Positive electrode material, electrochemical device, and electronic device

Abstract

This application provides a cathode material comprising a lithium transition metal oxide, wherein, as measured by X-ray diffraction, the full width at half maximum (FWHM) of the (101) crystal plane diffraction peak and the full width at half maximum (FWHM) of the (104) crystal plane diffraction peak satisfy the following: FWHM(101) / FWHM(104) ≤ 0.7. An electrochemical device and an electronic device incorporating this cathode material are also provided. This cathode material exhibits excellent structural stability under high temperature and high pressure, and excellent kinetic performance under high-rate charge-discharge conditions.

Description

Technical Field

[0001] This application relates to the field of energy storage, specifically to a cathode material, an electrochemical device, and an electronic device. Background Technology

[0002] With the widespread adoption of consumer electronics such as laptops, mobile phones, tablets, power banks, and drones, the requirements for their batteries are becoming increasingly stringent. For example, batteries are not only required to be lightweight, but also to have high capacity and long lifespan. Lithium-ion batteries, with their outstanding advantages such as high energy density, good safety, no memory effect, and long lifespan, have already gained a mainstream position in the market.

[0003] In pursuit of higher energy density, lithium-ion batteries have been continuously developed towards increasing voltage and lithium removal rate. However, under high voltage and high lithium removal rates, the problems of oxygen release and structural phase transitions on the cathode material surface are fully exposed, leading to issues such as rapid battery cycle degradation and gas generation. Furthermore, the poor kinetics of ternary cathode materials limit their capacity utilization, resulting in a series of problems such as severe battery temperature rise under high-rate charge-discharge conditions. Summary of the Invention

[0004] In view of the above-mentioned problems existing in the prior art, this application provides a cathode material and an electrochemical device including the cathode material to improve the structural stability of the cathode material under high temperature and high pressure and the kinetic performance under high rate charge and discharge conditions, thereby improving the plateau capacity of the electrochemical device under high pressure, reducing the storage gas generation of the electrochemical device under high temperature and high pressure and the temperature rise under high rate charge and discharge conditions, and improving the overall performance of the electrochemical device.

[0005] In a first aspect, this application provides a cathode material comprising a lithium transition metal oxide, wherein, as measured by X-ray diffraction, the full width at half maximum (FWHM) of the (101) crystal plane diffraction peak and the full width at half maximum (FWHM) of the (104) crystal plane diffraction peak satisfy the following: FWHM(101) / FWHM(104)≤0.7. The (104) crystal plane represents the maximum active surface for lithium ion insertion / extraction; the (101) crystal plane is generally related to the oxygen defect concentration. Due to the presence of oxygen defects, the regularity of the (104) crystal plane on the surface of the cathode material is lower than that of the (101) crystal plane. Simultaneously, as the oxygen defect concentration increases, the strength of the (101) crystal plane increases accordingly, and the regularity of the (101) crystal plane first increases and then decreases. The regularity of the (104) crystal plane also first increases and then decreases accordingly. That is, both FWHM(101) and FWHM(104) decrease and then increase with increasing oxygen defect concentration. The presence of oxygen defects can reduce the activity of oxygen on the material surface, stabilize oxygen ions in the outer layer of the material, and suppress oxygen release and gas generation during high-temperature cycling. Furthermore, a high oxygen defect concentration can activate the redox properties of transition metals, significantly increasing the energy density of the material. This application controls the FWHM(101) / FWHM(104) of the cathode material within the above range, which can effectively improve the structural stability of the cathode material under high temperature and high pressure, thereby increasing the platform capacity of the electrochemical device under high pressure, reducing the storage gas generation of the electrochemical device under high temperature and high pressure, and improving the high temperature cycle performance of the electrochemical device.

[0006] In some implementations, 0.5 ≤ FWHM(101) / FWHM(104) ≤ 0.7.

[0007] In some embodiments, 0.25° ≤ FWHM(104) ≤ 0.6°. At this point, the regularity of the (104) crystal plane on the surface of the cathode material is suitable, which is beneficial for lithium-ion insertion / extraction. In some embodiments, 0.25° ≤ FWHM(104) ≤ 0.5°.

[0008] In some implementations, 0.15°≤FWHM(101)≤0.35°. At this point, the concentration of oxygen defects on the surface of the cathode material is relatively high, which helps to improve the stability of the surface structure of the cathode material and suppress oxygen release during high-temperature cycling.

[0009] In some embodiments, the full width at half maximum (FWHM) of the diffraction peak of the (003) crystal plane of the cathode material satisfies: 0.5 ≤ FWHM(101) / FWHM(003) ≤ 1.5. The (003) crystal plane represents the active surface for lithium-ion insertion / extraction. When FWHM(101) / FWHM(003) is within the above range, the regularity of the (003) crystal plane on the surface of the cathode material is reduced, which is beneficial to the lithium-ion insertion / extraction kinetics.

[0010] In some implementations, 0.7 ≤ FWHM(101) / FWHM(003) ≤ 0.9.

[0011] In some embodiments, the full width at half maximum (FWHM) of the (003) crystal plane diffraction peak of the cathode material satisfies: 0.2° ≤ FWHM(003) ≤ 0.4°. When FWHM(003) is within the above range, the regularity of the (003) crystal plane on the surface of the cathode material is reduced, which is beneficial to the lithium-ion insertion / extraction kinetics.

[0012] In some embodiments, the lithium transition metal oxide includes a T element, which includes at least one of Ni, Co, or Mn.

[0013] In some embodiments, the molar percentage of Ni in the lithium transition metal oxide is greater than or equal to 50% based on the total molar amount of T in the lithium transition metal oxide. In some embodiments, the molar percentage of Ni in the lithium transition metal oxide is less than or equal to 98% based on the total molar amount of T in the lithium transition metal oxide.

[0014] In some implementations, the molar percentage of Mn in the lithium transition metal oxide is less than or equal to 50%, based on the total molar amount of T in the lithium transition metal oxide.

[0015] In some implementations, the molar percentage of Co in the lithium transition metal oxide is less than or equal to 50%, based on the total molar amount of T in the lithium transition metal oxide.

[0016] In some embodiments, the molar percentage of F in the lithium transition metal oxide is 0.01% to 0.5%, based on the total molar amount of T in the lithium transition metal oxide. By doping F into the cathode material, it is possible to introduce a certain amount of oxygen defects while further stabilizing oxygen ions on the surface of the material, thereby improving the high-temperature cycling performance of the electrochemical device.

