carbon-coated precursor or a compound containing a coating element, a ratio, a sintering condition, etc. according to the composition of the surface modification.
  • a suitable compound containing a doping element, a carbon-coated precursor or a compound containing a coating element, a ratio, a sintering condition, etc. according to the composition of the surface modification.
  • one or more of lithium nickel transition metal oxide A and/or lithium nickel transition metal oxide B and a certain amount of a compound containing a doping element, a compound containing a coating element, and a precursor of carbon coating The combination of species is placed in a mixing device for mixing, and then placed in an atmosphere furnace for sintering to form lithium nickel transition metal oxide A and/or lithium nickel transition metal oxide B.
  • the compound containing the doped metal element may be oxide, nitrate, carbon of at least one element of Mg, Al, Ti, Fe, Cd, Zr, Mo, Zn, B, Cu, V, Ag
  • the compound containing the coating element may be one or more containing Al, Ba, Zn, Ti, Co, W, Y, Si, Sn, B, P Oxides, nitrates, phosphates, carbonates, etc.
  • the usage amount of the doping metal element may be 0wt% to 2wt%
  • the usage amount of the coating element may be 0wt% to 2wt %
  • the sintering conditions may be 200°C to 700°C.
  • the preparation method of the cathode material provided by the present invention may further include: mixing lithium nickel transition metal oxide A with lithium nickel transition metal oxide B, the lithium nickel transition metal oxide A and/or the lithium nickel transition metal
  • the oxide B may be surface-modified, and the lithium-nickel transition metal oxide A and/or lithium-nickel transition metal oxide B may also not be surface-modified.
  • lithium nickel transition metal oxide A and lithium nickel transition metal oxide B are mixed in a mass ratio of 10:1 to 1:1 and mixed uniformly.
  • a third aspect of the present invention provides an electrochemical energy storage device including the cathode material described in the first aspect of the present invention.
  • 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 invention is not limited thereto.
  • a lithium-ion battery in a lithium-ion battery, it includes a positive pole piece, a negative pole piece, a separator that is spaced between the positive pole piece and the negative pole piece, and an electrolyte, wherein the positive pole piece includes the positive electrode according to the first aspect of the present invention material.
  • the method for preparing the lithium-ion battery should be known to those skilled in the art.
  • the positive pole piece, the separator, and the negative pole piece can each be a layered body, so that they can be cut to the target size in turn Stacked, it can also be wound to the target size for the formation of batteries, and can be further combined with the electrolyte to form a lithium-ion battery.
  • the positive electrode tab includes a positive electrode current collector and a positive electrode active material layer on the positive electrode current collector, the positive electrode active material layer includes the positive electrode material, binder, and electrical conductivity of the first aspect of the invention Agent.
  • a person skilled in the art may select a suitable method to prepare the positive electrode sheet.
  • the method may include the steps of mixing a positive electrode material, a binder, and a conductive agent to form a slurry, and then coating the positive electrode current collector.
  • the binder generally includes a fluorine-containing polyolefin-based binder.
  • 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, etc. or their modification (for example, carboxylic acid, Modified derivatives such as acrylic acid and acrylonitrile.
  • PVDF polyvinylidene fluoride
  • the mass percentage content of the binder may be due to the poor conductivity of the binder itself, so the amount of the binder may not be too high.
  • the mass percentage content of the binder in the positive electrode active material layer is less than or equal to 0.5 wt% to 3 wt%, so as to obtain a lower pole piece impedance.
  • the conductive agent of the positive pole piece may be various conductive agents suitable for lithium ion (secondary) batteries in the art, for example, may include but not limited to acetylene black, conductive carbon black, carbon fiber (VGCF), carbon nanotubes (CNT), Ketjen Black, etc. one or more combinations.
  • the weight of the conductive agent may account for 1 wt% to 10 wt% of the total mass of the positive electrode active material layer. More preferably, the weight ratio of the conductive agent to the positive electrode material in the positive electrode sheet is greater than or equal to 1.0 wt% to 5.0 wt%.
  • the positive electrode current collector of the positive electrode tab can generally be a layered body, the positive electrode current collector is usually a structure or part that can collect current, and the positive electrode current collector can be various
  • the material of the positive electrode current collector of the lithium ion battery for example, the positive electrode current collector may include but not limited to metal foil and the like, and more specifically may include but not limited to copper foil, aluminum foil and the like.
  • 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 negative electrode active materials of lithium ion batteries in the art, for example, may include but not limited to graphite, soft carbon, hard carbon, carbon fiber, mesophase carbon microspheres, silicon-based materials , Tin-based materials, lithium titanate or other metals that can be alloyed with lithium, etc., in one or more combinations.
  • 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 usually 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 a lithium ion battery in the art.
  • the negative electrode current collector may include but is not limited to The metal foil and the like may more specifically include but not limited to copper foil and the like.
  • the separator may be various materials suitable for the separator of the lithium ion battery in the art, for example, may include but not limited to polyethylene, polypropylene, polyvinylidene fluoride, aramid, and poly One or more combinations of ethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester and natural fiber.
  • the electrolyte may be various electrolytes suitable for lithium ion batteries in the art, for example, the electrolyte generally includes an electrolyte and a solvent, and the electrolyte may generally include a lithium salt and the like, more specifically
  • the lithium salt may be an inorganic lithium salt and/or an organic lithium salt, etc., and may specifically include but not limited to, the lithium salt may be selected from 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 between 0.8 mol/L and 1.5 mol/L.
  • the solvent may be any solvent suitable for an electrolyte of a lithium ion battery 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, carbonic acid Propylene ester, butylene carbonate, pentenyl carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, etc. or a combination of one or more of their halogenated derivatives.
  • one or more of the method steps mentioned in the present invention does not exclude that there may be other method steps before or after the combination step or that other method steps may be inserted between these explicitly mentioned steps unless otherwise Explained; It should also be understood that the combined connection relationship between one or more devices/devices mentioned in the present invention does not exclude that there may be other devices/devices or those mentioned explicitly in these before and after the combined device/device Other devices/apparatuses can also be inserted between the two devices/apparatuses unless otherwise stated.
  • each method step is only a convenient tool to identify each method step, not to limit the order of each method step or to limit the scope of the present invention, the change or adjustment of its relative relationship, in If the technical content is not substantially changed, it should be regarded as the scope of the invention.
  • the precursors of the above lithium nickel transition metal oxide A, Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 , and the Li-containing compound LiOH ⁇ H 2 O are mixed in a mixing device at a molar ratio of 1:1.05, and then mixed Put it in an atmosphere furnace at 800°C for sintering, and after cooling, it will be lithium nickel transition metal oxide A through mechanical grinding;
  • lithium nickel transition metal oxide A and 0.4wt% compound Al 2 O 3 containing the coating element Al in the mixing equipment for mixing, and then put it in an atmosphere furnace for sintering at 500°C for 5h to form lithium nickel
  • the coating layer of the transition metal oxide A is to obtain the surface-modified lithium nickel transition metal oxide A.
  • the precursor of the above lithium nickel transition metal oxide B Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 and the Li-containing compound LiOH ⁇ H 2 O in a molar ratio of 1:1.05 are placed in the mixing equipment for mixing, and then It is placed in an atmosphere furnace at 850°C for sintering, and after cooling, it is ground by the airflow powder to be lithium nickel transition metal oxide B;
  • Lithium-nickel transition metal oxide B and 0.2wt% of Al 2 O 3 compound containing coating element Al were placed in the mixing equipment for mixing, and then placed in an atmosphere furnace for sintering at 500°C for 5 hours to form a lithium nickel transition
  • the coating layer of the metal oxide B, that is, the surface-modified lithium nickel transition metal oxide B is obtained.
  • Step 1 Mix the positive electrode material obtained above, the binder polyvinylidene fluoride, and the conductive agent acetylene black according to a mass ratio of 98:1:1, add N-methylpyrrolidone (NMP), and stir evenly under the action of a vacuum mixer Obtain the positive electrode slurry; evenly coat the positive electrode slurry on an aluminum foil with a thickness of 12 ⁇ m;
  • NMP N-methylpyrrolidone
  • Step 2 The coated pole piece is dried in an oven at 100° C. to 130° C., cold pressed, and slit to obtain a positive electrode 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 fully dried lithium salt is dissolved in an organic solvent and mixed uniformly to obtain an electrolyte.
  • the concentration of the lithium salt is 1 mol/L.
