Positive electrode lithium supplementing agent, preparation method thereof, positive electrode sheet, secondary battery, battery module, battery pack and electric device

Abstract

The application provides a positive electrode lithium supplementing agent, which comprises a core and a coating layer. The core comprises a lithium-rich metal oxide; the coating layer is coated on the surface of the core, and the coating layer comprises a conductive polymer and a low-surface-energy material; the surface energy of the low-surface-energy material is 10 mJ / m 2 ~ 35 mJ / m 2 , and is optionally 10 mJ / m 2 ~ 22 mJ / m 2 .

Description

Technical Field

[0001] This application relates to the field of secondary batteries, specifically to a positive electrode lithium replenishing agent and its preparation method, a positive electrode sheet, a secondary battery, a battery module, a battery pack, and an electrical device. Background Technology

[0002] Lithium-ion batteries are widely used in consumer electronics due to their high energy density, power density, and long cycle life. With the continuous development of electric vehicles and energy storage systems, the demand for high energy density in lithium-ion batteries is constantly increasing. Therefore, developing high-energy-density, safe, and reliable lithium-ion batteries is particularly important. During the formation process of lithium-ion batteries, the formation of the SEI film on the negative electrode surface consumes a large amount of active lithium, leading to a decrease in the initial charge coulombic efficiency and significant irreversible capacity loss.

[0003] Lithium replenishment at the positive or negative electrode is one method to improve the reversible capacity and energy density of a battery. In positive electrode lithium replenishment, lithium-rich metal oxides, as lithium replenishing agents, possess high delithiation capacity and a suitable initial delithiation voltage, which can match the charging potential of the positive electrode active material, thus achieving a lithium replenishment effect and improving battery energy density. However, lithium-rich metal oxides suffer from poor conductivity and stability, limiting their application as lithium replenishing agents. Summary of the Invention

[0004] In view of the above problems, this application provides a positive electrode lithium replenishing agent and its preparation method, a positive electrode sheet, a secondary battery, a battery module, a battery pack and an electrical device. The positive electrode lithium replenishing agent has both good conductivity and moisture resistance, and can improve the energy density and cycle life of the secondary battery.

[0005] One aspect of this application provides a positive electrode lithium supplement agent, comprising:

[0006] The core, comprising a lithium-rich metal oxide; and

[0007] A coating layer is applied to the surface of the core, and the coating layer comprises a conductive polymer and a low surface energy material;

[0008] The surface energy of the low surface energy material is 10 mJ / m². 2 ~35mJ / m 2 10mJ / m 2 ~22mJ / m 2 .

[0009] The surface energy of the aforementioned low surface energy material is significantly lower than that of water. By setting a coating layer containing conductive polymer and low surface energy material on the core surface containing lithium-rich metal oxide, the aforementioned positive electrode lithium replenishing agent has good conductivity and hydrophobicity, which can improve the stability and lithium replenishment efficiency of the positive electrode lithium replenishing agent, thereby improving the energy density and cycle life of the secondary battery.

[0010] In some embodiments, the conductive polymer and the low surface energy material are bonded together by intermolecular forces within the coating layer to form a hydrophobic structure. This bonding between the conductive polymer and the low surface energy material on the lithium-rich metal oxide surface further enhances the water repellency of the positive electrode lithium replenishment agent, resulting in better material stability.

[0011] In some embodiments, the conductive polymer contains conjugated bonds or benzene ring groups capable of forming a delocalized electronic system.

[0012] In some embodiments, the conductivity of the conductive polymer at 25°C is 0.1 S / cm to 10 S / cm;

[0013] Optionally, the conductivity of the conductive polymer at 25°C is 5S / cm to 10S / cm.

[0014] In some embodiments, the conductive polymer includes at least one of polypyrrole, polyaniline, polythiophene, polyacetylene, polydiacetylene, and polyethylenedioxythiophene.

[0015] Optionally, the conductive polymer is a combination of at least one of polypyrrole and polyaniline with polyethylene dioxythiophene.

[0016] In some embodiments, the low surface energy material includes at least one of an organofluorine compound, a long-chain alkyl acid having 12 to 18 carbon atoms, and its salt.

[0017] In some embodiments, the organofluorine compound includes at least one of perfluorooctyl sulfonic acid and its salts, tetraethylamine perfluorooctyl sulfonic acid, and perfluorosedioic acid;

[0018] The long-chain alkyl acids and their salts include at least one of long-chain alkyl sulfonic acids and their salts, and long-chain alkyl sulfuric acids and their salts; optionally, the long-chain alkyl acids and their salts include at least one of dodecylbenzenesulfonic acid, dodecyl sulfonic acid, sodium tetradecyl sulfate, and sodium hexadecylbenzenesulfonate.

