WO2023077373A1 - 正极活性材料、正极极片、包含该正极极片的电化学装置和电子装置 - Google Patents

正极活性材料、正极极片、包含该正极极片的电化学装置和电子装置 Download PDF

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WO2023077373A1
WO2023077373A1 PCT/CN2021/128772 CN2021128772W WO2023077373A1 WO 2023077373 A1 WO2023077373 A1 WO 2023077373A1 CN 2021128772 W CN2021128772 W CN 2021128772W WO 2023077373 A1 WO2023077373 A1 WO 2023077373A1
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positive electrode
region
active material
electrode active
present application
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PCT/CN2021/128772
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English (en)
French (fr)
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王凯
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宁德新能源科技有限公司
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Priority to EP21962890.6A priority Critical patent/EP4428953A1/en
Priority to PCT/CN2021/128772 priority patent/WO2023077373A1/zh
Priority to CN202180013380.0A priority patent/CN115104204A/zh
Publication of WO2023077373A1 publication Critical patent/WO2023077373A1/zh
Priority to US18/654,440 priority patent/US20240282940A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • 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
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of electrochemistry, in particular to a positive electrode active material, a positive electrode sheet, an electrochemical device and an electronic device including the positive electrode sheet.
  • lithium-ion batteries Due to its high energy density, long cycle life and no memory effect, lithium-ion batteries are widely used in wearable devices, smart phones, drones, electric vehicles and large energy storage devices, and have become the most developed in the world today. potential new green chemical power sources.
  • the purpose of the present application is to provide a positive electrode active material, a positive electrode sheet, an electrochemical device and an electronic device including the positive electrode sheet, so as to improve the cycle performance of the electrochemical device under high voltage.
  • the first aspect of the present application provides a positive electrode active material, wherein the cross section of the positive electrode active material includes a first region and a second region, the first region has a first structure of P63mc crystal phase structure, and the second region has a R- In the second structure of at least one crystal phase structure of 3m, P2/m or P-3m1, the area ratio of the first region to the second region is 1.8 to 5.4.
  • the inventors of the present application found that although the P63mc crystal phase structure has good structural stability, it is not easy to undergo structural phase transition caused by atomic migration, and can maintain good stability under high voltage, but its In the process, strong repulsion occurs due to face-to-face facing, resulting in large expansion or contraction, which will not be conducive to the stability of the positive electrode material layer on the positive electrode sheet, resulting in a decrease in the cycle performance of the electrochemical device under high voltage; at this time , the introduction of a second structure (such as R-3m, etc.), which itself has a low degree of expansion or shrinkage, and because there is a certain delithiation time difference between it and the P63mc crystal phase structure, it can effectively reduce the overall expansion or shrinkage of the positive electrode active material particles.
  • a second structure such as R-3m, etc.
  • the volume expansion and shrinkage of the positive electrode active material during the process of lithium intercalation and deintercalation can be improved, thereby improving the cycle performance of the electrochemical device under high voltage.
  • the second region contains F elements, and the atomic ratio of F elements to O elements in the second region is 0.5% to 5%; due to the second structure (such as R-3m, etc.) at high voltage
  • the structural stability under the condition is not as good as the first structure with the P63mc crystal phase structure.
  • the first region includes Co, and based on the moles of transition metal elements in the first region, the mole percentage C1 of Co in the first region is greater than or equal to 90%; While the first region has better structural stability, it can further ensure that the first region has higher capacity.
  • the second region includes Co, and based on the moles of transition metal elements in the second region, the mole percentage C2 of Co in the second region is greater than or equal to 70%.
  • the first region includes element A and element M, based on the number of moles of element A in the first region, the mole percentage of element M is 0.1% to 10%, wherein element A includes Co , at least one of Mn or Ni; the element M includes at least one of Al, Ti, Ni, Nb, Mg, Ca, Zr, Zn, La, Y or Na.
  • the second region includes element A and element T, based on the mole number of element A in the second region, the mole percentage of element T is 0.1% to 1%, wherein, element A includes Co , at least one of Mn or Ni; the element T includes at least one of S, Se, Si or C.
  • the positive electrode active material satisfying at least one of the above-mentioned characteristics is beneficial to improving the structural stability of the positive electrode active material, thereby improving the cycle performance of the electrochemical device.
  • the first region includes region A1 and region A2, the second region includes region B1, and region B1 is located between region A1 and region A2; ) is arranged between the region A1 and the region A2 with the P63mc crystal phase structure, on the one hand, it can form better protection for the region B1 with a less stable crystal phase structure, and reduce the risk of its phase transition under high voltage; on the other hand
  • the region B1 can provide sufficient buffering effect for the regions A1 and A2 on both sides, reducing the overall expansion or contraction of the positive electrode material particles.
  • the second region includes region B2, and the distance D between region B2 and the surface of the positive electrode active material satisfies, D ⁇ 200nm; there are regions with crystal phase structures such as R-3m in the near surface region of the positive electrode active material B2, the stress generated on the surface of the positive electrode active material due to the expansion or contraction of the first structure can be reduced, thereby reducing the risk of cracking of the positive electrode active material particles.
  • the transition metal layers in the 3nm region of the interface layer are arranged in parallel; at this time, the interface compatibility between the first region and the second region is better, which can reduce the pressure between the first region and the second region during expansion or contraction. Risk of cracking.
  • the Dv50 of the positive electrode active material is 5 ⁇ m to 20 ⁇ m.
  • the intensity of the diffraction peak located in the range of 16° to 17.5° is I1
  • the intensity of the diffraction peak located in the range of 44.5° to 45.5° is I2
  • the intensity of the diffraction peak in the range of 17.5° to 19° is I3
  • the intensity of the diffraction peak in the range of 49.5° to 50.5° is I4, satisfying: I1+I2>I3+I4.
  • I1 and I2 correspond to the diffraction peaks of the inactive crystal plane and the active crystal plane of the first structure respectively
  • I3 and I4 respectively correspond to the diffraction peaks of the inactive crystal plane and the active crystal plane of the second structure.
  • the positive active material The crystal content of the first structure on the surface is relatively high, which can improve the surface stability of the positive electrode active material particles.
  • satisfying: I2>I4 indicates that on the surface of the positive electrode active material, there are relatively many active crystal planes of the first structure, which can improve the stability of the active surface of the positive electrode active material.
  • the second aspect of the present application provides a positive electrode sheet, which includes the positive electrode active material in any one of the foregoing embodiments.
  • the positive electrode active material provided by the present application has a lower volume expansion rate in the lithium intercalation process, so that the positive electrode sheet provided by the present application has a lower thickness change rate during the cycle of the electrochemical device.
  • the positive electrode sheet includes a positive electrode material layer, a positive electrode collector, and an intermediate layer between the positive electrode material layer and the positive electrode collector, the positive electrode material layer includes a positive electrode active material, and the intermediate layer and the positive electrode collector
  • the peeling force between them is F1
  • the peeling force between the positive electrode material layer and the intermediate layer is F2, satisfying that the smaller of F1 and F2 is greater than or equal to 10N/m. Further, the smaller of F1 and F2 is greater than or equal to 20N/m.
  • the positive electrode material layer can be further suppressed from falling off from the current collector due to the expansion and contraction of the positive electrode active material, and the structure of the positive electrode sheet can be improved. stability, which is conducive to improving the cycle performance of electrochemical devices.
  • the intermediate layer includes a binder and a conductive agent, and the mass percentage of the binder is 20% to 80% based on the mass of the intermediate layer .
  • the thickness of the positive electrode material layer is T1
  • the thickness of the intermediate layer is T2, satisfying: 10 ⁇ T1/T2 ⁇ 60.
  • the third aspect of the present application provides an electrochemical device, which includes the positive electrode active material in any of the foregoing embodiments or includes the positive electrode sheet in any of the foregoing embodiments.
  • the positive electrode active material provided by the present application has a low volume expansion rate in the process of lithium intercalation and deintercalation, and the positive electrode sheet provided by the present application has good structural stability, so that the electrochemical device provided by the present application has good cycle performance.
  • a fourth aspect of the present application provides an electronic device, which includes the electrochemical device in any one of the foregoing embodiments.
  • the electrochemical device provided by the present application has good cycle performance, so the electronic device provided by the present application has a long service life.
  • the application provides a positive electrode active material, the cross section of the positive electrode active material includes a first region and a second region, the first region has a first structure of P63mc crystal phase structure, and the second region has R-3m, P2/m or In the second structure of at least one crystal phase structure in P-3m1, the area ratio of the first region and the second region is 1.8 to 5.4.
  • the positive electrode active material provided by the present application includes both the first structure and the second structure. Since there is a certain time difference between the first structure and the second structure in the process of deintercalating lithium, the first structure and the second structure can be integrated in the deintercalation of lithium.
  • the structural changes in the process can reduce the overall strain of the positive electrode active material, so as to improve the volume expansion and shrinkage of the positive electrode active material in the process of deintercalating lithium, thereby improving the structural stability of the positive electrode sheet, and then improving the high voltage of the electrochemical device. Under the cycle performance.
  • Fig. 1 is the scanning electron micrograph of the positive electrode active material in the embodiment 1-1 of the present application.
  • Fig. 2 is the transmission electron micrograph of the positive electrode active material particle section in the embodiment 1-1 of the present application;
  • FIG. 3 is an X-ray diffraction pattern of the positive electrode active material in Example 1-1 of the present application.
  • a lithium-ion battery is used as an example of an electrochemical device to explain the present application, but the electrochemical device of the present application is not limited to the lithium-ion battery.
  • the first aspect of the present application provides a positive electrode active material, wherein the cross section of the positive electrode active material includes a first region and a second region, the first region has a first structure of P63mc crystal phase structure, and the second region has a R- In the second structure of at least one crystal phase structure of 3m, P2/m or P-3m1, the area ratio of the first region to the second region is 1.8 to 5.4.
  • the positive electrode active material provided by the present application includes both the first structure and the second structure.
  • the thickness change rate of the positive electrode sheet refers to the thickness change rate of the positive electrode sheet during the cycle of the electrochemical device.
  • the area ratio of the first region and the second region may be 1.8, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.4 or any range therebetween.
  • the inventors of the present application have found that when the area ratio of the first region and the second region is too small (for example, less than 1.8), the structural stability of the positive electrode active material at high voltage is reduced, thereby affecting the performance of the electrochemical device. cycle performance.
  • the area ratio of the first region and the second region is too large (for example, greater than 5.4), the volume expansion or shrinkage of the positive electrode active material in the lithium intercalation process increases, which affects the structural stability of the positive electrode sheet and the electrochemical device. Cycling performance at high voltage.
  • the second region comprises F.
  • the structural stability of the second structure (such as R-3m, etc.) under high voltage is not as good as that of the first structure with the P63mc crystal phase structure
  • fluorine element by introducing fluorine element, its oxygen skeleton can be stabilized and the oxygen displacement can be reduced. phase transition, thereby reducing the risk of its premature degradation leading to a reduction in the overall performance of the cathode material.
  • the atomic number ratio of F and O in the second region is 0.5% to 5%.
  • the first region includes Co, and based on the moles of transition metal elements in the first region, the mole percentage C1 of Co in the first region is greater than or equal to 90%; for example, in the first region
  • the molar percentage of Co can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or any range therebetween. In this case, while ensuring that the first region has better structural stability, it can further ensure that the first region has a higher capacity.
  • the second region includes Co, and based on the moles of transition metal elements in the second region, the mole percentage of Co in the second region is greater than or equal to 70%.
  • the mole percentage of Co in the second region can be 70%, 75%, 80%, 85%, 90%, 95%, or any range therebetween.
  • ⁇ 25% at this time, the compatibility between the first region and the second region can be improved, thereby ensuring that the overall positive electrode active material is under high voltage structural stability.
  • the first region includes element A and element M, based on the number of moles of element A in the first region, the mole percentage of element M is 0.1% to 10%, wherein element A includes Co , at least one of Mn or Ni; the element M includes at least one of Al, Ti, Ni, Nb, Mg, Ca, Zr, Zn, La, Y or Na.
