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

Abstract

The present disclosure provides a carbon-based material and a preparation method therefor, a secondary battery, and an electric apparatus. The carbon-based material is granular, and 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, D1 being the proportion of the total volume of particles in the carbon-based material having a particle size less than or equal to 3 μm to the total volume of all particles in the carbon-based material, D2 being the proportion of the total volume of particles in the carbon-based material having a particle size greater than 3 μm and less than 5 μm to the total volume of all particles in the carbon-based material, and D3 being the proportion of the total volume of particles in the carbon-based material having a particle size greater than or equal to 5 μm to the total volume of all 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. TECHNICAL FIELD

[0003] 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

[0004] In recent years, with the continuous increase in the power of electric devices 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.

[0005] However, the above-mentioned carbon-based material will damage the current collector when the pressure on the pole piece is increased to increase the compaction density of the pole piece, which will affect the safety.

[0006] 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-mentioned purpose, 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 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.

[0009] In the present disclosure, by adjusting the sphericity and particle size ratio of the carbon-based material particles, the current collector can be damaged without affecting the high compaction density, thereby improving 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 the D1 / D2, D2 / D3 of the carbon-based material particles within the above range, it is more conducive to achieving the integrity of the current collector under high compaction density, and more conducive to improving the safety of the battery.

[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 within the above range, it is possible to further reduce the damage to the current collector, and more conducive to improving the safety performance of the battery.

[0012] In some embodiments, the carbon-based material includes 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 within the above range, it is conducive to improving the realization of the particle integrity after the electrode plate is pressed.

[0014] 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 size D1, D2 and D3 of the carbon-based material within the above range, it is conducive to realizing the displacement and pore self-filling of the particles when pressed.

[0015] In some embodiments, the particle size number distribution Dn10 of the carbon-based material is 0.35 μm-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 conducive to realizing the closest packing of the particles and improving the compaction density.

[0016] 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 , and I G represents the G peak intensity of the Raman spectrum at 1580±50 cm -1 . The I D / I G of the carbon-based material within the above range makes the order degree of the surface carbon of the carbon-based material high and the surface defects few, which is conducive to improving the compaction density.

[0017] In some embodiments, the content of surface oxygen elements of the carbon-based material is 5% to 15%. The content of surface oxygen elements of the carbon-based material in the above range is beneficial to improve the processing performance and the compaction density of the secondary battery.

[0018] 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 The powder compaction density of the carbon-based material in the above range is beneficial to improve the compaction density of the negative electrode sheet.

[0019] The second aspect of the present disclosure provides a preparation method of a carbon-based material, comprising:

[0020] The processing step comprises dissolving three portions of carbon precursor in a solvent respectively, and forming a first carbon precursor, a second carbon precursor and a third carbon precursor by spray drying at 150°C to 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 μm to 4 μm, 9 μm to 10 μm and 15 μm to 20 μm respectively; the volume distribution particle size Dv10, Dv50 and Dv90 of the second precursor are 2 μm to 3 μm, 5 μm to 6 μm and 8 μm to 9 μm respectively, and the volume distribution particle size Dv10, Dv50 and Dv90 of the third precursor are 1 μm to 2 μm, 3 μm to 4 μm and 5 μm to 6 μm respectively.

[0021] The mixing step comprises 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 to 9):(0 to 4):(1 to 9) to form the carbon-based material; wherein the mass of the first precursor and the second precursor is not simultaneously 0.

[0022] The preparation method of the present disclosure can obtain the carbon-based material of the first aspect of the present disclosure.

[0023] In some embodiments, in the processing step, the carbon precursor and the solvent are mixed according to the mass ratio of (1:1) to (1:3) to form the first carbon precursor; and / or the carbon precursor and the solvent are mixed according to the mass ratio of (1:3) to (1:9) to form the second carbon precursor; and / or the carbon precursor and the solvent are mixed according to the mass ratio of (1:10) to (1:20) to form the third carbon precursor.

