Positive electrode lithium supplementing agent, preparation method thereof, lithium ion battery and electric device

Abstract

This application provides a positive electrode lithium replenisher, its preparation method, a lithium-ion battery, and an electrical device. The lithium-ion battery includes a positive electrode sheet, the positive electrode sheet includes a positive electrode lithium replenisher, the positive electrode lithium replenisher includes a core and a coating layer, the coating layer containing fluorine. By modifying at least a portion of the surface of the core with a fluorine-doped coating layer, the water absorption performance of the core is reduced, and its air stability is improved. This not only reduces the storage and transportation costs of the prepared positive electrode lithium replenisher, but also improves the cycle life of the lithium-ion battery.

Description

Technical Field

[0001] This application belongs to the field of secondary battery technology, specifically relating to a positive electrode lithium replenishing agent and its preparation method, a lithium-ion battery, and an electrical device. Background Technology

[0002] Secondary batteries, also known as rechargeable batteries, not only provide a powerful and long-lasting power source for various new energy vehicles, but also offer efficient energy management solutions for energy storage systems. During the first charge of a lithium-ion battery, the electrolyte undergoes reduction and decomposition on the surface of the negative electrode active material, such as graphite, forming an SEI film. This process permanently consumes a large amount of lithium from the positive electrode, resulting in a reduction in coulombic efficiency and cycle life during the first cycle. To compensate for the active lithium consumed during the first charge, lithium replenishing agents are typically added to lithium-ion batteries. These agents pre-lithiate the electrode materials, replenishing the lithium lost during the first charge and the lithium loss during cycling, thus helping to improve the battery's first-cycle efficiency and cycle life.

[0003] Cathode lithium replenishment agents are additives used in lithium-ion batteries to generate lithium ions during the first charge cycle, effectively compensating for the irreversible capacity loss caused by the formation of the SEI film during the formation stage. Currently explored cathode lithium replenishment agents for lithium-ion batteries mainly include inorganic lithium replenishment agents such as Li5FeO4 and Li2NiO2, as well as organic lithium replenishment agents represented by lithium oxalate. Among them, Li5FeO4 has been extensively studied due to its high capacity and low decomposition potential. However, due to its lithium-rich material characteristics, it has poor air stability, easily absorbing moisture and producing residual alkali, leading to deterioration. Even in dry air, it cannot be stored for long periods, significantly increasing storage and transportation costs and impacting production line control. Furthermore, if the cathode lithium replenishment agent absorbs excessive moisture from the air, it will undergo side reactions with the electrolyte after being used in lithium-ion batteries, affecting the cycle life of the lithium-ion battery. Summary of the Invention

[0004] This application is made in view of the above-mentioned problems, and its purpose is to provide a positive electrode lithium replenishing agent and its preparation method, a lithium-ion battery and an electrical device, so as to solve the problem of poor air stability of existing positive electrode lithium replenishing agents, reduce the storage and transportation costs of positive electrode lithium replenishing agents, and improve the cycle life of lithium-ion batteries.

[0005] This application provides a lithium-ion battery comprising a positive electrode sheet, the positive electrode sheet comprising a positive electrode lithium replenishing agent, the positive electrode lithium replenishing agent comprising a core and a coating layer, the core comprising a lithium-rich metal oxide, the coating layer being disposed on at least a portion of the surface of the core, and the coating layer containing fluorine. By providing a fluorine-doped coating layer on at least a portion of the surface of the positive electrode lithium replenishing agent, the water absorption of the positive electrode lithium replenishing agent is reduced, and its air stability is improved.

[0006] In any embodiment, the content of fluorine element in the coating layer accounts for 0.03%-0.45% of the positive electrode lithium compensation agent. This can balance the water absorption of the prepared positive electrode lithium compensation agent and the capacity of the lithium ion battery using the positive electrode lithium compensation agent.

[0007] In any embodiment, the water absorption of the positive electrode lithium compensation agent is 3000ppm-4000ppm. Compared with the positive electrode lithium compensation agent without fluorine doping and coating, the positive electrode lithium compensation agent prepared in the present application has lower water absorption and better air stability, which reduces the storage and transportation cost of the positive electrode lithium compensation agent, and can improve the cycle life of the lithium ion battery when applied thereto.

[0008] In any embodiment, the coating layer comprises at least one selected from the group consisting of a carbon coating layer, a metal oxide coating layer, a metal phosphide coating layer, a metal sulfide coating layer and a non-metal oxide coating layer, and may optionally comprise a carbon coating layer.

[0009] In any embodiment, the thickness of the carbon coating layer is 1nm-10nm. This can balance the lithium compensation effect of the prepared positive electrode lithium compensation agent and the capacity of the lithium ion battery.

[0010] In any embodiment, the lithium-rich metal oxide comprises at least one selected from the group consisting 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 respective highest oxidation states.

[0011] In any embodiment, the lithium-rich metal oxide comprises at least one selected from the group consisting of Li₂MnO₂, Li₅FeO₄, Li₆CoO₄, Li₂NiO₂, Li₂Cux1Ni1-x1-y1My1O₂, Li₃VO₄ and Li₃NbO₄; wherein 0 < x1 ≤ 1, 0 ≤ y1 < 0.1, 0 < x1+y1 ≤ 1, 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.

[0012] The second aspect of the present application provides a positive electrode lithium compensation agent, which comprises an inner core and a coating layer, wherein the inner core comprises a lithium-rich metal oxide, the coating layer is arranged on at least a part of the surface of the inner core, and the coating layer contains fluorine element. By arranging the fluorine-doped coating layer on at least a part of the surface of the positive electrode lithium compensation agent, the water absorption of the positive electrode lithium compensation agent is reduced and the air stability thereof is improved.

[0013] In any embodiment, the fluorine content in the coating layer accounts for 0.03%-0.45% of the positive electrode lithium supplement, thereby balancing the water absorption of the prepared positive electrode lithium supplement and the capacity of the positive electrode lithium supplement for lithium-ion batteries.

