Lithium ion battery negative electrode material, preparation method thereof and lithium ion battery

Abstract

The application discloses the technical field of lithium ion batteries, and particularly relates to a lithium ion battery negative electrode material, a preparation method thereof and a lithium ion battery. The lithium ion battery negative electrode material is graphene and graphdiyne modified graphite. Graphene and graphdiyne are coated on the surface of graphite particles. The mass percentage of graphene in the modified graphite is 0.1-1%. The mass percentage of graphdiyne in the modified graphite is 0.05-0.5%. The lithium ion battery negative electrode material can improve the fast charging performance and effectively improve the safety performance of the battery.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of lithium ion batteries, and particularly relates to a lithium ion battery negative electrode material, a preparation method thereof and a lithium ion battery. BACKGROUND

[0002] The statements herein are provided only to complement the background of the present application and are not necessarily indicative of the prior art.

[0003] Lithium ion batteries are rechargeable batteries, which are composed of four main materials, namely, positive electrode, negative electrode, separator and electrolyte, and other auxiliary materials. Among them, graphite is the main negative electrode material of the currently commercialized lithium ion battery. With the rapid growth of electric vehicles in recent years, the new problems of "charging difficulty and slow charging" are increasingly prominent, accompanied by the anxiety of endurance. Since the overall energy density of lithium ion batteries cannot be infinitely improved, the above problems can only be alleviated by improving the charging speed, and the demand for fast-charging graphite negative electrode materials has also increased explosively.

[0004] Due to the SP2 hybridization of C atoms, graphite presents a layered structure, and lithium ions can only be inserted and extracted from the edge of the graphite layer, but cannot enter and exit from the direction perpendicular to the graphite layer, which is the fundamental reason affecting the fast charging of graphite. In addition, during fast charging, the electrochemical polarization increases, and if lithium ions cannot diffuse into the graphite layer in time, they will be reduced into metallic lithium on the surface of the negative electrode, and the dendritic structure of the metallic lithium is easy to pierce the separator, thereby causing internal short circuit of the battery and leading to safety accidents; more importantly, during fast charging, due to the large current, the battery is rapidly heated, which may on the one hand cause the temperature rise to fail to match the temperature threshold of the system, and on the other hand may cause rapid aging of the battery, leading to performance reduction and increasing the risk of safety problems.

[0005] The industry usually adopts the methods of particle structure design and surface modification to realize the fast charging of graphite: for example, mixing petroleum coke / pitch coke and pitch-kneading-high temperature graphitization to obtain a secondary particle structure of artificial graphite material; for example, loading metal and / or metal compounds on graphite, and reacting the graphite loaded with catalyst with a reaction gas to obtain a porous graphite negative electrode material; for example, mixing graphite with a modifier, granulating, graphitizing and coating to obtain a spherical fast-charging graphite negative electrode material.

[0006] The inventors found that the above technologies only optimize the insertion / extraction space of lithium ions through structure modification or surface coating, but the temperature rise and safety problems under rapid charging are not substantially improved. SUMMARY

[0007] In view of the deficiencies of the prior art, the purpose of the present application is to provide a lithium ion battery negative electrode material, a preparation method thereof and a lithium ion battery, which can effectively improve the safety performance of the battery while improving the fast charging performance.

[0008] To achieve the above object, the present application is realized by the following technical scheme:

[0009] In the first aspect, the present application provides a lithium ion battery negative electrode material, which is graphene and graphdiyne modified graphite, graphene and graphdiyne are coated on the surface of graphite particles, the mass percentage of graphene in the modified graphite is 0.1-1%, and the mass percentage of graphdiyne in the modified graphite is 0.05-0.5%.

[0010] In the second aspect, the present application provides a preparation method of the lithium ion battery negative electrode material, which comprises the following steps:

[0011] After the graphene and the graphite are uniformly mixed in proportion, the mixed powder is subjected to mechanical fusion processing, so that the graphene is depolymerized and coated on the graphite substrate to obtain a graphite composite powder loaded with graphene;

[0012] After the graphite composite powder loaded with graphene and the graphdiyne are uniformly mixed in proportion, mechanical fusion is performed, so that the graphdiyne is depolymerized and coated on the graphite substrate, thereby obtaining the negative electrode material;

[0013] The rotational speed of the mechanical fusion machine is 100-1800 rpm, the width of the tool gap is 0.1-0.5 cm, and the fusion time is 0.5-2 h.