  • the second region includes element A and element T, and based on the moles of elements A and T in the second region, the mole percentage of element T is 0.1% to 1%, wherein element A includes At least one of Co, Mn or Ni; the element T includes at least one of S, Se, Si or C.
  • the positive electrode active material satisfying at least one of the above-mentioned characteristics is beneficial to improving the structural stability of the positive electrode active material, thereby improving the cycle performance of the electrochemical device.
  • the mole percentage of element M is 0.1%, 0.5%, 1%, 2%, 5%, 8%, or any range therebetween.
  • the introduction of element M can form doping with Co, improve the stability of the first region structure, effectively improve the problem of the collapse of the first region structure during the process of lithium intercalation and deintercalation, thereby improving the stability of the overall structure of the positive electrode active material .
  • the mole percentage of the element T is 0.1%, 0.3%, 0.5%, 0.7%, 0.8%, or any range therebetween.
  • the introduction of element T can make up for some oxygen defects and improve the local structural stability; in addition, element T can be used as a sacrificial agent to preferentially consume active oxygen, thereby inhibiting the occurrence of uncontrollable oxidation reactions and improving System stability.
  • the first region includes region A1 and region A2, the second region includes region B1, and region B1 is located between region A1 and region A2; ) is arranged between the region A1 and the region A2 with the P63mc crystal phase structure, on the one hand, it can form better protection for the region B1 with a less stable crystal phase structure, and reduce the risk of its phase transition under high voltage; on the other hand
  • the region B1 can provide sufficient buffering effect for the regions A1 and A2 on both sides, reducing the overall expansion or contraction of the positive electrode material particles.
  • the second region includes region B2, and the distance D between region B2 and the surface of the positive electrode active material satisfies, D ⁇ 200nm; there are regions with crystal phase structures such as R-3m in the near surface region of the positive electrode active material B2, the stress generated on the surface of the positive electrode active material due to the expansion of the first structure can be reduced, thereby reducing the risk of cracking of the particles of the positive electrode active material.
  • the transition metal layers in the 3nm region of the interface layer are arranged in parallel; at this time, the interface compatibility between the first region and the second region is better, which can reduce the cracking between the first region and the second region during the expansion and contraction process risks of.
  • the Dv50 of the positive electrode active material is 5 ⁇ m to 20 ⁇ m.
  • the Dv50 of the positive electrode active material may be 5 ⁇ m, 8 ⁇ m, 10 ⁇ m, 12 ⁇ m, 15 ⁇ m, 17 ⁇ m, 20 ⁇ m or any range therebetween.
  • the Dv50 of the positive electrode active material is within the above range, side reactions with the electrolyte can be reduced, and the cycle performance of the electrochemical device can be improved. At the same time, it can have sufficient active surface to ensure the kinetic performance of the electrochemical device.
  • the intensity of the diffraction peak located in the range of 16° to 17.5° is I1
  • the intensity of the diffraction peak located in the range of 44.5° to 45.5° is I2
  • the intensity of the diffraction peak in the range of 17.5° to 19° is I3
  • the intensity of the diffraction peak in the range of 49.5° to 50.5° is I4, satisfying: I1+I2>I3+I4.
  • the crystal content of the first structure on the surface of the positive electrode active material is relatively high, which can improve the surface stability of the positive electrode active material particles.
  • the diffraction peaks in the range of 16° to 17.5° and the diffraction peaks in the range of 44.5° to 45.5° are the diffraction peaks corresponding to the first structure
  • the diffraction peaks in the range of 17.5° to 19° and the diffraction peaks in the range of 49.5° to 50.5° are Diffraction peaks corresponding to the second structure.
  • satisfying: I2>I4 indicates that on the surface of the positive electrode active material, there are relatively many active crystal planes of the first structure, which can improve the stability of the active surface of the positive electrode active material.
  • the preparation method of the positive electrode active material may include but not limited to the following steps: mixing the raw materials of the first structure, first passing through the common Prepare the first precursor by precipitation method; mix the raw materials of the second structure, and prepare the second precursor by co-precipitation method; and selectively calcinate the first precursor or the second precursor, and then mix and calcinate to obtain the positive electrode active material .
  • the present application has no special limitation on the calcination temperature and time for obtaining the first precursor or the second precursor, as long as the purpose of the present application can be achieved, for example, the calcination temperature is 500-1100°C, and the calcination time is 1-12h.
  • the present application has no special limitation on the temperature and time of calcination after mixing the first precursor and the second precursor, as long as the purpose of the present application can be achieved, for example, the calcination temperature is 500-1100°C, and the calcination time is 1-12h.
  • raw materials for the first structure may include, but are not limited to, Co(NO 3 ) 2 , Ni(NO 3 ) 2 , CoCl 2 , CoSO 4 , Co(CH 3 COO) 2 , NiCl 2 , NiSO 4 , or Ni(CH 3 COO) at least one of 2 .
  • raw materials for the second structure may include, but are not limited to, Co(NO 3 ) 2 , MnSO 4 , Ni 2 SO 4 , CoCl 2 , CoSO 4 , Co(CH 3 COO) 2 , NiCl 2 , NiSO 4 , Ni(CH At least one of 3 COO) 2 , Ni(NO 3 ) 2 , MnCl 2 , MnSO 4 , Mn(CH 3 COO) 2 or Mn(NO 3 ) 2 .
  • the present application has no special restrictions on the method of introducing the above-mentioned element M or element T into the positive electrode active material, as long as the purpose of the application can be achieved, for example, the compound containing element M is added as the raw material of the first structure and then the first Precursor, or add it when calcining the first precursor; add the compound containing element T as the raw material of the second structure and then prepare the second precursor, or add it when calcining the second precursor.
  • the present application has no particular limitation on the compound containing the element M and the compound containing the element T, as long as the purpose of the present application can be achieved.
  • compounds containing the element M may include, but are not limited to, Al(NO 3 ) 3 , TiO 2 , Al 2 O 3 , MgO, Y 2 O 3 , La 2 O 3 , Nb 2 O 5 or W 2 O 3 at least one.
  • the compound containing the element T may include, but not limited to, at least one of NH 4 F, Se powder, or S powder.
  • the positive electrode active material includes Li x Na z Co 1-y X y O 2- ⁇ R ⁇ , wherein the element X includes Mn, Ni, Nb, B, Mg, Al, Si, P, S, Ti , at least one of Cr, Fe, Cu, Zn, Ga, Y, Zr, Mo, Ag, W, In, Sn, Pb, Sb, Se or Ce, R is halogen, 0.6 ⁇ x ⁇ 1.2, 0 ⁇ y ⁇ 0.15, 0 ⁇ z ⁇ 0.03, 0 ⁇ 0.1.
  • the second aspect of the present application provides a positive electrode sheet, which includes the positive electrode active material in any one of the foregoing embodiments.
  • the positive electrode active material provided by the present application has relatively low volume expansion or contraction during the lithium intercalation process, so that the positive electrode sheet provided by the present application has a low thickness change rate during the cycle of the electrochemical device.
  • the positive electrode sheet includes a positive electrode material layer, a positive electrode collector, and an intermediate layer between the positive electrode material layer and the positive electrode collector, the positive electrode material layer includes a positive electrode active material, and the intermediate layer and the positive electrode collector
  • the peeling force between them is F1
  • the peeling force between the positive electrode material layer and the intermediate layer is F2, satisfying that the smaller of F1 and F2 is greater than or equal to 10N/m.
  • the smaller of F1 and F2 is greater than or equal to 20N/m, the smaller of the peeling force F1 between the intermediate layer and the positive electrode current collector and the peeling force F2 between the positive electrode material layer and the intermediate layer is in the above Within the range, it shows that there is good adhesion between the positive electrode material layer and the intermediate layer, which can reduce the risk of the positive electrode material layer falling off the surface of the current collector, and is conducive to improving the structural stability of the positive electrode sheet, thereby facilitating the improvement of electrochemical devices. cycle performance.
  • the intermediate layer includes a binder and a conductive agent, and based on the quality of the intermediate layer, the mass percentage of the binder is 20% to 80%; for example, the mass percent of the binder It can be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 75%, 70%, 75%, or any range therebetween.
  • the mass percentage of the binder is 20% to 80%; for example, the mass percent of the binder It can be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 75%, 70%, 75%, or any range therebetween.
  • the binder may include but not limited to polyvinylidene fluoride, copolymer of vinylidene fluoride-hexafluoropropylene, polyamide , polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene or polyhexafluoropropylene.
  • the intermediate layer includes a conductive agent to facilitate electron conduction between the positive electrode material layer and the positive electrode current collector layer.
  • the present application is not particularly limited to the conductive agent, as long as the purpose of the application can be realized, for example, it can include but not limited to conductive carbon black (Super P), carbon nanotubes (CNTs), carbon fiber, flake graphite, Ketjen black, graphene , at least one of metallic materials or conductive polymers.
  • the aforementioned carbon nanotubes may include, but are not limited to, single-walled carbon nanotubes and/or multi-walled carbon nanotubes.
  • the aforementioned carbon fibers may include, but are not limited to, vapor grown carbon fibers (VGCF) and/or carbon nanofibers.
  • the above metal material may include but not limited to metal powder and/or metal fiber, specifically, the metal may include but not limited to at least one of copper, nickel, aluminum or silver.
  • the aforementioned conductive polymer may include but not limited to at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene or polypyrrole.
  • the thickness of the positive electrode material layer is T1
  • the thickness of the intermediate layer is T2, satisfying: 10 ⁇ T1/T2 ⁇ 60.
  • the present application has no special limitation on the thickness T1 of the positive electrode material layer and the thickness T2 of the intermediate layer, as long as the purpose of the present application can be achieved, for example, the thickness T1 of the positive electrode material layer is 40 ⁇ m to 60 ⁇ m, and the thickness T2 of the intermediate layer is 1 ⁇ m to 4 ⁇ m.
  • the thickness T1 of the positive electrode material layer and the thickness T2 of the intermediate layer within the above range, it is beneficial to obtain a positive electrode sheet with good structural stability, thereby improving the cycle performance of the electrochemical device.
  • the preparation method of the positive electrode sheet may include but not limited to the following steps: coating the slurry of the intermediate layer on the positive electrode assembly One surface of the fluid, after the drying treatment, the slurry of the positive electrode material layer is continued to be coated on the intermediate layer, and the positive electrode sheet with the intermediate layer and the positive electrode material layer coated on one side is obtained after the drying treatment. Repeat the above steps to obtain a positive electrode sheet coated with an intermediate layer and a positive electrode material layer on both sides.
  • the above-mentioned "surface” may be the entire area of the positive electrode current collector, or a partial area of the positive electrode current collector. This application is not particularly limited, as long as the purpose of this application can be achieved.
  • the third aspect of the present application provides an electrochemical device, which includes the positive electrode active material in any of the foregoing embodiments or includes the positive electrode sheet in any of the foregoing embodiments.
  • the positive electrode active material provided by the present application has a low volume expansion rate in the process of lithium intercalation and deintercalation, and the positive electrode sheet provided by the present application has good structural stability, so that the electrochemical device provided by the present application has good cycle performance.
  • the electrochemical device of the present application also includes a negative electrode sheet.
  • the negative electrode sheet usually includes a negative electrode collector and a negative electrode material layer arranged on the surface of the negative electrode collector.
  • the application has no special restrictions on the negative electrode collector, as long as the purpose of the application can be achieved.
  • it may include but not limited to copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam or composite current collectors.
  • the thickness of the negative electrode collector there is no particular limitation on the thickness of the negative electrode collector, as long as the purpose of the present application can be achieved, for example, the thickness is 4 ⁇ m to 12 ⁇ m.