[0019] In some of these embodiments, in the coating layer, the mass content of the low surface energy material is 0.05% to 10%; optionally, in the coating layer, the mass content of the low surface energy material is 1.5% to 5%. When the mass content of the low surface energy material in the coating layer is within the above range, the positive electrode lithium supplement agent has good conductivity and hydrophobicity.

[0020] In some of these embodiments, the lithium-rich metal oxide includes at least one of lithium nickel oxide, lithium cobalt oxide, lithium iron oxide, lithium manganese oxide, lithium zinc oxide, lithium magnesium oxide, lithium calcium oxide, lithium copper oxide, lithium tin oxide, lithium chromium oxide, lithium vanadium oxide, lithium niobium oxide, and lithium molybdenum oxide, where the valence states of nickel, cobalt, iron, manganese, zinc, magnesium, calcium, copper, tin, chromium, vanadium, niobium, and molybdenum are respectively lower than their own highest oxidation valence states.

[0021] In some of these embodiments, the lithium-rich metal oxide includes at least one of Li2MnO2, Li5FeO4, Li6CoO4, Li2NiO2, Li2Cu x1 Ni 1-x1-y1 M y1 O2, Li3VO4, and Li3NbO4;

[0022] where 0 < x1 ≤ 1, 0 ≤ y1 < 0.1, 0 < x1 + y1 ≤ 1, and M is selected from at least one of Zn, Sn, Mg, Fe, and Mn; optionally, 0.2 ≤ x1 ≤ 0.8, or 0.4 ≤ x1 ≤ 0.6.

[0023] In some of these embodiments, the Dv50 of the positive electrode lithium supplement agent is 2 μm to 50 μm; optionally, the Dv50 of the positive electrode lithium supplement agent is 2 μm to 10 μm. When the Dv50 of the positive electrode lithium supplement agent is within the above range, the positive electrode lithium supplement agent has a more appropriate lithium supplement rate.

[0024] In some of these embodiments, the thickness of the coating layer is 0.5 μm to 5 μm; optionally, the thickness of the coating layer is 0.5 μm to ~2 μm. When the thickness of the coating layer in the positive electrode lithium supplement agent is within the above range, it can ensure that the positive electrode lithium supplement agent has a more appropriate lithium supplement rate and has good conductivity and hydrophobicity.

[0025] In some of these embodiments, the contact angle of the coating layer with water is 120° to 160°; optionally, the contact angle of the coating layer with water is 140° to 150°. When the contact angle of the coating layer with water is within the above range, the positive electrode lithium supplement agent has good water repellency and can avoid the water absorption reaction of the positive electrode lithium supplement agent.

[0026] In some of these embodiments, according to the Karl Fischer method test, the water content of the positive electrode lithium supplement agent is 10 ppm to 200 ppm.

[0027] Secondly, this application also provides a method for preparing the aforementioned positive electrode lithium replenishing agent, comprising the following steps:

[0028] The lithium-rich metal oxide, the low surface energy material, and the monomers of the conductive polymer are mixed and polymerized to form the coating layer on the surface of the lithium-rich metal oxide.

[0029] Thirdly, this application also provides a positive electrode sheet, comprising:

[0030] Positive current collector; and

[0031] A positive electrode film layer, wherein the positive electrode film layer includes the aforementioned positive electrode lithium replenishing agent.

[0032] In some embodiments, the mass content of the positive electrode lithium replenishing agent in the positive electrode film layer is 0.1% to 10%;

[0033] Optionally, the mass content of the positive electrode lithium supplement in the positive electrode film layer is 2% to 7%.

[0034] Fourthly, this application also provides a secondary battery, including the aforementioned positive electrode plate.

[0035] Fifthly, this application also provides a battery module, including the aforementioned secondary battery.

[0036] Sixthly, this application also provides a battery pack, including the aforementioned battery module.

[0037] In a seventh aspect, this application also provides an electrical device, including at least one selected from the above-described secondary battery, the above-described battery module, or the above-described battery pack.

[0038] Details of one or more embodiments of this application are set forth in the following drawings and description, and other features, objects and advantages of this application will become apparent from the specification, drawings and claims. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of a secondary battery according to one embodiment of this application;

[0040] Figure 2 for Figure 1 An exploded view of a secondary battery according to an embodiment of this application is shown.

[0041] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application;

[0042] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application;

[0043] Figure 5 for Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown;

[0044] Figure 6 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to an embodiment of this application.

[0045] Explanation of reference numerals in the attached figures:

[0046] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Housing; 52 Electrode assembly; 53 Cover plate; 6 Electrical device.

[0047] To better describe and illustrate embodiments and / or examples of the inventions disclosed herein, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed inventions, the currently described embodiments and / or examples, or the best mode of these inventions as currently understood. Detailed Implementation

[0048] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this application.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0050] This application provides a positive electrode lithium replenishing agent, its preparation method, and positive electrode sheets, secondary batteries, battery modules, battery packs, and electrical devices using the positive electrode lithium replenishing agent. This secondary battery is suitable for various battery-powered electrical devices, such as mobile phones, portable devices, laptops, electric vehicles, electric toys, power tools, electric vehicles, ships, and spacecraft, including aircraft, rockets, space shuttles, and spacecraft.

