Carbon-based material and preparation method therefor, secondary battery and electric device

Abstract

Provided in the present disclosure are a carbon-based material and a preparation method therefor, a secondary battery and an electric device. The carbon-based material is granular, and has a degree of sphericity of 0.5-1.0. The carbon-based material satisfies: D1 / D2 being 0.4-0.62, and D2 / D3 being 0.1-0.16, wherein D1 is the proportion of the total volume of particles having a particle diameter of smaller than or equal to 3 μm in the carbon-based material to the total volume of all the particles in the carbon-based material; D2 is the proportion of the total volume of particles having a particle diameter of greater than 3 μm and less than 5 μm in the carbon-based material to the total volume of all the particles in the carbon-based material; and D3 is the proportion of the total volume of the particles having a particle diameter of greater than or equal to 5 μm in the carbon-based material to the total volume of all the particles in the carbon-based material.

Description

Carbon-based material, preparation method thereof, secondary battery, and electric device

[0001] Cross-reference to related applications

[0002] The present disclosure is based on and claims priority to Chinese Patent Application No. 202410479998.1, filed on April 19, 2024, entitled “Carbon-based material, preparation method thereof, secondary battery, and electric device,” the entire contents of which are incorporated herein by reference.

[0003] The present disclosure is based on and claims priority to International Patent Application No. PCT / CN2024 / 112176, filed on August 14, 2024, entitled “Carbon-based material, preparation method thereof, secondary battery, and electric device,” the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0004] The present disclosure relates to the technical field of secondary batteries, and in particular to a carbon-based material, a preparation method thereof, a secondary battery, and an electric device. BACKGROUND

[0005] In recent years, with the continuous improvement of the power of electric equipment such as mobile phones, computers, electric tools, and electric vehicles, people's requirements for the energy density of secondary batteries have also increased. Carbon-based materials have high energy density and excellent charge-discharge efficiency, and are widely used as negative electrode materials for secondary batteries.

[0006] However, the above-mentioned carbon-based material will damage the current collector when increasing the compaction density of the pole piece by pressing the pole piece, which will affect the safety. SUMMARY

[0007] The present disclosure is made in view of the above-mentioned problems, and aims to provide a carbon-based material, a preparation method thereof, a secondary battery, and an electric device, which can obtain high compaction density without damaging the current collector, thereby improving the safety of the battery.

[0008] To achieve the above object, the first aspect of the present disclosure provides a carbon-based material, which is in a granular form, and the sphericity of the carbon-based material particles is 0.5-1.0; the carbon-based material satisfies: D1 / D2 is 0.4-0.62, and D2 / D3 is 0.1-0.16; wherein, D1 is the proportion of the total volume of the particles with a particle size of 3 μm or less in the total volume of all particles in the carbon-based material; D2 is the proportion of the total volume of the particles with a particle size of greater than 3 μm and less than 5 μm in the total volume of all particles in the carbon-based material; and D3 is the proportion of the total volume of the particles with a particle size of 5 μm or greater in the total volume of all particles in the carbon-based material.

[0009] In the present disclosure, by adjusting the sphericity of the carbon-based material particles and the proportion of the particle size, the current collector can be not damaged in the case of achieving high compaction density, thereby facilitating the improvement of the safety of the battery.

[0010] In some embodiments, the carbon-based material satisfies: D1 / D2 is 0.45-0.62, and D2 / D3 is 0.14-0.16. By making D1 / D2 and D2 / D3 of the carbon-based material particles in the above range, the integrity of the current collector in the case of achieving high compaction density is more facilitated, and the safety of the battery is more facilitated to improve.

[0011] In some embodiments, the sphericity of the carbon-based material particles is 0.6-1.0. By making the sphericity of the carbon-based material particles in the above range, the damage to the current collector can be further reduced, and the safety performance of the battery is more facilitated to improve.

[0012] In some embodiments, the carbon-based material comprises porous carbon and / or silicon-carbon.

[0013] In some embodiments, the specific surface area of the porous carbon is 1200 m 2 / g-2100 m 2 / g. By making the specific surface area of the porous carbon in the above range, it is facilitated to improve the particle integrity after the electrode plate is pressed.

[0014] In some embodiments, the carbon-based material is a hard carbon material, or a mixture of a hard carbon material and at least one selected from a soft carbon material and graphite.

[0015] In some embodiments, the carbon-based material satisfies: D1 is 4%-8%, and / or, D2 is 9%-13%, and / or, D3 is 80%-90%. In the present disclosure, by making the volume distribution particle sizes D1, D2 and D3 of the carbon-based material in the above range, it is facilitated to achieve displacement and pore self-filling when the particles are pressed.

[0016] In some embodiments, the particle size number distribution Dn10 of the carbon-based material is 0.35-0.60 μm. In the present disclosure, by making the particle size number distribution Dn10 of the carbon-based material within the above range, it is beneficial to achieve the closest packing of particles and improve the compaction density.

[0017] In some embodiments, the I D / I G of the carbon-based material is 1.1-1.35, wherein I D represents the D-peak intensity of the Raman spectrum at 1350±50 cm -1 -1.35, wherein I G represents the G-peak intensity of the Raman spectrum at 1580±50 cm -1 -1.35. The I D / I G of the carbon-based material within the above range makes the surface carbon of the carbon-based material have a high degree of order and few surface defects, which is beneficial to improve the compaction density.

[0018] In some embodiments, the content of surface oxygen elements of the carbon-based material is 5%-15%. The content of surface oxygen elements of the carbon-based material within the above range is beneficial to improve the processing performance and compaction density of the secondary battery.

[0019] In some embodiments, the powder compaction density of the carbon-based material at 2 t is 0.8 g / cm 3 -1.1 g / cm 3 . When the powder compaction density of the carbon-based material is within the above range, it is beneficial to improve the compaction density of the negative electrode sheet.

[0020] The second aspect of the present disclosure provides a preparation method of a carbon-based material, comprising:

[0021] The processing step comprises dissolving three parts of carbon precursors in solvents respectively, forming a first carbon precursor, a second carbon precursor and a third carbon precursor by spray drying at 150-200°C; and then processing the first carbon precursor, the second carbon precursor and the third carbon precursor respectively to obtain a first precursor, a second precursor and a third precursor; the volume distribution particle size Dv10, Dv50 and Dv90 of the first precursor are 3-4 μm, 9-10 μm and 15-20 μm respectively; the volume distribution particle size Dv10, Dv50 and Dv90 of the second precursor are 2-3 μm, 5-6 μm and 8-9 μm respectively, and the volume distribution particle size Dv10, Dv50 and Dv90 of the third precursor are 1-2 μm, 3-4 μm and 5-6 μm respectively.

[0022] The first precursor, the second precursor and the third precursor are mixed in a mass ratio of (0-9):(0-4):(1-9) to form the carbon-based material; wherein the mass of the first precursor and the second precursor is not 0 at the same time.

[0023] The carbon-based material of the first aspect of the present disclosure can be obtained by the preparation method of the present disclosure.

[0024] In some embodiments, in the processing step, the carbon precursor and the solvent are mixed in a mass ratio of (1:1)-(1:3) to form the first carbon precursor; and / or the carbon precursor and the solvent are mixed in a mass ratio of (1:3)-(1:9) to form the second carbon precursor; and / or the carbon precursor and the solvent are mixed in a mass ratio of (1:10)-(1:20) to form the third carbon precursor.

[0025] In some embodiments, before the mixing step, the method further comprises a drying step of vacuum drying the first precursor, the second precursor and the third precursor.

