Carbon-coated phosphate material, preparation method therefor, positive electrode sheet, battery cell and electrical apparatus

Abstract

Disclosed in the present application are a carbon-coated phosphate material, a preparation method therefor, a positive electrode sheet, a battery cell, and an electrical apparatus. The battery cell comprises a positive electrode sheet, a negative electrode sheet, and an electrolyte. The positive electrode sheet comprises a positive electrode current collector, and a positive electrode film layer arranged on at least one surface of the positive electrode current collector and comprising a positive electrode active material. The positive electrode active material comprises a carbon-coated phosphate material, the specific surface area of the carbon-coated phosphate material being less than or equal to 8 m2 / g. The embodiments of the present application can improve the cycle performance of battery cells.

Description

Carbon-coated phosphate materials and their preparation methods, positive electrode sheets, battery cells and electrical devices

[0001] Cross-reference of related applications

[0002] This application claims priority to Chinese Patent Application No. 202411535962.7, filed on October 30, 2024, entitled “Carbon-coated phosphate material and preparation method thereof, positive electrode, battery cell and power device”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of battery technology, and in particular to a carbon-coated phosphate material and its preparation method, a positive electrode sheet, a battery cell, and an electrical device. Background Technology

[0004] Because batteries can convert chemical energy into electrical energy, they have become one of the important energy sources for human production and life, and are therefore widely used in many fields such as power tools, electric vehicles, and electronic devices to provide them with power.

[0005] With the widespread application of batteries in various fields, the requirements for their performance are becoming increasingly stringent, among which battery cycle performance has become a key focus. Therefore, how to improve battery cycle performance is one of the most pressing technical problems that needs to be solved in the battery industry. Summary of the Invention

[0006] This application provides a carbon-coated phosphate material and its preparation method, a positive electrode sheet, a battery cell, and an electrical device, which can improve the cycle performance of the battery cell.

[0007] In one aspect, embodiments of this application provide a battery cell, including a positive electrode, a negative electrode, and an electrolyte. 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 and including a positive electrode active material. The positive electrode active material includes a carbon-coated phosphate material, wherein the specific surface area of ​​the carbon-coated phosphate material is less than or equal to 8 m². 2 / g.

[0008] The embodiments of this application have a specific surface area less than or equal to 8m². 2 Using carbon-coated phosphate material with a concentration of / g as a positive electrode active material can reduce the water absorption rate of the carbon-coated phosphate material, thereby reducing the difficulty and cost of water removal from the material in industrial production and reducing the risk of adsorbed water deteriorating the cycle performance of the battery cell, thus improving the cycle performance of the battery cell.

[0009] In any embodiment of this application, the specific surface area of ​​the carbon-coated phosphate material is 5–8 m². 2 / g.

[0010] In any embodiment of this application, the surface of the carbon-coated phosphate material includes one or more of the following groups: hydroxyl, carboxyl, carbonyl, and lactone groups.

[0011] In any embodiment of this application, the phosphate material includes materials having the general formula Li a Fe (1-x) Mn x M y PO4 is one or more of the following materials; wherein x and y are natural numbers, with x ranging from 0 to 1 and y ranging from 0 to 0.1; a is 0 to 1.1; M includes one or more metallic elements from Groups IVB, VB, VIII, IIA, IIIA, IVA and VA.

[0012] In any embodiment of this application, the tap density of the carbon-coated phosphate material is 2.0–2.7 g / cm³. 3 .

[0013] In any embodiment of this application, the average thickness of the carbon coating layer of the carbon-coated phosphate material is 1–5 nm.

[0014] In any embodiment of this application, the mass content of the carbon coating layer is 0.1 wt% to 3.0 wt% based on the mass of the carbon-coated phosphate material.

[0015] Secondly, embodiments of this application provide a carbon-coated phosphate material, wherein the specific surface area of ​​the carbon-coated phosphate material is less than or equal to 8 m². 2 / g.

[0016] In any embodiment of this application, the water absorption rate is 1000-2800 ppm.

[0017] In any embodiment of this application, the water content of the carbon-coated phosphate material is 90 to 500 ppm.

[0018] Thirdly, embodiments of this application provide a method for preparing a carbon-coated phosphate material, comprising: injecting a carbon source and a carrier gas into a phosphate material at a preset flow rate; and depositing the carbon source on the surface or within the pores of the phosphate material at a preset temperature to obtain a carbon-coated phosphate cathode material; wherein the specific surface area of ​​the carbon-coated phosphate cathode material is less than or equal to 8 m². 2 / g.

[0019] In any embodiment of this application, the deposition of carbon source on the surface or pores of phosphate material includes: the carbon source is vaporized at a preset temperature into a raw material gas containing carbon free radicals, and the carbon free radicals are deposited on the surface and pores of the phosphate material.

[0020] In any embodiment of this application, the step of injecting the carbon source and carrier gas into the phosphate material at a preset flow rate includes: mixing the carbon source with an organic solvent to obtain a carbon source solution.

[0021] In any embodiment of this application, the gasification temperature of the carbon source is less than or equal to the preset temperature.

[0022] In any embodiment of this application, the carbon free radicals formed after the carbon source is vaporized include one or more of methyl, phenyl, tolyl, and hexadienyl.

[0023] In any embodiment of this application, the carbon source includes one or more of aromatic compounds containing benzene rings, alkanes without benzene rings, and long-chain polymers.

[0024] In any embodiment of this application, the aromatic compound containing a benzene ring includes one or more of benzene, toluene, and naphthalene.

[0025] In any embodiment of this application, the alkane that does not contain a benzene ring includes one or more of propylene and propane.

[0026] In any embodiment of this application, the long-chain polymer includes one or more of polyethylene and polyethylene glycol.

[0027] In any embodiment of this application, the carbon source includes an aromatic compound containing a benzene ring, which includes one or more of benzene, toluene, and naphthalene.

[0028] In any embodiment of this application, in the step of injecting a carbon source and a carrier gas into a phosphate material at a preset flow rate, the phosphate material comprises materials having the general formula C n / Li a Fe (1-x) Mn x M y One or more of the materials containing PO4; wherein n is 0 or 1, x and y are natural numbers, x ranges from 0 to 1, y ranges from 0 to 0.1; a is 0 to 1.1; M includes one or more metallic elements from Groups IVB, VB, VIII, IIA, IIIA, IVA and VA.

[0029] In any embodiment of this application, the step of injecting a carbon source and a carrier gas into the phosphate material at a preset flow rate includes: dispersing the phosphate material to obtain dispersed phosphate material particles; and injecting the carbon source and a carrier gas into the dispersed phosphate material particles at a preset flow rate.

[0030] In any embodiment of this application, the carrier gas includes an inactive gas, which includes one or more of nitrogen, neon, or argon.