[0014] The third aspect of this application provides a method for preparing a positive electrode lithium supplement, comprising mixing a lithium-rich metal oxide, a coating material and a fluorine source, and ball milling the mixture to obtain a precursor material; calcining the obtained precursor material under an inert atmosphere, keeping it at a constant temperature and allowing it to cool naturally to obtain a positive electrode lithium supplement, wherein the calcination temperature is greater than 550°C.

[0015] In any embodiment, 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 highest oxidation valence states.

[0016] In any embodiment, the coating material includes at least one of carbon-containing organic matter, metal oxide, metal phosphide, metal sulfide, and non-metal oxide, and optionally includes carbon-containing organic matter.

[0017] Carbon has good electrical conductivity. Using carbon as a coating layer can not only improve the air stability of lithium-rich metal oxides, but also improve their conductivity. When used in lithium-ion batteries, it can improve the lithium-ion transport rate, thereby improving the rate performance of lithium-ion batteries.

[0018] In any embodiment, the carbon-containing organic compound includes at least one of glucose, sucrose, citric acid, ethylene glycol, polyvinyl alcohol, and phenolic resin.

[0019] The porosity of glucose is moderate, and the porosity of the carbon coating layer on the final positive electrode lithium replenishing agent is moderate. The prepared positive electrode lithium replenishing agent can balance the lithium replenishing effect of the positive electrode lithium replenishing agent and the cycle life of the lithium-ion battery.

[0020] In any embodiment, the fluorine source comprises fluorinated olefins. This reduces the manufacturing cost of the cathode lithium supplement without introducing elements other than C and F, thus avoiding side reactions.

[0021] In any embodiment, the fluorinated olefin includes at least one of polyvinylidene fluoride and polytetrafluoroethylene. This reduces the manufacturing cost of the positive electrode lithium supplement.

[0022] In any embodiment, the calcination temperature is 550°C-700°C. This allows for the production of a uniformly coated fluorine-doped carbon cathode lithium supplement that does not affect the capacity of a lithium-ion battery.

[0023] In any embodiment, the heat preservation time is 3-8 hours. This balances the capacity of the lithium-ion battery with the cost of the cathode lithium replenishment agent preparation process.

[0024] In any embodiment, the sum of the mass of the coating material and the fluorine source accounts for 8%-15% of the total mass of the lithium-rich metal oxide, the coating material, and the fluorine source; the mass of the fluorine source accounts for 10%-35% of the sum of the mass of the coating material and the fluorine source. This balances the lithium replenishment effect, water absorption performance, and capacity of the prepared cathode lithium replenishing agent for lithium-ion batteries.

[0025] A fourth aspect of this application provides an electrical device that includes the lithium-ion battery described in the first aspect. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of a SEM image of one embodiment of the positive electrode lithium replenishment agent prepared in this application;

[0028] Figure 2 This is a schematic diagram of TEM, an embodiment of the positive electrode lithium replenishment agent prepared in this application;

[0029] Figure 3 This is a schematic diagram of TEM, an embodiment of the positive electrode lithium replenishment agent prepared in this application;

[0030] Figure 4 This is a schematic diagram of one embodiment of the secondary battery of this application;

[0031] Figure 5 This is an exploded view of one embodiment of the secondary battery of this application;

[0032] Figure 6 This is a schematic diagram of one embodiment of the battery module of this application;

[0033] Figure 7 This is a schematic diagram of one embodiment of the battery pack of this application;

[0034] Figure 8 yes Figure 5An exploded view of an embodiment of the battery pack shown;

[0035] Figure 9 This is a schematic diagram of one embodiment of an electrical device that uses a secondary battery as a power source, as described in this application.

[0036] The accompanying drawings are not necessarily drawn to scale. The reference numerals are as follows: 1 Battery pack, 2 Upper casing, 3 Lower casing, 4 Battery module, 5 Secondary battery, 51 Housing, 52 Electrode assembly, 53 Cover plate. Detailed Implementation

[0037] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the composite separator, its preparation method, secondary battery, and power-consuming 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 a 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 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 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: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" 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 "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0039] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0040] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0041] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0042] 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.

[0043] 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).

[0044] Unless otherwise specified, the terms used in this application have the common meanings as commonly understood by those skilled in the art.

[0045] Unless otherwise specified, the values ​​of the parameters mentioned in this application can be determined using various testing methods commonly used in the art, for example, according to the testing methods given in this application.

[0046] In this application, the terms "multiple" or "various" refer to two or more kinds of things.

[0047] Unless otherwise specified, in this application, the term "active ion" refers to ions that can be inserted and extracted back and forth between the positive and negative electrodes of a secondary battery, including but not limited to lithium ions.

[0048] Secondary batteries, also known as rechargeable batteries, not only provide a powerful and long-lasting power source for various new energy vehicles, but also offer efficient energy management solutions for energy storage systems. During the first charge of a lithium-ion battery, the electrolyte undergoes reduction and decomposition on the surface of the negative electrode active material, such as graphite, forming an SEI film. This process permanently consumes a large amount of lithium from the positive electrode, resulting in a reduction in coulombic efficiency and cycle life during the first cycle. To compensate for the active lithium consumed during the first charge, lithium replenishing agents are typically added to lithium-ion batteries. These agents pre-lithiate the electrode materials, replenishing the lithium lost during the first charge and the lithium loss during cycling, thus helping to improve the battery's first-cycle efficiency and cycle life.

[0049] Cathode lithium replenishment agents are additives used in lithium-ion batteries to generate lithium ions during the first charge cycle, effectively compensating for the irreversible capacity loss caused by the formation of the SEI film during the formation stage. Currently explored cathode lithium replenishment agents for lithium-ion batteries mainly include inorganic lithium replenishment agents such as Li5FeO4 and Li2NiO2, as well as organic lithium replenishment agents represented by lithium oxalate. Among them, Li5FeO4 has been extensively studied due to its high capacity and low decomposition potential. However, due to its lithium-rich material characteristics, it has poor air stability, easily absorbing moisture and producing residual alkali, leading to deterioration. Even in dry air, it cannot be stored for long periods, significantly increasing storage and transportation costs and impacting production line control. Furthermore, if the cathode lithium replenishment agent absorbs excessive moisture from the air, it will undergo side reactions with the electrolyte after being used in lithium-ion batteries, affecting the cycle life of the lithium-ion battery.

