Graphite material and preparation method thereof, electrochemical device and electronic equipment

Abstract

The invention discloses a graphite material and a preparation method thereof, an electrochemical device and electronic equipment, and the graphite material meets the following conditions: (a) S is more than or equal to 8 and less than or equal to 13, and S is a structural stability parameter; (b) 1.1 < = L < = 1.8, L being a secondary particle coefficient; (c) 1.0 < = d < = 1.2, d being the particle size distribution width. The graphite material has dynamic performance and wide temperature range adaptability.

Description

Technical Field

[0001] This invention relates to a graphite material and its preparation method, an electrochemical device, and an electronic device. Background Technology

[0002] Microcrystalline graphite raw materials are inexpensive, costing about 20-30% of the price of natural flake graphite of the same quality. However, its impurity content is extremely high, and the cost of removing impurities is about 2-3 times that of natural flake graphite of the same quality. Considering all factors, its cost is not advantageous.

[0003] Existing impurity removal technologies, such as CN104556022B, expand microcrystalline graphite through acid-base and intercalation heat treatment. Although this can increase kinetics, it greatly deteriorates the material's tapping and initial efficiency, significantly increases the specific surface area, significantly reduces its processability, and is detrimental to its wide temperature range adaptability.

[0004] Therefore, a graphite material that combines dynamic performance and wide temperature range adaptability is needed. Summary of the Invention

[0005] This invention aims to overcome the shortcomings of existing graphite materials in possessing both kinetic properties and wide temperature range adaptability, and provides a graphite material, its preparation method, an electrochemical device, and an electronic device. This graphite material possesses both kinetic properties and wide temperature range adaptability.

[0006] In a first aspect, the present invention provides a graphite material that satisfies the following conditions:

[0007] (a) 8≤S≤13, where S is the structural stability parameter;

[0008] (b) 1.1≤L≤1.8, where L is the secondary particle size coefficient;

[0009] (c) 1.0≤d≤1.2, where d is the particle size distribution width.

[0010] Secondly, the present invention provides a method for preparing the graphite material as described above, comprising the following steps:

[0011] The mixture is carbonized to obtain a graphite material; the mixture includes a graphite intermediate and a carbon source; the preparation method of the graphite intermediate includes mixing a first graphite precursor and a second graphite precursor, wherein the first graphite precursor is obtained by carboxylation of a graphite matrix and the second graphite precursor is obtained by hydroxylation of a graphite matrix.

[0012] Thirdly, the present invention provides an electrochemical device comprising a negative electrode sheet, the negative electrode sheet comprising a negative electrode material layer and a negative electrode current collector, the negative electrode material layer comprising the graphite material as described above.

[0013] Fourthly, the present invention provides an electronic device comprising the electrochemical device as described above.

[0014] The reagents and raw materials used in this invention are all commercially available.

[0015] The positive and progressive effects of this invention are as follows:

[0016] This invention prepares a high-performance graphite material by mixing a carboxylated and hydroxylated graphite precursor with a carbon source. This graphite material has excellent first-time efficiency, cycle count, and storage days, as well as excellent charge / discharge capacity, low-temperature capacity retention, and fast-charging time. Detailed Implementation

[0017] Graphite materials

[0018] The graphite material provided in the first aspect of this invention satisfies the following conditions:

[0019] (a) 8≤S≤13, where S is the structural stability parameter;

[0020] (b) 1.1≤L≤1.8, where L is the secondary particle size coefficient;

[0021] (c) 1.0≤d≤1.2, where d is the particle size distribution width.

[0022] In this invention, the structural stability parameter S is the structural stability index of secondary particles of graphite material (defined as 100.0 for a single particle). The specific testing method is as follows: Referring to the national standard GB / T24533-2019, the graphite powder sample is pressed into a sheet. Before testing, it is held at a standard pressure of 2T for 20 seconds. After depressurization, a 10-minute interval is allowed, followed by a 20-second holding period at 5T. After a 10-minute depressurization interval, the formal operation begins. The 5T powder pressure is recorded as P0. Then, the graphite powder sample is tested at pressures of 5.5T, 6T, 6.5T, ..., 5+0.5nT, ... The pressures are recorded as P1, P2, P3, ..., Pn, ... When Pn / Pn-1 ≥ 1.05, this Pn is called the particle structure failure pressure, and the structural stability parameter S = 5+0.5n / 5 is recorded.

[0023] In this invention, the specific test method for the secondary particle size coefficient L is as follows: Referring to the national standard GB / T24533-2019, the powder sample of graphite material is pressed into a sheet. Before testing, it is held at a standard pressure of 2T for 20s. After depressurization, after an interval of 10 minutes, it is held at 5T for 20s. After depressurization, after an interval of 10 minutes, the formal operation begins. The 5T powder pressure is recorded as P0. Then, the powder sample of graphite material is tested with pressures of 5.5T, 6T, 6.5T, ..., 5+0.5nT, ... The pressures are recorded as P1, P2, P3, ..., Pn, ... When Pn / Pn-1≥1.05, this Pn is called the particle structure failure pressure. The powder sample of graphite material at Pn is collected for particle size testing to obtain Dv50 new. The particle size of the powder sample of graphite material before pressing into a sheet is tested and recorded as Dv50. The secondary particle size coefficient L is Dv50 new / Dv50. Secondary particles are composed of primary particles, and their size is larger than that of the primary particles. The ratio of the size of the secondary particles to that of the primary particles is called the secondary particle coefficient.

[0024] In this invention, the particle size distribution width d is calculated as follows: d = (Dv90 - Dv10) / Dv50; where Dv90, Dv10, and Dv50 are the Dv90, Dv10, and Dv50 particle sizes of the graphite material, respectively. The particle size distribution width reflects the degree of dispersion of the particle size distribution of the graphite material.

[0025] In some specific embodiments of the present invention, the structural stability parameter S of the graphite material is 10-12.

[0026] In some specific embodiments of the present invention, the structural stability parameter S of the graphite material is 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12 or 12.5.

[0027] In some specific embodiments of the present invention, the secondary particle coefficient L of the graphite material is 1.3-1.8, and optionally 1.4-1.7.

[0028] In some specific embodiments of the present invention, the secondary particle size coefficient L of the graphite material is 1.1, 1.3, 1.4, 1.5, 1.6 or 1.8.

[0029] In some specific embodiments of the present invention, the particle size distribution width d of the graphite material is 1-1.12.

[0030] In some specific embodiments of the present invention, the particle size distribution width d of the graphite material is 1.07, 1.08, 1.1, 1.11, 1.13, 1.14, 1.15, 1.17 or 1.19.

[0031] In some specific embodiments of the present invention, the Dv90 particle size of the graphite material is 9-12 μm.

[0032] In some specific embodiments of the present invention, the Dv90 particle size of the graphite material is 9.4μm, 9.7μm, 9.8μm, 10.5μm, 10.8μm, 10.9μm, 11.1μm, 11.2μm or 11.7μm.

[0033] In some specific embodiments of the present invention, the Dv10 particle size of the graphite material is 2.5-3.6 μm.

