Negative electrode active material, battery and electric device

Abstract

The invention discloses a negative electrode active material, a battery and an electric device, and belongs to the technical field of new energy. The particle size Dv50, the particle size distribution width, the interlayer spacing d002 and the pore volume of the negative electrode active material are controlled in a suitable range, so that the side reaction between the negative electrode active material and the electrolyte is relatively few, the lithium ion transmission path is relatively short, and the negative electrode active material is relatively good in dynamic performance and cycle performance.

Description

Technical Field

[0001] The present application relates to the field of new energy technology, and in particular to a negative electrode active material, a battery and an electrical device. Background Art

[0002] At present, ion batteries, especially lithium-ion batteries (LIBs), have been widely used in portable electronic products due to their advantages such as light weight, low cost and long cycle life. However, with the continuous upgrading of electronic digital products, higher and higher requirements are placed on the kinetic performance of ion batteries. Therefore, it is necessary to develop a technology to improve the kinetic performance of ion batteries. Summary of the invention

[0003] Based on the defects of the prior art, the purpose of this application is to provide a negative electrode active material, a battery and an electrical device. This application effectively improves the kinetic performance of the negative electrode active material by controlling the particle size Dv50, particle size distribution width b, interlayer spacing d002 and pore volume in the negative electrode active material within an appropriate range.

[0004] In order to achieve the above-mentioned purpose, in the first aspect, the present application provides a negative electrode active material, wherein the particle size Dv50 of the negative electrode active material is 5-20 μm, the particle size distribution width is 0.7-1.5, the interlayer spacing d002 is 0.330-0.340 nm, and the pore volume is 0.001-0.02 cm 3 / g.

[0005] In some embodiments, the negative electrode active material further includes a polymer coating layer disposed on the surface of the carbon material.

[0006] In some embodiments, the negative electrode active material satisfies: D / 4≥75c+3s,

[0007] Wherein, D nm is the thickness of the polymer coating layer;

[0008] c cm 3 / g is the pore volume of the negative electrode active material;

[0009] sm 2 / g is the specific surface area of ​​the negative electrode active material.

[0010] In some embodiments, the negative electrode active material satisfies: 2.2<D / 10+b≤5.2;

[0011] Wherein, D nm is the thickness of the polymer coating layer;

[0012] b is the particle size distribution width of the negative electrode active material.

[0013] In some embodiments, the negative electrode active material satisfies at least one of the following conditions:

[0014] S1. The thickness of the polymer coating layer is 10-50nm;

[0015] S2. The specific surface area of ​​the negative electrode active material is 0.8-2.5m 2 / g.

[0016] In some embodiments, the polymer in the polymer coating layer includes a polymer containing an amino group and an ether bond.

[0017] In some embodiments, the polymer in the polymer coating layer includes polyetheramine.

[0018] In some embodiments, the carbon material includes at least one of artificial graphite and natural graphite.

[0019] In a second aspect, the present application provides a battery, comprising a negative electrode plate, wherein the negative electrode plate comprises a current collector and a negative electrode active material layer disposed on a surface of the current collector, wherein the negative electrode active material layer comprises the negative electrode active material.

[0020] In a third aspect, the present application provides an electrical device, comprising the battery, wherein the battery serves as a power supply for the electrical device.

[0021] Compared with the prior art, the beneficial effect of the present application is that the present application controls the particle size Dv50, particle size distribution width b, interlayer spacing d002 and pore volume of the negative electrode active material within an appropriate range, thereby ensuring fewer side reactions between the negative electrode active material and the electrolyte and a shorter lithium ion transmission path, thereby making the negative electrode active material have better kinetic performance and better cycle performance. DETAILED DESCRIPTION

[0022] In order to better illustrate the purpose, technical scheme and advantages of the present application, the present application will be further described below in conjunction with specific embodiments and comparative examples, the purpose of which is to understand the content of the present application in detail, rather than to limit the present application. All other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application. The experimental reagents and instruments involved in the implementation of this application are all commonly used ordinary reagents and instruments unless otherwise specified. In the present application, the technical features described in an open manner include closed technical schemes composed of the listed features, and also include open technical schemes containing the listed features.

[0023] The present application provides a negative electrode active material, which includes a carbon material. The particle size Dv50 of the negative electrode active material is 5-20 μm, the particle size distribution width is 0.7-1.5, the interlayer spacing d002 is 0.330-0.340 nm, and the pore volume is 0.001-0.02 cm 3 / g. Wherein, particle size distribution width = (Dn90-Dn10) / Dn50, Dn10 represents the particle size corresponding to when the cumulative number percentage reaches 10%, that is, the number of particles with a particle size smaller than the particle size corresponding to Dn10 accounts for 10% of the total number of all particles; Dn50 represents the particle size corresponding to when the cumulative number percentage reaches 50%, that is, the number of particles with a particle size smaller than the particle size corresponding to Dn50 accounts for 50% of the total number of all particles; Dn90 represents the particle size corresponding to when the cumulative number percentage reaches 90%, that is, the number of particles with a particle size smaller than the particle size corresponding to Dn90 accounts for 90% of the total number of all particles; Dv50 represents the particle size corresponding to when the cumulative volume percentage of the negative electrode active material reaches 50%, that is, the median particle size of the volume distribution.

[0024] The particle size Dv50 of the negative electrode active material will affect the high temperature performance, cycle performance, kinetic performance and other performances of the battery. If the particle size Dv50 of the negative electrode active material is too small, the surface defects will increase, and the side reactions with the electrolyte will increase, resulting in deterioration of the high temperature performance and cycle performance; if it is too large, the lithium ion transmission path will increase, the kinetic performance will be poor, and lithium precipitation will become serious.