[0050] Based on this, this application provides a positive electrode lithium replenishing agent and its preparation method, a lithium-ion battery and an electrical device, so as to improve the cycle life of lithium-ion batteries.

[0051] In a first aspect of this application, a lithium-ion battery is provided. The secondary battery includes a positive electrode, a negative electrode, a separator, and an electrolyte. During the charging and discharging process of the lithium-ion battery, lithium ions are inserted and extracted back and forth between the positive electrode and the negative electrode. The electrolyte plays a role in conducting lithium ions between the positive electrode and the negative electrode. The composite separator is disposed between the positive electrode and the negative electrode, serving to isolate the positive electrode and the negative electrode.

[0052] Positive electrode sheet

[0053] The positive electrode includes a positive current collector and a positive electrode film layer optionally disposed on at least one surface of the positive current collector. The positive electrode film layer includes a positive electrode active material.

[0054] 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.

[0055] 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 can 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.).

[0056] In some embodiments, the positive electrode film layer comprises a positive electrode active material. In some embodiments, 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 may 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, lithium nickel cobalt manganese oxides (such as LiNi1 / 3Co1 / 3Mn1 / 3O2 (also abbreviated as NCM333), LiNi0.5Co0.2Mn0.3O2 (also abbreviated as NCM523), LiNi0.5Co0.25Mn0.25O2 (also abbreviated as NCM211), and LiNi0.6Co0.2Mn0.2O2 (also abbreviated as N... At least one of the following: CM622), LiNi0.8Co0.1Mn0.1O2 (also abbreviated as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi0.85Co0.15Al0.05O2), and their modified compounds. Examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also abbreviated 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. The modified compounds of the above materials may be compounds that have been doped and / or surface-coated to modify the materials.

[0057] In some embodiments, the positive electrode active material layer 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.

[0058] In some embodiments, the positive electrode active material layer may optionally include a binder. As an example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0059] In some embodiments, the positive electrode active material layer may optionally include a lithium replenishing agent, which is the positive electrode lithium replenishing agent described in this application or a positive electrode lithium replenishing agent prepared according to the preparation method of the positive electrode lithium replenishing agent described in this application. The positive electrode lithium replenishing agent includes a core and a fluorine-containing coating layer, wherein the core is a lithium-rich metal oxide, and the coating layer is disposed on at least a portion of the surface of the lithium-rich metal oxide. Disposing of a fluorine-containing coating layer on at least a portion of the surface of the lithium-rich metal oxide can improve its air stability, reduce its water absorption, and reduce the storage and transportation costs of the lithium-rich metal oxide.

[0060] In this article, the term "lithium-rich metal oxide" refers to binary or multi-component compounds composed of oxygen and one or more other metallic chemical elements, with a relatively high lithium content, which are typically used as lithium replenishment materials in lithium-ion batteries.

[0061] To facilitate understanding, the principle behind the aforementioned beneficial effects of the positive electrode lithium supplement in this application is explained below:

[0062] Applying a coating layer to the surface of lithium-rich metal oxides can protect them from the influence of the external environment and prevent them from contacting moisture in the air, thereby improving their chemical stability. In addition, doping the coating layer with fluorine can further reduce the water absorption performance of the positive electrode lithium replenishment agent. Because fluorine has a high Gibbs free energy, it is difficult for it to combine with water molecules, which ultimately reduces the water absorption performance of the resulting positive electrode lithium replenishment agent and improves its air stability.

[0063] In some embodiments, the fluorine content in the coating layer accounts for 0.03%-0.45% of the positive electrode lithium supplement.

[0064] In some embodiments, the fluorine content in the coating layer may be 0.03%, 0.15%, 0.25%, 0.35%, 0.45% of the positive electrode lithium supplement, or any value between two of these.

[0065] If the fluorine content in the coating layer of the prepared positive electrode lithium supplement is too low, its effect on improving water absorption is not significant, and the resulting positive electrode lithium supplement has poor air stability. Conversely, if the fluorine content in the coating layer is too high, the poor conductivity of fluorine leads to poor conductivity in the prepared positive electrode lithium supplement, increasing polarization in lithium-ion batteries and ultimately affecting the battery capacity. Controlling the fluorine content in the coating layer of the positive electrode lithium supplement between 0.03% and 0.45% balances the air stability of the prepared positive electrode lithium supplement with its capacity in lithium-ion batteries.

[0066] In some implementations, the positive electrode lithium supplement absorbs 3000ppm-4000ppm of water.

[0067] In some embodiments, the water absorption capacity of the positive electrode lithium supplement can be 3000ppm, 3100ppm, 3200ppm, 3300ppm, 3400ppm, 3500ppm, 3600ppm, 3700ppm, 3800ppm, 3900ppm, 4000ppm or any value range between the two.

[0068] The positive electrode lithium replenishing agent prepared in this application has lower water absorption and better air stability compared to the positive electrode lithium replenishing agent without fluorine doping and coating, which reduces the storage and transportation costs of the positive electrode lithium replenishing agent and can improve the cycle life of lithium-ion batteries.

[0069] In some embodiments, the coating layer includes at least one of a carbon coating layer, a metal oxide coating layer, a metal phosphide coating layer, a metal sulfide coating layer, and a non-metal oxide coating layer, and optionally includes a carbon coating layer.

[0070] Carbon has good electrical conductivity. Using carbon as a coating layer can not only improve the air stability of lithium-rich metal oxides, but also improve the conductivity of the prepared positive electrode lithium replenishment agent. When used in lithium-ion batteries, it can improve the lithium-ion transport rate, thereby improving the rate performance of lithium-ion batteries.

