WO2022121400A1

WO2022121400A1 - Coating agent, fast-charging graphite, preparation method therefor and application thereof, and battery

Info

Publication number: WO2022121400A1
Application number: PCT/CN2021/117223
Authority: WO
Inventors: 潘福森; 范拯华; 王晓阳; 陈兵帅; 张秀云
Original assignee: 宁波杉杉新材料科技有限公司
Priority date: 2020-12-10
Filing date: 2021-09-08
Publication date: 2022-06-16
Also published as: CN112803001B; CN112803001A

Abstract

Disclosed are a coating agent, a fast-charging graphite, a preparation method therefor and an application thereof, and a battery. The coating agent comprises an amphiphilic carbon material, a pH adjusting agent, and water; the percentage by mass of the amphiphilic carbon material in the coating agent is 20%-70%; and the pH value of the coating agent is 12 or more. By coating and modifying graphite using the coating agent, a coating layer having uniform thickness and good compactness can be formed, and the obtained fast-charging graphite structure has excellent stability and fast-charging performance, and can be used as a negative electrode material of batteries, such as lithium-ion batteries and solid-state batteries; in addition, the preparation method is simple and feasible, and costs are low.

Description

Coating agent, fast charging graphite and preparation method and application thereof, battery

This application claims the priority of Chinese patent application 2020114518219 with an application date of 2020/12/10. This application cites the full text of the above Chinese patent application.

technical field

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

Background technique

Lithium-ion batteries have excellent performances such as high energy density, high working voltage, long cycle life, no pollution, good safety performance, environmental protection and durability, making them suitable for use in portable electronic devices to electric vehicles, from civilian fields to national defense and military fields, from conventional It has a wide range of applications in the fields of low temperature, high temperature and fast charging, and continues to deepen and expand. Lithium-ion battery technology is also one of the research hotspots that has received widespread attention in recent years, and has a profound impact on people's production and lifestyle.

Anode material is one of the key technologies restricting the continuous improvement of lithium-ion batteries, and it is also one of the main breakthroughs in improving lithium-ion performance. Commercial lithium-ion battery anode materials are mainly various carbon materials, such as natural graphite, artificial graphite, modified graphite, soft and hard carbon, etc. Although alloy materials and silicon materials have great application prospects, complex preparation and production processes, high costs, low safety and life characteristics make their future commercial applications extremely uncertain. Among the currently commercialized carbon materials, surface-modified natural graphite and artificial graphite occupy an absolute share.

The stable crystal structure characteristics and anisotropy of graphite materials make it impossible for lithium ions to diffuse quickly in graphite materials. In a perfect graphite crystal, the diffusion of lithium ions can only enter from the end faces of the graphite, parallel to the graphene sheets. Since lithium ions cannot pass through the graphene layer, the diffusion of lithium ions inside graphite exhibits obvious anisotropy. The typical interlayer spacing d002 of graphite is 0.336-0.338nm, which is relatively close to the diameter of lithium atoms. Therefore, lithium atoms need to overcome a large potential barrier when diffusing between graphite layers. The macroscopic performance is that the diffusion rate of lithium in graphite is small. , showing poor fast charge-discharge performance in electrochemical terms.

The study found that the main method to solve the fast charging and low temperature performance of graphite anode materials in lithium-ion battery systems is to modify the surface of graphite particles. Coating hard carbon structure on the surface of graphite is the most effective method to improve the fast charging performance and low temperature performance of graphite. Specifically, Japanese Patent JP11246209 impregnates graphite and hard carbon particles in pitch or tar at a temperature of 10-300°C, and then performs solvent discharge and carbonization heat treatment. This method is difficult to form on the surface of graphite and hard carbon with uniform thickness. The improvement of the structural stability of natural graphite will be limited. Chinese patent CN106848468B provides a method and equipment for preparing hard carbon-coated graphite by utilizing the recovered cleaning solution. Although this method can provide low-cost hard carbon-coated graphite materials, the source and composition of the coating agent are difficult to be continuously stabilized. Therefore, Large-scale production makes little sense.

