Graphite materials and methods for producing them, electrochemical apparatus, and electronic equipment.

Abstract

To provide graphite materials that guarantee excellent initial efficiency and rapid charging performance, and that combine excellent self-discharge performance, capacity performance, and cycle performance, as well as methods for producing them, electrochemical apparatus, and electronic equipment. [Solution] The graphite material satisfies the following conditions: La ≤ 72 nm, Lc ≤ 15 nm. Here, La is the lattice constant at the 110 plane of the graphite crystal in the graphite material, and Lc is the lattice constant at the 002 plane of the graphite crystal in the graphite material. F ≥ 15 mN. F is the particle crushing force.

Description

Technical Field

[0001] The present invention relates to a graphite material, a method for producing the same, an electrochemical device, and an electronic device.

Background Art

[0002] Microcrystalline graphite is a type of natural graphite. Since it has a small crystal lattice and a structure rich in pores, it has greater kinetic advantages than conventional flaky natural graphite and higher capacity and compaction than conventional artificial graphite. In addition, the raw material of microcrystalline graphite is very inexpensive, being about 20 to 30% of natural flaky graphite of the same quality, so the application prospect is good. However, naturally mined microcrystalline graphite has a very high impurity content. When used as the negative electrode material of a lithium-ion battery, first, a removal treatment needs to be carried out. However, the removal process is complicated and the removal cost is about 2 to 3 times that of natural flaky graphite of the same quality. Therefore, considering comprehensively, there is no cost advantage, which extremely limits the application of microcrystalline graphite.

[0003] As a conventional removal technology, in Patent Document 1, removal is performed on microcrystalline graphite by an acid-alkali and high-temperature heat treatment method. Although it claims low energy consumption, it requires the treatment of waste acid and waste alkali and a method of occupying a crucible furnace, which inevitably leads to a significant increase in cost and destroys the structure of the graphite material. Therefore, a lithium-ion battery containing it cannot guarantee excellent initial efficiency and rapid charging performance. In Patent Document 2, inorganic salts are added and coating is performed in a nitrogen atmosphere to improve the cycle performance of microcrystalline graphite. However, its experimental process is not suitable for large-scale commercial production, the price of the experimental supplies used is relatively high, which is disadvantageous for reducing the cost of the final product. Although the cycle performance of the lithium-ion battery adopting this microcrystalline graphite is improved to some extent, it cannot guarantee excellent initial efficiency and rapid charging performance. Therefore, how to ensure that a lithium-ion battery containing a graphite material can guarantee excellent initial efficiency and rapid charging performance is extremely important.

Prior Art Documents

[0004] [Patent Document 1] Chinese Patent Application CN107555426A [Patent Document 2] Chinese Patent Application CN109616640A [Overview of the project] [Problems that the invention aims to solve]

[0005] To address the problem that conventional lithium-ion batteries containing graphite materials cannot guarantee excellent initial efficiency and rapid charging performance, the present invention provides a graphite material, a method for producing the same, an electrochemical apparatus, and an electronic device. Because the graphite material has extremely small La and Lc particles and a relatively large particle crushing force F, an electrochemical apparatus (particularly a lithium-ion battery) containing it can guarantee excellent initial efficiency and rapid charging performance, and can also possess excellent self-discharge performance, capacity performance, and cycle performance. [Means for solving the problem]

[0006] To achieve the above-mentioned objectives, the present invention employs the following technical solution.

[0007] In a first embodiment, the present invention provides a graphite material that satisfies the following conditions. a, La ≤ 72 nm, Lc ≤ 15 nm. Here, La is the lattice constant at the 110 plane of the graphite crystal in the graphite material, and Lc is the lattice constant at the 002 plane of the graphite crystal in the graphite material. b, F ≥ 15 mN. F is the particle crushing force.

[0008] In a second embodiment, the present invention provides a method for producing the above-described graphite material, comprising the following steps. In step S1, a first mixing is performed with the graphite precursor and the binder, and a second mixing is performed by adding the solvent to obtain a mixture. Here, the temperature of the first mixing is 5 to 20°C lower than the softening point of the binder. S2, the mixture is press-formed to obtain graphite material. S3. The graphite material is laid on the surface of the graphitization equipment, a graphitization heat retention material is laid on the graphite material, and the graphitization treatment is performed to graphitize the graphite material and obtain graphitized graphite material. S4. The graphitized graphite material is crushed to obtain graphite material.

[0009] In a third embodiment, the present invention provides an electrochemical apparatus including 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 described above.

[0010] In a fourth embodiment, the present invention provides electronic equipment including the electrochemical apparatus described above. [Effects of the Invention]

[0011] The positive improvements of this invention are as follows: The present invention provides a graphite material. By controlling and designing parameters such as lattice constants La and Lc and particle crushing force F, electrochemical devices (particularly lithium-ion batteries) containing this graphite material can guarantee excellent initial efficiency and rapid charging performance, and can also possess excellent self-discharge performance, capacity performance, and cycle performance. [Modes for carrying out the invention]

[0012] The present invention will be further described below using the methods of the examples, but these are not intended to limit the present invention to the scope of the examples described above. For experimental methods in the following examples where specific conditions are not specified, the methods and conditions should be selected based on general methods and conditions, or based on the product description.