[0014] In the third aspect, the present application provides a lithium ion battery, the negative electrode material of which is the lithium ion battery negative electrode material.

[0015] The beneficial effects achieved by one or more embodiments of the present application are as follows:

[0016] Firstly, the super-large interlayer spacing (0.365 nm) of graphdiyne and the conjugated pi bond system composed of multiple carbon atoms in the plane can significantly reduce the lithium ion interface desolvation interface energy threshold and quickly and effectively provide more Li ion intercalation and deintercalation sites, thereby improving the fast charging performance and reducing the risk of lithium precipitation; secondly, the super-high conductivity of graphene can effectively improve the electron transmission rate and accelerate the electrochemical reaction rate, thereby improving the fast charging performance.

[0017] Furthermore, since the ohmic impedance of the battery cell does not change much during service, the electrochemical impedance caused by aging gradually increases, and the charge transfer impedance is particularly prominent. This will cause the heat generation to gradually increase during the cycle aging process, especially during fast charging. Graphene can reduce the charge transfer impedance and heat generation on the one hand due to its excellent conductivity and heat dissipation function, and on the other hand, it can quickly transfer the generated heat to the surface of the battery cell through the current collector, thereby avoiding the accumulation of heat and effectively reducing the temperature rise of the battery cell and improving the safety performance. BRIEF DESCRIPTION OF DRAWINGS

[0018] The accompanying drawings, which form a part of this specification, are included to provide a further understanding of the application and are incorporated herein for explanation.

[0019] Figure 1 is a SEM image of the fast-charging graphite composite powder B prepared in Example 1;

[0020] Figure 2 is a surface morphology image of the fast-charging graphite composite powder B prepared in Example 1;

[0021] Figure 3 is a structural schematic diagram of the fast-charging graphite of the fast-charging graphite composite powder B prepared in Example 1;

[0022] Figure 4 is a graphene morphology image in Example 1;

[0023] Figure 5 is a graphene surface morphology image in Example 1;

[0024] Figure 6 is a Raman spectrum of graphdiyne in Example 1;

[0025] Figure 7 is a coin cell charge-discharge performance diagram.

[0026] Figure 8 is a lithium intercalation curve (a) of the coin cell of Example 1 and Comparative Examples 1 and 2, and a partial enlarged view (b). DETAILED DESCRIPTION

[0027] It should be noted that the following detailed description is illustrative only, and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0028] In a first aspect, the present application provides a lithium ion battery negative electrode material, which is a modified graphite of graphene and graphdiyne, the graphene and graphdiyne are coated on the surface of graphite particles, the mass percentage of graphene in the modified graphite is 0.1-1%, and the mass percentage of graphdiyne in the modified graphite is 0.05-0.5%.

[0029] In order to improve the higher fast-charging performance of the existing graphite and solve the problems of high temperature rise and safety risk of fast-charging graphite in the prior art, in the present application, graphite and graphene are coated on the surface of the graphite, the super-large interlayer spacing (0.365 nm, 0.335 nm for graphite) and the large conjugated carbon bond system composed of multiple carbon atoms (generally more than 6, such as 18) of graphdiyne are used, and the Li receiving sites can be provided in the horizontal and vertical directions, which can significantly reduce the desolvation interface energy threshold of lithium ion interface and improve the fast-charging performance; and the stability of the layered structure of the bulk graphite can be improved.

[0030] At the same time, by means of the high conductivity and heat dissipation performance of graphene, the ohmic impedance and polarization impedance can be significantly reduced, the heat accumulation in the fast-charging process can be reduced, and the safety performance can be improved. Graphene and graphdiyne both have a planar two-dimensional structure, and are stacked to form a layered structure through van der Waals force and π-π interaction; but the difference is that graphene has sp2 hybridization, and graphdiyne has both sp2 hybridization and sp hybridization, and has high conjugation.

