WO2024011594A1 - 正极活性材料及其制备方法、正极极片、二次电池、电池模块、电池包及用电装置 - Google Patents

正极活性材料及其制备方法、正极极片、二次电池、电池模块、电池包及用电装置 Download PDF

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WO2024011594A1
WO2024011594A1 PCT/CN2022/105998 CN2022105998W WO2024011594A1 WO 2024011594 A1 WO2024011594 A1 WO 2024011594A1 CN 2022105998 W CN2022105998 W CN 2022105998W WO 2024011594 A1 WO2024011594 A1 WO 2024011594A1
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active material
cathode active
optionally
range
positive electrode
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PCT/CN2022/105998
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English (en)
French (fr)
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徐晓富
蒋耀
刘倩
叶永煌
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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 PCT/CN2022/105998 priority Critical patent/WO2024011594A1/zh
Priority to CN202280012894.9A priority patent/CN116830301A/zh
Publication of WO2024011594A1 publication Critical patent/WO2024011594A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/56—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of lead
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the technical field of secondary batteries, and in particular to a positive active material and a preparation method thereof, a positive electrode plate, a secondary battery, a battery module, a battery pack and an electrical device.
  • secondary batteries are widely used in energy storage power systems such as hydraulic, thermal, wind and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, Military equipment, aerospace and other fields. Due to the great development of secondary batteries, higher requirements have been put forward for their energy density, cycle performance and safety performance. As the existing cathode active material of secondary batteries, lithium manganese phosphate is prone to produce Li/Mn anti-site defects during the charge and discharge process, and the manganese dissolution is serious, which affects the gram capacity of the secondary battery and leads to the safety performance of the secondary battery. and poor cycle performance.
  • This application was made in view of the above issues, and its purpose is to provide a positive electrode active material, a preparation method of the positive electrode active material, a positive electrode plate, a secondary battery, a battery module, a battery pack and an electrical device to solve the problem of using current Secondary batteries made of positive electrode active materials have problems such as low cycle capacity retention, short cycle life, and low safety.
  • the first aspect of the present application provides a cathode active material, including a first cathode active material and a second cathode active material; wherein,
  • the first positive active material includes a compound LiNi b Co d Mn e M f O 2 , wherein b is selected from the range of 0.314-0.970, d is selected from the range of 0-0.320, optionally selected from the range of 0.047-0.320, and e Selected from the range of 0.006-0.390, and the sum of b, d, e and f is 1 and f is greater than 0, M is selected from Mn, Al, Mg, Ca, Na, Ti, W, Zr, Sr, Cr, Zn , one or more elements among Ba, B, S and Y, optionally, M is Mg and/or Al;
  • the second cathode active material includes a compound Li a A From the range of 0.001 to 0.5, z is selected from the range of 0.001 to 0.1, n is selected from the range of 0.001 to 0.1, A is selected from one or more of Zn, Al, Na, K, Mg, Nb, Mo and W Element, B is selected from one or more elements among Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb and Ge, C is selected from B (boron), S, Si and N One or more elements in, D is selected from one or more elements in S, F, Cl and Br.
  • the second positive electrode active material only has one-dimensional lithium ion transmission channels
  • the first positive electrode active material is a layered transition metal oxide with two-dimensional lithium ion transmission channels. Therefore, this application combines the first positive electrode active material and the second positive electrode active material.
  • the advantages of the two materials complement each other, which improves the cycle capacity retention rate of the secondary battery, extends the cycle life of the secondary battery, and improves the safety of the secondary battery.
  • the above limitation on the numerical range of The limitation of the stoichiometric number of each element as A is also the limitation of the sum of the stoichiometric numbers of each element as A.
  • the respective stoichiometric numbers x1, x2...xn of A1, A2...An must fall within the numerical range of x defined in this application, and x1
  • the sum of , x2...xn also needs to fall within this numerical range.
  • the mass of the first cathode active material is m 1
  • the mass of the second cathode active material is m 2
  • the value of m 1 /(m 1 +m 2 ) is 2%-55%, optionally 3%-50%. Therefore, the mass percentage of the first cathode active material in the two cathode active materials is within the above range, which can improve the stability and safety of the overall cathode active material.
  • the value of b ⁇ m 1 /(m 1 +m 2 ) is 0.017-0.457, optionally 0.025-0.415. This can further improve the stability and safety of the overall cathode active material.
  • the first cathode active material is a single crystal or quasi-single crystal material, and the particle size D v 50 of the first cathode active material is less than or equal to 5.8 ⁇ m, optionally 2.3-5.8 ⁇ m, more optionally 2.3-4.3 ⁇ m.
  • Making the particle size of the single crystal or quasi-single crystal first cathode active material within the above range can optimize the electrochemical reaction area, further reduce and inhibit the interfacial side reactions of the cathode during the secondary battery cycle, and reduce the cycle decay rate of the secondary battery. , extend the cycle life of secondary batteries.
  • d is selected from the range of 0.05-0.320, optionally selected from the range of 0.05-0.282; and/or,
  • b is greater than 0.314 and less than 0.97, and can be selected from the range of 0.55-0.869.
  • d and b within the above range are conducive to further improving the conductivity and rate performance of the cathode active material, further improving the cycle capacity retention rate of the secondary battery, and further extending the secondary battery life. Secondary battery cycle life.
  • the particle size D v 50 of the first positive active material is 3.5 to 13.5 ⁇ m; and/or,
  • the BET specific surface area of the first cathode active material is less than or equal to 1.32m 2 /g, optionally 0.28-1.32m 2 /g; and/or,
  • the compacted density of the first positive active material under a pressure of 3T is greater than or equal to 2.92g/cm 3 , and can be selected from 2.92 to 3.31g/cm 3 .
  • Making the particle size, specific surface area and compacted density of the polycrystalline first cathode active material within the above range can further improve the rate performance of the cathode active material, further reduce and suppress the interfacial side reactions of the cathode during the secondary battery cycle process, and reduce The cycle decay rate of the secondary battery extends the cycle life of the secondary battery.
  • the first positive active material further includes lithium carbonate and/or lithium hydroxide
  • the mass content of lithium carbonate is less than or equal to 1%, and/or the mass content of lithium hydroxide is less than or equal to 1%.
  • the residual water molecules brought in by the second positive electrode active material may react with the electrolyte to produce HF.
  • HF can easily cause damage to the positive electrode active material itself or the SEI film on the negative electrode sheet, thereby affecting the life of the secondary battery.
  • the lithium carbonate and/or lithium hydroxide further contained in the first positive electrode active material of the present application can perform a neutralization reaction with HF, reducing or inhibiting the destructive effect of HF on the positive electrode active material or the SEI film of the negative electrode sheet, thereby further improving the Cycle life of secondary batteries.
  • A is selected from any one element among Zn, Al, Na, K, Mg, Nb, Mo and W
  • B is selected from Ti, V, Zr, Fe, Ni , at least two elements among Mg, Co, Ga, Sn, Sb, Nb and Ge
  • C is selected from any one element among B (boron)
  • S, Si and N is selected from S, F, Cl and Any element in Br;
  • A is Mg or Nb, and/or,
  • B is selected from at least two elements selected from Fe, Ti, V, Co and Mg, and more preferably Fe and one or more elements selected from Ti, V, Co and Mg, and/or,
  • C is S, and/or
  • the lattice change rate during the delithiation process can be further reduced, thereby further improving the rate performance of the secondary battery.
  • the Mn site doping element within the above range the electronic conductivity can be further improved and the lattice change rate can be further reduced, thereby improving the rate performance and gram capacity of the secondary battery.
  • the P-site doping element within the above range the rate performance of the secondary battery can be further improved.
  • the O-site doping element within the above range the side reactions at the interface can be further reduced and the high-temperature performance of the secondary battery can be improved.
  • x is selected from the range of 0.001 to 0.005; and/or,
  • y is selected from the range of 0.01 to 0.5, optionally selected from the range of 0.25 to 0.5; and/or,
  • z is selected from the range of 0.001 to 0.005; and/or,
  • n is selected from the range of 0.001 to 0.005.
  • the gram capacity and rate performance of the material can be further improved.
  • the x value within the above range the dynamic properties of the material can be further improved.
  • the z value within the above range the rate performance of the secondary battery can be further improved.
  • the n value within the above range the high-temperature performance of the secondary battery can be further improved.
  • the value of (1-y):y is selected from the range of 1 to 4, optionally selected from the range of 1.5 to 3, and the value of a:x is selected from the range of 9 to 1100, optionally Select from the range of 190-998.
  • the lattice change rate of the second cathode active material before and after complete deintercalation of lithium is 8% or less, optionally 4% or less.
  • the lattice change rate can be measured by methods known in the art, such as X-ray diffraction (XRD).
  • the Li/Mn anti-site defect concentration of the second positive electrode active material is 2% or less, optionally 0.5% or less.
  • the so-called Li/Mn antisite defect refers to the interchange of positions between Li + and Mn 2+ in the LiMnPO 4 lattice.
  • the Li/Mn anti-site defect concentration refers to the percentage of Li + exchanged with Mn 2+ in the positive active material to the total amount of Li + . Mn 2+ with anti-site defects will hinder the transport of Li + .
  • the Li/Mn anti-site defect concentration can be measured by methods known in the art, such as XRD.
  • the surface oxygen valence state of the second cathode active material is -1.82 or less, optionally -1.89 to -1.98.
  • the interface side reaction between the positive electrode active material and the electrolyte can be reduced, thereby improving the cycle performance and high temperature stability of the secondary battery.
  • Surface oxygen valence state can be measured by methods known in the art, such as by electron energy loss spectroscopy (EELS).
  • the compacted density of the second cathode active material at 3T is 2.0 g/cm 3 or more, optionally 2.2 g/cm 3 or more.
  • the compacted density can be measured according to GB/T 24533-2009.
  • the second positive active material further includes carbon coated on the surface of the compound Li a Ax Mn 1-y By P 1-z C z O 4-n D n .
  • the conductivity of the positive electrode active material can be improved.
  • a second aspect of the application also provides a method for preparing a cathode active material, including the following steps:
  • the first positive active material includes the compound LiNi b Co d Mn e M f O 2
  • the second positive active material includes the compound Li a A x Mn 1-y B y P 1-z C z O 4-n D n , where, a, b, d, e, f, x, y, z, n, M, A, B, C and D are as defined in the first aspect of the application;
  • the first positive active material further includes lithium carbonate and/or lithium hydroxide
  • the second cathode active material further includes carbon coated on the surface of the compound Li a Ax Mn 1-y By P 1- z C z O 4-n D n .
  • the advantages of the two materials complement each other, which improves the cycle capacity retention rate of the secondary battery, prolongs the cycle life of the secondary battery, and improves Safety of secondary batteries.
  • a third aspect of the present application provides a positive electrode sheet, which includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode film layer includes the positive electrode active material of the first aspect of the application or is obtained by the application.
  • the cathode active material prepared by the method of the second aspect; optionally, the content of the cathode active material in the cathode film layer is more than 10% by weight, more optionally 95-99.5% by weight, based on the total weight of the cathode film layer.
  • a fourth aspect of the present application provides a secondary battery, including the positive active material of the first aspect of the present application or the positive active material prepared according to the method of the second aspect of the present application, or the positive electrode sheet of the third aspect of the present application.
  • a fifth aspect of the present application provides a battery module including the secondary battery of the fourth aspect of the present application.
  • a sixth aspect of the present application provides a battery pack, including the battery module of the fifth aspect of the present application.
  • a seventh aspect of the present application provides an electrical device, including at least one selected from the group consisting of the secondary battery of the fourth aspect of the present application, the battery module of the fifth aspect of the present application, and the battery pack of the sixth aspect of the present application. kind.
  • FIG. 1 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 1 .
  • FIG. 3 is a schematic diagram of a battery module according to an embodiment of the present application.
  • Figure 4 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 5 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG. 4 .
  • FIG. 6 is a schematic diagram of a power consumption device using a secondary battery as a power source according to an embodiment of the present application.
  • Figure 7 is an SEM photograph of the first positive electrode active material prepared in Preparation Example A10 of the present application.
  • Figure 8 is an SEM photograph of the first positive electrode active material prepared in Preparation Example A15 of the present application.
  • Ranges disclosed herein are defined in terms of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive of the endpoints, and may be arbitrarily combined, that is, any lower limit may be combined with any upper limit to form a range. For example, if the ranges of 60-120 and 80-110 are listed for a particular parameter, understand that ranges of 60-110 and 80-120 are also expected. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.
  • the numerical range “a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range “0-5" means that all real numbers between "0-5" have been listed in this article, and "0-5" is just an abbreviation of these numerical combinations.
  • a certain parameter is an integer ⁇ 2
  • a method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • step (c) means that step (c) can be added to the method in any order.
  • the method may include steps (a), (b) and (c), and may also include step (a). , (c) and (b), and may also include steps (c), (a) and (b), etc.
  • condition "A or B” is satisfied by any of the following conditions: 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).
  • Secondary batteries also known as rechargeable batteries or storage batteries, refer to batteries that can be recharged to activate active materials and continue to be used after the battery is discharged.
  • a secondary battery normally includes a positive electrode plate, a negative electrode plate, a separator and an electrolyte.
  • active ions such as lithium ions
  • the isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows active ions to pass through.
  • the electrolyte is between the positive electrode piece and the negative electrode piece and mainly plays the role of conducting active ions.
  • One embodiment of the present application provides a cathode active material, including a first cathode active material and a second cathode active material; wherein,
  • the first positive active material includes the compound LiNi b Co d Mn e M f O 2 , wherein b is selected from the range of 0.314-0.970, optionally selected from the range of 0.65-0.97, and d is selected from the range of 0-0.320, optionally.
  • M is selected from one or more elements among Mn, Al, Mg, Ca, Na, Ti, W, Zr, Sr, Cr, Zn, Ba, B, S and Y;
  • the second cathode active material includes a compound Li a A From the range of 0.001 to 0.5, z is selected from the range of 0.001 to 0.1, n is selected from the range of 0.001 to 0.1, A is selected from one or more of Zn, Al, Na, K, Mg, Nb, Mo and W Element, optionally Mg and/or Mo, B is selected from one or more elements among Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb and Ge, optionally One or more elements from V, Fe and Co, C is selected from one or more elements from B (boron), S, Si and N, optionally one or more elements selected from S, Si and N One or more elements, D is selected from one or more elements among S, F, Cl and Br, optionally F.
  • the first cathode active material is a layered transition metal oxide with a two-dimensional lithium ion transmission channel; the second cathode active material only has a one-dimensional lithium ion transmission channel.
  • the mixed use of the two complements each other and can improve the overall electrochemical performance.
  • the first Coulombic efficiency of the first cathode active material is usually lower than that of the second cathode active material.
  • the secondary battery still contains more reversible lithium ions after the negative electrode film formation of the chemical system is consumed, which improves the performance of the secondary battery.
  • the cycle capacity retention rate extends the cycle life of the secondary battery and improves the safety of the secondary battery.
  • the second cathode active material of the present application is obtained by element doping in the compound LiMnPO 4 , where A, B, C and D are respectively in the compound Li-site, Mn-site, P-site and O-site doped elements of LiMnPO 4 .
  • the inventor of the present application found that the performance improvement of lithium manganese phosphate is related to reducing the lattice change rate of lithium manganese phosphate and reducing surface activity during the process of deintercalating lithium.
  • the lattice change rate can reduce the lattice constant difference between the two phases at the grain boundary, reduce the interface stress, and enhance the transport capability of Li + at the interface, thereby improving the rate performance of the cathode active material.
  • High surface activity can easily lead to serious interface side reactions, aggravating gas production, electrolyte consumption and destroying the interface, thereby affecting the cycle performance of secondary batteries.
  • the lattice change rate is reduced by Li and Mn site doping. Mn site doping also effectively reduces surface activity, thereby inhibiting Mn dissolution and interface side reactions between the cathode active material and the electrolyte.
  • P-site doping makes the Mn-O bond length change faster and reduces the material's small polaron migration barrier, thereby benefiting the electronic conductivity.
  • O-site doping has a good effect on reducing interface side reactions.
  • the doping of P-site and O-site also affects the Mn dissolution and kinetic properties of anti-site defects. Therefore, doping reduces the concentration of anti-site defects in the material, improves the dynamic properties and gram capacity of the material, and can also change the morphology of the particles, thereby increasing the compaction density.
  • M is Mg and/or Al.