[0051] One embodiment of this application provides a positive electrode lithium replenishment agent, including a core and a coating layer. The core comprises a lithium-rich metal oxide. The coating layer coats the surface of the core and comprises a conductive polymer and a low surface energy material. The surface energy of the low surface energy material is 10 mJ / m². 2~35mJ / m 2 10mJ / m 2 ~22mJ / m 2 .

[0052] Lithium-rich metal oxides typically exhibit poor conductivity and are prone to reaction with moisture or carbon dioxide in the air, negatively impacting their lithium replenishment performance. The aforementioned low surface energy materials possess surface energies significantly lower than water. By applying a coating layer containing conductive polymers and low surface energy materials to the core surface of the lithium-rich metal oxide, the aforementioned cathode lithium replenisher exhibits better conductivity and hydrophobicity, improving its stability and lithium replenishment efficiency, thereby enhancing the energy density and cycle life of the secondary battery.

[0053] Specifically, the surface energy of a solid refers to the reversible non-expansion work required to increase the surface area of ​​a solid by a unit amount under certain temperature and pressure. The surface energy of a solid can be estimated using the γ-T curve extrapolation method. First, the surface tension of the solid material is measured when it becomes a liquid phase slightly above its melting point, according to the following formula:

[0054] γV 2 / 3 = k(Tc-T)

[0055] Wherein: γ - the measured surface energy of the solid, V - molar volume, k - constant, Tc - critical temperature, T - actual temperature, 2) plot the γ-T curve, and then use the extrapolation method to plot the extrapolation to below the freezing point to estimate the surface energy of the solid. The surface energies described in the embodiments of this application are all surface energies at 0K and under vacuum.

[0056] In some embodiments, the conductive polymer and low surface energy material are bonded together by intermolecular forces in the coating layer to form a hydrophobic structure. This bonding of the conductive polymer and low surface energy material on the lithium-rich metal oxide surface further enhances the water repellency of the cathode lithium replenishment agent, resulting in better material stability.

[0057] In some embodiments, the conductive polymer contains conjugated bonds or benzene ring groups capable of forming a delocalized electronic system.

[0058] In some embodiments, the conductivity of the conductive polymer at 25°C is 0.1 S / cm to 10 S / cm. A conductivity within this range effectively improves the conductivity of the positive electrode lithium supplement, thereby increasing its utilization efficiency. Optionally, the conductivity of the conductive polymer can be any of the following values: 0.1 S / cm, 0.5 S / cm, 1 S / cm, 2 S / cm, 4 S / cm, 5 S / cm, 6 S / cm, 8 S / cm, or 10 S / cm. Further, the conductivity of the conductive polymer at 25°C is 5 S / cm to 10 S / cm. Specifically, the conductivity of the conductive polymer can be tested using an RTS-4 four-probe tester, with five measurements taken and the average value calculated, in units of S / m. In the embodiments of this application, the conductivity of the conductive polymer was measured at 25°C.

[0059] In some embodiments, the conductive polymer includes at least one selected from polypyrrole, polyaniline, polythiophene, polyacetylene, polydiyne, and polyethylenedioxythiophene. Optionally, the conductive polymer is a combination of at least one selected from polypyrrole and polyaniline with polyethylenedioxythiophene. All of the above-mentioned conductive polymers possess good conductivity and, when used as a coating layer for the positive electrode lithium supplement, can effectively improve the conductivity of the positive electrode lithium supplement.

[0060] In some embodiments, the low surface energy material includes at least one of an organofluorine compound, a long-chain alkyl acid with 12 to 18 carbon atoms, and its salts. The long-chain alkyl acid and its salts may optionally have 12, 13, 14, 15, 16, 17, or 18 carbon atoms. Organofluorine compounds have low intermolecular cohesion, weak intermolecular forces at the air-organofluorine interface, low surface free energy, and a low coefficient of surface friction, resulting in good hydrophobic properties when used as a coating layer. The σ bonds in long-chain alkyl acids have very low polarity, and their molecular dipole moment is zero, exhibiting nonpolarity. When used in a coating layer, the long-chain alkyl ends have good hydrophobic properties on the surface of the positive electrode lithium supplement.

[0061] In some embodiments, the organofluorine compound includes at least one selected from perfluorooctyl sulfonic acid and its salts, tetraethylamine perfluorooctyl sulfonic acid, and perfluoroselenoic acid. The long-chain alkyl acid and its salts include at least one selected from long-chain alkyl sulfonic acid and its salts, and long-chain alkyl sulfuric acid and its salts. Optionally, the long-chain alkyl acid and its salts include at least one selected from dodecylbenzene sulfonic acid, dodecyl sulfonic acid, sodium tetradecyl sulfate, and sodium hexadecylbenzene sulfonate.

