CN112803001B

CN112803001B - Coating agent, quick-charge graphite, preparation method and application of coating agent and quick-charge graphite, and battery

Info

Publication number: CN112803001B
Application number: CN202011451821.9A
Authority: CN
Inventors: 潘福森; 沈龙; 曾繁俊; 范拯华; 王晓阳; 陈兵帅; 张秀云
Original assignee: Ningbo Shanshan New Material Tech Co ltd
Current assignee: Ningbo Shanshan New Material Tech Co ltd
Priority date: 2020-12-10
Filing date: 2020-12-10
Publication date: 2023-06-27
Anticipated expiration: 2040-12-10
Also published as: WO2022121400A1; CN112803001A

Abstract

The invention discloses a coating agent, quick-charge graphite, a preparation method and application thereof, and a battery. The coating agent comprises an amphiphilic carbon material, a pH regulator and water; the amphiphilic carbon material accounts for 20-70% of the coating agent by mass; the pH value of the coating agent is more than 12. The coating agent is used for coating and modifying graphite, so that a coating layer with uniform thickness and good compactness can be formed, the obtained quick-charge graphite has excellent structural stability and quick-charge performance, and can be used as a negative electrode material of batteries such as lithium ion batteries, solid batteries and the like, and the preparation method is simple and feasible and has low cost.

Description

Coating agent, quick-charge graphite, preparation method and application of coating agent and quick-charge graphite, and battery

Technical Field

The invention relates to a coating agent, quick-charge graphite, a preparation method and application thereof, and a battery.

Background

The lithium ion battery has the excellent performances of high energy density, high working voltage, long cycle life, no pollution, good safety performance, environmental protection, durability and the like, so that the lithium ion battery has wide application from portable electronic equipment to electric automobiles, from civil fields to national defense and military fields, and from conventional environments to low-temperature, high-temperature and quick-charge fields, and is further deepened and expanded. Lithium ion battery technology is one of research hotspots which are widely focused in recent years, and has profound effects on the production and living modes of people.

The negative electrode material is one of key technologies for limiting the continuous improvement of the lithium ion battery and is also one of main break-through openings for improving the lithium ion performance. Commercial lithium ion battery cathode materials are mainly various carbon materials, such as natural graphite, artificial graphite, modified graphite, soft and hard carbon and the like. Alloy materials and silicon materials have great application prospects, but complicated preparation and production processes, high cost and low safety and service life characteristics lead to great uncertainty of future commercial application. Among the carbon materials that have been commercialized at present, surface-modified natural graphite and artificial graphite occupy absolute proportions.

The stable crystal structure characteristics and anisotropy of the graphite material make it impossible to rapidly diffuse lithium ions within the graphite material. In perfect graphite crystals, the diffusion of lithium ions can only enter from the end faces of the graphite and is parallel to the graphene thin layers. Since lithium ions cannot traverse the graphene layer, diffusion of lithium ions inside graphite exhibits significant anisotropy. Typical interlayer spacing d002 of graphite is 0.336-0.338 nm, which is relatively close to the diameter of lithium atoms, so that lithium atoms need to overcome a larger potential barrier when diffusing between graphite layers, macroscopic appearance is that the diffusion rate of lithium in graphite is smaller, and rapid charge and discharge performance is poorer in electrochemical aspect.

The research shows that the main method for solving the rapid charging and low-temperature performance of the graphite cathode material in a lithium ion battery system is to carry out surface modification on graphite particles. Coating the hard carbon structure on the surface of the graphite is the most effective method for improving the quick charge performance and the low temperature performance of the graphite. Specifically, japanese patent JP11246209, in which graphite and hard carbon particles are immersed in pitch or tar at a temperature of 10 to 300 ℃ and then subjected to solvent discharge and carbonization heat treatment, has difficulty in forming a carbon layer structure having a uniform and thick thickness on the surfaces of graphite and hard carbon, has a limit to improvement in the structural stability of natural graphite. Chinese patent CN106848468B provides a method and apparatus for preparing hard carbon coated graphite using recovered cleaning fluid, and the method can provide low-cost hard carbon coated graphite material, but the source and components of the coating agent are difficult to be stable continuously, so that the significance of large-scale production is not great.

Disclosure of Invention

The invention aims to solve the defects that the stability and the quick charge performance of quick charge graphite are poor, the feasibility and the cost of a preparation method cannot be considered, and the like in the prior art, and provides a coating agent, quick charge graphite, a preparation method and application thereof, and a battery. The coating agent disclosed by the invention is used for coating and modifying graphite, so that a coating layer with uniform thickness and good compactness can be formed, the obtained quick-charge graphite has excellent structural stability and quick-charge performance, the coating agent can be used for negative electrode materials of batteries such as lithium ion batteries and solid batteries, and the preparation method is simple and feasible, and the cost is low.

