Positive electrode material, electrochemical apparatus and electronic apparatus

Abstract

Provided in the present application are a positive electrode material, an electrochemical apparatus and an electronic apparatus. The positive electrode material comprises a lithium nickel manganese composite oxide; the positive electrode material comprises a first region within 100 nm from the surface of the positive electrode material, and a second region above 500 nm from the surface of the positive electrode material; the positive electrode material comprises Al elements; on the basis of the total molar mass of Ni elements and Mn elements in the first region, the molar percentage of the Al elements in the first region is c1Al and, on the basis of the total molar mass of Ni elements and Mn elements in the second region, the molar percentage of the Al elements in the second region is c2Al, satisfying 2≤c1Al / c2Al≤50. When a button battery assembled from the positive electrode material and lithium metal is charged and discharged at the current of 0.04C in the voltage range of 2.8V to 4.5V, an obtained capacity-voltage differential dQ / dV curve has a first oxidation peak and a first reduction peak in the voltage range of 4.2V to 4.5V. The positive electrode material of the present application has relatively high structural stability and interface stability, and can improve the cycle performance and safety of electrochemical apparatuses at high temperature and high voltage.

Description

Cathode materials, electrochemical devices and electronic devices Technical Field

[0001] This application belongs to the field of electrochemistry, specifically relating to cathode materials, electrochemical devices, and electronic devices. Background Technology

[0002] Lithium-ion batteries are widely used in electronic products, energy storage, and electric vehicles due to their advantages such as high energy density, low cost, and no memory effect. The cathode material is crucial to the kinetics, cycle life, and capacity of lithium-ion batteries. Nickel-manganese-based oxide cathode materials have long been considered one of the preferred cathode materials for lithium-ion batteries due to their high discharge specific capacity, relatively low cost, and low toxicity. However, under high Ni content, high voltage, and high temperature conditions, they suffer from surface oxygen release and structural phase transitions, leading to defects such as rapid cycle performance and severe gas generation. Furthermore, because nickel-manganese-based oxide cathode materials contain various elements with different properties, doping modification of nickel-manganese-based oxides cannot significantly improve the cycle performance and gas generation under high temperature and high voltage conditions due to insufficient bonding between the dopant elements and the matrix, and unstable structure and interfaces. Summary of the Invention

[0003] In view of the above-mentioned problems in the prior art, this application provides a cathode material, an electrochemical device, and an electronic device to improve the cycle performance and gas production of an electrochemical device using nickel-manganese-based basal oxide as the cathode material under high temperature and high voltage conditions.

[0004] In a first aspect, this application provides a cathode material comprising a lithium nickel manganese composite oxide; the cathode material includes a first region within 100 nm of the surface of the cathode material and a second region at least 500 nm from the surface of the cathode material; the cathode material includes Al element; based on the total molar amount of Ni and Mn elements in the first region, the molar percentage content of Al element in the first region is c. 1Al Based on the total molar amounts of Ni and Mn elements in the second region, the molar percentage of Al element in the second region is c. 2Al Satisfies: 2≤c 1Al / c 2Al ≤50; The positive electrode material is assembled with lithium metal into a coin cell. 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 obtained capacity-voltage differential dQ / dV curve has a first oxidation peak and a first reduction peak in the range of 4.2V to 4.5V.

[0005] The cathode material of this application, on the one hand, by constructing oxygen defects in the lithium nickel manganese composite oxide, exhibits a significantly increased reversible charge-discharge capacity in the high voltage range of 4.2V to 4.5V. This significantly improves the charge-discharge capacity of the cathode material while giving it high structural stability and kinetic performance at high voltage. Furthermore, the presence of surface oxygen defects enhances the surface stability of the lithium nickel manganese composite oxide, suppressing oxygen release and structural phase transitions on the cathode material surface, thereby improving the cycle performance and gas generation of the electrochemical device under high temperature and high voltage conditions. On the other hand, by controlling the relatively high Al element concentration in the first region of the lithium nickel manganese composite oxide surface, Al elements can further combine with oxygen elements on the surface of the lithium nickel manganese composite oxide, thus working together with the surface oxygen defects to significantly improve the surface stability of the cathode material, thereby significantly improving the cycle performance and gas generation of the electrochemical device under high temperature and high voltage conditions.

[0006] In some implementations, c 1Al The concentration ranges from 0.15% to 20%. This further stabilizes the oxygen content on the surface of the lithium nickel manganese composite oxide, thereby better suppressing oxygen release and structural phase transitions on the cathode material surface, and further improving the cycle performance and gas production of the electrochemical device under high temperature and high voltage conditions.

[0007] In some implementations, c 2Al The content is 0.05% to 2%. Thus, the presence of an appropriate amount of Al element inside the lithium nickel manganese composite oxide particles can further improve the stability of the internal crystal structure of the particles, thereby further improving the cycle performance and gas production of the electrochemical device under high temperature and high voltage conditions.

[0008] In some embodiments, the cathode material includes Na; based on the total molar amount of Ni and Mn in the first region, the molar percentage of Na in the first region is c. 1Na Based on the total molar amounts of Ni and Mn elements in the second region, the molar percentage of Na element in the second region is c. 2Na ; Satisfies: 1.1≤c 1Na / c 2Na≤5. Thus, the first region on the surface of the cathode material is rich in Na. Under high voltage conditions, the first region on the surface of the cathode material has a higher degree of delithiation than the second region inside. Na can act as a support in the crystal lattice. The higher Na content can better support the crystal lattice after delithiation in the first region on the surface, thereby suppressing the structural phase transition of the cathode material surface. At the same time, inorganic compounds containing Na can further stabilize the oxygen on the surface of the cathode material, thereby further suppressing the release of oxygen from the cathode material surface and the decomposition and gas generation of the electrolyte, and further improving the cycle performance and gas generation of the electrochemical device under high temperature and high voltage conditions.

[0009] In some implementations, c 1Na The percentage is 5% to 15%. This allows for better stabilization of the lattice in the first region of the cathode material after delithiation, and protection of the cathode material's surface, thereby further improving the cycle performance and gas production of the electrochemical device under high temperature and high voltage conditions.

[0010] In some implementations, c 2Na The amount is 1% to 10%. Thus, the presence of an appropriate amount of Na in the second region inside the cathode material can further improve the lattice stability of the second region after delithiation, thereby further improving the cycle performance and gas production of the electrochemical device under high temperature and high voltage conditions.

[0011] In some embodiments, the cathode material includes Co; based on the total molar amount of Ni and Mn in the first region, the molar percentage of Co in the first region is c. 1Co Based on the total molar amounts of Ni and Mn elements in the second region, the molar percentage of Co element in the second region is c. 2Co ; Satisfies: 1.3≤c 1Co / c 2Co ≤10. Thus, the first region on the surface of the cathode material is rich in Co, which can synergistically form lithium cobalt composite oxide with Na with a P63mc crystal structure. At the same time, Al doping stabilizes this lithium cobalt composite oxide with a P63mc crystal structure, giving it higher structural stability under high voltage conditions. Therefore, it is beneficial to further suppress surface oxygen release and structural phase transition of the cathode material, thereby further improving the cycle performance and gas production of the electrochemical device under high temperature and high voltage conditions.

[0012] In some implementations, c 1CoThe concentration ranges from 0.2% to 10%. This promotes the formation of lithium cobalt composite oxides with a P63mc crystal structure, improves the stability of the crystal structure in the first region of the cathode material surface, suppresses surface oxygen release and structural phase transition of the cathode material, and thus further improves the cycle performance and gas production of the electrochemical device under high temperature and high voltage conditions.

[0013] In some implementations, c 2Co The concentration is 0.1% to 2%. Thus, the presence of an appropriate amount of Co in the second region inside the cathode material can improve the stability of the crystal structure after delithiation in the second region inside the cathode material, thereby further improving the cycle performance and gas production of the electrochemical device under high temperature and high voltage conditions.

[0014] In some embodiments, the cathode material is a secondary particle, the first region includes a first primary particle, and the second region includes a second primary particle; the second primary particle includes a third region within 20 nm of the surface of the second primary particle and a fourth region more than 50 nm of the surface of the second primary particle, and based on the total molar amount of Ni and Mn elements in the third region, the molar percentage of Al elements in the third region is c. 3Al Based on the total molar amount of Ni and Mn elements in the fourth region, the molar percentage of Al element in the fourth region is c. 4Al Satisfies: 2≤c 3Al / c 4Al ≤10. Thus, the surface layer of the primary particles inside the cathode material particles is rich in Al, which can further improve the stability of the surface layer of the primary particles inside the cathode material particles, thereby better suppressing the surface oxygen release and structural phase transition of the cathode material, and improving the cycle performance and gas production of the electrochemical device under high temperature and high voltage conditions.

[0015] In some implementations, c 3Al The concentration ranges from 0.08% to 3.5%. This improves the stability of the primary particle surface layer within the cathode material particles, thereby better suppressing surface oxygen release and structural phase transitions in the cathode material, and improving the cycle performance and gas production of the electrochemical device under high temperature and high voltage conditions.

[0016] In some implementations, c 4Al The content is 0.04% to 0.5%. Thus, the presence of an appropriate amount of Al element within the primary particles of the cathode material can further improve the stability of the crystal structure of the primary particles, thereby further improving the cycle performance and gas production of the electrochemical device under high temperature and high voltage conditions.

