A negative electrode material, a negative electrode sheet containing the same, an electrochemical device, and an electronic device

Abstract

The application provides a negative electrode material, a negative electrode sheet containing the same, an electrochemical device and an electronic device. The negative electrode material is SiM x C y , 0.5≤x≤2, 0.5≤y≤4, M includes at least one of boron, nitrogen, oxygen or aluminum; the SiM x C y The particle size of the number accumulation degree A% is D N A, the particle size of the volume accumulation degree B% is D V B, and the half peak width of the number distribution curve is ΔD N ; wherein: 2μm≤(D V 50‑D N 50)≤6μm, 1≤(D N 99‑D N 1) / ΔD N ≤1.3. The negative electrode material, the negative electrode sheet containing the same, the electrochemical device and the electronic device all have good cycle performance and energy density.

Description

Technical Field

[0001] The present application relates to the technical field of lithium-ion batteries, and in particular to a negative electrode material and a negative electrode plate, an electrochemical device, and an electronic device containing the negative electrode material. Background Art

[0002] Lithium-ion batteries have the characteristics of high specific energy, high operating voltage, low self-discharge rate, small size and light weight, and are widely used in the field of consumer electronics. With the rapid development of electric vehicles and mobile electronic devices, people have increasingly higher requirements for the energy density, safety, cycle performance and other related aspects of lithium-ion batteries. Among them, silicon materials have a high theoretical gram capacity (4200mAh / g) and have broad prospects for application in lithium-ion batteries. However, there are also some problems in the application of silicon materials. First, its volume expansion can reach 300% when lithium is inserted, which seriously affects its structural stability and cycle stability. It is also easy to cause damage to the diaphragm and form micro-short circuits. Second, by-products will continue to be generated on its surface, which will continuously consume the lithium source in the electrolyte. Especially at high temperatures, the consumption of electrolyte will be accelerated, thus affecting the cycle performance of lithium-ion batteries.

[0003] Therefore, there is an urgent need for a negative electrode material that can further improve the cycle stability of lithium-ion batteries and reduce the volume expansion of lithium-ion batteries. Summary of the Invention

[0004] Based on the defects of the prior art, the purpose of this application is to provide a negative electrode material and a negative electrode plate, electrochemical device and electronic device containing the same, so as to improve the battery cycle stability performance of lithium-ion batteries.

[0005] In a first aspect of the present application, a negative electrode material is provided, wherein the negative electrode material comprises SiM x C y , wherein 0.5≤x≤2, 0.5≤y≤4, M comprises at least one of boron, nitrogen, oxygen or aluminum; the SiM x C y The cumulative number of particles A% is D N A, the volume accumulation degree B% particle size is D V B, the half-peak width of the number distribution curve is ΔD N ;in:

[0006] 2μm≤(D V 50-D N 50)≤6μm, 1≤(D N 99-D N 1) / ΔD N ≤1.3.

[0007] In some embodiments of the first aspect of the present application, wherein D N99 the range satisfies: 12.0 to 20.0 pm; D N 1 the range satisfies: 0.1 to 1.0 pm, D V 50 the range satisfies: 4.0 to 10.0 pm.

[0008] In some embodiments of the first aspect of the present application, wherein the shift of the silicon element in the solid-state nuclear magnetic resonance test of the negative electrode material includes -5ppm, -35ppm, -75ppm, -110ppm.

[0009] In some embodiments of the first aspect of the present application, wherein the specific surface area of the negative electrode material satisfies: 1.0 to 8.0 m 2 / g.

[0010] In some embodiments of the first aspect of the present application, wherein the powder conductivity of the negative electrode material is 2.0 to 30 S / cm.

[0011] In some embodiments of the first aspect of the present application, wherein the nitrogen adsorption isotherm defined in IUPAC is type III.

[0012] In some embodiments of the first aspect of the present application, wherein at least one of carbon, a high molecular polymer or a composite of the above substances exists on the surface of the negative electrode material;

[0013] The carbon includes at least one of amorphous carbon, carbon nanotube, carbon nanoparticle, vapor deposition carbon fiber or graphene;

[0014] The high molecular polymer includes at least one of polyvinylidene fluoride, carboxymethyl cellulose, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyacrylic acid, polybutadiene rubber or derivatives of the above substances.

