A negative electrode material, a negative electrode sheet, a secondary battery, and an electronic device

Abstract

The application provides a negative electrode material, a negative electrode sheet, a secondary battery and an electronic device. The negative electrode material is artificial graphite. In an X-ray diffraction spectrum of the negative electrode material, a 2H(100) characteristic peak exists in the range of 42 degrees to 43 degrees, a 2H(101) characteristic peak exists in the range of 44 degrees to 45 degrees, and two characteristic peaks exist in the range of 41 degrees to 47 degrees. In a scanning electron microscope image of the negative electrode material, the sphericity of the negative electrode material particles is Ψ, the length of the negative electrode material particles is a microns, the width of the negative electrode material particles is b microns, 0.6<=Ψ<=0.7, and 0.6<=b / a<=0.7. The negative electrode material is artificial graphite, the X-ray diffraction spectrum of the negative electrode material meets the above characteristics, the sphericity and the width-length ratio of the negative electrode material particles are within the range of the application, and the above negative electrode material is applied to the secondary battery, so that the fast-charging performance and the low-temperature kinetic performance of the secondary battery are improved, and the secondary battery also has a relatively high energy density.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochemistry, and particularly relates to a negative electrode material, a negative electrode sheet, a secondary battery and an electronic device. BACKGROUND

[0002] Secondary batteries (for example, lithium ion batteries) are widely used in notebook computers, mobile phones and new energy electric vehicles as a new type of high-energy green battery. However, as the application of lithium ion batteries becomes more and more extensive, the endurance problem of various devices has been a bottleneck restricting the application of lithium ion batteries. Therefore, mobile device manufacturers and vehicle manufacturers are constantly improving the charging rate of lithium ion batteries to reduce the charging time. The key to limiting the charging rate of lithium ion batteries is the negative electrode material, such as graphite, which is close to the deposition potential of metal lithium in the lithium intercalation potential. Under the condition of high-rate charging, lithium deposition phenomenon is easy to occur, which brings serious safety hazards.

[0003] In order to solve the above problems, the method commonly used is to coat amorphous carbon on the surface of graphite to improve the diffusion speed of lithium ions. However, amorphous carbon often has problems such as too large specific surface area and too low compaction density, which will lead to the decrease of the first efficiency and energy density of lithium ion batteries, and amorphous carbon cannot change the essential characteristics such as lithium ion diffusion speed and electrical conductivity in the graphite core. Therefore, it is urgent to provide a negative electrode material which can improve the fast charging performance and low temperature kinetic performance of lithium ion batteries, and at the same time make the lithium ion batteries have higher energy density. SUMMARY

[0004] The present application aims to provide a negative electrode material, a negative electrode sheet, a secondary battery and an electronic device to improve the fast charging performance and low temperature kinetic performance of the secondary battery, and at the same time make the secondary battery have higher energy density. The specific technical solutions are as follows:

[0005] The first aspect of the present application provides a negative electrode material, the negative electrode material being artificial graphite; in an X-ray diffraction spectrum of the negative electrode material, a 2H(100) characteristic peak exists in a range of 42° to 43° in 2θ, a 2H(101) characteristic peak exists in a range of 44° to 45° in 2θ, and two characteristic peaks exist in a range of 41° to 47° in 2θ; in a scanning electron microscope image of the negative electrode material, the sphericity of the negative electrode material particles is Ψ, the length of the negative electrode material particles is a μm, and the width of the negative electrode material particles is b μm, 0.6≤Ψ≤0.7, and 0.6≤b / a≤0.7. The negative electrode material is artificial graphite, the X-ray diffraction spectrum of the negative electrode material satisfies the above characteristics, and in the scanning electron microscope image of the negative electrode material, the sphericity of the negative electrode material particles, and the ratio of the width b of the negative electrode material particles to the length a of the negative electrode material particles are within the scope of the present application. The above negative electrode material is applied to a secondary battery, which can improve the fast charging performance and low-temperature kinetic performance of the secondary battery, and also makes the secondary battery have a relatively high energy density.

[0006] In an embodiment of the present application, in the X-ray diffraction spectrum of the negative electrode material, the half-peak width of the 2H(100) characteristic peak is FWHM 2H(100) , the half-peak width of the 2H(101) characteristic peak is FWHM 2H(101) , the peak intensity of the 2H(100) characteristic peak is Int. 2H(100) , the peak intensity of the 2H(101) characteristic peak is Int. 2H(101) , 1.5≤Int. 2H(101) / Int. 2H(100) ≤2.0. The negative electrode material of the present application is artificial graphite, the value of Int. 2H(101) / Int. 2H(100) in the X-ray diffraction spectrum of the negative electrode material is within the scope of the present application, and the above negative electrode material is applied to a secondary battery, which can improve the fast charging performance and low-temperature kinetic performance of the secondary battery.

[0007] In an embodiment of the present application, 3≤a≤18, and / or 1≤b≤15. The negative electrode material of the present application is artificial graphite, the value of the length a of the negative electrode material particle is within the range of the present application in the scanning electron microscope image of the negative electrode material, and the above-mentioned negative electrode material is applied to a secondary battery, which can improve the fast charging performance and low-temperature kinetic performance of the secondary battery. The negative electrode material of the present application is artificial graphite, the value of the width b of the negative electrode material particle is within the range of the present application in the scanning electron microscope image of the negative electrode material, and the above-mentioned negative electrode material is applied to a secondary battery, which can improve the fast charging performance and low-temperature kinetic performance of the secondary battery. The negative electrode material of the present application is artificial graphite, the value of the length a of the negative electrode material particle and the value of the width b of the negative electrode material particle are within the range of the present application in the scanning electron microscope image of the negative electrode material, and the above-mentioned negative electrode material is applied to a secondary battery, which can further improve the fast charging performance and low-temperature kinetic performance of the secondary battery.

[0008] In an embodiment of the present application, 0.1≤FWHM 2H(100) ≤0.2, and / or 0.5≤FWHM 2H(101) ≤1.0. The negative electrode material of the present application is artificial graphite, the value of FWHM 2H(100) is within the range of the present application in the X-ray diffraction spectrum of the negative electrode material, and the above-mentioned negative electrode material is applied to a secondary battery, which can improve the fast charging performance and low-temperature kinetic performance of the secondary battery. The negative electrode material of the present application is artificial graphite, the value of FWHM 2H(101) is within the range of the present application in the X-ray diffraction spectrum of the negative electrode material, and the above-mentioned negative electrode material is applied to a secondary battery, which can improve the fast charging performance and low-temperature kinetic performance of the secondary battery. The negative electrode material of the present application is artificial graphite, the value of FWHM 2H(100) and the value of FWHM 2H(101) are within the range of the present application in the X-ray diffraction spectrum of the negative electrode material, and the above-mentioned negative electrode material is applied to a secondary battery, which can further improve the fast charging performance and low-temperature kinetic performance of the secondary battery.

[0009] In an embodiment of the present application, the negative electrode material satisfies at least one of the following conditions:

[0010] (1) the interplanar spacing of the (002) crystal plane of the negative electrode material is d 002 ,

[0011] (2) the peak intensity of the (004) crystal plane of the negative electrode material is I 004 , the peak intensity of the (110) crystal plane of the negative electrode material is I 110 , and 3.0≤I 004 / I 110 ≤8.0.

[0012] (3) In the Raman spectrum of the negative electrode material, at 1300 cm⁻¹ -1 Up to 1400cm -1 Within the range, there is a peak intensity of I. d The first characteristic peak is at 1550 cm⁻¹. -1 Up to 1650cm -1 Within the range, there is a peak intensity of I. g The second characteristic peak is at 2700 cm⁻¹. -1 Up to 2750cm -1 Within the range, there is a peak intensity of I. 2D The third characteristic peak, 0≤I d / I g ≤0.15, 0.38≤I 2D / I g ≤0.40;

[0013] (4) The negative electrode material includes at least one of a first element, a second element, or a third element, wherein the first element includes B, the second element includes Si, and the third element includes at least one of Mn, Fe, Co, Ni, Ca, Ti, or Cr; based on the mass of the negative electrode material, the mass percentage of each of the first element, the second element, or the third element is independently X%, 0%. <X≤1。

[0014] If the negative electrode material meets at least one of the above conditions, the application of the above negative electrode material in a secondary battery can further improve the fast charging performance and low-temperature dynamic performance of the secondary battery.

[0015] In one embodiment of this application, the negative electrode material satisfies at least one of the following characteristics:

[0016] (1) The powder conductivity σ is 600 S / m to 800 S / m;

[0017] (2) The specific surface area B is 3m² 2 / g to 10m 2 / g;

[0018] (3) Particle size Dv50 is 4μm to 12μm;

[0019] (4) The tap density TD is 0.7 g / cm³. 3 Up to 1.1 g / cm 3 .

[0020] A second aspect of this application provides a method for preparing the negative electrode material in any of the foregoing embodiments, comprising the following steps:

[0021] (1) mixing a catalyst, graphene oxide and deionized water uniformly to obtain a mixed solution, a mass ratio of the catalyst to the graphene oxide being 0.01 to 0.05; wherein the catalyst comprises at least one of a boron-containing compound, a silicon-containing compound, a metal salt or a nano metal oxide, the boron-containing compound comprises at least one of boric acid, boron oxide or sodium borate, the silicon-containing compound comprises at least one of silicon dioxide, silicon carbide or silicon tetrachloride, the metal salt comprises at least one of manganese chloride, ferric nitrate or nickel nitrate, and the nano metal oxide comprises at least one of triiron dioxides, tricobalt tetroxide, calcium oxide, titanium dioxide or dichromium trioxide;

[0022] (2) drying the mixed solution to obtain graphene oxide powder;

[0023] (3) performing first carbonization treatment on the graphene oxide powder, and then performing second carbonization treatment to obtain the negative electrode material; wherein a temperature T1 of the first carbonization treatment is 800-1200℃, a time t1 of the first carbonization treatment is 4-10h, and a heating rate v1 of the first carbonization treatment is 8-12℃ / min; a temperature T2 of the second carbonization treatment is 2300-3000℃, a time t2 of the second carbonization treatment is 12-20h, and a heating rate v2 of the second carbonization treatment is 3-7℃ / min.