[0025] The particle size distribution width of the negative electrode active material will affect the high temperature performance, cycle performance, charging energy loss and other performance of the battery. If the particle size distribution of the negative electrode active material is too wide, the particle size difference is too large. If it contains too many fine particles, the side reaction with the electrolyte will increase; if it contains too large particles, the charging energy will be easily lost.

[0026] The interlayer spacing d002 of the negative electrode active material is the inter-plane spacing between (002) crystal planes, which affects the battery's kinetic performance, energy density and other performance. If the interlayer spacing d002 of the negative electrode active material is too small, the lithium ion transmission channel is narrow, the resistance is large, the kinetic performance is poor, and lithium precipitation is more serious; if it is too large, the capacity compaction is low and the energy density is low.

[0027] The pore volume of the negative electrode active material will affect the high temperature performance, cycle performance, kinetic performance and other properties of the battery. If the pore volume of the negative electrode active material is too small, the pore formation degree is low, which is not conducive to lithium ion transmission and the kinetic performance is poor; if the pore volume is too large, the side reaction with the electrolyte increases, and the high temperature performance and cycle performance are poor.

[0028] Taking into account the effects of the particle size Dv50, particle size distribution width, interlayer spacing d002 and pore volume of the negative electrode active material on the high temperature performance, cycle performance and kinetic performance of the battery, the present application controls the particle size Dv50, particle size distribution width, interlayer spacing d002 and pore volume of the negative electrode active material within the above-mentioned appropriate range to ensure that there are fewer side reactions between the negative electrode active material and the electrolyte and the lithium ion transmission path is shorter, thereby making the negative electrode active material have better kinetic performance and better cycle performance.

[0029] The particle size Dv50 of the negative electrode active material is 5-20μm, such as 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, or a range formed by any two of the above values. When the particle size Dv50 of the negative electrode active material is 8-15μm, the balance between the high temperature performance, cycle performance and kinetic performance of the battery is better.

[0030] The particle size distribution width of the negative electrode active material is 0.7-1.5, such as 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5 or a range formed by any two of the above values. When the particle size distribution width of the negative electrode active material is 0.8-1.2, the balance relationship between the high temperature performance, cycle performance and charging energy loss of the battery is better.

[0031] The interlayer spacing d002 of the negative electrode active material is 0.330-0.340 nm, such as 0.330 nm, 0.331 nm, 0.332 nm, 0.333 nm, 0.334 nm, 0.335 nm, 0.336 nm, 0.337 nm, 0.338 nm, 0.339 nm, 0.340 nm, or a range formed by any two of the above values. When the interlayer spacing d002 of the negative electrode active material is 0.335-0.338 nm, the balance between kinetic performance and energy density is better.

[0032] The pore volume of the negative electrode active material is 0.001-0.02cm 3 / g, such as 0.001cm 3 / g, 0.002cm 3 / g, 0.004cm 3 / g, 0.006cm 3 / g, 0.008cm 3 / g, 0.010cm 3 / g, 0.012cm 3 / g, 0.014cm 3 / g, 0.016cm 3 / g, 0.018cm 3 / g, 0.02cm 3 / g, or the range formed by any two of the above values. When the pore volume of the negative electrode active material is 0.005-0.01cm 3 / g, the balance between the battery's high temperature performance, cycle performance and kinetic performance is better.

[0033] The present application does not limit the detection method of Dn10, Dn50, Dn90 and Dv50 of the negative electrode active material, which can be measured by screening method, microscopy method, sedimentation method, electronic sensor method, laser method or acoustic spectrum method. In some embodiments, Dn10, Dn50, Dn90 and Dv50 of the negative electrode active material are measured by laser method according to "Particle Size Distribution Laser Diffraction Method" (GB / T19077-2016).

[0034] The present application does not limit the detection method of the interlayer spacing d002 of the negative electrode active material. Exemplarily, it is measured according to the following test method: using an X-ray diffractometer (XRD), the instrument model is Bruker D8ADVANCE, testing the interlayer spacing of the (002) crystal plane of the negative electrode active material or the negative electrode active material in the negative electrode material layer, the test target is Cu Kα, the voltage is 40KV, the current is 40mA, the scanning angle range is 5° to 80°, the scanning step length is 0.00836°, and the time for each step is 0.3s;

[0035] The interlayer spacing d002 is calculated according to the following formula: interlayer spacing d002 = λ / (2 / sinθ),

[0036] Where θ° is the angle of the maximum peak intensity position of the (002) peak;

[0037] λnm is the wavelength.

[0038] This application does not limit the detection method of the pore volume of the negative electrode active material. Exemplarily, it is measured according to the following test method: the test instrument is ASAP2460-physical adsorption analyzer (manufacturer Guoyi Quantum), the sample after drying and degassing is placed in liquid nitrogen, different test pressures are adjusted, the adsorption amount of nitrogen is measured respectively, and the adsorption and desorption isotherms are drawn. The shape of the pore is determined according to the shape of the hysteresis loop, the pore distribution and pore volume are calculated according to different pore models, the BJH model is used to fit the pore size distribution curves of mesopores and macropores, and the DFT model is used to fit the pore size distribution curves of micropores.

[0039] In some embodiments, the negative electrode active material further comprises a polymer coating layer disposed on the surface of the carbon material. By coating the polymer coating layer on the surface of the carbon material, the occurrence of side reactions can be reduced, its kinetic performance can be improved, and the cycle stability and high temperature performance can be improved.

