Hard carbon material, secondary battery, and electric device

Abstract

The application provides a hard carbon material, a secondary battery and an electric device, to improve the first coulomb efficiency and energy density of the secondary battery by providing a high gravimetric capacity hard carbon material. The hard carbon material comprises: a spheroid with an irregular surface; wherein 0≤a / D≤0.5, 0.04≤b / D≤0.55, a is the depth of the irregular surface, b is the length of a line segment with endpoints on the edges of the vertical projection of the irregular surface, passing through the geometric center of the vertical projection, and perpendicular to the longest line segment on the vertical projection, the longest line segment on the vertical projection is the longest line segment with endpoints on the edges of the vertical projection and passing through the geometric center of the vertical projection, and D is the length of the longest line segment with endpoints on the surface of the spheroid and passing through the geometric center of the spheroid.

Description

Technical Field

[0001] This application relates to the field of secondary battery technology, and more particularly to a hard carbon material, a secondary battery, and an electrical device. Background Technology

[0002] Secondary batteries are widely used due to their advantages such as high energy density, low self-discharge rate, and excellent cycle performance. Graphite is a common anode material in secondary batteries; however, its application is limited because it can only be used in lithium-ion batteries and not directly in sodium-ion batteries. Hard carbon materials, on the other hand, can be used as anode materials in both lithium-ion and sodium-ion batteries, thus possessing broader application prospects. However, the specific capacity of current hard carbon materials still needs improvement. Summary of the Invention

[0003] This application provides a hard carbon material, a secondary battery, and an electrical device, which improves the initial coulombic efficiency and energy density of the secondary battery by providing a high-specific-capacity hard carbon material.

[0004] In a first aspect, embodiments of this application provide a hard carbon material, the hard carbon material comprising: a spherical shape with irregular surfaces; wherein, 0 ≤ a / D ≤ 0.5, 0.04 ≤ b / D ≤ 0.55,

[0005] 'a' represents the depth of the irregular surface, and 'b' represents the length of a line segment whose endpoint is located at the edge of the vertical projection of the irregular surface, passes through the geometric center of the vertical projection, and is perpendicular to the longest line segment on the vertical projection. The longest line segment on the vertical projection is the longest line segment whose endpoint is located at the edge of the vertical projection and passes through the geometric center of the vertical projection.

[0006] D is the length of the longest line segment whose endpoint is located on the surface of the sphere-like object and passes through the geometric center of the sphere-like object.

[0007] In one embodiment, b ≥ 1.41 μm.

[0008] In one embodiment, b ≥ 2.41 μm.

[0009] In one embodiment, b ≥ 3.76 μm.

[0010] In one embodiment, b < 10 μm.

[0011] In one embodiment, the hard carbon material is a spherical shape with irregular surfaces.

[0012] In one embodiment, 0 ≤ a / b ≤ 3.75.

[0013] In one embodiment, the hard carbon material satisfies at least one of the following conditions:

[0014] (1) 0.13 ≤ a / D ≤ 0.47;

[0015] (2) b / D ≥ 0.08;

[0016] (3) 0.39 ≤ a / b ≤ 2.35.

[0017] In one embodiment, 0.13 ≤ a / D ≤ 0.47.

[0018] In one embodiment, b / D ≥ 0.08.

[0019] In one embodiment, 0.39 ≤ a / b ≤ 2.35.

[0020] In one embodiment, 0.13 ≤ a / D ≤ 0.47, b / D ≥ 0.08, 0.39 ≤ a / b ≤ 2.35.

[0021] In one embodiment, in the SEM image at a magnification of 5000X, in at least one region of (20 ± 0.1) μm × (20 ± 0.1) μm, c / N ≥ 0.3; c is the number of the spheroid-like bodies having the irregular surface in the region, and N is the number of the particles of the hard carbon material in the region.

[0022] In one embodiment, in the SEM image at a magnification of 5000X, in at least one region of (20 ± 0.1) μm × (20 ± 0.1) μm, 0.8 < n / N < 5.1, n is the total number of the irregular surfaces in the region, and N is the number of the particles of the hard carbon material in the region.

[0023] In one embodiment, the tap density of the hard carbon material is 0.88~1.12 g / cm , , 3 ,

[0026] ,

[0027] .

[0024] In one embodiment, D v 50 is 1.6~18.0 μm, D v 90 is 4.2~35.0 μm.

[0025] In one embodiment, the tap density of the hard carbon material is 0.90~1.02 g / cm 3 .

[0026] Second, an embodiment of the present application provides a secondary battery, including a positive electrode sheet, a negative electrode sheet, and an electrolyte. The negative electrode sheet includes a current collector and a negative electrode material attached to at least one surface of the current collector. Among them,

[0027] The negative electrode material includes the hard carbon material described in the first aspect and any possible embodiment.

[0028] Thirdly, embodiments of this application provide an electrical appliance, including:

[0029] The secondary battery described in the second aspect.