  • the negative electrode material layer may be provided on one surface in the thickness direction of the negative electrode current collector, or on two surfaces in the thickness direction of the negative electrode current collector. It should be noted that the "surface” here may be the entire area of the negative electrode collector, or a partial area of the negative electrode collector. This application is not particularly limited, as long as the purpose of this application can be achieved.
  • the negative electrode material layer includes negative electrode active materials, wherein the negative electrode active material is not particularly limited, as long as the purpose of the application can be achieved, for example, it can include but not limited to natural graphite, artificial graphite, mesophase micro carbon spheres, hard Carbon, soft carbon, silicon, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO 2 , lithiated TiO 2 -Li 4 Ti 5 O 12 or Li with spinel structure - at least one of Al alloys.
  • the negative electrode active material is not particularly limited, as long as the purpose of the application can be achieved, for example, it can include but not limited to natural graphite, artificial graphite, mesophase micro carbon spheres, hard Carbon, soft carbon, silicon, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO 2 , lithiated TiO 2 -Li 4 Ti 5 O 12 or Li with spinel structure
  • the negative electrode material layer may also include a conductive agent.
  • the present application has no special limitation on the conductive agent, as long as the purpose of the present application can be achieved, for example, it may include but not limited to at least one of the above-mentioned conductive agents.
  • the negative electrode material layer may also include a binder, and the present application has no special restrictions on the binder, as long as the purpose of the application can be achieved, for example, it may include but not limited to at least one of the above-mentioned binders .
  • the negative electrode sheet may further include a conductive layer, and the conductive layer is located between the negative electrode current collector and the negative electrode material layer.
  • the present application has no particular limitation on the composition of the conductive layer, which may be a commonly used conductive layer in the field, and the conductive layer may include but not limited to the above-mentioned conductive agent and the above-mentioned binder.
  • the electrochemical device of the present application also includes a separator, which is not particularly limited in the present application, as long as the purpose of the application can be achieved, such as but not limited to polyethylene (PE), polypropylene (PP), polytetrafluoroethylene Ethylene-based polyolefin (PO) separator, polyester film (such as polyethylene terephthalate (PET) film), cellulose film, polyimide film (PI), polyamide film (PA) , spandex, aramid film, woven film, nonwoven film (non-woven fabric), microporous film, composite film, separator paper, rolled film or spinning film, preferably PP.
  • a separator which is not particularly limited in the present application, as long as the purpose of the application can be achieved, such as but not limited to polyethylene (PE), polypropylene (PP), polytetrafluoroethylene Ethylene-based polyolefin (PO) separator, polyester film (such as polyethylene terephthalate (PET) film),
  • the separator of the present application may have a porous structure, and the pore size is not particularly limited as long as the purpose of the present application can be achieved, for example, the pore size may be 0.01 ⁇ m to 1 ⁇ m.
  • the thickness of the isolation film is not particularly limited, as long as the purpose of the present application can be achieved, for example, the thickness may be 5 ⁇ m to 500 ⁇ m.
  • a separator may include a substrate layer and a surface treatment layer.
  • the substrate layer can be a non-woven fabric, film or composite film with a porous structure, and the material of the substrate layer can include but not limited to polyethylene, polypropylene, polyethylene terephthalate or polyimide at least one.
  • a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric, or a polypropylene-polyethylene-polypropylene porous composite film may be used.
  • at least one surface of the substrate layer is provided with a surface treatment layer, and the surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic material.
  • the inorganic material layer may include but not limited to inorganic particles and inorganic material layer binder.
  • the application has no special limitation on the inorganic particles, as long as the purpose of the application can be achieved.
  • it may include but not limited to alumina, silicon oxide, Magnesium oxide, titanium oxide, hafnium oxide, tin oxide, cerium oxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide or at least one of barium sulfate.
  • the present application has no particular limitation on the inorganic layer binder, for example, it may include but not limited to polyvinylidene fluoride, copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, At least one of polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethylmethacrylate, polytetrafluoroethylene or polyhexafluoropropylene.
  • polyvinylidene fluoride copolymer of vinylidene fluoride-hexafluoropropylene
  • polyamide polyacrylonitrile
  • polyacrylate polyacrylic acid
  • the polymer layer contains a polymer, and the polymer material may include but not limited to polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinyl pyrrolidone, polyvinyl ether, polyvinylidene fluoride At least one of ethylene or poly(vinylidene fluoride-hexafluoropropylene).
  • the electrochemical device of the present application also includes an electrolyte, which is not particularly limited in the present application, as long as the purpose of the present application can be achieved, for example, the electrolyte may include a non-aqueous solvent and a lithium salt.
  • the present application has no special limitation on the non-aqueous solvent, as long as the purpose of the present application can be achieved, for example, it may include but not limited to at least one of carbonate compounds, carboxylate compounds, ether compounds or other organic solvents.
  • the above-mentioned carbonate compound may include but not limited to at least one of a chain carbonate compound, a cyclic carbonate compound or a fluorocarbonate compound.
  • Above-mentioned chain carbonate compound can include but not limited to dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethylene propyl carbonate (EPC) or at least one of methyl ethyl carbonate (MEC).
  • the above-mentioned cyclic carbonate may include but not limited to at least one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC) or vinylethylene carbonate (VEC).
  • Fluorocarbonate compounds may include, but are not limited to, fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate Ethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2- At least one of difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethylethylene carbonate.
  • FEC fluoroethylene carbonate
  • 1,2-difluoroethylene carbonate 1,1-difluoroethylene carbonate
  • carboxylate compounds may include but are not limited to methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, ⁇ -butyl At least one of lactone, decanolactone, valerolactone, mevalonolactone or caprolactone.
  • the aforementioned ether compounds may include, but are not limited to, dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxy At least one of methoxyethane, 2-methyltetrahydrofuran or tetrahydrofuran.
  • the above-mentioned other organic solvents may include but not limited to dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2- At least one of pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate or phosphoric acid ester.
  • This application has no special restrictions on lithium salts, as long as the purpose of this application can be achieved, for example, it may include but not limited to LiPF 6 , LiBF 4 , LiAsF 6 , LiClO 4 , LiB(C 6 H 5 ) 4 , LiCH 3 SO 3. At least one of LiCF 3 SO 3 , LiN(SO 2 CF 3 ) 2 , LiC(SO 2 CF 3 ) 3 , LiSiF 6 , LiBOB or lithium difluoroborate.
  • the lithium salt comprises LiPF 6 .
  • the electrochemical device of the present application is not particularly limited, and it may include any device that undergoes an electrochemical reaction.
  • the electrochemical device may include, but is not limited to, a lithium metal secondary battery, a lithium ion secondary battery (lithium ion battery), a lithium polymer secondary battery, or a lithium ion polymer secondary battery, among others.
  • the preparation process of electrochemical devices is well known to those skilled in the art, and the present application is not particularly limited.
  • it may include but not limited to the following steps: stack the positive electrode sheet, separator and negative electrode sheet in sequence, and as required Winding, folding and other operations to obtain the electrode assembly with a winding structure, put the electrode assembly into the packaging bag, inject the electrolyte solution into the packaging bag and seal it to obtain an electrochemical device; or, put the positive electrode sheet, separator and negative electrode
  • the pole pieces are stacked in order, and then the four corners of the entire laminated structure are fixed with adhesive tape to obtain the electrode assembly of the laminated structure.
  • the electrode assembly is placed in the packaging bag, and the electrolyte is injected into the packaging bag and sealed to obtain an electrochemical device.
  • overcurrent prevention elements, guide plates, etc. can also be placed in the packaging bag as needed, so as to prevent pressure rise and overcharge and discharge inside the electrochemical device.
  • a fourth aspect of the present application provides an electronic device, which includes the electrochemical device in any one of the foregoing embodiments.
  • the electrochemical device provided by the present application has good cycle performance, so the electronic device provided by the present application has a long service life.
  • the electronic device of the present application is not particularly limited, and it may be used in any electronic device known in the prior art.
  • electronic devices may include, but are not limited to, notebook computers, pen-based computers, mobile computers, e-book players, cellular phones, portable fax machines, portable copiers, portable printers, headsets, VCRs, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic organizers, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, Lighting appliances, toys, game consoles, clocks, electric tools, flashlights, cameras, large household storage batteries and lithium-ion capacitors, etc.
  • An inductively coupled plasma spectrometer was used to test the contents of different elements in the positive electrode active material.
  • the lithium-ion battery is fully placed below 3.5V under the current density of 30mA/cm 2 , and after standing for 10min, the positive pole piece is disassembled in the glove box; the positive pole piece is transferred to a scanning electron microscope equipped with a focused ion beam (Model: FEI Vion Plasma FIB) cavity, processing samples that can be used for transmission scanning electron microscope (STEM, model: FEI Titan3 G2 60-300) analysis, the surface of the sample is required to be protected by Pt, and processed with Ga ion beam, the thickness of the sample is not More than 100nm; and cleaning in low voltage mode to remove residual surface of sample processing.
  • the sample is observed under STEM, and the X-ray energy spectrum analysis (EDS) function is used to collect data at a suitable magnification to obtain the element content in the first region or the second region of the positive electrode active material. Collect at least 3 different locations and take the average as the final result.
  • EDS X-ray energy spectrum analysis
  • the surface interface cutting and stretching system (model: Model: SAICAS-DN) is used for testing; first take a flat pole piece of 2cm ⁇ 0.5cm, place it on the sample stage in the instrument cavity, and fix the bottom. Then the blade moves at a speed of 0.2 mm/min, reads the measured value, and determines the smaller one between the peeling force F1 between the intermediate layer and the positive electrode current collector and the peeling force F2 between the positive electrode material layer and the intermediate layer as Peel force F.
  • FIG. 1 it is a scanning electron micrograph of the positive electrode active material in Example 1-1. It can be seen from the figure that the particles of the positive electrode active material in Example 1-1 are mainly in the form of flakes.
  • Fig. 2 is the transmission electron microscope photograph of the particle cross section of positive electrode active material in the embodiment 1-1, wherein, the crystal phase structure of area A1 and area A2 is P63mc, the crystal phase structure of area B1 is R-3m, it can be seen that the area B1 is located between area A1 and area A2, and there is an interface layer between area B1 and area A1 and area A2, along the direction perpendicular to the interface layer between area B1 and area A1, in the area 3nm away from the interface layer in area B1 The transition metal layer in the region A1 and the transition metal layer in the region 3 nm away from the interface layer are arranged in parallel.
  • the region B1 includes a region whose distance from the surface of the positive electrode active material is less than or equal to 200 nm, thereby reducing the stress on the surface of the positive electrode active material due to the expansion or contraction of the first structure, thereby reducing the risk of breaking the positive electrode active material particles.
  • FIG 3 it is the X-ray diffraction spectrum of the positive electrode active material in embodiment 1-1, and the intensity I1 of the diffraction peak of 16 ° to 17.5 ° range is 100, and the intensity I2 of the diffraction peak of 44.5 ° to 45.5 ° range
  • the intensity I3 of the diffraction peak in the range of 17.5° to 19° is 30, and the intensity I3 of the diffraction peak in the range of 49.5° to 50.5° is 23, satisfying: I1+I2>I3+I4. At the same time, I2>I4.
  • the negative active material artificial graphite Mix the negative active material artificial graphite, the binder styrene-butadiene rubber (SBR), and the thickener sodium carboxymethylcellulose (CMC) according to the mass ratio of 97:2:1, add deionized water, and work in a vacuum mixer Stir evenly to obtain the negative electrode slurry, wherein the solid content of the negative electrode slurry is 75%.
  • Copper foil is used as the negative electrode collector, the negative electrode slurry is evenly coated on the negative electrode collector, and the negative electrode sheet is obtained after drying, cold pressing and cutting.
  • a porous PE film with a thickness of 7 ⁇ m was used.
  • the above-prepared positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, and wound to obtain an electrode assembly.
  • Example 1-2 and Example 1-3 except that Co, Mn and Ni molar ratio are adjusted to 90:5:5, 70:15:15 respectively in the step (2) of ⁇ preparation of positive electrode active material> , and the rest are identical to Example 1-1.