[0024] The negative electrode material prepared by the preparation method has good ion conductivity and electronic conductivity, and has high compaction density.

[0025] The third aspect of the application provides a negative electrode sheet comprising the negative electrode material in any of the foregoing embodiments. Therefore, the negative electrode sheet provided by the application has high ion conductivity and electronic conductivity, and has high compaction density.

[0026] The fourth aspect of the application provides a secondary battery comprising the negative electrode sheet in any of the foregoing embodiments. Therefore, the secondary battery provided by the application has good fast charging performance, low-temperature kinetic performance, and has high energy density.

[0027] The fifth aspect of the application provides an electronic device comprising the secondary battery in any of the foregoing embodiments. Therefore, the electronic device provided by the application has good use performance.

[0028] The application has the following beneficial effects:

[0029] The application provides a negative electrode material, a negative electrode sheet, a secondary battery and an electronic device, the negative electrode material is artificial graphite; in the X-ray diffraction spectrum of the negative electrode material, a 2H(100) characteristic peak exists in the range of 42 degrees to 43 degrees in 2 theta, a 2H(101) characteristic peak exists in the range of 44 degrees to 45 degrees in 2 theta, and two characteristic peaks exist in the range of 41 degrees to 47 degrees in 2 theta; in the scanning electron microscope image of the negative electrode material, the sphericity of the negative electrode material particles is Ψ, the length of the negative electrode material particles is a microns, the width of the negative electrode material particles is b microns, 0.6<=Ψ<=0.7, and 0.6<=b / a<=0.7. The negative electrode material is artificial graphite, the X-ray diffraction spectrum of the negative electrode material meets the above characteristics, the sphericity and the width-length ratio of the negative electrode material particles are within the range of the application, and the above negative electrode material is applied to the secondary battery, so that the fast charging performance and the low-temperature kinetic performance of the secondary battery can be improved, and the secondary battery also has a relatively high energy density.

[0030] Of course, implementing any product or method of the application does not necessarily require achieving all the advantages described above at the same time. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only constitute some embodiments of the application, and other embodiments can also be obtained by those skilled in the art based on these drawings.

[0032] Figure 1 The X-ray diffraction spectrum of the negative electrode material in the application example 1-1 is shown in the figure.

[0033] Figure 2 The scanning electron microscope image of the negative electrode material in the application example 1-1 is shown in the figure.

[0034] Figure 3 The Raman spectrum of the negative electrode material in the application example 1-1 is shown in the figure.

[0035] Figure 4 The powder conductivity curve of the negative electrode material in the application example 1-1 under different pressures is shown in the figure. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments only constitute some of the embodiments of the application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on the application belong to the protection scope of the application.

[0037] It should be noted that in the specific embodiments of the present application, the lithium ion battery is taken as an example of the secondary battery, but the secondary battery of the present application is not limited to the lithium ion battery.

[0038] The first aspect of the present application provides a negative electrode material, the negative electrode material being artificial graphite; in the X-ray diffraction spectrum of the negative electrode material, there is a 2H(100) characteristic peak in the range of 42° to 43°, a 2H(101) characteristic peak in the range of 44° to 45°, and two characteristic peaks in the range of 41° to 47°. As shown in Figure 1 The X-ray diffraction spectrum of the negative electrode material in Example 1-1 of the present application shows that there is a 2H(100) characteristic peak in the range of 42° to 43°, a 2H(101) characteristic peak in the range of 44° to 45°, and two characteristic peaks in the range of 41° to 47°, the 2H(100) characteristic peak and the 2H(101) characteristic peak being characteristic peaks of artificial graphite, indicating that the negative electrode material is artificial graphite. The above "existence of characteristic peak" refers to the relative intensity of the peak intensity of the characteristic peak to the peak intensity of the graphite (002) peak being above 0.5%.

[0039] In the scanning electron microscope image of the negative electrode material, the sphericity of the negative electrode material particles is Ψ, the length of the negative electrode material particles is a μm, and the width of the negative electrode material particles is b μm, 0.6≤Ψ≤0.7, and exemplarily, the sphericity Ψ of the negative electrode material particles can be 0.6, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.7, or a range composed of any two of the above values; 0.6≤b / a≤0.7, and exemplarily, b / a can be 0.6, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.7, or a range composed of any two of the above values. As shown in Figure 2 The scanning electron microscope image of the negative electrode material in Example 1-1 of the present application shows that the morphology of the negative electrode material is flat, and the morphology of the negative electrode material is similar to that of natural flaky graphite, which is different from that of conventional artificial graphite. In the present application, the "length" of the negative electrode material particles refers to the Feret maximum diameter, that is, the maximum distance between the parallel lines of the two boundaries of the particle projection profile measured in a certain direction; the "width" of the negative electrode material particles refers to the Feret minimum diameter, that is, the minimum distance between the parallel lines of the two boundaries of the particle projection profile measured in a certain direction. As shown in Figure 2 The distance between straight line A1 and straight line A2 is the length a of the negative electrode material particles, and the distance between straight line A3 and straight line A4 is the width b of the negative electrode material particles. In the present application, the sphericity Ψ of the negative electrode material particles refers to the ratio of the equivalent circular area perimeter of the particles to the projected area perimeter of the particles, which is calculated by software fitting.

[0040] The inventors have found that by uniformly mixing graphene oxide with a specific catalyst, and then preparing the negative electrode material through catalytic graphitization, the negative electrode material is artificial graphite. Since the negative electrode material is prepared through catalytic graphitization of graphene oxide, the negative electrode material has the excellent properties of high lithium ion diffusion coefficient and high electrical conductivity possessed by graphene oxide, and the negative electrode material has a relatively complete interlayer structure and a relatively large interplanar spacing. The negative electrode material is artificial graphite, and the X-ray diffraction spectrum of the negative electrode material satisfies the above characteristics. In the scanning electron microscope image of the negative electrode material, the sphericity of the negative electrode material particles, the ratio of the width b of the negative electrode material particles to the length a of the negative electrode material particles are within the scope of the present application. The above negative electrode material is applied to a secondary battery, which can improve the fast charging performance and low temperature kinetic performance of the secondary battery, and also makes the secondary battery have a relatively high energy density. In the present application, the interplanar spacing refers to the interplanar spacing d 002 .

[0041] In an embodiment of the present application, in the X-ray diffraction spectrum of the negative electrode material, the half-peak width of the 2H(100) characteristic peak is FWHM 2H(100) , the half-peak width of the 2H(101) characteristic peak is FWHM 2H(101) , the peak intensity of the 2H(100) characteristic peak is Int. 2H(100) , the peak intensity of the 2H(101) characteristic peak is Int. 2H(101) , 1.5≤Int. 2H(101) / Int. 2H(100) ≤2.0. Exemplarily, the value of Int. 2H(101) / Int. 2H(100) may be 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2.0 or a range composed of any two of the above values. The negative electrode material of the present application is artificial graphite, and in the X-ray diffraction spectrum of the negative electrode material, the value of Int. 2H(101) / Int. 2H(100) is within the scope of the present application, and the above negative electrode material is applied to a secondary battery, which can improve the fast charging performance and low temperature kinetic performance of the secondary battery.

[0042] In an embodiment of the present application, 3≤a≤18, and exemplary values of a can be 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 or a range defined by any two of the above values. In an embodiment of the present application, 1≤b≤15, and exemplary values of b can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or a range defined by any two of the above values. In an embodiment of the present application, 3≤a≤18, 1≤b≤15, and exemplary values of a can be 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 or a range defined by any two of the above values, and exemplary values of b can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or a range defined by any two of the above values. The negative electrode material of the present application is artificial graphite, and in the scanning electron microscope image of the negative electrode material, the length a of the negative electrode material particles is within the range of the present application, and the above negative electrode material is applied to a secondary battery, which can improve the fast charging performance and low temperature kinetic performance of the secondary battery. The negative electrode material of the present application is artificial graphite, and in the scanning electron microscope image of the negative electrode material, the width b of the negative electrode material particles is within the range of the present application, and the above negative electrode material is applied to a secondary battery, which can improve the fast charging performance and low temperature kinetic performance of the secondary battery. The negative electrode material of the present application is artificial graphite, and in the scanning electron microscope image of the negative electrode material, the length a of the negative electrode material particles and the width b of the negative electrode material particles are within the range of the present application, and the above negative electrode material is applied to a secondary battery, which can further improve the fast charging performance and low temperature kinetic performance of the secondary battery.

[0043] In an embodiment of the present application, 0.1≤FWHM 2H(100) ≤0.2, and exemplary values of FWHM 2H(100) can be 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2 or a range defined by any two of the above values. In an embodiment of the present application, 0.5≤FWHM 2H(101) ≤1.0, and exemplary values of FWHM 2H(101) can be 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0 or a range defined by any two of the above values. In an embodiment of the present application, 0.1≤FWHM 2H(100) ≤0.2, 0.5≤FWHM 2H(101) ≤1.0, and exemplary values of FWHM 2H(100)The value of d002may be 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, or a range between any two of the above values; FWHM 2H(101) The value of d002may be 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, or a range between any two of the above values. The negative electrode material of the present application is artificial graphite, and in the X-ray diffraction spectrum of the negative electrode material, FWHM 2H(100) The value of d002may be 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, or a range between any two of the above values. The negative electrode material of the present application is artificial graphite, and in the X-ray diffraction spectrum of the negative electrode material, FWHM 2H(101) The value of d002may be 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, or a range between any two of the above values. The negative electrode material of the present application is artificial graphite, and in the X-ray diffraction spectrum of the negative electrode material, FWHM 2H(100) The value of d002may be 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, or a range between any two of the above values. The negative electrode material of the present application is artificial graphite, and in the X-ray diffraction spectrum of the negative electrode material, FWHM 2H(101) The value of d002may be 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, or a range between any two of the above values. The negative electrode material of the present application is artificial graphite, and in the X-ray diffraction spectrum of the negative electrode material, FWHM

[0044] In an embodiment of the present application, the interplanar spacing of the (002) crystal plane of the negative electrode material is d 002 , Exemplarily, d 002 may be or a range between any two of the above values. The negative electrode material of the present application is artificial graphite, and the value of d 002 is within the range of the present application, which is larger than the interplanar spacing of the (002) crystal plane of conventional artificial graphite, and thus has more excellent kinetic performance and is more conducive to the embedding and disembedding of lithium ions. The above negative electrode material is applied to a secondary battery, which can further improve the fast charging performance and low-temperature kinetic performance of the secondary battery.

