Positive electrode material, method for manufacturing the same, and secondary battery having the same

Abstract

The application discloses a positive electrode material and a manufacturing method thereof, and a secondary battery provided with the positive electrode material. The positive electrode material comprises: an inner core containing a lithium-rich manganese-based positive electrode material; and a coating layer coated on the outer surface of the inner core, wherein the coating layer comprises a composite material of a transition metal oxyacid salt and carbon, the transition metal in the transition metal oxyacid salt is selected from at least one of Ti, Mo, W, V, Ta, Nb or Nd, and the composite material is in a network structure. The secondary battery prepared by using the positive electrode material has high energy density, first charge-discharge efficiency, cycle characteristics and rate performance.

Description

Technical Field

[0001] This application relates to the field of electrochemistry, and more particularly to a cathode material and its preparation method, a secondary battery having the same, as well as a battery module, a battery pack and an electrical device. Background Technology

[0002] Lithium-rich manganese-based materials have a high discharge voltage plateau and a high theoretical discharge specific capacity, thus exhibiting a high theoretical specific energy density. However, during the initial high-voltage charging state (above 4.5V), some lithium ions in the transition metal layer are removed along with oxygen, forming Li₂O. These crystal vacancies are difficult to accept lithium ions in subsequent charge and discharge processes, resulting in a lower initial charge and discharge efficiency. Simultaneously, the formation of numerous oxygen vacancies causes transition metal ion migration, leading to crystal structure rearrangement and instability, thus worsening cycle life. Furthermore, the low electronic and ionic conductivity of lithium-rich materials, coupled with intensified side reactions between the material surface and the electrolyte at high voltages, results in extremely poor rate performance. Summary of the Invention

[0003] This application is made in view of the above-mentioned issues, and its purpose is to provide a positive electrode material and a method for preparing the same, a secondary battery having the same, as well as a battery module, a battery pack and an electrical device, wherein the secondary battery prepared by the positive electrode material has high energy density, first charge and discharge efficiency, cycle characteristics and rate characteristics.

[0004] To achieve the above objectives, a first aspect of this application provides a cathode material comprising: a core containing a lithium-rich manganese-based cathode material; and a coating layer covering the outer surface of the core, comprising a composite material of a transition metal oxometalate and carbon, wherein the transition metal in the transition metal oxometalate is selected from at least one of Ti, Mo, W, V, Ta, Nb, or Nd; and the composite material has a network structure.

[0005] By coating the surface of lithium-rich manganese-based materials with oxygen-vacancy-rich materials, unlike the conventional method of directly forming oxygen vacancies on the material surface, the surface structure does not undergo reconstruction or destruction, which is beneficial to the stability of the material's structure. Especially when the composite material with a network structure contains carbon, the synergistic effect of carbon coating promotes the formation and protection of oxygen vacancies, and also improves the material's low electronic conductivity. This reduces the release of lattice oxygen during high-voltage cycling, improves the reversibility of redox reactions of oxygen anions, and effectively enhances the material's rate performance. Therefore, the secondary battery prepared from the above-mentioned cathode material exhibits high energy density, high initial charge-discharge efficiency, high cycle characteristics, and high rate performance.

[0006] In some embodiments, the transition metal in the transition metal oxoate is selected from at least one of Ti, Mo, W, or V. This allows for the easy coating of a composite material of transition metal oxoates and carbon onto the surface of a lithium-rich manganese-based material.

[0007] In some embodiments, the transition metal oxoate is at least one of Li, Na, K, Mg, and Al salts; optionally, the transition metal oxoate is at least one of Li, Na, and K salts. Thus, composite materials of transition metal oxoates and carbon can be readily coated onto the surface of lithium-rich manganese-based materials.

[0008] In some embodiments, the molecular formula of the lithium-rich manganese-based cathode material is xLi₂MnO₃·(1-x)LiNi. y Co z Mn a M 1-y-z-a O r A 2-r Where 0 < x < 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1, 0 ≤ a ≤ 1, 0 < r ≤ 2, 0 < y + z + a ≤ 1; M is at least one of Mg, B, Al, V, Ti, Zr, Sn, and Mo, and A is at least one of F, S, N, and Cl. Thus, composite materials can be formed by coating transition metal oxoates and carbon onto the surface of various lithium-rich manganese-based materials.

[0009] In some embodiments, the transition metal oxophosphate in the coating layer contains oxygen vacancies; optionally, the transition metal oxophosphate satisfies the condition: IO2. 2- / IO 2- The peak intensity ratio is 0.5–1.2, optionally 0.6–0.8, of which IO2 2- The peak intensity of the oxygen vacancy at 531 eV in X-ray photoelectron spectroscopy (XPS) is IO. 2- This corresponds to the peak intensity of lattice oxygen at 529 eV in X-ray photoelectron spectroscopy (XPS). Therefore, oxygen vacancies on the surface of lithium-rich manganese-based cathode materials can be released through IO2 in the coating. 2- / IO 2- The peak intensity ratio is used to corroborate this; the more oxygen vacancies, the higher the peak intensity ratio. Maintaining the oxygen vacancies formed on the surface of lithium-rich manganese-based materials within a suitable range can, on the one hand, suppress oxygen release during charging and discharging, and on the other hand, ensure the material's capacity is fully utilized.