[0040] In some embodiments, the negative electrode active material satisfies: D / 4≥75c+3s,

[0041] Wherein, D nm is the thickness of the polymer coating layer;

[0042] c cm 3 / g is the pore volume of the negative electrode active material;

[0043] sm 2 / g is the specific surface area of ​​the negative electrode active material. The inventors found in the research process that the thickness D of the polymer coating layer, the pore volume c of the negative electrode active material and the specific surface area s of the negative electrode active material interact with each other in improving the side reaction between the negative electrode active material and the electrolyte and the lithium ion transmission. When they meet the above relationship, the specific surface area of ​​the negative electrode active material is more suitable, which can better balance the side reaction and kinetic performance.

[0044] As the charge rate increases, the surface density of the negative electrode coating becomes smaller and smaller, and coating appearance problems are prone to occur. For example, due to abnormal coating patterns, the charging and discharging effect at that location is affected, causing local lithium precipitation. Therefore, the requirements for slurry and coating processes are getting higher and higher. In some embodiments, the negative electrode active material satisfies: 2.2<D / 10+b≤5.2;

[0045] Wherein, D nm is the thickness of the polymer coating layer;

[0046] b is the particle size distribution width of the negative electrode active material. The inventors found in the research process that the thickness D of the polymer coating layer and the particle size distribution width of the negative electrode active material will affect the uniformity of the negative electrode slurry and have a certain mutual influence. When they meet the above relationship, it is beneficial to improve the uniformity of the negative electrode slurry, reduce the coating pattern, and avoid or reduce lithium precipitation. D / 10+b can be selected as 2.3, 2.4, 2.5, 2.6, 2.8, 3.0, 3.2, 3.4, 3.6, 3.8, 4.0, 4.2, 4.4, 4.6, 4.8, 5.0, 5.2 or the range formed by any two of the above values.

[0047] The thickness of the polymer coating layer represents the amount of coating. In certain embodiments, the thickness of the polymer coating layer is 10-50nm. The thickness of the polymer coating layer can be selected as 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm or the range formed by any two of the above numerical values. When the thickness of the polymer coating layer is 10-50nm, especially 20-40nm, the etching area is better covered, and the conductivity of the negative electrode active material is better, the internal resistance is lower, and the kinetic performance is better.

[0048] The present application does not limit the method for detecting the thickness of the polymer coating layer. For example, it can be measured by the following method: take 15 cross-sectional TEM images of the negative electrode active material particles, measure the thickness of the polymer layer, remove the maximum and minimum values ​​and take the average value.

[0049] The specific surface area of ​​the negative electrode active material is related to the electrolyte infiltration area and the side reactions. In some embodiments, the specific surface area of ​​the negative electrode active material is 0.8-2.5 m 2 / g. The specific surface area of ​​the negative electrode active material can be selected to be 0.8m 2 / g, 1.0m 2 / g, 1.2m 2 / g, 1.4m 2 / g, 1.6m 2 / g, 1.8m 2 / g, 2.0 2 / g, 2.2m 2 / g, 2.5m 2 / g or the range formed by any two of the above values. When the specific surface area of ​​the negative electrode active material is 0.5-2.0m 2 / g, especially 1.1-2.0m 2 / g, so that the electrolyte infiltration area is larger and the side reactions are less.

[0050] This application does not limit the detection method of the specific surface area s of the negative electrode active material. Exemplarily, it can be measured by the following method: a certain mass of sample (e.g., 1.5 g to 3.5 g) is placed in a sample tube, degassed at 200°C for 2 hours after drying, and then placed in a TristarII3020 instrument analysis station for testing to obtain the specific surface area of ​​the negative electrode active material. The adsorption gas during the test can be nitrogen, and the adsorption temperature can be 77K (K represents Kelvin temperature).

[0051] In some embodiments, the polymer in the polymer coating layer includes a polymer containing an amino group and an ether bond. Exemplarily, the polymer containing an amino group and an ether bond includes polyetheramine.

[0052] In some embodiments, the carbon material includes at least one of artificial graphite and natural graphite.

[0053] The present application does not limit the preparation method of the negative electrode active material. Exemplarily, the preparation method of the negative electrode active material includes the following steps:

[0054] The graphite precursor is rolled and ground to obtain a graphite precursor with a Dv50 of 2 to 15 μm, the obtained graphite precursor is mixed and dispersed with a binder in a mass ratio of (7 to 9): (1 to 2), the temperature is raised to 250 to 550° C. under closed conditions, and the reaction is kept at this temperature for 5 to 48 hours to obtain a granulated semi-finished product;

[0055] Graphitizing the obtained granulated semi-finished product at 2800-3500° C. for 15-40 days to obtain a graphite semi-finished product;

[0056] The obtained graphite semi-finished product is etched by passing air at 300-500°C to obtain etched graphite, that is, the negative electrode active material. Among them, the graphite precursor can be selected to include at least one of petroleum coke, needle coke, and asphalt coke; the binder can be selected as asphalt; the graphitization can be carried out in a reactor, such as a horizontal reactor, and the horizontal reactor can specifically include but is not limited to any one of an Acheson furnace, an internal series graphitization furnace, and a continuous graphitization furnace; controlling the etching time (i.e., the air passing time) can control the etching degree, i.e., the pore volume of the graphite. In one embodiment, the air passing time is 15 to 50 hours.