SUMMARY OF THE INVENTION

In order to solve the defects of poor stability and fast charging performance of fast-charging graphite in the prior art, and the practicability and cost of the preparation method cannot be taken into account, the present invention provides a coating agent, fast-charging graphite, and a preparation method and application thereof ,Battery. Using the coating agent of the present invention to coat and modify graphite can form a coating layer with uniform thickness and good compactness, and the obtained fast-charging graphite has excellent structural stability and fast-charging performance, and can be used for lithium ion batteries and solid-state batteries. The negative electrode material of the battery is simple and feasible, and the cost is low.

In order to solve the above problems, the present invention adopts the following technical solutions:

The present invention provides a coating agent, which comprises an amphiphilic carbon material, a pH adjusting agent and water; the amphiphilic carbon material accounts for 20% to 70% of the coating agent by mass; the coating The pH value of the coating agent is above 12.

In the present invention, the mass percentage of the amphiphilic carbon material in the coating agent is preferably 20% to 40%, such as 30%.

In the present invention, the amphiphilic carbon material refers to a conventional carbon material in the art that can be dissolved in an alkaline aqueous solution and also in 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, which is inconvenient to use.

The amphiphilic carbon material may be a pitch-based amphiphilic carbon material and/or a coke-based amphiphilic carbon material. Wherein, the pitch-based amphiphilic carbon material can be selected from coal tar pitch-based amphiphilic carbon materials, coal pitch-based amphiphilic carbon materials, petroleum pitch-based amphiphilic carbon materials and mesophase-based amphiphilic carbon materials one or more of. The green coke-based amphiphilic carbon material is selected from one or both of petroleum coke-based amphiphilic carbon materials and needle-shaped coke-based amphiphilic carbon materials. The amphiphilic carbon material is preferably a petroleum coke-based amphiphilic carbon material or a petroleum pitch-based amphiphilic carbon material. The carbon residue value of the amphiphilic carbon material may be 40% to 70%, preferably 50% to 65%, such as 52% or 61%.

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

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

In the present invention, the pH adjusting agent may be an alkaline substance commonly used in the field, and the pH value of the coating agent may be adjusted to 12 or above. The pH adjuster is preferably an alkaline substance that can be volatilized or completely decomposed into gas, preferably ammonia water or ethylenediamine.

In the present invention, preferably, the coating agent further includes a conductive additive. Wherein, the conductive additive may be a conventional conductive substance in the field, preferably one or more selected from carbon nanotubes, graphene and conductive graphite. The carbon nanotubes are preferably single-walled carbon nanotubes. According to the carbon residue value, the mass percentage of the conductive additive in the coating agent may be 1-30%, preferably 1-15%.

In the present invention, calculating according to the residual carbon value means that the mass of the substance taken during the calculation is "the actual mass of the substance x the residual carbon value of the substance". The detection standard of the average carbon residue value of the present invention is GB/T 268-1987.

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

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

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

The present invention also provides a preparation method of the coating agent, which comprises dissolving the amphiphilic carbon material and the pH adjusting agent 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 adjuster to adjust the pH to be above 12, that is;

Alternatively, the pH adjusting agent is dissolved in water to obtain an alkaline solution with a pH of 12 or higher, and then the amphiphilic carbon material is dissolved in the alkaline solution.

In the present invention, preferably, after dissolving the amphiphilic carbon material and the pH adjusting agent in water, they are filtered at a constant temperature. The temperature of the constant temperature may be 60˜90° C., preferably 80° C.; the time of the constant temperature may be 0.5˜3 h, preferably 1 h. The filtration can be performed by a conventional method in the art, and the purpose of the filtration is to filter out possible insoluble components.

In the present invention, when the coating agent further includes the conductive additive, the conductive additive is added after dissolving the amphiphilic carbon material and the pH adjuster in water. When the coating agent further includes the thickening agent, the thickening agent is added after dissolving the amphiphilic carbon material and the pH adjusting agent in water.