[0026] In some embodiments, in the processing step, the first carbon precursor, the second carbon precursor and the third carbon precursor are respectively subjected to pre-carbonization treatment at 300-800°C, then water vapor is introduced and subjected to activation treatment at 800-950°C, and then subjected to classification treatment to obtain the first precursor, the second precursor and the third precursor.

[0027] In some embodiments, the carbon-based material comprises porous carbon and / or silicon-carbon.

[0028] In some embodiments, the carbon-based material is a hard carbon material, or a mixture of a hard carbon material and at least one selected from a soft carbon material and graphite.

[0029] The third aspect of the present disclosure provides a secondary battery comprising a negative electrode sheet comprising a negative electrode current collector and a negative electrode film layer comprising a negative electrode active material on at least one surface of the negative electrode current collector, wherein the negative electrode active material comprises the carbon-based material of the first aspect of the present disclosure, or the carbon-based material obtained by the preparation method of the second aspect of the present disclosure.

[0030] In some embodiments, the secondary battery is at least one of a potassium ion battery, a sodium ion battery, a lithium ion battery, and a sodium-potassium ion hybrid battery.

[0031] The fourth aspect of the present disclosure provides an electric device comprising the secondary battery of the third aspect of the present disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0032] FIG. 1 is a schematic view of a battery cell according to an embodiment of the present disclosure.

[0033] FIG. 2 is an exploded view of the battery cell shown in FIG. 1 according to an embodiment of the present disclosure.

[0034] FIG. 3 is a schematic view of a battery module according to an embodiment of the present disclosure.

[0035] FIG. 4 is a schematic view of a battery pack according to an embodiment of the present disclosure.

[0036] FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to an embodiment of the present disclosure.

[0037] FIG. 6 is a schematic view of an electric device using a secondary battery as a power source according to an embodiment of the present disclosure.

[0038] FIG. 7 is a particle size-volume distribution curve of a carbon-based material according to Embodiment 1 of the present disclosure.

[0039] BRIEF DESCRIPTION OF DRAWINGS 1: battery pack; 2: upper case; 3: lower case; 4: battery module; 5: battery cell; 51: case; 52: electrode assembly; 53: top cover assembly DETAILED DESCRIPTION

[0040] Hereinafter, a carbon-based material, a method of manufacturing the same, a secondary battery, and an electric device according to the present disclosure will be described in detail with appropriate reference to the accompanying drawings. However, there can be cases where unnecessary detailed descriptions are omitted. For example, there can be cases where detailed descriptions of matters well known in the art, repetitive descriptions of substantially identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the accompanying drawings and the following description are provided so that those skilled in the art can fully understand the present disclosure, and are not intended to limit the subject matter recited in the claims.

[0041] The ranges disclosed herein are defined by their lower and upper endpoints, given that a range is defined by selecting a lower endpoint and an upper endpoint, the selected lower and upper endpoints define the boundaries of the particular range. Ranges defined by endpoints can be inclusive or exclusive without further qualification. Ranges are arbitrarily combinable, i.e., any lower endpoint of a range can be combined with any upper endpoint of another range, even if the other range's lower endpoint and this range's upper endpoint are the same, unless the context dictates otherwise. For example, if a range of 60-120 and a range of 80-110 are listed, it is understood that a range of 60-110 and a range of 80-120 are also contemplated. Furthermore, if a minimum range value of 1 and 2 are listed, and if a maximum range value of 3, 4, and 5 are listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In the present disclosure, unless otherwise stated, a numerical range "a-b" indicates a shorthand way of describing each and every number that is an integer within the given range of a and b, wherein a and b are both real numbers. For example, the numerical range "0-5" indicates herein that all real numbers between "0-5" have been listed, "0-5" is merely a shorthand way of describing each and every number that is an integer within the given range of 0 and 5. Also, when a parameter is stated to be an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0042] Unless otherwise specified, all embodiments and optional embodiments of the present disclosure can be combined with each other to form new technical solutions.

[0043] Unless otherwise specified, all technical features and optional technical features of the present disclosure can be combined with each other to form new technical solutions.

[0044] Unless otherwise specified, all steps of the present disclosure can be performed in sequence or randomly, and preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method also comprises step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0045] Unless otherwise specified, the terms used in the present disclosure have the commonly understood meanings understood by those skilled in the art.

[0046] Unless otherwise specified, the values of the parameters mentioned in the present disclosure can be measured by various test methods commonly used in the art, for example, can be measured according to the test methods given in the present disclosure.

[0047] Unless otherwise specified, in the present disclosure, the term "active ion" refers to an ion capable of being reversibly intercalated and deintercalated between the positive and negative electrodes of a secondary battery, including but not limited to lithium ions.

[0048] In recent years, carbon-based materials have rapidly developed in application due to their high energy density, excellent charge and discharge efficiency, and wide sources. In order to improve the reversible charge and discharge capacity of the battery, the carbon-based material needs a certain compressive strength. However, high-strength materials cause the following problems: during the cold pressing process of the pole piece, increasing the pressure to increase the compaction density of the pole piece, the corners of the high-strength material cause indentation or direct cutting of the current collector (for example, copper foil, etc.), which cannot obtain high pressure density, and affects the safety of the battery.

[0049] Based on this, the present disclosure provides a carbon-based material and a preparation method thereof, a secondary battery, and an electric device, wherein the carbon-based material is safe and does not damage the current collector (for example, copper foil, etc.), and can achieve higher compaction density of the pole piece.

[0050] Carbon-based material

[0051] The first aspect of the present disclosure provides a carbon-based material, wherein the carbon-based material is in the form of particles, and the sphericity of the carbon-based material particles is 0.5-1.0; the carbon-based material satisfies: D1 / D2 is 0.4-0.62, and D2 / D3 is 0.1-0.16; wherein D1 is the proportion of the total volume of particles with a particle size of less than or equal to 3 μm in the carbon-based material to the total volume of all particles in the carbon-based material; D2 is the proportion of the total volume of particles with a particle size of greater than 3 μm and less than 5 μm in the carbon-based material to the total volume of all particles in the carbon-based material; and D3 is the proportion of the total volume of particles with a particle size of greater than or equal to 5 μm in the carbon-based material to the total volume of all particles in the carbon-based material.

[0052] In the present disclosure, by adjusting the sphericity of the carbon-based material particles and the ratio of the particle size, different sizes of particles can achieve the closest packing under pressure, and in the process of absorbing stress, the particles slide, arrange and fill to form a stable state, reducing the stress and strain of the particles themselves and the current collector, so that the current collector is not damaged under the condition of achieving high compaction density, thereby improving the safety of the battery.

[0053] In addition, under high compaction density, the particles themselves slip and tightly fill, which can weaken the local stress of the current collector, reduce the risk of interruption in the cold pressing process, and improve the processability of the material.

[0054] The carbon-based material satisfies: D1 / D2 is 0.45-0.62, and D2 / D3 is 0.1-0.16. Optionally, the carbon-based material satisfies: D1 / D2 is 0.45-0.62, and D2 / D3 is 0.14-0.16. By making D1 / D2, D2 / D3 of the carbon-based material particles within the above ranges, it is more conducive to achieving high compaction density without damaging the current collector, and thus, it is more conducive to improving the safety of the battery.

[0055] In some embodiments, the sphericity of the carbon-based material particles is 0.6-1.0. By making the sphericity of the carbon-based material particles within the above ranges, it is possible to further reduce damage to the current collector, and it is more conducive to improving safety performance.

