阅读说明：本技术 一种快充高首效硬碳/人造石墨负极材料及其制备方法 (Fast-charging high-first-efficiency hard carbon/artificial graphite negative electrode material and preparation method thereof ) 是由 魏智伟 许晓落 贠晓亮 吴浩 于 2021-08-23 设计创作，主要内容包括：本发明涉及一种快充高首效硬碳人造石墨负极材料及其制备方法。所述制备方法包括：将含碳原材料进行热处理,得硬碳材料；将所述硬碳材料粉碎,然后与包覆剂混合均匀,进行热处理,制得包覆硬碳材料；将所述包覆硬碳材料进行石墨化高温热处理,完成后即得所述快充高首效硬碳人造石墨负极材料。所述制备方法选择硬碳作为主体,以提升负极材料的容量和快充性能；通过在硬碳表面包覆石墨降低硬碳比表面积、减少副反应,进而减少不可逆容量,提升首效；经过高温处理,减少硬碳中残留有缺陷结构,提升首效和循环稳定性。(The invention relates to a fast-charging high-first-efficiency hard carbon artificial graphite cathode material and a preparation method thereof. The preparation method comprises the following steps: carrying out heat treatment on the carbon-containing raw material to obtain a hard carbon material; crushing the hard carbon material, then uniformly mixing the crushed hard carbon material with a coating agent, and carrying out heat treatment to obtain a coated hard carbon material; and (3) carrying out graphitization high-temperature heat treatment on the coated hard carbon material to obtain the quick-charging high-first-effect hard carbon artificial graphite cathode material. The preparation method selects hard carbon as a main body to improve the capacity and the quick charging performance of the cathode material; the specific surface area of the hard carbon is reduced and side reactions are reduced by coating graphite on the surface of the hard carbon, so that the irreversible capacity is reduced, and the first effect is improved; through high temperature treatment, residual defective structures in hard carbon are reduced, and first effect and circulation stability are improved.)

1. A preparation method of a fast-charging high-first-efficiency hard carbon/artificial graphite negative electrode material is characterized by comprising the following steps:

(1) carrying out heat treatment on the carbon-containing raw material to obtain a hard carbon material;

(2) crushing the hard carbon material, then uniformly mixing the crushed hard carbon material with a coating agent, and carrying out heat treatment to obtain a coated hard carbon material;

(3) and (3) carrying out graphitization high-temperature heat treatment on the coated hard carbon material to obtain the quick-charging high-first-effect hard carbon artificial graphite cathode material.

2. The preparation method of the rapid-charging high-first-efficiency hard carbon/artificial graphite negative electrode material according to claim 1, wherein the rapid-charging high-first-efficiency hard carbon artificial graphite negative electrode material is of a core-shell structure, hard carbon is a core layer, and artificial graphite is a shell layer.

3. The method for preparing the fast-charging high-first-efficiency hard carbon/artificial graphite anode material according to claim 1, wherein in the step (1), the carbon-containing raw material is one or a combination of several of resin, carbon black, starch, asphalt, organic polymer or carbon-containing biological shell.

4. The preparation method of the fast-charging high-first-efficiency hard carbon/artificial graphite anode material according to claim 1, wherein in the step (1), the heat treatment is performed in an inert atmosphere; the heat treatment temperature is 700-1500 ℃, and the heat treatment time is 1-10 h.

5. The preparation method of the fast-charging high-first-efficiency hard carbon/artificial graphite anode material according to claim 1, wherein in the step (2), the crushing is carried out until the D50 is 8-30 μm.

6. The preparation method of the fast-charging high-first-efficiency hard carbon/artificial graphite negative electrode material according to claim 1, wherein in the step (2), the coating agent is one of asphalt, resin and coal tar; the content of the coating agent is 1-50% of the total weight.

7. The preparation method of the fast-charging high-first-efficiency hard carbon/artificial graphite anode material according to claim 1, wherein in the step (2), the mixing time is 0.5-3 h; the heat treatment temperature is 300-1000 ℃.

8. The preparation method of the fast-charging high-first-efficiency hard carbon/artificial graphite negative electrode material as claimed in claim 1, wherein in the step (3), the temperature of the high-temperature heat treatment is 2500-3000 ℃.

9. The fast-charging high-first-efficiency hard carbon/artificial graphite negative electrode material prepared by the method of any one of claims 1 to 8.

Technical Field

The invention belongs to the field of lithium ion battery materials, and particularly relates to a fast-charging high-first-efficiency hard carbon artificial graphite cathode material and a preparation method thereof.

