JP2015118911A - Silicon-based composite negative electrode material for lithium ion secondary batteries, manufacturing method, and battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silicon-based composite negative electrode material which is superior in cycle characteristics (the capacity-keeping rate for 300 cycles is 90% or higher), high in initial efficiency (>90%), and high in specific energy and press density, and which can fulfill the need for a high-output density lithium ion secondary battery, and is simple in its manufacturing process, low in raw material cost, environmentally friendly and pollution-free.SOLUTION: The problem can be solved by a silicon-based composite negative electrode material for lithium ion secondary batteries, which has an embedded composite core-shell structure. The silicon-based composite negative electrode material for lithium ion secondary batteries comprises: a core having a structure in which silicon nanoparticles are embedded in interior layer gaps of hollow graphite; and a shell including a non-graphite carbon material.

Description

  The present invention relates to the technical field of lithium ion secondary batteries. Specifically, the present invention relates to a silicon-based composite negative electrode material for a lithium ion secondary battery, a manufacturing method, and a battery.

  Lithium ion secondary batteries as energy storage devices have high operating voltage, long cycle life, no memory effect, small self-discharge, and eco-friendly advantages, so they are widely used in portable electronic products and electric vehicles. It has been. Conventionally, commercialized lithium ion secondary batteries mainly use a graphite negative electrode material, and its theoretical specific capacity is 372 mAh / g, but the specific capacity of the graphite negative electrode material developed by the conventional technology is Because it is close to the theoretical value, there is a limit to the possibility of development of graphite negative electrode materials. The development of miniaturization of various portable electronic devices and the high specific energy and high output density of lithium-ion secondary batteries of electric vehicles It is difficult to meet a wide range of demand.

  Since silicon materials have a relatively high lithium storage capacity (theoretical specific capacity 4200 mAh / g) and are abundant as resources, we will develop a new generation of high specific energy and high power density negative electrode materials for lithium ion secondary batteries. It is considered one of the ideal candidate materials. However, the practical use of silicon materials is limited to some extent because the battery capacity decays relatively quickly during use. Analysis shows that the volume expansion and contraction of lithium occlusion and release of silicon material is relatively large (> 300%), leading to material destruction and crushing, which is responsible for low material conductivity and relatively fast material capacity decay It is done. Therefore, suppression of the volume expansion of the silicon material and improvement of the stability of the material structure are important for improving the conductivity and cycle stability of the silicon material. At present, the volume expansion of silicon materials has been improved mainly by silicon nano-alloying, silicon-metal alloying, and silicon-active or inert material composites, of which silicon and active carbon composites Promising in a wide range of markets.

  Patent document CN1033326033A discloses a silicon carbon negative electrode material for a high-performance lithium ion secondary battery and a method for manufacturing the same, and the negative electrode material includes a Si-SiOx / C / DC composite system, and the composite system includes a C substrate, , Si-SiOx composite adhered in the C substrate, carbon nanotubes distributed in the C substrate and Si-SiOx-C, and the outermost organic pyrolytic carbon coating layer. The porous composite Si-SiOx produced according to the invention has large silicon particles and contains silicon oxide, thereby reducing its initial efficiency. The composite is manufactured by covering the surface with cracked carbon. However, in this method, the volume expansion of large-grain silicon is difficult to be suppressed and relatively poor cycle characteristics are caused.

  Patent document CN1030778092A discloses a method for producing a silicon carbon (Si / C) composite negative electrode material for a lithium ion secondary battery, and the invention relates to a silicon source (before or after etching treatment) and graphite as a second type additive. After the solvent is completely volatilized by controlling the temperature and the solvent is completely volatilized, a precursor solid is obtained and the precursor solid is subjected to amorphous carbon coating. Nanosilicon produced by etching according to the present invention has a large specific surface area and is difficult to disperse uniformly on the surface of graphite. Therefore, the silicon carbon material produced by this method has severe silicon agglomeration and causes silicon expansion. Which cannot be solved, leading to poor cycling properties of the material.

  Therefore, while manufacturing silicon with a small particle size and improving the dispersibility of the silicon particles, supplying a buffer to the silicon particles, the silicon negative electrode material relaxes the volume expansion and contraction when the lithium is occluded and released, Manufactures high performance silicon negative electrode materials. Achieving practical application of silicon-based negative electrode materials for lithium ion secondary batteries is a technical problem to be solved in this field.

Chinese Patent Application No. 1033226023 Chinese Patent Application Publication No. 1030778092

  An object of the present invention is to provide a silicon-based composite negative electrode material for a lithium ion secondary battery, a method for producing the same, and a battery including the negative electrode material. Good dispersibility, high press density and high initial Coulomb efficiency, and excellent cycle characteristics.

In order to achieve the object of the present invention, the following technical means are provided.
In a first aspect, the present invention provides a silicon-based composite negative electrode material for a lithium ion secondary battery, which has an embedded composite core-shell structure, in which nanosilicon particles are embedded in an inner layer gap of hollow graphite. The shell is a non-graphitic carbon material.

  In the silicon-based composite negative electrode material for a lithium ion secondary battery according to the present invention, the core nanosilicon particles are embedded in the inner space of the hollow graphite, and the dispersibility of the nanosilicon particles is good. It functions as a good buffer and effectively suppresses the volume expansion and contraction of the lithium occlusion / release of the silicon material.

  In the silicon-based composite negative electrode material for a lithium ion secondary battery according to the present invention, the inner layer gap of the hollow graphite may be a slit or a polygonal hole derived from the slit.

  The silicon-based composite negative electrode material for a lithium ion secondary battery preferably includes 1 to 50% (weight) of nanosilicon, 30 to 90% (weight) of graphite, and 5 to 40% (weight) of non-graphitic carbon material. . For example, nanosilicon may be 2% (weight), 5% (weight), 10% (weight), 20% (weight), 45% (weight), etc., and graphite is 35% (weight), 45%. % (Weight), 55% (weight), 70% (weight), 85% (weight), etc., and non-graphitic carbon material is 6% (weight), 10% (weight), 20% (weight) ), 30% (weight) or 35% (weight).

In a second aspect, the present invention provides a method for producing a silicon-based composite negative electrode material for a lithium ion secondary battery according to the first aspect,
(1) mechanically processing a graphite material to obtain hollow graphite;
(2) A step of mixing and drying nanosilicon, a dispersant and hollow graphite with an organic solvent to obtain a first precursor;
(3) performing a mechanical fusion process on the first precursor and then performing a carbon source coating process to obtain a second precursor;
(4) performing an isotropic pressure treatment on the second precursor to obtain a massive or columnar third precursor;
(5) high temperature sintering the third precursor to obtain the silicon-based composite negative electrode material.