[0034] In some specific embodiments of the present invention, the Dv10 particle size of the graphite material is 2.3μm, 2.9μm, 3.1μm, 3.3μm, 3.5μm or 3.6μm.

[0035] In some specific embodiments of the present invention, the Dv50 particle size of the graphite material is 5-8 μm.

[0036] In some specific embodiments of the present invention, the Dv50 particle size of the graphite material is 5.5μm, 5.9μm, 6.2μm, 6.3μm, 6.5μm, 6.8μm, 7μm, 7.1μm or 7.9μm.

[0037] In certain specific embodiments of the present invention, the porosity of the graphite material is 0.008-0.012 cm⁻¹. 3 / g.

[0038] In some specific embodiments of the present invention, the porosity of the graphite material is 0.008 cm⁻¹. 3 / g, 0.009cm 3 / g, 0.01 cm 3 / g, 0.011 cm 3 / g or 0.012.

[0039] Preparation methods of graphite materials

[0040] The second aspect of the present invention provides a method for preparing graphite material, which includes the following steps:

[0041] The mixture is carbonized to obtain a graphite material; the mixture includes a graphite intermediate and a carbon source; the preparation method of the graphite intermediate includes mixing a first graphite precursor and a second graphite precursor, wherein the first graphite precursor is obtained by carboxylation of a graphite matrix and the second graphite precursor is obtained by hydroxylation of a graphite matrix.

[0042] In some specific embodiments of the present invention, the sphericity of the graphite intermediate is 0.87 or higher.

[0043] In some specific embodiments of the present invention, the sphericity of the graphite intermediate is 0.89.

[0044] In some specific embodiments of the present invention, the Dv50 particle size of the graphite intermediate is 6-7.5 μm.

[0045] In some specific embodiments of the present invention, the Dv50 particle size of the graphite intermediate is 5.1μm, 5.5μm, 5.7μm, 5.8μm, 6.0μm, 6.1μm, 6.3μm, 6.5μm, 6.8μm or 7.4μm.

[0046] In some specific embodiments of the present invention, the Dv10 particle size of the graphite intermediate is 1.8-4 μm.

[0047] In some specific embodiments of the present invention, the Dv10 particle size of the graphite intermediate is 1.8μm, 1.9μm, 2.0μm, 2.1μm, 2.3μm, 2.4μm, 2.5μm, 2.6μm, 2.9μm or 3.3μm.

[0048] In some specific embodiments of the present invention, the Dv90 particle size of the graphite intermediate is 10-14 μm.

[0049] In some specific embodiments of the present invention, the Dv90 particle size of the graphite intermediate is 7.1μm, 7.8μm, 8.0μm, 8.1μm, 8.2μm, 8.7μm, 8.9μm, 9.2μm, 9.6μm, 10.3μm or 11.4μm.

[0050] In some specific embodiments of the present invention, the particle size distribution width of the graphite intermediate is less than 1.1. The particle size distribution width is calculated as: d = (Dv90 - Dv10) / Dv50; where Dv90, Dv10, and Dv50 are the Dv90, Dv10, and Dv50 particle sizes of the graphite intermediate, respectively.

[0051] In some embodiments of the present invention, the particle size distribution width of the graphite intermediate is 1.03, 1.05, 1.06, 1.07, 1.09 or 1.1.

[0052] In some specific embodiments of the present invention, the Dv50 particle size of the mixture is 6.5-9 μm.

[0053] In some specific embodiments of the present invention, the Dv50 particle size of the mixture is 5-9 μm.

[0054] In some specific embodiments of the present invention, the Dv50 particle size of the mixture is 5.1, 5.5, 5.7, 5.8, 6, 6.3, 6.5, 6.8 or 7.4.

[0055] In certain specific embodiments of the present invention, the mass content of the carbon source in the mixture is 0.6%-1%. Here, % means the percentage of the mass of the carbon source relative to the mass of the mixture.

[0056] In certain specific embodiments of the present invention, the mass content of the first graphite precursor in the mixture is 45%-49.9%. Here, % represents the percentage of the mass of the first graphite precursor relative to the mass of the mixture.

[0057] In some specific embodiments of the present invention, the mass content of the first graphite precursor in the mixture is 49.5% or 49.7%.

[0058] In certain specific embodiments of the present invention, the mass content of the second graphite precursor in the mixture is 45%-49.9%. Here, % represents the percentage of the mass of the second graphite precursor relative to the mass of the mixture.

[0059] In some specific embodiments of the present invention, the mass content of the second graphite precursor in the mixture is 49.5% or 49.7%.

[0060] In some alternative embodiments of the present invention, the carboxylation step involves mixing the graphite precursor and the treatment agent used in the carboxylation process.

[0061] In some specific embodiments of the present invention, the processing agent used in the carboxylation treatment is a carboxyl-containing acid solution.

[0062] In some specific embodiments of the present invention, the carboxyl-containing acid solution is a trichloroacetic acid solution.

[0063] In some alternative embodiments of the present invention, the hydroxylation step involves mixing the graphite precursor and the treatment agent used in the hydroxylation process.

[0064] In some specific embodiments of the present invention, the treatment agent used in the hydroxylation treatment is an alkaline solution.

[0065] In some specific embodiments of the present invention, the alkaline solution is a sodium hydroxide solution.

[0066] In certain embodiments of the present invention, the carbon source is one or more of sucrose, glucose, and resin.

[0067] In some specific embodiments of the present invention, the carbon source is sucrose.

[0068] In some specific embodiments of the present invention, the carbon source is glucose.

[0069] In certain embodiments of the present invention, the residual carbon value of the carbon source is less than 1%. The residual carbon value refers to the percentage of the mass of carbon formed from the carbon source relative to the mass of carbon formed from the graphite intermediate in the final prepared graphite material.

[0070] In some specific embodiments of the present invention, the coking value of the carbon source is below 60%.

[0071] In some specific embodiments of the present invention, the coking value of the carbon source is 50%.

[0072] In some specific embodiments of the present invention, the carbonization time is 2-8 hours.

[0073] In some specific embodiments of the present invention, the carbonization time is 4 hours.

[0074] In certain specific embodiments of the present invention, the preparation method of the mixture includes: the preparation method of the graphite intermediate includes: mixing the first graphite precursor and the second graphite precursor and then subjecting them to micro-shaping and grading treatments in sequence to obtain the graphite intermediate; the micro-shaping time is 1-2.5h, and the grading treatment frequency is 30-70Hz.

[0075] In some specific embodiments of the present invention, the duration of the micro-plastic surgery is 1.5 hours or 2 hours.

[0076] In some specific embodiments of the present invention, the frequency of the graded processing is 40Hz or 60Hz.

[0077] In some specific embodiments of the present invention, the carbonization temperature is 600-900°C.

[0078] In some specific embodiments of the present invention, the carbonization temperature is 650°C, 750°C or 800°C.

