Negative electrode material and preparation method thereof, electrochemical device and electronic device

Abstract

The application provides a negative electrode material and a preparation method thereof, an electrochemical device and an electronic device. The negative electrode material comprises graphite, and the graphite surface has pores. In a circular area with a diameter of 1 micrometer on the graphite surface, the number of the pores is 20 to 2000, and the average diameter of the pores is 10 nanometers to 100 nanometers. The negative electrode material contains a metal element, and the metal element comprises at least one of Fe, Co, Ni, Cr and Mn. The negative electrode material provided by the application can simultaneously improve the charging rate and the cycle life of the electrochemical device.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electrochemical energy storage, and in particular to a negative electrode material, a preparation method thereof, an electrochemical device using the negative electrode material, and an electronic device using the electrochemical device. BACKGROUND

[0002] With the wide application of lithium ion batteries in various fields, the demand for fast charging performance and cycle life is becoming more and more demanding. In the 3C digital field, the fast charging performance and long cycle life of lithium ion batteries are often incompatible. Generally, coating, modification and process adjustment can improve the charging rate, but at the same time, it will bring unstable interface in the cycle process. Therefore, it is necessary to develop a new modification process that can effectively improve the room temperature kinetics and fast charging anti-lithium precipitation ability of the negative electrode material, while also improving the cycle life of the lithium ion battery. SUMMARY

[0003] The present application provides a negative electrode material, a preparation method thereof, an electrochemical device and an electronic device.

[0004] The first aspect of the present application provides a negative electrode material, which comprises graphite, the surface of the graphite having pores, the number of pores in a circular region with a diameter of 1 μm on the surface of the graphite being 20 to 2000, and the average diameter of the pores being 10 nm to 100 nm; the negative electrode material containing a metal element, the metal element comprising at least one of Fe, Co, Ni, Cr and Mn.

[0005] In the present application, the number of pores on the surface of the graphite of the negative electrode material, the diameter of the pores and the metal element in the negative electrode material are regulated to form pores with uniform size on the surface of the graphite. When the negative electrode material is applied to an electrochemical device, the uniformity of lithium ion deposition in the lithium intercalation process of the negative electrode material can be improved, and lithium precipitation during fast charging can be reduced. Regulating the number of pores and the diameter of the pores can inhibit the nucleation and growth of lithium ions, form a uniform lithium plating layer without nucleation, and inhibit the diffusion and precipitation of lithium ions on the surface of the negative electrode material after the nucleation and growth of lithium ions, thereby improving the transmission efficiency of lithium ions, improving the room temperature kinetics and fast charging anti-lithium precipitation ability of the negative electrode material, and further improving the kinetics of the negative electrode material in combination with the doped metal element, thereby further improving the kinetics performance of the electrochemical device. When the negative electrode material is applied to an electrochemical device, the surface of the graphite has a specific number of pores and an average diameter of the pores, which is also beneficial to promoting the reduction of anions in the electrolyte, so as to form a SEI film containing more inorganic components (such as LiF and Li2CO3), which can improve the mechanical strength of the SEI film, inhibit the growth of lithium dendrites, thereby improving the cycle stability of the negative electrode material, and further improving the cycle life of the electrochemical device.

[0006] In some possible implementation manners based on the first aspect, the number of the pores is 100 to 1000, and the average diameter of the pores is 20 nm to 50 nm. The room-temperature kinetics, the fast-charging anti-lithium precipitation capability and the cycle stability of the negative electrode material can be further improved, and the kinetics performance and the cycle life of the electrochemical device can be improved.

[0007] In some possible implementation manners based on the first aspect, the mass proportion of the metal element is 20 ppm to 400 ppm based on the mass of the negative electrode material. The nucleation and growth of lithium ions can be inhibited, and the electronic conductivity can be improved, and the cycle stability and the kinetics performance of the negative electrode material can be improved.

[0008] In some possible implementation manners based on the first aspect, the absolute value of the Zeta potential of the negative electrode material is ZP≥20 mV in deionized water with pH=7. The uniformity and the stability of the dispersion in the slurry preparation process of the negative electrode material can be improved, and the room-temperature kinetics and the cycle stability of the electrochemical device can be improved.

[0009] In some possible implementation manners based on the first aspect, the pore volume of the negative electrode material is 0.003 cm 3 / g to 0.01 cm 3 / g. The electrolyte wettability and the lithium ion transmission rate can be improved, and the kinetics performance of the electrochemical device can be improved.

[0010] In some possible implementation manners based on the first aspect, the main pore diameter of the negative electrode material is 0.5 nm to 2 nm. In combination with the mesopores with the average pore diameter of 10 nm to 100 nm on the surface of the negative electrode material, the above-mentioned pore structures jointly improve the kinetics performance of the electrochemical device.

[0011] In some possible implementation manners based on the first aspect, the particle size Dv50 and Dv99 of the negative electrode material satisfy 2.0≤Dv99 / Dv50≤5.0. The energy density and the cycle stability of the electrochemical device can be considered.

[0012] In some possible implementation manners based on the first aspect, the particle size Dv50 of the negative electrode material satisfies 8 μm≤Dv50≤15 μm. The side reaction between the negative electrode material and the electrolyte can be reduced, and the fast-charging anti-lithium precipitation capability and the cycle performance of the electrochemical device can be improved.

[0013] In some possible implementation manners based on the first aspect, the specific surface area of the negative electrode material is 3 m 2 / g to 10 m 2 / g. The side reaction between the negative electrode material and the electrolyte can be reduced, and the electrochemical device has good cycle performance.

[0014] In some possible implementation manners based on the first aspect, the tap density of the negative electrode material is 0.9 g / cm3 to 1.0 g / cm3. The tap density in the range is conducive to improving the energy density of the negative electrode material, and when the slurry is prepared by using the negative electrode material, the amount of the binder used can be reduced, and the processing performance is good. 3 to 1.0 g / cm3 3 The tap density in the range is conducive to improving the energy density of the negative electrode material, and when the slurry is prepared by using the negative electrode material, the amount of the binder used can be reduced, and the processing performance is good.

[0015] In some possible implementation manners based on the first aspect, the graphitization degree of the negative electrode material is 92% to 96%. The negative electrode material can have higher capacity and excellent kinetic performance, and the kinetic performance of the electrochemical device can be improved.