  In the method according to the present invention, hollow graphite is obtained by mechanically processing a graphite material, the inner layer of the hollow graphite includes a gap, and provides a space for uniform and good dispersion of the nanosilicon particles therein. In the mechanical fusion process, nanosilicon particles and hollow graphite particles are constantly subjected to the action of pushing force and shearing force, so that the nanosilicon particles inside hollow graphite are arranged more orderly, and further, silicon and graphite sheet And by applying isotropic compressive stress to the second precursor powder in the isotropic pressure treatment process, the inner sheet of the hollow graphite particles extends along different axial directions. The nanosilicon particles embedded between the hollow graphite sheets are secondarily dispersed, and the soft organic carbon source powder expands on the surface of the hollow graphite particles by the action of isotropic compressive stress. , And a part of the organic carbon source powder is pressed into the inner layer of the hollow graphite, by greatly improve the adhesion of graphite sheet each other to obtain particles of high press density.

  In the present invention, preferably, after the step (5), the composite negative electrode material obtained in the step (5) is crushed, pulverized, sieved and demagnetized, and the median particle size is 5.0 to 45.0 μm. Preferably, the method includes a step (6) of obtaining a silicon-based composite negative electrode material of 10.0 to 35.0 μm, more preferably 13.0 to 25.0 μm.

  In the present invention, the mechanical processing in the step (1) is preferably performed by pulverizing, demagnetizing, and sieving the graphite material to obtain graphite particles having a median particle size of 5.0 to 25.0 μm, And performing mechanical polishing to obtain hollow graphite having a median particle size of 1.0 to 10.0 μm.

  The graphite material is preferably one or a combination of at least two of natural crystalline graphite, natural hidden crystalline graphite, natural crystalline veined graphite, artificial graphite and conductive graphite. As the above combinations, a combination of natural crystalline graphite and natural microcrystalline graphite, a combination of natural crystalline graphite and natural crystalline vein graphite, a combination of natural crystalline graphite and natural crystalline vein graphite, a natural crystalline vein A combination of graphite and artificial graphite, and a combination of artificial graphite and conductive graphite are given as typical examples, but are not limited thereto.

  The shape of the graphite material is preferably one or a combination of at least two of flaky, substantially spherical and spherical. The shape of the graphite material is not particularly limited.

  The pulverization is preferably one or a combination of at least two of ball mill pulverization, mechanical pulverization, jet mill pulverization, high-pressure fine pulverization, and rotary high-speed pulverization. Can do.

  The mechanical polishing is preferably dry polishing or wet polishing, more preferably wet polishing, and the wet polishing uses any of a high-speed stirring mill, a ball mill, a tube mill, a colloid mill, a rod mill, and a sand mill.

  The mechanical polishing medium is preferably copper, zinc, silver, tin, vanadium, chromium, tungsten, copper alloy, aluminum alloy, zinc alloy, iron carbon alloy, magnesium alloy, lithium alloy, boron oxide, silicon oxide, oxidation Zirconium, alumina, calcium carbonate, magnesium oxide, titanium dioxide, zinc oxide, tin oxide, ferric trioxide, ferric tetroxide, tungsten carbide, titanium carbide, titanium nitride, silicon carbide, silicon nitride, titanium carbonitride and carbonitride One or a combination of at least two of tungsten.

  The size of the mechanical polishing medium is preferably 0.01 to 10 mm, more preferably 0.03 to 8.0 mm, and particularly preferably 0.05 to 5.0 mm.

  The solvent used for the wet polishing is preferably water and / or an organic solvent, and the organic solvent is one or a combination of at least two of tetrahydrofuran, amide, alcohol and ketone, more preferably tetrahydrofuran, One or a combination of at least two of dimethylacetamide, C1-C6 alcohol and C3-C8 ketone, wherein the C1-C6 alcohol is methanol, ethanol, ethylene glycol, propanol, isopropanol, 1,2-propanediol, One or at least two of 1,3-propanediol, glycerol, n-butanol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, n-pentanol and 2-hexanol A combination of species, the C The -C8 ketone is one or a combination of at least two of acetone, methyl ethyl ketone, methyl propyl ketone, N-methyl pyrrolidone, ethyl propyl ketone, methyl butyl ketone, ethyl n-butyl ketone, methyl amyl ketone and methyl hexyl ketone. .

  In the mechanical polishing process, the graphite particles and the polishing medium collide or rub against each other, the graphite particles are constantly subjected to the action of impact force and shear force, and this action force is greater than the adhesion force between the sheets in the graphite. As a result, the graphite sheet is displaced to form a gap to form hollow graphite.

  In the present invention, the nanosilicon in the step (2) is preferably obtained by mechanically processing a silicon raw material.

  The mechanical processing is preferably performed by pulverizing, demagnetizing, and sieving a silicon raw material to obtain silicon particles having a median particle size of 5.0 to 40.0 μm, and then performing mechanical polishing to obtain a median particle size. Includes obtaining nano-silicon having a thickness of 10 to 500 nm.

  The pulverization is preferably one or a combination of at least two of ball mill pulverization, mechanical pulverization, jet mill pulverization, high-pressure fine pulverization, and rotary high-speed pulverization. Can do.

  The mechanical polishing is preferably dry polishing or wet polishing, and more preferably wet polishing.

  The mechanical polishing is preferably performed using any one of a high speed stirring mill, a ball mill, a tube mill, a colloid mill, a rod mill, and a sand mill.

  The sand mill polishing medium is preferably copper, zinc, silver, tin, vanadium, chromium, tungsten, copper alloy, aluminum alloy, zinc alloy, iron-carbon alloy, magnesium alloy, lithium alloy, boron oxide, silicon oxide, oxidation Zirconium, alumina, calcium carbonate, magnesium oxide, titanium dioxide, zinc oxide, tin oxide, ferric trioxide, ferric tetroxide, tungsten carbide, titanium carbide, titanium nitride, silicon carbide, silicon nitride, titanium carbonitride and carbonitride One or a combination of at least two of tungsten.

  The size of the mechanical polishing medium is preferably 0.01 to 1.00 mm, more preferably 0.02 to 0.80 mm, and particularly preferably 0.03 to 0.50 mm.