[0079] In certain specific embodiments of the present invention, the preparation method of the mixture includes mixing the graphite intermediate and a carbon source-containing solution and then drying; wherein, the mass fraction of the carbon source in the carbon source-containing solution is 0.5%-1.5%. Here, % means the percentage of the mass of the carbon source in the solution relative to the mass of the solution.

[0080] In some specific embodiments of the present invention, the mass fraction of the carbon source in the carbon source-containing solution is 1%.

[0081] In some specific embodiments of the present invention, the drying is spray drying.

[0082] graphite matrix

[0083] In some preferred embodiments of the present invention, the graphite matrix is ​​microcrystalline graphite.

[0084] In certain specific embodiments of the present invention, the graphite matrix satisfies the following conditions:

[0085] a. La ≤ 72 nm, Lc ≤ 15 nm; where La is the lattice constant of the graphite crystal in the graphite matrix on the 110 plane, and Lc is the lattice constant of the graphite crystal in the graphite matrix on the 002 plane.

[0086] b. F ≥ 15 mN, where F is the crushing force of the particles.

[0087] In this invention, the particle size Dv50 of the graphite matrix satisfies: 2μm <Dv50<5μm。

[0088] In some preferred embodiments, La ≤ 60 nm.

[0089] In some preferred embodiments, Lc ≤ 12 nm.

[0090] In some preferred embodiments, 15 mN ≤ F ≤ 25 mN.

[0091] In some preferred embodiments, the particle size distribution symmetry (S) of the graphite matrix satisfies 0 < S ≤ 0.1, preferably 0 < S ≤ 0.07.

[0092] In some preferred embodiments, the sphericity (D) of the graphite matrix is ​​preferably 0.5-1.0, more preferably 0.85-0.92, for example 0.9.

[0093] In some preferred embodiments, the carbon content of the graphite matrix is ​​greater than 99.9%, and the percentage is the mass percentage of the graphite matrix.

[0094] In a specific embodiment of the present invention, the graphite matrix satisfies the following conditions: La is 52, Lc is 66.4, particle crushing force F is 15, particle size distribution symmetry S is 0.32, and sphericity D is 0.78.

[0095] In a specific embodiment of the present invention, the graphite matrix satisfies the following conditions: La is 61, Lc is 9.3, particle crushing force F is 18, particle size distribution symmetry S is 0.51, and sphericity D is 0.89.

[0096] In a specific embodiment of the present invention, the graphite matrix satisfies the following conditions: La is 60, Lc is 11, particle crushing force F is 19, particle size distribution symmetry S is 0.047, and sphericity D is 0.78.

[0097] Wherein, La is composed of The values ​​were calculated. λ is 0.0027 nm, β is the full width at half maximum (FWHM), and θ is based on... The calculated values ​​are as follows: The graphite matrix and 50 mL of n-hexane are added to a beaker and ultrasonically vibrated for 5 min. Then, 100 μL of the solution is pipetted onto the TEM observation copper grid. The copper grid is quickly dried and then observed. β and d(110) are obtained by selective diffraction observation and calibration using TEM.

[0098] Wherein, Lc is composed of The values ​​were calculated. λ is 0.0027 nm, β is the full width at half maximum (FWHM), and θ' is based on... The calculated values ​​are as follows: The graphite matrix and 50 mL of n-hexane are added to a beaker and ultrasonically vibrated for 5 min. Then, 100 μL of the solution is pipetted onto the TEM observation copper grid. The copper grid is quickly dried and then observed. β and d(002) are obtained by selective diffraction observation and calibration using TEM.

[0099] The particle crushing force (F) refers to the critical pressure at which a single particle of the material breaks during a compressive strength test. The particle crushing force can be obtained using the Xiamen Yuaneng Technology Single Particle Mechanical Property Testing System (SPFT2000). The specific testing method is as follows: 0.5g of graphite matrix is ​​added to a beaker containing 20ml of anhydrous ethanol and ultrasonically dispersed for 5min to obtain a dispersion; 100μL of the dispersion is dropped onto a glass slide, and the slide is transferred to the SPFT2000 sample observation stage; the single particle is positioned using the optical microscope of the SPFT2000, and the indenter is pressed down at a uniform speed. The stress abrupt change point during particle compression is recorded as the particle crushing force.

[0100] The particle size distribution symmetry (S) is calculated from [D(3,4)-Dv50] / Dv50; where D(3,4) and Dv50 are obtained according to GB / T 41949-2022. The smaller the particle size distribution symmetry, the better the particle size distribution symmetry, and the higher the peak of the differential curve of the particle size volumetric force distribution.

[0101] Sphericity (D) refers to the ratio of the surface area of ​​a sphere of the same volume as the material particle to the surface area of ​​the material particle itself. Generally, the closer a particle's morphology is to a sphere, the closer its sphericity is to 1. The sphericity of a sphere is equal to 1, while the sphericity of other objects is less than 1.

[0102] In this invention, sphericity is tested in accordance with GB / T 37406-2019.

[0103] In certain specific embodiments of the present invention, the method for preparing the graphite matrix is ​​as follows:

[0104] S1. Microcrystalline graphite raw material and binder are first mixed, and solvent is added for second mixing to obtain a semi-solid mixture; wherein, the temperature of the first mixing is 5-20°C below the softening point of the coating agent;

[0105] S2. Press the semi-solid mixture to obtain a microcrystalline graphite blank;

[0106] S3. The microcrystalline graphite blank is laid on the surface of the graphitization furnace, and graphitized insulation material is laid on the microcrystalline graphite blank for graphitization treatment. The microcrystalline graphite blank is obtained by graphitization treatment.

[0107] S4. The graphitized microcrystalline graphite blank is crushed to obtain the graphite matrix.

[0108] In some specific embodiments of the present invention, the Dv50 particle size of the graphite matrix satisfies: 2μm. <Dv50<5μm。

[0109] Optionally, the temperature of the first mixing is 8-15°C below the softening point of the adhesive, for example, 10°C.

[0110] Optionally, in step S1, the sphericity D of the microcrystalline graphite raw material is 0.7-1.0.

[0111] Optionally, in step S1, the microcrystalline graphite raw material is natural microcrystalline graphite; wherein, the natural microcrystalline graphite is preferably obtained from microcrystalline graphite ore through pretreatment, wherein the pretreatment includes, for example, water washing and spheroidization treatment.

[0112] Optionally, in step S1, the fixed carbon content of the microcrystalline graphite raw material is 88%-91%.

[0113] Optionally, in step S1, the Dv50 particle size of the microcrystalline graphite raw material is 6-8 μm, for example, 7 μm.

[0114] Optionally, in step S1, the mass ratio of the microcrystalline graphite raw material to the binder is (4-7):1, for example, 5:1.

[0115] Optionally, in step S1, the binder includes one or more of petroleum asphalt, phenolic resin, epoxy resin, and coal tar.

[0116] Optionally, in step S1, the softening point of the adhesive is 100-250℃, preferably 100-130℃, for example 110℃.

[0117] Optionally, in step S1, the solvent is selected from one or more of xylene, toluene, and n-hexane.

