WO2021108945A1 - 一种用于二次电池的正极极片、二次电池、电池模块、电池包和装置 - Google Patents

一种用于二次电池的正极极片、二次电池、电池模块、电池包和装置 Download PDF

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WO2021108945A1
WO2021108945A1 PCT/CN2019/122332 CN2019122332W WO2021108945A1 WO 2021108945 A1 WO2021108945 A1 WO 2021108945A1 CN 2019122332 W CN2019122332 W CN 2019122332W WO 2021108945 A1 WO2021108945 A1 WO 2021108945A1
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metal oxide
transition metal
lithium nickel
nickel transition
active material
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PCT/CN2019/122332
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English (en)
French (fr)
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冷雪
杜锐
柳娜
刘勇超
倪欢
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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 CN201980100742.2A priority Critical patent/CN114556614A/zh
Priority to EP19930163.1A priority patent/EP4071846A4/en
Priority to PCT/CN2019/122332 priority patent/WO2021108945A1/zh
Priority to US17/123,544 priority patent/US11121362B2/en
Publication of WO2021108945A1 publication Critical patent/WO2021108945A1/zh

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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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    • 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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Definitions

  • the present invention relates to the field of electrochemistry, in particular to a positive pole piece, a secondary battery, a battery module, a battery pack and a device for a secondary battery.
  • Electric vehicles have higher and higher requirements for cruising range, which puts forward higher requirements on the energy density of power batteries.
  • the increase in energy density of power batteries depends largely on the choice of cathode materials.
  • lithium-nickel transition metal oxides for example, nickel-cobalt-manganese ternary materials
  • the increase of nickel content can significantly increase the gram capacity, thereby increasing the energy density. Therefore, lithium nickel transition metal oxide with high nickel content is currently a popular choice.
  • the increase in the nickel content in the lithium nickel transition metal oxide makes the preparation more difficult: high temperature, serious lithium volatilization; low temperature, crystal grains cannot grow sufficiently, and processing performance is poor.
  • the current mainstream lithium nickel transition metal oxide with high nickel content is the secondary polycrystalline large particles aggregated by small primary crystal grains, but due to the volume change in the c-axis direction during the charging and discharging process of the lithium nickel transition metal oxide with high nickel content Large, causing cracks to easily occur between the primary crystal grains, thereby deteriorating the cycle performance.
  • the increase of nickel content in lithium-nickel transition metal oxides also affects the stability of the material structure, intensifying the transformation of the surface layered structure to the rock salt phase, and the release of oxygen on the surface also intensifies the side reactions of the electrolyte on the surface of the material.
  • the purpose of the present invention is to provide a positive pole piece, a secondary battery, a battery module, a battery pack and a device for a secondary battery to solve the problems in the prior art.
  • a first aspect of the present invention provides a positive electrode piece for a secondary battery.
  • the positive electrode piece includes a positive electrode current collector and a positive electrode active material layer on the surface of the positive electrode current collector.
  • the positive active material layer includes a positive active material, the positive active material includes a first lithium nickel transition metal oxide and a second lithium nickel transition metal oxide, and the first lithium nickel transition metal oxide includes a first substrate and The first coating layer on the surface of the first substrate, the first substrate is a secondary particle, and the chemical formula of the first substrate is as shown in formula I:
  • M is selected from one or a combination of Al, Ti, Zr, Nb, Sr, Sc, Sb, Y, Ba, B, Co, Mn, and X is selected from F and/or Cl;
  • the first coating layer is selected from metal oxides and/or non-metal oxides
  • the second lithium nickel transition metal oxide is a particle with a single crystal or quasi-single crystal morphology
  • the particle size distribution of the positive active material satisfies: 40 ⁇ D v 90/D v 10*D v 50 ⁇ 80, unit: ⁇ m -1 ;
  • the OI of the positive pole piece is 10-40.
  • the second aspect of the present invention provides a method for preparing the positive pole piece for a secondary battery provided in the first aspect of the present invention.
  • a third aspect of the present invention provides a secondary battery, which includes the positive pole piece according to the first aspect of the present invention.
  • a fourth aspect of the present invention provides a battery module including the secondary battery according to the third aspect of the present invention.
  • a fifth aspect of the present invention provides a battery pack including the battery module according to the fourth aspect of the present invention.
  • a sixth aspect of the present invention provides a device including the secondary battery according to the third aspect of the present invention, and the secondary battery is used as a power source for the device.
  • the positive active material includes a first lithium nickel transition metal oxide and a second lithium nickel transition metal oxide, wherein the first lithium nickel transition metal oxide is coated
  • the secondary particles, the second lithium nickel transition metal oxides are single-crystal or single-crystal-like single particles.
  • the positive electrode active material in the positive electrode piece is increased
  • the compressive strength of the particles effectively suppresses the problem of particle cracking of the positive electrode active material particles, and at the same time reduces the relative content of the (003) crystal plane perpendicular to the positive pole pieces, so that the prepared secondary battery (for example, lithium ion battery) has a high It has the characteristics of low energy density, low gas production and low pole piece expansion rate, which has a good industrialization prospect.
  • the battery module, battery pack, and device of the present invention include the secondary battery, and thus have at least the same advantages as the secondary battery.
  • Fig. 1 is a perspective view of an embodiment of a battery.
  • Fig. 2 is an exploded view of an embodiment of a battery.
  • Fig. 3 is a perspective view of an embodiment of a battery module.
  • Fig. 4 is a perspective view of an embodiment of a battery pack.
  • Fig. 5 is an exploded view of Fig. 4.
  • Fig. 6 is a schematic diagram of an embodiment of a device in which a battery is used as a power source.
  • a first aspect of the present invention provides a positive pole piece for a secondary battery.
  • the positive pole piece includes a positive current collector and a positive active material layer on the surface of the positive current collector.
  • the positive active material layer includes a positive active material. It includes a first lithium nickel transition metal oxide and a second lithium nickel transition metal oxide.
  • the first lithium nickel transition metal oxide includes a first substrate and a first coating layer on the surface of the first substrate. The first substrate As secondary particles, the chemical formula of the first lithium nickel transition metal oxide is shown in formula I:
  • M is selected from one or a combination of Al, Ti, Zr, Nb, Sr, Sc, Sb, Y, Ba, B, Co, Mn, and X is selected from F and/or Cl;
  • the first coating layer is selected from metal oxides and/or non-metal oxides
  • the second lithium nickel transition metal oxide is a particle with a single crystal or quasi-single crystal morphology
  • the particle size distribution characteristic of the positive electrode active material satisfies: 40 ⁇ D v 90/D v 10*D v 50 ⁇ 80, unit: ⁇ m -1 ;
  • the OI of the positive pole piece is 10-40.
  • D v 10 is the corresponding particle size (unit: ⁇ m) when the volume cumulative distribution percentage of the positive active material reaches 10%
  • D v 50 is the corresponding particle size (unit: ⁇ m) when the volume cumulative distribution percentage of the sample reaches 50% : ⁇ m)
  • D v 90 is the corresponding particle size (unit: ⁇ m) when the cumulative volume distribution percentage of the sample reaches 90%.
  • the OI of the positive pole piece is the ratio of the diffraction peak area corresponding to the (003) crystal plane and the (110) crystal plane of the positive electrode active material in the XRD diffraction spectrum of the positive pole piece.
  • the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes a first lithium nickel transition metal oxide and a second lithium nickel transition metal oxide.
  • the first substrate in the nickel transition metal oxide has a polycrystalline morphology (secondary particles composed of primary particles) and is coated with metal oxides and/or non-metal oxides, and the second lithium nickel transition metal is oxidized
  • the object is a single crystal or similar single crystal morphology particles.
  • single crystal-like generally means that the size of primary particles is larger than 1 ⁇ m, but there is a certain agglomeration of the primary particles; single crystal generally means that the size of primary particles is larger than 1 ⁇ m without obvious agglomeration.
  • the present invention effectively suppresses the problem of particle cracking of the positive electrode active material particles, improves the compressive strength of the positive electrode active material particles in the positive electrode pole piece, and reduces the positive electrode.
  • the relative amount of the (003) crystal plane of the positive electrode active material in the pole piece effectively solves the problems of pole piece expansion rate and gas production, thereby obtaining electrochemical energy storage with high energy density, low pole piece expansion rate, and low gas production.
  • the OI of the positive pole piece when the compaction density of the positive pole piece is 3.3 g/cm 3 to 3.5 g/cm 3 , the OI of the positive pole piece can be 10-15, 15-20, 20-25, 25-30, 30-35, or 35-40, preferably 10-20.
  • the OI value of the positive pole piece reflects the overall orientation of the crystal plane of the positive electrode active material in the pole piece, and is closely related to the coating speed, drying, cold pressing and other process parameters of the pole piece manufacturing process.
  • the OI value of the positive pole piece is too high, indicating that the relative amount of the (003) crystal plane perpendicular to the length of the positive pole piece is too high, reflecting that the positive pole piece has a serious texture after cold pressing, and during the charging and discharging process of the battery
  • the pole piece is prone to swell; but if the OI value of the positive pole piece is too low, it indicates that there is no obvious orientation of the positive electrode active material in the positive pole piece at this time, and the particle strength is too low. Gas production problem.
  • the second lithium nickel transition metal oxide includes a second substrate, and the chemical formula of the second substrate is shown in Formula II:
  • M' is selected from one or more combinations of Al, Ti, Zr, Nb, Sr, Sc, Sb, Y, Ba, B, Co, Mn, and X'is selected from F and/or Cl .
  • the molecular formulas of the first substrate and the second substrate may independently include but are not limited to 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 0.65 Co 0.15 Mn 0.2 O 2 , LiNi 0.65 Co 0.12 Mn 0.23 O 2 , LiNi 0.65 Co 0.1 Mn 0.25 O 2 , LiNi 0.65 Co 0.05 Mn 0.3 O 2 , 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
  • M, M', X, and X' are partially substituted and modified.
  • M and M'are each independently selected from Al, Ti, Zr, Nb, Sr, Sc, Sb, Y, Ba, B, Co,
  • One or more combinations of Mn, X and X'are each independently selected from F and/or Cl.
  • the relative content x1 of the Ni element in the molecular formula of the first substrate may satisfy: 0.8 ⁇ x1 ⁇ 0.95, 0.8 ⁇ x1 ⁇ 0.85, 0.85 ⁇ x1 ⁇ 0.9, or 0.9 ⁇ x1 ⁇ 0.95
  • the relative content x2 of Ni element in the molecular formula of the second substrate can satisfy: 0.8 ⁇ x2 ⁇ 0.95, 0.8 ⁇ x1 ⁇ 0.85, 0.85 ⁇ x1 ⁇ 0.9, or 0.9 ⁇ x1 ⁇ 0.95, and the first substrate and the second
  • the relative content x1 and x2 of Ni element in the base material can satisfy: ⁇ x1-x2 ⁇ 0.1.