[0030] The one or more technical solutions provided in the embodiments of this application have at least the following beneficial effects:

[0031] This application embodiment utilizes the properties of hard carbon materials with irregularly shaped, spherical surfaces, satisfying 0 ≤ a / D ≤ 0.5 and 0.04 ≤ b / D ≤ 0.55, to increase the surface area of ​​the hard carbon material. This enhances its effectiveness as a secondary battery anode material, increasing the activity of ions (e.g., Li). + Na + The increased contact probability between active ions and hard carbon materials promotes the storage of active ions in hard carbon materials, thereby increasing the specific capacity of hard carbon materials.

[0032] Other features and advantages of this application will be set forth in the following description and will be apparent in part from the description or may be learned by practicing the application. The purposes and other advantages of this application may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings. It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not intended to limit this disclosure. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0034] Figure 1A This is a structural schematic diagram of a hard carbon material provided in an embodiment of this application;

[0035] Figure 1B A schematic diagram of an irregular surface of a hard carbon material provided in an embodiment of this application;

[0036] Figure 2 This is a SEM schematic diagram of a hard carbon material provided in an embodiment of this application. Detailed Implementation

[0037] To address the problem of low specific capacity in current hard carbon materials, this application provides a hard carbon material comprising a spheroid with an irregular surface. In the spheroid with an irregular surface, the ratio a / D of the depth 'a' of the irregular surface to the length 'D' of the longest line segment connecting two points on the surface of the spheroid and passing through its geometric center satisfies: 0 ≤ a / D ≤ 0.5.

[0038] Furthermore, the length b of the line segment whose endpoint is located at the edge of the vertical projection of the irregular surface, passes through the geometric center of the vertical projection, and is perpendicular to the longest line segment on the vertical projection, is in the ratio of the length b to the aforementioned D, b / D, which satisfies: 0.04≤b / D≤0.55.

[0039] It is evident that this hard carbon material has the advantage of a large particle surface area. Therefore, when it is applied in secondary batteries, this characteristic allows the hard carbon material to provide more contact sites for active ions (e.g., sodium ions, lithium ions), thereby increasing the specific capacity of the hard carbon material.

[0040] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with embodiments. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. The embodiments described herein are illustrative in nature and are used to provide a basic understanding of this application. The embodiments of this application should not be construed as limiting this application.

[0041] The terms "first" and "second" in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, rather than to describe a specific order.

[0042] For the sake of brevity, this article only discloses a few specific numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0043] In this description, unless otherwise stated, "above" and "below" include the stated number.

[0044] Unless otherwise stated, the terms used in this application have their common meanings as commonly understood by those skilled in the art. Unless otherwise stated, the values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application).

[0045] The list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another instance, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single component or multiple components. Item B may contain a single component or multiple components. Item C may contain a single component or multiple components.

[0046] This application first provides a hard carbon material, which includes a spheroid with irregular surfaces. The spheroid with irregular surfaces has the following geometric features, please refer to... Figure 1A-1B :

[0047] 0≤a / D≤0.5, 0.04≤b / D≤0.55.

[0048] Where 'a' represents the depth of the aforementioned irregular surface, in μm.

[0049] b is the length of the line segment whose endpoint lies on the edge of the vertical projection of the irregular surface, passes through the geometric center of the vertical projection, and is perpendicular to the first longest line segment on the vertical projection. Please refer to [reference needed]. Figure 1B , Unit: μm.

[0050] The longest line segment in the vertical projection is the longest line segment whose endpoint is located at the edge of the vertical projection and passes through the geometric center of the vertical projection. The dimensional parameters of the vertical projection and the edge contour of the irregular surface are equal.

[0051] D is the length of the longest line segment whose endpoint is located on the surface of the sphere-like object and passes through the geometric center of the sphere-like object, in μm.

[0052] The surface of particles of the same hard carbon material may include one or more irregular surfaces; please refer to [reference needed]. Figure 2 .

[0053] The aforementioned irregular surfaces may include curved surfaces and / or planes.

[0054] Among them, irregular surfaces, including curved surfaces, are surfaces with curvatures that differ from those of most parts of the spherical surface; specifically, they can be concave or convex surfaces.

[0055] A plane can be one or more surfaces extending in different directions. For example, it can form outwardly protruding angular surfaces or inwardly concave angular surfaces.

[0056] In the aforementioned irregular surface of the spheroidal particle, b ≥ 1.41 μm. Therefore, when the irregular surface of the spheroidal particle satisfies b ≥ 1.41 μm, the specific capacity of the hard carbon particles can be further improved. For example, the value of b can be 1.41, 1.91, 2.41, 2.90, 2.97, 3.20, 3.50, 3.70, 3.90, 4.10, 4.20, 4.50, 4.90, 5.30, 5.80, 6.20, 6.70, 7.20, 7.80, 8.20, 8.60, 9.00, 9.50, 9.99, or a range consisting of any two of these values. Preferably, b ≥ 2.41 μm. Or preferably, b ≥ 3.76 μm.

[0057] In one embodiment, b < 10 μm.

[0058] Furthermore, all of the aforementioned hard carbon materials are spherical or irregularly shaped.

[0059] The aforementioned hard carbon material can be primary particles. These primary particles may include spheroids with irregular surfaces, as well as ellipsoids and / or spheres. Alternatively, all primary particles may be spheroids with irregular surfaces.