[0017] In some embodiments, the cathode material includes element B; based on the total molar amount of elements Ni and Mn in the first region, the molar percentage of element B in the first region is c. 1B Based on the total molar amounts of Ni and Mn elements in the second region, the molar percentage of B element in the second region is c. 2B Satisfies: 5≤c 1B / c 2B ≤50. Boolean element can achieve good coating on the surface of cathode material at lower temperatures. On the one hand, it can avoid damaging the oxygen defects built in the cathode material. On the other hand, boolean element can combine with oxygen element on the surface of cathode material and separate it from electrolyte. This can further suppress oxygen release from the cathode material surface and decomposition and gas generation of electrolyte, and improve the cycle performance and gas generation of electrochemical device under high temperature and high voltage conditions.

[0018] In some implementations, c 1B The content ranges from 0.5% to 20%. In this way, element B can better protect the surface of the cathode material, further improving the cycle performance and gas production of the electrochemical device under high temperature and high voltage conditions.

[0019] In some implementations, c 2B The content is 0.1% to 0.5%. Thus, the presence of an appropriate amount of B element inside the cathode material particles can further improve the stability of the primary particle surface inside the cathode material particles, and improve the cycle performance and gas production of the electrochemical device under high temperature and high voltage conditions.

[0020] In some embodiments, based on the mass of the cathode material, the peak intensity of the first oxidation peak is greater than or equal to 1000 mAh / g / V, and the peak intensity of the first reduction peak is greater than or equal to 1000 mAh / g / V. Thus, the cathode material can exhibit high reversible charge-discharge capacity in the high-voltage range, thereby significantly improving the energy density of the electrochemical device.

[0021] In some embodiments, the peak voltage of the first oxidation peak is Vo1, and the peak voltage of the first reduction peak is Vr1, satisfying |Vo1-Vr1|≤0.15V. This results in better reversibility of the cathode material in the high-voltage range, thereby further improving the cycle performance of the electrochemical device under high-voltage conditions.

[0022] 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 obtained capacity-voltage curve exhibits a plateau in the 4.2V to 4.5V range. The capacity of the discharge curve in the 4.2V to 4.5V range is Q1, and the capacity of the discharge curve in the 3.0V to 4.5V range is Qt, satisfying: 0.2 ≤ Q1 / Qt ≤ 0.35. Thus, the cathode material can possess a high reversible charge-discharge capacity in the high-voltage range, thereby significantly improving the energy density of the electrochemical device.

[0023] In some embodiments, the capacity-voltage differential dQ / dV curve exhibits a second oxidation peak and a second reduction peak in the 3.6V to 4.0V range.

[0024] In some embodiments, the X-ray diffraction pattern of the cathode material exhibits characteristic diffraction peaks in the ranges of 2θ from 17° to 20°, 35° to 38°, and 42° to 46°.

[0025] In some embodiments, the cell parameter α of the cathode material satisfies

[0026] In some embodiments, the cell parameter c of the cathode material satisfies

[0027] In some embodiments, the cathode material has a layered crystal structure belonging to the R-3m space group.

[0028] In some embodiments, the molar percentage of Ni in the cathode material is greater than or equal to 45%, based on the total molar amount of Ni and Mn elements in the cathode material.

[0029] In some embodiments, the molar percentage of Mn in the cathode material is less than or equal to 50%, based on the total molar amount of Ni and Mn elements in the cathode material.

[0030] In some embodiments, the molar percentage of Li in the cathode material is 90% to 105%, based on the total molar amount of Ni and Mn elements in the cathode material.

[0031] In some embodiments, the molar percentage of Al in the cathode material is 0.1% to 5%, based on the total molar amount of Ni and Mn elements in the cathode material.

[0032] In some embodiments, the cathode material includes Co, and the molar percentage of Co in the cathode material is less than or equal to 10% based on the total molar amount of Ni and Mn in the cathode material.

[0033] In some embodiments, the cathode material includes Na, and the molar percentage of Na in the cathode material is 0.1% to 10% based on the total molar amount of Ni and Mn elements in the cathode material.

[0034] In some embodiments, the positive electrode material includes: Li x1 Na x2 Ni y1 Mn y2 Al y3 Co y4 M y5 O 2±m R n Wherein, M includes at least one of K, Mg, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, Ag, In, Sn, Sb, Ba, La, Ce, Hf, Ta, W, Pb, Bi, B, Si, P, or S; R includes at least one of F, Cl, Br, I, or N; 0.9≤x1≤1.05, 0.001≤x2≤0.1, 0.45≤y1≤1, 0≤y2≤0.5, 0.001≤y3≤0.05, 0≤y4≤0.1, 0≤y5≤0.05, 0≤m≤0.2, and 0≤n≤0.2.

[0035] Secondly, this application provides an electrochemical device including a positive electrode, the positive electrode including a positive electrode current collector and a positive electrode active material layer, characterized in that the positive electrode active material layer includes the aforementioned positive electrode material.

[0036] Thirdly, this application provides an electronic device including the aforementioned electrochemical device. Attached Figure Description

[0037] Figure 1 is an X-ray diffraction pattern of the cathode material prepared in Comparative Example 1 and Example 13 of this application.

[0038] Figure 2 is a scanning electron microscope image of the cathode material prepared in Comparative Example 1 of this application at 10,000x magnification.

[0039] Figure 3 is a scanning electron microscope image of the cathode material prepared in Example 13 of this application at 10,000x magnification.

[0040] Figure 4 is a scanning electron microscope image of the cross-section of the cathode material prepared in Comparative Example 1 of this application at 1000x magnification.

[0041] Figure 5 is a scanning electron microscope image of the cross-section of the positive electrode material prepared in Example 13 of this application at 1000x magnification.

[0042] Figure 6 shows the variation of Li, Ni, Mn, Na, Al, Co, and B contents with different etching depths obtained by time-of-flight secondary ion mass spectrometry testing of the cathode material prepared in Example 13 of this application.

[0043] Figure 7 shows the specific capacity-voltage curves of the coin cells assembled with the cathode materials prepared in Comparative Example 1 and Example 13 of this application during the first charge and discharge at a current density of 0.04C.

[0044] Figure 8 shows the capacity-voltage differential dQ / dV curves of the coin cells assembled with the cathode materials prepared in Comparative Example 1 and Example 13 of this application during the first charge and discharge at a current density of 0.04C. Detailed Implementation

[0045] To better illustrate the purpose, technical solution, and advantages of this application, the technical solution of this application will be clearly and completely described below in conjunction with embodiments. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. The embodiments described herein are illustrative in nature and are used to provide a basic understanding of this application. Furthermore, the embodiments of this application should not be construed as limiting this application.

[0046] 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.

[0047] In this description, unless otherwise stated, "above" and "below" include the stated number. 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 numerical values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art. In this description, a list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items.

[0048] To improve the cycling performance and gas production of electrochemical devices using nickel-manganese-based layered oxides as cathode materials under high temperature and high voltage conditions, this application provides a cathode material comprising a lithium-nickel-manganese composite oxide. The cathode material includes a first region within 100 nm of the surface of the cathode material and a second region more than 500 nm from the surface of the cathode material. The cathode material includes Al element. Based on the total molar amount of Ni and Mn elements in the first region, the molar percentage of Al element in the first region is c. 1Al Based on the total molar amounts of Ni and Mn elements in the second region, the molar percentage of Al element in the second region is c. 2Al Satisfies: 2≤c 1Al / c 2Al ≤50; The positive electrode material is assembled with lithium metal into a coin cell. 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 obtained capacity-voltage differential dQ / dV curve has a first oxidation peak and a first reduction peak in the range of 4.2V to 4.5V.

[0049] The cathode material of this application, on the one hand, by constructing oxygen defects in the lithium nickel manganese composite oxide, exhibits a significantly increased reversible charge-discharge capacity in the high voltage range of 4.2V to 4.5V. This significantly improves the charge-discharge capacity of the cathode material while giving it high structural stability and kinetic performance at high voltage. Furthermore, the presence of surface oxygen defects enhances the surface stability of the lithium nickel manganese composite oxide, suppressing oxygen release and structural phase transitions on the cathode material surface, thereby improving the cycle performance and gas generation of the electrochemical device under high temperature and high voltage conditions. On the other hand, by controlling the relatively high Al element concentration in the first region of the lithium nickel manganese composite oxide surface, Al elements can further combine with oxygen elements on the surface of the lithium nickel manganese composite oxide, thus working together with the surface oxygen defects to significantly improve the surface stability of the cathode material, thereby significantly improving the cycle performance and gas generation of the electrochemical device under high temperature and high voltage conditions.

[0050] In some implementations, c 1Al The concentration ranges from 0.15% to 20%. This further stabilizes the oxygen content on the surface of the lithium nickel manganese composite oxide, thereby better suppressing oxygen release and structural phase transitions on the cathode material surface, and further improving the cycle performance and gas production of the electrochemical device under high temperature and high voltage conditions. Specifically, c 1Al It can be 0.15%, 0.2%, 0.5%, 1%, 2%, 3.5%, 5%, 6.5%, 8%, 9.5%, 11%, 12.5%, 14%, 15.5%, 17%, 18.5%, 20%, or a range of any two of these values.

[0051] In some implementations, c 2Al The content is 0.05% to 2%. Thus, the presence of an appropriate amount of Al within the lithium nickel manganese composite oxide particles can further improve the stability of the internal crystal structure, thereby further improving the cycle performance and gas production of the electrochemical device under high temperature and high voltage conditions. Specifically, c 2Al It can be 0.05%, 0.1%, 0.15%, 0.2%, 0.4%, 0.6%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, or a range of any two of these values.