[0031] The flake diameter of graphene is 1-10 microns, and the flake diameter of graphdiyne is 10-100 nanometers, and the area ratio of a single graphene and graphdiyne is often about 50 times, Figure 3 The schematic diagram in the figure is to show that the area of graphdiyne is exaggerated, and the actual area of graphdiyne is much smaller. Therefore, in order to make graphene and graphdiyne work at the same time, graphene and graphite are mechanically mixed first, so that a layer of graphene is coated on the surface of the graphite, the high conductivity and heat dissipation performance are improved, and then graphdiyne is mixed with the above mixture, so that a layer of graphdiyne is coated on the outermost surface. Due to the super-large interlayer spacing (0.365 nm) of graphdiyne and the conjugated large π bond system composed of multiple carbon atoms in the plane, the desolvation interface energy threshold of lithium ion interface can be significantly reduced, and more Li ion insertion and extraction sites can be quickly and effectively provided.

[0032] The fast-charging negative electrode material prepared by the present application can significantly improve the fast-charging performance, and can effectively avoid the risk of thermal runaway caused by fast-charging, and effectively improve the safety performance.

[0033] If the amount of graphene is excessive, the specific surface area will be too large, which will cause the overall performance (including the compaction density, the first charge and discharge coulombic efficiency, the cycle performance, etc.) to decrease; if the amount of graphene is too small, the conductivity and heat dissipation performance will decrease.

[0034] If the amount of graphdiyne is too much, the specific surface area will also be too large, which will also cause the overall performance (including the compaction density, the first charge and discharge coulombic efficiency, the cycle performance, etc.) to decrease; if the amount of graphdiyne is too small, the number of lithium receiving sites will decrease, and the fast-charging performance will decrease.

[0035] In actual preparation, the inventors choose to coat graphene on graphite first, and then coat graphyne on the graphite composite powder loaded with graphene, and finally obtain graphene and graphyne modified graphite. Since graphene is located in the middle layer of the modified graphite, and graphyne is located at the outermost side of the modified graphite, this structure can make graphyne fully exposed at the outermost side of the modified graphite, and fully play the role of providing Li sites. Therefore, the graphyne is most preferably exposed at the outermost side of the negative electrode material.

[0036] In the test process, the inventors tried a preparation method of mixing graphyne and graphite first, and then mixing and coating with graphene, but the product prepared by this preparation method has poor performance. The reason is that the flake diameter of graphyne is small, and when coating large flake diameter graphene on the surface of graphite, a certain amount of graphyne will be wrapped in the inner layer by graphene, losing the role of lithium site, and further affecting the performance of the negative electrode material.

[0037] In addition, the inventors also tried to mix graphene and graphyne with graphite at the same time, and then perform mechanical fusion coating. However, due to the van der Waals force between the layers of graphene and graphyne, not only are they prone to agglomeration themselves, but also are prone to agglomeration with each other. Therefore, under the premise of realizing the deagglomeration and coating of graphene and graphyne on the surface of graphite particles respectively, unnecessary agglomeration of graphene and graphyne should be avoided as much as possible, which brings great trouble to the coating operation. In this case, it is also difficult to mix graphene and graphyne uniformly in graphite through mechanical mixing, and the subsequent mechanical fusion cannot guarantee that graphene and graphyne are deagglomerated and uniformly coated on the graphite particles, which further affects the performance of the negative electrode material.

[0038] Therefore, in order to enable graphene and graphyne to play their respective roles at the same time, graphene and graphite are first mechanically mixed to cover the surface of graphite with a layer of graphene, thereby improving the conductivity and heat dissipation performance of graphite, and then graphyne is coated on the outermost side of graphite. Due to the ultra-large interlayer spacing (0.365 nm) of graphyne and the conjugated pi bond system composed of multiple carbon atoms in the plane, the lithium ion interface desolvation interface energy threshold can be significantly reduced, and more Li ion intercalation and deintercalation sites can be provided quickly and effectively.