[0057] In one embodiment, the method for preparing the negative electrode active material further comprises the following steps:

[0058] 0.2-1 mol of benzylamine and 350-550 g of dimethyl sulfoxide are dissolved in 100-250 mL of propylene glycol methyl ether, and an inert protective gas is passed through and stirred; the obtained etching graphite is added, and the mass ratio of the etching graphite to the dimethyl sulfoxide is (1-8):10, the temperature is raised to 45-100° C. and kept warm for reaction for 3-6 hours, then the temperature is lowered to room temperature, and poured into 2000-5000 mL of deionized water to obtain a solid precipitate; the solid precipitate is repeatedly washed with deionized water, and then dried in a vacuum oven at 40-80° C. for 15-48 hours to obtain polyetheramine-coated etching graphite, and the obtained polyetheramine-coated etching graphite is graded and mixed according to the target to obtain the target negative electrode active material.

[0059] The present application also provides a battery, including a negative electrode plate, the negative electrode plate including a current collector and a negative electrode active material layer arranged on the surface of the current collector, and the negative electrode active material layer contains the above-mentioned negative electrode active material.

[0060] In some embodiments, the negative electrode active material layer further comprises a binder and a dispersant. The binder can bind the negative electrode active materials together to form a stable electrode structure; the dispersant can disperse the negative electrode active materials. The selection of the two is not limited. Exemplarily, the binder can be selected to include at least one of styrene-butadiene rubber and polyvinylidene fluoride; the dispersant can be selected to include at least one of sodium carboxymethyl cellulose, carboxymethyl cellulose, carboxyethyl cellulose, aminoethyl cellulose, and ethoxy cellulose.

[0061] In some embodiments, the negative electrode active material layer contains the following components by mass fraction: 95% to 99% of the above-mentioned negative electrode active material, 0.5% to 3% of a binder, and 0.5% to 3% of a dispersant, so that the negative electrode active material has a higher proportion in the negative electrode active material layer, and the negative electrode sheet structure is stable, and the negative electrode active material has good dispersion and does not agglomerate.

[0062] The current collector in the negative electrode plate may be selected to include at least one of copper foil, composite copper foil, and primer-coated copper foil.

[0063] In some embodiments, the preparation method of the negative electrode sheet includes the following steps: dispersing the above-mentioned negative electrode active material, binder and dispersant in a solvent to obtain a negative electrode slurry; coating the negative electrode slurry on both sides of the current collector, and performing cold pressing, trimming, cutting, stripping and other processes after drying to obtain a negative electrode sheet. The solvent can be water or the like.

[0064] In some embodiments, the battery further comprises a positive electrode plate, a separator and an electrolyte. When the battery is a lithium-ion battery, any conventional positive electrode plate of a lithium-ion battery in the art, any conventional separator of a lithium-ion battery in the art and any conventional electrolyte of a lithium-ion battery in the art can be selected, and the battery can be prepared by any conventional method for preparing a lithium-ion battery in the art. When the battery is a sodium-ion battery, any conventional positive electrode plate of a sodium-ion battery in the art, any conventional separator of a sodium-ion battery in the art and any conventional electrolyte of a sodium-ion battery in the art can be selected, and the battery can be prepared by any conventional method for preparing a lithium-ion battery in the art.

[0065] The present application further provides an electric device, comprising the battery, wherein the battery serves as a power supply for the electric device. Exemplarily, the electric device is a portable electronic product, such as a mobile phone, a tablet, a Bluetooth headset, a power bank, etc.

[0066] In order to make the invention purpose, technical solution and beneficial effects of the present application clearer, the present application is further described below in conjunction with embodiments. It should be understood that these embodiments are only used to illustrate the present application and are not used to limit the scope of the present invention.

[0067] Example 1

[0068] (1) Preparation method of negative electrode active material

[0069] Rolling and grinding the graphite precursor petroleum coke to obtain petroleum coke with a Dv50 of 9 μm, then mixing and dispersing the obtained petroleum coke with the binder asphalt in a mass ratio of 8:2, adding the mixture into a horizontal reactor, sealing the reactor, heating the reactor to 300°C, and keeping the reaction temperature for 24 hours to obtain a granulation semi-finished product;

[0070] The obtained granulated semi-finished product is graphitized at 2900° C. for 30 days to obtain a graphite semi-finished product;

[0071] The obtained graphite semi-finished product is etched by passing air at 400° C. for 30 hours to obtain etched graphite;

[0072] 0.5 mol of benzylamine and 400 g of dimethyl sulfoxide were dissolved in 200 mL of propylene glycol methyl ether, and an inert protective gas was passed through and stirred. The obtained etching graphite was added, and the mass ratio of etching graphite to dimethyl sulfoxide was 7:10. The temperature was raised to 90° C. and kept for reaction for 5 h. The temperature was lowered to room temperature and poured into 3000 mL of deionized water to obtain a solid precipitate. The solid precipitate was repeatedly washed with deionized water and dried in a vacuum oven at 60° C. for 24 h to obtain polyetheramine-coated etching graphite. The obtained polyetheramine-coated etching graphite was then added to the obtained polyetheramine-coated etching graphite. The etched graphite is classified using the equipment JFF-1250 of Mianyang Jiufang Intelligent. The fan frequency is set to 90KW, the classification power is set to 25KW, and the classification speed is set to 1500r / min. Three levels of particles are obtained, namely coarse-grained graphite, intermediate-grained graphite and fine-grained graphite. 15% of the volume of the coarse-grained graphite and the fine-grained graphite are removed (that is, 15% of the volume of the coarse-grained graphite is removed, and 15% of the volume of the fine-grained graphite is removed, and similar expressions are used in the subsequent descriptions) and then mixed with the intermediate-grained graphite to obtain the negative electrode active material.