[0015] The second aspect of the present application provides a negative electrode tab, which includes a current collector and the negative electrode material of any one of the above.

[0016] The third aspect of the present application provides an electrochemical device, which includes a positive electrode tab and the negative electrode tab of the above.

[0017] The fourth aspect of the present application provides an electronic device, which includes the electrochemical device of the above.

[0018] The negative electrode material provided by the present application improves the particle size distribution, optimizes the compaction density of the negative electrode active material, and improves the cycle performance and energy density of the negative electrode tab, the electrochemical device and the electronic device using the negative electrode material.

[0019] Herein, the term "Dv50" refers to the particle size at which the cumulative distribution of particles is 50% based on volume distribution; that is, the volume of particles smaller than this particle size accounts for 50% of the total volume of all particles. The particle size is measured using a laser particle size analyzer.

[0020] The term "D N "99" indicates the particle size at which the cumulative distribution of particles reaches 99% based on the number distribution; that is, the number of particles smaller than this particle size accounts for 99% of the total number of all particles. The particle size is measured using a laser particle size analyzer.

[0021] The term "D N "1" indicates the particle size at which the cumulative distribution of particles accounts for 1% based on the number distribution; that is, the number of particles smaller than this particle size accounts for 1% of the total number of all particles. The particle size is measured using a laser particle size analyzer.

[0022] The term "ΔD N " indicates the half-peak width of the number distribution curve of particle size based on the number distribution. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present application and the technical solutions of the prior art, the following briefly introduces the drawings required for use in the embodiments and the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0024] Figure 1 is the solid-state nuclear magnetic resonance spectrum of the negative electrode material SiOC of Example 1;

[0025] Figure 2 This is the nitrogen adsorption isotherm of the negative electrode material SiOC of Example 1 as specified in IUPAC. DETAILED DESCRIPTION

[0026] To make the objectives, technical solutions, and advantages of this application more clearly understood, the present application is further described below with reference to the accompanying drawings and examples. It is clear that the described examples are only some of the examples of this application, not all of them. All other examples derived by persons of ordinary skill in the art based on the examples in this application without inventive effort are within the scope of protection of this application.

[0027] It should be noted that, in the specific embodiments of the present application, a lithium-ion battery is used as an example of an electrochemical device to explain the present application, but the electrochemical device of the present application is not limited to a lithium-ion battery.

[0028] In a first aspect of the present application, a negative electrode material is provided, wherein the negative electrode material comprises SiMx C y , wherein 0.5≤x≤2, 0.5≤y≤4, M comprises at least one of boron, nitrogen, oxygen or aluminum; the SiM x C y , the number cumulative degree A% of the particle size is D N A, the volume cumulative degree B% of the particle size is D V B, and the half-peak width of the particle size number distribution curve is ΔD N ; wherein:

[0029] 2μm≤(D V 50-D N 50)≤6μm, 1≤(D N 99-D N 1) / ΔD N ≤1.3.

[0030] The inventors of the present application accidentally found, through in-depth research, that the negative electrode material SiM x C y of the present application, compared with the prior art, by adjusting the particle size distribution of the negative electrode material SiM x C y , the negative electrode sheet using the negative electrode material can have a higher compaction density while also ensuring good cycle performance. Without being limited by any theory, the inventors believe that the uniform distribution of the negative electrode material SiM x C y may on one hand improve the compaction density and on the other hand have less adverse effect on cycle performance.

[0031] In some embodiments of the first aspect of the present application, wherein the D N 99 range satisfies: 12.0 to 20.0 μm; the D N 1 range satisfies: 0.1 to 1.0 μm, and the D V 50 range satisfies: 4.0 to 10.0 μm.

[0032] The inventors found that in addition to controlling the uniform distribution of the particle size of the negative electrode material SiM x C y , the particle sizes D x 50, D y 99 and D V 1 of the negative electrode material SiM N C N also need to be improved. Without being limited by any theory, the inventors believe that the negative electrode material SiM x C yThe negative electrode material is easy to break during lithium extraction, resulting in poor cycle performance, and large particles of the negative electrode material can damage the separator during tabletting, causing self-discharge; small particles of the negative electrode material have intense side reactions, which can cause safety hazards. By controlling the particle size D x C y of the negative electrode material SiM V 50、D N 99 and D N 1 within the above range, a negative electrode tab with higher compaction density and better cycle performance can be obtained.