In order to solve the problems, the invention adopts the following technical scheme:

the invention provides a coating agent, which comprises an amphipathic carbon material, a pH regulator and water; the amphiphilic carbon material accounts for 20-70% of the coating agent by mass; the pH value of the coating agent is more than 12.

In the present invention, the amphiphilic carbon material preferably accounts for 20% -40%, for example 30% of the mass of the coating agent.

In the invention, the amphiphilic carbon material refers to a carbon material which is conventional in the art and can be dissolved in an alkaline aqueous solution and an organic solvent. When the pH value of the alkaline aqueous solution is lower than 12, the solubility of the amphiphilic carbon material is very low, and the use is inconvenient.

The amphiphilic carbon material can be an asphalt-based amphiphilic carbon material and/or a raw coke-based amphiphilic carbon material. Wherein the pitch-based amphiphilic carbon material can be selected from one or more of coal tar pitch-based amphiphilic carbon material, coal pitch-based amphiphilic carbon material, petroleum pitch-based amphiphilic carbon material and mesophase-based amphiphilic carbon material. The raw coke-based amphiphilic carbon material is one or two selected from petroleum coke-based amphiphilic carbon materials and needle-shaped Jiao Ji amphiphilic carbon materials. The amphiphilic carbon material is preferably a petroleum coke-based amphiphilic carbon material or a petroleum asphalt-based amphiphilic carbon material. The carbon residue value of the amphiphilic carbon material may be 40% to 70%, preferably 50% to 65%, for example 52% or 61%.

The amphiphilic carbon material can be prepared according to a conventional method in the field, and is preferably prepared by a conventional mixed acid method in the field. The specific operations of the mixed acid process generally include: and adding the raw material X into mixed acid, stirring and refluxing, cooling, filtering, and washing to neutrality to obtain the X-based amphiphilic carbon material.

Wherein, the raw material X can be coal tar pitch, coal pitch, petroleum coke or needle coke; the softening point of the petroleum pitch is preferably 200 ℃ or higher, for example 220 ℃. For example, when the raw material X is petroleum coke, preparing a petroleum coke-based amphiphilic carbon material according to the method; when the raw material X is petroleum asphalt, the petroleum asphalt-based amphiphilic carbon material is prepared according to the method. The particle diameter of the raw material X is preferably 10 μm or less. The mixed acid is preferably concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 3:7. The mass concentration of the raw material in the mixed acid is preferably 0.2g/mL. The temperature of the reflux is preferably 80 ℃; the time of the reflux is preferably 3 hours.

In the present invention, the pH adjuster may be an alkaline substance conventionally used in the art, and the pH of the coating agent may be adjusted to 12 or more. The pH regulator is preferably an alkaline substance which can volatilize or completely decompose into a gas, preferably ammonia or ethylenediamine.

In the present invention, preferably, the coating agent further includes a conductive additive. Wherein the conductive additive may be a conductive substance conventional in the art, preferably one or more selected from the group consisting of carbon nanotubes, graphene and conductive graphite. The carbon nanotubes are preferably single-walled carbon nanotubes. The conductive additive may be 1-30% by mass, preferably 1-15% by mass, of the coating agent, calculated as carbon residue.

In the present invention, the calculation according to the carbon residue value means that the mass of the substance taken at the time of calculation is "actual mass of the substance×carbon residue value of the substance". The detection standard of the carbon residue values of the invention is GB/T268-1987.

In the present invention, optionally, the coating agent further includes a thickener. The thickener may be a thickener conventional in the art, such as sodium carboxymethyl cellulose (CMC).

In a preferred embodiment of the present invention, the coating agent comprises a petroleum coke based amphiphilic carbon material, ethylenediamine and water; the petroleum coke-based amphiphilic carbon material accounts for 30% of the coating agent by mass; the pH value of the coating agent is 13.

In a preferred embodiment of the present invention, the coating agent comprises a petroleum pitch-based amphiphilic carbon material, ethylenediamine and water; the petroleum asphalt-based amphiphilic carbon material accounts for 30% of the coating agent by mass; the pH value of the coating agent is 13.

The invention also provides a preparation method of the coating agent, which comprises the step of dissolving the amphiphilic carbon material and the pH regulator in water.