[0039] In some embodiments, the mass percentage of graphene in the modified graphite is 0.2-0.8%, and particularly preferably 0.5%.

[0040] The mass percentage of graphyne in the modified graphite is 0.1-0.3%, and particularly preferably 0.25%.

[0041] In some embodiments, the D50 particle size of the graphite is 5-15 μm, and preferably 10 μm.

[0042] D50 particle size is the particle size corresponding to the cumulative particle size distribution percentage of 50% of a sample, also called median diameter or median particle size.

[0043] In some embodiments, the graphene has a thickness of 1-10 nm and a flake diameter of 1-10 μm.

[0044] In some embodiments, the graphyne has a thickness of 1-10 nm and a flake diameter of 10-100 nm.

[0045] In some embodiments, the graphene and the graphyne are embedded on the graphite substrate.

[0046] In a second aspect, the present application provides a preparation method of the lithium ion battery negative electrode material, comprising the following steps:

[0047] After the graphene and the graphite are mixed uniformly in a certain proportion, the mixed powder is subjected to mechanical fusion processing, so that the graphene is depolymerized and coated on the graphite substrate, thereby obtaining a graphite composite powder loaded with graphene;

[0048] After the graphite composite powder loaded with graphene and the graphyne are mixed uniformly in a certain proportion, mechanical fusion is performed, so that the graphyne is depolymerized and coated on the graphite substrate, thereby obtaining the negative electrode material.

[0049] The rotational speed of the mechanical fusion machine is 100-1800 rpm, the cutter gap width is 0.1-0.5 cm, and the fusion time is 0.5-2 h.

[0050] In some embodiments, when the graphene and / or the graphyne are mixed with the graphite, the mixing machine used is a V-shaped mixing machine, the stirring rotational speed is 100-500 rpm, and the stirring time is 10-60 min.

[0051] In some embodiments, when the mechanical fusion processing is performed, the rotational speed of the mechanical fusion machine is 1000-1800 rpm, the cutter gap width is 0.1-0.5 cm, and the fusion time is 0.5-2 h.

[0052] The graphene and the graphyne have the advantages of large specific surface area, etc., so that they are easy to agglomerate; in addition, due to the addition of a small amount of graphene and graphyne in the graphite, combined with the agglomeration effect, it is difficult to directly mix the unagglomerated graphene and / or graphyne with the graphite uniformly by using the conventional mixing method.

[0053] In order to realize the uniform modification of the graphene and the graphyne to the graphite, the inventors attempt to realize it by a two-step mixing method, i.e., first mixing the agglomerated graphene with the graphite, and then mechanically mixing the graphyne with the above mixture to obtain the final composite.

[0054] Since the amount of graphene and graphdiyne added to the graphite is small, and the amount of agglomeration is even smaller, it is difficult to uniformly disperse the agglomerated graphene and graphdiyne in the graphite. The inventors found through repeated experiments that when a V-shaped mixer is used, the stirring speed is 100-500 rpm, and the stirring time is 10-60 min, the small amount of agglomerated graphene and graphdiyne can be uniformly dispersed in the graphite.

[0055] When the mechanical fusion machine is used to mechanically fuse the mixed powder, the stirring speed of the mechanical fusion machine is 100-500 rpm, and the stirring time is 10-60 min. Under high-speed rotation, the powder passes through the narrow gap between the cutters and is uniformly dispersed in the graphite by using external mechanical force. The agglomerated graphene and graphdiyne are depolymerized, and the depolymerized graphene and graphdiyne are further dispersed in the graphite and uniformly embedded in the graphite matrix. This method is simple, stable, and easy to scale up in industry.

[0056] This method can be used to prepare a uniform material to ensure product quality.

[0057] In a third aspect, the present application provides a lithium ion battery, wherein the negative electrode material of the lithium ion battery is the negative electrode material.

[0058] The present application will be further described below with reference to specific examples.