[0056] In some embodiments, the carbon-based material includes porous carbon and / or silicon-carbon. In some embodiments, the carbon-based material is a silicon-carbon material, and silicon particles are distributed within a carbon skeleton having a hierarchical pore structure.

[0057] In some embodiments, the specific surface area of the porous carbon is 1200 m 2 / g-2100 m 2 / g; optionally, the specific surface area of the porous carbon is 1200 m 2 / g-1800 m 2 / g. By making the specific surface area of the porous carbon within the above ranges, it is conducive to improving the realization of the integrity of the particles after the electrode plate is pressed.

[0058] In some embodiments, the carbon-based material satisfies: D1 is 4%-8%, and / or, D2 is 9%-13%, and / or, D3 is 80%-90%. In the present disclosure, by making the volume distribution particle sizes D1, D2 and D3 of the carbon-based material within the above ranges, it is conducive to realizing displacement and pore self-filling when the particles are pressed.

[0059] In some embodiments, the particle size number distribution Dn10 of the carbon-based material is 0.35 μm-0.60 μm; optionally, Dn10 is 0.4 μm-0.55 μm. In the present disclosure, by making the particle size number distribution Dn10 of the carbon-based material within the above ranges, it is conducive to realizing the closest packing of the particles and improving the compaction density.

[0060] In some embodiments, the carbon-based material satisfies: I D / I G is 1.1-1.35, optionally, the carbon-based material satisfies: I D / I G is 1.3; wherein I D represents the D peak intensity of the Raman spectrum at 1350±50 cm -1 . In the present disclosure, by making the IG represents the intensity of the G peak of the Raman spectrum at 1580±50 cm -1 -1.1, 1.2, 1.3, 1.35, or any value within the range between any two of the values. The I D / I G of the carbon-based material is 1.1, 1.2, 1.3, 1.35, or any value within the range between any two of the values. The I D / I G within the above range, so that the carbon-based material has a high degree of order of surface carbon and few surface defects, which is conducive to improving the compaction density.

[0061] In some embodiments, the content of surface oxygen elements of the carbon-based material is 5% to 15%. Illustratively, the content of surface oxygen elements of the carbon-based material is 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or any value within the range between any two of the values. The content of surface oxygen elements of the carbon-based material within the above range can make the viscosity of the slurry containing the carbon-based material be within a suitable range, which is conducive to improving the processing performance and compaction density of the secondary battery.

[0062] In some embodiments, the powder compaction density of the carbon-based material at 2t is 0.8 g / cm 3 -1.1 g / cm 3 When the powder compaction density of the carbon-based material is within the above range, it is conducive to improving the compaction density of the negative electrode sheet.

[0063] In the present disclosure, the sphericity of the particles of the carbon-based material can be obtained by the following method: the aspect ratio (short side / long side) of not less than 10 particles in the material powder SEM or the sheet SEM is counted and averaged.

[0064] In the present disclosure, D1, D2, and D3 of the carbon-based material can be calculated by the following method:

[0065] First, the particle size distribution curve of the carbon-based material is tested, for example, the test can be performed according to GB / T 19077-2016. Specifically, the test includes a pretreatment process and a test process; pretreatment: a clean beaker is taken, and an appropriate amount of carbon-based material is weighed, and ultrasonic treatment is performed at 120 W for 5 min to ensure that the carbon-based material is completely dispersed in the dispersant; test: the carbon-based material is poured into the sample tower and circulated to the test light path system with the solution, and the particle size distribution curve of the particles can be obtained by receiving and measuring the energy distribution of the scattered light under the irradiation of the laser beam.

[0066] Secondly, D1, D2, and D3 can be obtained by fitting the particle size-volume distribution curve, gridding it, and counting the grid area. Specifically, the horizontal coordinate unit grid of the particle size-volume distribution curve is adjusted to 0.2, and the vertical coordinate unit grid is adjusted to 1.0, that is, the area of ​​the smallest unit grid is 0.2, and the proportion is expressed by counting the number of grids occupied by different areas. This method is used to obtain the proportions D1, D2, and D3 of particles less than or equal to 3μm, greater than 3μm and less than 5μm, and greater than or equal to 5μm.

[0067] In this disclosure, the particle size distribution Dn10 of a carbon-based material has a meaning generally known in the art. For example, a Dn10 of 10 μm indicates that the percentage of particles with a diameter less than or equal to 10 μm in the total number of particles is 10%. The particle size distribution Dn10 can be determined using methods generally known in the art, such as those described in GB / T 19077-2016.

[0068] In this disclosure, the specific surface area of ​​porous carbon, BET, is a well-known term in the art and can be measured using instruments and methods known in the art. For example, it can be measured using the nitrogen adsorption specific surface area analysis test method according to GB / T 19587-2017 and calculated using the BET (Brunauer Emmett Teller) method. The test instrument can be a Tri-Star 3020 specific surface area pore size analyzer from Micromeritics, USA.

[0069] In the present disclosure, the carbon-based material I D / I G The value can be tested using Raman spectrometer, I D The Raman spectrum of the material is 1350±50cm -1 The D peak intensity at I G The Raman spectrum of the material is 1580±50cm -1 The test conditions are: excitation wavelength 532nm, power 0.5%, grating 600 lines, objective lens 50 times, integration time 10s, accumulation times 3 times, surface scanning, obtain the D peak and G peak intensity of 100 points, calculate the I of 100 points D / I G , remove the largest and smallest 30 I D / I G The average value of the remaining 40 points is the I D / I G The testing instrument may be a Horiba LabRAM HR800 Raman spectrometer.

[0070] In the present disclosure, the surface oxygen element content of the carbon-based material can be obtained by semi-quantitative analysis of the surface functional groups of the carbon-based material, i.e., by X-ray photoelectron spectroscopy test of the carbon-based material, converting the signal intensity measured by X-ray photoelectron spectroscopy into the content of the element, and converting the peak area into the content of the corresponding element. The equipment model used is Axis Supra / Supra+, sensitivity 450W Al Kα / Ag Lα monochromatic X-ray source, energy resolution ≤0.45eV. Specifically, the XPS spectrum of the carbon-based material is fitted by XPS peak41, a fitting software, a suitable baseline is set, fitting peaks are added, and then Gaussian fitting is performed until the residual is less than 10.

[0071] In the present disclosure, the compacted density of the carbon-based material is the meaning known in the art, which can be measured by instruments and methods known in the art. For example, GB / T 24533-2009 can be referred to, and the compacted density can be measured by an electronic pressure testing machine (e.g., a UTM7305 type electronic pressure testing machine). An exemplary test method is as follows: 1g of sample powder is weighed and added to a mold with a bottom area of 1.327cm 2 , and is pressed to 2t, kept for 30s, then released, kept for 10s, and then the powder compacted density of the material under 2t pressure is recorded and calculated.

[0072] In the present disclosure, the volume distribution particle size Dv10, Dv50, Dv90 of the carbon-based material is the meaning known in the art, which respectively represents the particle size corresponding to the cumulative volume distribution percentage of 10%, 50%, and 90% of the material, and can be measured by instruments and methods known in the art. For example, GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method can be referred to, and a laser particle size analyzer can be conveniently used for measurement. The test instrument can be a Mastersizer 3000 type laser particle size analyzer of Malvern Instruments Ltd., UK.

[0073] In some embodiments, the carbon-based material is a hard carbon material, or a mixture of a hard carbon material and at least one selected from a soft carbon material and graphite. Alternatively, the carbon-based material is a hard carbon material.