[0013] Graphite material The graphite material provided by the first aspect of the present invention satisfies the following conditions. a. La ≤ 72 nm and Lc ≤ 15 nm. Here, La is the lattice constant of the 110 plane of the graphite crystal in the graphite material, and Lc is the lattice constant of the 002 plane of the graphite crystal in the graphite material. b. F ≥ 15 mN. F is the particle crushing force. In some preferred embodiments, La ≤ 60 nm. The La is, for example, 53 nm, 58 nm, 59 nm, 61 nm, 62 nm, 65 nm, 66 nm, or 67 nm. In some preferred embodiments, Lc ≤ 12 nm. The Lc is, for example, 8.8 nm, 9.6 nm, 10.3 nm, 10.8 nm, 10.9 nm, 11.1 nm, 12.9 nm, 13.1 nm, or 13.2 nm.

[0014] In the present invention, the La is calculated by the following formula.

Number

Number

Number

Number

[0015] Here, the specific measurement methods of β and d(002) are as follows. Add the graphite material and 50 mL of n-hexane to a beaker, and perform ultrasonic vibration for 5 minutes. Then, use a micropipette to aspirate 100 μL of the solution, drop it onto a copper mesh for TEM observation, quickly dry the copper mesh, and perform the observation. Perform restricted field diffraction observation using TEM to calibrate β and d(002).

[0016] In the present invention, the particle crushing force (F) refers to the critical pressure at which crushing occurs when a single material particle undergoes pressure resistance measurement. Preferably, 15 mN ≤ F ≤ 25 mN. The particle crushing force is, for example, 15 mN, 16 mN, 17 mN, 18 mN, 19 mN, 20 mN, 21 mN, or 23 mN.

[0017] In the present invention, the particle crushing force can be measured using the single particle force characteristic test system (SPFT2000) of IEST (Initial Energy Science & Technology (Xiamen) Co., Ltd). The specific measurement method is as follows. Add 0.5 g of the graphite material to a beaker containing 20 ml of absolute ethanol, and perform ultrasonic dispersion for 5 minutes to obtain a dispersion liquid. Drop 100 μL of the above-mentioned dispersion liquid onto a slide glass, and transfer the slide glass to the SPFT2000 sample observation stage. Use the optical microscope of SPFT2000 to position a single particle, and control the indenter to compress downward at a constant speed, and record the stress mutation point in the particle compression process as the particle crushing force.

[0018] In one preferred embodiment, the graphite material satisfies 0 < S ≤ 0.1, preferably 0 < S ≤ 0.07, and S is the particle size distribution symmetry.

[0019] In some specific embodiments, the particle size distribution symmetry is, for example, 0.01, 0.035, 0.038, 0.051, 0.052, 0.056, 0.067, 0.072, 0.083, 0.096, or 0.1.

[0020] Here, the particle size distribution symmetry (S) is calculated by [D(3,4)-Dv50] / Dv50, where D(3,4) and Dv50 are measured based on 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 volume distribution.

[0021] In one specific embodiment, the graphite material satisfies the following: the La is 62 nm, the Lc is 12 nm, the particle crushing force is 21 mN, and the particle size distribution symmetry is 0.051.

[0022] In one specific embodiment, the graphite material satisfies the following: the La is 58 nm, the Lc is 9.6 nm, the particle crushing force is 17 mN, and the particle size distribution symmetry is 0.1.

[0023] In one specific embodiment, the graphite material satisfies the following: the La is 72 nm, the Lc is 15 nm, the particle crushing force is 25 mN, and the particle size distribution symmetry is 0.01.

[0024] In one specific embodiment, the graphite material satisfies the following: the La is 60 nm, the Lc is 11.1 nm, the particle crushing force is 20 mN, and the particle size distribution symmetry is 0.052.

[0025] In one specific embodiment, the graphite material satisfies the following: the La is 65 nm, the Lc is 13.2 nm, the particle crushing force is 23 mN, and the particle size distribution symmetry is 0.067.

[0026] In one specific embodiment, the graphite material satisfies the following: the La is 61 nm, the Lc is 10.9 nm, the particle crushing force is 18 mN, and the particle size distribution symmetry is 0.038.

[0027] In one specific embodiment, the graphite material satisfies the following: the La is 66 nm, the Lc is 12.9 nm, the particle crushing force is 23 mN, and the particle size distribution symmetry is 0.067.

[0028] In one specific embodiment, the graphite material satisfies the following: the La is 62 nm, the Lc is 12 nm, the particle crushing force is 23 mN, and the particle size distribution symmetry is 0.056.

[0029] In one specific embodiment, the graphite material satisfies the following: the La is 59 nm, the Lc is 10.8 nm, the particle crushing force is 19 mN, and the particle size distribution symmetry is 0.072.

[0030] In one specific embodiment, the graphite material satisfies the following: the La is 53 nm, the Lc is 8.8 nm, the particle crushing force is 15 mN, and the particle size distribution symmetry is 0.051.

[0031] In one specific embodiment, the graphite material satisfies the following: the La is 67 nm, the Lc is 13.1 nm, the particle crushing force is 23 mN, and the particle size distribution symmetry is 0.083.

[0032] In one specific embodiment, the graphite material satisfies the following: the La is 58 nm, the Lc is 10.3 nm, the particle crushing force is 16 mN, and the particle size distribution symmetry is 0.096.

[0033] In some selectable embodiments, the Dv50 particle size of the graphite material is 10 to 13 μm, for example, 9.5 μm.

[0034] In the present invention, the sphericity (D) refers to the ratio of the surface area of ​​a sphere of the same volume as the material particles to the surface area of ​​the material particles. Generally, the closer the particle is to a sphere in terms of shape, the closer its sphericity is to 1. The sphericity of a sphere is equal to 1, and the sphericity of other objects is less than 1. The sphericity of the graphite material is preferably 0.5 to 1.0, for example, 0.58, 0.59, 0.68, 0.7, 0.71, 0.73, 0.75, or 0.92.

