CN115881895A - Amorphous carbon negative electrode material and its preparation method and application - Google Patents

Abstract

The invention discloses an amorphous carbon negative electrode material and its preparation method and application. The preparation method of the amorphous carbon negative electrode material comprises: ball milling graphite to obtain the amorphous carbon negative electrode material. Amorphous carbon anode materials are used in lithium-ion batteries as anode materials for lithium-ion batteries. The defects on the surface include edge structures, surface wrinkles, and abundant oxygen end groups that provide active sites for the redox reaction of lithium ions. Surface defects The increased density enhances the lithium storage capacity, which further enhances the specific capacity and cycle stability of the material.

Description

Amorphous carbon negative electrode material and its preparation method and application

technical field

The invention belongs to the technical field of amorphous carbon negative electrode materials, and specifically relates to an amorphous carbon negative electrode material and its preparation method and application.

Background technique

With the continuous development of secondary batteries, rechargeable lithium-ion batteries with high energy density, stable charge-discharge platform, wide operating temperature range, low self-discharge rate, and long cycle stability are important candidates for many types of batteries At present, energy storage technology represented by lithium-ion batteries plays an important role in the field of energy supply. Lithium-ion secondary batteries not only meet the rapidly changing development requirements of electronic products, but also have broader application prospects in high-end fields such as hybrid electric vehicles, military and aerospace.

The selection and improvement of electrode materials are critical to the durability and reliability of Li-ion batteries. Taking the anode of lithium-ion batteries as an example, since SONY's first-generation lithium-ion batteries were commercialized in 1991, graphitic carbon is still mainly used as the anode material of lithium-ion batteries. As an anode, graphite has a long cycle life and relatively low cost. Since Li ⁺ is intercalated into the layered structure of the graphite material, the formed LiC corresponds to a Li:C ratio of 1:6 between the graphite layers, making the theoretical capacity _of commercial bulk graphite limited (372mAh/g). Therefore, surface modification of graphite to improve its charge and discharge performance is an urgent problem to be solved.

Modification is an effective way to increase the capacity of carbon materials. The modification of graphite is mainly carried out from the following two aspects: one is the change of crystal structure, and the other is the change of surface properties. Modification routes of graphite can be found in ref. including oxidation, fluorination, coating and doping. Several approaches, such as graphite edge functionalization, chemical derivatization of graphite oxide, and chemical vapor deposition, have been applied to surface modification of carbon-based materials to enhance lithium storage performance. While graphene can be prepared using chemical deposition, this method is not conducive to large-scale production due to cost and technical challenges. Furthermore, the exfoliation of graphite into graphene involves dangerous oxidants such as _HNO3 or _H2SO4 and is _a tedious process. And this corrosive chemical oxidation method will cause serious damage to the surface of the graphite substrate due to the introduction of a large number of chemical substances. Therefore, it is crucial to develop an environmentally friendly and simple method to obtain commercial graphite lithium battery anode materials with higher lithium storage performance.

Contents of the invention

Aiming at the deficiencies of the prior art, the object of the present invention is to provide a method for preparing an amorphous carbon negative electrode material. The preparation method uses a high-energy ball milling method to manufacture a large number of defect sites on the surface of a graphite material, and the obtained amorphous carbon negative electrode material It has a high lithium storage capacity. The preparation method of the invention has the advantages of simple process, wide sources of raw materials, suitable for large-scale industrial production and the like.

Another object of the present invention is to provide the amorphous carbon negative electrode material obtained by the above preparation method.

Another object of the present invention is to provide the application of the above-mentioned amorphous carbon negative electrode material as the negative electrode material of the lithium ion battery in the lithium ion battery.

The purpose of the present invention is achieved through the following technical solutions.

A method for preparing an amorphous carbon negative electrode material, comprising: ball milling graphite to obtain the amorphous carbon negative electrode material.

In the above technical solution, the time for the ball milling is 1-4 hours, and the rotational speed of the ball milling is 1000-1200 r/min.

In the above technical solution, in terms of parts by mass, the ratio of the grinding balls and graphite in the ball mill is (10-20):1.

The amorphous carbon negative electrode material obtained by the above preparation method.