[0033] In some embodiments of the first aspect of the application, the chemical shift of silicon in the negative electrode material is -5ppm, -35ppm, -75ppm, and -110ppm, as determined by solid-state nuclear magnetic resonance.

[0034] The inventors have unexpectedly found that the negative electrode material SiM x C y of the application has a chemical shift of silicon of -5ppm, as determined by solid-state nuclear magnetic resonance, compared with some existing negative electrode materials such as carbon-silicon-oxygen. x C y The inventors have found that the negative electrode material SiM x C y of the application has lower expansion, without being limited to any theory. The inventors believe that this may be due to the crystallization degree of the negative electrode material SiM x C y of the application being different from that of the prior art, so that the negative electrode material SiM x C y of the application has lower expansion.

[0035] Figure 1 The negative electrode material SiM x C y of the application is shown in the solid-state nuclear magnetic resonance spectrum; wherein the chemical shift of silicon is -5ppm, -35ppm, -75ppm, and -110ppm.

[0036] In some embodiments of the first aspect of the application, the specific surface area of the negative electrode material satisfies 1.0 to 8.0m 2 / g.

[0037] The inventors have found through in-depth research that if the specific surface area of the negative electrode material is too small, the negative electrode material cannot release stress well and is easy to break during lithium extraction; and if the specific surface area of the negative electrode material is too large, the side reaction with the electrolyte is more intense at high temperatures, resulting in deterioration of high-temperature cycle performance.

[0038] In some embodiments of the first aspect of the application, the powder conductivity of the negative electrode material is 2.0 to 30S / cm.

[0039] In this application, increasing the carbon (C) content in the negative electrode material improves conductivity, but this reduces the compaction density of the negative electrode sheet, thus affecting the improvement of energy density. By controlling the powder conductivity of the negative electrode material within the above range, a good balance between conductivity, compaction density, and energy density can be achieved.

[0040] In some embodiments of the first aspect of the present application, the nitrogen adsorption isotherm specified in IUPAC is type III.

[0041] Figure 2 The nitrogen adsorption isotherm of the negative electrode material of the present application as specified in IUPAC is shown, and it can be seen that it is type III.

[0042] In some embodiments of the first aspect of the present application, at least one of carbon, a high molecular polymer, or a composite of the foregoing substances exists on the surface of the negative electrode material;

[0043] The carbon comprises at least one of amorphous carbon, carbon nanotubes, carbon nanoparticles, vapor deposited carbon fibers or graphene;

[0044] The high molecular polymer includes at least one of polyvinylidene fluoride, carboxymethyl cellulose, sodium carboxymethyl cellulose, polyvinyl pyrrolidone, polyacrylic acid, polystyrene-butadiene rubber or derivatives of the above substances.

[0045] The inventors also discovered that the presence of carbon on the surface of the negative electrode material can increase the conductivity of the negative electrode material and improve its electrical performance. In this application, there is no specific limitation on the method and content of adding carbon. For example, carbon can account for 1% to 30% of the mass of the negative electrode material.

[0046] A second aspect of the present application provides a negative electrode sheet, which includes a negative electrode current collector and a negative electrode active material layer, wherein the negative electrode active material layer contains the negative electrode material described in any of the above embodiments.

[0047] The negative electrode active material layer can be coated on one or both surfaces of the negative electrode current collector. Those skilled in the art can make a specific selection according to actual needs, and this application does not impose any limitation thereto.

[0048] The present application does not particularly limit the negative electrode current collector; any negative electrode current collector known to those skilled in the art may be used. For example, negative electrode current collectors made of iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, platinum, etc. may be used. Among them, copper foil or copper alloy foil is particularly preferred. These materials may be used alone or in combination of two or more in any proportion.

[0049] In some embodiments of the present application, the negative electrode active material layer further contains graphite, and the graphite may include at least one of natural graphite, artificial graphite or mesophase carbon microbeads. In some embodiments of the present application, a mixture of the negative electrode material of the present application and graphite may be used as the negative electrode active material.