  The solvent used in the wet polishing is preferably an organic solvent, and the organic solvent is one or a combination of at least two of tetrahydrofuran, amide, alcohol and ketone, more preferably tetrahydrofuran, dimethylacetamide, C1. One or a combination of at least two of -C6 alcohol and C3-C8 ketone, wherein the C1-C6 alcohol is methanol, ethanol, ethylene glycol, propanol, isopropanol, 1,2-propanediol, 1,3- One or a combination of at least two of propanediol, glycerol, n-butanol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, n-pentanol and 2-hexanol Yes, the C3-C8 keto Acetone, methyl ethyl ketone, methyl propyl ketone, N- methylpyrrolidone, ethyl propyl ketone, is one or at least two combinations of the methyl ketone, ethyl n- butyl ketone, methyl amyl ketone and methyl hexyl ketone.

  In the present invention, the mixing and drying treatment in the step (2) is preferably performed by adding nanosilicon and a dispersing agent to an organic solvent, ultrasonically stirring for 0.1 to 1 hour, and uniformly dispersing the nanosilicon suspension. Forming, further adding hollow graphite to the suspension, stirring at a rotational speed of 600-3000 rpm for 1-5 hours, and drying to obtain a first precursor.

  The dispersant is preferably sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphate, triethylhexyl phosphate, sodium dodecyl sulfate, methylpentanol, cellulose derivatives, polyacrylamide, guar gum, fatty acid polyethylene glycol ester, hexadecyltrimethyl bromide One or a combination of at least two of ammonium, polyethylene glycol p-isooctyl phenyl ether, polyacrylic acid, polyvinyl pyrrolidone, polyoxyethylene sorbitan monooleate, p-ethylbenzoic acid and polyetherimide.

  The drying is preferably performed using a spray dryer, a suction filter, a rotary evaporator or a freeze dryer.

  The inlet temperature of the spray dryer is more preferably 100 to 400 ° C, still more preferably 110 to 300 ° C, and particularly preferably 120 to 250 ° C. The outlet temperature of the spray dryer is more preferably 20 to 250 ° C, still more preferably 35 to 200 ° C, and particularly preferably 50 to 120 ° C. The pressure of the spray dryer is more preferably 5 to 150 MPa, still more preferably 7 to 120 MPa, and particularly preferably 10 to 100 MPa. The feed frequency of the spray dryer is more preferably 2 to 200 Hz, further preferably 5 to 160 Hz, and particularly preferably 10 to 100 Hz.

  The mass ratio of the nanosilicon, the dispersant, the hollow graphite, and the organic solvent is preferably (1-50) :( 0.5-10) :( 30-90) :( 90-800).

  In the present invention, the mechanical fusion treatment in the step (3) is preferably performed by putting the first precursor into the fusion machine, adjusting the rotation speed to 500 to 3000 rpm, and the blade clearance width to 0.01 to 1 cm, and at least 0. Fusing for 25 hours to obtain a fusion precursor material.

  The rotation speed of the fusion machine is preferably 800 to 2000 rpm, for example 900 rpm, 1100 rpm, 1300 rpm, 1600 rpm or 1800 rpm.

  The blade clearance width is preferably 0.1 to 0.3 cm, for example, 0.12 cm, 0.15 cm, 0.18 cm, 0.21 cm, 0.25 cm, or 0.28 cm.

The fusion time is preferably 0.25 to 8.0 hours, such as 0.3 hours, 0.5 hours, 1 hour, 3 hours, 5 hours or 7 hours, particularly preferably 0.5 to 4. hours. 0 hours.
In the mechanical fusion treatment process, the nanosilicon particles and the hollow graphite particles are constantly subjected to the action of the pushing force and the shearing force, so that the nanosilicon particles inside the hollow graphite are arranged more orderly, and the silicon and the graphite sheet The bonding force between the two can be improved.

  In the present invention, the carbon source coating treatment in the step (3) is preferably carried out by subjecting the fusion precursor material and the organic carbon source to solid phase coating or liquid phase coating treatment, more preferably solid phase coating treatment. Obtaining two precursors.

  The solid phase coating process preferably includes placing the fusion precursor material and the organic carbon source in a VC mixer and coating process for at least 0.5 hours to obtain a second precursor.

  The organic carbon source is preferably in a powder form, and has a median particle size of 0.5 to 25.0 μm, such as 1 μm, 5 μm, 10 μm, 15 μm, 18 μm, or 23 μm, and particularly preferably 1.0 to 8. 0 μm.

  The mass ratio of the fusion precursor material to the organic carbon source is preferably 1: 1 to 10: 1, such as 2: 1, 5: 1, 7: 1 or 9: 1, particularly preferably 2: 1. 6: 1.

  The organic carbon source is preferably coal pitch, petroleum pitch, mesophase pitch, coal tar, petroleum industry heavy oil, heavy aromatic hydrocarbon, epoxy resin, phenol resin, furfural resin, urea resin, polyvinyl alcohol, poly One or a combination of at least two of vinyl chloride, polyethylene glycol, polyethylene oxide, polyvinylidene fluoride, acrylic resin and polyacrylonitrile.

  In the present invention, the isotropic pressure treatment in the step (4) is preferably performed under pressure of 1000 to 20000 KN and a pressure treatment temperature of 20 to 300 ° C. for 0.05 to 4 hours. And obtaining a third precursor.

  The pressure treatment is preferably one or a combination of at least two of an extrusion molding process, a cold pressure process, a hot pressure process and an isotropic pressure process, that is, any one of the above Can be pressurized.

  The pressure is preferably 5000 to 10000 KN, for example 6000 KN, 8000 KN, 9000 KN or 9500 KN.

  The temperature of the pressure treatment is preferably 30 to 200 ° C., for example, 50 ° C., 70 ° C., 90 ° C., 120 ° C., 150 ° C., 180 ° C. or 190 ° C.

  The pressure treatment time is preferably 0.1 to 2 hours, for example, 0.2 hours, 0.5 hours, 0.7, 1.2 hours, or 1.8 hours.

  By applying isotropic compressive stress to the second precursor powder in the isotropic pressure treatment process, the inner sheet of graphite particles extends in different axial directions, and the nanosilicon particles embedded between the graphite sheets Is dispersed by the second, and by the action of isotropic compressive stress, the soft organic carbon source powder expands on the surface of the graphite particles, and a part of the organic carbon source powder is pressed into the inner layer of the graphite, and the graphite sheet Particles with high press density are obtained by greatly improving the adhesion between them.

  In the present invention, the high-temperature sintering in the step (5) is preferably performed in a protective gas atmosphere.

  The protective gas is preferably nitrogen gas, helium gas, neon gas, argon gas, krypton gas, xenon gas and hydrogen gas, and particularly preferably nitrogen gas, helium gas, argon One or a combination of at least two of gas and hydrogen gas.

  The flow rate of the protective gas is preferably 0.5 to 10.0 L / min, more preferably 0.5 to 5.0 L / min, and particularly preferably 1.0 to 4.0 L / min. .