[0010] In some embodiments, the powder resistivity of the cathode material at 12 MPa is less than or equal to 3000 Ω·cm, preferably less than or equal to 2000 Ω·cm. The oxygen vacancies on the surface of the lithium-rich manganese-based cathode material can promote the transport of electrons and lithium ions, and the carbon coating on the surface can further improve the electronic conductivity of the material, thereby further improving the initial charge-discharge efficiency and rate performance of the cathode material.

[0011] In some embodiments, the cathode material particles are secondary particles, single crystals, or near-single crystals, and the particle size D... v The particle size of 50 ranges from 1 to 20 μm, and can be selected from 3 to 15 μm. Therefore, the lithium-rich manganese-based cathode material exhibits a regular morphology, uniform particle size distribution, and stable structure, thus ensuring that the lithium-rich manganese-based battery has high energy density and excellent cycle performance.

[0012] In some embodiments, the specific surface area of ​​the positive electrode material is less than 2.0 m². 2 / g, which can be selected from 0.1 to 1m 2 / g. Therefore, lithium-rich manganese-based cathode materials have a low specific surface area and a high compaction density, thus ensuring that lithium-rich manganese-based batteries have high energy density and excellent cycle performance.

[0013] The second aspect of this application is to provide a method for preparing the cathode material according to the first aspect of this application, comprising the following steps: a solution preparation step: dispersing a transition metal oxide in deionized water, then adding an organic acid salt, adjusting the pH of the solution to a neutral to alkaline range, and stirring thoroughly to obtain a solution; a hydrothermal reaction step: slowly adding a lithium-rich manganese-based cathode material to the solution and reacting at a constant temperature of 50–100°C for 2–10 h; a drying step: filtering the product of the hydrothermal reaction step and drying the solid obtained by filtration; and a sintering step: sintering the dried solid at 300–600°C in an inert atmosphere for 4–15 h to obtain a surface-modified lithium-rich manganese-based cathode material, wherein the transition metal oxide comprises at least one oxide of Ti, Mo, W, V, Ta, Nb, or Nd, and the anion of the organic acid salt is at least one of acetate, oxalate, or citrate ions.

[0014] Using the above method, transition metal oxides and organic acid salts are uniformly coated on the surface of lithium-rich manganese-based materials via hydrothermal treatment. The organic acid salts are then pyrolyzed by heat treatment in an inert atmosphere. The carbon and transition metal oxides generated during the pyrolysis process react with the organic acid salts to simultaneously generate transition metal oxoates. The presence of carbon promotes the generation of oxygen vacancies in the transition metal oxoates. Finally, a composite material of transition metal oxoates containing oxygen vacancies and carbon is obtained and coated on the surface of lithium-rich manganese-based materials.

[0015] In some embodiments, the counterion of the organic acid salt is an ion of at least one metal selected from Li, Na, K, Mg, and Al, preferably an ion of at least one metal selected from Li, Na, and K. This allows for the easy coating of transition metal oxoates and carbon onto the surface of lithium-rich manganese-based materials.

[0016] In some embodiments, during the solution preparation process, the pH value of the solution is controlled at 7–15, preferably 8–10. This allows for the easy coating of transition metal oxoates and carbon onto the surface of lithium-rich manganese-based materials.

[0017] In some embodiments, the mass ratio of the transition metal oxide to the organic acid salt is (0.05-10):1, preferably (0.5-2):1. This allows for the stable formation of a composite material consisting of a transition metal oxoacid salt and carbon coated on the surface of a lithium-rich manganese-based material, and enables the appropriate adjustment of the oxygen vacancy content in the transition metal oxoacid salt.

[0018] In some embodiments, the mass ratio of the added lithium-rich manganese-based material to the sum of the mass of the transition metal oxide and the organic acid salt is 100:(0.1-30), preferably 100:(1-10). Therefore, by keeping the mass ratio of the lithium-rich manganese-based material to the sum of the mass of the transition metal oxide and the organic acid salt within the above range, it is beneficial to control the thickness of the coating layer. By increasing the coating amount, more oxygen vacancies in the transition metal oxoacid salt can be formed in the coating layer.

[0019] In some embodiments, during the drying process, the drying temperature is 60–120°C, preferably 80–100°C, and / or the drying time is 1–10 h, preferably 5–8 h, and / or the drying atmosphere is a vacuum atmosphere, with the vacuum degree maintained at -0.5 to -1 bar. Thus, by vacuum drying, excess moisture on the material surface is removed, oxidation of the material surface is avoided, and the destruction of oxygen vacancies formed on the surface is prevented, thereby appropriately adjusting the oxygen vacancy content in the transition metal oxometalate.

[0020] In some embodiments, the inert atmosphere during the sintering process is a nitrogen or argon atmosphere. This further promotes the formation of oxygen vacancies in transition metal oxometalates, while simultaneously achieving a uniform and tight coating effect on the surface of the coating material.

[0021] A third aspect of this application is to provide a secondary battery comprising a positive electrode material according to the first aspect of this application or a positive electrode material prepared according to the preparation method described in the second aspect of this application.

[0022] A fourth aspect of this application is to provide a battery module comprising a secondary battery as described in a third aspect of this application.

[0023] A fifth aspect of this application is to provide a battery pack that includes the battery module described in the fourth aspect of this application.