[0060] Accordingly, when the hard carbon material is a secondary particle, the secondary particle may include a spheroid with irregular surfaces, as well as an ellipsoid and / or a sphere. Alternatively, all the secondary particles may be spheroids with irregular surfaces.

[0061] For example, the ratio a / D of the depth 'a' of the irregular surface to the length 'D' of the longest line segment connecting two points on the surface of the sphere and passing through its geometric center can be 0.00, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, or a range of any two of these values.

[0062] The value of the ratio b / D can be 0.04, 0.09, 0.14, 0.19, 0.24, 0.27, 0.33, 0.39, 0.44, 0.49, 0.55, or a range of any two of these values.

[0063] To further improve the specific capacity of hard carbon materials, in one embodiment, 0.13 ≤ a / D ≤ 0.47, b / D ≥ 0.08. Exemplarily, the value of a / D can be 0.13, 0.16, 0.19, 0.22, 0.24, 0.26, 0.28, 0.29, 0.32, 0.35, 0.38, 0.41, 0.44, 0.47, or a range consisting of any two of these values.

[0064] For example, the value of b / D can be 0.08, 0.10, 0.12, 0.14, 0.20, 0.22, 0.24, 0.28, 0.30, 0.33, 0.36, 0.40, 0.43, 0.46, 0.50, 0.52, 0.55, or a range of any two of these values.

[0065] In one embodiment, D is 1.68~47.00 μm. Preferably, D ≥ 8.48 μm. Exemplarily, the value of D can be 8.48, 9.50, 10.50, 11.50, 12.50, 13.50, 14.50, 15.50, 16.50, 17.50, 18.50, 19.50, 20.50, 21.50, 22.50, 23.50, 24.50, 25.00, 26.00, 30.00, 33.00, 36.00, 43.00, 47.00, or a range of any two of these values.

[0066] In one embodiment, a ≤ 16.92 μm. Preferably, a ≥ 0.80 μm. Exemplarily, the value of a can be 0.80, 0.90, 1.00, 1.20, 1.40, 2.00, 3.00, 4.00, 5.00, 6.00, 7.00, 8.00, 9.00, 10.00, 11.00, 12.00, 13.00, 14.00, 15.00, 16.00, 16.92, or a range of any two of these values.

[0067] In one embodiment, in the aforementioned irregular surface spherical body, the ratio of the depth 'a' of the irregular surface to the length 'b' of the line segment whose endpoint is located at the edge of the vertical projection of the irregular surface, passes through the geometric center of the vertical projection, and is perpendicular to the longest line segment on the vertical projection satisfies the following condition: 0 ≤ a / b ≤ 3.75.

[0068] For example, the value of a / b can be 0.00, 0.40, 1.00, 1.50, 2.00, 2.50, 3.00, 3.50, 3.75 or a range of any two of these values.

[0069] To further improve the specific capacity of the hard carbon material, in one embodiment, 0.39 ≤ a / b ≤ 2.35. Exemplarily, the value of a / b can be 0.39, 0.41, 0.45, 0.49, 0.54, 0.59, 0.64, 0.69, 0.74, 0.77, 0.81, 0.82, 0.83, 0.88, 0.94, 0.99, 1.05, 1.08, 1.13, 1.18, 1.23, 1.28, 1.38, 1.40, 1.90, 2.10, 2.15, 2.25, 2.35 or the range composed of any two of these values.

[0070] In one embodiment, in the SEM image at a magnification of 5000X, there is at least one region of (20 ± 0.1) μm × (20 ± 0.1) μm that satisfies: c / N ≥ 0.3; c is the number of spheroids with irregular surfaces in this region, and N is the number of hard carbon material particles in the region.

[0071] Furthermore, in the SEM image at a magnification of 5000X, any region of (20 ± 0.1) μm × (20 ± 0.1) μm satisfies: c / N ≥ 0.3.

[0072] To avoid the problem that the hard carbon material is prone to breakage due to the large number of irregular surfaces on the particle surface, resulting in the easy extrusion of the edges (i.e., corners) of the irregular surfaces of adjacent particles, and further leading to a decrease in the strength of the electrode sheet. In one embodiment, in the SEM image at a magnification of 5000X, there is at least one region of (20 ± 0.1) μm × (20 ± 0.1) μm that satisfies: 0.8 < n / N < 5.1, where n is the total number of irregular surfaces of various spheroids in this region, and N is the number of hard carbon material particles in this region.

[0073] Furthermore, in the SEM image at a magnification of 5000X, any region of (20 ± 0.1) μm × (20 ± 0.1) μm satisfies: 0.8 < n / N < 5.1.

[0074] In one embodiment, the tap density of the above-mentioned hard carbon material is 0.88 - 1.12 g / cm 3 .

[0075] Exemplarily, the tap density of this hard carbon material can be 0.88 g / cm 3 , 0.89 g / cm 3 , 0.90 g / cm 3 , 0.91 g / cm 3 , 0.92 g / cm 3 , 0.93 g / cm 3 , 0.94 g / cm 3 , 0.95 g / cm3 0.96g / cm 3 0.97g / cm 3 0.98g / cm 3 0.99g / cm 3 1.00g / cm 3 1.01 g / cm 3 1.05g / cm 3 1.10 g / cm 3 1.12 g / cm 3 Or it can be the range formed by any two of these values.

