Composite hard carbon material, preparation method thereof, negative electrode slurry and electrode sheet, secondary battery and device

Abstract

The application provides a composite hard carbon material and a preparation method thereof, a negative electrode slurry and a negative electrode sheet, a secondary battery and an electric device. The composite hard carbon material comprises: a hard carbon material and a hydrophobic compound filled in the pores of the hard carbon material, the hydrophobic compound being a compound represented by the following formula (I). The composite hard carbon material provided by the application can reduce the foaming of the negative electrode slurry, and further improve the cycle performance of the secondary battery.

Description

Technical Field

[0001] This application relates to the field of alkali metal ion battery technology, and in particular to a composite hard carbon material and its preparation method, a negative electrode slurry and electrode sheet, a secondary battery and device. Background Technology

[0002] In recent years, with the increasingly wide application of alkali metal ion batteries, they have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and many other fields. Due to the significant development of alkali metal ion batteries, higher requirements have been placed on their energy density, cycle performance, and safety performance.

[0003] Currently, to improve the energy density, cycle performance, and safety performance of alkali metal ion batteries, it is necessary to improve the stability of the negative electrode sheet. In other words, it is necessary to improve the stability of the negative electrode slurry that forms the negative electrode sheet. Therefore, how to improve the stability of the negative electrode slurry, and thus improve the performance of alkali metal ion batteries, has become an urgent problem to be solved in this field. Summary of the Invention

[0004] This application addresses the aforementioned issues and aims to provide a composite hard carbon material and its preparation method to reduce foaming of the negative electrode slurry, thereby improving the cycle performance of the secondary battery. Furthermore, this application also aims to provide a negative electrode slurry and electrode sheet comprising the aforementioned composite hard carbon material, a secondary battery, and an apparatus.

[0005] To achieve the above objectives, this application provides a composite hard carbon material and its preparation method, a negative electrode slurry and electrode sheet, a secondary battery, and an apparatus.

[0006] A first aspect of this application provides a composite hard carbon material, the composite hard carbon material comprising: a hard carbon material and a hydrophobic compound filling the pores of the hard carbon material, the hydrophobic compound being a compound represented by the following formula (I):

[0007]

[0008] In the above formula (I), X represents O, S, C=O, and CR. 11 R 12 NR 21 PR 31 P(=O)R 32 Or P(=S)R 33 ;

[0009] Among them, R 11 R 12 R 21 R 31R 32 R 33 Each of the following is independently selected from H, SH, OH, NH2, halogen, unsubstituted or substituted C1-C10 alkyl, unsubstituted or substituted 5- to 10-membered heteroaryl or 6- to 10-membered aryl, unsubstituted or substituted 3- to 8-membered cycloalkyl or heterocycloalkyl, amide or thioformamido; when the C1- to C10 alkyl, 5- to 10-membered heteroaryl, 6- to 10-membered aryl, 3- to 8-membered cycloalkyl or heterocycloalkyl is substituted, their substituents each independently include at least one of OH, NH2, halogen, C1- to C10 alkyl, 6- to 10-membered aryl, 3- to 8-membered cycloalkyl or heterocycloalkyl;

[0010] R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 Each is independently selected from any one of R, OR, C(=O)R, COOR, 6-membered to 10-membered aryl and halogen, wherein each of R is independently selected from any one of H and C1 to C10 alkyl.

[0011] Therefore, the composite hard carbon material provided in this application includes a hard carbon material and a hydrophobic compound filling the pores of the hard carbon material, that is, the hydrophobic compound occupies the pores of the hard carbon material; in the subsequent process of forming a negative electrode slurry using the above-mentioned composite hard carbon material, the solvent in the negative electrode slurry, such as water molecules, cannot enter the pores of the composite hard carbon material, thereby effectively reducing the foaming of the negative electrode slurry and improving the stability of the negative electrode slurry.

[0012] In some embodiments, in formula (I), R 11 R 12 R 21 R 31 R 32 R 33 Each of the following is independently selected from H, SH, OH, NH2, halogen, unsubstituted or substituted C1-C4 alkyl, unsubstituted or substituted 5- to 6-membered heteroaryl or 6- to 10-membered aryl, unsubstituted or substituted 3- to 6-membered cycloalkyl or heterocycloalkyl, amide or thioformamido; when the C1- to C4 alkyl, 5- to 6-membered heteroaryl, 6- to 10-membered aryl, 3- to 6-membered cycloalkyl or heterocycloalkyl is substituted, each of the substituents independently includes at least one of OH, NH2, halogen, C1- to C4 alkyl, 6- to 10-membered aryl, 3- to 6-membered cycloalkyl or heterocycloalkyl;

[0013] R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10Each is independently selected from any one of R, OR, C(=O)R, COOR, phenyl and halogen, wherein each of R is independently selected from any one of H and C1 to C4 alkyl groups.

[0014] In any embodiment, in equation (I), R 11 R 12 R 21 R 31 R 32 R 33 Each is independently selected from any one of H, SH, OH, NH2, phenyl, 4-hydroxyphenyl, furanyl, thiophene, pyrrolyl, thiazolyl, imidazolyl, pyridinyl, piperidinyl, pyrazinyl, pyrimidinyl, pyridazinyl, ethylene oxide, cyclothioethyl alkyl, cyclohexyl, benzyl, thiocarbamate, 1-pyrrolidine-2-yl-methyl, and C1 to C4 alkyl groups.

[0015] In some embodiments, the hydrophobic compound is selected from at least one of the following compounds:

[0016]

[0017] In some embodiments, the weight ratio of the hydrophobic compound to the hard carbon material in the composite hard carbon material is 0.1 to 5:100.

[0018] By limiting the mixing weight ratio range between the hydrophobic compound and the hard carbon material, the hydrophobic compound can enter the pores of the hard carbon material and occupy the pores to form a composite hard carbon material; the solvent in the subsequent negative electrode slurry, such as water molecules, cannot enter the pores of the composite hard carbon material, thereby effectively reducing the foaming of the negative electrode slurry.

[0019] In some embodiments, the hydrophobic compound is immobilized within the pores of the hard carbon material through π-π conjugation interactions and / or van der Waals interactions.

[0020] Hydrophobic compounds can be fixed in the pores of hard carbon materials through π-π conjugation and / or van der Waals interactions to form composite hard carbon materials. Even if the composite hard carbon material is used to form the negative electrode slurry, the hydrophobic compounds have already occupied the pores of the hard carbon material, thereby reducing the probability of solvents such as water molecules in the negative electrode slurry entering the pores of the composite hard carbon material, and thus reducing the foaming of the negative electrode slurry.

[0021] A second aspect of this application provides a method for preparing a composite hard carbon material, the method comprising:

[0022] After the hard carbon material and the hydrophobic compound are mixed evenly, they are placed into the reaction vessel;

[0023] A supercritical fluid is introduced into the reactor to allow the hard carbon material and the hydrophobic compound to react in the supercritical fluid in order to obtain a composite hard carbon material.