[0052] In some embodiments, the cathode material includes Na; based on the total molar amount of Ni and Mn in the first region, the molar percentage of Na in the first region is c. 1Na Based on the total molar amounts of Ni and Mn elements in the second region, the molar percentage of Na element in the second region is c. 2Na ; Satisfies: 1.1≤c 1Na / c 2Na ≤5. Thus, the first region on the surface of the cathode material is rich in Na. Under high voltage conditions, the first region on the surface of the cathode material exhibits a higher degree of delithiation compared to the internal second region. Na acts as a support in the crystal lattice, and the higher Na content better supports the delithiated crystal lattice in the first region, thereby suppressing the structural phase transition of the cathode material surface. Simultaneously, Na-containing inorganic compounds can further stabilize the oxygen on the cathode material surface, thereby further suppressing oxygen release from the cathode material surface and the decomposition and gas generation of the electrolyte, further improving the cycle performance and gas generation of the electrochemical device under high temperature and high voltage conditions. 1Na / c 2Na The value can be 1.1, 1.3, 1.5, 1.6, 1.8, 2, 2.5, 3, 3.5, 4, 4.5, 5, or a range of any two of these values. In some implementations, 1.1 ≤ c 1Na / c 2Na ≤1.6.

[0053] In some implementations, c 1Na The percentage is 5% to 15%. This allows for better stabilization of the crystal lattice in the first region of the cathode material after lithium removal, and protects the surface of the cathode material, thereby further improving the cycle performance and gas production of the electrochemical device under high temperature and high voltage conditions. Specifically, c 1Na It can be 5%, 7%, 9%, 11%, 13%, 15%, or a range of any two of these values.

[0054] In some implementations, c 2Na The amount is 1% to 10%. Thus, the presence of an appropriate amount of Na in the second region within the cathode material can further improve the lattice stability of the second region after lithium delithiation, thereby further improving the cycle performance and gas production of the electrochemical device under high temperature and high voltage conditions. Specifically, c 2Na It can be 1%, 3%, 5%, 7%, 9%, 10%, or a range of any two of these values.

[0055] In some embodiments, the cathode material includes Co; based on the total molar amount of Ni and Mn in the first region, the molar percentage of Co in the first region is c. 1Co Based on the total molar amounts of Ni and Mn elements in the second region, the molar percentage of Co element in the second region is c. 2Co ; Satisfies: 1.3≤c 1Co / c 2Co ≤10. Thus, the first region on the surface of the cathode material is rich in Co, which can synergistically form a lithium-cobalt composite oxide with a P63mc crystal structure with Na. Simultaneously, Al doping stabilizes this lithium-cobalt composite oxide with a P63mc crystal structure, resulting in higher structural stability under high voltage conditions. Therefore, this is beneficial for further suppressing surface oxygen release and structural phase transitions in the cathode material, thereby further improving the cycle performance and gas production of the electrochemical device under high temperature and high voltage conditions. Specifically, c 1Co / c 2Co The value can be 1.3, 1.5, 2, 3, 4, 5, 6, 7, 8, 9, 10, or a range of any two of these values. In some implementations, 1.3 ≤ c 1Co / c 2Co ≤5.

[0056] In some implementations, c 1Co The concentration ranges from 0.2% to 10%. This promotes the formation of lithium-cobalt composite oxides with a P63mc crystal structure, improves the stability of the crystal structure in the first region of the cathode material surface, suppresses surface oxygen release and structural phase transitions in the cathode material, and thus further improves the cycle performance and gas production of the electrochemical device under high temperature and high voltage conditions. Specifically, c 1Co It can be 0.2%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range of any two of these values.

[0057] In some implementations, c 2CoThe concentration is 0.1% to 2%. Thus, the presence of an appropriate amount of Co in the second region within the cathode material can improve the stability of the crystal structure after lithium removal, thereby further improving the cycle performance and gas production of the electrochemical device under high temperature and high voltage conditions. Specifically, C... 2Co It can be 0.1%, 0.25%, 0.5%, 0.75%, 1%, 1.25%, 1.5%, 1.75%, 2%, or a range of any two of these values.

[0058] In some embodiments, the cathode material is a secondary particle, the first region includes a first primary particle, and the second region includes a second primary particle; the second primary particle includes a third region within 20 nm of the surface of the second primary particle and a fourth region more than 50 nm of the surface of the second primary particle, and based on the total molar amount of Ni and Mn elements in the third region, the molar percentage of Al elements in the third region is c. 3Al Based on the total molar amount of Ni and Mn elements in the fourth region, the molar percentage of Al element in the fourth region is c. 4Al Satisfies: 2≤c 3Al / c 4Al ≤10. Thus, the surface layer of the primary particles inside the cathode material is rich in Al, which can further improve the stability of the surface layer of the primary particles inside the cathode material, thereby better suppressing surface oxygen release and structural phase transition of the cathode material, and improving the cycle performance and gas production of the electrochemical device under high temperature and high voltage conditions. Specifically, c 3Al / c 4Al The value can be 2, 3, 4, 5, 6, 7, 8, 9, 10, or a range of any two of these values.

[0059] In some implementations, c 3Al The concentration ranges from 0.08% to 3.5%. This allows for better improvement in the stability of the primary particle surface layer within the cathode material, thereby better suppressing surface oxygen release and structural phase transitions in the cathode material, and improving the cycle performance and gas generation of the electrochemical device under high temperature and high voltage conditions. Specifically, c 3Al It can be 0.08%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, or a range of any two of these values.

[0060] In some implementations, c 4AlThe content is 0.04% to 0.5%. Thus, the presence of an appropriate amount of Al within the primary particles of the cathode material further improves the stability of the crystal structure of the primary particles, thereby further improving the cycle performance and gas production of the electrochemical device under high temperature and high voltage conditions. Specifically, c 4Al It can be 0.04%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or a range of any two of these values.

[0061] In some embodiments, the cathode material includes element B; based on the total molar amount of elements Ni and Mn in the first region, the molar percentage of element B in the first region is c. 1B Based on the total molar amounts of Ni and Mn elements in the second region, the molar percentage of B element in the second region is c. 2B Satisfies: 5≤c 1B / c 2B ≤50. Boolean (B) can achieve good coating of the cathode material surface at lower temperatures. On the one hand, it avoids damaging the oxygen vacancies built in the cathode material; on the other hand, B can combine with O on the cathode material surface and separate it from the electrolyte, thereby further suppressing surface oxygen release from the cathode material and decomposition gas generation in the electrolyte, improving the cycle performance and gas generation of the electrochemical device under high temperature and high voltage conditions. Specifically, c 1B / c 2B The value can be 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, or a range of any two of these values.

[0062] In some implementations, c 1B The content ranges from 0.5% to 20%. In this way, element B can better protect the surface of the cathode material, further improving the cycle performance and gas production of the electrochemical device under high temperature and high voltage conditions. Specifically, c 1B It can be 0.5%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, or a range of any two of these values.

[0063] In some implementations, c 2B The concentration is 0.1% to 0.5%. Thus, the presence of an appropriate amount of boron (B) within the cathode material particles can further improve the stability of the primary particle surface, thereby improving the cycle performance and gas production of the electrochemical device under high temperature and high voltage conditions. Specifically, c 2B It can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or a range of any two of these values.

[0064] In some embodiments, based on the mass of the cathode material, the peak intensity of the first oxidation peak is greater than or equal to 1000 mAh / g / V, and the peak intensity of the first reduction peak is greater than or equal to 1000 mAh / g / V. Thus, the cathode material can exhibit high reversible charge-discharge capacity in the high-voltage range, thereby significantly improving the energy density of the electrochemical device.

[0065] In some embodiments, the peak intensity of the first oxidation peak is from 1000 mAh / g / V to 2500 mAh / g / V. Specifically, the peak intensity of the first oxidation peak may be 1000 mAh / g / V, 1200 mAh / g / V, 1400 mAh / g / V, 1500 mAh / g / V, 1600 mAh / g / V, 1800 mAh / g / V, 2000 mAh / g / V, 2200 mAh / g / V, 2400 mAh / g / V, 2500 mAh / g / V, or a range of any two of these values.

[0066] In some embodiments, the peak intensity of the first reduction peak is from 1000 mAh / g / V to 2500 mAh / g / V. Specifically, the peak intensity of the first reduction peak may be 1000 mAh / g / V, 1200 mAh / g / V, 1400 mAh / g / V, 1500 mAh / g / V, 1600 mAh / g / V, 1800 mAh / g / V, 2000 mAh / g / V, 2200 mAh / g / V, 2400 mAh / g / V, 2500 mAh / g / V, or a range of any two of these values.

[0067] In some embodiments, the peak voltage of the first oxidation peak is Vo1, and the peak voltage of the first reduction peak is Vr1, satisfying |Vo1-Vr1|≤0.15V. The smaller the voltage difference |Vo1-Vr1| between the first oxidation peak and the first reduction peak, the better the electrochemical reversibility of the cathode material and the smaller the electrochemical polarization. In this application, the cathode material has |Vo1-Vr1|≤0.15V, indicating good reversibility in the high-voltage range, thereby further improving the cycle performance of the electrochemical device under high-voltage conditions. The value of |Vo1-Vr1| can be 0V, 0.025V, 0.05V, 0.075V, 0.1V, 0.125V, 0.15V, or any combination of these values.

[0068] In some implementations, Vo1 is 4.3V to 4.4V, specifically 4.3V, 4.31V, 4.32V, 4.33V, 4.35V, 4.37V, 4.38V, 4.39V, 4.4V, or a range of any two of these values.

