WO2021042989A1 - 正极活性材料、其制备方法、正极极片、锂离子二次电池及其相关的电池模块、电池包和装置 - Google Patents

正极活性材料、其制备方法、正极极片、锂离子二次电池及其相关的电池模块、电池包和装置 Download PDF

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WO2021042989A1
WO2021042989A1 PCT/CN2020/109987 CN2020109987W WO2021042989A1 WO 2021042989 A1 WO2021042989 A1 WO 2021042989A1 CN 2020109987 W CN2020109987 W CN 2020109987W WO 2021042989 A1 WO2021042989 A1 WO 2021042989A1
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active material
positive electrode
electrode active
oxide
lithium
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PCT/CN2020/109987
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English (en)
French (fr)
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钭舒适
胡春华
蒋耀
吴奇
何金华
邓斌
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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 EP20860496.7A priority Critical patent/EP3993095A4/en
Publication of WO2021042989A1 publication Critical patent/WO2021042989A1/zh
Priority to US17/683,392 priority patent/US20220185697A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • C01G53/40—Nickelates
    • C01G53/42—Nickelates containing alkali metals, e.g. LiNiO2
    • C01G53/44—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese
    • C01G53/50—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese of the type [MnO2]n-, e.g. Li(NixMn1-x)O2, Li(MyNixMn1-x-y)O2
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/50—Solid solutions
    • C01P2002/52—Solid solutions containing elements as dopants
    • C01P2002/54—Solid solutions containing elements as dopants one element only
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/10—Solid density
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/11—Powder tap density
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/12—Surface area
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/40—Electric properties
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • This application belongs to the technical field of secondary batteries, and specifically relates to a positive electrode active material, a preparation method thereof, a positive electrode pole piece, a lithium ion secondary battery and related battery modules, battery packs and devices.
  • Lithium-ion secondary battery is a kind of rechargeable battery, which mainly relies on the movement of lithium ions between the positive electrode and the negative electrode to work, and is a clean energy that is currently widely used.
  • the positive electrode active material provides lithium ions that reciprocate between the positive and negative electrodes for the battery charging and discharging process. Therefore, the positive electrode active material is very important to the performance of the battery.
  • the lithium-nickel-based cathode active material has a higher theoretical capacity.
  • the lithium-ion secondary battery using the lithium-nickel-based cathode active material can be expected to obtain a higher energy density, but research has found that the high-temperature cycle performance of this kind of lithium-ion secondary battery is better. difference.
  • the first aspect of the present application provides a positive electrode active material, which includes secondary particles aggregated from primary particles, the primary particles are lithium transition metal oxides, and the transition metal sites of the lithium transition metal oxides include nickel and doping elements; And the Young's modulus E of the primary particles satisfies 175GPa ⁇ E ⁇ 220GPa.
  • the cathode active material of the present application includes secondary particles aggregated from primary particles, the primary particles include lithium transition metal oxides, and the transition metal sites of the lithium transition metal oxides include nickel, thereby exhibiting higher charge and discharge voltages and The specific capacity characteristics make the lithium ion secondary battery have a higher energy density.
  • the transition metal sites of the lithium transition metal oxide also include doping elements, so that the Young's modulus E of the primary particles satisfies 175GPa ⁇ E ⁇ 220GPa.
  • the active material can better adapt to the insertion and extraction of lithium ions, thereby improving the structural stability and high temperature cycle stability of the positive electrode active material, and improving the high temperature cycle performance of the lithium ion secondary battery.
  • the use of the positive electrode active material of the present application enables the lithium ion secondary battery to have both higher energy density and high-temperature cycle performance at the same time.
  • the Young's modulus E of the primary particles may satisfy 180GPa ⁇ E ⁇ 210GPa.
  • 190GPa ⁇ E ⁇ 205GPa This can better exert the above-mentioned effects and further improve the high-temperature cycle performance of the battery.
  • the relative deviation of the local mass concentration of the doping element in the secondary particles may be 30% or less, and optionally 20% or less.
  • the uniformity of the distribution of doping elements in the secondary particles is high, which can further improve the overall structural stability, capacity development and high-temperature cycle performance of the positive electrode active material, thereby further improving the energy density and high-temperature cycle performance of the lithium ion secondary battery.
  • the valence of the doping element in the oxidation state is more than +3, and optionally one of +4, +5, +6, +7, and +8. kind or more.
  • the doping element has a higher oxidation valence state, which can support the positive electrode to release more lithium ions and further increase the energy density of the battery.
  • the high-valence doping element has a stronger binding ability with oxygen, which is beneficial to improve the Young's modulus E of the primary particles and further improve the high-temperature cycle performance of the battery.
  • the doping element may be selected from one of Si, Ti, V, Cr, Ge, Se, Zr, Nb, Mo, Ru, Rh, Pd, Sb, Te, Ce, and W Or multiple.
  • the doping element includes one or more of Si, Zr, Nb, Ru, Pd, Sb, Te, and W. The given doping element can better improve the energy density and high temperature cycle performance of the lithium ion secondary battery.
  • the positive electrode active material to meet the true density ⁇ true 4.6g / cm 3 ⁇ true ⁇ 4.9g / cm 3.
  • the positive electrode active material can have a higher specific capacity, which can increase the energy density of the battery.
  • the true doping concentration of the positive electrode active material Satisfiable Optional, Optional, Optional can improve the Young's modulus E of the primary particles, and also ensure that the positive electrode active material has a higher lithium ion transport and diffusion ability, thereby improving the energy density and high temperature of the battery Cycle performance.
  • the deviation of the mass concentration of the doping element in the positive electrode active material with respect to the average mass concentration of the doping element in the secondary particles is ⁇ 50%; optionally, ⁇ 30%; Optionally, ⁇ 20%.
  • the positive electrode active material satisfies ⁇ within the above range, and its macroscopic and microscopic consistency is good, and the particle stability is high, which is conducive to its high capacity performance and normal temperature and high temperature cycle performance. Therefore, the corresponding performance of the battery is also improved.
  • the volume average particle size D v 50 of the positive electrode active material may be 5 ⁇ m to 20 ⁇ m, optionally 8 ⁇ m to 15 ⁇ m, and further optionally 9 ⁇ m to 11 ⁇ m.
  • the D v 50 of the positive electrode active material is within the above range, which can improve the transmission and diffusion performance of lithium ions and electrons, thereby improving the cycle performance and rate performance of the lithium ion secondary battery.
  • the positive electrode active material can also have a higher compaction density, which can increase the energy density of the battery.
  • the specific surface area of the positive electrode active material may be 0.2m 2 /g ⁇ 1.5m 2 / g, alternatively it is 0.3m 2 / g ⁇ 1m 2 / g.
  • the specific surface area of the positive electrode active material within the above range can improve the capacity and cycle life of the positive electrode active material, and can also improve the processing performance of the positive electrode slurry, so that the battery can obtain higher energy density and cycle performance.
  • the tap density of the positive electrode active material may be 2.3 g/cm 3 to 2.8 g/cm 3 . If the tap density of the positive electrode active material is within the above range, the lithium ion secondary battery can have a higher energy density.
  • the compact density of the positive electrode active material under a pressure of 5 tons may be 3.1 g/cm 3 to 3.8 g/cm 3 .
  • the compaction density of the positive electrode active material is within the given range, which is beneficial for the lithium ion secondary battery to obtain higher energy density and cycle performance.
  • the second aspect of the present application provides a method for preparing a positive electrode active material, which includes the following steps:
  • the positive electrode active material precursor, the lithium source and the doping element precursor are mixed to obtain a mixture, wherein the positive electrode active material precursor is selected from oxides and hydroxides containing Ni, optional Co and optional Mn And one or more of carbonates;
  • the positive electrode active material includes secondary particles aggregated from primary particles, the primary particles include lithium transition metal oxide, and the transition metal sites of the lithium transition metal oxide include nickel and doping elements, and
  • the Young's modulus E of the primary particles satisfies 175GPa ⁇ E ⁇ 220GPa.
  • the positive electrode active material obtained by the preparation method provided in this application includes secondary particles aggregated from primary particles.
  • the primary particles include nickel-containing lithium transition metal oxides, and are modified by the transition metal site doping of the lithium transition metal oxides.
  • the properties enable the Young’s modulus E of the primary particles to meet 175GPa ⁇ E ⁇ 220GPa, which enables the positive electrode active material to have a higher gram capacity, while improving the structural stability and high-temperature cycle stability, so that the use of its lithium ion two
  • the secondary battery takes into account both high energy density and high temperature cycle performance.
  • the doping element precursor may be selected from silicon oxide, titanium oxide, vanadium oxide, chromium oxide, germanium oxide, selenium oxide, zirconium oxide, niobium oxide, molybdenum One or more of oxide, ruthenium oxide, rhodium oxide, palladium oxide, antimony oxide, tellurium oxide, cerium oxide, and tungsten oxide.
  • the doping element precursor is selected from SiO 2 , SiO, TiO 2 , TiO, V 2 O 5 , V 2 O 4 , V 2 O 3 , CrO 3 , Cr 2 O 3 , GeO 2 , SeO 2 , ZrO 2 , Nb 2 O 5 , NbO 2 , MoO 2 , MoO 3 , RuO 2 , Ru 2 O 3 , Rh 2 O 3 , PdO 2 , PdO, Sb 2 O 5 , Sb 2 O 3 , TeO 2 , One or more of CeO 2 , WO 2 and WO 3.
  • the oxygen-containing atmosphere may be an air atmosphere or an oxygen atmosphere.
  • the temperature of the sintering treatment may be 700°C to 900°C.
  • the sintering treatment time may be 5h-25h, and may be 10h-20h.
  • the doping element precursor can be equally divided into L parts or arbitrarily divided into L parts, and divided into L batches for doping, where L is 1 to 5, and optionally 2 ⁇ 3.
  • the options include: mixing the precursor of the positive electrode active material, the lithium source, and the first batch of doping element precursors, and performing the first sintering treatment; combining the product of the first sintering treatment with the second batch of doping elements The precursor is mixed, and the second sintering process is performed; and so on, until the product of the L-1 sintering process is mixed with the L batch of doping element precursors, and the L sintering process is performed to obtain Positive active material.
  • the temperature of each sintering treatment is 600°C to 1000°C, optionally 700°C to 900°C, and further optionally 800°C to 850°C.
  • the time for each sintering treatment is 3h-25h, and optionally 5h-10h.
  • the total sintering treatment time is 5h-25h, optionally 15h-25h.
  • a third aspect of the present application provides a positive pole piece, which includes a positive current collector and a positive active material layer disposed on the positive current collector, the positive active material layer includes the positive active material of the first aspect of the present application, or The positive electrode active material obtained by the preparation method of the second aspect of the present application.
  • the lithium ion secondary battery using the same can have higher energy density and high-temperature cycle performance.
  • a fourth aspect of the present application provides a lithium ion secondary battery, which includes the positive pole piece of the third aspect of the present application.
  • the lithium ion secondary battery of the present application includes the positive pole piece, it can have higher energy density and high-temperature cycle performance.
  • a fifth aspect of the present application provides a battery module, which includes the lithium ion secondary battery of the fourth aspect of the present application.
  • a sixth aspect of the present application provides a battery pack, which includes the lithium ion secondary battery of the fourth aspect of the present application or the battery module of the fifth aspect of the present application.
  • a seventh aspect of the present application provides a device, which includes at least one of the lithium ion secondary battery of the fourth aspect of the present application, the battery module of the fifth aspect of the present application, or the battery pack of the sixth aspect of the present application.
  • the battery module, battery pack, and device of the present application include the lithium ion secondary battery of the present application, and thus have at least the same or similar effects as the lithium ion secondary battery.
  • Figure 1 is the doping element distribution image of the secondary particle cross section of Example 1.
  • the cross section is prepared using a cross section polisher (CP), and the energy dispersive spectroscopy (EDS) is used to obtain the doping element distribution image.
  • the bright spots indicate doping elements, which are uniformly distributed in the particles.
  • FIG. 2 is a schematic diagram of the relative deviation test positions of the local mass concentration of doping elements in the secondary particles of Examples 1 to 26 and Comparative Examples 1 to 2.
  • Fig. 3 is a schematic diagram of an embodiment of a lithium ion secondary battery.
  • Fig. 4 is an exploded view of Fig. 3.
  • Fig. 5 is a schematic diagram of an embodiment of a battery module.
  • Fig. 6 is a schematic diagram of an embodiment of a battery pack.
  • Fig. 7 is an exploded view of Fig. 6.
  • FIG. 8 is a schematic diagram of an embodiment of a device in which a lithium ion secondary battery is used as a power source.
  • any lower limit may be combined with any upper limit to form an unspecified range; and any lower limit may be combined with other lower limits to form an unspecified range, and any upper limit may be combined with any other upper limit to form an unspecified range.
  • every point or single value between the end points of the range is included in the range. Therefore, each point or single numerical value can be used as its own lower limit or upper limit, combined with any other point or single numerical value, or combined with other lower or upper limits to form an unspecified range.
  • the term "or” is inclusive.
  • the phrase "A or (or) B” means “A, B, or both A and B.” More specifically, any of the following conditions satisfy the condition "A or B”: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; Or both A and B are true (or exist).
  • the first aspect of the present application provides a positive electrode active material, which includes secondary particles aggregated from primary particles, the primary particles include lithium transition metal oxides, and the transition metal sites of the lithium transition metal oxides include nickel and doping elements; And the Young's modulus E of the primary particles satisfies 175GPa ⁇ E ⁇ 220GPa.
  • a combined scanning electron microscope/scanning probe microscope (Scanning Electron Microscope/Scanning Probe Microscopy, SEM/SPM) can be used to determine the Young's modulus of primary particles.
  • SEM/SPM Scanning Electron Microscope/Scanning Probe Microscopy
  • the positive electrode active material powder Take the positive electrode active material powder, pulverize it with a jet mill, dilute it with alcohol, and place it on an ultrasonic oscillator to disperse the primary particles in the secondary particles, and drop them onto the silicon substrate with a straw.
  • the silicon substrate together with the silicon carbide substrate into the SEM/SPM joint test instrument (the role of the silicon carbide substrate is to act as a hard substrate to correct the bending amount of the cantilever beam during the test, and then the applied force can be obtained
  • the SPM motion system is controlled by a computer. After the tip of the scanning probe touches the primary particle, the piezoelectric ceramic is used to control the stepping rate to make the primary particle squeeze the tip for indentation experiment.
  • the cantilever beam of the probe is bent to deflect the laser light path, and the corresponding pressure value is obtained through computer conversion.
  • the displacement is obtained according to the movement of the piezoelectric ceramic, and then the force-displacement curve is obtained. .
  • E 2 is the Young's modulus of the tip
  • V 1 is the Poisson's ratio of the sample
  • V 2 is the Poisson's ratio of the tip.
  • the positive electrode active material provided in this application includes secondary particles aggregated from primary particles.
  • the primary particles include lithium transition metal oxides.
  • the transition metal sites of the lithium transition metal oxides include nickel, so that the positive electrode active material exhibits a higher charge. Discharge voltage and specific capacity characteristics, so that lithium-ion secondary batteries have higher capacity performance and energy density.
  • the transition metal sites of the lithium transition metal oxide also include doping elements.
  • the Young's modulus E of the primary particles satisfies 175GPa ⁇ E ⁇ 220GPa, which ensures that the positive electrode active material has a high resistance to deformation and prevents the primary and secondary particles from being compressed.