[0024] 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.

[0025] 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, followed by an activation treatment by introducing water vapor at 800-950°C, and then subjected to a grading treatment to obtain the first precursor, the second precursor and the third precursor.

[0026] A third aspect of the present disclosure provides a secondary battery comprising a negative electrode tab, the negative electrode tab 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 of the first aspect of the present disclosure or the carbon-based material obtained according to the preparation method of the second aspect of the present disclosure.

[0027] A 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

[0028] FIG. 1 is a schematic view of a battery cell according to an embodiment of the present disclosure.

[0029] FIG. 2 is an exploded view of the battery cell according to an embodiment of the present disclosure shown in FIG. 1.

[0030] FIG. 3 is a schematic view of a battery module according to an embodiment of the present disclosure.

[0031] FIG. 4 is a schematic view of a battery pack according to an embodiment of the present disclosure.

[0032] FIG. 5 is an exploded view of the battery pack according to an embodiment of the present disclosure shown in FIG. 4.

[0033] FIG. 6 is a schematic view of an electric device using the secondary battery according to an embodiment of the present disclosure as a power source.

[0034] FIG. 7 is a particle size-volume distribution curve of the carbon-based material according to Example 1 of the present disclosure.

[0035] BRIEF DESCRIPTION OF DRAWINGS DETAILED DESCRIPTION

[0036] Hereinafter, the carbon-based material, the method for producing the same, the secondary battery, and the electric device of the present disclosure will be described in detail with appropriate reference to the accompanying drawings. However, there will be cases where unnecessary detailed description is omitted. For example, there will be cases where detailed description of matters known well, repeated description 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. Furthermore, 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.

[0037] The "ranges" disclosed in the present disclosure are defined in the form of lower and upper limits, and a given range is defined by selecting one lower limit and one upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The ranges defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, it is understood that the ranges 60-110 and 80-120 are also contemplated. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 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" represents a shorthand manner of describing each and every numerical value that is contained within the range, wherein "a" and "b" are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0" and "5" have been listed herein, and "0-5" is merely a shorthand manner of describing each and every numerical value that is contained within the range. In addition, when it is stated that a parameter is 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, and the like.

[0038] Unless otherwise specified, all embodiments and optional embodiments of the present disclosure can be combined with each other to form new technical solutions.

[0039] 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.

[0040] Unless otherwise specified, all steps of the present disclosure can be performed in sequence or randomly, and are preferably performed in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) performed in sequence, or steps (b) and (a) performed 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.

[0041] Unless otherwise defined, all terms used in the disclosure, including technical or scientific terms, have the meaning commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0042] Unless otherwise specified, the values of the parameters mentioned in the 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 disclosure.

[0043] Unless otherwise specified, in the disclosure, the term "active ion" refers to an ion that can be reversibly inserted and extracted between the positive and negative electrodes of a secondary battery, including but not limited to lithium ion.

[0044] In recent years, carbon-based materials have rapidly developed in applications 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.

[0045] 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.

[0046] Carbon-based material

[0047] 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 the 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 the 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 the 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.

[0048] In the present disclosure, by adjusting the sphericity and size distribution of the carbon-based material particles, different size 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 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.

[0049] In addition, the particles can be tightly packed by self-slipping under high compaction density, which can weaken the local stress of the current collector, reduce the risk of breaking the tape in the cold pressing process, and improve the processability of the material.

[0050] The carbon-based material satisfies D1 / D2 is 0.45-0.62, and D2 / D3 is 0.1-0.16. Alternatively, the carbon-based material satisfies D1 / D2 is 0.45-0.62, and D2 / D3 is 0.14-0.16. By making the D1 / D2, D2 / D3 of the carbon-based material particles within the above range, it is more conducive to the current collector not being damaged under high compaction density, and thus, it is more conducive to improving the safety of the battery.