[0062] In some of these embodiments, in the coating layer, the mass content of the low surface energy material is 0.05% to 10%. When the mass content of the low surface energy material in the coating layer is within the above range, the positive electrode lithium supplement agent has good conductivity and hydrophobicity. If the content of the low surface energy material is too low, the hydrophobicity of the positive electrode lithium supplement agent decreases; if the content of the low surface energy material is too high, it will hinder the ion extraction and affect the lithium supplement efficiency. Optionally, in the coating layer, the mass content of the low surface energy material can be any range composed of the following values: 0.05%, 0.1%, 0.5%, 1%, 2%, 4%, 5%, 6%, 8%, or 10%. Further, in the coating layer, the mass content of the low surface energy material is 1.5% to 5%.

[0063] In some of these embodiments, the lithium-rich metal oxide may include, but is not limited to, at least one of lithium nickel oxide, lithium cobalt oxide, lithium iron oxide, lithium manganese oxide, lithium zinc oxide, lithium magnesium oxide, lithium calcium oxide, lithium copper oxide, lithium tin oxide, lithium chromium oxide, lithium vanadium oxide, lithium niobium oxide, and lithium molybdenum oxide, wherein the valence states of nickel, cobalt, iron, manganese, zinc, magnesium, calcium, copper, tin, chromium, vanadium, niobium, and molybdenum are respectively lower than their own highest oxidation valence states.

[0064] In some of these embodiments, the lithium-rich metal oxide may include, but is not limited to, at least one of Li2MnO2, Li5FeO4, Li6CoO4, Li2NiO2, Li2Cu x Ni 1-x-y M y1 O2, Li3VO4, and Li3NbO4;

[0065] where 0 < x ≤ 1, 0 ≤ y < 0.1, 0 < x1 + y1 ≤ 1, and M is selected from at least one of Zn, Sn, Mg, Fe, and Mn; optionally, 0.2 ≤ x ≤ 0.8, or 0.4 ≤ x ≤ 0.6.

[0066] In some of these embodiments, the Dv50 of the positive electrode lithium supplement agent is 2 μm to 50 μm. When the Dv50 of the positive electrode lithium supplement agent is within the above range, the positive electrode lithium supplement agent has a more appropriate lithium supplement rate. If the Dv50 particle size is too small, it is easy to cause agglomeration and gelation of the positive electrode lithium supplement agent material during the preparation of the slurry; if the Dv50 particle size is too large, the polarization of the lithium ion extraction reaction in the lithium supplement agent will increase, reducing the lithium supplement efficiency. Optionally, the Dv50 of the positive electrode lithium supplement agent can be any range composed of the following values: 2 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, or 50 μm. Further, the Dv50 of the positive electrode lithium supplement agent is 2 μm to 10 μm.

[0067] In this application, Dv50 refers to the particle size corresponding to the cumulative particle size distribution number reaching 50% in the volume cumulative distribution curve. Physically, it means that 50% of the particles are smaller (or larger) than Dv50. As an example, Dv50 can be conveniently determined using a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd., UK, in accordance with GB / T19077-2016 Particle Size Distribution Laser Diffraction Method.

[0068] In some embodiments, the thickness of the coating layer is 0.5 μm to 5 μm. A coating layer thickness within this range in the positive electrode lithium replenishment agent ensures a suitable lithium replenishment rate and good conductivity and hydrophobicity. Optionally, the thickness of the coating layer can be any of the following values: 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, or 5 μm. Further, the thickness of the coating layer is 0.5 μm to 2 μm.

[0069] The contact angle (θ) of a liquid on the surface of a solid material is an important parameter for measuring the wettability of the liquid on the material surface. If the contact angle θ between the material and water is <90°, the material surface is hydrophilic and easily wetted; if θ >90°, the material surface is hydrophobic and moisture-resistant. In some embodiments, the contact angle between the coating layer and water is 120° to 160°. Optionally, the contact angle between the coating layer and water is 140° to 150°. When the contact angle between the coating layer and water is within the above range, the positive electrode lithium supplement exhibits good water repellency, which can prevent the positive electrode lithium supplement from absorbing water. Specifically, the contact angle between the coating layer thin film material and water can be measured by a contact angle meter to obtain the contact angle between the coating layer and water.

[0070] In some of these embodiments, the water content of the positive electrode lithium replenisher is 10 ppm to 200 ppm, as determined by the Karl Fischer method.

[0071] Another embodiment of this application provides a method for preparing the above-mentioned positive electrode lithium replenishing agent, including the following steps:

[0072] A polymerization reaction is carried out by mixing monomers of lithium-rich metal oxide, low surface energy material and conductive polymer to form a coating layer on the surface of lithium-rich metal oxide.