[0073] (2) Preparation of negative electrode sheet

[0074] The obtained artificial graphite, binder styrene-butadiene rubber and dispersant sodium carboxymethyl cellulose were added into deionized water in a weight ratio of 98:1:1, and stirred and dispersed to obtain a negative electrode slurry with a solid content of 52 wt.%;

[0075] The obtained negative electrode slurry is coated on both sides of the negative electrode current collector copper foil, and after drying, cold pressing, trimming, cutting and striping are performed to obtain negative electrode sheets.

[0076] (3) Preparation of positive electrode sheet

[0077] The positive electrode active material NCM523, the conductive agent acetylene black and the binder PVDF were mixed in a mass ratio of 97:2:1, and the solvent NMP was added, and the mixture was stirred under a vacuum stirrer until the system was uniform to obtain a positive electrode slurry with a solid content of 76 wt.%;

[0078] The positive electrode slurry is coated on both sides of the positive electrode current collector aluminum foil, and after drying, it is cold pressed, trimmed, cut into pieces and stripped to obtain the positive electrode sheet.

[0079] (4) Preparation of electrolyte

[0080] Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) were mixed and dispersed in a volume ratio of 1:1:1 to obtain a mixed organic solvent, and then the dried lithium salt LiPF 6 Dissolved in mixed organic solvents to prepare LiPF 6 The concentration of the electrolyte is 1 mol / L.

[0081] (5) Preparation of lithium-ion batteries

[0082] The positive electrode sheet, the isolation film (polyethylene isolation film), and the negative electrode sheet are stacked in order, so that the isolation film is between the positive and negative electrode sheets to play an isolating role, and then wound to obtain a bare battery cell; the bare battery cell is placed in an outer packaging shell, and after drying, the electrolyte is injected, and after vacuum packaging, standing, forming and shaping processes, a lithium-ion battery is obtained.

[0083] Example 2

[0084] The difference from Example 1 is that the preparation method of the negative electrode active material is different, and the specific differences are as follows: in the process of preparing polyetheramine-coated etched graphite by etching graphite, the mass ratio of etched graphite to dimethyl sulfoxide is 7.2:10, and 18% of the volume of the coarse-grained graphite and the fine-grained graphite obtained after classification are removed and mixed with the intermediate-grained graphite. The particle size Dv50, particle size distribution width b, interlayer spacing d002, pore volume c and specific surface area s of the obtained negative electrode active material, and the thickness D of the polymer coating layer are shown in Table 1.

[0085] Example 3

[0086] The difference from Example 1 is that the preparation method of the negative electrode active material is different, and the specific differences are as follows: in the process of preparing polyetheramine-coated etched graphite by etching graphite, the mass ratio of etched graphite to dimethyl sulfoxide is 6.9:10, and 12% of the volume of the coarse-grained graphite and the fine-grained graphite obtained after classification are removed and mixed with the intermediate-grained graphite. The particle size Dv50, particle size distribution width b, interlayer spacing d002, pore volume c and specific surface area s of the obtained negative electrode active material, and the thickness D of the polymer coating layer are shown in Table 1.

[0087] Example 4

[0088] The difference from Example 1 is that the preparation method of the negative electrode active material is different, and the specific differences are as follows: in the process of preparing polyetheramine-coated etched graphite by etching graphite, the mass ratio of etched graphite to dimethyl sulfoxide is 6.7:10, and 10% of the volume of the coarse-grained graphite and the fine-grained graphite obtained after classification are removed and mixed with the intermediate-grained graphite. The particle size Dv50, particle size distribution width b, interlayer spacing d002, pore volume c and specific surface area s of the obtained negative electrode active material, and the thickness D of the polymer coating layer are shown in Table 1.

[0089] Example 5

[0090] The difference from Example 1 is that the preparation method of the negative electrode active material is different, and the specific differences are as follows: in the process of preparing polyetheramine-coated etched graphite by etching graphite, the mass ratio of etched graphite to dimethyl sulfoxide is 6.5:10, and 7% of the volume of the coarse-grained graphite and the fine-grained graphite obtained after classification are removed and mixed with the intermediate-grained graphite. The particle size Dv50, particle size distribution width b, interlayer spacing d002, pore volume c and specific surface area s of the obtained negative electrode active material, and the thickness D of the polymer coating layer are shown in Table 1.

[0091] Example 6

[0092] The difference from Example 1 is that the preparation method of the negative electrode active material is different, and the specific differences are as follows: the graphite precursor petroleum coke is roller-pressed and ground to obtain petroleum coke with a Dv50 of 2 μm, and the mass ratio of etched graphite to dimethyl sulfoxide in the process of etching graphite to prepare polyetheramine-coated etched graphite is 6:10, and the particle size Dv50, particle size distribution width b, interlayer spacing d002, pore volume c and specific surface area s of the obtained negative electrode active material, and the thickness D of the polymer coating layer are shown in Table 1.

[0093] Example 7

[0094] The difference from Example 1 is that the preparation method of the negative electrode active material is different, and the specific differences are as follows: the graphite precursor petroleum coke is roller-pressed and ground to obtain petroleum coke with a Dv50 of 5 μm, and the mass ratio of etched graphite to dimethyl sulfoxide in the process of etching graphite to prepare polyetheramine-coated etched graphite is 6.5:10, and the particle size Dv50, particle size distribution width b, interlayer spacing d002, pore volume c and specific surface area s of the obtained negative electrode active material, and the thickness D of the polymer coating layer are shown in Table 1.