[0024] The hydrophobic compound is a compound represented by the following formula (I):

[0025]

[0026] In the above formula (I), X represents O, S, C=O, and CR. 11 R 12 NR 21 PR 31 P(=O)R 32 Or P(=S)R 33 ;

[0027] Among them, R 11 R 12 R 21 R 31 R 32 R 33 Each of the following is independently selected from H, SH, OH, NH2, halogen, unsubstituted or substituted C1-C10 alkyl, unsubstituted or substituted 5- to 10-membered heteroaryl or 6- to 10-membered aryl, unsubstituted or substituted 3- to 8-membered cycloalkyl or heterocycloalkyl, amide or thioformamido; when the C1- to C10 alkyl, 5- to 10-membered heteroaryl, 6- to 10-membered aryl, 3- to 8-membered cycloalkyl or heterocycloalkyl is substituted, their substituents each independently include at least one of OH, NH2, halogen, C1- to C10 alkyl, 6- to 10-membered aryl, 3- to 8-membered cycloalkyl or heterocycloalkyl;

[0028] R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 Each is independently selected from any one of R, OR, C(=O)R, COOR, 6-membered to 10-membered aryl and halogen, wherein each of R is independently selected from any one of H and C1 to C10 alkyl.

[0029] Therefore, this application processes hard carbon materials to react with hydrophobic compounds in a supercritical fluid to obtain composite hard carbon materials. The pores of the composite hard carbon materials are filled with hydrophobic compounds. In the subsequent process of forming a negative electrode slurry using the above-mentioned composite hard carbon materials, solvents such as water molecules in the negative electrode slurry cannot enter the pores of the composite hard carbon materials, thereby effectively reducing foaming of the negative electrode slurry and improving the stability of the negative electrode slurry.

[0030] In some embodiments, in formula (I), R 11 R 12 R21 R 31 R 32 R 33 Each of the following is independently selected from H, SH, OH, NH2, halogen, unsubstituted or substituted C1-C4 alkyl, unsubstituted or substituted 5- to 6-membered heteroaryl or 6- to 10-membered aryl, unsubstituted or substituted 3- to 6-membered cycloalkyl or heterocycloalkyl, amide or thioformamido; when the C1- to C4 alkyl, 5- to 6-membered heteroaryl, 6- to 10-membered aryl, 3- to 6-membered cycloalkyl or heterocycloalkyl is substituted, each of the substituents independently includes at least one of OH, NH2, halogen, C1- to C4 alkyl, 6- to 10-membered aryl, 3- to 6-membered cycloalkyl or heterocycloalkyl;

[0031] R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 Each is independently selected from any one of R, OR, C(=O)R, COOR, phenyl and halogen, wherein each of R is independently selected from any one of H and C1 to C4 alkyl groups.

[0032] In some embodiments, in formula (I), R 11 R 12 R 21 R 31 R 32 R 33 Each is independently selected from any one of H, SH, OH, NH2, phenyl, 4-hydroxyphenyl, furanyl, thiophene, pyrrolyl, thiazolyl, imidazolyl, pyridinyl, piperidinyl, pyrazinyl, pyrimidinyl, pyridazinyl, ethylene oxide, cyclothioethyl alkyl, cyclohexyl, benzyl, thiocarbamate, 1-pyrrolidine-2-yl-methyl, and C1 to C4 alkyl groups.

[0033] In some embodiments, the hydrophobic compound is selected from at least one of the following compounds:

[0034]

[0035]

[0036] In some embodiments, the hydrophobic compound and the hard carbon material are mixed uniformly in a weight ratio of 0.1 to 5:100.

[0037] By limiting the mixing weight ratio range between the hydrophobic compound and the hard carbon material, the hydrophobic compound can enter the pores of the hard carbon material and occupy the pores to form a composite hard carbon material; the solvent in the negative electrode slurry, such as water molecules, cannot enter the pores of the composite hard carbon material, thereby effectively reducing the foaming of the negative electrode slurry.

[0038] In some embodiments, the supercritical fluid is selected from supercritical carbon dioxide, supercritical nitric oxide, supercritical acetylene, supercritical trifluoromethane, supercritical chloroform, supercritical methane, supercritical ethane, supercritical propane, supercritical ethylene, supercritical propylene, supercritical methanol, supercritical ethanol, supercritical acetone, supercritical chlorofluorocarbon, or supercritical xenon.

[0039] In some embodiments, the reaction time of the hard carbon material and the hydrophobic compound in the supercritical fluid is 2 h to 10 h.

[0040] By limiting the reaction time of hard carbon materials and hydrophobic compounds in supercritical fluids, it is beneficial for the hard carbon materials and hydrophobic compounds to react fully, allowing the hydrophobic compounds to enter the pores of the hard carbon materials to form composite hard carbon materials.

[0041] A third aspect of this application provides a negative electrode slurry comprising a composite hard carbon material and a solvent from the first aspect of this application, and at least one of a conductive agent, a dispersant, and a binder.

[0042] Therefore, the negative electrode slurry provided in this application includes the composite hard carbon material in the above-mentioned technical solution. The pores of the composite hard carbon material contain hydrophobic compounds, which prevent solvents such as water molecules in the negative electrode slurry from entering the pores of the composite hard carbon material, thereby effectively reducing foaming of the negative electrode slurry and improving its stability. Even after being left for several days, the negative electrode slurry will not foam, and its viscosity remains stable.

[0043] In some embodiments, the content of the composite hard carbon material is 85 wt% to 97 wt%, based on the solid content in the negative electrode slurry; the content of the conductive agent is 0 to 5 wt%; the content of the dispersant is 0.5 wt% to 5 wt%; and the content of the binder is 0.5 wt% to 5 wt%.

[0044] In some embodiments, the solvent is water.

[0045] In some embodiments, the total solids content of the negative electrode slurry is 40 wt% to 65 wt% relative to the total weight of the negative electrode slurry.

[0046] In some embodiments, the conductive agent is selected from at least one of carbon black, carbon nanotubes, and graphene;

[0047] And / or, the dispersant is selected from at least one of sodium carboxymethyl cellulose and lithium carboxymethyl cellulose;

[0048] And / or, the adhesive is selected from at least one of styrene-butadiene rubber, styrene-acrylic emulsion, and modified polyacrylic acid.

[0049] A fourth aspect of this application provides a negative electrode sheet, the negative electrode sheet comprising a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer comprising the composite hard carbon material of the first aspect of this application.

[0050] Therefore, the negative electrode film layer provided in this application includes the composite hard carbon material in the above technical solution. The negative electrode slurry has high stability and will not foam even after being left for several days. Subsequently, the negative electrode sheet is used to form a secondary battery, which can effectively improve the cycle performance of the secondary battery.

[0051] The fifth aspect of this application provides a secondary battery, the secondary battery including the negative electrode sheet of the fourth aspect of this application.

[0052] Therefore, the secondary battery provided in this application includes the negative electrode sheet in the above-mentioned technical solution, which can effectively improve the cycle performance of the secondary battery.

[0053] A sixth aspect of this application provides an electrical device, which includes a secondary battery according to the fifth aspect of this application.

[0054] This application provides a composite hard carbon material and its preparation method, a negative electrode slurry and electrode sheet, a secondary battery, and an apparatus. The composite hard carbon material includes a hard carbon material and a hydrophobic compound filling the pores of the hard carbon material. Subsequently, the negative electrode slurry is formed using the above-mentioned composite hard carbon material, which can effectively reduce foaming of the negative electrode slurry and thus improve the stability of the negative electrode slurry. Attached Figure Description

[0055] Figure 1 This is a schematic diagram of a battery cell according to one embodiment of this application.