The present invention also provides a preparation method of fast-charged graphite, which comprises the following steps:

S1, the coating agent is mixed with graphite aggregate to obtain slurry;

S2, drying and curing the slurry to obtain a precursor;

S2, carbonizing the precursor to obtain the fast-charged graphite.

In step S1, the graphite aggregate can be conventional natural graphite or artificial graphite that has been coated or not coated in the field. Wherein, the artificial graphite can be single particle or secondary particle. The particle size of the graphite aggregate is preferably 5-20 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 step S1, according to the value of residual carbon, the mass ratio of the coating agent to the graphite aggregate may be (1-20):100, preferably (2-10):100.

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

The mixing preferably includes: first mixing in a mixer or mixing in a kneader, and then performing mechanical fusion in a fusion machine. In the process of mechanical fusion, the relative velocity between different material particles is large, the surface temperature of the material is high, and it is subjected to extrusion, which makes the material contact more fully and mix more fully, which is conducive to making the amphiphilic carbon material more uniform. coated on the graphite surface.

The temperature of the mixing preferably does not exceed 80°C. The mixing temperature is the temperature of the material during mixing.

In step S2, the drying method may be freeze drying or heating drying. The freeze-drying can be performed in the freeze-drying machine according to methods conventional in the art. The heating drying can be carried out in a vacuum drying oven or a blast drying oven according to a conventional method in the art. The temperature of the heating and drying may be 80-200°C, preferably 100-150°C, for example, 110°C. The heating drying is preferably dynamic drying in an air atmosphere.

In step S2, the curing can be performed in conventional heating equipment in the art, preferably in a kiln or a heatable mixer, and the heatable mixer is preferably an electrically heated horizontal mixer.

During the curing process, the curing temperature may be 200-700°C. During the curing process, a gradual heating method is preferably adopted. During the curing process, the holding time at the curing temperature may be 2-8 hours.

During the curing process, a gas may be introduced, and the gas may be an inert gas, nitrogen, ozone or an oxygen-containing gas. The oxygen-containing gas refers to a mixed gas of oxygen and other gases. The oxygen content of the oxygen-containing gas may be 15% to 100%; the oxygen content refers to the volume percentage 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, and the percentage is by volume.

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

In step S2, the drying and curing may be performed in different equipments, or may be performed in the same equipment. Preferably, the drying and curing are performed in the same equipment, which can simplify the process, better realize automation and reduce costs. When the drying and curing are carried out in the same equipment, it is preferably carried out in a kiln or a heatable mixer, and the heatable mixer is preferably an electrically heated horizontal mixer.

When the drying and curing are performed in the same equipment, the drying and curing process may be staged heat treatment of the slurry, and the staged heat treatment includes: (1) The first stage of heat treatment: the temperature is 80 °C ～200℃, preferably 100～150℃; the holding time is 1～3h; (2) the second heat treatment, the temperature is 200～400℃, preferably 300℃; the holding time is 1～3h; ( 3) In the third stage of heat treatment, the temperature is 400-700°C, preferably 500-650°C; the holding time is 1-3h.

Wherein, the first-stage heat treatment corresponds to a drying process, and the second-stage heat treatment and the third-stage heat treatment correspond to a curing process. In the step-by-step heat treatment process, the heating rate is preferably 1˜5° C./min, for example, 3° C./min. During the staged heat treatment, gas may be introduced. The operation and conditions of the gas feed are as previously described.

In a preferred embodiment of the present invention, the specific operations of drying and curing include: feeding air into the electric heating horizontal mixer at a flow rate of 0.3L/(Kg min), and heating at a rate of 3°C/min Heat up to 110°C, hold at 110°C for 2h; continue to introduce air at a flow rate of 0.2L/(Kg min), continue to heat up to 300°C at 3°C/min, hold for 2h; continue to flow at a flow rate of 0.2L/(Kg min) Air was introduced, and the temperature was continued to rise to 500°C at 3°C/min, and the temperature was maintained for 1.5h to obtain the precursor.