[0045] In an embodiment of the present application, the peak intensity of the (004) crystal plane of the negative electrode material is I 004 , the peak intensity of the (110) crystal plane of the negative electrode material is I 110 , 3.0≤I 004 / I 110 ≤8.0, exemplarily, I 004 / I 110The value can be 3.0, 3.2, 3.4, 3.6, 3.8, 4.0, 4.2, 4.4, 4.6, 4.8, 5.0, 5.2, 5.4, 5.6, 5.8, 6.0, 6.2, 6.4, 6.6, 6.8, 7.0, 7.2, 7.4, 7.6, 7.8, 8.0, or a range of any two of the above values. The negative electrode material of this application is artificial graphite, I 004 / I 110 The value of I within the scope of this application is compared to that of conventional artificial graphite. 004 / I 110 Larger, I 004 / I 110 The value is related to the particle morphology of its natural flake graphite. However, within this range, the anode material also exhibits excellent conductivity and electrolyte wettability. When applied to secondary batteries, the above-mentioned anode material can further improve the fast-charging performance and low-temperature kinetic performance of the secondary battery.

[0046] In one embodiment of this application, in the Raman spectrum of the negative electrode material, at 1300 cm⁻¹... -1 Up to 1400cm -1 Within the range, there is a peak intensity of I. d The first characteristic peak is at 1550 cm⁻¹. -1 Up to 1650cm -1 Within the range, there is a peak intensity of I. g The second characteristic peak is at 2700 cm⁻¹. -1 Up to 2750cm -1 Within the range, there is a peak intensity of I. 2D The third characteristic peak, 0≤I d / I g ≤0.15, for example, I d / I g The value can be 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, or a range of any two of the above values. 0.38≤I 2D / I g ≤0.40, for example, I 2D / I g The value can be 0.38, 0.381, 0.382, 0.383, 0.384, 0.385, 0.386, 0.387, 0.388, 0.389, 0.39, 0.391, 0.392, 0.393, 0.394, 0.395, 0.396, 0.397, 0.398, 0.399, 0.40, or a range consisting of any two of the above values. In this application, the peak intensity I of the first characteristic peak...d The third characteristic peak can reflect the in-plane defects of the negative electrode material. 2D The third characteristic peak can reflect the in-plane defects of the negative electrode material. d The value of I / I g The value of I / I d The value of I / I g The value of I / I d The value of I / I g The value of I / I d The value of I / I g The value of I / I d The value of I / I g The value of I / I 2D The value of I / I g The value of I / I 2D The value of I / I g The value of I / I d The value of I / I g The value of I / I 2D The value of I / I g The value of I / I

[0047] In an embodiment of the present application, the negative electrode material comprises at least one of a first element, a second element or a third element, the first element comprises B, the second element comprises Si, and the third element comprises at least one of Mn, Fe, Co, Ni, Ca, Ti or Cr; the mass percentage of the first element, the second element or the third element is independently X% (0X≤1) based on the mass of the negative electrode material. For example, the value of X can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 or a range between any two of the above values. The negative electrode material comprises at least one of the first element, the second element or the third element, the types and contents of the first element, the second element and the third element are within the scope of the present application, the interplanar spacing of the negative electrode material is larger than that of the conventional artificial graphite, and the powder conductivity of the negative electrode material is higher, which is more conducive to the embedding and extraction of lithium ions. The above negative electrode material is applied to a secondary battery, which can further improve the fast charging performance and low-temperature kinetic performance of the secondary battery.

[0048] In an embodiment of the present application, the powder conductivity σ of the negative electrode material is 600 S / m to 800 S / m. For example, the powder conductivity σ of the negative electrode material can be 600 S / m, 620 S / m, 640 S / m, 660 S / m, 680 S / m, 700 S / m, 720 S / m, 740 S / m, 760 S / m, 780 S / m, 800 S / m or a range between any two of the above values. In the present application, the powder conductivity of the above negative electrode material refers to the powder conductivity of the negative electrode material under a pressure of 100 MPa. The powder conductivity of the negative electrode material of the present application is larger than that of the conventional artificial graphite, which is more conducive to the transmission of electrons. The above negative electrode material is applied to a secondary battery, which can further improve the fast charging performance and low-temperature kinetic performance of the secondary battery.

[0049] In an embodiment of the present application, the specific surface area B of the negative electrode material is 3 m 2 / g to 10 m 2 / g. For example, the specific surface area B 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 a range between any two of the above values. By adjusting the specific surface area B of the negative electrode material within the scope of the present application, the side reaction between the negative electrode material and the electrolyte can be reduced, and the secondary battery has good low-temperature cycle performance and good low-temperature kinetic performance.

[0050] In an embodiment of the present application, the particle size Dv50 of the negative electrode material is 4 μm to 12 μm. For example, the particle size Dv50 of the negative electrode material can be 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, or a range defined by any two of the above values. By adjusting the particle size Dv50 of the negative electrode material within the range of the present application, the side reaction between the negative electrode material and the electrolyte can be reduced, and the secondary battery can have good low-temperature cycle performance and good low-temperature kinetic performance.

[0051] In the present application, Dv50 refers to the particle size at which 50% of the volume of the material is accumulated, in the particle size distribution of the material on a volume basis.

[0052] In an embodiment of the present application, the tap density TD of the negative electrode material is 0.7 g / cm 3 to 1.1 g / cm 3 . For example, the tap density TD of the negative electrode material can be 0.7 g / cm 3 , 0.75 g / cm 3 , 0.8 g / cm 3 , 0.85 g / cm 3 , 0.9 g / cm 3 , 0.95 g / cm 3 , 1 g / cm 3 , 1.05 g / cm 3 , 1.1 g / cm 3 , or a range defined by any two of the above values. By adjusting the tap density TD of the negative electrode material within the range of the present application, the negative electrode sheet can have a high compaction density, and thus the secondary battery can have a high energy density in addition to good low-temperature cycle performance and low-temperature kinetic performance.

[0053] In an embodiment of the present application, the 1C gram capacity of the negative electrode material is 230 mAh / g to 260 mAh / g. For example, the 1C gram capacity of the negative electrode material can be 230 mAh / g, 235 mAh / g, 240 mAh / g, 245 mAh / g, 250 mAh / g, 255 mAh / g, 260 mAh / g, or a range defined by any two of the above values. In the present application, the negative electrode material is prepared by catalytic graphitization of graphene, and has a relatively complete interlayer structure, a relatively large interplanar spacing, and a relatively high powder conductivity, and thus has a relatively high 1C gram capacity. When the above negative electrode material is applied to a secondary battery, the secondary battery can have a high energy density.

[0054] In an embodiment of the present application, the 0.05C gram capacity of the negative electrode material is 350 mAh / g to 365 mAh / g. Illustratively, the 0.05C gram capacity of the negative electrode material can be 350 mAh / g, 352 mAh / g, 355 mAh / g, 357 mAh / g, 360 mAh / g, 362 mAh / g, 365 mAh / g, or a range defined by any two of the above values. In the present application, the negative electrode material is prepared by catalytic graphitization of graphene oxide, and the negative electrode material has a relatively complete interlayer structure, a relatively large interplanar spacing, and a relatively high powder conductivity, thus having a relatively high 0.05C gram capacity. When the above negative electrode material is applied to a secondary battery, the secondary battery has a relatively high energy density.

[0055] In an embodiment of the present application, the graphitization degree of the negative electrode material is 93.5% to 95%. Illustratively, the graphitization degree of the negative electrode material can be 93.5%, 93.7%, 93.9%, 94%, 94.1%, 94.3%, 94.5%, 94.7%, 94.9%, 95%, or a range defined by any two of the above values. The negative electrode material of the present application is applied to a secondary battery, and the secondary battery has good fast-charging performance, low-temperature kinetic performance, and also has a relatively high energy density.

[0056] The second aspect of the present application provides a preparation method of the negative electrode material in any of the foregoing embodiments, which comprises the following steps:

[0057] (1) uniformly mixing a catalyst, graphene oxide, and deionized water to obtain a mixed solution, the mass ratio of the catalyst to the graphene oxide being 0.01 to 0.05; wherein the catalyst comprises at least one of a boron-containing compound, a silicon-containing compound, a metal salt, or a nano metal oxide, the boron-containing compound comprises at least one of boric acid, boron oxide, or sodium borate, the silicon-containing compound comprises at least one of silicon dioxide, silicon carbide, or silicon tetrachloride, the metal salt comprises at least one of manganese chloride, iron nitrate, or nickel nitrate, and the nano metal oxide comprises at least one of triiron dioxides, tricobalt tetroxide, calcium oxide, titanium dioxide, or dichromium trioxide;

[0058] (2) drying the mixed solution to obtain graphene oxide powder;

[0059] (3) the graphene oxide powder is subjected to a first carbonization treatment and then subjected to a second carbonization treatment to obtain the negative electrode material; wherein the temperature T1 of the first carbonization treatment is 800-1200℃, the time t1 of the first carbonization treatment is 4-10h, and the temperature increasing rate v1 of the first carbonization treatment is 8-12℃ / min; the temperature T2 of the second carbonization treatment is 2300-3000℃, the time t2 of the second carbonization treatment is 12-20h, and the temperature increasing rate v2 of the second carbonization treatment is 3-7℃ / min.