  • the primary particles have proper toughness, which can effectively prevent the primary particles from brittle fracture when exposed to external pressure, and the positive electrode active material can better adapt to the insertion and extraction of lithium ions, thereby improving the structural stability of the positive electrode active material Performance and high-temperature cycle stability, so that the high-temperature cycle performance of the lithium-ion secondary battery has been improved.
  • the positive electrode active material can maintain high structural stability when subjected to external pressure, and the primary particles and secondary particles are not prone to cracking, avoiding the disconnection of the electronic conductive channels at the cracks, and ensuring the continuity of the conductive network in the positive electrode active material layer. Therefore, it can ensure that the battery has a small impedance, so that the battery has good electrochemical performance. Among them, the capacity of the battery is better, and the normal temperature and high temperature cycle performance are higher.
  • the high structural stability also inhibits the side reactions caused by the contact between the fresh surface exposed by the cracking of the primary particles and the secondary particles and the electrolyte, thereby reducing the consumption of reversible lithium ions, inhibiting the increase in electrode impedance, and improving the battery cycle at high temperatures.
  • the capacity retention rate enables the battery to have higher high temperature cycle performance.
  • pressurized and “external pressure” may include pressures such as cold pressing of the positive electrode active material during the preparation of positive pole pieces, and pressures such as expansion force of the positive active material during battery charge and discharge cycles.
  • the use of the positive electrode active material provided in the embodiments of the present application enables the lithium ion secondary battery to simultaneously take into account higher capacity performance, energy density, and high-temperature cycle performance. Applying the lithium-ion secondary battery using the positive electrode active material of the present application to an electric vehicle can enable the electric vehicle to obtain a long cruising range.
  • the Young's modulus E of the primary particles may be ⁇ 220GPa, ⁇ 218GPa, ⁇ 216 GPa, ⁇ 215GPa, ⁇ 212GPa, ⁇ 210GPa, ⁇ 208GPa, ⁇ 206GPa, ⁇ 205GPa, ⁇ 204GPa, ⁇ 202GPa, or ⁇ 200GPa.
  • E can be ⁇ 175GPa, ⁇ 177GPa, ⁇ 180GPa, ⁇ 182GPa, ⁇ 184GPa, ⁇ 186GPa, ⁇ 188GPa, ⁇ 191GPa, ⁇ 193GPa, ⁇ 195GPa, ⁇ 196GPa, or ⁇ 198GPa.
  • 180GPa ⁇ E ⁇ 210GPa optionally, 190GPa ⁇ E ⁇ 205GPa.
  • 195GPa ⁇ E ⁇ 205GPa This can better exert the above effects and improve the high temperature cycle performance of the battery.
  • the doping element one or more of transition metal elements other than nickel and elements of Group IIA to VIA other than carbon, nitrogen, oxygen, and sulfur may be selected.
  • the doping element has a strong bond energy with oxygen.
  • the bonding bond energy of the doping element and oxygen is higher than the bonding bond energy of Ni-O.
  • the doping element and oxygen have a strong bond energy, which can better improve the Young's modulus E of the primary particles, effectively stabilize the structure of the positive electrode active material, and improve the high-temperature cycle performance of the battery.
  • the valence of the doping element in the oxidation state is +3 or higher.
  • the valence of the doping element in the oxidation state is greater than +3.
  • the valence of the doping element in the oxidation state is one or more of +4, +5, +6, +7, and +8, and for example, +4, +5, One or more of +6 valence.
  • the valence of the doping element in the oxidation state refers to the valence of the doping element after the positive electrode active material is delithiated; in particular, the battery containing the positive electrode active material of the present application is in the range of reversible charge and discharge.
  • the battery is charged to the preset charging cut-off voltage, at which time the valence of the doped element in the positive electrode active material.
  • the preset charge cutoff voltage is one of the characteristic parameters of the battery set according to the types of the positive electrode active material, the negative electrode active material, and the electrolyte.
  • the valence of the doping element in the oxidation state is +3 or higher, especially greater than +3.
  • the doping element can contribute more electrons during the charge and discharge process, and support the positive electrode to release more lithium ions, thereby increasing
  • the charging and discharging voltage and capacity of lithium ion secondary batteries have improved the energy density of the battery.
  • the high-valence doping element has a stronger binding ability with oxygen, which is beneficial to improve the Young's modulus E of the primary particles, improve the structural stability of the positive electrode active material, and further improve the high-temperature cycle performance of the battery.
  • the doping element may be selected from one or more of Si, Ti, V, Cr, Ge, Se, Zr, Nb, Mo, Ru, Rh, Pd, Sb, Te, Ce, and W .
  • the doping element includes one or more of Si, Zr, Nb, Ru, Pd, Sb, Te, and W. The given doping elements can better exert the above effects, so that the lithium ion secondary battery has a higher energy density and good room temperature and high temperature cycle performance.
  • the doping element is uniformly distributed in the secondary particles.
  • the relative deviation of the local mass concentration of the doping element in the secondary particles may be 30% or less, optionally 20% or less, and further optionally 16% or less, or 13% or less.
  • the local mass concentration of doping elements in secondary particles is the mass concentration of doping elements in the finite volume element of any selected positioning point in the secondary particles, which can be determined by EDX (Energy Dispersive X-Ray Spectroscopy , Energy dispersive X-ray spectrometer) or EDS element analysis combined with TEM (Transmission Electron Microscope) or SEM (Scanning Electron Microscope) single-point scanning test element concentration distribution or other similar methods.
  • EDX Electronicgy Dispersive X-Ray Spectroscopy , Energy dispersive X-ray spectrometer
  • EDS element analysis combined with TEM (Transmission Electron Microscope) or SEM (Scanning Electron Microscope) single-point scanning test element concentration distribution or other similar methods.
  • the average mass concentration of doping elements in the secondary particles is the mass concentration of doping elements in a single secondary particle, which can be obtained by EDX or EDS element analysis combined with TEM or SEM surface scanning test element concentration distribution or other similar methods.
  • the test surface includes all the test sites in the single-point test (as shown in Fig. 2).
  • the average mass concentration of doped elements in the secondary particles is denoted as The unit is ⁇ g/g.
  • the relative deviation of the local mass concentration of the doping element in the secondary particles is less than 30%, and can be selected to be less than 20%, which means that the uniformity of the distribution of the doping element in the secondary particles is relatively high.
  • the properties of the uniformly doped positive electrode active material particles remain the same everywhere, and the migration and diffusion capabilities of lithium ions in different areas within the particles are at the same level.
  • the Young's modulus E of the uniformly doped particles is close to each other, that is, the anti-deformation ability and toughness of the particles are close to each other, so that the stress distribution in the particles is uniform, the structure of the particles is stable, and it is not easy to break. .
  • the capacity development and high-temperature cycle performance of the positive electrode active material can be improved, thereby further improving the capacity performance, energy density, and high-temperature cycle performance of the lithium ion secondary battery.
  • the true doping concentration of the positive electrode active material Satisfy Optional or
  • I the actual doping concentration of the positive electrode active material, in ⁇ g/cm 3 .
  • ⁇ true true density of the cathode active material in units of g / cm 3, which is equal to the ratio of the mass and the true volume of the positive electrode active material of the positive electrode active material, wherein the true volume is the actual volume of the solid material does not include pores inside of the particles .
  • ⁇ true can be measured by using instruments and methods known in the art, for example, the gas volume method can be performed by using a powder true density tester.
  • ⁇ is the mass concentration of the doping element in the positive electrode active material in ⁇ g/g, that is, the mass of the doping element contained in each gram of the positive electrode active material.
  • ⁇ represents the content of doping elements in the overall macroscopic positive electrode active material, including the doping elements doped into the secondary particles of the positive electrode active material, the doping elements enriched in other phases on the surface of the positive electrode active material, and the doping elements embedded in the positive electrode active material. Doping elements between material particles.
  • ⁇ can be obtained through the absorption spectrum of the positive electrode active material solution, such as ICP (Inductive Coupled Plasma Emission Spectrometer), XAFS (X-ray absorption fine structure spectroscopy, X-ray absorption fine structure spectroscopy) and other tests.
  • ICP Inductive Coupled Plasma Emission Spectrometer
  • XAFS X-ray absorption fine structure spectroscopy, X-ray absorption fine structure spectroscopy
  • the actual doping concentration of the positive electrode active material is within the above range, which can improve the Young's modulus E of the primary particles while also making the positive electrode active material have a good layered structure, ensuring that the positive electrode active material provides the deintercalation of lithium ions.
  • a good carrier effectively reducing the irreversible consumption of active lithium ions, enabling the positive electrode active material to have a higher initial capacity and cycle capacity retention rate, thereby improving the energy density and high temperature cycle performance of the battery.
  • the actual doping concentration of the positive electrode active material is within the above range, which also ensures that the doping element is doped in the transition metal layer, prevents it from entering the lithium layer, and ensures that the particles have a higher lithium ion transport and diffusion ability, so that the battery has a better performance. High capacity and cycle performance.
  • the true density ⁇ true positive electrode active material optionally 4.6g / cm 3 ⁇ true ⁇ 4.9g / cm 3.
  • the positive electrode active material can have a higher specific capacity, thereby improving the capacity performance and energy density of the battery.
  • the mass concentration ⁇ of the doping element in the positive electrode active material is relative to the average mass concentration of the doping element in the secondary particles
  • the deviation ⁇ satisfies ⁇ 50%.
  • the mass concentration of the doping element in the positive electrode active material is relative to the average mass concentration of the doping element in the secondary particles
  • the deviation of is calculated by the following formula (5):
  • the mass concentration of the doping element in the positive electrode active material is relative to the average mass concentration of the doping element in the secondary particles.
  • the deviation within the above range means that the doping elements are smoothly incorporated into the secondary particles.
  • the content of the doping elements distributed in other phases on the surface of the secondary particles and the doping elements embedded in the gaps of the positive electrode active material particles is higher.
  • the positive electrode active material has better macro and micro consistency, uniform structure, and high particle stability, which is conducive to making the positive electrode active material have higher capacity and cycle performance at room temperature and high temperature.
  • the lithium transition metal oxide has a layered crystal structure.
  • the molar amount of Ni in the transition metal layer of the lithium transition metal oxide is more than 50% of the total molar amount of elements in the transition metal layer, further more than 60%, and still further 70% Above, it is still more than 80%.
  • the high nickel cathode active material has higher specific capacity characteristics and can improve the capacity performance and energy density of lithium ion secondary batteries.
  • the high nickel positive electrode active material has high specific capacity characteristics and high structural stability, so that the lithium ion secondary battery has high capacity performance and energy density, as well as good room temperature and high temperature cycle performance.
  • the high-nickel ternary positive electrode active material has high energy density and good structural stability, so that the battery has high energy density and long cycle life.
  • M is selected from one or more of Si, Ti, V, Cr, Ge, Se, Zr, Nb, Mo, Ru, Rh, Pd, Sb, Te, Ce, and W.
  • M includes one or more of Si, Zr, Nb, Ru, Pd, Sb, Te, and W.
  • the doping element M Since the doping element M has a higher valence in the oxidation state, it exceeds the average valence (+3 valence) of the transition metals Ni, Co and Mn in the high nickel ternary cathode active material, which means that the doping element can be in Contribute more electrons during the charging process, so that the positive electrode active material releases more lithium ions, improve the charge and discharge voltage and capacity of the lithium ion secondary battery, so that the lithium ion secondary battery has higher capacity performance and energy density .
  • the use of the doping element M can effectively improve the Young's modulus E of the primary particles of the positive electrode active material, so that the positive electrode active material has higher deformation resistance and better toughness, is not prone to cracking, and improves the cycle performance of the battery.
  • the high nickel positive electrode active material has high specific capacity characteristics and high structural stability, so that the lithium ion secondary battery has high capacity performance and energy density, as well as good room temperature and high temperature cycle performance.
  • the high-nickel ternary positive electrode active material has high energy density and good structural stability, so that the battery has high energy density and long cycle life.
  • M' is selected from one or more of Si, Ti, V, Cr, Ge, Se, Zr, Nb, Mo, Ru, Rh, Pd, Sb, Te, Ce, and W.
  • the various lithium transition metal oxides in the above examples can be used independently for the positive electrode active material, or a combination of any two or more lithium transition metal oxides can be used for the positive electrode active material.
  • the volume average particle diameter D v 50 of the positive electrode active material can be 5 ⁇ m-20 ⁇ m, further can be 8 ⁇ m-15 ⁇ m, and can also be 9 ⁇ m-11 ⁇ m. If the D v 50 of the positive electrode active material is within the above range, the migration path of lithium ions and electrons in the material is relatively short, which can further improve the transmission and diffusion performance of lithium ions and electrons in the positive electrode active material, reduce battery polarization, and improve lithium The cycle performance and rate performance of the ion secondary battery; in addition, it can also make the positive electrode active material have a higher compaction density and improve the energy density of the battery.
  • the D v 50 of the positive electrode active material within the above range is also beneficial to reduce side reactions of the electrolyte on the surface of the positive electrode active material and reduce the agglomeration between the positive electrode active material particles, thereby improving the cycle performance and safety performance of the positive electrode active material.
  • the specific surface area of the positive electrode active material is selected to 0.2m 2 /g ⁇ 1.5m 2 / g, optionally further 0.3m 2 / g ⁇ 1m 2 / g.
  • the specific surface area of the positive electrode active material is within the above range, which ensures that the positive electrode active material has a higher active specific surface area, and at the same time helps to reduce the side reaction of the electrolyte on the surface of the positive electrode active material, thereby improving the capacity and cycle life of the positive electrode active material
  • it can also inhibit the agglomeration between particles of the positive electrode active material in the process of preparing the slurry and charging and discharging, which can improve the energy density and cycle performance of the battery.
  • the tap density of the positive electrode active material may be 2.3 g/cm 3 to 2.8 g/cm 3 . If the tap density of the positive electrode active material is within the above range, the lithium ion secondary battery can have higher capacity performance and energy density.
  • the compacted density of the positive electrode active material under a pressure of 5 tons can be selected from 3.1 g/cm 3 to 3.8 g/cm 3 .
  • the compaction density of the positive electrode active material is within this range, which is beneficial to make the lithium ion secondary battery have higher capacity performance and energy density, and at the same time have good normal temperature cycle performance and high temperature cycle performance.
  • the morphology of the positive electrode active material of the embodiment of the present application is one or more of a sphere and a sphere-like body.
  • the volume average particle size D v 50 of the positive electrode active material has a well-known meaning in the art, and is also referred to as the median particle size, which represents the particle size corresponding to 50% of the volume distribution of the positive electrode active material particles.
  • the average particle size D v 50 of the positive electrode active material can be measured by a well-known instrument and method in the art, such as a laser particle size analyzer (such as the Mastersizer 3000 of Malvern Instruments Co., Ltd., UK).
  • the specific surface area of the positive electrode active material is a well-known meaning in the art, and it can be measured by instruments and methods known in the art. For example, it can be measured by the nitrogen adsorption specific surface area analysis test method and calculated by the BET (Brunauer Emmett Teller) method, where The nitrogen adsorption specific surface area analysis test can be carried out by the NOVA 2000e specific surface area and pore size analyzer of the United States Conta Company.
  • the test method is as follows: take 8.000g ⁇ 15.000g of positive electrode active material in a weighed empty sample tube, stir and weigh the positive electrode active material, and put the sample tube into the NOVA 2000e degassing station for degassing , Weigh the total mass of the positive electrode active material and the sample tube after degassing, and calculate the mass G of the positive electrode active material after degassing by subtracting the mass of the empty sample tube from the total mass.