[0069] 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 obtained capacity-voltage curve exhibits a plateau in the 4.2V to 4.5V range. The capacity of the discharge curve in the 4.2V to 4.5V range is Q1, and the capacity of the discharge curve in the 3.0V to 4.5V range is Qt, satisfying: 0.2 ≤ Q1 / Qt ≤ 0.35. Thus, the cathode material can possess a high reversible charge-discharge capacity in the high-voltage range, thereby significantly improving the energy density of the electrochemical device. The value of Q1 / Qt can be 0.2, 0.22, 0.24, 0.26, 0.28, 0.3, 0.32, 0.34, 0.35, or any combination of these values. In some embodiments, 0.25 ≤ Q1 / Qt ≤ 0.30.

[0070] In some implementations, Q1 is from 10 mAh / g to 70 mAh / g, specifically 10 mAh / g, 20 mAh / g, 30 mAh / g, 40 mAh / g, 50 mAh / g, 60 mAh / g, 70 mAh / g, or a range of any two of these values.

[0071] In some implementations, Qt is from 100 mAh / g to 230 mAh / g, specifically 100 mAh / g, 130 mAh / g, 160 mAh / g, 190 mAh / g, 220 mAh / g, 230 mAh / g, or a range of any two of these values.

[0072] In some embodiments, the capacity-voltage differential dQ / dV curve exhibits a second oxidation peak and a second reduction peak in the 3.6V to 4.0V range.

[0073] In some embodiments, the X-ray diffraction pattern of the cathode material exhibits characteristic diffraction peaks in the 2θ ranges of 17° to 20°, 35° to 38°, and 42° to 46°. The diffraction peaks in the 2θ ranges of 17° to 20°, 35° to 38°, and 42° to 46° in the X-ray diffraction pattern of the cathode material are attributed to characteristic peaks of the (003), (101), and (104) crystal planes of the layered lithium nickel manganese composite oxide, respectively.

[0074] In some embodiments, the cell parameter α of the cathode material satisfies a can specifically be Or a range consisting of any two of these values.

[0075] In some embodiments, the cell parameter c of the cathode material satisfies c can specifically be Or a range consisting of any two of these values.

[0076] The lithium-nickel-manganese composite oxide in the cathode material of this application has a larger cell parameter than that of traditional cathode materials, which is beneficial to better lithium-ion transport kinetics.

[0077] In some embodiments, the cathode material has a layered crystal structure belonging to the R-3m space group.

[0078] In some embodiments, the positive electrode material particles contain pores; the cross-sectional porosity of the positive electrode material is 2% to 30%. Specifically, the cross-sectional porosity of the positive electrode material can be 2%, 6%, 8%, 10%, 14%, 18%, 22%, 26%, 30%, or any combination of these values. The cross-sectional porosity of the positive electrode material can be tested by the following method: cutting an electrode containing the positive electrode material with a three-ion beam to obtain a flat cross-section exposing the internal structure of the positive electrode material; taking a cross-sectional image using a scanning electron microscope (SEM); using ImageJ software to count the pore area in the cross-section of the positive electrode material particles; and using the ratio of the pore area to the total cross-sectional area of ​​the positive electrode material particles as the cross-sectional porosity of the positive electrode material.

[0079] In some embodiments, the BET specific surface area of ​​the cathode material is 1 m². 2 / g to 10m 2 / g. The BET specific surface area of ​​the cathode material can specifically be 1m². 2 / g、2m 2 / g、3m 2 / g、4m 2 / g、5m 2 / g、6m 2 / g、7m 2 / g、8m 2 / g、9m 2 / g, 10m 2 / g, or a range of any two of these values. The BET specific surface area is obtained by testing using the nitrogen adsorption BET method.

[0080] In some embodiments, the average particle size Dv50 of the cathode material is from 5 μm to 15 μm. Specifically, the Dv50 of the cathode material can be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or any combination of these values. Here, Dv50 represents the particle size corresponding to 50% of the cumulative volume from the smallest particle size side in a volumetric particle size distribution. Dv50 can be obtained by laser particle size distribution measurement.

[0081] In some embodiments, the X-ray photoelectron spectroscopy spectrum of the cathode material surface contains characteristic peaks of Al 2p in the binding energy range of 70 eV to 80 eV.

[0082] In some embodiments, the X-ray photoelectron spectroscopy spectrum of the cathode material surface contains a characteristic peak of Na 1s in the range of 1065 eV to 1078 eV.

[0083] In some embodiments, based on the total molar amount of Ni and Mn elements in the cathode material, the molar percentage content of Ni element in the cathode material is greater than or equal to 45%. Specifically, it can be 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or a range of any two of these values. In some embodiments, the molar percentage content of Ni element in the cathode material is between 45% and 70%.

[0084] In some embodiments, based on the total molar amount of Ni and Mn elements in the cathode material, the molar percentage of Mn element in the cathode material is less than or equal to 50%. Specifically, it can be 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, or a range of any two of these values. In some embodiments, the molar percentage of Mn element in the cathode material is from 20% to 50%.

[0085] In some embodiments, based on the total molar amount of Ni and Mn elements in the cathode material, the molar percentage of Li element in the cathode material is 90% to 105%, specifically, it can be 90%, 92%, 94%, 96%, 98%, 100%, 102%, 105%, or any combination of these values.

[0086] In some embodiments, based on the total molar amount of Ni and Mn elements in the cathode material, the molar percentage of Al element in the cathode material is 0.1% to 5%, specifically, it can be 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any combination of these values.

[0087] In some embodiments, the cathode material includes Co, and the molar percentage of Co in the cathode material is less than or equal to 10% based on the total molar amount of Ni and Mn in the cathode material. Specifically, it can be 0%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any combination of these values. In some embodiments, the molar percentage of Co in the cathode material is from 0.5% to 5%.

[0088] In some embodiments, the cathode material includes element B, and based on the total molar amount of elements Ni and Mn in the cathode material, the molar percentage of element B in the cathode material is less than or equal to 10%, specifically, it can be 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any combination of these values. In some embodiments, the molar percentage of element B in the cathode material is from 0.5% to 5%.

[0089] In some embodiments, the cathode material includes Na, and based on the total molar amount of Ni and Mn in the cathode material, the molar percentage of Na in the cathode material is from 0.1% to 10%, specifically, it can be 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any combination of these values. In some embodiments, the molar percentage of Na in the cathode material is from 5% to 10%.

[0090] In some embodiments, the positive electrode material includes: Li x1 Na x2 Ni y1 Mn y2 Al y3 Co y4 M y5 O 2±m R n Wherein, M includes at least one of K, Mg, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, Ag, In, Sn, Sb, Ba, La, Ce, Hf, Ta, W, Pb, Bi, B, Si, P, or S; R includes at least one of F, Cl, Br, I, or N; 0.9≤x1≤1.05, 0.001≤x2≤0.1, 0.45≤y1≤1, 0≤y2≤0.5, 0.001≤y3≤0.05, 0≤y4≤0.1, 0≤y5≤0.05, 0≤m≤0.2, and 0≤n≤0.2.

[0091] In some embodiments, the method for preparing the positive electrode material includes the following steps:

[0092] S1: Dissolve the nickel source and manganese source in water to obtain a first solution. Under a first atmosphere, mix the first solution with a precipitant and a complexing agent to react and obtain a first mixed solution containing a nickel-manganese-based precursor.

[0093] S2: Dissolve an aluminum source and an optional cobalt source in water to obtain a second solution, and add the second solution to the first mixed solution to react and obtain a first precursor;

[0094] S3: The first precursor is mixed with a sodium source and then calcined once under a second atmosphere. After cooling, the second precursor is obtained.

[0095] S4: After mixing the second precursor and the lithium source, the mixture is calcined twice under a third atmosphere and then quenched to obtain the cathode material.

[0096] In some embodiments, the reaction temperature in step S1 is between 25°C and 100°C. In some embodiments, the reaction time in step S1 is between 12 hours and 96 hours. In some embodiments, the first atmosphere in step S1 is an inert atmosphere.

[0097] In some embodiments, in step S1, the nickel source comprises a nickel salt. In some embodiments, the nickel salt comprises at least one of a nickel sulfate, a nickel nitrate, or a nickel acetate.

[0098] In some embodiments, in step S1, the manganese source comprises a manganese salt. In some embodiments, the manganese salt comprises at least one of manganese sulfate, manganese nitrate, or manganese acetate.

[0099] In some embodiments, in step S1, the precipitant comprises an alkaline solution. In some embodiments, the alkaline solution comprises at least one of sodium hydroxide solution or lithium hydroxide solution.

[0100] In some embodiments, in step S1, the complexing agent includes ammonia.

[0101] In some embodiments, in step S2, the aluminum source comprises an aluminum salt. In some embodiments, the aluminum salt comprises at least one of aluminum sulfate, aluminum nitrate, or aluminum acetate.

[0102] In some embodiments, in step S2, the cobalt source comprises a cobalt salt. In some embodiments, the cobalt salt comprises at least one of cobalt sulfate, cobalt nitrate, or cobalt acetate.

[0103] In some embodiments, in step S3, the sodium source includes at least one of a sodium salt, a sodium hydroxide, or a sodium oxide. In some embodiments, the sodium salt includes at least one of a sodium sulfate, a sodium nitrate, a sodium carbonate, or a sodium acetate.

[0104] In some embodiments, the temperature of the first calcination in step S3 is 600°C to 900°C. In some embodiments, the calcination time is 8 hours to 48 hours. In some embodiments, the second atmosphere in step S3 is an oxygen-containing atmosphere. In some embodiments, the oxygen-containing atmosphere in step S3 includes at least one of air, oxygen, or a mixture of air and oxygen. In some embodiments, the heating rate to the first calcination temperature in step S3 is 1°C / min to 10°C / min. In some embodiments, the cooling rate is 1°C / min to 7°C / min.