[0050] In some embodiments of the present application, the negative electrode active material layer may further include a binder. The binder is not particularly limited and may be any binder known to those skilled in the art or a combination thereof, for example, it may include at least one of polyacrylate, polyimide, polyamide, polyamideimide, polyvinylidene fluoride, styrene-butadiene rubber, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, sodium hydroxymethyl cellulose, or potassium hydroxymethyl cellulose. These binders may be used alone or in combination of two or more in any proportion.

[0051] In some embodiments of the present application, the negative electrode active material layer may further include a conductive agent. The conductive agent is not particularly limited and may be any conductive agent or combination thereof known to those skilled in the art. For example, at least one of a zero-dimensional conductive agent, a one-dimensional conductive agent or a two-dimensional conductive agent may be used. Preferably, the conductive agent may include at least one of carbon black, conductive graphite, carbon fiber, carbon nanotubes, VGCF (vapor-grown carbon fiber) or graphene. The amount of the conductive agent is not particularly limited and may be selected according to common knowledge in the art. The above conductive agents may be used alone or in combination of two or more in any proportion.

[0052] A third aspect of the present application provides an electrochemical device comprising a positive electrode sheet and the above-mentioned negative electrode sheet.

[0053] The electrochemical devices of this application include, but are not limited to, all types of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. A typical electrochemical device is a lithium-ion battery, which is a secondary battery. Electrochemical devices, such as lithium-ion batteries, generally include a negative electrode, a positive electrode, a separator, and an electrolyte.

[0054] Furthermore, the electrochemical device may be a lithium-ion battery provided in the present application.

[0055] The electrochemical device provided in the present application has a negative electrode sheet using the negative electrode sheet provided in the present application; and the other components, including the positive electrode sheet, separator and electrolyte, etc., are not particularly limited in the present application. For example, the positive electrode material contained in the positive electrode sheet may include but is not limited to lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, etc. The material of the separator may include but is not limited to glass fiber, polyester, polyethylene, polypropylene, polytetrafluoroethylene or a combination thereof. The electrolyte generally includes an organic solvent, a lithium salt and an additive. The organic solvent may include but is not limited to at least one of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate and ethyl propionate. The lithium salt may include at least one of an organic lithium salt or an inorganic lithium salt; for example, the lithium salt may include at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), lithium bis(trifluoromethanesulfonyl)imide LiN(CF3SO2)2 (LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO2F)2)(LiFSI), lithium bis(oxalatoborate) LiB(C2O4)2 (LiBOB), or lithium difluorooxalatoborate LiBF2(C2O4) (LiDFOB).

[0056] The preparation process of an electrochemical device is well known to those skilled in the art and is not particularly limited in this application. For example, a secondary battery can be manufactured by overlapping the positive and negative electrodes with a separator, winding and folding them as needed, and then placing them in a battery container. The electrolyte is then injected into the battery container and sealed. The negative electrode used is the negative electrode sheet provided in this application. Furthermore, overcurrent protection elements, guide plates, etc. can be placed in the battery container as needed to prevent internal pressure buildup and overcharge and discharge.

[0057] A fourth aspect of the present application provides an electronic device comprising the above-mentioned electrochemical device.

[0058] Test Method

[0059] Solid-state NMR:

[0060] 29 Si solid-state NMR spectroscopy was performed on an AVANCE III 400 WB wide-cavity solid-state NMR instrument with a rotation rate of 8 kHz. 29 Si.

[0061] Particle size test:

[0062] Add about 0.02 g of each sample powder to a 50 ml clean beaker, add about 20 ml of deionized water, and then add a few drops of 1% surfactant to completely disperse the negative electrode material powder in the water. Ultrasonicate in a 120 W ultrasonic cleaner for 5 minutes, and use a MasterSizer 2000 to test the particle size distribution.

[0063] Negative electrode material specific surface area test:

[0064] At constant temperature and low temperature, after measuring the adsorption amount of gas on the solid surface at different relative pressures, the monolayer adsorption amount of the sample is obtained based on the Brownauer-Ettel-Taylor adsorption theory and its formula (BET formula), thereby calculating the specific surface area of ​​the solid.