  The heating rate during the sintering is preferably 20.0 ° C./min or less, more preferably 1.0 to 15.0 ° C./min, and particularly preferably 2.0 to 10.0 ° C./min. Minutes.

  The sintering temperature is preferably 500 to 1150 ° C, more preferably 600 to 1050 ° C, and particularly preferably 800 to 1000 ° C.

  The sintering time is preferably at least 0.5 hours, more preferably 0.5 to 20.0 hours, and particularly preferably 1.0 to 10.0 hours.

  Preferably, in the step (5), after the high-temperature sintering is completed, it is naturally cooled to room temperature.

  In a third aspect, the present invention provides a silicon-based composite negative electrode material for a lithium ion secondary battery produced by the method described in the second aspect.

  The median particle size of the silicon composite negative electrode material is preferably 5.0 to 45.0 μm, more preferably 10.0 to 35.0 μm, and particularly preferably 13.0 to 25.0 μm.

The specific surface area of the silicon-based composite negative electrode material is preferably 1.0~20.0m ² / g, particularly preferably 2.0 to 10.0 m ² / g.

The powder press density of the silicon-based composite negative electrode material is preferably 1.0 to 2.0 g / cm ³ , particularly preferably 1.3 to 1.8 g / cm ³ .

  The median particle size of the nanosilicon particles is preferably 10 to 500 nm, more preferably 10 to 400 nm, and particularly preferably 10 to 300 nm.

  4th aspect WHEREIN: This invention provides a lithium ion secondary battery provided with a battery positive electrode, a battery negative electrode, and electrolyte solution, The said battery negative electrode contains a negative electrode active material, a electrically conductive agent, an adhesive agent, and a solvent, The said negative electrode The active material is the silicon-based composite negative electrode material for a lithium ion secondary battery according to the first aspect or the third aspect.

  The conductive agent is preferably graphite powder and / or nano conductive liquid.

  The nano conductive liquid is preferably composed of 0.5-20% (by weight) of a nano carbon material and a dispersion solvent.

  More preferably, the nanocarbon material is at least one of graphene, carbon nanotube, nanocarbon fiber, fullerene, carbon black, and acetylene black, and the number of graphite layers of the graphene is 1-100, The diameter of the nanocarbon fiber is 0.2 to 500 nm, and the particle sizes of fullerene, carbon black, and acetylene black are 1 to 200 nm.

  The dispersion solvent is more preferably water, methanol, ethanol, propanol, isopropanol, acetone, cyclohexanone, dichloromethane, chloroform, cyclohexane, benzene, toluene, xylene, ethylbenzene, aniline, tetrahydrofuran, dimethyl sulfoxide, N-methylpyrrolidone, N- N dimethylformamide, NN dimethylacetamide, pyridine, pyrrole, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium dicyanamide, 1-butyl-3-methylimidazolium hexa Fluorophosphate, 1-butyl-3-methylimidazolium bistrifluoromethanesulfonylimide, 1-butyl-3-methylimidazolium trifluoromethanes Honato and 1-ethyl-3 is one or at least two combinations of methylimidazolium acetate.

  The adhesive is preferably one or a combination of at least two of polyimide resin, acrylic resin, polyvinylidene difluoride, polyvinyl alcohol, sodium carboxymethyl cellulose, and styrene butadiene rubber.

  The solvent is preferably one or a combination of at least two of N-methylpyrrolidone, dimethylformamide, acetone and methyl ethyl ketone.

  Regarding the beneficial effects of the present invention, the silicon-based composite negative electrode material according to the present invention is a nano-silicon by combining mechanical polishing, mechanical fusion, isotropic pressure treatment and carbon coating technology compared to the conventional technology. Realizing that the particles are embedded in the inner layer of graphite, achieving a uniform coating on the surface of the graphite particles, obtaining a high-performance silicon-based material, and nano-silicon particles are uniformly dispersed inside the graphite particles as the buffer substrate This embedded composite core structure fundamentally mitigates the expansion of the silicon particles, greatly improves the conductivity of the material and avoids direct contact between the silicon particles and the electrolyte, thereby enabling the cycle characteristics of the material. (The capacity retention rate of 300 cycles is 90% or more) and the initial efficiency (> 90%) is greatly improved, and the silicon composite negative electrode material according to the present invention has a specific energy and press density. Can be high, meet the needs of the lithium ion secondary battery having a high output density. The negative electrode material has a simple manufacturing process, a low raw material cost, and is eco-friendly and non-polluting.

FIG. 1 is a scanning electron microscope (SEM) image of the silicon-based composite negative electrode material produced in Example 1 of the present invention. FIG. 2 is a cross-sectional scanning electron microscope (SEM) image of the silicon-based composite negative electrode material produced in Example 1 of the present invention, in which nanosilicon particles are embedded between graphite layers to form a composite core, In addition, it can be seen that the dispersibility of the nanosilicon particles is relatively good and that the outer layer of the composite core has one uniform cracked carbon coating layer. FIG. 3 is an XRD diagram of the silicon composite negative electrode material produced in Example 1 of the present invention. In the figure, relatively strong diffraction peaks of graphite and silicon are observed. FIG. 4 is a cycle characteristic curve of the silicon composite negative electrode material produced in Example 1 of the present invention. As can be seen from the figure, the material has excellent cycle characteristics and a 300 cycle capacity retention rate of 90.1. %.

  Hereinafter, embodiments of the present invention will be described in detail with reference to examples. Those skilled in the art should understand that the following examples are preferred examples of the present invention, and are not intended to limit the scope of the present invention, for further understanding of the present invention. Those skilled in the art may make various changes and modifications to the present invention, and all modifications, equivalent substitutions, improvements, etc. implemented without departing from the spirit and principle of the present invention are protected by the present invention. Should belong to a range.