  • Example 1-5 in addition to adjusting the mass ratios of the first precursor and the second precursor to 1.5:1 and 4.5:1 respectively in step (3) of ⁇ Preparation of Positive Electrode Active Material> Other than that, the others are the same as in Example 1-1.
  • Example 2-1 except that an intermediate layer is first coated on the surface of the positive electrode collector according to the following steps, the rest is the same as that of Example 1-1.
  • the binder PVDF, conductive carbon black (Super P), and carbon nanotubes (CNT) were mixed according to a mass ratio of 35:55:10, NMP was added, and stirred evenly under the action of a vacuum mixer to obtain a middle layer slurry.
  • the intermediate layer slurry is uniformly coated on the surface of the positive electrode current collector, and the coating amount is 0.002 mg/mm 2 , and the intermediate layer is formed on the surface of the positive electrode current collector after drying.
  • the thickness of the positive electrode material layer in the positive electrode sheet is 54 ⁇ m, and the thickness of the intermediate layer is 1 ⁇ m.
  • Example 2-2 except that the mass ratios of binder PVDF, conductive carbon black (Super P), and carbon nanotubes (CNT) are 60:35:5, the thickness of the positive electrode material layer is 42 ⁇ m, and the thickness of the intermediate layer is 3 ⁇ m Other than that, the others are the same as in Example 2-1.
  • Example 2-3 except that the mass ratio of binder PVDF, conductive carbon black (Super P), and carbon nanotube (CNT) is 60:35:5, the thickness of the positive electrode material layer is 42 ⁇ m, and the thickness of the intermediate layer is 2 ⁇ m Other than that, the others are the same as in Example 2-1.
  • Example 3-1 to Example 3-4 except that the NH 4 F added in the step (2) of ⁇ Preparation of Positive Electrode Active Material> is 1%, 0.6%, 6%, and 10% of Co molar amounts respectively, The rest are the same as in Example 1-1.
  • Example 4-1 except that steps (1) and (2) in ⁇ Preparation of Positive Electrode Active Material> are carried out according to the following steps, all the other are the same as Example 1-1:
  • the calcination temperature is 600°C and the calcination time is 3h.
  • the mole percent content of Ti in TiO2 is 0.1% based on the total moles of Co and Ni.
  • Example 4-2 except that the molar ratio of Co, Ni and Al in step (1) of ⁇ Preparation of Positive Electrode Active Material> is 95:5:0.1, the rest is the same as Example 3-1.
  • Example 4-3 except that the molar ratio of Co, Ni and Al in step (1) of ⁇ Preparation of Positive Electrode Active Material> is 95:5:10, the rest is the same as Example 3-1.
  • Example 4-4 except that Se in the total molar amount of Co, Mn and Ni is added in step (2) of ⁇ Preparation of Positive Electrode Active Material>, the rest is the same as Example 3-1.
  • Example 4-5 except that Se in the total molar mass of Co, Mn and Ni was added in step (2) of ⁇ Preparation of Positive Electrode Active Material>, the rest was the same as Example 3-1.
  • Example 1-1 In Comparative Example 1-2, except that the first precursor prepared by step (1) was used in ⁇ Preparation of positive electrode active material> to prepare the positive electrode active material according to the following steps, the rest were the same as in Example 1-1:
  • the first precursor was mixed with Na 2 CO 3 at a transition metal to Na molar ratio of 1:1.05, and then calcined in an air atmosphere to obtain an intermediate product.
  • the calcination temperature was 1000°C
  • the calcination time was 12 h
  • the air flow rate was 8 L/ min.
  • the intermediate product and lithium nitrate were mixed uniformly according to the mass ratio of 1:3, and reacted at 260°C for 6 hours, then washed with water and dried, and the product was ground and sieved to obtain the positive electrode active material.
  • Example 1-1 to Example 1-4 when C1-C2 ⁇ 25%, the obtained lithium ion battery has better cycle performance.
  • the possible reason is that the difference in Co content between the first region and the second region is small, which can improve the compatibility between the first region and the second region, thereby ensuring the overall structural stability of the positive electrode active material under high voltage. sex.
  • Example 1-1 From Example 1-1, Example 2-1 to Example 2-3, it can be seen that when the peeling force between the intermediate layer and the positive electrode current collector and the peeling force between the positive electrode material layer and the intermediate layer are smaller When F is greater than or equal to 20N/m, there is stronger cohesive force between the intermediate layer in the positive electrode sheet and the positive electrode current collector and the positive electrode material layer, which can further improve the stability of the positive electrode material layer in the positive electrode sheet. Thereby improving the cycle performance of lithium-ion batteries.
  • Example 3-1 to Example 3-4 From Example 1-1, Example 3-1 to Example 3-4, it can be seen that the atomic number ratio of F and O in the second region has more excellent cycle stability in the range of 0.5% to 5%, which is due to The structural stability of the second structure (such as R-3m, etc.) under high voltage is not as good as that of the first structure with the P63mc crystal phase structure.