[0095] Example 8

[0096] The difference from Example 1 is that the preparation method of the negative electrode active material is different, and the specific differences are as follows: the graphite precursor petroleum coke is roller-pressed and ground to obtain petroleum coke with a Dv50 of 11 μm, and the mass ratio of etched graphite to dimethyl sulfoxide in the process of etching graphite to prepare polyetheramine-coated etched graphite is 7:10, and the particle size Dv50, particle size distribution width b, interlayer spacing d002, pore volume c and specific surface area s of the obtained negative electrode active material, and the thickness D of the polymer coating layer are shown in Table 1.

[0097] Example 9

[0098] The difference from Example 1 is that the preparation method of the negative electrode active material is different, and the specific differences are as follows: the graphite precursor petroleum coke is roller-pressed and ground to obtain petroleum coke with a Dv50 of 15 μm, and the mass ratio of etched graphite to dimethyl sulfoxide in the process of etching graphite to prepare polyetheramine-coated etched graphite is 7.2:10, and the particle size Dv50, particle size distribution width b, interlayer spacing d002, pore volume c and specific surface area s of the obtained negative electrode active material, and the thickness D of the polymer coating layer are shown in Table 1.

[0099] Example 10

[0100] The difference from Example 1 is that the preparation method of the negative electrode active material is different, and the specific differences are as follows: the time for introducing air during the preparation of the graphite semi-finished product and etching graphite is 15 hours, and the mass ratio of etched graphite to dimethyl sulfoxide during the preparation of polyetheramine-coated etched graphite by etching graphite is 8:10, and the particle size Dv50, particle size distribution width b, interlayer spacing d002, pore volume c and specific surface area s of the obtained negative electrode active material, and the thickness D of the polymer coating layer are shown in Table 1.

[0101] Embodiment 11

[0102] The difference from Example 1 is that the preparation method of the negative electrode active material is different, and the specific differences are as follows: the time for introducing air during the preparation of etched graphite from the graphite semi-finished product is 35 hours, and the mass ratio of etched graphite to dimethyl sulfoxide during the preparation of polyetheramine-coated etched graphite from etched graphite is 6.8:10, and the particle size Dv50, particle size distribution width b, interlayer spacing d002, pore volume c and specific surface area s of the obtained negative electrode active material, and the thickness D of the polymer coating layer are shown in Table 1.

[0103] Example 12

[0104] The difference from Example 1 is that the preparation method of the negative electrode active material is different, and the specific differences are as follows: the time for introducing air during the preparation of etched graphite from the graphite semi-finished product is 42 hours, and the mass ratio of etched graphite to dimethyl sulfoxide during the preparation of polyetheramine-coated etched graphite from etched graphite is 6.4:10, and the particle size Dv50, particle size distribution width b, interlayer spacing d002, pore volume c and specific surface area s of the obtained negative electrode active material, and the thickness D of the polymer coating layer are shown in Table 1.

[0105] Embodiment 13

[0106] The difference from Example 1 is that the preparation method of the negative electrode active material is different, and the specific differences are as follows: the time for air to be introduced during the preparation of the etched graphite from the graphite semi-finished product is 50 hours, and the mass ratio of etched graphite to dimethyl sulfoxide during the preparation of polyetheramine-coated etched graphite from the etched graphite is 5.8:10, and the particle size Dv50, particle size distribution width b, interlayer spacing d002, pore volume c and specific surface area s of the obtained negative electrode active material, and the thickness D of the polymer coating layer are shown in Table 1.

[0107] Embodiment 14

[0108] The difference from Example 1 is that the preparation method of the negative electrode active material is different, and the specific differences are as follows: the graphitization time in the process of preparing the graphite semi-finished product from the granulated semi-finished product is 25 days, and the particle size Dv50, particle size distribution width b, interlayer spacing d002, pore volume c and specific surface area s of the obtained negative electrode active material, and the thickness D of the polymer coating layer are shown in Table 1.

[0109] Embodiment 15

[0110] The difference from Example 1 is that the preparation method of the negative electrode active material is different, and the specific differences are as follows: the graphitization time in the process of preparing the graphite semi-finished product from the granulated semi-finished product is 35 days, and the particle size Dv50, particle size distribution width b, interlayer spacing d002, pore volume c and specific surface area s of the obtained negative electrode active material, and the thickness D of the polymer coating layer are shown in Table 1.

[0111] Example 16

[0112] The difference from Example 1 is that the preparation method of the negative electrode active material is different, and the specific differences are as follows: the graphitization time in the process of preparing the graphite semi-finished product from the granulated semi-finished product is 40 days, and the particle size Dv50, particle size distribution width b, interlayer spacing d002, pore volume c and specific surface area s of the obtained negative electrode active material, and the thickness D of the polymer coating layer are shown in Table 1.

[0113] Embodiment 17

[0114] The difference from Example 1 is that the preparation method of the negative electrode active material is different, and the specific differences are as follows: the time for introducing air during the preparation of etched graphite from the graphite semi-finished product is 35 hours, and the mass ratio of etched graphite to dimethyl sulfoxide during the preparation of polyetheramine-coated etched graphite from etched graphite is 9:10, and the particle size Dv50, particle size distribution width b, interlayer spacing d002, pore volume c and specific surface area s of the obtained negative electrode active material, and the thickness D of the polymer coating layer are shown in Table 1.