  • the tap density of the positive electrode active material is a well-known meaning in the art, and can be measured with a well-known instrument and method in the art, for example, a tap density meter (such as FZS4-4B type) can be conveniently measured.
  • a tap density meter such as FZS4-4B type
  • the compaction density of the positive electrode active material is a well-known meaning in the art, and can be measured with a well-known instrument and method in the art, such as an electronic pressure tester (such as UTM7305).
  • the preparation method includes:
  • the positive electrode active material precursor, the lithium source, and the doping element precursor are mixed, and sintered to obtain the positive electrode active material.
  • the foregoing positive electrode active material precursor may be one or more of oxides, hydroxides, and carbonates containing Ni and optionally Co and/or Mn in a stoichiometric ratio, for example, containing Ni in a stoichiometric ratio. Hydroxides of Ni, Co and Mn.
  • the positive electrode active material precursor can be obtained by a method known in the art, for example, prepared by a co-precipitation method, a gel method, or a solid phase method.
  • the Ni source, Co source, and Mn source are dispersed in a solvent to obtain a mixed solution; the mixed solution, strong alkali solution and complexing agent solution are simultaneously pumped into a stirred reactor by means of continuous co-current reaction. , Control the pH of the reaction solution to be 10-13, the temperature in the reactor is 25°C to 90°C, and pass inert gas protection during the reaction; after the reaction is completed, it is aged, filtered, washed and vacuum dried to obtain Ni , Co and Mn hydroxides.
  • the Ni source may be a soluble nickel salt, such as one or more of nickel sulfate, nickel nitrate, nickel chloride, nickel oxalate, and nickel acetate, and another example, one or more of nickel sulfate and nickel nitrate, Another example is nickel sulfate;
  • the Co source can be a soluble cobalt salt, such as one or more of cobalt sulfate, cobalt nitrate, cobalt chloride, cobalt oxalate, and cobalt acetate, and another example is cobalt sulfate and cobalt nitrate.
  • the Mn source may be a soluble manganese salt, such as one or more of manganese sulfate, manganese nitrate, manganese chloride, manganese oxalate and manganese acetate, and another example is sulfuric acid One or more of manganese and manganese nitrate, and another example is manganese sulfate.
  • the strong base may be one or more of LiOH, NaOH, and KOH, for example, NaOH.
  • the complexing agent may be one or more of ammonia, ammonium sulfate, ammonium nitrate, ammonium chloride, ammonium citrate, and disodium ethylenediaminetetraacetate (EDTA), for example, ammonia.
  • the solvents of the mixed solution, strong base solution and complexing agent solution are each independently deionized water, methanol, ethanol, acetone, and isopropyl.
  • the solvents of the mixed solution, strong base solution and complexing agent solution are each independently deionized water, methanol, ethanol, acetone, and isopropyl.
  • the inert gas introduced during the reaction is, for example, one or more of nitrogen, argon, and helium.
  • the above-mentioned lithium source may be lithium oxide (Li 2 O), lithium phosphate (Li 3 PO 4 ), lithium dihydrogen phosphate (LiH 2 PO 4 ), lithium acetate (CH 3 COOLi), lithium hydroxide (LiOH), lithium carbonate One or more of (Li 2 CO 3 ) and lithium nitrate (LiNO 3 ). Further, the lithium source is one or more of lithium carbonate, lithium hydroxide, and lithium nitrate; further, the lithium source is lithium carbonate.
  • the aforementioned doping element precursor may be one or more of oxides of doping elements, nitric acid compounds, carbonic acid compounds, hydroxide compounds, and acetic acid compounds.
  • oxides of doping elements such as silicon oxide (such as SiO 2 , SiO, etc.), titanium oxide (such as TiO 2 , TiO, etc.), vanadium oxide (such as V 2 O 5 , V 2 O 4 , V 2 O 3 ), chromium oxide (such as CrO 3 , Cr 2 O 3, etc.), germanium oxide (such as GeO 2 ), selenium oxide (such as SeO 2 ), zirconium oxide (such as ZrO 2 ), niobium oxide (such as Nb 2 O 5 , NbO 2, etc.), molybdenum oxide (such as MoO 2 , MoO 3, etc.), ruthenium oxide (such as Ru 2 O 3 , RuO 2, etc.), rhodium oxide (such as Rh 2 O 3, etc.), palladium oxide (
  • the precursor of the positive electrode active material, the lithium source and the precursor of the doping element can be mixed by a ball mill mixer or a high-speed mixer.
  • the mixed materials are put into the atmosphere sintering furnace for sintering.
  • the sintering atmosphere is an oxygen-containing atmosphere, for example, an air atmosphere or an oxygen atmosphere.
  • the sintering temperature is, for example, 600°C to 1000°C.
  • the sintering temperature is 700°C to 900°C, which is beneficial to make the doped elements have a higher uniformity of distribution.
  • the sintering time can be adjusted according to actual conditions, for example, 5h-25h, and for example 10h-20h.
  • the doping element precursor may be divided into L batches for doping of the doping element, where L may be 1-5, such as 2-3.
  • the preparation method of the positive electrode active material may include the following steps: mixing the positive electrode active material precursor, the lithium source, and the first batch of doping element precursors, and performing the first sintering treatment; The product of the second sintering treatment is mixed with the second batch of doping element precursors, and the second sintering treatment is carried out; and so on, until the products of the L-1 sintering treatment are combined with the L batch of doping element precursors The body is mixed and subjected to the L-th sintering treatment to obtain a positive electrode active material.
  • the doping element precursor can be equally divided into L parts or arbitrarily divided into L parts to perform L batches of doping.
  • the temperature of each sintering process is the same or different.
  • the time of each sintering treatment is the same or different. Those skilled in the art can adjust the sintering temperature and time according to the type and amount of doping elements.
  • the temperature of each sintering treatment may be 600°C to 1000°C, such as 700°C to 900°C, and then 800°C to 850°C.
  • the time of each sintering treatment can be 3h-25h, such as 5h-10h.
  • the total sintering time can be 5h-25h, such as 15h-25h.
  • the doping uniformity can be improved by increasing the sintering temperature and/or prolonging the sintering time.
  • the sintered product can also be crushed and sieved to obtain a positive electrode active material with optimized particle size distribution and specific surface area.
  • a particle crusher There are no special restrictions on the crushing method, and it can be selected according to actual needs, such as using a particle crusher.
  • This application provides a positive electrode sheet, which uses any one or several positive electrode active materials of this application.
  • the lithium ion secondary battery can take into account both good room temperature and high temperature cycle performance and higher energy density at the same time.
  • the positive pole piece includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector.
  • the positive electrode current collector includes two opposite surfaces in its thickness direction, and the positive electrode active material layer is stacked on either or both of the two surfaces of the positive electrode current collector.
  • the positive active material layer includes the positive active material of the present application.
  • the positive electrode active material layer may further include a conductive agent and a binder.
  • a conductive agent and a binder This application does not specifically limit the types of conductive agents and binders in the positive active material layer, and can be selected according to actual needs.
  • the conductive agent may be one or more of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers;
  • the binder may be styrene-butadiene Rubber (SBR), water-based acrylic resin, carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB) ), ethylene-vinyl acetate copolymer (EVA), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene
  • SBR styrene-butadiene Rubber
  • EVA ethylene-vinyl acetate copoly
  • the positive electrode current collector can be a metal foil or porous metal plate with good electrical conductivity and mechanical properties, and its material can be one or more of aluminum, copper, nickel, titanium, silver, and their respective alloys.
  • the positive electrode current collector is, for example, aluminum foil.
  • the positive pole piece can be prepared according to conventional methods in the art. For example, disperse the positive electrode active material, conductive agent, and binder in a solvent.
  • the solvent can be N-methylpyrrolidone (NMP) or deionized water to form a uniform positive electrode slurry.
  • NMP N-methylpyrrolidone
  • the positive electrode slurry is coated on the positive electrode current collector. Above, after drying, rolling and other processes, the positive pole piece is obtained.
  • the present application provides a lithium ion secondary battery, which includes a positive pole piece, a negative pole piece, a separator and an electrolyte, wherein the positive pole piece is any positive pole piece of the application.
  • the lithium ion secondary battery of the present application adopts the positive pole piece of the present application, it can take into account both good room temperature and high temperature cycle performance and high energy density at the same time.
  • the negative pole piece may be a metal lithium piece.
  • the negative pole piece may also include a negative current collector and a negative active material layer provided on at least one surface of the negative current collector.
  • the negative electrode current collector includes two opposite surfaces in the thickness direction of the negative electrode current collector, and the negative electrode active material layer is stacked on either or both of the two surfaces of the negative electrode current collector.
  • the anode active material layer includes an anode active material.
  • the embodiments of the present application do not specifically limit the types of negative electrode active materials, and can be selected according to actual needs.
  • the negative active material layer may further include a conductive agent and a binder.
  • a conductive agent is one or more of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers
  • the binder is styrene butadiene rubber One or more of (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), and water-based acrylic resin.
  • the negative active material layer may also optionally include a thickener, such as sodium carboxymethyl cellulose (CMC-Na).
  • a thickener such as sodium carboxymethyl cellulose (CMC-Na).
  • the negative electrode current collector can be a metal foil or porous metal plate with good electrical conductivity and mechanical properties, and its material can be one or more of copper, nickel, titanium, iron, and their respective alloys.
  • the negative electrode current collector is, for example, copper foil.
  • the negative pole piece can be prepared according to conventional methods in the art. For example, disperse the negative electrode active material, conductive agent, binder and thickener in a solvent.
  • the solvent can be N-methylpyrrolidone (NMP) or deionized water to form a uniform negative electrode slurry, and then coat the negative electrode slurry.
  • NMP N-methylpyrrolidone
  • the electrolyte may be a solid electrolyte, such as a polymer electrolyte, an inorganic solid electrolyte, etc., but it is not limited thereto. Electrolyte can also be used as the electrolyte.
  • a solvent and a lithium salt dissolved in the solvent are included.
  • the solvent may be a non-aqueous organic solvent, such as ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC) , Dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethylene propyl carbonate (EPC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate ( One or more of PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB) and ethyl butyrate (EB), For example, two or more.
  • EC ethylene carbonate
  • PC propylene carbonate
  • EMC diethyl carbonate
  • DMC dimethyl carbonate
  • DPC dipropyl carbonate
  • MPC methyl propyl carbonate
  • MPC methyl propy
  • the lithium salt can be LiPF 6 (lithium hexafluorophosphate), LiBF 4 (lithium tetrafluoroborate), LiClO 4 (lithium perchlorate), LiAsF 6 (lithium hexafluoroarsenate), LiFSI (lithium bisfluorosulfonimide), LiTFSI (Lithium bistrifluoromethanesulfonimide), LiTFS (lithium trifluoromethanesulfonate), LiDFOB (lithium difluorooxalate borate), LiBOB (lithium bisoxalate borate), LiPO 2 F 2 (lithium difluorophosphate), One or more of LiDFOP (lithium difluorooxalate phosphate) and LiTFOP (lithium tetrafluorooxalate phosphate), such as LiPF 6 (lithium hexafluorophosphate), LiBF 4 (lithium tetrafluoroborate), LiBOB (lithium
  • the electrolyte may also optionally contain other additives, such as vinylene carbonate (VC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), three Fluoromethyl ethylene carbonate (TFPC), succinonitrile (SN), adiponitrile (ADN), glutaronitrile (GLN), hexanetrinitrile (HTN), 1,3-propane sultone (1 ,3-PS), ethylene sulfate (DTD), methylene disulfonate (MMDS), 1-propene-1,3-sultone (PST), 4-methyl ethylene sulfate (PCS), 4-ethyl ethylene sulfate (PES), 4-propyl ethylene sulfate (PEGLST), propylene sulfate (TS), 1,4-butane sultone (1,4- BS), ethylene sulfite (DTO), dimethyl sulfite (
  • the lithium ion secondary battery in the embodiments of the present application has no special restrictions on the separator.
  • Any well-known separator with a porous structure with electrochemical stability and mechanical stability can be selected, such as glass fiber, non-woven fabric, polyethylene (PE ), polypropylene (PP) and polyvinylidene fluoride (PVDF) one or more of single-layer or multi-layer films.
  • PE polyethylene
  • PP polypropylene
  • PVDF polyvinylidene fluoride
  • the positive pole piece and the negative pole piece are alternately stacked, and an isolation film is arranged between the positive pole piece and the negative pole piece for isolation to obtain a battery core, which can also be obtained after winding. Placing the electric core in the casing, injecting electrolyte, and sealing to obtain a lithium ion secondary battery.
  • FIG. 3 shows a lithium ion secondary battery 5 with a square structure as an example.
  • the secondary battery may include an outer package.
  • the outer packaging is used to encapsulate the positive pole piece, the negative pole piece and the electrolyte.
  • the outer package may include a housing 51 and a cover 53.
  • the housing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose to form an accommodating cavity.
  • the housing 51 has an opening communicating with the containing cavity, and a cover plate 53 can cover the opening to close the containing cavity.
  • the positive pole piece, the negative pole piece, and the separator may be formed into the cell 52 through a winding process or a lamination process.
  • the battery core 52 is encapsulated in the containing cavity.
  • the electrolyte can be an electrolyte, and the electrolyte is infiltrated in the cell 52.
  • the number of battery cells 52 contained in the lithium ion secondary battery 5 can be one or several, which can be adjusted according to requirements.
  • the outer packaging of the lithium ion secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, or the like.
  • the outer packaging of the secondary battery may also be a soft bag, such as a pouch type soft bag.
  • the material of the soft bag can be plastic, for example, it can include one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), and the like.
  • the lithium ion secondary battery can be assembled into a battery module, and the number of lithium ion secondary batteries contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.
  • Fig. 5 is a battery module 4 as an example.
  • a plurality of lithium ion secondary batteries 5 may be arranged in order along the length direction of the battery module 4. Of course, it can also be arranged in any other manner. Furthermore, the plurality of lithium ion secondary batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having an accommodating space, and a plurality of lithium ion secondary batteries 5 are accommodated in the accommodating space.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.
  • Fig. 6 and Fig. 7 are the battery pack 1 as an example. 6 and 7, the battery pack 1 may include a battery box and a plurality of battery modules 4 provided in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3.
  • the upper box body 2 can be covered on the lower box body 3 and forms a closed space for accommodating the battery module 4.
  • a plurality of battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides a device, which includes at least one of the lithium ion secondary battery, battery module, or battery pack described in the present application.
  • the lithium ion secondary battery, battery module or battery pack can be used as a power source of the device, and can also be used as an energy storage unit of the device.
  • the device can be, but is not limited to, mobile devices (such as mobile phones, laptop computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf Vehicles, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • the device can select a lithium ion secondary battery, battery module, or battery pack according to its usage requirements.
  • Fig. 8 is a device as an example.
  • the device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.
  • a battery pack or a battery module can be used.
  • the device may be a mobile phone, a tablet computer, a notebook computer, and the like.
  • the device is generally required to be light and thin, and a lithium ion secondary battery can be used as a power source.
  • the doping element is Sb, and the doping element precursor antimony oxide (Sb 2 O 3 ) is roughly equally divided into three batches for Sb doping.