The above-mentioned amorphous carbon negative electrode material is used as the lithium ion battery negative electrode material in the application of the lithium ion battery.

In the above technical solution, the preparation method of the negative electrode of the lithium ion battery is: uniformly mix the amorphous carbon negative electrode material, binder, conductive agent and solvent to obtain a slurry, and apply the slurry to the coated on a copper foil current collector, and dried under a vacuum environment to obtain the negative electrode.

In the above technical scheme, the solvent is N-methylpyrrolidone.

In the above technical solution, in terms of parts by mass, the ratio of the amorphous carbon negative electrode material, the binder and the conductive agent is (7-8):1:(1-2).

In the above technical solution, the drying temperature is 80-100° C., and the drying time is 12-24 hours.

In the above technical solution, the conductive agent is acetylene black, and the binder is PVDF.

In the above technical solution, the positive electrode of the lithium ion battery is a metal lithium sheet.

In the above technical solution, the concentration of the amorphous carbon negative electrode material in the slurry is 70-80 wt%.

Compared with the prior art, the present invention has the advantages of:

1) The present invention uses commercial graphite as a raw material, and undergoes high-energy ball milling to obtain an amorphous carbon material with a controllable surface defect density. Advanced chemical reagents, environment-friendly, have obvious economic benefits, and are beneficial to industrial production.

2) The amorphous carbon negative electrode material of the present invention uses commercial graphite as a raw material, expands the distance between graphite sheets after high-energy ball milling, and obtains an amorphous carbon negative electrode material with controllable defect density through the control of ball milling time. The increased defects on the surface of the material include edge structures, surface wrinkles, and abundant oxygen end groups that provide active sites for the redox reaction of lithium ions. The increase in the surface defect density improves the lithium storage capacity and further improves the specific capacity and cycle of the material. stability.

Description of drawings

Fig. 1 is the XRD pattern of the amorphous carbon negative electrode material prepared by embodiment 1;

Fig. 2 is the SEM picture of the amorphous carbon negative electrode material prepared by embodiment 1;

Fig. 3 is the Raman diagram of the amorphous carbon negative electrode material prepared by embodiment 1;

Fig. 4 is the performance test result figure that is assembled into CR2032 type button battery by the amorphous carbon negative electrode material prepared by embodiment 1;

Fig. 5 is the XRD pattern of the amorphous carbon negative electrode material prepared by embodiment 2;

Fig. 6 is the SEM picture of the amorphous carbon negative electrode material prepared by embodiment 2;

Fig. 7 is the Raman diagram of the amorphous carbon negative electrode material prepared by embodiment 2;

Fig. 8 is the performance test result figure that is assembled into CR2032 type button battery by the amorphous carbon negative electrode material prepared by embodiment 2;

Fig. 9 is the XRD pattern of the amorphous carbon negative electrode material prepared in embodiment 3;

Fig. 10 is the SEM picture of the amorphous carbon negative electrode material prepared by embodiment 3;

Fig. 11 is the Raman diagram of the amorphous carbon negative electrode material prepared by embodiment 3;

Fig. 12 is the result figure of the performance test of CR2032 type button battery assembled into the amorphous carbon negative electrode material prepared by embodiment 3;

Fig. 13 is the XRD pattern of the amorphous carbon negative electrode material prepared in embodiment 4;

Fig. 14 is the SEM picture of the amorphous carbon negative electrode material prepared by embodiment 4;

Fig. 15 is the Raman diagram of the amorphous carbon negative electrode material prepared in embodiment 4;

Fig. 16 is the result figure of the performance test of CR2032 type button battery assembled into the amorphous carbon negative electrode material prepared by embodiment 4;

Fig. 17 is the XRD pattern of commercial graphite in comparative example 1;

Fig. 18 is the SEM figure of commercial graphite in comparative example 1;

Fig. 19 is the Raman diagram of commercial graphite in comparative example 1;

FIG. 20 is a graph showing the performance test results of the CR2032 button battery obtained in Comparative Example 1.

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with specific embodiments.