[0016] The second aspect of the application provides a preparation method of a negative electrode material. The preparation method comprises the following steps: dissolving an anionic surfactant in water, adding a metal salt compound, uniformly mixing, and obtaining a treatment agent solution; adding a carbon material into the treatment agent solution, uniformly mixing, and drying to obtain a powder; performing heat treatment on the powder in an inert atmosphere, heating to 500°C to 600°C at a rate of 5°C / min to 30°C / min, and maintaining for 3h to 6h to obtain an intermediate; performing acid pickling treatment on the intermediate, and washing to neutral, and drying to obtain the negative electrode material. In the above preparation method, the anionic surfactant forms some negative charges, and the negative charges combine with metal ions to form a salt. The salt is decomposed to form an oxide nucleus in the subsequent heat treatment process. By controlling the heating rate of the powder and the heat treatment temperature, the size of the oxide nucleus is regulated, so that the average diameter of the pores can be changed. The anionic surfactant and the metal salt compound act on the carbon material to form more uniform pores on the surface of the carbon material, and the number of pores in a specific area is regulated.

[0017] In some possible implementation manners based on the second aspect, the metal salt compound accounts for 10% to 30% of the mass of the carbon material. The metal salt compound is fully combined with the anionic surfactant to act on the carbon material, so that uniform pores and an appropriate average diameter of the pores are formed on the surface of the carbon material.

[0018] In some possible implementation manners based on the second aspect, the metal salt compound comprises at least one of a chloride salt, a nitrate salt, and a sulfate salt of Fe, Co, Ni, Cr, and Mn; or / and the anionic surfactant comprises at least one of sodium oleate, sodium lauryl sulfate, sodium lauryl ether sulfate, sodium stearate, and sodium myristate; or / and the carbon material is at least one of artificial graphite, natural graphite, hard carbon, and soft carbon. The anionic surfactant described above forms some negative charges, and the negative charges combine with metal ions to form a salt, the salt is decomposed to form an oxide crystal nucleus in a subsequent heat treatment process, and after pickling, pores are generated in the carbon material, and the metal salt compound is combined to act on the carbon material to form pores that are more uniformly distributed on the surface of the carbon material.

[0019] The third aspect of the present application provides an electrochemical device, the electrochemical device comprising a positive electrode sheet, a negative electrode sheet, and an electrolyte, the negative electrode sheet comprising the negative electrode material. The electrochemical device comprising the negative electrode material can improve the kinetic performance and cycle life of the electrochemical device.

[0020] The fourth aspect of the present application provides an electronic device, the electronic device comprising the electrochemical device. The electrochemical device supplies power for a load in the electronic device, and the electrochemical device comprising the negative electrode material is beneficial to improve the service life and fast charging performance of the electronic device. BRIEF DESCRIPTION OF DRAWINGS

[0021] The above and / or additional aspects and advantages of the present application will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, in which:

[0022] Figure 1 In the figure, (a) is a scanning electron microscope image of the negative electrode material in Example 1 of the present application; and (b) is a partial enlarged view of (a).

[0023] Figure 2 The figure is a pore size distribution curve of the negative electrode material in Example 1 and Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be described in detail below. Obviously, the described embodiments are some embodiments of the present application, rather than all the embodiments of the present application. Unless otherwise defined, all the technical and scientific terms used in the present application have the same meanings as those commonly understood by those skilled in the art to which the present application belongs. The terms used in the specification of the present application are only for the purpose of describing the specific embodiments, and are not intended to limit the present application.

[0025] The present application provides a negative electrode material and a preparation method thereof, an electrochemical device, and an electronic device.

[0026] An embodiment of the present application provides an electrochemical device, which comprises a shell, an electrode assembly and an electrolyte. The electrode assembly and the electrolyte are both located in the shell.

[0027] The shell can be a packaging bag obtained by packaging with a packaging film (such as an aluminum plastic film), and the electrochemical device is a soft package battery. In other embodiments, the electrochemical device can also be a steel shell battery, an aluminum shell battery or the like.

[0028] The electrode assembly comprises a positive electrode sheet, a negative electrode sheet and a separator film, and the separator film is arranged between the positive electrode sheet and the negative electrode sheet. The electrode assembly can be a laminated structure formed by alternately laminating the positive electrode sheet, the separator film and the negative electrode sheet. In other embodiments, the electrode assembly can also be a winding structure formed by winding the laminated positive electrode sheet, the separator film and the negative electrode sheet.

[0029] The negative electrode sheet

[0030] The present application provides a negative electrode material, which comprises graphite. The graphite surface has pores, and the number of pores in a circular region with a diameter of 1 μm on the graphite surface is 20 to 2000, and the average diameter of the pores is 10 nm to 100 nm; the negative electrode material further contains a metal element, and the metal element comprises at least one of Fe, Co, Ni, Cr and Mn.

[0031] In the present application, the number of pores on the graphite surface of the negative electrode material, the diameter of the pores and the metal element in the negative electrode material are regulated to form pores with uniform sizes on the graphite surface. When the negative electrode material is applied to an electrochemical device, the uniformity of lithium ion deposition in the lithium intercalation process of the negative electrode material can be improved, and the lithium precipitation during fast charging can be reduced. The regulation of the number of pores and the diameter of the pores can inhibit the nucleation growth of lithium ions, form a uniform lithium plating layer without nucleation, and inhibit the diffusion and precipitation of lithium ions on the surface of the negative electrode material after the nucleation growth of lithium ions, so as to improve the transmission efficiency of lithium ions, improve the room temperature kinetics and fast charging anti-lithium precipitation capacity of the negative electrode material, and further improve the kinetics of the negative electrode material in combination with the doped metal element, so as to further improve the kinetic performance of the electrochemical device. When the negative electrode material is applied to an electrochemical device, the graphite surface with a specific number of pores and an average diameter of the pores is also beneficial to promoting the reduction of anions in the electrolyte, so as to form an SEI film containing more inorganic components (such as LiF and Li2CO3), which can improve the mechanical strength of the SEI film, inhibit the growth of lithium dendrites, thereby improving the cycle stability of the negative electrode material and the cycle life of the electrochemical device.