  • the doping of Al element in the first cathode active material can improve the structural stability and thermal stability of the material, and improve the cycle performance; the doping of Mg element in the first cathode active material can cause the valence state of transition metal ions to increase or decrease, thus The generation of holes or electrons changes the energy band structure of the material, increases the intrinsic electronic conductivity of the material, and improves the cycle performance of the secondary battery; Mg and Al are co-doped into the host material lattice, which can collaboratively stabilize the material structure. , improve the mixing degree of material cations, inhibit the precipitation of oxygen, and further improve the cycle performance and thermal stability of secondary batteries.
  • the above limitation on the numerical range of The limitation of the stoichiometric number of each element as A is also the limitation of the sum of the stoichiometric numbers of each element as A.
  • the respective stoichiometric numbers x1, x2...xn of A1, A2...An must fall within the numerical range of x defined in this application, and x1
  • the sum of , x2...xn also needs to fall within this numerical range.
  • the compounds LiNibCodMneMfO2 and LiaAxMn1 - yByP1 - zCzO4 - nDn both remain electrically neutral .
  • the mass of the first cathode active material is m 1
  • the mass of the second cathode active material is m 2
  • the value of m 1 /(m 1 +m 2 ) is 2%-55%, optionally 3%-50%. Therefore, the mass percentage of the first cathode active material in the two cathode active materials is within the above range, which can improve the stability and safety of the overall cathode active material.
  • the value of b ⁇ m 1 /(m 1 +m 2 ) is 0.017-0.457, optionally 0.025-0.415. This can further improve the stability and safety of the overall cathode active material.
  • the first cathode active material is a single crystal or quasi-single crystal material, and the particle size D v 50 of the first cathode active material is less than or equal to 5.8 ⁇ m, optionally 2.3-5.8 ⁇ m, more optionally 2.3-4.3 ⁇ m.
  • Making the particle size of the single crystal or quasi-single crystal first cathode active material within the above range can optimize the electrochemical reaction area, further reduce and inhibit the interface side reactions of the cathode during the secondary battery cycle, and reduce the cycle decay rate of the secondary battery. , extend the cycle life of secondary batteries.
  • the first cathode active material is a single crystal or quasi-single crystal material, and the BET specific surface area of the first cathode active material is less than or equal to 1.15m 2 /g, optionally 0.45-1.15m 2 /g; and /or,
  • the compacted density of the first positive active material under a pressure of 3T is greater than or equal to 3.11g/cm 3 , and can be selected from 3.11 to 3.4g/cm 3 .
  • d is selected from the range of 0.05-0.320, optionally selected from the range of 0.05-0.282; and/or,
  • b is greater than 0.314 and less than 0.97, and can be selected from the range of 0.55-0.869.
  • d and b within the above range are conducive to further improving the conductivity and rate performance of the cathode active material, further improving the cycle capacity retention rate of the secondary battery, and further extending the secondary battery life. Secondary battery cycle life.
  • the particle size D v 50 of the first positive active material is 3.5 to 13.5 ⁇ m; and/or,
  • the BET specific surface area of the first cathode active material is less than or equal to 1.32m 2 /g, optionally 0.28-1.32m 2 /g; and/or,
  • the compacted density of the first positive active material under a pressure of 3T is greater than or equal to 2.92g/cm 3 , and can be selected from 2.92 to 3.31g/cm 3 .
  • Making the particle size, specific surface area and compacted density of the polycrystalline first cathode active material within the above range can further improve the rate performance of the cathode active material, further reduce and suppress the interfacial side reactions of the cathode during the secondary battery cycle process, and reduce The cycle decay rate of the secondary battery extends the cycle life of the secondary battery.
  • the first cathode active material further includes lithium carbonate and/or lithium hydroxide
  • the mass content of lithium carbonate is less than or equal to 1%, and/or the mass content of lithium hydroxide is less than or equal to 1%.
  • the residual water molecules brought in by the second positive electrode active material may react with the electrolyte to produce HF.
  • HF can easily cause damage to the positive electrode active material itself or the SEI film on the negative electrode sheet, thereby affecting the life of the secondary battery.
  • the lithium carbonate and/or lithium hydroxide further contained in the first positive electrode active material of the present application can perform a neutralization reaction with HF, reducing or inhibiting the destructive effect of HF on the positive electrode active material or the SEI film of the negative electrode sheet, thereby further improving the Cycle life of secondary batteries.
  • A is selected from any element among Zn, Al, Na, K, Mg, Nb, Mo and W
  • B is selected from Ti, V, Zr, Fe, Ni , at least two elements among Mg, Co, Ga, Sn, Sb, Nb and Ge
  • C is selected from any one element among B (boron)
  • S, Si and N is selected from S, F, Cl and Any element in Br;
  • A is Mg or Nb, and/or,
  • B is selected from at least two elements selected from Fe, Ti, V, Co and Mg, and more preferably Fe and one or more elements selected from Ti, V, Co and Mg, and/or,
  • C is S, and/or
  • the lattice change rate during the delithiation process can be further reduced, thereby further improving the rate performance of the secondary battery.
  • the Mn site doping element within the above range the electronic conductivity can be further improved and the lattice change rate can be further reduced, thereby improving the rate performance and gram capacity of the secondary battery.
  • the P-site doping element within the above range the rate performance of the secondary battery can be further improved.
  • the O-site doping element within the above range the side reactions at the interface can be further reduced and the high-temperature performance of the secondary battery can be improved.
  • x is selected from the range of 0.001 to 0.005; and/or,
  • y is selected from the range of 0.01 to 0.5, optionally selected from the range of 0.25 to 0.5; and/or,
  • z is selected from the range of 0.001 to 0.005; and/or,
  • n is selected from the range of 0.001 to 0.005.
  • the gram capacity and rate performance of the material can be further improved.
  • the x value within the above range the dynamic properties of the material can be further improved.
  • the z value within the above range the rate performance of the secondary battery can be further improved.
  • the n value within the above range the high-temperature performance of the secondary battery can be further improved.
  • the value of (1-y):y is selected from the range of 1 to 4, optionally selected from the range of 1.5 to 3, and the value of a:x is selected from the range of 9 to 1100, which may be Select from the range of 190-998.
  • the energy density and cycle performance of the cathode active material can be further improved.
  • the lattice change rate of the second cathode active material before and after complete deintercalation of lithium is 8% or less, optionally 4% or less.
  • Li ion transport can be made easier, that is, Li ions have a stronger migration ability in the material, which is beneficial to improving the rate performance of secondary batteries.
  • the lattice change rate can be measured by methods known in the art, such as X-ray diffraction (XRD).
  • the Li/Mn anti-site defect concentration of the second cathode active material is 2% or less, optionally 0.5% or less.
  • the so-called Li/Mn antisite defect refers to the interchange of positions between Li + and Mn 2+ in the LiMnPO 4 lattice.
  • the Li/Mn anti-site defect concentration refers to the percentage of Li + exchanged with Mn 2+ in the positive active material to the total amount of Li + . Mn 2+ with anti-site defects will hinder the transport of Li + .
  • the Li/Mn anti-site defect concentration can be measured by methods known in the art, such as XRD.
  • the surface oxygen valence state of the second cathode active material is -1.82 or less, optionally -1.89 to -1.98.
  • the interface side reaction between the positive electrode active material and the electrolyte can be alleviated, thereby improving the cycle performance and high-temperature stability of the secondary battery.
  • Surface oxygen valence state can be measured by methods known in the art, such as by electron energy loss spectroscopy (EELS).
  • the compacted density of the second cathode active material at 3T is above 2.0 g/cm 3 , optionally above 2.2 g/cm 3 .
  • the compacted density can be measured according to GB/T 24533-2009.
  • the second cathode active material further includes carbon coated on the surface of the compound Li a Ax Mn 1-y By P 1-z C z O 4-n D n . Thereby, the conductivity of the positive electrode active material can be improved.
  • b may be, for example, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9.
  • d can be, for example, 0.05, 0.1, 0.15, 0.2, 0.25, or 0.3.
  • e may be, for example, 0.01, 0.02, 0.05, 0.1, 0.15, 0.2, 0.26, 0.3, or 0.35.
  • One embodiment of the present application provides a method for preparing a cathode active material, including the following steps:
  • the first positive active material includes the compound LiNi b Co d Mn e M f O 2
  • the second positive active material includes the compound Li a A x Mn 1-y B y P 1-z C z O 4-n D n , where, The definitions of a, b, d, e, f, x, y, z, n, M, A, B, C and D are as described in [Cathode Active Material];
  • the first positive active material further includes lithium carbonate and/or lithium hydroxide
  • the second cathode active material further includes carbon coated on the surface of the compound Li a Ax Mn 1-y By P 1- z C z O 4-n D n .
  • the advantages of the two materials complement each other, which improves the cycle capacity retention rate of the secondary battery, prolongs the cycle life of the secondary battery, and improves Safety of secondary batteries.
  • the first cathode active material is prepared by the following steps:
  • step 2) the cooled first cathode active material is pulverized and sieved, or the cooled first cathode active material is pulverized, sintered again, crushed, and sieved.
  • step 1) the reaction is performed at a pH value of 9-13, optionally, at a pH value of 9-12 or 10-13.
  • the reaction temperature is 40°C-80°C, such as 50°C, 55°C, or 60°C.
  • the reaction time is 8-70h, such as 20h, 55h, 60h, 65h.
  • step 1) the reaction is performed at a rotation speed of 150-1000 r/min, such as 300 r/min, 500 r/min.
  • step 1) solid-liquid separation is filtration.
  • the solid phase is washed and dried; optionally, it can be vacuum dried at 100°C-140°C for 12-48h, for example, vacuum dried at 120°C for 24h.
  • the rotation speed of the ball mill is 200-500r/s, such as 300r/s, 500r/s.
  • the ball milling time is 1-5 hours, such as 2, 3, or 4 hours.
  • step 2) sintering is performed in an air atmosphere; optionally, sintering is performed in an air atmosphere of 0.1-0.4MPa.
  • the sintering procedure is: heating to 750°C-950°C and holding for 12-20 hours for pre-sintering, with a heating rate of 1°C/min; optionally, and then cooling to 600°C at the same rate. Keep the temperature at °C for 8 hours for sintering; after sintering, cool down to 300°C at a rate of 1°C/min.
  • step 2) the re-sintering procedure is: heating to 400°C at a heating rate of 20°C/min and holding for 20 hours for sintering, and then cooling to 300°C at a rate of 1°C/min after sintering.
  • an airflow pulverizer is used for pulverization; optionally, the rotation speed of the airflow pulverizer is 2500-3500r/min, such as 3000r/min; optionally, the air volume of the airflow pulverizer is 400 -600m 3 /h, for example 500m 3 /h.
  • a 450-550 mesh (for example, 500 mesh) mesh is used for sieving.
  • the second cathode active material is prepared by the following steps:
  • Step (1) Mix a manganese source, a source of element B, an acid and an optional solvent to obtain a mixture;
  • Step (2) Mix the mixture with a lithium source, a phosphorus source, a source of element A, a source of element C and a source of element D, an optional carbon source and an optional solvent, dry and sinter to obtain Li m
  • a to D are as defined above.
  • step (1) is performed at 60°C-120°C, optionally at 70°C-120°C (for example, about 60°C, about 70°C, about 80°C, about 90°C, about 100°C, about 110°C ° C or about 120 ° C); and/or, in step (1), mixing is performed by stirring at a speed of 200-800 rpm (such as 200 rpm, 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm, 800 rpm), optionally stirring 1 -9h (more optionally 3-7h, such as about 2 hours, about 3 hours, about 4 hours, about 5 hours, about 6 hours, about 7 hours, about 8 hours or about 9 hours).
  • 200-800 rpm such as 200 rpm, 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm, 800 rpm
  • stirring 1 -9h more optionally 3-7h, such as about 2 hours, about 3 hours, about 4 hours, about 5 hours, about
  • step (2) mixing is performed for 8-15 hours (e.g., about 8 hours, about 9 hours, about 10 hours, about 11 hours, about 12 hours, about 13 hours, about 14 hours, or about 15 hours). hours), optionally at 20-120°C, optionally 40-120°C (for example, about 30°C, about 50°C, about 60°C, about 70°C, about 80°C, about 90°C, about 100°C, about Mix at a temperature of 110°C or about 120°C).
  • 8-15 hours e.g., about 8 hours, about 9 hours, about 10 hours, about 11 hours, about 12 hours, about 13 hours, about 14 hours, or about 15 hours.
  • hours optionally at 20-120°C, optionally 40-120°C (for example, about 30°C, about 50°C, about 60°C, about 70°C, about 80°C, about 90°C, about 100°C, about Mix at a temperature of 110°C or about 120°C).
  • the prepared second positive electrode active material has fewer lattice defects, which is beneficial to inhibiting manganese dissolution, reducing the interface side reaction between the positive electrode active material and the electrolyte, thereby improving the second positive electrode active material. Cycle performance and safety performance of secondary batteries.
  • step (2) mixing is performed at a pH of 3.5-6, optionally a pH of 4-6, more optionally a pH of 4-5.
  • the pH can be adjusted by methods commonly used in the art, for example, by adding acid or alkali.
  • the molar ratio of the mixture or element B-doped manganese salt particles to the lithium source and phosphorus source is 1:0.4-2.1:0.1-2.1, optionally It is about 1:0.4-0.5:0.1-1.
  • step (2) sintering is performed at 600-900°C for 4-10 hours; optionally, sintering can be performed at about 650°C, about 700°C, about 750°C, about 800°C, about 850°C Or sintering at about 900° C. for about 2 hours, about 3 hours, about 4 hours, about 5 hours, about 6 hours, about 7 hours, about 8 hours, about 9 hours or about 10 hours; optionally, in an inert gas or Sintering under the protection of a mixed atmosphere of inert gas and hydrogen.
  • the protective atmosphere is a mixed gas of 70-90 volume % nitrogen and 10-30 volume % hydrogen; the sintering temperature and sintering time can be within any range of any of the above values. , can increase the crystallinity, reduce the generation of impurities, maintain a certain particle size, thereby increasing the gram capacity and compaction density of the positive active material, and improving the overall performance of the secondary battery, including rate performance.
  • the mixture obtained in step (1) is filtered, dried, and ground to obtain element B-doped manganese salt particles with a particle size Dv50 of 50-200 nm, and the element B-doped manganese salt particles are
  • the manganese salt particles are used in step (2) to be mixed with a lithium source, a phosphorus source, a source of element A, a source of element C, a source of element D and an optional solvent.
  • step (2) drying is performed by spray drying equipment.
  • step (2) grinding is performed while mixing.
  • the preparation method of the present application has no special restrictions on the source of materials.
  • the source of a certain element may include the element, sulfate, halide, nitrate, phosphate, oxalate, carbonate, oxide and One or more of the hydroxides, provided that the source can achieve the purpose of the preparation method of the present application.
  • the source of element A is selected from one or more of elements, oxides, phosphates, oxalates, carbonates and sulfates of element A; and/or,
  • the source of element B is one or more selected from the group consisting of elemental elements, oxides, phosphates, oxalates, carbonates and sulfates of element B; and/or,
  • the source of element C is one or more selected from sulfate, borate, nitrate and silicate of element C; and/or,
  • the source of element D is one or more selected from the group consisting of elemental elements and ammonium salts of element D.
  • the source of element M is one or more selected from the group consisting of elemental elements, carbonates, sulfates, halides, nitrates, organic acid salts, oxides and hydroxides of element M.
  • the added amounts of the respective sources of elements A, B, C, D, and M depend on the target doping amount, and the ratio of the amounts of lithium source, manganese source, and phosphorus source conforms to the stoichiometric ratio.
  • the manganese source may be a manganese-containing material known in the art that can be used to prepare lithium manganese phosphate.
  • the manganese source may be one or more selected from the group consisting of elemental manganese, manganese dioxide, manganese phosphate, manganese oxalate, and manganese carbonate.
  • the acid may be one or more selected from organic acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, silicic acid, silicic acid, etc., and organic acids such as oxalic acid.
  • the acid is a dilute organic acid with a concentration of 60% by weight or less.
  • the lithium source may be a lithium-containing substance known in the art that can be used to prepare lithium manganese phosphate.
  • the lithium source is one or more selected from lithium carbonate, lithium hydroxide, lithium phosphate, and lithium dihydrogen phosphate.
  • the phosphorus source may be a phosphorus-containing material known in the art that can be used to prepare lithium manganese phosphate.
  • the phosphorus source is one or more selected from diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate and phosphoric acid.
  • the carbon source is one or more selected from starch, sucrose, glucose, polyvinyl alcohol, polyethylene glycol, and citric acid.