  • fluorine By introducing fluorine, it can stabilize its oxygen skeleton and reduce the phase transition caused by oxygen displacement, thereby reducing the Its premature degradation leads to the risk of lower overall performance of the cathode active material.
  • Example 4-1 to Example 4-5 From Example 1-1, Example 4-1 to Example 4-5, it can be seen that the element M (such as Al, Ti) is further doped in the first structure, and the element T (such as Al, Ti) is doped in the second structure. Se), which can further improve the structural stability of the first structure and the second structure under high voltage, thereby improving the high-voltage cycle performance of the lithium-ion battery.
  • element M such as Al, Ti
  • T such as Al, Ti

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Abstract

本申请提供了一种正极活性材料、正极极片、包含该正极极片的电化学装置和电子装置，正极活性材料的截面中包括第一区域和第二区域，第一区域具有P63mc晶相结构的第一结构，第二区域具有R-3m、P2/m或P-3m1中的至少一种晶相结构的第二结构，第一区域和第二区域的面积比为1.8至5.4。通过调控第一区域和第二区域的晶相结构和面积比，能够改善正极活性材料在脱嵌锂过程中的体积膨胀和收缩问题，从而降低正极极片的厚度变化率、提高电化学装置在高电压下的循环性能。

Description

正极活性材料、正极极片、包含该正极极片的电化学装置和电子装置 技术领域
本申请涉及电化学领域，特别是涉及一种正极活性材料、正极极片、包含该正极极片的电化学装置和电子装置。
背景技术
锂离子电池由于具有高能量密度、长循环寿命及无记忆效应等优点而被广泛应用于穿戴设备、智能手机、无人机、电动汽车及大型储能设备等领域，已成为当今世界最具发展潜力的新型绿色化学电源。为了满足人们对锂离子电池能量密度越来越高的要求，提高锂离子电池的工作电压是一种可行的方式，但同时也对锂离子电池在高电压下的循环性能提出了更高的要求。
发明内容
本申请的目的在于提供一种正极活性材料、正极极片、包含该正极极片的电化学装置和电子装置，以提高电化学装置在高电压下的循环性能。
本申请的第一方面提供了一种正极活性材料，其中，正极活性材料的截面中包括第一区域和第二区域，第一区域具有P63mc晶相结构的第一结构，第二区域具有R-3m、P2/m或P-3m1中的至少一种晶相结构的第二结构，第一区域和第二区域的面积比为1.8至5.4。本申请的发明人研究发现：P63mc晶相结构虽然具备较好的结构稳定性，不易发生由原子迁移引起的结构相变，能够在高电压下维持较好的稳定性，但其在充放电过程中，由于面面相对而产生较强的排斥，从而产生较大的膨胀或收缩，这将不利于正极极片上正极材料层的稳定，导致电化学装置在高电压下的循环性能降低；此时，引入第二结构(如R-3m等)，其本身的膨胀或收缩程度较低，并且由于其与P63mc晶相结构存在一定的脱锂时间差，从而可以有效降低正极活性材料颗粒整体的膨胀或收缩。因此，通过调控第一区域和第二区域的晶相结构和面积比，能够改善正极活性材料在脱嵌锂过程中的体积膨胀和收缩问题，从而提高电化学装置在高电压下的循环性能。
在本申请的一些实施方案中，第二区域包含F元素，第二区域中F元素与O元素的原子数比为0.5％至5％；由于第二结构(如R-3m等)在高电压下的结构稳定性不如具有P63mc晶相结构的第一结构，通过引入氟元素，可以稳定其氧骨架，减少氧位移引发的相变，进而可以极大提升正极活性材料整体在高电压下的结构稳定性。
在本申请的一些实施方案中，第一区域包括Co，基于第一区域中过渡金属元素的摩尔数，第一区域中Co的摩尔百分含量C1大于或等于90％；此时，在保证第一区域具有较好的结构稳定性的同时，能够进一步保证第一区域具有较高的容量。
在本申请的一些实施方案中，第二区域包括Co，基于第二区域中过渡金属元素的摩尔数，第二区域中Co的摩尔百分含量C2大于或等于70％。
进一步地，在本申请的一些实施方案中，|C1-C2|≤25％，此时，能够提高第一区域和第二区域之间的相容性，进而保证正极活性材料整体在高电压下的结构稳定性。
在本申请的一些实施方案中，第一区域包括元素A和元素M，基于第一区域中元素A的摩尔数，元素M的摩尔百分含量为0.1％至10％，其中，元素A包括Co、Mn或Ni中的至少一种；元素M包括Al、Ti、Ni、Nb、Mg、Ca、Zr、Zn、La、Y或Na中的至少一种。在本申请的一些实施方案中，第二区域包括元素A和元素T，基于第二区域中元素A的摩尔数，元素T的摩尔百分含量为0.1％至1％，其中，元素A包括Co、Mn或Ni中的至少一种；元素T包括S、Se、Si或C中的至少一种。正极活性材料满足上述特征中的至少一者，均有利于提高正极活性材料的结构稳定性，进而提高电化学装置的循环性能。
在本申请的一些实施方案中，第一区域包括区域A1和区域A2，第二区域包括区域B1，区域B1位于区域A1和区域A2之间；通过将区域B1(具有R-3m等晶相结构)设置在具有P63mc晶相结构的区域A1和区域A2之间，一方面，能够对晶相结构较不稳定的区域B1形成更好的保护，降低其在高电压下相变的风险；另一方面，区域B1能够为两侧的区域A1和区域A2提供充分的缓冲作用，降低正极材料颗粒整体的膨胀或收缩。
在本申请的一些实施方案中，第二区域包括区域B2，区域B2与正极活性材料表面的距离D满足，D≤200nm；在正极活性材料近表面区域存在具有R-3m等晶相结构的区域B2，能够降低正极活性材料表面由于第一结构膨胀或收缩所产生的应力，进而降低正极活性材料颗粒破裂的风险。
在本申请的一些实施方案中，第一区域和第二区域之间具有界面层，沿垂直界面层的方向，第一区域中距离界面层3nm的区域中的过渡金属层和第二区域中距离界面层3nm的区域中的过渡金属层呈平行排列；此时，第一区域和第二区域之间界面相容性较好，能够降低在膨胀或收缩过程中第一区域和第二区域之间开裂的风险。
在本申请的一些实施方案中，正极活性材料的Dv50为5μm至20μm。
在本申请的一些实施方案中，在正极活性材料的XRD谱图中，位于16°至17.5°范围 的衍射峰的强度为I1，位于44.5°至45.5°范围的衍射峰的强度为I2；位于17.5°至19°范围的衍射峰的强度为I3，位于49.5°至50.5°范围的衍射峰的强度为I4，满足：I1+I2>I3+I4。其中，I1和I2分别对应第一结构的非活性晶面和活性晶面的衍射峰，I3和I4分别对应第二结构的非活性晶面和活性晶面的衍射峰，此时，正极活性材料表面的第一结构的晶体含量占比较高，能够提高正极活性材料颗粒的表面稳定性。进一步地，满足：I2>I4，表明在正极活性材料表面，第一结构的活性晶面相对较多，能够提高正极活性材料活性表面的稳定性。
本申请的第二方面提供了一种正极极片，其包括前述任一实施方案中的正极活性材料。本申请提供的正极活性材料在脱嵌锂过程中具有较低的体积膨胀率，从而本申请提供的正极极片在电化学装置循环过程中则具有较低的厚度变化率。
在本申请的一些实施方案中，正极极片包括正极材料层、正极集流体和位于正极材料层和正极集流体之间的中间层，正极材料层包括正极活性材料，中间层与正极集流体之间的剥离力为F1，正极材料层与中间层之间的剥离力为F2，满足：F1和F2中的较小者大于或等于10N/m。进一步地，F1和F2中的较小者大于或等于20N/m，此时，能够进一步抑制由于正极活性材料的膨胀和收缩导致的正极材料层从集流体上的脱落，提高正极极片的结构稳定性，从而有利于提高电化学装置的循环性能。
在本申请的一些实施方案中，中间层包括粘结剂和导电剂，基于中间层的质量，粘结剂的质量百分含量为20％至80％ 。
在本申请的一些实施方案中，正极材料层的厚度为T1，中间层的厚度为T2，满足：10≤T1/T2≤60。
本申请的第三方面提供了一种电化学装置，其包括前述任一实施方案中的正极活性材料或包括前述任一实施方案中的正极极片。本申请提供的正极活性材料在脱嵌锂过程中具有较低的体积膨胀率，本申请提供的正极极片具有良好的结构稳定性，从而本申请提供的电化学装置具有良好的循环性能。
本申请的第四方面提供了一种电子装置，其包括前述任一实施方案中的电化学装置。本申请提供的电化学装置具有良好的循环性能，从而本申请提供的电子装置具有较长的使用寿命。
本申请提供了一种正极活性材料，正极活性材料的截面中包括第一区域和第二区域，第一区域具有P63mc晶相结构的第一结构，第二区域具有R-3m、P2/m或P-3m1中的至少 一种晶相结构的第二结构，第一区域和第二区域的面积比为1.8至5.4。本申请提供的正极活性材料同时包括第一结构和第二结构，由于第一结构和第二结构在脱嵌锂的过程中存在一定的时间差，可以综合第一结构和第二结构在脱嵌锂过程中的结构变化，降低正极活性材料整体的应变，以改善正极活性材料在脱嵌锂过程中的体积膨胀和收缩问题，从而提高正极极片的结构稳定性、进而提高电化学装置在高电压下的循环性能。
附图说明
为了更清楚地说明本申请实施例和现有技术的技术方案，下面对实施例和现有技术中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例。
图1为本申请实施例1-1中的正极活性材料的扫描电镜照片；
图2为本申请实施例1-1中的正极活性材料颗粒截面的透射电镜照片；
图3为本申请实施例1-1中正极活性材料的X射线衍射图谱。
具体实施方式
为使本申请的目的、技术方案、及优点更加清楚明白，以下参照附图并举实施例，对本申请进一步详细说明。显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员所获得的所有其他实施例，都属于本申请保护的范围。
需要说明的是，本申请的具体实施方式中，以锂离子电池作为电化学装置的例子来解释本申请，但是本申请的电化学装置并不仅限于锂离子电池。
本申请的第一方面提供了一种正极活性材料，其中，正极活性材料的截面中包括第一区域和第二区域，第一区域具有P63mc晶相结构的第一结构，第二区域具有R-3m、P2/m或P-3m1中的至少一种晶相结构的第二结构，第一区域和第二区域的面积比为1.8至5.4。不限于任何理论，本申请的发明人发现，本申请提供的正极活性材料同时包括第一结构和第二结构，由于第一结构和第二结构在脱嵌锂的过程中存在一定的时间差，可以综合第一结构和第二结构在脱嵌锂过程中的结构变化，降低正极活性材料整体的应变，以改善正极活性材料在脱嵌锂过程中的体积膨胀问题，从而降低正极极片的厚度变化率、提高电化学装置在高电压下的循环性能。在本申请中，正极极片的厚度变化率是指在电化学装置循环中正极极片的厚度变化率。
例如，第一区域和第二区域的面积比可以为1.8、2、2.5、3、3.5、4、4.5、5、5.4或 为其间的任意范围。不限于任何理论，本申请的发明人发现，当第一区域和第二区域的面积比过小时(例如小于1.8)，正极活性材料在高电压下的结构稳定性降低，从而影响电化学装置的循环性能。当第一区域和第二区域的面积比过大时(例如大于5.4)，正极活性材料在脱嵌锂过程中的体积膨胀或收缩增大，影响正极极片的结构稳定性和电化学装置在高电压下的循环性能。通过调控第一区域和第二区域的面积比在上述范围内，有利于得到结构稳定且在脱嵌锂过程中体积膨胀或收缩较低的正极活性材料，从而降低正极极片的厚度变化率、提高电化学装置在高电压下的循环性能。
在本申请的一些实施方案中，第二区域包含F。不限于任何理论，由于第二结构(如R-3m等)在高电压下的结构稳定性不如具有P63mc晶相结构的第一结构，通过引入氟元素，可以稳定其氧骨架，减少氧位移引发的相变，从而降低其过早劣化导致正极材料整体性能降低的风险。进一步地，第二区域中F与O的原子数比为0.5％至5％。