  • the preparation method includes:
  • the precursor of the positive electrode active material [Ni 0.8 Co 0.1 Mn 0.1 ](OH) 2 , lithium hydroxide LiOH and the first batch of antimony oxide were added to the high-speed mixer for mixing for 1 hour to obtain a mixed material, wherein the positive electrode active
  • the molar ratio of the material precursor to lithium hydroxide Li/Me is 1.05, and Me represents the total molar amount of Ni, Co, and Mn in the precursor of the positive electrode active material; the mixture is placed in an atmosphere sintering furnace for the first sintering and sintering
  • the temperature is 830°C
  • the sintering time is 5h
  • the sintering atmosphere is an oxygen-containing atmosphere with an O 2 concentration of 90%.
  • the product of the first sintering treatment and the second batch of antimony oxide were added to the high-speed mixer to mix for 1 hour, and the second sintering was carried out.
  • the sintering temperature, sintering time and sintering atmosphere were the same as those of the first sintering.
  • the product of the second sintering treatment and the third batch of antimony oxide were added to the high-speed mixer for 1h, and the third sintering was carried out.
  • the sintering temperature and sintering atmosphere were the same as the previous two sintering, and the sintering time was 10h.
  • the total sintering time is 20h.
  • the high nickel ternary positive electrode active material After the product of the third sintering treatment is crushed and sieved, the high nickel ternary positive electrode active material can be obtained.
  • the amount of antimony oxide added makes the true doping concentration of Sb in the positive electrode active material 25100 ⁇ g/cm 3 .
  • the positive pole piece, the separator and the metal lithium sheet are stacked in sequence, and the above-mentioned electrolyte is injected to assemble the button cell.
  • SBR binder styrene butadiene rubber
  • CMC-Na thickener sodium carboxymethyl cellulose
  • PE Polyethylene
  • Example 1 The difference from Example 1 is that the relevant parameters in the preparation steps of the positive electrode active material are changed, the doping element oxide is selected as its source, and the batch content and the sintering temperature of the doping element are adjusted to be 800 °C ⁇ 850 °C when the doping element is mixed.
  • the sintering time is 15h-25h, and the positive electrode active material with predetermined doping element type, doping amount and doping uniformity is obtained. See Table 1 and Table 2 for details.
  • each doping element is basically the same.
  • the precursor of the positive electrode active material in Examples 22-24 is [Ni 0.5 Co 0.2 Mn 0.3 ](OH) 2 .
  • Example 14 The difference from Example 1 is that the doping elements in Example 14 are added in a single batch, and the sintering temperature is 780°C; other parameters are shown in Table 1 and Table 2.
  • Example 1 The difference from Example 1 is that the doping elements in Example 15 are added in a single batch, and the sintering temperature is 700° C.; other parameters are shown in Table 1 and Table 2.
  • Example 25 The difference from Example 1 is that in Example 25, the doping element precursor is divided into 3 batches according to the weight ratio of 47.5:47.5:5 for doping; the first two sintering temperatures are both 700 °C, the first two The time of the second sintering is 4h; the temperature of the third sintering is 600°C, and the time is 2h; other parameters are shown in Table 1 and Table 2.
  • Example 26 The difference from Example 1 is that in Example 26, the doping element precursor is divided into 3 batches according to the weight ratio of 45:45:10 for doping; the first two sintering temperatures are both 600°C, and the first two The time of the second sintering is 3h; the temperature of the third sintering is 500°C, and the time is 1h; other parameters are shown in Table 1 and Table 2.
  • Example 2 The difference from Example 1 is that no doping elements are added; and the precursor of the positive electrode active material in Comparative Example 2 is [Ni 0.5 Co 0.2 Mn 0.3 ](OH) 2 ; other parameters are shown in Table 1 and Table 2.
  • the mass concentration of miscellaneous elements, the test method is as follows: select Li, O, Ni, Co, Mn and doping elements for detection elements, set the SEM parameters to 20kV acceleration voltage, 60 ⁇ m aperture, 8.5mm working distance, 2.335A current, and perform EDS During the test, stop the test when the spectrum area reaches more than 250,000 cts (controlled by the acquisition time and acquisition rate), and collect the data to obtain the mass concentration of the doping elements at each point, which are recorded as ⁇ 1 , ⁇ 2 , ⁇ 3 , ..., ⁇ 17 .
  • Average mass concentration of doped elements in secondary particles Measurement method the above-mentioned EDS-SEM testing method is adopted, as shown in the dashed box in Figure 2, the test area covers all the points scanned by the secondary particles, and does not exceed the cross-section of the secondary particles.
  • the relative deviation ⁇ of the local mass concentration of the doping element in the secondary particles is calculated.
  • the true density ⁇ true of the positive electrode active material is measured by the TD2400 powder true density tester of Beijing Biood Electronic Technology Co., Ltd.
  • n is the molar mass of gas in the sample cup
  • R is the ideal gas constant, which is 8.314
  • T is the ambient temperature, which is 298.15K.
  • the 7000DV inductively coupled plasma-optical emission spectrometer (ICP-OES) of Platinum Elmer (PE) is used to test the mass concentration ⁇ of doping elements in the positive electrode active material.
  • the test method is as follows: Take the pole piece containing the positive electrode active material and punch it into a disc with a total mass greater than 0.5g or take at least 5g of the positive electrode active material powder sample, weigh and record the mass of the sample, put it into the digestion tank, and slowly add 10 mL of aqua regia as a digestion reagent.
  • the Young's modulus E of the primary particles was measured using the SEM/SPM measurement method described above.
  • the jet mill is the GTJ-250 jet mill manufactured by Yixing Tsinghua Powder Machinery Equipment Co., Ltd.
  • the mass ratio of each batch of doping element precursors the mass of the first batch of doping element precursors: the mass of the second batch of doping element precursors: the mass of the third batch of doping element precursors
  • E is the Young's modulus of primary particles
  • Is the actual doping concentration of the positive electrode active material
  • ⁇ is the relative deviation of the local mass concentration of the doping element in the secondary particles
  • ⁇ is the mass concentration of the doping element in the positive electrode active material relative to the average of the doping elements in the secondary particles Deviation in mass concentration.
  • the channels and barriers for the diffusion of lithium ions inside the cathode active material particles are inconsistent, and the structural stability and anti-deformation ability of each region are different, resulting in The internal stress of the material is unevenly distributed, and the area with high internal stress is prone to cracks, which exposes the fresh surface of the positive electrode active material, which increases the impedance and deteriorates the capacity and high-temperature cycle performance.