  • the positive electrode, separator and negative electrode in order, so that the separator is between the positive and negative electrodes to play the role of isolation, and then wound into a square bare cell, put into aluminum plastic film, and then in 80 After baking and removing water at °C, inject the corresponding non-aqueous electrolyte and seal, after standing, hot and cold pressing, formation, jig, volume division and other processes, the finished battery is obtained.
  • the difference lies in the preparation method of the cathode material: the precursor particle size of the lithium nickel transition metal oxide B is 4 ⁇ m, the surface modified lithium nickel transition metal oxide A and the surface modified lithium nickel transition metal The mass ratio of oxide B is 7:3.
  • the difference is in the preparation method of the cathode material: the precursor particle size of the lithium nickel transition metal oxide B is 6 ⁇ m, the surface modified lithium nickel transition metal oxide A and the surface modified lithium nickel transition metal The mass ratio of oxide B is 6:4.
  • the difference is in the preparation method of the cathode material: the precursor particle size of the lithium nickel transition metal oxide B is 7 ⁇ m, the surface modified lithium nickel transition metal oxide A and the surface modified lithium nickel transition metal The mass ratio of oxide B is 5:5.
  • the difference is in the preparation method of the cathode material: the precursor particle size of the lithium nickel transition metal oxide B is 2 ⁇ m, the surface modified lithium nickel transition metal oxide A and the surface modified lithium nickel transition metal The mass ratio of oxide B is 9:1.
  • the precursor of lithium nickel transition metal oxide A (polycrystalline LiNi 0.90 Co 0.05 Mn 0.05 O 2 ) is Ni 0.90 Co 0.05 Mn with a particle size of 15 ⁇ m 0.05 (OH) 2
  • the precursor of lithium nickel transition metal oxide B (single crystal LiNi 0.90 Co 0.05 Mn 0.05 O 2 ) is Ni 0.90 Co 0.05 Mn 0.05 (OH) 2 .
  • the preparation method of the positive electrode material the precursor of lithium nickel transition metal oxide A (polycrystalline LiNi 0.70 Co 0.15 Mn 0.15 O 2 ) is Ni 0.70 Co 0.15 Mn with a particle size of 12 ⁇ m 0.15 (OH) 2
  • the precursor of lithium nickel transition metal oxide B single crystal LiNi 0.96 Co 0.02 Mn 0.02 O 2
  • the precursor of lithium nickel transition metal oxide B single crystal LiNi 0.96 Co 0.02 Mn 0.02 O 2
  • Ni 0.96 Co 0.02 Mn 0.02 (OH) 2 the precursor of lithium nickel transition metal oxide A (polycrystalline LiNi 0.70 Co 0.15 Mn 0.15 O 2 ) is Ni 0.70 Co 0.15 Mn with a particle size of 12 ⁇ m 0.15 (OH) 2
  • the precursor of lithium nickel transition metal oxide B single crystal LiNi 0.96 Co 0.02 Mn 0.02 O 2
  • Ni 0.96 Co 0.02 Mn 0.02 (OH) 2 the precursor of lithium nickel transition metal oxide A (polycrystalline LiNi 0.70 Co 0.15 Mn 0.15
  • the preparation method of the positive electrode material the precursor of lithium nickel transition metal oxide A (polycrystalline LiNi 0.96 Co 0.02 Mn 0.02 O 2 ) is Ni 0.96 Co 0.02 Mn with a particle size of 8 ⁇ m 0.02 (OH) 2
  • the precursor of lithium nickel transition metal oxide B single crystal LiNi 0.70 Co 0.15 Mn 0.15 O 2
  • the precursor of lithium nickel transition metal oxide B single crystal LiNi 0.70 Co 0.15 Mn 0.15 O 2
  • Ni 0.70 Co 0.15 Mn 0.15 (OH) 2 the precursor of lithium nickel transition metal oxide A (polycrystalline LiNi 0.96 Co 0.02 Mn 0.02 O 2 ) is Ni 0.96 Co 0.02 Mn with a particle size of 8 ⁇ m 0.02 (OH) 2
  • the precursor of lithium nickel transition metal oxide B single crystal LiNi 0.70 Co 0.15 Mn 0.15 O 2
  • Ni 0.70 Co 0.15 Mn 0.15 (OH) 2 the precursor of lithium nickel transition metal oxide A (polycrystalline LiNi 0.96 Co 0.02 Mn 0.02
  • the difference lies in the preparation method of the positive electrode material: the lithium nickel transition metal oxide A precursor Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 , the Li-containing compound LiOH ⁇ H 2 O, and M
  • the compound ZrO 2 is placed in a mixing equipment for mixing at a molar ratio of 0.995:1.05:0.005, and then placed in an atmosphere furnace at 800°C for sintering. After cooling, it is lithium nickel transition metal oxide A (more Crystalline Li(Ni 0.8 Co 0.1 Mn 0.1 ) 0.995 Zr 0.005 O 2 ).
  • the difference lies in the preparation method of the positive electrode material: the lithium nickel transition metal oxide B precursor Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 , the Li-containing compound LiOH ⁇ H 2 O, and M '
  • the compound ZrO 2 is placed in a mixing equipment for mixing at a molar ratio of 0.995:1.05:0.005, and then placed in an atmosphere furnace for sintering at 850°C. After cooling, it is lithium nickel transition metal oxide B (by mechanical grinding) Single crystal Li(Ni 0.8 Co 0.1 Mn 0.1 ) 0.995 Zr 0.005 O 2 ).
  • the difference lies in the preparation method of the cathode material: the difference is that the precursor of lithium nickel transition metal oxide A is Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 , and the Li-containing compound LiOH ⁇ H 2 O ⁇ The compound X containing LiF with a molar ratio of 1:1.05:0.01 is placed in the mixing equipment for mixing, and then placed in an atmosphere furnace at 800°C for sintering. After cooling, it is lithium nickel transition metal oxide A through mechanical grinding (Polycrystalline LiNi 0.8 Co 0.1 Mn 0.1 O 1.99 F 0.01 ).
  • the difference lies in the preparation method of the positive electrode material: the lithium nickel transition metal oxide B precursor Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 , the Li-containing compound LiOH ⁇ H 2 O, and X '
  • the compound LiF has a molar ratio of 1:1.05:0.01, placed in the mixing equipment for mixing, and then placed in an atmosphere furnace at 800 °C for sintering, and after cooling, mechanically ground to obtain lithium nickel transition metal oxide B (single crystal LiNi 0.8 Co 0.1 Mn 0.1 O 1.99 F 0.01 ).
  • the particle size of the precursor of lithium nickel transition metal oxide A is 8 ⁇ m.
  • the particle size of the precursor of lithium nickel transition metal oxide A is 15 ⁇ m.
  • Example 2 The same as Example 1, except that when preparing the lithium nickel transition metal oxide A and the lithium nickel transition metal oxide B, no coating treatment is performed.
  • the positive electrode active material contains only lithium nickel transition metal oxide A (polycrystalline LiNi 0.8 Co 0.1 Mn 0.1 O 2 ) and no lithium nickel transition metal oxide B (Single crystal LiNi 0.8 Co 0.1 Mn 0.1 O 2 ).
  • the cathode active material contains only lithium nickel transition metal oxide B (single crystal LiNi 0.8 Co 0.1 Mn 0.1 O 2 ), and no lithium nickel transition metal oxide A (Polycrystalline LiNi 0.8 Co 0.1 Mn 0.1 O 2 ).
  • lithium nickel transition metal oxide B is polycrystalline LiNi 0.8 Co 0.1 Mn 0.1 O 2 , and the particle size of the precursor of lithium nickel transition metal oxide B is 3 ⁇ m.
  • the precursor of lithium nickel transition metal oxide B (single crystal LiNi 0.5 Co 0.2 Mn 0.3 O 2 ) is Ni 0.5 Co 0.2 Mn 0.3 (OH) 2
  • the mass ratio of the surface-modified lithium nickel transition metal oxide A to the surface-modified lithium nickel transition metal oxide B is 7:3.
  • the precursor of lithium nickel transition metal oxide A (polycrystalline LiNi 0.5 Co 0.2 Mn 0.3 O 2 ) is Ni 0.5 Co 0.2 Mn 0.3 (OH) 2
  • the mass ratio of the surface-modified lithium nickel transition metal oxide A to the surface-modified lithium nickel transition metal oxide B is 7:3.