[0076] In one embodiment, D v 50 ranges from 1.6 to 18.0 μm, D v 90 is 4.2~35.0μm.

[0077] Among them, D v 50 is the median particle size. D v 90 refers to the particle size that, in a volumetric particle size distribution, reaches 90% of the total volume of particles from the smallest particle size side. That is, the volume of the negative electrode active material smaller than this particle size accounts for 90% of the total volume of the negative electrode active material.

[0078] For example, D v 50 can be: 1.6μm, 2.0μm, 3.0μm, 4.0μm, 5.0μm, 6.0μm, 7.0μm, 8.0μm, 9.0μm, 10.0μm, 11.0μm, 12.0μm, 13.0μm, 14.0μm, 15.0μm, 18.0μm, or a range of any two values.

[0079] D v 90 can be 4.2μm, 5.0μm, 8μm, 11μm, 14μm, 17μm, 18μm, 19μm, 20μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, 27μm, 28μm, 29μm, 30μm, or a range of any two of these values.

[0080] In one embodiment, 2μm≤(D v 90-D v 50) ≤17μm. Preferably, (D v 90-D v 50) ≥10μm.

[0081] Based on the same inventive concept, this application also provides a method for preparing hard carbon material, which includes the following steps:

[0082] Step 201: Perform a solvothermal reaction on the hard carbon precursor to generate the first intermediate.

[0083] Specifically, the temperature conditions for the solvothermal reaction are 180~300℃; for example, it can be 60℃, 100℃, 140℃, 180℃, 250℃ or a range of any two of these values.

[0084] The time required for this solvothermal reaction is 12 to 24 hours.

[0085] The aforementioned hard carbon precursors include at least one of carbon-containing polymers, bituminous materials, biomass materials, and carbon derived from biomass materials.

[0086] In the aforementioned carbon-containing polymers, carbon forms the basic framework. These carbon-containing polymers include at least one of epoxy resin, phenolic resin, polysaccharide alcohol, polyvinyl alcohol, and polythiophene.

[0087] The aforementioned asphalt types may include at least one of petroleum asphalt, coal tar pitch, and natural asphalt.

[0088] The aforementioned biomass materials include at least one of glucose, fructose, sucrose, maltose, starch, and tannins.

[0089] The derived carbon of biomass materials includes at least one of polymer carbon, biomass carbon, and mesophase carbon microspheres.

[0090] Furthermore, the solvent used in the above-mentioned solvothermal reaction includes at least one of water, ethanol, isopropanol, benzene, ethylene glycol and hydrazine hydrate.

[0091] Step 202: Sinter the first intermediate material in an inert atmosphere to obtain a porous carbon material.

[0092] The inert atmosphere can be at least one of nitrogen, argon, and helium.

[0093] The sintering temperature can be 600~1000℃, and the time can be 2~15 hours.

[0094] Step 203: The porous carbon material is crushed to obtain hard carbon material.

[0095] The crushing process can be at least one of airflow crushing, mechanical crushing, or ball milling.

[0096] The preferred method is airflow fragmentation. The conditions for airflow fragmentation include: airflow pressure of 0.30~0.85MPa and time of 10~30min. The airflow velocity can be 9m / s. 3 / min, 10m 3 / min, 11m 3 / min, 12m 3 / min etc.

[0097] Based on the same inventive concept, embodiments of this application also provide a negative electrode sheet, which includes a current collector and a negative electrode material attached to at least one surface of the current collector. The negative electrode material includes the hard carbon material as described above.

[0098] Specifically, the current collector can be: aluminum foil, copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or a polymer substrate coated with a conductive metal. The conductive metal includes, but is not limited to, copper, nickel, or titanium. The polymer substrate components include, but are not limited to, at least one of polyethylene, polypropylene, ethylene-propylene copolymer, polyethylene terephthalate, polyethylene terephthalate, and poly(p-phenylene terephthalamide).

[0099] In one embodiment, the thickness of the negative electrode current collector is 4~12μm.

[0100] The thickness of the negative electrode material layer on any side surface of the negative electrode current collector is 30~130μm.

[0101] In one embodiment, the mass percentage of hard carbon material is 10% to 100% based on the negative electrode material.

[0102] The aforementioned negative electrode material also includes at least one of a thickener, a conductive agent, and a binder.

[0103] Thickeners can be, for example, sodium carboxymethyl cellulose.

[0104] The conductive agent may include, but is not limited to, carbon materials, metals, or conductive polymers. Carbon materials may include at least one of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon nanofibers, natural graphite, artificial graphite, flake graphite, carbon dots, and graphene. Metals may include at least one of copper, iron, aluminum, and other metal powders and fibers. Conductive polymers may include at least one of polythiophene, polypyrrole, polyaniline, and polyphenylenevinyl chloride.

[0105] The adhesive may include, but is not limited to, at least one of the following: polyacrylol, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, polyamide-imide, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinylpyrrolidone, polyethylene, polypropylene, epoxy resin, nylon, styrene-butadiene rubber (SBR), polyvinyl alcohol (PVA), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral, waterborne acrylic resin, carboxymethyl cellulose (CMC), and sodium carboxymethyl cellulose (CMC Na).