[0035] In the present invention, the sphericity can be measured based on GB / T 37406-2019.

[0036] In some selectable embodiments, the carbon content of the graphite material is 99.9% or more, and this percentage represents the mass percentage of the graphite material.

[0037] In some selectable embodiments, the graphite material is microcrystalline graphite.

[0038] Method for preparing graphite material The method for producing the graphite material described above, provided in a second aspect of the present invention, includes the following steps: In step S1, a first mixing is performed with the graphite precursor and the binder, and a second mixing is performed by adding the solvent to obtain a mixture. Here, the temperature of the first mixing is 5 to 20°C lower than the softening point of the binder. S2, the mixture is press-formed to obtain graphite material. S3. The graphite material is laid on the surface of the graphitization equipment, a graphitization heat retention material is laid on the graphite material, and the graphitization treatment is performed to graphitize the graphite material and obtain graphitized graphite material. S4. The graphitized graphite material is crushed to obtain graphite material.

[0039] In some preferred embodiments, the temperature of the first mixture is 8 to 15°C lower than the softening point of the binder, for example, 10°C.

[0040] In some selectable embodiments, in step S1, the sphericity D of the graphite precursor is 0.7 to 1.0.

[0041] In some selectable embodiments, in step S1, the graphite precursor is natural microcrystalline graphite, which is preferably obtained by pre-treating microcrystalline graphite ore. The pre-treatment preferably includes washing and spheroidizing.

[0042] In some selectable embodiments, in step S1, the fixed carbon content of the graphite precursor is 88% to 91%.

[0043] In some selectable embodiments, in step S1, the Dv50 particle size of the graphite precursor is 6 to 8 μm, for example, 7 μm.

[0044] In some selectable embodiments, in step S1, the mass ratio of the graphite precursor to the binder is (4-7):1, for example, 5:1.

[0045] In some selectable embodiments, in step S1, the binder comprises one or more of petroleum asphalt, phenolic resin, epoxy resin, and coal tar.

[0046] In some selectable embodiments, in step S1, the softening point of the binder is 100 to 250°C, preferably 100 to 130°C, for example, 110°C.

[0047] In some selectable embodiments, in step S1, the solvent is selected from one or more of xylene, toluene, and n-hexane.

[0048] In some selectable embodiments, in step S1, the solid content of the mixture is 40% to 60%, for example, 45%, where the percentage is the percentage of the mass of the solid components of the mixture relative to the mass of the mixture.

[0049] In some selectable embodiments, in step S1, the first mixing method is stirring, where the stirring time is preferably 0.5 to 2 hours, for example, 1 hour. The stirring speed is preferably 30 to 90 r / min.

[0050] In some selectable embodiments, in step S1, the second mixing method is stirring, where the stirring time is preferably 0.5 to 2 hours, for example, 1 hour. The stirring speed is preferably 60 to 120 r / min. The stirring temperature is preferably room temperature.

[0051] In some selectable embodiments, step S1 includes the following steps for producing the graphite precursor: After washing and flotation of the graphite ore, it is crushed and spheroidized to obtain the graphite precursor. Here, the time for the spheroidization treatment is preferably 4 to 24 hours. The spheroidization treatment is preferably carried out using a honeycomb mill.

[0052] In some selectable embodiments, in step S2, the press forming is performed by hydrostatic pressing. Here, the duration of the hydrostatic pressing is preferably 18 to 30 hours, for example, 24 hours. The pressure of the hydrostatic pressing is preferably 150 to 300 MPa, for example, 200 MPa.

[0053] In some selectable embodiments, in step S3, the temperature of the graphitization treatment is higher than 1600°C.

[0054] In some selectable embodiments, the duration of the graphitization treatment in step S3 is 18 to 40 hours, preferably 24 to 36 hours.

[0055] In some optional embodiments, in step S3, the graphitized insulation material is petroleum coke and / or pitch coke.

[0056] In some selectable embodiments, in step S3, the graphitization equipment is a graphitization furnace.

[0057] In some select embodiments, in step S4, after the grinding process, sieving and magnetic purification are performed.

[0058] In some selectable embodiments, in step S4, the grinding process is performed until the particle size Dv50 is 10 to 13 μm.

[0059] Electrochemical apparatus An electrochemical apparatus provided in a third aspect of the present invention includes a negative electrode sheet, the negative electrode sheet includes a negative electrode material layer and a negative electrode current collector, the negative electrode material layer includes the graphite material described above.

[0060] In the present invention, the electrochemical apparatus is preferably a battery.

[0061] In one selectable embodiment, the electrochemical apparatus is a lithium-ion battery. The lithium-ion battery further comprises a positive electrode sheet, a separator, and an electrolyte.

[0062] Negative electrode sheet In the present invention, the negative electrode material layer is installed on at least one surface of the negative electrode current collector.

[0063] In some embodiments, the negative electrode material layer further includes a thickening agent.

[0064] Here, the thickening agent can improve the system viscosity of each component in the negative electrode slurry when added, and may be a thickening agent commonly used in the production of negative electrode sheets in this field, for example, sodium carboxymethyl cellulose (CMC).

[0065] In some embodiments, the negative electrode material layer further includes a conductive agent.