In step S3, the carbonization can be carried out in conventional equipment in the art by using a conventional method in the art. The carbonization equipment can be furnace equipment such as atmosphere furnace, rotary furnace, tube furnace, box furnace, push-plate kiln, tunnel kiln, roller kiln and the like.

The carbonization temperature may be 900-1500°C, preferably 900-1200°C. It is preferable to adopt a temperature-programmed manner, and the heating rate is preferably 1 to 5°C/min, for example, 4°C/min.

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 the protection of a gas, and the gas can be nitrogen, an inert gas or a reducing gas, and the inert gas is preferably argon. The flow rate of the gas is preferably 0.001 to 0.05 L/(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, after the carbonization, the obtained carbonized product is classified or screened.

The present invention also provides a fast-charged graphite, which is prepared according to the above preparation method.

The fast-charging graphite of the present invention can have the following properties: particle size D50 is 5-30 μm (eg 8.2 μm or 15.3 μm), specific surface area (BET method) ≤ 5m ² /g (eg 2.1m ² /g, 3.3m ^{2 )} /g).

The present invention also provides an application of the fast-charging graphite as an electrode material in a battery. The electrode material is preferably a negative electrode material.

The present invention also provides an electrode, the electrode material of which includes the fast-charging graphite. The electrode is preferably a negative electrode.

The present invention also provides a battery including 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 common knowledge in the art, the above preferred conditions can be combined arbitrarily to obtain preferred examples of the present invention.

The reagents and raw materials used in the present invention are all commercially available. For steps and methods that are not described in detail in the present invention, reference may be made to conventional methods in the industry or descriptions of related equipment.

The positive progressive effect of the present invention is:

1. The fast-charging graphite particles of the present invention have natural distribution, smooth surface, no obvious defects and bonding, and the structure of spherical graphite is well maintained and stable, and has excellent lithium ion rapid insertion and extraction ability and excellent cycle ability.

2. The lithium ion battery using the fast-charging graphite of the present invention as the electrode material has high capacity and good cycle stability, and the fast-charging performance is greatly improved. Specifically, the initial charge capacity of the button half battery is 340-375mAh/g, the capacity retention rate after 1000 cycles can reach more than 95%, and the 3C fast discharge constant current ratio is higher than 40%.

3. The preparation method of the fast-charged graphite of the present invention is simple and feasible, has a wide range of raw material sources, and is environmentally friendly. The preparation process does not require harsh environmental conditions, nor does it require environmentally hazardous reagents and methods, and has the advantages of large-scale production and low cost. , green environmental protection, easy to use and other advantages.

4. The fast-charging graphite of the present invention is compatible with the existing lithium-ion battery preparation process, and is suitable for use in the fields of lithium-ion batteries, solid-state batteries and the like.

Description of drawings

FIG. 1 is a SEM image of the fast-charged graphite obtained in Example 2 of the present invention.

FIG. 2 is an XRD pattern of the fast-charged graphite obtained in Example 2 of the present invention.

Detailed ways

In the following examples and comparative examples:

Natural graphite was purchased from Qingdao Haida, the particle size D50 was 8.2 μm, the carbon content was 99.9%, and the ash content was less than 0.1%.

The artificial graphite was purchased from the single-particle graphitized product of Shanghai Shanshan Technology Co., Ltd., and the particle size D50 was 9.1 μm.

Example 1

1. Preparation of Amphiphilic Carbon Materials

Using petroleum coke crushed below 10 μm as raw material, the amphiphilic carbon material was prepared by the mixed acid method. The specific process was as follows: firstly, 500 mL of mixed acid of concentrated nitric acid and concentrated sulfuric acid was prepared according to the volume ratio of 3:7, then 100 g of petroleum coke was added, and the mixture was heated to 80 The mixture was stirred and refluxed for 3 hours at ℃, and after cooling, a filter cake was obtained by filtration, and the filter cake was washed to neutrality to obtain a petroleum coke-based amphiphilic carbon material. According to GB/T 268-1987, the carbon residue value of the petroleum coke-based amphiphilic carbon material was determined to be 61%.