[0031] In any embodiment of this application, the injection flow rate of the carbon source is 0.1 to 10 mL / h, the injection time is 10 min to 10 h, and the injection flow rate of the carrier gas is 50 to 1000 mL / min.

[0032] In any embodiment of this application, the preset temperature is 600–900°C.

[0033] In any embodiment of this application, the carbon source and the organic solvent are mixed to obtain a carbon source solution in which the mass ratio of carbon source to organic solvent is 0.25% to 10%.

[0034] In any embodiment of this application, the carbon source and the organic solvent are mixed to obtain a carbon source solution in which the mass ratio of carbon source to organic solvent is 1% to 5%.

[0035] Fourthly, embodiments of this application provide a positive electrode sheet, which includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector and including a positive electrode active material; the positive electrode active material includes a carbon-coated phosphate material as described in the second aspect.

[0036] Fifthly, an embodiment of this application provides an electrical device comprising a battery cell as described in the first aspect. Attached Figure Description

[0037] 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 introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 shows a schematic diagram of a battery cell provided in some embodiments of this application.

[0039] Figure 2 shows an exploded view of a battery cell provided in some embodiments of this application.

[0040] Figure 3 shows a schematic diagram of a battery module provided in some embodiments of this application.

[0041] Figure 4 shows a schematic diagram of a battery pack provided in some embodiments of this application.

[0042] Figure 5 is an exploded view of the battery pack shown in Figure 4.

[0043] Figure 6 shows a schematic diagram of an electrical device provided in some embodiments of this application.

[0044] Figure 7 shows the carbon-coated LiFeO without a carbon source obtained by chemical vapor deposition in this application. 0.4 Mn 0.6 TEM image of PO.

[0045] Figures 8 and 9 show the carbon-coated LiFe after chemical vapor deposition of toluene in Example 1. 0.4 Mn 0.6 TEM image of PO4.

[0046] The accompanying drawings are not necessarily drawn to scale.

[0047] The reference numerals in the attached diagram are explained as follows: 1. Battery pack; 2. Upper casing; 3. Lower casing; 4. Battery module; 5. Battery cell; 51. Housing; 52. Electrode assembly; 53. Cover plate. Detailed Implementation

[0048] To better understand the above-mentioned objectives, features, and advantages of this application, the solution of this application will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0049] Many specific details are set forth in the following description in order to provide a full understanding of this application, but this application may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of this application, and not all embodiments.

[0050] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the carbon-coated phosphate material, its preparation method, positive electrode sheet, battery cell, and electrical device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for a full understanding of this application by those skilled in the art and are not intended to limit the subject matter of the claims.

[0051] 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 understood that ranges of 60–110 and 80–120 are also expected. 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 "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] Phosphate materials and their carbon-coated materials in related technologies both have high specific surface areas, generally ranging from 12 to 20 m². 2 The low concentration of water per gram (g) results in these materials having strong water absorption, and the presence of water reduces the reliability of individual battery cells.

[0056] Therefore, embodiments of this application provide a carbon-coated phosphate material and its preparation method, a positive electrode sheet, a battery cell, and an electrical device, which can improve the cycle performance of the battery cell.

[0057] battery cell

[0058] This application provides a battery cell including a positive electrode, a negative electrode, and an electrolyte. 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 and including a positive electrode active material. The positive electrode active material includes a carbon-coated phosphate material, and the specific surface area of ​​the carbon-coated phosphate material is less than or equal to 8 m². 2 / g.

[0059] The embodiments of this application have a specific surface area less than or equal to 8m². 2 Carbon-coated phosphate materials with a surface energy of / g can be used as positive electrode active materials to reduce the surface energy of the material, thereby reducing the interaction force between the surface molecules and water molecules. This reduces the material's water absorption rate and simplifies the dehydration process in industrial production, lowering the difficulty and cost of water removal. When used in secondary batteries, it can reduce the risk of adsorbed water degrading the cycle performance of individual battery cells.

[0060] The specific surface area of ​​the carbon-coated phosphate material in this application embodiment has a meaning known in the art and can be measured using instruments and methods known in the art. For example, it can be tested using the nitrogen adsorption specific surface area analysis method and calculated using the BET (Brunauer Emmett Teller) method. The nitrogen adsorption specific surface area analysis can be performed using a NOVA 2000e specific surface area and pore size analyzer from Quanta Computer Corporation, USA. As a specific example, the test method is as follows: Take 8.000g to 15.000g of carbon-coated phosphate material in a weighed empty sample tube, stir the carbon-coated phosphate material evenly and weigh it, put the sample tube into the NOVA 2000e degassing station for degassing, weigh the total mass of the degassed carbon-coated phosphate material and the sample tube, and calculate the mass G of the degassed carbon-coated phosphate material after degassing by subtracting the mass of the empty sample tube from the total mass. The sample tube was placed in a NOVA 2000e to measure the amount of nitrogen adsorbed on the surface of carbon-coated phosphate material under different relative pressures. The amount of monolayer adsorption was obtained based on the Brownnor-Etter-Taylor multilayer adsorption theory and its formula, and then the total surface area A of the carbon-coated phosphate material was calculated. The specific surface area of ​​the carbon-coated phosphate material was obtained by calculating A / G.

[0061] In some embodiments, the specific surface area of ​​the carbon-coated phosphate material is 5–8 m². 2 / g.

[0062] The carbon-coated phosphate material in this application embodiment can reduce the material's water absorption rate, thereby reducing the difficulty and cost of dehydration in industrial production and mitigating the risk of adsorbed water degrading the cycle performance of battery cells. Simultaneously, it can reduce the likelihood of longer electron and ion conduction paths within the material due to reduced contact area between the electrode and electrolyte, thus lowering the risk of increased internal resistance and ultimately improving the cycle performance of battery cells.

[0063] Optionally, the specific surface area of ​​the carbon-coated phosphate material is independently selected from 5.0 m². 2 / g, 5.5m 2 / g, 6.0m 2 / g, 6.5m 2 / g, 7.0m 2 / g, 7.5m 2 / g、8m 2 Any value in / g or any range between the two.

[0064] In some embodiments, phosphate materials include those having the general formula Li a Fe (1-x) Mn x M y PO4 is one or more of the following materials; wherein x and y are natural numbers, with x ranging from 0 to 1 and y ranging from 0 to 0.1; a is 0 to 1.1; M includes one or more metallic elements from Groups IVB, VB, VIII, IIA, IIIA, IVA and VA.

[0065] The carbon-coated phosphate material in this application contains one or more metal elements from Groups IVB, VB, VIII, IIA, IIIA, IVA, and VA, such as Fe and Mn. These elements can reduce the activation energy of carbon coating layer formation during the carbon coating process, promote the formation of the carbon coating layer, and help form a uniform and dense carbon coating layer on the surface of the phosphate material. This can reduce the specific surface area of ​​the carbon-coated phosphate material while forming metal-carbon bonds or metal carbides to improve the conductivity of the carbon coating layer.