[0056] Figure 2 yes Figure 1 An exploded view of a battery cell according to one embodiment of this application is shown.

[0057] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application.

[0058] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0059] Figure 5 yes Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0060] Figure 6 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0061] Figure 7The images are photographs of the negative electrode slurry containing the composite hard carbon material of Example 1, wherein (a) is a photograph of the negative electrode slurry after stirring; and (b) is a photograph of the negative electrode slurry after being left to stand for 7 days.

[0062] Figure 8 The images are photographs of the negative electrode slurry containing the hard carbon material of Comparative Example 1, wherein (a) is a photograph of the negative electrode slurry after stirring; and (b) is a photograph of the negative electrode slurry after standing for 12 hours.

[0063] Explanation of reference numerals in the attached figures:

[0064] 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

[0065] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the composite hard carbon material, its preparation method, negative electrode slurry and electrode sheet, secondary battery, and 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 providing a full understanding of this application by those skilled in the art and are not intended to limit the subject matter of the claims.

[0066] 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.

[0067] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0068] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0069] 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.

[0070] Hard carbon refers to carbon materials that do not transform into graphite even at temperatures above 3000℃. Hard carbon materials possess advantages such as low energy storage voltage, high capacity, and good cycle stability. They also have advantages like abundant sources and simple preparation processes, making them one of the most promising anode materials currently available, with a large market potential in alkali metal-ion batteries. The synthesis of hard carbon mainly relies on organic compounds or biomass-derived precursors obtained through heating or chemical processes. For example, the macromolecular polymer structures of natural or artificially synthesized materials decompose at elevated pyrolysis temperatures. During precursor carbonization, a series of small molecules are released, such as H2O, CO2, and N2. This gas release process typically leads to increased porosity in hard carbon materials. For hard carbon materials with particularly well-developed pores, during the settling process after stirring, solvents such as water molecules in the anode slurry easily enter the pores and expel the gas, causing foaming of the anode slurry. Consequently, when the anode film prepared using foamed anode slurry is applied to a secondary battery, it leads to severe deterioration of the battery's cycle performance.

[0071] Based on this, this application proposes a composite hard carbon material and its preparation method, a negative electrode slurry and electrode sheet, a secondary battery and device.

[0072] A first aspect of this application provides a composite hard carbon material, the composite hard carbon material comprising: a hard carbon material and a hydrophobic compound filling the pores of the hard carbon material, the hydrophobic compound being a compound represented by the following formula (I):

[0073]

[0074] In the above formula (I), X represents O, S, C=O, and CR. 11 R12 NR 21 PR 31 P(=O)R 32 Or P(=S)R 33 ;

[0075] Among them, R 11 R 12 R 21 R 31 R 32 R 33 Each of the following is independently selected from H, SH, OH, NH2, halogen, unsubstituted or substituted C1-C10 alkyl, unsubstituted or substituted 5- to 10-membered heteroaryl or 6- to 10-membered aryl, unsubstituted or substituted 3- to 8-membered cycloalkyl or heterocycloalkyl, amide or thioformamido; when the C1- to C10 alkyl, 5- to 10-membered heteroaryl, 6- to 10-membered aryl, 3- to 8-membered cycloalkyl or heterocycloalkyl is substituted, their substituents each independently include at least one of OH, NH2, halogen, C1- to C10 alkyl, 6- to 10-membered aryl, 3- to 8-membered cycloalkyl or heterocycloalkyl;

[0076] R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 Each is independently selected from any one of R, OR, C(=O)R, COOR, 6-membered to 10-membered aryl and halogen, wherein each of R is independently selected from any one of H and C1 to C10 alkyl.

[0077] The term "halogen" in this application includes fluorine, chlorine, bromine, or iodine, optionally fluorine or chlorine.

[0078] The term "C1-C10 alkyl" in this application includes straight-chain alkyl or branched alkyl having 1 to 10 carbon atoms. Optionally, C1-C10 alkyl includes straight-chain or branched C1-C8 alkyl having 1 to 8 carbon atoms. Optionally, C1-C10 alkyl includes straight-chain or branched C1-C6 alkyl having 1 to 6 carbon atoms. Optionally, C1-C10 alkyl includes straight-chain or branched C1-C4 alkyl having 1 to 4 carbon atoms. Optionally, C1-C10 alkyl includes C1-C2 alkyl having 1 to 2 carbon atoms. Examples of C1-C10 alkyl include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, sec-pentyl, hexyl, heptyl, octyl, isooctyl, nonyl, and decyl.

[0079] The term "heteroaryl" as used in this application refers to an aryl group having one to three heteroatoms selected from O, N, and S in a ring structure. Examples of heteroaryl groups include, but are not limited to, pyrroleyl, furanyl, thiophenyl, thiazolyl, isothiazolyl, imidazolyl, triazolyl, tetrazolyl, pyrazolyl, oxazolyl, isoxazolyl, pyridinyl, pyrazinyl, pyridinyl, pyrimidinyl, etc.

[0080] In this application, the term "aryl" refers to a 6- to 14-membered all-carbon monocyclic or fused polycyclic group having a conjugated π-electron system, preferably a 6- to 10-membered group. Examples of aryl groups include, but are not limited to, phenyl, naphthyl, etc.

[0081] The term "cycloalkyl" in this application refers to a group having 3 to 30 carbon atoms (e.g., C3 to C4). 12 C3~C 10 Cycloalkyl groups are monocyclic or polycyclic (e.g., fused rings, bridging rings, or spirocyclic) systems of saturated or unsaturated non-aromatic hydrocarbons (C3-C8). Examples of cycloalkyl groups include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclopentenyl, cyclohexenyl, cycloheptenyl, 1,2,3,4-tetrahydronaphthyl, and adamantyl.

[0082] The term "heterocyclic alkyl" as used in this application refers to a saturated or unsaturated non-aromatic 3- to 8-membered monocyclic, 7- to 12-membered bicyclic (fused, bridged, or spirocyclic), or 11- to 14-membered tricyclic (fused, bridged, or spirocyclic) system containing 1 to 3 heteroatoms selected from O, N, or S, unless otherwise specified. Examples of heterocyclic alkyl groups include, but are not limited to, piperidinyl, piperazine, pyrrolyl, dioxyl, tetrahydrofuranyl, isoindolinyl, indolinyl, imidazoalkyl, pyrazolyl, oxazolyl, isoxazolyl, triazolyl, ethylene oxide, cyclothioethyl, azacyclic butyl, oxacyclic butyl, thiocyclic butyl, 1,2,3,6-tetrahydropyridinyl, tetrahydropyranyl, dihydropyranyl, pyranyl, morpholinyl, and tetrahydrothiaranyl.

[0083] The terms “alkyl,” “cycloalkyl,” “heterocycloalkyl,” “aryl,” and “heteroaryl” in this application may be substituted or unsubstituted. When the above groups are substituted, their substituents each independently include at least one of OH, NH2, halogen, C1 to C10 alkyl, 6- to 10-membered aryl, 3- to 8-membered cycloalkyl, or heterocycloalkyl.