[0017] In some embodiments, the molar percentage of nitrogen (N) in the lithium transition metal oxide is 0.01% to 1%, based on the total molar amount of nitrogen (T) in the lithium transition metal oxide. By introducing nitrogen doping into the cathode material, more electronic defects are generated in the material, further improving the electronic conductivity and thus enhancing the rate performance of the material.

[0018] In some embodiments, the lithium transition metal oxide further comprises Na, optional R, and optional Q, wherein the molar amount of Na in the lithium transition metal oxide is n. Na The molar amount of Ni is n Ni The molar amount of Co is n CoThe molar amount of Mn is n Mn The molar amount of element R is n R The molar amount of element Q is n Q The total molar amount of element T is n T Where 0 < n Na / n T ≤0.02, 0.5≤n Ni / n T ≤1, 0≤n Co / n T ≤0.5, 0≤n Mn / n T ≤0.5, 0≤n R / n T ≤0.2, 0≤n Q / n T ≤0.2, R element includes at least one of Mg, Al, Ti, Zr, Nb, Y, Cr, V, Ge, Mo, Fe, Cu, Zn, Ga, Ag, W, In, Sn, Pb, Sb, La, Ce, Ca, Ba or Sr, and Q element includes at least one of F, Cl, Br or N.

[0019] This application also provides a method for preparing the aforementioned cathode material, comprising the following steps: S1: mixing a cathode material precursor with a lithium source, an optional sodium source, and an optional R element source, and calcining the mixture with a first mixed gas at a first temperature to obtain a first product; S2: calcining the first product with a second mixed gas at a second temperature to obtain a second product; S3: quenching the second product to room temperature to obtain the cathode material; wherein the first mixed gas contains hydrogen fluoride; the second mixed gas contains ammonia; and the R element includes at least one selected from Mg, Al, Ti, Zr, Nb, Y, Cr, V, Ge, Mo, Fe, Cu, Zn, Ga, Ag, W, In, Sn, Pb, Sb, La, Ce, Ca, Ba, or Sr.

[0020] In some embodiments, the first temperature is 700°C to 900°C; the first calcination time is 10h to 48h.

[0021] In some embodiments, the second temperature is 400°C to 650°C; the second calcination time is 4 hours to 24 hours.

[0022] In some embodiments, the first mixture further comprises at least one of air, oxygen, or a mixture of air and oxygen.

[0023] In some embodiments, the volume percentage of hydrogen fluoride is 1% to 15% based on the total volume of the first mixed gas.

[0024] In some embodiments, the second mixture further comprises an inert gas, including at least one of nitrogen, argon, and helium.

[0025] In some embodiments, the volume percentage of ammonia is 1% to 15% based on the total volume of the second mixture.

[0026] In some embodiments, the cathode material precursor comprises a hydroxide of element T, wherein element T includes at least one of Ni, Co, or Mn.

[0027] In some embodiments, the lithium source includes at least one of lithium carbonate or lithium hydroxide.

[0028] In some embodiments, the sodium source includes at least one of sodium carbonate, sodium bicarbonate, or sodium hydroxide.

[0029] In some embodiments, the source of element R includes an oxide of element R.

[0030] In some embodiments, the quenching rate is from 30°C / min to 70°C / min.

[0031] In a second aspect, this application provides an electrochemical device comprising a positive electrode, the positive electrode comprising a positive electrode active material layer, wherein the positive electrode active material layer comprises the positive electrode material of the first aspect or the positive electrode material prepared by the preparation method of the first aspect.

[0032] In some embodiments, after the electrochemical device is fully discharged, the positive electrode and lithium metal are assembled into a coin cell. The initial open-circuit voltage of the coin cell is Va V. The coin cell is first charged at a constant current of 0.1C to 4.6V, then charged at a constant voltage of 4.6V to 0.05C, allowed to stand for 5 minutes, and then discharged at a constant current of 0.1C to 2.8V. After standing for 5 minutes, the voltage is Vc V, which satisfies the condition: (Vc-2.8) / Va≤20%. The equilibrium potential of the coin cell is in a relaxed state, and the relaxation voltage is only slightly different from 2.8V, indicating that the kinetics of the positive electrode material are good.

[0033] In some implementations, when a coin cell is charged and discharged at a current of 0.04C within a voltage range of 2.8V to 4.5V, the voltage-capacity differential dQ / dV curve obtained shows at least two oxidation peaks in the voltage range of 3.6V to 4.5V.

[0034] In some embodiments, when the coin cell is charged and discharged at a current of 0.04C within a voltage range of 2.8V to 4.5V, the voltage-capacity differential dQ / dV curve shows a first oxidation peak in the 4.2V to 4.5V voltage range, wherein the peak intensity of the first oxidation peak is ≥300mAh / g / V based on the mass of the cathode material. This indicates that the cathode material can have a higher charging capacity in the high voltage range of 4.2V to 4.5V, thereby improving the charging capacity of the electrochemical device.

[0035] In some embodiments, when the coin cell is charged and discharged at a current of 0.04C within a voltage range of 2.8V to 4.5V, the voltage-capacity differential dQ / dV curve shows a first reduction peak in the 4.2V to 4.5V voltage range, wherein the peak intensity of the first reduction peak is ≥300mAh / g / V based on the mass of the cathode material. This indicates that the cathode material can have a high reversible discharge capacity in the high voltage range of 4.2V to 4.5V, thereby improving the energy density of the electrochemical device.

[0036] In some embodiments, when the coin cell is charged and discharged at a current of 0.04C within a voltage range of 2.8V to 4.5V, the discharge curve in the obtained voltage-capacity curve shows a plateau within the 4.2V to 4.5V voltage range. This indicates that the cathode material can have reversible discharge capacity in the high voltage range of 4.2V to 4.5V.

[0037] In some embodiments, when the coin cell is charged and discharged at a current of 0.04C within a voltage range of 2.8V to 4.5V, the discharge curve of the voltage-capacity curve shows a capacity of Q1 in the 4.2V to 4.5V voltage range and a capacity of Qt in the 3.0V to 4.5V voltage range, where 0.2 ≤ Q1 / Qt ≤ 0.4. This indicates that the cathode material has a higher reversible discharge capacity in the high voltage range of 4.2V to 4.5V, thereby improving the energy density of the electrochemical device.