在本申请的一些实施方案中，第一区域包括Co，基于第一区域中过渡金属元素的摩尔数，第一区域中Co的摩尔百分含量C1大于或等于90％；例如，第一区域中Co的摩尔百分含量可以为90％、91％、92％、93％、94％、95％、96％、97％、98％、99％或为其间的任意范围。此时，在保证第一区域具有较好的结构稳定性的同时，能够进一步保证第一区域具有较高的容量。
在本申请的一些实施方案中，第二区域包括Co，基于第二区域中过渡金属元素的摩尔数，第二区域中Co的摩尔百分含量大于或等于70％。第二区域中Co的摩尔百分含量可以为70％、75％、80％、85％、90％、95％或为其间的任意范围。进一步地，在本申请的一些实施方案中，|C1-C2|≤25％，此时，能够提高第一区域和第二区域之间的相容性，进而保证正极活性材料整体在高电压下的结构稳定性。
在本申请的一些实施方案中，第一区域包括元素A和元素M，基于第一区域中元素A的摩尔数，元素M的摩尔百分含量为0.1％至10％，其中，元素A包括Co、Mn或Ni中的至少一种；元素M包括Al、Ti、Ni、Nb、Mg、Ca、Zr、Zn、La、Y或Na中的至少一种。在本申请的一些实施方案中，第二区域包括元素A和元素T，基于第二区域中元素A和的摩尔数，元素T的摩尔百分含量为0.1％至1％，其中，元素A包括Co、Mn或Ni中的至少一种；元素T包括S、Se、Si或C中的至少一种。正极活性材料满足上述特征中的至少一者，均有利于提高正极活性材料的结构稳定性，进而提高电化学装置的循环性能。
例如，元素M的摩尔百分含量为0.1％、0.5％、1％、2％、5％、8％或为其间的任意范 围。不限于任何理论，元素M的引入可以与Co形成掺杂，提高第一区域结构的稳定性，有效改善脱嵌锂过程中第一区域结构坍塌的问题，从而提高正极活性材料整体结构的稳定性。
例如，元素T的摩尔百分含量为0.1％、0.3％、0.5％、0.7％、0.8％或为其间的任意范围。不限于任何理论，元素T的引入可以对部分氧缺陷形成弥补，提升局域的结构稳定性；此外，元素T可以作为牺牲剂，优先消耗活性氧，从而抑制不可控的氧化反应的发生，提升体系的稳定性。
在本申请的一些实施方案中，第一区域包括区域A1和区域A2，第二区域包括区域B1，区域B1位于区域A1和区域A2之间；通过将区域B1(具有R-3m等晶相结构)设置在具有P63mc晶相结构的区域A1和区域A2之间，一方面，能够对晶相结构较不稳定的区域B1形成更好的保护，降低其在高电压下相变的风险；另一方面，区域B1能够为两侧的区域A1和区域A2提供充分的缓冲作用，降低正极材料颗粒整体的膨胀或收缩。
在本申请的一些实施方案中，第二区域包括区域B2，区域B2与正极活性材料表面的距离D满足，D≤200nm；在正极活性材料近表面区域存在具有R-3m等晶相结构的区域B2，能够降低正极活性材料表面由于第一结构膨胀所产生的应力，进而降低正极活性材料颗粒破裂的风险。
在本申请的一些实施方案中，第一区域和第二区域之间具有界面层，沿垂直界面层的方向，第一区域中距离界面层3nm的区域中的过渡金属层和第二区域中距离界面层3nm的区域中的过渡金属层呈平行排列；此时，第一区域和第二区域之间界面相容性较好，能够降低在膨胀收缩过程中第一区域和第二区域之间开裂的风险。
在本申请的一些实施方案中，正极活性材料的Dv50为5μm至20μm。例如，正极活性材料的Dv50可以为5μm、8μm、10μm、12μm、15μm、17μm、20μm或为其间的任意范围。不限于任何理论，正极活性材料的Dv50在上述范围内，能够降低与电解液的副反应，提高电化学装置的循环性能。同时，能够具有充足的活性表面，保证电化学装置的动力学性能。
在本申请的一些实施方案中，在正极活性材料的XRD谱图中，位于16°至17.5°范围的衍射峰的强度为I1，位于44.5°至45.5°范围的衍射峰的强度为I2；位于17.5°至19°范围的衍射峰的强度为I3，位于49.5°至50.5°范围的衍射峰的强度为I4，满足：I1+I2>I3+I4。此时，正极活性材料表面的第一结构的晶体含量占比较高，能够提高正极活性材料颗粒的 表面稳定性。其中，16°至17.5°范围的衍射峰和44.5°至45.5°范围的衍射峰为第一结构对应的衍射峰，17.5°至19°范围的衍射峰和49.5°至50.5°范围的衍射峰为第二结构对应的衍射峰。进一步地，满足：I2>I4，表明在正极活性材料表面，第一结构的活性晶面相对较多，能够提高正极活性材料活性表面的稳定性。
本申请对正极活性材料的制备方法没有特别限制，只要能实现本申请的目的即可，例如，正极活性材料的制备方法可以包括但不限于以下步骤：将第一结构的原料混合，先通过共沉淀法制得第一前驱体；将第二结构的原料混合，通过共沉淀法制得第二前驱体；并对第一前驱体或第二前驱体选择性进行煅烧，然后混合后煅烧得到正极活性材料。本申请对获得第一前驱体或第二前驱体的煅烧温度和时间没有特别限制，只要能实现本申请的目的即可，例如，煅烧温度为500-1100℃，煅烧时间为1-12h。本申请对第一前驱体和第二前驱体混合后煅烧的温度和时间没有特别限制，只要能实现本申请的目的即可，例如煅烧温度为500-1100℃，煅烧时间为1-12h。
本申请对制备第一结构的原料和第二结构的原料没有特别限制，只要能实现本申请的目的即可。例如，第一结构的原料可包括但不限于Co(NO 3) 2、Ni(NO 3) 2、CoCl 2、CoSO 4、Co(CH 3COO) 2、NiCl 2、NiSO 4或Ni(CH 3COO) 2中的至少一种。例如，第二结构的原料可包括但不限于Co(NO 3) 2、MnSO 4、Ni 2SO 4、CoCl 2、CoSO 4、Co(CH 3COO) 2、NiCl 2、NiSO 4、Ni(CH 3COO) 2、Ni(NO 3) 2、MnCl 2、MnSO 4、Mn(CH 3COO) 2或Mn(NO 3) 2中的至少一种。
本申请对于在正极活性材料中引入上述元素M或元素T的方法没有特别限制，只要能实现本申请的目的即可，例如，将含有元素M的化合物作为第一结构的原料加入然后制备第一前驱体，或者煅烧第一前驱体时加入；将含有元素T的化合物作为第二结构的原料加入然后制备第二前驱体，或者煅烧第二前驱体时加入。本申请对含有元素M的化合物和含有元素T的化合物没有特别限制，只要能实现本申请的目的即可。例如，含有元素M的化合物可包括但不限于Al(NO 3) 3、TiO 2、Al 2O 3、MgO、Y 2O 3、La 2O 3、Nb 2O 5或W 2O 3中的至少一种。例如，含有元素T的化合物可包括但不限于NH 4F、Se粉或S粉中的至少一种。
在本申请中，正极活性材料包括Li xNa zCo 1-yX yO 2-δR δ，其中，X元素包括Mn、Ni、Nb、B、Mg、Al、Si、P、S、Ti、Cr、Fe、Cu、Zn、Ga、Y、Zr、Mo、Ag、W、In、Sn、Pb、Sb、Se或Ce中的至少一种，R为卤素，0.6≤x≤1.2，0≤y<0.15，0≤z<0.03，0≤δ≤0.1。
本申请的第二方面提供了一种正极极片，其包括前述任一实施方案中的正极活性材料。 本申请提供的正极活性材料在脱嵌锂过程中具有较低的体积膨胀或收缩，从而本申请提供的正极极片在电化学装置循环过程中则具有较低的厚度变化率。
在本申请的一些实施方案中，正极极片包括正极材料层、正极集流体和位于正极材料层和正极集流体之间的中间层，正极材料层包括正极活性材料，中间层与正极集流体之间的剥离力为F1，正极材料层与中间层之间的剥离力为F2，满足：F1和F2中的较小者大于或等于10N/m。进一步地，F1和F2中的较小者大于或等于20N/m，中间层与正极集流体之间的剥离力F1和正极材料层与中间层之间的剥离力F2中的较小者在上述范围内，说明正极材料层与中间层之间具有良好的粘结力，能够降低正极材料层从集流体表面脱落的风险，有利于提高正极极片的结构稳定性，从而有利于提高电化学装置的循环性能。
在本申请的一些实施方案中，中间层包括粘结剂和导电剂，基于中间层的质量，粘结剂的质量百分含量为20％至80％；例如，粘结剂的质量百分含量可以为30％、35％、40％、45％、50％、55％、60％、75％、70％、75％或为其间的任意范围。不限于任何理论，通过调控粘结剂的质量百分含量在上述范围内，有利于得到具有良好的结构稳定性的正极极片，进而提高电化学装置的循环性能。本申请对粘结剂的种类没有特别限制，只要能实现本申请的目的即可，例如，粘结剂可以包括但不限于聚偏氟乙烯、偏氟乙烯-六氟丙烯的共聚物、聚酰胺、聚丙烯腈、聚丙烯酸酯、聚丙烯酸、聚丙烯酸盐、聚乙烯呲咯烷酮、聚乙烯醚、聚甲基丙烯酸甲酯、聚四氟乙烯或聚六氟丙烯中的至少一种。
中间层中包括导电剂，以利于正极材料层与正极集流体层之间的电子传导。本申请对导电剂没有特别限制，只要能够实现本申请目的即可，例如可以包括但不限于导电炭黑(Super P)、碳纳米管(CNTs)、碳纤维、鳞片石墨、科琴黑、石墨烯、金属材料或导电聚合物中的至少一种。上述碳纳米管可以包括但不限于单壁碳纳米管和/或多壁碳纳米管。上述碳纤维可以包括但不限于气相生长碳纤维(VGCF)和/或纳米碳纤维。上述金属材料可以包括但不限于金属粉和/或金属纤维，具体地，金属可以包括但不限于铜、镍、铝或银中的至少一种。上述导电聚合物可以包括但不限于聚亚苯基衍生物、聚苯胺、聚噻吩、聚乙炔或聚吡咯中的至少一种。
在本申请的一些实施方案中，正极材料层的厚度为T1，中间层的厚度为T2，满足：10≤T1/T2≤60。
本申请对正极材料层的厚度T1和中间层的厚度T2的大小没有特别限制，只要能实现本申请的目的即可，例如，正极材料层的厚度T1为40μm至60μm，中间层的厚度T2为 1μm至4μm。通过调控正极材料层的厚度T1和中间层的厚度T2在上述范围内，有利于得到具有良好的结构稳定性的正极极片，进而提高电化学装置的循环性能。
本申请对正极极片的制备方法没有特别限制，只要能实现本申请的目的即可，例如，正极极片的制备方法可以包括但不限于以下步骤：将中间层的浆料涂覆在正极集流体的一个表面，烘干处理后在中间层上继续涂覆正极材料层的浆料，烘干处理后得到单面涂覆中间层和正极材料层的正极极片。重复上述步骤，得到双面涂覆中间层和正极材料层的正极极片。需要说明，上述“表面”可以是正极集流体的全部区域，也可以是正极集流体的部分区域，本申请没有特别限制，只要能实现本申请目的即可。
本申请的第三方面提供了一种电化学装置，其包括前述任一实施方案中的正极活性材料或包括前述任一实施方案中的正极极片。本申请提供的正极活性材料在脱嵌锂过程中具有较低的体积膨胀率，本申请提供的正极极片具有良好的结构稳定性，从而本申请提供的电化学装置具有良好的循环性能。
本申请的电化学装置还包括负极极片，负极极片通常包括负极集流体和设置在负极集流体表面的负极材料层，本申请对负极集流体没有特别限制，只要能够实现本申请目的即可，例如，可以包括但不限于铜箔、铜合金箔、镍箔、不锈钢箔、钛箔、泡沫镍、泡沫铜或复合集流体等。在本申请中，对负极集流体的厚度没有特别限制，只要能够实现本申请目的即可，例如厚度为4μm至12μm。在本申请中，负极材料层可以设置于负极集流体厚度方向上的一个表面上，也可以设置于负极集流体厚度方向上的两个表面上。需要说明，这里的“表面”可以是负极集流体的全部区域，也可以是负极集流体的部分区域，本申请没有特别限制，只要能实现本申请目的即可。
本申请中，负极材料层包括负极活性材料，其中，负极活性材料没有特别限制，只要能实现本申请的目的即可，例如可以包括但不限于天然石墨、人造石墨、中间相微碳球、硬碳、软碳、硅、硅-碳复合物、Li-Sn合金、Li-Sn-O合金、Sn、SnO、SnO 2、尖晶石结构的锂化TiO 2-Li 4Ti 5O 12或Li-Al合金中的至少一种。
在本申请中，负极材料层中还可以包括导电剂，本申请对导电剂没有特别限制，只要能够实现本申请目的即可，例如可以包括但不限于上述导电剂中的至少一种。
在本申请中，负极材料层中还可以包括粘结剂，本申请对粘结剂没有特别限制，只要能够实现本申请目的即可，例如可以包括但不限于上述粘结剂中的至少一种。
任选地，负极极片还可以包括导电层，导电层位于负极集流体和负极材料层之间。本 申请对导电层的组成没有特别限制，可以是本领域常用的导电层，导电层可以包括但不限于上述导电剂和上述粘结剂。
本申请的电化学装置还包括隔离膜，本申请对隔离膜没有特别限制，只要能够实现本申请目的即可，例如可以包括但不限于聚乙烯(PE)、聚丙烯(PP)、聚四氟乙烯为主的聚烯烃(PO)类隔膜、聚酯膜(例如聚对苯二甲酸二乙酯(PET)膜)、纤维素膜、聚酰亚胺膜(PI)、聚酰胺膜(PA)、氨纶、芳纶膜、织造膜、非织造膜(无纺布)、微孔膜、复合膜、隔膜纸、碾压膜或纺丝膜中的至少一种，优选为PP。本申请的隔离膜可以具有多孔结构，孔径的尺寸没有特别限制，只要能实现本申请的目的即可，例如，孔径的尺寸可以为0.01μm至1μm。在本申请中，隔离膜的厚度没有特别限制，只要能实现本申请的目的即可，例如厚度可以为5μm至500μm。