[0066] Here, the conductive agent is not particularly limited and should be any material that is conductive and does not cause a chemical change in the battery. Specifically, it can be a carbon-based material such as natural graphite or artificial graphite, carbon black (Super P), acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, or carbon fiber, metal powder or metal fiber 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.

[0067] In some embodiments, the negative electrode material layer further includes a binder.

[0068] Here, the type of binder is not particularly limited and can be arbitrarily selected from polyvinylidene fluoride, polyvinyl fluoride, polyvinyl alcohol, carboxymethylcellulose, starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid (PAA), ethylene-propylene-diene ternary copolymer and its sulfonates, styrene-butadiene rubber (SBR), fluororubber, and various copolymers, for example, PAA and SBR.

[0069] 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.

[0070] In the present invention, the negative electrode current collector may be a negative electrode current collector commonly used in the art. The negative electrode current collector is a metal foil having a thickness of 3 to 500 micrometers as a substrate for supporting the negative electrode material layer. The material is not particularly limited and should have high conductivity and not cause chemical reactions in the secondary battery system. For example, it may be a foil material formed by surface treatment of nickel, titanium, aluminum, nickel, silver, stainless steel, carbon, etc. The negative electrode current collector usually has a smooth surface, but fine patterns may be formed on its surface, thereby increasing the adhesion between the negative electrode material layer and the current collector. In addition to foil materials, the negative electrode current collector can be any one or more of the various forms such as film, mesh, porous, foam, or nonwoven fabric. Generally, the negative electrode current collector is copper foil.

[0071] In some embodiments, the method for producing the negative electrode sheet includes the following steps: After thoroughly stirring and uniformly mixing each component of the negative electrode material layer in a solvent, the resulting negative electrode slurry is applied to at least one surface of the negative electrode current collector, and then dried, cold-rolled, and slit to obtain a negative electrode sheet.

[0072] Positive electrode sheet In the present invention, the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer installed on at least one surface of the positive electrode current collector.

[0073] In the present invention, the positive electrode active material in the positive electrode material layer may be any positive electrode active material commonly used in the art, such as one or more of the following: lithium nickel cobalt manganese oxide, lithium nickel manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, and lithium cobalt oxide.

[0074] In some selectable embodiments, the positive electrode material layer further includes a binder.

[0075] Here, the type of binder is not particularly limited and can be arbitrarily selected from polyvinylidene fluoride, polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose, starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid (PAA), ethylene-propylene-diene ternary copolymer and its sulfonates, styrene-butadiene rubber (SBR), fluororubber, and various copolymers, for example, PVDF.

[0076] In some selectable embodiments, the binder content is 1% to 10%, for example, 1.8%, where the percentage is a percentage of the total mass of the positive electrode material layer.

[0077] In some selectable embodiments, the positive electrode material layer further comprises a conductive agent.

[0078] Here, the type of conductive agent is not particularly limited and is a reagent used to ensure that the electrode has excellent charge-discharge performance. It can be arbitrarily selected from graphite-based materials such as natural graphite and artificial graphite, carbon black-based materials such as carbon black SP, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black, conductive fibers such as carbon fibers and metal fibers, metal powders such as carbon fluoride 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.

[0079] In one specific embodiment, the conductive agent is conductive carbon SP.

[0080] In some selectable embodiments, the content of the conductive agent is 0.2% to 3%, for example, 1.2%, where the percentage is a percentage of the total mass of the positive electrode material layer.

[0081] In some specific embodiments, the mass ratio of the positive electrode active material, the conductive agent, and the binder in the positive electrode material layer is 97:1.2:1.8.

[0082] In the present invention, the positive electrode current collector may be a positive electrode current collector commonly used in the art. The positive electrode current collector is a metal foil having a thickness of 3 to 500 micrometers as a substrate for supporting the positive electrode material layer. The material is not particularly limited and should have high conductivity and not cause chemical reactions in the secondary battery system. For example, it may be a foil material formed by surface treatment of nickel, titanium, aluminum, nickel, silver, stainless steel, carbon, etc. The positive electrode current collector usually has a smooth surface, but fine patterns may be formed on its surface, thereby increasing the adhesion between the positive electrode material layer and the current collector. In addition to foil materials, the positive electrode current collector can be any one or more of the various forms such as film, mesh, porous, foam, or nonwoven fabric. Generally, the positive electrode current collector is aluminum foil.

[0083] In some embodiments, the method for producing the positive electrode sheet includes the following steps: After thoroughly stirring and uniformly mixing each component of the positive electrode material layer in a solvent, the resulting positive electrode slurry is applied to at least one surface of a positive electrode current collector, dried, and roll-pressed to obtain a positive electrode sheet.

[0084] In some selectable embodiments, the solvent comprises one or more of N-methylpyrrolidone (NMP), dimethyl carbonate, ethylene carbonate, and diethylene carbonate, for example, NMP.

[0085] Separator In the present invention, the separator may be a separator commonly used in the art.

[0086] In some selectable embodiments, the separator can be a polypropylene film or a polyethylene film.

[0087] Here, the permeability of the separator may be 180 to 380 seconds / 100 mL.

[0088] Here, the porosity of the separator may be 30% to 50%.

[0089] Here, the thickness of the separator may be 9 to 18 μm.

[0090] In one specific embodiment, the separator is a polyethylene film. The thickness of the separator is 11 μm. The air permeability of the separator is 230 seconds / 100 mL. The porosity of the separator is 40%.

[0091] electrolyte In some embodiments, the electrolyte may be an electrolyte commonly used in batteries in the art, and generally comprises a non-aqueous solvent, a lithium salt, and additives.

