CN110395728A - Preparation method of porous carbon sphere negative electrode material for lithium battery - Google Patents

Abstract

The invention discloses a preparation method of a porous carbon sphere negative electrode material for a lithium battery. The method obtains nano-carbon spheres by depositing a carbon source gas under conditions of no catalyst and low temperature, and then undergoes alkali activation and strong acid acidification treatment. The porous carbon sphere negative electrode material is obtained. The invention not only increases the surface defects of carbon spheres, effectively shortens the diffusion and migration path of lithium ions, but also increases the surface functional groups and specific surface area of the porous carbon sphere material, effectively alleviates the film-forming stability of nanoporous carbon spheres in the material, and is conducive to high-current charging. Discharge, to ensure the appropriate volumetric energy density and Coulombic efficiency of the negative electrode material. The nanoporous carbon sphere negative electrode material for lithium ion batteries prepared by the present invention has a small and uniform particle size and a large specific surface area. Under the high-current charging and discharging mechanism, the specific capacity of the first discharge is nearly 1400 mAh/g, and the specific capacity can be stable after 100 cycles. Above 400mAh/g, it has high specific capacity, good rate performance and cycle performance, and has a good application prospect.

Description

A kind of preparation method of porous carbon sphere negative electrode material for lithium battery

technical field

The invention belongs to the technical field of lithium ion batteries, and in particular relates to a preparation method of a porous carbon ball negative electrode material for lithium batteries.

Background technique

Lithium-ion batteries have been widely used in mobile phones, game consoles, notebook computers, electric vehicles, aerospace and new energy due to their high energy density, high open circuit voltage, good cycle performance, no memory effect, green environmental protection, and small self-discharge. power grid and other fields. Lithium-ion batteries have always been a hot spot of research and development by scholars around the world. Anode materials are one of the key factors affecting the comprehensive electrochemical performance of lithium-ion batteries.

Carbon materials are the earliest commercialized lithium battery anode materials. This is because the carbon-based material has good electrical conductivity and mechanical stability, and the material has good cycle stability and rate performance during battery charging and discharging. Secondly, its raw materials are cheap and can be seen everywhere, and the preparation process is simple and mature. For lithium The deintercalation mechanism and reaction mechanism of ions in carbon materials have been well known by researchers. Carbon-based anode materials can be divided into two categories: graphite and amorphous carbon. The theoretical specific capacity of graphite is 372mAh/g, while the actual capacity of commercial graphite anodes is close to the theoretical value, and the room for improvement is very limited, making it difficult to meet the needs of high energy density batteries. Graphite itself still has certain problems, such as relatively high requirements for electrolytes. Although amorphous carbon materials do not require as much electrolyte as graphite, the reversible capacity of the battery is low for the first charge and discharge, and the amorphous carbon materials contain more hydrogen atoms, which makes the battery have obvious voltage hysteresis during the cycle. . Therefore, the development of new anode materials with high capacity is one of the important research directions in the field of lithium-ion batteries.

Researchers have conducted a lot of experimental research on the above problems. It is mainly aimed at problems such as low capacity, low energy density, insufficient battery life, high requirements for electrolyte, and voltage hysteresis, which lead to the inability of the material to perform electrochemical performance of the carbon negative electrode material. It mainly starts from two aspects: 1. For the traditional Modification of carbon anode materials; 2. Development of new carbon-based materials. For example, the invention patent CN201410103033.9 discloses a Si/C composite as a negative electrode material for a lithium-ion battery. The method includes providing an active material containing silicon, providing lignin, and combining the active material with a C precursor containing lignin Contacting converts lignin into inorganic carbon at a temperature of at least 400°C in an inert gas atmosphere. However, the degree of carbon graphitization obtained by this method is low, and when the obtained Si/C composite is used in a lithium-ion battery, the cycle performance and capacity are not ideal, and the capacity is only about 800mAh/g. Invention patent CN201310522221.0 discloses a porous carbon microsphere, a preparation method and a lithium-ion battery negative electrode material. The porous carbon microsphere prepared by emulsion polymerization has micropore, mesopore and macropore structure at the same time. The porous carbon microsphere When used as a negative electrode material for lithium-ion batteries, the macroporous structure provides a channel for rapid migration of the electrolyte, the mesopore structure is equivalent to the size of ions in the organic electrolyte, and is conducive to the rapid adsorption and desorption of ions, and the microporous structure is conducive to lithium ions. Insertion, so that the lithium-ion secondary battery has a higher specific capacity and better high-rate charge-discharge performance, but it has fewer active sites for lithium-ion storage, and the space for capacity increase is small, so it exists The problem is low energy density and insufficient battery life.