[0105] In some embodiments, the temperature of the secondary calcination in step S4 is 200°C to 500°C. In some embodiments, the time for the secondary calcination in step S4 is 1 hour to 12 hours. In some embodiments, the third atmosphere in step S4 is selected from at least one of an inert gas or a reducing atmosphere. In some embodiments, the inert gas in step S4 includes at least one of nitrogen, argon, and helium. In some embodiments, the reducing atmosphere in step S4 includes hydrogen.

[0106] In some implementations, in step S4, the volume percentage of H2 in the third atmosphere is less than or equal to 10% based on the total volume of the third atmosphere.

[0107] In some implementations, step S4, after quenching, further includes washing, drying, and sieving.

[0108] In some embodiments, in step S4, the lithium source includes at least one of a lithium salt, a lithium hydroxide, or a lithium oxide. In some embodiments, in step S4, the lithium salt includes at least one of a lithium sulfate, a lithium nitrate, a lithium carbonate, or a lithium acetate.

[0109] In some embodiments, in step S4, the heating rate to the secondary calcination temperature is 1°C / min to 5°C / min. In some embodiments, in step S4, the quenching cooling rate is 30°C / min to 70°C / min.

[0110] In some embodiments, the preparation method of the cathode material further includes step S5: mixing the cathode material product from step S4 with a boron source, calcining it three times under a fourth atmosphere, and then cooling it to obtain the cathode material.

[0111] In some embodiments, in step S5, the boron source includes at least one of borate, boric acid, or boron oxide.

[0112] In some embodiments, in step S5, the temperature of the three calcinations is 200°C to 500°C. In some embodiments, in step S5, the time for the three calcinations is 2 hours to 24 hours. In some embodiments, in step S5, the fourth atmosphere is an oxygen-containing atmosphere. In some embodiments, in step S5, the oxygen-containing atmosphere includes at least one of air, oxygen, or a mixture of air and oxygen. In some embodiments, in step S5, the heating rate to the temperature of the three calcinations is 1°C / min to 10°C / min. In some embodiments, in step S5, the cooling rate is 1°C / min to 7°C / min.

[0113] In a second aspect, this application provides an electrochemical device including a positive electrode, the positive electrode including a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer including the positive electrode material described in the first aspect of this application.

[0114] In some embodiments, the positive electrode active material layer further includes an adhesive and a conductive agent.

[0115] In some embodiments, the adhesive comprises at least one of styrene-butadiene rubber (SBR), waterborne acrylic resin, carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), ethylene-vinyl acetate copolymer (EVA), or polyvinyl alcohol (PVA), and is not limited to the above types; the adhesive can be selected according to actual needs. In some embodiments, the mass percentage of the adhesive is less than or equal to 5% based on the total mass of the positive electrode active material layer.

[0116] In some embodiments, the conductive agent includes at least one of graphite, acetylene black, carbon black, Ketjen black, carbon nanotubes, graphene, or carbon nanofibers, but is not limited to these. The conductive agent can be selected according to actual needs. In some embodiments, the mass percentage of the conductive agent is 1% to 3% based on the total mass of the positive electrode active material layer.

[0117] In some embodiments, the positive current collector includes a sheet of metal material, such as aluminum, nickel, silver, titanium, or aluminum foil, but is not limited thereto.

[0118] The positive electrode can be prepared by conventional methods in the art. For example, a method for preparing a positive electrode includes the following steps: mixing a solvent, a conductive agent, a binder, and a positive electrode material to obtain a positive electrode slurry; coating the positive electrode slurry onto a positive electrode current collector, and then drying and cold pressing to obtain the positive electrode. In some embodiments, the solvent may include N-methylpyrrolidone (NMP), but is not limited thereto.

[0119] In some embodiments, the electrochemical device further includes a negative electrode, which comprises a negative electrode active material layer and a negative electrode current collector.

[0120] In some embodiments, the negative electrode active material includes at least one of graphite, mesophase carbon microspheres, hard carbon, soft carbon, silicon, silicon-carbon materials, silicon-oxygen materials, Li alloys, and metallic lithium, but is not limited thereto.

[0121] In some embodiments, the negative current collector can be a sheet of metal such as copper, nickel, stainless steel or titanium, for example, copper foil, but is not limited thereto.

[0122] In some embodiments, the electrochemical device further includes a separator membrane located between the positive and negative electrodes. In some embodiments, the separator membrane comprises a porous sheet-like or nonwoven resin, the resin comprising, but not limited to, at least one of, polyolefins, aromatic polyamides, polytetrafluoroethylene, or polyethersulfone.

[0123] In some embodiments, the electrochemical device also includes an electrolyte.

[0124] In some embodiments, the electrolyte may include organic solvents, lithium salts, and additives. This application does not impose specific limitations on the types of organic solvents and lithium salts; they can be selected according to actual needs.

[0125] In some embodiments, the organic solvent may be at least one of methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butenyl carbonate (BC), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), or diethyl sulfone (ESE).

[0126] In some embodiments, the lithium salt may be at least one of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium difluorophosphate (LiPO2F2), lithium difluorodioxophosphate (LiDFOP), lithium tetrafluorooxophosphate (LiTFOP), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxophosphate borate (LiDFOB), or lithium dioxophosphate borate (LiBOB).

[0127] In some embodiments, the additive is not particularly limited and can be selected according to actual needs. For example, the additive may include nitrile compounds. In some embodiments, the nitrile compound includes at least one selected from butadionitrile, glutaronitrile, adiponitrile, or 1,3,6-hexanetrionitrile.

[0128] The electrochemical device of this application can be prepared according to conventional methods in the art; such preparation methods may specifically include the following steps: stacking the above-mentioned positive electrode, separator and negative electrode in sequence, with the separator between the positive electrode and the negative electrode, and then winding them to obtain an electrode assembly; placing the electrode assembly in a packaging shell, injecting electrolyte and sealing it to obtain the electrochemical device.

[0129] Thirdly, this application provides an electronic device, including the electrochemical device described in the second aspect of this application.

[0130] The electrochemical device of this application can be used in various fields such as electronic products, energy storage, and electric vehicles, including mobile phones, laptops, power tools, video recorders, backup power supplies, electric vehicles, electric motorcycles, game consoles, cameras, and drones.

[0131] The technical solution of this application will be described below with reference to specific embodiments and comparative examples. Unless otherwise specified, the materials, reagents, equipment, etc. used can all be obtained commercially.

[0132] I. Preparation of cathode materials

[0133] Example 1

[0134] S1: Prepare a first aqueous solution containing NiSO4 and MnSO4 according to the molar ratio of Ni to Mn = 50:50. In a nitrogen atmosphere, mix the first aqueous solution with a precipitant (NaOH solution) and a complexing agent (ammonia water) to react. Control the concentration of ammonia water in the system to be 1 mol / L, the pH of the system to be 12.5, and the total reaction time to be 48 hours to obtain the first mixed solution.

[0135] S2: Prepare a second aqueous solution containing Al2(SO4)3, slowly add the second aqueous solution to the first mixed solution to carry out the reaction, and control the ratio of the total molar amount of Ni and Mn elements to the molar amount of Al element to be TM(Ni+Mn):Al=1∶0.001. After the reaction is completed, filter, wash with water and dry to obtain the first precursor.

[0136] S3: According to the ratio of the total molar amount of Ni and Mn to the molar amount of Na, TM(Ni+Mn):Na=1∶1.05, the first precursor in step S2 and sodium carbonate are ground and mixed evenly, and then calcined at 800°C at a rate of 5°C / min in air atmosphere for 15 hours, and then cooled to room temperature at a rate of 5°C / min to obtain the second precursor.

[0137] S4: Lithium hydroxide, lithium chloride, and lithium nitrate are mixed in a molar ratio of 1:1:1 to obtain a lithium source. The second precursor obtained in step S3 and the lithium source are thoroughly mixed in a ratio of total molar amount of Ni and Mn to molar amount of Li of TM(Ni+Mn):Li = 1:3. The mixture is then heated to 400℃ at a rate of 3℃ / min under a nitrogen atmosphere and calcined for 5 hours. After calcination, the mixture is cooled to room temperature at a rate of 50℃ / min. Finally, the mixture is washed with deionized water, dried, and sieved to obtain a cathode material with an average particle size Dv50 of 11μm.

[0138] Example 2

[0139] The difference between this embodiment and Embodiment 1 is that in step S2, a second solution containing Al2(SO4)3 is prepared with a ratio of the total molar amount of Ni and Mn to the molar amount of Al of TM(Ni+Mn):Al = 1:0.005. The rest are the same.

[0140] Example 3

[0141] The difference between this embodiment and Embodiment 1 is that in step S2, a second solution containing Al2(SO4)3 is prepared with a ratio of the total molar amount of Ni and Mn to the molar amount of Al of TM(Ni+Mn):Al = 1:0.01, while the rest are the same.

[0142] Example 4

[0143] The difference between this embodiment and Embodiment 1 is that in step S2, a second solution containing Al2(SO4)3 is prepared with a ratio of the total molar amount of Ni and Mn to the molar amount of Al of TM(Ni+Mn):Al = 1:0.03. The rest are the same.

[0144] Example 5

[0145] The difference between this embodiment and Embodiment 1 is that in step S2, a second solution containing Al2(SO4)3 is prepared with a ratio of the total molar amount of Ni and Mn to the molar amount of Al of TM(Ni+Mn):Al = 1:0.05. The rest are the same.