  • Examples 1, 25, and 26 can be seen that when the deviation ⁇ of the mass concentration of the doping element in the positive electrode active material relative to the average mass concentration of the doping element in the secondary particles is within the range of less than 30%, more The doping elements of ZnO have been smoothly incorporated into the secondary particles, and there are fewer doping elements distributed in the gaps or surfaces of the secondary particles.
  • the positive electrode active material has good macro and micro consistency, uniform structure, and high particle stability, which is beneficial to Its capacity and normal temperature and high temperature cycle performance.
  • ⁇ is greater than 30%, more doping elements are distributed in the gap or surface of the secondary particles, which makes the internal structural stability of the primary particles insufficient, but the doping elements distributed on the surface play a role in covering and isolating electrolysis. Liquid side reaction, so the cell capacity and high temperature cycle performance are slightly reduced at this time.

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Abstract

本申请公开了一种正极活性材料、其制备方法、正极极片、锂离子二次电池及其相关的电池模块、电池包和装置。正极活性材料包括由一次颗粒聚集而成的二次颗粒，一次颗粒为锂过渡金属氧化物，锂过渡金属氧化物的过渡金属位包括镍及掺杂元素；以及一次颗粒的杨氏模量E为175 GPa≤E≤220 GPa。

Description

正极活性材料、其制备方法、正极极片、锂离子二次电池及其相关的电池模块、电池包和装置
相关申请的交叉引用
本申请要求享有于2019年09月02日提交的名称为“正极活性材料、正极极片及锂离子二次电池”的中国专利申请201910824732.5的优先权，该申请的全部内容通过引用并入本文中。
技术领域
本申请属于二次电池技术领域，具体涉及一种正极活性材料、其制备方法、正极极片、锂离子二次电池及其相关的电池模块、电池包和装置。
背景技术
锂离子二次电池是一种充电电池，它主要依靠锂离子在正极和负极之间移动来工作，是当前被广泛应用的清洁能源。正极活性材料作为锂离子二次电池的重要组成部分，为电池充放电过程提供在正负极往复移动的锂离子，因此正极活性材料对电池性能的发挥至关重要。
锂镍基正极活性材料具有较高的理论容量，采用锂镍基正极活性材料的锂离子二次电池可期望获得较高的能量密度，但是研究发现该种锂离子二次电池的高温循环性能较差。
发明内容
本申请第一方面提供一种正极活性材料，其包括由一次颗粒聚集而成的二次颗粒，一次颗粒为锂过渡金属氧化物，锂过渡金属氧化物的过渡金属位包括镍及掺杂元素；以及一次颗粒的杨氏模量E满足175GPa≤E≤220GPa。
本申请的正极活性材料包括由一次颗粒聚集而成的二次颗粒，一次颗粒包括锂过渡金属氧化物，锂过渡金属氧化物的过渡金属位包括镍，由此表现出较高的充放电电压和比容量特性，使锂离子二次电池具有较高的能量密度。锂过渡金属氧化物的过渡金属位 还包括掺杂元素，使得一次颗粒的杨氏模量E满足175GPa≤E≤220GPa。这提高了正极活性材料的抗变形能力，防止一次颗粒及二次颗粒在受压过程中发生破裂，同时使一次颗粒具有适当的韧性，有效防止一次颗粒在受到外界压力时发生脆性破裂，并且正极活性材料能较好地适应锂离子的嵌入和脱出，从而提高正极活性材料的结构稳定性及高温循环稳定性，使锂离子二次电池的高温循环性能得到提升。采用本申请的正极活性材料，能使锂离子二次电池同时兼顾较高的能量密度及高温循环性能。
在上述任意实施方式中，所述一次颗粒的杨氏模量E可满足180GPa≤E≤210GPa。可选的，190GPa≤E≤205GPa。这样能更好地发挥上述效果，进一步提高电池的高温循环性能。
在上述任意实施方式中，所述二次颗粒中掺杂元素的局部质量浓度的相对偏差可以为30％以下，可选的为20％以下。掺杂元素在二次颗粒中的分布均匀性较高，能进一步提高正极活性材料整体的结构稳定性、容量发挥和高温循环性能，从而进一步提升锂离子二次电池的能量密度和高温循环性能。
在上述任意实施方式中，所述掺杂元素在氧化态时的化合价为+3价以上，可选的为+4价、+5价、+6价、+7价及+8价中的一种或多种。掺杂元素具有较高的氧化价态，能支持正极释放更多的锂离子，使电池的能量密度进一步提升。高价态的掺杂元素与氧的结合能力更强，有利于改善一次颗粒的杨氏模量E，进一步提高电池的高温循环性能。
在上述任意实施方式中，所述掺杂元素可选自Si、Ti、V、Cr、Ge、Se、Zr、Nb、Mo、Ru、Rh、Pd、Sb、Te、Ce及W中的一种或多种。可选的，所述掺杂元素包括Si、Zr、Nb、Ru、Pd、Sb、Te及W中的一种或多种。所给掺杂元素能更好地改善锂离子二次电池的能量密度和高温循环性能。
在上述任意实施方式中，所述正极活性材料的真密度ρ 真可满足4.6g/cm 3≤ρ 真≤4.9g/cm 3。正极活性材料能具有较高的比容量，从而可提高电池的能量密度。
在上述任意实施方式中，所述正极活性材料的真实掺杂浓度
Figure PCTCN2020109987-appb-000001
可满足
Figure PCTCN2020109987-appb-000002
Figure PCTCN2020109987-appb-000003
可选的，
Figure PCTCN2020109987-appb-000004
可选的，
Figure PCTCN2020109987-appb-000005
Figure PCTCN2020109987-appb-000006
可选的，
Figure PCTCN2020109987-appb-000007
正极活性材料的真实掺杂浓度在上述范围内，能改善一次颗粒的杨氏模量E，还能保证正极活性材料具有较高的锂离子传输扩散能力，由此能提高电池的能量密度和高温循环性能。
在上述任意实施方式中，所述正极活性材料中掺杂元素的质量浓度相对于所述二次颗粒中掺杂元素的平均质量浓度的偏差ε<50％；可选的，ε≤30％；可选的，ε≤20％。正极活性材料满足ε在上述范围内，其宏观和微观一致性较好，颗粒稳定性高，有利于其具 有较高的容量发挥及常温和高温循环性能。因此，电池的相应性能也得到提升。
在上述任意实施方式中，所述正极活性材料的体积平均粒径D v50可以为5μm～20μm，可选的为8μm～15μm，进一步可选的为9μm～11μm。正极活性材料的D v50在上述范围内，能提高锂离子和电子的传输扩散性能，从而提高锂离子二次电池的循环性能及倍率性能。正极活性材料还能具有较高的压实密度，可提升电池的能量密度。
在上述任意实施方式中，所述正极活性材料的比表面积可以为0.2m 2/g～1.5m 2/g，可选的为0.3m 2/g～1m 2/g。正极活性材料的比表面积在上述范围内，能提高正极活性材料的容量发挥及循环寿命，还能改善正极浆料的加工性能，从而使电池获得较高的能量密度和循环性能。
在上述任意实施方式中，所述正极活性材料的振实密度可以为2.3g/cm 3～2.8g/cm 3。正极活性材料的振实密度在上述范围内，可以使锂离子二次电池具有较高的能量密度。
在上述任意实施方式中，所述正极活性材料在5吨(相当于49kN)压力下的压实密度可以为3.1g/cm 3～3.8g/cm 3。正极活性材料的压实密度在所给范围内，有利于使锂离子二次电池获得较高的能量密度和循环性能。
在上述任意实施方式中，锂过渡金属氧化物可满足化学式Li 1+a[Ni xCo yMn zM b]O 2，其中，M为所述掺杂元素，M选自Si、Ti、V、Cr、Ge、Se、Zr、Nb、Mo、Ru、Rh、Pd、Sb、Te、Ce及W中的一种或多种，0.5≤x<1，0≤y<0.3，0≤z<0.3，0≤a<0.2，0<b<0.3，x+y+z+b＝1。
在上述任意实施方式中，锂过渡金属氧化物可满足化学式Li 1+c[Ni r-dCo sMn tM’ d]O 2，其中，M’为所述掺杂元素，M’选自Si、Ti、V、Cr、Ge、Se、Zr、Nb、Mo、Ru、Rh、Pd、Sb、Te、Ce及W中的一种或多种，0.5≤r-d<1，0≤s<0.3，0≤t<0.3，0≤c<0.2，0<d<0.3，r+s+t＝1。
本申请第二方面提供一种正极活性材料的制备方法，其包括以下步骤：
将正极活性材料前驱体、锂源和掺杂元素前驱体混合，得到混合料，其中所述正极活性材料前驱体选自含有Ni、可选的Co和可选的Mn的氧化物、氢氧化物及碳酸盐中的一种或多种；
在含氧气氛、600℃～1000℃温度下对所述混合料烧结处理，得到正极活性材料；
其中，所述正极活性材料包括由一次颗粒聚集而成的二次颗粒，所述一次颗粒包括锂过渡金属氧化物，所述锂过渡金属氧化物的过渡金属位包括镍及掺杂元素，以及所述一次颗粒的杨氏模量E满足175GPa≤E≤220GPa。
本申请提供的制备方法所得到的正极活性材料包括由一次颗粒聚集而成的二次颗 粒，一次颗粒包括含镍的锂过渡金属氧化物，并且通过锂过渡金属氧化物的过渡金属位掺杂改性使一次颗粒的杨氏模量E满足175GPa≤E≤220GPa，由此能使正极活性材料具有较高克容量的同时，提高结构稳定性及高温循环稳定性，从而使采用其的锂离子二次电池同时兼顾较高的能量密度及高温循环性能。
在上述任意实施方式中，所述掺杂元素前驱体可选自硅氧化物、钛氧化物、钒氧化物、铬氧化物、锗氧化物、硒氧化物、锆氧化物、铌氧化物、钼氧化物、钌氧化物、铑氧化物、钯氧化物、锑氧化物、碲氧化物、铈氧化物和钨氧化物中的一种或多种。可选的，所述掺杂元素前驱体选自SiO 2、SiO、TiO 2、TiO、V 2O 5、V 2O 4、V 2O 3、CrO 3、Cr 2O 3、GeO 2、SeO 2、ZrO 2、Nb 2O 5、NbO 2、MoO 2、MoO 3、RuO 2、Ru 2O 3、Rh 2O 3、PdO 2、PdO、Sb 2O 5、Sb 2O 3、TeO 2、CeO 2、WO 2和WO 3中的一种或多种。
在上述任意实施方式中，所述含氧气氛可以为空气气氛或氧气气氛。
在上述任意实施方式中，烧结处理的温度可以为700℃～900℃。
在上述任意实施方式中，烧结处理的时间可以为5h～25h，可选的为10h～20h。
在上述任意实施方式中，可以将所述掺杂元素前驱体等分为L份或任意分为L份，分为L个批次进行掺杂，其中L为1～5，可选的为2～3。可选的包括：将正极活性材料前驱体、锂源及第1批次掺杂元素前驱体混合，并进行第1次烧结处理；将第1次烧结处理的产物与第2批次掺杂元素前驱体进行混合，并进行第2次烧结处理；以此类推，直至将第L-1次烧结处理的产物与第L批次掺杂元素前驱体进行混合，并进行第L次烧结处理，得到正极活性材料。
在上述任意实施方式中，每次烧结处理的温度为600℃～1000℃，可选的为700℃～900℃，进一步可选的为800℃～850℃。
在上述任意实施方式中，每次烧结处理的时间为3h～25h，可选的为5h～10h。
在上述任意实施方式中，总的烧结处理时间为5h～25h，可选的为15h～25h。
本申请第三方面提供一种正极极片，其包括正极集流体以及设置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申请第一方面的正极活性材料、或本申请第二方面的制备方法得到的正极活性材料。
本申请的正极极片由于包含所述的正极活性材料，因而能使采用其的锂离子二次电池具有较高的能量密度和高温循环性能。
本申请第四方面提供一种锂离子二次电池，其包括本申请第三方面的正极极片。
本申请的锂离子二次电池由于包含所述的正极极片，因而能具有较高的能量密度和高温循环性能。
本申请第五方面提供一种电池模块，其包括本申请第四方面的锂离子二次电池。
本申请第六方面提供一种电池包，其包括本申请第四方面的锂离子二次电池、或本申请第五方面的电池模块。
本申请第七方面提供一种装置，其包括本申请第四方面的锂离子二次电池、本申请第五方面的电池模块、或本申请第六方面的电池包中的至少一种。
本申请的电池模块、电池包和装置包括本申请的锂离子二次电池，因而至少具有与所述锂离子二次电池相同或相似的效果。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对本申请实施例中所需要使用的附图作简单地介绍，显而易见地，下面所描述的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图获得其他的附图。
图1为实施例1的二次颗粒截面的掺杂元素分布图像，采用截面抛光仪(Cross Section Polisher，CP)制备截面，采用能谱仪(Energy Dispersive Spectroscopy，EDS)获得掺杂元素分布图像，其中亮点表示掺杂元素，掺杂元素在颗粒中均匀分布。
图2为实施例1～26及对比例1～2的二次颗粒中掺杂元素的局部质量浓度的相对偏差测试位置示意图。
图3是锂离子二次电池的一实施方式的示意图。
图4是图3的分解图。
图5是电池模块的一实施方式的示意图。
图6是电池包的一实施方式的示意图。
图7是图6的分解图。
图8是锂离子二次电池用作电源的装置的一实施方式的示意图。
具体实施方式
为了使本申请的发明目的、技术方案和有益技术效果更加清晰，以下结合实施例对本申请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申请，并非为了限定本申请。
为了简便，本文仅明确地公开了一些数值范围。然而，任意下限可以与任何上限组合形成未明确记载的范围；以及任意下限可以与其它下限组合形成未明确记载的范围， 同样任意上限可以与任意其它上限组合形成未明确记载的范围。此外，尽管未明确记载，但是范围端点间的每个点或单个数值都包含在该范围内。因而，每个点或单个数值可以作为自身的下限或上限与任意其它点或单个数值组合或与其它下限或上限组合形成未明确记载的范围。
在本文的描述中，需要说明的是，除非另有说明，“以上”、“以下”为包含本数，“一种或多种”中的“多种”的含义是两种以上，“一个或多个”中的“多个”的含义是两个以上。
在本文的描述中，除非另有说明，术语“或(or)”是包括性的。举例来说，短语“A或(or)B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
本申请的上述发明内容并不意欲描述本申请中的每个公开的实施方式或每种实现方式。如下描述更具体地举例说明示例性实施方式。在整篇申请中的多处，通过一系列实施例提供了指导，这些实施例可以以各种组合形式使用。在各个实例中，列举仅作为代表性组，不应解释为穷举。
正极活性材料
本申请第一方面提供一种正极活性材料，其包括由一次颗粒聚集而成的二次颗粒，一次颗粒包括锂过渡金属氧化物，锂过渡金属氧化物的过渡金属位包括镍及掺杂元素；以及一次颗粒的杨氏模量E满足175GPa≤E≤220GPa。
在本文中，可以用扫描电子显微镜/扫描探针显微镜联合测试系统(Scanning Electron Microscope/Scanning Probe Microscopy，SEM/SPM)测定一次颗粒的杨氏模量。示例性测定方法如下：
取正极活性材料粉末，采用气流粉碎机进行粉碎，再用酒精稀释，放到超声振荡器离散，使二次颗粒中的一次颗粒分散，用吸管滴到硅基片上。将此硅基片连同碳化硅基片一同放入到SEM/SPM联合测试仪器中(碳化硅基片的作用是作为硬质基底，来校正测试时悬臂梁的弯曲量，进而可以得到施加的力的大小)，用计算机控制SPM运动系统，使扫描探针针尖接触到一次颗粒后，用压电陶瓷控制步进速率，使一次颗粒挤压针尖进行压痕实验。在针尖对一次颗粒进行压痕过程中，探针的悬臂梁弯曲，使激光光路发生偏转，经过计算机转化得到相应的压力值，根据压电陶瓷的移动量得到位移量，进而得到力-位移曲线。对测试得到的力-位移曲线进行分析，结合式(1)可以计算得到一次颗粒的 折减模量E 1：