[0074] In some embodiments, the carbon-based material is a mixture of a hard carbon material and a soft carbon material, wherein the mass ratio of the soft carbon material in the mixture is 20% to 80%, and alternatively, 30% to 60%.

[0075] In some embodiments, the carbon-based material is a mixture of a hard carbon material and graphite, wherein the mass ratio of the graphite in the mixture is 10% to 40%, and alternatively, 10% to 30%.

[0076] In some embodiments, when the carbon-based material is a mixture of hard carbon material and soft carbon material, the hard carbon material and the soft carbon material can be distinguished by thermal gravimetric analysis. Specifically, the thermal stabilities of the hard carbon material and the soft carbon material are different. The soft carbon material is relatively stable at high temperature due to having a certain graphitization structure, and the thermal weight loss curve is relatively flat. The hard carbon material contains more amorphous carbon and heteroatoms, and thermal decomposition and oxidation reactions can occur at a relatively low temperature, and the thermal weight loss is relatively large, and the thermal weight loss curve has a large slope in a certain temperature range. By analyzing the thermal weight loss curve of the carbon-based material, it can be determined whether the carbon-based material contains hard carbon material and soft carbon material.

[0077] In some embodiments, when the carbon-based material is a mixture of hard carbon material and graphite, the hard carbon material and the graphite can be distinguished by Raman test combined with X-ray diffraction test. Specifically, the graphite has a very obvious (002) crystal face diffraction peak, and the I D / I G of the graphite is generally close to 0.1, while the I D / I G of the hard carbon material is >1. By analyzing the X-ray diffraction peak and Raman spectrum of the carbon-based material, it can be determined whether the carbon-based material contains hard carbon material and graphite.

[0078] The second aspect of the present disclosure provides a preparation method of a carbon-based material, the method comprising: a processing step of dissolving three carbon precursors in a solvent respectively, and forming a first carbon precursor, a second carbon precursor and a third carbon precursor by spray drying at 150-200°C; then processing the first carbon precursor, the second carbon precursor and the third carbon precursor respectively to obtain a first precursor, a second precursor and a third precursor; the volume distribution particle size Dv10, Dv50 and Dv90 of the first precursor are 3-4 μm, 9-10 μm and 15-20 μm respectively; the volume distribution particle size Dv10, Dv50 and Dv90 of the second precursor are 2-3 μm, 5-6 μm and 8-9 μm respectively, and the volume distribution particle size Dv10, Dv50 and Dv90 of the third precursor are 1-2 μm, 3-4 μm and 5-6 μm respectively; and a mixing step of mixing the first precursor, the second precursor and the third precursor according to the mass ratio of the first precursor, the second precursor and the third precursor being (0-9):(0-4):(1-9) to form the carbon-based material; wherein the masses of the first precursor and the second precursor are not both 0.

[0079] In the present disclosure, by forming the first precursor, the second precursor and the third precursor with different particle sizes through the processing step, mixing the first precursor, the second precursor and the third precursor with different particle sizes in a specific ratio, the carbon-based material of the first aspect of the present disclosure can be prepared, which can obtain high compactness without damaging the current collector, and is beneficial to improve the safety of the battery.

[0080] Exemplarily, the carbon precursor can be linear phenolic resin, soluble phenolic resin, epoxy resin, polyurethane, furan resin, urea-formaldehyde resin, silicone resin, etc. Optionally, the carbon precursor can be linear phenolic resin, soluble phenolic resin, epoxy resin; the solvent can be methanol, ethanol, ethylene glycol, polyethylene glycol, glycerol, isopropyl alcohol or polyol; optionally, the solvent is methanol, ethanol, ethylene glycol, etc.

[0081] In some embodiments, in the processing step, the carbon precursor and the solvent are mixed in a mass ratio of (1:1)-(1:3) to form the first carbon precursor; and / or the carbon precursor and the solvent are mixed in a mass ratio of (1:3)-(1:9) to form the second carbon precursor; and / or the carbon precursor and the solvent are mixed in a mass ratio of (1:10)-(1:20) to form the third carbon precursor. The mass ratio of the carbon precursor and the solvent in the above range is beneficial to form carbon precursors with suitable particle sizes.

[0082] In some embodiments, the viscosity of the mixed solution of the carbon precursor and the solvent for preparing the first carbon precursor is 10-25 Pa·s, the viscosity of the mixed solution of the carbon precursor and the solvent for preparing the second carbon precursor is 5-10 Pa·s, and the viscosity of the mixed solution of the carbon precursor and the solvent for preparing the third carbon precursor is 1-5 Pa·s. By setting the viscosity of the mixed solution of the carbon precursor and the solvent in the above range, the effect of spraying can be optimized, and the particle size of the prepared first carbon precursor, second carbon precursor and third carbon precursor can meet the requirements.

[0083] In some embodiments, the spraying process is carried out in a spraying tower, and the temperature of the spraying tower is 150-200℃. By setting the temperature of the spraying tower in the above range, the drying speed of the atomized particles can be processed in a suitable range, which is beneficial to improve the sphericity and particle size of the formed carbon precursor.

[0084] In some embodiments, in the processing step, an oxidation step of oxidizing and cross-linking the first carbon precursor, the second carbon precursor and the third carbon precursor is further included. The oxidation step is carried out in an oven at 260-300℃, which can make the structure of the macromolecules of the first carbon precursor, the second carbon precursor and the third carbon precursor more compact and stable, thereby improving the carbonization yield.

[0085] In some embodiments, in the processing step, the first carbon precursor, the second carbon precursor and the third carbon precursor are respectively subjected to a pre-carbonization treatment at 300-800°C, then water vapor is introduced and an activation treatment is performed at 800-950°C, and then a classification treatment is performed to obtain the first precursor, the second precursor and the third precursor.

[0086] In some embodiments, the first carbon precursor, the second carbon precursor and the third carbon precursor are respectively subjected to a pre-carbonization treatment at 300-800°C to obtain a first pre-carbonized body, a second pre-carbonized body and a third pre-carbonized body. The pre-carbonization treatment is performed at a temperature increasing rate of 1-10°C / min, and optionally, at a temperature increasing rate of 1-5°C / min. The pre-carbonization treatment under the above conditions can retain a certain porosity to facilitate improving the subsequent activation efficiency.

[0087] In some embodiments, the first pre-carbonized body, the second pre-carbonized body and the third pre-carbonized body are respectively subjected to an activation treatment at 800-950°C with water vapor introduced to obtain a first activated carbon precursor, a second activated carbon precursor and a third activated carbon precursor. The activation treatment is performed under the condition that a carrier gas is introduced, the carrier gas and the water vapor are introduced at the same time, and the carrier gas rate is 2L / min. The water vapor introduction rate is 120-200L / h, and optionally, the water vapor introduction rate is 120-150L / h. The carrier gas can be nitrogen or an inert gas. The activation treatment under the above conditions can achieve a higher microporosity and powder yield.

[0088] In some embodiments, the first activated carbon precursor, the second activated carbon precursor and the third activated carbon precursor are respectively subjected to a classification treatment in a gas flow classification device to obtain the first precursor, the second precursor and the third precursor. The manufacturers and models of the above gas flow classification devices are respectively Xinghua Powder and AB03 type. Specifically, the device adjustment frequency converter is turned on, the classification host frequency converter frequency is adjusted to 30-45Hz, the induced draft fan is turned on and the fan current is adjusted, the feeding frequency is adjusted to 26-32Hz for uniform feeding after stabilization, the discharge particle size is continuously monitored and tested, until the Dv10, Dv50, Dv90 and particle size distribution width meet the requirements, and the classification is completed. The classification treatment of the first activated carbon precursor, the second activated carbon precursor and the third activated carbon precursor can obtain the first precursor, the second precursor and the third precursor with different volume distribution particle sizes, which is beneficial to subsequent mixing to form a carbon-based material.