[0038] In a third aspect, this application provides an electronic device that includes the electrochemical device of the second aspect.

[0039] This application introduces oxygen defects into the surface layer of the cathode material and controls FWHM(101) / FWHM(104)≤0.7, which can reduce the activity of oxygen on the material surface, stabilize oxygen ions in the outer layer of the material, and suppress oxygen release and gas generation during high-temperature cycling. At the same time, it can also activate the redox properties of transition metals, significantly improving the energy density of the material. Attached Figure Description

[0040] Figure 1The image shows the XRD patterns of the cathode material powders of Comparative Example 1 and Example 9.

[0041] Figure 2 The voltage-capacity curves and voltage-capacity differential dQ / dV curves of the coin cells of Comparative Example 1 and Example 9 are shown. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with embodiments. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. The embodiments described herein are illustrative in nature and are used to provide a basic understanding of this application. The embodiments of this application should not be construed as limiting this application.

[0043] For the sake of brevity, this article only discloses a few specific numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0044] In this description, unless otherwise stated, "above" and "below" include the stated number.

[0045] Unless otherwise stated, the terms used in this application have their common meanings as commonly understood by those skilled in the art. Unless otherwise stated, the values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application).

[0046] The list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another instance, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single component or multiple components. Item B may contain a single component or multiple components. Item C may contain a single component or multiple components.

[0047] In a first aspect, this application provides a cathode material comprising a lithium transition metal oxide, wherein, as measured by X-ray diffraction, the full width at half maximum (FWHM) of the (101) crystal plane diffraction peak and the full width at half maximum (FWHM) of the (104) crystal plane diffraction peak satisfy the following: FWHM(101) / FWHM(104)≤0.7. The (104) crystal plane represents the maximum active surface for lithium ion insertion / extraction; the (101) crystal plane is generally related to the oxygen defect concentration. Due to the presence of oxygen defects, the regularity of the (104) crystal plane on the surface of the cathode material is lower than that of the (101) crystal plane. Simultaneously, as the oxygen defect concentration increases, the strength of the (101) crystal plane increases accordingly, and the regularity of the (101) crystal plane first increases and then decreases. The regularity of the (104) crystal plane also first increases and then decreases accordingly. That is, both FWHM(101) and FWHM(104) decrease and then increase with increasing oxygen defect concentration. The presence of oxygen defects can reduce the activity of oxygen on the material surface, stabilize oxygen ions in the outer layer of the material, and suppress oxygen release and gas generation during high-temperature cycling. Furthermore, a high oxygen defect concentration can activate the redox properties of transition metals, significantly increasing the energy density of the material. This application controls the FWHM(101) / FWHM(104) ratio of the cathode material within the aforementioned range, which can effectively improve the structural stability of the cathode material under high temperature and high pressure, thereby increasing the plateau capacity of the electrochemical device under high pressure, reducing the storage gas generation of the electrochemical device under high temperature and high pressure, and improving the high-temperature cycling performance of the electrochemical device. In the X-ray diffraction pattern, the diffraction peaks of the (101) crystal plane of the cathode material are in the range of 35° to 37°; the diffraction peaks of the (104) crystal plane are in the range of 42° to 44°.

[0048] In some implementations, FWHM(101) / FWHM(104) is a range of 0.1, 0.2, 0.3, 0.4, 0.5, 0.55, 0.6, 0.65, 0.7, or any combination of these values. In some implementations, 0.5 ≤ FWHM(101) / FWHM(104) ≤ 0.7.

[0049] In some embodiments, 0.25° ≤ FWHM(104) ≤ 0.6°. In this case, the regularity of the crystal plane of the cathode material surface layer (104) is suitable, which is beneficial for lithium-ion insertion / extraction. In some embodiments, FWHM(104) is a range of 0.25°, 0.3°, 0.35°, 0.4°, 0.45°, 0.5°, 0.55°, 0.6°, or any combination of these values. In some embodiments, 0.25° ≤ FWHM(104) ≤ 0.5°.

[0050] In some embodiments, 0.15° ≤ FWHM(101) ≤ 0.35°. At this value, the concentration of oxygen defects on the surface of the cathode material is relatively high, which is beneficial for improving the stability of the cathode material's surface structure and suppressing oxygen release during high-temperature cycling. In some embodiments, FWHM(101) is a range of 0.15°, 0.17°, 0.2°, 0.23°, 0.25°, 0.27°, 0.3°, 0.33°, 0.35°, or any combination of these values.

[0051] In some embodiments, the full width at half maximum (FWHM) of the diffraction peak of the (003) crystal plane of the cathode material satisfies: 0.5 ≤ FWHM(101) / FWHM(003) ≤ 1.5. The (003) crystal plane represents the lithium-ion insertion / extraction active surface. When FWHM(101) / FWHM(003) is within the above range, the regularity of the (003) crystal plane on the surface of the cathode material is reduced, which is beneficial to the lithium-ion insertion / extraction kinetics. In some embodiments, FWHM(101) / FWHM(003) is 0.5, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, or any combination of these values. In some implementations, 0.7 ≤ FWHM(101) / FWHM(003) ≤ 0.9.

[0052] In some embodiments, the full width at half maximum (FWHM) of the (003) crystal plane diffraction peak of the cathode material satisfies: 0.2° ≤ FWHM(003) ≤ 0.4°. Within this range, the regularity of the (003) crystal plane on the surface of the cathode material is reduced, which is beneficial to lithium-ion insertion / extraction kinetics. In some embodiments, FWHM(003) is a range of 0.2°, 0.25°, 0.3°, 0.35°, 0.4°, or any combination of these values.

[0053] In some embodiments, the lithium transition metal oxide includes a T element, which includes at least one of Ni, Co, or Mn. In some embodiments, the molar percentage of Ni in the lithium transition metal oxide is greater than or equal to 50% based on the total molar amount of T element in the lithium transition metal oxide. In some embodiments, the molar percentage of Ni in the lithium transition metal oxide is less than or equal to 98% based on the total molar amount of T element in the lithium transition metal oxide. For example, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 98%, or a range of any two of these values.

[0054] In some embodiments, the molar percentage of Mn in the lithium transition metal oxide is less than or equal to 50%, based on the total molar amount of T in the lithium transition metal oxide. For example, 0.5%, 1%, 5%, 10%, 20%, 30%, 40%, 50%, or a range of any two of these values.