Example 1
Spherical natural graphite is mechanically pulverized into graphite particles having a median particle size of 5.0 to 15.0 μm, placed in a ball mill containing 4 mm silicon nitride beads and a propanol solvent, and pulverized by ball milling. Obtain hollow graphite of 1.0 to 10.0 μm, jet mill pulverize the silicon raw material to obtain silicon particles having a median particle size of 5.0 to 30.0 μm, and then add it to 0.01 mm tungsten carbide beads And polishing in a sand mill containing methanol solvent to obtain nanosilicon powder having a median particle size of 10 to 300 nm, and adding the prepared nanosilicon powder and fatty acid polyethylene glycol ester to methanol at a mass ratio of 15: 0.5. , Ultrasonically stirred for 0.5 hours to obtain a uniformly dispersed nanosilicon suspension, and hollow graphite (mass ratio of nanosilicon: hollow graphite is 15:50) Is added to the suspension, stirred for 2 hours at a stirring rotational speed of 2000 rpm, dried to obtain the first precursor, and the first precursor is put into the fusion machine and fused for 1 hour. A material is obtained, and the manufactured fusion precursor material and pitch powder having a median particle size of 0.8 to 4.0 μm are placed in a VC mixer at a mass ratio of 5: 1, mixed and coated for 0.5 hours, Obtain a precursor, put the second precursor in a cold press, apply an isotropic pressure of 10000 KN, hold the pressure for 0.5 hours, get a third precursor, put the third precursor in a tunnel kiln, In a protective atmosphere of argon gas at a flow rate of 1.0 L / min, the temperature was raised to 1150.0 ° C. at a rate of 15.0 ° C./min, kept constant for 8 hours, naturally cooled to room temperature, Crushing, crushing, sieving with 325 mesh, silicon composite negative electrode with a median particle size of 10.0-20.0 μm It was obtained.

Example 2
The flake natural graphite is mechanically pulverized into graphite particles having a median particle size of 10.0 to 25.0 μm, and then put into a ball mill containing 0.01 mm silicon nitride beads and an ethylene glycol solvent. Hollow graphite having a particle size of 1.0-10.0 μm is obtained, silicon raw material is mechanically pulverized to obtain silicon particles having a median particle size of 5.0-40.0 μm, and then 0.02 mm Polishing by putting in a sand mill containing zirconium oxide beads and ethylene glycol solvent to obtain nanosilicon powder having a median particle size of 10 to 400 nm. The prepared nanosilicon powder and polyetherimide are converted into ethylene glycol at a mass ratio of 50: 1. Added, ultrasonically stirred for 1 hour to form a uniformly dispersed nanosilicon suspension, and hollow graphite (mass ratio of nanosilicon: hollow graphite is 50:30) Is added to the suspension, stirred for 5 hours at a stirring rotational speed of 3000 rpm, dried to obtain a first precursor, and the first precursor is put into a fusion machine, fused for 4 hours, and fused precursor. A material is obtained, and the prepared fusion precursor material and a phenol resin powder having a median particle size of 10.0 to 25.0 μm are put into a VC high-speed mixer at a mass ratio of 1: 1 and mixed and coated for 1 hour. A precursor is obtained, the second precursor is put into a hot press, an isotropic pressure of 20000 KN is applied, the temperature is 90 ° C., the pressure is maintained for 0.05 hours, and a third precursor is obtained. The precursor is put into a tunnel kiln, heated to 1000.0 ° C. at a temperature rising rate of 5.0 ° C./min in a nitrogen gas protective atmosphere with a flow rate of 10.0 L / min, and kept at a constant temperature for 20 hours. Cool naturally, then crush, pulverize, sieve through 325 mesh, median particle size is 5.0 ~ A 15.0 μm silicon composite negative electrode material was obtained.

Example 3
Spherical artificial graphite is finely pulverized into graphite particles having a median particle size of 5.0 to 10.0 μm under high pressure, put into a ball mill containing 10 mm silicon nitride beads and an acetone solvent, and pulverized by ball milling to obtain a median particle size of 1. 0.0-10.0 μm hollow graphite is obtained, and the silicon raw material is jet milled to obtain silicon particles having a median particle size of 5.0-20.0 μm, which are then divided into 1 mm silicon carbide beads and N- It is put into a sand mill containing a methylpyrrolidone solvent and polished to obtain a nanosilicon powder having a median particle size of 50 to 500 nm, and the prepared nanosilicon powder and polyacrylic acid are added to ethanol at a mass ratio of 1:10. Ultrasonic agitation for 1 hour to form a uniformly dispersed nanosilicon suspension, and hollow graphite (nanosilicon: hollow graphite mass ratio is 1:90) is added to the suspension. Stir at an agitation rotational speed of rpm for 1 hour, dry to obtain the first precursor, put the first precursor into the fusion machine, fuse for 0.25 hour to obtain the fusion precursor material, the fusion produced above The precursor material and mesophase pitch powder having a median particle size of 0.5 to 25.0 μm are put into a VC high-speed mixer at a mass ratio of 10: 1 and mixed and coated for 0.5 hours to obtain a second precursor, Put the second precursor in a hot press, apply an isotropic pressure of 1000 KN, the temperature is 300 ° C., hold the pressure for 4 hours, obtain a third precursor, put the third precursor in a tunnel kiln, In a protective atmosphere of nitrogen gas at a flow rate of 0.5 L / min, the temperature is raised to 1150.0 ° C. at a rate of temperature increase of 20.0 ° C./min, kept constant for 15 hours, naturally cooled to room temperature, Crushed, ground and sieved with 325 mesh, silicon with a median particle size of 20.0-45.0 μm To obtain a composite negative electrode material.

Example 4
The bulk conductive graphite is jet milled into graphite particles having a median particle size of 10.0 to 15.0 μm, put into a ball mill containing 3 mm silicon nitride beads and an ethanol solvent, and ball milled to obtain a median particle size. Obtain hollow graphite of 1.0 to 10.0 μm, mechanically pulverize the silicon raw material to obtain silicon particles having a median particle size of 5.0 to 25.0 μm, and then add it to 0.05 mm silicon carbonitride It is put into a sand mill containing beads and an ethanol solvent and polished to obtain a nanosilicon powder having a median particle size of 10 to 200 nm. The prepared nanosilicon powder and polyvinylpyrrolidone are added to ethanol at a mass ratio of 30: 5. Ultrasonic stirring for 5 hours to form a uniformly dispersed nanosilicon suspension and adding hollow graphite (nanosilicon: hollow graphite mass ratio is 30:60) to the suspension , Stirred for 3 hours at a stirring rotational speed of 2000 rpm, dried to obtain a first precursor, put the first precursor into a fusion machine, fused for 2 hours to obtain a fusion precursor material, and the manufactured fusion precursor The body material and citric acid powder having a median particle size of 1.0-10.0 μm were put into a VC high speed mixer at a mass ratio of 5: 1, mixed and coated for 1.5 hours to obtain a second precursor, Put the precursor in a cold press, apply an isotropic pressure of 15000 KN, the temperature is 30 ° C., hold the pressure for 0.5 hours to obtain a third precursor, put the third precursor in a tunnel kiln, In a protective atmosphere of nitrogen gas at a flow rate of 3 L / min, the temperature was raised to 500.0 ° C. at a rate of temperature increase of 6.0 ° C./min, kept constant for 5 hours, naturally cooled to room temperature, then crushed, A silicon composite negative electrode material having a median particle size of 10.0 to 25.0 μm by pulverizing and sieving with 325 mesh It was.