例如，隔离膜可以包括基材层和表面处理层。基材层可以为具有多孔结构的无纺布、膜或复合膜，基材层的材料可以包括但不限于聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯或聚酰亚胺中的至少一种。任选地，可以使用聚丙烯多孔膜、聚乙烯多孔膜、聚丙烯无纺布、聚乙烯无纺布或聚丙烯-聚乙烯-聚丙烯多孔复合膜。任选地，基材层的至少一个表面上设置有表面处理层，表面处理层可以是聚合物层或无机物层，也可以是混合聚合物与无机物所形成的层。
无机物层可以包括但不限于无机颗粒和无机物层粘结剂，本申请对无机颗粒没有特别限制，只要能实现本申请的目的即可，例如，可以包括但不限于氧化铝、氧化硅、氧化镁、氧化钛、二氧化铪、氧化锡、二氧化铈、氧化镍、氧化锌、氧化钙、氧化锆、氧化钇、碳化硅、勃姆石、氢氧化铝、氢氧化镁、氢氧化钙或硫酸钡中的至少一种。本申请对无机物层粘结剂没有特别限制，例如，可以包括但不限于聚偏氟乙烯、偏氟乙烯-六氟丙烯的共聚物、聚酰胺、聚丙烯腈、聚丙烯酸酯、聚丙烯酸、聚丙烯酸盐、聚乙烯呲咯烷酮、聚乙烯醚、聚甲基丙烯酸甲酯、聚四氟乙烯或聚六氟丙烯中的至少一种。聚合物层中包含聚合物，聚合物的材料可以包括但不限于聚酰胺、聚丙烯腈、丙烯酸酯聚合物、聚丙烯酸、聚丙烯酸盐、聚乙烯呲咯烷酮、聚乙烯醚、聚偏氟乙烯或聚(偏氟乙烯-六氟丙烯)中的至少一种。
本申请的电化学装置还包括电解液，本申请对电解液没有特别限制，只要能实现本申请的目的即可，例如电解液可以包括非水溶剂和锂盐。
本申请对非水溶剂没有特别限制，只要能实现本申请的目的即可，例如，可以包括但不限于碳酸酯化合物、羧酸酯化合物、醚化合物或其它有机溶剂中的至少一种。上述碳酸 酯化合物可以包括但不限于链状碳酸酯化合物、环状碳酸酯化合物或氟代碳酸酯化合物中的至少一种。上述链状碳酸酯化合物可以包括但不限于碳酸二甲酯(DMC)、碳酸二乙酯(DEC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)或碳酸甲乙酯(MEC)中的至少一种。上述环状碳酸酯可以包括但不限于碳酸乙烯酯(EC)、碳酸亚丙酯(PC)、碳酸亚丁酯(BC)或碳酸乙烯基亚乙酯(VEC)中的至少一种。氟代碳酸酯化合物可以包括但不限于氟代碳酸乙烯酯(FEC)、碳酸1,2-二氟亚乙酯、碳酸1,1-二氟亚乙酯、碳酸1,1,2-三氟亚乙酯、碳酸1,1,2,2-四氟亚乙酯、碳酸1-氟-2-甲基亚乙酯、碳酸1-氟-1-甲基亚乙酯、碳酸1,2-二氟-1-甲基亚乙酯、碳酸1,1,2-三氟-2-甲基亚乙酯或碳酸三氟甲基亚乙酯中的至少一种。上述羧酸酯化合物可以包括但不限于甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸正丙酯、乙酸叔丁酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、γ-丁内酯、癸内酯、戊内酯、甲瓦龙酸内酯或己内酯中的至少一种。上述醚化合物可以包括但不限于二丁醚、四甘醇二甲醚、二甘醇二甲醚、1,2-二甲氧基乙烷、1,2-二乙氧基乙烷、乙氧基甲氧基乙烷、2-甲基四氢呋喃或四氢呋喃中的至少一种。上述其它有机溶剂可以包括但不限于二甲亚砜、1,2-二氧戊环、环丁砜、甲基环丁砜、1,3-二甲基-2-咪唑烷酮、N-甲基-2-吡咯烷酮、甲酰胺、二甲基甲酰胺、乙腈、磷酸三甲酯、磷酸三乙酯、磷酸三辛酯或磷酸酯中的至少一种。
本申请对锂盐没有特别限制，只要能实现本申请的目的即可，例如，可以包括但不限于LiPF 6、LiBF 4、LiAsF 6、LiClO 4、LiB(C 6H 5) 4、LiCH 3SO 3、LiCF 3SO 3、LiN(SO 2CF 3) 2、LiC(SO 2CF 3) 3、LiSiF 6、LiBOB或二氟硼酸锂中的至少一种。优选地，锂盐包括LiPF 6。
本申请的电化学装置没有特别限制，其可以包括发生电化学反应的任何装置。在一些实施方案中，电化学装置可以包括但不限于：锂金属二次电池、锂离子二次电池(锂离子电池)、锂聚合物二次电池或锂离子聚合物二次电池等。
电化学装置的制备过程为本领域技术人员所熟知的，本申请没有特别的限制，例如，可以包括但不限于以下步骤：将正极极片、隔离膜和负极极片按顺序堆叠，并根据需要将其卷绕、折叠等操作得到卷绕结构的电极组件，将电极组件放入包装袋内，将电解液注入包装袋并封口，得到电化学装置；或者，将正极极片、隔离膜和负极极片按顺序堆叠，然后用胶带将整个叠片结构的四个角固定好得到叠片结构的电极组件，将电极组件置入包装袋内，将电解液注入包装袋并封口，得到电化学装置。此外，也可以根据需要将防过电流元件、导板等置于包装袋中，从而防止电化学装置内部的压力上升、过充放电。
本申请的第四方面提供了一种电子装置，其包括前述任一实施方案中的电化学装置。 本申请提供的电化学装置具有良好的循环性能，从而本申请提供的电子装置具有较长的使用寿命。
本申请的电子装置没有特别限定，其可以是用于现有技术中已知的任何电子装置。在一些实施例中，电子装置可以包括，但不限于，笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池和锂离子电容器等。
实施例
以下，举出实施例及对比例来对本申请的实施方式进行更具体地说明。各种的试验及评价按照下述的方法进行。另外，只要无特别说明，“份”、“％”为质量基准。
测试方法和设备：
第一区域和第二区域的面积比测试：
采用透射电子显微镜拍摄正极活性材料颗粒截面的照片，确定截面照片中具有P63mc晶相结构的第一区域和具有第二结构的第二区域，通过图像解析软件，测量第一区域的面积大小为S1、第二区域的面积大小为S2，则第一区域和第二区域的面积比为S1/S2。
元素含量的测试：
采用电感耦合等离子光谱发生仪测试正极活性材料中不同元素的含量。
将锂离子电池在30mA/cm 2的电流密度下满放至3.5V以下，并且静置10min后在手套箱内拆解获得正极极片；将正极极片转移至配备聚焦离子束的扫描电镜(型号：FEI Vion Plasma FIB)腔体内，加工得到可用于透射扫描电镜(STEM，型号：FEI Titan3 G2 60-300)分析的样品，要求样品表面用Pt保护，并且用Ga离子束加工，样品厚度不超过100nm；并且用低电压模式进行清洗，除去样品加工的残留表面。将样品在STEM下观察，在合适的倍率下利用X射线能谱分析(EDS)功能进行数据采集，获得正极活性材料第一区域或第二区域内的元素含量。采集至少3处不同位置，取平均值作为最终结果。
循环容量保持率测试：
采用电池测试仪(Land CT2001A)在25℃下将锂离子电池先20mA/cm 2恒流充电至4.6V，然后恒压充电至电流小于50μA；此后再用20mA/cm 2的电流恒流放电至3.0V，此 为一个循环，记录首次循环的放电容量；重复上述循环200次，记录第200次循环的放电容量，循环容量保持率＝第200次循环的放电容量/首次循环的放电容量×100％。
剥离力F测试：
采用表界面切割拉伸系统(型号：Model:SAICAS-DN)进行测试；先取一片2cm×0.5cm的平整极片，放置于仪器腔体内的样品台，底部固定。然后刀片以0.2mm/分钟的速度进行移动，读取测量数值，将中间层与正极集流体之间的剥离力F1和正极材料层与中间层之间的剥离力F2中的较小者确定为剥离力F。
厚度测试：
先将锂离子电池在常温下，10mA/cm 2放电至3.5V以下，并静置0.5h。拆解锂离子电池，并按照部件依次放好，防止正极极片和负极极片接触。此后，利用扫描电镜拍摄正极极片的横断面照片，随机选取边缘、中心等不同的10个位置测量，分别获得10个正极极片的总厚度数据、10个正极集流体和中间层的总厚度数据、10个正极集流体的厚度数据，将10个数据计算平均值即获得正极极片总厚度T0、正极集流体和中间层的总厚度T0’、正极集流体的厚度TA。
若为单面涂覆，正极材料层的厚度T1＝T0-T0’，中间层的厚度T2＝T0’-TA；
若为双面涂覆，正极材料层的厚度T1＝(T0-T0’)/2，中间层的厚度T2＝(T0’-TA)/2。
扫描电镜和透射电镜测试：
如图1所示，为实施例1-1中的正极活性材料的扫描电镜照片，从图中可以看出，实施例1-1中的正极活性材料的颗粒以片状为主。图2为实施例1-1中的正极活性材料颗粒截面的透射电镜照片，其中，区域A1和区域A2的晶相结构为P63mc，区域B1的晶相结构为R-3m，可以看出，区域B1位于区域A1和区域A2之间，且区域B1与区域A1和区域A2之间均存在界面层，沿垂直区域B1与区域A1之间界面层的方向，区域B1中距离界面层3nm的区域中的过渡金属层和区域A1中距离界面层3nm的区域中的过渡金属层呈平行排列。同时，区域B1包括与正极活性材料表面的距离小于或等于200nm的区域，从而能够降低正极活性材料表面由于第一结构膨胀或收缩所产生的应力，进而降低正极活性材料颗粒破裂的风险。
X射线衍射图谱测试：
首先将锂离子电池在10mA/s的电流密度下放电至3.0V，静置5min后，在手套箱或者干燥房拆解锂离子电池。选取正极极片的中心部位，裁剪得到3×3cm大小的试样。在布鲁克X射线粉末衍射仪上进行表征，采集10°至80°范围的衍射峰，采集速度是1°/min。
如图3所示，为实施例1-1中的正极活性材料的X射线衍射图谱，16°至17.5°范围的衍射峰的强度I1为100，44.5°至45.5°范围的衍射峰的强度I2为30，17.5°至19°范围的衍射峰的强度I3为57，49.5°至50.5°范围的衍射峰的强度I4为23，满足：I1+I2>I3+I4。同时，I2>I4。
实施例1-1
<正极活性材料的制备>
(1)将Co(NO 3) 2和Ni(NO 3) 2按照Co和Ni的摩尔比为95:5进行混合配置成水溶液，加入氨水和NaOH，调节pH至8.6以上，通过共沉淀法获得Co 0.97Ni 0.03(OH) 2沉淀，然后在空气氛围中进行一次煅烧得到第一前驱体，煅烧温度为600℃，煅烧时间为3h。
(2)将Co(NO 3) 2、MnSO 4、NiSO 4按照Co、Mn和Ni摩尔比为80:10:10进行混合配置成水溶液，然后加入Co摩尔量3％的NH 4F，并利用(NH 4) 2CO 3调节pH至8.6以上，形成碳酸盐共沉淀作为第二前驱体。
(3)将第一前驱体和第二前驱体按照质量比为3:1进行混合，并且加入Li 2CO 3，然后在空气氛围中进行二次煅烧，产物经研磨过筛得到Dv50为17μm的正极活性材料，煅烧温度为1000℃，煅烧时间为12h，空气流速为8L/min。第一前驱体和第二前驱体中过渡金属元素(Co、Mn和Ni)总的摩尔数与Li 2CO 3中Li的摩尔数比为1:1.05。
<正极极片的制备>
将上述正极活性材料、导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按照质量比为97:1.4:1.6进行混合，加入N-甲基吡咯烷酮(NMP)，在真空搅拌机作用下搅拌均匀，获得正极浆料，其中正极浆料的固含量为70wt％。采用铝箔作为正极集流体，将正极浆料均匀涂覆于正极集流体上，经过干燥、冷压、裁切后得到正极极片。
<负极极片的制备>
将负极活性材料人造石墨、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC)按照质量比为97:2:1进行混合，加入去离子水，在真空搅拌机作用下搅拌均匀，获得负极浆料，其中负极浆料的固含量为75％。采用铜箔作为负极集流体，将负极浆料均匀涂覆于负极集流体上，经过干燥、冷压、裁切后得到负极极片。
<电解液的制备>
在干燥的氩气气氛手套箱中，将碳酸亚丙酯(PC)、EC、DEC按照质量比为1:1:1进行混合得到有机溶剂，然后向有机溶剂中加入锂盐LiPF 6溶解并混合均匀，得到电解液。 其中，LiPF 6在电解液中的质量浓度为12.5％。
<隔离膜的制备>
采用厚度为7μm的多孔PE薄膜。
<锂离子电池的制备>
将上述制备得到的正极极片、隔离膜、负极极片按顺序叠好，卷绕得到电极组件。将电极组件置于铝塑膜包装袋中，干燥后注入电解液，经过真空封装、静置、化成、脱气、切边等工序得到锂离子电池。
实施例1-2和实施例1-3中，除了将<正极活性材料的制备>的步骤(2)中Co、Mn和Ni摩尔比分别调整为90:5:5、70:15:15以外，其余与实施例1-1相同。
实施例1-4中，除了将<正极活性材料的制备>的步骤(1)中Co、Mn和Ni摩尔比分别调整为88:6:6、步骤(2)中Co、Mn和Ni摩尔比分别调整为60:20:20以外，其余与实施例1-1相同。
实施例1-5和实施例1-6中，除了将<正极活性材料的制备>的步骤(3)中第一前驱体和第二前驱体的质量比分别调整为1.5:1、4.5:1以外，其余与实施例1-1相同。