[0051] 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 range, the damage to the current collector can be further reduced, and it is more conducive to improving the safety performance.

[0052] 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 in a carbon skeleton with a multi-level pore structure.

[0053] In some embodiments, the specific surface area of the porous carbon is 1200m 2 / g-2100m 2 / g; alternatively, the specific surface area of the porous carbon is 1200m 2 / g-1800m 2 / g. By making the specific surface area of the porous carbon within the above range, it is conducive to improving the particle integrity after the electrode plate is pressed.

[0054] 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 size D1, D2 and D3 of the carbon-based material within the above range, it is conducive to realizing displacement and pore self-filling when the particles are pressed.

[0055] In some embodiments, the particle size number distribution Dn10 of the carbon-based material is 0.35μm-0.60μm; alternatively, Dn10 is 0.4μm-0.55μm. In the present disclosure, by making the particle size number distribution Dn10 of the carbon-based material within the above range, it is conducive to realizing the closest packing of the particles and improving the compaction density.

[0056] In some embodiments, the I D / I G of the carbon-based material is 1.1-1.35, and the ID / I G is 1.3; wherein, I D represents the intensity of the D peak of the Raman spectrum at 1350±50 cm -1 -1, and I G represents the intensity of the G peak of the Raman spectrum at 1580±50 cm -1 -1. Illustratively, the I D / I G 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 is 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.

[0057] In some embodiments, the content of surface oxygen elements of the carbon-based material is 5%-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 is within the above range, which can make the viscosity of the slurry containing the carbon-based material within a suitable range, which is conducive to improving the processing performance and compaction density of the secondary battery.

[0058] 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.

[0059] 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 SEM of the material powder or the SEM of the sheet is counted and averaged.

[0060] In the present disclosure, D1, D2, and D3 of the carbon-based material can be calculated by the following method:

[0061] First, the particle size distribution curve of the carbon-based material is tested, for example, according to GB / T 19077-2016. Specifically, the process includes pretreatment and testing; pretreatment: take a clean beaker, weigh an appropriate amount of carbon-based material, and ultrasonic 120W / 5min to ensure that the carbon-based material is completely dispersed in the dispersant; testing: pour the carbon-based material into the sample tower and circulate to the test light path system with the solution, under the irradiation of the laser beam, the particle size distribution curve of the particles can be obtained by receiving and measuring the energy distribution of the scattered light.

[0062] Secondly, D1, D2 and D3 can be obtained by fitting the particle size-volume distribution curve and gridding, and then counting the grid area. Specifically, the unit grid of the particle size-volume distribution curve is adjusted to 0.2 in the horizontal direction and 1.0 in the vertical direction, i.e., the area of the smallest unit grid is 0.2, and the proportion of different regions is represented by counting the number of grids occupied by the regions. Through this method, the proportion of particles in the intervals less than or equal to 3 μm, greater than 3 μm and less than 5 μm, and greater than or equal to 5 μm, i.e., D1, D2 and D3, are obtained in sequence.

[0063] In the present disclosure, the particle size number distribution Dn10 of the carbon-based material has the meaning known in the art, for example, Dn10 of 10 μm means that the number of particles with a diameter less than or equal to 10 μm accounts for 10% of the total number of particles. The particle size number distribution Dn10 can be determined by methods known in the art, for example, it can be tested according to GB / T 19077-2016.

[0064] In the present disclosure, the specific surface area BET of the porous carbon has the meaning known in the art and can be determined by instruments and methods known in the art. For example, it can be tested by the nitrogen adsorption specific surface area analysis test method according to GB / T 19587-2017 and calculated by the BET (Brunauer Emmett Teller) method. The testing instrument can be a Tri-Star 3020 type specific surface area and pore size analysis tester of Micromeritics Company, USA.