[0115] Embodiment 18

[0116] The difference from Example 1 is that the preparation method of the negative electrode active material is different, and the specific differences are as follows: the time for introducing air during the preparation of the graphite semi-finished product and etching graphite is 35 hours, and the mass ratio of etched graphite to dimethyl sulfoxide during the preparation of polyetheramine-coated etched graphite by etching graphite is 8:10, and the particle size Dv50, particle size distribution width b, interlayer spacing d002, pore volume c and specific surface area s of the obtained negative electrode active material, and the thickness D of the polymer coating layer are shown in Table 1.

[0117] Embodiment 19

[0118] The difference from Example 1 is that the preparation method of the negative electrode active material is different, and the specific differences are as follows: the time for introducing air during the preparation of etched graphite from the graphite semi-finished product is 35 hours, and the mass ratio of etched graphite to dimethyl sulfoxide during the preparation of polyetheramine-coated etched graphite from etched graphite is 6:10, and the particle size Dv50, particle size distribution width b, interlayer spacing d002, pore volume c and specific surface area s of the obtained negative electrode active material, and the thickness D of the polymer coating layer are shown in Table 1.

[0119] Embodiment 20

[0120] The difference from Example 1 is that the preparation method of the negative electrode active material is different, and the specific differences are as follows: the time for air to be introduced during the preparation of etched graphite from the graphite semi-finished product is 35 hours, the mass ratio of etched graphite to dimethyl sulfoxide during the preparation of polyetheramine-coated etched graphite from etched graphite is 5.4:10, and 10% of the volume of the coarse-grained graphite and the fine-grained graphite obtained after classification are removed and mixed with the intermediate-grained graphite, and the particle size Dv50, particle size distribution width b, interlayer spacing d002, pore volume c and specific surface area s of the obtained negative electrode active material, and the thickness D of the polymer coating layer are shown in Table 1.

[0121] Embodiment 21

[0122] The difference from Example 1 is that the preparation method of the negative electrode active material is different, and the specific differences are as follows: the time for introducing air during the preparation of etched graphite from the graphite semi-finished product is 42 hours, and the mass ratio of etched graphite to dimethyl sulfoxide during the preparation of polyetheramine-coated etched graphite from etching graphite is 5.8:10, and the particle size Dv50, particle size distribution width b, interlayer spacing d002, pore volume c and specific surface area s of the obtained negative electrode active material, and the thickness D of the polymer coating layer are shown in Table 1.

[0123] Embodiment 22

[0124] The difference from Example 1 is that the preparation method of the negative electrode active material is different, and the specific differences are as follows: in the process of preparing polyetheramine-coated etched graphite by etching graphite, the mass ratio of etched graphite to dimethyl sulfoxide is 5:10, and 7% of the volume of the coarse-grained graphite and the fine-grained graphite obtained after classification are removed and mixed with the intermediate-grained graphite. The particle size Dv50, particle size distribution width b, interlayer spacing d002, pore volume c and specific surface area s of the obtained negative electrode active material, and the thickness D of the polymer coating layer are shown in Table 1.

[0125] Embodiment 23

[0126] The difference from Example 1 is that the preparation method of the negative electrode active material is different, and the specific differences are as follows: in the process of preparing polyetheramine-coated etched graphite by etching graphite, the mass ratio of etched graphite to dimethyl sulfoxide is 6.2:10, and the particle size Dv50, particle size distribution width b, interlayer spacing d002, pore volume c and specific surface area s of the obtained negative electrode active material, and the thickness D of the polymer coating layer are shown in Table 1.

[0127] Embodiment 24

[0128] The difference from Example 1 is that the preparation method of the negative electrode active material is different, and the specific differences are as follows: the time for introducing air during the preparation of etched graphite from the graphite semi-finished product is 42 hours, and the mass ratio of etched graphite to dimethyl sulfoxide during the preparation of polyetheramine-coated etched graphite from etched graphite is 7:10, and the particle size Dv50, particle size distribution width b, interlayer spacing d002, pore volume c and specific surface area s of the obtained negative electrode active material, and the thickness D of the polymer coating layer are shown in Table 1.

[0129] Embodiment 25

[0130] The difference from Example 1 is that the preparation method of the negative electrode active material is different, and the specific differences are as follows: the etched graphite is not coated with polyetheramine, that is, the etched graphite is the negative electrode active material, and the particle size Dv50, particle size distribution width b, interlayer spacing d002, pore volume c and specific surface area s of the obtained negative electrode active material, and the thickness D of the polymer coating layer are shown in Table 1.

[0131] Comparative Example 1

[0132] The difference from Example 1 is that the preparation method of the negative electrode active material is different, and the specific differences are as follows: in the process of preparing polyetheramine-coated etched graphite by etching graphite, the mass ratio of etched graphite to dimethyl sulfoxide is 6.2:10, and 3% of the volume of the coarse-grained graphite and the fine-grained graphite obtained after classification are removed and mixed with the intermediate-grained graphite. The particle size Dv50, particle size distribution width b, interlayer spacing d002, pore volume c and specific surface area s of the obtained negative electrode active material, and the thickness D of the polymer coating layer are shown in Table 1.

[0133] Comparative Example 2

[0134] The difference from Example 1 is that the preparation method of the negative electrode active material is different, and the specific differences are as follows: the graphite precursor petroleum coke is roller-pressed and ground to obtain petroleum coke with a Dv50 of 11 μm, the time for air to be introduced into the graphite semi-finished product during the preparation of etched graphite is 60 hours, and the mass ratio of etched graphite to dimethyl sulfoxide during the preparation of polyetheramine-coated etched graphite by etching graphite is 5:10, and the particle size Dv50, particle size distribution width b, interlayer spacing d002, pore volume c and specific surface area s of the obtained negative electrode active material, and the thickness D of the polymer coating layer are shown in Table 1.