  • Example 1 Compared with Example 1, the difference is in the preparation method of the positive electrode material: the particle size of the precursor of the lithium nickel transition metal oxide B is 7 ⁇ m, the surface modified lithium nickel transition metal oxide A and the surface modified lithium nickel transition The mass ratio of metal oxide B is 2:8.
  • Example 1 Compared with Example 1, the difference is the preparation method of the positive electrode material: the particle size of the precursor of the lithium nickel transition metal oxide B is 1 ⁇ m, the surface modified lithium nickel transition metal oxide A and the surface modified lithium nickel transition The mass ratio of metal oxide B is 2:8.
  • FIG. 1 is an electron micrograph of the positive electrode material prepared in Example 1 of the present invention. As shown in FIG. 1, the particles are not crushed, and the gaps between the polycrystalline large particles are filled with single crystals, and the compaction density is high.
  • FIG. 2 is an electron micrograph of the positive electrode material prepared in Comparative Example 1 of the present invention. As shown in FIG. 2, the particles are crushed, which is likely to cause serious gas production, and there are many gaps between the particles, and the compacted density is low.
  • ⁇ PSD (Dv90-Dv10)/Dv50.
  • the volume expansion rate (%) of the battery (volume after standing for 30 days/initial volume-1) ⁇ 100%.
  • Lithium-ion battery was allowed to stand for 2h at a constant temperature of 25°C, then charged to 4.2V according to 1/3C under 2.8V ⁇ 4.2V, then charged at 4.2V with constant voltage to current ⁇ 0.05mA, and left for 5min , And then discharge to 2.8V according to 1C, and record the capacity of the lithium ion battery.
  • the test results are shown in Table 2.
  • Table 1 and Table 2 are specific parameters and performance test results of the positive electrode materials of Examples 1 to 15 and Comparative Examples 1 to 7. It can be seen from the comparison between the examples and the comparative examples that the examples of the present invention mix the large-particle lithium nickel transition metal oxide A with the small-particle lithium nickel transition metal oxide B and control the crystallization of the high nickel active material after mixing Degree and particle size distribution, effectively improve the problem of particle crushing during cold pressing and circulation, increase the compaction density of high nickel powder, while ensuring low gas production and excellent cycle performance.
  • Comparative Example 1 and Comparative Example 2 since the positive electrode material contains only secondary particles or single crystal particles, the compacted density of the prepared positive electrode sheet is relatively low, which is not conducive to increasing the volumetric energy density of the battery; The positive electrode active materials of ratio 1 and comparison 2 are prone to particle breakage during cold pressing and circulation of the pole piece, resulting in serious gas production problems and high volume expansion rate of the battery.
  • Comparative Example 3 although a high-nickel positive electrode material with a mixture of large and small particle diameters is used, the secondary particles with small particle diameters have a larger specific surface area and a higher amount of residual lithium on the surface, which degrades the gas production of lithium-ion batteries. performance.
  • the mixed cathode materials of Comparative Examples 4 and 5 include LiNi 0.5 Co 0.2 Mn 0.3 O 2 with a relatively low nickel content, although by controlling the crystallinity and particle size distribution of the high nickel active material after mixing, the production of lithium ion batteries The gas problem is improved, but it cannot meet the high energy density requirements of the battery.