[0084] The term "thioformamide group" in this application refers to C(=S)NH2.

[0085] In this application, the term "amide group" refers to C(=O)NH2.

[0086] The "pores of hard carbon materials" mentioned in this article refer to the pores inherent in the hard carbon materials themselves, rather than the gaps between the particles of hard carbon materials.

[0087] The applicant discovered that during the formation of negative electrode slurry using hard carbon materials, solvent molecules, such as water molecules, easily enter the pores of the hard carbon material during placement and expel gas from the pores, causing foaming of the negative electrode slurry. Therefore, the applicant treats the hard carbon material with a hydrophobic compound, allowing the hydrophobic compound to enter the pores of the hard carbon material, i.e., occupying the pores of the hard carbon material to form a composite hard carbon material. Subsequently, during the formation of the negative electrode slurry using this composite hard carbon material, solvent molecules, such as water molecules, cannot enter the pores of the composite hard carbon material, thereby effectively reducing foaming of the negative electrode slurry and improving its stability.

[0088] In some embodiments of this application, in formula (I), R 11 R 12 R 21 R 31 R 32 R 33 Each of the following is independently selected from H, SH, OH, NH2, halogen, unsubstituted or substituted C1-C4 alkyl, unsubstituted or substituted 5- to 6-membered heteroaryl or 6- to 10-membered aryl, unsubstituted or substituted 3- to 6-membered cycloalkyl or heterocycloalkyl, amide or thioformamido; when the C1- to C4 alkyl, 5- to 6-membered heteroaryl, 6- to 10-membered aryl, 3- to 6-membered cycloalkyl or heterocycloalkyl is substituted, each of the substituents independently includes at least one of OH, NH2, halogen, C1- to C4 alkyl, 6- to 10-membered aryl, 3- to 6-membered cycloalkyl or heterocycloalkyl;

[0089] R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 Each is independently selected from any one of R, OR, C(=O)R, COOR, phenyl and halogen, wherein each of R is independently selected from any one of H and C1 to C4 alkyl groups.

[0090] The term "C1-C4 alkyl" in this application includes straight-chain alkyl or branched alkyl having 1 to 4 carbon atoms. Optionally, C1-C4 alkyl includes C1-C2 alkyl having 1 to 2 carbon atoms. Examples of C1-C4 alkyl include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, and tert-butyl.

[0091] In some embodiments of this application, in formula (I), R 11 R 12 R 21 R31 R 32 R 33 Each is independently selected from any one of H, SH, OH, NH2, phenyl, 4-hydroxyphenyl, furanyl, thiophene, pyrrolyl, thiazolyl, imidazolyl, pyridinyl, piperidinyl, pyrazinyl, pyrimidinyl, pyridazinyl, ethylene oxide, cyclothioethyl alkyl, cyclohexyl, benzyl, thiocarbamate, 1-pyrrolidine-2-yl-methyl, and C1 to C4 alkyl groups.

[0092] For example, the hydrophobic compound in this application may be the following:

[0093]

[0094]

[0095] In some embodiments of this application, the weight ratio of the hydrophobic compound to the hard carbon material in the composite hard carbon material is 0.1 to 5:100.

[0096] Optionally, in the composite hard carbon material, the weight ratio of hydrophobic compound to hard carbon material is 1.0 to 4.0:100. For example, the weight ratio of hydrophobic compound to hard carbon material is 1.5:100, 2.0:100, 2.5:100, 3.0:100, or 3.5:100.

[0097] By limiting the weight ratio range between the hydrophobic compound and the hard carbon material, the hydrophobic compound can enter the pores of the hard carbon material and occupy the pores to form a composite hard carbon material; the solvent in the subsequent negative electrode slurry, such as water molecules, cannot enter the pores of the composite hard carbon material, thereby effectively reducing the foaming of the negative electrode slurry.

[0098] In some embodiments of this application, the hydrophobic compound is fixed within the pores of the hard carbon material through π-π conjugation interactions and / or van der Waals interactions.

[0099] Hydrophobic compounds can be fixed in the pores of hard carbon materials through π-π conjugation and / or van der Waals interactions to form composite hard carbon materials. Even if the composite hard carbon material is used to form the negative electrode slurry, the hydrophobic compounds have already occupied the pores of the hard carbon material, thereby reducing the probability of solvents such as water molecules in the negative electrode slurry entering the pores of the composite hard carbon material, and thus reducing the foaming of the negative electrode slurry.

[0100] A second aspect of this application provides a method for preparing a composite hard carbon material, the method comprising:

[0101] After the hard carbon material and the hydrophobic compound are mixed evenly, they are placed into the reaction vessel;

[0102] A supercritical fluid is introduced into the reactor to allow the hard carbon material and the hydrophobic compound to react in the supercritical fluid to obtain a composite hard carbon material; wherein the hydrophobic compound is defined as the compound represented by formula (I) above.

[0103] The term "supercritical fluid" in this application refers to a state in which the temperature and pressure of a substance are simultaneously above the critical temperature and critical pressure. In this state, the properties of gases and liquids gradually become similar, eventually forming a homogeneous fluid. Supercritical fluids have properties that differ from those of gases and liquids, including but not limited to (1) the density of supercritical fluids is not much different from that of liquids, but the density of supercritical fluids is much greater than that of gases, which helps supercritical fluids dissolve and disperse media; (2) the viscosity of supercritical fluids is closer to that of gases, resulting in better fluidity; (3) the diffusion coefficient of supercritical fluids is between that of gases and liquids; and (4) supercritical fluids have low viscosity, high density, and low surface tension, resulting in good mass transfer performance.

[0104] The phrase "reaction of hard carbon materials and hydrophobic compounds in supercritical fluid" mentioned in this article refers to the reaction temperature and pressure conditions in the reactor meeting the temperature and pressure ranges required to form a supercritical fluid, thus allowing the hard carbon materials and hydrophobic compounds to react in the supercritical fluid.

[0105] This application treats hard carbon materials, causing them to react with hydrophobic compounds in a supercritical fluid to form a composite hard carbon material. The pores of this composite hard carbon material are filled with the hydrophobic compound. During the subsequent formation of the negative electrode slurry using this composite hard carbon material, solvents such as water molecules in the negative electrode slurry cannot enter the pores of the composite hard carbon material, thereby effectively reducing foaming of the negative electrode slurry and improving its stability. Here, the characteristics of supercritical carbon dioxide fluid are utilized to introduce the hydrophobic compound into the pores of the hard carbon material. Due to π-π conjugation interactions and / or van der Waals forces, the hydrophobic compound is fixed within the pores of the hard carbon material. During the preparation of the aqueous slurry, the combined effect of the hydrophobic compound and steric hindrance prevents water molecules from entering the pores of the hard carbon material, thus eliminating the possibility of air leakage.

[0106] In addition, the use of supercritical fluids to introduce hydrophobic compounds into the pores of hard carbon materials reduces the use of traditional solvents and lowers pollution levels.

[0107] In some embodiments, the hydrophobic compound and the hard carbon material are mixed uniformly in a weight ratio of 0.1 to 5:100. Exemplarily, the weight ratio of the hydrophobic compound and the hard carbon material is 1.0:100, 1.5:100, 2.0:100, 2.5:100, 3.0:100, 3.5:100, or 4.0:100.