[0059] Example 1

[0060] Take 1000g of artificial graphite with a D50 of 8.5μm, add 2g of graphene with an average thickness of 2.3nm and an average flake diameter of 1.5μm (the morphology is shown in Figure 4 and Figure 5 ), and stir and disperse in a V-shaped mixer with a speed of 200rpm for 30min to discharge;

[0061] Put the above material into a mechanical fusion machine, adjust the speed to 1200rpm, the cutter gap width to 0.3cm, and the fusion time to 1h to discharge, thereby preparing a composite powder A of nanosheet graphene loaded on graphite.

[0062] Again, stir and disperse the composite powder A with 1g of graphdiyne with an average thickness of 2.5nm and an average flake diameter of 40nm in a V-shaped mixer with a speed of 200rpm for 30min to discharge;

[0063] Put the above material into a mechanical fusion machine, adjust the speed to 1500rpm, the cutter gap width to 0.2cm, and the fusion time to 2h to discharge, thereby preparing a composite powder B of nanosheet graphdiyne loaded on graphene modified graphite.

[0064] The Raman spectrum of graphdiyne is as follows: Figure 6As shown, 1349.3 cm -1 The peak represents the breathing vibration of the sp hybrid carbon atom of the benzene ring, which is the D band of the graphdiyne, and is related to the structural defects of the graphdiyne. -1 The peak represents the in-plane stretching vibration of the sp2 hybrid carbon atom of the benzene ring, which is equivalent to the G band of the graphdiyne, and is an ordered band.

[0065] The SEM image of the prepared fast-charging graphite composite powder B is shown in the following figure. Figure 1 As shown.

[0066] The surface morphology image of the fast-charging graphite composite powder B is shown in the following figure. Figure 2 As shown. Figure 3 As shown.

[0067] Example 2

[0068] Take 1000g of artificial graphite with D50 of 10.1pm, add 4g of graphene with average thickness of 2.5nm and average flake diameter of 1.5pm, stir and disperse in a V-type mixer at a speed of 400rpm for 40min, and discharge;

[0069] Put the above materials into a mechanical fusion machine, adjust the speed to 1500rpm, the cutter gap width to 0.3cm, and the fusion time to 1.5h, and discharge, to prepare a nanosheet graphene loaded on graphite composite powder A;

[0070] Again, disperse the composite powder A with 2g of graphdiyne with an average thickness of 2.5nm and an average flake diameter of 50nm in a V-type mixer at a speed of 300rpm for 40min, and discharge;

[0071] Put the above materials into a mechanical fusion machine, adjust the speed to 1500rpm, the cutter gap width to 0.2cm, and the fusion time to 1.5h, and discharge, to prepare a nanosheet graphene loaded on graphite composite powder A;

[0072] Example 3

[0073] Take 1000g of artificial graphite with D50 of 12.3pm, add 5g of graphene with average thickness of 2.7nm and average flake diameter of 1.8pm, stir and disperse in a V-type mixer at a speed of 200rpm for 50min, and discharge;

[0074] Put the above materials into a mechanical fusion machine, adjust the speed to 1200rpm, the cutter gap width to 0.3cm, and the fusion time to 1h, and discharge, to prepare a nanosheet graphene loaded on graphite composite powder A;

[0075] The composite powder A is mixed with 2.5 g of graphdiyne with an average thickness of 2.5 nm and an average flake diameter of 40 nm in a V-shaped mixer at a rotation speed of 200 rpm for 50 min, and then discharged.

[0076] The above material is added to a mechanical fusion machine, the rotation speed is adjusted to 1500 rpm, the cutter gap width is 0.2 cm, and the fusion time is 2 h, and then the composite powder B of nanosheet-layer graphdiyne loaded on graphene-modified graphite is obtained.

[0077] Example 4

[0078] 1000 g of artificial graphite with a D50 of 14.3 μm is taken, 1 g of graphene is added, and the mixture is stirred and dispersed in a V-shaped mixer at a rotation speed of 500 rpm for 40 min, and then discharged. The average thickness of the graphene is 4.4 nm, and the average flake diameter is 6.6 μm.

[0079] The above material is added to a mechanical fusion machine, the rotation speed is adjusted to 1000 rpm, the cutter gap width is 0.3 cm, and the fusion time is 1 h, and then the composite powder A of nanosheet-layer graphene loaded on graphite is obtained.