[0073] It should be noted that the method of forming a coating layer on the surface of lithium-rich metal oxide is not limited to the in-situ polymerization method mentioned above. Commonly known methods in the art can also be used, such as liquid phase solvothermal coating method, electrochemical deposition method, etc.

[0074] In addition, the positive electrode, secondary battery, battery module, battery pack and power supply device of this application will be described below with appropriate reference to the accompanying drawings.

[0075] In one embodiment of this application, a secondary battery is provided.

[0076] Typically, a secondary battery consists of a positive electrode, a negative 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.

[0077] Positive electrode sheet

[0078] 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 includes a positive active material and the aforementioned positive lithium supplement agent.

[0079] 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.

[0080] 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 such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy on the polymer substrate. The polymer substrate includes substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0081] In some embodiments, the mass content of the positive electrode lithium replenisher in the positive electrode film is 0.1% to 10%, optionally 2% to 7%. When the content of the positive electrode lithium replenisher is within the above range, the positive electrode sheet has a suitable lithium replenishment rate, which can improve the cycle life and energy density of the secondary battery. If the content of the positive electrode lithium replenisher is too low, it cannot compensate for the loss of active lithium in the positive electrode sheet; if the content of the positive electrode lithium replenisher is too high, it will cause insufficient reversible lithium intercalation vacancies in the positive electrode, affecting the energy density of the secondary battery.

[0082] In some embodiments, the positive electrode active material may be a known positive electrode active material for 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 positive electrode active materials for batteries 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 LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 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 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 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.

[0083] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0084] 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.

[0085] 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, positive lithium supplement, 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 current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0086] In some embodiments, the positive electrode film layer includes a positive electrode active material layer and a positive electrode lithium replenishment layer. The positive electrode lithium replenishment layer contains the aforementioned positive electrode lithium replenishing agent. The positive electrode current collector, the positive electrode active material layer, and the positive electrode lithium replenishment layer are sequentially stacked, with the positive electrode lithium replenishment layer located on the surface of the positive electrode active material layer away from the positive electrode current collector. This arrangement provides good ionic conductivity and a short ion transport path, fully utilizing the lithium replenishment capability and improving the lithium replenishment efficiency.

[0087] Negative electrode sheet

[0088] The negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector, wherein the negative active material layer includes a negative active material.

[0089] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0090] 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 such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy on the polymer substrate. The polymer substrate includes substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0091] 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. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials 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.

[0092] In some embodiments, the negative electrode active material 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).

[0093] In some embodiments, the negative electrode active material layer 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.

[0094] In some embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0095] 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.

[0096] electrolytes

[0097] 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.

[0098] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] Separating membrane

[0103] 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.

[0104] 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.

[0105] In some embodiments, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding process or a stacking process.

[0106] 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.

[0107] 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 soft pack can be made of plastic, and examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0108] 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 1 This is an example of a square-structured secondary battery 5.

[0109] In some of these embodiments, reference is made to Figure 2 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. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 52 by a winding process or a 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.

[0110] In some embodiments, 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.

[0111] Figure 3 This is battery module 4, used as an example. (See reference...) Figure 3 In 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.

[0112] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0113] 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.

[0114] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5 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.

[0115] 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 the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc. Among them, mobile devices may be, for example, mobile phones, laptops, etc.; electric vehicles may be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to.

[0116] As an electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0117] Figure 6 This is an example of an electrical device 6. This electrical device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this electrical device, a battery pack or battery module can be used.

[0118] 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.

[0119] Example

[0120] 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.

[0121] Example 1:

[0122] Preparation of positive electrode lithium supplement: 8g of lithium ferrite with a Dv50 of 2μm was dispersed in a chloroform solution containing 0.1mol / L pyrrole. Then, 0.015mol / L potassium perfluorooctyl sulfonate was slowly added dropwise to the mixed solution. The polymerization reaction was carried out by stirring at room temperature (25℃) for 12h, forming a coating layer on the surface of lithium ferrite. The resulting solid was washed three times by centrifugation with chloroform and dried under vacuum at 60℃ for 12h to obtain the positive electrode lithium supplement. The composition and thickness of the coating layer of the positive electrode lithium supplement are recorded in Table 1. The thickness of the coating layer of the positive electrode lithium supplement can be obtained by observation and statistical analysis of transmission electron microscopy (TEM) images of the positive electrode lithium supplement.

[0123] Moisture absorption test method: The positive electrode lithium supplement was stored in an environment with RH 80% humidity for 7 days, and the water content of the positive electrode lithium supplement was tested using a Karl Fischer volumetric moisture analyzer.