[0024] A sixth aspect of this application is to provide an electrical device comprising at least one of the secondary battery described in the third aspect of this application, the battery module described in the fourth aspect of this application, and the battery pack described in the fifth aspect of this application.

[0025] According to this application, secondary batteries can be made to have higher energy density, first charge / discharge efficiency, cycle characteristics, and rate performance. Attached Figure Description

[0026] Figure 1 This is a scanning electron microscope image of the positive electrode material according to one embodiment of this application.

[0027] Figure 2 for Figure 1 The image shows scanning electron microscope (SEM) images of the cathode material at different magnifications.

[0028] Figure 3 This is the XPS spectrum of the cathode material according to one embodiment of this application.

[0029] Figure 4 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0030] Figure 5 yes Figure 4 An exploded view of a secondary battery according to an embodiment of this application is shown.

[0031] Figure 6 This is a schematic diagram of a battery module according to one embodiment of this application.

[0032] Figure 7 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0033] Figure 8 yes Figure 7 An exploded view of a battery pack according to one embodiment of this application is shown.

[0034] Figure 9 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0035] Explanation of reference numerals in the attached figures:

[0036] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Casing; 52 Electrode assembly; 53 Top cover assembly Detailed Implementation

[0037] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the positive electrode material and its manufacturing method, secondary battery, battery module, battery pack, and electrical device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0038] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a specific parameter, it is also expected that ranges of 60 to 110 and 80 to 120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise stated, the numerical range "a to b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 and 5" have been listed in this article; "0 to 5" is just a shortened representation of these numerical combinations. In addition, when a parameter is stated as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0039] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0040] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0041] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0042] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0043] In one embodiment of this application, a cathode material is proposed, comprising: a core containing a lithium-rich manganese-based cathode material; and a coating layer covering the outer surface of the core, comprising a composite material of transition metal oxoates and carbon, wherein the transition metal in the transition metal oxoates is selected from at least one of Ti, Mo, W, V, Ta, Nb, or Nd; and the composite material has a mesh structure.

[0044] Although the mechanism is not yet clear, the inventors of this application have unexpectedly discovered that by coating the outer surface of lithium-rich manganese-based cathode material with transition metal oxoates and composite materials with a network structure, secondary batteries can have higher energy density, first charge-discharge efficiency, cycle characteristics, and rate characteristics.

[0045] The inventors of this application hypothesize that by coating the surface of lithium-rich manganese-based materials with oxygen-vacancy-rich transition metal oxoates and a network structure, a method different from the conventional approach of directly forming oxygen vacancies on the material surface, the surface structure does not undergo reconstruction or destruction, which is beneficial to the stability of the material's structure. Especially when the network structure contains carbon, the synergistic effect of the carbon coating promotes both the formation and protection of oxygen vacancies, and improves the material's low electronic conductivity. This reduces the release of lattice oxygen during high-voltage cycling, enhances the reversibility of redox reactions involving oxygen anions, and effectively improves the material's rate performance.

[0046] Figure 1 This is a scanning electron microscope image of the cathode material obtained in Example 1 described later in this application. Figure 2 for Figure 1 The image shows scanning electron microscope (SEM) images of the cathode material at different magnifications. From Figure 1 , 2 It can be seen that the outer surface of the lithium-rich manganese-based material is coated with a composite material of transition metal oxoates and carbon. The composite material has a network structure. By using a composite material with a network structure in the coating layer, the stability of the coating structure can be maintained, and the electrical conductivity of the lithium-rich manganese-based material can be increased.

[0047] In some embodiments, the transition metal in the transition metal oxoate is selected from at least one of Ti, Mo, W, or V. This allows for the easy coating of a composite material of transition metal oxoates and carbon onto the surface of a lithium-rich manganese-based material.

[0048] In some embodiments, the transition metal oxoate is at least one of Li, Na, K, Mg, and Al salts; optionally, the transition metal oxoate is at least one of Li, Na, and K salts. Thus, composite materials of transition metal oxoates and carbon can be readily coated onto the surface of lithium-rich manganese-based materials.

[0049] In some embodiments, the molecular formula of the lithium-rich manganese-based cathode material is xLi₂MnO₃·(1-x)LiNi. y Co z Mn a M 1-y-z-a O r A 2-r Where 0 < x < 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1, 0 ≤ a ≤ 1, 0 < r ≤ 2, 0 < y + z + a ≤ 1; M is at least one of Mg, B, Al, V, Ti, Zr, Sn, and Mo, and A is at least one of F, S, N, and Cl. Thus, composite materials can be formed by coating transition metal oxoates and carbon onto the surface of various lithium-rich manganese-based materials.

[0050] Figure 3 The above is the XPS spectrum of the cathode material of Example 1 described later in this application.

[0051] In some embodiments, optionally, the transition metal oxophosphate in the coating layer contains oxygen vacancies; optionally, the transition metal oxophosphate satisfies the following condition: IO2 2- / IO 2- The peak intensity ratio is 0.5–1.2, optionally 0.6–0.8, of which IO2 2- The peak intensity of the oxygen vacancy at 531 eV in X-ray photoelectron spectroscopy (XPS) is IO. 2- The peak intensity of lattice oxygen at 529 eV in X-ray photoelectron spectroscopy (XPS) (reference) Figure 3 Therefore, oxygen vacancies on the surface of lithium-rich manganese-based cathode materials can be released through IO2 in the coating. 2- / IO 2- The peak intensity ratio is used to corroborate this; the more oxygen vacancies, the higher the peak intensity ratio. Maintaining the oxygen vacancies formed on the surface of lithium-rich manganese-based materials within a suitable range can, on the one hand, suppress oxygen release during charging and discharging, and on the other hand, ensure the material's capacity is fully utilized.