Figure PCTCN2020109987-appb-000008
其中，e是常数，可通过用F＝el 1.5方程拟合力(F)-位移(l)曲线得到；R是针尖的半径。
进一步通过式(2)计算得到一次颗粒的杨氏模量E：
Figure PCTCN2020109987-appb-000009
其中，E 2为针尖的杨氏模量，V 1为样品的泊松比，V 2为针尖的泊松比。
本申请提供的正极活性材料包括由一次颗粒聚集而成的二次颗粒，一次颗粒包括锂过渡金属氧化物，锂过渡金属氧化物的过渡金属位包括镍，使正极活性材料表现出较高的充放电电压和比容量特性，从而使锂离子二次电池具有较高的容量性能及能量密度。
锂过渡金属氧化物的过渡金属位还包括掺杂元素。通过对锂过渡金属氧化物掺杂改性使得一次颗粒的杨氏模量E满足175GPa≤E≤220GPa，保证正极活性材料具有较高的抗变形能力，防止一次颗粒及二次颗粒在受压过程中发生破裂，同时使一次颗粒具有适当的韧性，有效防止一次颗粒在受到外界压力时发生脆性破裂，并且正极活性材料能够较好地适应锂离子的嵌入和脱出，从而提高正极活性材料的结构稳定性及高温循环稳定性，使锂离子二次电池的高温循环性能得到提升。
正极活性材料在受到外界压力时能保持较高的结构稳定性，一次颗粒及二次颗粒不易发生破裂，避免了裂纹处的电子导电通道断开，保证了正极活性物质层内保持导电网络的连续性，从而保证电池具有较小的阻抗，使电池具有良好的电化学性能，其中电池的容量发挥较好、常温及高温循环性能均较高。较高的结构稳定性还抑制了因一次颗粒及二次颗粒开裂暴露出的新鲜表面与电解液接触产生的副反应，从而减少可逆锂离子的消耗，抑制电极阻抗增加，提高电池高温下的循环容量保持率，使电池具有更高的高温循环性能。
在本文中，“受压”及“受到外界压力”可包括正极活性材料制备正极极片过程中受到设备冷压等压力，以及正极活性材料在电池充放电循环过程中受到膨胀力等压力。
采用本申请实施例提供的正极活性材料，能使锂离子二次电池同时兼顾较高的容量性能、能量密度及高温循环性能。将采用本申请正极活性材料的锂离子二次电池应用于电动汽车上，能使电动汽车获得长续航里程。
在一些可选的实施例中，一次颗粒的杨氏模量E可以≤220GPa、≤218GPa、≤216 GPa、≤215GPa、≤212GPa、≤210GPa、≤208GPa、≤206GPa、≤205GPa、≤204GPa、≤202GPa、或≤200GPa。E可以≥175GPa、≥177GPa、≥180GPa、≥182GPa、≥184GPa、≥186GPa、≥188GPa、≥191GPa、≥193GPa、≥195GPa、≥196GPa、或≥198GPa。
可选的，180GPa≤E≤210GPa。可选的，190GPa≤E≤205GPa。可选的，195GPa≤E≤205GPa。这样能更好地发挥上述效果，提高电池的高温循环性能。
作为掺杂元素，可以选自除镍以外的过渡金属元素及除碳、氮、氧、硫以外的第IIA族至第VIA族的元素中的一种或多种。可选的，掺杂元素与氧具有较强的结合键能。进一步地可选的，掺杂元素与氧的结合键能高于Ni-O结合键能。掺杂元素与氧具有较强的结合键能，能更好地改善一次颗粒的杨氏模量E，有效稳定正极活性材料的结构，提高电池的高温循环性能。
在一些实施方式中，掺杂元素在氧化态时的化合价为+3价以上。可选的，掺杂元素在氧化态时的化合价大于+3价。例如，掺杂元素在氧化态时的化合价为+4价、+5价、+6价、+7价及+8价中的一种或多种，再例如为+4价、+5价、+6价中的一种或多种。
此处，“掺杂元素在氧化态时的化合价”指的是正极活性材料脱锂后，掺杂元素的化合价；尤其是包含本申请正极活性材料的正极组成的电池在进行可逆充放电的范围内被充电至预设充电截止电压，此时正极活性材料中掺杂元素的化合价。预设充电截止电压是根据正极活性材料、负极活性材料及电解质的种类等设定的电池的特性参数之一。
掺杂元素在氧化态时的化合价为+3价以上，尤其为大于+3价，则掺杂元素能在充放电过程中贡献更多的电子，支持正极释放出更多的锂离子，从而提高锂离子二次电池的充放电电压及容量发挥，使得电池的能量密度得到提升。
另外，高价态的掺杂元素与氧的结合能力更强，有利于改善一次颗粒的杨氏模量E，提高正极活性材料的结构稳定性，使电池的高温循环性能得到进一步提高。
在一些实施方式中，掺杂元素可选自Si、Ti、V、Cr、Ge、Se、Zr、Nb、Mo、Ru、Rh、Pd、Sb、Te、Ce及W中的一种或多种。可选的，掺杂元素包括Si、Zr、Nb、Ru、Pd、Sb、Te及W中的一种或多种。所给掺杂元素能更好地发挥上述效果，使锂离子二次电池具有较高的能量密度和良好的常温及高温循环性能。
在一些可选的实施方式中，请参照图1，掺杂元素在二次颗粒中均匀分布。进一步地，二次颗粒中掺杂元素的局部质量浓度的相对偏差可以为30％以下，可选的为20％以下，进一步可选的为16％以下，或13％以下。
在本文中，二次颗粒中掺杂元素的局部质量浓度为在二次颗粒中任意选定位点的有 限体积元内，掺杂元素占所有元素的质量浓度，可由EDX(Energy Dispersive X-Ray Spectroscopy，能量色散X射线光谱仪)或EDS元素分析结合TEM(Transmission Electron Microscope，透射电子显微镜)或SEM(Scanning Electron Microscope，扫描电子显微镜)单点扫描测试元素浓度分布或其它类似方式得到。其中以EDX或EDS元素分析结合TEM或SEM单点扫描测试时，二次颗粒中不同位点处以μg/g计的掺杂元素的质量浓度分别记作η 1、η 2、η 3、…、η n，n为大于15的正整数(如图2所示)。
二次颗粒中掺杂元素的平均质量浓度为在单个二次颗粒内掺杂元素占所有元素的质量浓度，可由EDX或EDS元素分析结合TEM或SEM面扫描测试元素浓度分布或其它类似方式得到。其中以EDX或EDS元素分析结合TEM或SEM面扫描测试元素浓度分布的方式测试时，测试面包括上述单点测试中的所有测试位点(如图2所示)。二次颗粒中掺杂元素的平均质量浓度记作
Figure PCTCN2020109987-appb-000010
单位为μg/g。
二次颗粒中掺杂元素的局部质量浓度的相对偏差σ根据式(3)计算得到：
Figure PCTCN2020109987-appb-000011
二次颗粒中掺杂元素的局部质量浓度的相对偏差在30％以下，可选为在20％以下，意味着掺杂元素在二次颗粒中的分布均匀性较高。均匀掺杂的正极活性材料颗粒内部各处的性质保持一致，锂离子在颗粒内部不同区域的迁移扩散能力处于同一水平。同时，均匀掺杂的颗粒内部各处的杨氏模量E接近，也即颗粒各处的抗变形能力及韧性接近，使得颗粒内的应力分布均匀，颗粒的结构稳定性较高，不易发生破裂。由此，正极活性材料的容量发挥和高温循环性能均能得到提升，从而进一步提升锂离子二次电池的容量性能、能量密度及高温循环性能。
二次颗粒中掺杂元素的局部质量浓度的相对偏差越小，则二次颗粒中掺杂元素的分布越均匀，越能提高正极活性材料整体的结构稳定性、容量发挥和高温循环性能。
在一些可选的实施方式中，正极活性材料的真实掺杂浓度
Figure PCTCN2020109987-appb-000012
满足
Figure PCTCN2020109987-appb-000013
Figure PCTCN2020109987-appb-000014
可选的，
Figure PCTCN2020109987-appb-000015
Figure PCTCN2020109987-appb-000016
或
Figure PCTCN2020109987-appb-000017
Figure PCTCN2020109987-appb-000018
在本文中，正极活性材料的真实掺杂浓度
Figure PCTCN2020109987-appb-000019
可以由下式(4)计算所得：
Figure PCTCN2020109987-appb-000020
式(2)中，
Figure PCTCN2020109987-appb-000021
为正极活性材料的真实掺杂浓度，单位为μg/cm 3。
ρ 真为正极活性材料的真密度，单位为g/cm 3，其等于正极活性材料的质量与正极活性 材料的真体积的比值，其中真体积是固体物质的实际体积，不包括粒子内部的孔隙。ρ 真可以用本领域公知的仪器及方法进行测定，例如气体容积法，可以采用粉末真密度测试仪进行。
ω为正极活性材料中以μg/g为单位的掺杂元素的质量浓度，即每克正极活性材料中所含有的掺杂元素的质量。ω代表宏观正极活性材料整体中掺杂元素的含量，包括掺入正极活性材料二次颗粒中的掺杂元素，在正极活性材料表面其他相中富集的掺杂元素，以及包埋于正极活性材料颗粒间的掺杂元素。ω可通过正极活性材料溶液吸收光谱，如ICP(Inductive Coupled Plasma Emission Spectrometer，电感耦合等离子光谱发生仪)、XAFS(X-ray absorption fine structure spectroscopy，X射线吸收精细结构谱)等测试得到。
正极活性材料的真实掺杂浓度在上述范围内，实现改善一次颗粒的杨氏模量E的同时，还使得正极活性材料具有良好的层状结构，保证了正极活性材料为锂离子的脱嵌提供良好载体，有效降低活性锂离子的不可逆消耗，使正极活性材料具有更高的初始容量及循环容量保持率，从而提高电池的能量密度和高温循环性能。
此外，正极活性材料的真实掺杂浓度在上述范围内，还保证了掺杂元素掺杂于过渡金属层，防止其进入锂层，保证颗粒具有较高的锂离子传输扩散能力，使得电池具有较高的容量发挥及循环性能。
正极活性材料的真密度ρ 真可选为4.6g/cm 3≤ρ 真≤4.9g/cm 3。该正极活性材料能具有较高的比容量，从而能提高电池的容量性能及能量密度。
在一些可选的实施方式中，正极活性材料中掺杂元素的质量浓度ω相对于二次颗粒中掺杂元素的平均质量浓度
Figure PCTCN2020109987-appb-000022
的偏差ε满足ε<50％。可选的，ε≤30％。可选的，ε≤20％。还可选的，ε≤13％，或ε≤10％。
正极活性材料中掺杂元素的质量浓度ω相对于二次颗粒中掺杂元素的平均质量浓度
Figure PCTCN2020109987-appb-000023
的偏差由下式(5)计算得到：
Figure PCTCN2020109987-appb-000024
正极活性材料中掺杂元素的质量浓度ω相对于二次颗粒中掺杂元素的平均质量浓度
Figure PCTCN2020109987-appb-000025
的偏差在上述范围内，意味着掺杂元素顺利掺入二次颗粒中，在二次颗粒表面其他相中分布的掺杂元素以及包埋于正极活性材料颗粒缝隙间的掺杂元素的含量较少，正极活性材料的宏观和微观一致性较好，结构均一，颗粒稳定性高，有利于使正极活性材料具有较高的容量发挥及常温和高温循环性能。
本申请实施例提供的正极活性材料中，锂过渡金属氧化物具有层状晶体结构。在一些可选的实施方式中，锂过渡金属氧化物的过渡金属层中Ni的摩尔量为过渡金属层中元素总摩尔量的50％以上，进一步地为60％以上，再进一步地为70％以上，更进一步地为80％以上。高镍正极活性材料具有更高的比容量特性，能提高锂离子二次电池的容量性能及能量密度。
作为一些示例，锂过渡金属氧化物可满足化学式Li 1+a[Ni xCo yMn zM b]O 2，其中，M为前文所述的掺杂元素，其对过渡金属位掺杂，并且0.5≤x<1，0≤y<0.3，0≤z<0.3，0≤a<0.2，0<b<0.3，x+y+z+b＝1。该高镍正极活性材料具有高比容量特性和高结构稳定性，从而使得锂离子二次电池具有高的容量性能和能量密度、以及良好的常温及高温循环性能。
可选的，0<y<0.3，0<z<0.3。该高镍三元正极活性材料的能量密度高、结构稳定性好，从而使得电池具有高能量密度及长循环寿命。
可选的，M选自Si、Ti、V、Cr、Ge、Se、Zr、Nb、Mo、Ru、Rh、Pd、Sb、Te、Ce及W中的一种或多种。可选的，M包括Si、Zr、Nb、Ru、Pd、Sb、Te及W中的一种或多种。由于该掺杂元素M在氧化态时具有较高的化合价，超过了高镍三元正极活性材料中过渡金属Ni、Co及Mn的平均价态(+3价)，意味着掺杂元素能在充电过程中贡献更多的电子，使得正极活性材料释放出更多的锂离子，提高锂离子二次电池的充放电电压及容量发挥，使得锂离子二次电池具有更高的容量性能及能量密度。采用该掺杂元素M能有效改善正极活性材料一次颗粒的杨氏模量E，使正极活性材料具有较高的抗变形能力和较好的韧性，不易发生破裂，提高电池的循环性能。
作为另一些示例，锂过渡金属氧化物可满足化学式Li 1+c[Ni r-dCo sMn tM’ d]O 2，其中，M’为掺杂元素，其是对过渡金属层的镍进行了部分取代，并且0.5≤r-d<1，0≤s<0.3，0≤t<0.3，0≤c<0.2，0<d<0.3，r+s+t＝1。该高镍正极活性材料具有高比容量特性和高结构稳定性，从而使得锂离子二次电池具有高的容量性能和能量密度、以及良好的常温及高温循环性能。
可选的，0<s<0.3，0<t<0.3。该高镍三元正极活性材料的能量密度高、结构稳定性好，从而使得电池具有高能量密度及长循环寿命。
可选的，M’选自Si、Ti、V、Cr、Ge、Se、Zr、Nb、Mo、Ru、Rh、Pd、Sb、Te、Ce及W中的一种或多种。可选的，M’包括Si、Zr、Nb、Ru、Pd、Sb、Te及W中的一种或多种。同理，采用该掺杂元素M’能使得锂离子二次电池具有更高的容量性能、能量密度及循环性能。
上述示例中的各种锂过渡金属氧化物可以分别独立地用于正极活性材料，也可以是任意两种以上的锂过渡金属氧化物的组合用于正极活性材料。
本申请实施例中，正极活性材料的体积平均粒径D v50可选为5μm～20μm，进一步可选为8μm～15μm，还可选为9μm～11μm。正极活性材料的D v50在上述范围内，锂离子和电子在材料中的迁移路径较短，能进一步提高正极活性材料中锂离子和电子的传输扩散性能，减小电池极化，从而提高锂离子二次电池的循环性能及倍率性能；此外还能使正极活性材料具有较高的压实密度，提升电池的能量密度。
正极活性材料的D v50在上述范围内，还有利于减少电解液在正极活性材料表面的副反应，以及减少正极活性材料颗粒之间的团聚，从而提高正极活性材料的循环性能和安全性能。
本申请实施例中，正极活性材料的比表面积可选为0.2m 2/g～1.5m 2/g，进一步可选为0.3m 2/g～1m 2/g。正极活性材料的比表面积在上述范围内，保证了正极活性材料具有较高的活性比表面积，同时有利于减少电解液在正极活性材料表面的副反应，从而提高正极活性材料的容量发挥及循环寿命；此外，还能抑制正极活性材料在制备浆料及充放电过程中发生颗粒与颗粒之间的团聚，这能提高电池的能量密度及循环性能。
本申请实施例中，正极活性材料的振实密度可选为2.3g/cm 3～2.8g/cm 3。正极活性材料的振实密度在上述范围内，可以使锂离子二次电池具有较高的容量性能及能量密度。
本申请实施例中，正极活性材料在5吨(相当于49kN)压力下的压实密度可选为3.1g/cm 3～3.8g/cm 3。正极活性材料的压实密度在此范围内，有利于使锂离子二次电池具有较高的容量性能及能量密度，同时具有很好的常温循环性能和高温循环性能。
可选地，本申请实施例的正极活性材料的形貌为球体及类球体中的一种或多种。
在本文中，正极活性材料的体积平均粒径D v50为本领域公知的含义，又称为中值粒径，表示正极活性材料颗粒的体积分布50％对应的粒径。正极活性材料的平均粒径D v50可以用本领域公知的仪器及方法进行测定，例如激光粒度分析仪(如英国马尔文仪器有限公司的Mastersizer 3000型)。
正极活性材料的比表面积为本领域公知的含义，可以用本领域公知的仪器及方法进行测定，例如可以用氮气吸附比表面积分析测试方法测试，并用BET(Brunauer Emmett Teller)法计算得出，其中氮气吸附比表面积分析测试可以是通过美国康塔公司的NOVA 2000e型比表面积与孔径分析仪进行。作为具体的示例，测试方法如下：用称重后的空样品管取8.000g～15.000g正极活性材料，将正极活性材料搅拌均匀并称重，把样品管放入NOVA 2000e脱气站中脱气，称量脱气后的正极活性材料和样品管总质量，用总质量减去 空样品管的质量计算得到脱气后正极活性材料的质量G。将样品管放入NOVA 2000e，测定不同相对压力下的氮气在正极活性材料表面的吸附量，基于布朗诺尔-埃特-泰勒多层吸附理论及其公式求得单分子层吸附量，进而计算出正极活性材料总表面积A，通过A/G计算得到正极活性材料的比表面积。
正极活性材料的振实密度为本领域公知的含义，可以用本领域公知的仪器及方法进行测定，例如用振实密度测定仪(如FZS4-4B型)方便地测定。
正极活性材料的压实密度为本领域公知的含义，可以用本领域公知的仪器及方法进行测定，例如用电子压力试验机(如UTM7305型)方便地测定。
接下来示意性地说明一种正极活性材料的制备方法。根据该制备方法能够制备得到上述任意一种正极活性材料。制备方法包括：
将正极活性材料前驱体、锂源及掺杂元素前驱体混合，并进行烧结处理，得到正极活性材料。