[0089] In some embodiments, after the grading process, a demagnetization process can also be included, which is performed in a demagnetization device. Specifically, the demagnetization device is turned on, the object to be demagnetized is uniformly conveyed into the bin of the demagnetization device, the current size and working time of the demagnetization coil are adjusted, the demagnetization rod is placed near the object, the power controller is turned on to automatically adjust the current of the demagnetization rod, which is gradually reduced until the magnetism of the demagnetized object disappears and the object is discharged. The demagnetization sub-step can remove the magnetic metals such as Ni and Fe introduced by the above carbonization, crushing, and activation processes.

[0090] In some embodiments, the carbon-based material can be a silicon-carbon negative electrode material, and after the above activation process, a deposition process is further included. The deposition process is as follows: the mass concentration of the silicon source gas is 6% to 20%, the flow rate of the silicon source gas is 1 L / min to 4 L / min, and the deposition temperature is 400°C to 600°C. The silicon content in the formed silicon-carbon material is 40% to 55%. Optionally, the silicon-carbon has a carbon coating layer, and the coating process is as follows: the mass concentration of the carbon source gas is 10% to 40%, the flow rate of the carbon source gas is 1 L / min to 4 L / min, and the coating temperature is 550°C to 800°C. The carbon source gas can be, for example, acetylene gas. The deposition process under the above conditions can realize stable adsorption of the Si source gas to the substrate carbon and decomposition, and improve the utilization rate of the substrate pores.

[0091] In some embodiments, before the mixing step, a drying step of vacuum drying the first precursor, the second precursor, and the third precursor is further included. Optionally, the vacuum drying is performed at 100°C to 150°C. The vacuum drying step is beneficial to remove the adsorbed water in the first precursor, the second precursor, and the third precursor, and is beneficial to subsequent mixing according to the true mass ratio.

[0092] In some embodiments, after the vacuum drying, the natural cooling zone is cooled to room temperature, and then the mixing step is performed.

[0093] In some embodiments, the mixing step is performed under low-humidity and constant-temperature conditions. After the vacuum drying of the first precursor, the second precursor, and the third precursor, further mixing is performed by a mixer for 3 h to 5 h under the conditions of 25°C and humidity of 20% to 40% RH.

[0094] In addition, the secondary battery and the power-using device of the present disclosure are described below with appropriate reference to the accompanying drawings.

[0095] In some embodiments, the carbon-based material includes porous carbon and / or silicon-carbon.

[0096] In some embodiments, the carbon-based material is a hard carbon material, or a mixture of a hard carbon material and at least one selected from a soft carbon material and graphite.

[0097] The third aspect of the present disclosure provides a secondary battery. The term "secondary battery" referred to herein means a battery cell, a battery module, or a battery pack. The following are explained separately.

[0098] Generally, a secondary battery cell includes a positive electrode tab, a negative electrode tab, an electrolyte, and a separator. During charging and discharging of the battery, active ions are inserted and extracted between the positive electrode tab and the negative electrode tab. The electrolyte functions to conduct ions between the positive electrode tab and the negative electrode tab. The separator is disposed between the positive electrode tab and the negative electrode tab and functions to prevent short circuiting between the positive and negative electrodes while allowing ions to pass through.

[0099] Positive electrode tab

[0100] The positive electrode tab includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer including the positive electrode active material of the first aspect of the present disclosure.

[0101] As an example, the positive electrode current collector has two surfaces opposite in the thickness direction thereof, and the positive electrode film layer is disposed on either one or both of the two opposite surfaces of the positive electrode current collector.

[0102] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, an aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material base material (e.g., a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0103] In some embodiments, when the battery cell is a lithium ion battery, the positive electrode active material can use a positive electrode active material for a lithium ion battery known in the art. As an example, the positive electrode active material can include at least one of a lithium-containing phosphate having an olivine structure, a lithium transition metal oxide, and a modified compound of each thereof. However, the present disclosure is not limited to these materials, and other conventional materials that can be used as a battery positive electrode active material can also be used. These positive electrode active materials can be used alone or in combination of two or more. Among them, examples of the lithium transition metal oxide can include, but are not limited to, lithium cobalt oxide (e.g., LiCoO2), lithium nickel oxide (e.g., LiNiO2), lithium manganese oxide (e.g., LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., LiNi1 / 3Co1 / 3Mn1 / 3O2), lithium manganese nickel oxide, lithium manganese nickel cobalt oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese aluminum oxide, lithium manganese iron phosphate, lithium iron phosphate, lithium titanium oxide, lithium vanadium oxide, and lithium nickel manganese cobalt aluminum oxide. However, the present disclosure is not limited to these materials, and other conventional materials that can be used as a battery positive electrode active material can also be used. 1 / 3 Co 1 / 3 Mn 1 / 3O2(also can be referred to as NCM 333 LiNi 0.5 Co 0.2 Mn 0.3 O2(also can be referred to as NCM 523 LiNi 0.5 Co 0.25 Mn 0.25 O2(also can be referred to as NCM 211 LiNi 0.6 Co 0.2 Mn 0.2 O2(also can be referred to as NCM 622 LiNi 0.8 Co 0.1 Mn 0.1 O2(also can be referred to as NCM 811 lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.1 Al 0.05 O2) and modified compounds thereof. Examples of lithium-containing phosphates of olivine structure can include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4(also can be referred to as LFP)), a composite of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite of lithium manganese iron phosphate and carbon.

[0104] It should be noted that the above chemical formula is the chemical formula of the material used in the preparation of the secondary battery. In the positive electrode sheet, the battery cell, and the electric device, due to the processes such as formation and cycling, the elements in the above chemical formula can be lost, which can be understood by those skilled in the art. For example, in the positive electrode sheet, the battery cell, and the electric device, due to the processes such as cycling, the oxygen element in the positive electrode active material is lost, so there is a situation that the measured oxygen content in the positive electrode active material is reduced.

[0105] In some embodiments, when the battery cell is a sodium ion battery, the positive electrode active material can use a positive electrode active material for sodium ion batteries known in the art. As an example, the positive electrode active material can include sodium transition metal oxides, polyanionic compounds, prussian blue compounds, etc.

[0106] In some embodiments, the positive electrode film layer can also optionally include a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylic ester resin.

[0107] In some embodiments, the positive electrode film layer can also optionally include a conductive agent. As an example, the conductive agent can include at least one of super-P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0108] In some embodiments, the positive electrode tab can be prepared by dispersing the above-mentioned components for preparing the positive electrode tab, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent (e.g., N-methyl pyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on a positive electrode current collector, and after processes such as drying, cold pressing, etc., the positive electrode tab can be obtained.

[0109] Negative electrode tab

[0110] The negative electrode tab includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material. The negative electrode active material includes the carbon-based material of the present disclosure as described above.

[0111] The carbon-based material described above has unique physical and chemical properties such as disordered crystal structure, large interlayer spacing, abundant pores, etc., which enable the carbon-based material to adapt to different ion storage and transport requirements. The carbon-based material can be used as a negative electrode material in energy storage devices such as lithium ion batteries, sodium ion batteries, sodium-potassium ion hybrid batteries, potassium ion batteries, etc.