[0108] By limiting the mixing weight ratio range between the hydrophobic compound and the hard carbon material, the hydrophobic compound can enter the pores of the hard carbon material and occupy the pores to form a composite hard carbon material; the solvent in the negative electrode slurry, such as water molecules, cannot enter the pores of the composite hard carbon material, thereby effectively reducing the foaming of the negative electrode slurry.

[0109] In some embodiments, the supercritical fluid is selected from supercritical carbon dioxide, supercritical nitric oxide, supercritical acetylene, supercritical trifluoromethane, supercritical chloroform, supercritical methane, supercritical ethane, supercritical propane, supercritical ethylene, supercritical propylene, supercritical methanol, supercritical ethanol, supercritical acetone, supercritical chlorofluorocarbon, or supercritical xenon. Optionally, the supercritical fluid is supercritical carbon dioxide.

[0110] For example, supercritical fluid can be supercritical carbon dioxide. The supercritical state of carbon dioxide is relatively easy to achieve, with a critical temperature of 304.2 K (i.e., 31.05 °C) and a critical pressure of 7.38 MPa. Supercritical carbon dioxide also possesses advantages such as chemical stability, non-toxicity, and low cost. In the process of treating hard carbon materials and hydrophobic compounds using supercritical carbon dioxide, the reaction temperature range is 35 °C to 100 °C, and the reaction pressure range is 8 MPa to 15 MPa. Optionally, the reaction temperature range is 38 °C to 90 °C. Optionally, the reaction temperature range is 40 °C to 80 °C. Optionally, the reaction pressure range is 9 MPa to 14 MPa. Optionally, the reaction pressure range is 9 MPa to 13 MPa.

[0111] It should be noted that hard carbon materials and hydrophobic compounds react in supercritical fluids to obtain composite hard carbon materials. Different types of supercritical fluids require different temperature and pressure conditions to achieve the supercritical state. Therefore, appropriate temperature and pressure conditions can be selected as the reaction temperature and pressure for preparing composite hard carbon materials, depending on the type of supercritical fluid chosen.

[0112] In some embodiments, the reaction time of the hard carbon material and the hydrophobic compound in the supercritical fluid is 2 to 10 hours. Optionally, the reaction time is 3 to 9 hours. Optionally, the reaction time can be 4 to 8 hours. For example, the reaction time can be 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, or 9 hours.

[0113] By limiting the reaction time of hard carbon materials and hydrophobic compounds in supercritical fluids, it is beneficial for the hard carbon materials and hydrophobic compounds to react fully, allowing the hydrophobic compounds to enter the pores of the hard carbon materials to form composite hard carbon materials.

[0114] A third aspect of this application provides a negative electrode slurry comprising a composite hard carbon material and a solvent from the first aspect of this application, and at least one of a conductive agent, a dispersant, and a binder.

[0115] Therefore, the negative electrode slurry provided in this application includes the composite hard carbon material in the above-mentioned technical solution. The pores of the composite hard carbon material contain hydrophobic compounds, which prevent solvents such as water molecules in the negative electrode slurry from entering the pores of the composite hard carbon material, thereby effectively reducing foaming of the negative electrode slurry and improving its stability. Even after being left for several days, the negative electrode slurry will not foam, and its viscosity remains stable.

[0116] In some embodiments, the content of the composite hard carbon material is 85 wt% to 97 wt%, based on the solid content in the negative electrode slurry; the content of the conductive agent is 0 to 5 wt%; the content of the dispersant is 0.5 wt% to 5 wt%; and the content of the binder is 0.5 wt% to 5 wt%.

[0117] Optionally, the content of the composite hard carbon material is 90% to 96%. Optionally, the content of the composite hard carbon material can be 90% to 93%.

[0118] Optionally, the content of the conductive agent is 0.5% to 4%. Optionally, the content of the conductive agent can be 1% to 2%.

[0119] Optionally, the content of the dispersant is 0.8% to 3%. Optionally, the content of the dispersant can be 1.5% to 2%.

[0120] Optionally, the adhesive content is 1.0% to 4%. Optionally, the adhesive content can be 2.4% to 3%.

[0121] In some embodiments, the solvent is water.

[0122] In some embodiments, the total solids content of the negative electrode slurry is 40 wt% to 65 wt% relative to the total weight of the negative electrode slurry.

[0123] Optionally, the total solids content of the negative electrode slurry can be 45% to 62%. Optionally, the total solids content of the negative electrode slurry can be 50% to 60%.

[0124] In some embodiments, the conductive agent is selected from at least one of carbon black, carbon nanotubes, and graphene;

[0125] And / or, the dispersant is selected from at least one of sodium carboxymethyl cellulose and lithium carboxymethyl cellulose;

[0126] And / or, the adhesive is selected from at least one of styrene-butadiene rubber, styrene-acrylic emulsion, and modified polyacrylic acid.

[0127] A fourth aspect of this application provides a negative electrode sheet, the negative electrode sheet comprising a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer comprising the composite hard carbon material of the first aspect of this application.

[0128] Negative electrode sheet

[0129] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including the composite hard carbon material of the first aspect of this application.

[0130] 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.

[0131] 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.).

[0132] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as composite hard carbon material, conductive agent, binder, dispersant and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0133] In addition, the secondary battery and power-consuming device of this application will be described below with appropriate reference to the accompanying drawings.

[0134] The fifth aspect of this application provides a secondary battery, the secondary battery including the negative electrode sheet of the fourth aspect of this application.

[0135] The term "secondary battery" used in this article refers to a single battery cell, a battery module, or a battery pack. These will be explained separately below.

[0136] Typically, a single secondary battery cell includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0137] Positive electrode sheet

[0138] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material.

[0139] 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.

[0140] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0141] In some embodiments, when the battery cell is a lithium-ion battery, the positive electrode active material may be a positive electrode active material known in the art for lithium-ion batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM)523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0142] In some embodiments, when the battery cell is a sodium-ion battery, the positive electrode active material can be any positive electrode active material known in the art for use in sodium-ion batteries. As examples, the positive electrode active material may include sodium transition metal oxides, polyanionic compounds (phosphates, fluorophosphates, pyrophosphates, sulfates), Prussian blue compounds, etc. 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.

[0143] As an optional technical solution in this application, the transition metal in the sodium transition metal oxide can be at least one selected from Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. For example, the sodium transition metal oxide is Na. x MO2, where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, and 0 < x ≤ 1. Examples include sodium-iron composite oxides (NaFeO2), sodium-cobalt composite oxides (NaCoO2), sodium-chromium composite oxides (NaCrO2), sodium-manganese composite oxides (NaMnO2), sodium-nickel composite oxides (NaNiO2), and sodium-nickel-titanium composite oxides (NaNiO2). 1 / 2 Ti 1 / 2 O2), sodium nickel manganese composite oxide (NaNi) 1 / 2 Mn 1 / 2 O2), sodium iron manganese composite oxide (Na) 2 / 3 Fe 1 / 3 Mn 2 / 3O2), sodium nickel cobalt manganese composite oxide (NaNi) 1 / 3 Co 1 / 3 Mn 1 / 3 O2).