[0065] In the present disclosure, the I D / I G value of the carbon-based material can be tested using a Raman spectrometer, I D represents the D peak intensity of the Raman spectrum of the material at 1350±50 cm -1 -1. G represents the G peak intensity of the Raman spectrum of the material at 1580±50 cm -1 -1. The test conditions are as follows: excitation wavelength is 532 nm, power is 0.5%, grating is 600 lines, objective lens is 50 times, integration time is 10 s, cumulative number is 3 times, surface scanning, 100 points of D peak and G peak intensity are obtained, I D / I G of 100 points are calculated, 30 I D / I G with the largest and smallest values are removed, and the average value of the remaining 40 points is the I D / I G of the material. The testing instrument can be a Horiba LabRAM HR800 Raman spectrometer.

[0066] 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 hard carbon 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 hard carbon material is fitted by XPS peak41, a peak fitting software, the appropriate baseline is set, the fitting peak is added, and then Gaussian fitting is performed until the residual is less than 10.

[0067] In the present disclosure, the compaction 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 compaction density can be measured by an electronic pressure testing machine (for example, 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 compaction density of the material under 2t pressure is recorded and calculated.

[0068] 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 laser particle size analyzer can be used to conveniently measure. The test instrument can be Mastersizer 3000 type laser particle size analyzer of Malvern Instruments Ltd., UK.

[0069] The second aspect of the present disclosure provides a method for preparing a carbon-based material, the method comprising: a processing step of dissolving three portions of a carbon precursor in a solvent to form 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 to obtain a first precursor, a second precursor and a third precursor, respectively; 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; 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 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.

[0070] In the present disclosure, the first precursor, the second precursor and the third precursor with different particle sizes are formed by the processing step, and the first precursor, the second precursor and the third precursor with different particle sizes are mixed in a specific ratio, so that the carbon-based material of the first aspect of the present disclosure can be prepared, which can obtain high compaction density without damaging the current collector, and is beneficial to improve the safety of the battery.

[0071] 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 or 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.

[0072] 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.

[0073] In some embodiments, the viscosity of the mixed solution of the carbon precursor of the first carbon precursor and the solvent is 10-25 Pa·s, the viscosity of the mixed solution of the carbon precursor of the second carbon precursor and the solvent is 5-10 Pa·s, and the viscosity of the mixed solution of the carbon precursor of the third carbon precursor and the solvent 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, so that the particle size of the prepared first carbon precursor, second carbon precursor and third carbon precursor meets the requirements.

[0074] In some embodiments, the spraying process is carried out in a spraying tower, and the temperature of the spraying tower is 150-200°C. 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 of the formed carbon precursor and the particle size of the particles.

[0075] In some embodiments, in the treatment 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°C. The oxidation step 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.

[0076] In some embodiments, in the treatment 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 activation treatment is carried out at 800-950°C, and then grading treatment is carried out to obtain the first precursor, the second precursor and the third precursor.

[0077] In some embodiments, the first carbon precursor, the second carbon precursor and the third carbon precursor are respectively subjected to 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 carried out 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 and facilitate the subsequent activation efficiency.

[0078] 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 under the condition of water vapor at 800-950°C 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 of a carrier gas, the carrier gas and the water vapor are simultaneously introduced, and the carrier gas rate is 2 L / min. The water vapor introduction rate is 120-200 L / h, and the water vapor introduction rate is 120-150 L / h, optionally. The carrier gas can be nitrogen or inert gas. The activation treatment under the above conditions can achieve a higher microporosity and powder yield.

[0079] 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 30-45 Hz, the induced draft fan is turned on and the fan current is adjusted, the feeding frequency is adjusted to 26-32 Hz 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.

[0080] In some embodiments, after the classification treatment, a demagnetization treatment can also be included, and the demagnetization treatment is performed in a demagnetization device. Specifically, the demagnetization device is turned on, the object to be demagnetized is uniformly conveyed into the demagnetization machine inner bin, 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 magnetic rod current, which is gradually reduced until the magnetism of the demagnetized object disappears. The demagnetization sub-step can remove the magnetic metals such as Ni and Fe introduced in the above carbonization, crushing, activation and other processes.