  • the positive electrode sheet usually includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode film layer includes the above-mentioned positive electrode active material or the positive electrode active material prepared by the above-mentioned method.
  • the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil can be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode film layer optionally further includes a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene tripolymer. At least one of a meta-copolymer, a tetrafluoroethylene-hexafluoropropylene copolymer and a fluorine-containing acrylate resin.
  • the positive electrode film layer optionally further includes a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components in a solvent (such as N -methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode piece can be obtained.
  • a solvent such as N -methylpyrrolidone
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector.
  • the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two opposite surfaces in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material.
  • the composite current collector can be formed by forming metal materials (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative active material may be a negative active material known in the art for batteries.
  • the negative active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon carbon composites, silicon nitrogen composites and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxide compounds and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as battery negative electrode active materials can also be used. Only one type of these negative electrode active materials may be used alone, or two or more types may be used in combination.
  • the negative electrode film layer optionally further includes a binder.
  • the binder may be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), At least one of polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer optionally further includes a conductive agent.
  • the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode film layer optionally includes other auxiliaries, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.
  • thickeners such as sodium carboxymethylcellulose (CMC-Na)
  • the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative active materials, conductive agents, binders and any other components in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode piece can be obtained.
  • a solvent such as deionized water
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the type of electrolyte in this application can be selected according to needs.
  • the electrolyte can be liquid, gel, or completely solid.
  • the electrolyte is liquid and includes an electrolyte salt and a solvent.
  • the electrolyte salt may be selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonimide, lithium bistrifluoromethanesulfonimide, trifluoromethane At least one of lithium sulfonate, lithium difluorophosphate, lithium difluoroborate, lithium dioxaloborate, lithium difluorodioxalate phosphate and lithium tetrafluoroxalate phosphate.
  • the solvent may be selected from the group consisting of ethylene carbonate, propylene carbonate, methylethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, Butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate At least one of ester, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte optionally also includes additives.
  • additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.
  • the secondary battery further includes a separator film.
  • a separator film There is no particular restriction on the type of isolation membrane in this application. Any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film can be a single-layer film or a multi-layer composite film, with no special restrictions. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.
  • the positive electrode piece, the negative electrode piece and the separator film can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer packaging.
  • the outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • FIG. 1 shows a square-structured secondary battery 5 as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity.
  • the housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 can cover the opening to close the accommodation cavity.
  • the positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the containing cavity.
  • the electrolyte soaks into the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • secondary batteries can be assembled into battery modules, and the number of secondary batteries contained in the battery module can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery module.
  • FIG. 3 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space in which a plurality of secondary batteries 5 are received.
  • the above-mentioned battery modules can also be assembled into a battery pack.
  • the number of battery modules contained in the battery pack can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box 2 and a lower box 3.
  • the upper box 2 can be covered with the lower box 3 and form a closed space for accommodating the battery module 4.
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided by the present application.
  • the secondary battery, battery module, or battery pack can be used as a power source for the power-consuming device, or as an energy storage unit of the power-consuming device.
  • Electric devices may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric Trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.
  • secondary batteries, battery modules or battery packs can be selected according to its usage requirements.
  • FIG. 6 is an electrical device as an example.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc.
  • a battery pack or battery module can be used.
  • Li 2 CO 3 (based on the molar amount of Li element), precursor (based on Ni, Co and Mn in the mixed solution)
  • the molar ratio of Al 2 O 3 (based on the molar amount of Al element) and MgO is 1.05:0.94:0.04:0.02.
  • the heating rate is 1°C/min, and then lower the temperature to 600°C for 8 hours at a rate of 1°C/min for sintering. Then it is cooled to 300°C at a rate of 1°C/min, and continues to be naturally cooled to room temperature. Then it is crushed by a jet mill at a speed of 3000r/min and an air volume of 500m3 /h. It is crushed for 0.5h and then passed through a 500 mesh filter. sieve to obtain the first positive electrode active material.
  • the first positive electrode active materials of Preparation Examples A1, A2, A4 to A11, A22 and Comparative Preparation Example A1 were prepared in a manner similar to Preparation Example A3. The differences in preparation are shown in Table 1. The rest are the same as those in Preparation Example A3. ;
  • Preparation Examples A12 to A15 and A17 to A21 were prepared in a manner similar to Preparation Example A16. The differences in preparation are shown in Table 1. The rest are the same as those in Preparation Example A16.
  • Preparation of doped manganese oxalate Mix 1.3mol MnSO 4 ⁇ H 2 O and 0.7mol FeSO 4 ⁇ H 2 O thoroughly in a mixer for 6 hours; transfer the mixture to the reaction kettle, add 10L deionized water and 2mol Dihydrate oxalic acid, heat to 80°C, and then stir at 600 rpm for 6 hours. The reaction is terminated (no bubbles are generated), and a suspension of Fe-doped manganese oxalate is obtained; filter the suspension, and dry the filter cake at 120°C and grind it. , obtaining Fe-doped manganese oxalate particles with a particle size Dv 50 of about 100nm;
  • Preparation of doped lithium manganese phosphate Take 1 mol of Fe-doped manganese oxalate particles, 0.497 mol of lithium carbonate, 0.001 mol of Mo(SO 4 ) 3 , an 85% phosphoric acid aqueous solution containing 0.999 mol of phosphoric acid, and 0.001 mol of H 4 SiO 4 , 0.0005 mol NH 4 HF 2 and 0.005 mol sucrose were added to 20L deionized water, and the mixture was transferred to a sand mill and fully ground and stirred for 10 hours to obtain a slurry; the slurry was transferred to a spray drying equipment for spraying Dry and granulate, set the drying temperature to 250°C, and dry for 4 hours to obtain particles; in a nitrogen (90% v/v) + hydrogen (10% v/v) protective atmosphere, sinter the particles at 700°C for 10 hours , obtaining the second positive active material, carbon-coated Li 0.994 Mo 0.001 Mn 0.
  • the cathode active material was prepared in the same manner as Preparation Example B1, but the stirring speed, temperature, grinding and stirring time in the sand mill, sintering temperature and sintering time when preparing doped manganese oxalate were changed, as shown in Table 2 below. .
  • the cathode active material was prepared in the same manner as Preparation Example B1, but the sources of lithium source, manganese source, phosphorus source and doping elements A, B, C, and D were changed, as shown in Table 3 below.
  • the composition of the prepared cathode active material is the same as that of Preparation Example B1, that is, both are Li 0.994 Mo 0.001 Mn 0.65 Fe 0.35 P 0.999 Si 0.001 O 3.999 F 0.001 .
  • ICP Inductively coupled plasma emission spectroscopy
  • step (2) lithium carbonate is 0.55 mol, MgSO 4 is 0.001 mol, and NH 4 HF 2 is 0.001 mol, the rest is the same as Preparation Example B55; the positive active material Li 1.1 Mg 0.001 Mn 0.6 Fe 0.395 V 0.005 is obtained P 0.9 Si 0.1 O 3.998 F 0.002 .
  • step (2) MgSO 4 is 0.1 mol
  • the phosphoric acid aqueous solution with a concentration of 85% contains 0.95 mol phosphoric acid
  • H 4 SiO 4 is 0.05 mol
  • NH 4 HF 2 is 0.025 mol
  • the rest is the same as Preparation Example B55; obtained Cathode active material Li 0.9 Mg 0.1 Mn 0.6 Fe 0.395 V 0.005 P 0.95 Si 0.05 O 3.95 F 0.05 .
  • step (1) MnSO 4 ⁇ H 2 O is 1.998 mol, FeSO 4 ⁇ H 2 O is 0.002 mol, and VCl 2 is not used; and except that in step (2), lithium carbonate is 0.475 mol, and the concentration is 85%.
  • the phosphoric acid aqueous solution contains 0.96 mol of phosphoric acid, 0.04 mol of H 4 SiO 4 and 0.01 mol of NH 4 HF 2 ; the rest is the same as Preparation Example B55; the positive active material Li 0.95 Mg 0.05 Mn 0.999 Fe 0.001 P 0.96 Si 0.04 O 3.99 is obtained. F 0.01 .
  • step (1) MnSO 4 ⁇ H 2 O is 1.98 mol, FeSO 4 ⁇ H 2 O is 0.02 mol, and VCl 2 is not used; and except that in step (2), lithium carbonate is 0.475 mol, and the concentration is 85%.
  • the phosphoric acid aqueous solution contains 0.96 mol of phosphoric acid, 0.04 mol of H 4 SiO 4 and 0.01 mol of NH 4 HF 2 ; the rest is the same as Preparation Example B55; the positive active material Li 0.95 Mg 0.05 Mn 0.99 Fe 0.01 P 0.96 Si 0.04 O 3.99 is obtained F 0.01 .
  • step (1) MnSO 4 ⁇ H 2 O is 1.6 mol, FeSO 4 ⁇ H 2 O is 0.4 mol, and VCl 2 is not used; and except that in step (2), lithium carbonate is 0.475 mol, and the concentration is 85%.
  • the phosphoric acid aqueous solution contains 0.96 mol of phosphoric acid, 0.04 mol of H 4 SiO 4 and 0.01 mol of NH 4 HF 2 ; the rest is the same as Preparation Example B55; the positive active material Li 0.95 Mg 0.05 Mn 0.8 Fe 0.2 P 0.96 Si 0.04 O 3.99 is obtained F 0.01 .
  • Preparation of manganese oxalate add 1 mol of MnSO 4 . H 2 O was added to the reaction kettle, and 10 L of deionized water and 1 mol of oxalic acid dihydrate (calculated as oxalic acid) were added. The reaction kettle was heated to 80°C and stirred at 600 rpm for 6 hours. The reaction was terminated (no bubbles were generated), and a manganese oxalate suspension was obtained. The suspension is then filtered, and the filter cake is dried at 120° C. and then ground to obtain manganese oxalate particles with a median particle size Dv 50 of 50-200 nm.
  • Preparation of lithium manganese phosphate Take 1 mol of the above manganese oxalate particles, 0.5 mol of lithium carbonate, an 85% phosphoric acid aqueous solution containing 1 mol of phosphoric acid, and 0.005 mol of sucrose and add them to 20 L of deionized water. The mixture was transferred to a sand mill and thoroughly ground and stirred for 10 hours to obtain a slurry. Transfer the slurry to spray drying equipment for spray drying and granulation. Set the drying temperature to 250°C and dry for 4 hours to obtain granules. In a protective atmosphere of nitrogen (90 volume %) + hydrogen (10 volume %), the above powder was sintered at 700° C. for 10 hours to obtain carbon-coated LiMnPO 4 .
  • the first cathode active material and the second cathode material are stirred and mixed in a stirring tank.
  • the mass of the first cathode material is m 1
  • the mass of the second cathode material is m 2
  • the mass of the mixed cathode active material is m 1 +m 2 .
  • the positive active material Mix the positive active material, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) in the N-methylpyrrolidone solvent system at a weight ratio of 92:2.5:5.5, then apply it on the aluminum foil and dry it. , cold pressing to obtain the positive electrode piece.
  • the coating amount is 0.4g/cm 2 and the compacted density is 2.4g/cm 3 .
  • PE polyethylene
  • Lithium sheets are used as the negative electrode, and 1 mol/L LiPF 6 is dissolved in ethylene carbonate (EC), diethyl carbonate (DEC) and dimethyl carbonate (DMC) with a volume ratio of 1:1:1 as an electrolyte.
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • DMC dimethyl carbonate
  • the above-mentioned positive electrode active material may be a first positive electrode active material, a second positive electrode active material or a mixed positive electrode active material.
  • ACSTEM Spherical aberration electron microscopy
  • the positive active material is prepared into a buckle battery according to the above "Preparation of Button Battery", and the above buckle battery is charged at a small rate of 0.05C until the current is reduced to 0.01C. Then take out the positive electrode piece from the battery and soak it in DMC for 8 hours. Then it is dried, scraped into powder, and particles with a particle size less than 500nm are screened out. Take a sample and calculate its lattice constant v1 in the same way as the above-mentioned test of the fresh sample. (v0-v1)/v0 ⁇ 100% is shown in the table as the lattice change rate before and after complete deintercalation of lithium.
  • the positive active material sample was prepared into a full battery according to the above "Preparation of Full Battery”.
  • the full battery which has been cycled at 45°C until the capacity decays to 80%, is discharged to a cut-off voltage of 2.0V using a 0.1C rate. Then disassemble the battery, take out the negative electrode piece, randomly pick 30 discs of unit area (1540.25mm 2 ) on the negative electrode piece, and use Agilent ICP-OES730 to test the inductively coupled plasma emission spectrum (ICP). Calculate the amounts of Fe (if the Mn site of the cathode active material is doped with Fe) and Mn based on the ICP results, and then calculate the dissolution amount of Mn (and Fe doped at the Mn site) after cycles. The test standard is based on EPA-6010D-2014.
  • the drainage method is to first separately measure the gravity F 1 of the battery cell using a balance that automatically converts units based on the dial data, then completely places the battery core in deionized water (density is known to be 1g/cm 3 ), and measures the battery core at this time.
  • the battery of the embodiment always maintained an SOC of more than 99% during the experiment until the end of storage.
  • the specific surface area of the cathode active material was tested using the specific surface area porosity analyzer TRISTAR II3020 (Micro Instruments, USA). Before testing, place the positive active material in a vacuum oven to dry at 200°C for ⁇ 2 hours, and the sample required is > 20g.
  • a Mastersizer 3000 laser diffraction particle size analyzer (Malvern Panalytical) was used to measure the particle size Dv50 of the positive active material.
  • Deionized water was used as the solvent, and the positive active material was ultrasonically treated for 5 minutes before testing.
  • iCAP 7400 inductively coupled plasma optical emission spectrometer was used to conduct element content testing, and aqua regia was used as the solvent;
  • element content (mass %) 100% ⁇ element mass/(sample mass - current collector mass).
  • a 905 potentiometric titrator is used for testing. Immediately after sampling, aluminum plastic film bags are used for vacuum sealing. The minimum sample amount for a single test is ⁇ 30g.
  • single crystal/quasi-single crystal particles means single particles (i.e. primary particles) and/or agglomerated particles, wherein the agglomerated particles are agglomerated by no more than 100 (especially about 5 to 50) primary particles with an average particle diameter in the range of 50 nm to 10000 nm particles formed.
  • secondary particles and “polycrystalline material particles” generally have similar meanings, which mean agglomeration of more than 100 primary particles with an average particle size in the range of 50-800 nm. particles formed.
  • the cathode active material is determined to be a polycrystalline material; otherwise, it is determined to be a single Crystalline or quasi-single crystal materials.
  • the test refers to the "Heating" chapter of the safety test in GB 38031-2020, and explores the upper limit boundary.
  • the optimized test conditions are as follows:
  • Test conditions Prepare an explosion-proof oven that can heat and connect the circuit; the test cells are fresh bare cells (number of cycles ⁇ 10 times), and affix temperature sensing wires around the cells, poles, etc. for temperature monitoring. It is also equipped with temperature recording equipment;
  • Battery core treatment before testing use 0.33C rate current for constant current and constant voltage charging, and the battery core is fully charged to the nominal voltage (for example, the voltage in the present invention is 4.3V).
  • 2Testing process Place the sample in a high-temperature oven, and raise the temperature from room temperature to 100°C at a rate of 5°C/min, and keep it for 2 hours; then raise the temperature at a rate of 5°C/min, and maintain it for 30 minutes every 5°C until the battery core loses control ( Out-of-control standard: voltage drops by ⁇ 50% within 1 minute, battery core temperature increases by ⁇ 50% within 1 minute) or heating reaches 200°C and stops heating.
  • 3Data processing Find the failure point according to the above conditions, and obtain the corresponding insulation temperature and insulation time, recorded as: time@temperature, such as 21min@150°C.
  • Samples that continue to be tested for a longer time during the test process are safer; samples that continue to be tested for a longer time can be: samples with the same failure point temperature but longer time; samples with the same failure point time but higher temperature; failure point A sample with a different temperature and time but with a higher temperature.
  • Comparing Examples 1-43 and Comparative Example 1 it can be seen that compared with the secondary battery prepared in Comparative Example 1, the cycle capacity of the secondary battery prepared by mixing the first cathode active material and the second cathode active material of the present application is maintained The efficiency is higher and the cycle life is longer; and, the safety of the secondary batteries made of the mixed positive electrode active materials of Examples 1, 3-7, 9, 12-13, 23-25, and 28 of the present application is compared with that of Comparative Example 1 The safety of secondary batteries is better.