[0055] In some embodiments, the molar percentage of Co in the lithium transition metal oxide is less than or equal to 50%, based on the total molar amount of T in the lithium transition metal oxide. For example, 0.5%, 1%, 5%, 10%, 20%, 30%, 40%, 50%, or a range of any two of these values.

[0056] In some embodiments, the molar percentage of fluorine (F) in the lithium transition metal oxide is 0.01% to 0.5%, based on the total molar amount of nitrogen (T) in the lithium transition metal oxide. By doping the cathode material with F, a certain amount of oxygen vacancies can be introduced while further stabilizing oxygen ions on the material surface, thereby improving the high-temperature cycling performance of the electrochemical device. In some embodiments, the molar percentage of fluorine is 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, or any combination of these values.

[0057] In some embodiments, the molar percentage of nitrogen in the lithium transition metal oxide is from 0.01% to 1%, based on the total molar amount of nitrogen (T) in the lithium transition metal oxide. In some embodiments, the molar percentage of nitrogen is 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.8%, 1%, or any combination of these values. This application improves the electronic conductivity of the material by introducing nitrogen doping into the cathode material, thereby increasing the rate performance of the material and creating more electronic defects.

[0058] In some embodiments, the lithium transition metal oxide further comprises Na, optional R, and optional Q, wherein the molar amount of Na in the lithium transition metal oxide is n. Na The molar amount of Ni is n Ni The molar amount of Co is n Co The molar amount of Mn is n Mn The molar amount of element R is n R The molar amount of element Q is nQ The total molar amount of element T is n T Where 0 < n Na / n T ≤0.02, 0.5≤n Ni / n T ≤1, 0≤n Co / n T ≤0.5, 0≤n Mn / n T ≤0.5, 0≤n R / n T ≤0.2, 0≤n Q / n T ≤0.2, R element includes at least one of Mg, Al, Ti, Zr, Nb, Y, Cr, V, Ge, Mo, Fe, Cu, Zn, Ga, Ag, W, In, Sn, Pb, Sb, La, Ce, Ca, Ba or Sr, and Q element includes at least one of F, Cl, Br or N.

[0059] This application also provides a method for preparing the above-mentioned cathode material, which includes:

[0060] S1: The cathode material precursor is mixed with a lithium source, an optional sodium source and an optional R element source, and a first mixed gas is introduced at a first temperature to perform a first calcination to obtain a first product;

[0061] S2: The first product is calcined by introducing a second mixed gas at a second temperature to obtain the second product;

[0062] S3: Quench the second product to room temperature to obtain the cathode material; wherein the first mixed gas contains hydrogen fluoride; the second mixed gas contains ammonia; and the R element includes at least one of Mg, Al, Ti, Zr, Nb, Y, Cr, V, Ge, Mo, Fe, Cu, Zn, Ga, Ag, W, In, Sn, Pb, Sb, La, Ce, Ca, Ba, or Sr.

[0063] According to some embodiments of this application, the first temperature is from 700°C to 900°C, for example, 700°C, 750°C, 800°C, 850°C, or 900°C. In some embodiments, the first mixture further comprises at least one of air, oxygen, or a mixture of air and oxygen. In some embodiments, the first mixture comprises air and hydrogen fluoride. In some embodiments, the volume percentage of hydrogen fluoride is from 1% to 15% based on the total volume of the first mixture, for example, 1%, 3%, 4%, 6%, 8%, 9%, 10%, 12%, 14%, or 15%.

[0064] According to some embodiments of this application, the second temperature is from 400°C to 650°C, for example, 450°C, 500°C, 550°C, or 600°C. In some embodiments, the second mixture further comprises an inert gas, said inert gas including at least one of nitrogen, argon, and helium. In some embodiments, the second mixture comprises nitrogen and ammonia. In some embodiments, based on the total volume of the second mixture, the volume percentage of ammonia is from 1% to 15%, for example, 1%, 3%, 5%, 7%, 8%, 9%, 10%, 12%, 14%, or 15%.

[0065] According to some embodiments of this application, the cathode material precursor is a hydroxide containing the element T, wherein the element T includes at least one of Ni, Co, or Mn.

[0066] According to some embodiments of this application, the number of moles of Ni element in the cathode material precursor is n. Ni The number of moles of Co is n Co The number of moles of Mn is n Mn The number of moles of element R is n R The total number of moles of element T is n T Where 0.5≤n Ni / n M ≤1, 0≤n Co / n M ≤0.5, 0≤n Mn / n M ≤0.5, 0≤n R / n M ≤0.2, where R is an element including at least one of Mg, Al, Ti, Zr, Nb, Y, Cr, V, Ge, Mo, Fe, Cu, Zn, Ga, Ag, W, In, Sn, Pb, Sb, La, Ce, Ca, Ba, or Sr.

[0067] In some embodiments, the lithium source is selected from lithium carbonate and / or lithium hydroxide. In some embodiments, the sodium source includes at least one of sodium carbonate, sodium bicarbonate, or sodium hydroxide. In some embodiments, the R element source includes an oxide of the R element.

[0068] In some embodiments, the quenching rate is from 30°C / min to 70°C / min, for example 40°C / min, 50°C / min or 60°C / min.

[0069] Secondly, this application provides an electrochemical device comprising a positive electrode, the positive electrode comprising a positive electrode current collector and a positive electrode active material layer, wherein the positive electrode active material layer comprises the positive electrode material of the first aspect or the positive electrode material prepared by the preparation method of the first aspect.

[0070] According to some embodiments of this application, after the electrochemical device is fully discharged, the positive electrode and lithium metal are assembled into a coin cell. The initial open-circuit voltage of the coin cell is Va V. The coin cell is first charged at a constant current of 0.1C to 4.6V, then charged at a constant voltage of 4.6V to 0.05C, allowed to stand for 5 minutes, and then discharged at a constant current of 0.1C to 2.8V. After standing for 5 minutes, the voltage is Vc V, satisfying (Vc-2.8) / Va≤20%. The equilibrium potential of the coin cell is in a relaxed state, and the relaxation voltage differs little from 2.8V, indicating good kinetics of the positive electrode material.

[0071] According to some embodiments of this application, after the electrochemical device is fully discharged, the positive electrode and lithium metal are assembled into a coin cell. When the coin cell is charged and discharged at a current of 0.04C within a voltage range of 2.8V to 4.5V, the voltage-capacity differential dQ / dV curve obtained shows at least two oxidation peaks within the voltage range of 3.6V to 4.5V. In this case, the positive electrode material can exhibit a high charging capacity.