[0135] Performance testing method:

[0136] (1) Dynamic performance test: At 25°C, the lithium-ion batteries prepared in the examples and comparative examples were fully charged at 5C and then fully discharged at 1C. After repeating this process 50 times, the lithium-ion batteries were fully charged at 5C, and then the negative electrode sheets were disassembled and the lithium deposition at the tabs was observed. If the width of lithium deposition is greater than 0 and less than 1 mm, it is slight lithium deposition; if it is greater than 1 mm and less than 3 mm, it is moderate lithium deposition; and if it is greater than 3 mm, it is severe lithium deposition.

[0137] (2) High temperature cycle performance test: The lithium ion batteries prepared in the examples and comparative examples were placed at 45°C for 6 h, and the volume of the battery was tested and recorded as V0. Then, the battery was charged at a rate of 4.5C and discharged at a rate of 1C at the same temperature for 800 full charge and discharge cycles. The volume of the battery was tested and recorded as V1. The capacity retention rate and volume expansion rate of the battery after 800 charge and discharge cycles were calculated, wherein the capacity retention rate of the battery after 800 cycles = 800th discharge capacity / 1st discharge capacity * 100%; the volume expansion rate of the battery after 800 cycles = (V1-V0) / V0*100%.

[0138] (3) Coating pattern width measurement method: Use a film ruler to measure the width of the negative electrode pattern. The test results are shown in Table 1.

[0139] Table 1

[0140]

[0141] It can be seen from the above data that the batteries obtained in each embodiment of the present application have good kinetic performance and cycle performance, such as the degree of lithium deposition is no lithium deposition, slight lithium deposition or moderate lithium deposition, that is, the lithium deposition width is less than 3mm; after 800 cycles at 45°C, the capacity retention rate is above 76.5%, and the volume expansion rate is below 14.8%.

[0142] By comparing Examples 1 to 5 with Comparative Example 1, it can be seen that a larger particle size distribution width of the negative electrode active material will lead to decreased kinetic performance and cycle performance; by comparing Examples 1, 10 to 13 with Comparative Example 2, it can be seen that too large a pore volume of the negative electrode active material will lead to a significant deterioration in high temperature performance, severe gas production, poor interface contact, and further severe interface lithium precipitation.

[0143] By comparing Example 1 with Example 25, it can be seen that coating the polymer on the surface of the carbon material can significantly improve the high-temperature cycle stability and reduce the width of the coating pattern of the negative electrode plate.

[0144] Comparison of Examples 1 to 12, 14 to 16, 18 to 21 and 23 with Examples 13 and 24 shows that when the negative electrode active material satisfies D / 4 ≥ 75c + 3s, the exposure of active sites can be effectively reduced, side reactions can be reduced and the dual balance of kinetics can be ensured.

[0145] Comparison of Examples 1 to 12, 14 to 16, 18 to 21 and 23 with Examples 17 and 22 shows that when the negative electrode active material satisfies 2.2<D / 10+b≤5.2, the homogenization effect can be improved, and the coating pattern can be avoided from being too wide, thereby reducing the lithium plating problem caused thereby.

[0146] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present application rather than to limit the scope of protection of the present application. Although the present application has been described in detail with reference to the preferred embodiments, ordinary technicians in this field should understand that the technical solution of the present application can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present application.

Claims

1. A negative electrode active material, characterized in that: The negative electrode active material comprises a carbon material, the particle size Dv50 of the negative electrode active material is 5-20 μm, the particle size distribution width is 0.7-1.5, the interlayer spacing d002 is 0.330-0.340 nm, and the pore volume is 0.001-0.02 cm 3 / g.

2. The negative electrode active material according to claim 1, characterized in that The negative electrode active material further includes a polymer coating layer disposed on the surface of the carbon material.

3. The negative electrode active material according to claim 2, characterized in that Satisfy: D / 4 ≥ 75c + 3s, Wherein, D nm is the thickness of the polymer coating layer; c cm 3 / g is the pore volume of the negative electrode active material; sm 2 / g is the specific surface area of ​​the negative electrode active material.

4. The negative electrode active material according to claim 2, characterized in that Satisfy: 2.2<D / 10+b≤5.2; Wherein, D nm is the thickness of the polymer coating layer; b is the particle size distribution width of the negative electrode active material.

5. The negative electrode active material according to claim 2, characterized in that At least one of the following conditions is met: S1. The thickness of the polymer coating layer is 10-50nm; S2. The specific surface area of ​​the negative electrode active material is 0.8-2.5m 2 / g.

6. The negative electrode active material according to claim 2, characterized in that The polymer in the polymer coating layer includes a polymer containing an amino group and an ether bond.

7. The negative electrode active material according to claim 2, characterized in that The polymer in the polymer coating layer includes polyetheramine.

8. The negative electrode active material according to claim 1, characterized in that The carbon material includes at least one of artificial graphite and natural graphite.

9. A battery, characterized in that: The invention comprises a negative electrode plate, wherein the negative electrode plate comprises a current collector and a negative electrode active material layer arranged on the surface of the current collector, wherein the negative electrode active material layer comprises the negative electrode active material according to any one of claims 1 to 8.

10. An electrical device, characterized in that: The battery as claimed in claim 9 is used as a power supply for the electrical device.

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