[0106] Based on the same inventive concept, embodiments of this application also provide a secondary battery, which includes the aforementioned negative electrode sheet.

[0107] The secondary battery also includes a positive electrode, a separator, and an electrolyte.

[0108] The separator can be, for example, polypropylene (PP) or polyethylene (PE).

[0109] The positive electrode includes a current collector and a positive electrode material disposed on the surface of the current collector on the side opposite to the negative electrode. The current collector can be aluminum foil, aluminum foam, aluminum composite current collector (i.e., a current collector with a polymer support layer in the middle and aluminum metal layers on both sides), nickel foil, or nickel foam.

[0110] In one embodiment, the secondary battery is a lithium-ion battery; then the positive electrode material is a lithium-ion positive electrode material, such as lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium cobalt oxide, lithium iron phosphate, lithium manganese oxide, Prussian blue, etc.

[0111] The aforementioned electrolyte includes lithium salts and non-aqueous solvents.

[0112] The lithium salt includes at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, Li2SiF6, C4BLiO8, LiBO2 and BF2H2LiO.

[0113] Non-aqueous solvents may include, but are not limited to, carbonate compounds, carboxylic acid ester compounds, ether compounds, or other organic solvents.

[0114] In one embodiment, the secondary battery is a sodium-ion battery. The positive electrode material could be, for example, Prussian white.

[0115] The electrolyte includes sodium salts and non-aqueous solvents. Sodium salts may include at least one of NaPF6, NaClO4, NaBCl4, NaSO3CF3, and Na(CH3)C6H4SO3.

[0116] Non-aqueous solvents include, but are not limited to, carbonate compounds, carboxylic acid ester compounds, ether compounds, or other organic solvents.

[0117] In one embodiment, the carboxylic acid ester compound in the above-mentioned non-aqueous solvent may include, but is not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolide, valproic acid lactone, and caprolactone.

[0118] In one embodiment, the ether compound in the above-mentioned non-aqueous solvent may include, but is not limited to, at least one of dibutyl ether, tetraethylene dimethyl ether, diethylene dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran, and tetrahydrofuran.

[0119] In one embodiment, the other organic solvents among the above-mentioned non-aqueous solvents may include, but are not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate.

[0120] In one embodiment, the carbonate compound in the non-aqueous solvent may include, but is not limited to, at least one of chain carbonate compounds, cyclic carbonate compounds, and fluorocarbonate compounds.

[0121] The aforementioned chain carbonate compounds may include, but are not limited to, at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), and methyl ethyl carbonate (MEC).

[0122] The aforementioned cyclic carbonates may include, but are not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), and vinyl ethylene carbonate (VEC).

[0123] Fluorocarbonate compounds may include, but are not limited to, at least one of fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, and trifluoromethylethylene carbonate.

[0124] Based on the same inventive concept, this application also provides an electrical device.

[0125] This electrical equipment includes, but is not limited to, laptops, pen-based computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors.

[0126] The following detailed description is provided through examples and comparative examples:

[0127] The following examples describe the disclosure of this invention in more detail. These examples are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of this disclosure. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized by conventional methods and can be used directly without further processing. The instruments used in the examples are also commercially available.

[0128] (a) Test methods and equipment

[0129] (1) Based on the SEM image, test the parameters of the spheroids with irregular surfaces in the hard carbon material.

[0130] In multiple SEM images of hard carbon particles taken at a magnification of 5000X, 10 hard carbon particles with complete morphology were randomly selected first.

[0131] Then, three-dimensional morphology images of hard carbon particles are fitted separately, and the geometric center of the hard carbon particles is determined in the three-dimensional morphology images. The length of the longest line segment whose endpoint is located on the surface of the three-dimensional morphology image and passes through its geometric center is measured as the first target value. The average value of the first target values ​​of the aforementioned 10 hard carbon particles is calculated to obtain D.

[0132] For the irregular surfaces of the aforementioned 10 hard carbon particles, measure b: Fit the vertical projection of each irregular surface of the hard carbon particle to determine the geometric center of the vertical projection; determine the longest line segment on the vertical projection whose endpoint is located at the edge of the vertical projection and which passes through the geometric center of the vertical projection; determine the length of the line segment whose endpoint is located at the edge of the vertical projection, passes through the geometric center of the vertical projection, and is perpendicular to the longest line segment on the vertical projection as the second target value; this second target value is the second target value of the irregular surface. Calculate the average of the second target values ​​for each irregular surface on the hard carbon particle to obtain b.

[0133] It should be noted that, in order to avoid the problem of excessive error in b caused by large vertical projection error when measuring the irregular surface of the side of hard carbon particles using the above method, the irregular surface with clear edges and located below the SEM imaging field of view (i.e. facing the SEM electron microscope lens) is selected when measuring b in this embodiment of the application.