[0052] In some embodiments, the powder resistivity of the cathode material at 12 MPa is less than or equal to 3000 Ω·cm, preferably less than or equal to 2000 Ω·cm. The oxygen vacancies on the surface of the lithium-rich manganese-based cathode material can promote the transport of electrons and lithium ions, and the carbon coating on the surface can further improve the electronic conductivity of the material, thereby further improving the initial charge-discharge efficiency and rate performance of the cathode material.

[0053] In some embodiments, the cathode material particles are secondary particles, single crystals, or near-single crystals, and the particle size D... v The particle size of 50 ranges from 1 to 20 μm, and can be selected from 3 to 15 μm. Therefore, the lithium-rich manganese-based cathode material exhibits a regular morphology, uniform particle size distribution, and stable structure, thus ensuring that the lithium-rich manganese-based battery has high energy density and excellent cycle performance.

[0054] In some embodiments, the specific surface area of ​​the positive electrode material is less than 2.0 m². 2 / g, which can be selected from 0.1 to 1m 2 / g. Therefore, lithium-rich manganese-based cathode materials have a low specific surface area and a high compaction density, thus ensuring that lithium-rich manganese-based batteries have high energy density and excellent cycle performance.

[0055] Furthermore, in another embodiment of this application, a method for preparing a cathode material is proposed, comprising the following steps: a solution preparation step: dispersing a transition metal oxide in deionized water, then adding an organic acid salt, adjusting the pH of the solution to a neutral to alkaline range, and stirring thoroughly to obtain a solution; a hydrothermal reaction step: slowly adding a lithium-rich manganese-based cathode material to the solution and reacting at a constant temperature of 50–100°C for 2–10 hours; a drying step: filtering the product of the hydrothermal reaction step and drying the solid obtained from the filter; and a sintering step: sintering the dried solid at 300–600°C in an inert atmosphere for 4–15 hours to obtain a surface-modified lithium-rich manganese-based cathode material, wherein the transition metal oxide comprises at least one oxide of Ti, Mo, W, V, Ta, Nb, or Nd, and the anion of the organic acid salt is at least one of acetate, oxalate, or citrate ions.

[0056] Using the above method, transition metal oxides and organic acid salts are uniformly coated on the surface of lithium-rich manganese-based materials via hydrothermal treatment. The organic acid salts are then pyrolyzed by heat treatment in an inert atmosphere. The carbon and transition metal oxides generated during the pyrolysis process react with the organic acid salts to simultaneously generate transition metal oxoates. The presence of carbon promotes the generation of oxygen vacancies in the transition metal oxoates. Finally, a composite material of transition metal oxoates containing oxygen vacancies and carbon is obtained and coated on the surface of lithium-rich manganese-based materials.

[0057] In some embodiments, the counterion of the organic acid salt is an ion of at least one metal selected from Li, Na, K, Mg, and Al, preferably an ion of at least one metal selected from Li, Na, and K. This allows for the easy coating of transition metal oxoates and carbon onto the surface of lithium-rich manganese-based materials.

[0058] In some embodiments, during the solution preparation process, the pH value of the solution is controlled at 7–15, preferably 8–10. This allows for the easy coating of transition metal oxoates and carbon onto the surface of lithium-rich manganese-based materials.

[0059] In some embodiments, the mass ratio of the transition metal oxide to the organic acid salt is (0.05-10):1, preferably (0.5-2):1. This allows for the stable formation of a composite material consisting of a transition metal oxoacid salt and carbon coated on the surface of a lithium-rich manganese-based material, and enables the appropriate adjustment of the oxygen vacancy content in the transition metal oxoacid salt.

[0060] In some embodiments, the mass ratio of the added lithium-rich manganese-based material to the sum of the mass of the transition metal oxide and the organic acid salt is 100:(0.1-30), preferably 100:(1-10). Therefore, by keeping the mass ratio of the lithium-rich manganese-based material to the sum of the mass of the transition metal oxide and the organic acid salt within the above range, it is beneficial to control the thickness of the coating layer. By increasing the coating amount, more oxygen vacancies in the transition metal oxoacid salt can be formed in the coating layer.

[0061] In some embodiments, during the drying process, the drying temperature is 60–120°C, preferably 80–100°C, and / or the drying time is 1–10 h, preferably 5–8 h, and / or the drying atmosphere is a vacuum atmosphere, with the vacuum degree maintained at -0.5 to -1 bar. Thus, by vacuum drying, excess moisture on the material surface is removed, oxidation of the material surface is avoided, and the destruction of oxygen vacancies formed on the surface is prevented, thereby appropriately adjusting the oxygen vacancy content in the transition metal oxometalate.

[0062] In some embodiments, the inert atmosphere during the sintering process is a nitrogen or argon atmosphere. This further promotes the formation of oxygen vacancies in transition metal oxometalates, while simultaneously achieving a uniform and tight coating effect on the surface of the coating material.