[0066] In some embodiments, the tap density of the carbon-coated phosphate material is 2.0–2.7 g / cm³. 3 .

[0067] The tap density of the carbon-coated phosphate material in this embodiment indicates smaller gaps between material particles and a more compact particle arrangement. This compact particle arrangement provides a better adhesion surface for the carbon coating. This helps form a denser, more uniform carbon coating layer, thereby reducing the water absorption rate of the carbon-coated phosphate material. Simultaneously, a tap density within this range means that more phosphate material is tightly coated together, which can improve the volumetric capacity and energy density of the phosphate material.

[0068] Optionally, the tap density of the carbon-coated phosphate material is independently selected from 2.0 g / cm³. 3 2.1g / cm 3 2.2g / cm 3 2.3g / cm 3 2.4g / cm 3 2.5g / cm 3 2.6g / cm 3 2.7g / cm 3 Any value in the range or any value between the two.

[0069] The tap density of carbon-coated phosphate materials can be determined using instruments and methods known in the art. For example, it can be determined by referring to GB / T 5162-2006 Method for Determination of Tap Density of Metal Powders, using a tap density meter, such as the FZS4-4B type tap density meter.

[0070] In some embodiments, the surface of the carbon-coated phosphate material includes one or more groups selected from hydroxyl, carboxyl, carbonyl, and lactone groups.

[0071] Compared to carbon-coated phosphate materials in related technologies, the carbon-coated phosphate material in this application has special groups introduced on its surface. On one hand, these special groups exhibit strong hydrophobicity, reducing the adsorption rate of water molecules. On the other hand, the binding force between these special groups and the small amount of adsorbed water molecules is weak, making it easier to remove the bound water molecules and thus increasing the water content after dehydration. Therefore, within this range, both the water absorption capacity and the water content after dehydration can be reduced, thus lowering the difficulty and cost of dehydration in industrial production and further improving the cycle performance of battery cells.

[0072] In some embodiments, the average thickness of the carbon coating layer of the carbon-coated phosphate material is 1–5 nm.

[0073] In the carbon-coated phosphate materials of this application embodiment, the carbon coating layer within this range can effectively improve the conductivity of the phosphate material and, when used in battery electrodes, improve its compaction performance. Simultaneously, it can reduce the risk of water absorption and storage in the carbon coating layer due to excessive thickness resulting in large pores, and reduce the impact of an excessively thick carbon coating layer on ion extraction and insertion, thereby increasing the specific capacity of the phosphate material. The standard deviation of the carbon coating layer thickness within this range indicates uniform thickness, resulting in a more uniform pore distribution within the carbon layer, which is beneficial for forming a dense carbon layer structure. This reduces the water absorption of the carbon coating layer while ensuring good conductivity, guaranteeing ion pathways, and thus improving the cycle performance of the battery cell.

[0074] Optionally, the average thickness of the carbon coating layer of the carbon-coated phosphate material is independently selected from any value of 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, or any range between both.

[0075] The thickness of the carbon coating layer can be measured as follows: A thin slice approximately 100 nm thick is cut from the center of a single carbon-coated phosphate particle using FIB (fiber optics). The slice is then subjected to TEM (thermometry) to obtain the original TEM image, which is saved in the original image format (xx.dm3). The original TEM image is opened in Digital Micrograph software. The carbon coating layer is identified using lattice spacing and angle information, and its thickness is measured.

[0076] In some embodiments, the mass content of the carbon coating layer is 0.1 wt% to 3.0 wt%, based on the mass of the carbon-coated phosphate material.

[0077] The carbon-coated phosphate material in this application embodiment has a carbon coating quality within the range that can improve electron transport between carbon-coated phosphate material particles, promote lithium ion migration, thereby improving the conductivity of the material, and reduce the risk of material specific capacity deterioration due to excessive carbon content.

[0078] Optionally, based on the mass of the carbon-coated phosphate material, the mass content of the carbon coating layer is independently selected from any value or a range between 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, 2.0 wt%, 2.1 wt%, 2.2 wt%, 2.3 wt%, 2.4 wt%, 2.5 wt%, 2.6 wt%, 2.7 wt%, 2.8 wt%, 2.9 wt%, and 3.0 wt%.

[0079] Optionally, the mass content of the carbon coating layer is 0.5 wt% to 1.5 wt%, depending on the mass of the carbon-coated phosphate material.

[0080] A battery cell includes an electrode assembly and an electrolyte. The electrode assembly consists of a positive electrode, a negative electrode, and a separator. The battery cell primarily functions by the movement of metal ions between the positive and negative electrodes. The positive electrode includes a positive current collector and a positive active material layer. The positive active material layer is coated on the surface of the positive current collector, and the uncoated positive current collector protrudes beyond the coated positive current collector, serving as the positive electrode tab.

[0081] In addition, the battery cell also includes a housing for housing the electrode assembly and electrolyte, wherein the electrolyte can play a role in transferring electrons between the positive and negative electrode plates.

[0082] [Positive electrode plate]

[0083] In some embodiments, 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 and comprising a positive electrode active material. For example, the positive current collector has two surfaces opposite each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector. The positive electrode active material includes the aforementioned carbon-coated phosphate material and its modified compounds.

[0084] The modified compounds of the above-mentioned positive electrode active material can be obtained by doping and / or surface coating modification of the positive electrode active material.

[0085] In some embodiments, the positive electrode film may optionally include a positive electrode conductive agent. As an example, the positive electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0086] In some embodiments, the positive electrode film layer may optionally include a positive electrode binder. As an example, the positive electrode binder may include, but is not limited to, one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyethylene oxide, fluorinated acrylate resins, 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).

[0087] In some embodiments, the positive current collector may be a metal foil or a composite current collector. An example of a metal foil is aluminum foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. As an example, the metal material may include, but is not limited to, one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymer substrate may include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0088] The positive electrode film is typically formed by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is usually formed by dispersing positive electrode active materials, positive electrode conductive agents, positive electrode binders, and any other components in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP), but is not limited to this.

[0089] [Negative electrode plate]

[0090] The structure and composition of the negative electrode can be adjusted according to the type of battery cell.

[0091] In some embodiments, the negative electrode sheet may include a negative current collector and a metal layer disposed on at least one surface of the negative current collector, wherein the metal material in the metal layer may include, but is not limited to, one or more of elemental lithium, lithium alloy, sodium, and sodium alloy.

[0092] Lithium alloys can be alloys formed from metallic lithium with other metallic or non-metallic elements. For example, other metallic elements in lithium alloys may include one or more of tin, zinc, aluminum, magnesium, silver, gold, gallium, indium, and platinum, while non-metallic elements may include one or more of boron, carbon, and silicon.