[0071] In some embodiments, the thickness of the carbon coating layer is 1 nm to 10 nm.

[0072] In some implementations, the thickness of the carbon coating can be 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, or any value between the two.

[0073] If the carbon coating layer of the prepared positive electrode lithium supplement is too thick, the content of lithium-ion-providing components in the positive electrode lithium supplement will be low, affecting the lithium supplementation effect of the positive electrode lithium supplement in lithium-ion batteries. If the carbon coating layer of the prepared positive electrode lithium supplement is too thin, the conductivity of the positive electrode lithium supplement will be poor, resulting in increased polarization after use in lithium-ion batteries, ultimately affecting the capacity of lithium-ion batteries. Controlling the thickness of the coating layer to 1nm-10nm can balance the lithium supplementation effect of the prepared positive electrode lithium supplement and the capacity of lithium-ion batteries.

[0074] In some 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, wherein the valence states of nickel, cobalt, iron, manganese, zinc, magnesium, calcium, copper, tin, chromium, vanadium, niobium, and molybdenum are respectively lower than their highest oxidation valence states.

[0075] In some embodiments, the lithium-rich metal oxide includes at least one of Li2MnO2, Li5FeO4, Li6CoO4, Li2NiO2, Li2Cux1Ni1-x1-y1My1O2, 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; optionally, 0.2 ≤ x1 ≤ 0.8, or 0.4 ≤ x1 ≤ 0.6.

[0076] The above-mentioned positive electrode lithium replenishing agent is prepared by the following method: first, lithium-rich metal oxide, coating material and fluorine source are mixed and ball-milled to obtain a precursor material; then, the obtained precursor material is calcined, kept warm and naturally cooled in an inert atmosphere at a temperature greater than 550°C to obtain the positive electrode lithium replenishing agent.

[0077] The fluorine-doped lithium-rich metal oxide prepared by the above method can protect the lithium-rich metal oxide from the influence of the external environment and prevent it from contacting moisture in the air, thereby improving its chemical stability. In addition, doping the coating layer with fluorine can further reduce the water absorption performance of the positive electrode lithium replenishment agent. Because the Gibbs free energy of fluorine is high, it is difficult for it to combine with water molecules, which ultimately reduces the water absorption performance of the obtained positive electrode lithium replenishment agent and improves its air stability.

[0078] The reason for calcining at a temperature greater than 550°C is that if the reaction temperature is too low, the carbon-containing organic matter will be difficult to carbonize and form a carbon coating layer. The resulting positive electrode lithium replenishing agent will not be conductive. The increased polarization of the positive electrode lithium replenishing agent in lithium-ion batteries will affect the battery's capacity and fast charging performance.

[0079] In some 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, wherein the valence states of nickel, cobalt, iron, manganese, zinc, magnesium, calcium, copper, tin, chromium, vanadium, niobium, and molybdenum are respectively lower than their highest oxidation valence states.

[0080] In some embodiments, the coating material includes at least one of carbon-containing organic compounds, metal oxides, metal phosphides, metal sulfides, and non-metal oxides, and optionally includes carbon-containing organic compounds.

[0081] Carbon has good electrical conductivity. Using carbon as a coating layer can not only improve the air stability of lithium-rich metal oxides, but also improve their conductivity. When used in lithium-ion batteries, it can improve the lithium-ion transport rate, thereby improving the rate performance of lithium-ion batteries.

[0082] In some embodiments, the carbon-containing organic matter includes at least one of glucose, sucrose, citric acid, ethylene glycol, polyvinyl alcohol, and phenolic resin.

[0083] Glucose has moderate porosity. Using glucose as a raw material for the carbon coating layer results in a positive electrode lithium supplement with a carbon coating layer that is neither too large nor too small. This allows the prepared positive electrode lithium supplement to balance the lithium supplementation effect and the cycle life of the lithium-ion battery. If the porosity of the carbon coating layer is too small, the wetting between the positive electrode lithium supplement and the electrolyte will be insufficient, leading to incomplete decomposition of the positive electrode lithium supplement in the electrolyte, which will affect the lithium supplementation effect. If the porosity of the coating layer in the prepared positive electrode lithium supplement is too large, the electrolyte and the positive electrode lithium supplement will have sufficient contact and wetting, resulting in strong interaction between the positive electrode lithium supplement and the electrolyte, which can easily lead to side reactions and deteriorate the storage and cycling performance of the lithium-ion battery.

[0084] In some implementations, the fluorine source includes fluorinated olefins.

[0085] Fluorinated olefins typically contain only carbon (C), sulfur (F), and hydrogen (H) and no other elements. Using fluorinated olefins as a fluorine source prevents the introduction of other elements into the resulting cathode lithium supplement, thus avoiding side reactions in lithium-ion batteries. Furthermore, fluorine gas is not used as a fluorine source for several reasons. First, fluorine gas has strong oxidizing properties and can react chemically with many materials, potentially causing corrosion and blockage of the pipe walls. Second, using fluorine gas as a doping source makes it difficult to introduce fluorine during the coating process of lithium-rich metal oxides; the fluorine source must be introduced after coating, complicating the process. Using fluorinated olefins, however, allows for introduction during the coating process, simplifying the process, reducing costs, and ensuring more uniform fluorine doping in the coating layer.

[0086] In some embodiments, the fluorinated olefin includes at least one of polyvinylidene fluoride and polytetrafluoroethylene.

[0087] Polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) are relatively inexpensive, and using these two types of substances as fluorine sources can reduce the cost of the cathode lithium supplementation process.

[0088] In some embodiments, the calcination temperature is 550°C-700°C.

[0089] In some embodiments, the calcination temperature can be 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, 610°C, 620°C, 630°C, 640°C, 650°C, 660°C, 670°C, 680°C, 690°C, 700°C, or any range between two of these.