[0112] A sodium-lithium ion hybrid battery generally uses a positive electrode material of a sodium ion battery and a negative electrode active material of a lithium ion battery, or a positive electrode material of a lithium ion battery and a negative electrode material of a sodium ion battery. During charging and discharging, sodium ions and lithium ions migrate between the positive and negative electrodes, respectively, to achieve storage and release of electric charge. In some embodiments, the carbon-based material can be used as a negative electrode active material of a lithium ion battery, or as a negative electrode active material of a sodium ion battery.

[0113] As an example, the negative electrode current collector has two opposite surfaces in the thickness direction of the negative electrode current collector, and the negative electrode film layer is disposed on either one or both of the two opposite surfaces of the negative electrode current collector.

[0114] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, as a metal foil, a copper foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material base layer (such as a base layer of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0115]

[0115] In some embodiments, the negative electrode film layer further optionally comprises a binder. The binder can be selected from at least one of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0116] In some embodiments, the negative electrode film layer further optionally comprises a conductive agent. The conductive agent can be selected from at least one of super-P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0117] In some embodiments, the negative electrode film layer further optionally comprises other auxiliary agents, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)), etc.

[0118] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry on a negative electrode current collector, and after processes such as drying, cold pressing, etc., a negative electrode sheet is obtained.

[0119] Electrolyte

[0120] The electrolyte functions to conduct ions between the positive electrode sheet and the negative electrode sheet. The type of electrolyte is not specifically limited in the present disclosure and can be selected as needed. For example, the electrolyte can be liquid, gel, or all-solid.

[0121] In some embodiments, the electrolyte employs an electrolyte solution. The electrolyte solution comprises an electrolyte salt and a solvent.

[0122] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoro oxalate borate, lithium di-oxalate borate, lithium difluoro di-oxalate phosphate, and lithium tetrafluoro oxalate phosphate.

[0123] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0124] In some embodiments, the electrolyte solution can optionally further include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can further include an additive capable of improving certain performance of the battery, such as an additive capable of improving overcharge performance of the battery, an additive capable of improving high-temperature or low-temperature performance of the battery, etc.

[0125] Separator film

[0126] In some embodiments, a separator film is further included in the battery cell. The type of the separator film is not particularly limited in the present disclosure, and any publicly known porous structure separator film having good chemical stability and mechanical stability can be used.

[0127] In some embodiments, the material of the separator film can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator film can be a single layer film or a multi-layer composite film, and is not particularly limited. When the separator film is a multi-layer composite film, the materials of the respective layers can be the same or different, and are not particularly limited.

[0128] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator film can be formed into an electrode assembly through a winding process or a stacking process.

[0129] In some embodiments, the battery cell can include an outer package. The outer package can be used to package the electrode assembly and the electrolyte solution described above.

[0130] In some embodiments, the outer package of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the battery cell can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, and as the plastic, polypropylene, polybutylene terephthalate, polybutylene succinate, etc. can be listed.

[0131] The shape of the battery cell is not particularly limited in the present disclosure, and can be cylindrical, square, or any other shape. For example, FIG. 1 is a battery cell 5 having a square structure as an example.

[0132] In some embodiments, referring to FIG. 2, the outer package can include a housing 51 and a top cover assembly 53. The housing 51 can include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the top cover assembly 53 can be provided on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator film can be formed into an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is packaged in the receiving cavity. The electrolyte solution is impregnated in the electrode assembly 52. The number of the electrode assembly 52 included in the battery cell 5 can be one or more, and a person skilled in the art can select according to the specific actual needs.

[0133] In some embodiments, the battery cells can be assembled into a battery module, and the number of battery cells contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0134] FIG. 3 is a battery module 4 as an example. Referring to FIG. 3, in the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, other arbitrary arrangements can also be used. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0135] Optionally, the battery module 4 can further include a housing having an accommodation space, and the plurality of battery cells 5 can be accommodated in the accommodation space.

[0136] In some embodiments, the above-mentioned battery module can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0137] FIGS. 4 and 5 are a battery pack 1 as an example. Referring to FIGS. 4 and 5, the battery pack 1 can include a battery box and a plurality of battery modules 4 arranged in the battery box. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be arranged on the lower box body 3 to form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0138] In addition, the present disclosure also provides a power consuming device including the secondary battery provided by the present disclosure. The secondary battery can be used as a power source of the power consuming device, or can be used as an energy storage unit of the power consuming device. The power consuming device can include a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto.

[0139] As the power consuming device, the battery cell, the battery module, or the battery pack can be selected according to the use requirements thereof.

[0140] FIG. 6 is a power consuming device as an example. The power consuming device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the secondary battery for the power consuming device, a battery pack or a battery module can be used.

[0141] As another example of the device, it can be a mobile phone, a tablet computer, a notebook computer, etc. The device usually requires thinness, and a battery cell can be used as a power source.

[0142] Examples

[0143] Hereinafter, the embodiments of the present disclosure will be described. The embodiments described below are exemplary and are for the purpose of explaining the present disclosure only and are not to be understood as limiting the present disclosure. In the embodiments, the specific techniques or conditions not mentioned are performed in accordance with the techniques or conditions described in the literature in the field or in accordance with the product manual. The reagents or instruments not mentioned by the manufacturer are all conventional products that can be obtained commercially.

[0144] Example 1

[0145] Preparation of hard carbon material

[0146] 1) Treatment step, comprising:

[0147] a. Take 3 parts of 1000 g of phenolic resin (Huakai Resin-2150 model) in a container, respectively add ethanol (mass fraction greater than 95%) at a mass ratio of 1:3, 1:5 and 1:10, and stir until the phenolic resin is dissolved into a uniform solution to form a first solution, a second solution and a third solution. The viscosities of the first solution, the second solution and the third solution are 12 mPa·s, 5 mPa·s and 3 mPa·s, respectively. Then, the first solution, the second solution and the third solution are introduced into a spray drying tower at a speed of 1 cm / s by a peristaltic pump, the temperature is set to 180℃, the nozzle is connected to nitrogen, the outlet air temperature is greater than 100℃, and the powder is collected to obtain a first carbon precursor, a second carbon precursor and a third carbon precursor, respectively. Then, the obtained first carbon precursor, second carbon precursor and third carbon precursor are respectively loaded into a crucible, and the temperature of the high-low temperature box is set to 260℃ for oxidation crosslinking. 3

[0148] b. Pre-carbonization treatment: the first carbon precursor, the second carbon precursor and the third carbon precursor obtained in step a are respectively transferred to a rotary furnace, nitrogen is introduced and the temperature is raised to 600℃ at a rate of 2℃ / min, and the temperature is maintained for 4h to obtain a first pre-carbonized body, a second pre-carbonized body and a third pre-carbonized body, respectively;

[0149] c. Activation treatment: after the pre-carbonization treatment, the nitrogen atmosphere is maintained, the temperature is raised to 850℃ at a rate of 2℃ / min, and water vapor is introduced at a rate of 180 L / h, the first pre-carbonized body, the second pre-carbonized body and the third pre-carbonized body are treated for 4h respectively, and then cooled to room temperature to obtain a first activated carbon precursor, a second activated carbon precursor and a third activated carbon precursor; then, the first activated carbon precursor, the second activated carbon precursor and the third activated carbon precursor are transferred to a chemical vapor deposition machine, silane gas is introduced at a flow rate of 4 L / min, silicon deposition is carried out at 500℃, and then acetylene gas is introduced for coating at 600℃;

[0150] ​d. Grading treatment: The first activated carbon precursor, the second activated carbon precursor and the third activated carbon precursor after the deposition of silicon in step c are sequentially subjected to grading treatment. Specifically, the equipment adjusting frequency converter is turned on, and the grading host frequency converter is set to 40 Hz, 35 Hz and 30 Hz respectively to uniformly feed. The discharge particle size is continuously monitored and tested until the particle size distribution meets the requirements, the grading is completed, and the first precursor, the second precursor and the third precursor shown in Table 1 are obtained.