[0093] Sodium alloys can be alloys formed from metallic sodium with other metallic or non-metallic elements. For example, other metallic elements in a sodium alloy may include one or more of tin, zinc, aluminum, magnesium, silver, gold, gallium, indium, and platinum, while non-metallic elements may include one or more of boron, carbon, and silicon.

[0094] In some embodiments, the negative electrode may include a negative current collector and does not include a metal layer, to assemble a negative electrode-free metal battery cell.

[0095] In some embodiments, to improve battery performance, the negative electrode side of a metal-free battery cell may also contain conventional materials that can be used as negative electrode active materials, such as carbon materials. Although these materials have a certain capacity, because their content is small and they are not used as the main negative electrode active material in the battery cell, the battery cell constructed in this way can still be regarded as a metal-free battery cell.

[0096] In some embodiments, the negative electrode current collector may include a metal foil, a three-dimensional porous current collector, or a composite current collector. Examples of metal foils include copper foil, copper alloy foil, nickel foil, nickel alloy foil, aluminum foil, and aluminum alloy foil. Examples of three-dimensional porous current collectors include copper mesh, nickel mesh, aluminum mesh, copper foam, nickel foam, and aluminum foam. The composite current collector may include a polymer material substrate and a metal material layer formed on at least one surface of the polymer material substrate. Examples of metal materials include, but are not limited to, one or more of copper, copper alloys, aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Examples of polymer material substrates include, but are not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0097] [Electrolytes]

[0098] This application does not impose specific limitations on the type of electrolyte, which can be selected according to requirements. For example, the electrolyte can be selected from at least one of solid electrolytes and liquid electrolytes (i.e., electrolyte solutions).

[0099] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0100] The type of electrolyte salt is not specifically limited and can be selected according to actual needs. In some embodiments, as an example, the electrolyte salt may include at least one of NaPF6, NaClO4, NaBCl4, NaSO3CF3, Na(CH3)C6H4SO3, LiPF6, LiBF4, LiFSI, LiBOB, and LiTFSI.

[0101] 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 at least one of 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 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).

[0102] 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 battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature power performance.

[0103] [Isolation membrane]

[0104] Battery cells using electrolytes, as well as some battery cells using solid electrolytes, also include a separator. The separator is disposed between the positive and negative electrodes, primarily serving to prevent short circuits between the positive and negative electrodes, while allowing metal ions to pass through. 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.

[0105] In some embodiments, the material of the separator may include at least one selected from 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.

[0106] In some embodiments, the positive electrode, the separator, and the negative electrode can be fabricated into an electrode assembly using a winding process or a stacking process.

[0107] In some embodiments, the battery cell may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0108] In some embodiments, the outer packaging of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell can also be a soft pack, such as a pouch. The material of the soft pack can be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0109] This application does not impose any particular restrictions on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. Figure 1 shows a square battery cell 5 as an example.

[0110] In some embodiments, as shown in FIG2, the outer packaging may include a housing 51 and a cover plate 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 plate 53 is used to cover the opening to close the receiving cavity. A positive electrode sheet, a negative electrode sheet, and a 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 number of electrode assemblies 52 contained in a single battery cell 5 may be one or more, and can be adjusted according to requirements.

[0111] The method for preparing the battery cell of 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 battery cell. As an example, the positive electrode, separator, and negative electrode can be formed into an electrode assembly through a winding process or a stacking process. The electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping processes, a battery cell is obtained.

[0112] In some embodiments, the battery cells according to this application can be assembled into a battery module, and the number of battery cells contained in the battery module can be multiple, the specific number of which can be adjusted according to the application and capacity of the battery module.

[0113] Figure 3 is a schematic diagram of a battery module 4 as an example. As shown in Figure 3, in the battery module 4, multiple battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other way. Furthermore, the multiple battery cells 5 can be fixed in place using fasteners.

[0114] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0115] 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.

[0116] Figures 4 and 5 are schematic diagrams of a battery pack 1 as an example. As shown in Figures 4 and 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 box 2 and a lower box 3. The upper box 2 covers the lower box 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.

[0117] Carbon-coated phosphate materials

[0118] This application provides a carbon-coated phosphate material, wherein the specific surface area of ​​the carbon-coated phosphate material is less than or equal to 8 m². 2 / g.

[0119] The carbon-coated phosphate material of this application, when used in battery cells within this range, can reduce the contact sites where side reactions occur and reduce the risk of adsorbed water deteriorating the cycle performance of the battery cells, thereby improving the cycle performance of the battery cells.

[0120] In some embodiments, the water absorption of the carbon-coated phosphate material is 1000–2900 ppm.

[0121] The water absorption capacity of carbon-coated phosphate materials can be tested using the following method:

[0122] Under air and relative humidity of 60%, the material to be tested was left to stand for 24 hours, and the moisture content of the material was tested at 170°C using a Karl Fischer solid moisture analyzer to obtain the water absorption of the material.

[0123] Optionally, the water absorption of the carbon-coated phosphate material is independently selected from any value or a range between 1000ppm, 1100ppm, 1200ppm, 1300ppm, 1400ppm, 1500ppm, 1600ppm, 1700ppm, 1800ppm, 1900ppm, 2000ppm, 2100ppm, 2200ppm, 2300ppm, 2400ppm, 2500ppm, 2600ppm, 2700ppm, 2800ppm, and 2900ppm.

[0124] In some embodiments, the water content of the carbon-coated phosphate material is 90 to 500 ppm.

[0125] The carbon-coated phosphate material of this application embodiment can reduce the difficulty and cost of dehydration of the material in industrial production and reduce the risk of adsorbed water deteriorating the cycle performance of battery cells.

[0126] The water content of carbon-coated phosphate materials refers to the water content of the material after dehydration treatment, which can be obtained by testing using the following methods:

[0127] Under air and relative humidity of 60%, the test material was left to stand for 24 hours, and then transferred to a 110℃ oven for vacuum drying for 5 hours. The moisture content of the test material was then measured at 170℃ using a Karl Fischer solids moisture analyzer to obtain the water content of the test material after water removal.

[0128] Optionally, the water content of the carbon-coated phosphate material is independently selected from any value or a range between 90ppm, 100ppm, 150ppm, 200ppm, 250ppm, 300ppm, 350ppm, 400ppm, 450ppm, and 500ppm.

[0129] Preparation method of carbon-coated phosphate materials

[0130] This application provides a method for preparing a carbon-coated phosphate material, comprising: injecting a carbon source and a carrier gas into the phosphate material at a preset flow rate; and depositing the carbon source on the surface or within the pores of the phosphate material at a preset temperature to obtain a carbon-coated phosphate cathode material; wherein the specific surface area of ​​the carbon-coated phosphate cathode material is less than or equal to 8 m². 2 / g.