[0092] In some embodiments, the method for manufacturing the lithium-ion battery includes the following steps: stacking a positive electrode sheet, a separator, and a negative electrode sheet in order, with the separator positioned between the positive and negative electrode sheets to provide isolation; then enclosing the stack with an aluminum plastic film, drying it, injecting the electrolyte, and performing processes such as sealing, standing, and chemical conversion to finally manufacture a soft pack battery.

[0093] electronic equipment A fourth aspect of the present invention provides an electronic device that includes the electrochemical apparatus described above.

[0094] Exemplary examples of electronic devices described in the present invention include mobile devices (e.g., mobile phones, tablet computers, laptop computers, video cameras, portable printers / copiers, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), trains, ships and satellites, energy storage systems and backup power supplies, etc., but the present invention is not limited to these.

[0095] Based on the common sense of this field, the above-mentioned preferred conditions can be arbitrarily combined to obtain more preferred examples of the present invention.

[0096] All reagents and raw materials used in this invention are commercially available.

[0097] The main reagents used in the following examples and comparative examples are as follows: The microcrystalline graphite ore was purchased from the Lutang Graphite Processing Plant in Chen Prefecture, Hunan Province. It is classified as Grade 1 Earthy Graphite, with a carbon content of >85%, and contains silicon and metallic impurities. The petroleum pitch (softening point 110°C) was purchased from Liaoning Xinde New Material Technology Co., Ltd., and its model number is XD-110. The petroleum pitch (softening point 130°C) was purchased from Ryonei Shindo New Material Technology Co., Ltd., and its model number is XD-130. The petroleum pitch (softening point 250°C) was purchased from Ryonei Shindo New Material Technology Co., Ltd., and its model number is XD-250. The petroleum pitch (softening point 280°C) was purchased from Ryonei Shindo New Material Technology Co., Ltd., and its model number is XD-280. The commercially available graphite material was purchased from Shanghai Shanshan Technology Co., Ltd., and its model number is FSN-1.

[0098] Example 1 (1) Preparation of graphite material S0, microcrystalline graphite ore is pre-washed and flotated to remove soil, and its fixed carbon content is increased to 90%. After coarse crushing, it is subjected to a spheroidizing treatment using a honeycomb mill for 6 hours to obtain graphite precursors with a spheroidity of 0.83 (Dv50 particle size of 7 μm). S1. The graphite precursor described above and petroleum pitch with a softening point of 110°C are mixed in a mass ratio of 5:1, and the mixture is heated to a temperature 10°C lower than the softening point (100°C) and stirred for 1 hour (stirring speed of 15 r / min to 20 r / min). Then, an appropriate amount of xylene solvent is added to aid in the dispersion of petroleum pitch, and stirring is continued for 1 hour to obtain a mixture (solid content of 45%). S2. Subsequently, the mixture is added to a 40 x 30 cm x 30 cm rubber mold, and then press-molded at a hydrostatic pressure of 200 MPa for 24 hours. After that, the mold is demolded to obtain graphite material. In S3, the aforementioned graphite material is laid on the surface of the Acheson graphitization furnace as a graphitization insulation material, and then a layer of petroleum coke is laid continuously to perform graphitization and vaporization removal. The graphitization temperature is 3000°C and the time is 48 hours. At this point, the graphite material forms graphitized embryos. In step S4, the graphitized embryo obtained in step S3 is removed, ground, sieved, and magnetically purified to obtain graphite material (Dv50 particle size 10 μm, sphericity 0.73, carbon content 99.9%).

[0099] (2) Manufacturing of lithium-ion batteries The positive electrode sheet, separator, and negative electrode sheet are wound together to obtain a cell, which is then packaged in a packaging case and injected with electrolyte. The preparation of the negative electrode sheet involves 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 carboxymethylcellulose (CMC) are mixed in a mass ratio of 97.2:0.5:1.8:0.5 (total 100 parts by mass). Then, 82 parts by mass of deionized water are added and mixed uniformly to obtain a negative electrode slurry. The negative electrode slurry is then uniformly applied onto copper foil. Finally, processes such as drying, rolling, and cutting are carried out to produce a negative electrode sheet. The preparation of the positive electrode sheet involves the following steps: Mixing the positive electrode active materials NCM622, PVDF, and SP in a mass ratio of 97:1.8:1.2 (total 100 parts by mass), then adding 82 parts by mass of NMP to obtain a positive electrode slurry. Applying the obtained positive electrode slurry to at least one surface of an aluminum foil, drying, and roll pressing to obtain a positive electrode sheet. Here, the separator is a polyethylene thin film. The thickness of the separator is 11 μm. The air permeability of the separator is 230 seconds / 100 mL. The porosity of the separator is 40%. Here, we will use a commercially available electrolyte (manufacturer: New Asia Shanshan New Material (Quzhou) Co., Ltd., model number: E3).

[0100] Example 2 The only difference between Example 2 and Example 1 is the following: In the preparation of the graphite material, the spheroidization treatment time in step S0 is 4 hours, and the spheroidity of the obtained graphite precursor is 0.7. All other conditions are the same as in Example 1.

[0101] Example 3 The only difference between Example 3 and Example 1 is the following: In the preparation of the graphite material, the spheroidization treatment time in step S0 is 24 hours, and the spheroidity of the obtained graphite precursor is 0.98. All other conditions are the same as in Example 1.

[0102] Example 4 The only difference between Example 4 and Example 1 is the following: In the preparation of the graphite material, in step S1, the softening point of petroleum pitch is 130°C, and it is heated to 120°C. All other conditions are the same as in Example 1.