[0065] Charge and discharge performance test:

[0066] The negative electrode material, conductive carbon black, and binder polyacrylic acid (PAA) were mixed with deionized water in a mass ratio of 80:10:10 and stirred into a slurry. A 100μm-thick coating was applied using a doctor blade. After drying in a vacuum oven at 85°C for 12 hours, the coating was cut into 1cm-diameter discs using a punch in a dry environment. In a glove box, button cells were assembled using a metal lithium sheet as the counter electrode and a Ceglar composite film as the separator. Electrolyte was added and the cells were then charged and discharged using a LAND series battery testing system to verify their charge and discharge performance.

[0067] Cyclic performance test:

[0068] The test temperature is 25 / 45℃, and the battery is charged to 4.4V at a constant current of 0.7C, then charged to 0.025C at a constant voltage. After standing for 5 minutes, the battery is discharged to 3.0V at 0.5C. The capacity obtained in this step is taken as the initial capacity, and a cycle test is performed with 0.7C charge / 0.5C discharge. The capacity at each step is compared with the initial capacity to obtain the capacity decay curve. The number of cycles at 25℃ until the capacity retention rate reaches 80% is recorded as the room temperature cycle performance of the lithium-ion battery, and the number of cycles at 45℃ until the capacity retention rate reaches 80% is recorded as the high temperature cycle performance of the lithium-ion battery. The cycle performance of the material is obtained by comparing the number of cycles under the above two conditions.

[0069] K value test:

[0070] After testing the capacity of the lithium-ion battery, let it stand at room temperature for 48 hours, and measure its voltage as V1. After the lithium-ion battery is allowed to stand for another 48 hours, measure its voltage as V2. The K value is calculated according to the following formula: K = (V1-V2) / 48; the unit is mV / h.

[0071] Negative electrode material compaction density test:

[0072] Using GB / T 24533-2009, "Graphite-Based Anode Materials for Lithium-Ion Batteries," a certain amount of anode material powder is placed in a dedicated compaction mold (of known diameter). The mold has a hollow center with two metal discs above and below. The powder is placed between the discs and a metal cylinder is placed on top. The mold is then placed on a compaction density instrument and set to different pressures. The instrument reads the thickness of the anode material powder at different pressures and calculates the compaction density of the anode material using the equation ρ = m / v.

[0073] Carbon content test:

[0074] The sample is heated and burned at high temperature in a high-frequency furnace under oxygen-rich conditions, oxidizing carbon and sulfur into carbon dioxide and sulfur dioxide. After treatment, the gases enter the corresponding absorption cell, where they absorb the corresponding infrared radiation and are then converted into corresponding signals by the detector. This signal is sampled by a computer and converted into a value proportional to the concentration of carbon dioxide and sulfur dioxide after linear correction. The values ​​obtained throughout the entire analysis process are then accumulated. After the analysis is completed, this accumulated value is divided by the weight value in the computer, multiplied by the correction factor, and the blank is subtracted to obtain the percentage of carbon and sulfur in the sample. Sample testing is performed using a high-frequency infrared carbon and sulfur analyzer (Shanghai Dekai HCS-140).

[0075] Negative electrode material powder electronic conductivity test:

[0076] The four-wire two-terminal method is used to determine the fixed body resistance by measuring the voltage across the resistor to be tested (i.e., the sample press) and the current flowing through it. The conductivity is calculated based on the height and bottom area of ​​the resistor to be tested. A certain amount of negative electrode material powder is added to the test mold, gently shaken flat, and then the gasket on the mold is placed on the sample; after the sample is loaded, the mold is placed on the workbench of the electronic pressure testing machine, and the pressure is increased to 500kg (159Mpa) at a rate of 5mm / min, constant pressure is maintained for 60s, and then the pressure is released to 0; when the sample is constant pressured to 5000±2kg (about 15 to 25 seconds after the pressure reaches 5000kg), the sample pressure is recorded, and the sample deformation height is read. The value displayed by the resistance tester (Suzhou Jingge Electronics ST-2255A) at this time is recorded, and the electronic conductivity can be calculated using the following formula:

[0077] δ=h / (S*R) / 1000

[0078] Where δ is the electronic conductivity, h is the height of the sample press, S is the bottom area of ​​the sample press, and R is the read resistance.