[0090] If the calcination temperature is below 550℃, the reaction temperature is too low, making it difficult for carbon-containing organic matter to carbonize and form a carbon coating layer. The resulting positive electrode lithium supplement will be non-conductive, increasing polarization in lithium-ion batteries and affecting battery capacity and fast-charging performance. If the calcination temperature is above 700℃, the reaction temperature is too high, and the prepared positive electrode lithium supplement will decompose at high temperatures. Controlling the calcination temperature between 550℃ and 700℃ yields a positive electrode lithium supplement with uniform fluorine-doped carbon coating.

[0091] In some implementations, the heat preservation time is 3-8 hours.

[0092] In some implementations, the heat preservation time can be 3h, 4h, 5h, 6h, 7h, 8h, or any value between two of these.

[0093] If the holding time after calcination is less than 3 hours, the decomposition of carbon-containing organic matter will be incomplete, resulting in insufficient carbonization. This leads to poor conductivity of the carbon coating layer in the resulting positive electrode lithium supplement, increasing polarization in lithium-ion batteries and ultimately affecting battery capacity. Conversely, if the holding time after calcination exceeds 8 hours, it will increase the cost of the positive electrode lithium supplement preparation process. Controlling the holding time after calcination between 3 and 8 hours balances the lithium-ion battery capacity and the cost of the positive electrode lithium supplement preparation process.

[0094] In some embodiments, the sum of the mass of the coating material and the fluorine source accounts for 8%-15% of the total mass of the lithium-rich metal oxide, the coating material, and the fluorine source; the mass of the fluorine source accounts for 10%-35% of the sum of the mass of the coating material and the fluorine source.

[0095] In some embodiments, the sum of the mass of the coating material and the fluorine source can be 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15% of the total mass of the lithium-rich metal oxide, the coating material, and the fluorine source, or any value between the two.

[0096] If the sum of the mass of the coating material and the fluorine source accounts for more than 15% of the total mass of the lithium-rich metal oxide, the coating material, and the fluorine source, the prepared positive electrode lithium replenishment agent will have too much coating material and fluorine doping, and too little lithium-rich metal oxide content in the core. This will affect the amount of lithium replenishment generated by the prepared positive electrode lithium replenishment agent in the lithium-ion battery, and thus affect the cycle life of the lithium-ion battery.

[0097] If the sum of the mass of the coating material and the fluorine source accounts for less than 8% of the total mass of the lithium-rich metal oxide, coating material, and fluorine source, the coating layer in the prepared positive electrode lithium supplement is incomplete, and the effect on reducing the water absorption performance and improving the air stability of the positive electrode lithium supplement is not obvious.

[0098] In some embodiments, the mass of the fluorine source as a percentage of the sum of the mass of the coating material and the fluorine source can be 10%, 15%, 20%, 25%, 30%, 35%, or any value between the two.

[0099] If the mass of the fluorine source accounts for less than 10% of the sum of the mass of the coating material and the fluorine source, the fluorine content in the prepared positive electrode lithium supplement coating layer is too low, and its effect on reducing the water absorption of the positive electrode lithium supplement is not obvious.

[0100] If the mass of the fluorine source accounts for more than 35% of the sum of the mass of the coating material and the fluorine source, the fluorine content in the prepared positive electrode lithium replenishment coating layer will be too high, the conductivity of the positive electrode lithium replenishment will decrease, and its use in lithium-ion batteries will cause capacity decay.

[0101] Figure 1 and Figure 2The images show SEM and TEM images of the positive electrode lithium replenishment agent prepared in this application. The images show that at least a portion of the surface of the prepared positive electrode lithium replenishment agent is coated with a coating layer. Figure 3 This is also a TEM image of the positive electrode lithium replenisher prepared in this application. The elemental distribution of the prepared positive electrode lithium replenisher can be seen from the image, indicating that the coating layer of the prepared positive electrode lithium replenisher is a carbon coating layer.

[0102] In some embodiments, the positive electrode sheet can be prepared by dispersing the positive electrode active material, conductive agent, binder, lithium supplementer 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 after drying, cold pressing and other processes, forming a positive electrode active material layer; and then using spraying, secondary coating or other methods to composite the lithium supplementer with the positive electrode active material layer on the surface of the positive electrode active material layer.

[0103] Negative electrode sheet

[0104] The negative electrode includes a negative current collector and a negative electrode film layer optionally disposed on at least one surface of the negative current collector. The negative electrode film layer includes a negative electrode active material.

[0105] 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.

[0106] 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.).

[0107] In some embodiments, the negative electrode film layer comprises a negative electrode active material. In some embodiments, the negative electrode active material includes, but is not limited to, one or more of conventional natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may include one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy materials. The tin-based material may include one or more of elemental tin, tin oxide, and tin alloy materials.

[0108] In some embodiments, the negative electrode film layer may optionally include a negative electrode conductive agent. This application does not impose any particular limitation on the type of negative electrode conductive agent. As an example, the negative electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0109] In some embodiments, the negative electrode film layer may optionally include a negative electrode binder. This application does not impose any particular limitation on the type of negative electrode binder. As an example, the negative electrode binder may include one or more of the following: styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0110] In some embodiments, the negative electrode film may optionally include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0111] The negative electrode film layer is typically formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is typically formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0112] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of this application further includes a conductive undercoat layer (e.g., composed of a conductive agent and an adhesive) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector; in some embodiments, the negative electrode sheet of this application further includes a protective layer covering the surface of the negative electrode film layer.

[0113] Separating membrane

[0114] This application does not impose any particular restrictions on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0115] In some embodiments, the material of the separator may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0116] electrolytes

[0117] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0118] The type of electrolyte salt is not specifically limited and can be selected according to actual needs. As an example, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0119] The type of solvent is not specifically limited and can be selected according to actual needs. In some embodiments, as an example, the solvent may include one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl ester carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0120] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain performance characteristics of the secondary battery, such as additives that improve the overcharge performance of the secondary battery, additives that improve the high-temperature performance of the secondary battery, and additives that improve the low-temperature power performance of the secondary battery.