[0060] Exemplarily, the mass ratio of the catalyst to the graphene oxide can be 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05, or a range formed by any two of the above values. The temperature T1 of the first carbonization treatment can be 800℃, 850℃, 900℃, 950℃, 1000℃, 1050℃, 1100℃, 1150℃, 1200℃, or a range formed by any two of the above values. The time t1 of the first carbonization treatment can be 4h, 5h, 6h, 7h, 8h, 9h, 10h, or a range formed by any two of the above values. The temperature increasing rate v1 of the first carbonization treatment can be 8℃ / min, 9℃ / min, 10℃ / min, 11℃ / min, 12℃ / min, or a range formed by any two of the above values. The temperature T2 of the second carbonization treatment can be 2300℃, 2400℃, 2500℃, 2600℃, 2700℃, 2800℃, 2900℃, 3000℃, or a range formed by any two of the above values. The time t2 of the second carbonization treatment can be 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, or a range formed by any two of the above values. The temperature increasing rate v2 of the second carbonization treatment can be 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, or a range formed by any two of the above values.

[0061] The kind of graphene oxide in the present application is not particularly limited as long as the purpose of the present application can be achieved. For example, the graphene oxide can be chemically exfoliated graphene oxide or physically exfoliated graphene oxide.

[0062] In the preparation method of the negative electrode material of the present application, the graphene oxide is uniformly mixed with the catalyst first, which can improve the catalytic effect, and the prepared negative electrode material is applied to a secondary battery, which can further improve the cycle stability of the secondary battery.

[0063] The catalyst of the present application is selected from the above-mentioned substances, which can effectively regulate the interplanar spacing of the negative electrode material prepared by catalytic graphitization, and can reduce the temperature of the second carbonization treatment (i.e. the graphitization temperature), thereby reducing energy consumption. In the present application, when the mass ratio of the catalyst to graphene oxide is too low, for example, less than 0.01, the catalytic effect is not obvious, and a conventional graphitization temperature needs to be used for high-temperature graphitization, and the interplanar spacing of the artificial graphite obtained is close to the theoretical value, and the graphitization degree is high, which is not conducive to the rapid deintercalation of lithium ions; when the mass ratio of the catalyst to graphene oxide is too high, for example, greater than 0.05, too much non-active material (impurities) will remain in the negative electrode material, making it difficult to remove impurities, and too high a catalytic degree will also lead to too high a graphitization degree of the negative electrode material and too small an interplanar spacing, which is not conducive to the improvement of the electrochemical performance. By regulating the mass ratio of the catalyst to graphene oxide within the range of the present application, the interplanar spacing of the negative electrode material prepared is larger than that of conventional artificial graphite, and the powder conductivity is higher, which is more conducive to the intercalation and deintercalation of lithium ions. The above-mentioned negative electrode material is applied to a secondary battery, which can further improve the fast-charging performance and low-temperature kinetic performance of the secondary battery.

[0064] The drying method in the present application is not particularly limited as long as the purpose of the present application can be achieved. For example, the mixed solution can be transferred to a rotary evaporator for drying.

[0065] In the present application, the first carbonization treatment and the second carbonization treatment can be carried out in a graphitization furnace under a protective atmosphere, and the protective atmosphere during the first carbonization treatment and the second carbonization treatment can be a nitrogen atmosphere or an argon atmosphere.

[0066] In the present application, the sample subjected to the first carbonization treatment and the second carbonization treatment can be subjected to impurity removal, crushing and grinding treatment.

[0067] The method for regulating the sphericity Ψ and the width-length ratio b / a of the negative electrode material particles in the present application is not particularly limited as long as the purpose of the present application can be achieved. Illustratively, the sphericity Ψ and the width-length ratio b / a of the negative electrode material particles can be regulated by regulating the temperature T1 of the first carbonization treatment. For example, when other conditions are unchanged, increasing the temperature T1 of the first carbonization treatment decreases the sphericity Ψ and the width-length ratio b / a; decreasing the temperature T1 of the first carbonization treatment increases the sphericity Ψ and the width-length ratio b / a.

[0068] The method for regulating the length a and the width b of the negative electrode material particles in the present application is not particularly limited as long as the purpose of the present application can be achieved. Illustratively, the length a and the width b of the negative electrode material particles can be regulated by regulating the temperature T1 of the first carbonization treatment.

[0069] The present application does not particularly limit the method for regulating the value of the FWHM 2H(100) of the negative electrode material, as long as the purpose of the present application can be achieved. Illustratively, the value of the FWHM of the negative electrode material can be regulated by regulating the temperature T1 of the first carbonization treatment.2H(101) the value of Int. 2H(101) the value of Int. 2H(100) The method for regulating the value of the FWHM of the (002) crystal plane of the negative electrode material, the value of the FWHM of the (101) crystal plane of the negative electrode material, and the value of Int. 2H(100) the value of Int. 2H(101) the value of Int. 2H(101) the value of Int. 2H(100) the value of Int.

[0070] The method for regulating the value of the interplanar spacing d 002 of the (002) crystal plane of the negative electrode material, the degree of graphitization is not particularly limited as long as the purpose of the present application can be achieved. Illustratively, the value of the interplanar spacing d 002 of the (002) crystal plane of the negative electrode material, the degree of graphitization can be regulated by regulating the type of catalyst, the mass ratio of catalyst to graphene oxide, or the temperature T2 of the second carbonization treatment. For example, when the type of catalyst is unchanged and the mass ratio of catalyst to graphene oxide is within a certain range, as the mass ratio of catalyst to graphene oxide increases, the value of d 002 decreases, and the degree of graphitization increases; as the mass ratio of catalyst to graphene oxide decreases, the value of d 002 increases, and the degree of graphitization decreases. For example, when other conditions are unchanged, as the temperature T2 of the second carbonization treatment increases, the value of d 002 decreases, and the degree of graphitization increases; as the temperature T2 of the second carbonization treatment decreases, the value of d 002 increases, and the degree of graphitization decreases.

[0071] The method for regulating the value of I 004 / I 110 of the negative electrode material is not particularly limited as long as the purpose of the present application can be achieved. Illustratively, the value of I 004 / I 110 of the negative electrode material can be regulated by regulating the temperature T1 of the first carbonization treatment and the temperature T2 of the second carbonization treatment.

[0072] The method for regulating the value of I d / I g of the negative electrode material, the value of I 2D / I g is not particularly limited as long as the purpose of the present application can be achieved. Illustratively, the value of I d / I g of the negative electrode material, the value of I 2D / I g can be regulated by regulating the temperature T1 of the first carbonization treatment and the temperature T2 of the second carbonization treatment.

[0073] The method for regulating the type and content of the first element, the second element or the third element in the negative electrode material is not particularly limited in the present application, as long as the purpose of the present application can be achieved. Illustratively, the type and content of the first element, the second element or the third element in the negative electrode material can be regulated by regulating the type of the catalyst, the mass ratio of the catalyst to graphene oxide.

[0074] The method for regulating the powder conductivity s of the negative electrode material is not particularly limited in the present application, as long as the purpose of the present application can be achieved. Illustratively, the powder conductivity s of the negative electrode material can be regulated by regulating the type of the catalyst, the mass ratio of the catalyst to graphene oxide or the temperature T2 of the second carbonization treatment.

[0075] The method for regulating the specific surface area B and the particle size Dv50 of the negative electrode material is not particularly limited in the present application, as long as the purpose of the present application can be achieved. Illustratively, the specific surface area B and the particle size Dv50 of the negative electrode material can be regulated by grinding the negative electrode material. Illustratively, when other conditions are unchanged, the specific surface area B of the negative electrode material increases and the Dv50 of the negative electrode material decreases as the grinding time is prolonged; the specific surface area B of the negative electrode material decreases and the Dv50 of the negative electrode material increases as the grinding time is shortened.

[0076] The third aspect of the present application provides a negative electrode tab, which comprises the negative electrode material in any of the preceding embodiments. Therefore, the negative electrode tab provided by the present application has high ionic conductivity and electronic conductivity, and at the same time has high compaction density.

[0077] In the present application, the negative electrode tab comprises a negative electrode current collector and a negative electrode material layer arranged on at least one surface of the negative electrode current collector. The above-mentioned "negative electrode material layer arranged on at least one surface of the negative electrode current collector" means that the negative electrode material layer can be arranged on one surface of the negative electrode current collector along the thickness direction of the negative electrode current collector, or can be arranged on two surfaces of the negative electrode current collector along the thickness direction of the negative electrode current collector. It should be noted that the "surface" here can be the entire area of the negative electrode current collector, or can be part of the area of the negative electrode current collector, which is not particularly limited in the present application, as long as the purpose of the present application can be achieved. The negative electrode current collector is not particularly limited in the present application, as long as the purpose of the present application can be achieved, for example, it can comprise a copper foil, a copper alloy foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foam, a copper foam or a composite current collector, etc.

[0078] The negative electrode material layer of the present application comprises the negative electrode material described above. The negative electrode material layer of the present application further comprises at least one of a conductive agent, a thickening agent or a binder. The present application does not have a particular limitation on the type of conductive agent and binder as long as the purpose of the present application can be achieved, for example, 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, ethylene oxide-containing polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, butadiene-styrene rubber, acrylated butadiene-styrene rubber, epoxy resin or nylon; the conductive agent can include but is not limited to at least one of carbon-based material, metal-based material or conductive polymer. Exemplarily, the carbon-based material can include at least one of natural graphite, artificial graphite, acetylene black, ketjen black or carbon fiber, the metal-based material can include but is not limited to at least one of metal powder or metal fiber, the above-mentioned metal can include but is not limited to at least one of copper, nickel, aluminum or silver; the conductive polymer can include but is not limited to polyphenylene derivative. The present application does not have a particular limitation on the type of thickening agent as long as the purpose of the present application can be achieved, for example, the thickening agent can include but is not limited to sodium carboxymethyl cellulose. The present application does not have a particular limitation on the mass ratio of the negative electrode material, the conductive agent, the thickening agent and the binder in the negative electrode material layer, which can be selected according to actual needs as long as the purpose of the present application can be achieved.