[0063] In addition, the secondary battery, battery module, battery pack and power device of this application will be described below with appropriate reference to the accompanying drawings.

[0064] [Rechargeable Battery]

[0065] In one embodiment of this application, a secondary battery is provided.

[0066] Typically, a secondary battery consists of a negative electrode, a positive electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0067] [Positive electrode plate]

[0068] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including the positive electrode active material of the first aspect of this application.

[0069] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0070] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0071] In some embodiments, in addition to the positive electrode material comprising the first aspect of this application, other positive electrode active materials may also be included. These positive electrode active materials may be those known in the art for use in batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNiO2). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 C o0.2Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 C o0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 C o0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0072] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0073] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0074] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0075] [Negative electrode plate]

[0076] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0077] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0078] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0079] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0080] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0081] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0082] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0083] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0084] [Electrolytes]

[0085] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0086] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0087] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0088] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0089] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0090] [Isolation membrane]

[0091] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0092] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0093] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0094] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0095] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0096] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 4 This is an example of a square-structured secondary battery 5.

[0097] In some implementations, refer to Figure 5 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 using a winding or stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0098] Battery Module

[0099] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0100] Figure 6 This is battery module 4, used as an example. (See reference...) Figure 6In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0101] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0102] battery pack

[0103] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0104] Figure 7 and Figure 8 This is battery pack 1 as an example. (See reference...) Figure 7 and Figure 8 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0105] Electrical appliances

[0106] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0107] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0108] Figure 9 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0109] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0110] Example

[0111] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0112] <Example 1>

[0113] ①Preparation method

[0114] Preparation of cathode materials

[0115] In Example 1, the method for preparing the positive electrode material includes the following steps:

[0116] (1) Disperse vanadium pentoxide and potassium citrate in deionized water at a mass ratio of 2:1, adjust the pH of the solution to 8 and stir thoroughly;

[0117] (2) Slowly add 0.5Li2MnO3·0.5LiNi, a lithium-rich manganese-based material. 0.33 Co 0.33 Mn 0.33 The O2 added to the solution in step 1 was in a ratio of 100:5 to the total mass of vanadium pentoxide and potassium citrate, and the mixture was reacted at a constant temperature of 80°C for 10 hours.

[0118] (3) The product of the constant temperature reaction was filtered and dried at a temperature of 100°C for 8 hours in a vacuum atmosphere with a vacuum degree of -1 bar.

[0119] (4) The dried sample was sintered at 500°C in an argon atmosphere for 10 hours to obtain a lithium-rich manganese-based cathode material with a surface coated with potassium vanadate and carbon containing oxygen vacancies.

[0120] Preparation of negative electrode sheet

[0121] The negative electrode active material artificial graphite, conductive agent carbon black, and binder SBR are mixed in a mass ratio of 96:2.5:1.5 and stirred thoroughly in an appropriate amount of deionized water to form a uniform negative electrode slurry. The negative electrode slurry is coated on the surface of the negative electrode current collector copper foil, and after drying and cold pressing, the negative electrode sheet is obtained.

[0122] Preparation of positive electrode sheet

[0123] SP (carbon black) is used as a conductive agent, polyvinylidene fluoride (PVDF) as a binder, and N-methylpyrrolidone (NMP) as a solvent. PVDF and NMP are mixed in a mass ratio of 2:8 to form a binder. A positive electrode slurry is prepared according to the mass ratio of the positive electrode material prepared by the above method, SP and PVDF in a ratio of 90:7:3. The positive electrode slurry is coated on the surface of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet is obtained.

[0124] Preparation of electrolyte

[0125] Ethyl carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1, and then LiPF6 was uniformly dissolved in the above solution to obtain an electrolyte with a concentration of 1 mol / L.

[0126] Separating membrane

[0127] Polyethylene (PE) film is used.

[0128] Preparation of secondary batteries

[0129] The positive electrode, separator, and negative electrode are stacked in sequence and wound to obtain an electrode assembly. The electrode assembly is then placed in an outer package, and the electrolyte is added. After processes such as encapsulation, settling, formation, and aging, a secondary battery is obtained.

[0130] ② Performance Evaluation

[0131] The positive electrode material, positive electrode sheet, and secondary battery prepared in step ① above were subjected to performance tests using the following methods. The results are shown in Table 1.

[0132] (i) Morphology of the positive electrode active material

[0133] The morphology of the positive electrode active material can be confirmed and measured using known methods, such as scanning electron microscopy or transmission electron microscopy.

[0134] (ii) Peak intensity ratio of oxygen vacancies to lattice oxygen in the coating layer of the positive electrode active material

[0135] The peak intensity ratio of oxygen vacancies to lattice oxygen in the coating layer of the positive electrode active material can be confirmed and measured using known methods, such as X-ray photoelectron spectroscopy (XPS). The peak intensity ratio of oxygen vacancies to lattice oxygen in the coating layer containing oxygen vacancies will be increased.

[0136] (iii) Determination of powder resistivity

[0137] The resistivity of the positive electrode active material is confirmed and measured using known methods, such as referring to standard GBT30853-2014 and using a powder resistivity tester (such as the lattice ST-2722).