Commercial graphite (P15X) was purchased from DuodoChem; polyvinylidene fluoride (PVDF, AR), copper foil current collector and acetylene black were purchased from Shenzhen Kejing Zhida Co., Ltd.; nitrogen methyl pyrrolidone (NMP, AR) was purchased from Sinopharm.

XRD test model: ARL Equinox 3000 using Cu Kα1 radiation, France

The model of the SEM testing instrument is: Quanta FEG, USA

The model of Raman testing instrument is: HORIBA JOBIN YVON S.A.S., France

The model of Land Electric Test Instrument is: Land CT2001A, China

The model of the high energy ball mill is: MSK-SFM-3, China

Example 1

A method for preparing an amorphous carbon negative electrode material, comprising: in a 100ml corundum ball mill jar, ball milling 1g of commercial graphite at a speed of 1200r/min for 1h to obtain an amorphous carbon negative electrode material, wherein, in parts by mass, the ball milled The ratio of grinding balls to graphite is 20:1.

Example 2

A method for preparing an amorphous carbon negative electrode material, comprising: in a 100ml corundum ball mill jar, ball milling 1g of commercial graphite at a speed of 1200r/min for 2h to obtain an amorphous carbon negative electrode material, wherein, in parts by mass, the ball milled The ratio of grinding balls to graphite is 20:1.

Example 3

A method for preparing an amorphous carbon negative electrode material, comprising: in a 100ml corundum ball mill jar, ball milling 1g of commercial graphite at a speed of 1200r/min for 3h to obtain an amorphous carbon negative electrode material, wherein, in parts by mass, the ball milled The ratio of grinding balls to graphite is 20:1.

Example 4

A method for preparing an amorphous carbon negative electrode material, comprising: in a 100ml corundum ball mill jar, ball milling 1g of commercial graphite at a speed of 1200r/min for 4h to obtain an amorphous carbon negative electrode material, wherein, in parts by mass, the ball milled The ratio of grinding balls to graphite is 20:1.

The above-mentioned amorphous carbon negative electrode material can be used as a lithium ion battery negative electrode material in lithium ion batteries.

Wherein, the preparation method of the negative electrode of the lithium ion battery is: a kind of amorphous carbon negative electrode material, binding agent, conductive agent and N-methylpyrrolidone (NMP) in embodiment 1-4 are mixed evenly, after fully grinding, obtain Black paste slurry, the slurry is coated on the copper foil current collector by the coating method, and dried in a vacuum oven at 80°C for 12h in a vacuum environment to remove N-methylpyrrolidone and obtain a negative electrode, wherein, The conductive agent is acetylene black, and the binding agent is PVDF. In terms of parts by mass, the ratio of amorphous carbon negative electrode material, binding agent and conductive agent is 8:1:1, and the concentration of amorphous carbon negative electrode material in the slurry is 80 wt%.

Assemble CR2032 type button battery with above-mentioned negative electrode: positive electrode is metal lithium sheet, electrolyte is the mixture of LiPF ₆ , ethylene carbonate and diethyl carbonate, the concentration of LiPF ₆ in the electrolyte is 1M, ethylene carbonate and diethyl carbonate The volume ratio of ethyl ester is 1:1, and the separator is Celgard2400.

Comparative example 1

The preparation method of a kind of negative pole is: commercial graphite, binding agent, conductive agent and N-methylpyrrolidone (NMP) are mixed evenly, after fully grinding, obtain black pasty slurry, adopt coating method to coat the slurry Coated on the copper foil current collector, dried in a vacuum oven at 80°C for 12 hours in a vacuum environment to remove N-methylpyrrolidone to obtain a negative electrode, wherein the conductive agent is acetylene black, and the binder is PVDF, in parts by mass Counting, the ratio of the amorphous carbon negative electrode material, binder and conductive agent is 8:1:1, and the concentration of the amorphous carbon negative electrode material in the slurry is 80wt%.

Assemble CR2032 type button battery with above-mentioned negative electrode: positive electrode is metal lithium sheet, electrolyte is the mixture of LiPF ₆ , ethylene carbonate and diethyl carbonate, the concentration of LiPF ₆ in the electrolyte is 1M, ethylene carbonate and diethyl carbonate The volume ratio of ethyl ester is 1:1, and the separator is Celgard2400.