[0124] Preparation of positive electrode sheet: LiFePO4 (LFP), positive lithium supplement with different hygroscopic degrees, conductive agent acetylene black, and binder are mixed in a mass ratio of 93:4:1:2. The volume average particle size of LFP particles is 1.2 μm. After being thoroughly stirred and mixed evenly in an N-methylpyrrolidone solvent NMP system, the mixture is coated onto Al foil, dried, and cold-pressed to obtain the positive electrode sheet.

[0125] Preparation of negative electrode sheet: The active material artificial graphite, the conductive agent acetylene black, the binder styrene-butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) are mixed evenly in a deionized water solvent system at a weight ratio of 96.5:0.7:1.8:1. The mixture is then coated onto Cu foil, dried, and cold-pressed to obtain the negative electrode sheet.

[0126] Separator: A 12μm PE / PP porous polymer film is used as the separator.

[0127] Electrolyte preparation: Ethyl carbonate (EC) and diethyl carbonate (DEC) were mixed in a 50 / 50 mass ratio and 1.1M LiPF6 lithium salt was dissolved to form an electrolyte.

[0128] Secondary battery preparation: The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The electrodes are then wound to obtain a bare cell. The bare cell is placed in an outer package, filled with the prepared basic electrolyte, and sealed.

[0129] Examples 2-3:

[0130] The difference between Examples 2 and 3 and Example 1 lies in the different Dv50 particle sizes of the lithium ferrite. The Dv50 particle sizes of the lithium ferrite used in the positive electrode lithium replenishment agents of Examples 2 and 3 are recorded in Table 1.

[0131] Examples 4-5:

[0132] The difference between Examples 4 and 5 and Example 1 lies in the type of conductive polymer. The conductive polymers used in the positive electrode lithium replenishing agents of Examples 4 and 5 are recorded in Table 1. The positive electrode lithium replenishing agents of Examples 4 and 5 can be prepared by selecting the monomers to replace them according to the conductive polymers.

[0133] Examples 6-7:

[0134] The difference between Examples 6 and 7 and Example 1 lies in the type of low surface energy material used. The low surface energy materials used in the cathode lithium replenishment agents of Examples 6 and 7 are recorded in Table 1.

[0135] Examples 8-12:

[0136] The difference between Examples 8-12 and Example 1 lies in the different mass content of the low surface energy material in the coating layer. The mass content of the low surface energy material in the coating layer of the positive electrode lithium supplement in Examples 8-12 is recorded in Table 1. The positive electrode lithium supplement in Examples 8-12 can be obtained by adjusting the amount of low surface energy material added according to its content.

[0137] Examples 13-15:

[0138] The difference between Examples 13-15 and Example 1 is that the number of days the positive electrode lithium replenishment agent was stored in an RH80% environment during the moisture absorption test is different.

[0139] Example 16:

[0140] The difference between Example 16 and Example 1 is that the electrolyte in the secondary battery of Example 16 is replaced with a solid-liquid mixed electrolyte. Specifically, the solid-liquid mixed electrolyte is prepared as follows: 5g of polymer matrix CA, 5g of crosslinking agent PEGDA (Mn=400) and 0.05g of initiator AIBN are added to 50g of 1M LiPF6 / EC+DEC liquid electrolyte and stirred at room temperature for 12h to obtain an electrolyte precursor solution. The above precursor solution is kept at 70°C for 1h to obtain CA / PEGDA gel electrolyte. The secondary battery is prepared as follows: the positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation, and then wound to obtain a bare cell. The electrolyte precursor solution is then injected into the battery and left to stand for 6h to ensure that the electrodes and separator are completely wetted. Finally, the battery is heated at 70°C for 1h to allow the electrolyte precursor solution to polymerize and crosslink in situ within the battery.

[0141] Comparative Example 1:

[0142] The difference between Comparative Example 1 and Example 1 is that the positive electrode lithium replenishing agent is lithium ferrite without coating treatment.

[0143] Comparative Example 2:

[0144] The difference between Comparative Example 2 and Example 1 is that the positive electrode lithium replenishment coating does not contain low surface energy materials.

[0145] Comparative Examples 3-4:

[0146] The difference between Comparative Examples 3 and 4 and Comparative Example 2 is that the positive electrode lithium replenishment agent was stored for different number of days in an RH80% environment during the moisture absorption test.

[0147] Table 1. Composition and water content of the positive electrode lithium supplement in Examples 1-15 and Comparative Examples 1-4

[0148]

[0149]

[0150] Note: The mass contents in Table 1 are the mass contents of the substances in the coating layer.

[0151] As can be seen from the data in Table 1, compared with the positive electrode lithium replenishment agents of Comparative Examples 1 to 4, the positive electrode lithium replenishment agents of Examples 1 to 15, after being placed in an RH 80% environment for 3 to 20 days, have a water content of 20ppm to 200ppm, which is significantly lower than that of the positive electrode lithium replenishment agents of Comparative Examples 1 to 4. The positive electrode lithium replenishment agents of Examples 1 to 15 have better hydrophobicity and better material stability.