[0144] As an optional technical solution in this application, the polyanionic compound can be a compound containing sodium ions, transition metal ions, or a tetrahedral (YO4) structure. n- A class of compounds with anionic units. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si; n represents (YO4). n- The price state.

[0145] Polyanionic compounds can also contain sodium ions, transition metal ions, or tetrahedral (YO4) ions. n- A class of compounds containing anionic units and halide anions. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si, and n represents (YO4). n- The valence state; the halogen can be at least one of F, Cl and Br.

[0146] Polyanionic compounds can also be sodium-containing tetrahedral (YO4) compounds. n- Anionic unit, polyhedral unit (ZO) y ) m+ And a class of compounds with optional halide anions. Y can be at least one of P, S, and Si, and n represents (YO4). n- The valence state; Z represents a transition metal, which can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; m represents (ZO) y ) m+ The valence state; the halogen can be at least one of F, Cl and Br.

[0147] Polyanionic compounds include, for example, NaFePO4, Na3V2(PO4)3, NaM'PO4F (where M' is one or more of V, Fe, Mn, and Ni) and Na3(VO y )2(PO4)2F 3-2y At least one of (0≤y≤1).

[0148] Prussian blue compounds can be a class of compounds containing sodium ions, transition metal ions, and cyanide ions (CN-). The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Examples of Prussian blue compounds include Na. a Meb Me' c (CN)6, wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co, and Zn, 0 <a≤2,0<b<1,0<c<1。

[0149] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0150] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0151] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0152] electrolytes

[0153] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0154] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0155] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0156] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0157] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0158] Separating membrane

[0159] In some embodiments, the battery cell also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0160] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0161] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0162] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0163] In some embodiments, the outer packaging of the battery cell can be a rigid 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 flexible package, such as a pouch. The material of the flexible package can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0164] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 The example shown is a square-structured battery cell 5.

[0165] In some implementations, refer to Figure 2 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 can be placed over the opening to close the receiving cavity. The positive electrode sheet, negative electrode sheet, and separator can be formed into an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0166] In some implementations, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0167] Figure 3 This is battery module 4, used as an example. (See reference...) Figure 3 In battery module 4, multiple battery cells 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 battery cells 5 can be fixed in place using fasteners.

[0168] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0169] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0170] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0171] In addition, this application also provides an electrical device, which includes the secondary battery provided in this application. The secondary battery can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as 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.

[0172] As an electrical device, you can choose individual battery cells, battery modules, or battery packs according to your usage requirements.

[0173] Figure 6 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0174] Another example 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.

[0175] Example

[0176] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0177] Preparation of hard carbon materials

[0178] Coconut shell / starch / lignin is pre-carbonized at 200°C to 300°C. The pre-carbonized coconut shell is then crushed into particles approximately 2 mm in diameter using a roller mill, and impurities are removed by sieving. The particles are then heat-treated at 400°C to 800°C, optionally with the introduction of halogen or hydrogen halide gas to remove ash, resulting in particles easily ball-milled. The particles are then ball-milled. The ball-milled particles are placed in an inert atmosphere and maintained at 1150°C to carbonize them. Optionally, acetylene gas can be introduced to perform vapor-phase carbon deposition on the ball-milled particles, thereby preparing hard carbon particles with irregular shapes.

[0179] Preparation of composite hard carbon materials

[0180] Example 1

[0181] Hard carbon material and hydrophobic compound 1 were mixed evenly and placed in a reaction vessel; the weight ratio of hydrophobic compound 1 to hard carbon material was 2:100; supercritical carbon dioxide was introduced into the reaction vessel to allow the hard carbon material and hydrophobic compound 1 to react in supercritical carbon dioxide to obtain a composite hard carbon material; the reaction temperature was 50℃, the reaction pressure was 8MPa, and the reaction time was 8h. The chemical formula of hydrophobic compound 1 is as follows:

[0182]

[0183] Examples 2 to 24

[0184] All other conditions were the same as in Example 1, except that hydrophobic compound 1 was replaced sequentially with hydrophobic compounds 2 through 24. The chemical formulas of hydrophobic compounds 2 through 24 are as follows:

[0185]

[0186]

[0187] Examples 25 to 26

[0188] All other conditions were the same as in Example 1, except that the weight ratios of hydrophobic compound 1 and hard carbon material were 0.1:100 and 5:100, respectively.

[0189] Comparative Example 1

[0190] The hard carbon material in Comparative Example 1 was prepared by the method described above without any further treatment. That is, the pores of this hard carbon material were not filled with hydrophobic compounds.

[0191] As shown in Table 1, composite hard carbon materials were prepared using hydrophobic compounds 1 to 24 in Examples 1 to 24, respectively. The X group and the substituents R1 to R2 on the benzene ring in each hydrophobic compound... 10 Please refer to Table 1.

[0192] Table 1

[0193]

[0194]

[0195] Preparation of negative electrode slurry

[0196] The composite hard carbon material, conductive carbon black, dispersant sodium carboxymethyl cellulose and binder styrene-acrylic emulsion from Example 1 were fully dispersed and stirred in water at a weight ratio of 95:1:1.2:2.8 to obtain a negative electrode slurry with a solid content of 55%.

[0197] Similarly, the composite hard carbon materials in Examples 2 to 26 and the hard carbon materials in Comparative Example 1 were used to replace the composite hard carbon materials in Example 1, respectively, to prepare the corresponding negative electrode slurries.

[0198] Testing of negative electrode slurry

[0199] (1) Testing of foaming properties of negative electrode slurry

[0200] Visually inspect whether the negative electrode slurry foams after thorough stirring and standing. For example, observe whether the volume of the slurry changes or whether it becomes spongy, and take photos to record the observations.

[0201] (2) Testing the viscosity stability of the negative electrode slurry

[0202] The viscosity of the negative electrode slurry was measured at room temperature (20–35°C) using a viscometer (model DVESLVTJ0, purchased from Brookfield). After thorough stirring, the negative electrode slurry was allowed to stand for 5 minutes, and its viscosity was tested every 2 hours for a total of 24 hours. Viscosity changes were observed, and a viscosity change rate ≤2000 mPa·s within 24 hours was considered stable.

[0203] Preparation of secondary batteries

[0204] (1) Preparation of positive electrode sheet

[0205] The positive electrode active material is sodium-nickel-manganese composite oxide (NaNi). 1 / 2 Mn 1 / 2 O2), conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are thoroughly mixed in an appropriate amount of N-methylpyrrolidone (NMP) at a weight ratio of 92:5:3 to form a uniform positive electrode slurry. The positive electrode slurry is coated onto a 13μm thick positive electrode current collector aluminum foil, dried at 100℃, and then pressed to obtain a positive electrode sheet.

[0206] (2) Preparation of negative electrode sheet

[0207] After the above negative electrode slurry is thoroughly stirred, it is allowed to stand for 24 hours, coated on both surfaces of the negative electrode current collector copper foil with a thickness of 8 μm, dried at 100°C, and then pressed to obtain the negative electrode sheet.