[0032] If the number of pores is small, such as less than 20, or the average diameter of the pores is small, such as less than 10 nm, the uniformity of lithium ion deposition is not obviously improved, and the formation of the lithium-plated layer is not obvious, which is not conducive to improving the room temperature kinetics and fast charging anti-lithium precipitation ability of the negative electrode material; if the number of pores is large, such as greater than 2000, the structural stability of the negative electrode material may be affected, and the cycle performance of the negative electrode material is affected; if the average diameter of the pores is large, such as greater than 100 nm, the effect of inhibiting the nucleation and growth of lithium ions is small, which will affect the room temperature kinetics and fast charging anti-lithium precipitation ability of the negative electrode material.

[0033] In some embodiments, the number of pores in a circular area with a diameter of 1 μm on the surface of the graphite can be 20, 30, 50, 100, 200, 300, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1500, 1700, 1800, 1900, 2000 or any value within a range defined by any two of the above values. The average diameter of the pores can be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm or any value within a range defined by any two of the above values.

[0034] In some embodiments, the number of pores in a circular area with a diameter of 1 μm on the surface of the graphite is 100 to 1000, and the average diameter of the pores is 20 nm to 50 nm. The room temperature kinetics, fast charging anti-lithium precipitation ability and cycle stability of the negative electrode material can be further improved, and the kinetics performance and cycle life of the electrochemical device can be improved.

[0035] In some embodiments, the mass percentage of the metal element is 20 ppm to 400 ppm based on the mass of the negative electrode material. The mass percentage of the metal element in the above range can help improve the electronic conductivity and improve the kinetic performance of the negative electrode material. The smaller the diameter of the grid-like nanoscale pore structure, the more conducive to inhibiting the thermodynamic process of lithium metal nucleation in the early stage, so that the lithium ion nucleation is limited, thereby forming a nucleation-free uniform lithium plating layer, and improving the stability of the negative electrode material cycle. At the same time, a higher content of metal elements will also lead to an increase in the main pore diameter of the graphite with a grid-like nanoscale pore structure on the surface, which is not conducive to inhibiting the nucleation and growth of lithium ions. And containing a higher content of magnetic metal elements is not conducive to the stability of the battery cycle, so the content of the metal element in the negative electrode material should not be too high. In some embodiments, the mass percentage of the metal element can be 20 ppm, 50 ppm, 70 ppm, 80 ppm, 100 ppm, 120 ppm, 150 ppm, 170 ppm, 200 ppm, 250 ppm, 270 ppm, 300 ppm, 350 ppm, 370 ppm, 400 ppm, or any value within the range formed by any two of the above values.

[0036] In some embodiments, the absolute value of the Zeta potential of the negative electrode material is ZP≥20 mV in deionized water with pH=7. When the absolute value of the Zeta potential of the negative electrode material satisfies the above condition, it indicates that the negative electrode material surface has more -OH and other hydrophilic groups, and the surface with pores has good hydrophilicity, which is conducive to improving the uniformity and stability of the dispersion in the slurry preparation process of the negative electrode material, thereby improving the room temperature kinetics and cycle stability of the electrochemical device. In some embodiments, the absolute value of the Zeta potential of the negative electrode material can be 20 mV, 21 mV, 22 mV, 24 mV, 26 mV, 27 mV, 28 mV, 29 mV, 30 mV, 31 mV, 32 mV, 34 mV, 36 mV, 38 mV, 39 mV, 40 mV, or any value within the range formed by any two of the above values.

[0037] In some embodiments, the pore volume of the negative electrode material is 0.003 cm 3 / g to 0.01 cm 3 / g. Within this range, the negative electrode material has a porous structure, which is conducive to improving the electrolyte wettability and lithium ion transmission rate, thereby improving the kinetic performance of the electrochemical device. In some embodiments, the pore volume of the negative electrode material can be 0.003 cm 3 / g, 0.005 cm 3 / g, 0.006 cm 3 / g, 0.007 cm 3 / g, 0.008 cm 3 / g, 0.009 cm 3 / g, 0.01 cm 3 / g or any value within a range between any two of the above values.

[0038] In some embodiments, the main pore size of the negative electrode material is 0.5 nm to 2 nm, which can ensure that the main contribution of the pore volume of the negative electrode material comes from micropores with a pore size of 0.5 nm to 2 nm, in combination with the mesopores on the surface of the negative electrode material having an average pore size of 10 nm to 100 nm, which together work to improve the kinetic performance of the electrochemical device.

[0039] In some embodiments, the particle size Dv50 and Dv99 of the negative electrode material satisfy: 2.0≤Dv99 / Dv50≤5.0, which can balance the energy density and cycle stability of the electrochemical device. The Dv99 / Dv50 can be 2, 2.5, 3, 3.5, 4, 4.5, 5 or any value within a range between any two of the above values.

[0040] In some embodiments, the particle size Dv50 of the negative electrode material satisfies: 8 μm≤Dv50≤15 μm. This is conducive to reducing the side reaction between the negative electrode material and the electrolyte, and is conducive to improving the fast-charging lithium precipitation resistance and cycle performance of the electrochemical device. The Dv50 can be 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm or any value within a range between any two of the above values. V 50 is also called "median particle size", which represents the particle size of the negative electrode material at which 50% of the total volume of the particles of the negative electrode material is reached in the particle size distribution on a volume basis, i.e., the volume of the particles of the negative electrode material smaller than this particle size accounts for 50% of the total volume of the particles of the negative electrode material. In some embodiments, the particle size Dv50 of the negative electrode material can be 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm or any value within a range between any two of the above values.

[0041] In some embodiments, the specific surface area of the negative electrode material is 3 m 2 / g to 10 m 2 / g; the specific surface area of the negative electrode material within the above range is conducive to reducing the side reaction between the negative electrode material and the electrolyte, so that the electrochemical device has good cycle performance. In some embodiments, the specific surface area of the negative electrode material can be 3 m 2 / g, 4 m 2 / g, 5 m 2 / g, 6 m 2 / g, 7 m 2 / g, 8 m 2 / g, 9 m 2 / g, 10 m 2 / g or any value within a range between any two of the above values.