In the present invention, the preparation method of the coating agent preferably includes:

dissolving the amphiphilic carbon material in the water, and then adding the pH regulator to adjust the pH to be more than 12 to obtain the water;

or dissolving the pH regulator in water to obtain an alkaline solution with the pH value of more than 12, and dissolving the amphiphilic carbon material in the alkaline solution.

In the present invention, it is preferable that the amphiphilic carbon material and the pH adjuster are dissolved in water and then filtered at a constant temperature. The constant temperature may be 60 to 90 ℃, preferably 80 ℃; the time of the constant temperature may be 0.5 to 3 hours, preferably 1 hour. The filtration may be carried out by methods conventional in the art, the purpose of which is to filter out undissolved constituents that may be present.

In the present invention, when the coating agent further includes the conductive additive, the conductive additive is added after the amphiphilic carbon material and the pH adjuster are dissolved in water. When the coating agent further includes the thickener, the thickener is added after the amphiphilic carbon material and the pH adjustor are dissolved in water.

The invention also provides a preparation method of the quick-charging graphite, which comprises the following steps:

s1, mixing the coating agent with graphite aggregate to obtain slurry;

s2, drying and curing the slurry to obtain a precursor;

and S2, carbonizing the precursor to obtain the quick-charge graphite.

In step S1, the graphite aggregate may be natural graphite or artificial graphite, which may or may not be coated, as is conventional in the art. Wherein the artificial graphite may be single particles or secondary particles. The particle size of the graphite aggregate is preferably 5 to 20 μm. The carbon content of the graphite aggregate is preferably not less than 99.9%. The graphitization degree of the graphite aggregate is preferably 93% -99%.

In the step S1, the mass ratio of the coating agent to the graphite aggregate is (1-20) according to the carbon residue value: 100, preferably (2 to 10): 100.

in step S1, the mixing may be performed in a mixing manner conventional in the art. The mixing equipment can be a mixer, kneader or fusion machine. The mixer is preferably an electrically heated horizontal mixer.

The mixing preferably comprises: mixing in a mixer or a kneader, and mechanically fusing in a fusion machine. In the mechanical fusion process, the relative speed between different material particles is very big, and material surface temperature is higher to receive the extrusion effect, make the material contact more abundant, mix more abundant, be favorable to making the cladding that amphipathy charcoal material can be more even on graphite surface.

The temperature of the mixing preferably does not exceed 80 ℃. The mixing temperature is the temperature of the materials during mixing.

In step S2, the drying may be freeze drying or heat drying. The freeze-drying may be performed in the freeze-dryer according to a method conventional in the art. The heat drying may be performed in a vacuum drying oven or a forced air drying oven according to a method conventional in the art. The temperature of the heat drying may be 80 to 200 ℃, preferably 100 to 150 ℃, for example 110 ℃. The heat drying is preferably dynamic drying under an air atmosphere.

In step S2, the curing may be performed in a heating device conventional in the art, preferably in a kiln or a heatable mixer, preferably an electrically heated horizontal mixer.

In the curing process, the curing temperature may be 200 to 700 ℃. During the curing process, a gradual heating mode is preferably adopted. In the curing process, the holding time at the curing temperature may be 2 to 8 hours.

A gas may be introduced during the curing process, which may be an inert gas, nitrogen, ozone or an oxygen-containing gas. Wherein the oxygen-containing gas is a mixed gas of oxygen and other gases. The oxygen content of the oxygen-containing gas can be 15% -100%; the oxygen content refers to the volume percent of oxygen in the oxygen-containing gas. The oxygen-containing gas is preferably a mixed gas of oxygen and nitrogen, more preferably air, or a mixed gas of 21% oxygen and 79% nitrogen, in percentage by volume.

Preferably, a plurality of different gases are sequentially introduced during the curing process. For example, in the curing process, air is introduced below 500 ℃, and nitrogen is introduced above 500 ℃. Wherein the flow rate of the air can be 0.01-1L/(Kg.min), and preferably 0.2-0.3L/(Kg.min); the flow rate of the nitrogen gas may be 0.001 to 0.05L/(Kg.min).

In step S2, the drying and curing may be performed in different apparatuses or may be performed in the same apparatus. The drying and curing are preferably performed in the same equipment, so that the process can be simplified, the automation can be better realized, and the cost can be reduced. When the drying and curing are carried out in the same apparatus, they are preferably carried out in a kiln or in a heatable mixer, preferably an electrically heated horizontal mixer.