  • the secondary battery produced by the application in which b*m 1/ m 1 +m 2 of the first positive electrode active material and the second positive electrode active material is less than or equal to 0.457 has high cycle capacity retention rate, long cycle life and high safety; it will be implemented Comparing Example 16 and Examples 23-29, it can be seen that the mass relationship b ⁇ m 1 /(m 1 +m 2 ) of the first cathode active material and the second cathode active material of the present application is in the range of 0.025-0.415.
  • the cycle capacity retention rate of the secondary battery is further improved, the cycle life is further extended, and the safety is further improved.
  • the first cathode active material of the present application is selected from the range of 0.314-0.970.
  • the secondary battery produced has high cycle capacity retention rate, long cycle life and high safety; it will be implemented Comparing Examples 1-11 and 22, it can be seen that when the first positive active material is a single crystal or quasi-single crystal material, the cycle capacity retention rate of the secondary battery produced by b is greater than 0.314 and less than 0.97 (excluding the values 0.314 and 0.97). High, longer cycle life.
  • the mass content of lithium carbonate in the first positive electrode active material of the present application is less than or equal to 1% and the mass content of lithium hydroxide is less than or equal to 1%. Higher, longer cycle life and higher safety.
  • the secondary battery made of the mixed positive active material containing the corresponding first positive active material of the present application is safer; compared with the use of Preparation Examples A14-A17 and A19 - Compared with the secondary battery made of the first positive active material of A21, the secondary battery made of the mixed positive active material containing the corresponding first positive active material of the present application has a higher cycle capacity retention rate and a longer cycle life.
  • the present application contains a mixture of corresponding second positive electrode active materials.
  • Secondary batteries made of positive active materials have a higher cycle capacity retention rate and longer cycle life.

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Abstract

本申请提供了混合的正极活性材料及其制备方法、正极极片、二次电池、电池模块、电池包和用电装置。正极活性材料，包含第一正极活性材料和第二正极活性材料；其中，第一正极活性材料包含化合物LiNi bCo dMn eM fO 2，第二正极活性材料包含化合物Li aA xMn 1-yB yP 1- zC zO 4-nD n。本申请通过将第一正极活性材料和第二正极活性材料混合使用，提高了二次电池的循环容量保持率，延长了二次电池的循环寿命，提高了二次电池的安全性。

Description

正极活性材料及其制备方法、正极极片、二次电池、电池模块、电池包及用电装置 技术领域
本申请涉及二次电池技术领域，尤其涉及一种正极活性材料及其制备方法、正极极片、二次电池、电池模块、电池包和用电装置。
背景技术
近年来，随着二次电池的应用范围越来越广泛，二次电池广泛应用于水力、火力、风力和太阳能电站等储能电源***，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。由于二次电池取得了极大的发展，因此对其能量密度、循环性能和安全性能等也提出了更高的要求。作为二次电池现有的正极活性材料，磷酸锰锂在充放电过程中，容易产生Li/Mn反位缺陷，锰溶出较严重，影响了二次电池的克容量，导致二次电池的安全性能和循环性能差。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供一种正极活性材料、正极活性材料的制备方法、正极极片、二次电池、电池模块、电池包及用电装置，以解决采用现有正极活性材料所制二次电池的循环容量保持率低、循环寿命短、安全性低的问题。
为了达到上述目的，本申请第一方面提供了一种正极活性材料，包含第一正极活性材料和第二正极活性材料；其中，
第一正极活性材料包含化合物LiNi bCo dMn eM fO 2，其中，b选自0.314-0.970的范围，d选自0-0.320的范围、可选为选自0.047-0.320的范围，e选自0.006-0.390的范围，并且，b、d、e和f的总和为1且f大于0，M选自Mn、Al、Mg、Ca、Na、Ti、W、Zr、Sr、Cr、 Zn、Ba、B、S和Y中的一种或多种元素，可选地，M为Mg和/或Al；
第二正极活性材料包含化合物Li aA xMn 1-yB yP 1-zC zO 4-nD n，a选自0.9至1.1的范围，x选自0.001至0.1的范围，y选自0.001至0.5的范围，z选自0.001至0.1的范围，n选自0.001至0.1的范围，A选自Zn、Al、Na、K、Mg、Nb、Mo和W中的一种或多种元素，B选自Ti、V、Zr、Fe、Ni、Mg、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素，C选自B(硼)、S、Si和N中的一种或多种元素，D选自S、F、Cl和Br中的一种或多种元素。
由此，本申请人意外地发现：通过在化合物LiMnPO 4的Li位、Mn位、P位和O位同时以特定量掺杂特定的元素获得第二正极活性材料，能获得明显改善的倍率性能，同时显著减少Mn与Mn位掺杂元素的溶出，获得显著改善的循环性能和/或高温稳定性，并且材料的克容量和压实密度也得到提高，界面副反应减少。但是第二正极活性材料仅有一维锂离子传输通道，而第一正极活性材料为层状过渡金属氧化物、具有二维锂离子传输通道，因此，本申请通过将第一正极活性材料和第二正极活性材料混合使用，两种材料的优势互补，提高了二次电池的循环容量保持率，延长了二次电池的循环寿命，提高了二次电池的安全性。
除非另有说明，否则化学式Li aA xMn 1-yB yP 1-zC zO 4-nD n中，当A为两种以上元素时，上述对于x数值范围的限定不仅是对每种作为A的元素的化学计量数的限定，也是对各个作为A的元素的化学计量数之和的限定。例如当A为两种以上元素A1、A2……An时，A1、A2……An各自的化学计量数x1、x2……xn各自均需落入本申请对x限定的数值范围内，且x1、x2……xn之和也需落入该数值范围内。类似地，对于B、C和D为两种以上元素的情况，本申请中对B、C和D化学计量数的数值范围的限定也具有上述含义。类似地，对于化学式LiNi bCo dMn eM fO 2中的M为两种以上元素的情况，本申请对M化学计量数的数值范围的限定也具有上述含义。
在任意实施方式中，第一正极活性材料的质量为m 1，第二正极 活性材料的质量为m 2，并且m 1/(m 1+m 2)的值为2％-55％，可选为3％-50％。由此，第一正极活性材料在两种正极活性材料中所占的质量百分比在上述范围内，能提高整体正极活性材料的稳定性和安全性。
在任意实施方式中，b×m 1/(m 1+m 2)的值为0.017-0.457，可选为0.025-0.415。由此能进一步改善整体正极活性材料的稳定性和安全性。
在任意实施方式中，第一正极活性材料为单晶或准单晶材料，第一正极活性材料的粒径D v50为小于或等于5.8μm，可选为2.3-5.8μm，更可选为2.3-4.3μm。
使单晶或准单晶的第一正极活性材料的粒径在上述范围能优化电化学反应面积，进一步减少和抑制二次电池循环过程中正极的界面副反应，降低二次电池的循环衰减速率，延长二次电池的循环寿命。
在任意实施方式中，第一正极活性材料为单晶或准单晶材料时，d选自0.05-0.320的范围，可选为选自0.05-0.282的范围；和/或，
b大于0.314且小于0.97，可选为选自0.55-0.869的范围。
第一正极活性材料为单晶或准单晶材料时，d和b在上述范围内有利于进一步提高正极活性材料的电导率和倍率性能，进一步提高二次电池的循环容量保持率，进一步延长二次电池的循环寿命。
在任意实施方式中，第一正极活性材料为多晶材料时，第一正极活性材料的粒径D v50为3.5～13.5μm；和/或，
第一正极活性材料的BET比表面积小于或等于1.32m 2/g，可选为0.28-1.32m 2/g；和/或，
第一正极活性材料在3T压力下的压实密度大于或等于2.92g/cm 3，可选为2.92-3.31g/cm 3。
使多晶的第一正极活性材料的粒径、比表面积和压实密度在上述范围内能进一步提高正极活性材料的倍率性能，进一步减少和抑制二次电池循环过程中正极的界面副反应，降低二次电池的循环衰减速率，延长二次电池的循环寿命。
在任意实施方式中，第一正极活性材料还包含碳酸锂和/或氢氧化锂；
可选地，基于第一正极活性材料的质量计，碳酸锂的质量含量小 于或等于1％，和/或，氢氧化锂的质量含量小于或等于1％。
第二正极活性材料带入的残留水分子可能与电解液反应产生HF，HF易会对正极活性材料本身或负极极片上的SEI膜产生破坏作用，进而影响二次电池寿命。本申请第一正极活性材料中进一步含有的碳酸锂和/或氢氧化锂能与HF进行中和反应，减少或抑制了HF对于正极活性材料或负极极片SEI膜的破坏作用，从而进一步提高了二次电池的循环寿命。
在任意实施方式中，第二正极活性材料中，A选自Zn、Al、Na、K、Mg、Nb、Mo和W中的任一种元素，B选自Ti、V、Zr、Fe、Ni、Mg、Co、Ga、Sn、Sb、Nb和Ge中的至少两种元素，C选自B(硼)、S、Si和N中的任一种元素，D选自S、F、Cl和Br中的任一种元素；
可选地，A为Mg或Nb，和/或，
B选自Fe、Ti、V、Co和Mg中的至少两种元素，更可选为Fe与选自Ti、V、Co和Mg中的一种或多种元素，和/或，
C为S，和/或，
D为F。
通过在上述范围内对Li位掺杂元素进行选择，能够进一步减小脱锂过程中的晶格变化率，从而进一步改善二次电池的倍率性能。通过在上述范围内对Mn位掺杂元素进行选择，能够进一步提高电子电导率并进一步减小晶格变化率，从而提升二次电池的倍率性能和克容量。通过在上述范围内对P位掺杂元素进行选择，能够进一步改善二次电池的倍率性能。通过在上述范围内对O位掺杂元素进行选择，能够进一步减轻界面的副反应，提升二次电池的高温性能。
在任意实施方式中，第二正极活性材料中，x选自0.001至0.005的范围；和/或，
y选自0.01至0.5的范围，可选为选自0.25至0.5的范围；和/或，
z选自0.001至0.005的范围；和/或，
n选自0.001至0.005的范围。
通过在上述范围内对y值进行选择，能够进一步提升材料的克容 量和倍率性能。通过在上述范围内对x值进行选择，能够进一步提升材料的动力学性能。通过在上述范围内对z值进行选择，能够进一步提升二次电池的倍率性能。通过在上述范围内对n值进行选择，能够进一步提升二次电池的高温性能。
在任意实施方式中，(1-y):y的值选自1至4的范围，可选为选自1.5至3的范围，并且，a:x的值选自9到1100的范围，可选为选自190-998的范围。由此，正极活性材料的能量密度和循环性能可进一步提升。
在任意实施方式中，第二正极活性材料在完全脱嵌锂前后的晶格变化率为8％以下，可选为4％以下。通过降低晶格变化率，能够使得Li离子传输更容易，即Li离子在材料中的迁移能力更强，有利于改善二次电池的倍率性能。晶格变化率可通过本领域中已知的方法，例如X射线衍射图谱(XRD)测得。
在任意实施方式中，第二正极活性材料的Li/Mn反位缺陷浓度为2％以下，可选为0.5％以下。所谓Li/Mn反位缺陷，指的是LiMnPO 4晶格中，Li +与Mn 2+的位置发生互换。Li/Mn反位缺陷浓度指的是正极活性材料中与Mn 2+发生互换的Li +占Li +总量的百分比。反位缺陷的Mn 2+会阻碍Li +的传输，通过降低Li/Mn反位缺陷浓度，有利于提高正极活性材料的克容量和倍率性能。Li/Mn反位缺陷浓度可通过本领域中已知的方法，例如XRD测得。
在任意实施方式中，第二正极活性材料的表面氧价态为-1.82以下，可选地为-1.89～-1.98。通过降低表面氧价态，能够减轻正极活性材料与电解液的界面副反应，从而改善二次电池的循环性能和高温稳定性。表面氧价态可通过本领域中已知的方法测量，例如通过电子能量损失谱(EELS)测量。
在任意实施方式中，第二正极活性材料在3T下的压实密度为2.0g/cm 3以上，可选为2.2g/cm 3以上。压实密度越高，单位体积活性材料的重量越大，因此提高压实密度有利于提高电芯的体积能量密度。压实密度可依据GB/T 24533-2009测量。
在任意实施方式中，第二正极活性材料还包含碳，碳包覆在化合 物Li aA xMn 1-yB yP 1-zC zO 4-nD n的表面。由此，可以改善正极活性材料的导电性。
本申请的第二方面还提供一种制备正极活性材料的方法，包括如下步骤：
提供第一正极活性材料和第二正极活性材料；
将第一正极活性材料和第二正极活性材料混合即可；
第一正极活性材料包含化合物LiNi bCo dMn eM fO 2，第二正极活性材料包含化合物Li aA xMn 1-yB yP 1-zC zO 4-nD n，其中，a、b、d、e、f、x、y、z、n、M、A、B、C和D的定义如本申请第一方面中所述；
可选地，第一正极活性材料还包含碳酸锂和/或氢氧化锂；
可选地，第二正极活性材料还包含包覆在化合物Li aA xMn 1-yB yP 1- zC zO 4-nD n表面的碳。
由此，本申请通过将第一正极活性材料和第二正极活性材料混合使用，两种材料的优势互补，提高了二次电池的循环容量保持率，延长了二次电池的循环寿命，提高了二次电池的安全性。
本申请的第三方面提供一种正极极片，其包括正极集流体以及设置在正极集流体的至少一个表面的正极膜层，正极膜层包括本申请第一方面的正极活性材料或者通过本申请第二方面的方法制备的正极活性材料；可选地，正极活性材料在正极膜层中的含量为10重量％以上，更可选为95-99.5重量％，基于正极膜层的总重量计。
本申请的第四方面提供一种二次电池，包括本申请第一方面的正极活性材料或者根据本申请第二方面的方法制备的正极活性材料或者本申请第三方面的正极极片。
本申请的第五方面提供一种电池模块，包括本申请的第四方面的二次电池。
本申请的第六方面提供一种电池包，包括本申请的第五方面的电池模块。
本申请的第七方面提供一种用电装置，包括选自本申请的第四方面的二次电池、本申请的第五方面的电池模块和本申请的第六方面的电池包中的至少一种。
附图说明
图1是本申请一实施方式的二次电池的示意图。
图2是图1所示的本申请一实施方式的二次电池的分解图。
图3是本申请一实施方式的电池模块的示意图。
图4是本申请一实施方式的电池包的示意图。
图5是图4所示的本申请一实施方式的电池包的分解图。