[0081] In some embodiments, the carbon-based material can be a silicon-carbon negative electrode material, and after the activation treatment, a deposition treatment is further included. The deposition process of the deposition treatment 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 treatment 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.

[0082] 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.

[0083] In some embodiments, after the vacuum drying, the natural cooling zone is cooled to room temperature, and then the mixing step is performed.

[0084] 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 3h to 5h under the conditions of 25°C and humidity of 20% to 40% RH.

[0085] In addition, the secondary battery and the power-using device of the present disclosure are described below with appropriate reference to the accompanying drawings.

[0086] A 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 described respectively.

[0087] Generally, a secondary battery cell includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the charging and discharging of the battery, active ions are inserted and extracted between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly playing a role in preventing short circuit between the positive and negative electrodes, while allowing ions to pass through.

[0088] Positive electrode sheet

[0089] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, and the positive electrode film layer includes the positive electrode active material of the first aspect of the present disclosure.

[0090] As an example, the positive electrode current collector has two surfaces opposite in the thickness direction thereof, and the positive electrode film layer is provided on either one or both of the two opposite surfaces of the positive electrode current collector.

[0091] In some embodiments, the positive electrode current collector can employ a metal foil or a composite current collector. For example, as the metal foil, an aluminum foil can be employed. 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.).

[0092] In some embodiments, when the battery cell is a lithium ion battery, the positive electrode active material can employ 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 of 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 only one 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., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2(also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2(also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2(also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2(also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (e.g., LiNi0.85 Co 0.1 Al 0.05 O2) and modified compounds thereof, etc. Examples of the olivine-structured lithium-containing phosphate can include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (which can also 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.

[0093] 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, as 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 the measured oxygen content in the positive electrode active material decreases.

[0094] In some embodiments, when the battery cell is a sodium-ion battery, the positive electrode active material can use a positive electrode active material known in the art for sodium-ion batteries. As an example, the positive electrode active material can include sodium transition metal oxides, polyanionic compounds, prussian blue compounds, etc.

[0095] 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.

[0096] 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.

[0097] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on a positive electrode current collector, and after processes such as drying and cold pressing, the positive electrode sheet can be obtained.

[0098] Negative electrode sheet

[0099] The negative electrode sheet 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.

[0100] As an example, the negative electrode current collector has two surfaces opposite in the thickness direction thereof, and the negative electrode film layer is disposed on either one or both of the two surfaces of the negative electrode current collector.

[0101] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, as the 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.

[0102] In some embodiments, the negative electrode film layer can further optionally include 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).

[0103] In some embodiments, the negative electrode film layer can further optionally include a conductive agent. The conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0104] In some embodiments, the negative electrode film layer can further optionally include other auxiliary agents, such as a thickening agent (e.g., sodium carboxymethyl cellulose (CMC-Na)) and the like.

[0105] In some embodiments, the negative electrode sheet can be prepared by dispersing the components for preparing the negative electrode sheet described above, 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 the negative electrode current collector, and then performing processes such as drying, cold pressing, etc., to obtain the negative electrode sheet.

[0106] Electrolyte

[0107] The electrolyte functions to conduct ions between the positive electrode sheet and the negative electrode sheet. The type of the electrolyte is not particularly limited in the present disclosure and can be selected as needed. For example, the electrolyte can be in a liquid state, a gel state, or a full solid state.

[0108] In some embodiments, the electrolyte employs an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0109] 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 bistrifluoromethylsulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorobisoxalate borate, lithium bisoxalate borate, lithium difluorobisoxalate phosphate, and lithium tetrafluorobisoxalate phosphate.

[0110] 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, cyclobutane sulfone, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0111] In some embodiments, the electrolyte solution can also optionally include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can also include an additive capable of improving certain properties of the battery, such as an additive for improving overcharge performance of the battery, an additive for improving high-temperature or low-temperature performance of the battery, etc.