[0121] This application does not impose any particular restrictions on the type of secondary battery. For example, the secondary battery can be a lithium-ion battery, a sodium-ion battery, a lithium-sulfur battery, etc.

[0122] 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. Figure 4 This is an example of a square-structured secondary battery 5.

[0123] In some embodiments, such as Figure 5As shown, 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 is used to cover 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 in 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 adjusted according to requirements.

[0124] The method for preparing the secondary battery described in this application is well known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form a secondary battery. As an example, the positive electrode, separator, and negative electrode can be formed into an electrode assembly through a winding or stacking process. The electrode assembly is then placed in an outer packaging, dried, and injected with an electrolyte. After vacuum sealing, settling, formation, and shaping, a secondary battery is obtained.

[0125] In some embodiments of this application, the secondary battery according to this application can be assembled into a battery module. The number of secondary batteries contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0126] Figure 6 This is a schematic diagram of battery module 4 as an example. Figure 6 As shown, 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.

[0127] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0128] 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 adjusted according to the application and capacity of the battery pack.

[0129] Figure 7 and Figure 8 This is a schematic diagram of battery pack 1 as an example. Figure 7 and Figure 8 As shown, 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. The upper body 2 covers the lower body 3, forming a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0130] A second aspect of this application provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack described 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 be, but is not limited to, mobile devices (e.g., mobile phones, tablets, 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.

[0131] The electrical device can be equipped with a secondary battery, battery module, or battery pack according to its usage requirements.

[0132] Figure 9 This is a schematic diagram of an example electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0133] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use rechargeable batteries as their power source.

[0134] Example

[0135] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0136] (1) Preparation of positive electrode lithium supplement

[0137] Example 1

[0138] 90g of lithium-rich metal oxide Li5FeO4 was used as the core, 7.5g of glucose as the coating material, and 2.5g of PVDF as the fluorine source. After mixing, the mixture was ball-milled at high energy for 12 hours to obtain the precursor material. The precursor was then placed in a tube furnace, and the temperature was raised to 600℃ at a rate of 10℃ / min in an argon atmosphere. The temperature was held for four hours, and after natural cooling, the particles were collected to obtain the F-Li5FeO4@C cathode lithium supplement.

[0139] Example 2

[0140] The preparation method of Example 2 is basically the same as that of Example 1, except that the type of coating layer used is changed, as shown in Table 1.

[0141] Example 3

[0142] The preparation method of Example 3 is basically the same as that of Example 1, except that the type of kernel is changed, as shown in Table 1.

[0143] Examples 4-6

[0144] The preparation methods of Examples 4-6 are basically the same as those of Example 1, except that the calcination temperature is changed, as shown in Table 1.

[0145] Examples 7-8

[0146] The preparation methods of Examples 7-8 are basically the same as those of Example 1, except that the heat preservation time is changed, as shown in Table 1.

[0147] Examples 9-12

[0148] The preparation methods of Examples 9-12 are basically the same as those of Example 1, except that the percentage of the mass of the fluorine source to the sum of the mass of the coating material and the fluorine source is changed, as shown in Table 1.

[0149] Example 13

[0150] The preparation method of Example 13 is basically the same as that of Example 1, except that the coating material is changed, as shown in Table 1.

[0151] Example 14

[0152] The preparation method of Example 14 is basically the same as that of Example 1, except that the fluorine source is changed, as shown in Table 1.

[0153] Comparative Example 1

[0154] In Comparative Example 1, the positive electrode lithium replenishing agent had no coating layer and no fluorine doping.

[0155] Comparative Example 2

[0156] The preparation method of Comparative Example 2 is basically the same as that of Example 1, except that no fluorine source is added in the preparation process of the positive electrode lithium replenishment agent.

[0157] Comparative Example 3

[0158] The preparation method of Comparative Example 3 is basically the same as that of Example 1, except that the calcination temperature is changed, as shown in Table 1.

[0159] (2) Preparation of positive electrode lithium supplement electrode

[0160] The prepared positive electrode lithium supplement, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) were mixed evenly in a weight ratio of 80:10:10. Then, a certain amount of N-methylpyrrolidone solvent was added, and a positive electrode slurry was obtained under the action of a vacuum stirrer. The positive electrode slurry was uniformly coated on aluminum foil. After the aluminum foil was dried at room temperature, it was transferred to a 120℃ oven to dry for 4 hours. Then, it was cold-pressed and slit to obtain the positive electrode sheet.

[0161] (3) Preparation of lithium-ion batteries

[0162] (a) Positive electrode plate

[0163] The positive electrode active material lithium iron phosphate (LFP), positive electrode lithium supplementer, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) are mixed evenly in a weight ratio of 90:5:2.5:2.5. The above slurry is then mixed evenly and coated evenly on aluminum foil. After the aluminum foil is dried at room temperature, it is transferred to a 120°C oven to dry for 4 hours. Then, it is cold-pressed and slit to obtain the positive electrode sheet.

[0164] (b) Negative electrode plate

[0165] The negative electrode active material graphite, conductive agent carbon black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) were dissolved in deionized water at a weight ratio of 96.2:0.8:0.8:1.2 and a negative electrode slurry was obtained under vacuum stirring. The negative electrode slurry was uniformly coated onto copper foil. After the copper foil was dried at room temperature, it was transferred to a 120°C oven to dry for 4 hours. Then, it was cold-pressed and slit to obtain the negative electrode sheet.

[0166] (c) Separating membrane

[0167] Polypropylene film is used as the base film.

[0168] (d) Electrolyte

[0169] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed evenly at a volume ratio of 3:7. Then, 12.5% ​​(w / w) of lithium LiPF6 is added and dissolved in the organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC). The mixture is stirred evenly to obtain the electrolyte.

[0170] (e) Assembling the battery

[0171] The positive electrode, separator, and negative electrode obtained in the above steps are stacked in sequence, so that the separator is between the positive electrode and the negative electrode and can isolate the positive electrode from the copper foil. Then, the stacked components are stacked to obtain an electrode assembly. The electrode assembly is placed in the housing, dried, and then injected with electrolyte. After formation, settling, and other processes, a lithium-ion battery is obtained.