[0146] Example 6

[0147] The difference between this embodiment and Embodiment 1 is that in step S2, a second solution containing Al2(SO4)3 and CoSO4 is prepared with the ratio of the total molar amount of Ni and Mn elements to the molar amount of Al and Co elements being TM(Ni+Mn)∶Al∶Co=1∶0.001∶0.001. The rest is the same.

[0148] Example 7

[0149] The difference between this embodiment and embodiment 1 is that in step S2, a second solution containing Al2(SO4)3 and CoSO4 is prepared with the ratio of the total molar amount of Ni and Mn elements to the molar amount of Al and Co elements being TM(Ni+Mn)∶Al∶Co=1∶0.005∶0.005.

[0150] Example 8

[0151] The difference between this embodiment and embodiment 1 is that in step S2, a second solution containing Al2(SO4)3 and CoSO4 is prepared with the ratio of the total molar amount of Ni and Mn elements to the molar amount of Al and Co elements being TM(Ni+Mn)∶Al∶Co=1∶0.01∶0.01.

[0152] Example 9

[0153] The difference between this embodiment and embodiment 1 is that in step S2, a second solution containing Al2(SO4)3 and CoSO4 is prepared with the ratio of the total molar amount of Ni and Mn elements to the molar amount of Al and Co elements being TM(Ni+Mn)∶Al∶Co=1∶0.03∶0.03.

[0154] Example 10

[0155] The difference between this embodiment and Embodiment 1 is that in step S2, a second solution containing Al2(SO4)3 and CoSO4 is prepared with the ratio of the total molar amount of Ni and Mn elements to the molar amount of Al and Co elements being TM(Ni+Mn):Al:Co = 1:0.05:0.05. The rest are the same.

[0156] Example 11

[0157] According to the ratio of the total molar amount of Ni and Mn to the molar amount of B, TM(Ni+Mn):Na=1∶0.005, the cathode material prepared in Example 8 above and boric acid were ground and mixed evenly. Then, the mixture was heated to 300°C at a rate of 5°C / min in air atmosphere and calcined three times for 12 hours. The mixture was then cooled to room temperature at a rate of 5°C / min and sieved to obtain the cathode material.

[0158] Example 12

[0159] The difference between this embodiment and embodiment 11 is that, according to the ratio of the total molar amount of Ni and Mn elements to the molar amount of B element being TM(Ni+Mn)∶Na=1∶0.01, the positive electrode material obtained in embodiment 8 above and boric acid are ground and mixed evenly, while the rest are the same.

[0160] Example 13

[0161] The difference between this embodiment and embodiment 11 is that, according to the ratio of the total molar amount of Ni and Mn elements to the molar amount of B element being TM(Ni+Mn):Na=1∶0.03, the positive electrode material obtained in embodiment 8 above and boric acid are ground and mixed evenly, while the rest are the same.

[0162] Example 14

[0163] The difference between this embodiment and embodiment 11 is that, according to the ratio of the total molar amount of Ni and Mn elements to the molar amount of B element being TM(Ni+Mn)∶Na=1∶0.05, the positive electrode material obtained in embodiment 8 above and boric acid are ground and mixed evenly, while the rest are the same.

[0164] Example 15

[0165] The difference between this embodiment and embodiment 11 is that, according to the ratio of the total molar amount of Ni and Mn elements to the molar amount of B element being TM(Ni+Mn):Na=1∶0.1, the positive electrode material obtained in embodiment 8 above and boric acid are ground and mixed evenly, while the rest are the same.

[0166] Comparative Example 1

[0167] This comparative example demonstrates the preparation of a conventional NM cathode, specifically including the following steps:

[0168] S1: Prepare a first solution containing NiSO4 and MnSO4 according to the molar ratio of Ni:Mn = 50:50. Under a nitrogen atmosphere, mix the first solution with a precipitant (NaOH solution) and a complexing agent (ammonia water) to carry out the reaction. Control the concentration of ammonia water in the system to be 1 mol / L, the pH of the system to be 12.5, and the total reaction time to be 48 hours. After the reaction is completed, filter and wash with water to obtain the nickel-manganese-based precursor.

[0169] S2: According to the ratio of the total molar amount of Ni and Mn to the molar amount of Li, TM(Ni+Mn):Li=1∶1.05, the nickel-manganese-based precursor and lithium carbonate in step S1 above are ground and mixed evenly. Then, the mixture is heated to 800℃ at a rate of 5℃ / min in air atmosphere and calcined for 15h. After that, it is cooled to room temperature at a rate of 5℃ / min. Finally, it is washed with deionized water, dried, and sieved to obtain the cathode material.

[0170] Comparative Example 2

[0171] Compared with Example 1, this comparative example does not add Al, and specifically includes the following steps:

[0172] S1: Prepare a first solution containing NiSO4 and MnSO4 according to the molar ratio of Ni to Mn = 50:50. Under a nitrogen atmosphere, mix the first solution with a precipitant (NaOH solution) and a complexing agent (ammonia water) to carry out the reaction. Control the concentration of ammonia water in the system to be 1 mol / L, the pH of the system to be 12.5, and the total reaction time to be 48 hours. After filtration, washing with water and drying, the first precursor is obtained.

[0173] S2: According to the ratio of the total molar amount of Ni and Mn to the molar amount of Na, TM(Ni+Mn):Na=1∶1.05, the first precursor in step S1 and sodium carbonate are ground and mixed evenly, and then heated to 800℃ at a rate of 5℃ / min in air atmosphere, calcined for 15h, and then cooled to room temperature at a rate of 5℃ / min to obtain the second precursor.

[0174] S3: Lithium hydroxide, lithium chloride, and lithium nitrate are mixed in a molar ratio of 1:1:1 to obtain a lithium source. The second precursor obtained in step S3 and the lithium source are thoroughly mixed in a ratio of total molar amount of Ni and Mn to molar amount of Li of TM(Ni+Mn):Li = 1:3. The mixture is then heated to 400°C at a rate of 3°C / min under a nitrogen atmosphere and calcined for 5 hours. After calcination, the mixture is cooled to room temperature at a rate of 50°C / min. Finally, the mixture is washed with deionized water, dried, and sieved to obtain the cathode material.

[0175] II. Preparation of Button Cells

[0176] (1) Add the positive electrode material, polyvinylidene fluoride (PVDF) and conductive carbon black (SuperP) to N-methylpyrrolidone (NMP), mix them evenly, and prepare a positive electrode slurry with a solid content of 45wt%, wherein the weight ratio of the positive electrode material, polyvinylidene fluoride (PVDF) and conductive carbon black (SuperP) is 90:5:5.

[0177] (2) The positive electrode slurry is uniformly coated on aluminum foil, with a single-sided coating thickness of 40 μm; after drying, it is rolled to form the desired electrode, wherein the areal density of the positive electrode active layer is 14 mg / cm³. 2 The positive electrode sheet is obtained by drying and then punched into 14mm round sheets;

[0178] (3) The separator (using a porous polyethylene film as the separator) is punched into 18mm round pieces, and the negative electrode is a lithium metal sheet with a diameter of 18mm; LiPF6 is added to a solvent in which propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC) are mixed in a weight ratio of 1:1:1, and the mixture is stirred evenly to obtain an electrolyte; the mass concentration of LiPF6 is 12.5% ​​based on the mass of the electrolyte; the positive electrode, separator, negative electrode, electrolyte, battery case and other accessories are moved into a glove box (the water content must be less than 11ppm);

[0179] (4) Assemble the batteries in a stacking order from bottom to top and inject electrolyte. Then, seal them on a packaging machine to obtain button cells.

[0180] III. Preparation of Lithium-ion Batteries

[0181] Preparation of the positive electrode:

[0182] (1) Add the positive electrode material, polyvinylidene fluoride (PVDF) and conductive carbon black (SuperP) to N-methylpyrrolidone (NMP), mix them evenly, and prepare a positive electrode slurry with a solid content of 70wt%, wherein the weight ratio of the positive electrode material, polyvinylidene fluoride (PVDF) and conductive carbon black (SuperP) is 96∶2∶2.

[0183] (2) The positive electrode slurry is uniformly coated on one side of the aluminum foil, with a single-sided coating thickness of 40 μm. After drying, the above steps are repeated on the other side of the aluminum foil to obtain a double-sided coated positive electrode sheet. Then, the sheet is rolled, cut, and the tabs are welded to obtain the desired positive electrode. The areal density of the positive electrode active layer on one side is 14 mg / cm³. 2 .

[0184] Preparation of the negative electrode:

[0185] (1) Artificial graphite, styrene-butadiene rubber and sodium carboxymethyl cellulose (CMC) are mixed with deionized water at a mass ratio of 96:2:2 and stirred evenly to obtain negative electrode slurry.

[0186] (2) The negative electrode slurry is uniformly coated on one side of the copper foil. After drying, the above steps are repeated on the other side of the copper foil to obtain a double-coated negative electrode sheet. After cold pressing, cutting, and welding of the tabs, the negative electrode is obtained.

[0187] Electrolyte preparation:

[0188] In a dry argon atmosphere, LiPF6 was added to a solvent consisting of propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC) in a weight ratio of 1:1:1, and the mixture was stirred until homogeneous to obtain an electrolyte. The mass concentration of LiPF6 was 12.5% ​​based on the mass of the electrolyte.

[0189] Preparation of the separating membrane:

[0190] Polyethylene (PE) porous film is used as the separator.

[0191] The fabrication of lithium-ion batteries:

[0192] (1) Stack the positive electrode, separator, and negative electrode in sequence, with the separator in the middle of the positive and negative electrodes to provide isolation, and then wind them to obtain the electrode assembly.