  • Both the first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide in the present invention select a layered lithium transition metal oxide with a relatively high nickel content, which can effectively increase the energy density of the battery, and the first substrate and the The difference between the relative content x1 and x2 of the Ni element in the second substrate is not more than 0.1, which can realize that the first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide have a close relationship under the same charge and discharge voltage.
  • the degree of lithium removal/intercalation is beneficial to improve the battery's charge-discharge cycle life.
  • the relative contents x1 and x2 of Ni elements in the first substrate and the second substrate satisfy: 0 ⁇ x1-x2 ⁇ 0.1.
  • the Ni element content x1 of the first lithium nickel transition metal oxide is slightly higher than that of the second lithium nickel transition metal oxide x2, which effectively balances the degree of lithium removal/intercalation of the two positive electrode active materials, and is beneficial to battery performance. A higher energy density.
  • the particle size and tap density TD of the positive active material satisfy: 4.4 ⁇ (D v 90-D v 10)/TD ⁇ 8.
  • the value range of (D v 90-D v 10)/TD can be 7.5-8, 7-7.5, 6.5-7, 6-6.5, 5.5-6, 5-5.5, 4.4-5.
  • the unit of D v 10 and D v 90 is ⁇ m;
  • TD is the tap density of the positive electrode active material (unit: g/cm 3 ).
  • the particle size distribution of the particles of different morphologies of the positive electrode active material is moderate, and the gap volume between the particles is low, which is beneficial to The compaction density of the positive pole piece is improved.
  • the tap density TD of the positive active material can be 2.2g/cm 3 ⁇ 2.8g/cm 3 , 2.2g/cm 3 ⁇ 2.3g/cm 3 , 2.3g/cm 3 ⁇ 2.4g/cm 3 , 2.4g/cm 3 ⁇ 2.5g/cm 3 , 2.5g/cm 3 ⁇ 2.6g/cm 3 , 2.6g/cm 3 ⁇ 2.7g/cm 3 , or 2.7g/cm 3 ⁇ 2.8 g/cm 3 .
  • TD is the tap density of the powder of the positive electrode active material.
  • the specific measurement method of the tap density of the powder may include: filling the powder in a container (for example, a 25mL container, or another example, the container used) It can be a graduated cylinder). After the container is vibrated (for example, the specific conditions of vibration can be: vibration frequency of 250 times/min, amplitude of 3mm, and vibration of 5000 times), the mass of the powder per unit volume is the tap density of the powder .
  • the specific conditions of vibration can be: vibration frequency of 250 times/min, amplitude of 3mm, and vibration of 5000 times
  • the mass of the powder per unit volume is the tap density of the powder .
  • the larger the TD the more conducive to achieving high compaction density, but TD is affected by factors such as the compactness of a single particle of the material, the particle size distribution of the material, and the shape of the particle, and has a certain upper limit.
  • the first lithium nickel transition metal oxide may be spherical particles, and the sphericity ⁇ of the first lithium nickel transition metal oxide may be 0.7-1. Specifically, the sphericity ⁇ of the first lithium nickel transition metal oxide may be 0.7-0.9, 0.7-0.8, 0.8-0.9, or 0.9-1.
  • the sphericity can be measured in the following way: in the SEM picture of the cross section of the positive pole piece, select at least 30 secondary particles with a cross-sectional diameter above the value of D v 10 of the positive electrode active material, and measure the cross-sectional SEM picture The ratio of the maximum inscribed circle radius (R max ) to the minimum circumscribed circle radius (R min ) of the respective secondary particles in each secondary particle, and the average value can be obtained.
  • the first lithium nickel transition metal oxide is a secondary particle. When the sphericity of the secondary particle is within the above range, it indicates that the size of the primary particle in the secondary particle is uniform, the distribution is relatively uniform, and the secondary particle is tight. Real, high mechanical strength.
  • the size ratio of the longest diameter L max to the shortest diameter L min of the second lithium nickel transition metal oxide satisfies: 1 ⁇ L max /L min ⁇ 3, 1 ⁇ L max /L min ⁇ 1.5, 1.5 ⁇ L max /L min ⁇ 2, 2 ⁇ L max /L min ⁇ 2.5, or 2.5 ⁇ L max /L min ⁇ 3.
  • the L max /L min can be measured in the following way: in the SEM photograph of the cross section of the positive pole piece, at least 30 single crystals or single crystals with a cross-sectional diameter greater than the value of the positive active material D v 10 are selected.
  • the second lithium nickel transition metal oxide is a particle with a single crystal or quasi-single crystal morphology, and when the L max /L min of the single particle is within the above-mentioned range, it is equal to the sphericity between 0.7 and 1.
  • the interstitial volume of the secondary particles can be better filled. While improving the compaction density of the positive pole piece and the volume energy density of the battery, it can also effectively suppress the volume expansion rate of the positive pole piece during the cycle and improve Cycle performance.
  • the D v 50 (L) of the first lithium nickel transition metal oxide may be 5 ⁇ m to 18 ⁇ m, 5 ⁇ m to 6 ⁇ m, 6 ⁇ m to 8 ⁇ m, 8 ⁇ m to 10 ⁇ m, 10 ⁇ m to 12 ⁇ m, 12 ⁇ m to 14 ⁇ m , 14 ⁇ m-16 ⁇ m, or 16 ⁇ m-18 ⁇ m, preferably 8 ⁇ m-12um.
  • the D v 50 (S) of the second lithium nickel transition metal oxide may be 1 ⁇ m to 5 ⁇ m, 1 ⁇ m to 2 ⁇ m, 2 ⁇ m to 3 ⁇ m, 3 ⁇ m to 4 ⁇ m, or 4 ⁇ m to 5 ⁇ m.
  • the base material in the first lithium nickel transition metal oxide is polycrystalline (secondary particles formed by agglomeration of multiple primary particles), and the second lithium nickel transition metal oxide is single crystal or quasi-single crystal morphology particles.
  • the first lithium nickel transition metal oxide has a larger particle size distribution as a whole relative to the second lithium nickel transition metal oxide, and the particle size distribution between the two is more preferably D v 50 (L) and D v 50 (S) Can satisfy: 2 ⁇ D v 50(L)/D v 50(S) ⁇ 7, 2 ⁇ D v 50(L)/D v 50(S) ⁇ 3, 3 ⁇ D v 50(L)/D v 50(S) ⁇ 4, 4 ⁇ D v 50(L)/D v 50(S) ⁇ 5, 5 ⁇ D v 50(L)/D v 50(S) ⁇ 6, or 6 ⁇ D v 50( L)/D v 50(S) ⁇ 7.
  • the ratio of the first lithium nickel transition metal oxide D v 50 (L) to the second lithium nickel transition metal oxide D v 50 (S) is within the above range, it is beneficial to suppress the larger particle size.
  • the particle cracking problem of the secondary particle high nickel material ensures that the positive electrode active material can exert a higher gram capacity, and at the same time improves the mechanical strength and compaction density of the overall positive electrode piece.
  • the weight percentage content of the first lithium nickel transition metal oxide can be 50% to 90%, 85% to 90%, 80% to 85%, 75% to 80%, 70% ⁇ 75%, 65% to 70%, 60% to 65%, 55% to 60%, or 50% to 55%, preferably 60% to 85%.
  • the weight percentage content of the second lithium nickel transition metal oxide can be 10% to 50%, 10% to 15%, 15% to 20%, 20% to 25%, 25% to 30%, 30% to 35%, 35% to 40%, 40% to 45%, or 45% to 50%, preferably 15% to 40%.
  • the weight percentage of the first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide in the positive pole piece is controlled within the above-mentioned range. To a certain extent, the OI value of the positive pole piece can be adjusted and the OI value of the positive pole piece can be adjusted and increased at the same time. The compacted density and mechanical strength of the pole piece.
  • the second lithium nickel transition metal oxide may further include a second coating layer on the surface of the second substrate, and the second coating layer is a metal oxide and/or a non-metal oxide .
  • the first coating layer and/or the second coating layer may be metal oxides and/or non-metal oxides, for example, they may be oxides containing only metal or non-metal elements. It may also contain oxides of metal elements and non-metal elements at the same time.
  • the metal element may generally be, for example, aluminum, zirconium, zinc, titanium, silicon, tin, tungsten, yttrium, cobalt, barium, etc.
  • the non-metal element may generally be, for example, phosphorus, boron, etc.
  • the first coating layer and/or the second coating layer may include but not limited to aluminum oxide, zirconium oxide, zinc oxide, titanium oxide, silicon oxide, tin oxide, tungsten oxide, yttrium oxide, cobalt oxide, oxide Barium, phosphorus oxide, boron oxide, and lithium aluminum oxide, lithium zirconium oxide, lithium zinc oxide, lithium magnesium oxide, lithium tungsten oxide, lithium yttrium oxide, lithium cobalt oxide, lithium barium oxide, lithium A combination of one or more of phosphorus oxide or lithium boron oxide.
  • the above-mentioned metal oxides and/or non-metal oxides are selected for the coating layer of the positive electrode active material.
  • the oxide coating layer has a good bonding force with the base material, and the coating layer is not easy to fall off during the charge and discharge process, and the base is reduced.
  • the part of the contact area between the material and the electrolyte can effectively modify the surface of the high-nickel positive electrode material, reduce the side reaction of the positive electrode material and the electrolyte, and effectively suppress the gas generation phenomenon of the battery.
  • the first coating layer preferably contains at least one metal element oxide and one non-metal element oxide at the same time.
  • the oxides containing the above elements can not only improve the stability of the coating layer’s adhesion on the surface of the secondary particle substrate, but also make the coating layer have a certain degree of ion conductivity and conductivity, and reduce the impact of the coating layer on the positive electrode material. The impact of chemical problems.
  • the second aspect of the present invention provides the method for preparing the positive pole piece for the secondary battery provided in the first aspect of the present invention.
  • Suitable methods for preparing the positive pole piece should be known to those skilled in the art, for example,
  • the positive pole piece can include:
  • a positive electrode active material including a first lithium nickel transition metal oxide and a second lithium nickel transition metal oxide
  • the positive electrode active material After mixing the positive electrode active material, the binder, and the conductive agent to form a slurry, it is coated on the positive electrode current collector.
  • the first lithium nickel transition metal oxide and/or the second lithium nickel transition metal oxide may be surface-modified.
  • the first lithium nickel transition metal oxide may be And/or the second lithium nickel transition metal oxide is separately surface-modified and then mixed, wherein the surface modification methods of the first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide may be the same or different; It is also possible to mix the first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide first, and then perform the surface modification process together.
  • the method for preparing a positive pole piece provided by the present invention may include: providing a first lithium nickel transition metal oxide.
  • the method for providing the first lithium nickel transition metal oxide should be known to those skilled in the art. For example, it may include: mixing and sintering the raw materials of the first lithium nickel transition metal oxide substrate to provide the first lithium nickel transition metal oxide. A substrate; the first substrate is coated to provide a first lithium nickel transition metal oxide.
  • Those skilled in the art can select appropriate raw materials and proportions according to the elemental composition of the first lithium nickel transition metal oxide to further prepare the first substrate.