Example 5
Scale-like natural graphite is pulverized at high speed by rotation into graphite particles having a median particle size of 5.0-10.0 μm, put into a ball mill containing 0.4 mm zirconium oxide beads and water, and pulverized by ball mill. Hollow graphite having a diameter of 1.0 to 10.0 μm is obtained, and silicon raw material is mechanically pulverized to obtain silicon particles having a median particle diameter of 5.0 to 25.0 μm. Polishing by putting in a sand mill containing silicon nitride beads and ethanol solvent to obtain nanosilicon powder having a median particle diameter of 10 to 200 nm, ethanol produced at a mass ratio of 10: 1 with the prepared nanosilicon powder and hexadecyltrimethylammonium bromide And stirred with ultrasonic waves for 0.5 hour to form a uniformly dispersed nanosilicon suspension, and hollow graphite (the mass ratio of nanosilicon: hollow graphite is 10:60). Add to the turbid liquid, stir at 2500 rpm stirring speed for 2 hours, dry to obtain the first precursor, put the first precursor into the fusion machine and fuse for 1.5 hours to obtain the fusion precursor material The prepared fusion precursor material and polyvinyl alcohol powder having a median particle size of 1.0 to 5.0 μm are placed in a VC high speed mixer at a mass ratio of 2: 1 and mixed and coated for 2 hours to obtain a second precursor. The second precursor is put into a cold press, isotropic pressure of 9000 KN is applied, the temperature is 20 ° C., the pressure is kept for 1 hour, the third precursor is obtained, and the third precursor is tunnel kiln In a protective atmosphere of nitrogen gas at a flow rate of 5 L / min, the temperature is raised to 800.0 ° C. at a rate of temperature increase of 12.0 ° C./min, kept constant for 5 hours, naturally cooled to room temperature, Crushing, crushing, sieving with 325 mesh, and a median particle size of 10.0-25.0 μm To obtain a down-based composite negative electrode material.

Comparative Example 1
A silicon-based negative electrode material was produced in substantially the same manner as in Example 1 except that the spherical natural graphite was not crushed and ball milled, and a battery was produced in the same manner as in Example 1.

Comparative Example 2
A silicon-based negative electrode material was produced in substantially the same manner as in Example 2 except that the isotropic hot pressing treatment was not performed on the precursor II, and a battery was produced in the same manner as in Example 2.

The negative electrode materials of Examples 1 to 5 and Comparative Examples 1 and 2 were tested by the following method.
The powder press density according to the present invention was actually tested using a CARVER powder press. Powder press density = mass of test sample / volume of test sample, pole piece press density = (negative electrode pole piece mass−copper foil mass) / (Pole piece area × Thickness after pole piece compaction).

  The specific surface area of the material was tested using a Tristar 3000 fully automatic specific surface area and porosity analyzer from Micromeritics Instrument, USA.

  The material particle size range and the average particle size of the raw material particles were tested using a Malvern laser particle size analyzer MS 2000.

  The material structure was tested using an X-ray diffractometer X'Pert Pro, PANalytical.

  The surface morphology of the sample and the size of the particles were observed with an S4800 scanning electron microscope from Hitachi, Ltd.

The electrochemical cycle characteristics were tested by the following method, and the negative electrode material, the conductive agent and the adhesive were dissolved and mixed in a solvent at a mass ratio of 94: 1: 5, and the solid content was controlled to 50%. A negative electrode piece is obtained by applying to an electric body and vacuum-drying, and then producing a ternary positive electrode piece manufactured by a conventional mature process, 1 mol / L LiPF ₆ / EC + DMC + EMC (v / v = 1: 1: 1) The electrolyte, Celgard 2400 separator, and case were assembled into 18650 cylindrical cells by a normal production process. Cylindrical battery charge / discharge test is performed by LAND battery test system of Wuhan Jinyi Electronics Co., Ltd., charge / discharge with constant current of 0.2C under normal temperature condition, and charge / discharge voltage to 2.75 ~ 4.2V Restricted.

  Table 1 shows the electrochemical measurement results of the negative electrode materials produced in Examples 1 to 5 and Comparative Examples 1 and 2.

  Table 1 Electrochemical measurement results of negative electrode material

As can be seen from the above table, the comparative example has a low discharge capacity and initial charge / discharge efficiency, the initial efficiency is only 85.5%, and the capacity retention rate after 300 cycles is as low as 75%. In contrast, the silicon-based composite negative electrode material produced by the method according to the present application has a low specific surface area (2.0 to 4.0 m ² / g) and a high press density (1.6 to 1.8 g / g). cm ³ ), the discharge capacity exceeded 400 mAh / g, the initial coulombic efficiency exceeded 90.0%, and the 300 cycle capacity retention rate was 90% or more.

  The applicant has described specific features and specific methods of the present invention with the above embodiments, but the present invention is not limited to the specific features and specific methods described above. It is stated that the present invention is not meant to be implemented by the specific features and methods set forth above. Those skilled in the art will understand that all modifications to the present invention, equivalent substitution of components to be selected and addition of auxiliary components, selection of specific methods, etc. are all within the protection scope and disclosure scope of the present invention. Should.

Claims (10)