图6是本申请一实施方式的二次电池用作电源的用电装置的示意图。
图7是本申请制备例A10所制的第一正极活性材料的SEM照片。
图8是本申请制备例A15所制的第一正极活性材料的SEM照片。
附图标记说明：
1电池包；2上箱体；3下箱体；4电池模块；5二次电池；51壳体；52电极组件；53顶盖组件。
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的正极活性材料及其制备方法、正极极片、二次电池、电池模块、电池包和用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的 范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，方法包括步骤(a)和(b)，表示方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，提到方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到方法，例如，方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或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)。
[二次电池]
二次电池又称为充电电池或蓄电池，是指在电池放电后可通过充电的方式使活性材料激活而继续使用的电池。
通常情况下，二次电池包括正极极片、负极极片、隔离膜及电解液。在电池充放电过程中，活性离子(例如锂离子)在正极极片和负极极片之间往返嵌入和脱出。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使活性离子通过。电解液在正极极片和负极极片之间，主要起到传导活性离子的作用。
[正极活性材料]
本申请的一个实施方式提供一种正极活性材料，包含第一正极活性材料和第二正极活性材料；其中，
第一正极活性材料包含化合物LiNi bCo dMn eM fO 2，其中，b选自0.314-0.970的范围、可选为选自0.65-0.97的范围，d选自0-0.320的范围、可选为选自0.047-0.320的范围或为选自0.005-0.188的范围，e选自0.006-0.390的范围、可选为选自0.006-0.102的范围，并且，b、d、e和f的总和为1且f大于0，M选自Mn、Al、Mg、Ca、Na、Ti、W、Zr、Sr、Cr、Zn、Ba、B、S和Y中的一种或多种元素；
第二正极活性材料包含化合物Li aA xMn 1-yB yP 1-zC zO 4-nD n，a选自0.9至1.1的范围，x选自0.001至0.1的范围，y选自0.001至0.5的范围，z选自0.001至0.1的范围，n选自0.001至0.1的范围，A选自Zn、Al、Na、K、Mg、Nb、Mo和W中的一种或多种元素、可选为Mg和/或Mo，B选自Ti、V、Zr、Fe、Ni、Mg、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素、可选为选自V、Fe和Co中的一种或多种元素，C选自B(硼)、S、Si和N中的一种或多种元素、可选为选自S、Si和N中的一种或多种元素，D选自S、F、Cl和Br中的一种或多种元素，可选为F。
第一正极活性材料为层状过渡金属氧化物，具有二维锂离子传输通道；第二正极活性材料仅有一维锂离子传输通道，二者混合使用、优势互补，能够提高整体的电化学性能。第一正极活性材料的首次库伦效率通常低于第二正极活性材料，二者混合使用后，二次电池在化学体系负极成膜消耗后仍含有较多的可逆锂离子，提高了二次电池的循环容量保持率，延长了二次电池的循环寿命，提高了二次电池的安 全性。
另外，虽然机理尚不明确，但本申请人意外地发现：本申请的第二正极活性材料通过在化合物LiMnPO 4中进行元素掺杂而获得，其中，A、B、C和D分别为在化合物LiMnPO 4的Li位、Mn位、P位和O位掺杂的元素。不希望囿于理论，本申请发明人发现磷酸锰锂的性能提升与减小脱嵌锂过程中磷酸锰锂的晶格变化率和降低表面活性有关。减小晶格变化率可减小晶界处两相间的晶格常数差异，减小界面应力，增强Li +在界面处的传输能力，从而提升正极活性材料的倍率性能。而表面活性高容易导致界面副反应严重，加剧产气、电解液消耗和破坏界面，从而影响二次电池的循环等性能。本申请中，通过Li和Mn位掺杂减小了晶格变化率。Mn位掺杂还有效降低表面活性，从而抑制Mn溶出和正极活性材料与电解液的界面副反应。P位掺杂使Mn-O键长的变化速率更快，降低材料的小极化子迁移势垒，从而有利于电子电导率。O位掺杂对减小界面副反应有良好的作用。P位和O位的掺杂还对反位缺陷的Mn溶出及动力学性能产生影响。因此，掺杂减小了材料中反位缺陷浓度，提高材料的动力学性能和克容量，还可以改变颗粒的形貌，从而提升压实密度。本申请人意外地发现：通过在化合物LiMnPO 4的Li位、Mn位、P位和O位同时以特定量掺杂特定的元素，能够获得明显改善的倍率性能，同时显著减少了Mn与Mn位掺杂元素的溶出，获得了显著改善的循环性能和/或高温稳定性，并且材料的克容量和压实密度也可以得到提高。
在一些实施方式中，M为Mg和/或Al。第一正极活性材料中掺杂Al元素能提升材料的结构稳定性和热稳定性，提高循环性能；第一正极活性材料中掺杂Mg元素会导致过渡金属离子价态的升高或降低，从而产生空穴或电子，改变了材料的能带结构，提高了材料的本征电子电导率，改善了二次电池的循环性能；Mg和Al共掺杂进入主体材料晶格，能协同稳定材料结构，改善材料阳离子的混排程度，抑制氧的析出，进一步改善二次电池的循环性能和热稳定性。
除非另有说明，否则化学式Li aA xMn 1-yB yP 1-zC zO 4-nD n中，当A为两种以上元素时，上述对于x数值范围的限定不仅是对每种作为A的 元素的化学计量数的限定，也是对各个作为A的元素的化学计量数之和的限定。例如当A为两种以上元素A1、A2……An时，A1、A2……An各自的化学计量数x1、x2……xn各自均需落入本申请对x限定的数值范围内，且x1、x2……xn之和也需落入该数值范围内。类似地，对于B、C和D为两种以上元素的情况，本申请中对B、C和D化学计量数的数值范围的限定也具有上述含义。类似地，对于化学式LiNi bCo dMn eM fO 2中的M为两种以上元素的情况，本申请对M化学计量数的数值范围的限定也具有上述含义。
在一些实施方式中，化合物LiNi bCo dMn eM fO 2和Li aA xMn 1-yB yP 1- zC zO 4-nD n均保持电中性。
在一些实施方式中，第一正极活性材料的质量为m 1，第二正极活性材料的质量为m 2，并且m 1/(m 1+m 2)的值为2％-55％，可选为3％-50％。由此，第一正极活性材料在两种正极活性材料中所占的质量百分比在上述范围内，能提高整体正极活性材料的稳定性和安全性。
在一些实施方式中，b×m 1/(m 1+m 2)的值为0.017-0.457，可选为0.025-0.415。由此能进一步改善整体正极活性材料的稳定性和安全性。
在一些实施方式中，第一正极活性材料为单晶或准单晶材料，第一正极活性材料的粒径D v50为小于或等于5.8μm，可选为2.3-5.8μm，更可选为2.3-4.3μm。
使单晶或准单晶的第一正极活性材料的粒径在上述范围能优化电化学反应面积，进一步减少和抑制二次电池循环过程中正极的界面副反应，降低二次电池的循环衰减速率，延长二次电池的循环寿命。
在一些实施方式中，第一正极活性材料为单晶或准单晶材料，第一正极活性材料的BET比表面积小于或等于1.15m 2/g，可选为0.45-1.15m 2/g；和/或，
第一正极活性材料在3T压力下的压实密度大于或等于3.11g/cm 3，可选为3.11-3.4g/cm 3。
在一些实施方式中，第一正极活性材料为单晶或准单晶材料时，d选自0.05-0.320的范围，可选为选自0.05-0.282的范围；和/或，
b大于0.314且小于0.97，可选为选自0.55-0.869的范围。
第一正极活性材料为单晶或准单晶材料时，d和b在上述范围内有利于进一步提高正极活性材料的电导率和倍率性能，进一步提高二次电池的循环容量保持率，进一步延长二次电池的循环寿命。
在一些实施方式中，第一正极活性材料为多晶材料时，第一正极活性材料的粒径D v50为3.5～13.5μm；和/或，
第一正极活性材料的BET比表面积小于或等于1.32m 2/g，可选为0.28-1.32m 2/g；和/或，
第一正极活性材料在3T压力下的压实密度大于或等于2.92g/cm 3，可选为2.92-3.31g/cm 3。
使多晶的第一正极活性材料的粒径、比表面积和压实密度在上述范围内能进一步提高正极活性材料的倍率性能，进一步减少和抑制二次电池循环过程中正极的界面副反应，降低二次电池的循环衰减速率，延长二次电池的循环寿命。
在一些实施方式中，第一正极活性材料还包含碳酸锂和/或氢氧化锂；
可选地，基于第一正极活性材料的质量计，碳酸锂的质量含量小于或等于1％，和/或，氢氧化锂的质量含量小于或等于1％。
第二正极活性材料带入的残留水分子可能与电解液反应产生HF，HF易会对正极活性材料本身或负极极片上的SEI膜产生破坏作用，进而影响二次电池寿命。本申请第一正极活性材料中进一步含有的碳酸锂和/或氢氧化锂能与HF进行中和反应，减少或抑制了HF对于正极活性材料或负极极片SEI膜的破坏作用，从而进一步提高了二次电池的循环寿命。
在一些实施方式中，第二正极活性材料中，A选自Zn、Al、Na、K、Mg、Nb、Mo和W中的任一种元素，B选自Ti、V、Zr、Fe、Ni、Mg、Co、Ga、Sn、Sb、Nb和Ge中的至少两种元素，C选自B(硼)、S、Si和N中的任一种元素，D选自S、F、Cl和Br中的任一种元素；
可选地，A为Mg或Nb，和/或，
B选自Fe、Ti、V、Co和Mg中的至少两种元素，更可选为Fe与选自Ti、V、Co和Mg中的一种或多种元素，和/或，
C为S，和/或，
D为F。
通过在上述范围内对Li位掺杂元素进行选择，能够进一步减小脱锂过程中的晶格变化率，从而进一步改善二次电池的倍率性能。通过在上述范围内对Mn位掺杂元素进行选择，能够进一步提高电子电导率并进一步减小晶格变化率，从而提升二次电池的倍率性能和克容量。通过在上述范围内对P位掺杂元素进行选择，能够进一步改善二次电池的倍率性能。通过在上述范围内对O位掺杂元素进行选择，能够进一步减轻界面的副反应，提升二次电池的高温性能。
在一些实施方式中，第二正极活性材料中，x选自0.001至0.005的范围；和/或，
y选自0.01至0.5的范围，可选为选自0.25至0.5的范围；和/或，
z选自0.001至0.005的范围；和/或，
n选自0.001至0.005的范围。
通过在上述范围内对y值进行选择，能够进一步提升材料的克容量和倍率性能。通过在上述范围内对x值进行选择，能够进一步提升材料的动力学性能。通过在上述范围内对z值进行选择，能够进一步提升二次电池的倍率性能。通过在上述范围内对n值进行选择，能够进一步提升二次电池的高温性能。
在一些实施方式中，(1-y):y的值选自1至4的范围，可选为选自1.5至3的范围，并且，a:x的值选自9到1100的范围，可选为选自190-998的范围。由此，正极活性材料的能量密度和循环性能可进一步提升。
在一些实施方式中，第二正极活性材料在完全脱嵌锂前后的晶格变化率为8％以下，可选为4％以下。通过降低晶格变化率，能够使得Li离子传输更容易，即Li离子在材料中的迁移能力更强，有利于改善二次电池的倍率性能。晶格变化率可通过本领域中已知的方法，例如X射线衍射图谱(XRD)测得。
在一些实施方式中，第二正极活性材料的Li/Mn反位缺陷浓度为 2％以下，可选为0.5％以下。所谓Li/Mn反位缺陷，指的是LiMnPO 4晶格中，Li +与Mn 2+的位置发生互换。Li/Mn反位缺陷浓度指的是正极活性材料中与Mn 2+发生互换的Li +占Li +总量的百分比。反位缺陷的Mn 2+会阻碍Li +的传输，通过降低Li/Mn反位缺陷浓度，有利于提高正极活性材料的克容量和倍率性能。Li/Mn反位缺陷浓度可通过本领域中已知的方法，例如XRD测得。
在一些实施方式中，第二正极活性材料的表面氧价态为-1.82以下，可选地为-1.89～-1.98。通过降低表面氧价态，能够减轻正极活性材料与电解液的界面副反应，从而改善二次电池的循环性能和高温稳定性。表面氧价态可通过本领域中已知的方法测量，例如通过电子能量损失谱(EELS)测量。
在一些实施方式中，第二正极活性材料在3T下的压实密度为2.0g/cm 3以上，可选为2.2g/cm 3以上。压实密度越高，单位体积活性材料的重量越大，因此提高压实密度有利于提高电芯的体积能量密度。压实密度可依据GB/T 24533-2009测量。
在一些实施方式中，第二正极活性材料还包含碳，碳包覆在化合物Li aA xMn 1-yB yP 1-zC zO 4-nD n的表面。由此，可以改善正极活性材料的导电性。
在一些实施方式中，b例如可以为0.4、0.5、0.6、0.7、0.8或0.9。
在一些实施方式中，d例如可以为0.05、0.1、0.15、0.2、0.25或0.3。
在一些实施方式中，e例如可以为0.01、0.02、0.05、0.1、0.15、0.2、0.26、0.3或0.35。
[制备正极活性材料的方法]
本申请的一个实施方式提供一种制备正极活性材料的方法，包括如下步骤：
提供第一正极活性材料和第二正极活性材料；
将第一正极活性材料和第二正极活性材料混合即可；
第一正极活性材料包含化合物LiNi bCo dMn eM fO 2，第二正极活性 材料包含化合物Li aA xMn 1-yB yP 1-zC zO 4-nD n，其中，a、b、d、e、f、x、y、z、n、M、A、B、C和D的定义如[正极活性材料]中所述；
可选地，第一正极活性材料还包含碳酸锂和/或氢氧化锂；
可选地，第二正极活性材料还包含包覆在化合物Li aA xMn 1-yB yP 1- zC zO 4-nD n表面的碳。
由此，本申请通过将第一正极活性材料和第二正极活性材料混合使用，两种材料的优势互补，提高了二次电池的循环容量保持率，延长了二次电池的循环寿命，提高了二次电池的安全性。
在一些实施方式中，第一正极活性材料通过如下的步骤制备：
步骤1)：将Ni盐、Co盐、Mn盐与碱在溶剂中反应，固液分离，收集固相物；
步骤2)：将固相物、锂源和元素M的源混合，球磨，烧结，冷却，得到第一正极活性材料；
可选地，步骤2)中，将冷却后的第一正极活性材料粉碎，过筛，或者将冷却后的第一正极活性材料粉碎，再次烧结，破碎，过筛。
在一些实施方式中，步骤1)中，在pH值为9-13的条件下反应，可选地，在pH值为9-12或10-13的条件下反应。
在一些实施方式中，步骤1)中，反应的温度为40℃-80℃，例如50℃、55℃、60℃。
在一些实施方式中，步骤1)中，反应的时间为8-70h，例如20h、55h、60h、65h。
在一些实施方式中，步骤1)中，在150-1000r/min转速的条件下反应，例如300r/min、500r/min。
在一些实施方式中，步骤1)中，固液分离为过滤。
在一些实施方式中，在步骤2)之前，将固相物洗涤，干燥；可选为在100℃-140℃下真空干燥12-48h，例如在120℃下真空干燥24h。
在一些实施方式中，步骤2)中，球磨的转速为200-500r/s，例如300r/s、500r/s。
在一些实施方式中，步骤2)中，球磨的时间为1-5h，例如2、3、4h。
在一些实施方式中，步骤2)中，在空气气氛下烧结；可选地，在0.1-0.4MPa的空气气氛下烧结。
在一些实施方式中，步骤2)中，烧结的程序为：升温至750℃-950℃保温12-20h进行预烧，升温速率为1℃/min；可选地，然后以同样速率降温至600℃保温8h进行烧结；烧结后以1℃/min速率降温至300℃。
在一些实施方式中，步骤2)中，再次烧结的程序为：以升温速率20℃/min升温至400℃保温20h进行烧结，烧结后以1℃/min速率降温至300℃。
在一些实施方式中，步骤2)中，采用气流粉碎机进行粉碎；可选地，气流粉碎机的转速为2500-3500r/min，例如3000r/min；可选地，气流粉碎机的风量为400-600m 3/h，例如500m 3/h。
在一些实施方式中，步骤2)中，采用450-550目(例如500目)的滤网过筛。
在一些实施方式中，第二正极活性材料通过如下的步骤制备：
步骤(1)：将锰源、元素B的源、酸和可选的溶剂混合，得到混合物；
步骤(2)：将混合物与锂源、磷源、元素A的源、元素C的源和元素D的源、可选的碳源及可选的溶剂混合，干燥，烧结，得到包含Li mA xMn 1-yB yP 1-zC zO 4-nD n的内核材料。A至D的定义如前述。
在一些实施方式中，步骤(1)在60℃-120℃、可选为在70℃-120℃(例如约60℃、约70℃、约80℃、约90℃、约100℃、约110℃或约120℃)下进行；和/或，步骤(1)中，通过以200-800rpm(例如200rpm、300rpm、400rpm、500rpm、600rpm、700rpm、800rpm)转速搅拌进行混合，可选为搅拌1-9h(更可选为3-7h，例如约2小时、约3小时、约4小时、约5小时、约6小时、约7小时、约8小时或约9小时)。
在一些实施方式中，步骤(2)中，混合进行8-15h(例如约约8小时、约9小时、约10小时、约11小时、约12小时、约13小时、约14小时或约15小时)，可选地在20-120℃、可选为40-120℃(例 如约30℃、约50℃、约60℃、约70℃、约80℃、约90℃、约100℃、约110℃或约120℃)的温度下混合。
当制备过程中的温度和时间处于上述范围内时，制备获得的第二正极活性材料的晶格缺陷较少，有利于抑制锰溶出，减少正极活性材料与电解液的界面副反应，从而改善二次电池的循环性能和安全性能。