[0131] In related technologies, carbon coatings are typically formed by sintering organic carbon sources in a solid-state environment. These organic carbon sources may contain oxygen-containing groups or carry oxygen atoms. During the sintering process, some oxygen elements are released into the external environment as gases such as carbon dioxide and carbon monoxide. This gas release leads to the formation of numerous micropores and mesopores in the carbon coating, increasing its specific surface area and consequently its water absorption. This increases the difficulty and cost of water removal in industrial production. Furthermore, after the organic carbon source is heat-treated and carbonized into a carbon coating, the oxygen elements in the organic carbon source may not be completely removed, resulting in excessive oxygen content in the carbon coating. Since oxygen elements are mostly present in the form of oxygen-containing groups, these groups can also adsorb water vapor from the environment, further increasing the water content of the positive electrode active material and exacerbating the difficulty and cost of water removal in industrial production.

[0132] When phosphate materials are used as active materials in battery cells, the carbon coating layer contains a large number of micropores and mesopores, which increases the risk of electrolyte entering the positive electrode active material through the pore structure and reacting with phosphate. Moreover, the high reactivity of oxygen-containing groups makes them prone to catalyzing the decomposition of the electrolyte upon contact, exacerbating the interfacial side reactions between the positive electrode active material and the electrolyte, leading to increased gas production, swelling of the battery cell, and affecting its reliability. In addition, the decomposed electrolyte may produce hydrofluoric acid (HF), which can further dissolve the positive electrode active material, causing the dissolution of transition metal ions such as manganese ions and deteriorating the cycle performance of the battery cell.

[0133] This application utilizes vapor deposition to vaporize carbon sources into carbon radicals at lower temperatures. The lower temperature required for carbon radical deposition and carbonization on the surface or within the pores of phosphate materials reduces the likelihood of side reactions between carbon and phosphate materials caused by excessively high reaction temperatures. Furthermore, the lower activation energy required for carbon radicals allows for better migration and rearrangement, resulting in a highly graphitized and dense carbon coating layer. Simultaneously, the vaporization of carbon sources into carbon radicals occurs in a gaseous environment. Compared to conventional high-temperature carbon coating processes in molten systems, where oxygen-containing groups are released as gases such as carbon dioxide and carbon monoxide, leading to the formation of numerous micropores and mesopores in the carbon coating layer and increasing its specific surface area, vapor deposition reduces the likelihood of pore formation and can effectively seal pores in the material. This significantly reduces the specific surface area of ​​the carbon-coated phosphate material.

[0134] In some embodiments, carbon source deposition on the surface or pores of the phosphate material includes: the carbon source being vaporized at a preset temperature into a raw material gas containing carbon free radicals, and the carbon free radicals being deposited on the surface and pores of the phosphate material.

[0135] In some embodiments, the step of injecting the carbon source and carrier gas into the phosphate material at a preset flow rate includes: mixing the carbon source with an organic solvent to obtain a carbon source solution. The carbon source can be a solid or a liquid. Mixing the carbon source with the organic solvent allows the carbon source to be injected in liquid form, facilitating control of the carbon source injection rate, thereby controlling the formation and deposition rates of carbon free radicals, and improving the graphitization degree of the carbon coating layer.

[0136] In some embodiments, the vaporization temperature of the carbon source is less than or equal to a preset temperature. Within this range, the possibility of side reactions between carbon and phosphate materials caused by excessively high reaction temperatures can be reduced, thereby improving the graphitization degree and density of the carbon coating layer.

[0137] In some embodiments, the carbon radicals formed after the carbon source is gasified include one or more of methyl, phenyl, tolyl, and hexadienyl groups. Within this range, the activation energy required for the carbon radicals is relatively low, allowing for better migration and rearrangement to form a highly graphitized and dense carbon coating layer. Simultaneously, the carbon coating layer formed by the carbon radicals within this range possesses strong hydrophobic groups, reducing the adsorption rate of water molecules; furthermore, the binding force between the carbon coating layer formed by the carbon radicals and the adsorbed water molecules is weak, making it easier to remove the bound water molecules and increase the water content after dehydration. This results in carbon-coated phosphate materials with high water content after dehydration and low saturated water absorption, reducing the difficulty and cost of dehydration in industrial production and further improving the cycle performance of battery cells.

[0138] In some embodiments, the carbon source includes one or more of aromatic compounds containing benzene rings, alkanes without benzene rings, and long-chain polymers. Within this range, carbon-coated phosphate materials with high water content after dehydration and low saturated water absorption can be better obtained, thereby reducing the difficulty and cost of dehydration of the material in industrial production and further improving the cycle performance of battery cells.

[0139] In some embodiments, the aromatic compound containing a benzene ring includes one or more of benzene, toluene, and naphthalene. Within this range, carbon-coated phosphate materials with high water content after dehydration and low saturated water absorption can be better obtained, thereby reducing the difficulty and cost of dehydration of the material in industrial production and further improving the cycle performance of battery cells.

[0140] In some embodiments, in the step of injecting a carbon source and a carrier gas into a phosphate material at a preset flow rate, the phosphate material comprises materials having the general formula C n / Li a Fe (1-x) Mn x M y One or more of the materials containing PO4; wherein n is 0 or 1, x and y are natural numbers, x ranges from 0 to 1, y ranges from 0 to 0.1; a is 0 to 1.1; M includes one or more metallic elements from Groups IVB, VB, VIII, IIA, IIIA, IVA and VA.

[0141] In this embodiment, carbon free radicals are deposited and carbonized on the surface or within the pores of a phosphate material. The phosphate material used as a substrate can be either carbon-coated or uncoated. Using a carbon-coated phosphate material as a substrate can further improve its conductivity.

[0142] In some embodiments, the step of injecting a carbon source and a carrier gas into a phosphate material at a preset flow rate includes: injecting LiFe...(1-x) Mn x M y PO4 is mixed with one or more of starch, sucrose, glucose, citric acid, and PEG, and then heat-treated to obtain C / LiFe with a porous structure. (1-x) Mn x M y PO4. Carbon-coated phosphate materials within this range can be used as substrates for chemical vapor deposition to further improve their conductivity.

[0143] In some embodiments, the step of injecting a carbon source and a carrier gas into the phosphate material at a preset flow rate includes: dispersing the phosphate material to obtain dispersed phosphate material particles; and injecting the carbon source and a carrier gas into the dispersed phosphate material particles at a preset flow rate. In this step, dispersing the phosphate material can be performed, for example, by placing the phosphate material in a rotary kiln. Under the action of the rotary kiln, dispersed phosphate material particles can be obtained, thereby allowing carbon free radicals to migrate and rearrange uniformly on the surface of the phosphate material particles, thereby improving the graphitization degree and density of the carbon coating layer.