上述正极活性材料前驱体可以为按照化学计量比含有Ni及可选的含有Co和/或Mn的氧化物、氢氧化物及碳酸盐中的一种或多种，例如为按照化学计量比含有Ni、Co及Mn的氢氧化物。
正极活性材料前驱体可以通过本领域已知的方法获得，例如通过共沉淀法、凝胶法或固相法制备获得。
作为一个示例，将Ni源、Co源及Mn源分散在溶剂中得到混合溶液；采用连续并流反应的方式，将混合溶液、强碱溶液和络合剂溶液同时泵入带搅拌的反应釜中，控制反应溶液的pH值为10～13，反应釜内的温度为25℃～90℃，反应过程中通惰性气体保护；反应完成后，经陈化、过滤、洗涤和真空干燥，得到含有Ni、Co及Mn的氢氧化物。
Ni源可以为可溶性的镍盐，例如为硫酸镍、硝酸镍、氯化镍、草酸镍及醋酸镍中的一种或多种，再例如为硫酸镍及硝酸镍中的一种或多种，再例如为硫酸镍；Co源可以为可溶性的钴盐，例如为硫酸钴、硝酸钴、氯化钴、草酸钴及醋酸钴中的一种或多种，再例如为硫酸钴及硝酸钴中的一种或多种，再例如为硫酸钴；Mn源可以为可溶性的锰盐，例如为硫酸锰、硝酸锰、氯化锰、草酸锰及醋酸锰中的一种或多种，再例如为硫酸锰及硝酸锰中的一种或多种，再例如为硫酸锰。
强碱可以为LiOH、NaOH及KOH中的一种或多种，例如为NaOH。络合剂可以为氨水、硫酸铵、硝酸铵、氯化铵、柠檬酸铵及乙二胺四乙酸二钠(EDTA)中的一种或多种，例如为氨水。
对混合溶液、强碱溶液和络合剂溶液的溶剂均没有特别的限制，例如混合溶液、强 碱溶液和络合剂溶液的溶剂各自独立地为去离子水、甲醇、乙醇、丙酮、异丙醇及正己醇中的一种或多种，如为去离子水。
反应过程中通入的惰性气体例如为氮气、氩气、氦气中的一种或多种。
上述锂源可以为氧化锂(Li 2O)、磷酸锂(Li 3PO 4)、磷酸二氢锂(LiH 2PO 4)、醋酸锂(CH 3COOLi)、氢氧化锂(LiOH)、碳酸锂(Li 2CO 3)及硝酸锂(LiNO 3)中的一种或多种。进一步地，锂源为碳酸锂、氢氧化锂及硝酸锂中的一种或多种；更进一步地，锂源为碳酸锂。
上述掺杂元素前驱体可以为掺杂元素的氧化物、硝酸化合物、碳酸化合物、氢氧化合物及醋酸化合物中的一种或多种。例如为掺杂元素的氧化物，例如为氧化硅(如SiO 2、SiO等)、氧化钛(如TiO 2、TiO等)、氧化钒(如V 2O 5、V 2O 4、V 2O 3等)、氧化铬(如CrO 3、Cr 2O 3等)、氧化锗(如GeO 2等)、氧化硒(如SeO 2等)、氧化锆(如ZrO 2等)、氧化铌(如Nb 2O 5、NbO 2等)、氧化钼(如MoO 2、MoO 3等)、氧化钌(如Ru 2O 3、RuO 2等)、氧化铑(如Rh 2O 3等)、氧化钯(如PdO 2、PdO等)、氧化锑(如Sb 2O 5、Sb 2O 3等)、氧化碲(如TeO 2等)、氧化铈(如CeO 2等)及氧化钨(如WO 2、WO 3等)中的一种或多种。
正极活性材料前驱体、锂源及掺杂元素前驱体可以采用球磨混合机或高速混合机来进行混合。将混合后的物料加入气氛烧结炉中进行烧结。烧结气氛为含氧气氛，例如为空气气氛或氧气气氛。烧结温度例如为600℃～1000℃。可选的，烧结温度为700℃～900℃，这有利于使掺杂元素具有较高的分布均匀性。烧结时间可根据实际情况进行调节，例如为5h～25h，再例如为10h～20h。
需要说明的是，在正极活性材料制备时，具有多种理论可行的方式可以调控形成二次颗粒，并影响一次颗粒的杨氏模量，如在一定范围内提高烧结温度和/或延长烧结时间均可提高一次颗粒的杨氏模量，在本申请中，列举了固相烧结掺杂方式的一些措施，通过调整烧结次数、分批掺入掺杂元素、控制整体烧结时间和烧结温度等方式，获得具有不同一次颗粒杨氏模量的锂过渡金属氧化物正极活性材料。应当理解的是，本说明书中所描述的方法，仅是为了解释本申请，并非为了限定本申请。
作为示例，可以将掺杂元素前驱体分为L个批次进行掺杂元素的掺杂，其中L可以是1～5，如2～3。在这些实施例中，正极活性材料的制备方法可以包括以下步骤：将正极活性材料前驱体、锂源及第1批次掺杂元素前驱体混合，并进行第1次烧结处理；之后将第1次烧结处理的产物与第2批次掺杂元素前驱体进行混合，并进行第2次烧结处理；以此类推，直至将第L-1次烧结处理的产物与第L批次掺杂元素前驱体进行混合，并进行第 L次烧结处理，得到正极活性材料。
其中，可以将掺杂元素前驱体等分为L份或任意分为L份，来进行L个批次的掺杂。
每次烧结处理的温度相同或不同。每次烧结处理的时间相同或不同。本领域技术人员可以根据掺杂元素的种类及掺杂量来进行烧结温度和时间的调整。例如，每次烧结处理的温度可以为600℃～1000℃，如700℃～900℃，再如800℃～850℃。每次烧结处理的时间可以为3h～25h，如5h～10h。总的烧结时间可以为5h～25h，如15h～25h。
针对较难掺杂的元素，如原子半径大的掺杂元素，可以通过提高烧结温度和/或延长烧结时间来提高掺杂均匀性。
在一些实施例中，还可以将烧结产物进行破碎处理并筛分，以获得具有优化的粒径分布及比表面积的正极活性材料。其中对破碎的方式并没有特别的限制，可根据实际需求进行选择，例如使用颗粒破碎机。
正极极片
本申请提供一种正极极片，其采用本申请任意一种或几种正极活性材料。
本申请实施例的正极极片由于采用了本申请的正极活性材料，因而能使锂离子二次电池同时兼顾良好的常温及高温循环性能和较高的能量密度。
具体地，正极极片包括正极集流体以及设置于正极集流体至少一个表面上的正极活性物质层。例如，正极集流体在自身厚度方向上包括相对的两个表面，正极活性物质层层叠设置于正极集流体的两个表面中的任意一者或两者上。
正极活性物质层包括本申请的正极活性材料。
另外，正极活性物质层中还可以包括导电剂和粘结剂。本申请对正极活性物质层中的导电剂及粘结剂的种类不做具体限制，可以根据实际需求进行选择。
作为示例，导电剂可以为石墨、超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中一种或多种；粘结剂可以为丁苯橡胶(SBR)、水性丙烯酸树脂(water-based acrylic resin)、羧甲基纤维素(CMC)、聚偏二氟乙烯(PVDF)、聚四氟乙烯(PTFE)、聚乙烯醇缩丁醛(PVB)、乙烯-醋酸乙烯酯共聚物(EVA)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物、含氟丙烯酸树脂及聚乙烯醇(PVA)中的一种或多种。
正极集流体可采用导电性能及力学性能良好的金属箔材或多孔金属板，其材质可以为铝、铜、镍、钛、银及它们各自的合金中的一种或多种。正极集流体例如为铝箔。
正极极片可以按照本领域常规方法制备。例如将正极活性材料、导电剂及粘结剂分散于溶剂中，溶剂可以是N-甲基吡咯烷酮(NMP)或去离子水，形成均匀的正极浆料， 将正极浆料涂覆在正极集流体上，经烘干、辊压等工序后，得到正极极片。
锂离子二次电池
本申请提供一种锂离子二次电池，其包括正极极片、负极极片、隔离膜和电解质，其中正极极片为本申请任意的正极极片。
本申请的锂离子二次电池由于采用了本申请的正极极片，因而能同时兼顾良好的常温及高温循环性能和较高的能量密度。
负极极片可以是金属锂片。
负极极片还可以是包括负极集流体以及设置于负极集流体至少一个表面上的负极活性物质层。例如，负极集流体在自身厚度方向上包括相对的两个表面，负极活性物质层层叠设置于负极集流体的两个表面中的任意一者或两者上。
负极活性物质层包括负极活性材料。本申请实施例对负极活性材料的种类不做具体地限制，可以根据实际需求进行选择。作为示例，负极活性材料可以是天然石墨、人造石墨、中间相微碳球(MCMB)、硬碳、软碳、硅、硅-碳复合物、SiO m(0<m<2，如m＝1)、Li-Sn合金、Li-Sn-O合金、Sn、SnO、SnO 2、尖晶石结构的钛酸锂Li 4Ti 5O 12、Li-Al合金及金属锂中的一种或多种。
负极活性物质层还可以包括导电剂和粘结剂。本申请实施例对负极活性物质层中的导电剂和粘结剂的种类不做具体限制，可以根据实际需求进行选择。作为示例，导电剂为石墨、超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的一种或多种；粘结剂为丁苯橡胶(SBR)、聚偏二氟乙烯(PVDF)、聚四氟乙烯(PTFE)、聚乙烯醇缩丁醛(PVB)、水性丙烯酸树脂中的一种或多种。
负极活性物质层还可选地包括增稠剂，例如羧甲基纤维素钠(CMC-Na)。
负极集流体可以采用具有良好导电性能及力学性能的金属箔材或多孔金属板，其材质可以为铜、镍、钛、铁及它们各自的合金中的一种或多种。负极集流体例如为铜箔。
负极极片可以按照本领域常规方法制备。例如将负极活性材料、导电剂、粘结剂及增稠剂分散于溶剂中，溶剂可以是N-甲基吡咯烷酮(NMP)或去离子水，形成均匀的负极浆料，将负极浆料涂覆在负极集流体上，经烘干、辊压等工序后，得到负极极片。
本申请实施例的锂离子二次电池，电解质可以采用固体电解质，如聚合物电解质、无机固态电解质等，但并不限于此。电解质也可以采用电解液。作为上述电解液，包括溶剂和溶解于溶剂中的锂盐。
其中，溶剂可以为非水有机溶剂，例如碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、 碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)及丁酸乙酯(EB)中的一种或多种，例如两种以上。
锂盐可以为LiPF 6(六氟磷酸锂)、LiBF 4(四氟硼酸锂)、LiClO 4(高氯酸锂)、LiAsF 6(六氟砷酸锂)、LiFSI(双氟磺酰亚胺锂)、LiTFSI(双三氟甲磺酰亚胺锂)、LiTFS(三氟甲磺酸锂)、LiDFOB(二氟草酸硼酸锂)、LiBOB(双草酸硼酸锂)、LiPO 2F 2(二氟磷酸锂)、LiDFOP(二氟草酸磷酸锂)及LiTFOP(四氟草酸磷酸锂)中的一种或多种，例如为LiPF 6(六氟磷酸锂)、LiBF 4(四氟硼酸锂)、LiBOB(双草酸硼酸锂)、LiDFOB(二氟草酸硼酸锂)、LiTFSI(双三氟甲磺酰亚胺锂)及LiFSI(双氟磺酰亚胺锂)中的一种或多种。
电解液中还可选地含有其它添加剂，例如碳酸亚乙烯酯(VC)、碳酸乙烯亚乙酯(VEC)、氟代碳酸亚乙酯(FEC)、二氟碳酸亚乙酯(DFEC)、三氟甲基碳酸亚乙酯(TFPC)、丁二腈(SN)、己二腈(ADN)、戊二腈(GLN)、己烷三腈(HTN)、1,3-丙烷磺内酯(1,3-PS)、硫酸亚乙酯(DTD)、甲基二磺酸亚甲酯(MMDS)、1-丙烯-1,3-磺酸内酯(PST)、4-甲基硫酸亚乙酯(PCS)、4-乙基硫酸亚乙酯(PES)、4-丙基硫酸亚乙酯(PEGLST)、硫酸亚丙酯(TS)、1,4-丁烷磺内酯(1,4-BS)、亚硫酸亚乙酯(DTO)、二甲基亚硫酸酯(DMS)、二乙基亚硫酸酯(DES)、磺酸酯环状季铵盐、三(三甲基硅烷)磷酸酯(TMSP)及三(三甲基硅烷)硼酸酯(TMSB)中的一种或多种，但并不限于此。
本申请实施例的锂离子二次电池对隔离膜没有特别的限制，可以选用任意公知的具有电化学稳定性和机械稳定性的多孔结构隔离膜，例如玻璃纤维、无纺布、聚乙烯(PE)、聚丙烯(PP)及聚偏二氟乙烯(PVDF)中的一种或多种的单层或多层薄膜。
将正极极片和负极极片交替层叠设置，并在正极极片与负极极片之间设置隔离膜以起到隔离的作用，得到电芯，也可以是经卷绕后得到电芯。将电芯置于外壳中，注入电解液，并封口，得到锂离子二次电池。
本申请对锂离子二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。如图3是作为一个示例的方形结构的锂离子二次电池5。
在一些实施例中，二次电池可包括外包装。该外包装用于封装正极极片、负极极片和电解质。
在一些实施例中，参照图4，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的 开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。
正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电芯52。电芯52封装于所述容纳腔。电解质可采用电解液，电解液浸润于电芯52中。锂离子二次电池5所含电芯52的数量可以为一个或几个，可根据需求来调节。
在一些实施例中，锂离子二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，如可包括聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)、聚丁二酸丁二醇酯(PBS)等中的一种或几种。
在一些实施例中，锂离子二次电池可以组装成电池模块，电池模块所含锂离子二次电池的数量可以为多个，具体数量可根据电池模块的应用和容量来调节。
图5是作为一个示例的电池模块4。参照图5，在电池模块4中，多个锂离子二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个锂离子二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个锂离子二次电池5容纳于该容纳空间。
在一些实施例中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以根据电池包的应用和容量进行调节。
图6和图7是作为一个示例的电池包1。参照图6和图7，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
本申请还提供一种装置，所述装置包括本申请所述的锂离子二次电池、电池模块、或电池包中的至少一种。所述锂离子二次电池、电池模块或电池包可以用作所述装置的电源，也可以作为所述装置的能量存储单元。所述装置可以但不限于是移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等。
所述装置可以根据其使用需求来选择锂离子二次电池、电池模块或电池包。
图8是作为一个示例的装置。该装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用锂离子二次电池作为电源。
实施例
下述实施例更具体地描述了本申请公开的内容，这些实施例仅仅用于阐述性说明，因为在本申请公开内容的范围内进行各种修改和变化对本领域技术人员来说是明显的。除非另有声明，以下实施例中所报道的所有份、百分比、和比值都是基于重量计，而且实施例中使用的所有试剂都可商购获得或是按照常规方法进行合成获得，并且可直接使用而无需进一步处理，以及实施例中使用的仪器均可商购获得。
实施例1
正极活性材料的制备
掺杂元素为Sb，将掺杂元素前驱体氧化锑(Sb 2O 3)大致等分为3个批次进行Sb的掺杂。制备方法包括：
将正极活性材料前驱体[Ni 0.8Co 0.1Mn 0.1](OH) 2、氢氧化锂LiOH及第1批次的氧化锑加入高速混料机中进行混料1h，得到混合物料，其中，正极活性材料前驱体与氢氧化锂的摩尔比Li/Me为1.05，Me表示正极活性材料前驱体中Ni、Co、Mn的总摩尔量；将混合物料放入气氛烧结炉中进行第1次烧结，烧结温度为830℃，烧结时间为5h，烧结气氛为O 2浓度为90％的含氧气氛。
将第1次烧结处理的产物与第2批次的氧化锑加入高速混料机中混料1h，并进行第2次烧结，烧结温度、烧结时间及烧结气氛与第1次烧结相同。
将第2次烧结处理的产物与第3批次的氧化锑加入高速混料机中混料1h，并进行第3次烧结，烧结温度及烧结气氛与前两次烧结相同，烧结时间为10h。总烧结时间为20h。
第3次烧结处理的产物经破碎、过筛后，即可得到高镍三元正极活性材料。氧化锑的加入量使得正极活性材料中Sb的真实掺杂浓度为25100μg/cm 3。
电解液的制备
将EC、DEC、DMC按照体积比1:1:1进行混合后，得到溶剂，再将锂盐LiPF 6溶解于上述溶剂中，获得电解液，其中LiPF 6的浓度为1mol/L。
扣式电池的制备
将上述制备的正极活性材料、导电炭黑及粘结剂PVDF按照重量比90:5:5分散至溶剂N-甲基吡咯烷酮(NMP)中进行混合均匀，得到正极浆料；将正极浆料均匀涂布于正极集流体铝箔上，经烘干、冷压后，得到正极极片。
在扣电箱中，将正极极片、隔离膜及金属锂片依次层叠设置，并注入上述电解液， 组装得到扣式电池。
全电池的制备
将上述制备的正极活性材料、导电剂乙炔黑及粘结剂PVDF按照重量比94:3:3分散至溶剂NMP中进行混合均匀，得到正极浆料；将正极浆料均匀涂布于正极集流体铝箔上，经烘干、冷压后，得到正极极片。
将负极活性材料人造石墨、硬碳、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC-Na)按照重量比90:5:2:2:1分散至去离子水中进行混合均匀，得到负极浆料；将负极浆料均匀涂布于负极集流体铝箔上，经烘干、冷压后，得到负极极片。
以聚乙烯(PE)多孔聚合薄膜作为隔离膜。将正极极片、隔离膜、负极极片按顺序叠好得到裸电芯，将裸电芯置于外包装中，注入上述电解液并封装，得到全电池。
实施例2～13及实施例16～24
与实施例1不同的是，改变正极活性材料的制备步骤中的相关参数，选择掺杂元素氧化物作为其来源，并调整掺杂元素混入时各批量含量、烧结温度800℃～850℃，总烧结时间15h～25h，获得具有预定掺杂元素种类、掺杂量及掺杂均匀性的正极活性材料，详见表1和表2。
涉及多元素掺杂的实施例4和实施例12，各掺杂元素含量基本相同。