在一些实施方式中，步骤(2)中，在pH为3.5-6条件下混合，可选地pH为4-6，更可选地pH为4-5。需要说明的是，在本申请中可通过本领域通常使用的方法调节pH，例如可通过添加酸或碱。
在一些实施方式中，可选地，在步骤(2)中，混合物或经元素B掺杂的锰盐颗粒与锂源、磷源的摩尔比为1：0.4-2.1：0.1-2.1，可选为约1：0.4-0.5：0.1-1。
在一些实施方式中，步骤(2)中，在600-900℃下烧结4-10小时；可选地，烧结可在约650℃、约700℃、约750℃、约800℃、约850℃或约900℃下烧结约2小时、约3小时、约4小时、约5小时、约6小时、约7小时、约8小时、约9小时或约10小时；可选地，在惰性气体或惰性气体与氢气混合气氛保护下烧结，更可选地，保护气氛为70-90体积％氮气和10-30体积％氢气的混合气体；烧结的温度、烧结时间可在上述任意数值的任意范围内，能提高结晶度，减少杂相生成，维持一定的颗粒度，从而提高正极活性材料的克容量、压实密度，提高二次电池的整体性能包括倍率性能。
在一些可选实施方式中，将步骤(1)获得的混合物过滤，烘干，并进行研磨以得到粒径Dv50为50-200nm的经元素B掺杂的锰盐颗粒，将经元素B掺杂的锰盐颗粒用于步骤(2)中与锂源、磷源、元素A的源、元素C的源和元素D的源及可选的溶剂混合。
在一些可选实施方式中，步骤(2)中，通过喷雾干燥设备进行干燥。
在一些可选实施方式中，步骤(2)中，混合的同时进行研磨。
本申请的制备方法对材料的来源并没有特别的限制，某种元素的来源可包括该元素的单质、硫酸盐、卤化物、硝酸盐、磷酸盐、草酸 盐、碳酸盐、氧化物和氢氧化物中的一种或多种，前提是该来源可实现本申请制备方法的目的。
在一些实施方式中，元素A的源选自元素A的单质、氧化物、磷酸盐、草酸盐、碳酸盐和硫酸盐中的一种或多种；和/或，
元素B的源为选自元素B的单质、氧化物、磷酸盐、草酸盐、碳酸盐和硫酸盐中的一种或多种；和/或，
元素C的源为选自元素C的硫酸盐、硼酸盐、硝酸盐和硅酸盐中的一种或多种；和/或，
元素D的源为选自元素D的单质和铵盐中的一种或多种。
在一些实施方式中，元素M的源为选自元素M的单质、碳酸盐、硫酸盐、卤化物、硝酸盐、有机酸盐、氧化物和氢氧化物中的一种或多种。
元素A、B、C、D、M各自的源的加入量取决于目标掺杂量，锂源、锰源和磷源的用量之比符合化学计量比。
本申请中，锰源可为本领域已知的可用于制备磷酸锰锂的含锰物质。作为示例，锰源可为选自单质锰、二氧化锰、磷酸锰、草酸锰、碳酸锰中的一种或多种。
本申请中，酸可为选自盐酸、硫酸、硝酸、磷酸、硅酸、亚硅酸等有机酸和有机酸如草酸中的一种或多种。在一些实施方式中，酸为浓度为60重量％以下的稀的有机酸。
本申请中，锂源可为本领域已知的可用于制备磷酸锰锂的含锂物质。作为示例，锂源为选自碳酸锂、氢氧化锂、磷酸锂、磷酸二氢锂中的一种或多种。
本申请中，磷源可为本领域已知的可用于制备磷酸锰锂的含磷物质。作为示例，磷源为选自磷酸氢二铵、磷酸二氢铵、磷酸铵和磷酸中的一种或多种。
本申请中，作为示例，碳源为选自淀粉、蔗糖、葡萄糖、聚乙烯醇、聚乙二醇、柠檬酸中的一种或多种。
[正极极片]
正极极片通常包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，正极膜层包括上述的正极活性材料或上述方法制备的正极活性材料。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、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-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，导电剂可以包括超导碳、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至少一种。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
[负极极片]
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，负极膜层包括负极活性材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面， 负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方式中，负极膜层还可选地包括粘结剂。作为示例，粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
在一些实施方式中，负极膜层还可选地包括导电剂。作为示例，导电剂可选自超导碳、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至少一种。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
[电解质]
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在一些实施方式中，电解质为液态的，且包括电解质盐和溶剂。
在一些实施方式中，电解质盐可选自六氟磷酸锂、四氟硼酸锂、高氯酸锂、六氟砷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。
在一些实施方式中，溶剂可选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
在一些实施方式中，电解液还可选地包括添加剂。作为示例，添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
[隔离膜]
在一些实施方式中，二次电池中还包括隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封 装上述电极组件及电解质。
在一些实施方式中，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，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对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。例如，图1是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图2，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能够盖设于开口，以封闭容纳腔。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极组件52。电极组件52封装于容纳腔内。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
在一些实施方式中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图3是作为一个示例的电池模块4。参照图3，在电池模块4中，多个二次电池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，多个二次电池5容纳于该容纳空间。
在一些实施方式中，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为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
图4和图5是作为一个示例的电池包1。参照图4和图5，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。
另外，本申请还提供一种用电装置，用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。二次电池、电池模块、或电池包可以用作用电装置的电源，也可以用作用电装置的能量存储单元。用电装置可以包括移动设备(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***等，但不限于此。
作为用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。
图6是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电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。
[实施例]
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
第一正极活性材料的制备
制备例A3：LiNi 0.55Co 0.113Mn 0.277Al 0.04Mg 0.02O 2(类单晶)
(1)将NiSO 4、CoSO 4和MnSO 4按照0.55:0.113:0.277的摩尔比加水配成混合溶液，其中，混合溶液中NiSO 4的浓度为2mol/L；配制5mol/L的NaOH溶液；
(2)将50L混合溶液通入反应釜中，再将50L NaOH溶液和适量的0.5mol/L的氨水溶液通入到反应釜中，使反应釜内pH值为9.0-12.0，反应温度为40℃-80℃，在搅拌条件下反应60h，搅拌转速为300-1000r/min，完成后，过滤出沉淀并洗涤，洗涤后的沉淀在120℃ 下真空干燥24h，得到前驱体；
(3)将Li 2CO 3、前驱体、Al 2O 3和MgO混合，其中，Li 2CO 3(以Li元素的摩尔量计)、前驱体(以混合溶液中Ni、Co和Mn三种元素的总摩尔量计)、Al 2O 3(以Al元素的摩尔量计)与MgO的摩尔比为1.05:0.94:0.04:0.02，混合后置于球磨罐中以300r/s转速球磨2h，再置于厢式炉中，在0.2MPa空气气氛下，升温至950℃保温12h进行预烧，升温速率为1℃/min，然后以1℃/min速率降温至600℃保温8h进行烧结，烧结后以1℃/min速率降温至300℃，继续自然冷却至室温，之后经气流粉碎机以3000r/min的转速、500m 3/h的风量进行粉碎，破碎0.5h，然后经500目滤网过筛，得到第一正极活性材料。
制备例A16：LiNi 0.83Co 0.114Mn 0.006Al 0.04Mg 0.01O 2(多晶)
(1)将NiSO 4、CoSO 4和MnSO 4按照0.83:0.114:0.006的摩尔比加水配成混合溶液，其中，混合溶液中NiSO 4的浓度为2mol/L；配制6mol/L的NaOH溶液；
(2)将50L混合溶液通入反应釜中，再将50L NaOH溶液和适量的0.5mol/L氨水溶液通入到反应釜中，使反应釜内pH值为10-13，反应温度为40℃-80℃，在搅拌条件下反应8～20h，搅拌转速为150-300r/min，完成后，过滤出沉淀并洗涤，洗涤后的沉淀在120℃下真空干燥24h，得到前驱体；
(3)将LiOH、前驱体、Al 2O 3和MgO混合，其中，LiOH、前驱体(以混合溶液中Ni、Co和Mn三种元素的总摩尔量计)、Al 2O 3(以Al元素的摩尔量计)与MgO的摩尔比为1.05：0.95：0.04：0.01，混合后置于球磨罐中以500r/s转速球磨2h，再置于厢式炉中，在0.2MPa空气气氛下，升温至750℃保温20h进行预烧，升温速率为20℃/min，烧结后以1℃/min速率降温至300℃，继续自然冷却至室温，使用2000r/min的转速破碎5h，然后将混合物以升温速率20℃/min升温至400℃保温20h进行烧结，烧结后以1℃/min速率降温至300℃，继续自然冷却至室温，之后经气流粉碎机以3000r/min的转速、500m 3/h的风量进行破碎，破碎0.5h，然后经400目滤网过筛，得到第一正极活 性材料。
制备例A1、A2、A4至A15、A17至A22及对比制备例A1
以类似于制备例A3的方法制作制备例A1、A2、A4至A11、A22和对比制备例A1的第一正极活性材料，制备中的不同之处参见表1，其余与制备例A3中的相同；
以类似于制备例A16的方法制作制备例A12至A15、A17至A21，制备中的不同之处参见表1，其余与制备例A16中的相同。
Figure PCTCN2022105998-appb-000001
Figure PCTCN2022105998-appb-000002
Figure PCTCN2022105998-appb-000003
Figure PCTCN2022105998-appb-000004
Figure PCTCN2022105998-appb-000005
Figure PCTCN2022105998-appb-000006
Figure PCTCN2022105998-appb-000007
Figure PCTCN2022105998-appb-000008
Figure PCTCN2022105998-appb-000009
第二正极活性材料的制备
制备例B1
制备掺杂的草酸锰：将1.3mol MnSO 4·H 2O与0.7mol FeSO 4·H 2O在混料机中充分混合6小时；将混合物转移至反应釜中，加入10L去离子水和2mol二水合草酸，加热至80℃，之后以600rpm转速搅拌6小时，反应终止(无气泡产生)，得到Fe掺杂的草酸锰的悬浮液；过滤悬浮液，滤饼在120℃下烘干，研磨，得到粒径Dv 50为100nm左右的Fe掺杂的草酸锰颗粒；
制备掺杂的磷酸锰锂：取1mol Fe掺杂的草酸锰颗粒、0.497mol碳酸锂、0.001mol的Mo(SO 4) 3、含有0.999mol磷酸的浓度85％的磷酸水溶液、0.001mol的H 4SiO 4、0.0005mol的NH 4HF 2和0.005mol蔗糖加入到20L去离子水中，将混合物转入砂磨机中充分研磨搅拌10小时，得到浆料；将浆料转移到喷雾干燥设备中进行喷雾干燥造粒，设定干燥温度为250℃，干燥4小时，得到颗粒；在氮气(90％v/v)+氢气(10％v/v)保护气氛中，将颗粒在700℃下烧结10小时，得到第二正极活性材料，碳包覆的Li 0.994Mo 0.001Mn 0.65Fe 0.35P 0.999Si 0.001O 3.999F 0.001。正极活性材料可用电感耦合等离子体发射光谱(ICP)进行元素含量的检测。
制备例B2
除了将高纯Li 2CO 3的量改变为0.4885mol，将Mo(SO 4) 3换成等摩尔的MgSO 4，将FeSO 4﹒H 2O的量改变为0.68mol，在制备掺杂的草酸锰时还加入0.02mol的Ti(SO 4) 2，并将H 4SiO 4换成等摩尔的HNO 3之外，其他与制备例B1相同。
制备例B3
除了在将高纯Li 2CO 3的量改变为0.496mol，将Mo(SO 4) 3换成等摩尔的W(SO 4) 3，将H 4SiO 4换成等摩尔的H 2SO 4之外，其他与制备例B1相同。
制备例B4
除了将高纯Li 2CO 3的量改变为0.4985mol，将0.001mol的Mo(SO 4) 3换成0.0005mol的Al 2(SO 4) 3和NH 4HF 2换成等摩尔的NH 4HCl 2之外，其他与制备例B1相同。
制备例B5
除了将0.7mol的FeSO 4﹒H 2O改为0.69mol，在制备掺杂的草酸锰时还加入0.01molVCl 2，将Li 2CO 3的量改变为0.4965mol，将0.001mol的Mo(SO 4) 3换成0.0005mol的Nb 2(SO 4) 5和H 4SiO 4换成等摩尔的H 2SO 4之外，其他与制备例B1相同。
制备例B6
除了将FeSO 4﹒H 2O的量改为0.68mol，在制备掺杂的草酸锰时还加入0.01mol的VCl 2和0.01mol的MgSO 4，将Li 2CO 3的量改变为0.4965mol，将0.001mol的Mo(SO 4) 3换成0.0005mol的Nb 2(SO 4) 5和H 4SiO 4换成等摩尔的H 2SO 4之外，其他与制备例B1相同。
制备例B7
除了将MgSO 4换成等摩尔的CoSO 4之外，其他与制备例B6相同。
制备例B8
除了将MgSO 4换成等摩尔的NiSO 4之外，其他与制备例B6相同。
制备例B9
除了将FeSO 4﹒H 2O的量改为0.698mol，在制备掺杂的草酸锰时还加入0.002mol的Ti(SO 4) 2，将Li 2CO 3的量改变为0.4955mol，将0.001mol的Mo(SO 4) 3换成0.0005mol的Nb 2(SO 4) 5，H 4SiO 4换成等摩尔的H 2SO 4，NH 4HF 2换成等摩尔的NH 4HCl 2之外，其他与制备例B1 相同。
制备例B10
除了将FeSO 4﹒H 2O的量改为0.68mol，在制备掺杂的草酸锰时还加入0.01mol的VCl 2和0.01mol的MgSO 4，将Li 2CO 3的量改变为0.4975mol，将0.001mol的Mo(SO 4) 3换成0.0005mol的Nb 2(SO 4) 5和NH 4HF 2换成等摩尔的NH 4HBr 2之外，其他与制备例B1相同。
制备例B11
除了将FeSO 4﹒H 2O的量改为0.69mol，在制备掺杂的草酸锰时还加入0.01mol的VCl 2，将Li 2CO 3的量改变为0.499mol，将Mo(SO 4) 3换成等摩尔的MgSO 4和NH 4HF 2换成等摩尔的NH 4HBr 2之外，其他与制备例B1相同。
制备例B12
除了将MnSO 4﹒H 2O的量改为1.36mol，将FeSO 4﹒H 2O的量改为0.6mol，在制备掺杂的草酸锰时还加入0.04mol的VCl 2，将Li 2CO 3的量改变为0.4985mol，将Mo(SO 4) 3换成等摩尔的MgSO 4和H 4SiO 4换成等摩尔的HNO 3之外，其他与制备例B1相同。
制备例B13