2. Preparation of the coating agent

Dissolve ethylenediamine in water to obtain an alkaline solution with a pH value of 13 (pH test paper test), then dissolve the prepared petroleum coke-based amphiphilic carbon material in the alkaline solution, and filter at a constant temperature of 80°C for 1 hour. The filtrate is obtained to obtain a coating agent, wherein the percentage by mass of the petroleum coke-based amphiphilic carbon material in the coating agent is 30%.

3. Preparation of fast-charged graphite

S1. According to the coating agent (calculated according to the residual carbon value): natural graphite = 10:100, the ingredients are mixed, and the electric heating horizontal mixer is used for mixing. The mixing temperature is 80 °C, and the slurry is obtained after mixing evenly.

S2. Pour air into the electric heating horizontal mixer, the flow rate is 0.3L/(Kg min), the temperature is raised to 110°C at a heating rate of 3°C/min, and the temperature is kept at 110°C for 2h;

Continue to introduce air, the flow rate is 0.2L/(Kg min), continue to heat up to 300°C at 3°C/min, and keep at 300°C for 2h;

Continue to introduce air, continue to heat up to 500°C at 3°C/min (what kind of atmosphere is in this section?), and end at 500°C for 1.5h to obtain the precursor.

S3. Carbonizing the precursor: carbonization is carried out in an atmosphere furnace, the nitrogen atmosphere flow rate is 0.05L/(Kg min), the temperature is raised to 1000°C at 4°C/min, and the temperature is maintained for 3 hours. After cooling down to room temperature naturally, fast-charged graphite is obtained.

Example 2

The other conditions and steps are the same as in Example 1, except that in step S1 of the preparation of fast-charging graphite, the ingredients are carried out according to the coating agent (calculated according to the residual carbon value): natural graphite=5:100.

Example 3

Except that artificial graphite is used in step S1 of the preparation of fast-charging graphite, other conditions and steps are the same as those in Example 1.

Example 4

Except that the carbonization temperature in step S3 of the preparation of fast-charged graphite is 1200° C., other conditions and steps are the same as those in Example 1.

Example 5

According to the preparation method of the amphiphilic carbon material in Example 1, the petroleum pitch-based amphiphilic carbon material was prepared by using petroleum pitch with a softening point of 220° C. pulverized to less than 10 μm as a raw material. According to GB/T268-1987, the carbon residue value of the petroleum pitch-based amphiphilic carbon material was determined to be 52%.

With this petroleum pitch-based amphiphilic carbon material, the preparation of the coating agent and the preparation of the fast-charged graphite are carried out. Except for this, the remaining conditions and steps are the same as those in Example 1.

Comparative Example 1

In this comparative example, the raw material 8.2 μm natural graphite is used for direct testing.

Comparative Example 2

In this comparative example, the remaining conditions and steps are the same as those in Example 1, except that the petroleum coke-based amphiphilic carbon material accounts for 1% by mass of the coating agent in the preparation process of the coating agent.

Comparative Example 3

In this comparative example, conventional coated artificial graphite was used for testing. Here, the conventionally coated artificial graphite is FSN-1, a commercially available product of Shanghai Shanshan Technology. Conventional coating method: mix pitch and graphite powder in a ratio of 2 to 10:90 to 98, then heat up to 500 to 700 °C in an electric heating mixer in a nitrogen atmosphere, keep the temperature for 1 to 3 hours, and cool down to a natural temperature. The temperature is then transferred to the kiln for carbonization. The carbonization temperature is 1000～1300℃, and the holding time is 1～4 hours.

Comparative Example 4

In this comparative example, the 220°C softening point petroleum pitch crushed to 8 μm is directly used as the coating agent, and the preparation is carried out according to the preparation method of fast-charging graphite in Example 1, wherein in step S1, the petroleum pitch (calculated according to the residual carbon value) is used. : Natural graphite = 10:100 for batching.