[0144] In some embodiments, the carrier gas includes an inactive gas, which includes one or more of nitrogen, neon, or argon.

[0145] In some embodiments, the injection flow rate of the carbon source is 0.1 to 10 mL / h, the injection time is 10 min to 10 h, and the injection flow rate of the carrier gas is 50 to 1000 mL / min.

[0146] In some embodiments, the preset temperature is 600–900°C.

[0147] The injection flow rate, injection time, and carrier gas injection flow rate of the carbon source in this embodiment can match the carbon free radical generation rate and deposition rate to improve the graphitization degree of the carbon coating layer. The preset temperature is the vaporization temperature of the carbon source, which allows carbon free radicals to migrate and rearrange, forming a highly graphitized carbon coating layer. Simultaneously, this preset temperature is lower than the temperature at which carbon reacts with phosphate materials, thus improving the conductivity of the carbon coating layer while simultaneously increasing its graphitization degree.

[0148] Optionally, the injection flow rate of the carbon source is independently selected from 0.1 mL / h, 0.2 mL / h, 0.3 mL / h, 0.4 mL / h, 0.5 mL / h, 0.6 mL / h, 0.7 mL / h, 0.8 mL / h, 0.9 mL / h, 1.0 mL / h, 1.1 mL / h, 1.2 mL / h, 1.3 mL / h, 1.4 mL / h, 1.5 mL / h, 1.6 mL / h, 1.7 mL / h, 1.8 mL / h, 1.9 mL / h, 2.0 mL / h, 2.1 mL / h, 2.2 mL / h, 2.3 mL / h, and 2.4 mL / h. , 2.5mL / h, 2.6mL / h, 2.7mL / h, 2.8mL / h, 2.9mL / h, 3.0mL / h, 3.1mL / h, 3.2mL / h, 3.3mL / h, 3.4mL / h, 3.5mL / h, 3.6mL / h, 3.7mL / h , 3.8mL / h, 3.9mL / h, 4.0mL / h, 4.1mL / h, 4.2mL / h, 4.3mL / h, 4.4mL / h, 4.5mL / h, 4.6mL / h, 4.7mL / h, 4.8mL / h, 4.9mL / h, 5.0mL / h ,5.1mL / h, 5.2mL / h, 5.3mL / h, 5.4mL / h, 5.5mL / h, 5.6mL / h, 5.7mL / h, 5.8mL / h, 5.9mL / h, 6.0mL / h, 6.1mL / h, 6.2mL / h, 6.3mL / h , 6.4mL / h, 6.5mL / h, 6.6mL / h, 6.7mL / h, 6.8mL / h, 6.9mL / h, 7.0mL / h, 7.1mL / h, 7.2mL / h, 7.3mL / h, 7.4mL / h, 7.5mL / h, 7.6mL / h The value can be any one of the following: 7.7 mL / h, 7.8 mL / h, 7.9 mL / h, 8.0 mL / h, 8.1 mL / h, 8.2 mL / h, 8.3 mL / h, 8.4 mL / h, 8.5 mL / h, 8.6 mL / h, 8.7 mL / h, 8.8 mL / h, 8.9 mL / h, 9.0 mL / h, 9.1 mL / h, 9.2 mL / h, 9.3 mL / h, 9.4 mL / h, 9.5 mL / h, 9.6 mL / h, 9.7 mL / h, 9.8 mL / h, 9.9 mL / h, or 10 mL / h, or any value between any two.

[0149] Optionally, the carbon source injection time is independently selected from any value or a range between any two of 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 1.5 h, 2.0 h, 2.5 h, 3.0 h, 3.5 h, 4.0 h, 4.5 h, 5.0 h, 5.5 h, 6.0 h, 6.5 h, 7.0 h, 7.5 h, 8.0 h, 8.5 h, 9.0 h, 9.5 h, and 10 h.

[0150] Optionally, the carrier gas injection flow rate is independently selected from 50 mL / min, 60 mL / min, 70 mL / min, 80 mL / min, 90 mL / min, 100 mL / min, 110 mL / min, 120 mL / min, 130 mL / min, 140 mL / min, 150 mL / min, 160 mL / min, 170 mL / min, 180 mL / min, 190 mL / min, 200 mL / min, 210 mL / min, 220 mL / min, 230 mL / min, 240 mL / min, 250 mL / min, 260 mL / min, 270 mL / min, 280 mL / min. min, 290mL / min, 300mL / min, 310mL / min, 320mL / min, 330mL / min, 340mL / min, 350mL / min, 360mL / min, 370mL / min, 380mL / min, 390mL / min, 400mL / min , 410mL / min, 420mL / min, 430mL / min, 440mL / min, 450mL / min, 460mL / min, 470mL / min, 480mL / min, 490mL / min, 500mL / min, 510mL / min, 520mL / min, 530 mL / min, 540mL / min, 550mL / min, 560mL / min, 570mL / min, 580mL / min, 590mL / min, 600mL / min, 610mL / min, 620mL / min, 630mL / min, 640mL / min, 650mL / min, 660mL / min, 670mL / min, 680mL / min, 690mL / min, 700mL / min, 710mL / min, 720mL / min, 730mL / min, 740mL / min, 750mL / min, 760mL / min, 770mL / min, Any value or a range between any two of the following: 780 mL / min, 790 mL / min, 800 mL / min, 810 mL / min, 820 mL / min, 830 mL / min, 840 mL / min, 850 mL / min, 860 mL / min, 870 mL / min, 880 mL / min, 890 mL / min, 900 mL / min, 910 mL / min, 920 mL / min, 930 mL / min, 940 mL / min, 950 mL / min, 960 mL / min, 970 mL / min, 980 mL / min, 990 mL / min, and 1000 mL / min.

[0151] Optionally, the preset temperature is independently selected from any value or a range between 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, and 900℃.

[0152] Optionally, the carbon source is injected at a flow rate of 0.5–5 mL / h, the injection time is 10 min–5 h, and the carrier gas is injected at a flow rate of 100–500 mL / min.

[0153] In some embodiments, the carbon source is mixed with an organic solvent to obtain a carbon source solution in which the mass ratio of carbon source to organic solvent is 0.25% to 10%.

[0154] In some embodiments, in order to improve the reliability of the carbon source, the carbon source is mixed with an organic solvent to obtain a carbon source solution in which the mass ratio of carbon source to organic solvent is 1% to 5%.

[0155] Optionally, the carbon source and organic solvent are mixed to obtain a carbon source solution in which the mass ratio of carbon source to organic solvent is independently selected from any value or any range between 0.25%, 0.35%, 0.45%, 0.55%, 0.65%, 0.75%, 0.85%, 0.95%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, and 10%.