除了将MnSO 4﹒H 2O的量改为1.16mol，FeSO 4﹒H 2O的量改为0.8mol之外，其他与制备例B12相同。
制备例B14
除了将MnSO 4﹒H 2O的量改为1.3mol，VCl 2的量改为0.1mol之外，其他与制备例B12相同。
制备例B15
除了将MnSO 4﹒H 2O的量改为1.2mol，在制备掺杂的草酸锰时 还加入0.1mol的VCl 2，将Li 2CO 3的量改变为0.494mol，将0.001mol的Mo(SO 4) 3换成0.005mol的MgSO 4和H 4SiO 4换成等摩尔的H 2SO 4之外，其他与制备例B1相同。
制备例B16
除了将MnSO 4﹒H 2O的量改为1.2mol，在制备掺杂的草酸锰时还加入0.1mol的VCl 2，将Li 2CO 3的量改变为0.467mol，将0.001mol的Mo(SO 4) 3换成0.005mol的MgSO 4，0.001mol的H 4SiO 4换成0.005mol的H 2SO 4和1.175mol浓度为85％的磷酸换成1.171mol浓度为85％的磷酸之外，其他与制备例B1相同。
制备例B17
除了将MnSO 4﹒H 2O的量改为1.2mol，在制备掺杂的草酸锰时还加入0.1mol的VCl 2，将Li 2CO 3的量改变为0.492mol，将0.001mol的Mo(SO 4) 3换成0.005mol的MgSO 4，H 4SiO 4换成等摩尔的H 2SO 4和0.0005mol的NH 4HF 2改成0.0025mol之外，其他与制备例B1相同。
制备例B18
除了将FeSO 4﹒H 2O的量改为0.5mol，在制备掺杂的草酸锰时还加入0.1mol的VCl 2和0.1mol的CoSO 4，将Li 2CO 3的量改变为0.492mol，将0.001mol的Mo(SO 4) 3换成0.005mol的MgSO 4，H 4SiO 4换成等摩尔的H 2SO 4和0.0005mol的NH 4HF 2改成0.0025mol之外，其他与制备例B1相同。
制备例B19
除了将FeSO 4﹒H 2O的量改为0.4mol，将0.1mol的CoSO 4改为0.2mol之外，其他与制备例B18相同。
制备例B20
除了将MnSO 4﹒H 2O的量改为1.5mol，FeSO 4﹒H 2O的量改为 0.1mol，CoSO 4的量改为0.3mol之外，其他与制备例B18相同。
制备例B21
除了将0.1mol的CoSO 4换成0.1mol的NiSO 4之外，其他与制备例B18相同。
制备例B22
除了将MnSO 4﹒H 2O的量改为1.5mol，FeSO 4﹒H 2O的量改为0.2mol，将0.1mol的CoSO 4换成0.2mol的NiSO 4之外，其他与制备例B18相同。
制备例B23
除了将MnSO 4﹒H 2O的量改为1.4mol，FeSO 4﹒H 2O的量改为0.3mol，CoSO 4的量改为0.2mol之外，其他与制备例B18相同。
制备例B24
除了将1.3mol的MnSO 4﹒H 2O改为1.2mol，0.7mol的FeSO 4﹒H 2O改为0.5mol，在制备掺杂的草酸锰时还加入0.1mol的VCl 2和0.2mol的CoSO 4，将Li 2CO 3的量改变为0.497mol，将0.001mol的Mo(SO 4) 3换成0.005mol的MgSO 4，H 4SiO 4换成等摩尔的H 2SO 4和0.0005mol的NH 4HF 2改成0.0025mol之外，其他与制备例B1相同。
制备例B25
除了将MnSO 4﹒H 2O的量改为1.0mol，FeSO 4﹒H 2O的量改为0.7mol，CoSO 4的量改为0.2mol之外，其他与制备例B18相同。
制备例B26
除了将MnSO 4﹒H 2O的量改为1.4mol，FeSO 4﹒H 2O的量改为0.3mol，在制备掺杂的草酸锰时还加入0.1mol的VCl 2和0.2mol的CoSO 4，将Li 2CO 3的量改变为0.4825mol，将0.001mol的Mo(SO 4) 3 换成0.005mol的MgSO 4，H 4SiO 4的量改成0.1mol，磷酸的量改成0.9mol和NH 4HF 2的量改成0.04mol之外，其他与制备例B1相同。
制备例B27
除了将MnSO 4﹒H 2O的量改为1.4mol，FeSO 4﹒H 2O的量改为0.3mol，在制备掺杂的草酸锰时还加入0.1mol的VCl 2和0.2mol的CoSO 4，将Li 2CO 3的量改变为0.485mol，将0.001mol的Mo(SO 4) 3换成0.005mol的MgSO 4，H 4SiO 4的量改成0.08mol，磷酸的量改成0.92mol和NH 4HF 2的量改成0.05mol之外，其他与制备例B1相同。
制备例B28-B41
按照与制备例B1相同的方式制备正极活性材料，但改变制备掺杂的草酸锰时的搅拌转速、温度、在砂磨机中研磨搅拌的时间、烧结温度和烧结时间，具体如下表2所示。
表2制备例B28-B41中制备掺杂的草酸锰时的搅拌转速、温度、在砂磨机中研磨搅拌的时间、烧结温度和烧结时间
Figure PCTCN2022105998-appb-000010
Figure PCTCN2022105998-appb-000011
制备例B42-B54
按照与制备例B1相同的方式制备正极活性材料，但改变锂源、锰源、磷源和掺杂元素A、B、C、D的源，具体如下表3所示。制得的正极活性材料组成与制备例B1相同，即，均为Li 0.994Mo 0.001Mn 0.65Fe 0.35P 0.999Si 0.001O 3.999F 0.001。
表3制备例B42-B54中锂源、锰源、磷源和掺杂元素A、B、C、D的源
Figure PCTCN2022105998-appb-000012
Figure PCTCN2022105998-appb-000013
制备例B55
(1)制备掺杂的草酸锰
将1.2mol MnSO 4·H 2O与0.79mol FeSO 4·H 2O在混料机中充分混合6小时；将混合物转移至反应釜中，加入10L去离子水和2mol二水合草酸、0.01molVCl 2，加热至80℃，之后以600rpm转速搅拌6小 时，反应终止(无气泡产生)，得到Fe掺杂的草酸锰的悬浮液；过滤悬浮液，滤饼在120℃下烘干，研磨，得到粒径Dv 50为100nm左右的Fe掺杂的草酸锰颗粒；
(2)制备掺杂的磷酸锰锂
取1mol Fe掺杂的草酸锰颗粒、0.45mol碳酸锂、0.05mol的MgSO 4、含有0.9mol磷酸的浓度85％的磷酸水溶液、0.1mol的H 4SiO 4、0.05mol的NH 4HF 2和0.005mol蔗糖加入到20L去离子水中，将混合物转入砂磨机中充分研磨搅拌10小时，得到浆料；将浆料转移到喷雾干燥设备中进行喷雾干燥造粒，设定干燥温度为250℃，干燥4小时，得到颗粒；在氮气(90％v/v)+氢气(10％v/v)保护气氛中，将颗粒在700℃下烧结10小时，得到正极活性材料。采用电感耦合等离子体发射光谱(ICP)对进行元素含量检测，得到化学式Li 0.9Mg 0.05Mn 0.6Fe 0.395V 0.005P 0.9Si 0.1O 3.9F 0.1。
制备例B56
除了步骤(2)中，碳酸锂为0.55mol，MgSO 4为0.001mol，NH 4HF 2为0.001mol之外，其余与制备例B55相同；得到正极活性材料Li 1.1Mg 0.001Mn 0.6Fe 0.395V 0.005P 0.9Si 0.1O 3.998F 0.002。
制备例B57
除了步骤(2)中，MgSO 4为0.1mol，浓度85％的磷酸水溶液含0.95mol磷酸，H 4SiO 4为0.05mol，NH 4HF 2为0.025mol之外，其余与制备例B55相同；得到正极活性材料Li 0.9Mg 0.1Mn 0.6Fe 0.395V 0.005P 0.95Si 0.05O 3.95F 0.05。
制备例B58
除了步骤(1)中MnSO 4·H 2O为1.998mol，FeSO 4·H 2O为0.002mol和不使用VCl 2之外；以及除了步骤(2)中碳酸锂为0.475mol，浓度85％的磷酸水溶液含0.96mol磷酸，H 4SiO 4为0.04mol，NH 4HF 2为0.01mol之外；其余与制备例B55相同；得到正极活性材料 Li 0.95Mg 0.05Mn 0.999Fe 0.001P 0.96Si 0.04O 3.99F 0.01。
制备例B59
除了步骤(1)中MnSO 4·H 2O为1.98mol，FeSO 4·H 2O为0.02mol和不使用VCl 2之外；以及除了步骤(2)中碳酸锂为0.475mol，浓度85％的磷酸水溶液含0.96mol磷酸，H 4SiO 4为0.04mol，NH 4HF 2为0.01mol之外；其余与制备例B55相同；得到正极活性材料Li 0.95Mg 0.05Mn 0.99Fe 0.01P 0.96Si 0.04O 3.99F 0.01。
制备例B60
除了步骤(1)中MnSO 4·H 2O为1.6mol，FeSO 4·H 2O为0.4mol和不使用VCl 2之外；以及除了步骤(2)中碳酸锂为0.475mol，浓度85％的磷酸水溶液含0.96mol磷酸，H 4SiO 4为0.04mol，NH 4HF 2为0.01mol之外；其余与制备例B55相同；得到正极活性材料Li 0.95Mg 0.05Mn 0.8Fe 0.2P 0.96Si 0.04O 3.99F 0.01。
对比制备例B1
制备草酸锰：将1mol的MnSO 4﹒H 2O加至反应釜中，并加入10L去离子水和1mol二水合草酸(以草酸计)。将反应釜加热至80℃，以600rpm的转速搅拌6小时,反应终止(无气泡产生)，得到草酸锰悬浮液。然后过滤悬浮液，将滤饼在120℃下烘干，之后进行研磨，得到中值粒径Dv 50为50-200nm的草酸锰颗粒。
制备磷酸锰锂：取1mol上述草酸锰颗粒、0.5mol碳酸锂、含有1mol磷酸的浓度为85％的磷酸水溶液和0.005mol蔗糖加入到20L去离子水中。将混合物转入砂磨机中充分研磨搅拌10小时，得到浆料。将浆料转移到喷雾干燥设备中进行喷雾干燥造粒，设定干燥温度为250℃，干燥4小时，得到颗粒。在氮气(90体积％)+氢气(10体积％)保护气氛中，将上述粉料在700℃下烧结10小时，得到碳包覆的LiMnPO 4。
对比制备例B2
除了在对比例1中，将1mol的MnSO 4﹒H 2O换成0.85mol的MnSO 4﹒H 2O和0.15mol的FeSO 4﹒H 2O，并加入到混料机中充分混合6小时之后再加入反应釜之外，其它与对比制备例B 1相同。
对比制备例B3
除了将MnSO 4﹒H 2O的量改为1.9mol，0.7mol的FeSO 4﹒H 2O换成0.1mol的ZnSO 4，将Li 2CO 3的量改变为0.495mol，将0.001mol的Mo(SO 4) 3换成0.005mol的MgSO 4，将磷酸的量改成1mol，不加入H 4SiO 4和NH 4HF 2之外，其他与制备例B1相同。
对比制备例B4
除了将MnSO 4﹒H 2O的量改为1.2mol，FeSO 4﹒H 2O的量改为0.8mol，将Li 2CO 3的量改变为0.45mol，将0.001mol的Mo(SO 4) 3换成0.005mol的Nb 2(SO 4) 5，将0.999mol的磷酸改成1mol，0.0005mol的NH 4HF 2改成0.025mol，不加入H 4SiO 4之外，其他与制备例B1相同。
对比制备例B5
除了将MnSO 4﹒H 2O的量改为1.4mol，FeSO 4﹒H 2O的量改为0.6mol，将Li 2CO 3的量改变为0.38mol，将0.001mol的Mo(SO 4) 3换成0.12mol的MgSO 4之外，其他与制备例B1相同。
对比制备例B6
除了将MnSO 4﹒H 2O的量改为0.8mol，0.7mol的FeSO 4﹒H 2O换成1.2mol的ZnSO 4，将Li 2CO 3的量改变为0.499mol，将0.001mol的Mo(SO 4) 3换成0.001mol的MgSO 4之外，其他与制备例B1相同。
对比制备例B7
除了将MnSO 4﹒H 2O的量改为1.4mol，FeSO 4﹒H 2O的量改为 0.6mol，将Li 2CO 3的量改变为0.534mol，将0.001mol的Mo(SO 4) 3换成0.001mol的MgSO 4，将磷酸的量改成0.88mol，H 4SiO 4的量改成0.12mol，NH 4HF 2的量改成0.025mol之外，其他与制备例B1相同。
对比制备例B8
除了将MnSO 4﹒H 2O的量改为1.2mol，FeSO 4﹒H 2O的量改为0.8mol，将Li 2CO 3的量改变为0.474mol，将0.001mol的Mo(SO 4) 3换成0.001mol的MgSO 4，将磷酸的量改成0.93mol，H 4SiO 4的量改成0.07mol，NH 4HF 2的量改成0.06mol之外，其他与制备例B1相同。
混合正极活性材料的制备
实施例1至43及对比例1
将第一正极活性材料与第二正极材料在搅拌罐中搅拌混合，第一正极材料的质量m 1，第二正极材料的质量m 2，混合正极活性材料的质量为m 1+m 2。
各实施例及对比例的参数见表4。
表4实施例1至43及对比例1的参数
Figure PCTCN2022105998-appb-000014
Figure PCTCN2022105998-appb-000015
Figure PCTCN2022105998-appb-000016
Figure PCTCN2022105998-appb-000017
全电池的制备
将正极活性材料与导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按重量比92：2.5：5.5在N-甲基吡咯烷酮溶剂体系中混合均匀后，涂覆于铝箔上并烘干、冷压，得到正极极片。涂覆量为0.4g/cm 2，压实密度为2.4g/cm 3。
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)按照重量比90：5：2：2：1在去离子水中混合均匀后，涂覆于铜箔上烘干、冷压，得到负极极片。涂覆量为0.2g/cm 2，压实密度为1.7g/cm 3。
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，使隔离膜处于正负极中间起到隔离的作用，并卷绕得到裸电芯。将裸电芯置于外包装中，注入与上述制备扣电时相同的电解液并封装，得到全电池(下文也称“全电”)。
扣式电池的制备
将正极活性材料、聚偏二氟乙烯(PVDF)、乙炔黑以90：5：5的重量比加入至N-甲基吡咯烷酮(NMP)中，在干燥房中搅拌制成浆料。在铝箔上涂覆上述浆料，干燥、冷压制成正极极片。涂覆量为0.2g/cm 2，压实密度为2.0g/cm 3。
采用锂片作为负极，采用1mol/L的LiPF 6在体积比1：1：1的碳酸乙烯酯(EC)、碳酸二乙酯(DEC)和碳酸二甲酯(DMC)中溶解为电解液，与上述制备的正极极片一起在扣电箱中组装成扣式电池(下文也称“扣电”)。
上述的正极活性材料可以为第一正极活性材料、第二正极活性材料或混合正极活性材料。
材料性能测试
1.正极活性材料化学式的测定
采用球差电镜仪(ACSTEM)对正极活性材料内部微观结构和表面结构进行高空间分辨率表征，结合三维重构技术得到正极活性材料的化学式。
2.晶格变化率测量方法
在25℃恒温环境下，将正极活性材料样品置于XRD(型号为Bruker D8 Discover)中，采用1°/min对样品进行测试，并对测试数据进行整理分析，参照标准PDF卡片，计算出此时的晶格常数a0、b0、c0和v0(a0,b0和c0表示晶胞各个方面上的长度大小，v0表示晶胞体积，可通过XRD精修结果直接获取)。
将正极活性材料按照上述“扣式电池的制备”制备成扣电，并对上述扣电以0.05C小倍率进行充电，直至电流减小至0.01C。然后将扣 电中的正极极片取出，并置于DMC中浸泡8小时。然后烘干，刮粉，并筛选出其中粒径小于500nm的颗粒。取样并按照与上述测试新鲜样品同样的方式计算出其晶格常数v1，将(v0-v1)/v0×100％作为其完全脱嵌锂前后的晶格变化率示于表中。
3.Li/Mn反位缺陷浓度测量方法
将“晶格变化率测量方法”中测试的XRD结果与标准晶体的PDF(Powder Diffraction File)卡片对比，得出Li/Mn反位缺陷浓度。具体而言，将“晶格变化率测量方法”中测试的XRD结果导入通用结构分析***(GSAS)软件中，自动获得精修结果，其中包含了不同原子的占位情况，通过读取精修结果获得Li/Mn反位缺陷浓度。
4.表面氧价态测量方法
取5g正极活性材料样品按照上述“扣式电池的制备”制备成扣电。对扣电采用0.05C小倍率进行充电，直至电流减小至0.01C。然后将扣电中的正极极片取出，并置于DMC中浸泡8小时。然后烘干，刮粉，并筛选出其中粒径小于500nm的颗粒。将所得颗粒用电子能量损失谱(EELS，所用仪器型号为Talos F200S)进行测量，获取能量损失近边结构(ELNES)，其反映元素的态密度和能级分布情况。根据态密度和能级分布，通过对价带态密度数据进行积分，算出占据的电子数，从而推算出充电后的表面氧的价态。
5.压实密度测量方法
取5g正极活性材料的粉末放于压实专用模具(美国CARVER模具，型号13mm)中，然后将模具放在压实密度仪器上。对正极活性材料施加3T的压力，在设备上读出压力下粉末的厚度(卸压后的厚度)，通过ρ＝m/v，计算出压实密度。
6.循环后Mn(以及Mn位掺杂的Fe)溶出量测量方法
将正极活性材料样品按照上述“全电池的制备”制备成全电池。
采用将45℃下循环至容量衰减至80％后的全电池采用0.1C倍率进行放电至截止电压2.0V。然后将电池拆开，取出负极极片，在负极极片上随机取30个单位面积(1540.25mm 2)的圆片，用Agilent ICP-OES730测试电感耦合等离子体发射光谱(ICP)。根据ICP结果计算其中Fe(如果正极活性材料的Mn位掺杂有Fe的话)和Mn的量，从而计算循环后Mn(以及Mn位掺杂的Fe)的溶出量。测试标准依据EPA-6010D-2014。