  • the raw material of the first lithium nickel transition metal oxide may include a precursor of the first lithium nickel transition metal oxide, a lithium source, a source of M, a source of X, etc., and the ratio of each raw material is generally referred to that of the first lithium nickel transition metal.
  • the ratio of each element in the oxide is mixed.
  • the precursor of the first lithium nickel transition metal oxide may include, but is not limited to, 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 0.65 Co 0.15 Mn 0.2 (OH) 2 , Ni 0.65 Co 0.12 Mn 0.23 (OH) 2 , Ni 0.65 Co 0.1 Mn 0.25 (OH) 2 , Ni 0.65 Co 0.05 Mn 0.3 (OH) 2 , 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 , Ni 0.92 Co 0.03 M
  • the M source can usually be M-containing Compounds of elements, the above-mentioned compounds containing M elements may be oxides, nitrates, and carbonates containing at least one element of Al, Ti, Zr, Nb, Sr, Sc, Sb, Y, Ba, Co, and Mn
  • the X source may be a compound containing X element, and the above-mentioned compound containing X element may include but not limited to one or a combination of LiF, NaCl, and the like.
  • the sintering conditions of the raw material of the first lithium nickel transition metal oxide base material may be 700° C. to 900° C., and oxygen concentration ⁇ 20%.
  • the method for coating the first substrate may specifically include: sintering the first substrate in the presence of a compound containing a coating element, and the compound containing a coating element may contain Al, Ba, Zn, Ti, Oxides, nitrates, phosphates, carbonates, etc. of one or more elements of Co, W, Y, Si, Sn, B, P, etc., and the usage amount of the coating element can be generally ⁇ 2wt%,
  • the sintering conditions in the coating treatment may be 200°C to 700°C.
  • the method for preparing a positive pole piece provided by the present invention may include: providing a second lithium nickel transition metal oxide.
  • the method of providing the second lithium nickel transition metal oxide should be known to those skilled in the art. For example, it may include: mixing and sintering the raw materials of the second lithium nickel transition metal oxide substrate to provide the second lithium nickel transition metal oxide. Two substrates; coating the second substrate to provide a second lithium nickel transition metal oxide.
  • the raw material of the second lithium nickel transition metal oxide may include the precursor, lithium source, M'source, X'source, etc.
  • the precursor of the second lithium nickel transition metal oxide may include, but is not limited to, 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 0.65 Co 0.15 Mn 0.2 (OH) 2 , Ni 0.65 Co 0.12 Mn 0.23 (OH) 2 , Ni 0.65 Co 0.1 Mn 0.25 (OH) 2 , Ni 0.65 Co 0.05 Mn 0.3 (OH) 2 , Ni 0.7 Co 0.1 Mn 0.2 (OH) 2 , Ni 0.75 Co 0.1 Mn 0.15 (OH )
  • the source of M' usually contains Compounds of M elements
  • the above-mentioned compounds containing M'elements may be oxides, nitrates, carbonic acid containing at least one element of Al, Ti, Zr, Nb, Sr, Sc, Sb, Y, Ba, Co, and Mn
  • the source of X' may be a compound containing X'
  • the above-mentioned compound containing X' may include but not limited to one or a combination of LiF, NaCl, and the like.
  • the sintering conditions of the raw material of the second lithium nickel transition metal oxide base material may be sintering conditions of 750° C. to 950° C. and oxygen concentration ⁇ 20%.
  • the method for coating the second substrate may specifically include: sintering the second substrate in the presence of a compound containing a coating element, and the compound containing a coating element may contain Al, Ba, Zn, Ti, Oxides, nitrates, phosphates, carbonates, etc. of one or more elements of Co, W, Y, Si, Sn, B, P, etc., and the usage amount of the coating element can be generally ⁇ 2wt%,
  • the sintering conditions in the coating treatment may be 200°C to 700°C.
  • the binder usually includes a fluorine-containing polyolefin binder.
  • water is usually a good solvent, that is, a fluorine-containing polyolefin binder.
  • Olefin binders usually have good solubility in water.
  • fluorine-containing polyolefin binders can include but are not limited to polyvinylidene fluoride (PVDF), vinylidene fluoride copolymers, etc. or their modifications ( For example, modified derivatives of carboxylic acid, acrylic acid, acrylonitrile and the like.
  • the mass percentage content of the binder may be due to the poor conductivity of the binder itself, so the amount of the binder cannot be too high.
  • the mass percentage 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 can be various conductive agents suitable for lithium ion (secondary) batteries in the field, for example, it can include but not limited to acetylene black, conductive One or a combination of carbon black, carbon fiber (VGCF), carbon nanotube (CNT), Ketjen black, etc.
  • the weight of the conductive agent may account for 1 wt% to 10 wt% of the total mass of the positive active material layer. More preferably, the weight ratio of the conductive agent to the positive electrode active material in the positive pole piece is 1.0 wt% to 5.0 wt%.
  • the positive electrode current collector of the positive pole piece can usually 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 types suitable for use in the field.
  • the positive electrode current collector may include but is not limited to metal foil, etc., and more specifically may include but not limited to copper foil, aluminum foil, and the like.
  • the third aspect of the present invention provides a secondary battery, including the positive pole piece provided in the first aspect of the present invention.
  • the secondary battery may be a super capacitor, a lithium ion battery, a lithium metal battery, or a sodium ion battery.
  • the secondary battery is a lithium ion battery is shown, but the present invention is not limited to this.
  • FIG. 1 is a perspective view of a specific embodiment of a lithium ion battery.
  • Fig. 2 is an exploded view of Fig. 1. 1 to 2, the battery 5 includes a case 51, an electrode assembly 52, a top cover assembly 53, and an electrolyte (not shown).
  • the electrode assembly 52 is housed in the housing 51.
  • the number of electrode assemblies 52 is not limited, and may be one or more.
  • the battery 5 shown in FIG. 1 is a can type battery, but is not limited to this.
  • the battery 5 may be a pouch type battery, that is, the shell 51 is replaced by a metal plastic film and the top cover assembly 53 is eliminated.
  • a lithium ion battery it may include a positive pole piece, a negative pole piece, a separator between the positive pole piece and the negative pole piece, and an electrolyte.
  • the positive pole piece may be the positive electrode provided in the first aspect of the present invention. Pole piece.
  • the method for preparing lithium-ion batteries 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 a target size and stacked one after another. It can be wound to a target size to form a battery cell, and can be further combined with an electrolyte to form a lithium ion battery.
  • the negative electrode piece may generally include 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 can be various materials suitable for the negative electrode active material of lithium ion batteries in the field, for example, it can include but not limited to graphite, soft carbon, hard carbon, carbon fiber, mesophase carbon microspheres, silicon-based materials, tin A combination of one or more of the base material, lithium titanate, or other metals that can form an alloy with lithium.
  • graphite can be selected from one or a combination of artificial graphite, natural graphite, and modified graphite; silicon-based material can be selected from one of elemental silicon, silicon-oxygen compounds, silicon-carbon composites, and silicon alloys. Combinations of multiple; tin-based materials can 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 can be various materials suitable for use as the negative electrode current collector of a lithium ion battery in the art.
  • the negative electrode current collector can include but is not limited to metal foil, etc., more specifically It can include but is not limited to copper foil and the like.
  • the separator can be various materials suitable for lithium-ion battery separators in the field.
  • it can include but not limited to polyethylene, polypropylene, polyvinylidene fluoride, aramid, and polyterephthalate.
  • polyethylene glycol formate polytetrafluoroethylene
  • polyacrylonitrile polyimide
  • polyamide polyamide
  • polyester polyamide
  • natural fibers natural fibers
  • the electrolyte may generally include an electrolyte and a solvent.
  • Suitable electrolytes suitable for lithium-ion batteries should be known to those skilled in the art.
  • the electrolyte may generally include a lithium salt, etc., more specifically Yes, the lithium salt may be an inorganic lithium salt and/or an organic lithium salt, etc., specifically including but not limited to LiPF 6 , LiBF 4 , LiN(SO 2 F) 2 (LiFSI), LiN(CF 3 SO 2 ) 2 ( One or a combination of one or more of LiTFSI), LiClO 4 , LiAsF 6 , LiB(C 2 O 4 ) 2 (LiBOB), LiBF 2 C 2 O 4 (LiDFOB), etc.; for another example, the electrolyte concentration may be 0.8 mol/L ⁇ 1.5mol/L; for another example, the solvent used in the electrolyte may be various solvents suitable for the electrolyte of lithium ion batteries in the field,
  • a battery module which includes the secondary battery provided in the third aspect of the present application.
  • the battery module can generally include one or more secondary batteries, the battery module can be used as a power source or an energy storage device, and the number of batteries in the battery module can be adjusted according to the application and capacity of the battery module.
  • Fig. 3 is a perspective view of a specific embodiment of a battery module.
  • the battery module 4 includes a plurality of batteries 5.
  • the plurality of batteries 5 are arranged in the longitudinal direction.
  • a battery pack which includes the secondary battery provided in the third aspect of the present application, or the battery module block provided in the fourth aspect.
  • FIG. 4 is a perspective view of a specific embodiment of the battery pack 1.
  • Fig. 5 is an exploded view of Fig. 4.
  • the battery pack 1 includes an upper case 2, a lower case 3 and a battery module 4.
  • the upper case 2 and the lower case 3 are assembled together to form a space for accommodating the battery module 4.
  • the battery module 4 is placed in the space of the upper case 2 and the lower case 3 assembled together.
  • the output pole of the battery module 4 passes through one or between the upper case 2 and the lower case 3 to supply power to the outside or charge from the outside.
  • the number and arrangement of the battery modules 4 used in the battery pack 1 can be determined according to actual needs.
  • the battery pack 1 can be used as a power source or an energy storage device.
  • a sixth aspect of the present invention provides a device including the secondary battery provided in the third aspect of the present invention, and the secondary battery is used as a power source for the device.
  • Fig. 6 is a perspective view of a specific embodiment of the above-mentioned device.
  • the device using the battery 5 is an electric vehicle.
  • the device using the battery 5 can be any electric vehicle other than electric vehicles (for example, electric buses, electric trams, electric bicycles, electric motorcycles, electric scooters, electric golf carts, electric trucks), Electric ships, electric tools, electronic equipment and energy storage systems.
  • the electric vehicle can be an electric pure electric vehicle, a hybrid electric vehicle, and a plug-in hybrid electric vehicle.
  • the device provided in the sixth aspect of the application may include the battery module 4 provided in the fourth aspect of the application.
  • the device provided in the sixth aspect of the application may also include the fifth aspect of the application. Supplied battery pack 1.
  • one or more method steps mentioned in the present invention do not exclude that there may be other method steps before and after the combined steps or other method steps may be inserted between these explicitly mentioned steps, unless otherwise stated.
  • 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 before and after the combined device/device or are explicitly mentioned in these Other devices/devices can also be inserted between the two devices/devices, unless otherwise specified.