  A silicon-based composite negative electrode material for a lithium ion secondary battery having an embedded composite core-shell structure, wherein the core has a structure in which nanosilicon particles are embedded in an inner layer gap of hollow graphite, and the shell is non-graphite A silicon-based composite negative electrode material for a lithium ion secondary battery, which is a carbon material.   The gap is a slit or a polygonal hole derived from the slit, and the silicon-based composite negative electrode material for a lithium ion secondary battery is preferably nanosilicon 1-50% (weight), graphite 30-90% (weight) ) And a non-graphitic carbon material in an amount of 5 to 40% (by weight). The silicon-based composite negative electrode material for a lithium ion secondary battery according to claim 1. A method for producing a silicon-based composite negative electrode material for a lithium ion secondary battery according to claim 1 or 2,
(1) mechanically processing a graphite material to obtain hollow graphite;
(2) A step of mixing and drying nanosilicon, a dispersant and hollow graphite with an organic solvent to obtain a first precursor;
(3) performing a mechanical fusion process on the first precursor and then performing a carbon source coating process to obtain a second precursor;
(4) performing an isotropic pressure treatment on the second precursor to obtain a massive or columnar third precursor;
(5) a step of high-temperature sintering the third precursor to obtain the silicon-based composite negative electrode material;
Including a method.   After the step (5), the composite negative electrode material obtained in the step (5) is crushed, pulverized and sieved to demagnetize, and the median particle size is 5.0 to 45.0 μm, preferably 10 The method according to claim 3, wherein a step of obtaining a silicon composite negative electrode material having a thickness of 0.0 to 35.0 μm, more preferably 13.0 to 25.0 μm is performed. The mechanical processing of the step (1) pulverizes, demagnetizes and sieves the graphite material to obtain graphite particles having a median particle size of 5.0 to 25.0 μm, and then performs mechanical polishing. Obtaining hollow graphite having a median particle size of 1.0-10.0 μm,
The graphite material is preferably one or a combination of at least two of natural crystalline graphite, natural microcrystalline graphite, natural crystalline vein graphite, artificial graphite and conductive graphite,
The shape of the graphite material is preferably one or a combination of at least two of flaky, substantially spherical and spherical,
Said grinding is preferably one or a combination of at least two of ball milling, mechanical grinding, jet milling, high pressure fine grinding and rotary high speed grinding,
The mechanical polishing is preferably dry polishing or wet polishing, more preferably wet polishing,
The wet polishing is more preferably performed using any one of a high-speed stirring mill, a ball mill, a tube mill, a colloid mill, a rod mill, and a sand mill.
The mechanical polishing medium is preferably copper, zinc, silver, tin, vanadium, chromium, tungsten, copper alloy, aluminum alloy, zinc alloy, iron-carbon alloy, magnesium alloy, lithium alloy, boron oxide, silicon oxide, oxidation Zirconium, alumina, calcium carbonate, magnesium oxide, titanium dioxide, zinc oxide, tin oxide, ferric trioxide, ferric tetroxide, tungsten carbide, titanium carbide, titanium nitride, silicon carbide, silicon nitride, titanium carbonitride and carbonitride One or a combination of at least two of tungsten;
The size of the mechanical polishing medium is preferably 0.01 to 10 mm, more preferably 0.03 to 8.0 mm, and particularly preferably 0.05 to 5.0 mm.
The solvent used for the wet polishing is preferably water and / or an organic solvent,
More preferably, the organic solvent is one or a combination of at least two of tetrahydrofuran, amide, alcohol and ketone, and more preferably one of tetrahydrofuran, dimethylacetamide, C1-C6 alcohol and C3-C8 ketone. Or a combination of at least two, and the C1-C6 alcohol is methanol, ethanol, ethylene glycol, propanol, isopropanol, 1,2-propanediol, 1,3-propanediol, glycerol, n-butanol, 1,2 -Butanediol, 1,3-butanediol, 1,4-butanediol, n-pentanol, and a combination of at least two of 2-hexanol, and the C3-C8 ketone is acetone, methyl ethyl ketone, Methylp 5. A combination of one or at least two of pyrrole ketone, N-methyl pyrrolidone, ethyl propyl ketone, methyl butyl ketone, ethyl n-butyl ketone, methyl amyl ketone and methyl hexyl ketone. The method described in 1. The nanosilicon of the step (2) is obtained by mechanically processing a silicon raw material,
The mechanical processing is preferably performed by grinding, demagnetizing, and sieving the silicon raw material to obtain silicon particles having a median particle size of 5.0 to 40.0 μm, followed by mechanical polishing. Obtaining nanosilicon that is 10 to 500 nm,
Said grinding is preferably one or a combination of at least two of ball milling, mechanical grinding, jet milling, high pressure fine grinding and rotary high speed grinding,
The mechanical polishing is preferably dry polishing or wet polishing, more preferably wet polishing,
The mechanical polishing is preferably performed using any one of a high speed stirring mill, a ball mill, a tube mill, a colloid mill, a rod mill and a sand mill.
The sand mill polishing medium is preferably copper, zinc, silver, tin, vanadium, chromium, tungsten, copper alloy, aluminum alloy, zinc alloy, iron-carbon alloy, magnesium alloy, lithium alloy, boron oxide, silicon oxide, oxidation Zirconium, alumina, calcium carbonate, magnesium oxide, titanium dioxide, zinc oxide, tin oxide, ferric trioxide, ferric tetroxide, tungsten carbide, titanium carbide, titanium nitride, silicon carbide, silicon nitride, titanium carbonitride and carbonitride One or a combination of at least two of tungsten;
The size of the mechanical polishing medium is preferably 0.01 to 1.00 mm, more preferably 0.02 to 0.80 mm, and particularly preferably 0.03 to 0.50 mm.
The solvent used for the wet polishing is preferably an organic solvent,
More preferably, the organic solvent is one or a combination of at least two of tetrahydrofuran, amide, alcohol and ketone, and more preferably one of tetrahydrofuran, dimethylacetamide, C1-C6 alcohol and C3-C8 ketone. Or a combination of at least two, and the C1-C6 alcohol is methanol, ethanol, ethylene glycol, propanol, isopropanol, 1,2-propanediol, 1,3-propanediol, glycerol, n-butanol, 1,2 -Butanediol, 1,3-butanediol, 1,4-butanediol, n-pentanol, and a combination of at least two of 2-hexanol, and the C3-C8 ketone is acetone, methyl ethyl ketone, Methylp Piruketon, N- methylpyrrolidone, ethyl propyl ketone, is one or at least two combinations of the methyl ketone, ethyl n- butyl ketone, methyl amyl ketone and methyl hexyl ketone,
The mixing and drying treatment in the step (2) is preferably performed by adding nanosilicon and a dispersant to an organic solvent, and ultrasonically stirring for 0.1 to 1 hour to form a uniformly dispersed nanosilicon suspension, Adding hollow graphite to the suspension, stirring at a rotational speed of 600-3000 rpm for 1-5 hours, and drying to obtain a first precursor;