[0072] According to some embodiments of this application, after the electrochemical device is fully discharged, the positive electrode and lithium metal are assembled into a coin cell. When the coin cell is charged and discharged at a current of 0.04C within a voltage range of 2.8V to 4.5V, the voltage-capacity differential dQ / dV curve obtained shows a first oxidation peak within the voltage range of 4.2V to 4.5V. Based on the mass of the positive electrode material, the peak intensity of the first oxidation peak is ≥300mAh / g / V. At this time, the positive electrode material can have a higher charging capacity in the high voltage range of 4.2V to 4.5V, thereby improving the charging capacity of the electrochemical device.

[0073] According to some embodiments of this application, when a coin cell is charged and discharged at a current of 0.04C within a voltage range of 2.8V to 4.5V, the voltage-capacity differential dQ / dV curve obtained shows a first reduction peak in the voltage range of 4.2V to 4.5V. The peak intensity of this first reduction peak is ≥300mAh / g / V, based on the mass of the cathode material. In this case, the cathode material can exhibit a higher reversible discharge capacity in the high voltage range of 4.2V to 4.5V, thereby improving the energy density of the electrochemical device.

[0074] According to some embodiments of this application, after the electrochemical device is fully discharged, the positive electrode and lithium metal are assembled into a coin cell. When the coin cell is charged and discharged at a current of 0.04C within a voltage range of 2.8V to 4.5V, the discharge curve in the obtained voltage-capacity curve shows a plateau within the voltage range of 4.2V to 4.5V. At this time, the positive electrode material can have a stable discharge plateau in the high voltage range of 4.2V to 4.5V, which is beneficial for the electrochemical device to provide stable high-voltage discharge.

[0075] According to some embodiments of this application, after the electrochemical device is fully discharged, the positive electrode and lithium metal are assembled into a coin cell. When the coin cell is charged and discharged at a current of 0.04C within a voltage range of 2.8V to 4.5V, the discharge curve of the obtained voltage-capacity curve shows a capacity of Q1 in the 4.2V to 4.5V voltage range and a capacity of Qt in the 3.0V to 4.5V voltage range, where 0.2 ≤ Q1 / Qt ≤ 0.4. In this case, the positive electrode material exhibits a higher reversible discharge capacity in the high voltage range of 4.2V to 4.5V, thereby improving the energy density of the electrochemical device.

[0076] According to some embodiments of this application, the positive electrode active material layer further includes a conductive agent and a binder. In some embodiments, the binder includes, but is not limited to: polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, styrene-butadiene rubber, or acrylated styrene-butadiene rubber, etc. In some embodiments, the conductive agent includes, but is not limited to: carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof. In some embodiments, the carbon-based material is selected from graphite, carbon black, acetylene black, Ketjen black, carbon nanotubes, carbon fibers, graphene, or any combination thereof. In some embodiments, the metal-based material is selected from metal powder, metal fibers, copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer is a polyphenylene derivative.

[0077] According to some embodiments of this application, the positive electrode further includes a positive electrode current collector, which can be a metal foil or a composite current collector. For example, aluminum foil can be used. The composite current collector can be formed by forming a metallic material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer substrate.

[0078] The electrochemical device of this application also includes a negative electrode, which includes a negative electrode active material layer and a negative electrode current collector.

[0079] According to some embodiments of this application, the negative electrode active material layer includes a negative electrode active material, a conductive agent, and a binder. In some embodiments, the negative electrode active material may include a material that reversibly inserts / deintercalates lithium ions, lithium metal, lithium metal alloys, or transition metal oxides. In some embodiments, the negative electrode active material includes at least one of carbon materials or silicon materials, wherein the carbon material includes at least one of graphite and hard carbon, and the silicon material includes at least one of silicon, silicon oxides, silicon carbide compounds, or silicon alloys. In some embodiments, the binder may include various binder polymers. In some embodiments, the binder includes at least one of polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polytetrafluoroethylene, polyhexafluoropropylene, or styrene-butadiene rubber. In some embodiments, the conductive agent may be any conductive material, as long as it does not cause a chemical change. In some embodiments, the conductive agent includes at least one of conductive carbon black, acetylene black, carbon nanotubes, Ketjen black, carbon fibers, or graphene.

[0080] According to some embodiments of this application, the negative electrode current collector can be copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or a combination thereof.

[0081] The electrochemical device of this application also includes an electrolyte, which includes lithium salts and non-aqueous solvents.

[0082] In some embodiments of this application, the lithium salt is selected from one or more of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, LiBOB, and lithium difluoroborate. For example, LiPF6 can be selected as the lithium salt.

[0083] The non-aqueous solvent may be a carbonate compound, a carboxylic acid ester compound, an ether compound, other organic solvents, or a combination thereof.

[0084] The aforementioned carbonate compounds may be chain carbonate compounds, cyclic carbonate compounds, fluorocarbonate compounds, or combinations thereof.

[0085] Examples of the aforementioned chain carbonate compounds are dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), and combinations thereof. Examples of cyclic carbonate compounds are ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), vinyl ethylene carbonate (VEC), and combinations thereof. Examples of fluorinated carbonate compounds are fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, and combinations thereof.

[0086] Examples of the above-mentioned carboxylic acid ester compounds are methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanoic acid lactone, valerate lactone, mevalonic acid lactone, caprolactone, and combinations thereof.

[0087] Examples of the above-mentioned ether compounds are dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and combinations thereof.

[0088] Examples of other organic solvents mentioned above include dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters and combinations thereof.

[0089] According to some embodiments of this application, in this electrochemical device, a separator is provided between the positive and negative electrodes to prevent short circuits. The material and shape of the separator used in the embodiments of this application are not particularly limited, and can be any technology disclosed in the prior art. In some embodiments, the separator comprises a polymer or inorganic material formed from a material stable to the electrolyte of this application. For example, the separator may include a substrate layer and a surface treatment layer. The substrate layer is a nonwoven fabric, membrane, or composite membrane with a porous structure, and the material of the substrate layer includes at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide. Specifically, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane can be selected. At least one surface of the substrate layer is provided with a surface treatment layer, which can be a polymer layer or an inorganic layer, or a layer formed by mixing polymers and inorganic materials. The inorganic layer comprises inorganic particles and a binder. The inorganic particles include at least one of alumina, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. The binder includes at least one of polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, or polyhexafluoropropylene. The polymer layer contains a polymer, the polymer material of which includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, or poly(vinylidene fluoride-hexafluoropropylene).