  • the D 104 ⁇ PSD of the high-nickel cathode material after mixing is too high, indicating that the particle size distribution range of the material is too large, and the relative content of fine particles with small particle diameters is too high, so the cycle performance is poor and the gas production problem is relatively high. serious.
  • Example 8 and Example 14 It can be seen from Example 8 and Example 14 that, under the control of the crystallinity and particle size distribution of the high nickel active material after mixing, the compressive strength of the secondary particles and single crystal particles constituting the material is optimized, The pressure resistance of the positive electrode material can be further improved, which is more conducive to improving gas production and safety problems of high-capacity batteries and increasing the volume energy density of lithium ion batteries.

Abstract

本发明涉及电池技术领域，特别是涉及一种高压实密度正极材料及电化学储能装置，所述正极材料包括锂镍过渡金属氧化物A和锂镍过渡金属氧化物B，所述锂镍过渡金属氧化物A为二次颗粒，其化学式如式I所示：Lia1(Nib1Coc1Mnd1)x1M1-x1O2-e1Xe1；所述锂镍过渡金属氧化物B为单晶结构或类单晶结构，其化学式如式II所示：Lia2(Nib2Coc2Mnd2)x2M'1-x2O2-e2X'e2(II)；所述正极材料的晶粒尺寸D104与所述正极材料的粒径分布变化率ΔPSD满足：50nm≤D 104×ΔPSD≤600nm。本发明中的正极材料包括大颗粒的锂镍过渡金属氧化物A以及小颗粒锂镍过渡金属氧化物B，提高电池的能量密度；通过调控混合后正极材料的结晶度和粒径分布，改善高镍粉体在冷压以及循环过程中的颗粒破碎问题，提高高镍活性材料的粉体压实密度，保证产气量较低，循环性能优良。

Description

一种高压实密度正极材料及电化学储能装置 技术领域
本发明涉及电池技术领域，特别是涉及一种高压实密度正极材料及电化学储能装置。
背景技术
正极材料为了追求高能量密度，一般会从两个方面进行优化。一方面提高正极材料的镍含量以提高其可逆克容量，另外一方面，通过大小颗粒搭配以提高其粉体压实密度。目前高镍三元材料具备了高的可逆克容量，但并不具备高的粉末压实密度。
目前，常见的高粉体压实密度有两种方案。一种为大颗粒多晶混合小颗粒多晶。此种方法通常用于低镍三元材料中，其克容量偏低，导致正极材料的能量密度低。少数采用了大颗粒高镍多晶混合小颗粒高镍多晶，这种设计的能量密度高，但由于小颗粒高镍多晶的在冷压过程中容易破碎，导致产气严重。另外一种方案为颗粒分布较宽的高镍多晶材料，但过宽的颗粒分布在冷压及循环过程中也容易破碎，产生同样的产气问题。
发明内容
鉴于以上所述现有技术的缺点，本发明的目的在于提供一种高压实密度正极材料以及使用该正极材料的电化学储能装置。本发明的正极材料可以改善冷压过程中的颗粒破碎对产气性能问题。
为实现上述目的及其他相关目的，本发明的一方面提供一种正极材料，正极材料包括锂镍过渡金属氧化物A和锂镍过渡金属氧化物B，所述锂镍过渡金属氧化物A为二次颗粒，所述锂镍过渡金属氧化物A的化学式如式I所示：
Li a1(Ni b1Co c1Mn d1) x1M 1-x1O 2-e1X e1         (I)
式I中，0.95≤a1≤1.05，0.7≤b1≤0.98，0.01≤c1≤0.15，0.01≤d1≤0.3，0.95≤x1≤1，0≤e1≤0.1；其中，M选自Al、Ti、Zr、Nb、Sr、Sc、Sb、Y、Ba、B、C、Co、Mn中的一种或多种的组合，X选自F和/或Cl；
所述锂镍过渡金属氧化物B为单晶或类单晶形貌颗粒，所述锂镍过渡金属氧化物B的化学式如式II所示：
Li a2(Ni b2Co c2Mn d2) x2M’ 1-x2O 2-e2X’ e2          (II)
式II中，0.95≤a2≤1.05，0.7≤b2≤0.98，0.01≤c2≤0.15，0.01≤d2≤0.3，0.95≤x2≤1，0≤e2≤0.1； M’选自Al、Ti、Zr、Nb、Sr、Sc、Sb、Y、Ba、B、C、Co、Mn中的一种或多种的组合，X’选自F和/或Cl；
所述正极材料的晶粒尺寸D 104与所述正极材料的粒径分布变化率ΔPSD满足：50nm≤D 104×ΔPSD≤450nm，其中，ΔPSD为所述正极材料经体积粒度分布测量粒径，按照公式ΔPSD＝(D v90-D v10)/D v50计算得出的粒径分布变化率；D 104为所述正极材料经XRD射线衍射测试，对104晶面对应峰值拟合得到的晶粒尺寸。
本发明另一方面提供电化学储能装置，包括本发明的正极材料。
相对于现有技术，本发明的有益效果为：
本发明中的正极材料包括大颗粒的锂镍过渡金属氧化物A(大颗粒高镍三元多晶正极材料)以及小颗粒锂镍过渡金属氧化物B(小颗粒高镍三元单晶或类单晶正极材料)，由于正极材料A和正极材料B的镍含量较高，能够提高电池的能量密度；同时，通过调控混合后正极材料的结晶度和粒径分布，有效地改善高镍活性材料在冷压以及循环过程中的颗粒破碎问题，提高高镍活性材料的粉体压实密度，保证产气量较低，循环性能优良。
附图说明
图1本发明实施例1制备的正极材料的电镜图。
图2本发明对比例1制备的正极材料的电镜图。
具体实施方式
下面详细说明根据本发明的高压实密度正极材料以及使用该正极材料的电化学储能装置。
本发明的第一方面提供一种正极材料，所述正极材料包括锂镍过渡金属氧化物A和锂镍过渡金属氧化物B，所述锂镍过渡金属氧化物A为二次颗粒，所述锂镍过渡金属氧化物A的化学式如式I所示：
Li a1(Ni b1Co c1Mn d1) x1M 1-x1O 2-e1X e1         (I)
式I中，0.95≤a1≤1.05，0.7≤b1≤0.98，0.01≤c1≤0.15，0.01≤d1≤0.3，0.95≤x1≤1，0≤e1≤0.1；其中，M选自Al、Ti、Zr、Nb、Sr、Sc、Sb、Y、Ba、B、C、Co、Mn中的一种或多种的组合，X选自F和/或Cl；
所述锂镍过渡金属氧化物B为单晶或类单晶形貌颗粒，所述锂镍过渡金属氧化物B的化学 式如式II所示：
Li a2(Ni b2Co c2Mn d2) x2M’ 1-x2O 2-e2X’ e2          (II)
式II中，0.95≤a2≤1.05，0.7≤b2≤0.98，0.01≤c2≤0.15，0.01≤d2≤0.3，0.95≤x2≤1，0≤e2≤0.1；M’选自Al、Ti、Zr、Nb、Sr、Sc、Sb、Y、Ba、B、C、Co、Mn中的一种或多种的组合，X’选自F和/或Cl；
所述正极材料的晶粒尺寸与所述正极材料的粒径分布变化率ΔPSD满足：50nm≤D 104×ΔPSD≤450nm，其中，ΔPSD为所述正极材料经体积粒度分布测量粒径，按照公式ΔPSD＝(D v90-D v10)/D v50计算得出的粒径分布变化率；D 104为所述正极材料经XRD射线衍射测试，对104晶面对应峰值拟合得到的晶粒尺寸，D 104单位为nm。
本发明所提供的正极材料使用含有大颗粒的锂镍过渡金属氧化物A(大颗粒高镍三元多晶正极材料)与小颗粒锂镍过渡金属氧化物B(小颗粒高镍三元单晶正极材料)的混合材料，通过控制混合后高镍活性材料的结晶度和粒径分布，有效地改善冷压和循环过程中的颗粒破碎问题，提高高镍粉体的压实密度，同时保证产气量较低，循环性能优良。
本发明所提供的正极材料中，所述类单晶是指一次颗粒的尺寸大于1μm，但一次颗粒存在一定团聚。而单晶是指一次颗粒的尺寸大于1μm，且无明显团聚。
本发明所提供的正极材料中，所述D 104×ΔPSD的范围可选的为50nm～450nm、50nm～80nm、80nm～120nm、80nm～250nm、120nm～250nm、250nm～350nm、350nm～450nm。
优选地，所述D 104×ΔPSD的范围为80nm～250nm。