[0079] The present application does not have a particular limitation on the thickness of the negative electrode current collector as long as the purpose of the present application can be achieved, for example, the thickness of the negative electrode current collector is 6 μm to 12 μm. The present application does not have a particular limitation on the thickness of the negative electrode material layer as long as the purpose of the present application can be achieved, for example, the thickness of the single-sided negative electrode material layer is 30 μm to 130 μm. The present application does not have a particular limitation on the thickness of the negative electrode sheet as long as the purpose of the present application can be achieved, for example, the thickness of the negative electrode sheet is 50 μm to 280 μm.

[0080] Optionally, the negative electrode sheet can further comprise a conductive layer, which is located between the negative electrode current collector and the negative electrode material layer. The present application does not have a particular limitation on the composition of the conductive layer, which can be a commonly used conductive layer in the art. The conductive layer comprises a conductive agent and a binder. The present application does not have a particular limitation on the conductive agent and the binder in the conductive layer, which can be at least one of the conductive agent and the binder described above. The present application does not have a particular limitation on the mass ratio of the conductive agent and the binder in the conductive layer, which can be selected by a person skilled in the art according to actual needs as long as the purpose of the present application can be achieved.

[0081] The fourth aspect of the present application provides a secondary battery comprising the negative electrode sheet in any of the foregoing embodiments. Therefore, the secondary battery provided by the present application has good fast charging performance, low temperature kinetic performance, and takes into account a relatively high energy density.

[0082] The secondary battery of the present application further includes a positive electrode tab. The positive electrode tab includes a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector. The “positive electrode material layer disposed on at least one surface of the positive current collector” means that the positive electrode material layer can be disposed on one surface of the positive current collector in the thickness direction of the positive current collector, or can be disposed on both surfaces of the positive current collector in the thickness direction of the positive current collector. It should be noted that the “surface” herein can be the entire area of the positive current collector, or can be a partial area of the positive current collector, and the present application does not have a particular limitation as long as the purpose of the present application can be achieved.

[0083] The positive current collector of the present application is not particularly limited as long as the purpose of the present application can be achieved, and for example, can include an aluminum foil, an aluminum alloy foil, or a composite current collector (e.g., an aluminum-carbon composite current collector), etc.

[0084] The positive electrode material layer of the present application includes a positive electrode active material, and the positive electrode active material includes a substance capable of reversibly intercalating and deintercalating active ions such as lithium ions. The positive electrode material layer can be one layer or multiple layers, and each layer of the multiple layers of the positive electrode material layer can include the same or different positive electrode active material. The positive electrode active material of the present application is not particularly limited as long as the purpose of the present application can be achieved, and for example, the positive electrode active material can include, but is not limited to, at least one of lithium nickel cobalt manganese oxide (e.g., NCM811, NCM622, NCM523, NCM111), lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based material, lithium cobaltate (LiCoO2), lithium manganate, lithium manganese iron phosphate, or lithium titanate. The positive electrode material layer of the present application further includes a conductive agent and a binder, and the conductive agent and the binder in the positive electrode material layer of the present application are not particularly limited as long as the purpose of the present application can be achieved. For example, the conductive agent can include at least one of the above-mentioned conductive agents; and the binder can include at least one of the above-mentioned binders. The mass ratio of the positive electrode active material, the conductive agent, and the binder in the positive electrode material layer of the present application is not particularly limited, and a person skilled in the art can select according to actual needs as long as the purpose of the present application can be achieved.

[0085] The thickness of the positive current collector of the present application is not particularly limited as long as the purpose of the present application can be achieved, and for example, the thickness of the positive current collector is 6 μm to 12 μm. The thickness of the positive electrode material layer of the present application is not particularly limited as long as the purpose of the present application can be achieved, and for example, the thickness of the single-sided positive electrode material layer is 30 μm to 120 μm. The thickness of the positive electrode tab of the present application is not particularly limited as long as the purpose of the present application can be achieved, and for example, the thickness of the positive electrode tab is 50 μm to 250 μm.

[0086] Optionally, the positive electrode sheet can further include a conductive layer between the positive current collector and the positive electrode material layer. The composition of the conductive layer is not particularly limited in the present application and can be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. The conductive agent and the binder in the conductive layer are not particularly limited in the present application and can be at least one of the aforementioned conductive agents and the aforementioned binders. The mass ratio of the conductive agent and the binder in the conductive layer is not particularly limited in the present application and can be selected by a person skilled in the art as needed, as long as the purpose of the present application can be achieved.

[0087] The secondary battery of the present application further includes a separator. The separator is used to separate the positive electrode sheet and the negative electrode sheet, prevent internal short circuit of the secondary battery, allow electrolyte ions to pass freely, and not affect the electrochemical charging and discharging process. The separator is not particularly limited in the present application as long as the purpose of the present application can be achieved. For example, the material of the separator can include, but is not limited to, at least one of polyethylene (PE), polyolefin (PO) based on polypropylene (PP), polyester (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex, or aramid; and the type of the separator can include at least one of woven film, non-woven film, microporous film, composite film, calendered film, or spunlaced film.

[0088] In the present application, the separator can include a base material and a surface treatment layer. The base material can be a non-woven fabric or a composite film having a porous structure, and the material of the base material can include at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide. Optionally, a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric, or a polypropylene-polyethylene-polypropylene porous composite film can be used. Optionally, a surface treatment layer is provided on at least one surface of the base material, and the surface treatment layer can be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic substance. For example, the inorganic layer includes inorganic particles and a binder, and the inorganic particles are not particularly limited in the present application and can include at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. The binder is not particularly limited in the present application and can be at least one of the aforementioned binders. The mass ratio of the conductive agent and the binder in the conductive layer is not particularly limited in the present application and can be selected by a person skilled in the art as needed, as long as the purpose of the present application can be achieved.

[0089] The secondary battery of the present application further includes an electrolyte. The electrolyte includes a lithium salt. The kind of the lithium salt is not particularly limited in the present application, and a lithium salt known in the art can be used. Exemplarily, the lithium salt can include, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium bis-trifluoromethanesulfonimide (LiN(CF3SO2)2, LiTFSI), lithium bis(fluorosulfonyl)imide (Li(N(SO2F)2), LiFSI), lithium difluorophosphate (LiPO2F2), lithium bis(oxalato)borate (LiB(C2O4)2, LiBOB), or lithium difluoro(oxalato)borate (LiBF2(C2O4), LiDFOB). The mass percentage content of the lithium salt in the electrolyte is not particularly limited in the present application, as long as the object of the present application can be achieved. The electrolyte includes a non-aqueous organic solvent. The non-aqueous organic solvent is not particularly limited in the present application, as long as the object of the present application can be achieved. For example, the non-aqueous organic solvent can include at least one of a carbonate compound, a carboxylate compound, an ether compound, or other organic solvents. The carbonate compound can include, but is not limited to, at least one of a chain carbonate compound, a cyclic carbonate compound, or a fluorinated carbonate compound. The chain carbonate compound can include, but is not limited to, at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), or methyl ethyl carbonate (EMC). The cyclic carbonate compound can include, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), or vinyl ethylene carbonate (VEC). The fluorinated carbonate compound can include, but is not limited to, at least one of fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methyl ethylene carbonate, 1-fluoro-1-methyl ethylene carbonate, 1,2-difluoro-1-methyl ethylene carbonate, 1,1,2-trifluoro-2-methyl ethylene carbonate, or trifluoromethyl ethylene carbonate. The carboxylate compound can include, but is not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, or propyl propionate. The ether compound can include, but is not limited to, at least one of dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyl tetrahydrofuran, or tetrahydrofuran. The other organic solvents can include, but is not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidinone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, or phosphoric acid ester.The mass percentage content of the non-aqueous organic solvent in the electrolyte is not particularly limited in the present application, as long as the purpose of the present application can be achieved.

[0090] The secondary battery of the present application further includes a packaging bag for containing the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte, and other components known in the art in the secondary battery, which are not limited in the present application. The packaging bag is not particularly limited in the present application, and can be a packaging bag known in the art, as long as the purpose of the present application can be achieved. For example, an aluminum-plastic film packaging bag can be used.

[0091] The type of the secondary battery is not particularly limited in the present application, and it can include any device that generates an electrochemical reaction. In the present application, the secondary battery can include, but is not limited to, a lithium metal secondary battery, a lithium ion secondary battery (lithium ion battery), a lithium polymer secondary battery or a lithium ion polymer secondary battery (lithium ion polymer battery), etc.

[0092] The preparation process of the secondary battery of the present application is well known to those skilled in the art, and is not particularly limited in the present application, for example, it can include, but is not limited to, the following steps: stacking the positive electrode sheet, the separator and the negative electrode sheet in order, and winding, folding, etc. according to the need to obtain a wound electrode assembly structure, placing the electrode assembly into a packaging bag, injecting the electrolyte into the packaging bag and sealing it to obtain a secondary battery; or stacking the positive electrode sheet, the separator and the negative electrode sheet in order, then fixing the four corners of the entire stack structure with adhesive tape to obtain a stack structure electrode assembly, placing the electrode assembly into a packaging bag, injecting the electrolyte into the packaging bag and sealing it to obtain a secondary battery. In addition, a current overprotection element, a guide plate, etc. can also be placed in the packaging bag as needed to prevent the pressure inside the secondary battery from rising and overcharging and discharging.

[0093] The fifth aspect of the present application provides an electronic device comprising the secondary battery of any of the preceding embodiments. Therefore, the electronic device provided by the present application has good use performance.

[0094] The type of the electronic device is not particularly limited in the present application, and it can be any electronic device known in the prior art. In some embodiments, 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 head-mounted stereo headset, 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 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, etc.

[0095] Examples

[0096] Hereinafter, the embodiments of the present application will be described more specifically by citing examples and comparative examples. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are on a mass basis.