Effect Example 1

The following performance tests were performed on the fast-charged graphites prepared in Examples 1-5 and Comparative Examples 1-3 by using conventional methods in the art.

(1) Adopt Mastersize 2000 (Malvern 2000) to measure the particle size D50 of the fast-charged graphite prepared in Examples 1 to 5 and Comparative Examples 1 to 3, and the results are shown in Table 1.

(2) The specific surface areas of the fast-charged graphites prepared in Examples 1-5 and Comparative Examples 1-3 were measured according to the conventional BET method in the art. The results are shown in Table 1.

(3) The SEM image of the fast-charged graphite obtained in Example 1 was measured using a ZEISS 500 field emission scanning electron microscope, and the results are shown in Figure 1. It can be seen from Figure 1 that the particle distribution of fast-charged graphite is uniform and natural, the surface is smooth, there is no obvious defect and bonding, and the structure of spherical graphite is well maintained.

(4) The XRD pattern of the fast-charged graphite obtained in Example 1 was measured by using (Bruker D8 X-ray diffractometer, scanning mode θ-2θ, step 2°/s), and the result is shown in FIG. 2 . As can be seen from Figure 2, the degree of crystallization of the fast-charged graphite prepared in Example 1 is lower than that of the natural graphite without coating modification, and the diffraction peaks of other impurities do not appear in the diffraction pattern, which shows that the coating agent of the present invention is adopted. A uniformly coated graphite sample can be obtained, which is very beneficial to the improvement of the electrical properties of the negative electrode material.

Effect Example 2

(1) Preparation of electrodes

At room temperature, the fast-charged graphite anode materials, acetylene black conductive agent, and PVDF binder obtained in Examples 1 to 5 and Comparative Examples 1 to 3 were mixed in a mass ratio of 8:1:1 with NMP as a solvent. Homogeneous slurry, uniformly coat the slurry on the copper foil, the coating surface density is about 6mg/cm ² , and then put the copper foil in a vacuum drying oven at 80°C for drying for 12h. Cut the dried copper foil into a 2cm ² circle to make a working electrode.

(2) Assembly of button half battery

At room temperature, the metal lithium sheet was used as the negative electrode and the counter electrode, the product obtained in step (1) was used as the working electrode, the Celgard2400 polypropylene porous membrane was used as the separator, and 1 mol/L LiPF ₆ /EC:DEC (volume ratio was 1:1) ) solution as electrolyte, assembled into a CR-2032 button battery in a vacuum glove box, and tightly mechanically sealed.

(3) Test of specific capacity and capacitance retention

The assembled battery was allowed to stand at room temperature for 24 h before the electrochemical test was started. On the Arbin battery test system, according to the design capacity of 360mAh/g, the current of 0.1C was used in the first week of the test, and the charge and discharge voltage range was 5mV to 1.5V. Set aside for 5 minutes after charging or discharging. The 3C fast discharge constant current ratio test of the button battery uses the button battery after 3 weeks of 0.1C cycle. Now it is charged at 0.1C to 2V, then firstly discharged at 3C to 5mV to obtain the capacity a, and then discharged at 0.1C to 5mV to obtain capacity b. 3C fast discharge constant current ratio=a/(a+b)*100%. The capacity retention rate after 1000 cycles was charged and discharged with a constant current of 0.5C. The capacity retention rate after 1000 cycles=the 1003th charge capacity/the third charge capacity*100%.

After testing, the fast-charging graphite prepared in Examples 1-5 and Comparative Examples 1-3 are used in the capacity of lithium-ion batteries, the 3C fast discharge constant current ratio and the effect of capacity retention rate after 1000 cycles are shown in Table 1.