本发明所提供的正极材料中，所述ΔPSD为1.2～2.5、1.5～2.2、1.2～1.5、1.5～2.1、2.1～2.5、2.5～3.1。当ΔPSD在上述范围时，正极材料的粒度分布较集中，一方面可以降低小粒径颗粒的相对含量，避免劣化产气问题；同时提高制成极片的压实密度，满足高容量电池的能量发挥，同时降低正极材料颗粒在高压力下被压碎的几率，颗粒不容易在挤压过程中开裂。
优选地，所述ΔPSD的范围为1.5～2.2。
本发明所提供的正极材料中，所述正极材料的D v50为5μm～15μm、5μm～8μm、8μm～12μm、12μm～15μm，D v10为1μm～5μm、1μm～3μm、3μm～5μm，D v90为12μm～25μm、12μm～15μm、15μm～20μm、20μm～25μm。D v10为样品的体积累计分布百分数达到10％时对应的粒径；D v50为样品的体积累计分布百分数达到50％时对应的粒径；D v90为样品的体积累计分布百分数达到90％时对应的粒径。
优选地，所述正极材料的D v50为8μm～12μm，D v10为1μm～3μm，D v90为15μm～20μm。
本发明所提供的正极材料中，所述D 104为40nm～200nm、40nm～50nm、50nm～100nm、100nm～150nm、150nm～200nm。本发明中D 104为二次颗粒锂镍过渡金属氧化物A与单晶/类单晶锂镍过渡金属氧化物B的混合体系，经X射线衍射测试，以104晶面峰强进行拟合后计算得出的，体现的是将混合体系看作一个整体时，对应的晶体的平均晶粒尺寸。D 104在上述范围内时，正极材料的容量发挥较好，循环过程中正极材料的极化较小，与电解液的副反应较少。
优选地，所述D 104为50nm～100nm。
本发明所提供的正极材料中，所述正极材料的压实密度为3.3g/cm 3～3.7g/cm 3。通常情况下，如果压实密度＜3.3g/cm 3，会导致压实密度过小，使得能量密度过低。而如果压实密度＞3.7g/cm 3，会导致压实密度过大，从而使得颗粒破碎严重，导致产气严重。
本发明所提供的正极材料中，所述正极材料的比表面积为0.5m 2/g～1.5m 2/g、0.5m 2/g～0.6m 2/g、0.6m 2/g～1.0m 2/g、1m 2/g～1.5m 2/g。本发明所述的正极活性材料中，正极活性材料的真实比表面积在上述范围内，电解液与其接触面积较少，有利于抑制副反应，避免破坏正极活性材料的晶体结构、加速电池胀气问题。同时正极活性材料的比表面积在上述范围内，有利于在混合形成正极浆料时，使用较少的辅料既可以满足正极活性材料与粘结剂、导电剂吸附性能相对较强，有利于提升电池的能量密度。
优选地，所述正极材料的比表面积为0.6m 2/g～1.0m 2/g。
本发明所提供的正极材料中，所述锂镍过渡金属氧化物A的化学式的式I中0.95≤a1≤1、1≤a1≤1.05。通常来说，如果a1＜0.95时，会使得材料缺锂导致克容量过低，而如果a1＞1.05时，由于富锂会导致材料表面残锂过高，从而恶化产气。
本发明所提供的正极材料中，所述锂镍过渡金属氧化物A的化学式的式I中0.7≤b1≤0.75、0.75≤b1≤0.8、0.8≤b1≤0.85、0.85≤b1≤0.9、0.9≤b1≤0.98。本发明中的锂镍过渡金属氧化物A选择镍含量较高的层状锂过渡金属氧化物，提高电池的能量密度；而如果b1＞0.98，会导致锂镍混排严重，从而使得产气量过高。具体的，所述锂镍过渡金属氧化物A可以为LiNi 0.7Co 0.1Mn 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，也可以为对上述物质进行M和/或X取代改性后的材料，其中M选自Al、Ti、Zr、Nb、Sr、Sc、Sb、Y、Ba、B、C、Co、Mn中的一种或多种的组合，X选自F和/或Cl。
本发明所提供的正极材料中，所述锂镍过渡金属氧化物B的化学式的式II中0.7≤b2≤0.75、 0.75≤b2≤0.8、0.8≤b2≤0.85、0.85≤b2≤0.9、0.9≤b2≤0.98。本发明中的锂镍过渡金属氧化物B选择镍含量较高的层状锂过渡金属氧化物，提高电池的能量密度；而如果b2＞0.98，会导致锂镍混排严重，从而使得产气量过高。具体的，所述锂镍过渡金属氧化物B可以为LiNi 0.7Co 0.1Mn 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，也可以为对上述物质进行M’和/或X’取代改性后的材料，其中M’选自Al、Ti、Zr、Nb、Sr、Sc、Sb、Y、Ba、B、C、Co、Mn中的一种或多种的组合，X’选自F和/或Cl。
本发明所提供的正极材料中，所述锂镍过渡金属氧化物A的单颗粒抗压强度≥100MPa，所述锂镍过渡金属氧化物B的单颗粒抗压强度≥50MPa。本发明中选择上述两种单颗粒抗压强度的锂镍过渡金属氧化物经混合得到正极材料，可以提高整体正极材料的抗压性能，其中粒径较小的单晶/类单晶颗粒主要用于填充粒径较大的二次颗粒粉体之间的间隙、受力相对较小，但是抗压强度过低时在极片膨胀或外力作用下仍然可能发生破碎；而粒径较大的二次颗粒在极片的膨胀或受压作用时承担着大部分外力作用，由于二次颗粒内部存在大量晶界、外力或循环过程中容易产生微裂纹。本发明中选择锂镍过渡金属氧化物B的单颗粒抗压强度≥50MPa、锂镍过渡金属氧化物A的单颗粒抗压强度≥100MPa的混合正极材料，保证混合后的正极材料抗压性能能够满足极片制备以及循环过程的外力挤压。优选的，所述锂镍过渡金属氧化物A的单颗粒抗压强度高于所述锂镍过渡金属氧化物B的单颗粒抗压强度。
本发明所提供的正极活性材料中，所述单颗粒抗压强度，是指“粒径在平均粒径D v50上下波动10％范围、单独的一个二次颗粒作为单颗粒，在外力作用下，压碎时的最小压强”。
本发明所提供的正极材料中，所述锂镍过渡金属氧化物A的D v50为8μm～15μm、8μm～10μm、10μm～12μm、12μm～15μm；D v10为3μm～8μm、3μm～5μm、5μm～8μm；D v90为15μm～25μm、15μm～18μm、18μm～20μm、20μm～25μm。
本发明所提供的正极材料中，所述锂镍过渡金属氧化物A为由一次颗粒组成的二次颗粒，所述一次颗粒的粒径为30nm～800nm、30nm～100m、100nm～200nm、200nm～500nm、500nm～800nm。通常来说，一次颗粒的粒径如果过小，会导致容量升高，与电解液的副反应增加，而一次颗粒的粒径如果太大，则会导致容量过低。
优选地，所述一次颗粒的粒径为200nm～500nm。
本发明所提供的正极材料中，所述锂镍过渡金属氧化物B的D v50为1μm～7μm、1μm～3μm、3μm～5μm、5μm～7μm，D v10为1μm～3μm，D v90为5μm～10μm、5μm～8μm、8μm～10μm。
优选地，所述锂镍过渡金属氧化物B的D v50为3μm～5μm。
本发明所提供的正极材料中，所述锂镍过渡金属氧化物A与所述锂镍过渡金属氧化物B的质量比为10:1～1:1、10:1～4:1、4:1～2:1、2:1～1:1。
优选地，所述锂镍过渡金属氧化物A与所述锂镍过渡金属氧化物B的质量比为4:1～2:1。
本发明所提供的正极材料中，所述锂镍过渡金属氧化物A与所述锂镍过渡金属氧化物B中的至少一种活性物质的表面经过表面修饰，所述表面修饰的方法至少包括在颗粒表面掺杂、在颗粒表面包覆氧化物、在颗粒表面包覆碳的一种或多种的组合，所述掺杂以及包覆的元素选自Mg、Al、Ti、Co、Fe、Cd、Zr、Mo、Zn、B、P、Cu、V、Ag中的一种或多种的组合。
本发明所提供的正极材料中，锂镍过渡金属氧化物A与所述锂镍过渡金属氧化物B中的至少一种活性物质的表面经过表面修饰的层为表面修饰层，所述表面修饰层的重量为正极材料重量的0.01wt％～0.5wt％。
本发明的第二方面提供本发明第一方面的正极材料的制备方法，包括：
提供锂镍过渡金属氧化物A；
提供锂镍过渡金属氧化物B；
将锂镍过渡金属氧化物A和锂镍过渡金属氧化物B混合。
本发明所提供的正极材料的制备方法中，所述锂镍过渡金属氧化物A和/或锂镍过渡金属氧化物B可以是经过表面修饰的，例如，将锂镍过渡金属氧化物A和/或锂镍过渡金属氧化物B分别进行表面修饰后，再进行混合，其中锂镍过渡金属氧化物A与锂镍过渡金属氧化物B的表面修饰方法可以相同、也可以不同；也可以将锂镍过渡金属氧化物A与锂镍过渡金属氧化物B先混合，再一起进行表面修饰工艺。
本发明所提供的正极材料的制备方法中，可以包括：提供锂镍过渡金属氧化物A。提供所述提供锂镍过渡金属氧化物A的方法对于本领域技术人员来说应该是已知的，例如，可以包括：将锂镍过渡金属氧化物A的原料混合、烧结，以提供锂镍过渡金属氧化物A。本领域技术人员可根据锂镍过渡金属氧化物A的元素组成，选择合适的原料和配比。例如：所述锂镍过渡金属氧化物A的原料可以包括锂镍过渡金属氧化物A的前驱体、锂源、M源、X源等，各原料之间的比例通常参照锂镍过渡金属氧化物A中各元素的比例进行配比。更具体的，所述锂镍过渡金属氧化物A的前驱体可以是包括但不限于Ni 0.7Co 0.1Mn 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，所述锂源可以是含锂的 化合物，所述含锂化合物可以是包括但不限于LiOH·H 2O、LiOH、Li 2CO 3、Li 2O等中的一种或多种的组合，所述M源通常可以是含M元素的化合物，所述含M元素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、碳酸盐中的一种或几种，所述X源可以是含X元素的化合物，所述含X元素的化合物可以是包括但不限于LiF、NaCl等中的一种或多种的组合。再例如，所述烧结的条件可以是800℃、氧气浓度≥20％。