[0172] (4) Preparation of lithium-ion batteries with no active material in the positive electrode

[0173] (a) Positive electrode plate

[0174] The positive electrode lithium supplement, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) are mixed evenly in a weight ratio of 80:10:10. The above slurry is then mixed evenly and coated evenly on aluminum foil. After the aluminum foil is dried at room temperature, it is transferred to an oven at 120°C and dried for 4 hours. Then, it is cold-pressed and slit to obtain the positive electrode sheet.

[0175] (b) Negative electrode plate

[0176] The negative electrode active material graphite, conductive agent carbon black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) were dissolved in deionized water at a weight ratio of 96.2:0.8:0.8:1.2 and a negative electrode slurry was obtained under vacuum stirring. The negative electrode slurry was uniformly coated onto copper foil. After the copper foil was dried at room temperature, it was transferred to a 120°C oven to dry for 4 hours. Then, it was cold-pressed and slit to obtain the negative electrode sheet.

[0177] (c) Separating membrane

[0178] Polypropylene film is used as the base film.

[0179] (d) Electrolyte

[0180] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed evenly at a volume ratio of 3:7. Then, 12.5% ​​(w / w) of lithium LiPF6 is added and dissolved in the organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC). The mixture is stirred evenly to obtain the electrolyte.

[0181] (e) Assembling the battery

[0182] The positive electrode, separator, and negative electrode obtained in the above steps are stacked in sequence, so that the separator is between the positive electrode and the negative electrode and can isolate the positive electrode from the copper foil. Then, the stacked components are stacked to obtain an electrode assembly. The electrode assembly is placed in the housing, dried, and then injected with electrolyte. After formation, settling, and other processes, a lithium-ion battery is obtained.

[0183] Performance testing

[0184] (1) Test of fluorine content in the prepared positive electrode lithium replenishment coating layer

[0185] The fluorine content in the prepared cathode lithium supplement coating was determined using X-ray electron spectroscopy (XPS). The specific steps are as follows: ① Prepare a clean In film (>1cm×1cm); ② Spread the sample on the In film and use a clean stainless steel sampling spoon to evenly spread the powder across the entire tape, making it as thin as possible; ③ Take another piece of In film wiped clean with acetone or clean weighing paper and cover the sample; ④ Place the In film or clean weighing paper + sample between two flat stainless steel modules, ready for tableting; ⑤ Place the stainless steel module or clean weighing paper + sample on the tableting machine platform, and hold the stainless steel block with your left hand to... To prevent movement, unscrew the pressure column clockwise to remove the clamping module (above the press); ⑥ Tighten the drain knob clockwise (front knob of the press), pull the right-side pressure lever to raise the pressure to about 10MPa, and hold for about ten seconds; ⑦ To release the pressure, first loosen the drain knob counterclockwise, then loosen the pressure column counterclockwise, and remove the stainless steel module + sample from the tablet press; ⑧ Remove the In film or clean weighing paper covering the sample, gently tap the In film with the sample attached to remove any residual powder from the surface; ⑨ Cut off the In film around the pressed sample to make a tablet sample of ~1cm×1cm, then attach it to the XPS sample stage with double-sided tape for XPS testing.

[0186] (2) Test of the thickness of the prepared positive electrode lithium replenishment coating layer

[0187] The thickness of the prepared positive electrode lithium replenishment coating was tested using transmission electron microscopy. The specific steps are as follows: First, the powder was dispersed in a dispersant (anhydrous ethanol) using ultrasound or stirring to form a suspension. Then, a copper mesh covered with a support film was held with tweezers, and a few drops of the suspension were dropped onto the support film with a dropper, keeping it in a clamped state until it was dry. After the droplets on the support film were fully dried, the sample preparation was completed, and then electron microscopy observation could be performed.

[0188] (3) Water content test in the prepared positive electrode lithium replenishment agent

[0189] The water content of the prepared cathode lithium supplement is determined by Karl Fischer coulometric solid moisture analysis, which includes the following steps: ① Confirm the weight of the test sample, usually 3-5g is recommended; ② Place the sample in the Karl Fischer moisture analyzer and ensure it is sealed tightly; ③ Turn on the Karl Fischer moisture analyzer and set the temperature (170℃); ④ After the test begins, the Karl Fischer moisture analyzer will automatically heat the sample; ⑤ After a period of heating, the water in the sample begins to evaporate; ⑥ After the heating time ends, the Karl Fischer moisture analyzer will automatically stop heating and then begin calculating the water loss; ⑦ The calculation results will be displayed on the Karl Fischer moisture analyzer's screen, including information such as the sample weight change and moisture content.

[0190] (4) Decomposition capacity of the prepared positive electrode lithium replenishment agent

[0191] The capacity of the prepared positive electrode lithium-ion battery without active material is determined by charging it at 25°C with a current density of 0.1C to 4.15V.

[0192] (5) First-cycle discharge capacity of the prepared lithium-ion battery

[0193] At a temperature of 45℃, the capacitor is charged to 4.3V with a constant current of 0.1C, and then charged to 0.02C with a constant voltage (4.3V). After resting for 5 minutes, it is discharged to 2.0V with 0.1C. The discharge capacity D0 of the first cycle is recorded.

[0194] (6) Lithium-ion battery cycle capacity retention test

[0195] At 25°C, the battery is charged at a constant current of 1C to 4.3V, then charged at a constant voltage of 4.3V to a current of 0.05C. The lithium-ion battery is then left to rest for 5 minutes, followed by discharge at 0.1C to 2.0V, and then left to rest for another 5 minutes. This process is repeated for the same battery, and the discharge capacity Dn of the battery after the nth cycle is recorded. The battery cycle capacity retention rate after each cycle is Pn = Dn / D0 * 100%. The battery cycle capacity retention rate after the 1000th cycle is recorded.