Table 1

It can be seen from Table 1 that the fast-charged graphite negative electrode 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 terms of 3C discharge constant current ratio and long cycle life, and is difficult to use in commercial lithium-ion battery anode materials. In Comparative Example 2, the proportion of amphiphilic carbon materials in the coating agent is too low, and both the 3C discharge constant current ratio and the long cycle life are extremely low, and there is almost no improvement compared with the uncoated Comparative Example 1. Although the capacity of Comparative Examples 3 and 4 is close to that of the Example and the cycle life is higher, the 3C discharge constant current ratio is much lower than that of the Example.

For the current commercial lithium-ion batteries, great progress has been made in the issues of capacity and life, and they basically meet people's production and living needs. However, the problem of charging anxiety of lithium-ion batteries has only made significant progress, especially the fast charging of 3C and above has not been substantially solved. For the negative electrode material, the fast charging of the lithium-ion battery corresponds to the fast discharging of the graphite negative button battery. The 3C discharge constant current ratio of any of the examples in this example is more than 5 times that of the comparative example. This has very important practical significance for solving the charging anxiety problem of lithium-ion batteries.

Although the specific embodiments of the present invention have been described above, those skilled in the art should understand that these are only examples, and various changes may be made to these embodiments without departing from the principle and essence of the present invention. Revise. Accordingly, the scope of protection of the present invention is defined by the appended claims.

Claims

A coating agent, comprising an amphiphilic carbon material, a pH adjusting agent and water; the mass percentage of the amphiphilic carbon material in the coating agent is 20% to 70%; the pH of the coating agent The value is 12 or more.
The coating agent according to claim 1, wherein the mass percentage of the amphiphilic carbon material in the coating agent is 20% to 40%, such as 30%;

And/or, the amphiphilic carbon material is a pitch-based amphiphilic carbon material and/or a coke-based amphiphilic carbon material; wherein, the pitch-based amphiphilic carbon material is preferably selected from coal tar pitch One or more of the based amphiphilic carbon materials, coal pitch based amphiphilic carbon materials, petroleum pitch based amphiphilic carbon materials and mesophase based amphiphilic carbon materials;

The green coke-based amphiphilic carbon material is preferably selected from one or both of petroleum coke-based amphiphilic carbon materials and needle-shaped coke-based amphiphilic carbon materials;

The amphiphilic carbon material is preferably a petroleum coke-based amphiphilic carbon material or a petroleum pitch-based amphiphilic carbon material;

And/or, the amphiphilic carbon material has a residual carbon value of 40% to 70%, preferably 50% to 65%, such as 52% or 61%;

And/or, the pH adjusting agent is an alkaline substance that can be volatilized or completely decomposed into gas, preferably ammonia water or ethylenediamine;

And/or, the coating agent further includes a conductive additive; wherein, the conductive additive is preferably selected from one or more of carbon nanotubes, graphene and conductive graphite; the carbon nanotubes are preferably It is a single-walled carbon nanotube; according to the residual carbon value, the mass percentage of the conductive additive in the coating agent is preferably 1% to 30%, more preferably 1% to 15%;

And/or, the coating agent also includes a thickening agent; wherein, the thickening agent is preferably sodium carboxymethyl cellulose;

Preferably, 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 mass of the coating agent; the The pH of the coating agent is 13;

Preferably, the coating agent comprises petroleum pitch-based amphiphilic carbon material, ethylenediamine and water; the petroleum pitch-based amphiphilic carbon material accounts for 30% of the mass of the coating agent; the The pH of the coating was 13.
A preparation method of the coating agent according to claim 1 or 2, which comprises dissolving the amphiphilic carbon material and the pH adjusting agent in the water;

Preferably, the preparation method of the coating agent comprises: dissolving the amphiphilic carbon material in the water, and then adding the pH adjusting agent to adjust the pH to be above 12; or, dissolving the pH The regulator is dissolved in the water to obtain an alkaline solution with a pH above 12, and then the amphiphilic carbon material is dissolved in the alkaline solution.
A preparation method of fast-charging graphite, which comprises the following steps:

S1, the coating agent described in claim 1 or 2 is mixed with graphite aggregate to obtain slurry;