Figure 1 is the XRD pattern of the amorphous carbon negative electrode material obtained in Example 1. It can be seen from the figure that the intensity of the diffraction peak of the obtained material weakens, indicating that the crystallinity of the material decreases and the material is in an amorphous state.

Fig. 2 is the SEM image of the amorphous carbon negative electrode material obtained in Example 1. It can be seen from the figure that the obtained material is in the form of scales.

Fig. 3 is the Raman diagram of the amorphous carbon negative electrode material obtained in Example 1. It can be seen from the figure that the defect (D) peak at 1350cm ^-1 represents the disordered vibration peak of carbon materials and the G peak at ^{1580cm -1} represents the in-plane vibration of sp2 carbon atoms. The amorphous structure of the sample is composed of The intensity ratio of the D band to the G band (I _D /I _G ), evidenced, is used to represent the defect density of the carbon material. It can be seen from the figure that the I _D / _IG value is 0.81.

Fig. 4 is a graph showing the performance test results of a CR2032 button battery assembled from the amorphous carbon negative electrode material obtained in Example 1. It can be seen from the figure that the lithium-ion battery negative electrode prepared in this example has good electrochemical performance: at a current density of 0.2A/g, its first cycle Coulombic efficiency is 52%, and its first cycle discharge capacity is 757.6mAh/g , after 200 cycles, the capacity remains 404.1mAh/g.

Figure 5 is the XRD pattern of the amorphous carbon negative electrode material obtained in Example 2. It can be seen from the figure that the intensity of the diffraction peak of the obtained material weakens, indicating that the crystallinity of the material decreases and the material is in an amorphous state.

Fig. 6 is the SEM image of the amorphous carbon negative electrode material obtained in Example 2. It can be seen from the figure that the obtained material is in the shape of a non-uniform block.

Fig. 7 is the Raman diagram of the amorphous carbon negative electrode material obtained in Example 2. It can be seen from the figure that the defect (D) peak at 1350cm ^-1 represents the disordered vibration peak of carbon materials and the G peak at ^{1580cm -1} represents the in-plane vibration of sp2 carbon atoms. The amorphous structure of the sample is composed of The intensity ratio of the D band to the G band (I _D /I _G ), evidenced, is used to represent the defect density of the carbon material. It can be seen from the figure that the I _D / _IG value is 1.15.

Fig. 8 is a graph showing the performance test results of a CR2032 button battery assembled from the amorphous carbon negative electrode material obtained in Example 2. It can be seen from the figure that the lithium-ion battery negative electrode prepared in this example has good electrochemical performance: at a current density of 0.2A/g, its first cycle coulombic efficiency is 56%, and its first cycle discharge capacity is 828.3mAh/g , after 200 cycles, the capacity remains 451.3mAh/g.

9 is an XRD pattern of the amorphous carbon negative electrode material obtained in Example 3. It can be seen from the figure that the intensity of the diffraction peak of the obtained material weakens, indicating that the crystallinity of the material decreases and the material is in an amorphous state.

10 is a SEM image of the amorphous carbon negative electrode material obtained in Example 3. It can be seen from the figure that the obtained material is in the shape of a uniform block.

Fig. 11 is the Raman diagram of the amorphous carbon negative electrode material obtained in Example 3. It can be seen from the figure that the defect (D) peak at 1350cm ^-1 represents the disordered vibration peak of carbon materials and the G peak at ^{1580cm -1} represents the in-plane vibration of sp2 carbon atoms. The amorphous structure of the sample is composed of The intensity ratio of the D band to the G band (I _D /I _G ), evidenced, is used to represent the defect density of the carbon material. It can be seen from the figure that the I _D / _IG value is 1.38.

Fig. 12 is a graph showing the performance test results of a CR2032 button battery assembled from the amorphous carbon negative electrode material obtained in Example 3. It can be seen from the figure that the lithium-ion battery negative electrode prepared in this example has good electrochemical performance: at a current density of 0.2A/g, its first cycle coulombic efficiency is 76%, and its first cycle discharge capacity is 1118.6mAh/g , after 200 cycles, the capacity remains 622.5mAh/g.