Contents of the invention

In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a preparation method of porous carbon sphere negative electrode material for lithium batteries, which solves the problems of large particle size, large irreversible capacity, low reversible capacity and low energy density of existing negative electrode materials. Insufficient battery life, high requirements on the electrolyte, and poor wettability with the electrode, resulting in poor electrochemical performance and other problems.

In order to achieve the above object, the present invention adopts the following technical scheme: a preparation method of porous carbon sphere negative electrode material for lithium batteries, comprising the following steps:

1) Under an inert atmosphere, the tube furnace is heated up to 450-580°C at a heating rate of 5-10°C/min, and then the carbon source gas is introduced, and the chemical vapor deposition reaction is carried out under the action of no catalyst to obtain nano-carbon spheres ;

In this way, the carbon source gas is chemically cracked at a lower temperature (450~580°C), and the gas is deposited because the gas does not reach the temperature of complete carbonization (cracking), and there are more carbon spheres inside and on the surface. Hydrogen-containing compounds, such compounds are easier to be removed in an acidic environment and cause defects in carbon materials, and without catalyst action and proper air flow, the deposition rate is slow, and the produced carbon materials have smaller particle sizes and fewer defects. Lots of carbon spheres.

2) Add the carbon nanospheres obtained in step 1) into the alkaline substance, mix them thoroughly, then sinter under the protection of an inert atmosphere, perform activation treatment, cool to room temperature, wash until neutral, dry, and then grind them with a porous Sieve 300~400 mesh to get porous carbon spheres;

In the protective gas environment, when the ambient temperature rises to the dissolution temperature of the alkali, the alkaline substance on the carbon nanosphere will be decomposed into oxide and water, and holes will be formed on the surface of the carbon nanosphere, which will be activated for the first time. When the temperature continues to rise to the decomposition temperature and vaporization temperature of the above-mentioned oxides, the oxides will undergo a partial redox reaction with the carbon material, appropriately increasing the specific surface area of the carbon material, thereby increasing the defects of the material, and accelerating the intercalation and extraction of lithium ions. Increase the storage situation.

3) Put the porous carbon spheres prepared in step 2) into a strong acid solution for reaction. After the reaction, perform suction filtration, wash until neutral, and dry to obtain the porous carbon sphere negative electrode material for lithium-ion batteries.

Through strong acid acidification, on the one hand, in order to remove the hydrogen-containing compounds existing inside and on the surface of carbon spheres, hole defects are formed on the surface and inside of the material, which is conducive to the rapid deintercalation and storage of lithium ions; on the other hand, increasing the functional groups on the surface of carbon materials, It can effectively alleviate the stability of the film formation of nanoporous carbon spheres in the material, which is conducive to high-current charging and discharging, and ensures the appropriate volumetric energy density and Coulombic efficiency of the negative electrode material.

Preferably, the carbon source is natural gas or acetylene.

Preferably, the alkaline substance is potassium hydroxide, sodium hydroxide, lithium hydroxide, sodium carbonate, potassium carbonate, lithium carbonate or ammonium carbonate.

Preferably, the flow rate of the carbon source gas is 100-500 mL/min.