[0097] Test methods and apparatus:

[0098] X-ray diffraction (XRD) test:

[0099] A lithium ion battery that was completely discharged (meaning discharged to 3.0 V) was disassembled, and the negative electrode sheet was taken out. The negative electrode sheet was soaked in dimethyl carbonate (DMC) for 20 min, and then rinsed with DMC and acetone in turn. Thereafter, the negative electrode sheet was placed in an oven and baked at 80°C for 12 h to obtain a treated negative electrode sheet. The negative electrode material layer on the negative electrode sheet was scraped off with a spatula, and the powder of the scraped-off negative electrode material layer was heat-treated at 400°C for 4 h in a tube furnace under the condition of argon protection to obtain a negative electrode material.

[0100] The negative electrode material was tested by using an X-ray powder diffractometer (instrument model: Bruker D8 ADVANCE), with CuKa as the target material, a voltage of 40 KV, a current of 40 mA, a scanning angle range of 5° to 80°, a scanning step length of 0.00836°, and a time of 0.3 s for each step length. At the same time, 15% of silicon powder by mass based on the mass of the negative electrode material was added, and according to the principle of the internal standard method, the peak position of the silicon standard was used to calibrate the instrument and test error, so as to accurately calculate the characteristic peak position of the negative electrode material. The X-ray diffraction spectrum of the negative electrode material was obtained, and the half-peak width FWHM of the 2H(100) characteristic peak of the negative electrode material, the half-peak width FWHM of the 2H(101) characteristic peak of the negative electrode material, the peak intensity Int. of the 2H(101) characteristic peak of the negative electrode material, the ratio of the peak intensity Int. of the 2H(100) characteristic peak to the peak intensity Int. of the 2H(101) characteristic peak of the negative electrode material, the interplanar spacing d of the (002) crystal plane, the graphitization degree, the ratio of the peak intensity I of the (004) crystal plane to the peak intensity I of the (110) crystal plane, and the like were obtained. 2H(100) 2H(101) 2H(101) 2H(100) 002 004 110 002

[0101] Scanning electron microscope (SEM) test:

[0102] ​​​​​​​​The lithium ion battery was completely discharged (referring to discharge to 3.0 V), disassembled, and the negative electrode sheet was taken out. The negative electrode sheet was soaked in dimethyl carbonate (DMC) for 20 min, then rinsed with DMC and acetone in turn, and then placed in an oven and baked at 80°C for 12 h to obtain the treated negative electrode sheet. The negative electrode material layer on the negative electrode sheet was scraped off with a scraper, and the powder of the scraped negative electrode material layer was heat-treated at 400°C for 4 h in a tube furnace under the condition of argon protection to obtain the negative electrode material.

[0103] According to the national standard GB / T 38887-2020, a scanning electron microscope with a model number of ZEIS-SEM (Sigma-02-33) was used to paste the negative electrode material dispersed in ethanol on the sample table with conductive glue. The sample table was loaded into the sample chamber and ensured to be fixed, and the sample chamber was closed. Vacuum was started, and the following parameters were set: acceleration voltage 10 kV, diaphragm 30 μm, working distance 2 mm to 9 mm, current 2.335 A. After the parameters were determined, the test was started, the high voltage was turned on, the focusing was performed, the magnification was 3000 times, and the negative electrode material was photographed. The negative electrode material particles in the field of view were selected, and the width b, length a, equivalent circle area perimeter, and particle projection area perimeter of each negative electrode material particle were obtained by image analysis software. The sphericity of the negative electrode material particles was the ratio of the equivalent circle area perimeter of the particles to the particle projection area perimeter, and the average value of the sphericity of the negative electrode material particles in the field of view was taken as the sphericity of the negative electrode material particles. The average value of the aspect ratio of the negative electrode material particles in the field of view was taken as the aspect ratio of the negative electrode material particles.

[0104] Raman spectrum test:

[0105] The lithium ion battery was completely discharged (referring to discharge to 3.0 V), disassembled, and the negative electrode sheet was taken out. The negative electrode sheet was soaked in dimethyl carbonate (DMC) for 20 min, then rinsed with DMC and acetone in turn, and then placed in an oven and baked at 80°C for 12 h to obtain the treated negative electrode sheet. The negative electrode material layer on the negative electrode sheet was scraped off with a scraper, and the powder of the scraped negative electrode material layer was heat-treated at 400°C for 4 h in a tube furnace under the condition of argon protection to obtain the negative electrode material.

[0106] The Raman spectrum of the negative electrode material was tested by a laser microscopic confocal Raman spectrometer (model number: HR Evolution, HORIBA Scientific Instrument Division). The peak intensity of the negative electrode material at 1350 cm -1 was I d , the peak intensity at 1580 cm -1 was I g , and the peak intensity at 2700 cm -1 was I 2D . The I d / I g The value is obtained by the following method: Take the obtained negative electrode material, test 100 points, and obtain 100 corresponding I values. d / I g The value of 100 I values ​​was calculated. d / I g The average value of I is the negative electrode material. d / I g The value of I in the negative electrode material. 2D / I g The test method for the value is the same as above.

[0107] Element content test in anode materials:

[0108] The types of elements in the negative electrode material and the percentage of each element by mass in the negative electrode material were tested using a German Elementar elemental analyzer.

[0109] Powder conductivity test:

[0110] The negative electrode material was subjected to pressure conductivity testing using a powder resistance meter (model PRCD1100, IEST-Yuaneng Technology). The four-probe testing principle was used, with the applied pressure range from 10MPa to 200MPa, the pressure interval being 10MPa, and the holding time after each pressure application being 10s. In this application, the powder conductivity of the negative electrode material at a pressure of 100MPa was taken as the powder conductivity σ of the negative electrode material.

[0111] Specific surface area test:

[0112] According to the national standard "Determination of Specific Surface Area of ​​Solid Substances by Gas Adsorption BET Method" (GB / T 19587-2017), the specific surface area of ​​the negative electrode material was tested by nitrogen adsorption using a specific surface area analyzer (model TristarⅡ3020M).

[0113] Particle size testing:

[0114] The particle size of the negative electrode material was measured using a Malvern particle size analyzer (MasterSizer 2000). 0.02 g of negative electrode material particles were added to a 50 mL clean beaker, along with 20 mL of ethanol as a dispersant. The mixture was ultrasonicated for 30 min in a 120 W ultrasonic cleaner to completely disperse the negative electrode material particles in the ethanol, obtaining a sample dispersion. The particle size Dv50 of the negative electrode material particles was then measured using the Malvern particle size analyzer.

[0115] Tap density test:

[0116] The tap density TD of the negative electrode material was tested by a density analyzer (model: GeoPyc 1365) according to the national standard GB / T 24533-2019.

[0117] 0.05C and 1C capacity tests of the negative electrode material:

[0118] Referring to the national standard: GB / T 24533-2019, Lithium Ion Battery Graphite Negative Electrode Material, after mixing, coating, rolling, cutting, and drying, the negative electrode material was prepared into a negative electrode sheet (the specific process was consistent with the negative electrode sheet preparation method in Example 1-1), the negative electrode sheet was cut into small round pieces with a diameter of 14 mm, a lithium sheet with a diameter of 16 mm was used as the counter electrode, the separator in Example 1-1 was used, and a button cell was assembled for testing. The button cell was kept at 25°C for 12h, discharged at 0.05C constant current to 5.0mV, rested for 5min, discharged at 50μA constant current to 5.0mV, rested for 5min, and discharged at 20μA constant current to 5.0mV; charged at 0.1C constant current to 2.0V, and the charge capacity of the button cell at this time was recorded as the 0.05C capacity. Then, the button cell was kept at 25°C for 2h, discharged at 1C constant current to 5.0mV, rested for 5min, and charged at 0.1C constant current to 2.0V, and the charge capacity of the button cell at this time was recorded as the 1C capacity.

[0119] Direct current resistance (DCR) test:

[0120] In an environment of 0°C, the lithium ion battery was charged at 1C constant current to 4.48V, and then charged at 4.48V constant voltage to 0.05C, and rested for 30min. Then, the lithium ion battery was discharged at 0.5C constant current to a state of charge (SOC) of 10% SOC. The voltage value was recorded as U by discharging at 0.1C constant current for 10s, and the voltage value was recorded as U' by discharging at 1C constant current for 1s. The above charging and discharging steps were repeated 5 times.

[0121] The direct current resistance DCR of the lithium ion battery at 0°C was calculated by the following formula:

[0122] DCR = (U'-U) / (0.1C-1C), wherein "1C" is the current value for completely discharging the capacity of the lithium ion battery in 1 hour, and "0.1C" is the current value for completely discharging the capacity of the lithium ion battery in 10 hours.

[0123] The average value of the direct current resistances DCR of the 5 discharging steps was taken as the final result.

[0124] The DCR described in the present application refers to the direct current resistance of the lithium ion battery at a state of charge (SOC) of 10%.

[0125] Charge rate performance test:

[0126] The lithium ion battery is repeatedly charged and discharged by the following steps, and the capacity 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 voltage reaches 4.48V, and the charging is stopped when the current is lower than 0.05C. The above charging mode is CC+CV charging mode, and then it is placed for 5min. Then discharge at 0.2C constant current to 3V, and place for 5min to ensure the integrity of the subsequent charging and discharging process. Then charge the lithium ion battery at a charge rate of 3C according to the aforementioned CC+CV charging mode, and calculate the capacity ratio of the CC stage at 3C charge rate.

[0127] The calculation formula is as follows:

[0128] The capacity ratio of the CC stage at 3C charge rate = [the charging capacity of the CC stage at 3C charge rate / the total capacity of (CC+CV) charging at 3C charge rate] x 100%.

[0129] 5 lithium ion batteries of each comparative example and example are tested, and the average value of the capacity ratio of the CC stage at 3C charge rate of the 5 batteries is taken as the final result.

[0130] In this application, the higher the capacity ratio of the CC stage at 3C charge rate of the lithium ion battery, the larger the capacity of the lithium ion battery at high rate charging, and the smaller the polarization of the lithium ion battery, which indicates that the charging rate performance of the lithium ion battery is better; the lower the capacity ratio of the CC stage at 3C charge rate of the lithium ion battery, the smaller the capacity of the lithium ion battery at high rate charging, and the larger the polarization of the lithium ion battery, which indicates that the charging rate performance of the lithium ion battery is worse.