[0134] Using image processing software, the depth of the irregular surface on the hard carbon particles was measured, and the average value was calculated to obtain 'a'. This depth can be measured as follows: First, a three-dimensional image of the irregular surface is fitted. The two points furthest apart on the edge of the irregular surface are determined, and one of these points is randomly selected as a reference point. A target point is then determined on the edge of the irregular surface, with the distance between the target point and the reference point being 1 / 4 of the perimeter of the edge of the irregular surface. A plane containing the edge of the irregular surface is fitted using the two furthest points and the target point. Next, in the three-dimensional image of the irregular surface, the point furthest from this plane is determined and denoted as the furthest point; the vertical distance between this furthest point and the plane is the depth.

[0135] Next, in the SEM image at a magnification of 5000X, select any three regions of (20±0.1)μm×(20±0.1)μm. Count the number of hard carbon particles in each region and calculate the average number of hard carbon particles in each of the three regions to obtain N.

[0136] Count the number of irregular surfaces in each region and calculate the average number of irregular surfaces in each of the three regions to obtain n.

[0137] (2) Test the compaction density of hard carbon materials

[0138] The compaction density test method is performed in accordance with GB / T 24533-2009 "Graphite Anode Materials for Lithium-ion Batteries".

[0139] Specifically, weigh 1.0000±0.0500g of hard carbon material as a test sample.

[0140] Then, the weighed hard carbon material was placed in the test mold model: CARVER#3619 (13mm), and then placed together with the test mold in the test equipment (model: Sansi Zongheng UTM7305) for testing.

[0141] The test involved a tonnage of 5.0 tons, a pressurization rate of 10 mm / min, a pressurization holding time of 30 s, a depressurization rate of 30 mm / min, and a depressurization holding time of 10 s.

[0142] The compaction density can then be measured during depressurization. This compaction density D is calculated using the following formula:

[0143] ;

[0144] Where m is the mass of the hard carbon material, S is the area of ​​the hard carbon material subjected to force during the test, and h is the thickness of the hard carbon material during the test.

[0145] (3) Test the particle size of hard carbon materials

[0146] The particle size testing method here refers to GB / T 19077-2016 "Particle size analysis by laser diffraction".

[0147] First, weigh 1g of the sample, mix it evenly with 20mL of deionized water and a trace dispersant, and then sonicate it in an ultrasonic device for 5 minutes.

[0148] Then, the sonicated solution was poured into the Hydro 2000SM sample introduction system for testing. The testing equipment used was the Mastersizer 3000 manufactured by Malvern Corporation.

[0149] The refractive index of the particles used in the test was 1.8. Each sample was tested three times, and the particle size test results (Dv10 and Dv90) were the average of the three test results.

[0150] (4) The electrochemical performance of hard carbon materials was tested by testing secondary batteries in which hard carbon materials were used as the negative electrode material.

[0151] ①Preparation of secondary batteries

[0152] Hard carbon anode material, styrene-butadiene rubber (SBR) binder, and sodium carboxymethyl cellulose (CMC) thickener were thoroughly mixed in deionized water at a mass ratio of 97:2:1 to form a negative electrode slurry with a solid content of 40 wt%. The negative electrode slurry was coated on both sides of the copper foil current collector, with a thickness of 60 micrometers on each side. After drying at 85°C, it was cold-pressed, cut, and slit, and then vacuum-dried at 120°C for 12 hours to obtain the negative electrode sheet.

[0153] Preparation of positive electrode sheet

[0154] D v 50 is a ternary material (LiNi) with a positive electrode active material of 10μm. 0.8 Co 0.1 Mn 0.1 O2), porous carbon additive, conductive agent Super P, and binder polyvinylidene fluoride (PVDF) are thoroughly mixed in N-methylpyrrolidone (NMP) solvent at a mass ratio of 96:1:1.4:1.6 to form a positive electrode slurry with a solid content of 72wt%.

[0155] The positive electrode material is coated onto the positive current collector aluminum foil, dried at 85°C, and then cold-pressed, cut, and slit before being dried under vacuum at 85°C for 4 hours to obtain the positive electrode sheet.

[0156] Preparation of electrolyte

[0157] In a dry argon-atmospheric glove box, ethylene carbonate (EC), propylene carbonate (PC), propyl propionate (PP), and ethyl propionate (EP) were mixed in a mass ratio of EC:PC:EP:PP = 25:10:25:40. Then, 1,3-propanesulfonyl lactone and fluoroethylene carbonate were added, dissolved, and thoroughly stirred. Lithium salt LiPF6 was then added and mixed evenly to obtain the electrolyte. The electrolyte contained 2.5% 1,3-propanesulfonyl lactone, 3.6% fluoroethylene carbonate, and 12.5% ​​LiPF6. All contents refer to the mass percentage in the electrolyte.

[0158] Preparation of the separating membrane

[0159] A 7μm thick porous polyethylene (PE) polymer film was used as the separator.

[0160] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. Then, the electrodes are wound, the tabs are welded, and the battery is placed in an outer packaging foil-aluminum-plastic film. Electrolyte is injected, and the battery undergoes vacuum sealing, settling, formation, and shaping processes to obtain a soft-pack lithium-ion battery.