[0112] Separator film

[0113] In some embodiments, the battery cell further includes a separator film. The type of 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.

[0114] 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.

[0115] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator film can be made into an electrode assembly through a winding process or a stacking process.

[0116] In some embodiments, the battery cell can include an outer package. The outer package can be used to package the above-mentioned electrode assembly and electrolyte.

[0117] 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 soft package. The material of the soft package can be plastic, and as plastic, polypropylene, polybutylene terephthalate, polybutylene succinate, etc. can be listed.

[0118] The present disclosure does not have a particular limitation on the shape of the battery cell, which can be cylindrical, square, or any other arbitrary shape. For example, FIG. 1 is a battery cell 5 of a square structure as an example.

[0119] In some embodiments, referring to FIG. 2, the outer package can include a shell 51 and a top cover assembly 53. The shell 51 can include a bottom plate and a side plate connected to the bottom plate, which enclose a receiving cavity. The shell 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 form an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is packaged in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, which can be selected by those skilled in the art according to specific actual needs.

[0120] In some embodiments, the battery cell 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.

[0121] 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 made. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0122] Optionally, the battery module 4 can also include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

[0123] 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.

[0124] 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 provided on the lower box body 3 to form a closed space for receiving the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0125] In addition, the present disclosure also provides a power utilization device comprising the secondary battery provided by the present disclosure. The secondary battery can be used as a power source of the power utilization device, or can be used as an energy storage unit of the power utilization device. The power utilization 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.

[0126] As the power utilization device, a battery cell, a battery module or a battery pack can be selected according to the use requirement thereof.

[0127] FIG. 6 is a power utilization device as an example. The power utilization device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirement of high power and high energy density of the secondary battery for the power utilization device, a battery pack or a battery module can be used.

[0128] The device as another example can be a mobile phone, a tablet computer, a notebook computer, etc. The device usually requires thinning, and a battery cell can be used as a power source.

[0129] Embodiment

[0130] Hereinafter, the embodiments of the present disclosure are described. The embodiments described below are exemplary and are only used to explain the present disclosure, and cannot be understood as a limitation of the present disclosure. If a specific technology or condition is not specified in the embodiments, the technology or condition described in the literature in the art or according to the product instruction is used. If the reagent or instrument used is not specified by the manufacturer, it is a conventional product that can be obtained by purchase.

[0131] Embodiment 1

[0132] Preparation of carbon-based material

[0133] 1) Treatment step, comprising:

[0134] a. 3 parts of 1000 g of phenolic resin (Huakai Resin-2150 model) were weighed in a container, and 1:3, 1:5 and 1:10 of ethanol (mass fraction greater than 95%) were added respectively to dissolve and stir until the phenolic resin was dissolved into a uniform solution, forming a first solution, a second solution and a third solution. The viscosities of the first solution, the second solution and the third solution were 12 mPa·s, 5 mPa·s and 3 mPa·s, respectively. Subsequently, the first solution, the second solution and the third solution were pumped through a peristaltic pump at a flow rate of 1 cm 3The first carbon precursor, the second carbon precursor and the third carbon precursor are obtained by introducing the solution into a spray drying tower at a speed of 5 m / s, setting the temperature to 180°C, introducing nitrogen into the spray head, and collecting the powder. The first carbon precursor, the second carbon precursor and the third carbon precursor are then loaded into a crucible, and an oxidation crosslinking is performed by setting the temperature of a high-low temperature box to 260°C.