[0131] -10℃ capacity retention rate test:

[0132] In a 25℃ environment, the lithium ion battery is first charged and discharged, and charged at 0.5C constant current to a voltage of 4.48V, and charged at 4.48V constant voltage to a current of 0.05C, and then discharged at 0.2C constant current to 3V. The discharge capacity of the lithium ion battery is A; then the temperature is lowered to-10℃, and the lithium ion battery is placed for 6h, and charged and discharged in the-10℃ environment according to the above charging and discharging steps, and the discharge capacity of the lithium ion battery at-10℃ is B, and the-10℃ capacity retention rate is calculated according to the following formula.

[0133] -10℃ capacity retention rate = B / A x 100%.

[0134] Five lithium ion batteries of each of the comparative examples and the examples were tested, and the average of the -10℃ capacity retention rates of the five lithium ion batteries was taken as the final result.

[0135] Example 1-1

[0136] Preparation of the negative electrode material

[0137] (1) 5 g of the catalyst boric acid was added to 200 mL of deionized water and stirred to dissolve uniformly to obtain a catalyst solution. The catalyst solution was added to 1 kg of an aqueous graphene oxide solution and stirred to disperse uniformly to obtain a mixed solution. The solid content of the aqueous graphene oxide solution was 10 wt%, and the mass ratio of the catalyst to the graphene oxide was 0.05.

[0138] (2) The mixed solution was transferred to a rotary evaporator, and the aqueous solution was evaporated to dryness to obtain graphene oxide powder.

[0139] (3) The graphene oxide powder was transferred to a graphitization furnace, and a first carbonization treatment was performed under a nitrogen atmosphere. The first carbonization treatment had a temperature increase rate v1 of 10 ℃ / min, a temperature T1 of 1000 ℃, and a time t1 of 6 h. Subsequently, a second carbonization treatment was performed under a nitrogen atmosphere. The second carbonization treatment had a temperature increase rate v2 of 5 ℃ / min, a temperature T2 of 2700 ℃, and a time t2 of 16 h to obtain a carbonized sample. Finally, the carbonized sample was subjected to impurity removal, crushing, and grinding to obtain the negative electrode material.

[0140] The negative electrode material comprises a first element B, and the mass percentage X% of the first element B in the negative electrode material is 0.5%. The interplanar spacing d of the (002) crystal plane of the negative electrode material is 0.336 nm. 002 The graphitization degree, 0.05C specific capacity, 1C specific capacity, the sphericity Ψ, b / a, I d / I g , I 2D / I g , I 004 / I 110 , a, b, Int. 2H(101) / Int. 2H(100) , FWHM 2H(100) , FWHM 2H(101) , powder conductivity σ under a pressure of 100 MPa, specific surface area B, particle size Dv50, and tap density TD are shown in Table 2.

[0141] Preparation of the negative electrode sheet

[0142] The prepared negative electrode material, thickening agent sodium carboxymethyl cellulose (CMC-Na), and binder styrene-butadiene rubber (SBR) were mixed in a mass ratio of 95:2:3, deionized water was added as a solvent, and a negative electrode slurry with a solid content of 75 wt% was prepared. The negative electrode slurry was uniformly coated on one surface of a negative electrode current collector copper foil with a thickness of 12 μm, and dried at 120°C to obtain a negative electrode tab with a single-side coated negative electrode material layer. Then, the above steps were repeated on the other surface of the copper foil to obtain a negative electrode tab with a double-side coated negative electrode material layer. The negative electrode tab was dried at 120°C under vacuum for 1 h, and then subjected to cold pressing, cutting, and slitting to obtain a negative electrode tab with a size of 78 mm x 875 mm. The single-side thickness of the negative electrode material layer after cold pressing was 65 μm.

[0143] <Preparation of a positive electrode tab>

[0144] The positive electrode active material lithium cobaltate (LiCoO2), conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 96:2:2, N-methyl pyrrolidone (NMP) was added as a solvent, and a positive electrode slurry with a solid content of 70 wt% was prepared. The positive electrode slurry was uniformly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 12 μm, and dried at 120°C for 1 h to obtain a positive electrode tab with a single-side coated positive electrode material layer. Then, the above steps were repeated on the other surface of the aluminum foil to obtain a positive electrode tab with a double-side coated positive electrode material layer. The positive electrode tab was dried at 120°C under vacuum for 1 h, and then subjected to cold pressing, cutting, and slitting to obtain a positive electrode tab with a size of 74 mm x 867 mm. The single-side thickness of the positive electrode material layer after cold pressing was 50 μm.

[0145] <Preparation of an electrolyte>

[0146] In an argon atmosphere glove box with a water content of less than 10 ppm, ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) were mixed in a weight ratio of 1:1:1 to obtain a base solvent, and then lithium salt lithium hexafluorophosphate (LiPF6) was added to the base solvent to obtain an electrolyte. The mass percentage of the lithium salt in the electrolyte was 12.5%, and the balance was the base solvent.

[0147] <Preparation of a separator>

[0148] A porous polyethylene film (provided by Celgard) with a thickness of 7 μm was used as a separator.

[0149] <Preparation of a lithium ion battery>

[0150] The positive electrode sheet, the separator, the negative electrode sheet and the separator are stacked in order, the separator is between the positive electrode sheet and the negative electrode sheet to play a role of isolation, and the electrode assembly is obtained by winding. After the welding of the tab, the electrode assembly is placed in an aluminum plastic film packaging bag, dried at 80 DEG C, and then injected with electrolyte. After vacuum packaging, standing, formation (formation upper limit voltage is 4.5V, formation temperature is 70 DEG C, and formation standing time is 2h), degassing and edge cutting, the lithium ion battery is obtained.

[0151] Examples 1-2 to 1-16

[0152] Except that the related preparation parameters are adjusted according to Table 1 in the <preparation of the negative electrode material>, the rest is the same as Example 1-1. Among them, when the mass ratio of the catalyst to the graphene oxide changes, the mass of the catalyst added changes, and the mass and solid content of the graphene oxide aqueous solution remain unchanged.

[0153] Comparative Example 1

[0154] Except that the negative electrode material is prepared according to the following method and the related preparation parameters are adjusted according to Table 1, the rest is the same as Example 1-1.

[0155] <Preparation of the negative electrode material>

[0156] 500g of needle coke is placed in a graphitization furnace for first carbonization treatment under a nitrogen atmosphere, the first carbonization treatment has a temperature rise rate v1 of 10 DEG C / min, a temperature T1 of 1000 DEG C, and a time t1 of 6h; then second carbonization treatment is carried out under a nitrogen atmosphere, the second carbonization treatment has a temperature rise rate v2 of 5 DEG C / min, a temperature T2 of 3000 DEG C, and a time t2 of 18h, to obtain a carbonized sample. Finally, the carbonized sample is subjected to impurity removal, crushing and grinding treatment to obtain the negative electrode material. In this application, the above-mentioned "conventional artificial graphite" refers to the negative electrode material prepared in Comparative Example 1.

[0157] Comparative Example 2

[0158] Except that the related preparation parameters are adjusted according to Table 1 in the <preparation of the negative electrode material>, the rest is the same as Comparative Example 1.

[0159] Comparative Example 3

[0160] Except that the related preparation parameters are adjusted according to Table 1 in the <preparation of the negative electrode material>, the rest is the same as Example 1-1. Among them, when the mass ratio of the catalyst to the graphene oxide changes, the mass of the catalyst added changes, and the mass and solid content of the graphene oxide aqueous solution remain unchanged.

[0161] The preparation parameters and electrical performance parameters of each example and comparative example are shown in Tables 1 to 3.

[0162] Table 1

[0163]

[0164] Note: In Table 1, " / " represents no relevant preparation parameters.

[0165] Table 2

[0166]

[0167] Table 3

[0168]

[0169]

[0170] As can be seen from Table 1, Table 2 and Table 3, and Examples 1-1 to 1-16 and Comparative Examples 1 to 3, when the negative electrode material is prepared by the preparation method of the present application, and each preparation parameter is within the range of the present application, the 0.05C specific capacity of the negative electrode material is higher, and the 1C specific capacity is higher. When the lithium ion battery is prepared by using the above negative electrode material, the lithium ion battery has lower DCR, higher capacity ratio at the CC stage at 3C charging rate, and higher capacity retention rate at -10°C, thereby indicating that when the negative electrode material is prepared by the preparation method of the present application, and each preparation parameter is within the range of the present application, and the above negative electrode material is applied to the lithium ion battery, the lithium ion battery has lower direct current impedance, better fast charging performance and low temperature kinetic performance, and also has higher energy density.

[0171] As can be seen from Examples 1-1 to 1-4 and Comparative Examples 1 to 3, the mass ratio of the catalyst to graphene oxide plays a key role in regulating the interlayer spacing d 002 of the (002) crystal plane of the negative electrode material and the graphitization degree. Compared with Example 1-1, in Comparative Example 1, no catalyst is added, the graphitization temperature is higher, the energy consumption is larger, and the interlayer spacing of the prepared negative electrode material is smaller, and the graphitization degree is higher. Compared with Example 1-1, the conditions of the first carbonization treatment and the second carbonization treatment are the same in Comparative Example 2, no catalyst is added in Comparative Example 2, and the interlayer spacing d 002 of the (002) crystal plane of the negative electrode material of Comparative Example 2 is too large, and the graphitization degree is too low, which is not conducive to the integrity of the interlayer structure of the negative electrode material and the capacity performance. With the increase of the mass ratio of the catalyst to graphene oxide, the content of the catalyst increases, and under high-temperature carbonization treatment, the interlayer recombination of the negative electrode material can be induced, so that the interlayer order degree increases. With the increase of the content of the catalyst, the interlayer spacing d 002decreases, and the graphitization degree increases. When the mass ratio of the catalyst to the graphene oxide is too large, such as Comparative Example 3, too much catalyst makes the graphitization degree of the negative electrode material too high, the interplanar spacing d 002 of the (002) crystal plane is too small, which is not conducive to the desolvation, intercalation and extraction of lithium ions, and is not conducive to the capacity of the negative electrode material.