[0138] (iv)Dv 50 Measurement

[0139] Dv of positive electrode active material 50 As is well known in the art, the particle size distribution can be determined using methods known in the art. For example, it can be determined using a laser particle size analyzer (such as the Malvem Master Size 3000) according to standard GB / T 19077.1-2016. Wherein, Dv 50 The physical definition of is: the particle size corresponding to the cumulative volume distribution percentage of the positive electrode active material reaching 50%.

[0140] (v) Measurement of specific surface area

[0141] The specific surface area of ​​the positive electrode active material is a well-known concept in the art and can be tested using methods known in the art. For example, it can be tested using the nitrogen adsorption specific surface area analysis method according to GB / T 19587-2017, and calculated using the BET (Brunauer Emmett Teller) method. The nitrogen adsorption specific surface area analysis can be performed using a Tri-Star 3020 specific surface area and pore size analyzer from Micromeritics, Inc.

[0142] (vi) Setting the thickness of the coating layer

[0143] The thickness of the coating layer of the positive electrode active material is a well-known concept in the art and can be measured using methods known in the art. As an example, it can be measured using a high-resolution transmission electron microscope. More precisely, the thickness values ​​of the coating layer at multiple (more than 3, such as 8, 10, 12, etc.) different locations can be measured, and the average value is recorded as the thickness of the coating layer.

[0144] (vii) Initial Efficiency Test

[0145] After being injected with electrolyte, the soft-pack battery was charged at a constant current of 0.02C to 3.4V at 45℃, allowed to stand for 5 minutes, and then charged at a constant current of 0.1C to 3.75V. The capacity was recorded as Z1. Then, the battery was vented and resealed. The resealed battery was placed at 25℃ and charged at a constant current of 0.33C to 4.5V, then charged at a constant voltage of 0.02C, allowed to stand for 5 minutes, and the capacity was recorded as Z2. Then, the battery was discharged at 0.33C to 2.0V, and the capacity was recorded as D1.

[0146] The formula for calculating the initial efficiency is as follows: Initial efficiency = D1 / (Z1+Z2)

[0147] (viii) Discharge capacity test

[0148] Under constant temperature conditions of 25℃, the lithium-ion battery was charged at 0.33C to 4.5V within a range of 2.0V to 4.5V. Then, it was charged at 4.5V with a constant voltage until a current of 0.05C was reached. After resting for 5 minutes, it was discharged at 0.33C to 2.0V. The capacity of the lithium-ion battery at the 0.33C discharge rate was recorded.

[0149] (ix) Cyclic testing of full batteries

[0150] Cyclic testing: Under constant temperature conditions of 25℃ or 45℃, the full battery is charged at a constant current of 0.5C to a voltage of 4.46V, then charged at a constant voltage of 4.46V to a current of 0.05C. After resting for 5 minutes, it is discharged at a constant current of 0.5C to a voltage of 2.3V. This constitutes one charge-discharge cycle, and the discharge capacity of this cycle is the discharge capacity of the first cycle. After performing 500 charge-discharge cycles of the full battery using the above method, the remaining reversible discharge capacity is recorded.

[0151] <Example 2>

[0152] Except for the steps of preparing the positive electrode material, the same preparation method as in Example 1 was used to obtain the positive electrode sheet.

[0153] (1) Disperse titanium dioxide and sodium oxalate in deionized water at a mass ratio of 1.5:1, adjust the pH of the solution to 8 and stir thoroughly;

[0154] (2) Slowly add 0.5Li2MnO3·0.5LiNi, a lithium-rich manganese-based material. 0.33 Co 0.33 Mn 0.33 The solution in step 1 was added with O2 in a ratio of 100:10 to the total mass of titanium dioxide and sodium oxalate, and the mixture was reacted at a constant temperature of 80°C for 10 hours.

[0155] (3) The product of the constant temperature reaction was filtered and dried at a temperature of 100°C for 8 hours in a vacuum atmosphere with a vacuum degree of -1 bar.

[0156] (4) The dried sample was sintered at 500°C in an argon atmosphere for 10 hours to obtain a lithium-rich manganese-based cathode material with a surface coated with sodium titanate and carbon containing oxygen vacancies.

[0157] <Example 3>

[0158] Except for the steps of preparing the positive electrode material, the same preparation method as in Example 1 was used to obtain the positive electrode sheet.

[0159] (1) Disperse molybdenum trioxide and potassium acetate in deionized water at a mass ratio of 1:1, adjust the pH of the solution to 8 and stir thoroughly;

[0160] (2) Slowly add 0.5Li2MnO3·0.5LiNi, a lithium-rich manganese-based material. 0.33 Co 0.33 Mn 0.33 The solution in step 1 was added with O2 in a ratio of 100:8 to the total mass of molybdenum trioxide and potassium acetate, and the mixture was reacted at a constant temperature of 80°C for 10 hours.

[0161] (3) The product of the constant temperature reaction was filtered and dried at a temperature of 100°C for 8 hours in a vacuum atmosphere with a vacuum degree of -1 bar.

[0162] (4) The dried sample was sintered at 500°C in an argon atmosphere for 10 hours to obtain a lithium-rich manganese-based cathode material with a surface coated with potassium molybdate and carbon containing oxygen vacancies.

[0163] <Example 4> to <Example 5>

[0164] In Examples 4 and 5, except for the changes in the core composition of the cathode material as shown in Table 1, the same preparation method as in Example 1 was used to obtain the cathode material.