When the drying and curing are performed in the same equipment, the drying and curing process may be a staged heat treatment of the slurry, the staged heat treatment including: (1) first stage heat treatment: the temperature is 80-200 ℃, preferably 100-150 ℃; the heat preservation time is 1-3 h; (2) A second heat treatment at 200-400 deg.c, preferably 300 deg.c; the heat preservation time is 1-3 h; (3) The third heat treatment, the temperature is 400-700 ℃, preferably 500-650 ℃; the heat preservation time is 1-3 h.

The first heat treatment corresponds to a drying process, and the second heat treatment and the third heat treatment correspond to a curing process. During the staged heat treatment, the rate of temperature increase is preferably 1 to 5 ℃/min, for example 3 ℃/min. During the staged heat treatment, a gas may be introduced. The operation and conditions of the aeration are as described above.

In a preferred embodiment of the present invention, the specific operations of drying and curing include: introducing air into the electric heating horizontal mixer at the flow rate of 0.3L/(Kg min), heating to 110 ℃ at the heating rate of 3 ℃/min, and preserving heat for 2h at 110 ℃; continuously introducing air at the flow rate of 0.2L/(Kg min), continuously heating to 300 ℃ at the speed of 3 ℃/min, and preserving heat for 2h; continuously introducing air at the flow rate of 0.2L/(Kg min), continuously heating to 500 ℃ at the speed of 3 ℃/min, and preserving heat for 1.5h to obtain the precursor.

In step S3, the carbonization may be performed in a device conventional in the art using a method conventional in the art. The carbonization equipment can be kiln equipment such as an atmosphere furnace, a rotary furnace, a tubular furnace, a box furnace, a pusher kiln, a tunnel kiln, a roller kiln and the like.

The carbonization temperature may be 900 to 1500 ℃, preferably 900 to 1200 ℃. Preferably, the temperature is raised by a programmed temperature, preferably at a rate of 1 to 5℃per minute, for example, 4℃per minute.

In the carbonization process, the holding time at the carbonization temperature may be 1 to 6 hours, for example, 3 hours.

The carbonization is preferably carried out under a gas blanket, which may be nitrogen, an inert gas, preferably argon, or a reducing gas. The flow rate of the gas is preferably 0.001 to 0.05L/(Kg.min).

The carbonization can also be vacuum carbonization, and the negative pressure is not higher than 100Pa.

In the present invention, in step S3, optionally, the carbonized product obtained after the carbonization is classified or screened.

The invention also provides the quick-charging graphite which is prepared according to the preparation method.

The quick charge graphite of the invention can have the following properties: the particle diameter D50 is 5 to 30 μm (e.g., 8.2 μm or 15.3 μm), and the specific surface area (BET method) is less than or equal to 5m ² /g (e.g. 2.1m ² /g、3.3m ² /g)。

The invention also provides application of the quick-charge graphite serving as an electrode material in a battery. The electrode material is preferably a negative electrode material.

The invention also provides an electrode, and an electrode material of the electrode comprises the quick-charging graphite. The electrode is preferably a negative electrode.

The invention also provides a battery comprising the electrode.

In the present invention, the battery may be a lithium ion battery or a solid state battery.

On the basis of conforming to the common knowledge in the field, the above preferred conditions can be arbitrarily combined to obtain the preferred examples of the invention.

The reagents and materials used in the present invention are commercially available. Steps and methods not described in detail herein may be described with reference to conventional methods or related apparatus in the industry.

The invention has the positive progress effects that:

1. the quick-charging graphite particles are natural in distribution and smooth in surface, obvious defects and adhesion are avoided, the structure of the spherical graphite is kept good, the structure is stable, and the quick-charging graphite particles have excellent quick lithium ion intercalation and deintercalation capability and excellent circulation capability.

2. The lithium ion battery using the quick-charge graphite as the electrode material has high capacity and good cycle stability, and the quick-charge performance is greatly improved. Specifically, the first charge capacity of the button half-cell is 340-375 mA h/g, the capacity retention rate after 1000 times of circulation can reach more than 95%, and the 3C rapid discharge constant current ratio is higher than 40%.

3. The preparation method of the quick-charging graphite has the advantages of simple and feasible process, wide raw material sources, environmental friendliness, no need of harsh environmental conditions, no need of reagents and methods with environmental hazard in the preparation process, mass production, low cost, environmental friendliness, convenience in use and the like.

4. The quick-charge graphite is compatible with the existing lithium ion battery preparation process, and is suitable for the fields of lithium ion batteries, solid-state batteries and the like.

Drawings

Fig. 1 is an SEM image of the rapidly charged graphite obtained in example 2 of the present invention.