[0118] Optionally, in step S1, the semi-solid mixture is 40%-60%, for example, 45%, where the percentage is the mass percentage of the solid component in the semi-solid mixture relative to the mass of the semi-solid mixture.

[0119] Optionally, in step S1, the first mixing method is stirring; wherein the stirring time is preferably 0.5-2 hours, for example, 1 hour; and the stirring speed is preferably 30-90 r / min.

[0120] Optionally, in step S1, the second mixing method is stirring; wherein the stirring time is preferably 0.5-2 hours, for example 1 hour; the stirring speed is preferably 60-120 r / min; and the stirring temperature is preferably room temperature.

[0121] Optionally, in step S1, the preparation method of the microcrystalline graphite raw material includes the following steps: washing and flotation the microcrystalline graphite ore with water, and then performing coarse crushing and spheroidization treatment to obtain the graphite precursor; wherein, the spheroidization treatment time is preferably 4-24 hours; the spheroidization treatment is preferably carried out using a honeycomb mill.

[0122] Optionally, in step S2, the pressing is isostatic pressing; wherein the isostatic pressing time is preferably 18-30 hours, for example 24 hours; and the isostatic pressing pressure is preferably 150-300 MPa, for example 200 MPa.

[0123] Optionally, in step S3, the temperature of the graphitization treatment is greater than 1600℃.

[0124] Optionally, in step S3, the graphitization treatment time is 18-40 hours, preferably 24-36 hours.

[0125] Optionally, in step S3, the graphitized insulation material is petroleum coke and / or pitch coke.

[0126] Optionally, in step S3, the equipment for graphitization treatment is a graphitization furnace.

[0127] Optionally, in step S4, the pulverization process further includes sieving and magnetic impurity removal.

[0128] Optionally, in step S4, the pulverization process involves pulverizing the particles until the Dv50 particle size is 10-13 μm.

[0129] Electrochemical device

[0130] The electrochemical device provided in the third aspect of the present invention includes a negative electrode sheet, the negative electrode sheet including a negative electrode material layer and a negative electrode current collector, the negative electrode material layer including the graphite material as described above.

[0131] In this invention, the electrochemical device is preferably a battery.

[0132] In some alternative embodiments, the electrochemical device is a lithium-ion battery; the lithium-ion battery further includes a positive electrode, a separator, and an electrolyte.

[0133] negative electrode sheet

[0134] In this invention, the negative electrode material layer is disposed on at least one surface of the negative electrode current collector.

[0135] In some implementations, the negative electrode material layer also includes a thickener.

[0136] The addition of the thickener can increase the viscosity of the system of each component in the negative electrode slurry. It can be a thickener commonly used in the art to prepare negative electrode sheets, such as sodium carboxymethyl cellulose (CMC).

[0137] In some implementations, the negative electrode material layer further includes a conductive agent.

[0138] The conductive agent is not particularly limited, as long as it is conductive and does not cause chemical changes in the battery. For example, specific materials that can be used include: graphite, such as natural or artificial graphite; carbon-based materials, such as carbon black (Super P), acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, or carbon fiber; metal powders or metal fibers, such as copper, nickel, aluminum, or silver; conductive whiskers, such as zinc oxide whiskers or potassium titanate whiskers; conductive metal oxides, such as titanium dioxide; or conductive polymers, such as polyphenylene derivatives, etc.

[0139] In some implementations, the negative electrode material layer further includes a binder.

[0140] The type of adhesive is not particularly limited and can be selected from polyvinylidene fluoride, polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid (PAA), ethylene-propylene-diene terpolymer and its sulfonates, styrene-butadiene rubber (SBR), fluororubber and various copolymers, such as PAA and SBR.

[0141] In some specific embodiments, the mass ratio of the graphite material, conductive agent, binder and thickener in the negative electrode material layer is 97.2:0.5:1.8:0.5.

[0142] In this invention, the negative electrode current collector can be a conventional negative electrode current collector in the art. As a substrate supporting the negative electrode active material, the negative electrode current collector is typically a metal foil with a thickness of 3-500 micrometers. There are no particular restrictions on the material, as long as it has high conductivity and will not produce a chemical reaction in the secondary battery system. For example, it can be a foil formed by surface treatment of nickel, titanium, aluminum, silver, stainless steel, carbon, etc. The negative electrode current collector usually has a smooth surface, but fine textures can also be formed on its surface to improve the adhesion between the positive electrode active material and the current collector. Besides foil, the negative electrode current collector can also be used in any one or more combinations of various forms such as film, mesh, porous, foam, or non-woven fabric. Generally, the negative electrode current collector is copper foil.

[0143] In some embodiments, the method for preparing the negative electrode sheet includes the following steps: coating the negative electrode slurry obtained by thoroughly mixing the components of the negative electrode material layer in a solvent onto at least one surface of the negative electrode current collector, drying, cold pressing, and slitting to obtain the final product.

[0144] Positive electrode film

[0145] In this invention, the positive electrode sheet includes a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector.

[0146] In this invention, the positive electrode active material in the positive electrode material layer can be a positive electrode active material conventionally used in the art, such as one or more of lithium nickel cobalt manganese oxide, lithium nickel manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, and lithium cobalt oxide.

[0147] In some implementations, the positive electrode material layer further includes a binder.

[0148] The type of adhesive is not particularly limited and can be selected from polyvinylidene fluoride, polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid (PAA), ethylene-propylene-diene terpolymer and its sulfonates, styrene-butadiene rubber (SBR), fluororubber and various copolymers, such as PVDF.

[0149] In some embodiments, the binder content is 1%-10%, for example 1.8%, which is a percentage of the total mass of the positive electrode material layer.

[0150] In some embodiments, the positive electrode material layer further includes a conductive agent.

[0151] The type of conductive agent is not particularly limited; it is a reagent used to ensure that the electrode has good charge and discharge performance. It can be selected from graphite materials such as natural graphite and artificial graphite; carbon black materials such as SP, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal cracking black; conductive fibers such as carbon fiber and metal fiber; metal powders such as fluorinated carbon powder, aluminum powder, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; and conductive metal oxides or polyphenylene derivatives such as titanium dioxide.

[0152] In some specific implementations, the conductive agent is conductive carbon SP.

[0153] In some embodiments, the content of the conductive agent is 0.2%-3%, for example 1.2%, which is a percentage of the total mass of the positive electrode material layer.

[0154] In some specific embodiments, the mass ratio of the positive electrode active material, conductive agent, and binder in the positive electrode material layer is 97:1.2:1.8.

[0155] In this invention, the positive electrode current collector can be a conventional positive electrode current collector in the art. As a substrate supporting the positive electrode material layer, the positive electrode current collector is typically a metal foil with a thickness of 3-500 micrometers. There are no particular limitations on the material, as long as it has high conductivity and will not produce a chemical reaction in the secondary battery system. For example, it can be a foil formed by surface treatment of nickel, titanium, aluminum, silver, stainless steel, carbon, etc. The positive electrode current collector usually has a smooth surface, but fine textures can also be formed on its surface to improve the adhesion between the positive electrode active material and the current collector. Besides foil, the positive electrode current collector can also be used in any one or more combinations of various forms such as film, mesh, porous, foam, or non-woven fabric. Generally, the positive electrode current collector is aluminum foil.