[0042] In some embodiments, the tap density of the negative electrode material is 0.9 g / cm3to 1.0 g / cm3. 3 to 1.0 g / cm3. 3 The tap density within this range is conducive to improving the energy density of the negative electrode material, and when a slurry is prepared using the negative electrode material, it is also conducive to reducing the amount of binder used and good processing performance. In some embodiments, the tap density of the negative electrode material can be 0.9 g / cm3, 0.93 g / cm3, 0.95 g / cm3, 0.96 g / cm3, 0.97 g / cm3, 0.98 g / cm3, 0.99 g / cm3, or any value within a range defined by any two of the above-mentioned values. 3 3 3 3 3 3 or any value within a range defined by any two of the above-mentioned values.

[0043] In some embodiments, the graphitization degree of the negative electrode material is 92% to 96%. The graphitization degree of the negative electrode material within the above-mentioned range can make the negative electrode material have higher capacity and excellent kinetic performance, which is conducive to improving the kinetic performance of the electrochemical device; and the graphitization degree of the negative electrode material within the above-mentioned range can fully develop the performance of graphite. In some embodiments, the graphitization degree of the negative electrode material can be 92%, 92.5%, 93%, 93.5%, 94%, 94.5%, 95%, 95.5%, 96%, or any value within a range defined by any two of the above-mentioned values.

[0044] The application also provides a preparation method of the negative electrode material, which comprises the following steps:

[0045] S1. Dissolve an anionic surfactant in water and add a metal salt compound, and after mixing uniformly, obtain a treatment agent solution. The mass ratio of the anionic surfactant and the metal salt compound is 1:1 to 3:1.

[0046] In some embodiments, the metal salt compound comprises at least one of a chloride salt, a nitrate salt, and a sulfate salt of Fe, Co, Ni, Cr, and Mn; such as ferric chloride hexahydrate, cobalt chloride, cobalt nitrate, etc.

[0047] The anionic surfactant comprises at least one of sodium oleate, sodium lauryl sulfate, sodium lauryl ether sulfate, sodium stearate, and sodium myristate.

[0048] In the treatment agent solution, the anionic surfactant described above will form some negative charges, and the negative charges will combine with metal ions to form salts, the formed salts will decompose to form oxide crystal nuclei in the subsequent heat treatment process, and after pickling, pores will be generated in the carbon material, and the added metal salt compound will act on the carbon material to form pores that are more uniformly distributed on the surface of the carbon material.

[0049] ​​​​​In some embodiments, the mass ratio of the anionic surfactant and the metal salt compound can be 1:1, 1.5:1, 2:1, 2.5:1, 3:1, or any value within a range defined by any two of the above values.

[0050] In some embodiments, the treatment agent solution is further subjected to a heating treatment, the temperature of the heating treatment is 80-100°C, and the heating time is 1-2 hours. The heating treatment can be performed using an oil bath. In some embodiments, the temperature of the heating treatment can be 80°C, 85°C, 90°C, 95°C, 100°C, or any value within a range defined by any two of the above values, and the heating time can be 1 hour, 1.2 hours, 1.5 hours, 1.8 hours, 2 hours, or any value within a range defined by any two of the above values. After the treatment agent is subjected to the heating treatment, the metal salt compound can be fully dissolved, thereby improving the uniformity of the metal salt compound.

[0051] S2. The carbon material is added to the treatment agent solution, mixed uniformly, and dried to obtain a powder.

[0052] The metal salt compound accounts for 10-30% of the mass of the carbon material. The mass ratio of the metal salt compound within the above range facilitates the full cooperation of the metal salt compound with the anionic surfactant for the carbon material, so as to form uniform pores and appropriate average diameters of the pores on the surface of the carbon material. In some embodiments, the mass ratio of the metal salt compound to the carbon material can be 10%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, or any value within a range defined by any two of the above values.

[0053] The carbon material is selected from at least one of artificial graphite, natural graphite, hard carbon, and soft carbon. The artificial graphite and the natural graphite can improve the lithium ion transmission performance of the negative electrode material, thereby enabling the electrochemical device to have higher energy density and better charging performance, and even better cycle performance. The hard carbon and the soft carbon can improve the charge-discharge capacity or cycle life of the negative electrode material, thereby improving the cycle life of the electrochemical device.

[0054] S3. The powder is subjected to a heat treatment in an inert atmosphere, heated to 500-600°C at a rate of 5-30°C / min, and held for 3-6 hours to obtain an intermediate.

[0055] In some embodiments, the inert atmosphere can be nitrogen or argon.

[0056] In some embodiments, the powder is heated to 500°C to 600°C at a rate of 5°C / min to 30°C / min in an inert atmosphere, and the holding time is 3h to 6h. The heating rate of the powder can be 5°C / min, 10°C / min, 15°C / min, 20°C / min, 25°C / min, 30°C / min, or any value within a range defined by any two of the above values. The temperature of the powder treatment can be 500°C, 530°C, 550°C, 580°C, or 600°C, or any value within a range defined by any two of the above values. The holding time can be 3h, 4h, 5h, 6h, or any value within a range defined by any two of the above values.

[0057] S4. The intermediate is subjected to acid washing, washed with water to neutral, and dried to obtain the negative electrode material.

[0058] In some embodiments, the concentration of the acid washing is 0.5mol / L to 3mol / L. The concentration of the acid washing can be 0.5mol / L, 1mol / L, 1.5mol / L, 2mol / L, 2.5mol / L, 3mol / L, or any value within a range defined by any two of the above values. The acid used in the acid washing can be dilute hydrochloric acid or dilute nitric acid.

[0059] In some embodiments, before the intermediate is washed with water, the intermediate is heated to 80°C to 100°C and stirred for 3h to 6h, so that the metal in the intermediate dissolves in the solution, facilitating the cleaning.

[0060] In the above preparation method, the anionic surfactant forms some negative charges, and the negative charges combine with metal ions to form salts, which decompose to form oxide nuclei during subsequent heat treatment. By controlling the heating rate of the powder in step S3 and the heat treatment temperature, the size of the oxide nuclei can be controlled, thereby changing the average diameter of the pores. The anionic surfactant and the metal salt compound act on the carbon material to form pores with more uniform distribution on the surface of the carbon material, and the number of pores in a specific area is controlled. In the preparation method provided in the present application, the metal nano-oxide in the powder uniformly nucleates on the surface of the graphite by controlling the thermal decomposition process, forming a regular nano-sized pore structure. Then, the metal oxide is etched away by the acid solution, obtaining a negative electrode material with a more uniformly distributed grid nano-sized pore structure.