[0135] b. Pre-carbonization treatment: the first carbon precursor, the second carbon precursor and the third carbon precursor obtained in step a. are transferred into a rotary furnace, nitrogen is introduced, and the temperature is raised to 600°C at a rate of 2°C / min for 4 h, to obtain a first pre-carbonized body, a second pre-carbonized body and a third pre-carbonized body, respectively;

[0136] c. Activation treatment: after the pre-carbonization treatment, the temperature is raised to 850°C at a rate of 2°C / min under a nitrogen atmosphere, 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 4 h, 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 performed at 500°C, and then acetylene gas is introduced for coating at 600°C;

[0137] d. Classification 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 classification treatment. Specifically, the equipment is adjusted by opening the frequency converter, and the frequency of the classification main machine frequency converter is set to 40 Hz, 35 Hz and 30 Hz, respectively, for uniform feeding. The particle size distribution is continuously monitored and tested until the particle size distribution meets the requirements, and the classification is completed to obtain the first precursor, the second precursor and the third precursor shown in Table 1. The final classification results are shown in Table 1.

[0138] Table 1:

[0139] 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.

[0140] 3) Mixing step: the first precursor, the second precursor and the third precursor obtained by vacuum drying are mixed uniformly according to a mass ratio of 5:1:4 to obtain a carbon-based material.

[0141] Performance test of the carbon-based material

[0142] 1) Sphericity test

[0143] Select a cross-sectional SEM image magnified 2000 times, record the lateral extension direction of the pole piece as the x-axis, and the vertical direction from the current collector to the outer surface as the y-axis. Randomly select a cross section and count 10 particles so that they fall within the above coordinate area. Measure the horizontal diameters (lengths) X1, X2, .... X of the 10 particles. 10 And vertical diameter (width) Y1, Y2....Y 10 , sphericity Φ=(X1 / Y1+X2 / Y2+…+X 10 / Y 10 ) / 10.

[0144] 2) D1, D2, and D3 tests

[0145] 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%.

[0146] Preparation of negative electrode sheet

[0147] The carbon-based material, conductive carbon black, thickener sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber latex (SBR) obtained above are fully stirred and mixed in an appropriate amount of deionized water at 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.

[0148] Performance test of negative electrode

[0149] 1) Compaction density test of negative electrode

[0150] 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 of substrate (m 基材 ) and the thickness of the substrate (h 基 材 ) The following formula is used to calculate the density: ρ = (m 极片 -m 基材 ) / [(h 极片 -h 基材 )*S 极片 ], S 极片 =Pole length*pole width.

[0151] 2) Cross-section test of negative electrode

[0152] Referring to JY / T010-1996, the active material obtained by mixing the above-mentioned carbon-based material and graphite (a mixture of carbon-based material and 25% graphite) is mixed with CMC in a ratio of 95:5, stirred, and then coated to form an electrode. Use scissors to cut the complete and smooth electrode into 6mm*6mm size and stick it on the CP sample table. The sample can protrude within 1mm from the sample table. Under the voltage of 7.5KV, the above-mentioned electrode is cut and then sampling is started to observe the degree of damage to the electrode.

[0153] Preparation of secondary batteries

[0154] The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2 is mixed with carbon black (Super P), a conductive agent, and polyvinylidene fluoride (PVDF) as a binder in a weight ratio of 96:2:2. An appropriate amount of NMP solvent is added and stirred evenly to obtain a positive electrode slurry. The positive electrode slurry is then coated on both surfaces of the positive electrode current collector aluminum foil. After drying and cold pressing, a positive electrode sheet is obtained.

[0155] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in 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.

[0156] A polyethylene film is used as a separator film, and the positive electrode sheet and the negative electrode sheet prepared above are sequentially placed with the separator film in the middle of the positive electrode sheet and the negative electrode sheet to play a separating role, and then wound to obtain an electrode assembly; the electrode assembly is placed in an outer package, and after drying, an electrolyte is injected, and after vacuum packaging, standing, formation, shaping and other processes, a secondary battery is obtained.

[0157] Examples 2-6

[0158] The carbon-based material is prepared according to the method described in Example 1 and assembled into a secondary battery, with the difference 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 Table 2 below.