[0152] Test section:

[0153] Charge / discharge specific capacity test:

[0154] At room temperature (25℃), the battery is charged at a constant current rate of 0.33C to the charging termination voltage, and then charged at a constant voltage to 0.05C. The charging capacity Ec0 is measured. The specific charging capacity is obtained by dividing Ec0 by the mass of the positive electrode active material. That is, the specific charging capacity (mAh / g) = first charge capacity / mass of positive electrode active material.

[0155] Take the battery that has been fully charged and discharge it at a constant current rate of 0.33C until the discharge termination voltage is reached. Measure the discharge capacity as Ed0. Divide Ed0 by the mass of the positive electrode active material to obtain the discharge specific capacity. That is, discharge specific capacity (mAh / g) = first discharge capacity / mass of positive electrode active material.

[0156] The above tests for charging specific capacity and discharging specific capacity were repeated 5 times each, and the average value is the charging specific capacity and discharging specific capacity listed in Table 2 below.

[0157] High-temperature storage performance test of secondary batteries:

[0158] For each embodiment, five secondary batteries were used for parallel testing. Each secondary battery was charged at room temperature at a 1C rate to a voltage of 3.65V, and then discharged at a 1C rate to a voltage of 2.5V. The reversible capacity was measured as E0. The fully charged batteries were then placed in a 60°C oven for 100 days. Afterward, the secondary batteries were removed, and their reversible capacity was immediately measured and recorded as En. The capacity retention rate ε after 100 days of storage at 60°C was calculated using the following formula: ε = (En - E0) / E0 × 100%.

[0159] The electrochemical performance test results of the secondary batteries of Examples 1-16 and Comparative Examples 1-4 are recorded in Table 2.

[0160] Table 2 Electrochemical performance of secondary batteries in Examples 1-16 and Comparative Examples 1-4

[0161]

[0162] As can be seen from the data in Table 2, in the secondary batteries of Examples 1-16, the water content of the positive electrode lithium replenishing agent is 20ppm-200ppm, the charge specific capacity of the secondary batteries is 154mAh / g-181.5mAh / g, the discharge specific capacity is 138mAh / g-147mAh / g, and the capacity retention rate after 100 days of storage at 60℃ is 90.4%-97.9%. It is evident that in the first charge and discharge process, the positive electrode lithium replenishing agent in the secondary batteries of Examples 1-16 can effectively replenish lithium, improve the energy density of the secondary batteries, and the secondary batteries have high charge specific capacity and good high-temperature storage stability.

[0163] In the secondary battery of Comparative Example 1, the positive electrode lithium replenisher was uncoated lithium ferrite with a water content of 660 ppm. The charge specific capacity and capacity retention rate of the secondary battery after 100 days of storage at 60°C were significantly lower than those of Examples 1-16. The lithium replenishment effect of the positive electrode lithium replenisher and the high-temperature storage stability of the secondary battery were poor.

[0164] In the secondary batteries of Comparative Examples 2-4, the coating layer of the positive electrode lithium replenisher did not contain low surface energy materials, and the water content of the positive electrode lithium replenisher was 230ppm-580ppm. The charge specific capacity and capacity retention rate after 100 days of storage at 60°C were better than those of Comparative Example 1, but still lower than those of Examples 1-16. It can be seen that positive electrode lithium replenishers coated only by conductive polymers can only improve the lithium replenishment effect of the positive electrode lithium replenisher and the high-temperature storage stability of the secondary battery to a limited extent.

[0165] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0166] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A positive electrode lithium supplement, comprising: a core, the core comprising a lithium-rich metal oxide; and a coating layer, the coating layer covering the surface of the core, the coating layer comprising a conductive polymer and a low surface energy material; The surface energy of the low surface energy material is 10 mJ / m 2 ~35 mJ / m 2 In the coating layer, the conductive polymer and the low surface energy material are bonded together by intermolecular forces to form a hydrophobic structure.

2. The positive electrode lithium replenishing agent according to claim 1, wherein, The surface energy of the low surface energy material is 10 mJ / m 2 ~22mJ / m 2 .

3. The positive electrode lithium replenishing agent according to claim 1, wherein, the conductive polymer contains a conjugated bond or a benzene ring group capable of forming a delocalized electron system.

4. The positive electrode lithium replenishing agent according to claim 1, wherein, The conductivity of the conductive polymer at 25 °C is 0.1 S / cm to 10 S / cm.

5. The positive electrode lithium replenishing agent according to claim 4, wherein, The conductivity of the conductive polymer at 25 °C is 5 S / cm to 10 S / cm.

6. The positive electrode lithium replenishing agent according to claim 1, wherein, The conductive polymer includes at least one of polypyrrole, polyaniline, polythiophene, polyacetylene, polydiyne, and poly(ethylenedioxythiophene).