S2, drying and curing the slurry to obtain a precursor;

S2, carbonizing the precursor to obtain the fast-charged graphite.
The method for preparing fast-charged graphite according to claim 4, wherein in step S1, according to the residual carbon value, the mass ratio of the coating agent to the graphite aggregate is (1-20):100 , preferably (2-10): 100;

And/or, the graphite aggregate is natural graphite or artificial graphite that is coated or not coated; wherein, the artificial graphite is single particle or secondary particle;

And/or, the particle size of the graphite aggregate is 5-20 μm;

And/or, the carbon content of the graphite aggregate is not less than 99.9%;

And/or, the graphitization degree of the graphite aggregate is 93% to 99%;

And/or, the mixing equipment is a mixer, a kneader or a fusion machine; the mixer is preferably an electric heating horizontal mixer; the mixing preferably includes: first in the mixer Mixing in the middle or mixing in a kneader, and then performing mechanical fusion in a fusion machine;

And/or, the temperature of the mixing does not exceed 80°C.
The method for preparing fast-charged graphite according to claim 4 or 5, wherein in step S2, the drying method is freeze-drying or heating-drying; the temperature of the heating-drying is preferably 80-200°C , more preferably 100-150°C, such as 110°C; the heating drying is preferably dynamic drying in an air atmosphere;

And/or, during the curing process, the curing temperature is 200 to 700°C; during the curing process, a gradual heating method is preferably adopted; during the curing process, the heat preservation at the curing temperature is The time is preferably 2 to 8 hours;

And/or, gas is introduced into the solidification process, and the gas is preferably an inert gas, nitrogen, ozone or an oxygen-containing gas; wherein, the oxygen content of the oxygen-containing gas is preferably 15% to 100%. %; 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, and the percentage is a volume percentage;

And/or, the drying and curing are carried out in the same equipment; preferably in a kiln or a heatable mixer, and the heatable mixer is preferably an electrically heated horizontal mixer;

Preferably, the drying and curing are carried out in the same equipment, and the drying and curing process is to perform subsection heat treatment on the slurry, and the subsection heat treatment includes:

(1) The first heat treatment: the temperature is 80～200℃, preferably 100～150℃; the holding time is 1～3h;

(2) the second stage of heat treatment, the temperature is 200～400℃, preferably 300℃; the holding time is 1～3h;

(3) The third stage of heat treatment, the temperature is 400～700℃, preferably 500～650℃; the holding time is 1～3h;

In the segmented heat treatment process, the heating rate is preferably 1 to 5°C/min, such as 3°C/min;

During the staged heat treatment, gas is preferably introduced.
The method for preparing fast-charged graphite according to any one of claims 4 to 6, wherein in step S3, the carbonization equipment is an atmosphere furnace, a rotary furnace, a tube furnace, a box furnace, and a push plate kiln, tunnel kiln, or roller kiln;

And/or, the temperature of the carbonization is 900-1500°C, preferably 900-1200°C; preferably, a temperature-programmed mode is adopted, and the heating rate is preferably 1-5°C/min, such as 4°C/min;

And/or, in the carbonization process, the holding time at the carbonization temperature is 1 to 6 hours, for example, 3 hours;

And/or, the carbonization is carried out under the protection of a gas, and the gas is nitrogen, an inert gas or a reducing gas; the inert gas is preferably argon; the flow rate of the gas is preferably 0.001-0.05L /(Kg min);

And/or, the carbonization is vacuum carbonization; preferably, the negative pressure of the vacuum carbonization is not higher than 100Pa;

And/or, after the carbonization, the obtained carbonized product is classified or screened.
A fast-charged graphite, which is prepared according to the preparation method of fast-charged graphite according to any one of claims 4 to 7.
An electrode, the electrode material comprising the fast-charging graphite of claim 8; the electrode is preferably a negative electrode.
A battery comprising the electrode of claim 9; the battery is preferably a lithium ion battery or a solid state battery.