Fig. 2 is an XRD pattern of the rapidly charged graphite obtained in example 2 of the present invention.

Detailed Description

The invention is further illustrated by means of the following examples, which are not intended to limit the scope of the invention. The experimental methods, in which specific conditions are not noted in the following examples, were selected according to conventional methods and conditions, or according to the commercial specifications.

In the following examples and comparative examples:

natural graphite is purchased from Qingda sea, particle size D50 is 8.2 μm, carbon content is 99.9%, ash content is less than 0.1%.

The artificial graphite was purchased from a single particle graphitized product of Shanghai fir family technology Co., ltd, and had a particle size D50 of 9.1. Mu.m.

Example 1

1. Preparation of amphiphilic carbon material

Petroleum coke crushed to below 10 mu m is used as a raw material, and an amphipathic carbon material is prepared by adopting a mixed acid method, and the specific process is as follows: firstly, preparing 500mL of mixed acid of concentrated nitric acid and concentrated sulfuric acid according to a volume ratio of 3:7, then adding 100g of petroleum coke, stirring and refluxing for 3 hours at 80 ℃, cooling, filtering to obtain a filter cake, and washing the filter cake to be neutral to obtain the petroleum coke-based amphiphilic carbon material. The carbon residue value of the petroleum coke-based amphiphilic carbon material is 61 percent according to GB/T268-1987.

2. Preparation of the coating agent

Dissolving ethylenediamine in water to obtain an alkaline solution with a pH value of 13 (pH test paper test), dissolving the prepared petroleum coke-based amphiphilic carbon material in the alkaline solution, keeping the temperature at 80 ℃ for 1 hour, and filtering to obtain a filtrate to obtain the coating agent, wherein the petroleum coke-based amphiphilic carbon material accounts for 30% of the coating agent by mass.

3. Preparation of quick-charging graphite

S1, according to a coating agent (calculated according to carbon residue value): mixing the ingredients of the natural graphite with the ratio of 10:100, and mixing by adopting an electric heating horizontal mixer at the mixing temperature of 80 ℃ to obtain the slurry after uniform mixing.

S2, introducing air into the electric heating horizontal mixer, wherein the flow is 0.3L/(Kg min), heating to 110 ℃ at a heating speed of 3 ℃/min, and preserving heat for 2 hours at 110 ℃;

continuously introducing air with the flow of 0.2L/(Kg min), continuously heating to 300 ℃ at 3 ℃/min, and preserving heat for 2h at 300 ℃;

continuously introducing air, continuously heating to 500 ℃ at 3 ℃/min, and continuously keeping the temperature at 500 ℃ for 1.5 hours to obtain the precursor.

S3, carbonizing the precursor: carbonizing by an atmosphere furnace, wherein the flow rate of nitrogen atmosphere is 0.05L/(Kg min), heating to 1000 ℃ at 4 ℃/min, and preserving heat for 3 hours. And naturally cooling to room temperature, and discharging to obtain the quick-charging graphite.

Example 2

In the step S1 of preparing the quick graphite filling, the coating agent (calculated according to carbon residue value) is adopted: natural graphite = 5:100 the formulation was carried out under the same conditions and procedure as in example 1.

Example 3

The conditions and steps were the same as in example 1, except that artificial graphite was used in step S1 of the preparation of quick charge graphite.

Example 4

The conditions and steps were the same as in example 1, except that the carbonization temperature in step S3 of the preparation of the quick charge graphite was 1200 ℃.

Example 5

According to the method for preparing the amphiphilic carbon material in the embodiment 1, petroleum pitch with the softening point of 220 ℃ which is crushed to be less than 10 mu m is taken as a raw material to prepare the petroleum pitch-based amphiphilic carbon material. The carbon residue value of the petroleum asphalt-based amphiphilic carbon material is measured to be 52 percent according to GB/T268-1987.

Except that the petroleum pitch-based amphiphilic carbon material was used for preparing the coating agent and the quick graphite charge, the other conditions and steps were the same as in example 1.

Comparative example 1

In this comparative example, the test was directly performed using raw material 8.2 μm natural graphite.

Comparative example 2

In this comparative example, the conditions and steps were the same as in example 1 except that the petroleum coke-based amphiphilic carbon material was 1% by mass of the coating agent in the preparation process of the coating agent.