The dispersant is preferably sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphate, triethylhexyl phosphate, sodium dodecyl sulfate, methylpentanol, cellulose derivatives, polyacrylamide, guar gum, fatty acid polyethylene glycol ester, hexadecyltrimethyl bromide One or a combination of at least two of ammonium, polyethylene glycol p-isooctyl phenyl ether, polyacrylic acid, polyvinyl pyrrolidone, polyoxyethylene sorbitan monooleate, p-ethylbenzoic acid and polyetherimide,
The drying is preferably performed using a spray dryer, a suction filter, a rotary evaporator or a freeze dryer,
The inlet temperature of the spray dryer is more preferably 100 to 400 ° C, still more preferably 110 to 300 ° C, and particularly preferably 120 to 250 ° C.
The outlet temperature of the spray dryer is more preferably 20 to 250 ° C, still more preferably 35 to 200 ° C, and particularly preferably 50 to 120 ° C.
The pressure of the spray dryer is more preferably 5 to 150 MPa, still more preferably 7 to 120 MPa, particularly preferably 10 to 100 MPa,
The feed frequency of the spray dryer is more preferably 2 to 200 Hz, further preferably 5 to 160 Hz, and particularly preferably 10 to 100 Hz.
The mass ratio of the nanosilicon, the dispersant, the hollow graphite, and the organic solvent is preferably (1-50) :( 0.5-10) :( 30-90) :( 90-800). The method according to any one of claims 3 to 5. In the mechanical fusion process of the step (3), the first precursor is put into a fusion machine, the rotational speed is adjusted to 500 to 3000 rpm, the blade clearance width is adjusted to 0.01 to 1 cm, and the fusion is performed for at least 0.25 hours. Obtaining a fusion precursor material,
The rotational speed of the fusion machine is preferably 800 to 2000 rpm,
The blade clearance width is preferably 0.1 to 0.3 cm,
The fusion time is preferably 0.25 to 8.0 hours, particularly preferably 0.5 to 4.0 hours,
In the carbon source coating treatment in the step (3), preferably, the fusion precursor material and the organic carbon source are subjected to a solid phase coating or a liquid phase coating treatment, more preferably a solid phase coating treatment. Including obtaining
The solid phase coating preferably comprises placing the fusion precursor material and the organic carbon source in a VC mixer and coating for at least 0.5 hours to obtain a second precursor;
The organic carbon source is preferably in a powder form, and the median particle size is 0.5 to 25.0 μm, particularly preferably 1.0 to 8.0 μm,
The mass ratio of the fusion precursor material to the organic carbon source is preferably 1: 1 to 10: 1, particularly preferably 2: 1 to 6: 1.
The organic carbon source is preferably coal pitch, petroleum pitch, mesophase pitch, coal tar, petroleum industry heavy oil, heavy aromatic hydrocarbon, epoxy resin, phenol resin, furfural resin, urea resin, polyvinyl alcohol, poly The method according to any one of claims 3 to 6, which is one or a combination of at least two of vinyl chloride, polyethylene glycol, polyethylene oxide, polyvinylidene fluoride, acrylic resin and polyacrylonitrile. . The isotropic pressure treatment in the step (4) is performed by pressure-treating the second precursor for 0.05 to 4 hours under conditions of a pressure of 1000 to 20000 KN and a pressure treatment temperature of 20 to 300 ° C. Including obtaining the body,
The pressure treatment is preferably one or a combination of at least two of extrusion treatment, cold pressure treatment, hot pressure treatment and isotropic pressure treatment,
The pressure is preferably 5000 to 10,000 KN,
The temperature of the pressure treatment is preferably 30 to 200 ° C.,
The pressure treatment time is preferably 0.1 to 2 hours,
The high-temperature sintering of the step (5) is preferably performed in a protective gas atmosphere,
The protective gas is preferably nitrogen gas, helium gas, neon gas, argon gas, krypton gas, xenon gas and hydrogen gas, and particularly preferably nitrogen gas, helium gas, argon One or a combination of at least two of gas and hydrogen gas,
The flow rate of the protective gas is preferably 0.5 to 10.0 L / min, more preferably 0.5 to 5.0 L / min, and particularly preferably 1.0 to 4.0 L / min. ,
The heating rate during the sintering is preferably 20.0 ° C./min or less, more preferably 1.0-15.0 ° C./min, and particularly preferably 2.0-10.0 ° C./min. And
The sintering temperature is preferably 500 to 1150 ° C, more preferably 600 to 1050 ° C, particularly preferably 800 to 1000 ° C,
The sintering time is preferably at least 0.5 hours, more preferably 0.5 to 20.0 hours, particularly preferably 1.0 to 10.0 hours,
The method according to any one of claims 3 to 7, wherein, in the step (5), preferably, after high-temperature sintering is finished, natural cooling to room temperature is performed. A silicon-based composite negative electrode material for a lithium ion secondary battery manufactured by the method according to any one of claims 3 to 8,
The median particle size of the silicon-based composite negative electrode material is preferably 5.0 to 45.0 μm, more preferably 10.0 to 35.0 μm, and particularly preferably 13.0 to 25.0 μm.
The specific surface area of the silicon-based composite negative electrode material is preferably 1.0~20.0m ² / g, particularly preferably 2.0 to 10.0 m ² / g,
The powder press density of the silicon-based composite negative electrode material is preferably 1.0 to 2.0 g / cm ³ , particularly preferably 1.3 to 1.8 g / cm ³ ,
The center particle size of the nanosilicon particles is preferably 10 to 500 nm, more preferably 10 to 400 nm, and particularly preferably 10 to 300 nm, a silicon-based composite negative electrode for a lithium ion secondary battery Wood. A lithium ion secondary battery comprising a battery positive electrode, a battery negative electrode, and an electrolyte, wherein the battery negative electrode includes a negative electrode active material, a conductive agent, an adhesive, and a solvent, and the negative electrode active material is a claim 1, 2 or 9 is a silicon-based composite negative electrode material for a lithium ion secondary battery according to 9,
The conductive agent is preferably graphite powder and / or nano conductive liquid,
The nano conductive liquid preferably comprises 0.5 to 20% (by weight) of a nanocarbon material and a dispersion solvent,
More preferably, the nanocarbon material is at least one of graphene, carbon nanotube, nanocarbon fiber, fullerene, carbon black and acetylene black, and the number of graphite layers of the graphene is 1 to 100, And the diameter of the nano carbon fiber is 0.2 to 500 nm, and the particle sizes of fullerene, carbon black and acetylene black are 1 to 200 nm,
More preferably, the dispersion solvent is water, methanol, ethanol, propanol, isopropanol, acetone, cyclohexanone, dichloromethane, chloroform, cyclohexane, benzene, toluene, xylene, ethylbenzene, aniline, tetrahydrofuran, dimethyl sulfoxide, N-methylpyrrolidone, N- N dimethylformamide, NN dimethylacetamide, pyridine, pyrrole, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium dicyanamide, 1-butyl-3-methylimidazolium hexa Fluorophosphate, 1-butyl-3-methylimidazolium bistrifluoromethanesulfonylimide, 1-butyl-3-methylimidazolium trifluoromethanes Is one or at least two combinations of Honato and 1-ethyl-3-methylimidazolium acetate,
The adhesive is preferably one or a combination of at least two of polyimide resin, acrylic resin, polyvinylidene difluoride, polyvinyl alcohol, sodium carboxymethylcellulose and styrene butadiene rubber,
A lithium ion secondary battery, wherein the solvent is preferably one or a combination of at least two of N-methylpyrrolidone, dimethylformamide, acetone and methyl ethyl ketone.