[0172] As can be seen from Example 1-1, Example 1-5, Example 1-6, Comparative Example 1 and Comparative Example 2, the higher the temperature T2 of the second carbonization treatment, the smaller the interplanar spacing d 002 of the (002) crystal plane of the negative electrode material, and the higher the graphitization degree. When the catalyst content is kept constant, the temperature T2 of the second carbonization treatment, i.e. the graphitization temperature, also has an optimal range. Compared with Example 1-1, the interplanar spacing d 002 of the (002) crystal plane of the negative electrode material in Example 1-6 is larger, but the 1C capacity is relatively small. This is because lithium ions need a suitable interplanar spacing to induce their desolvation during intercalation, and too large an interplanar spacing will also affect the capacity of the negative electrode material. Comparative Example 1 and Comparative Example 2 do not add catalysts, and a higher temperature T2 of the second carbonization treatment is required to achieve a higher graphitization degree, but the energy consumption and cost required will be greatly increased.

[0173] As can be seen from Example 1-1, Example 1-7 and Example 1-8, the temperature T1 of the first carbonization treatment affects the release of the carbon layer structure of the graphene oxide powder during the first carbonization treatment, and the temperature T1 of the first carbonization treatment has little effect on the interplanar spacing d 002 of the (002) crystal plane and the graphitization degree of the negative electrode material, but it affects the sphericity Ψ and the width-length ratio b / a of the negative electrode material particles. The higher the temperature T1 of the first carbonization treatment, the higher the disorder degree between the carbon layers of the graphene oxide powder after the first carbonization treatment, which will affect the growth of the carbon layers during the subsequent second carbonization treatment, so the sphericity Ψ of the negative electrode material is lower, and the width-length ratio b / a is lower. The morphology and stacking mode of the negative electrode material particles will also indirectly affect the fast-charging performance and low-temperature kinetic performance of the lithium ion battery prepared from the negative electrode material.

[0174] The type of catalyst affects the interplanar spacing of the negative electrode material, and further affects the fast-charging performance and low-temperature kinetic performance of the lithium ion battery. As can be seen from Example 1-1, Example 1-9 to Example 1-12, by adjusting the type of catalyst within the scope of the present application, the negative electrode material can have a relatively large interplanar spacing, while the temperature required for catalytic graphitization can be reduced, and the energy consumption can be reduced; at the same time, the lithium ion battery has a lower direct current impedance, better fast-charging performance and low-temperature kinetic performance.

[0175] The time t1 of the first carbonization treatment affects the release of the carbon layer structure of the negative electrode material, thereby affecting the fast-charging performance and low-temperature kinetic performance of the lithium-ion battery. As shown in Examples 1-1, 1-13, and 1-14, by adjusting the time t1 of the first carbonization treatment within the scope of this application, the negative electrode material can fully release structural pressure during the first carbonization treatment, resulting in a more complete interlayer structure. The lithium-ion battery ultimately prepared has lower DC resistance, better fast-charging performance, and better low-temperature kinetic performance.

[0176] The time t2 of the second carbonization treatment affects the growth of the carbon layer in the negative electrode material during the second carbonization process, thereby affecting the fast-charging performance and low-temperature kinetic performance of the lithium-ion battery. As can be seen from Examples 1-1, 1-15, and 1-16, by adjusting the time t2 of the second carbonization treatment within the scope of this application, a more regular graphitized carbon layer can be obtained in the negative electrode material, and the final prepared lithium-ion battery has lower DC resistance, better fast-charging performance, and better low-temperature kinetic performance.

[0177] Depend on Figure 1 It can be seen that in the X-ray diffraction pattern of the negative electrode material in Example 1-1 of this application, there is a 2H(100) characteristic peak in the range of 42° to 43°, a 2H(101) characteristic peak in the range of 44° to 45°, and two characteristic peaks in the range of 41° to 47°, indicating that the negative electrode material in Example 1-1 of this application is artificial graphite.

[0178] Depend on Figure 2 As can be seen from the scanning electron microscope images of the negative electrode material in Embodiments 1-1 of this application, the morphology of the negative electrode material is flat and similar to that of natural flake graphite, unlike conventional artificial graphite. The length a of the negative electrode material particles is 5.9 μm, and the width b of the negative electrode material particles is 3.9 μm.

[0179] Depend on Figure 3 As can be seen from the Raman spectrum of the negative electrode material in Embodiments 1-1 of this application, the negative electrode material at 1300 cm⁻¹... -1 Up to 1400cm -1 The first characteristic peak is found within the range, at 1550 cm⁻¹. -1 Up to 1650cm -1 There is a second characteristic peak within the range, at 2700 cm⁻¹. -1 Up to 2750cm -1 There is a third characteristic peak within the range.

[0180] Depend on Figure 4It can be seen that the powder conductivity of the negative electrode material in Example 1-1 under a pressure of 100 MPa is 700 S / m, indicating that the negative electrode material has excellent electronic conductivity, and the lithium ion battery has low direct current impedance, good fast charging performance, and low temperature kinetic performance.

[0181] It should be noted that the relational terms herein such as first and second and the like are used solely to distinguish one entity or action from another, without necessarily requiring or implying any actual relationship or order between or among such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0182] Each of the embodiments in the specification is described in a relevant manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the difference from other embodiments.

[0183] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A negative electrode material, the negative electrode material being artificial graphite; in an X-ray diffraction spectrum of the negative electrode material, a 2H (100) characteristic peak exists at 2Q in a range of 42° to 43°, a 2H (101) characteristic peak exists at 2Q in a range of 44° to 45°, and two characteristic peaks exist at 2Q in a range of 41° to 47°; in a scanning electron microscope image of the negative electrode material, a sphericity of the negative electrode material particle is Ψ, a length of the negative electrode material particle is a μm, and a width of the negative electrode material particle is b μm, 0.6 ≤ Ψ ≤ 0.7, and 0.6 ≤ b / a ≤ 0.

7.

2. The negative electrode material of claim 1, wherein, In the X-ray diffraction spectrum of the negative electrode material, the half-peak width of the 2H(100) characteristic peak is FWHM 2H(100) , the half-peak width of the 2H(101) characteristic peak is FWHM 2H(101) , the peak intensity of the 2H(100) characteristic peak is Int. 2H(100) , the peak intensity of the 2H(101) characteristic peak is Int. 2H(101) , 1.5≤Int. 2H(101) / Int. 2H(100) ≤2.

0.

3. The negative electrode material according to claim 1 or 2, wherein 3 ≤ a ≤ 18, and / or 1 ≤ b ≤ 15.

4. The negative electrode material of claim 2, wherein, 0.1 < FWHM 2H(100) ≤0.2, and / or 0.5 < FWHM 2H(101) ≤1.

0.

5. The negative electrode material according to claim 1 or 2, wherein The negative electrode material satisfies at least one of the following conditions: (1) the interplanar spacing of the (002) crystal plane of the negative electrode material is d 002 , (2) the peak intensity of the (004) crystal face of the negative electrode material is I 004 , the peak intensity of the (110) crystal face of the negative electrode material is I 110 , 3.0≤I 004 / I 110 ≤8.0; (3) In the Raman spectrum of the negative electrode material, at 1300 cm⁻¹ -1 Up to 1400cm -1 There is a peak intensity of I within the range d The first characteristic peak is at 1550 cm⁻¹. -1 Up to 1650cm -1 There is a peak intensity of I within the range g The second characteristic peak is at 2700 cm⁻¹. -1 Up to 2750cm -1 There is a peak intensity of I within the range 2D The third characteristic peak, 0≤I d / I g ≤0.15, 0.38≤I 2D / I g ≤0.40; (4) the negative electrode material comprises at least one of a first element, a second element, or a third element, the first element comprises B, the second element comprises Si, and the third element comprises at least one of Mn, Fe, Co, Ni, Ca, Ti, or Cr; a mass percentage content of the first element, the second element, or the third element is X% independently, and 0 < X ≤ 1 based on a mass of the negative electrode material.

6. The negative electrode material according to claim 1 or 2, wherein The negative electrode material satisfies at least one of the following characteristics: (1) a powder conductivity σ is 600 S / m to 800 S / m; (2) the specific surface area B is 3 m 2 / g to 10 m 2 / g; (3) a particle size Dv50 is 4 μm to 12 μm; (4) tapped density TD is 0.7 g / cm 3 up to 1.1 g / cm 3 .

7. A preparation method of the negative electrode material according to any one of claims 1 to 6, comprising the following steps: (1) mixing a catalyst, graphene oxide, and deionized water uniformly to obtain a mixed solution, a mass ratio of the catalyst to the graphene oxide is 0.01 to 0.05; wherein the catalyst comprises at least one of a boron-containing compound, a silicon-containing compound, a metal salt, or a nano metal oxide, the boron-containing compound comprises at least one of boric acid, boron oxide, or sodium borate, the silicon-containing compound comprises at least one of silicon dioxide, silicon carbide, or silicon tetrachloride, the metal salt comprises at least one of manganese chloride, ferric nitrate, or nickel nitrate, and the nano metal oxide comprises at least one of triiron dioxides, tricobalt tetroxide, calcium oxide, titanium dioxide, or dichromium trioxide; (2) drying the mixed solution to obtain graphene oxide powder; (3) performing first carbonization treatment on the graphene oxide powder, and then performing second carbonization treatment to obtain the negative electrode material; wherein a temperature T1 of the first carbonization treatment is 800°C to 1200°C, a time t1 of the first carbonization treatment is 4h to 10h, and a heating rate v1 of the first carbonization treatment is 8°C / min to 12°C / min; a temperature T2 of the second carbonization treatment is 2300°C to 3000°C, a time t2 of the second carbonization treatment is 12h to 20h, and a heating rate v2 of the second carbonization treatment is 3°C / min to 7°C / min.

8. A negative electrode tab comprising the negative electrode material according to any one of claims 1 to 6.

9. A secondary battery comprising the negative electrode tab according to claim 8.

10. An electronic device comprising the secondary battery according to claim 9.

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