Comparative example 3

In this comparative example, a test was performed using conventional coated artificial graphite. The artificial graphite after conventional coating is selected from FSN-1 which is a product sold in Shanghai fir family technology market. Conventional cladding modes: mixing asphalt and graphite powder in the ratio of 2-10 to 90-98, heating to 500-700 deg.c in an electrically heated mixer in nitrogen atmosphere, maintaining for 1-3 hr, cooling to natural temperature and carbonizing in kiln. The carbonization temperature is 1000-1300 ℃, and the heat preservation time is 1-4 hours.

Comparative example 4

In this comparative example, the preparation was carried out in accordance with the preparation method of quick graphite charging in example 1, using 220 ℃ softening point petroleum asphalt pulverized to 8 μm as a coating agent directly, wherein in step S1, the petroleum asphalt (calculated as carbon residue value) was used: natural graphite = 10:100.

Effect example 1

The quick charge graphites prepared in examples 1-5 and comparative examples 1-3 were tested for the following properties using methods conventional in the art.

(1) The particle diameters D50 of the quick graphite particles obtained in examples 1 to 5 and comparative examples 1 to 3 were measured using a Mastersize 2000 (Mark 2000), and the results are shown in Table 1.

(2) Specific surface areas of the quick-charge graphites prepared in examples 1 to 5 and comparative examples 1 to 3 were measured according to the BET method conventional in the art, and the results are shown in Table 1.

(3) SEM images of the fast charge graphite obtained in example 1 were measured using ZEISS 500 field emission Scanning Electron Microscope (SEM), and the results are shown in fig. 1. As can be seen from FIG. 1, the particles of the rapidly filled graphite are uniformly and naturally distributed, the surface is smooth, no obvious defects and adhesion are caused, and the structure of the spherical graphite is kept good.

(4) XRD patterns of the rapidly-charged graphite obtained in example 1 were measured using a (Brookfield D8X-ray diffractometer, scanning mode θ -2θ, step 2 °/s), and the results are shown in FIG. 2. As can be seen from fig. 2, the crystallization degree of the quick-charging graphite prepared in example 1 is lower than that of the natural graphite which is not subjected to coating modification, and diffraction peaks of other impurities do not appear in the diffraction pattern, which indicates that a uniformly coated graphite sample can be obtained by adopting the coating agent of the invention, and the improvement of the electrical property of the anode material is very favorable.

Effect example 2

(1) Preparation of electrodes

Mixing the quick graphite charging anode materials obtained in examples 1-5 and comparative examples 1-3, an acetylene black conductive agent and a PVDF binder according to a mass ratio of 8:1:1 under the condition of room temperature, using NMP as a solvent to prepare uniform slurry, uniformly coating the slurry on a copper foil, wherein the coating surface density is about 6mg/cm ² Then the copper foil is put into a vacuum drying oven to be dried for 12 hours at 80 ℃. Cutting the dried copper foil into 2cm in area ² The wafer of (2) is made into a working electrode.

(2) Assembly of button half-cell

Under the room temperature condition, taking a metal lithium sheet as a negative electrode and a counter electrode, taking the product obtained in the step (1) as a working electrode, taking a Celgard2400 polypropylene porous membrane as a diaphragm, and taking 1mol/L LiPF ₆ And (3) using the EC/DEC (volume ratio of 1:1) solution as electrolyte, assembling the CR-2032 type button cell in a vacuum glove box, and tightly sealing mechanically.

(3) Specific volume and capacitance retention test

The assembled cell was allowed to stand at room temperature for 24 hours and then electrochemical testing was started. On an Arbin battery test system, according to the design capacity of 360mAh/g, the current of 0.1C is adopted in the first week of test, and the charge-discharge voltage interval is 5 mV-1.5V. And (5) standing for 5 minutes after the charge or discharge is finished. The button cell 3C rapid discharge constant current ratio test adopts a button cell after 3 weeks of 0.1C circulation, 0.1C is charged to 2V, then 3C is firstly used for discharging to 5mV to obtain capacity a, and then 0.1C is used for discharging to 5mV to obtain capacity b.3C rapid discharge constant current ratio=a/(a+b) ×100%. After 1000 cycles, the capacity retention rate was subjected to charge and discharge cycles using a constant current of 0.5C. Capacity retention after 1000 cycles = 1003 th charge capacity/third charge capacity 100%.

The results of the test on the capacity of the lithium ion battery, the 3C rapid discharge constant current ratio and the capacity retention rate after 1000 cycles of the rapid charging graphite prepared in examples 1 to 5 and comparative examples 1 to 3 are shown in Table 1.