[0079] Hereinafter, the present application will be specifically described based on examples, but the present application is not limited to these examples.

[0080] Full battery preparation

[0081] Preparation Example 1 Preparation of positive electrode sheet:

[0082] The active material LiCoO2, conductive carbon black, and binder polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 96.7:1.7:1.6 in an N-methylpyrrolidone solvent system to form a slurry with a solid content of 75 wt%, and stirred uniformly. The slurry was uniformly coated on one surface of an aluminum foil positive electrode current collector with a thickness of 12 μm, dried at 90°C with a coating thickness of 115 μm, cold-pressed to obtain a positive electrode sheet, and the electrode sheet was cut into a sheet with a size of 74 mm x 867 mm for use.

[0083] Preparation of the negative electrode sheet of Preparation Example 2:

[0084] The negative electrode material prepared in each example and comparative example was mixed with graphite in a certain proportion to obtain a negative electrode active material powder with a design mixed gram capacity of 500 mAh / g. After the negative electrode active material powder, conductive agent acetylene black, and PAA were thoroughly stirred and mixed uniformly in a weight ratio of 95:1.2:3.8 in a deionized water solvent system, a slurry with a solid content of 45 wt% was obtained. The slurry was coated on both surfaces of a copper foil current collector with a thickness of 10 μm, and the coating thickness was 100 μm. After the electrode sheet was dried and cold-pressed, the double-sided compacted density was 1.8 g / cm 3 , to obtain a negative electrode sheet, which was cut into a sheet with a size of 74 mm x 867 mm for use.

[0085] Preparation of the lithium ion battery of Preparation Example 3:

[0086] A PE porous polymer film with a thickness of 15 μm was used as a separator. The positive electrode sheet, the separator, and the negative electrode sheet were stacked in order, with the separator between the positive and negative electrodes to play a role of separation, and wound to obtain an electrode assembly.

[0087] The electrode assembly was placed in an outer package, injected with prepared electrolyte (EC:DMC:DEC=1:1:1 vol%, 10 wt% FEC, 1 mol / L LiPF6), and packaged. After formation, degassing, and edge cutting processes, a lithium ion battery was obtained.

[0088] Preparation of the negative electrode material

[0089] A carbon source (including at least one of glucose or sucrose) was dissolved in a dimethylbenzene solvent. After complete dissolution, an organosilicon (including at least one of polysiloxane, polycarbosilane, polysilazane, polycarboborane methylsiloxane, or polysilaborazane) was added in a certain proportion, stirred for 4 h to completely immerse the carbon source solution and the organosilicon solution, and then heated at 80°C to remove the solvent. The product was then placed in an oven at 80°C for drying for 24 h.

[0090] The obtained product is placed in a tube furnace for high-temperature cracking. Using nitrogen or argon as the protective atmosphere, the temperature is raised to 500°C at 1°C / min, kept at this temperature for 30 minutes, and then raised to 900-1500°C at 3°C / min and kept at this temperature for 3 hours. The negative electrode material SiM is obtained by high-temperature cracking. x C y .

[0091] Example 1

[0092] 50g of glucose was dissolved in 100mL of xylene solvent, and then 50g of polysiloxane was added thereto. The mixture was stirred for 4h to completely immerse the glucose solution and the polysiloxane solution. The solvent was then removed by stirring and heating at 80°C. The product was then placed in an 80°C oven and dried for 24h. The obtained product was placed in a tube furnace for high-temperature cracking. Specifically, with Ar as the protective atmosphere, the temperature was raised to 500°C at 1°C / min, kept warm for 30min, and further raised to 900°C at 3°C / min and kept for 3h. The negative electrode material SiOC (silicon oxygen carbon ceramic material) was obtained by high-temperature cracking.

[0093] The prepared negative electrode material SiOC was placed in a ball mill, milled at 50 Hz for 40 min, and then filtered through a 200-mesh filter. The particle size distribution was D V 50=8μm、D N 50=5μm, D N 99=15μm、D N 1=0.5μm、ΔD N =13μm, BET is 5m 2 / g, negative electrode material SiOC with a conductivity of 15S / cm.