[0208] (3) Preparation of electrolyte

[0209] Equal volumes of ethylene carbonate (EC) and propylene carbonate (PC) were mixed uniformly to obtain an organic solvent. Then, NaPF6 was uniformly dissolved in the organic solvent to obtain an electrolyte, wherein the concentration of NaPF6 was 1 mol / L.

[0210] (4) Preparation of secondary batteries

[0211] Polyethylene film (PE) is used as the separator. The prepared positive electrode sheet, separator, and negative electrode sheet prepared using the composite hard carbon material in Examples 1 to 26 or the hard carbon material in Comparative Example 1 are stacked in sequence, with the separator placed between the positive and negative electrodes to provide isolation. The cells are then wound to obtain bare cells, tabs are welded on, and the bare cells are placed in outer packaging. The electrolyte is injected into the dried cells, and the cells are then encapsulated, left to stand, formed, shaped, and tested for capacity to obtain a secondary battery.

[0212] Porosity testing of hard carbon materials and composite hard carbon materials

[0213] The porosity of the hard carbon material was determined using a specific surface area and porosity analyzer, specifically a TriStar II 3020 instrument. The porosity of the hard carbon material in Comparative Example 1 was obtained, and the porosity of the composite hard carbon materials in Examples 1 to 26 was also tested.

[0214] Testing of secondary batteries

[0215] Cyclic performance testing

[0216] At 25℃, the secondary battery is charged to 4.0V at a constant current of 1 / 3C, then charged to 0.05C at a constant voltage of 4.2V. After resting for 5 minutes, it is discharged to 2.8V at 1 / 3C. The resulting capacity is recorded as the initial capacity C0. The above steps are repeated for the same battery, and the discharge capacity Cn of the battery after the nth cycle is recorded. The battery capacity retention rate after each cycle is Pn = Cn / C0 * 100%. The minimum n value corresponding to Pn ≤ 80% is taken as the cycle life of the secondary battery.

[0217] Table 2

[0218]

[0219]

[0220] As shown in Table 2, in Examples 1 to 26, hydrophobic compounds 1 to 26 were used to treat the hard carbon materials, respectively, to obtain composite hard carbon materials with pores filled with hydrophobic compounds. In Comparative Example 1, no hydrophobic compounds were used to treat the hard carbon materials, and the pores of the hard carbon materials were not filled with hydrophobic compounds. Compared with the porosity of the hard carbon materials in Comparative Example 1, in Examples 1 to 24, different hydrophobic compounds were filled into the pores of the hard carbon materials, and the weight ratio between the hydrophobic compounds and the hard carbon materials was the same, 2:100. As can be seen from the data in Table 1, the porosity of the composite hard carbon materials decreased after filling with hydrophobic compounds. Compared to the porosity of the hard carbon material in Comparative Example 1, in Examples 1, 25 and 26, after filling the pores of the hard carbon material with hydrophobic compound 1, the weight ratio between the hydrophobic compound and the hard carbon material was different, namely 2:100, 0.1:100 and 5:100 respectively. As can be seen from the data in Table 1, the porosity of the composite hard carbon material decreased after filling with hydrophobic compound.

[0221] Table 3

[0222]

[0223]

[0224] Table 3 also illustrates the foaming behavior of the negative electrode slurry prepared using the composite hard carbon materials of Examples 1 to 26 and the negative electrode slurry prepared using the hard carbon material of Comparative Example 1. The negative electrode slurries prepared using the composite hard carbon materials of Examples 1 to 26 can be left to stand for 6 or 7 days without foaming. However, the negative electrode slurry prepared using the hard carbon material of Comparative Example 1 foams after only 12 hours.

[0225] Figure 7 The image shows the state of the negative electrode slurry obtained from the preparation of the composite hard carbon material in Example 1 after thorough stirring. For example... Figure 7 As shown in Figure (a), the negative electrode slurry was prepared using the composite hard carbon material in Example 1. After stirring, the negative electrode slurry was a homogeneous slurry system; Figure 7 As shown in Figure (b), after the negative electrode slurry was left to stand for 7 days, the negative electrode slurry still remained a homogeneous slurry system.

[0226] like Figure 8 As shown in Figure (a), the negative electrode slurry was prepared using the hard carbon material in Comparative Example 1. After stirring, the negative electrode slurry was a homogeneous slurry system; Figure 8 As shown in Figure (b), after the negative electrode slurry was left to stand for only 12 hours, the negative electrode slurry foamed and became a non-uniform slurry system.

[0227] As shown in Table 3, the negative electrode slurry formed by the composite hard carbon materials provided in Examples 1 to 26 remained a uniform slurry system after 24 hours of storage. Therefore, the viscosity fluctuation after 24 hours was ≤2000 mPa·s. The negative electrode slurry formed by the hard carbon material provided in Comparative Example 1 foamed after 12 hours of storage, becoming a non-uniform slurry system. Therefore, the viscosity fluctuation after 24 hours was >10000 mPa·s.

[0228] As shown in Table 3, the cycle performance of the secondary batteries formed with the composite hard carbon materials provided in Examples 1 to 26 is significantly better than that of the secondary batteries formed with the hard carbon materials provided in Comparative Example 1. This is because the negative electrode slurry formed with the composite hard carbon materials foams, becoming a non-uniform slurry system, resulting in poor uniformity and high weight loss of the negative electrode sheet formed by coating and cold pressing, ultimately leading to a deterioration in the cycle performance of the secondary battery.

[0229] 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 composite hard carbon material, characterized in that, The composite hard carbon material comprises: a hard carbon material and a hydrophobic compound filling the pores of the hard carbon material, wherein the hydrophobic compound is a compound represented by the following formula (I): ； In the formula (I), X is O, S, C=O, CR 11 R 12 , NR 21 , PR 31 , P(=O)R 32 or P(=S)R 33 ; Among them, R 11 R 12 R 21 R 31 R 32 R 33 Each of the following is independently selected from H, SH, OH, NH2, halogen, unsubstituted or substituted C1-C10 alkyl, unsubstituted or substituted 5- to 10-membered heteroaryl or 6- to 10-membered aryl, unsubstituted or substituted 3- to 8-membered cycloalkyl or heterocycloalkyl, amide or thioformamido; when the C1- to C10 alkyl, 5- to 10-membered heteroaryl, 6- to 10-membered aryl, 3- to 8-membered cycloalkyl or heterocycloalkyl is substituted, their substituents each independently include at least one of OH, NH2, halogen, C1- to C10 alkyl, 6- to 10-membered aryl, 3- to 8-membered cycloalkyl or heterocycloalkyl; R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 Each is independently selected from any one of R, OR, C(=O)R, COOR, 6-membered to 10-membered aryl and halogen, wherein each of R is independently selected from any one of H and C1 to C10 alkyl.

2. The composite hard carbon material according to claim 1, characterized in that, In the above formula (I), R 11 R 12 R 21 R 31 R 32 R 33 Each of the following is independently selected from H, SH, OH, NH2, halogen, unsubstituted or substituted C1-C4 alkyl, unsubstituted or substituted 5- to 6-membered heteroaryl or 6- to 10-membered aryl, unsubstituted or substituted 3- to 6-membered cycloalkyl or heterocycloalkyl, amide or thioformamido; when the C1- to C4 alkyl, 5- to 6-membered heteroaryl, 6- to 10-membered aryl, 3- to 6-membered cycloalkyl or heterocycloalkyl is substituted, their substituents each independently include at least one of OH, NH2, halogen, C1- to C4 alkyl, 6- to 10-membered aryl, 3- to 6-membered cycloalkyl or heterocycloalkyl; R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 Each is independently selected from any one of R, OR, C(=O)R, COOR, phenyl and halogen, wherein each of R is independently selected from any one of H and C1~C4 alkyl.