[0061] Separator film

[0062] The material and shape of the separator film used in the electrochemical device of the present application are not particularly limited, and can be any technology disclosed in the prior art. In some embodiments, the separator film includes a polymer or inorganic material formed of a material stable to the electrolyte of the present application, etc.

[0063] The separation film can include a substrate layer and a surface treatment layer. The substrate layer is a nonwoven fabric, a film, or a composite film having a porous structure, and the material of the substrate layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate, and polyimide. Specifically, a polypropylene porous film, a polyethylene porous film, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite film can be used.

[0064] The surface treatment layer is provided on at least one surface of the substrate layer, and can be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic substance. The inorganic layer includes inorganic particles and a binder, and the inorganic particles are selected from at least one of alumina, silica, magnesia, titania, hafnia, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconia, yttria, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate. The binder is selected from at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylic acid salt, polyvinylpyrrolidone, polyvinylalkoxide, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene. The polymer layer includes a polymer, and the material of the polymer is selected from at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylic acid salt, polyvinylpyrrolidone, polyvinylalkoxide, polyvinylidene fluoride, and poly(vinylidene fluoride-hexafluoropropylene).

[0065] Electrolyte solution

[0066] According to some embodiments of the present application, the electrolyte includes an organic solvent, a lithium salt, and optionally an additive. The organic solvent in the electrolyte of the present application can be any organic solvent known in the art that can be used as a solvent for an electrolyte. The electrolyte used in the electrolyte of the present application is not limited and can be any electrolyte known in the art. The additive of the electrolyte of the present application can be any additive known in the art that can be used as an additive for an electrolyte. In some embodiments, the organic solvent includes, but is not limited to, ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate, or ethyl propionate. In some embodiments, the organic solvent includes an ether-based solvent, such as including at least one of 1,3-dioxolane (DOL) and dimethoxyethane (DME). In some embodiments, the lithium salt includes at least one of an organic lithium salt or an inorganic lithium salt. In some embodiments, the lithium salt includes, but is not limited to, lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), lithium bis-trifluoromethanesulfonimide LiN(CF3SO2)2 (LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO2F)2) (LiFSI), lithium bis(oxalato)borate LiB(C2O4)2 (LiBOB), or lithium difluoro(oxalato)borate LiBF2(C2O4) (LiDFOB). In some embodiments, the additive includes at least one of fluoroethylene carbonate and adiponitrile.

[0067] Positive electrode tab

[0068] The positive electrode tab includes a positive current collector and a positive active layer disposed on the positive current collector. The positive current collector can use an aluminum foil or a nickel foil, etc., and can be any composite current collector disclosed in the art, such as, but not limited to, a current collector formed by combining the aforementioned conductive foil and a polymer substrate. The positive active layer contains a positive active material, which includes a compound that reversibly intercalates and deintercalates lithium ions (i.e., a lithiated intercalation compound). In some embodiments, the positive active material can include a lithium transition metal composite oxide. The lithium transition metal composite oxide contains lithium and at least one element selected from cobalt, manganese, and nickel. In some embodiments, the positive active material can include, but is not limited to, at least one of lithium cobaltate, lithium nickel manganese cobaltate, lithium nickel manganese aluminate, lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium iron silicate, lithium vanadium silicate, lithium cobalt silicate, lithium manganese silicate, spinel-type lithium manganate, spinel-type lithium nickel manganate, and lithium titanate.

[0069] The positive active layer can further include a binder to bind the positive active material particles to facilitate formation of a film layer and to improve the adhesion between the positive active layer and the positive current collector. In some embodiments, the binder can include, but is not limited to, at least one of polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene butadiene rubber, acrylated styrene butadiene rubber, epoxy resin, or nylon.

[0070] The positive active layer can further include a conductive material, which can include, but is not limited to, a carbon-based material, a metal-based material, a conductive polymer, or any combination thereof. In some embodiments, the carbon-based material can include, but is not limited to, at least one of natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based material can include, but is not limited to, metal powder or metal fiber, such as copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer can be a polyphenylene derivative.

[0071] The above-described electrochemical device can be applied to an electronic device to provide power to a load in the electronic device. Moreover, the negative active material in the above-described electrochemical device has excellent kinetics, fast-charging anti-lithium precipitation ability, and cycle stability, which are beneficial to improving the service life and fast-charging performance of the electronic device. The electronic device can include, but is not limited to, a notebook computer, a pen-input computer, a mobile computer, an electronic book player, a portable telephone, a portable facsimile machine, a portable copying machine, a portable printer, a headphone, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable audio recorder, a radio, a backup power supply, an electric motor, an automobile, a motorcycle, a power-assisted bicycle, a bicycle, a lighting appliance, a toy, a game machine, a clock, a power tool, a flashlight, a camera, a household large storage battery, and a lithium ion capacitor.

[0072] The present application is described below by way of specific examples and comparative examples. Those skilled in the art will understand that the preparation methods described in the present application are only examples, and any other suitable preparation method is within the scope of the present application.

[0073] Example 1

[0074] <Preparation of the negative active material>

[0075] 1. 300 g of sodium oleate was uniformly dissolved in 3 L of water, and 100 g of iron chloride hexahydrate powder was added, and stirred at 80 °C in an oil bath for 2 h to obtain a treatment agent solution.

[0076] 2. Slowly add 1 kg of graphite powder into the solution of the treating agent while stirring to mix the graphite powder evenly with the treating agent. After stirring for 6 hours at 80°C in an oil bath, transfer the mixture into an oven for drying. The powder is obtained.

[0077] 3. Transfer the powder into a box furnace for heat treatment. Increase the temperature to 500°C at a rate of 20°C / min in an inert atmosphere and keep the temperature for 3 hours. The intermediate, i.e. the treated graphite, is obtained.

[0078] 4. Add the treated graphite into a hydrochloric acid solution with a concentration of 3 mol / L. After stirring for 6 hours at 80°C in an oil bath, wash the mixture with water until neutral. Dry the mixture to obtain the negative electrode material.