本发明所提供的正极材料的制备方法中，可以包括：提供锂镍过渡金属氧化物B。提供所述提供锂镍过渡金属氧化物B的方法对于本领域技术人员来说应该是已知的，例如，可以包括：将锂镍过渡金属氧化物B的原料混合、烧结，以提供锂镍过渡金属氧化物B。本领域技术人员可根据锂镍过渡金属氧化物B的元素组成，选择合适的原料和配比。所述锂镍过渡金属氧化物B的原料可以包括锂镍过渡金属氧化物B的前驱体、锂源、M’源、X’源等，各原料之间的比例通常参照锂镍过渡金属氧化物B中各元素的比例进行配比。更具体的，所述锂镍过渡金属氧化物B的前驱体可以是包括但不限于Ni 0.7Co 0.1Mn 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，所述锂源可以是含锂的化合物，所述含锂化合物可以是包括但不限于LiOH·H 2O、LiOH、Li 2CO 3、Li 2O等中的一种或多种的组合，所述M’源通常可以是含M’元素的化合物，所述含M’元素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、碳酸盐中的一种或几种，所述X’源可以是含X’元素的化合物，所述含X’元素的化合物可以是包括但不限于LiF、NaCl等中的一种或多种的组合。再例如，所述烧结的条件可以是700℃～900℃，氧气浓度≥15％。
本发明所提供的正极材料的制备方法中，还可以包括：在锂镍过渡金属氧化物A和/或锂镍过渡金属氧化物B表面进行修饰。在锂镍过渡金属氧化物A和/或锂镍过渡金属氧化物B表面进行表面修饰的方法对于本领域技术人员来说应该是已知的，例如，可以包括：将锂镍过渡金属氧化物A和/或锂镍过渡金属氧化物B在含掺杂元素的化合物、含包覆元素的化合物或包覆碳的前驱体存在的条件下烧结，以对锂镍过渡金属氧化物A和/或锂镍过渡金属氧化物B表面进行表面修饰。本领域技术人员可根据表面修饰物的组成，选择合适的含掺杂元素的化合物、包覆碳的前驱体或含包覆元素的化合物的种类、配比和烧结条件等。例如，将锂镍过渡金属氧化物A和/或锂镍过渡金属氧化物B与一定含量的含掺杂元素的化合物、含包覆元素的化合物、包覆碳的前驱体中的一种或多种的组合置于混料设备中进行混料，然后置 于气氛炉中进行烧结，形成锂镍过渡金属氧化物A和/或锂镍过渡金属氧化物B。再例如，所述含掺杂金属元素的化合物可以是Mg、Al、Ti、Fe、Cd、Zr、Mo、Zn、B、Cu、V、Ag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、碳酸盐等，再例如，所述掺杂金属元素的使用量是可以是0wt％～2wt％，包覆元素的使用量可以是0wt％～2wt％，再例如，所述烧结的条件可以是200℃～700℃。
本发明所提供的正极材料的制备方法中，还可以包括：将锂镍过渡金属氧化物A与锂镍过渡金属氧化物B混合，所述锂镍过渡金属氧化物A和/或锂镍过渡金属氧化物B可以是经过表面修饰，所述锂镍过渡金属氧化物A和/或锂镍过渡金属氧化物B也可以是未经过表面修饰。例如，将锂镍过渡金属氧化物A与锂镍过渡金属氧化物B混合以质量比为10:1～1:1混合均匀。
本发明的第三方面提供一种电化学储能装置，包括本发明第一方面所述的正极材料。
在本发明第三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。在本发明的实施例中，仅示出电化学储能装置为锂离子电池的实施例，但本发明不限于此。
在锂离子电池中，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，所述正极极片包括本发明第一方面所述的正极材料。制备所述锂离子电池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，以用于形成电芯，并可以进一步与电解液结合以形成锂离子电池。
在锂离子电池中，所述正极极片包含正极集流体和位于所述正极集流体上的正极活性物质层，所述正极活性物质层包括本发明第一方面的正极材料、粘结剂、导电剂。本领域技术人员可选择合适的方法制备所述正极极片，例如，可以包括如下步骤：将正极材料、粘结剂、导电剂混合形成浆料后，涂布于正极集流体上。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)、偏氟乙烯共聚物等或它们的改性(例如，羧酸、丙烯酸、丙烯腈等改性)衍生物等。在所述正极活性物质层中，粘结剂的质量百分比含量可以是由于粘结剂本身的导电性较差，因此粘结剂的用量不能过高。优选地，正极活性物质层中粘结剂的质量百分含量小于等于0.5wt％～3wt％，以获得较低的极片阻抗。
在锂离子电池中，所述正极极片的导电剂可以是本领域各种适用于锂离子(二次)电池的导电剂，例如，可以是包括但不限于乙炔黑、导电炭黑、碳纤维(VGCF)、碳纳米管(CNT)、科琴黑等中的一种或多种的组合。所述导电剂的重量可以占正极活性物质层总质量的1wt％～10wt％。更优选地，正极极片中导电剂与正极材料的重量比大于等于1.0wt％～5.0wt％。
在锂离子电池中，所述正极极片的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锂离子电池正极集流体的材料，例如，所述正极集流体可以是包括但不限于金属箔等，更具体可以是包括但不限于铜箔、铝箔等。
在锂离子电池中，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物质层，所述负极活性物质层通常包括负极活性物质。所述负极活性物质可以是本领域各种适用于锂离子电池的负极活性物质的材料，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等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锂离子电池负极集流体的材料，例如，所述负极集流体可以是包括但不限于金属箔等，更具体可以是包括但不限于铜箔等。
在锂离子电池中，所述隔离膜可以是本领域各种适用于锂离子电池隔离膜的材料，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、聚酯和天然纤维等中的一种或多种的组合。
在锂离子电池中，所述电解液可以是本领域各种适用于锂离子电池的电解液，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等，更具体的，所述锂盐可以是无机锂盐和/或有机锂盐等，具体可以是包括但不限于，所述锂盐可选自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之间。所述溶剂可以是本领域各种适用于锂离子电池的电解液的溶剂，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、碳酸甲乙酯等或它们的卤代衍生物中的一种或多种的组合。
以下结合实施例进一步说明本发明的有益效果。
为了使本发明的发明目的、技术方案和有益技术效果更加清晰，以下结合实施例进一步详细描述本发明。但是，应当理解的是，本发明的实施例仅仅是为了解释本发明，并非为了限制本发明，且本发明的实施例并不局限于说明书中给出的实施例。实施例中未注明具体实验条件或操作条件的按常规条件制作，或按材料供应商推荐的条件制作。
此外应理解，本发明中提到的一个或多个方法步骤并不排斥在所述组合步骤前后还可以存在其他方法步骤或在这些明确提到的步骤之间还可以插入其他方法步骤，除非另有说明；还应理解，本发明中提到的一个或多个设备/装置之间的组合连接关系并不排斥在所述组合设备/装置前后还可以存在其他设备/装置或在这些明确提到的两个设备/装置之间还可以插入其他设备/装置，除非另有说明。而且，除非另有说明，各方法步骤的编号仅为鉴别各方法步骤的便利工具，而非为限制各方法步骤的排列次序或限定本发明可实施的范围，其相对关系的改变或调整，在无实质变更技术内容的情况下，当亦视为本发明可实施的范畴。
在下述实施例中，所使用到的试剂、材料以及仪器如没有特殊的说明，均可商购获得。
实施例1
1、正极材料的制备
1)制备锂镍过渡金属氧化物A和B的前驱体：将硫酸镍、硫酸锰、硫酸钴按摩尔比配置成1mol/L溶液，利用氢氧化物共沉淀技术制备得到粒径为10μm的大颗粒锂镍过渡金属氧化物A的前驱体；硫酸镍、硫酸锰、硫酸钴按摩尔比配置成1mol/L溶液，利用氢氧化物共沉淀技术制备得到粒径为3μm的小颗粒锂镍过渡金属氧化物B的前驱体。制备前躯体的过程中，通过控制反应时间、共沉淀时的pH值，氨浓度实现对颗粒粒径的控制；
2)锂镍过渡金属氧化物A(多晶LiNi 0.8Co 0.1Mn 0.1O 2)的制备方法：