[0151] Table 1:

[0152] 2) Drying step: The first precursor, the second precursor and the third precursor are subjected to magnetic removal treatment, and then vacuum drying is performed at 110°C.

[0153] 3) Mixing step: The first precursor, the second precursor and the third precursor obtained by vacuum drying are uniformly mixed in a mass ratio of 5:1:4 to obtain a hard carbon material.

[0154] Performance test of hard carbon material

[0155] 1) Sphericity test

[0156] Select a 2000x SEM cross-section image, with the cross-section horizontal extension direction as the x-axis, the vertical direction from the current collector to the outer surface as the y-axis, randomly select a cross-section and count 10 particles, and make them fall into the above coordinate area. The horizontal diameter (length) X1, X2……X 10 and the vertical diameter (width) Y1, Y2……Y 10 of 10 particles are measured, and the sphericity Ф = (X1 / Y1+X2 / Y2+…+X 10 / Y 10 ) / 10.

[0157] 2) D1, D2 and D3 test

[0158] Based on GB / T 19077-2016, pretreatment: take a clean beaker, weigh an appropriate amount of the sample to be tested, add a surfactant dropwise, and then add 20 ml of dispersant. Ultrasonication at 120W / 5min ensures that the sample is completely dispersed in the dispersant. Test: After the sample is poured into the injection tower, it circulates with the solution to the test optical system. The particles are irradiated by the laser beam, and the particle size distribution characteristics of the particles can be obtained by receiving and measuring the energy distribution of the scattered light. The particle size-volume distribution curve obtained in Example 1 is shown in Figure 7. Next, the particle size-volume distribution curve shown in Figure 7 is gridded (not shown), and the horizontal and vertical coordinates of the particle size-volume distribution curve are adjusted to a fixed value. D1 is determined by counting the number of grids y1 occupied by the area with a particle size less than or equal to 3 μm, D2 is determined by counting the number of grids y2 occupied by the area with a particle size greater than 3 μm and less than 5 μm, and D3 is determined by counting the number of grids y3 occupied by the area with a particle size greater than or equal to 5 μm. According to grid statistics, y1 is 24.3, y2 is 54.7, and y3 is 341. The total grid number y of the particle size-volume distribution curve is 总 is 420. Therefore, D1 can be calculated as (y1 / y 总 )*100%=(24.3 / 420)*100%=5.8%; D2 is (y2 / y 总 )*100%=(54.7 / 420)*100%=13%; D3 is (y3 / y 总 )*100%=(341 / 420)*100%=81.2%.

[0159] Preparation of negative electrode sheet

[0160] The hard carbon material, conductive carbon black, thickener sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber emulsion (SBR) obtained above are fully stirred and mixed in an appropriate amount of deionized water in a weight ratio of 96.5:1.0:1.0:1.5 to form a uniform negative electrode slurry; the negative electrode slurry is coated on the front and back sides of the negative electrode collector, and after drying and other processes, a double-sided negative electrode sheet is obtained.

[0161] Performance test of negative electrode

[0162] 1) Compaction density test of negative electrode

[0163] Select double-sided electrodes with smooth and complete surfaces, and cut them into strips with a length of 3m and a width of 0.2m. Turn on the cold press and adjust the distance between the two rollers to perform cold pressing. Take 10 points in a fixed area and use a micrometer to measure the thickness of the collected electrodes (h 极片 ), and measure the mass of the pole piece (m 极片 ), then according to the thickness of the pole piece (h 极片 ), the mass of the electrode (m 极片mass (m 基材 ) of the substrate 基 材 The compaction is calculated using the following formula: p = (m 极片 -m 基材 ) / [(h 极片 -h 基材 )*S 极片 ], S 极片 = length of the pole piece * width of the pole piece.

[0164] 2) Cross-section test of the negative pole piece

[0165] Referring to JY / T010-1996, the active material (hard carbon material and 25% graphite mixture) after mixing the above hard carbon material and graphite is mixed with CMC at a ratio of 95:5, stirred and coated to form a pole piece. The complete and smooth pole piece is cut into a size of 6mm*6mm with scissors and attached to the CP sample table. The sample protrudes within 1mm of the sample table. Under the condition of a voltage of 7.5KV, the pole piece is cut and then the sample is observed to determine the damage degree of the pole piece.

[0166] Preparation of the secondary battery

[0167] The positive active material LiNi 0.8 Co 0.1 Mn 0.1 O2, the conductive agent carbon black (Super P) and the binder polyvinylidene fluoride are mixed at a weight ratio of 96:2:2, an appropriate amount of solvent NMP is added, and the mixture is stirred uniformly to obtain a positive electrode slurry. The positive electrode slurry is coated on both surfaces of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode pole piece is obtained.

[0168] Vinyl carbonate (EC), methyl ethyl carbonate (EMC) and diethyl carbonate (DEC) are mixed at a volume ratio of 1:1:1 to obtain an organic solvent, and then LiPF6 is dissolved in the above organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0169] A polyethylene film is used as a separator film, and the above prepared positive electrode pole piece and negative electrode pole piece are placed in order with the separator film in the middle of the positive electrode pole piece and the negative electrode pole piece to play a separating role. Then, a electrode assembly is obtained by winding. The electrode assembly is placed in an outer package, dried, and then injected with electrolyte. After vacuum packaging, standing, formation, shaping and other processes, a secondary battery is obtained.

[0170] Examples 2-6

[0171] The hard carbon material is prepared according to the method described in Example 1, and assembled into a secondary battery. The difference lies in that the temperature of the spray drying of the treatment step or the mass ratio of the first precursor, the second precursor and the third precursor in the mixing step is changed according to the following Table 2.

[0172] Comparative Example 1

[0173] A hard carbon material was prepared according to the method described in Example 1 and assembled into a secondary battery, with the difference that the spray-drying temperature of the treatment step was 130°C, so that the sphericity of the hard carbon material was 0.3.

[0174] Comparative Example 2

[0175] A hard carbon material was prepared according to the method described in Example 1 and assembled into a secondary battery, with the difference that the mass ratio of the first, second and third precursors in the mixing step was changed according to Table 2 below, so that the hard carbon material had a D1 / D2 of 0.29.

[0176] Comparative Example 3

[0177] A hard carbon material was prepared according to the method described in Example 1 and assembled into a secondary battery, with the difference that the mass ratio of the first, second and third precursors in the mixing step was changed according to Table 2 below, so that the hard carbon material had a D1 / D2 of 0.65.

[0178] Comparative Example 4

[0179] A hard carbon material was prepared according to the method described in Example 1 and assembled into a secondary battery, with the difference that the mass ratio of the first, second and third precursors in the mixing step was changed according to Table 2 below, so that the hard carbon material had a D2 / D3 of 0.06.

[0180] Comparative Example 5

[0181] A hard carbon material was prepared according to the method described in Example 1 and assembled into a secondary battery, with the difference that the mass ratio of the first, second and third precursors in the mixing step was changed according to Table 2 below, so that the hard carbon material had a D2 / D3 of 0.23.

[0182] Table 2 and Table 3 below show the parameters of the hard carbon materials of Examples 1-6 and Comparative Examples 1-5 and the results of the performance tests.