[0103] Example 5 The only difference between Example 5 and Example 1 is the following: In the preparation of the graphite material, in step S1, the softening point of petroleum pitch is 100°C, and it is heated to 90°C. All other conditions are the same as in Example 1.

[0104] Example 6 The only difference between Example 6 and Example 1 is the following: In the preparation of the graphite material, the graphitization temperature in step S3 is 2800°C. All other conditions are the same as in Example 1.

[0105] Example 7 The only difference between Example 7 and Example 1 is the following: In the preparation of the graphite material, the graphitization temperature in step S3 is 3200°C. All other conditions are the same as in Example 1.

[0106] Example 8 The only difference between Example 8 and Example 1 is the following: In the preparation of the graphite material, in step S4, the graphitized embryo is crushed, sieved, and magnetically purified to control the Dv50 particle size to 13 μm. All other conditions are the same as in Example 1.

[0107] Example 9 The only difference between Example 9 and Example 1 is the following: In the preparation of the graphite material, in step S1, the softening point of petroleum pitch is 250°C, and it is heated to 240°C. All other conditions are the same as in Example 1.

[0108] Example 10 The only difference between Example 10 and Example 1 is the following: In the preparation of the graphite material, in step S1, the mass ratio of graphite precursor to petroleum pitch is 4:1. All other conditions are the same as in Example 1.

[0109] Example 11 The only difference between Example 11 and Example 1 is the following: In the preparation of the graphite material, in step S1, the mass ratio of graphite precursor to petroleum pitch is 7:1, and simultaneously, in step S4, the graphitized embryo is crushed, sieved, and magnetically purified to control the Dv50 particle size to 9.5 μm. All other conditions are the same as in Example 1.

[0110] Example 12 The only difference between Example 12 and Example 1 is the following: In the preparation of the graphite material, the graphitization temperature in step S3 is 1700°C. All other conditions are the same as in Example 1.

[0111] Comparative Example 1 The only difference between this comparative example and Example 1 is the following: In the preparation of the graphite material, the spheroidization treatment time in step S0 is 2 hours, and the spheroidity of the obtained graphite precursor is 0.6. All other conditions are the same as in Example 1.

[0112] Comparative Example 2 The only difference between this comparative example and Example 1 is the following: In the preparation of the graphite material, in step S1, the softening point of petroleum pitch is 280°C, and it is heated to 270°C. All other conditions are the same as in Example 1.

[0113] Comparative Example 3 The only difference between this comparative example and Example 1 is the following: In the preparation of the graphite material, the graphitization temperature in step S3 is 3500°C. All other conditions are the same as in Example 1.

[0114] Comparative Example 4 The only difference between this comparative example and Example 1 is the following: In the preparation of the graphite material, in step S4, the graphitized embryo is crushed, sieved, and magnetically purified to control the Dv50 particle size to 7 μm. All other conditions are the same as in Example 1.

[0115] Comparative Example 5 The only difference between this comparative example and Example 1 is the following: Instead of fabricating a graphite material, a commercially available graphite material (FSN-1) is used as the negative electrode active material in the production of the lithium-ion battery. All other conditions are the same as in Example 1.

[0116] Comparative Example 6 The only difference between this comparative example and Example 1 is the following: In the preparation of the graphite material, in step S3, a petroleum coke layer is not laid, and simultaneously, in step S4, the graphitized embryo is crushed, sieved, and magnetically purified to control the Dv50 particle size to 11.5 μm. All other conditions are the same as in Example 1.

[0117] Comparative Example 7 The only difference between this comparative example and Example 1 is the following: In the preparation of the graphite material, in step S1, the material is heated to a temperature 4°C lower than the softening point (106°C). All other conditions are the same as in Example 1.

[0118] Comparative Example 8 The only difference between this comparative example and Example 1 is the following: In the preparation of the graphite material, steps S2 to S3 are replaced with the following steps. S2. The mixture is subjected to heat treatment (temperature: 700°C, time: 3 hours). S3. Graphitization treatment is performed (temperature: 3000°C, duration: 48 hours). Other conditions are the same as in Example 1.

[0119] Comparative Example 9 The only difference between this comparative example and Example 1 is the following: In the preparation of the graphite material, step S3 is replaced with the following step. S3-1, Acid-alkali treatment is performed. First, acid treatment is performed using aqua regia (30% by mass fraction) and hydrofluoric acid (40% by mass fraction) in that order, and then treatment is performed with a 40% by mass fraction sodium hydroxide solution. S3-2. Subsequently, high-temperature removal is performed (temperature: 1200°C, duration: 6 hours). Simultaneously, in step S4, the graphitized embryos are crushed, sieved, and magnetically purified to control the Dv50 particle size to 6.3 μm. Other conditions are the same as in Example 1.

[0120] Effect Example 1 The graphite materials obtained in Examples 1-12 and Comparative Examples 1-9 were subjected to measurements of lattice constants La and Lc, particle crushing force F, particle size distribution symmetry S, and sphericity D.