7. The positive electrode lithium replenishing agent according to claim 5, wherein, The conductive polymer is a combination of at least one of polypyrrole and polyaniline and poly(ethylenedioxythiophene).

8. The positive electrode lithium replenishing agent according to claim 1, wherein, The low surface energy material includes at least one of an organic fluorine compound, a long-chain alkyl acid having 12 to 18 carbon atoms, and its salt.

9. The positive electrode lithium replenishing agent according to claim 8, wherein, The organic fluorine compound includes at least one of perfluorooctanesulfonic acid and its salt, tetraethylammonium perfluorooctanesulfonate, and perfluorodecanedioic acid; The long-chain alkyl acid and its salt include at least one of a long-chain alkyl sulfonic acid and its salt, and a long-chain alkyl sulfate and its salt.

10. The positive electrode lithium replenishing agent according to claim 8, wherein, The long-chain alkyl acid and its salt includes at least one of dodecylbenzenesulfonic acid, dodecylsulfonic acid, sodium tetradecyl sulfate, and sodium hexadecylbenzenesulfonate.

11. The positive electrode lithium replenishing agent according to claim 1, wherein, In the coating layer, the mass content of the low surface energy material is 0.05% to 10%.

12. The positive electrode lithium replenishing agent according to claim 11, wherein, In the coating layer, the mass content of the low surface energy material is 1.5% to 5%.

13. The positive electrode lithium replenishing agent according to claim 1, wherein, The lithium-rich metal oxide includes at least one of lithium nickel oxide, lithium cobalt oxide, lithium iron oxide, lithium manganese oxide, lithium zinc oxide, lithium magnesium oxide, lithium calcium oxide, lithium copper oxide, lithium tin oxide, lithium chromium oxide, lithium vanadium oxide, lithium niobium oxide, and lithium molybdenum oxide, wherein the valence states of nickel, cobalt, iron, manganese, zinc, magnesium, calcium, copper, tin, chromium, vanadium, niobium, and molybdenum are respectively lower than their own highest oxidation valence states.

14. The positive electrode lithium replenishing agent according to claim 1, wherein, The lithium-rich metal oxides include Li₂MnO₂, Li₅FeO₄, Li₆CoO₄, Li₂NiO₂, and Li₂Cu. x1 Ni 1-x1-y1 M y1 At least one of O2, Li3VO4 and Li3NbO4; Wherein, 0 < x1 ≤ 1, 0 ≤ y1 < 0.1, 0 < x1 + y1 ≤ 1, and M is selected from at least one of Zn, Sn, Mg, Fe, and Mn.

15. The positive electrode lithium replenishing agent according to claim 14, wherein, 0.2 ≤ x1 ≤ 0.8, or 0.4 ≤ x1 ≤ 0.

6.

16. The positive electrode lithium replenishing agent according to claim 1, wherein, The Dv50 of the positive electrode lithium supplement is 2 μm to 50 μm.

17. The positive electrode lithium replenishing agent according to claim 16, wherein, The Dv50 of the positive electrode lithium supplement is 2 μm to 10 μm.

18. The positive electrode lithium replenishing agent according to claim 1, wherein, The thickness of the coating layer is 0.5 μm to 5 μm.

19. The positive electrode lithium replenishing agent according to claim 18, wherein, The thickness of the coating layer is 0.5 μm to 2 μm.

20. The positive electrode lithium replenishing agent according to claim 1, wherein, The contact angle of the coating layer with water is 120° to 160°.

21. The positive electrode lithium replenishing agent according to claim 20, wherein, The contact angle of the coating layer with water is 140° to 150°.

22. The positive electrode lithium replenishing agent according to any one of claims 1 to 21, wherein, According to the Karl Fischer method test, the water content of the positive electrode lithium supplement is 10 ppm to 200 ppm.

23. The preparation method of the positive electrode lithium supplement according to any one of claims 1 to 22, comprising the following steps: Mix the lithium-rich metal oxide, the low surface energy material, and the monomer of the conductive polymer, and carry out a polymerization reaction to form the coating layer on the surface of the lithium-rich metal oxide.

24. A positive electrode sheet, comprising: a positive electrode current collector; and A positive electrode film layer, wherein the positive electrode film layer comprises a positive electrode lithium supplement as described in any one of claims 1 to 22.

25. The positive electrode sheet according to claim 24, wherein, In the positive electrode film layer, the mass content of the positive electrode lithium supplement is 0.1% to 10%.

26. The positive electrode sheet according to claim 25, wherein, In the positive electrode film layer, the mass content of the positive electrode lithium replenishing agent is 2% to 7%.

27. A secondary battery comprising the positive electrode sheet as described in any one of claims 24 to 26.

28. A battery module comprising the secondary battery of claim 27.

29. A battery pack comprising the battery module of claim 28.

30. An electrical device comprising at least one selected from the secondary battery of claim 27, the battery module of claim 28, or the battery pack of claim 29.

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