[0159] Comparative Example 1

[0160] The carbon-based material is prepared according to the method described in Example 1 and assembled into a secondary battery, with the difference that the temperature of the spray drying of the treatment step is 130°C, so that the sphericity of the carbon-based material is 0.3.

[0161] Comparative Example 2

[0162] The carbon-based material is 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 precursor, the second precursor and the third precursor in the mixing step is changed according to Table 2 below, obtaining a carbon-based material with D1 / D2 of 0.29.

[0163] Comparative Example 3

[0164] The carbon-based material is 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 precursor, the second precursor and the third precursor in the mixing step is changed according to Table 2 below, obtaining a carbon-based material with D1 / D2 of 0.65.

[0165] Comparative Example 4

[0166] The carbon-based material is 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 precursor, the second precursor and the third precursor in the mixing step is changed according to Table 2 below, obtaining a carbon-based material with D2 / D3 of 0.06.

[0167] Comparative Example 5

[0168] The carbon-based material is 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 precursor, the second precursor and the third precursor in the mixing step is changed according to Table 2 below, obtaining a carbon-based material with D2 / D3 of 0.23.

[0169] Table 2 and Table 3 below show the parameters and performance test results of the carbon-based materials of Examples 1-6 and Comparative Examples 1-5.

[0170] Table 2:

[0171] Table 3:

[0172] 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 carbon-based material to be 0.5-1.0, and making the carbon-based material satisfy: D1 / D2 is 0.4-0.62, D2 / D3 is 0.1-0.16, the high compactness density can be maintained while not damaging the current collector, and the safety of the battery is improved.

[0173] It should be noted that the present disclosure is not limited to the above-described embodiments. The above-described embodiments are only examples, and embodiments having substantially the same configuration and playing the same role and effect as the technical idea 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 are applied to the embodiments, and other modes constructed by combining part of the constituent elements 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 granular form, and a 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 a ratio of a total volume of particles with a particle size less than or equal to 3 μm in the carbon-based material to a total volume of all particles in the carbon-based material; D2 is a ratio of a total volume of particles with a particle size 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 a ratio of a total volume of particles with a particle size greater than or equal to 5 μm 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 of 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 satisfies: D1 is 4%-8%, and / or, D2 is 9%-13%, and / or, D3 is 80%-90%.

7. The carbon-based material according to any one of claims 1-6, wherein, The carbon-based material has a particle size number distribution Dn10 of 0.35 μm-0.60 μm.

8. The carbon-based material according to any one of claims 1-7, 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.

9. The carbon-based material according to any one of claims 1-8, wherein, The carbon-based material has a content of surface oxygen elements of 5%-15%.

10. The carbon-based material according to any one of claims 1-9, wherein, The powder compaction density of the carbon-based material at 2t is 0.8 g / cm 3 -1.1 g / cm 3 . 11.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 first precursor has a volume distribution particle size Dv10, Dv50 and Dv90 of 3-4 μm, 9-10 μm and 15-20 μm respectively, the second precursor has a volume distribution particle size Dv10, Dv50 and Dv90 of 2-3 μm, 5-6 μm and 8-9 μm respectively, and the third precursor has a volume distribution particle size Dv10, Dv50 and Dv90 of 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 0 at the same time.

12. The production method according to claim 11, 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.

13. The production method according to claim 11 or 12, wherein, In the processing step, the first carbon precursor, the second carbon precursor and the third carbon precursor are respectively pre-carbonized at 300-800 ℃, then water vapor is introduced and activated at 800-950 ℃, and then subjected to a grading treatment to obtain the first precursor, the second precursor and the third precursor.

14. The production method according to any one of claims 11 to 13, wherein Before the mixing step, a drying step of vacuum drying the first precursor, the second precursor and the third precursor is further included.

15. 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 1-10, or obtained by the preparation method according to any one of claims 11-14.

16. An electric device comprising the secondary battery according to claim 15.

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