[0165] <Example 6> to <Example 10>

[0166] In Examples 6 to 10, except for the changes in the conditions of each preparation step as shown in Table 2, the same raw material composition and similar preparation method as in Example 1 were used to obtain the cathode material.

[0167] <Comparative Example 1>

[0168] The cathode material of Comparative Example 1 was prepared using the following steps.

[0169] Potassium vanadate and lithium-rich manganese-based material 0.5Li2MnO3·0.5LiNi 0.33 Co 0.33 Mn 0.33O2 was ball-milled at a mass ratio of 5:100 for 2 hours and then sintered at 500℃ in an inert atmosphere for 10 hours to obtain a lithium-rich manganese-based cathode material with potassium vanadate coating.

[0170] <Comparative Example 2>

[0171] The cathode material of Comparative Example 2 was prepared using the following steps.

[0172] Glucose and lithium-rich manganese-based material 0.5Li2MnO3·0.5LiNi 0.33 Co 0.33 Mn 0.33 O2 was ball-milled at a mass ratio of 2:100 for 2 hours and then sintered at 500℃ in an inert atmosphere for 10 hours to obtain a lithium-rich manganese-based cathode material with carbon coating on the surface.

[0173] <Comparative Example 3>

[0174] The cathode material of Comparative Example 3 was prepared using the following steps.

[0175] Potassium vanadate and glucose were mixed at a mass ratio of 2:1, and then 0.5Li₂MnO₃·0.5LiNi₂ was added. 0.33 Co 0.33 Mn 0.33 O2 was added in a mass ratio of 100:5 to potassium vanadate and glucose. The mixture was ball-milled for 2 hours and then sintered at 500°C in an inert atmosphere for 10 hours to obtain a lithium-rich manganese-based cathode material with potassium vanadate and carbon coated on the surface.

[0176] The test results of the cathode materials and secondary batteries obtained in Examples 1 to 10 and Comparative Examples 1 to 3 are listed in Table 1.

[0177] <Example 11> to <Example 16>

[0178] In Examples 11 to 16, except for the change in the raw material ratio in the solution preparation process as shown in Table 2, the same preparation method as in Example 1 was used to obtain the cathode material.

[0179] <Example 17> to <Example 22>

[0180] In Examples 17 to 22, except for the change in the raw material ratio in the hydrothermal reaction process as shown in Table 2, the same preparation method as in Example 1 was used to obtain the cathode material.

[0181] The peak intensity ratio of oxygen vacancies to lattice oxygen in the coating layer of the cathode materials obtained in Examples 1 to 3, 6 to 22, and Comparative Examples 1 to 3, as well as the coating layer thickness, are listed in Table 2.

[0182]

[0183]

[0184] As shown in Table 1, Examples 1-10, which use a composite material containing oxygen vacancies in transition metal oxoates and carbon to coat lithium-rich manganese-based cathode materials, exhibit excellent initial efficiency, 0.33C and 0.5C discharge capacity (rate characteristics), and cycling characteristics at 25°C and 45°C. In contrast, Comparative Examples 1-3, although the lithium-rich manganese-based cathode materials are coated with a coating layer, the coating layer is simply composed of transition metal oxoates, carbon, or a mixture of both, without the formation of oxygen vacancies. Consequently, their initial efficiency, 0.33C and 0.5C discharge capacity, and cycling characteristics at 25°C and 45°C are all poor.

[0185] Furthermore, a comparison of Examples 6 and 10 with Examples 7 to 9 shows that by setting the oxygen vacancies in the coating layer within a suitable range, the initial efficiency, 0.33C and 0.5C discharge capacity, and cycling characteristics at 25°C and 45°C can be further improved.

[0186] As shown in Table 2, from Examples 6 to 10, by changing the temperature and time in the hydrothermal reaction process, the drying process, and the sintering process, the oxygen vacancy content in the coating layer can be changed, thereby altering the IO2 content. 2- / IO 2- The peak intensity ratio. As shown in Examples 11 to 16, by changing the mass ratio of transition metal oxides and organic acid salts in the solution preparation process, the oxygen vacancy content in the coating layer can also be changed, thereby altering the IO2 content. 2- / IO 2- The peak intensity ratio. As shown in Examples 17 to 22, changing the mass ratio of lithium-rich manganese-based material to transition metal oxides and organic acid salts in the hydrothermal reaction process has a significant impact on the coating thickness. The thicker the coating, the more oxygen vacancies there are in the coating. Coatings that are too thin or too thick will affect the coating effect and thus the performance of the material's electrical properties.

[0187] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A positive electrode material, in, include: The core comprises lithium-rich manganese-based oxide cathode material; and The coating layer, covering the outer surface of the core, comprises a composite material of transition metal oxoates and carbon, wherein... The transition metal in the transition metal oxoate is selected from at least one of Ti, Mo, W, V, Ta, or Nb; the transition metal oxoate contains oxygen vacancies; and the transition metal oxoate satisfies the following condition: IO2 2- / IO 2- The peak intensity ratio is 0.5–1.2, of which IO2 2- The peak intensity of the oxygen vacancy at 531 eV in X-ray photoelectron spectroscopy (XPS) is IO. 2- This corresponds to the peak intensity of lattice oxygen at 529 eV in X-ray photoelectron spectroscopy (XPS). The composite material has a mesh structure.