[0183] Table 2

[0184] Table 3:

[0185] According to Table 2 and Table 3, compared with Comparative Example 1 (sphericity < 0.5), Comparative Example 2 (D1 / D2 < 0.4), Comparative Example 3 (D1 / D2 > 0.62), Comparative Example 4 (D2 / D3 < 0.1) and Comparative Example 5 (D2 / D3 > 0.16), in Examples 1-6, by controlling the sphericity of the hard carbon material to be 0.5-1.0, and making the hard carbon material satisfy: D1 / D2 is 0.4-0.62, D2 / D3 is 0.1-0.16, the current collector can be not damaged while maintaining high tap density, and the safety of the battery can be improved.

[0186] Example 7

[0187] A secondary battery was prepared in a similar manner to Example 1, except that the preparation of the negative electrode sheet was carried out in the following manner:

[0188] The carbon-based material (the mass ratio of soft carbon material to hard carbon material prepared in Example 1 is 5:5), conductive carbon black, thickening agent carboxymethyl cellulose sodium (CMC), binder styrene-butadiene rubber emulsion (SBR) were mixed in a weight ratio of 96.5:1.0:1.0:1.5 in an appropriate amount of deionized water, and stirred to form a uniform negative electrode slurry; the negative electrode slurry was coated on both sides of the negative electrode current collector, and after drying and other processes, a double-sided negative electrode sheet was obtained.

[0189] The carbon-based material in Example 7 was tested in a similar manner to Example 1, and the secondary battery in Example 7 was tested in a similar manner to Example 1, and the specific test results are shown in Table 3 and Table 4 below.

[0190] Table 3

[0191] Table 4

[0192] As can be seen from Table 3 and Table 4, when the carbon-based material in Example 7 is a mixture of soft carbon and hard carbon, similar effects to Example 1 can be obtained, the current collector can be not damaged while maintaining high tap density, and the safety of the battery can be improved.

[0193] It should be noted that the present disclosure is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and embodiments having substantially the same technical idea and playing the same role and effect within the scope of the technical solutions of the present disclosure are all included in the technical scope of the present disclosure. In addition, within the scope of the main idea of the present disclosure, various modifications that can be thought of by those skilled in the art, and other ways constructed by combining part of the components in the embodiments are also included in the scope of the present disclosure.

Claims

1. A carbon-based material, wherein the carbon-based material is in a particulate form, and wherein the sphericity of the carbon-based material is 0.5-1.0; The carbon-based material satisfies: D1 / D2 is 0.4-0.62, and D2 / D3 is 0.1-0.16; wherein D1 is the ratio of the total volume of particles with a particle size of 3 μm or less in the carbon-based material to the total volume of all particles in the carbon-based material; D2 is the ratio of the total volume of particles with a particle size of greater than 3 μm and less than 5 μm in the carbon-based material to the total volume of all particles in the carbon-based material; D3 is the ratio of the total volume of particles with a particle size of 5 μm or greater in the carbon-based material to the total volume of all particles in the carbon-based material.

2. The carbon-based material of claim 1, wherein, The carbon-based material satisfies: D1 / D2 is 0.45-0.62, and D2 / D3 is 0.14-0.

16.

3. The carbon-based material according to claim 1 or 2, wherein, The sphericity of the carbon-based material is 0.6-1.

0.

4. The carbon-based material according to any one of claims 1-3, wherein, The carbon-based material comprises porous carbon and / or silicon carbon.

5. The carbon-based material according to claim 4, wherein, The specific surface area of the porous carbon is 1200 m 2 / g-2100 m 2 / g.

6. The carbon-based material according to any one of claims 1-5, wherein, The carbon-based material is a hard carbon material, or is a mixture of a hard carbon material and at least one selected from a soft carbon material and graphite.

7. The carbon-based material according to any one of claims 1-6, wherein, The carbon-based material satisfies: D1 is 4%-8%, and / or, D2 is 9%-13%, and / or, D3 is 80%-90%.

8. The carbon-based material according to any one of claims 1-7, wherein, The particle size number distribution Dn10 of the carbon-based material is 0.35 μm-0.60 μm.

9. The carbon-based material according to any one of claims 1-8, wherein, I D / I G 1.1-1.35; where I D represents the intensity of the D peak of the Raman spectrum at 1350 ± 50 cm -1 -1, I G represents the intensity of the G peak of the Raman spectrum at 1580 ± 50 cm -1 -1.

10. The carbon-based material according to any one of claims 1-9, wherein, The content of surface oxygen elements of the carbon-based material is 5%-15%.

11. The carbon-based material according to any one of claims 1-10, wherein, The powder compaction density of the carbon-based material at 2t is 0.8 g / cm 3 -1.1 g / cm 3 . 12.A method for preparing a carbon-based material, comprising: a treatment step of dissolving three portions of carbon precursor in a solvent respectively to form a first carbon precursor, a second carbon precursor and a third carbon precursor by spray drying at 150-200 ℃, and then treating the first carbon precursor, the second carbon precursor and the third carbon precursor respectively to obtain a first precursor, a second precursor and a third precursor, wherein the volume distribution particle sizes Dv10, Dv50 and Dv90 of the first precursor are 3-4 μm, 9-10 μm and 15-20 μm respectively, the volume distribution particle sizes Dv10, Dv50 and Dv90 of the second precursor are 2-3 μm, 5-6 μm and 8-9 μm respectively, and the volume distribution particle sizes Dv10, Dv50 and Dv90 of the third precursor are 1-2 μm, 3-4 μm and 5-6 μm respectively; and a mixing step of mixing the first precursor, the second precursor and the third precursor according to a mass ratio of (0-9):(0-4):(1-9) of the first precursor, the second precursor and the third precursor to form the carbon-based material, wherein the mass of the first precursor and the second precursor is not simultaneously 0.

13. The production method according to claim 12, wherein In the treatment step, the carbon precursor and the solvent are mixed according to a mass ratio of (1:1)-(1:3) to form the first carbon precursor; and / or, the carbon precursor and the solvent are mixed according to a mass ratio of (1:3)-(1:9) to form the second carbon precursor; and / or, the carbon precursor and the solvent are mixed according to a mass ratio of (1:10)-(1:20) to form the third carbon precursor.

14. The production method according to claim 12 or 13, wherein In the processing step, the first carbon precursor, the second carbon precursor and the third carbon precursor are respectively subjected to pre-carbonization treatment at 300-800°C, then water vapor is introduced and subjected to activation treatment at 800-950°C, and then subjected to grading treatment to obtain the first precursor, the second precursor and the third precursor.

15. The method of manufacturing according to any one of claims 12-14, wherein, Before the mixing step, further comprising a drying step of vacuum drying the first precursor, the second precursor and the third precursor.

16. The method of manufacturing according to any one of claims 12-15, wherein, The carbon-based material comprises porous carbon and / or silicon-carbon.

17. The method of manufacturing according to any one of claims 12-16, wherein, The carbon-based material is a hard carbon material, or a mixture of a hard carbon material and at least one selected from a soft carbon material and graphite.

18. A secondary battery comprising a negative electrode sheet comprising a negative electrode current collector and a negative electrode film layer on at least one surface of the negative electrode current collector and comprising a negative electrode active material, the negative electrode active material comprising the carbon-based material according to any one of claims 1-11, or the carbon-based material obtained according to the production method of any one of claims 12-17.

19. The secondary battery according to claim 18, which is at least one of a potassium ion battery, a sodium ion battery, a lithium ion battery, and a sodium-potassium ion hybrid battery.

20. An electric device comprising the secondary battery according to claim 18 or 19.

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