Background

The lithium ion battery has the characteristics of long cycle life, high energy density, environmental friendliness and the like, and is widely applied to the fields of new energy such as electric vehicles, energy storage, 3C and the like. In the current commercial power lithium ion battery, the negative electrode material is mainly graphite. However, the theoretical capacity of the graphite cathode material is 372mAh/g, the capacity of the current commercialized graphite cathode material is close to the theoretical capacity, and the increase of the capacity of the graphite cathode is difficult. In addition, the graphite has the characteristic of a crystallized layered structure, the theoretical interlayer spacing is small, the requirement of large-current charging cannot be met, the risk of lithium precipitation exists during rapid charging, and serious potential safety hazards are brought to batteries and the whole power utilization system. Along with the continuous improvement of the endurance mileage and the quick charge performance of the electric automobile in domestic and foreign markets, the capacity and the quick charge performance of the cathode material also need to be improved urgently. Thus, graphite negative electrodes have been difficult to meet the demands of the future market.

Hard carbon is amorphous carbon which is difficult to graphitize under high temperature condition (more than or equal to 3000 ℃). The hard carbon is formed by stacking and crosslinking graphite microcrystals and has more disordered layer structures and pores, so that the hard carbon can store more lithium ions and has higher capacity. The (002) crystal face spacing is larger than that of graphite, which is more beneficial to the rapid intercalation and deintercalation of lithium ions, thereby having better rapid charging performance and low temperature performance. However, the hard carbon has many pores, rough surface appearance, large specific surface area and more side reactions, and the defect structure in the hard carbon is in lithium ion reaction, so that the initial irreversible capacity loss is large, and the initial coulombic efficiency is low. In addition, the hard carbon defect structure is unstable upon cycling, and the capacity decays as cycling progresses. This makes the lithium ion battery prepared therefrom have low capacity and poor cycle performance.

The prior patent technology improves the capacity and the quick charging performance of graphite or improves the first effect of hard carbon by modifying the graphite or the hard carbon. Patent CN 111244407 discloses a method for preparing a hard carbon/graphite composite material by preparing a hard carbon precursor from pitch, bonding the hard carbon precursor and graphite with an additive, and coating the surface of the bonded hard carbon precursor and graphite. In patent CN 1095992660 a, a hard carbon precursor is prepared from a carbonaceous biomass shell, and then the hard carbon precursor, graphite and an additive are mixed and carbonized at a high temperature to prepare a hard carbon/graphite composite material. The first effect is improved, but the improvement of the capacity is not obvious.

Therefore, the technical scheme of the invention is provided.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a quick-charging high-first-efficiency hard carbon artificial graphite cathode material and a preparation method thereof. The preparation method selects hard carbon as a main body to improve the capacity and the quick charging performance of the cathode material; the specific surface area of the hard carbon is reduced and side reactions are reduced by coating graphite on the surface of the hard carbon, so that the irreversible capacity is reduced, and the first effect is improved; through high temperature treatment, residual defective structures in hard carbon are reduced, and first effect and circulation stability are improved.

The scheme of the invention is to provide a preparation method of a fast-charging high-first-efficiency hard carbon/artificial graphite cathode material, which comprises the following steps:

(1) carrying out heat treatment on the carbon-containing raw material to obtain a hard carbon material;

(2) crushing the hard carbon material, then uniformly mixing the crushed hard carbon material with a coating agent, and carrying out heat treatment to obtain a coated hard carbon material;

(3) and (3) carrying out graphitization high-temperature heat treatment on the coated hard carbon material to obtain the quick-charging high-first-effect hard carbon artificial graphite cathode material.

Preferably, the fast-charging high-first-efficiency hard carbon artificial graphite cathode material is of a core-shell structure, hard carbon is a core layer, and artificial graphite is a shell layer.

Preferably, the carbon-containing raw material is one or a combination of several of resin, carbon black, starch, asphalt, organic polymer or carbon-containing biological shell.

Preferably, in step (1), the heat treatment is performed in an inert atmosphere; the heat treatment temperature is 700-1500 ℃, and the heat treatment time is 1-10 h.

Preferably, in the step (2), the crushing is carried out until the D50 is 8-30 μm.

Preferably, in the step (2), the coating agent is one of asphalt, resin and coal tar; the content of the coating agent is 1-50% of the total weight.

Preferably, in the step (2), the mixing time is 0.5-3 h; the heat treatment temperature is 300-1000 ℃.

Wherein, in the step (2), the heat treatment is carried out in an atmosphere furnace, a well furnace, a reaction kettle, a tubular furnace, a roller furnace, a pushed slab kiln or a roller kiln.

Preferably, in the step (3), the temperature of the high-temperature heat treatment is 2500-3000 ℃.

In the step (3), the graphitization high-temperature heat treatment equipment is one of an Acheson furnace or a van furnace.

Based on the same technical concept, the invention further provides the fast-charging high-first-efficiency hard carbon/artificial graphite negative electrode material prepared by the method.