[0094] Example 2

[0095] In addition to screening out the negative electrode material SiOC D V Except that 50 is changed to 10 μm, the rest is the same as in Example 1.

[0096] Examples 3 to 4

[0097] In addition to screening out the negative electrode material SiOC D N Except that 50 is changed to 3μm and 6μm respectively, the rest is the same as Example 1.

[0098] Examples 5 to 6

[0099] In addition to screening out the negative electrode material SiOC D N Except that 99 is changed to 14μm and 17μm respectively, the rest is the same as Example 1.

[0100] Examples 7 to 8

[0101] D50 of the negative electrode material SiOC selected by the screen N 1 was changed to 0.1 μm, 1 μm, and the rest was the same as in Example 1.

[0102] Example 9

[0103] D50 of the negative electrode material SiOC selected by the screen N was changed to 14 μm, and the rest was the same as in Example 1.

[0104] Example 10

[0105] D50 of the negative electrode material SiOC selected by the screen V 50 was changed to 5 μm, D N 50 was changed to 3 μm, D N 99 was changed to 13 μm, D N 1 was changed to 0.4 μm, ΔD N was changed to 10 μm, and the rest was the same as in Example 1.

[0106] Example 11

[0107] D50 of the negative electrode material SiOC selected by the screen V 50 was changed to 10 μm, D N 50 was changed to 6 μm, D N 99 was changed to 18 μm, D N 1 was changed to 1 μm, ΔD N was changed to 14 μm, and the rest was the same as in Example 1.

[0108] Example 12

[0109] D50 of the negative electrode material SiOC selected by the screen V 50 was changed to 7 μm, D N 50 was changed to 4 μm, D N 99 was changed to 14 μm, D N 1 was changed to 0.4 μm, ΔD N was changed to 12 μm, and the rest was the same as in Example 1.

[0110] Example 13

[0111] D50 of the negative electrode material SiOC selected by the screen V 50 was changed to 4 μm, D N 50 was changed to 1.5 μm, D N 99 was changed to 11 μm, D N 1 was changed to 0.2 μm, ΔD N was changed to 9 μm, and the rest was the same as in Example 1.

[0112] Example 14

[0113] The process is the same as that of Example 1 except that the conductivity of the negative electrode material SiOC is changed to 30 S / cm.

[0114] Comparative Example 1

[0115] In addition to screening out the negative electrode material SiOC D V Except that 50 is changed to 6 μm, the rest is the same as in Example 1.

[0116] Comparative Example 2

[0117] In addition to screening out the negative electrode material SiOC D N Except that 50 is changed to 1 μm, the rest is the same as in Example 1.

[0118] Comparative Example 3

[0119] In addition to screening out the negative electrode material SiOC D N Except that 99 is changed to 22 μm, the rest is the same as Example 1.

[0120] Comparative Example 4

[0121] In addition to screening out the negative electrode material SiOC D N Except that 1 is changed to 0.01 μm, the rest is the same as in Example 1.

[0122] Comparative Example 5

[0123] In addition to screening out the ΔD of the negative electrode material SiOC N Except for being changed to 3 μm, the rest is the same as Example 1.

[0124] Comparative Example 6

[0125] In addition to screening out the negative electrode material SiOC D V 50 becomes 14μm, D N 50 becomes 7μm, D N 99 becomes 15μm, D N 1 becomes 0.5μm, ΔD N Except for the change to 13 μm, the rest is the same as Example 1.

[0126] Comparative Example 7

[0127] In addition to screening out the D of the negative electrode material SiOC V 50 becomes 3μm, D N Except that 50 is changed to 2 μm, the rest is the same as in Example 1.

[0128] The parameters and test results of each embodiment and comparative example are shown in Table 1 and Table 2.

[0129] Table 1 Parameters and test results of various embodiments and comparative examples

[0130]

[0131]

[0132] Table 2 Test results of each example and comparative example

[0133]

[0134] As can be seen from Examples 1 to 4 and Comparative Examples 1 and 2, when (D V 50-D N 50) is too small (such as Comparative Example 1), the compaction density is low due to the concentrated particle size distribution; when (D V 50-D N 50) is too large (such as Comparative Example 2), there are more fine powders in the particle distribution, which results in a low compaction density and poor high-temperature cycle performance.