[0156] In some embodiments, the method for preparing the positive electrode sheet includes: coating a positive electrode slurry obtained by thoroughly mixing the components of the positive electrode material layer in a solvent onto at least one surface of the positive electrode current collector, drying, and rolling to compact it, thereby obtaining the positive electrode sheet.

[0157] In some alternative embodiments, the solvent includes one or more of N-methylpyrrolidone (NMP), dimethyl carbonate, ethylene carbonate, and diethylene carbonate, for example, NMP.

[0158] diaphragm

[0159] In this invention, the diaphragm can be a diaphragm conventionally used in the art.

[0160] In some alternative embodiments, the diaphragm may be a polypropylene film or a polyethylene film.

[0161] The air permeability of the diaphragm can be 180-380 s / 100mL.

[0162] The porosity of the diaphragm can be 30%-50%.

[0163] The thickness of the diaphragm can be 9-18 μm.

[0164] In one specific embodiment, the diaphragm is a polyethylene film; the thickness of the diaphragm is 11 μm; the air permeability of the diaphragm is 230 s / 100 mL; and the porosity of the diaphragm is 40%.

[0165] electrolyte

[0166] In some embodiments, the electrolyte may be a conventional electrolyte used in batteries in the art, generally including non-aqueous solvents, lithium salts, and additives.

[0167] In some embodiments, the method for preparing the lithium-ion battery includes the following steps: stacking the positive electrode, separator, and negative electrode in sequence, with the separator positioned between the positive and negative electrodes to act as a separator; then wrapping with an aluminum-plastic film, drying, and injecting the electrolyte; and finally preparing a soft-pack battery through processes such as encapsulation, settling, and formation.

[0168] electronic devices

[0169] The electronic device provided in the fourth aspect of the present invention includes the electrochemical device as described above.

[0170] For example, the electronic devices described in this invention may be, but are not limited to, mobile devices (such as mobile phones, tablets, laptops, video recorders, portable printers / copiers, 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 and backup power supplies, etc.

[0171] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0172] Example 1

[0173] (1) Preparation of graphite materials:

[0174] ① Preparation of graphite matrix

[0175] S1. The microcrystalline graphite ore (purchased from Lutang microcrystalline graphite in Hunan, with carbon content > 85% in the microcrystalline graphite ore) is subjected to preliminary water washing and flotation to make its fixed carbon content reach 88 - 91%. After coarse crushing, it is spheroidized by a honeycomb mill for 24 h to obtain microcrystalline graphite raw materials with a sphericity of 0.9. The above microcrystalline graphite raw materials and petroleum pitch with a softening point of 110 °C (purchased from Xinde New Materials, model XD - 110) are mixed in a mass ratio of 5:2 for the first time, then heated to 10 °C below the softening point of the petroleum pitch and stirred at a low speed for 1 h. Then, xylene solvent twice the mass of the obtained material is added to assist the dispersion of the petroleum pitch, and stirring continues for 1 h to obtain a semi-solid mixture.

[0176] S2. The above semi-solid mixture is added to a 40 * 30 cm * 30 cm rubber mold, and isostatic pressing is carried out at 200 Mpa for 24 h, and then demolding is carried out to obtain a microcrystalline graphite rough blank.

[0177] S3. The above microcrystalline graphite rough blank is paved on the surface layer of a conventional Acheson graphite furnace, and then a layer of conventional graphite insulation material is further paved and then graphitized. Among them, the graphitization temperature is 3000 °C; the graphitization time is 36 h.

[0178] S4. The graphitized microcrystalline graphite rough blank is crushed and shaped, and the fraction with 2 μm < Dv50 < 5 μm is collected as the graphite matrix. The prepared graphite matrix has La of 60, Lc of 11, particle crushing force F of 19, particle size distribution symmetry S of 0.047, sphericity D of 0.78, and carbon content greater than 99.9%.

[0179] ② Preparation of the first graphite precursor, the second graphite precursor and graphite intermediate

[0180] Take a part of the above graphite precursor and add it to a 2 mol / L trichloroacetic acid solution for carboxylation treatment for 6 h to obtain the first graphite precursor; take a part of the above graphite precursor and add it to a 2 mol / L sodium hydroxide solution for hydroxylation treatment for 6 h to obtain the second graphite precursor, and the first graphite precursor and the second graphite precursor are mixed and a total of 100 kg are subjected to micro-shaping and classification treatment in sequence to obtain a graphite intermediate.

[0181] ③ Preparation of graphite material

[0182] The above graphite intermediate is dissolved in a solution containing a carbon source (the carbon source is a 1% sucrose solution by mass fraction), heated to 80 °C and stirred for 4 h, and then dried by a spray dryer to form a powder; the powder is carbonized at 750 °C for 4 h in a nitrogen atmosphere to obtain a graphite material with Dv50 of 6 μm.

[0183] The micro-shaping time was 2 hours, the grading frequency was 60 Hz, the sphericity of the graphite intermediate was 0.89, and the Dv50, Dv10, Dv90 and particle size distribution width of the graphite intermediate are listed in Table 1.

[0184] The sphericity was tested in accordance with GB / T 37406-2019.

[0185] (2) Preparation of lithium-ion batteries

[0186] The positive electrode, separator, and negative electrode are wound together to form a battery cell, which is then packaged in a casing and injected with electrolyte to produce a soft-pack battery.

[0187] The preparation of the negative electrode sheet includes the following steps: the obtained graphite material, conductive agent (SP), binder (PAA and SBR, with a mass ratio of 1.3:0.5) and thickener carboxymethyl cellulose (CMC) are mixed in a mass ratio of 97.2:0.5:1.8:0.5 (100 parts by mass in total), and then 82 parts by mass of deionized water are added and mixed evenly to obtain a negative electrode slurry; then the negative electrode slurry is evenly coated on copper foil; and then the negative electrode sheet is prepared by drying, rolling, cutting and other processes.

[0188] The preparation of the positive electrode sheet includes the following steps: mixing positive electrode active materials NCM622, PVDF and SP in a mass ratio of 97:1.8:1.2 (100 parts by mass in total), adding 82 parts by mass of NMP to obtain a positive electrode slurry; coating the obtained positive electrode slurry onto at least one surface of an aluminum foil, drying, and rolling to compact it, thus obtaining the positive electrode sheet.

[0189] The diaphragm is a polyethylene film with a thickness of 11 μm, an air permeability of 230 s / 100 mL, and a porosity of 40%.

[0190] The electrolyte used is a commercially available electrolyte (manufacturer: Xinya Shanshan New Material Technology (Quzhou) Co., Ltd., model: E3).