[0121] (1) Lattice constants La and Lc The obtained graphite material is used as the measurement sample. The graphite material and 50 mL of n-hexane are added to a beaker, and ultrasonic vibration is performed for 5 minutes. Then, 100 μL of the solution is drawn up using a micropipette and dropped onto a copper mesh for TEM observation. The copper mesh is then quickly dried, and observation is performed. Selected field diffraction observation is performed using a TEM to determine the d(110) and full width at half maximum of the sample. Subsequently, θ can be calculated based on the following d(110).

number

number

number

number

[0122] (2) Particle crushing force F We will measure the particle crushing force using IEST's single-particle force characterization test system (SPFT2000). Specifically, the procedure is as follows: 0.5 g of graphite material is added to a beaker containing 20 ml of anhydrous ethanol, and ultrasonic dispersion is performed for 5 minutes to obtain a dispersion. 100 μL of the above dispersion is dropped onto a glass slide, and the glass slide is transferred to the SPFT2000 sample observation stage. A single particle is positioned using the SPFT2000 optical microscope, and the indenter is controlled to compress downwards at a constant velocity, and the stress transition point during the particle compression process is recorded as the particle crushing force.

[0123] (3) Particle size distribution symmetry S Referencing GB / T 41949-2022, the graphite material is measured using a laser particle size diffractometer (Malvern 3000). From the measurement results, the D(3,4) and Dv50 particle size data are directly read, and S can be obtained by calculating based on S = [D(3,4) - Dv50] / Dv50.

[0124] (4) Sphericity D Sphericity is measured according to GB / T 37406-2019.

[0125] (5) 2T powder compression density (2T powder pressure) Referencing the national standard GB / T 24533-2019, the 2T powder compression density was measured for graphite material powder.

[0126] The measurement results described above are shown in Table 1.

[0127] Effect Example 2 The following electrochemical performance measurements were performed on the lithium-ion batteries prepared in Examples 1-12 and Comparative Examples 1-9. Before measurement, first, the prepared lithium-ion battery is activated by performing one charge-discharge cycle at 25°C using 0.1C within the battery operating voltage range of 2.8V (discharge cutoff voltage) to 4.35V (charge cutoff voltage). After that, the following items are measured.

[0128] (1) Charging capacity and discharging capacity A lithium-ion battery is connected to a blue-green charge / discharge test device, and long-term cycle charging and discharging is performed to measure its charge and discharge capacities. The operating voltage range for battery measurement is 2.8V (discharge cutoff voltage) to 4.35V (charge cutoff voltage), and the measurement magnification is 0.3C. Initial efficiency = Discharge capacity / Charge capacity × 100%

[0129] (2) Quick charging time The cell is directly charged to an 8% SOC state with a current of 0.33C. Then, based on the measurement of the window of the actual cell's 3-electrode test, the charging windows of 10%, 20%, 30%, 40%, 50%, 60%, 70%, and 80% are designated as C1, C2, C3, C4, C5, C6, C7, and C8, respectively, and the cell is gradually charged up to 80%. That is, C1 is used from 8% to 10%, C2 is used from 10% to 20%, and so on, and the charging time to the SOC state from 8% to 80% is recorded as the evaluation criterion for rapid 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.

[0130] (3) Number of cycles A lithium-ion battery is connected to a blue-green charge / discharge test device, and then a long-term cycle is performed at a multiplier of 0.3C until the ratio of the capacity of the nth cycle to the capacity of the first cycle at 0.3C falls below 80%. The capacity retention rate of the (n-1)th cycle is defined as 80%, the number of cycles is recorded as (n-1), and the measurement is stopped.

[0131] (4) Number of storage days At 25°C, the constant capacitance is recorded as C0 using a current of 0.33C, and then the cell is stored under high-temperature conditions of 60°C. Subsequently, the cell is removed at 7-day intervals, its capacitance is measured at room temperature, and recorded as C1, C2...Cn. The number of days until Cn first falls below 80% of C0 is the storage time.

[0132] (5) Self-discharge performance At 25°C, the full charge capacity is recorded as C0 using a current of 0.33C, and the voltage at that time is recorded as V1. If the voltage obtained after 90 days of storage is V2, then the self-discharge voltage is V1 - V2. The measurement results described above are shown in Table 2.

[0133] [Table 1]

[0134] [Table 2]

[0135] As can be seen from Tables 1 and 2, the La of the graphite materials prepared in Examples 1-12 was between 53 and 72 nm, the Lc was between 8.8 and 15 nm, the particle crushing force F was between 15 and 25 mN, the particle size distribution symmetry S was between 0.01 and 0.1, the Dv50 particle size was between 9.5 and 13 μm, the sphericity D was between 0.58 and 0.92, and the 2T powder pressure was between 1.59 and 1.75 g.cc. -1This is within the range. A lithium-ion battery obtained using this graphite material as the negative electrode material can guarantee excellent initial efficiency and rapid charging performance, and combines excellent self-discharge performance, capacity performance, and cycle performance. Specifically, the initial efficiency can reach 90% or more, and the rapid charging time can reach 30 seconds or less, and even 15 seconds or less. Based on this, the discharge capacity can reach 355 mAh / g or more, the number of cycles can reach 1700 or more, the storage period can reach 180 days or more, and the self-discharge voltage can be lower than 0.7V.

[0136] The inventors' research has shown that when La and Lc are too small, compaction and capacity problems occur, and when the particle crushing force F is too small, the cycling performance is poor. Only with the specific La, Lc, and particle crushing force F of the present invention can the above-mentioned electrochemical performance be achieved.

[0137] Compared to Example 1, Comparative Examples 1, 3, and 6-9 have excessively large La and Lc values ​​in the graphite material, resulting in excessively low particle crushing force F. The resulting lithium-ion batteries exhibit significantly reduced discharge capacity, poor initial efficiency, long rapid charging times, and clearly worse cycle count, storage life, and self-discharge voltage.