  • the number of each method step is only a convenient tool for identifying each method step, and is not intended to limit the arrangement order of each method step or limit the scope of implementation of the present invention. The change or adjustment of the relative relationship is If there is no substantial change in the technical content, it shall be regarded as the scope where the present invention can be implemented.
  • the precursors of the first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide nickel sulfate, manganese sulfate, and cobalt sulfate are configured into a 1mol/L solution with a molar ratio of 8:1:1, using hydrogen
  • the precursor of the first lithium nickel transition metal oxide with a particle size D v 50 (L) of 9.7 ⁇ m is prepared by the oxide co-precipitation technology; nickel sulfate, manganese sulfate, and cobalt sulfate are configured into a 1mol/L solution by mole.
  • the hydroxide co-precipitation technology prepares the precursor of the second lithium nickel transition metal oxide with a particle size of 2.9 ⁇ m.
  • the particle size and morphology of the precursors of the first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide are determined by controlling the reaction time, the pH value during the co-precipitation, and the ammonia concentration. Regulation
  • the precursor of the first lithium nickel transition metal oxide Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 and the Li-containing compound LiOH ⁇ H 2 O at a molar ratio of 1:1.05 in a mixing device for mixing, Then it is placed in an atmosphere furnace at 830°C for sintering, and after cooling, it becomes the substrate of the first lithium nickel transition metal oxide by mechanical grinding;
  • the base material of the first lithium nickel transition metal oxide with 0.2 wt% of Al 2 O 3 containing the coating element Al and 0.2 wt% of the compound boric acid containing B of the coating element in a mixing device for mixing
  • the material is then placed in an atmosphere furnace for sintering at 500°C for 5 hours to form the first coating layer of the first lithium nickel transition metal oxide, that is, the first lithium nickel transition metal oxide coated on the surface is obtained.
  • the D v of the above material 50 See Table 1 for sphericity and coating materials.
  • the precursor of the second lithium nickel transition metal oxide Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 and the Li-containing compound LiOH ⁇ H 2 O at a molar ratio of 1:1.05 place them in a mixing device for mixing, Then, it is placed in an atmosphere furnace with an oxygen concentration of 30% for sintering at 870°C for 4 hours, and after cooling, it is ground by air flow powder to form the substrate of the second lithium nickel transition metal oxide;
  • the coating layer of the lithium nickel transition metal oxide B is formed, that is, the surface-modified second lithium nickel transition metal oxide is obtained .
  • the ratio of D v 50 and L max /L min of the material and the coating material are shown in Table 1.
  • the above-mentioned surface-modified first lithium nickel transition metal oxide and the surface-modified second lithium nickel transition metal oxide are uniformly mixed in a mass ratio of 7:3 to obtain the positive electrode active material of Example 1.
  • the positive electrode of Example 1 Refer to Table 1 for the TD, (D v 90-D v 10)/TD, D v 90/D v 10*D v 50 and OI of the positive pole piece of the active material.
  • Step 1 Mix the positive active material, the binder polyvinylidene fluoride, and the conductive agent acetylene black at a mass ratio of 98:1:1, add N-methylpyrrolidone (NMP), and stir under the action of a vacuum mixer Obtain the positive electrode slurry uniformly; uniformly coat the positive electrode slurry on the aluminum foil with a thickness of 12 ⁇ m;
  • NMP N-methylpyrrolidone
  • Step 2 Dry the coated pole piece in an oven at 100°C to 130°C, cold press and cut to obtain a positive electrode piece.
  • the negative active material graphite, thickener sodium carboxymethyl cellulose, binder styrene butadiene rubber, conductive agent acetylene black are mixed according to the mass ratio of 97:1:1:1, add deionized water, and act in a vacuum mixer
  • the negative electrode slurry is obtained under the following conditions; the negative electrode slurry is uniformly coated on a copper foil with a thickness of 8 ⁇ m; the copper foil is dried at room temperature and then transferred to an oven for drying at 120° C. for 1 hour, and then cold pressed and slit to obtain a negative electrode sheet.
  • 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 concentration of lithium salt is 1 mol/L.
  • the positive electrode sheet, the separator film, and the negative electrode sheet in order, so that the separator film is located between the positive electrode and the negative electrode sheet for isolation. After winding into a square bare cell, it is filled with aluminum plastic film. After baking at °C to remove water, the corresponding non-aqueous electrolyte is injected and sealed, and the finished battery is obtained after the processes of standing, hot and cold pressing, forming, fixture, and sub-volume.
  • the preparation method of the positive pole piece and the battery in Example 2 refers to Example 1, except that the mass ratio between the first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide is 9:1.
  • Example 3 The preparation method of the positive pole piece and battery in Example 3 refers to Example 1, except that the mass ratio between the first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide is 6:4.
  • Table 1 for the TD, (D v 90-D v 10)/TD, D v 90/D v 10*D v 50 and the OI of the positive electrode active material of the positive electrode active material.
  • Example 4 The preparation method of the positive pole piece and battery in Example 4 refers to Example 1. The difference is that the element ratio of Ni:Co:Mn in the second lithium nickel transition metal oxide is 5:2:3, and the second lithium nickel transition metal oxide has a Ni:Co:Mn element ratio of 5:2:3.
  • Example 6 The preparation method of the positive pole piece and battery in Example 6 refers to Example 1. The difference is that the element ratio of Ni:Co:Mn in the second lithium nickel transition metal oxide is 9:0.5:0.5, and the first lithium nickel transition metal The mass ratio between the oxide and the second lithium nickel transition metal oxide is 8:2, and the TD, (D v 90-D v 10)/TD, D v 90/D v 10* of the prepared positive electrode active material See Table 1 for D v 50 and positive pole piece OI.
  • the preparation method of the positive pole piece and battery in Example 7 refers to Example 1.
  • the difference is that the first lithium nickel transition metal oxide and the coating element are B, that is, the compound corresponding to Al is not used for sintering, and the preparation is obtained.
  • the preparation method of the positive pole piece and battery in Example 8 refers to Example 1.
  • the coating element of the first lithium nickel transition metal oxide and the coating element is B, that is, the compound corresponding to Al is not used for sintering
  • the second The coating elements of the lithium nickel transition metal oxide are Al and B, and the compounds used in the sintering process are alumina and boron oxide.
  • the TD, (D v 90-D v 10)/TD, (D v 90-D v 10)/TD See Table 1 for D v 90/D v 10*D v 50 and positive pole piece OI.
  • the preparation method of the positive pole piece and battery in Example 9 refers to Example 1.
  • the element ratio of Ni:Co:Mn in the first lithium nickel transition metal oxide is 8.3:1.4:0.3
  • the coating element is Ba
  • the corresponding compound used for coating is barium oxide
  • L max /L min 1.7
  • the mass ratio between the first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide is 6:4, and the prepared positive electrode activity
  • the material TD, (D v 90-D v 10)/TD, D v 90/D v 10*D v 50 and positive pole piece OI are shown in Table 1.
  • the preparation method of the positive pole piece and battery in Example 10 refers to Example 1.
  • the element ratio of Ni:Co:Mn in the first lithium nickel transition metal oxide is 8.3:1.4:0.3
  • the corresponding compound used for coating is barium oxide
  • the element ratio of Ni:Co:Mn in the second lithium nickel transition metal oxide is 5:2:3
  • the particle size of the second lithium nickel transition metal oxide D v 50 (S) 4.3 ⁇ m
  • Lmax/Lmin 1.5
  • the coating elements are Al and Ti
  • the compound used in the sintering process is oxidation
  • the mass ratio between the first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide is 5:5
  • the TD, (D v 90-D v 10) of the positive electrode active material prepared is /TD, D v 90/D v
  • the preparation method of the positive pole piece and battery in Comparative Example 1 refers to Example 1.
  • the second lithium nickel transition metal is The element ratio of Ni:Co:Mn in the oxide is 5:2:3
  • L max /L min 1.5
  • the coating element is Al
  • Ti the compounds used in the sintering process are aluminum oxide and titanium oxide
  • the preparation method of the positive pole piece and battery in Comparative Example 2 refers to Example 1. The difference is that in the preparation method of the positive electrode active material, the second lithium nickel transition metal oxide is not used, and the obtained positive electrode active material TD, ( Refer to Table 1 for D v 90-D v 10)/TD, D v 90/D v 10*D v 50 and positive pole piece OI.
  • the preparation method of the positive pole piece and battery in Comparative Example 3 refers to Example 1.
  • the difference is that the mass ratio between the first lithium nickel transition metal oxide and the second lithium nickel transition metal oxide is 4:6, and the preparation is obtained See Table 1 for the TD, (Dv90-Dv10)/TD, Dv90/Dv10*Dv50 and the OI of the positive electrode active material of the positive electrode active material.
  • the preparation method of the positive pole piece and battery in Comparative Example 4 refers to Example 9.
  • the preparation method of the positive pole piece and battery in Comparative Example 5 refers to Example 1. The difference is that the first lithium nickel transition metal oxide is not used in the process of preparing the positive pole piece, and the TD, (Dv90) of the positive electrode active material obtained are prepared. -Dv10)/TD, Dv90/Dv10*Dv50 and positive pole piece OI refer to Table 1.
  • the preparation method of the positive pole piece and battery in Comparative Example 6 refers to Example 1. The difference is that in the process of preparing the first lithium nickel transition metal oxide, the coating process is not performed, and the obtained positive electrode active material TD, ( Dv90-Dv10)/TD, Dv90/Dv10*Dv50 and positive pole piece OI are shown in Table 1.
  • the positive pole piece is rolled under a certain pressure. Due to the ductility of the aluminum foil, the length of the diaphragm is 1006mm;
  • the first lithium nickel transition metal oxide in the form of secondary particles and the second lithium nickel transition metal oxide in the form of single crystal or similar single crystal particles are mixed and controlled.
  • the particle size distribution of the positive active material and the OI value of the positive pole pieces after mixing can improve the compaction density and at the same time improve the particle cracking during the cycle, improve the cycle life and the DCR growth during the cycle.
  • Surface-coated metal oxides and non-metal oxides can significantly improve cycle life and cycle DCR growth.