[0156] Positive electrode sheet

[0157] This application provides a positive electrode sheet, which includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector and including a positive electrode active material; the positive electrode active material includes a carbon-coated phosphate material as described in the second aspect.

[0158] Electrical appliances

[0159] This application provides an electrical device comprising a battery cell according to a first aspect. The electrical device includes the battery cell of this application and at least one of a battery module and a battery pack assembled from the battery cell. The battery cell, battery module, and 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, 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.

[0160] The electrical device can select individual battery cells, or battery modules or battery packs assembled from the individual battery cells, according to its usage requirements.

[0161] Figure 6 is a schematic diagram of an example electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0162] 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 a single battery cell as their power source.

[0163] Example

[0164] 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.

[0165] Examples 1-13, Comparative Example 1

[0166] Carbon-coated phosphate materials were prepared according to the formulation parameters shown in Table 1 below:

[0167] Weigh 10g of phosphate material and add it to the CVD rotary furnace. Start the rotation to ensure the powder is in flow. After the air is purged by introducing inactive gas (inactive gas is introduced throughout the process), start the heating program and heat to the target temperature at a heating rate of 5℃ / min. Then, inject the easily graphitized carbon source into the rotary furnace along with the inactive gas at a certain flow rate. After maintaining the carbon source injection for a certain period of time, stop the carbon source injection and continue to hold the temperature for half an hour. After the holding time is completed, the rotary furnace is cooled to room temperature along with the furnace to obtain carbon-coated phosphate material.

[0168] Table 1

[0169] How to make a button cell battery:

[0170] (1) Preparation of positive electrode sheet: The carbon-coated phosphate material prepared in Examples 1-13 and Comparative Example 1 is used as the positive electrode active material, the binder polyvinylidene fluoride (PVDF) and the conductive agent acetylene black are dissolved in the solvent N-methylpyrrolidone (NMP) in a weight ratio of 92:5.5:2.5, and the mixture is stirred and mixed evenly to prepare a positive electrode slurry; the positive electrode slurry is uniformly coated on the positive electrode current collector aluminum foil, and then dried, cold pressed and cut to obtain the positive electrode sheet.

[0171] (2) Negative electrode: Lithium metal sheet is used as the negative electrode.

[0172] (3) Separation membrane: Polypropylene membrane is used, with an aluminum oxide coating on one side.

[0173] (4) Preparation of electrolyte: Ethyl carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 1:1:1. LiPF6 was then uniformly dissolved in the above solution to obtain the electrolyte. The concentration of LiPF6 in the electrolyte was 1 mol / L.

[0174] (5) Preparation of button cell: The above positive electrode, separator and negative electrode are assembled in the button cell box and injected with electrolyte to obtain button cell.

[0175] Method for manufacturing stacked battery:

[0176] (1) Preparation of positive electrode sheet: The carbon-coated phosphate material prepared in Examples 1-13 and Comparative Example 1 is used as the positive electrode active material, the binder polyvinylidene fluoride (PVDF) and the conductive agent acetylene black are dissolved in the solvent N-methylpyrrolidone (NMP) in a weight ratio of 92:5.5:2.5, and the mixture is stirred and mixed evenly to prepare a positive electrode slurry; the positive electrode slurry is uniformly coated on the positive electrode current collector aluminum foil, and then dried, cold pressed and cut to obtain the positive electrode sheet.

[0177] (2) Negative electrode sheet: Graphite, polystyrene rubber, sodium carboxymethyl cellulose, SP and plasticizer BD-3 are mixed in a mass ratio of 0.965:0.018:0.01:0.007:0.002 and deionized water is added and stirred evenly to prepare a negative electrode slurry. The negative electrode slurry is evenly coated on the negative electrode current collector copper foil, and then dried, cold pressed and cut to obtain the positive electrode sheet.

[0178] (3) Separation membrane: Polypropylene membrane is used, with an aluminum oxide coating on one side.

[0179] (4) Preparation of electrolyte: Ethyl carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 1:1:1. LiPF6 was then uniformly dissolved in the above solution to obtain the electrolyte. The concentration of LiPF6 in the electrolyte was 1 mol / L.

[0180] (5) Weld the positive and negative electrode tabs together and add a separator in the middle to stack them to make a stacked battery. Encapsulate the stacked battery in an aluminum-plastic film that retains the electrolyte injection area. Then inject the electrolyte and vacuum seal the battery. Finally, put the stacked battery into the fixture to obtain a complete stacked battery for testing.

[0181] Data Analysis

[0182] The carbon-coated phosphate materials prepared in Examples 1-13 and Comparative Example 1 were tested according to the following methods:

[0183] Specific surface area: The specific surface area of ​​the carbon-coated phosphate material was calculated by measuring the nitrogen adsorption-desorption curve using a specific surface area and pore size analyzer (American Micro Instruments, model ASAP-2460).

[0184] The morphology of the material was characterized using TEM (UK Oxford Instruments Group X-Max EDS combined with US Thermo Scientific-Talos F200S G2 TEM).

[0185] Water absorption: Under air and relative humidity of 60%, the material to be tested was left to stand for 24 hours, and the moisture content of the material was tested at 170℃ using a Karl Fischer solid moisture analyzer to obtain the saturated water absorption of the material.

[0186] Water content: Under air and relative humidity of 60%, the test material was left to stand for 24 hours, and then transferred to a 110℃ oven for vacuum drying for 5 hours. The water content (ppm) of the test material was measured at 170℃ using a Karl Fischer solid moisture analyzer to obtain the water content of the test material after water removal.

[0187] The test results are shown in Table 2 and Figures 7-9.

[0188] The button cells or stacked cells prepared in Examples 1-13 and Comparative Example 1 were tested according to the following methods:

[0189] (1) Battery specific capacity test:

[0190] At 25℃, a coin cell battery is charged at a constant current of 0.1C to 4.3V, then charged at a constant voltage of 4.3V to a current of 0.01C. After resting for 5 minutes, it is discharged at 0.1C to 2.0V. The resulting discharge capacity is recorded as c1. The discharge capacity obtained after one cycle is recorded as c2. Three parallel samples are prepared. The average value of c2 for the three parallel samples is taken and divided by the weight of the positive electrode material to obtain the specific capacity of the battery.

[0191] (2) Loop Test

[0192] At 45℃, the stacked battery is first charged at a constant current of 0.1C to 4.3V, then charged at a constant voltage of 4.3V to a current of 0.01C, left to stand for 5 minutes, and then discharged at 0.1C to 2.0V. This completes one charge-discharge cycle and activates the battery.