2. The cathode material according to claim 1, wherein, The transition metal in the transition metal oxometalate is selected from at least one of Ti, Mo, W, or V.

3. The cathode material according to claim 1 or 2, wherein, The transition metal oxophosphate is at least one of Li, Na, K, Mg, and Al salts.

4. The cathode material according to claim 3, wherein, The transition metal oxophosphate is at least one of Li, Na, and K salts.

5. The cathode material according to any one of claims 1 to 4, wherein, The molecular formula of the lithium-rich manganese-based oxide cathode material is xLi2MnO3·(1-x)LiNi y Co z Mn a M 1-y-z-a O r A 2-r , where 0 < x < 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1, 0 ≤ a ≤ 1, 0 < r ≤ 2, 0 < y + z + a ≤ 1; M is at least one of Mg, B, Al, V, Ti, Zr, Sn and Mo, and A is at least one of F, S, N and Cl.

6. The cathode material according to any one of claims 1 to 5, wherein, The transition metal oxophosphate satisfies the following condition: IO2 2- / IO 2- The peak intensity ratio is 0.6 to 0.

8.

7. The cathode material according to any one of claims 1 to 6, wherein, The resistivity of the positive electrode material at 12 MPa is less than or equal to 3000 Ω·cm.

8. The cathode material according to claim 7, wherein, The resistivity of the positive electrode material at 12 MPa is less than or equal to 2000 Ω·cm.

9. The cathode material according to any one of claims 1 to 8, wherein, The cathode material is composed of secondary particles, single crystals, or near-single crystals, and the particle size D is... v 50 represents 1–20 μm.

10. The cathode material according to claim 9, wherein, The particle size D v 50 is 3-15 μm.

11. The cathode material according to any one of claims 1 to 10, wherein, The specific surface area of ​​the cathode material is less than 2.0 m². 2 / g.

12. The cathode material according to claim 11, wherein, The specific surface area of ​​the positive electrode material is 0.1–1 m². 2 / g.

13. The method for preparing the cathode material according to any one of claims 1-12, wherein, The process includes the following steps: Solution preparation process: Disperse the transition metal oxide in deionized water, then add organic acid salts, adjust the pH of the solution to the neutral to alkaline range, and stir thoroughly to obtain the solution; Hydrothermal reaction process: Slowly add lithium-rich manganese-based oxide cathode material to the solution and react at a constant temperature of 50-100℃ for 2-10 hours. Drying process: The product of the hydrothermal reaction process is filtered, and the solid obtained by filtration is dried; Sintering process: The dried solid is sintered at 300–600℃ in an inert atmosphere for 4–15 hours to obtain a surface-modified lithium-rich manganese-based oxide cathode material. The transition metal oxide comprises at least one oxide of Ti, Mo, W, V, Ta, or Nb. The anion of the organic acid salt is at least one of acetate, oxalate, or citrate.

14. The method for preparing the cathode material according to claim 13, wherein, The counterion of the organic acid anion in the organic acid salt is an ion of at least one metal selected from Li, Na, K, Mg, and Al.

15. The method for preparing the cathode material according to claim 14, wherein, The counterion of the organic acid anion in the organic acid salt is an ion of at least one metal selected from Li, Na, and K.

16. The method for preparing the cathode material according to any one of claims 13 to 15, wherein, In the solution preparation process, the pH value of the solution is controlled between 7 and 15.

17. The method for preparing the cathode material according to claim 16, wherein, In the solution preparation process, the pH value of the solution is controlled between 8 and 10.

18. The method for preparing the cathode material according to any one of claims 13 to 17, wherein, The mass ratio of the transition metal oxide to the organic acid salt is (0.05-10):

1.

19. The method for preparing the cathode material according to claim 18, wherein, The mass ratio of the transition metal oxide to the organic acid salt is (0.5-2):

1.

20. The method for preparing the cathode material according to any one of claims 13 to 19, wherein, The mass ratio of the added lithium-rich manganese-based oxide cathode material to the combined mass of the transition metal oxide and the organic acid salt is 100:(0.1-30).

21. The method for preparing the cathode material according to any one of claims 13 to 20, wherein, The mass ratio of the added lithium-rich manganese-based oxide cathode material to the combined mass of the transition metal oxide and the organic acid salt is 100:(1-10).

22. The method for preparing the cathode material according to any one of claims 13 to 21, wherein, In the drying process, The drying temperature is 60–120°C, and / or, The drying time is 1–10 hours, and / or, The drying atmosphere is a vacuum atmosphere, and the vacuum degree is maintained at -0.5 to -1 bar.

23. The method for preparing the cathode material according to claim 22, wherein, In the drying process, The drying temperature is 80–100℃, and / or, The drying time is 5 to 8 hours.

24. The method for preparing the cathode material according to any one of claims 13 to 23, wherein, In the sintering process, the inert atmosphere is a nitrogen or argon atmosphere.

25. A secondary battery, wherein, The secondary battery includes the positive electrode material according to any one of claims 1 to 12 or the positive electrode material prepared by any one of claims 13 to 24.

26. A battery module, wherein, The battery module includes the secondary battery as described in claim 25.

27. A battery pack, wherein, The battery pack includes the battery module of claim 26.

28. An electrical appliance, wherein, The electrical device includes at least one selected from the secondary battery of claim 25, the battery module of claim 26, and the battery pack of claim 27.

Images