将上述锂镍过渡金属氧化物A的前驱体Ni 0.8Co 0.1Mn 0.1(OH) 2、含Li化合物LiOH·H 2O以摩尔比为1:1.05，置于混料设备中进行混料，然后置于气氛炉中800℃进行烧结，冷却后通过机械研磨即为锂镍过渡金属氧化物A；
将上述锂镍过渡金属氧化物A与0.4wt％的含包覆元素Al的化合物Al 2O 3置于混料设备中进行混料，然后置于气氛炉中进行500℃烧结5h，形成锂镍过渡金属氧化物A的包覆层，即得到表面修饰的锂镍过渡金属氧化物A。
3)锂镍过渡金属氧化物B(单晶LiNi 0.8Co 0.1Mn 0.1O 2)的制备方法：
将上述锂镍过渡金属氧化物B的前驱体Ni 0.8Co 0.1Mn 0.1(OH) 2、含Li化合物LiOH·H 2O以摩尔比为1:1.05，置于混料设备中进行混料，然后置于气氛炉中850℃进行烧结，冷却后通过气流粉末进行研磨即为锂镍过渡金属氧化物B；
将锂镍过渡金属氧化物B与0.2wt％的含包覆元素Al的化合物Al 2O 3置于混料设备中进行混料，然后置于气氛炉中进行500℃烧结5h，形成锂镍过渡金属氧化物B的包覆层，即得到表面修饰的锂镍过渡金属氧化物B。
4)将上述表面修饰的锂镍过渡金属氧化物A与表面修饰的锂镍过渡金属氧化物B以8:2的质量比混合均匀，得到实施例1的正极材料。
2、电池的制备
1)正极极片的制备
步骤1：将上述得到的正极材料、粘接剂聚偏氟乙烯、导电剂乙炔黑按照质量比98:1:1进行混合，加入N-甲基吡咯烷酮(NMP)，在真空搅拌机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的铝箔上；
步骤2：将涂覆后的极片经过100℃～130℃烘箱干燥，经过冷压、分切得到正极片。
2)负极片制备
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；将铜箔在室温晾干后转移至120℃烘箱干燥1h，然后经过冷压、分切得到负极片。
3)电解液制备
有机溶剂为含有碳酸亚乙酯(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。
4)隔离膜的制备
选用12μm厚的聚丙烯隔离膜。
5)电池的制备
将正极片、隔离膜、负极片按顺序叠好，使隔离膜处于正、负极片之间起到隔离的作用，再卷绕成方形的裸电芯后，装入铝塑膜，然后在80℃下烘烤除水后，注入相应的非水电解液、封口，经静置、热冷压、化成、夹具、分容等工序后，得到成品电池。
实施例2
与实施例1相比，不同之处在于正极材料的制备方法：锂镍过渡金属氧化物B的前驱体粒径为4μm，表面修饰的锂镍过渡金属氧化物A与表面修饰的锂镍过渡金属氧化物B质量比为7:3。
实施例3
与实施例1相比，不同之处在于正极材料的制备方法：锂镍过渡金属氧化物B的前驱体粒径为6μm，表面修饰的锂镍过渡金属氧化物A与表面修饰的锂镍过渡金属氧化物B质量比为6:4。
实施例4
与实施例1相比，不同之处在于正极材料的制备方法：锂镍过渡金属氧化物B的前驱体粒径为7μm，表面修饰的锂镍过渡金属氧化物A与表面修饰的锂镍过渡金属氧化物B质量比为5:5。
实施例5
与实施例1相比，不同之处在于正极材料的制备方法：锂镍过渡金属氧化物B的前驱体粒径为2μm，表面修饰的锂镍过渡金属氧化物A与表面修饰的锂镍过渡金属氧化物B质量比为9:1。
实施例6
与实施例2相比，不同之处在于正极材料的制备方法：锂镍过渡金属氧化物A(多晶LiNi 0.90Co 0.05Mn 0.05O 2)的前驱体为粒径为15μm的Ni 0.90Co 0.05Mn 0.05(OH) 2，锂镍过渡金属氧化物B(单晶LiNi 0.90Co 0.05Mn 0.05O 2)的前驱体为Ni 0.90Co 0.05Mn 0.05(OH) 2。
实施例7
与实施例2相比，不同之处在于正极材料的制备方法：锂镍过渡金属氧化物A(多晶LiNi 0.70Co 0.15Mn 0.15O 2)的前驱体为粒径为12μm的Ni 0.70Co 0.15Mn 0.15(OH) 2，锂镍过渡金属氧化物B(单晶LiNi 0.96Co 0.02Mn 0.02O 2)的前驱体为Ni 0.96Co 0.02Mn 0.02(OH) 2。
实施例8
与实施例2相比，不同之处在于正极材料的制备方法：锂镍过渡金属氧化物A(多晶LiNi 0.96Co 0.02Mn 0.02O 2)的前驱体为粒径为8μm的Ni 0.96Co 0.02Mn 0.02(OH) 2，锂镍过渡金属氧化物B(单晶LiNi 0.70Co 0.15Mn 0.15O 2)的前驱体为Ni 0.70Co 0.15Mn 0.15(OH) 2。
实施例9
与实施例2相比，不同之处在于正极材料的制备方法：将锂镍过渡金属氧化物A的前驱体Ni 0.8Co 0.1Mn 0.1(OH) 2、含Li化合物LiOH·H 2O、含M化合物ZrO 2以摩尔比为0.995：1.05：0.005，置于混料设备中进行混料，然后置于气氛炉中800℃进行烧结，冷却后通过机械研磨即为锂镍过渡金属氧化物A(多晶Li(Ni 0.8Co 0.1Mn 0.1) 0.995Zr 0.005O 2)。
实施例10
与实施例2相比，不同之处在于正极材料的制备方法：将锂镍过渡金属氧化物B的前驱体Ni 0.8Co 0.1Mn 0.1(OH) 2、含Li化合物LiOH·H 2O、含M’化合物ZrO 2以摩尔比为0.995：1.05：0.005，置于混料设备中进行混料，然后置于气氛炉中850℃进行烧结，冷却后通过机械研磨即为锂镍过渡金属氧化物B(单晶Li(Ni 0.8Co 0.1Mn 0.1) 0.995Zr 0.005O 2)。
实施例11
与实施例2相比，不同之处在于正极材料的制备方法：不同之处为锂镍过渡金属氧化物A的前驱体Ni 0.8Co 0.1Mn 0.1(OH) 2、含Li化合物LiOH·H 2O、含X化合物LiF以摩尔比为1：1.05：0.01，置于混料设备中进行混料，然后置于气氛炉中800℃进行烧结，冷却后通过机械研磨即为锂镍过渡金属氧化物A(多晶LiNi 0.8Co 0.1Mn 0.1O 1.99F 0.01)。
实施例12
与实施例2相比，不同之处在于正极材料的制备方法：将锂镍过渡金属氧化物B的前驱体Ni 0.8Co 0.1Mn 0.1(OH) 2、含Li化合物LiOH·H 2O、含X’化合物LiF以摩尔比为1：1.05：0.01，置于混料设备中进行混料，然后置于气氛炉中800℃进行烧结，冷却后通过机械研磨得锂镍过渡金属氧化物B(单晶LiNi 0.8Co 0.1Mn 0.1O 1.99F 0.01)。
实施例13
与实施例2基本相同，不同之处在于正极材料的制备方法：锂镍过渡金属氧化物A的前驱体粒径为8μm。
实施例14
与实施例2基本相同，不同之处在于正极材料的制备方法：锂镍过渡金属氧化物A的前驱体粒径为15μm。
实施例15
同实施例1，不同之处为：在制备锂镍过渡金属氧化物A和锂镍过渡金属氧化物B时，未经过包覆处理。
对比例1
与实施例1相比，不同之处在于正极材料的制备方法：正极活性材料中只有锂镍过渡金属氧化物A(多晶LiNi 0.8Co 0.1Mn 0.1O 2)，没有锂镍过渡金属氧化物B(单晶LiNi 0.8Co 0.1Mn 0.1O 2)。
对比例2
与实施例1相比，不同之处在于正极材料的制备方法：正极活性材料中只有锂镍过渡金属氧化物B(单晶LiNi 0.8Co 0.1Mn 0.1O 2)，没有锂镍过渡金属氧化物A(多晶LiNi 0.8Co 0.1Mn 0.1O 2)。
对比例3
与实施例2相比，不同之处在于正极材料的制备方法：锂镍过渡金属氧化物B为多晶LiNi 0.8Co 0.1Mn 0.1O 2，锂镍过渡金属氧化物B的前驱体的粒径为3μm。
对比例4
与实施例1相比，不同之处在于正极材料的制备方法：锂镍过渡金属氧化物B(单晶LiNi 0.5Co 0.2Mn 0.3O 2)的前驱体为Ni 0.5Co 0.2Mn 0.3(OH) 2，表面修饰的锂镍过渡金属氧化物A与表面修饰的锂镍过渡金属氧化物B的质量比为7:3。
对比例5
与实施例1相比，不同之处在于正极材料的制备方法：锂镍过渡金属氧化物A(多晶LiNi 0.5Co 0.2Mn 0.3O 2)的前驱体为Ni 0.5Co 0.2Mn 0.3(OH) 2，表面修饰的锂镍过渡金属氧化物A与表面修饰的锂镍过渡金属氧化物B的质量比为7:3。
对比例6
与实施例1相比，不同之处在于正极材料的制备方法：锂镍过渡金属氧化物B的前驱体的粒径为7μm，表面修饰的锂镍过渡金属氧化物A与表面修饰的锂镍过渡金属氧化物B的质量比为2:8。
对比例7
与实施例1相比，不同之处在于正极材料的制备方法：锂镍过渡金属氧化物B的前驱体的粒径为1μm，表面修饰的锂镍过渡金属氧化物A与表面修饰的锂镍过渡金属氧化物B的质量比为2:8。
图1是本发明实施例1制备的正极材料的电镜图，如图1所示，颗粒没被压碎，且多晶大颗粒之间的缝隙被单晶填充，压实密度高。
图2是本发明对比例1制备的正极材料的电镜图，如图2所示，颗粒被压碎，容易导致产气严重，且颗粒之间的缝隙很多，压实密度低。
二、检测方法
1、D104的测试方法
首先通过XRD设备进行测试，得到该正极材料的衍射图谱，计算晶面(104)的衍射峰峰强；
然后通过谢乐公式计算：D＝kλ/βcosθ，其中：