实施例1-7和实施例1-8中，除了将<正极活性材料的制备>的步骤(1)中Co和Ni的摩尔比分别调整为90:10、98:2以外，其余与实施例1-1相同。
实施例1-9中，除了<正极活性材料的制备>按照以下步骤进行以外，其余与实施例1-1相同：
(1)将Co(NO 3) 2和Ni(NO 3) 2按照Co和Ni的摩尔比为95:5进行混合配置成水溶液，加入氨水和NaOH，调节pH至8.6以上，通过共沉淀法获得Co 0.97Ni 0.03(OH) 2沉淀作为第一前驱体。
(2)将Co(CH 3COO) 2、Mn(CH 3COO) 2、Ni(CH 3COO) 2按照Co、Mn和Ni摩尔比为80:10:10进行混合配置成水溶液，并利用(NH 4) 2CO 3和氨水调节pH至8.6以上并使其形成沉淀，沉淀老化24小时后，加入Co摩尔量5％的Li元素的Li 2CO 3在空气氛围中进行一次煅烧得到第二前驱体，煅烧温度为650℃，煅烧时间为4h。
(3)将第一前驱体和第二前驱体按照质量比为3:1进行混合，并且加入Li 2CO 3和NaOH，然后在空气氛围中进行二次煅烧，煅烧温度为850℃，煅烧时间为12h，空气流速为6L/min。第一前驱体和第二前驱体中过渡金属元素总的摩尔数、Li 2CO 3中Li的摩尔数和NaOH中Na的摩尔数比为1:0.8:0.2。
(4)将(3)中得到的产物与草酸锂、溴化锂和硝酸锂以重量比1:0.2:0.3:0.3混合均匀，并在250℃反应4小时，反应产物用水洗涤3次以上并抽滤，在80℃真空烘箱内烘12h，产物经研磨过筛得到正极活性材料。
实施例1-10中，除了<正极活性材料的制备>按照以下步骤进行以外，其余与实施例1-1相同：
(1)将Co(NO 3) 2和Ni(NO 3) 2按照Co和Ni的摩尔比为95:5进行混合配置成水溶液，加入氨水和NaOH，调节pH至8.6以上，通过共沉淀法获得Co 0.97Ni 0.03(OH) 2沉淀作为第一前驱体。
(2)将Co(CH 3COO) 2、Mn(CH 3COO) 2、Ni(CH 3COO) 2按照Co、Mn和Ni摩尔比为80:10:10进行混合配置成水溶液，并利用(NH 4) 2CO 3和氨水调节pH至8.6以上并使其形成沉淀，沉淀老化24小时后，在空气氛围中进行一次煅烧得到第二前驱体，煅烧温度为800℃，煅烧时间为8h。
(3)将第一前驱体和第二前驱体按照质量比为3:1进行混合，并且加入Li 2CO 3和NaOH，然后在空气氛围中进行二次煅烧，煅烧温度为850℃，煅烧时间为12h，空气流速为6L/min。第一前驱体和第二前驱体中过渡金属元素总的摩尔数、Li 2CO 3中Li的摩尔数和NaOH中Na的摩尔数比为1:0.85:0.2。
(4)将(3)中得到的产物、醋酸锂和硝酸锂按照质量比1:0.5:0.5混合均匀，并在260℃反应3小时，反应产物用水洗涤3次以上并抽滤，在80℃真空烘箱内烘12h，产物经研磨过筛得到正极活性材料。
实施例2-1中，除了按下述步骤先在正极集流体表面涂覆中间层以外，其余与实施例1-1相同。
将粘结剂PVDF、导电炭黑(Super P)、碳纳米管(CNT)按照质量比为35:55:10进行混合，加入NMP，在真空搅拌机作用下搅拌均匀，获得中间层浆料。将中间层浆料均匀涂布于正极集流体表面，涂覆量为0.002mg/mm 2，干燥后即在正极集流体的表面形成中间层。最终，正极极片中正极材料层的厚度为54μm、中间层的厚度为1μm。
实施例2-2中，除了粘结剂PVDF、导电炭黑(Super P)、碳纳米管(CNT)的质量比分别为60:35:5、正极材料层厚度为42μm、中间层厚度为3μm以外，其余与实施例2-1相同。
实施例2-3中，除了粘结剂PVDF、导电炭黑(Super P)、碳纳米管(CNT)的质量比 分别为60:35:5、正极材料层厚度为42μm、中间层厚度为2μm以外，其余与实施例2-1相同。
实施例3-1至实施例3-4中，除了<正极活性材料的制备>的步骤(2)中加入的NH 4F分别为Co摩尔量1％、0.6％、6％、10％以外，其余与实施例1-1相同。
实施例4-1中，除了<正极活性材料的制备>中的步骤(1)和(2)按照以下步骤进行以外，其余与实施例1-1相同：
(1)将Co(NO 3) 2、Ni(NO 3) 2和Al(NO 3) 3按照Co、Ni和Al的摩尔比为95:5:0.2进行混合配置成水溶液，加入氨水和NaOH，调节pH至8.6以上，通过共沉淀法获得沉淀，然后与TiO 2混合在空气氛围中进行一次煅烧得到第一前驱体，煅烧温度为600℃，煅烧时间为3h。基于Co和Ni的摩尔总数，TiO 2中Ti的摩尔百分含量为0.1％。
(2)将Co(NO 3) 2、MnSO 4、NiSO 4按照Co、Mn和Ni摩尔比为80:10:10进行混合配置成水溶液，然后加入Co摩尔量3％的NH 4F，并利用(NH 4) 2CO 3调节pH至8.6以上并使其形成碳酸盐共沉淀，然后与Se单质以(Co+Mn+Ni):Se＝1：0.005的摩尔比混合，在350℃下反应2h得到第二前驱体。
实施例4-2中，除了<正极活性材料的制备>的步骤(1)中Co、Ni和Al的摩尔比为95:5:0.1以外，其余与实施例3-1相同。
实施例4-3中，除了<正极活性材料的制备>的步骤(1)中Co、Ni和Al的摩尔比为95:5:10以外，其余与实施例3-1相同。
实施例4-4中，除了<正极活性材料的制备>的步骤(2)中加入Co、Mn和Ni总摩尔量0.1％的Se以外，其余与实施例3-1相同。
实施例4-5中，除了<正极活性材料的制备>的步骤(2)中加入Co、Mn和Ni总摩尔量1％的Se以外，其余与实施例3-1相同。
对比例1-1中，除了将<正极活性材料的制备>的步骤(3)中第一前驱体和第二前驱体按照质量比调整为1.1:1以外，其余与实施例1-1相同。
对比例1-2中，除了<正极活性材料的制备>中利用步骤(1)制备得到的第一前驱体按照以下步骤制备正极活性材料以外，其余与实施例1-1相同：
将第一前驱体与Na 2CO 3以过渡金属与Na的摩尔比为1:1.05混合，然后在空气氛围中煅烧得到中间产物，煅烧温度为1000℃，煅烧时间为12h，空气流速为8L/min。将中间产物和硝酸锂按照质量比1:3混合均匀，并在260℃反应6小时，然后用水洗涤并烘干，产 物经研磨过筛得到正极活性材料。
表1
Figure PCTCN2021128772-appb-000001
注：表1中的“/”表示不存在对应的参数或物质。
从实施例1-1至实施例1-10、对比例1-1和对比例1-2可以看出，当第一区域和第二区域的面积比在本申请的范围内时，得到的锂离子电池具有更好的高电压循环性能。这是由于第一结构和第二结构在脱嵌锂的过程中存在一定的时间差，可以综合第一结构和第二结构在脱嵌锂过程中的结构变化，降低正极活性材料在脱嵌锂过程中的体积膨胀和收缩，从而提高正极材料层在循环过程中的结构稳定性。进一步地，从实施例1-1至实施例1-4可以看出，当C1-C2≤25％时，得到的锂离子电池具有更好的循环性能。可能的原因在于：第一区域和第二区域之间的Co含量差异较小，能够提高第一区域和第二区域之间的相容性，进而保证正极活性材料整体在高电压下的结构稳定性。
表2
Figure PCTCN2021128772-appb-000002
注：表2中的“/”表示不存在对应的参数或物质。
从实施例1-1、实施例2-1至实施例2-3可以看出，当中间层与正极集流体之间的剥离力和正极材料层与中间层之间的剥离力中的较小者F大于或等于20N/m时，正极极片中的中间层与正极集流体和正极材料层之间均具有较强的粘结力，能够进一步提升正极极片中正极材料层的稳定性，从而提高锂离子电池的循环性能。
表3
Figure PCTCN2021128772-appb-000003
注：表3中的“/”表示不存在对应的参数或物质。
从实施例1-1、实施例3-1至实施例3-4可以看出，第二区域中F与O的原子数比在0.5％至5％具有更加优异的循环稳定性，这是由于第二结构(如R-3m等)在高电压下的结构稳定性不如具有P63mc晶相结构的第一结构，通过引入氟元素，可以稳定其氧骨架，减少氧位移引发的相变，从而降低其过早劣化导致正极活性材料整体性能降低的风险。从实施例1-1、实施例4-1至实施例4-5可以看出，在第一结构中进一步掺杂元素M(如Al、Ti)、在第二结构中掺杂元素T(如Se)，能够进一步提高第一结构和第二结构在高电压下的结构稳定性，进而提升锂离子电池的高电压循环性能。
以上所述仅为本申请的较佳实施例，并不用以限制本申请，凡在本申请的精神和原则之内，所做的任何修改、等同替换、改进等，均应包含在本申请保护的范围之内。

Claims (12)

  1. 一种正极活性材料，其中，所述正极活性材料的截面中包括第一区域和第二区域，所述第一区域具有P63mc晶相结构的第一结构，所述第二区域具有R-3m、P2/m或P-3m1中的至少一种晶相结构的第二结构，所述第一区域和所述第二区域的面积比为1.8至5.4。
  2. 根据权利要求1所述的正极活性材料，其中，所述第二区域包含F元素，所述第二区域中F元素与O元素的原子数比为0.5％至5％。
  3. 根据权利要求1所述的正极活性材料，其中，所述正极活性材料满足以下特征中的至少一者：
    (i)所述第一区域包括Co，基于所述第一区域中过渡金属元素的摩尔数，所述第一区域中Co的摩尔百分含量C1大于或等于90％；
    (ii)所述第二区域包括Co，基于所述第二区域中过渡金属元素的摩尔数，所述第二区域中Co的摩尔百分含量C2大于或等于70％；
    (iii)所述第一区域包括元素A和元素M，基于第一区域中元素A的摩尔数，元素M的摩尔百分含量为0.1％至10％，其中，所述元素A包括Co、Mn或Ni中的至少一种；所述元素M包括Al、Ti、Ni、Nb、Mg、Ca、Zr、Zn、La、Y或Na中的至少一种；
    (iv)所述第二区域包括元素A和元素T，基于第二区域中元素A的摩尔数，元素T的摩尔百分含量为0.1％至1％，其中，所述元素A包括Co、Mn或Ni中的至少一种；所述元素T包括S、Se、Si或C中的至少一种。
  4. 根据权利要求3所述的正极活性材料，其中，|C1-C2|≤25％。
  5. 根据权利要求1所述的正极活性材料，其中，所述正极活性材料满足以下特征中的至少一者：
    (v)所述第一区域包括区域A1和区域A2，所述第二区域包括区域B1，所述区域B1位于所述区域A1和所述区域A2之间；
    (vi)所述第二区域包括区域B2，所述区域B2与所述正极活性材料表面的距离D满足，D≤200nm；
    (vii)所述第一区域和所述第二区域之间具有界面层，沿垂直所述界面层的方向，所述第一区域中距离所述界面层3nm的区域中的过渡金属层和所述第二区域中距离所述界面层3nm的区域中的过渡金属层呈平行排列；
    (viii)所述正极活性材料的Dv50为5μm至20μm。
  6. 根据权利要求1所述的正极活性材料，其中，在所述正极活性材料的XRD谱图中，位于16°至17.5°范围的衍射峰的强度为I1，位于44.5°至45.5°范围的衍射峰的强度为I2；位于17.5°至19°范围的衍射峰的强度为I3，位于49.5°至50.5°范围的衍射峰的强度为I4，满足：I1+I2>I3+I4。
  7. 根据权利要求6所述的正极活性材料，其中，I2>I4。
  8. 一种正极极片，其包括权利要求1至7中任一项所述的正极活性材料。
  9. 根据权利要求8所述的正极极片，所述正极极片包括正极材料层、正极集流体和位于所述正极材料层和所述正极集流体之间的中间层，所述正极材料层包括所述正极活性材料，所述中间层与所述正极集流体之间的剥离力为F1，所述正极材料层与所述中间层之间的剥离力为F2，满足：F1和F2中的较小者大于或等于20N/m。
  10. 根据权利要求9所述的正极极片，其中，所述正极极片满足以下特征中的至少一者：
    (xi)所述中间层包括粘结剂和导电剂，基于所述中间层的质量，所述粘结剂的质量百分含量为20％至80％；
    (xii)所述正极材料层的厚度为T1，所述中间层的厚度为T2，满足10≤T1/T2≤60。
  11. 一种电化学装置，其包括权利要求1至7中任一项所述的正极活性材料或权利要求8至10中任一项所述的正极极片。
  12. 一种电子装置，其包括权利要求11所述的电化学装置。
PCT/CN2021/128772 2021-11-04 2021-11-04 正极活性材料、正极极片、包含该正极极片的电化学装置和电子装置 WO2023077373A1 (zh)

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