Figure 13 is the XRD pattern of the amorphous carbon negative electrode material obtained in Example 4. It can be seen from the figure that the intensity of the diffraction peak of the obtained material weakens, indicating that the crystallinity of the material decreases and the material is in an amorphous state.

Fig. 14 is the SEM image of the amorphous carbon negative electrode material obtained in Example 4. It can be seen from the figure that the obtained material part is in the shape of agglomerated blocks.

Figure 15 is the Raman diagram of the amorphous carbon negative electrode material obtained in Example 4. It can be seen from the figure that the defect (D) peak at 1350cm ^-1 represents the disordered vibration peak of carbon materials and the G peak at ^{1580cm -1} represents the in-plane vibration of sp2 carbon atoms. The amorphous structure of the sample is composed of The intensity ratio of the D band to the G band (I _D /I _G ), evidenced, is used to represent the defect density of the carbon material. It can be seen from the figure that the I _D / _IG value is 1.30.

Fig. 16 is a graph showing the performance test results of a CR2032 button battery assembled from the amorphous carbon negative electrode material obtained in Example 4. It can be seen from the figure that the lithium-ion battery negative electrode prepared in the embodiment has good electrochemical performance: at a current density of 0.2A/g, its first cycle coulombic efficiency is 59%, and the first cycle discharge capacity is 1007.3mAh/g, After 200 cycles, the capacity remains 482.1mAh/g.

FIG. 17 is an XRD pattern of commercial graphite in Comparative Example 1. It can be seen from the figure that the diffraction peak intensity of commercial graphite is strong, indicating that the crystallinity of the material is good, and the material is in a crystalline state.

FIG. 18 is a SEM image of commercial graphite in Comparative Example 1. It can be seen from the figure that the material is in the form of large size blocks.

FIG. 19 is a Raman diagram of commercial graphite in Comparative Example 1. The G peak of this material is obviously stronger than the D peak. It can be seen from the figure that the I _D / I _G value is only 0.64, indicating that the material has few surface defects.

Fig. 20 is a graph showing the performance test results of the CR2032 button battery assembled in Comparative Example 1. It can be seen from the figure that the lithium-ion battery negative electrode prepared in this comparative example has electrochemical performance with low capacity: at a current density of 0.2A/g, its first-cycle Coulombic efficiency is 44%, and its first-cycle discharge capacity is 400.5mAh /g, after 200 cycles, the capacity remains 289.4mAh/g.

The present invention has been described as an example above, and it should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacements that can be made by those skilled in the art without creative labor all fall within the scope of this invention. protection scope of the invention.

Claims (10)

1. A preparation method of an amorphous carbon negative electrode material is characterized by comprising the following steps: and (3) carrying out ball milling on graphite to obtain the amorphous carbon negative electrode material.

2. The preparation method of claim 1, wherein the ball milling time is 1-4 h, and the rotation speed of the ball milling is 1000-1200 r/min.

3. The preparation method according to claim 1 or 2, characterized in that the ratio of the ball-milled grinding balls to the graphite is (10-20): 1 in parts by mass.

4. An amorphous carbon anode material obtained by the production method according to claim 1.

5. Use of the amorphous carbon negative electrode material of claim 4 as a negative electrode material for a lithium ion battery in a lithium ion battery.

6. The application of claim 5, wherein the preparation method of the negative electrode of the lithium ion battery is as follows: and uniformly mixing the amorphous carbon negative electrode material, the binder, the conductive agent and the solvent to obtain slurry, coating the slurry on a copper foil current collector by adopting a coating method, and drying in a vacuum environment to obtain the negative electrode.

7. Use according to claim 5, characterized in that the solvent is N-methylpyrrolidone, the conductive agent is acetylene black and the binder is PVDF.

8. The use according to claim 5, characterized in that the ratio of the amorphous carbon negative electrode material, the binder and the conductive agent is (7-8): 1 (1-2), and the concentration of the amorphous carbon negative electrode material in the slurry is 70-80 wt%.

9. Use according to claim 5, wherein the drying temperature is between 80 and 100 ℃ and the drying time is between 12 and 24 hours.

10. The use of claim 5, wherein the positive electrode of the lithium ion battery is a metallic lithium sheet.

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