D—垂直于(104)晶面的晶粒平均粒度
K—谢乐常数，0.89
θ—衍射角
λ—入射X射线波长
测试结果见表1。
2、ΔPSD的测试方法
通过激光粒度测试仪测出该正极材料的Dv10、Dv50、Dv90的实际值，然后利用公式：ΔPSD＝(Dv90-Dv10)/Dv50，计算正极材料的ΔPSD。
测试结果见表1。
3、抗压强度的测试方法
1)将样品放置于载物台上；
2)将压头以恒定的速度向下靠近样品，直至与样品可以接触；
3)接触的瞬间开始记录压头的压强和位移；
4)持续以恒定速度向下挤压颗粒，直至颗粒碎裂。
测试结果见表1。
4、压实密度的测试方法
1)将极片裁剪为1000mm长度的膜片；
2)将正极极片通过一定压力进行碾压，由于铝箔具备延展性，使其膜片长度为1006mm；
3.)冲切1540.25mm 2的小圆片，测量小圆片重量及厚度，即可计算压实密度；
测试结果见表2。
5、电池的高温产气测试方法
将电池以1C满充电至4.2V后，于70℃恒温箱中静置30天。并通过排水法测定电池的初始体积与静置30天后的体积，得到电池的体积膨胀率。
电池的体积膨胀率(％)＝(静置30天后的体积/初始体积-1)×100％。
测试结果见表2。
6、电池的容量测试
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，按照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，然后按照1C放电至2.8V，记录该锂离子电池的容量。测试结果见表2。
表1 实施例1～15对比例1～7的正极材料组成
Figure PCTCN2019120591-appb-000001
Figure PCTCN2019120591-appb-000002
Figure PCTCN2019120591-appb-000003
表2 实施例1～15对比例1～7的性能测试
  压实密度(g/cm 3) 1/3C容量(mAh/g) 存储体积膨胀率
实施例1 3.50 196 78％
实施例2 3.55 195 75％
实施例3 3.55 194 72％
实施例4 3.45 193 81％
实施例5 3.45 196 84％
实施例6 3.55 198 81％
实施例7 3.55 192 90％
实施例8 3.55 194 99％
实施例9 3.55 195 69％
实施例10 3.55 195 72％
实施例11 3.55 195 69％
实施例12 3.55 195 72％
实施例13 3.50 196 85％
实施例14 3.55 196 91％
实施例15 3.50 197 82％
对比例1 3.35 197 114％
对比例2 3.45 191 105％
对比例3 3.50 197 168％
对比例4 3.50 185 75％
对比例5 3.50 173 55％
对比例6 3.35 187 105％
对比例7 3.35 197 156％
表1和表2是实施例1～15以及对比例1～7的正极材料的具体参数及性能测试结果。通过实施例和对比例的比较可以看出，本发明实施例通过将大颗粒锂的镍过渡金属氧化物A与小颗粒锂镍过渡金属氧化物B混合，通过控制混合后高镍活性材料的结晶度和粒径分布，有效 地改善冷压和循环过程中的颗粒破碎问题，提高高镍粉体的压实密度，同时保证产气量较低，循环性能优良。
在对比例1和对比例2中，由于正极材料中仅包含二次颗粒或单晶颗粒，制备的正极极片的压实密度相对较低，不利于提高电池的体积能量密度；同时，由于对比例1和对比例2的正极活性物质容易在极片冷压和循环过程中发生颗粒破碎，导致产气问题较严重，电池的体积膨胀率较高。在对比例3中，虽然使用了大、小粒径混合的高镍正极材料，但是小粒径的二次颗粒比表面积较大、表面残锂量较高，因此反而劣化锂离子电池的产气性能。对比例4和对比例5的混合正极材料中包括镍含量相对较低的LiNi 0.5Co 0.2Mn 0.3O 2，虽然通过控制混合后高镍活性材料的结晶度和粒径分布，锂离子电池的产气问题得到改善，但是无法满足电池的高能量密度需求。在对比例6中，由于混合后高镍正极材料的D 104×ΔPSD过高，表明该材料的粒度分布范围过大，小粒径的微粉相对含量过高，因此循环性能差、产气问题较严重。在对比例7中，混合后高镍正极材料的D 104×ΔPSD偏低，表明该材料的粒度分布范围较集中、但是形成材料的晶体粒径过小、内部界面较多，因此电池产气问题仍较差。
从实施例8和实施例14可以看出，在控制混合后高镍活性材料的结晶度和粒径分布的情况下，优化组成该材料的二次颗粒以及单晶颗粒的各自的抗压强度，能够进一步提升该正极材料的抗压性，更有利于改善高容量电池的产气及安全问题、提升锂离子电池的体积能量密度。
以上所述，仅为本发明的较佳实施例，并非对本发明任何形式上和实质上的限制，应当指出，对于本技术领域的普通技术人员，在不脱离本发明方法的前提下，还将可以做出若干改进和补充，这些改进和补充也应视为本发明的保护范围。凡熟悉本专业的技术人员，在不脱离本发明的精神和范围的情况下，当可利用以上所揭示的技术内容而做出的些许更动、修饰与演变的等同变化，均为本发明的等效实施例；同时，凡依据本发明的实质技术对上述实施例所作的任何等同变化的更动、修饰与演变，均仍属于本发明的技术方案的范围内。

Claims (12)

  1. 一种正极材料，所述正极材料包括锂镍过渡金属氧化物A和锂镍过渡金属氧化物B，所述锂镍过渡金属氧化物A为二次颗粒，所述锂镍过渡金属氧化物A的化学式如式I所示：
    Li a1(Ni b1Co c1Mn d1) x1M 1-x1O 2-e1X e1  (I)
    式I中，0.95≤a1≤1.05，0.7≤b1≤0.98，0.01≤c1≤0.15，0.01≤d1≤0.3，0.95≤x1≤1，0≤e1≤0.1；其中，M选自Al、Ti、Zr、Nb、Sr、Sc、Sb、Y、Ba、B、C、Co、Mn中的一种或多种的组合，X选自F和/或Cl；
    所述锂镍过渡金属氧化物B为单晶或类单晶形貌颗粒，所述锂镍过渡金属氧化物B的化学式如式II所示：
    Li a2(Ni b2Co c2Mn d2) x2M’ 1-x2O 2-e2X’ e2  (II)
    式II中，0.95≤a2≤1.05，0.7≤b2≤0.98，0.01≤c2≤0.15，0.01≤d2≤0.3，0.95≤x2≤1，0≤e2≤0.1；M’选自Al、Ti、Zr、Nb、Sr、Sc、Sb、Y、Ba、B、C、Co、Mn中的一种或多种的组合，X’选自F和/或Cl；
    所述正极材料的晶粒尺寸D 104与所述正极材料的粒径分布变化率ΔPSD满足：
    50nm≤D 104×ΔPSD≤450nm
    其中，ΔPSD为所述正极材料经体积粒度分布测量粒径，按照公式ΔPSD＝(D v90-D v10)/D v50计算得出的粒径分布变化率；D 104为所述正极材料经XRD射线衍射测试，对104晶面对应峰值拟合得到的晶粒尺寸。
  2. 根据权利要求1所述的正极材料，其特征在于，所述正极材料满足：80nm≤D 104×ΔPSD≤250nm。
  3. 根据权利要求1所述的正极材料，其特征在于，所述ΔPSD的范围为1.2～3.1，优选的，所述ΔPSD的范围为1.5～2.2。
  4. 根据权利要求1所述的正极材料，其特征在于，所述锂镍过渡金属氧化物A的单颗粒抗压强度≥100MPa，所述锂镍过渡金属氧化物B的单颗粒抗压强度≥50MPa。
  5. 根据权利要求1所述的正极材料，其特征在于，所述锂镍过渡金属氧化物A的D v50为8μm～15μm，D v10为3μm～8μm，D v90为15μm～25μm。
  6. 根据权利要求1所述的正极材料，其特征在于，所述锂镍过渡金属氧化物A包括由一次颗粒组成的二次颗粒，所述一次颗粒的粒径为30nm～800nm，优选的，所述一次颗粒的粒径为200nm～500nm。
  7. 根据权利要求1所述的正极材料，其特征在于，所述锂镍过渡金属氧化物B的D v50为 1μm～7μm，D v10为1μm～3μm，D v90为5μm～10μm，所述D v50优选为3μm～5μm。
  8. 根据权利要求1所述的正极材料，其特征在于，所述锂镍过渡金属氧化物A与所述锂镍过渡金属氧化物B的质量比为10:1～1:1，优选为4:1～2:1。
  9. 根据权利要求1所述的正极材料，其特征在于，所述正极材料的比表面积为0.5m 2/g～1.5m 2/g，优选为0.6m 2/g～1.0m 2/g。
  10. 根据权利要求1所述的正极材料，其特征在于，所述正极材料的压实密度为3.3g/cm 3～3.7g/cm 3。
  11. 根据权利要求1所述的正极材料，其特征在于，所述锂镍过渡金属氧化物A和/或锂镍过渡金属氧化物B经过表面修饰，所述表面修饰的方法包括在颗粒表面掺杂、在颗粒表面包覆氧化物、在颗粒表面包覆碳的一种或多种的组合，所述掺杂以及包覆的元素选自Mg、Al、Ti、Co、Fe、Cd、Zr、Mo、Zn、B、P、Cu、V、Ag中的一种或多种的组合。
  12. 一种电化学储能装置，包括权利要求1～11任一项所述的正极材料。
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