The carbon source gas is cracked at a lower temperature. If the flow rate of the carbon source gas is too fast, the gas will be discharged in an uncracked state or the initial state of cracking, resulting in no deposition material; if the flow rate of the carbon source gas is too slow , so that the deposition amount is too large, the particle size is too large, and the defects on the surface will be reduced accordingly, which is not conducive to the rapid transmission of lithium ions and the storage capacity will be reduced.

Preferably, the mass ratio of the carbon nanospheres to the alkaline substance is 1:1-8.

Preferably, the sintering temperature is 600-900° C., and the sintering time is 1-4 hours.

Preferably, the concentration of the strong acid solution is 1-6 mol, and the strong acid is one or more of nitric acid and sulfuric acid mixed in any proportion.

Preferably, the reaction temperature in step 3) is 60-90° C., and the reaction time is 1-3 h.

Preferably, the inert atmosphere is nitrogen or argon, and the flow rate of the inert atmosphere is 100-300 mL/min.

The invention also provides the porous carbon sphere negative electrode material for lithium batteries prepared by the method.

A lithium ion battery, comprising the above-mentioned porous carbon sphere negative electrode material.

Compared with the prior art, the present invention has the following beneficial effects:

1. In the preparation of nanoporous carbon sphere negative electrode materials for lithium-ion batteries, the present invention adopts chemical vapor deposition technology to prepare uniform, stable, and well-dispersed nanocarbon spheres by controlling the carbon source gas flow rate and low temperature settings. Nanocarbon spheres The average diameter of the nano-carbon spheres is between 80 and 100 nm; the secondary activation of the nano-carbon spheres by alkaline substances increases the defects and specific surface area of the nano-carbon spheres, making the pore diameter more uniform; Pore defects are formed on the surface and inside of the porous carbon spheres, and more oxygen-containing functional groups are formed on the surface of the nano-carbon spheres. Therefore, the present invention not only increases the surface defects of carbon spheres, effectively shortens the diffusion and migration path of lithium ions, but also increases the surface functional groups and specific surface area of the porous carbon sphere material, effectively alleviating the film-forming stability of nanoporous carbon spheres in the material, which is beneficial to large Current charging and discharging ensures proper volumetric energy density and coulombic efficiency of negative electrode materials, and effectively solves the problems of low capacity, low energy density, insufficient battery life, high requirements for electrolyte, and voltage hysteresis in existing carbon materials. chemical properties etc.

2. The nanoporous carbon sphere negative electrode material for lithium-ion batteries prepared by the present invention has a small and uniform particle size and a large specific surface area. Under the high-current charging and discharging mechanism, the specific capacity of the first discharge is nearly 1400 mAh/g, and the specific capacity after 100 cycles Can be stable above 400mAh/g, with high specific capacity, good rate performance and cycle performance. The preparation method of the invention has simple technological process, low cost, easy large-scale production and good application prospect.

Description of drawings

Fig. 1 is the XRD pattern of the porous carbon sphere negative electrode material that embodiment 1 makes;

Fig. 2 is the SEM figure of the porous carbon sphere negative electrode material that embodiment 1 makes;

Fig. 3 is the cycle diagram of specific capacity and cycle number under 200mA/g of the negative electrode material of porous carbon spheres prepared in Example 1 as a negative electrode button battery.

Detailed ways

The present invention will be described in further detail below in conjunction with specific embodiments and accompanying drawings. In the following examples, the experimental methods that are not specifically described are all routine operations, and the reagents used are generally commercially available.