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Abstract

一种用于二次电池的正极极片、二次电池(5)、电池模块(4)、电池包(1)和装置。所述正极极片包括正极集流体和位于正极集流体表面的正极活性物质层，所述正极活性物质层包括正极活性物质，所述正极活性物质包括第一锂镍过渡金属氧化物和第二锂镍过渡金属氧化物，所述第一锂镍过渡金属氧化物包括第一基材和位于第一基材表面的第一包覆层，所述第一基材为二次颗粒，所述第二锂镍过渡金属氧化物为单晶或类单晶形貌颗粒。通过调控混合后正极活性物质的粒径分布和极片OI值，提高了正极极片中正极活性物质颗粒的抗压强度，有效抑制正极活性物质颗粒的颗粒开裂问题。

Description

一种用于二次电池的正极极片、二次电池、电池模块、电池包和装置 技术领域
本发明涉及电化学领域，特别是涉及一种用于二次电池的正极极片、二次电池、电池模块、电池包和装置。
背景技术
电动汽车对续航里程的要求越来越高，这就对动力电池的能量密度提出了更高要求。动力电池能量密度的提升，很大程度上取决于正极材料的选择。根据高容量、高放电电压平台的选取原则，锂镍过渡金属氧化物(例如，镍钴锰三元材料)的应用越来越多。其中，镍含量增加可以显著提升克容量，从而提高能量密度，因此高镍含量的锂镍过渡金属氧化物是当前的热门选择。
但是，锂镍过渡金属氧化物中镍含量的增加使得制备更加困难：温度高，则锂挥发严重；温度低，则晶粒不能充分长大，加工性能差。现在主流的高镍含量的锂镍过渡金属氧化物是由一次小晶粒聚集成的二次多晶大颗粒，但由于高镍含量的锂镍过渡金属氧化物充放电过程中c轴方向体积变化大，导致一次晶粒间易产生裂纹，从而恶化循环性能。
另外，锂镍过渡金属氧化物中镍含量的增加也影响了材料结构的稳定性，加剧了表面层状结构向岩盐相的转变，而且表面释氧也加剧了材料表面电解液的副反应。
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用于二次电池的正极极片、二次电池、电池模块、电池包和装置，用于解决现有技术中的问题。
为实现上述目的及其他相关目的，本发明的第一方面提供一种用于二次电池的正极极片，所述正极极片包括正极集流体和位于正极集流体表面的正极活性物质层，所述正极活性物质层包括正极活性物质，所述正极活性物质包括第一锂镍过渡金属氧化物和第二锂镍过渡金属氧化物，所述第一锂镍过渡金属氧化物包括第一基材和位于第一基材表面的第一包覆层，所述第一基材为二次颗粒，所述第一基材的化学式如式I所示：
Li 1+a1Ni x1Co y1Mn z1M b1O 2-e1X e1      (I)
式I中，-0.1<a1<0.1，0.5≤x1≤0.95，0.05≤y1≤0.2，0.03≤z1≤0.4，0≤b1≤0.05，0≤e1≤0.1，且x1+y1+z1+b1＝1；其中，M选自Al、Ti、Zr、Nb、Sr、Sc、Sb、Y、Ba、B、Co、Mn中的一种或多种的组合，X选自F和/或Cl；
所述第一包覆层选自金属氧化物和/或非金属氧化物；
所述第二锂镍过渡金属氧化物为单晶或类单晶形貌颗粒；
所述正极活性物质的粒径分布满足：40<D v90/D v10*D v50<80，单位：μm -1；
所述正极极片的压实密度为3.3g/cm 3～3.5g/cm 3时，所述正极极片的OI为10～40。
本发明第二方面提供本发明第一方面所提供的用于二次电池的正极极片的制备方法。
本发明第三方面提供一种二次电池，其包括本发明的第一方面所述的正极极片。
本发明第四方面提供一种电池模块，其包括本发明的第三方面所述的二次电池。
本发明第五方面提供一种电池包，其包括本发明的第四方面所述的电池模块。
本发明第六方面提供一种装置，其包括本发明的第三方面所述的二次电池，所述二次电池用作所述装置的电源。
相对于现有技术，本发明的有益效果为：
本发明用于二次电池的正极极片中，正极活性物质包括第一锂镍过渡金属氧化物和第二锂镍过渡金属氧化物，其中第一锂镍过渡金属氧化物为经包覆处理的二次颗粒，第二锂镍过渡金属氧化物为单晶或类单晶结构的单颗粒，通过调控混合后正极活性物质的粒径分布和极片OI值，提高了正极极片中正极活性物质颗粒的抗压强度，有效抑制正极活性物质颗粒的颗粒开裂问题，同时降低垂直于正极极片的(003)晶面的相对含量，使得制备获得的二次电池(例如，锂离子电池)具有高能量密度、产气量低、极片膨胀率低等特点，具有良好的产业化前景。
本发明的电池模块、电池包和装置包括所述的二次电池，因而至少具有与所述二次电池相同的优势。
附图说明
图1是电池的一实施方式的立体图。
图2是电池的一实施方式的分解图。
图3是电池模块的一实施方式的立体图。
图4是电池包的一实施方式的立体图。
图5是图4的分解图。
图6是电池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 电池
51 壳体
52 电极组件
53 顶盖组件
具体实施方式
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，以下结合实施例对本发明进行进一步详细说明。应当理解的是，本说明书中描述的实施例仅仅是为了解释本发明，并非为了限定本发明。
正极极片
本发明的第一方面提供一种用于二次电池的正极极片，正极极片包括正极集流体和位于正极集流体表面的正极活性物质层，正极活性物质层包括正极活性物质，正极活性物质包括第一锂镍过渡金属氧化物和第二锂镍过渡金属氧化物，第一锂镍过渡金属氧化物包括第一基材和位于第一基材表面的第一包覆层，第一基材为二次颗粒，第一锂镍过渡金属氧化物的化学式如式I所示：
Li 1+a1Ni x1Co y1Mn z1M b1O 2-e1X e1      (I)
式I中，-0.1<a1<0.1，0.5≤x1≤0.95，0.05≤y1≤0.2，0.03≤z1≤0.4，0≤b1≤0.05，0≤e1≤0.1，且x1+y1+z1+b1＝1；其中，M选自Al、Ti、Zr、Nb、Sr、Sc、Sb、Y、Ba、B、Co、Mn中的一种或多种的组合，X选自F和/或Cl；
第一包覆层选自金属氧化物和/或非金属氧化物；
第二锂镍过渡金属氧化物为单晶或类单晶形貌颗粒；
正极活性物质的粒径分布特征满足：40<D v90/D v10*D v50<80，单位：μm -1；
正极极片的压实密度为3.3g/cm 3～3.5g/cm 3时，正极极片的OI为10～40。
本发明中，D v10为正极活性物质的体积累计分布百分数达到10％时对应的粒径(单位：μm)；D v50为样品的体积累计分布百分数达到50％时对应的粒径(单位：μm)；D v90为样品的 体积累计分布百分数达到90％时对应的粒径(单位：μm)。正极极片的OI为正极极片的XRD衍射谱中正极活性材料的(003)晶面与(110)晶面相应的衍射峰面积的比值。
本发明所提供的用于二次电池的正极极片中，正极活性物质层包括正极活性物质，正极活性物质包括第一锂镍过渡金属氧化物和第二锂镍过渡金属氧化物，第一锂镍过渡金属氧化物中的第一基材为多晶形貌(由一次颗粒组成的二次颗粒)、且经金属氧化物和/或非金属氧化物包覆处理，第二锂镍过渡金属氧化物为单晶或类单晶形貌颗粒。本发明中，类单晶通常是指一次颗粒的尺寸大于1μm，但一次颗粒存在一定团聚；单晶通常是指一次颗粒的尺寸大于1μm，且无明显团聚。本发明通过调控混合后正极活性物质的粒径分布和正极极片OI值，有效正极活性物质颗粒的抑制颗粒开裂问题，在提高正极极片中正极活性物质颗粒的抗压强度的同时，降低正极极片中的正极活性材料的(003)晶面的相对量，有效解决极片膨胀率和产气的问题，从而获得了高能量密度、低极片膨胀率、产气量低的电化学储能装置。
本发明所提供的正极极片中，正极极片的压实密度为3.3g/cm 3～3.5g/cm 3时，正极极片的OI可以为10～15、15～20、20～25、25～30、30～35、或35～40，优选可以为10～20。通常来说，正极极片OI值反映了极片中正极活性材料晶面的整体取向程度，与极片制程工艺的涂布速度、烘干、冷压等多种过程参数密切相关。正极极片的OI值过高，表示垂直于正极极片长度方向的(003)晶面相对量过高，反映出正极极片在冷压后出现较严重的织构，在电池充放电过程中极片容易发生膨胀；但是如果正极极片OI值过低，表明此时正极极片中正极活性物质没有明显的取向性，颗粒强度过低，在冷压及循环中后期易发生颗粒破碎，引发产气问题。
本发明所提供的正极极片中，第二锂镍过渡金属氧化物包括第二基材，第二基材的化学式如式II所示：
Li 1+a2Ni x2Co y2Mn z2M’ b2O 2-e2X’ e2      (II)
式II中，-0.1<a2<0.1，0.5≤x2≤0.95，0.05≤y2≤0.2，0.03≤z2≤0.4，0≤b2≤0.05，0≤e2≤0.1，且x2+y2+z2+b2＝1；其中，M’选自Al、Ti、Zr、Nb、Sr、Sc、Sb、Y、Ba、B、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极片中，第一基材和第二基材的分子式可以各自独立的包括但不限于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 0.65Co 0.15Mn 0.2O 2、LiNi 0.65Co 0.12Mn 0.23O 2、LiNi 0.65Co 0.1Mn 0.25O 2、LiNi 0.65Co 0.05Mn 0.3O 2、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、 LiNi 0.92Co 0.03Mn 0.05O 2、LiNi 0.95Co 0.02Mn 0.03O 2等，也可以为上述物质经过掺杂元素M、M’、X、X’进行部分取代改性后的物质，M、M’各自独立的选自Al、Ti、Zr、Nb、Sr、Sc、Sb、Y、Ba、B、Co、Mn中的一种或多种的组合，X、X’各自独立的选自F和/或Cl。
在本发明一些优选的实施方式中，第一基材的分子式中Ni元素的相对含量x1可以满足：0.8≤x1≤0.95、0.8≤x1≤0.85、0.85≤x1≤0.9、或0.9≤x1≤0.95，第二基材的分子式中Ni元素的相对含量x2可以满足：0.8≤x2≤0.95，0.8≤x1≤0.85、0.85≤x1≤0.9、或0.9≤x1≤0.95，且第一基材与第二基材中Ni元素的相对含量x1、x2可以满足：∣x1-x2∣≤0.1。本发明中的第一锂镍过渡金属氧化物和第二锂镍过渡金属氧化物均选择镍含量较高的层状锂过渡金属氧化物，能够有效提高电池的能量密度，同时第一基材与第二基材中Ni元素的相对含量x1、x2的差值不大于0.1，可以实现当在同一充放电电压下，第一锂镍过渡金属氧化物和第二锂镍过渡金属氧化物具有较接近的脱/嵌锂程度，有利于提高电池的充放电循环寿命。
在本发明一些更优选的实施方式中，第一基材与第二基材中Ni元素的相对含量x1、x2满足：0<x1-x2<0.1。本发明中第一锂镍过渡金属氧化物的Ni元素含量x1略高于第二锂镍过渡金属氧化物x2，在有效平衡两种正极活性物质的脱/嵌锂程度的同时，有利于电池发挥出较高的能量密度。
本发明所提供的正极极片中，正极活性物质的粒径以及振实密度TD满足：4.4<(D v90-D v10)/TD<8。具体的，(D v90-D v10)/TD的取值范围可以为7.5～8、7～7.5、6.5～7、6～6.5、5.5～6、5～5.5、4.4～5。优选的，4.6<(D v90-D v10)/TD<6.5。其中，D v10、D v90单位为μm；TD为所述正极活性物质的振实密度(单位：g/cm 3)。本发明中当正极活性物质进一步满足(D v90-D v10)/TD的取值在上述范围时，正极活性物质不同形貌颗粒的粒度分布适中、颗粒间的间隙体积较低，有利于正极极片压实密度的提高。