3. The composite hard carbon material according to claim 1, characterized in that, In the above formula (I), R 11 R 12 R 21 R 31 R 32 R 33 Each is independently selected from any one of H, SH, OH, NH2, phenyl, 4-hydroxyphenyl, furanyl, thiophene, pyrrolyl, thiazolyl, imidazolyl, pyridinyl, piperidinyl, pyrazinyl, pyrimidinyl, pyridazinyl, ethylene oxide, cyclothioethyl alkyl, cyclohexyl, benzyl, thiocarbamate, 1-pyrrolidine-2-yl-methyl, and C1-C4 alkyl.

4. The composite hard carbon material according to any one of claims 1 to 3, characterized in that, The hydrophobic compound is selected from at least one of the following compounds: 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 。 5. The composite hard carbon material according to any one of claims 1 to 3, characterized in that, In the composite hard carbon material, the weight ratio of the hydrophobic compound to the hard carbon material is 0.1~5:

100.

6. The composite hard carbon material according to any one of claims 1 to 3, characterized in that, The hydrophobic compound is fixed within the pores of the hard carbon material through π-π conjugation interactions and / or van der Waals forces.

7. A method for preparing a composite hard carbon material, characterized in that, The method includes: After the hard carbon material and the hydrophobic compound are mixed evenly, they are placed into the reaction vessel; A supercritical fluid is introduced into the reactor to allow the hard carbon material and the hydrophobic compound to react in the supercritical fluid in order to obtain a composite hard carbon material. Wherein, the hydrophobic compound is a compound represented by the following formula (I): ； In the above formula (I), X represents O, S, C=O, and CR. 11 R 12 NR 21 PR 31 P(=O)R 32 Or P(=S)R 33 ; Among them, R 11 R 12 R 21 R 31 R 32 R 33 Each of the following is independently selected from H, SH, OH, NH2, halogen, unsubstituted or substituted C1-C10 alkyl, unsubstituted or substituted 5- to 10-membered heteroaryl or 6- to 10-membered aryl, unsubstituted or substituted 3- to 8-membered cycloalkyl or heterocycloalkyl, amide or thioformamido; when the C1- to C10 alkyl, 5- to 10-membered heteroaryl, 6- to 10-membered aryl, 3- to 8-membered cycloalkyl or heterocycloalkyl is substituted, their substituents each independently include at least one of OH, NH2, halogen, C1- to C10 alkyl, 6- to 10-membered aryl, 3- to 8-membered cycloalkyl or heterocycloalkyl; R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 Each is independently selected from any one of R, OR, C(=O)R, COOR, 6-membered to 10-membered aryl and halogen, wherein each of R is independently selected from any one of H and C1 to C10 alkyl.

8. The preparation method according to claim 7, characterized in that, In the above formula (I), R 11 R 12 R 21 R 31 R 32 R 33 Each of the following is independently selected from H, SH, OH, NH2, halogen, unsubstituted or substituted C1-C4 alkyl, unsubstituted or substituted 5- to 6-membered heteroaryl or 6- to 10-membered aryl, unsubstituted or substituted 3- to 6-membered cycloalkyl or heterocycloalkyl, amide or thioformamido; when the C1- to C4 alkyl, 5- to 6-membered heteroaryl, 6- to 10-membered aryl, 3- to 6-membered cycloalkyl or heterocycloalkyl is substituted, their substituents each independently include at least one of OH, NH2, halogen, C1- to C4 alkyl, 6- to 10-membered aryl, 3- to 6-membered cycloalkyl or heterocycloalkyl; R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 Each is independently selected from any one of R, OR, C(=O)R, COOR, phenyl and halogen, wherein each of R is independently selected from any one of H and C1~C4 alkyl.

9. The preparation method according to claim 7, characterized in that, In the above formula (I), R 11 R 12 R 21 R 31 R 32 R 33 Each is independently selected from any one of H, SH, OH, NH2, phenyl, 4-hydroxyphenyl, furanyl, thiophene, pyrrolyl, thiazolyl, imidazolyl, pyridinyl, piperidinyl, pyrazinyl, pyrimidinyl, pyridazinyl, ethylene oxide, cyclothioethyl alkyl, cyclohexyl, benzyl, thiocarbamate, 1-pyrrolidine-2-yl-methyl, and C1-C4 alkyl.

10. The preparation method according to any one of claims 7 to 9, characterized in that, The hydrophobic compound is selected from at least one of the following compounds: 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 。 11. The preparation method according to any one of claims 7 to 9, characterized in that, The hydrophobic compound and the hard carbon material are mixed evenly in a weight ratio of 0.1~5:

100.

12. The preparation method according to any one of claims 7 to 9, characterized in that, The supercritical fluid is selected from supercritical carbon dioxide, supercritical nitric oxide, supercritical acetylene, supercritical trifluoromethane, supercritical chloroform, supercritical methane, supercritical ethane, supercritical propane, supercritical ethylene, supercritical propylene, supercritical methanol, supercritical ethanol, supercritical acetone, supercritical chlorofluorocarbon, or supercritical xenon.

13. The preparation method according to any one of claims 7 to 9, characterized in that, The reaction time of the hard carbon material and the hydrophobic compound in the supercritical fluid is 2 to 10 hours.

14. A negative electrode slurry, characterized in that, The negative electrode slurry comprises the composite hard carbon material and solvent as described in any one of claims 1 to 6, and at least one of a conductive agent, a dispersant, and a binder.

15. The negative electrode slurry according to claim 14, characterized in that, Based on the solid content in the negative electrode slurry, the content of the composite hard carbon material is 85wt% to 97wt%; the content of the conductive agent is 0wt% to 5wt%; the content of the dispersant is 0.5wt% to 5wt%; and the content of the binder is 0.5wt% to 5wt%.

16. The negative electrode slurry according to claim 14, characterized in that, The solvent is water.

17. The negative electrode slurry according to any one of claims 14 to 16, characterized in that, The total solids content of the negative electrode slurry is 40 wt% to 65 wt% relative to the total weight of the negative electrode slurry.

18. The negative electrode slurry according to any one of claims 14 to 16, characterized in that, The conductive agent is selected from at least one of carbon black, carbon nanotubes, and graphene; And / or, the dispersant is selected from at least one of sodium carboxymethyl cellulose and lithium carboxymethyl cellulose; And / or, the adhesive is selected from at least one of styrene-butadiene rubber, styrene-acrylic emulsion, and modified polyacrylic acid.

19. A negative electrode sheet, characterized in that, The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, wherein the negative electrode film layer includes the composite hard carbon material according to any one of claims 1 to 6.

20. A secondary battery, characterized in that, The secondary battery includes the negative electrode sheet as described in claim 19.

21. An electrical appliance, characterized in that, The electrical device includes the secondary battery as described in claim 20.

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