[0138] Compared to Example 1, Comparative Example 5 is distinguished by having excessively large La and Lc values ​​in the graphite material, resulting in an excessively small particle crushing force F. Although the resulting lithium-ion battery exhibits high initial efficiency, a high number of cycles, and long storage life, and a low self-discharge voltage, its discharge capacity is reduced, and the rapid charging time is significantly extended, thus failing to combine excellent initial efficiency and rapid charging performance.

[0139] Compared to Example 1, Comparative Examples 2 and 7 are distinguished by their high particle crushing force in the graphite material, but by excessively high La and Lc values. The resulting lithium-ion batteries exhibit significantly reduced discharge capacity, poor initial efficiency, long rapid charging times, and clearly worse cycle count, storage life, and self-discharge voltage.

[0140] Compared to Example 1, Comparative Example 4 is distinguished by having equivalent La and Lc in the graphite material, but with a significantly lower particle crushing force F. The resulting lithium-ion battery exhibits a short rapid charging time, but its discharge capacity, initial efficiency, number of cycles, storage life, and self-discharge voltage are all clearly inferior, failing to combine excellent rapid charging time and initial efficiency.

[0141] Although specific embodiments of the present invention have been described above, those skilled in the art should understand that this is merely an illustrative description and that the scope of protection of the present invention is limited by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and substance of the present invention, and such changes and modifications will all be within the scope of protection of the present invention. [Industrial applicability]

[0142] This invention relates to graphite materials, methods for producing the same, electrochemical apparatus, and electronic equipment, and has industrial applicability.

Claims

1. A graphite material that meets the following conditions. a) La ≤ 72 nm and Lc ≤ 15 nm, where La is the lattice constant at the 110 plane of the graphite crystal in the graphite material, and Lc is the lattice constant at the 002 plane of the graphite crystal in the graphite material. b. F ≥ 15 mN, where F is the particle crushing force.

2. The graphite material according to claim 1 that satisfies one or more of the following conditions. a, La≦60 nm. b, Lc≦12 nm. c, 15 mN≦F≦25 mN. d, 0 < S ≤ 0.1, where S is the particle size distribution symmetry.

3. The graphite material according to claim 1 that satisfies one or more of the following conditions. a. The Dv50 particle size of the graphite material is 10 to 13 μm. b. The sphericity of the graphite material is 0.5 to 1.

0. c. The carbon content of the graphite material is 99.9% or more, and the percentage represents the proportion of the mass percentage of the graphite material. d. The graphite material is microcrystalline graphite.

4. S1. A first mixing is performed with the graphite precursor and the binder, a solvent is added and a second mixing is performed to obtain the mixture, and the temperature of the first mixing is 5 to 20°C above the softening point of the binder. Low steps, S2, The step of press molding the mixture to obtain a graphite material, S3, the steps of laying the graphite material on the surface of the graphitization equipment, laying a graphitization heat-insulating material on the graphite material, performing a graphitization treatment to graphitize the graphite material and obtain graphitized graphite material, S4, the step of crushing the graphitized graphite material to obtain graphite material, A method for producing a graphite material according to any one of claims 1 to 3, including the following:

5. The method for producing a graphite material according to claim 4, wherein in step S1, the temperature of the first mixing is 8 to 15°C lower than the softening point of the binder.

6. The method for producing a graphite material according to claim 4, wherein step S1 satisfies one or more of the following conditions a to i. a. In step S1, the sphericity of the graphite precursor is 0.7 to 1.

0. b. In step S1, the graphite precursor is natural microcrystalline graphite. c. In step S1, the fixed carbon content of the graphite precursor is 88% to 91%, and the percentage represents the proportion of the mass percentage of the graphite precursor. d. In step S1, the Dv50 particle size of the graphite precursor is 6 to 8 μm. e. In step S1, the mass ratio of the graphite precursor to the binder is (4-7):

1. f. In step S1, the binder comprises one or more of petroleum asphalt, phenolic resin, epoxy resin, and coal tar. g. In step S1, the softening point of the binder is 100 to 250°C. h, in step S1, the solvent is selected from one or more of xylene, toluene, and n-hexane. i. In step S1, the solid content of the mixture is 40% to 60%, and the percentage represents the mass percentage of the solid component of the mixture relative to the total mass of the mixture.

7. The method for producing a graphite material according to claim 4, wherein step S1 and step S2 satisfy one or more of the following conditions a to d. a. In step S1, the first mixing method is stirring. b. In step S1, the second mixing method is stirring. c. In step S1, the method for producing the graphite precursor includes the steps of washing and flotation the graphite ore, followed by crushing and spheroidizing to obtain the graphite precursor. d. In step S2, the press forming is performed by a hydrostatic press.

8. The method for producing a graphite material according to claim 4, wherein step S3 and step S4 satisfy one or more of the following conditions a to f. a. In step S3, the temperature of the graphitization treatment is higher than 1600°C. b. In step S3, the time for the graphitization treatment is 18 to 40 hours. c. In step S3, the graphitized heat-insulating material is petroleum coke and / or pitch coke. d. In step S3, the graphitization equipment is a graphitization furnace. e. Step S4 further includes sieving and magnetic purification after the grinding process. f. In step S4, the grinding process is performed until the particle size Dv50 of the particles is 10 to 13 μm.

9. An electrochemical apparatus comprising a negative electrode sheet, wherein the negative electrode sheet comprises a negative electrode material layer and a negative electrode current collector, and the negative electrode material layer comprises the graphite material described in any one of claims 1 to 3.

10. Electronic equipment including the electrochemical apparatus described in claim 9.

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