[0191] Example 2-10

[0192] (1) Preparation of graphite materials:

[0193] The preparation process of the graphite materials in Examples 2-10 was the same as that in Example 1, except for the parameters listed in Tables 1 and 2. Table 1 shows the Dv50, Dv10, Dv90, and particle size distribution width of the graphite intermediates in Examples 1-10, and the sphericity of the graphite intermediates in Examples 1-10 was 0.89. Table 2 shows the relevant parameters for mixing, carbonization, micro-shaping, and classification treatments.

[0194] In Examples 6 and 7, the carbon source solutions contained carbon source mass fractions of 0.5% and 1.5%, respectively. The carbon source mass content in the mixture was controlled to be 1% by using more and less carbon source solution, respectively.

[0195] (2) Preparation of lithium-ion batteries: Same as in Example 1.

[0196] Example 11

[0197] The difference from Example 1 is that petroleum asphalt with a softening point of 130℃ (purchased from Xinde New Materials, model XD-130) was used in S1 above, while the experimental conditions for preparing the graphite matrix remained unchanged. The obtained graphite matrix had a La of 61, an Lc of 9.3, a particle crushing force F of 18, a particle size distribution symmetry S of 0.51, a sphericity D of 0.89, and a carbon content greater than 99.9%.

[0198] The other preparation steps are the same as in Example 1.

[0199] Example 12

[0200] The difference from Example 1 is that in S1 above, the sphericity treatment time is 4 hours, the sphericity of the obtained microcrystalline graphite raw material is 0.7, and the experimental conditions for other graphite matrix preparation processes remain unchanged. The obtained graphite matrix has a La of 52, an Lc of 66.4, a particle crushing force F of 15, a particle size distribution symmetry S of 0.32, a sphericity D of 0.78, and a carbon content greater than 99.9%.

[0201] The other preparation steps are the same as in Example 1.

[0202] Comparative Examples 1-8

[0203] (1) Preparation of graphite materials:

[0204] The preparation processes of the graphite materials in Comparative Examples 1-8 were the same as those in Example 1, except for the parameters listed in Tables 1 and 2. The Dv50, Dv10, Dv90, and particle size distribution width of the graphite intermediates in Comparative Examples 1-8 are listed in Table 1, and Table 2 shows the relevant parameters for mixing, carbonization, micro-shaping, and classification treatments.

[0205] In Comparative Example 6, the carbon source solution contained a carbon source mass fraction of 2%, and by using less carbon source solution, the mass content of carbon source in the mixture was controlled to be 1%.

[0206] (2) Preparation of lithium-ion batteries: Same as in Example 1.

[0207] Table 1

[0208] Particle size distribution width of graphite intermediates Dv50 particle size (μm) of graphite intermediates Dv10 particle size (μm) of graphite intermediates Dv90 particle size (μm) of graphite intermediates Example 1 1.06 6.0 2.3 8.7 Example 2 1.03 5.1 1.8 7.1 Example 3 1.1 7.4 3.3 11.4 Example 4 1.07 6.5 2.6 9.6 Example 5 1.05 5.7 2.1 8.1 Example 6 1.05 5.5 2.0 7.8 Example 7 1.09 6.8 2.9 10.3 Example 8 1.06 6.3 2.5 9.2 Example 9 1.06 5.8 2.1 8.2 Example 10 1.06 5.8 1.9 8.0 Example 11 1.07 6.1 2.4 8.9 Example 12 1.1 7.4 3.3 11.4 Comparative Example 1 1.08 4.2 1.5 6.0 Comparative Example 2 1.1 8.6 4.2 13.7 Comparative Example 3 1.08 6.4 2.2 9.1 Comparative Example 4 1.03 5 1.9 7.1 Comparative Example 5 1.05 5.4 2.1 7.8 Comparative Example 6 1.08 7.1 3.0 10.7 Comparative Example 7 1.1 7.4 3.2 11.3 Comparative Example 8 1.06 5.3 1.8 7.4

[0209] Table 2

[0210] Dv50 particle size (μm) of the mixture Mass content of carbon source in the mixture Mass content of the first graphite precursor in the mixture Mass content of the second graphite precursor in the mixture Coking value of carbon source Time required for minimally invasive cosmetic procedures (hours) Frequency of hierarchical processing Types of carbon sources Mass fraction of carbon source in carbon source solution Carbonization temperature (°C) Example 1 6 1% 49.5% 49.5% 60% 2 60 sucrose 1% 750 Example 2 5.1 1% 49.5% 49.5% 60% 1.2 60 sucrose 1% 750 Example 3 7.4 1% 49.5% 49.5% 60% 2.5 60 sucrose 1% 750 Example 4 6.5 1% 49.5% 49.5% 60% 2 40 sucrose 1% 750 Example 5 5.7 1% 49.5% 49.5% 60% 2 70 sucrose 1% 750 Example 6 5.5 1% 49.5% 49.5% 60% 2 60 sucrose 0.5% 750 Example 7 6.8 1% 49.5% 49.5% 60% 2 60 sucrose 1.5% 750 Example 8 6.3 1% 49.5% 49.5% 60% 2 60 sucrose 1% 650 Example 9 5.8 1% 49.5% 49.5% 60% 2 60 sucrose 1% 800 Example 10 5.8 1% 49.5% 49.5% 50% 2 60 glucose 1% 750 Example 11 6 1% 49.5% 49.5% 60% 2 60 sucrose 1% 750 Example 12 6 1% 49.5% 49.5% 60% 2 60 sucrose 1% 750 Comparative Example 1 4.2 1% 49.5% 49.5% 60% 0 60 sucrose 1% 750 Comparative Example 2 8.6 1% 49.5% 49.5% 60% 3 60 sucrose 1% 750 Comparative Example 3 6.4 1% 49.5% 49.5% 60% 2 25 sucrose 1% 750 Comparative Example 4 5 1% 49.5% 49.5% 60% 2 80 sucrose 1% 750 Comparative Example 5 5.4 0 49.5% 49.5% 60% 2 60 sucrose 0 750 Comparative Example 6 7.1 1% 49.5% 49.5% 60% 2 60 sucrose 2% 750 Comparative Example 7 7.4 1% 49.5% 49.5% 60% 2 60 sucrose 1% 500 Comparative Example 8 5.3 1% 49.5% 49.5% 60% 2 60 sucrose 1% 1000

[0211] Example 1

[0212] The graphite materials prepared in Examples 1-10 and Comparative Examples 1-8 were subjected to the following tests:

[0213] 1. Test of structural stability parameter S: Referring to the national standard GB / T24533-2019, the powder sample of graphite material is pressed into a sheet. Before testing, it is held at a standard pressure of 2T for 20s. After depressurization, after an interval of 10min, it is held at 5T for 20s. After depressurization, after an interval of 10min, the formal operation begins. The 5T powder pressure is recorded as P0. Then, the powder sample of graphite material is tested with pressures of 5.5T, 6T, 6.5T, ..., 5+0.5nT, ... The compressibility is recorded as P1, P2, P3, ..., Pn, ... When Pn / Pn-1≥1.05, this Pn is called the particle structure failure compressibility, and the structural stability parameter S=5+0.5n / 5 is recorded.