The invention has the beneficial effects that:

1. according to the invention, hard carbon is selected as a main body, so that the capacity and the quick charging performance of the cathode material are improved;

2. according to the invention, the specific surface area of the hard carbon is reduced and side reactions are reduced by coating graphite on the surface of the hard carbon, so that the irreversible capacity is reduced, and the high first efficiency of the cathode material is ensured;

3. the invention reduces residual defective structures in hard carbon by graphitization high-temperature heat treatment, and ensures high first efficiency and high cycle stability.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic structural diagram of the fast-charging high-first-efficiency hard carbon artificial graphite negative electrode material.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the examples given herein without any inventive step, are within the scope of the present invention.

Example 1

The embodiment provides a preparation method of a fast-charging high-first-efficiency hard carbon/artificial graphite negative electrode material, which comprises the following steps:

(1) adding 20kg of ammonium dihydrogen phosphate into 70kg of furfural phenol resin, dispersing for 40min at the speed of 2500r/m by using a dispersion machine, and curing for 5h in air at the temperature of 260 ℃ to obtain a precured precursor; crushing the precured precursor to powder with the diameter of D50 being 15 mu m by a mill, adding 30kg of hexamethylene diamine curing agent into the powder, uniformly stirring, and curing for 7h in air at 230 ℃ to obtain a cured precursor; placing the cured precursor into a roller kiln at N₂Heating to 700 ℃ under the protection of atmosphere for heat treatment for 10h to obtain a hard carbon material;

(2) mechanically grinding the hard carbon material to 8 mu m of D50, uniformly mixing the hard carbon material and asphalt in a V-shaped mixer according to a weight ratio of 90:10, and putting the mixture in a roller kiln, wherein N is₂Heating to 1000 ℃ under the protection of atmosphere, and pyrolyzing for 0.5h to obtain a coated hard carbon material;

(3) and (3) putting the coated hard carbon material into an Acheson furnace, heating to 2800 ℃, preserving the heat for 10 days, and then naturally cooling to obtain the fast-charging high-first-efficiency hard carbon artificial graphite cathode material.

Example 2

The embodiment provides a preparation method of a fast-charging high-first-efficiency hard carbon/artificial graphite negative electrode material, which comprises the following steps:

(1) mechanically pulverizing starch to D50 ═ 10 μm, placing in rotary furnace, drying at 250 deg.C for 5 hr, naturally cooling to room temperature, placing in reaction kettle, and adding N₂Carbonizing at 600 deg.C for 5h under atmosphere protection, cooling to room temperature, placing in roller kiln, and adding N₂Carrying out heat treatment at 1200 ℃ for 4h under the atmosphere protection, and naturally cooling to room temperature to obtain a hard carbon material;

(2) mechanically grinding the hard carbon material to D50 of 30 mu m, uniformly mixing the hard carbon material and asphalt in a V-shaped mixer according to a weight ratio of 80:20, and putting the mixture in a roller kiln, wherein N is₂Heating to 300 ℃ for pyrolysis for 3h under the protection of atmosphere to obtain a coated hard carbon material;

(3) and (3) putting the coated hard carbon material into a box furnace, heating to 2500 ℃, preserving heat for 10 days, and then naturally cooling to obtain the fast-charging high-first-efficiency hard carbon artificial graphite cathode material.

Example 3

The embodiment provides a preparation method of a fast-charging high-first-efficiency hard carbon/artificial graphite negative electrode material, which comprises the following steps:

(1) mixing 70kg of polyurethane and 22kg of furfuryl alcohol resin, adding 22kg of stannic chloride, dispersing for 2h at 1000r/m by using a dispersion machine, and curing for 10h at 160 ℃ in the air; grinding the powder to D50 ═ 40 μm by mechanical grinding; then put into a box-type resistance furnace in N₂Pyrolyzing at 1500 ℃ for 1h under the protection of atmosphere, and naturally cooling to room temperature to obtain hard carbon;

(2) mechanically grinding the hard carbon material to D50 of 20 μm, uniformly mixing the hard carbon material and asphalt in a V-shaped mixer according to a weight ratio of 50:50, and placing the mixture in a roller kiln, wherein N is₂Heating to 650 ℃ under the protection of atmosphere, and pyrolyzing for 2h to obtain a coated hard carbon material;

(3) and (3) putting the coated hard carbon material into a box furnace, heating to 3000 ℃, preserving the heat for 10 days, and then naturally cooling to obtain the fast-charging high-first-efficiency hard carbon artificial graphite cathode material.

Comparative example

The present comparative example provides a natural graphite/artificial graphite negative electrode material, which was prepared by the same procedure as in example 1 except that the hard carbon material was changed to natural graphite, and thus, the details thereof are not repeated.

The electrical properties of the fast-charging high-first-efficiency hard carbon artificial graphite anode materials prepared in the embodiments 1 to 3 were measured, and the results are shown in table 1.

The result shows that the graphite capacity of the quick-charging high-first-efficiency hard carbon artificial graphite negative electrode material is more than 372mAh/g, the 5C rate discharge capacity is more than 372mAh/g and is far higher than the theoretical limit capacity of graphite; the first effect is more than 90 percent and is far higher than the first effect of hard carbon.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.