[0090] According to some embodiments of this application, the electrochemical device of this application includes, but is not limited to, all types of primary or secondary batteries. In some embodiments, the electrochemical device is a lithium secondary battery. In some embodiments, the lithium secondary battery includes, but is not limited to, lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries.

[0091] Thirdly, the electronic device of this application can be any device that uses the electrochemical device of the second aspect of this application.

[0092] In some embodiments, the electronic device includes, but is not limited to: laptop computers, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries or lithium-ion capacitors, etc.

[0093] Examples and Comparative Examples

[0094] 1. Preparation of cathode materials

[0095] Comparative Example 1

[0096] Step 1: Prepare a mixed solution containing NiSO4 and MnSO4 according to the elemental molar ratio Ni:Mn = 50:50. Mix this solution with a precipitant (NaOH solution) and a complexing agent (ammonia water) and react them. Control the reaction time to 40 hours, the ammonia water concentration to 1 mol / L, and the pH value to 12.00 to obtain a nickel-manganese precursor Ni with an average particle size Dv50 of 11 μm. 0.5 Mn 0.5 (OH)2;

[0097] Step 2: Grind and mix the nickel-manganese precursor, lithium carbonate, and sodium carbonate from Step 1 in a molar ratio of Li:Na:M = 1.05:0.01:1 (M is the sum of transition metal elements Ni and Mn) until homogeneous. Calcinate the mixture at 800℃ in air for 20 hours, then cool it to room temperature at a rate of 10℃ / min. Finally, crush and sieve the mixture to obtain the cathode material.

[0098] Examples 1 to 12

[0099] Step 1, same as Comparative Example 1;

[0100] Step 2: Grind and mix the nickel-manganese precursor, lithium carbonate, and sodium carbonate from Step 1 at a molar ratio of Li:Na:M = 1.05:0.01:1 (M is the sum of transition metal elements Ni and Mn) until homogeneous. Calcinate the mixture at a first temperature T1℃ (see Table 1 for details) with a first mixed gas (see Table 1 for details) for 20 hours to obtain the first product. Then switch to air and cool to a second temperature T2℃ at a rate of 10℃ / min (see Table 1 for details). Introduce a second mixed gas (see Table 1 for details) and maintain this condition for 6 hours. Finally, quench the mixture at 50℃ / min to room temperature. After crushing and sieving, obtain the cathode material.

[0101] Table 1

[0102]

[0103] Note: The percentage content of each component in the gas mixture is by volume.

[0104] 2. Preparation of lithium-ion batteries

[0105] (1) Preparation of lithium-ion button batteries

[0106] A positive electrode slurry was prepared by thoroughly mixing polyvinylidene fluoride (PVDF) as a binder, conductive carbon black (Super P) as a conductive agent, and the positive electrode material in a specific weight ratio (5:5:95) in N-methylpyrrolidone (NMP). The viscosity of the positive electrode slurry was adjusted to 3000 mPa·s to 6000 mPa·s. The mixed slurry was then uniformly coated onto aluminum foil to a thickness of 40 μm on one side. After drying, the slurry was rolled to form the desired electrode. The humidity during electrode processing and transport was 45%. The areal density of the coated electrode was 14 mg / cm³. 2 The positive electrode is obtained by drying and then punched into a circular sheet with a diameter of 14 mm.

[0107] The separator is punched into a circular piece with a diameter of 18 mm; the negative electrode used is a lithium metal sheet with a diameter of 18 mm; LiPF6 is added to a solvent composed of propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC) in a weight ratio of 1:1:1 and mixed evenly to obtain an electrolyte, wherein the mass concentration of LiPF6 is 12.5% ​​based on the mass of the electrolyte.

[0108] The positive electrode, separator, negative electrode (lithium sheet), electrolyte, battery casing, and other accessories are moved into a glove box (the water content must be less than 11 ppm); the battery is assembled in a bottom-to-top stacking order and the electrolyte is injected. It is then packaged on a packaging machine to obtain a button cell.

[0109] (2) Preparation of lithium-ion pouch batteries

[0110] Preparation of positive electrode

[0111] A positive electrode slurry was prepared by thoroughly mixing polyvinylidene fluoride (PVDF), conductive carbon black (Super P), and positive electrode material in a specific weight ratio (2:2:96) in N-methylpyrrolidone (NMP). The viscosity of the positive electrode slurry was adjusted to 3000 mPa·s to 6000 mPa·s. The mixed slurry was then uniformly coated onto aluminum foil with a single-sided coating thickness of 40 μm, and double-sided coating was performed. After drying and cold pressing, the electrode was cut and tabs were welded to obtain the positive electrode. The humidity of the electrode processing and transportation environment was 45%, and the surface density of the coated electrode was 14 mg / cm³. 2 .

[0112] Preparation of negative electrode

[0113] Artificial graphite, styrene-butadiene rubber, and sodium carboxymethyl cellulose (CMC) were mixed with deionized water at a mass ratio of 96:2:2 and stirred until homogeneous to obtain a negative electrode slurry. This negative electrode slurry was then coated onto a 12 μm thick copper foil. After drying and cold pressing, the foil was cut and tabs were welded to obtain the negative electrode.

[0114] Preparation of electrolyte

[0115] In a dry argon atmosphere, LiPF6 was added to a solvent composed of propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC) in a weight ratio of 1:1:1, and mixed thoroughly to obtain an electrolyte. The mass concentration of LiPF6 was 12.5% ​​based on the mass of the electrolyte.

[0116] Preparation of the separating membrane

[0117] Polyethylene (PE) porous polymer film is used as the separator.

[0118] Preparation of lithium-ion batteries

[0119] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes for isolation. The electrode assembly is then wound to form the electrode assembly. This assembly is placed in an outer aluminum-plastic film package, electrolyte is injected, and the package is sealed. After formation, degassing, and edge trimming processes, a lithium-ion pouch battery is obtained.

[0120] Test methods

[0121] 1. XRD Testing

[0122] The cathode material was tested using an X-ray powder diffractometer (XRD, instrument model: Bruker D8 ADVANCE) to obtain the full width at half maximum (FWHM) of the diffraction peaks of the (101), (104), and (003) crystal planes; the target material was Cu Kα; the voltage and current were 40 kV / 40 mA, and the scanning angle range was 10° to 70°.