[0080] The composite powder A is mixed with 0.5 g of graphdiyne powder with an average thickness of 6.5 nm and an average flake diameter of 60 nm in a V-shaped mixer at a rotation speed of 200 rpm for 50 min, and then discharged.

[0081] The above material is added to a mechanical fusion machine, the rotation speed is adjusted to 1800 rpm, the cutter gap width is 0.5 cm, and the fusion time is 0.5 h, and then the composite powder B of nanosheet-layer graphdiyne graphdiyne coating loaded on graphene-modified graphite is obtained.

[0082] Example 5

[0083] 1000 g of artificial graphite with a D50 of 5.8 μm is taken, 10 g of graphene is added, and the mixture is stirred and dispersed in a V-shaped mixer at a rotation speed of 100 rpm for 10 min, and then discharged. The average thickness of the graphene is 7.6 nm, and the average flake diameter is 6.5 μm.

[0084] The above material is added to a mechanical fusion machine, the rotation speed is adjusted to 100 rpm, the cutter gap width is 0.1 cm, and the fusion time is 0.5 h, and then the composite powder A of nanosheet-layer graphene loaded on graphite is obtained.

[0085] The composite powder A is mixed with 5 g of graphdiyne powder with an average thickness of 4.7 nm and an average flake diameter of 68 nm in a V-shaped mixer at a rotation speed of 200 rpm for 60 min, and then discharged.

[0086] The above materials were added into a mechanical fusion machine, the rotating speed was adjusted to 900 rpm, the cutter gap width was 0.2 cm, and the fusion time was 1 h, and the product was discharged, to obtain the composite powder B of the nanosheet graphite and the modified graphite coated with the graphdiyne-based graphdiyne.

[0087] Comparative Example 1

[0088] 1000 g of artificial graphite with a D50 of 8.5 μm was taken, 20 g of coal-based pitch with a median particle size of 3.8 μm and a softening point of 250 ℃ was added, and the mixture was stirred and dispersed in a V-type mixer at a rotating speed of 200 rpm for 30 min, and then discharged. The above materials were added into a mechanical fusion machine, the rotating speed was adjusted to 1200 rpm, the cutter gap width was 0.3 cm, and the fusion time was 1 h, and then the product was discharged and loaded into a crucible, and then heat-treated at 1000 ℃ for 4 h under a nitrogen atmosphere, and then cooled and discharged to obtain the modified graphite coated with pitch pyrolytic carbon.

[0089] Comparative Example 2

[0090] 1000 g of artificial graphite with a D50 of 8.5 μm was taken, and the mixture was stirred and dispersed in a V-type mixer at a rotating speed of 200 rpm for 30 min, and then discharged. The above materials were added into a mechanical fusion machine, the rotating speed was adjusted to 1200 rpm, the cutter gap width was 0.3 cm, and the fusion time was 1 h, and then the product was discharged and loaded into a crucible, and then heat-treated at 1000 ℃ for 4 h under a nitrogen atmosphere, and then cooled and discharged to obtain the modified graphite coated with pitch pyrolytic carbon.

[0091] Preparation of the button cell: carboxymethyl cellulose (CMC) aqueous solution was added with conductive carbon black, then the negative electrode material prepared in the examples or comparative examples was added, and finally styrene-butadiene rubber (SBR) was added, and the mixture was stirred uniformly, and then the slurry was uniformly coated on a copper foil on a coating machine to form an electrode sheet. The coated electrode sheet was placed in a vacuum drying oven at a temperature of 120 ℃ for vacuum drying for 6 hours, and then the electrode sheet was taken out and rolled on a rolling machine for standby use. The button cell was assembled in a glove box under an argon atmosphere, and the electrolyte was 1M LiPF6+EC:DEC:DMC=1:1:1 (volume ratio), and a lithium metal sheet was used as the counter electrode. The capacity test was performed on a U.S. Arbin BT2000 battery tester, and the charge and discharge voltage range was 0.01 to 2.0 V, and the charge and discharge rate was 0.1 C.