[0135] As can be seen from Examples 1, 5 to 6 and Comparative Example 3, when D N 1 and ΔD N are unchanged and D N 99 is too large (such as Comparative Example 3), on the one hand, it will lead to uneven particle distribution, thus resulting in a low compaction density, and on the other hand, it will result in more large particles, thus both the cycle performance and K value will be poor.

[0136] As can be seen from Examples 7 and 8 and Comparative Example 4, when D N 99 and ΔD N are unchanged, with the increase of D N 1, on the one hand, the particle distribution is more uniform, thus increasing the compaction density; on the other hand, it results in fewer small particles, thus improving the high-temperature cycle performance; when D N 1 is too small (such as Comparative Example 4), the compaction density is low and the high-temperature cycle performance is poor.

[0137] As can be seen from Examples 1, 9 and Comparative Example 5, when D N 99 and D N 1 are unchanged and ΔD N is larger, it will result in a more uniform particle distribution, thus effectively increasing the compaction density, while having a small effect on the cycle performance.

[0138] As can be seen from Examples 10 to 13, with the decrease of the average particle size (D V 50) of the negative electrode material powder, the powder BET becomes larger, thus resulting in a larger powder compaction density and a smaller K value.

[0139] It can be seen from Comparative Examples 6 and 7 that a too small BET (such as Comparative Example 6) is easy to break due to the large average particle size and large particle stress, which will result in poor cycle performance. A too large BET (such as Comparative Example 7) will increase side reactions, thereby worsening the cycle performance.

[0140] It can be seen from Examples 1 to 14 and Comparative Example 6 that the powder compaction density of the negative electrode material with a conductivity in the range of 2 to 30 S / cm is higher.

[0141] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A negative electrode material, wherein The negative electrode material includes SiM x C y , 0.5≤x≤2, 0.5≤y≤4, M includes at least one of boron, nitrogen, oxygen or aluminum; The SiM x C y Particle size D v 50. D N 50. D N 99.D N 1 and ΔD N satisfy: 2μm≤(D V 50-D N 50)≤6μm,1≤(D N 99-D N 1) / ΔD N ≤1.3; Among them, D N 99 range meets: 12.0 to 20.0 μm; D N 1 Range: 0.1 to 1.0 μm, D V 50 range meets: 4.0 to 10.0 μm; D v 50 means the particle size at which the cumulative distribution of particles is 50% based on the volume distribution; D N 50 means the particle size at which the cumulative distribution of particles is 50% based on the number distribution; D N 99 means the particle size at which the cumulative distribution of particles is 99% based on the number distribution; D N 1 means the particle size at which the cumulative distribution of particles is 1% based on the number distribution; ΔD N It indicates the half-peak width of the particle size distribution curve based on the number distribution.

2. The negative electrode material according to claim 1, wherein Solid-state nuclear magnetic resonance testing shows that the displacement of silicon elements in the negative electrode material includes -5ppm, -35ppm, -75ppm and -110ppm.

3. The negative electrode material according to claim 1, wherein The specific surface area of ​​the negative electrode material satisfies: 1.0 to 8.0 m 2 / g.

4. The negative electrode material according to claim 1, wherein The powder conductivity of the negative electrode material is 2.0 to 30 S / cm.

5. The negative electrode material according to claim 1, wherein The nitrogen adsorption isotherm specified by IUPAC is type III.

6. The negative electrode material according to claim 1, wherein At least one of carbon, high molecular polymer or a composite of the above substances exists on the surface of the negative electrode material; The carbon comprises at least one of amorphous carbon, carbon nanotubes, carbon nanoparticles, vapor deposited carbon fibers or graphene; The high molecular polymer includes at least one of polyvinylidene fluoride, carboxymethyl cellulose, sodium carboxymethyl cellulose, polyvinyl pyrrolidone, polyacrylic acid, polystyrene-butadiene rubber or derivatives of the above substances.

7. A negative electrode sheet comprising a current collector and the negative electrode material according to any one of claims 1 to 6. An electrochemical device comprising a positive electrode sheet and the negative electrode sheet according to claim 7.

9. An electronic device comprising the electrochemical device according to claim 8.

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