[0193] Cyclic testing: Cyclic testing was then started at 25℃. The test procedure was as follows: first, the device was charged at a constant current of 0.33C to 4.15V, then charged at a constant voltage of 4.15V to a current of 0.01C; after resting for 5 minutes, it was discharged at a rate of 0.33C to 2.0V, then rested for 5 minutes, and discharged at a constant current of 0.05C to 2.0V. This constitutes one charge-discharge cycle.

[0194] Cycle life evaluation method: The percentage is calculated by dividing the discharge capacity after 200 cycles by the discharge capacity of the first cycle. The larger the value, the better the capacity retention and the longer the cycle life.

[0195] Storage Test: First, the cell was run three times using the same charge-discharge cycle as the cyclic test to obtain the cell capacity data, denoted as C0. Then, the cell was placed in a 60℃ constant temperature chamber for storage. After 30 days, it was removed and subjected to three charge-discharge cycles to obtain the cell's post-storage capacity, C1. The storage performance evaluation index is the percentage ratio of C1 to C0. A higher ratio indicates a higher capacity retention rate and a longer storage life.

[0196] The test results are shown in Table 2.

[0197] Table 2

[0198] As shown in Examples 1-13 and Comparative Example 1, phosphate materials with specific carbon sources obtained by chemical vapor deposition have low specific surface area, low water absorption rate, and low water content. When used in battery cells, they exhibit good cycle stability.

[0199] The above description is merely a specific implementation of this application. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, modules, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here. It should be understood that the protection scope of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the protection scope of this application.

Claims

1. A battery cell, comprising a positive electrode, a negative electrode, and an electrolyte, wherein, The positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector and including a positive active material; The positive electrode active material includes a carbon-coated phosphate material, wherein the specific surface area of ​​the carbon-coated phosphate material is less than or equal to 8 m². 2 / g.

2. The battery cell according to claim 1, wherein, The carbon-coated phosphate material has a specific surface area of ​​5–8 m². 2 / g.

3. The battery cell according to claim 1 or 2, wherein, The surface of the carbon-coated phosphate material includes one or more of the following groups: hydroxyl, carboxyl, carbonyl, and lactone groups.

4. The battery cell according to any one of claims 1-3, wherein, The phosphate material includes materials having the general formula Li a Fe (1-x) Mn x M y One or more of the materials containing PO4; Where x and y are natural numbers, with x ranging from 0 to 1 and y ranging from 0 to 0.1; a is from 0 to 1.

1. M includes one or more metallic elements from Groups IVB, VB, VIII, IIA, IIIA, IVA, and VA.

5. The battery cell according to any one of claims 1-4, wherein, The tap density of the carbon-coated phosphate material is 2.0–2.7 g / cm³. 3 .

6. The battery cell according to any one of claims 1-5, wherein, The average thickness of the carbon coating layer of the carbon-coated phosphate material is 1–5 nm; and / or, Based on the mass of the carbon-coated phosphate material, the mass content of the carbon coating layer is 0.1 wt% to 3.0 wt%.

7. A carbon-coated phosphate material, wherein, The specific surface area of ​​the carbon-coated phosphate material is less than or equal to 8 m². 2 / g.

8. The carbon-coated phosphate material according to claim 7, wherein, The water absorption of the carbon-coated phosphate material is 1000–2800 ppm.

9. The carbon-coated phosphate material according to claim 7 or 8, wherein, The water content of the carbon-coated phosphate material is 90–500 ppm.

10. A method for preparing a carbon-coated phosphate material, wherein, include: A carbon source and a carrier gas are injected into a phosphate material at a preset flow rate. At a preset temperature, the carbon source is deposited on the surface or in the pores of the phosphate material to obtain a carbon-coated phosphate cathode material. The specific surface area of ​​the carbon-coated phosphate cathode material is less than or equal to 8 m². 2 / g.

11. The preparation method according to claim 10, wherein, The carbon source deposition on the surface or pores of the phosphate material includes: the carbon source being vaporized at a preset temperature into a raw material gas containing carbon free radicals, and the carbon free radicals being deposited on the surface and pores of the phosphate material.

12. The preparation method according to claim 10 or 11, wherein, The step of injecting the carbon source and carrier gas into the phosphate material at a preset flow rate includes: mixing the carbon source with an organic solvent to obtain a carbon source solution.

13. The preparation method according to any one of claims 10-12, wherein, The gasification temperature of the carbon source is less than or equal to the preset temperature; and / or, The carbon free radicals formed after the carbon source is gasified include one or more of methyl, phenyl, tolyl, and hexadienyl.

14. The preparation method according to any one of claims 10-13, wherein, The carbon source includes one or more of the following: aromatic compounds containing benzene rings, alkanes without benzene rings, and long-chain polymers; The aromatic compounds containing a benzene ring include one or more of benzene, toluene, and naphthalene; The alkane that does not contain a benzene ring includes one or more of propylene and propane; The long-chain polymer includes one or more of polyethylene and polyethylene glycol.

15. The preparation method according to claim 14, wherein, The carbon source includes an aromatic compound containing a benzene ring, which includes one or more of benzene, toluene, and naphthalene.

16. The preparation method according to any one of claims 10-15, wherein, In the step of injecting a carbon source and a carrier gas into a phosphate material at a preset flow rate, the phosphate material comprises materials having the general formula C n / Li a Fe (1-x) Mn x M y One or more of the materials containing PO4; Where n is 0 or 1, x and y are natural numbers, with x ranging from 0 to 1 and y ranging from 0 to 0.1; a is 0 to 1.1; M includes one or more metallic elements from Groups IVB, VB, VIII, IIA, IIIA, IVA, and VA.

17. The preparation method according to any one of claims 10-16, wherein, The step of injecting the carbon source and carrier gas into the phosphate material at a preset flow rate includes: The phosphate material is dispersed to obtain dispersed phosphate material particles; The carbon source and carrier gas are injected into the dispersed phosphate material particles at a preset flow rate.

18. The preparation method according to any one of claims 10-17, wherein, The carrier gas includes an inactive gas, which includes one or more of nitrogen, neon, or argon.

19. The preparation method according to any one of claims 10-18, wherein, The carbon source is injected at a flow rate of 0.1–10 mL / h for 10 min–10 h, and the carrier gas is injected at a flow rate of 50–1000 mL / min; and / or, The preset temperature is 600–900°C.

20. The preparation method according to claim 12, wherein, A carbon source is mixed with an organic solvent to obtain a carbon source solution, wherein the mass ratio of the carbon source to the organic solvent is 0.25% to 10%; and / or, A carbon source is mixed with an organic solvent to obtain a carbon source solution, wherein the mass ratio of the carbon source to the organic solvent is 1% to 5%.

21. A positive electrode plate, wherein, The positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector and including a positive active material; The positive electrode active material includes the carbon-coated phosphate material as described in claim 7.

22. An electrical appliance, wherein, Includes the battery cell according to any one of claims 1-6.

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