本发明所提供的正极极片中，正极活性物质的振实密度TD可以为2.2g/cm 3～2.8g/cm 3、2.2g/cm 3～2.3g/cm 3、2.3g/cm 3～2.4g/cm 3、2.4g/cm 3～2.5g/cm 3、2.5g/cm 3～2.6g/cm 3、2.6g/cm 3～2.7g/cm 3、或2.7g/cm 3～2.8g/cm 3。本发明中，TD为正极活性物质的粉体振实密度，粉体振实密度的具体测量方法可以包括：将粉体填装于容器中(例如，25mL的容器，再例如，所使用的容器可以为量筒)，对容器进行振动后(例如，振动的具体条件可以为：振动频率为250次/分，振幅为3mm，振动5000次)，单位体积粉体的质量即为粉体振实密度。通常来说，TD越大，越利于实现高压实密度，但TD受材料单个颗粒的紧实度、材料的粒径分布、颗粒的形态等因素影响，有一定的上限。
本发明所提供的正极极片中，第一锂镍过渡金属氧化物可以为球形颗粒，第一锂镍过渡金属氧化物的球形度γ可以为0.7～1。具体的，第一锂镍过渡金属氧化物的球形度γ可以为0.7～0.9、0.7～0.8、0.8～0.9、或0.9～1。本发明中，所述球形度可以通过以下方式测量得到：在正极极片横截面的SEM照片中，选择至少30个截面直径在正极活性物质D v10数值以上的二次颗粒，测量截面SEM图片中各自二次颗粒的最大内接圆半径(R max)与最小外接圆半径(R min)的比值，求平均值，即可以得到γ。本发明中，第一锂镍过渡金属氧化物为二次颗粒，当二次颗粒的球形度在上述范围内时，表明二次颗粒内一次颗粒的尺寸均一、分布较均匀，二次颗粒较紧实，力学强度较高。
本发明所提供的正极极片中，第二锂镍过渡金属氧化物的最长径L max与最短径L min的尺寸比例满足：1≤L max/L min≤3、1≤L max/L min≤1.5、1.5≤L max/L min≤2、2≤L max/L min≤2.5、或2.5≤L max/L min≤3。本发明中，所述L max/L min可以通过以下方式测量得到：在正极极片横截面的SEM照片中，选择至少30个截面直径在正极活性物质D v10数值以上的单晶或类单晶形貌颗粒，测量截面SEM图片各自颗粒的最长直径(L max)与最短直径(L min)的比值，求平均值，即可以得到L max/L min。本发明中，第二锂镍过渡金属氧化物为单晶或类单晶形貌的颗粒，当单颗粒的L max/L min在上述范围内时，与球形度在0.7～1之间的二次颗粒混合后，能够更好的填充二次颗粒的间隙体积，在提升正极极片的压实密度、电池体积能量密度的同时，还可以有效抑制循环过程中正极极片的体积膨胀率，改善循环性能。
本发明所提供的正极极片中，第一锂镍过渡金属氧化物的D v50(L)可以为5μm～18μm、5μm～6μm、6μm～8μm、8μm～10μm、10μm～12μm、12μm～14μm、14μm～16μm、或16μm～18μm，优选可以为8μm～12um。第二锂镍过渡金属氧化物的D v50(S)可以为1μm～5μm、1μm～2μm、2μm～3μm、3μm～4μm、或4μm～5μm。第一锂镍过渡金属氧化物中的基材为多晶形态(由多个一次颗粒团聚形成的二次颗粒)，第二锂镍过渡金属氧化物为单晶或类单晶形貌颗粒，第一锂镍过渡金属氧化物相对于第二锂镍过渡金属氧化物整体上具有较大的粒径分布，两者之间的粒径分布D v50(L)与D v50(S)更优选可以满足：2≤D v50(L)/D v50(S)≤7、2≤D v50(L)/D v50(S)≤3、3≤D v50(L)/D v50(S)≤4、4≤D v50(L)/D v50(S)≤5、5≤D v50(L)/D v50(S)≤6、或6≤D v50(L)/D v50(S)≤7。本发明中，第一锂镍过渡金属氧化物D v50(L)和第二锂镍过渡金属氧化物D v50(S)的比值在上述范围内时，有利于抑制粒径尺寸较大的二次颗粒高镍材料的颗粒开裂问题，保证正极活性物质能够发挥出较高的克容量，同时提高整体正极极片的力学强度和压实密度。
本发明所提供的正极极片中，第一锂镍过渡金属氧化物的重量百分比含量可以为 50％～90％、85％～90％、80％～85％、75％～80％、70％～75％、65％～70％、60％～65％、55％～60％、或50％～55％，优选可以为60％～85％。第二锂镍过渡金属氧化物的重量百分比含量可以为10％～50％、10％～15％、15％～20％、20％～25％、25％～30％、30％～35％、35％～40％、40％～45％、或45％～50％，优选可以为15％～40％。本发明中，第一锂镍过渡金属氧化物以及第二锂镍过渡金属氧化物在正极极片中的重量百分比控制在上述范围内，在一定程度上可以调控正极极片的OI值，同时提高极片的压实密度和力学强度。
本发明所提供的正极极片中，第二锂镍过渡金属氧化物还可以包括位于第二基材表面的第二包覆层，第二包覆层为金属氧化物和/或非金属氧化物。
本发明所提供的正极极片中，第一包覆层和/或第二包覆层可以是金属氧化物和/或非金属氧化物，例如，可以是仅含有金属元素或者非金属元素的氧化物，也可以同时含有金属元素和非金属元素的氧化物。上述氧化物中，金属元素通常可以是例如铝、锆、锌、钛、硅、锡、钨、钇、钴、钡等，非金属元素通常可以是例如磷、硼等。具体的，第一包覆层和/或第二包覆层可以是包括但不限于氧化铝、氧化锆、氧化锌、氧化钛、氧化硅、氧化锡、氧化钨、氧化钇、氧化钴、氧化钡、氧化磷、氧化硼、以及锂铝氧化物、锂锆氧化物、锂锌氧化物、锂镁氧化物、锂钨氧化物、锂钇氧化物、锂钴氧化物、锂钡氧化物、锂磷氧化物或者锂硼氧化物等中的一种或多种的组合。本发明中，正极活性物质的包覆层选用上述金属氧化物和/或非金属氧化物，氧化物包覆层与基材的结合力良好，在充放电过程中包覆层不易脱落，减少基材与电解液接触面积的部分，可以有效地对高镍正极材料的表面进行改性，降低正极材料与电解液的副反应，从而可以有效抑制电池的产气现象。
本发明所提供的正极材料中，第一包覆层中优选至少同时含有一种金属元素的氧化物和一种非金属元素的氧化物。含有上述元素的氧化物不仅能够提高包覆层在二次颗粒基材表面附着的稳定性，还可以使包覆层兼具一定的导离子性和导电子性，减少包覆层对正极材料极化问题的影响。
正极极片的制备方法
本发明第二方面提供本发明第一方面所提供的用于二次电池的正极极片的制备方法，合适的制备正极极片的方法对于本领域技术人员来说应该是已知的，例如，正极极片可以包括：
提供包括第一锂镍过渡金属氧化物和第二锂镍过渡金属氧化物的正极活性物质；
将正极活性物质、粘结剂、导电剂混合形成浆料后，涂布于正极集流体上。
本发明所提供的正极材料的制备方法中，第一锂镍过渡金属氧化物和/或第二锂镍过渡金属氧化物可以是经过表面修饰的，例如，可以将第一锂镍过渡金属氧化物和/或第二锂镍过渡金属氧化物分别进行表面修饰后，再进行混合，其中第一锂镍过渡金属氧化物与第二锂镍过渡金属氧化物的表面修饰方法可以相同、也可以不同；也可以将第一锂镍过渡金属氧化物与第二锂镍过渡金属氧化物先混合，再一起进行表面修饰工艺。
本发明所提供的正极极片的制备方法中，可以包括：提供第一锂镍过渡金属氧化物。提供第一锂镍过渡金属氧化物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：将第一锂镍过渡金属氧化物的基材的原料混合、烧结，以提供第一基材；将第一基材进行包覆处理，以提供第一锂镍过渡金属氧化物。本领域技术人员可根据第一锂镍过渡金属氧化物的元素组成，选择合适的原料和配比，以进一步制备获得第一基材。例如，第一锂镍过渡金属氧化物的原料可以包括第一锂镍过渡金属氧化物的前驱体、锂源、M源、X源等，各原料之间的比例通常参照第一锂镍过渡金属氧化物中各元素的比例进行配比。更具体的，第一锂镍过渡金属氧化物的前驱体可以是包括但不限于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 0.65Co 0.15Mn 0.2(OH) 2、Ni 0.65Co 0.12Mn 0.23(OH) 2、Ni 0.65Co 0.1Mn 0.25(OH) 2、Ni 0.65Co 0.05Mn 0.3(OH) 2、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、Ni 0.92Co 0.03Mn 0.05(OH) 2、Ni 0.95Co 0.02Mn 0.03(OH) 2等，锂源可以是含锂的化合物，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，M源通常可以是含M元素的化合物，上述含M元素的化合物可以是含有Al、Ti、Zr、Nb、Sr、Sc、Sb、Y、Ba、Co、Mn中至少一种元素的氧化物、硝酸盐、碳酸盐中的一种或几种，X源可以是含X元素的化合物，上述含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。第一锂镍过渡金属氧化物的基材的原料的烧结的条件可以是700℃～900℃、氧气浓度≥20％的烧结条件。将第一基材进行包覆处理的方法具体可以包括：将第一基材在含包覆元素的化合物存在的条件下烧结，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等中的一种或多种元素的氧化物、硝酸盐、磷酸盐、碳酸盐等，包覆元素的使用量可以是通常≤2wt％，包覆处理中的烧结的条件可以是200℃～700℃。
本发明所提供的正极极片的制备方法中，可以包括：提供第二锂镍过渡金属氧化物。提供第二锂镍过渡金属氧化物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：将第二锂镍过渡金属氧化物的基材的原料混合、烧结，以提供第二基材；将第二基材进行包 覆处理，以提供第二锂镍过渡金属氧化物。本领域技术人员可根据第二锂镍过渡金属氧化物的元素组成，选择合适的原料和配比，以进一步制备获得第二基材。例如，第二锂镍过渡金属氧化物的原料可以包括第二锂镍过渡金属氧化物的前驱体、锂源、M’源、X’源等，各原料之间的比例通常参照第二锂镍过渡金属氧化物中各元素的比例进行配比。更具体的，第二锂镍过渡金属氧化物的前驱体可以是包括但不限于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 0.65Co 0.15Mn 0.2(OH) 2、Ni 0.65Co 0.12Mn 0.23(OH) 2、Ni 0.65Co 0.1Mn 0.25(OH) 2、Ni 0.65Co 0.05Mn 0.3(OH) 2、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、Ni 0.92Co 0.03Mn 0.05(OH) 2、Ni 0.95Co 0.02Mn 0.03(OH) 2等，锂源可以是含锂的化合物，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，M’源通常可以是含M元素的化合物，上述含M’元素的化合物可以是含有Al、Ti、Zr、Nb、Sr、Sc、Sb、Y、Ba、Co、Mn中至少一种元素的氧化物、硝酸盐、碳酸盐中的一种或几种，X’源可以是含X’元素的化合物，上述含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。第二锂镍过渡金属氧化物的基材的原料的烧结的条件可以是750℃～950℃、氧气浓度≥20％的烧结条件。将第二基材进行包覆处理的方法具体可以包括：将第二基材在含包覆元素的化合物存在的条件下烧结，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等中的一种或多种元素的氧化物、硝酸盐、磷酸盐、碳酸盐等，包覆元素的使用量可以是通常≤2wt％，包覆处理中的烧结的条件可以是200℃～700℃。