[0161] ② Test specific capacity and initial coulombic efficiency

[0162] The negative electrode sheet was cut into a circular piece with a diameter of 14 mm to serve as the working electrode. A lithium sheet was used as the primary electrode, and a porous polyethylene membrane was used as the separator. After injecting electrolyte, the cells were assembled to form a button cell. The electrolyte consisted of a base solvent and a lithium salt. The base solvent was obtained by mixing ethylene carbonate (EC) and diethyl carbonate (DEC) in a 1:1 mass ratio. The lithium salt was LiPF6, and the lithium salt concentration was 1 mol / L.

[0163] The button cell battery was first discharged to 0V using three stages of small current: 0.05C, 0.01C, and 0.005C, and the initial discharge capacity was recorded. Then, it was charged to 2.5V using a constant current of 0.1C, and the initial charge capacity was recorded.

[0164] The mass of hard carbon material on the negative electrode is calculated based on the coating quality and area of ​​the slurry during electrode preparation. The initial coulombic efficiency is calculated using the following formula: Initial coulombic efficiency = (Initial charge capacity / Initial discharge capacity) × 100%.

[0165] The first reversible specific capacity of hard carbon material from 0V to 2.5V, i.e., the total specific capacity after lithium removal, Q = first charge capacity / mass of hard carbon material, in mAh / g.

[0166] Li / Li from 0V to 0.1V + The specific capacity of hard carbon materials within the potential range is denoted as Q1;

[0167] Li / Li from 0V to 0.8V + The specific capacity of hard carbon materials within the potential range is denoted as Q2.

[0168] ③ Test energy density (ED)

[0169] The soft-pack lithium-ion batteries corresponding to each embodiment and comparative example were charged to 4.48V at 0.2C under room temperature conditions, followed by constant voltage charging; then discharged to 2.0V at a constant current of 0.2C, which was recorded as one cycle. The discharge capacity D and discharge energy E of the first cycle were recorded. The length, width, and thickness of the cell were measured at 50% charge, and the cell volume V was calculated. The average discharge voltage U = E / D, and the volumetric energy density was calculated as: VED = (D × U) / V.

[0170] (II) Preparation

[0171] Example 1

[0172] S1. Dissolve 120g of glucose in 300mL of deionized water.

[0173] S2. Transfer the solution to a 500mL hydrothermal reactor and react at 180℃ for 12 hours. After the reaction is complete, cool, wash, and dry to obtain a dry powder.

[0174] S3. Keep the dry powder at 750℃ in an argon atmosphere for 2 hours, then cool it down to obtain carbonized powder.

[0175] S4. The carbonized powder is subjected to airflow abrasion to obtain hard carbon material. The airflow abrasion conditions are: airflow pressure of 0.8 MPa and airflow velocity of 10 m / s². 3 / min, processing time is 30min.

[0176] Example 2

[0177] The same steps and parameters as in Example 1 were used; the only difference was the airflow breaking conditions in step S4: the airflow pressure was 0.8 MPa and the airflow velocity was 10 m / s. 3 / min, processing time is 20min.

[0178] Example 3

[0179] The same steps and parameters as in Example 1 were used; the only difference was the airflow breaking conditions in step S4: the airflow pressure was 0.8 MPa and the airflow velocity was 10 m / s. 3 / min, processing time is 15min.

[0180] Example 4

[0181] The same steps and parameters as in Example 1 were used; the only difference was the airflow breaking conditions in step S4: the airflow pressure was 0.6 MPa and the airflow velocity was 10 m / s. 3 / min, processing time is 15min.

[0182] Example 5

[0183] The same steps and parameters as in Example 1 were used; the only difference was the airflow breaking conditions in step S4: the airflow pressure was 0.6 MPa and the airflow velocity was 10 m / s. 3 / min, processing time is 10min.

[0184] Example 6

[0185] The same steps and parameters as in Example 1 were used; the only difference was the airflow breaking conditions in step S4: the airflow pressure was 0.3 MPa and the airflow velocity was 10 m / s. 3 / min, processing time is 30min.

[0186] Example 7

[0187] The steps and parameters are the same as in Example 1; the difference is:

[0188] In S2, the reaction is carried out at 200°C for 24 hours in a hydrothermal reactor.

[0189] In S4, the airflow breaking conditions are: airflow pressure 0.3 MPa and airflow velocity 10 m / s². 3 / min, processing time is 20min.

[0190] Example 8

[0191] The steps and parameters are the same as in Example 1; the difference is:

[0192] In S2, the reaction is carried out at 250°C for 24 hours in a hydrothermal reactor.

[0193] In S4, the airflow breaking conditions are: airflow pressure 0.3 MPa and airflow velocity 10 m / s². 3 / min, processing time is 10min.

[0194] Example 9

[0195] The steps and parameters are the same as in Example 1; the difference is:

[0196] In step S3, the dry powder is kept at 1000℃ in an argon atmosphere for 2 hours, then cooled to obtain carbonized powder.

[0197] Example 10

[0198] The steps and parameters are the same as in Example 1; the difference is:

[0199] In step S3, the dry powder is kept at 600℃ in an argon atmosphere for 2 hours, then cooled to obtain carbonized powder.