[0193] (2) The electrode assembly is placed in the outer packaging aluminum-plastic film, the electrolyte is injected, and it is sealed. The lithium-ion battery is obtained through processes such as formation, degassing, and edge trimming.

[0194] Lithium-ion battery testing methods

[0195] (1) Thickness expansion rate test:

[0196] The lithium-ion battery was charged at a constant current rate of 1.5C to 4.35V at 25℃, and then charged at a constant voltage rate of 0.05C at 4.35V to achieve a fully charged state. The fully charged lithium-ion battery was then stored in a constant temperature chamber at 85℃ for 24 hours. The thickness change of the lithium-ion battery was measured with a micrometer. The initial thickness of the lithium-ion battery before storage was defined as H0, and the thickness after storage was defined as H1. The thickness expansion rate was: (H1-H0) / H0×100%.

[0197] (2) 45℃ Cyclic Capacity Retention Rate Test:

[0198] The lithium-ion battery was placed in a 45°C constant temperature chamber and charged at a constant current rate of 1.5C to 4.35V. Then, it was charged at a constant voltage rate of 4.35V to a current of 0.05C. Finally, it was discharged at a constant current rate of 4C to 3.0V. This constitutes one charge-discharge cycle. The lithium-ion battery was subjected to 500 charge-discharge cycles in the above manner. The discharge capacity of the lithium-ion battery in the first cycle and the discharge capacity in the 500th cycle were recorded. The cycle capacity retention rate = discharge capacity in the 500th cycle / discharge capacity in the first cycle × 100%.

[0199] Button cell battery test

[0200] In an environment of 25℃, the coin cell was charged at a constant current of 0.04C to 4.5V within a voltage range of 2.8V to 4.5V, and then charged at a constant voltage of 4.5V until the current reached 50uA. The charging capacity of the coin cell was recorded. Then, it was discharged at a constant current of 0.04C until the lower limit voltage reached 2.8V. The capacity-voltage relationship curve and the capacity-voltage differential dQ / dV curve were recorded. From the capacity-voltage differential dQ / dV curve, the peak intensity and peak voltage Vo1 of the first oxidation peak, and the peak intensity and peak voltage Vr1 of the first reduction peak were obtained. From the capacity-voltage relationship curve, the capacity Q1 in the voltage range of 4.2 to 4.5V and the capacity Qt in the voltage range of 3.0V to 4.5V could be obtained. Wherein, the specific capacity of the positive electrode material is equal to the charging capacity of the coin cell divided by the mass of the positive electrode material.

[0201] Cathode material testing

[0202] (1) X-ray diffraction test:

[0203] The cathode material was tested using an X-ray powder diffractometer (XRD, instrument model: Bruker D8 ADVANCE). The target material was Cu Kα, the voltage and current were 40 kV / 40 mA, and the scanning angle range was 10° to 80°. The XRD patterns of the cathode material obtained from the test were matched with crystals to obtain the crystal phase structure and unit cell parameter information of the cathode material.

[0204] (2) Scanning electron microscopy test:

[0205] The cathode material sample was tested under a scanning electron microscope, and photographs of the cathode material and its cross-section were taken at magnifications of 1000 and 10000, respectively.

[0206] (3) Time-of-flight secondary ion mass spectrometry:

[0207] The cathode material particles were fixed with conductive adhesive, and the content distribution of Li, Ni, Mn, Al, Na, Co and B elements at different etching depths was tested using a time-of-flight secondary ion mass spectrometer (model: PHI nanoTOFII Time-of-Flight SIMS).

[0208] (4) Electron probe microanalysis (EPMA) test:

[0209] The electrode containing the positive electrode material is cut with a three-ion beam to obtain a flat cross-section that exposes the internal structure of the positive electrode material. Select any cross-section of the positive electrode material particle and use an electron probe microanalyzer (EPMA, JXA-8230) to test the content of Ni, Mn, Al, Na, Co, and B elements in the first region within 100 nm of the particle surface and the second region above 500 nm of the particle surface, as well as the content of Ni, Mn, and Al elements in the third and fourth regions of the second primary particles in the second region of the positive electrode material.

[0210] (5) Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) Test:

[0211] The contents of Na, Li, Ni, Mn, Co, Al and other elements in the cathode material were tested using ICP-OES.

[0212] The partial test results of the cathode materials, coin cells, and lithium-ion batteries of Examples 1-15 and Comparative Examples 1-2 are shown in Tables 1-4 and Figures 1-8.

[0213] In Examples 1-15 and Comparative Examples 1-2, the molar percentage C of Na in the cathode material was determined based on the total molar amounts of Ni and Mn elements in the cathode material. Na The molar percentage of Al element C Al The molar percentage of Co element C Co The molar percentage of element B, C B Molar percentage of Li element C Li As shown in Table 1. Meanwhile, the molar percentage of Al relative to the total molar amount of Ni and Mn elements in the first, second, third, and fourth regions of the cathode material, and their corresponding ratios: c 1Al c 2Al c 1Al / c 2Al c 3Al c 4Al c 3Al / c 4Al As shown in Table 1.

[0214] Table 1

[0215] The content of Co, B, and Na elements and their corresponding ratios in the first and second regions of the cathode materials in Examples 1-15 and Comparative Examples 1-2: c 1Co c 2Co c 1Co / c 2Co c 1B c 2B c 1B / c 2B c 1Na / c 2Na As shown in Table 2.

[0216] Table 2

[0217] The cell parameters a and c of the cathode materials in Examples 1-15 and Comparative Examples 1-2 are shown in Table 3.

[0218] Table 3

[0219] The peak intensity of the first oxidation peak, peak voltage Vo1, peak intensity of the first reduction peak, |Vo1-Vr1|, and Q1 / Qt obtained from the coin cells prepared with the cathode materials corresponding to Examples 1-15 and Comparative Examples 1-2 are shown in Table 4. Meanwhile, the thickness expansion rate and 45°C cycle capacity retention rate obtained from the lithium-ion batteries prepared with the cathode materials corresponding to Examples 1-15 and Comparative Examples 1-2 are also shown in Table 4.

[0220] Table 4

[0221] Figure 1 shows the X-ray diffraction patterns of the cathode materials in Comparative Example 1 and Example 13. Analysis of Figure 1 reveals that the X-ray diffraction patterns of the cathode materials of this application exhibit characteristic diffraction peaks in the 2θ ranges of 17° to 20°, 35° to 38°, and 42° to 46°, respectively. These peaks belong to the characteristic peaks of the (003), (101), and (104) crystal planes of the layered lithium nickel manganese composite oxide, with the corresponding space group R-3m. A larger half-width at half-maximum (FWHM) of the characteristic peaks in the X-ray diffraction pattern indicates smaller grain size. The FWHM of the characteristic peaks in the cathode material of this application is higher than that of the conventional cathode material in Comparative Example 1, indicating that the cathode material of this application has finer grain size. Furthermore, as shown in Table 3, the cell parameters of the cathode material in this application are also larger than those of the conventional cathode material in Comparative Example 1, which is more conducive to lithium-ion transport and further improves the transport kinetics of the cathode material.

[0222] As shown in Figures 2 and 4, the morphology of the cathode material in Comparative Example 1 consists of micron-sized secondary particles formed by the close packing of approximately equiaxed primary nanocrystals, with relatively low cross-sectional porosity inside the particles. As shown in Figures 3 and 5, the morphology of the cathode material in Example 13 consists of micron-sized secondary particles formed by the loose packing of slender primary nanocrystals, with relatively high cross-sectional porosity inside the particles.

[0223] As can be seen from Tables 1-4, when the cathode materials of Examples 1-10 satisfy: 2≤c 1Al / c 2Al ≤50; 1.1≤c 1Na / c 2NaWhen the concentration is ≤5, the design of the Al and Na element concentration gradient distribution reduces the interfacial reaction activity between surface oxygen and electrolyte. In addition, the higher Na content in the first region of the cathode material surface layer can better support the lattice after delithiation in the first region of the surface layer, thereby better suppressing the structural phase transition of the cathode material surface layer, and thus improving the high-temperature storage gas generation and high-temperature cycle performance of lithium-ion batteries.

[0224] As shown in Figure 6, the Li content in the cathode material of Example 13 remains essentially constant with increasing etching depth; the Ni and Mn contents gradually increase with increasing etching depth, while the Na, Al, Co, and B contents gradually decrease with increasing etching depth. The first region within 100 nm of the cathode material surface is the cathode material surface layer, and the second region above 500 nm of the cathode material surface is the cathode material interior. The Na, Al, Co, and B contents gradually decrease from the cathode surface to the cathode material interior, forming a concentration gradient distribution of multiple elements. This reduces the interfacial reactivity of highly active metal ions and oxygen ions on the surface with the electrolyte, improves the structural stability, interfacial stability, and lithium-ion diffusion capacity of the material, and is beneficial for improving the cycle performance and high-temperature storage performance of lithium-ion batteries.

[0225] As can be seen from Figure 7, the discharge curve of the coin cell in Comparative Example 1 does not have a significant plateau in the 4.2V to 4.5V range, while the discharge curve of the coin cell in Example 13 does have a plateau in the 4.2V to 4.5V range. Meanwhile, according to Table 4, the coin cell constructed with the cathode material of this application also satisfies the condition: 0.2≤Q1 / Qt≤0.35, indicating that the cathode material of this application has a high reversible charge-discharge capacity in the high voltage range, thereby enabling the lithium-ion battery to have a high energy density.