[0214] 2. Test of secondary particle size coefficient L: Referring to the national standard GB / T24533-2019, the graphite powder sample is pressed into a sheet. Before testing, it is held at a standard pressure of 2T for 20s. After depressurization, after an interval of 10 minutes, it is held at 5T for 20s. After depressurization, after an interval of 10 minutes, the formal operation begins. The 5T powder pressure is recorded as P0. Then, the graphite powder sample is tested with pressures of 5.5T, 6T, 6.5T, ..., 5+0.5nT, ... The compressibility is recorded as P1, P2, P3, ..., Pn, ... When Pn / Pn-1≥1.05, this Pn is called the particle structure failure compressibility. The graphite powder sample at Pn is collected for particle size testing to obtain Dv50 new. The particle size of the graphite powder sample before pressing into a sheet is tested and recorded as Dv50. The secondary particle size coefficient L is Dv50 new / Dv50.

[0215] 3. Testing of Dv10, Dv50, and Dv90: The testing instrument was Malvern 3000, and the testing was conducted in accordance with GB / T 41949-2022.

[0216] 4. Calculation method of particle size distribution width d: d = (Dv90 - Dv10) / Dv50; where Dv90, Dv10, and Dv50 are the Dv90, Dv10, and Dv50 particle sizes of graphite materials, respectively. The particle size distribution width can reflect the dispersion of the particle size distribution of graphite materials.

[0217] 5. Porosity testing: The testing instrument was a Micron ASAP2460 from the United States, and the test was conducted in accordance with GB / T 19587-2017.

[0218] The test results are listed in Table 3:

[0219] Table 3

[0220] S L d Dv90 particle size (μm) of graphite materials Dv10 particle size (μm) of graphite materials Dv50 particle size (μm) of graphite materials <![CDATA[Porosity (cm 3 / g)]]> Example 1 10.5 1.5 1.13 10.8 3.5 6.5 0.009 Example 2 12.5 1.3 1.07 9.4 3.5 5.5 0.012 Example 3 8.5 1.8 1.19 11.7 2.3 7.9 0.008 Example 4 9.5 1.6 1.15 11.1 3.1 7 0.008 Example 5 11 1.4 1.11 9.8 2.9 6.2 0.011 Example 6 11.5 1.4 1.08 9.7 3.3 5.9 0.009 Example 7 9 1.8 1.17 11.2 2.9 7.1 0.01 Example 8 10 1.5 1.14 10.9 3.1 6.8 0.012 Example 9 12 1.5 1.1 10.5 3.6 6.3 0.009 Example 10 10.8 1.6 1.15 10.8 3.7 6.2 0.01 Example 11 10.6 1.5 1.12 10.9 3.6 6.5 0.01 Example 12 12.0 1.1 1.07 10.3 3.2 6.4 0.008 Comparative Example 1 15.5 1.1 1.34 8.3 1.9 4.8 0.016 Comparative Example 2 6.5 2.3 1.38 16.1 3.3 9.3 0.011 Comparative Example 3 5.5 1.2 1.45 11.4 1.4 6.9 0.012 Comparative Example 4 16.5 1.2 1.22 9.4 2.7 5.5 0.014 Comparative Example 5 13.5 1.2 1.27 9.8 2.4 5.8 0.014 Comparative Example 6 7.5 1.9 1.12 13.2 4.8 7.5 0.013 Comparative Example 7 6 2.1 1.52 13.6 1.9 7.7 0.013 Comparative Example 8 14.5 1.2 1.23 11.4 3.9 6.1 0.012

[0221] Example 2

[0222] The batteries prepared in Examples 1-10 and Comparative Examples 1-8 were subjected to the following tests:

[0223] First, at 25°C, the battery was activated by performing one cycle of charge-discharge at 0.1C within the operating voltage range of 2.8V (discharge cut-off voltage) to 4.35V (charge cut-off voltage). Afterward, various tests were conducted.

[0224] 1. Charging capacity, discharging capacity, and first-time efficiency

[0225] The activated lithium-ion battery was connected to the Blue Electric Charge-Discharge Tester for its first long-cycle charge-discharge test. Its charging capacity and discharging capacity were measured. The working voltage range of the battery test was 2.8V (discharge cutoff voltage) to 4.35V (charging cutoff voltage), and the test rate was 0.3C.

[0226] First-time efficiency = (First discharge capacity / First charge capacity) × 100%.

[0227] 2. Low-temperature capacity retention

[0228] The activated lithium-ion battery was connected to the Blue Electric Charge-Discharge Tester and subjected to long-cycle charge-discharge to measure its charging and discharging capacity. The working voltage range of the battery test was 2.8V (discharge cut-off voltage) to 4.35V (charging cut-off voltage), and the test rate was 0.3C. Then, the cell was placed in a -20℃ temperature chamber and discharged at 0.05C. The ratio of the discharge capacity at 2.8V to the discharge capacity at room temperature is the low-temperature capacity retention rate.

[0229] 3. Fast charging time

[0230] The battery cell was directly charged to 8% SOC state at a current of 0.33C. Then, based on the actual measured three-electrode window of the battery cell, the charging windows for 10%, 20%, 30%, 40%, 50%, 60%, 70%, and 80% were C1, C2, C3, C4, C5, C6, C7, and C8, respectively. Gradual charging to 80% was adopted, that is, C1 was used for 8%-10%, C2 was used for 10%-20%, and so on. The charging time from 8% to 80% SOC state was recorded as a standard for measuring fast charging capability. The calculation formula is T = (0.02 / C1 + 0.1 / C2 + 0.1 / C3 + 0.1 / C4 + 0.1 / C5 + 0.1 / C6 + 0.1 / C7 + 0.1 / C8) × 60.

[0231] 4. Fast charging cycle count

[0232] The activated lithium-ion battery was connected to the Blue Electric Charge-Discharge Tester and then subjected to long-term cycling at a 2C rate until the ratio of the capacity of the nth cycle to the capacity of the first 2C cycle was less than 80%. The capacity retention rate of the (n-1)th cycle was defined as 80%, and the number of cycles was recorded as n-1. The test was then stopped.

[0233] 5. Storage days

[0234] At 25℃, the cell is calibrated with a current of 0.33C and denoted as C0. Then, the cell is stored at a high temperature of 60℃. After that, the cell is taken out every 7 days and its capacity is tested at room temperature and denoted as C1, C2, ..., Cn. Cn is defined as the number of days when the cell is first less than or equal to 80% of C0, which is the storage time.