TABLE 1

As is clear from Table 1, the fast-charge graphite anode materials prepared in examples 1 to 5 have the characteristics of high capacity, high 3C discharge constant current ratio and long cycle life at the same time. However, the natural graphite raw material of comparative example 1 is extremely low in both 3C discharge constant current ratio and long cycle life, and is difficult to use in a commercial lithium ion battery anode material. In comparative example 2, the ratio of the amphiphilic carbon material in the coating agent is too low, both the 3C discharge constant current ratio and the long cycle life are extremely low, and little improvement is achieved compared with the uncoated comparative example 1. Comparative examples 3 and 4, although having a capacity close to that of the examples and a cycle life higher, have a 3C discharge constant current ratio far lower than that of the examples.

For the current commercial lithium ion batteries, the capacity problem and the service life problem have been greatly improved, and the production and life requirements of people are basically met. However, the problem of charge anxiety of lithium ion batteries is only significantly advanced at a later time, and particularly, fast charging of 3C and above is not substantially solved. For negative electrode materials, the fast charge of lithium ion batteries corresponds to the fast discharge of graphite negative button batteries. The 3C discharge constant current ratio of any one of the present examples was 5 times or more that of the comparative example. The method has very important practical significance for solving the charge anxiety problem of the lithium ion battery.

Claims

1. The preparation method of the quick-charging graphite comprises the following steps:

s1, mixing a coating agent with graphite aggregate to obtain slurry; the coating agent comprises an amphiphilic carbon material, a pH regulator and water; the carbon residue value of the amphiphilic carbon material is 40% -70%; the amphiphilic carbon material accounts for 20-70% of the coating agent by mass; the pH value of the coating agent is more than 12;

the particle size of the graphite aggregate is 5-20 mu m; the carbon content of the graphite aggregate is not less than 99.9%; the graphitization degree of the graphite aggregate is 93% -99%;

s2, drying and curing the slurry to obtain a precursor; the drying and curing are carried out in the same equipment, the drying and curing process is to carry out sectional heat treatment on the slurry, and the sectional heat treatment comprises the following steps:

(1) First stage heat treatment: the temperature is 80-200 ℃ and the heat preservation time is 1-3 h;

(2) The second stage of heat treatment, the temperature is 200-400 ℃, and the heat preservation time is 1-3 h;

(3) The third heat treatment, the temperature is 400-700 ℃, and the heat preservation time is 1-3 h;

and S3, carbonizing the precursor to obtain the quick-charge graphite.

2. The method for preparing the quick graphite filling according to claim 1, wherein the amphiphilic carbon material accounts for 20-40% of the coating agent by mass percent;

and/or the amphiphilic carbon material is an asphalt-based amphiphilic carbon material and/or a raw coke-based amphiphilic carbon material;

and/or the carbon residue value of the amphiphilic carbon material is 50% -65%;

and/or the pH regulator is an alkaline substance which can volatilize or completely decompose into gas;

and/or, the coating agent further comprises a conductive additive;

and/or, the coating agent further comprises a thickener.

3. The method for preparing the quick graphite according to claim 2, wherein the amphiphilic carbon material accounts for 30% of the coating agent by mass;

and/or the pitch-based amphiphilic carbon material is selected from one or more of a coal tar pitch-based amphiphilic carbon material, a coal pitch-based amphiphilic carbon material, a petroleum pitch-based amphiphilic carbon material and a mesophase-based amphiphilic carbon material;

and/or the raw coke-based amphiphilic carbon material is one or two selected from petroleum coke-based amphiphilic carbon materials and needle-shaped Jiao Ji amphiphilic carbon materials;

and/or the carbon residue value of the amphiphilic carbon material is 52% or 61%;

and/or the pH regulator is ammonia water or ethylenediamine;

and/or the conductive additive is selected from one or more of carbon nanotubes, graphene and conductive graphite;

and/or, according to carbon residue value calculation, the conductive additive accounts for 1-30% of the coating agent by mass;

and/or the thickener is sodium carboxymethyl cellulose.

4. The method for preparing quick graphite according to claim 3, wherein the amphiphilic carbon material is petroleum coke-based amphiphilic carbon material or petroleum pitch-based amphiphilic carbon material;

and/or, the carbon nanotubes are single-walled carbon nanotubes;

and/or, the conductive additive accounts for 1-15% of the coating agent by mass percent according to carbon residue value.

5. The method for preparing quick graphite according to claim 2, wherein the coating agent comprises petroleum coke-based amphiphilic carbon material, ethylenediamine and water; the petroleum coke-based amphiphilic carbon material accounts for 30% of the coating agent by mass; the pH value of the coating agent is 13;

or the coating agent comprises petroleum asphalt-based amphiphilic carbon material, ethylenediamine and water; the petroleum asphalt-based amphiphilic carbon material accounts for 30% of the coating agent by mass; the pH value of the coating agent is 13.