[0079] Mix the negative electrode material, thickening agent carboxymethyl cellulose sodium (CMC-Na) and binder styrene-butadiene rubber (SBR) according to a weight ratio of 95:2:3. Add deionized water and stir to mix the mixture evenly. The solid content of the negative electrode slurry is 75 wt%. Coat the negative electrode slurry on one surface of a negative electrode current collector copper foil with a thickness of 10 μm. Dry the copper foil at 120°C to obtain a negative electrode tab with a single negative electrode material layer with a thickness of 80 μm. Repeat the above steps on the other surface of the copper foil to obtain a negative electrode tab with double negative electrode material layers. Dry the copper foil at 120°C under vacuum for 1 hour. Then, after cold pressing, cutting and slitting, a negative electrode tab with a size of 78 mm x 875 mm is obtained.

[0080] <Preparation of a positive electrode tab>

[0081] Mix the positive electrode active material lithium cobalt oxide (LiCoO2), conductive agent acetylene black and binder polyvinylidene fluoride (PVDF) according to a weight ratio of 96:2:2. Add N-methyl pyrrolidone (NMP) and stir to mix the mixture evenly. The solid content of the positive electrode slurry is 70 wt%. Coat the positive electrode slurry on one surface of a positive electrode current collector aluminum foil with a thickness of 10 μm. Dry the aluminum foil at 120°C for 1 hour to obtain a positive electrode tab with a single positive electrode material layer with a thickness of 60 μm. Repeat the above steps on the other surface of the aluminum foil to obtain a positive electrode tab with double positive electrode material layers. Dry the aluminum foil at 120°C under vacuum for 1 hour. Then, after cold pressing, cutting and slitting, a positive electrode tab with a size of 74 mm x 867 mm is obtained.

[0082] <Preparation of an electrolyte>

[0083] In an argon atmosphere glove box with water content less than 10 ppm, non-aqueous organic solvents ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC) were mixed in a weight ratio of 1:1:1, then lithium salt lithium hexafluorophosphate (LiPF6) was added and mixed uniformly to obtain an electrolyte. The mass percentage of lithium salt LiPF6 based on the mass of the electrolyte was 12.5%, and the balance was non-aqueous organic solvent.

[0084] <Preparation of the separator film>

[0085] A polypropylene / polyethylene composite film with a thickness of 7 μm was used as the separator film.

[0086] <Preparation of the lithium ion battery>

[0087] The positive electrode sheet, the separator film, and the negative electrode sheet prepared above were stacked in order, with the separator film between the positive electrode sheet and the negative electrode sheet to play a separating role, and were wound to obtain an electrode assembly. After welding the tabs, the electrode assembly was placed in an aluminum plastic film packaging bag, dried, and then injected with electrolyte. After vacuum packaging, standing, formation (formation upper limit voltage was 4.5 V, formation temperature was 70°C, formation standing time was 2 hours), degassing, and edge cutting, a lithium ion battery was obtained.

[0088] Example 2

[0089] Example 2 differed from Example 1 in that, in addition to the heat treatment in the preparation of the negative electrode material-step 3, the heating rate was 25°C / min, and the remaining steps were the same as in Example 1.

[0090] Example 3

[0091] Example 3 differed from Example 1 in that, in addition to the heat treatment in the preparation of the negative electrode material-step 3, the heating rate was 10°C / min, and the remaining steps were the same as in Example 1.

[0092] Example 4

[0093] Example 4 differed from Example 1 in that, in addition to the heat treatment in the preparation of the negative electrode material-step 3, the heating rate was 30°C / min, and the remaining steps were the same as in Example 1.

[0094] Example 5

[0095] Example 5 differed from Example 1 in that, in the preparation of the negative electrode material-step 1, 200 g of ferric chloride hexahydrate was added to water; and in the preparation of the negative electrode material-step 3, the heating rate was 5°C / min, and the remaining steps were the same as in Example 1.

[0096] Example 6

[0097] Example 6 differs from Example 3 in that, except for replacing "100 g of iron chloride hexahydrate" with "150 g of nickel nitrate hexahydrate" in the preparation of the negative electrode material - Step 1, and replacing "500 °C, holding for 3 h" with "600 °C, holding for 3 h" in the preparation of the negative electrode material - Step 3, the remaining steps are the same as Example 3.

[0098] Example 7

[0099] Example 7 differs from Example 3 in that, except for replacing "100 g of iron chloride hexahydrate" with "150 g of chromium chloride trihydrate hexahydrate" in the preparation of the negative electrode material - Step 1, and replacing "500 °C, holding for 3 h" with "600 °C, holding for 3 h" in the preparation of the negative electrode material - Step 3, the remaining steps are the same as Example 3.

[0100] Example 8

[0101] Example 8 differs from Example 3 in that, except for replacing "100 g of iron chloride hexahydrate" with "300 g of manganese chloride tetrahydrate" in the preparation of the negative electrode material - Step 1, and replacing "500 °C, holding for 3 h" with "600 °C, holding for 3 h" in the preparation of the negative electrode material - Step 3, the remaining steps are the same as Example 3.

[0102] Comparative Example 1

[0103] Only the graphite raw material in the preparation of the negative electrode material - Step 2 is taken as the negative electrode material, without further processing.

[0104] Comparative Example 2

[0105] Except for replacing the heating rate of the heat treatment to 35 °C / min in the preparation of the negative electrode material - Step 3, the remaining steps are the same as Example 1.

[0106] Comparative Example 3

[0107] Except for adding 350 g of iron chloride hexahydrate into water in the preparation of the negative electrode material - Step 1, and the heating rate of the heat treatment is 2 °C / min in the preparation of the negative electrode material - Step 3, the remaining steps are the same as Example 1.

[0108] The negative electrode materials prepared in each example and comparative example, and the lithium ion batteries assembled, are tested.

[0109] Test method:

[0110] Tested negative electrode material: Take the completely discharged lithium ion battery, disassemble and take out the negative electrode, soak in ethylene carbonate (DMC) for 20 min, then wash with DMC and acetone respectively, to remove the electrolyte and the surface solid electrolyte interface (SEI) film, then place it in an oven at 80°C for 12h, to obtain the treated negative electrode sheet. Scrape the negative electrode material layer on the negative electrode sheet with a scraper, and heat treat the scraped negative electrode material layer powder in a tube furnace at 350°C for 4h under argon protection to obtain the negative electrode material.