本发明所提供的正极极片的制备方法中，粘结剂通常包括含氟聚烯烃类粘结剂，相对于含氟聚烯烃类粘结剂来说，水通常是良溶剂，即含氟聚烯烃类粘结剂通常在水中具有良好的溶解性，例如，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。
本发明所提供的正极极片的制备方法中，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。导电剂的重量可以占正极活性物质层总质量的1wt％～10wt％。更优选的，正极极片中导电剂与正极活性物质的重量比为 1.0wt％～5.0wt％。
本发明所提供的正极极片的制备方法中，正极极片的正极集流体通常可以为层体，正极集流体通常是可以汇集电流的结构或零件，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，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。
二次电池
本发明的第三方面提供一种二次电池，包括本发明第一方面所提供的正极极片。
在本发明所提供的二次电池中，需要说明的是，二次电池可为超级电容器、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，仅示出二次电池为锂离子电池的实施例，但本发明不限于此。
图1是锂离子电池的一具体实施例的立体图。图2是图1的分解图。参照图1至图2，电池5包括壳体51、电极组件52、顶盖组件53以及电解液(未示出)。电极组件52收容于壳体51内。电极组件52的数量不受限制，可以为一个或多个。
需要注意的是图1所示的电池5为罐型电池，但不限于此，电池5可以是袋型电池，即壳体51由金属塑膜替代且取消顶盖组件53。
在锂离子电池中，可以包括正极极片、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，正极极片可以是本发明第一方面所提供的正极极片。制备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，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，负极极片通常可以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，负极活性物质层通常包括负极活性物质。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，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；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；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。负极集流体通常是汇集电流的结构或零件，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， 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，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，电解液通常可以包括电解质和溶剂，合适的适用于锂离子电池的电解液对于本领域技术人员来说应该是已知的，例如，电解质通常可以包括锂盐等，更具体的，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LiPF 6、LiBF 4、LiN(SO 2F) 2(LiFSI)、LiN(CF 3SO 2) 2(LiTFSI)、LiClO 4、LiAsF 6、LiB(C 2O 4) 2(LiBOB)、LiBF 2C 2O 4(LiDFOB)等中的一种或多种的组合；再例如，电解质的浓度可以为0.8mol/L～1.5mol/L之间；再例如，电解液中所使用的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，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。
电池模块
在本申请的第四方面提供了一种电池模块，其包括本申请的第三方面所提供的二次电池。电池模块中通常可以包括一个或多个二次电池，电池模块可以作为电源或储能装置，电池模块中的电池的数量可以根据电池模块的应用和容量进行调节。
图3是电池模块的一具体实施例的立体图。
参照图3，电池模块4包括多个电池5。多个电池5沿纵向排列。
电池包
在本申请的第五方面提供了一种电池包，其包括本申请的第三方面所提供的二次电池，或第四方面所提供的电池模组块。
图4是电池包1的一具体实施例的立体图。图5是图4的分解图。
参照图4和图5，电池包1包括上箱体2、下箱体3以及电池模块4。
上箱体2和下箱体3组装在一起并形成收容电池模块4的空间。电池模块4置于组装在一起的上箱体2和下箱体3的空间内。电池模块4的输出极从上箱体2和下箱体3的其中之一或二者之间穿出，以向外部供电或从外部充电。电池包1采用的电池模块4的数量和排列可以依据实际 需要来确定。电池包1可以作为电源或储能装置。
装置
本发明第六方面提供一种装置，其包括本发明的第三方面所提供的二次电池，二次电池用作所述装置的电源。
图6是上述装置的一具体实施例的立体图。在图6中，采用电池5的装置为电动汽车。当然不限于此，采用电池5的装置可以为除电动汽车外的任何电动车辆(例如电动大巴、电动有轨电车、电动自行车、电动摩托车、电动踏板车、电动高尔夫球车、电动卡车)、电动船舶、电动工具、电子设备及储能系统。电动汽车可以为电动纯电动车、混合动力电动车、插电式混合动力电动车。当然，依据实际使用形式，本申请第六方面所提供的装置可包括本申请的第四方面所提供的电池模块4，当然，本申请第六方面提供的装置也可包括本申请的第五方面所提供的电池包1。
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、正极活性物质的制备
1)制备第一锂镍过渡金属氧化物和第二锂镍过渡金属氧化物的前驱体：将硫酸镍、硫酸 锰、硫酸钴按摩尔比8:1:1配置成1mol/L溶液，利用氢氧化物共沉淀技术制备得到粒径D v50(L)为9.7μm的第一锂镍过渡金属氧化物的前驱体；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2.9μm的第二锂镍过渡金属氧化物的前驱体。制备前躯体的过程中，通过控制反应时间、共沉淀时的pH值、氨浓度实现对第一锂镍过渡金属氧化物和第二锂镍过渡金属氧化物的前驱体的颗粒粒径、形态的调控；
2)第一锂镍过渡金属氧化物(多晶LiNi 0.8Co 0.1Mn 0.1O 2)的制备方法：
将上述第一锂镍过渡金属氧化物的前驱体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830℃进行烧结，冷却后通过机械研磨即为第一锂镍过渡金属氧化物的基材；
将上述第一锂镍过渡金属氧化物的基材与0.2wt％的含包覆元素Al的化合物Al 2O 3、0.2wt％的含包覆元素B的化合物硼酸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，形成第一锂镍过渡金属氧化物的第一包覆层，即得到表面包覆的第一锂镍过渡金属氧化物，上述材料的D v50、球形度和包覆材料参见表1。
3)第二锂镍过渡金属氧化物(单晶LiNi 0.8Co 0.1Mn 0.1O 2)的制备方法：
将上述第二锂镍过渡金属氧化物的前驱体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，然后置于氧气浓度30％的气氛炉中在870℃进行烧结4h，冷却后通过气流粉末进行研磨即为第二锂镍过渡金属氧化物的基材；
将第二锂镍过渡金属氧化物的基材与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，即得到表面修饰的第二锂镍过渡金属氧化物，材料的D v50、L max/L min的比值和包覆材料参见表1。
4)将上述表面修饰的第一锂镍过渡金属氧化物与表面修饰的第二锂镍过渡金属氧化物以7:3的质量比混合均匀，得到实施例1的正极活性物质，实施例1正极活性物质的TD、(D v90-D v10)/TD、D v90/D v10*D v50和正极极片OI参见表1。
2、电池的制备
1)正极极片的制备
步骤1：将上述得到的正极活性物质、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
实施例2中正极极片和电池的制备方法参照实施例1，不同之处在于第一锂镍过渡金属氧化物与第二锂镍过渡金属氧化物之间的质量比为9:1，制备获得的正极活性物质的TD、(D v90-D v10)/TD、D v90/D v10*D v50和正极极片OI参见表1。
实施例3
实施例3中正极极片和电池的制备方法参照实施例1，不同之处在于第一锂镍过渡金属氧化物与第二锂镍过渡金属氧化物之间的质量比为6:4，制备获得的正极活性物质的TD、(D v90-D v10)/TD、D v90/D v10*D v50和正极极片OI参见表1。
实施例4
实施例4中正极极片和电池的制备方法参照实施例1，不同之处在于第二锂镍过渡金属 氧化物中Ni:Co:Mn元素比为5:2:3，第二锂镍过渡金属氧化物的粒径D v50(S)＝4.3μm，L max/L min＝1.5，包覆元素为Al、Ti，烧结过程中所使用的化合物为氧化铝和氧化钛，第一锂镍过渡金属氧化物与第二锂镍过渡金属氧化物之间的质量比为8:2，制备获得的正极活性物质的TD、(D v90-D v10)/TD、D v90/D v10*D v50和正极极片OI参见表1。
实施例5
实施例5中正极极片和电池的制备方法参照实施例1，不同之处在于第一锂镍过渡金属氧化物中Ni:Co:Mn元素比为6:2:2，第一锂镍过渡金属氧化物的粒径D v50(L)＝9.6μm，球形度γ＝0.81，制备获得的正极活性物质的TD、(D v90-D v10)/TD、D v90/D v10*D v50和正极极片OI参见表1。
实施例6
实施例6中正极极片和电池的制备方法参照实施例1，不同之处在于第二锂镍过渡金属氧化物中Ni:Co:Mn元素比为9:0.5:0.5，第一锂镍过渡金属氧化物与第二锂镍过渡金属氧化物之间的质量比为8:2，制备获得的正极活性物质的TD、(D v90-D v10)/TD、D v90/D v10*D v50和正极极片OI参见表1。
实施例7
实施例7中正极极片和电池的制备方法参照实施例1，不同之处在于第一锂镍过渡金属氧化物与的包覆元素为B，即未使用Al所对应的化合物进行烧结，制备获得的正极活性物质的TD、(D v90-D v10)/TD、D v90/D v10*D v50和正极极片OI参见表1。
实施例8
实施例8中正极极片和电池的制备方法参照实施例1，不同之处在于第一锂镍过渡金属氧化物与的包覆元素为B，即未使用Al所对应的化合物进行烧结，第二锂镍过渡金属氧化物的包覆元素为Al、B，烧结过程中所使用的化合物为氧化铝和氧化硼，制备获得的正极活性物质的TD、(D v90-D v10)/TD、D v90/D v10*D v50和正极极片OI参见表1。