6. The method of producing a quick charge graphite as claimed in any one of claims 1 to 5, wherein the method of producing a coating agent comprises dissolving the amphiphilic carbon material and the pH adjuster in the water.

7. The method for preparing quick charge graphite as claimed in claim 6, wherein the method for preparing the coating agent comprises: dissolving the amphiphilic carbon material in the water, and then adding the pH regulator to adjust the pH to be more than 12 to obtain the water; or dissolving the pH regulator in the water to obtain an alkaline solution with the pH of more than 12, and then dissolving the amphiphilic carbon material in the alkaline solution to obtain the modified carbon material.

8. The method of claim 1, wherein in step S1, the mass ratio of the coating agent to the graphite aggregate is (1-20): 100;

and/or the graphite aggregate is natural graphite or artificial graphite which is subjected to coating treatment or not subjected to coating treatment; wherein the artificial graphite is single particle or secondary particle;

and/or the mixing equipment is a mixer, a kneader or a fusion machine;

and/or the temperature of the mixing does not exceed 80 ℃.

9. The method of claim 8, wherein in step S1, the mass ratio of the coating agent to the graphite aggregate is (2-10) calculated according to carbon residue value: 100;

and/or the mixer is an electric heating horizontal mixer;

and/or, the mixing comprises: mixing in a mixer or a kneader, and mechanically fusing in a fusion machine.

10. The method for preparing quick charge graphite according to claim 1, wherein the first stage heat treatment is dynamically dried in an air atmosphere; introducing gas in the curing process;

and/or, the drying and curing are carried out in a kiln or a heatable mixer;

and/or the temperature of the first section heat treatment is 100-150 ℃;

and/or, the temperature of the second stage heat treatment is 300 ℃;

and/or the temperature of the third heat treatment is 500-650 ℃;

and/or, in the sectional heat treatment process, the heating speed is 1-5 ℃/min.

11. The method of claim 10, wherein during the curing, the gas is an inert gas, nitrogen, ozone or an oxygen-containing gas;

and/or the heatable mixer is an electric heating horizontal mixer;

and/or, in the sectional heat treatment process, the heating rate is 3 ℃/min;

and/or introducing gas in the sectional heat treatment process.

12. The method for preparing quick graphite according to claim 11, wherein the oxygen content of the oxygen-containing gas is 15% to 100%;

and/or the oxygen-containing gas is a mixed gas of oxygen and nitrogen.

13. The method for preparing quick graphite according to claim 11, wherein the oxygen-containing gas is air or a mixed gas of 21% oxygen and 79% nitrogen, and the percentages are volume percentages.

14. The method for preparing quick graphite according to claim 1, wherein in step S3, the carbonization equipment is an atmosphere furnace, a rotary furnace, a tube furnace, a box furnace, a pusher kiln, a tunnel kiln, or a roller kiln;

and/or, the carbonization temperature is 900-1500 ℃;

and/or, in the carbonization process, the heat preservation time at the carbonization temperature is 1-6 hours;

and/or the carbonization is performed under the protection of gas, wherein the gas is nitrogen, inert gas or reducing gas;

and/or, the carbonization is vacuum carbonization;

and/or, grading or screening the carbonized product after carbonization.

15. The method for preparing quick charge graphite as set forth in claim 14, wherein in step S3, the carbonization temperature is 900-1200 ℃;

and/or, the carbonization adopts a temperature programming mode;

and/or, in the carbonization process, the holding time at the carbonization temperature is 3 hours;

and/or the inert gas is argon;

and/or the flow rate of the gas is 0.001-0.05L/(Kg.min);

and/or, the negative pressure of the vacuum carbonization is not higher than 100Pa.

16. The method of claim 15, wherein in step S3, the carbonization is performed at a heating rate of 1 to 5 ℃/min.

17. The method of claim 16, wherein in step S3, the carbonization is performed at a temperature rise rate of 4 ℃/min.

18. A quick charge graphite prepared according to the method for preparing a quick charge graphite as described in any one of claims 1 to 17.

19. An electrode whose electrode material comprises the fast-charging graphite of claim 18.

20. The electrode of claim 19, wherein the electrode is a negative electrode.

21. A battery comprising the electrode of claim 19 or 20.

22. The battery of claim 21, wherein the battery is a lithium ion battery or a solid state battery.