[0235] The test results are listed in Table 4 below:

[0236] Table 4

[0237] Charging capacity (mAh / g) Discharge capacity (mAh / g) First-efficacy (%) Low-temperature capacity retention rate (%) Fast charging time (min) Fast charging cycle count Number of days stored at 60℃ Example 1 391.2 356.8 91.2 85 8.3 1935 287 Example 2 391.9 354.3 90.4 88 8.5 2153 252 Example 3 390.6 357.8 91.6 92 7.4 1696 224 Example 4 393.2 357 90.8 89 7.9 1815 231 Example 5 389.0 355.2 91.3 86 8.5 1987 259 Example 6 390.7 354.8 90.8 87 8.4 1936 245 Example 7 391.7 357.2 91.2 89 8 1765 210 Example 8 393.4 356.4 90.6 87 8.3 1865 245 Example 9 390.9 356.5 91.2 89 8.1 1723 252 Example 10 392.4 357.1 91 87 8.2 1917 280 Example 11 391.0 357.0 91.3 86 8.7 1822 273 Example 12 395.2 356.3 90.0 85 9.0 2003 259 Comparative Example 1 400.5 353.2 88.2 82 9.4 1165 154 Comparative Example 2 399.3 356.2 89.2 85 8.9 1032 140 Comparative Example 3 404.6 355.2 87.8 84 9.3 1124 112 Comparative Example 4 397.9 354.9 89.2 83 8.9 1256 140 Comparative Example 5 395.0 355.5 90 76 10.2 1178 133 Comparative Example 6 401.1 353.8 88.2 84 9 865 105 Comparative Example 7 409.9 355 86.6 87 8.5 1053 98 Comparative Example 8 395.5 356.7 90.2 83 9.2 1365 175

[0238] The graphite materials prepared in Examples 1-12, when applied to batteries, enable the batteries to maintain a low-temperature capacity retention rate of over 85% and a storage life of over 210 days at 60°C, demonstrating excellent wide-temperature adaptability. The batteries also exhibit fast-charging times of less than 9 minutes and over 1696 fast-charging cycles, indicating excellent kinetic performance. Furthermore, the graphite materials prepared in Examples 1-12, when applied to batteries, also enable the batteries to achieve a charging capacity of over 389 mAh / g, a discharging capacity of over 354.3 mAh / g, and an initial efficiency of over 90%.

[0239] The comparison of Examples 1-12 shows that the structural stability parameters S, secondary particle coefficient L, and particle size distribution width d of different graphite materials affect their electrical performance in applications. When graphite materials with S, L, and d within the scope of this invention are applied in batteries, k can simultaneously exhibit excellent kinetic performance and wide temperature range adaptability.

[0240] In Comparative Examples 1, 4, 5, and 8, the value of S is greater than the scope of the present invention; in Comparative Examples 2, 3, 6, and 7, the value of S is less than the scope of the present invention. Similarly, in Comparative Examples 1, 3-5, and 8, the value of L is less than the scope of the present invention; in Comparative Examples 2, 6, and 7, the value of L is greater than the scope of the present invention; and in Comparative Examples 1-5 and 7-8, the value of d is greater than the scope of the present invention. The graphite materials prepared in Comparative Examples 1-8 can only achieve a maximum of 1365 fast-charging cycles, far less than the 1696+ cycles of Examples 1-12. The graphite materials prepared in Comparative Examples 1-8 can only be stored at 60°C for a maximum of 154 days, far less than the 210+ days of Examples 1-12. Other effects also show varying degrees of deterioration. It can be seen that excessively large or small values ​​of S, L, and d cannot achieve the effects of the present invention.

[0241] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A graphite material, characterized in that, It meets the following conditions: (a) 8≤S≤13, where S is the structural stability parameter; (b) 1.1≤L≤1.8, where L is the secondary particle size coefficient; (c) 1.0≤d≤1.2, where d is the particle size distribution width.

2. The graphite material as described in claim 1, characterized in that, It satisfies one or more of the following conditions (a)-(c): (a) S is 10⁻¹²; (b) L is 1.4-1.7; (c)d is 1-1.

12.

3. The graphite material as described in claim 1, characterized in that, It satisfies one or more of the following conditions (a)-(d): (a) The Dv90 particle size of the graphite material is 9-12 μm; (b) The Dv10 particle size of the graphite material is 2.5-3.6 μm; (c) The Dv50 particle size of the graphite material is 5-8 μm; (d) The porosity of the graphite material is 0.008-0.012 cm⁻¹ 3 / g.

4. A method for preparing a graphite material as described in any one of claims 1-3, characterized in that, It includes the following steps: The mixture is carbonized to obtain a graphite material; the mixture includes a graphite intermediate and a carbon source; the preparation method of the graphite intermediate includes mixing a first graphite precursor and a second graphite precursor, wherein the first graphite precursor is obtained by carboxylation of a graphite matrix and the second graphite precursor is obtained by hydroxylation of a graphite matrix.

5. The method for preparing graphite material as described in claim 4, characterized in that, It satisfies one or more of the following conditions (a)-(e): (a) The sphericity of the graphite intermediate is 0.87 or higher; (b) The Dv50 particle size of the graphite intermediate is 6-7.5 μm; (c) The Dv10 particle size of the graphite intermediate is 1.8-4 μm; (d) The Dv90 particle size of the graphite intermediate is 10-14 μm; (e) The Dv50 particle size of the mixture is 5-9 μm.

6. The method for preparing graphite material as described in claim 4, characterized in that, It satisfies one or more of the following conditions (a)-(c): (a) The mass content of the carbon source in the mixture is 0.6%-1%; (b) The mass content of the first graphite precursor in the mixture is 45%-49.9%; (c) The mass content of the second graphite precursor in the mixture is 45%-49.9%.

7. The method for preparing graphite material as described in claim 4, characterized in that, It satisfies one or more of the following conditions (a)-(d): (a) The processing agent used in the carboxylation treatment is an acid solution containing carboxyl groups; (b) The treatment agent used in the hydroxylation treatment is an alkaline solution; (c) The carbon source is one or more of sucrose, glucose, and resin; (d) The coking value of the carbon source is less than 60%.

8. The method for preparing graphite material as described in claim 4, characterized in that, It satisfies one or more of the following conditions (a)-(f): (a) The carbonization time is 2-8 hours; (b) The method for preparing the graphite intermediate includes: mixing the first graphite precursor and the second graphite precursor and then subjecting them to micro-shaping and grading processes in sequence to obtain the graphite intermediate; the micro-shaping time is 1-2.5h, and the grading frequency is 30-70Hz; (c) The carbonization temperature is 600-900℃; (d) The preparation method of the mixture includes mixing the graphite intermediate and a carbon source-containing solution and then drying; wherein the mass fraction of the carbon source in the carbon source-containing solution is 0.5%-1.5%; (e) The graphite matrix satisfies the following conditions: La≤72 nm, Lc≤15 nm, F≥15 mN; Wherein, La is the lattice constant of the graphite crystal in the graphite matrix on the 110 plane, Lc is the lattice constant of the graphite crystal in the graphite matrix on the 002 plane, and F is the particle crushing force; (f) The graphite matrix is ​​microcrystalline graphite.

9. An electrochemical device comprising a negative electrode, characterized in that, The negative electrode sheet includes a negative electrode material layer and a negative electrode current collector, wherein the negative electrode material layer includes graphite material as described in any one of claims 1-3 and 8.

10. An electronic device, characterized in that, It includes the electrochemical device as described in claim 9.