[0111] Pore number and average pore diameter test: use a scanning electron microscope with model ZEIS-SEM (Sigma-02-33) to paste the negative electrode material dispersed in ethanol on the sample table with conductive glue, install the sample table into the sample chamber and ensure it is fixed, close the sample chamber. Turn on the vacuum, set the following parameters: acceleration voltage 10kV, aperture 30μm, working distance 2mm to 9mm, current 2.335A, after determining the parameters, start the test, turn on the high voltage, focus, magnification 30000 times, take a picture of the negative electrode material. Select the negative electrode material particles in the field of view, and through the image analysis software, the number of pores and the average diameter of the pores in any 1μm diameter circular area can be obtained. Test the number of pores in 10 areas (1μm diameter circular area), calculate the average value, which is the number of pores in the 1μm diameter circular area on the surface of the graphite. Test the diameter of the pores on the surface of a single 1μm diameter circular area (the diameter of the pore refers to the distance between the two farthest points on the circumference of the pore), and obtain the average diameter of the pores on the surface of a single area, then test 10 areas (1μm circular area), finally obtain the average diameter of the pores on the surface.

[0112] Metal element content test: use microwave digestion method and PEICP-OES Optima7000DV to test the mass percentage content of metal elements in the negative electrode material.

[0113] Pore size distribution test: use iPore620 specific surface and pore size analyzer to test the pore size distribution of the negative electrode material under Ar atmosphere, refer to GB / T21650.3-2011 "Mercury intrusion porosimetry and gas adsorption method for the determination of the pore size distribution and the porosity of solid materials Part 3: Gas adsorption method for the analysis of micropores", to obtain the pore volume and the main pore diameter of the negative electrode material, the main pore diameter refers to the pore diameter with the highest pore volume peak in the pore volume distribution graph.

[0114] Zeta potential test:

[0115] The negative electrode material powder is prepared into a deionized water solution with a concentration of 0.0025 g / mL, Zeta potential is tested for 3 times, and an average value is obtained to obtain the absolute value ZP of the Zeta potential of the negative electrode material.

[0116] Particle size test:

[0117] A Malvern particle size tester (Model MasterSizer2000) is used to measure the particle size of the negative electrode material particles. 0.02 g of negative electrode material particles is added to a 50 mL clean beaker, 20 mL of dispersant ethanol is added, and the negative electrode material particles are completely dispersed in the ethanol in a 120 W ultrasonic cleaner for 30 min to obtain a sample dispersion liquid. The above sample dispersion liquid is tested using a Malvern particle size tester to obtain the particle size Dv50 and Dv99 of the negative electrode material particles.

[0118] Specific surface area (SSA) test:

[0119] According to the national standard "Gas adsorption BET method for determining the specific surface area of solid substances" (GB / T19587-2017), a specific surface area analyzer (Model TristarⅡ3020M) is used to test the specific surface area of the negative electrode material by nitrogen adsorption method.

[0120] Tap density TD test:

[0121] According to the national standard GB / T24533-2019, a density analyzer (Model GeoPyc1365) is used to test the tap density TD of the negative electrode material.

[0122] Graphitization degree test:

[0123] An X-ray powder diffractometer (XRD, instrument model: Bruker D8 ADVANCE) is used to test the negative electrode material, the target material is Cu Kα, the voltage and current are 40 KV / 40 mA, the scanning angle range is 5° to 80°, the scanning step is 0.00836°, and the time for each step is 0.3 s. At the same time, 15% of silicon powder is added, according to the principle of internal standard method, the peak position of silicon standard is used to calibrate the instrument and test error, so as to accurately calculate the characteristic peak position of the graphite negative electrode material, and obtain the graphitization degree of the graphite negative electrode material.

[0124] Lithium ion battery charging rate performance test:

[0125] The lithium ion battery is repeatedly charged and discharged by the following steps, and the capacity of each stage of charging is counted, and the capacity proportion of the constant current charging (CC) stage is calculated. The specific steps are as follows: first, place the lithium ion battery in a 25℃ environment for 6h. The lithium ion battery is charged at a charge rate of 1C, and the constant current charging is converted to constant voltage charging (CV) when the constant current charging reaches 4.48V, and the charging current is lower than 0.05C, then the above charging mode is CC+CV charging mode, and then the lithium ion battery is charged at a charge rate of 3C according to the above CC+CV charging mode, and the capacity proportion of the CC stage under the charge rate of 3C is calculated. The calculation formula is as follows:

[0126] The capacity proportion of the CC stage under the charge rate of 3C is calculated as follows: [the charging capacity of the CC stage under the charge rate of 3C / the total capacity of the (CC+CV) charging under the charge rate of 3C]x100%.

[0127] The capacity proportion of the CC stage under the charge rate of 3C is calculated as follows: [the charging capacity of the CC stage under the charge rate of 3C / the total capacity of the (CC+CV) charging under the charge rate of 3C]x100%.

[0128] In this application, the higher the capacity proportion of the CC stage under the charge rate of 3C of the lithium ion battery, the larger the capacity of the lithium ion battery under high rate charging, and the smaller the polarization of the lithium ion battery, which indicates that the charge rate performance of the lithium ion battery is better; the lower the capacity proportion of the CC stage under the charge rate of 3C of the lithium ion battery, the smaller the capacity of the lithium ion battery under high rate charging, and the larger the polarization of the lithium ion battery, which indicates that the charge rate performance of the lithium ion battery is worse.

[0129] Lithium ion battery 3C cycle capacity retention rate test:

[0130] In a 25℃ environment, the lithium ion battery is charged and discharged for the first time, and the constant current and constant voltage charging is carried out at a charging current of 3C until the upper limit voltage is 4.48V, and then the constant current discharging is carried out at a discharging current of 1C, and the discharging cut-off voltage is 3V, and the discharging capacity A of the lithium ion battery is measured; then, according to the above steps, the lithium ion battery is charged and discharged for 1000 times in a 0℃ environment, and the discharging capacity B of the lithium ion battery is measured, and then the 3C cycle capacity retention rate of the lithium ion battery is calculated as B / Ax100%; 5 lithium ion batteries are taken from each of the comparative examples and examples, and the average value is taken as the final result.