[0123] 2.85℃ Storage Thickness Expansion Rate Test

[0124] The lithium-ion pouch battery was charged to 4.45V at 0.5C at 25℃, and then charged at a constant voltage of 4.45V to 0.05C. The thickness of the lithium-ion battery at this point was measured and recorded using a micrometer and denoted as H. 11 The lithium-ion battery was then placed in an 85°C oven for 12 hours. After 12 hours, the thickness of the lithium-ion battery was measured and recorded using a micrometer, denoted as H. 12 .

[0125] Thickness expansion rate (%) of lithium-ion battery after storage at 85℃ for 12 hours = (H12 -H 11 ) / H 11 ×100%.

[0126] 3.45℃ Cyclic Capacity Retention Test

[0127] The lithium-ion pouch battery was placed in a 45°C constant temperature chamber and left to stand for 30 minutes to allow it to reach a constant temperature. The lithium-ion battery that had reached a constant temperature was then charged at a constant current of 1.5C to 4.35V at 45°C, and then charged at a constant voltage of 0.02C at 4.35V. After standing for 5 minutes, it was discharged at a constant current of 4C to 2.8V and left to stand for 5 minutes. The discharge capacity of this discharge cycle was recorded as the first cycle discharge capacity. This charge-discharge cycle was repeated 300 times, and the discharge capacity of the battery on the 300th cycle was recorded as the 300th cycle discharge capacity.

[0128] The capacity retention rate (%) of a lithium-ion battery after 300 cycles at 45°C = discharge capacity of the 300th cycle / discharge capacity of the first cycle × 100%.

[0129] 4.1.5C / 8C discharge temperature rise

[0130] The lithium-ion pouch battery was placed in a 25°C constant temperature chamber and left to stand for 30 minutes to allow it to reach a constant temperature. The battery was then charged at a constant current of 1.5C to a voltage of 4.35V, followed by constant voltage charging at 4.35V to a current of 0.05C. Finally, it was discharged at a constant current of 8C to a voltage of 2.7V. During this process, the lithium-ion battery was wrapped in heat-insulating cotton, and the temperature at the top, bottom, and middle of the battery was measured using a multi-channel temperature measuring instrument, and the average value was recorded.

[0131] 5. Gram Capacity Test

[0132] In an environment of 25°C, the lithium-ion coin cell battery is charged at a constant current of 0.5C (i.e., the current value at which the theoretical capacity is completely discharged within 2 hours) until the upper limit voltage is 4.5V. The initial charge capacity of the lithium-ion coin cell battery is recorded. Then, it is discharged at a constant current of 0.2C until the final voltage is 2.8V. The initial discharge capacity of the lithium-ion coin cell battery is recorded.

[0133] The ratio of the initial charge capacity of a lithium-ion coin cell to the mass of the cathode material is denoted as the charge capacity of the cathode material.

[0134] The ratio of the initial discharge capacity of a lithium-ion coin cell to the mass of the cathode material is denoted as the 0.2C g capacity of the cathode material at 25°C.

[0135] 6. Voltage rebound test

[0136] The initial open-circuit voltage of a lithium-ion coin cell is Va V. In an environment of 25°C, the lithium-ion coin cell is charged to 4.6V at a constant current of 0.1C, then charged to 0.05C at a constant voltage of 4.6V, left to stand for 5 minutes, and then discharged to 2.8V at a constant current of 0.1C and left to stand for 5 minutes. The voltage rebound percentage after discharge is (Vc-2.8) / Va×100%.

[0137] 7. Q1 / Qt Testing

[0138] Using an electrochemical workstation, discharge curves of lithium-ion coin cells were obtained at a voltage range of 2.8V to 4.5V and a rate of 0.04C. The capacity in the voltage range of 4.2V to 4.5V was calculated as Q1, and the capacity in the voltage range of 3.0V to 4.5V was calculated as Qt.

[0139] Test Results

[0140] Table 2-1

[0141]

[0142] Table 2-2

[0143]

[0144] A comparison of Examples 1 to 6 with Comparative Example 1 shows that as the gas composition changes, the concentration of oxygen defects inside the cathode material increases. Due to the presence of oxygen defects, the regularity of the (104) crystal plane on the surface of the cathode material decreases compared to the regularity of the (101) crystal plane. The presence of oxygen defects can reduce the activity of oxygen on the material surface, stabilize oxygen ions in the outer layer of the material, and suppress oxygen release and gas generation during high-temperature cycling. As the concentration of oxygen defects increases, the half-width at half maximum (WHM) of the (104) crystal plane increases, corresponding to a gradual decrease in the FWHM(101) / FWHM(104) ratio. A high concentration of oxygen defects can activate the redox properties of transition metals, reducing the redox valence state of transition metals in the material, resulting in a higher plateau capacity in the high-voltage range and a higher Q1 / Qt ratio. Furthermore, from Figure 1 It can be seen that as the oxygen defect concentration increases, the strength of the (101) crystal plane of the cathode material becomes stronger.

[0145] As can be seen from Examples 7 to 11, due to the further increase in the doping amount of N element, more electronic defects are generated in the material, which further improves the electronic conductivity of the material, thereby improving the rate performance of the material, resulting in improved temperature rise during high-rate discharge of lithium-ion batteries and lower voltage rebound at the end of discharge.

[0146] While some exemplary embodiments of this application have been described and illustrated, this application is not limited to the disclosed embodiments. Rather, those skilled in the art will recognize that modifications and changes may be made to the described embodiments without departing from the spirit and scope of this application as described in the appended claims.

Claims

1. A positive electrode material comprising a lithium transition metal oxide, wherein, X-ray diffraction tests showed that the full width at half maximum (FWHM) of the (101) crystal plane diffraction peak and the full width at half maximum (FWHM) of the (104) crystal plane diffraction peak of the cathode material satisfy the following condition: 0.5 ≤ FWHM(101) / FWHM(104) ≤ 0.