以及实施例22～24中正极活性材料前驱体为[Ni 0.5Co 0.2Mn 0.3](OH) 2。
实施例14
与实施例1不同的是，实施例14中掺杂元素单批次加入，烧结温度780℃；其余参数见表1和表2。
实施例15
与实施例1不同的是，实施例15中的掺杂元素单批次加入，烧结温度700℃；其余参数见表1和表2。
实施例25
与实施例1不同的是，实施例25中，将掺杂元素前驱体按照47.5:47.5:5的重量比分为3个批次进行掺杂；前两次烧结的温度均为700℃，前两次烧结的时间均为4h；第3次烧结的温度为600℃，时间为2h；其余参数见表1和表2。
实施例26
与实施例1不同的是，实施例26中，将掺杂元素前驱体按照45:45:10的重量比分为3个批次进行掺杂；前两次烧结的温度均为600℃，前两次烧结的时间均为3h；第3次烧结的温度为500℃，时间为1h；其余参数见表1和表2。
对比例1～2
与实施例1不同的是，未加入掺杂元素；以及对比例2中正极活性材料前驱体为[Ni 0.5Co 0.2Mn 0.3](OH) 2；其余参数见表1和表2。
测试部分
(1)二次颗粒中掺杂元素的局部质量浓度的相对偏差测试
称取2g正极活性材料粉末样品，将样品均匀洒落在粘有导电胶的样品台上，再轻压使粉末固定，或者从电池正极极片中裁剪出1cm×1cm的极片，粘贴到样品台上作为待测样品。将样品台装入真空样品仓内并固定好，采用日本电子(JEOL)公司的IB-09010CP截面抛光仪制备二次颗粒的截面，参照图2所示二次颗粒截面的17个位置取点，每个位点的大小为20nm×20nm，采用英国牛津仪器集团的X-Max型能谱仪(EDS)结合德国ZEISS的Sigma-02-33型扫描电子显微镜(SEM)测试该17个位点掺杂元素的质量浓度，测试方法如下：检测元素选择Li、O、Ni、Co、Mn和掺杂元素，设置SEM参数为20kV加速电压，60μm光栏，8.5mm工作距离，2.335A电流，进行EDS测试时须待谱图面积达到250000cts以上(通过采集时间和采集速率来控制)时停止测试，并采集数据，得到各位点掺杂元素的质量浓度，分别记为η 1、η 2、η 3、…、η 17。
二次颗粒中掺杂元素的平均质量浓度
Figure PCTCN2020109987-appb-000026
测定方法：采取上述EDS-SEM测试法，如图2中虚线框所示，测试面积覆盖上述二次颗粒扫描的所有点，且不超出二次颗粒的截面。
根据前文所述的式(3)计算得到二次颗粒中掺杂元素的局部质量浓度的相对偏差σ。
为了测试电池中的正极活性材料，可以在干燥房中拆解电池，取出正极极片的中间部分放入烧杯中，倒入适量高纯无水碳酸二甲酯(DMC)，每8小时更换DMC，连续清洗3次，然后放入干燥房的真空静置箱中，保持抽真空状态(-0.096MPa)，干燥12小时，干燥后裁取1cm×1cm以上大小的极片样品，将极片样品粘贴在粘有导电胶的样品台上；或者用刀片在干燥房中刮取2g正极活性材料粉末作为测试样品，按照上述方法测试。
(2)正极活性材料的真实掺杂浓度测试
采用北京彼奥德电子技术有限公司的TD2400型粉末真密度测试仪测定正极活性材料的真密度ρ 真，测试方法如下：25℃下取一定质量的正极活性材料置于样品杯中，记录正极活性材料的质量m；把装有正极活性材料的样品杯放入真密度仪测试腔中，密闭测试系统，通入氦气或氮气等小分子直径的惰性气体，通过检测样品室和膨胀室中的气体的压力，再根据玻尔定律PV＝nRT测量被测材料的真体积V，通过m/V计算得到二次颗粒的真密度ρ 真。其中n为样品杯中气体的摩尔量；R为理想气体常数，取8.314；T为环境温度，为298.15K。
采用美国铂金埃尔默(PE)公司的7000DV型电感耦合等离子体-发射光谱仪(inductively coupled plasma-Optical Emission spectrometers，ICP-OES)测试正极活性材料中掺杂元素的质量浓度ω，测试方法如下：取包含正极活性材料的极片冲成总质量大于0.5g的圆片或取至少5g正极活性材料粉末样品，称取并记录样品质量后放入消解罐中，缓慢加入10mL王水作为消解试剂，之后放入美国CEM公司的Mars5微波消解仪中，以2450Hz微波发射频率进行消解；将消解后的样品溶液转移到容量瓶中摇匀，取样放入ICP-OES进样系统，以0.6MPa氩气压力，1300W射频功率进行正极活性材料的掺杂元素质量浓度测试。
之后根据前文所述的式(4)计算正极活性材料的真实掺杂浓度
Figure PCTCN2020109987-appb-000027
(3)一次颗粒的杨氏模量测试
采用前文所述的SEM/SPM测定方法测试一次颗粒的杨氏模量E。本测试中，气流粉碎机采用宜兴市清华粉体机械设备有限公司的GTJ-250型气流粉碎机。
(4)扣式电池的初始克容量测试
在25℃下，将电池以0.1C恒流充电至充放电截止电压上限，再恒压充电至电流小于等于0.05mA，之后搁置2分钟，然后以0.1C恒流放电至充放电截止电压下限，此次的放电容量即为扣式电池的初始克容量。
(5)全电池的初始克容量测试
在25℃下，将电池以1/3C恒流充电至充放电截止电压上限，再恒压充电至电流小于等于0.05mA，之后搁置5分钟，然后以1/3C恒流放电至充放电截止电压下限，此次的放电容量即为全电池的初始克容量。
(6)全电池的高温循环性能测试
在45℃下，将电池以1C恒流充电至充放电截止电压上限，再恒压充电至电流小于等于0.05mA，之后搁置5分钟，再以1C恒流放电至充放电截止电压下限，此为一个充放电循环，此次的放电容量记为第1次循环的放电比容量D 1。将电池按照上述方法进行400次循环充放电测试，记录第400次循环的放电比容量D 400。
全电池45℃、1C/1C循环400次容量保持率(％)＝D 400/D 1×100％
在测试(4)、(5)、(6)中，
在实施例1～21、25、26及对比例1，扣式电池的充放电截止电压为2.8V～4.25V，全电池的充放电截止电压为2.8V～4.2V。
在实施例22～24及对比例2，扣式电池的充放电截止电压为2.8V～4.35V，全电池的充放电截止电压为2.8V～4.3V。
实施例1～26和对比例1～2的测试结果示于表2。
表1：正极活性材料制备中的相关参数
Figure PCTCN2020109987-appb-000028
表1中，各批次掺杂元素前驱体质量比＝第1批次掺杂元素前驱体的质量∶第2批次掺杂元素前驱体的质量∶第3批次掺杂元素前驱体的质量
表2
Figure PCTCN2020109987-appb-000029
表2中，E为一次颗粒的杨氏模量；
Figure PCTCN2020109987-appb-000030
为正极活性材料的真实掺杂浓度；σ为二次颗粒中掺杂元素的局部质量浓度的相对偏差；ε为正极活性材料中掺杂元素的质量浓度相对于二次颗粒中掺杂元素的平均质量浓度的偏差。
由实施例1～21、25、26与对比例1以及实施例22～24与对比例2的比较结果可以看出，通过使正极活性材料的过渡金属位包括镍及掺杂元素，且一次颗粒的杨氏模量E为175GPa≤E≤220GPa，锂离子二次电池不仅拥有较高的初始克容量，而且还兼具较高的 高温循环性能。
实施例1、5～11的结果可以看出，当掺杂量小于2300μg/cm 3时，正极材料的一次颗粒杨氏模量提升不明显，高温循环性能及容量性能的改善效果较小。当掺杂量超过50000μg/cm 3时，由于正极活性材料本体结构破坏，其容量和45℃高温循环性能同样不如真实掺杂浓度
Figure PCTCN2020109987-appb-000031
为2300μg/cm 3～50000μg/cm 3的正极活性材料。
实施例16～21的结果可以看出，若掺杂元素种类选择不当，导致正极活性材料一次颗粒的杨氏模量小于175GPa时，正极活性材料会在制造过程和充放电过程中发生破裂，导致容量降低和循环性能下降；导致正极活性材料一次颗粒的杨氏模量大于220GPa时，正极活性材料的刚度随之变大而表现出很强的脆性，在此情况下正极活性材料容易发生脆性破裂，破裂产生的新鲜表面与电解液发生副反应增大阻抗，也将恶化电池的容量和高温循环性能。
实施例12～15的结果可以看出，二次颗粒中掺杂元素的局部质量浓度的相对偏差为20％以下时，掺杂均匀性较好，正极活性材料颗粒内部各处的性质保持一致，锂离子在颗粒内部不同区域的迁移扩散能力处于同一水平；同时，均匀掺杂的正极活性材料一次颗粒各个部分的杨氏模量接近，也即抗变形能力及韧性接近，使得材料内应力分布均匀，不易发生破裂，因此电池的容量和循环性能提升效果显著。二次颗粒中掺杂元素的局部质量浓度的相对偏差大于20％时，正极活性材料颗粒内部各处锂离子扩散的通道和势垒不一致，各区域的结构稳定性和抗变形能力存在差异，导致材料内部应力分布不均，内应力大的区域易出现破裂，使得正极活性材料暴露出新鲜表面，增大阻抗进而恶化容量和高温循环性能。
实施例1、25、26的结果可以看出，当正极活性材料中掺杂元素的质量浓度相对于二次颗粒中掺杂元素的平均质量浓度的偏差ε在小于30％范围内时，较多的掺杂元素已顺利掺入二次颗粒中，分布于二次颗粒的缝隙或表面的掺杂元素较少，正极活性材料宏观和微观一致性较好，结构均一，颗粒稳定性高，有利于其容量发挥及常温和高温循环性能。当ε大于30％时，较多的掺杂元素分布在二次颗粒的缝隙或表面，使得一次颗粒内部的结构稳定性提升不足，但分布在表面的掺杂元素起到一定的包覆隔绝电解液副反应作用，因此此时电芯容量和高温循环性能略有下降。
以上所述，仅为本申请的具体实施方式，但本申请的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本申请揭露的技术范围内，可轻易想到各种等效的修改或替换，这些修改或替换都应涵盖在本申请的保护范围之内。因此，本申请的保护范围应以权利要求的保护范围为准。

Claims (20)

  1. 一种正极活性材料，包括由一次颗粒聚集而成的二次颗粒，所述一次颗粒包括锂过渡金属氧化物，所述锂过渡金属氧化物的过渡金属位包括镍及掺杂元素；以及
    所述一次颗粒的杨氏模量E满足175GPa≤E≤220GPa。
  2. 根据权利要求1所述的正极活性材料，其中，所述一次颗粒的杨氏模量E满足180GPa≤E≤210GPa；可选的，190GPa≤E≤205GPa。
  3. 根据权利要求1或2所述的正极活性材料，其中，所述二次颗粒中掺杂元素的局部质量浓度的相对偏差为30％以下，可选的为20％以下。
  4. 根据权利要求1-3任一项所述的正极活性材料，其中，所述掺杂元素在氧化态时的化合价为+3价以上，可选的为+4价、+5价、+6价、+7价及+8价中的一种或多种。
  5. 根据权利要求1-4任一项所述的正极活性材料，其中，所述掺杂元素选自Si、Ti、V、Cr、Ge、Se、Zr、Nb、Mo、Ru、Rh、Pd、Sb、Te、Ce及W中的一种或多种；可选的，所述掺杂元素包括Si、Zr、Nb、Ru、Pd、Sb、Te及W中的一种或多种。
  6. 根据权利要求1-5任一项所述的正极活性材料，其中，所述正极活性材料的真密度ρ 真满足4.6g/cm 3≤ρ 真≤4.9g/cm 3。
  7. 根据权利要求1-6任一项所述的正极活性材料，其中，所述正极活性材料的真实掺杂浓度
    Figure PCTCN2020109987-appb-100001
    满足
    Figure PCTCN2020109987-appb-100002
    可选的，
    Figure PCTCN2020109987-appb-100003
    Figure PCTCN2020109987-appb-100004
    可选的，
    Figure PCTCN2020109987-appb-100005
    可选的，
    Figure PCTCN2020109987-appb-100006
    Figure PCTCN2020109987-appb-100007
  8. 根据权利要求1-7任一项所述的正极活性材料，其中，所述正极活性材料中掺杂元素的质量浓度相对于所述二次颗粒中掺杂元素的平均质量浓度的偏差ε<50％；可选的，ε≤30％；可选的，ε≤20％。
  9. 根据权利要求1-8任一项所述的正极活性材料，其中，所述正极活性材料还满足如下(1)～(4)中的一个或多个：
    (1)所述正极活性材料的体积平均粒径D v50为5μm～20μm，可选的为8μm～15μm，进一步可选的为9μm～11μm；
    (2)所述正极活性材料的比表面积为0.2m 2/g～1.5m 2/g，可选的为0.3m 2/g～1m 2/g；
    (3)所述正极活性材料的振实密度为2.3g/cm 3～2.8g/cm 3；
    (4)所述正极活性材料在5吨(相当于49kN)压力下的压实密度为3.1g/cm 3～3.8g/cm 3。
  10. 根据权利要求1-9任一项所述的正极活性材料，其中，
    所述锂过渡金属氧化物满足化学式Li 1+a[Ni xCo yMn zM b]O 2，其中，M为所述掺杂元素，M选自Si、Ti、V、Cr、Ge、Se、Zr、Nb、Mo、Ru、Rh、Pd、Sb、Te、Ce及W中的一种或多种，0.5≤x<1，0≤y<0.3，0≤z<0.3，0≤a<0.2，0<b<0.3，x+y+z+b＝1；或，
    所述锂过渡金属氧化物满足化学式Li 1+c[Ni r-dCo sMn tM’ d]O 2，其中，M’为所述掺杂元素，M’选自Si、Ti、V、Cr、Ge、Se、Zr、Nb、Mo、Ru、Rh、Pd、Sb、Te、Ce及W中的一种或多种，0.5≤r-d<1，0≤s<0.3，0≤t<0.3，0≤c<0.2，0<d<0.3，r+s+t＝1。
  11. 一种正极活性材料的制备方法，包括以下步骤：
    将正极活性材料前驱体、锂源和掺杂元素前驱体混合，得到混合料，其中所述正极活性材料前驱体选自含有Ni、可选的Co和可选的Mn的氧化物、氢氧化物及碳酸盐中的一种或多种；
    在含氧气氛、600℃～1000℃温度下对所述混合料烧结处理，得到正极活性材料；
    其中，所述正极活性材料包括由一次颗粒聚集而成的二次颗粒，所述一次颗粒包括锂过渡金属氧化物，所述锂过渡金属氧化物的过渡金属位包括镍及掺杂元素，以及所述一次颗粒的杨氏模量E满足175GPa≤E≤220GPa。
  12. 根据权利要求11所述的方法，其中，所述掺杂元素前驱体选自硅氧化物、钛氧化物、钒氧化物、铬氧化物、锗氧化物、硒氧化物、锆氧化物、铌氧化物、钼氧化物、钌氧化物、铑氧化物、钯氧化物、锑氧化物、碲氧化物、铈氧化物和钨氧化物中的一种或多种；可选的，所述掺杂元素前驱体选自SiO 2、SiO、TiO 2、TiO、V 2O 5、V 2O 4、V 2O 3、CrO 3、Cr 2O 3、GeO 2、SeO 2、ZrO 2、Nb 2O 5、NbO 2、MoO 2、MoO 3、RuO 2、Ru 2O 3、Rh 2O 3、PdO 2、PdO、Sb 2O 5、Sb 2O 3、TeO 2、CeO 2、WO 2和WO 3中的一种或多种。
  13. 根据权利要求11或12所述的方法，其中，所述烧结处理满足如下(a)～(c)中的至少一项：
    (a)所述含氧气氛为空气气氛或氧气气氛；
    (b)烧结处理的温度为700℃～900℃；
    (c)烧结处理的时间为5h～25h，可选的为10h～20h。
  14. 根据权利要求11-13任一项所述的方法，其中，将所述掺杂元素前驱体等分为L份或任意分为L份，分为L个批次进行掺杂，其中L为1～5，可选的为2～3；
    可选的包括：将正极活性材料前驱体、锂源及第1批次掺杂元素前驱体混合，并进行第1次烧结处理；将第1次烧结处理的产物与第2批次掺杂元素前驱体进行混合，并进行第2次烧结处理；以此类推，直至将第L-1次烧结处理的产物与第L批次掺杂元素前驱体进行混合，并进行第L次烧结处理，得到正极活性材料。
  15. 根据权利要求14所述的方法，其中，所述方法还满足如下(a)～(c)中的至少一项：
    (a)每次烧结处理的温度为600℃～1000℃，可选的为700℃～900℃，还可选的为800℃～850℃；
    (b)每次烧结处理的时间为3h～25h，可选的为5h～10h；
    (c)总的烧结处理时间为5h～25h，可选的为15h～25h。
  16. 一种正极极片，包括正极集流体以及设置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根据权利要求1-10任一项所述的正极活性材料、或根据权利要求11-15任一项所述的制备方法得到的正极活性材料。
  17. 一种锂离子二次电池，包括根据权利要求16所述的正极极片。
  18. 一种电池模块，包括根据权利要求17所述的锂离子二次电池。
  19. 一种电池包，包括根据权利要求17所述的锂离子二次电池、或根据权利要求18所述的电池模块。
  20. 一种装置，包括根据权利要求17所述的锂离子二次电池、根据权利要求18所述的电池模块、或根据权利要求19所述的电池包中的至少一种。
PCT/CN2020/109987 2019-09-02 2020-08-19 正极活性材料、其制备方法、正极极片、锂离子二次电池及其相关的电池模块、电池包和装置 WO2021042989A1 (zh)

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