[0196] Table 1

[0197]

[0198]

[0199] Table 2

[0200]

[0201]

[0202]

[0203] As can be seen from Example 1 and Comparative Example 1, modifying at least a portion of the core surface with a fluorine-doped coating layer can reduce the water absorption of the prepared positive electrode lithium replenishing agent, and the prepared positive electrode lithium replenishing agent can improve the cycle life of lithium-ion batteries.

[0204] As can be seen from Example 1 and Comparative Example 2, by modifying at least a portion of the core surface with a coating layer and then doping the coating layer with fluorine, the water absorption of the prepared positive electrode lithium replenishing agent can be further reduced, and the prepared positive electrode lithium replenishing agent can further improve the cycle life of lithium-ion batteries.

[0205] As can be seen from Example 1 and Comparative Example 3, when the calcination temperature is less than 600°C, the prepared positive electrode lithium replenishing agent has a higher water absorption capacity, resulting in a lower cycle life when used in lithium-ion batteries.

[0206] As can be seen from Examples 1 and 4-6, the higher the calcination temperature, the lower the water absorption of the prepared positive electrode lithium replenishing agent. However, when the calcination temperature is greater than 700°C, the decomposition capacity and first-cycle discharge capacity of the prepared positive electrode lithium replenishing agent decrease.

[0207] As can be seen from Examples 1 and 9-12, as the percentage of the mass of the fluorine source in the sum of the mass of the coating material and the fluorine source increases, the water absorption of the prepared positive electrode lithium replenishing agent decreases. However, when the percentage of the mass of the fluorine source in the sum of the mass of the coating material and the fluorine source exceeds 35%, the decomposition capacity and first-cycle discharge capacity of the prepared positive electrode lithium replenishing agent decrease significantly.

[0208] 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 lithium-ion battery, characterized in that, Comprising a positive electrode plate, wherein the positive electrode plate comprises a positive electrode lithium compensating agent, and the positive electrode lithium compensating agent comprises: a core, wherein the core comprises a lithium-rich metal oxide; and a coating layer, wherein the coating layer is arranged on at least a part of a surface of the core, the coating layer contains fluorine element.

2. The lithium-ion battery according to claim 1, characterized in that, the content of fluorine element in the coating layer accounts for 0.03%-0.45% of the positive electrode lithium compensating agent.

3. The lithium-ion battery according to any one of claims 1-2, characterized in that, the water absorption of the positive electrode lithium compensating agent is 3000ppm-4000ppm.

4. The lithium-ion battery according to any one of claims 1-3, characterized in that, the coating layer comprises at least one of a carbon coating layer, a metal oxide coating layer, a metal phosphide coating layer, a metal sulfide coating layer and a non-metal oxide coating layer, and optionally comprises a carbon coating layer.

5. The lithium-ion battery according to claims 1-4, characterized in that, the thickness of the carbon coating layer is 1nm-10nm.

6. The lithium-ion battery according to any one of claims 1-5, characterized in that, the lithium-rich metal oxide comprises 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 respective highest oxidation valence states.

7. The lithium-ion battery according to any one of claims 1-6, characterized in that, the lithium-rich metal oxide comprises at least one of Li2MnO2, Li5FeO4, Li6CoO4, Li2NiO2, Li2Cux1Ni1-x1-y1My1O2, Li3VO4 and Li3NbO4; wherein, 0<x1≤1, 0≤y1<0.1, 0<x1+y1≤1, 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.

8. A positive electrode lithium replenishing agent, characterized in that, comprising a core, wherein the core comprises a lithium-rich metal oxide; and a coating layer, wherein the coating layer is arranged on at least a part of a surface of the core, the coating layer contains fluorine element.

9. The positive electrode lithium replenishing agent according to claim 8, characterized in that, the content of fluorine element in the coating layer accounts for 0.03%-0.45% of the positive electrode lithium compensating agent.

10. A method for preparing a positive electrode lithium replenishing agent, characterized in that, comprising the following steps: mixing a lithium-rich metal oxide, a coating layer material and a fluorine source, and performing ball milling to obtain a precursor material; calcining the obtained precursor material in an inert atmosphere, keeping the temperature, and naturally cooling to obtain the positive electrode lithium compensating agent, wherein the calcining temperature is greater than 550°C.

11. The method for preparing the positive electrode lithium replenishing agent according to claim 10, characterized in that, the lithium-rich metal oxide comprises 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 respective highest oxidation valence states.

12. The method for preparing the positive electrode lithium replenishing agent according to claims 10-11, characterized in that, the coating layer material comprises at least one of carbon-containing organic matter, metal oxide, metal phosphide, metal sulfide and non-metal oxide, and optionally comprises carbon-containing organic matter.

13. The method for preparing the positive electrode lithium replenishing agent according to claims 10-12, characterized in that, the carbon-containing organic matter comprises at least one of glucose, sucrose, citric acid, ethylene glycol, polyvinyl alcohol and phenolic resin.

14. The method for preparing the positive electrode lithium replenishing agent according to claims 10-13, characterized in that, the fluorine source comprises fluoroolefin.

15. The method for preparing the positive electrode lithium replenishing agent according to claims 10-14, characterized in that, the fluoroolefin comprises at least one of polyvinylidene fluoride and polytetrafluoroethylene.

16. The method for preparing the positive electrode lithium replenishing agent according to any one of claims 10-15, characterized in that, the calcining temperature is 550°C-700°C.

17. The method for preparing the positive electrode lithium replenishing agent according to any one of claims 10-16, characterized in that, The heat preservation time is 3-8 hours.

18. The method for preparing the positive electrode lithium replenishing agent according to any one of claims 10-17, characterized in that, The combined mass of the coating material and the fluorine source accounts for 8%-15% of the total mass of the lithium-rich metal oxide, the coating material, and the fluorine source. The mass of the fluorine source accounts for 10%-35% of the sum of the mass of the coating material and the fluorine source.

19. An electrical appliance, characterized in that, The lithium-ion battery includes any one of claims 1-7.

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