One, a kind of preparation method of porous carbon sphere negative electrode material for lithium battery

Example 1

1) Under the protection of an argon gas atmosphere with a flow rate of 200mL/min, the tube furnace was heated to 450°C at a heating rate of 5°C/min, and kept for 30 minutes, and then acetylene gas was introduced at a flow rate of 200mL/min for 1 hour to obtain nano carbon spheres;

2) Add alkaline substances (the molar ratio of sodium hydroxide and sodium carbonate is 1:3) to the nanocarbon spheres obtained in step 1) so that the mass ratio of nanocarbon spheres to alkaline substances is 1:4, and then at 200 Under the protection of mL/min argon gas flow rate, heat up to 900 °C at a heating rate of 5 °C/min for 30 min, then sinter for 4 h for activation treatment, cool to room temperature, wash until neutral, and pass through a 300-mesh porous sieve after grinding Porous carbon spheres are obtained after sieving;

3) Put the porous carbon spheres prepared in step 2) in 2 mol/L nitric acid solution, and stir at 60°C for 3 hours at a constant temperature. After the reaction, perform suction filtration, wash until neutral, and dry to obtain lithium-ion battery. Porous carbon sphere anode material.

Example 2

1) Under the protection of argon gas at a flow rate of 100mL/min, the tube furnace was heated to 550°C at a heating rate of 5°C/min, kept for 40min, and then acetylene gas at a flow rate of 100mL/min was introduced for 2h for cracking reaction to obtain nano carbon spheres;

2) Add alkaline substances (the molar ratio of potassium hydroxide and ammonium carbonate is 1:1) to the carbon nanospheres obtained in step 1), so that the mass ratio of carbon nanospheres to alkaline substances is 1:5, and then Under the protection of 100 mL/min inert gas flow rate, the temperature was raised to 800 °C at a heating rate of 5 °C/min for 40 min, and then sintered for 3 h for activation treatment, cooled to room temperature, washed to neutral, and passed through a 400-mesh porous sieve after grinding Porous carbon spheres are obtained after sieving;

3) Put the porous carbon spheres prepared in step 2) in a 6mol/L nitric acid solution, and stir at a constant temperature of 80°C for 2 hours. After the reaction, perform suction filtration, wash until neutral, and dry to obtain the porous carbon spheres for lithium-ion batteries. Carbon sphere anode material.

Example 3

1) Under the protection of argon gas at a flow rate of 400mL/min, the tube furnace was heated to 580°C at a heating rate of 10°C/min, kept for 30 minutes, and then acetylene gas at a flow rate of 400mL/min was introduced for 2 hours to obtain nano carbon spheres;

2) Add sodium hydroxide to the nanocarbon spheres obtained in step 1), so that the mass ratio of nanocarbon spheres to alkaline substances is 1:8, and then under the protection of 400 mL/min inert gas flow rate, according to 10 ℃ / The heating rate is raised to 900°C for 30 minutes, then sintered for 1 hour for activation treatment, cooled to room temperature, washed to neutrality, and sieved with a 300-mesh porous sieve to obtain porous carbon spheres after grinding;

3) Put the porous carbon spheres prepared in step 2) in a 5 mol/L nitric acid solution, and stir at 90°C for 2 hours at a constant temperature. After the reaction, filter with suction, wash until neutral, and dry to obtain lithium-ion batteries. Porous carbon sphere anode material.

2. Performance verification

1. Use an X-ray diffraction analyzer to analyze the structure of the nanoporous carbon sphere negative electrode material obtained in Example 1, as shown in FIG. 1 .

It can be seen from Figure 1 that the nanoporous carbon sphere negative electrode material prepared in Example 1 provided by the present invention has a sharp diffraction peak at 2θ = 26°, corresponding to the (002) crystal plane of carbon, at 2θ = 43° There is a sub-strong peak at , which corresponds to (100) of carbon, indicating that the preparation method provided by the present invention has prepared a pure-phase nanoporous carbon sphere negative electrode material.

2. Use a scanning electron microscope to observe the morphology of the activated precursor porous carbon sphere material obtained in Example 1, as shown in FIG. 2 .

It can be seen from Figure 2 that the particle size of the precursor nanoporous carbon spheres is uniform, the particle agglomeration phenomenon is weak, the average diameter distribution is about 80-100nm, and there are a few cracks on the surface, which indicates that the improvement of the activation degree will also lead to the erosion of the surface of the material. Seriously, the more pores and defects the material has, theoretically these defects and pores will increase the specific surface area of the material, which will help store lithium ions and increase the lithium storage capacity of the material.