[0131] Table 1

[0132]

[0133] Table 2

[0134]

[0135] Referring to Figure 1 , the surface of the negative electrode material prepared in Example 1 forms a grid nano-sized pore structure, and the grid nano-sized pore structure is uniformly and orderly distributed on the surface of the negative electrode material in (a) and (b). Referring to Figure 2 , Figure 2 The pore size distribution curves of the negative electrode materials in Example 1 and Comparative Example 1 are shown in FIG. 1. The pore volume of the negative electrode material prepared in Example 1 is obviously larger than that of the negative electrode material prepared in Comparative Example 1.

[0136] As can be seen from Examples 1 to 5 and Comparative Examples 2 and 3, the heating rate has a direct impact on the average diameter of the final pores. The higher the heating rate, the smaller the average diameter of the pores, and vice versa. This is because the metal nano-oxide is formed by salt decomposition of the metal salt and the anionic surfactant, and the crystal nucleus particles are formed when the critical saturation is exceeded. These crystal nucleus particles continue to grow in the growth stage until all the metal salt is consumed. The monomer concentration formed at a low heating rate only reaches the critical supersaturation, thereby forming a small number of crystal nucleus particles, resulting in a large final grain size. A high heating rate forms a large number of crystal nucleus particles, resulting in a small grain size, and finally forming a small pore diameter.

[0137] Compared with Comparative Example 1, the ZP potential of the negative electrode material prepared in Examples 1 to 8 is improved after the surface grid nano-sized pore structure treatment. This is because the negative electrode material is treated, and the hydrophilic groups such as -OH are added to the surface of the graphite, so that the surface of the graphite with the grid nano-sized pore structure has good hydrophilicity, which is beneficial to the uniformity and stability of the dispersion in the slurry.

[0138] Compared with Comparative Examples 2 and 3, the larger the average diameter of the surface pores of the negative electrode material prepared in Examples 1 to 8, the larger the element content in the negative electrode material. A higher content of magnetic metal elements affects the stability of the battery cycle, so the element content should not be too high. At the same time, a higher element content will also lead to an increase in the main pore diameter of the surface pore structure. It is generally believed that the average diameter of the grid nano-sized pore structure is between 10 nm and 100 nm, preferably between 20 nm and 50 nm, which is more conducive to inhibiting the thermodynamic process of lithium metal nucleation in the early stage, so that the nucleation is limited, thereby forming a nucleation-free uniform lithium plating layer, and promoting the stability of the cycle. In addition, the number of pores is between 20 and 2000, preferably between 100 and 1000, which can improve the kinetic performance of the electrochemical device within the corresponding pore diameter range, while having excellent cycle stability.

[0139] In Table 2, the diameter of the pore structure in Example 1 is moderate, with an average diameter of 30 nm, and the capacity ratio in the CC section at a 3C charge rate is high, indicating that a pore diameter within the preferred range is beneficial to the improvement of kinetic performance at high rates. At the same time, it can inhibit the process of lithium precipitation nucleation, so that Example 1 has excellent cycle retention rate at a 3C charge rate.

[0140] The above disclosure is only the preferred embodiment of the present application, and of course cannot be used to limit the present application, so the equivalent changes made by the present application still fall within the scope covered by the present application.

Claims

1. A negative electrode material, characterized by, The graphite has pores on a surface thereof, and in a circular region of 1 μm in diameter on the surface of the graphite, the number of the pores is 20 to 2000, and the average diameter of the pores is 10 nm to 100 nm. The negative electrode material contains a metal element, and the metal element includes at least one of Fe, Co, Ni, Cr, and Mn.

2. The negative electrode material of claim 1, wherein, The mass ratio of the metal element to the mass of the negative electrode material is 20 ppm to 400 ppm.

3. The negative electrode material of claim 1, wherein, In deionized water with pH=7, the absolute value of the Zeta potential of the negative electrode material is ZP≥20 mV.

4. The negative electrode material according to any one of claims 1 to 3, characterized in that, The negative electrode material at least meets one of the following conditions: (1) the pore volume of the negative electrode material is 0.003 cm 3 / g to 0.01 cm 3 / g; (2) The main pore diameter of the negative electrode material is 0.5 nm to 2 nm. (3) The number of the pores is 100 to 1000, and the average diameter of the pores is 20 nm to 50 nm.

5. The negative electrode material according to any one of claims 1 to 3, characterized in that, The negative electrode material at least meets one of the following conditions: (1) the specific surface area of the negative electrode material is 3 m 2 / g to 10 m 2 / g; (2) the tap density of the negative electrode material is 0.9 g / cm 3 to 1.0 g / cm 3 ; (3) The graphitization degree of the negative electrode material is 92% to 96%. (4) The particle size Dv50 and Dv99 of the negative electrode material satisfy 2.0≤Dv99 / Dv50≤5.

0. (5) The particle size Dv50 of the negative electrode material satisfies 8 μm≤Dv50≤15 μm.

6. A method for producing the negative electrode material according to any one of claims 1 to 5, characterized by, The preparation method comprises the following steps: dissolving an anionic surfactant in water, adding a metal salt compound, uniformly mixing, and obtaining a treatment agent solution; adding a carbon material to the treatment agent solution, uniformly mixing, and drying to obtain a powder; in an inert atmosphere, heat treating the powder, heating to 500°C to 600°C at 5°C / min to 30°C / min, and holding for 3 h to 6 h to obtain an intermediate; acid pickling the intermediate, washing to neutral, and drying to obtain the negative electrode material.

7. The production method according to claim 6, characterized by, The mass of the metal salt compound accounts for 10% to 30% of the mass of the carbon material.

8. The production method according to claim 6 or 7, characterized by, The metal salt compound includes at least one of a chloride salt, a nitrate salt, and a sulfate salt of Fe, Co, Ni, Cr, and Mn; or / and The anionic surfactant includes at least one of sodium oleate, sodium lauryl sulfate, sodium lauryl ether sulfate, sodium stearate, and sodium myristate; or / and The carbon material is selected from at least one of artificial graphite, natural graphite, hard carbon, and soft carbon.

9. An electrochemical device, characterized by, The electrochemical device comprises a positive electrode sheet, a negative electrode sheet, and an electrolyte, and the negative electrode sheet comprises the negative electrode material in any one of claims 1 to 5 or the negative electrode material prepared according to the preparation method in any one of claims 6 to 8.

10. An electronic device, comprising: The electronic device comprises the electrochemical device in claim 9.

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