7.扣式电池初始克容量测量方法
在2.5～4.3V下，将扣式电池按照0.1C充电至4.3V，然后在4.3V下恒压充电至电流小于等于0.05mA，静置5min，然后按照0.1C放电至2.0V，此时的放电容量为初始克容量，记为D0。
8.3C充电恒流比测量方法
在25℃恒温环境下，将新鲜全电池静置5min，按照1/3C放电至2.5V。静置5min，按照1/3C充电至4.3V，然后在4.3V下恒压充电至电流小于等于0.05mA。静置5min，记录此时的充电容量为C0。按照1/3C放电至2.5V，静置5min，再按照3C充电至4.3V，静置5min，记录此时的充电容量为C1。3C充电恒流比即为C1/C0×100％。
3C充电恒流比越高，说明电池的倍率性能越好。
9.全电池45℃循环性能测试
在45℃的恒温环境下，在2.5～4.3V下，将全电池按照1C充电至4.3V，然后在4.3V下恒压充电至电流小于等于0.05mA。静置5min，然后按照1C放电至2.5V，记录此时的放电容量为D0。重复前述充放电循环，直至放电容量降低到D0的80％。记录此时电池经过的循环圈数。
10.全电池60℃胀气测试
在60℃下，存储100％充电状态(SOC)的全电池。在存储前后 及过程中测量电芯的开路电压(OCV)和交流内阻(IMP)以监控SOC，并测量电芯的体积。其中在每存储48h后取出全电池，静置1h后测试开路电压(OCV)、内阻(IMP)，并在冷却至室温后用排水法测量电芯体积。排水法即先用表盘数据自动进行单位转换的天平单独测量电芯的重力F 1，然后将电芯完全置于去离子水(密度已知为1g/cm 3)中，测量此时的电芯的重力F 2，电芯受到的浮力F 浮即为F 1-F 2，然后根据阿基米德原理F 浮＝ρ×g×V 排，计算得到电芯体积V＝(F 1-F 2)/(ρ×g)。
由OCV、IMP测试结果来看，本实验过程中直至存储结束，实施例的电池始终保持99％以上的SOC。
存储30天后，测量电芯体积，并计算相对于存储前的电芯体积，存储后的电芯体积增加的百分比。
另外，测量电芯残余容量。在2.5～4.3V下，将全电池按照1C充电至4.3V，然后在4.3V下恒压充电至电流小于等于0.05mA。静置5min，记录此时的充电容量为电芯残余容量。
11.比表面积(BET)测量方法
参考GB/T 19587-2004，用比表面积孔隙度分析仪TRISTAR II3020(美国麦克仪器公司)对正极活性材料进行比表面积测试。测试前将正极活性材料置于真空烘箱200℃干燥≥2h，样品需求量＞20g。
12.颗粒度Dv50测试
参考GB/T19077-2016，采用Mastersizer 3000激光衍射粒度分析仪(马尔文帕纳科公司)测定正极活性材料的颗粒度Dv50，其中，溶剂使用去离子水，测试前将正极活性材料超声处理5min。
13.ICP测试(电感耦合等离子体发射光谱法)
参考EPA 6010D-2014，采用iCAP 7400电感耦合等离子体发射光谱仪进行元素含量测试，溶剂选用王水；
粉末类元素含量计算公式：元素含量(质量％)＝100％×元素质量 /样品质量；
极片类元素含量计算公式：元素含量(质量％)＝100％×元素质量/(样品质量-集流体质量)。
14.Li 2CO 3和LiOH的含量测试(游离锂电位滴定测试)
参考GB/T 9736-2008，采用905电位滴定仪进行测试，取样后立即使用铝塑膜袋进行真空密封，单次测试最少样品量≥30g。
15.晶体类型测试
如果没有特别的说明，在本申请中，术语“单晶/类单晶颗粒”、“准单晶颗粒”、“单晶颗粒”、“单晶材料颗粒”或其类似表述具有基本相似的含义，其意指单个颗粒(即一次颗粒)和/或团聚颗粒，其中的团聚颗粒是由不多于100个(特别是约5至50个)平均粒径在50nm至10000nm范围内的一次颗粒团聚形成的颗粒。
如果没有特别的说明，在本申请中，术语“二次颗粒”和“多晶材料颗粒”通常具有类似的含义，其意指由超过100个平均粒径在50-800nm范围内的一次颗粒团聚形成的颗粒。
采用扫描电镜对正极活性材料进行测试，调整样品和放大倍数使视野内具有大于10个的团聚颗粒，计量组成每个团聚颗粒的一次颗粒数量，并用标尺测量一次颗粒长度方向的尺寸记为粒径，将每个团聚颗粒中的一次颗粒的粒径由大至小排序，去除1/10的粒径最大数据和1/10的粒径最小的数据，剩余粒径数据取平均值作为该团聚颗粒中一次颗粒的平均粒径。如果50％以上(包括50％)数量的团聚颗粒中的一次颗粒的数量和平均粒径符合上述“多晶材料颗粒”的定义，则判定该正极活性材料为多晶材料，否则，判定为单晶或类单晶材料。
其中，制备例A10和制备例A15所制的第一正极活性材料的SEM照片如图7-8所示。
16.热箱安全测试
测试参考GB 38031-2020中安全测试的《加热》章节，并针对上 限边界进行探索，优化测试条件如下：
①预准备：
测试条件：准备一个防爆烘箱，可以加热和线路连接口；测试电芯为新鲜裸电芯(循环次数≤10次)，在电芯四周、极柱等位置贴上感温线用于温度监控，同时配置有温度记录设备；
测试前电芯处理：采用0.33C倍率电流做恒流恒压充电，电芯满充至标称电压(如本发明中电压为4.3V)。
②测试过程：将样品放在高温箱中，温箱以5℃/min，由室温升至100℃，保持2h；再以5℃/min升温，每5℃保持30min，直至电芯失控(失控标准：电压在1min内下降幅度≥50％，电芯温度在1min升高幅度≥50％)或加热到200℃，停止加热。
③数据处理：根据上述条件找到失效点，得到对应的保温温度和保温时间，记为：时间@温度，如21min@150℃。
④结果对标：
测试过程中持续更长时间测试的样品安全性更高；持续进行更长时间测试的样品可以为：失效点温度相同但时间更长的样品；失效点时间相同但温度更高的样品；失效点的温度和时间均不同但温度更高的样品。
Figure PCTCN2022105998-appb-000018
Figure PCTCN2022105998-appb-000019
Figure PCTCN2022105998-appb-000020
Figure PCTCN2022105998-appb-000021
Figure PCTCN2022105998-appb-000022
Figure PCTCN2022105998-appb-000023
Figure PCTCN2022105998-appb-000024
Figure PCTCN2022105998-appb-000025
Figure PCTCN2022105998-appb-000026
Figure PCTCN2022105998-appb-000027
Figure PCTCN2022105998-appb-000028
Figure PCTCN2022105998-appb-000029
Figure PCTCN2022105998-appb-000030
Figure PCTCN2022105998-appb-000031
Figure PCTCN2022105998-appb-000032
由表12可知：
将实施例1-43和对比例1相比较可知，与对比例1所制的二次电池相比，本申请第一正极活性材料与第二正极活性材料混合所制二次电池的循环容量保持率更高，循环寿命更长；并且，本申请实施例1、3-7、9、12-13、23-25、28的混合正极活性材料所制二次电池的安全性比对比例1所制二次电池的安全性更好。
将实施例16、实施例23-29相比较可知，本申请第一正极活性材料和第二正极活性材料的质量关系m 1/(m 1+m 2)在3％-50％之间所制二次电池的循环容量保持率进一步提高，循环寿命进一步延长；
本申请第一正极活性材料和第二正极活性材料的b*m 1/m 1+m 2小于或等于0.457所制二次电池的循环容量保持率高，循环寿命长，安全性高；将实施例16、实施例23-29相比较可知，本申请第一正极活性材料和第二正极活性材料的质量关系b×m 1/(m 1+m 2)在0.025-0.415范围内，所制二次电池的循环容量保持率进一步提高，循环寿命进一步延长，安全性进一步提高。
将实施例1-11、22相比较可知，本申请第一正极活性材料为类单晶时，第一正极活性材料的D v50粒径小于或等于5.8μm时所制二次电池的循环容量保持率高，循环寿命长，安全性高；并且，第一正极活性材料的D v50粒径为小于或等于4.3μm，所制二次电池的循环容量保持率更高，循环寿命更长。
将实施例12-21相比较可知，本申请第一正极活性材料为多晶时，第一正极活性材料的D v50粒径为3.5～13.5μm、BET比表面积小于或等于1.32m 2/g且在3T压力下的压实密度大于或等于2.92g/cm 3所制二次电池的循环容量保持率更高，循环寿命更长。
将实施例1-8、10-11、22相比较可知，本申请第一正极活性材料为类单晶时，第一正极活性材料LiNi bCo dMn eM fO 2中的d选自0.047-0.320所制二次电池的循环容量保持率更高，循环寿命更长。
本申请第一正极活性材料LiNi bCo dMn eM fO 2中的b选自0.314-0.970的范围，所制二次电池的循环容量保持率高，循环寿命长，安全性高；将实施例1-11、22相比较可知，第一正极活性材料为单晶或 准单晶材料时，b大于0.314且小于0.97(不包括0.314、0.97数值)所制二次电池的循环容量保持率更高，循环寿命更长。
将实施例10、22相比较可知，本申请第一正极活性材料中的碳酸锂质量含量小于或等于1％且氢氧化锂的质量含量小于或等于1％所制二次电池的循环容量保持率更高，循环寿命更长，安全性更高。
将表5和表12比较可知：
与第一正极活性材料所制的二次电池相比，本申请含有相应的第一正极活性材料的混合正极活性材料所制二次电池的安全性更高；与采用制备例A14-A17、A19-A21的第一正极活性材料所制的二次电池相比，本申请含有相应的第一正极活性材料的混合正极活性材料所制二次电池的循环容量保持率更高，循环寿命更长。
将表7、9、10、11和表12比较可知：
与采用制备例B1、B14、B16、B25、B26、B27、B31、B47、B55-B60的第二正极活性材料所制的二次电池相比，本申请含有相应的第二正极活性材料的混合正极活性材料所制二次电池的循环容量保持率更高，循环寿命更长。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (21)

  1. 一种正极活性材料，包含第一正极活性材料和第二正极活性材料；其中，
    所述第一正极活性材料包含化合物LiNi bCo dMn eM fO 2，其中，所述b选自0.314-0.970的范围，所述d选自0-0.320的范围、可选为选自0.047-0.320的范围，所述e选自0.006-0.390的范围，并且，所述b、d、e和f的总和为1且f大于0，所述M选自Mn、Al、Mg、Ca、Na、Ti、W、Zr、Sr、Cr、Zn、Ba、B、S和Y中的一种或多种元素，可选地，所述M为Mg和/或Al；
    所述第二正极活性材料包含化合物Li aA xMn 1-yB yP 1-zC zO 4-nD n，所述a选自0.9至1.1的范围，所述x选自0.001至0.1的范围，所述y选自0.001至0.5的范围，所述z选自0.001至0.1的范围，所述n选自0.001至0.1的范围，所述A选自Zn、Al、Na、K、Mg、Nb、Mo和W中的一种或多种元素，所述B选自Ti、V、Zr、Fe、Ni、Mg、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素，所述C选自B、S、Si和N中的一种或多种元素，所述D选自S、F、Cl和Br中的一种或多种元素。
  2. 根据权利要求1所述的正极活性材料，其中，所述第一正极活性材料的质量为m 1，所述第二正极活性材料的质量为m 2，并且m 1/(m 1+m 2)的值为2％-55％，可选为3％-50％。
  3. 根据权利要求1或2所述的正极活性材料，其中，b×m 1/(m 1+m 2)的值为0.017-0.457，可选为0.025-0.415。
  4. 根据权利要求1至3中任一项所述的正极活性材料，其中，所述第一正极活性材料为单晶或准单晶材料，所述第一正极活性材料的粒径D v50为小于或等于5.8μm，可选为2.3-5.8μm，更可选为2.3-4.3μm。
  5. 根据权利要求1至4中任一项所述的正极活性材料，其中，所述第一正极活性材料为单晶或准单晶材料时，
    所述d选自0.05-0.320的范围，可选为选自0.05-0.282的范围；和/或，
    所述b大于0.314且小于0.97，可选为选自0.55-0.869的范围。
  6. 根据权利要求1至5中任一项所述的正极活性材料，其中，所述第一正极活性材料为多晶材料时，所述第一正极活性材料的粒径D v50为3.0～13.5μm、可选为3.5～13.5μm；和/或，
    所述第一正极活性材料的BET比表面积小于或等于1.73m 2/g、可选为小于或等于1.32m 2/g，更可选为0.28-1.32m 2/g；和/或，
    所述第一正极活性材料在3T压力下的压实密度大于或等于2.90g/cm 3，可选为大于或等于2.92g/cm 3，更可选为2.92-3.31g/cm 3。
  7. 根据权利要求1至6中任一项所述的正极活性材料，其中，所述第一正极活性材料还包含碳酸锂和/或氢氧化锂；
    可选地，基于所述第一正极活性材料的质量计，所述碳酸锂的质量含量小于或等于1.05％、可选为小于或等于1％，和/或，所述氢氧化锂的质量含量小于或等于1.02％、可选为小于或等于1％。
  8. 根据权利要求1至7中任一项所述的正极活性材料，其中，所述A选自Zn、Al、Na、K、Mg、Nb、Mo和W中的任一种元素，所述B选自Ti、V、Zr、Fe、Ni、Mg、Co、Ga、Sn、Sb、Nb和Ge中的至少两种元素，所述C选自B、S、Si和N中的任一种元素，所述D选自S、F、Cl和Br中的任一种元素；
    可选地，所述A为Mg或Nb，和/或，
    所述B选自Fe、Ti、V、Co和Mg中的至少两种元素，更可选为Fe与选自Ti、V、Co和Mg中的一种或多种元素，和/或，
    所述C为S，和/或，
    所述D为F。
  9. 根据权利要求1至8中任一项所述的正极活性材料，其中，所述x选自0.001至0.005的范围；和/或，
    所述y选自0.01至0.5的范围，可选为选自0.25至0.5的范围；和/或，
    所述z选自0.001至0.005的范围；和/或，
    所述n选自0.001至0.005的范围。
  10. 根据权利要求1至9中任一项所述的正极活性材料，其中，(1-y):y的值选自1至4的范围，可选为选自1.5至3的范围，并且，a:x的值选自9到1100的范围，可选为选自190-998的范围。
  11. 根据权利要求1至10中任一项所述的正极活性材料，其中，所述第二正极活性材料在完全脱嵌锂前后的晶格变化率为8％以下，可选为4％以下。
  12. 根据权利要求1至11中任一项所述的正极活性材料，其中，所述第二正极活性材料的Li/Mn反位缺陷浓度为2％以下，可选为0.5％以下。
  13. 根据权利要求1至12中任一项所述的正极活性材料，其中，所述第二正极活性材料的表面氧价态为-1.82以下，可选地为-1.89～-1.98。
  14. 根据权利要求1至13中任一项所述的正极活性材料，其中，所述第二正极活性材料在3T下的压实密度为2.0g/cm 3以上，可选为2.2g/cm 3以上。
  15. 根据权利要求1至14中任一项所述的正极活性材料，其中， 所述第二正极活性材料还包含碳，所述碳包覆在化合物Li aA xMn 1- yB yP 1-zC zO 4-nD n的表面。
  16. 一种制备正极活性材料的方法，包括如下步骤：
    提供第一正极活性材料和第二正极活性材料；
    将所述第一正极活性材料和所述第二正极活性材料混合即可；
    所述第一正极活性材料包含化合物LiNi bCo dMn eM fO 2，所述第二正极活性材料包含化合物Li aA xMn 1-yB yP 1-zC zO 4-nD n，其中，a、b、d、e、f、x、y、z、n、M、A、B、C和D的定义如权利要求1至15任一项中所述；
    可选地，所述第一正极活性材料还包含碳酸锂和/或氢氧化锂；
    可选地，所述第二正极活性材料还包含包覆在化合物Li aA xMn 1- yB yP 1-zC zO 4-nD n表面的碳。
  17. 一种正极极片，其包括正极集流体以及设置在所述正极集流体的至少一个表面的正极膜层，所述正极膜层包括权利要求1至15中任一项所述的正极活性材料或者通过权利要求16所述的方法制备的正极活性材料；可选地，所述正极活性材料在所述正极膜层中的含量为10重量％以上，更可选为95-99.5重量％，基于所述正极膜层的总重量计。
  18. 一种二次电池，包括权利要求1至15中任一项所述的正极活性材料或者通过权利要求16所述的方法制备的正极活性材料或者权利要求17所述的正极极片。
  19. 一种电池模块，包括权利要求18所述的二次电池。
  20. 一种电池包，包括权利要求19所述的电池模块。
  21. 一种用电装置，包括选自权利要求18所述的二次电池、权利 要求19所述的电池模块和权利要求20所述的电池包中的至少一种。
PCT/CN2022/105998 2022-07-15 2022-07-15 正极活性材料及其制备方法、正极极片、二次电池、电池模块、电池包及用电装置 WO2024011594A1 (zh)

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