[0200] Example 11

[0201] The steps and parameters are the same as in Example 1; the difference is:

[0202] In step S3, the dry powder is kept at 600℃ in an argon atmosphere for 1 hour, then cooled to obtain carbonized powder.

[0203] Example 12

[0204] The steps and parameters are the same as in Example 1; the difference is:

[0205] In step S3, the dry powder is kept at 600℃ in an argon atmosphere for 15 hours, then cooled to obtain carbonized powder.

[0206] Comparative Example 1

[0207] The steps and parameters are the same as in Example 1; the difference is:

[0208] In S4, the airflow breaking conditions are: airflow pressure 0.85 MPa and airflow velocity 20 m / s². 3 / min, processing time is 100min.

[0209] Comparative Example 2

[0210] The steps and parameters are the same as in Example 1; the difference is:

[0211] In S2, the reaction conditions in the hydrothermal reactor are set as follows: 300℃, reaction time 24 hours.

[0212] In S4, the airflow breaking conditions are: airflow pressure 0.2 MPa, airflow velocity 5 m / s². 3 / min, processing time is 5min.

[0213] For ease of reading, the main parameters in the above hard carbon material preparation process are summarized in Table 1 below. Where T1 is the reaction temperature in the hydrothermal reactor in S2, and t1 is the reaction time in the hydrothermal reactor in S2. T2 is the holding temperature in the argon atmosphere in S3, and t2 is the holding time in the argon atmosphere in S3. P is the gas flow breaking pressure in S4, v is the gas flow rate in S4, and t3 is the duration of the gas flow breaking treatment in S4.

[0214] Table 1

[0215]

[0216] The test results of the intrinsic properties of the hard carbon materials in the above embodiments and comparative examples are shown in Tables 2 to 3.

[0217] Table 2

[0218]

[0219] Table 3

[0220]

[0221] The test data of the electrochemical performance of the hard carbon materials in the above embodiments and comparative examples are shown in Table 4.

[0222] Table 4

[0223]

[0224] It is evident that when the irregularly shaped spheres in hard carbon materials satisfy the conditions 0 ≤ a / D ≤ 0.5 and 0.04 ≤ b / D ≤ 0.55, hard carbon materials exhibit high specific capacity; they also exhibit high initial coulombic efficiency and energy density.

[0225] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A hard carbon material, characterized in that, The hard carbon material includes: spheroids with irregular surfaces; where 0 ≤ a / D ≤ 0.5, 0.04 ≤ b / D ≤ 0.55, 0 ≤ a / b ≤ 3.75; 1.68μm≤D≤47.00μm, 0.00μm≤a≤16.92μm, 0.11μm≤b≤9.90μm, 2μm≤Dv50≤18μm, 4.2μm≤Dv90≤35μm, and 2μm≤D v 90-D v 50≤17μm, a is the depth of the irregular surface, b is the length of the line segment whose endpoint is located at the edge of the vertical projection of the irregular surface, passes through the geometric center of the vertical projection, and is perpendicular to the longest line segment on the vertical projection, the longest line segment on the vertical projection is the longest line segment whose endpoint is located at the edge of the vertical projection and passes through the geometric center of the vertical projection, and D is the length of the longest line segment whose endpoint is located on the surface of the spheroid and passes through the geometric center of the spheroid. The compaction density of the hard carbon material is 0.88~1.12 g / cm³. 3 The preparation process of the hard carbon material includes airflow agitation, wherein the airflow pressure of the airflow agitation is 0.30~0.85MPa and the duration of the airflow agitation is 10~30min.

2. The hard carbon material as described in claim 1, characterized in that, 2.41 μm ≤ b ≤ 9.90 μm.

3. The hard carbon material as described in claim 1, characterized in that, 3.76 μm ≤ b ≤ 9.90 μm.

4. The hard carbon material as described in claim 1, characterized in that, The hard carbon material satisfies at least one of the following conditions: (1) 0.13 ≤ a / D ≤ 0.47; (2) 0.08 ≤ b / D ≤ 0.55; (3) 0.39 ≤ a / b ≤ 2.

35.

5. The hard carbon material as described in claim 1, characterized in that, In an SEM image at a magnification of 5000 times, in at least one area of 20 ± 0.1 μm × 20 ± 0.1 μm, c / N ≥ 0.3; c is the number of the spheroids with the irregular surfaces in the area, and N is the number of the particles of the hard carbon material in the area.

6. The hard carbon material as described in claim 1, characterized in that, In an SEM image at a magnification of 5000 times, in at least one area of 20 ± 0.1 μm × 20 ± 0.1 μm, 0.8 < n / N < 5.1, n is the total number of the irregular surfaces in the area, and N is the number of the particles of the hard carbon material in the area.

7. The hard carbon material as described in claim 1, characterized in that, The compaction density of the hard carbon material is 0.90~1.02 g / cm³. 3 .

8. A secondary battery, characterized in that, It includes a positive electrode sheet, a negative electrode sheet, and an electrolyte. The negative electrode sheet includes a current collector and a negative electrode material attached to at least one surface of the current collector. Among them, the negative electrode material includes the hard carbon material according to any one of claims 1 to 7.

9. An electrical appliance, characterized in that, It includes: The secondary battery according to claim 8.

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