[0226] As shown in Figure 8, the capacity-voltage differential dQ / dV curve of the coin cell in Comparative Example 1 shows no oxidation or reduction peaks in the 4.2V to 4.5V range. In contrast, the capacity-voltage differential dQ / dV curve of the coin cell in Example 13 exhibits a first oxidation peak and a first reduction peak in the 4.2V to 4.5V range, and a second oxidation peak and a second reduction peak in the 3.6V to 4.0V range. Referring to Table 4, the coin cell constructed using the cathode material of this application has a Vo1 of 4.3V to 4.4V and also satisfies |Vo1-Vr1|≤0.15V. The smaller the voltage difference |Vo1-Vr1| between the first oxidation peak and the first reduction peak, the better the electrochemical reversibility and the smaller the electrochemical polarization of the cathode material. The |Vo1-Vr1|≤0.15V of the cathode material in this application indicates good reversibility in the high-voltage range, which can further improve the cycle performance of lithium-ion batteries under high-voltage conditions.

[0227] As can be seen from Examples 1-15 and Comparative Example 1 in Table 4, compared with traditional cathode materials, the cathode material of this application can significantly reduce the high-temperature storage thickness expansion rate of the battery and improve the high-temperature cycle capacity retention rate of the battery, thereby improving the safety and cycle performance of the battery.

[0228] As can be seen from Examples 1-5 and Comparative Example 2 in Table 4, compared with the cathode material without an Al element concentration gradient distribution, this application constructs a cathode material with an Al element concentration gradient decreasing from the surface to the interior. This reduces the interfacial reaction activity between highly active metal ions and oxygen ions on the surface and the electrolyte, improves the structural stability and interfacial stability of the material, and helps to reduce the thickness expansion rate of the battery under high temperature and high voltage conditions and improve the cycle capacity retention rate of the battery, thereby improving the safety and cycle performance of the battery.

[0229] Compared to Examples 1-5, Examples 6-10 show that the cathode material in Examples 6-10, with its surface rich in Co, results in a lower thickness expansion rate and higher cycle capacity retention for the corresponding lithium-ion battery under high temperature and high voltage conditions. It is evident that Co, in conjunction with Al and Na, can further reduce the thickness expansion rate of the battery under high temperature and high voltage conditions and improve the cycle capacity retention. This is because the first region on the surface of the cathode material is rich in Co, which can synergistically form a lithium cobalt composite oxide with a P63mc crystal structure with Na. Simultaneously, Al doping stabilizes this lithium cobalt composite oxide with a P63mc crystal structure, giving it higher structural stability under high voltage conditions. Therefore, it is beneficial to further suppress surface oxygen release and structural phase transition of the cathode material, thereby further improving the cycle performance and gas generation of the lithium-ion battery under high temperature and high voltage conditions.

[0230] Compared with Example 8, the cathode material in Examples 11-15 has an added B element coating. The B element can further stabilize the O element on the surface of the cathode material and separate it from the electrolyte, thereby further suppressing the release of oxygen from the surface of the cathode material and the decomposition and gas generation of the electrolyte, further reducing the thickness expansion rate of the battery under high temperature and high voltage conditions, and improving the cycle capacity retention rate of the battery.

[0231] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit the scope of protection of this application. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the substance and scope of the technical solutions of this application.

Claims

1. A positive electrode material, characterized in that, The cathode material includes a lithium-nickel-manganese composite oxide; The cathode material includes a first region within 100 nm of the surface of the cathode material and a second region more than 500 nm of the surface of the cathode material. The cathode material includes Al; based on the total molar amount of Ni and Mn in the first region, the molar percentage of Al in the first region is c. 1Al Based on the total molar amounts of Ni and Mn elements in the second region, the molar percentage of Al element in the second region is c. 2Al Satisfies: 2≤c 1Al / c 2Al ≤50; The positive electrode material is assembled with lithium metal to form a coin cell. 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 obtained capacity-voltage differential dQ / dV curve has a first oxidation peak and a first reduction peak in the range of 4.2V to 4.5V.

2. The cathode material as described in claim 1, characterized in that, The cathode material satisfies at least one of the following conditions: (1)c 1Al The percentage ranges from 0.15% to 20%. (2)c 2Al It ranges from 0.05% to 2%.

3. The positive electrode material as described in claim 1, characterized in that, The cathode material satisfies at least one of the following conditions: (1) The cathode material includes Na; based on the total molar amount of Ni and Mn in the first region, the molar percentage of Na in the first region is c. 1Na Based on the total molar amounts of Ni and Mn elements in the second region, the molar percentage of Na element in the second region is c. 2Na ; Satisfies: 1.1≤c 1Na / c 2Na ≤5; (2) The cathode material includes Co; based on the total molar amount of Ni and Mn in the first region, the molar percentage of Co in the first region is c. 1Co Based on the total molar amounts of Ni and Mn elements in the second region, the molar percentage of Co element in the second region is c. 2Co ; Satisfies: 1.3≤c 1Co / c 2Co ≤10.

4. The cathode material as described in claim 3, characterized in that, The cathode material satisfies at least one of the following conditions: (1)c 1Na It ranges from 5% to 15%; (2)c 2Na It ranges from 1% to 10%; (3)c 1Co It ranges from 0.2% to 10%; (4)c 2Co It ranges from 0.1% to 2%.

5. The positive electrode material as described in claim 1, characterized in that, The cathode material is a secondary particle. The first region includes a first primary particle, and the second region includes a second primary particle. The second primary particle includes a third region within 20 nm of its surface and a fourth region more than 50 nm of its surface. Based on the total molar amount of Ni and Mn elements in the third region, the molar percentage of Al elements in the third region is c. 3Al Based on the total molar amount of Ni and Mn elements in the fourth region, the molar percentage of Al element in the fourth region is c. 4Al Satisfies: 2≤c 3Al / c 4Al ≤10.

6. The cathode material as described in claim 5, characterized in that, The cathode material satisfies at least one of the following conditions: (1)c 3Al The percentage ranges from 0.08% to 3.5%. (2)c 4Al It ranges from 0.04% to 0.5%.

7. The positive electrode material as described in claim 1, characterized in that, The cathode material includes element B; based on the total molar amount of elements Ni and Mn in the first region, the molar percentage of element B in the first region is c. 1B Based on the total molar amounts of Ni and Mn elements in the second region, the molar percentage of B element in the second region is c. 2B Satisfies: 5≤c 1B / c 2B ≤50.

8. The cathode material as described in claim 7, characterized in that, The cathode material satisfies at least one of the following conditions: (1)c 1B It ranges from 0.5% to 20%; (2)c 2B It ranges from 0.1% to 0.5%.

9. The cathode material according to any one of claims 1 to 8, characterized in that, The cathode material satisfies at least one of the following conditions: (1) Based on the mass of the cathode material, the peak intensity of the first oxidation peak is greater than or equal to 1000 mAh / g / V, and the peak intensity of the first reduction peak is greater than or equal to 1000 mAh / g / V. (2) The peak voltage of the first oxidation peak is Vo1, and the peak voltage of the first reduction peak is Vr1, and the following conditions are met: |Vo1-Vr1|≤0.15V; (3) 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 capacity-voltage curve has a plateau in the range of 4.2V to 4.5V. The capacity of the discharge curve in the range of 4.2V to 4.5V is Q1, and the capacity of the discharge curve in the range of 3.0V to 4.5V is Qt, satisfying: 0.2≤Q1 / Qt≤0.35; (4) The capacitance-voltage differential dQ / dV curve has a second oxidation peak and a second reduction peak in the range of 3.6V to 4.0V; (5) The X-ray diffraction pattern of the cathode material has characteristic diffraction peaks in the ranges of 2θ from 17° to 20°, 35° to 38° and 42° to 46°. (6) The cell parameter a of the cathode material satisfies (7) The cell parameter c of the cathode material satisfies (8) The cathode material has a layered crystal structure belonging to the R-3m space group.

10. The cathode material as described in claim 1, characterized in that, The cathode material satisfies at least one of the following conditions: (1) Based on the total molar amount of Ni and Mn elements in the cathode material, the molar percentage of Ni element in the cathode material is greater than or equal to 45%; (2) Based on the total molar amount of Ni and Mn elements in the cathode material, the molar percentage of Mn element in the cathode material is less than or equal to 50%; (3) Based on the total molar amount of Ni and Mn elements in the cathode material, the molar percentage of Li element in the cathode material is 90% to 105%; (4) Based on the total molar amount of Ni and Mn elements in the cathode material, the molar percentage of Al element in the cathode material is 0.1% to 5%; (5) The cathode material includes Co element, and based on the total molar amount of Ni and Mn elements in the cathode material, the molar percentage of Co element in the cathode material is less than or equal to 10%; (6) The cathode material includes Na element, and based on the total molar amount of Ni and Mn elements in the cathode material, the molar percentage of Na element in the cathode material is 0.1% to 10%; (7) The cathode material includes: Li x1 Na x2 Ni y1 Mn y2 Al y3 Co y4 M y5 O 2±m R n Wherein, M includes at least one of K, Mg, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, Ag, In, Sn, Sb, Ba, La, Ce, Hf, Ta, W, Pb, Bi, B, Si, P, or S; R includes at least one of F, Cl, Br, I, or N; 0.9≤x1≤1.05, 0.001≤x2≤0.1, 0.45≤y1≤1, 0≤y2≤0.5, 0.001≤y3≤0.05, 0≤y4≤0.1, 0≤y5≤0.05, 0≤m≤0.2, and 0≤n≤0.

2.

11. An electrochemical device comprising a positive electrode, said positive electrode comprising a positive electrode current collector and a positive electrode active material layer, characterized in that, The positive electrode active material layer comprises the positive electrode material according to any one of claims 1 to 10.

12. An electronic device, characterized in that, Includes the electrochemical device as described in claim 11.

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