7. The full width at half maximum (FWHM) of the (003) crystal plane diffraction peak of the cathode material satisfies: 0.2°≤FWHM(003)≤0.4°; The lithium transition metal oxide includes element T, which includes at least one of Ni, Co, or Mn. Based on the total molar amount of element T in the lithium transition metal oxide, the molar percentage of element Ni in the lithium transition metal oxide is greater than or equal to 50%, the molar percentage of element fluorine in the lithium transition metal oxide is 0.01% to 0.5%, and the molar percentage of element nitrogen in the lithium transition metal oxide is 0.01% to 1%. The lithium transition metal oxide further comprises Na element, and the molar amount of the Na element in the lithium transition metal oxide is n Na , and the total molar amount of T elements is n T , wherein 0 Na / n T ≤0.

02.

2. The positive electrode material of claim 1, wherein, 0.15°≤FWHM(101)≤0.35° and / or 0.25°≤FWHM(104)≤0.6°.

3. The positive electrode material of claim 1, wherein, The full width at half maximum (FWHM) of the (003) crystal plane diffraction peak of the cathode material satisfies: 0.5 ≤ FWHM(101) / FWHM(003) ≤ 1.

5.

4. The cathode material of claim 1, wherein, The cathode material satisfies the following condition (i): (i) 0.7≤FWHM(101) / FWHM(003)≤0.

9.

5. The cathode material according to claim 1, wherein the cathode material satisfies at least one of the following conditions (b) to (e): (b) Based on the total molar amount of T in the lithium transition metal oxide, the molar percentage of Mn in the lithium transition metal oxide is less than or equal to 50%; and / or, based on the total molar amount of T in the lithium transition metal oxide, the molar percentage of Co in the lithium transition metal oxide is less than or equal to 50%; (e) the lithium transition metal oxide further comprises an R element and a Q element, the molar amount of the Ni element in the lithium transition metal oxide is n Ni , the molar amount of the Co element is n Co , the molar amount of the Mn element is n Mn , the molar amount of the R element is n R , the molar amount of the Q element is n Q wherein 0.5≤n Ni / n T ≤1, 0≤n Co / n T ≤0.5, 0≤n Mn / n T ≤0.5, 0 R / n T ≤0.2, 0 Q / n T ≤0.2, the R element includes at least one of Mg, Al, Ti, Zr, Nb, Y, Cr, V, Ge, Mo, Fe, Cu, Zn, Ga, Ag, W, In, Sn, Pb, Sb, La, Ce, Ca, Ba, or Sr, and the Q element includes at least one of F, Cl, Br, or N.

6. A method for preparing a cathode material according to any one of claims 1 to 5, comprising the steps of: S1: Mix the cathode material precursor with a lithium source, a sodium source and an R element source, and calcine the mixture with a first mixed gas at a first temperature to obtain the first product. S2: The first product is calcined by introducing a second mixed gas at a second temperature to obtain a second product; S3: Quench the second product to room temperature to obtain the cathode material; The first mixed gas contains hydrogen fluoride; the second mixed gas contains ammonia; and the R element includes at least one of Mg, Al, Ti, Zr, Nb, Y, Cr, V, Ge, Mo, Fe, Cu, Zn, Ga, Ag, W, In, Sn, Pb, Sb, La, Ce, Ca, Ba, or Sr.

7. The method for preparing the cathode material according to claim 6, wherein, The preparation method satisfies at least one of the following conditions (1) to (11): (1) The first temperature is 700℃ to 900℃; the first calcination time is 10h to 48h; (2) The second temperature is 400℃ to 650℃; the second roasting time is 4h to 24h; (3) The first mixture further comprises at least one of air, oxygen, or a mixture of air and oxygen; (4) Based on the total volume of the first mixture, the volume percentage of the hydrogen fluoride is 1% to 15%; (5) The second mixture further comprises an inert gas, wherein the inert gas includes at least one of nitrogen, argon, and helium; (6) Based on the total volume of the second mixture, the volume percentage of ammonia is 1% to 15%; (7) The cathode material precursor includes a hydroxide of element T, wherein element T includes at least one of Ni, Co or Mn; (8) The lithium source includes at least one of lithium carbonate or lithium hydroxide; (9) The sodium source includes at least one of sodium carbonate, sodium bicarbonate or sodium hydroxide; (10) The source of element R includes oxides of element R; (11) The quenching rate is 30℃ / min to 70℃ / min.

8. An electrochemical device comprising a positive electrode, the positive electrode comprising a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer comprising the positive electrode material according to any one of claims 1 to 5 or the positive electrode material prepared by the preparation method according to any one of claims 6 to 7.

9. The electrochemical device according to claim 8, wherein, After the electrochemical device is fully discharged, the positive electrode is assembled with lithium metal to form a coin cell, wherein the coin cell satisfies at least one of the following conditions (f) to (k): (f) The initial open-circuit voltage of the coin cell is Va V. The coin cell is first charged to 4.6V at a constant current of 0.1C, then charged to 0.05C at a constant voltage of 4.6V, left to stand for 5 minutes, then discharged to 2.8V at a constant current of 0.1C, and left to stand for 5 minutes. The voltage is VcV, which satisfies: (Vc-2.8) / Va≤20%; (g) When the coin cell is charged and discharged at a current of 0.04C in the voltage range of 2.8V to 4.5V, at least two oxidation peaks are present in the voltage range of 3.6V to 4.5V in the voltage differential dQ / dV curve obtained; (h) When the coin cell is charged and discharged at a current of 0.04C in the voltage range of 2.8V to 4.5V, the voltage-capacity differential dQ / dV curve obtained has a first oxidation peak in the voltage range of 4.2V to 4.5V, wherein, based on the mass of the cathode material, the peak intensity of the first oxidation peak is ≥300mAh / g / V; (i) When the coin cell is charged and discharged at a current of 0.04C in the voltage range of 2.8V to 4.5V, the voltage-capacity differential dQ / dV curve obtained has a first reduction peak in the voltage range of 4.2V to 4.5V, wherein, based on the mass of the cathode material, the peak intensity of the first reduction peak is ≥300mAh / g / V; (j) When the button cell is charged and discharged at a current of 0.04C in the voltage range of 2.8V to 4.5V, the discharge curve in the obtained voltage capacity curve has a plateau in the voltage range of 4.2V to 4.5V. (k) When the button cell is charged and discharged at a current of 0.04C in the voltage range of 2.8V to 4.5V, the discharge curve of the voltage capacity curve obtained has a capacity of Q1 in the voltage range of 4.2V to 4.5V and a capacity of Qt in the voltage range of 3.0V to 4.5V, where 0.2≤Q1 / Qt≤0.

4.

10. An electronic device comprising the electrochemical device of claim 8 or 9.

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