3. The nanoporous carbon sphere negative electrode composite material prepared in Example 1, acetylene black and water-based binder are batched according to a mass ratio of 8:1:1, and placed in a mortar to grind to prepare a moderately viscous slurry, uniform coated on copper foil to make electrode sheets, and then assembled into CR2032 button cells in a glove box to test its electrochemical performance.

The assembled CR2032 button battery was subjected to a 100-cycle performance test at a current density of 200mA/g, and the results are shown in Figure 3.

It can be seen from Figure 3 that after 100 cycles, the nanoporous carbon sphere negative electrode composite material, except for the serious attenuation of the first cycle, the other cycle specific capacity capacity is relatively stable, the initial capacity remains at about 1357mAh/g, and after 100 cycles After that, it remained at about 480mAh/g; the better cycle performance was attributed to the higher specific surface area and sufficient functional groups to ease the film-forming stability of nanoporous carbon spheres in the material, and also greatly improved the electrochemical activity of the material.

Finally, it is noted that the above embodiments are only used to illustrate the technical solutions of the present invention without limitation. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be carried out Modifications or equivalent replacements without departing from the spirit and scope of the technical solution of the present invention shall be covered by the claims of the present invention.

Claims (10)

1. a kind of lithium battery preparation method of porous carbon ball negative electrode material, which comprises the following steps:

1) 450 ~ 580 DEG C under an inert atmosphere by tube furnace, are warming up to according to 5 ~ 10 DEG C/min heating rate, then passes to carbon source Gas carries out deposition reaction under the action of no catalyst, obtains nano carbon microsphere；

2) alkaline matter is added into the nano carbon microsphere that step 1) obtains, is sufficiently mixed, be then sintered under inert atmosphere protection, It is cooled to room temperature after reaction, washing to neutrality, then obtains porous carbon after being sieved after being ground with 300 ~ 400 mesh of porous sieve Ball；

3) porous carbon ball prepared by step 2 is placed in strong acid solution and is reacted, after reaction, filtered, washed into Property, it is dry to get arriving lithium ion battery porous carbon ball negative electrode material.

2. the preparation method of lithium battery porous carbon ball negative electrode material according to claim 1, which is characterized in that the carbon source Gas is natural gas or acetylene；The alkaline matter is potassium hydroxide, sodium hydroxide, lithium hydroxide, sodium carbonate, potassium carbonate, carbon Sour lithium or ammonium carbonate.

3. the preparation method of lithium battery porous carbon ball negative electrode material according to claim 1, which is characterized in that the carbon source The flow of gas is 100 ~ 500mL/min.

4. the preparation method of lithium battery porous carbon ball negative electrode material according to claim 1, which is characterized in that the nanometer The mass ratio of carbon ball and alkaline matter is 1:1 ~ 8.

5. the preparation method of lithium battery porous carbon ball negative electrode material according to claim 1, which is characterized in that the sintering Temperature is 600~900 DEG C, and sintering time is 1~4h.

6. the preparation method of lithium battery porous carbon ball negative electrode material according to claim 1, which is characterized in that the strong acid The concentration of solution is 1 ~ 6mol, and the strong acid is one of nitric acid and sulfuric acid or a variety of mixes in any proportion.

7. the preparation method of lithium battery porous carbon ball negative electrode material according to claim 1, which is characterized in that step 3) institute Stating reaction temperature is 60 ~ 90 DEG C, and the reaction time is 1 ~ 3h.

8. the preparation method of lithium battery porous carbon ball negative electrode material according to claim 1, which is characterized in that the inertia Atmosphere is nitrogen or argon gas, and the flow of the inert atmosphere is 100~300mL/min.

9. using the lithium battery porous carbon ball negative electrode material of any one of claim 1 ~ 8 method preparation.

10. a kind of lithium ion battery includes porous carbon ball negative electrode material described in claim 9.