实施例9
实施例9中正极极片和电池的制备方法参照实施例1，不同之处在于第一锂镍过渡金属氧化物中Ni:Co:Mn元素比为8.3:1.4:0.3，第一锂镍过渡金属氧化物的粒径D v50(L)＝12.3μm，球形度γ＝0.85，包覆元素为Ba，对应包覆时所使用的化合物为氧化钡，第二锂镍过渡金属氧化物的粒径D v50(S)＝2.2μm，L max/L min＝1.7，第一锂镍过渡金属氧化物与第二锂镍过渡金属氧化物之间的质量比为6:4，制备获得的正极活性物质的TD、(D v90-D v10)/TD、D v90/D v10*D v50和正极极片OI参见表1。
实施例10
实施例10中正极极片和电池的制备方法参照实施例1，不同之处在于第一锂镍过渡金属氧化物中Ni:Co:Mn元素比为8.3:1.4:0.3，第一锂镍过渡金属氧化物的粒径D v50(L)＝12.3μm，球形度γ＝0.85，对应包覆时所使用的化合物为氧化钡，第二锂镍过渡金属氧化物中Ni:Co:Mn元素比为5:2:3，第二锂镍过渡金属氧化物的粒径D v50(S)＝4.3μm，Lmax/Lmin＝1.5，包覆元素为Al、Ti，烧结过程中所使用的化合物为氧化铝、氧化钛，第一锂镍过渡金属氧化物与第二锂镍过渡金属氧化物之间的质量比为5:5，制备获得的正极活性物质的TD、(D v90-D v10)/TD、D v90/D v10*D v50和正极极片OI参见表1。
对比例1
对比例1中正极极片和电池的制备方法参照实施例1，第一锂镍过渡金属氧化物的粒径D v50(L)＝7.8μm，球形度γ＝0.77，第二锂镍过渡金属氧化物中Ni:Co:Mn元素比为5:2:3，第二锂镍过渡金属氧化物的粒径D v50(S)＝4.3μm，L max/L min＝1.5，包覆元素为Al、Ti，烧结过程中所使用的化合物为氧化铝、氧化钛，制备获得的正极活性物质的TD、(D v90-D v10)/TD、D v90/D v10*D v50和正极极片OI参见表1。
对比例2
对比例2中正极极片和电池的制备方法参照实施例1，不同之处在于正极活性物质的制备方法中，未使用第二锂镍过渡金属氧化物，制备获得的正极活性物质的TD、(D v90-D v10)/TD、D v90/D v10*D v50和正极极片OI参见表1。
对比例3
对比例3中正极极片和电池的制备方法参照实施例1，不同之处在于第一锂镍过渡金属氧化物与第二锂镍过渡金属氧化物之间的质量比为4:6，制备获得的正极活性物质的TD、(Dv90-Dv10)/TD、Dv90/Dv10*Dv50和正极极片OI参见表1。
对比例4
对比例4中正极极片和电池的制备方法参照实施例9，不同之处在于第一锂镍过渡金属氧化物的粒径D v50(L)＝16.8μm，第二锂镍过渡金属氧化物的粒径D v50(S)＝2.9μm，L max/L min＝2，第一锂镍过渡金属氧化物与第二锂镍过渡金属氧化物之间的质量比为9:1，制备获得的正极活性物质的TD、(D v90-D v10)/TD、D v90/D v10*D v50和正极极片OI参见表1。
对比例5
对比例5中正极极片和电池的制备方法参照实施例1，不同之处在于制备正极极片的过程中未使用第一锂镍过渡金属氧化物，制备获得的正极活性物质的TD、(Dv90-Dv10)/TD、Dv90/Dv10*Dv50和正极极片OI参见表1。
对比例6
对比例6中正极极片和电池的制备方法参照实施例1，不同之处在于制备第一锂镍过渡金属氧化物的过程中，未进行包覆处理，制备获得的正极活性物质的TD、(Dv90-Dv10)/TD、Dv90/Dv10*Dv50和正极极片OI参见表1。
检测方法
(1)二次颗粒球形度的测试方法：
对正极极片的横截面拍摄SEM照片，选择至少30个截面直径在正极活性物质D v10数值以上的二次颗粒，测量SEM图片中每个二次颗粒的最大内接圆半径(R max)与最小外接圆半径(R min)的比值，求平均值，即可以得到二次颗粒的球形度γ。
(2)单晶/类单晶颗粒Lmax/Lmin的测试方法：
对正极极片横截面的SEM照片中，选择至少30个截面直径在正极活性物质D v10数值以上的单晶或类单晶形貌颗粒，测量SEM图片各自颗粒的最长直径(L max)与最短直径(L min)的比值，求平均值，即可以得到L max/L min。各实施例及对比例的测试结果见表2。
(3)振实密度TD的测试方法：
将10g粉体填装于量程为25mL的量筒中，对填料后的量筒以振动频率为250次/分，振幅为3mm，振动5000次，读取此时粉料在量筒中占用的体积，即可计算得出单位体积粉体的质量，即为粉体振实密度TD。各实施例及对比例的测试结果见表2。
(4)正极极片OI值的测试方法：
将制备好的正极极片，水平放置于XRD衍射仪中测试正极极片的XRD衍射谱，计算该XRD衍射图谱中正极活性物质的(003)晶面与(110)晶面对应的衍射峰面积的比值，即为正极极片的OI值。各实施例及对比例的测试结果见表2。
(5)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；
各实施例及对比例的测试结果见表2。
(6)45℃循环400周容量保持率的测试方法：
在45℃下，将锂离子电池以1C恒流充电至电压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400周期，并记录400周期以后的放电容量。根据首次循环的放电容量和400周期以后的放电容量，计算获得45℃循环400周容量保持率。
各实施例及对比例的测试结果见表2。
(7)循环DCR增长的测试：
25℃下，将电池以1C恒流/恒压(以1C恒流充电到4.2V，然后4.2V恒压充电至0.05C)充电到100％SOC，然后以1C恒流放电30min，搁置60min，记录搁置后电压U1；然后以4C恒定电流放电至30s，记录放电后的电压U2；
依照公式计算锂离子电池的直流阻抗：DCR＝(U2-U1)/(4C-1C)。
各实施例及对比例的测试结果见表2。
表1
Figure PCTCN2019122332-appb-000001
Figure PCTCN2019122332-appb-000002
表2
Figure PCTCN2019122332-appb-000003
Figure PCTCN2019122332-appb-000004
通过实施例和对比例的比较，可以看出，将二次颗粒形态的第一锂镍过渡金属氧化物和单晶或类单晶形貌颗粒的第二锂镍过渡金属氧化物混合，并控制混合后正极活性物质的粒径分布以及正极极片的OI值，在改善压实密度的同时，可以改善循环过程中的颗粒开裂、改善循环寿命和循环过程中的DCR增长。表面包覆的金属氧化物和非金属氧化物，可以显著改善循环寿命和循环DCR增长。
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 (14)

  1. 一种用于二次电池的正极极片，所述正极极片包括正极集流体和位于正极集流体表面的正极活性物质层，所述正极活性物质层包括正极活性物质，所述正极活性物质包括第一锂镍过渡金属氧化物和第二锂镍过渡金属氧化物，所述第一锂镍过渡金属氧化物包括第一基材和位于第一基材表面的第一包覆层，所述第一基材为二次颗粒，所述第一基材的化学式如式I所示：
    Li 1+a1Ni x1Co y1Mn z1M b1O 2-e1X e1  (I)
    式I中，-0.1<a1<0.1，0.5≤x1≤0.95，0.05≤y1≤0.2，0.03≤z1≤0.4，0≤b1≤0.05，0≤e1≤0.1，且x1+y1+z1+b1＝1；其中，M选自Al、Ti、Zr、Nb、Sr、Sc、Sb、Y、Ba、B、Co、Mn中的一种或多种的组合，X选自F和/或Cl；
    所述第一包覆层选自金属氧化物和/或非金属氧化物；
    所述第二锂镍过渡金属氧化物为单晶或类单晶形貌颗粒；
    所述正极活性物质的粒径分布满足：40<D v90/D v10*D v50<80，单位：μm -1；
    所述正极极片的压实密度为3.3g/cm 3～3.5g/cm 3时，所述正极极片的OI为10～40。
  2. 如权利要求1所述的正极极片，其特征在于，所述第二锂镍过渡金属氧化物包括第二基材，所述第二基材的化学式如式II所示：
    Li 1+a2Ni x2Co y2Mn z2M’ b2O 2-e2X’ e2  (II)
    式II中，-0.1<a2<0.1，0.5≤x2≤0.95，0.05≤y2≤0.2，0.03≤z2≤0.4，0≤b2≤0.05，0≤e2≤0.1，且x2+y2+z2+b2＝1；其中，M’选自Al、Ti、Zr、Nb、Sr、Sc、Sb、Y、Ba、B、Co、Mn中的一种或多种的组合，X’选自F和/或Cl；
    优选的，所述第一基材与所述第二基材的分子式中Ni元素的相对含量x1、x2满足：
    0.8≤x1≤0.95，0.8≤x2≤0.95，且∣x1-x2∣≤0.1；
    更优选的，所述x1、x2满足：0<x1-x2<0.1。
  3. 如权利要求1或2所述的正极极片，其特征在于，所述正极极片的压实密度为3.3g/cm 3～3.5g/cm 3时，所述正极极片的OI为10～20。
  4. 如权利要求1～3中任一项所述的正极极片，其特征在于，所述正极活性物质满足：4.4<(D v90-D v10)/TD<8，优选的，4.6<(D v90-D v10)/TD<6.5，
    其中，D v10、D v90单位为μm；TD为所述正极活性物质的振实密度(单位：g/cm 3)。
  5. 如权利要求4所述的正极极片，其特征在于，所述正极活性物质的振实密度TD为2.2g/cm 3～2.8g/cm 3。
  6. 如权利要求1～5中任一项所述的正极极片，其特征在于，所述第一锂镍过渡金属氧化物为球形颗粒，所述第一锂镍过渡金属氧化物颗粒的球形度γ为0.7～1。
  7. 如权利要求1～6中任一项所述的正极极片，其特征在于，所述第二锂镍过渡金属氧化物颗粒的最长径L max与最短径L min的尺寸比例满足：1≤L max/L min≤3。
  8. 如权利要求1～7中任一项所述的正极极片，其特征在于，所述第一锂镍过渡金属氧化物的D v50(L)为5μm～18μm，所述第二锂镍过渡金属氧化物的D v50(S)为1μm～5μm；
    优选的，所述D v50(L)与D v50(S)满足：2≤D v50(L)/D v50(S)≤7。
  9. 如权利要求1～8中任一项所述的正极极片，其特征在于，所述正极活性物质中，所述第一锂镍过渡金属氧化物的重量百分比含量为50％～90％，优选为60％～85％；
    且所述第二锂镍过渡金属氧化物的重量百分比含量为10％～50％，优选为15％～40％。
  10. 如权利要求2所述的正极极片，其特征在于，所述第二锂镍过渡金属氧化物还包括位于第二基材表面的第二包覆层，所述第二包覆层为金属氧化物和/或非金属氧化物，优选的，所述第二包覆层物质为金属氧化物。
  11. 一种二次电池，包括如权利要求1～10任一项所述的正极极片。
  12. 一种电池模块，其特征在于，包括如权利要求11所述的二次电池。
  13. 一种电池包，其特征在于，包括如权利要求12所述的电池模块。
  14. 一种装置，其特征在于，包括如权利要求11所述的二次电池，所述二次电池用作所述装置的电源，优选的，所述装置包括电动车辆、混合动力电动车辆、插电式混合动力电动车辆、电动自行车、电动踏板车、电动高尔夫球车、电动卡车、电动船舶、储能系统。
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