[0092] The charge and discharge performance of the button cell is shown in Figure 7 .

[0093] The lithium intercalation curve of the button cell is shown in Figure 8 .

[0094] Preparation of soft package lithium ion battery: the alkene-acetylene graphite composite negative electrode material prepared in each example and comparative example was dispersed in deionized water in a mass ratio of 97:0.3:1.5:1.2 with a conductive agent Super P, a binder styrene-butadiene rubber (SBR), and sodium carboxymethyl cellulose (CMC), and stirred uniformly to obtain electrode slurry.

[0095] The electrode slurry was coated on the surface of a copper foil, dried at 85 DEG C to obtain a negative electrode sheet. The negative electrode sheet was combined with a commercial lithium iron phosphate positive electrode, an electrolyte was 1 mol / L LiPF6 / EC+PC+DEC+EMC (volume ratio 1:0.3:1:1), a separator was a PP / PE / PP three-layer separator with a thickness of 14 microns, and a soft package battery with a capacity of about 3 Ah was prepared, and full battery performance test was carried out in the range of 2.5V-3.8V.

[0096] Table 1: Comparison of phase performance of examples and comparative examples

[0097]

[0098]

[0099] As shown in Table 1, the coating of graphene and graphdiyne can effectively improve the electronic conductivity of the composite material, which is beneficial to the performance of electrochemistry.

[0100] Table 2: Comparison of fast charging performance of examples and comparative examples

[0101]

[0102] As shown in Table 2, due to the super-large interlayer spacing and the large circular ring structure of the graphene, more Li ions can be quickly and effectively provided for intercalation and deintercalation, thereby improving the fast charging performance. In addition, the super-high conductivity of graphene can effectively improve the electron transmission rate and accelerate the electrochemical reaction rate, thereby improving the fast charging performance. Furthermore, due to the excellent conductivity and heat dissipation function, on the one hand, the charge transfer impedance can be reduced, and the heat generation can be reduced; on the other hand, the generated heat can be quickly transferred to the surface of the battery cell through the current collector, thereby avoiding the accumulation of heat, effectively reducing the temperature rise of the battery cell, and improving the safety performance.

[0103] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A lithium-ion battery anode material, characterized in that: The graphene and graphyne-modified graphite is coated on the surface of graphite particles. The graphene accounts for 0.1-1% of the mass of the modified graphite, and the graphyne accounts for 0.05-0.5% of the mass of the modified graphite. The graphyne is exposed on the outermost side of the negative electrode material. Specifically, graphene is first coated on the graphite, and then graphyne is coated on the graphene-loaded graphite composite powder. The D50 particle size of the graphite is 5-15 μm; The graphene has a thickness of 1-10 nm and a sheet diameter of 1-10 μm; The thickness of the graphdiene is 1-10 nm, and the sheet diameter is 10-100 nm.

2. The lithium-ion battery anode material according to claim 1, characterized in that: The mass percentage of graphene in the modified graphite is 0.2-0.8%; the mass percentage of graphynylene in the modified graphite is 0.1-0.3%.

3. The method for preparing the lithium-ion battery anode material according to any one of claims 1-2, characterized in that: Includes the following steps: After graphene and graphite are mixed evenly in a certain proportion, the mixed powder is mechanically fused to depolymerize the graphene and coat it onto the graphite substrate, thus obtaining graphene-loaded graphite composite powder. After uniformly mixing graphene-loaded graphite composite powder with graphylene in a certain proportion, mechanical fusion processing is carried out to depolymerize the graphylene and coat it onto the graphite substrate to obtain the anode material. During mechanical fusion machining, the rotation speed of the mechanical fusion machine is 100-1800 rpm, the tool gap width is 0.1-0.5 cm, and the fusion time is 0.5-2 h; When mixing graphene and / or graphylene with graphite, a V-type mixer is used, with a stirring speed of 100-500 rpm and a stirring time of 10-60 min.

4. A lithium-ion battery, characterized in that: Its negative electrode material is the lithium-ion battery negative electrode material according to any one of claims 1-2.

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