CN105336958B - Graphene/CNTs/Super P combined conductive agents, combined conductive agent slurry and preparation method thereof - Google Patents

Abstract

The invention discloses a Graphene/CNTs/Super‑P composite conductive agent, a composite conductive agent slurry and a preparation method thereof. The composite conductive agent consists of Graphene (graphene), CNTs (carbon nanotubes) and Super‑P (conductive carbon black) composition. The preparation method is as follows: adding graphene oxide slurry, carbon nanotubes, conductive carbon black and surfactant into a reaction kettle and stirring evenly, and then undergoing sufficient ultrasonic dispersion, then drying and pulverizing; adding the pulverized mixture to a horse In the furnace, puffing in the air, cooling to room temperature after reduction in an inert atmosphere, the composite conductive agent powder is obtained; the powder composite conductive agent can also be mixed with a solvent, stirred, and ultrasonically dispersed to obtain a composite conductive agent slurry. The composite conductive agent of the invention has excellent electrical properties and is suitable for use as a conductive agent for power ion batteries. The adopted preparation process is simple and convenient, with low energy consumption, and is suitable for large-scale industrial production.

Description

Graphene/CNTs/Super-P composite conductive agent, composite conductive agent slurry and its preparation preparation method

technical field

The invention belongs to the field of energy and new materials, and relates to a composite conductive agent for a power lithium-ion secondary battery and a preparation method thereof, in particular to a Graphene/CNTs/Super-P composite conductive agent, a composite conductive agent slurry and a preparation method thereof .

Background technique

Lithium-ion batteries are widely used in portable electronic devices such as mobile phones, notebook computers, and cameras because of their high capacity, high voltage, long cycle life, good safety, and no memory effect. As people are increasingly concerned about the environmental pollution caused by fuel vehicles, in recent years, the application of lithium-ion batteries as a power source in electric vehicles has attracted people's attention. The application of lithium-ion batteries as a power source in electric vehicles must first meet the needs of fast charging and discharging. In order to improve the rapid charge and discharge performance of lithium-ion batteries, there are mainly the following approaches: ① Modify the existing positive and negative electrode materials for lithium-ion batteries to improve the conduction and migration capabilities of electrons or lithium ions, so as to improve their rapid charging and discharging performance. The purpose of charging and discharging; ②Discover new positive and negative electrode materials suitable for fast charging and discharging; ③Add conductive additives during the preparation of electrode sheets to improve the surface electronic conductivity of positive and negative active materials. At present, commercialized lithium-ion batteries mostly use graphite-based carbon materials as negative electrode materials. Compared with positive electrodes, graphite-based carbon negative electrode materials have better conductivity. In principle, no conductive agent is added to increase the conductivity of the material. However, due to the volume expansion and contraction of graphite-like carbon materials during the process of inserting and extracting lithium, after several cycles, the contact between the materials will decrease, or gaps will appear, resulting in a sharp increase in the polarization of the electrode. Add conductive agent. Granular carbon black, acetylene black, or fibrous conductive agent can fill the gaps between carbon negative electrode materials well, maintain the stability of the electrode during the cycle, and will not lead to a sharp increase in the conductivity of the electrode due to the increase in the number of cycles. decline. The positive electrode materials of lithium-ion batteries are generally transition metal oxides, such as: LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , and LiNi _x Co _y Mn _(1-xy) O ₂ , etc., and transition metal phosphates, such as LiMPO ₄ ( M is Fe or Mn), they have low conductivity and are generally semiconductors or insulators. In order to ensure the normal operation of lithium-ion batteries, conductive additives must be added during the electrode preparation process.

An excellent conductive agent needs to have the following characteristics: 1. High electrical conductivity, materials with high conductivity can increase the transfer rate of electrons; 2. Small particle size, materials with small particle size can fill the positive and negative electrodes of lithium-ion batteries The gaps in the material make the contact between the materials better and facilitate the migration of lithium ions; three, high specific surface area, materials with large specific surface area can better contact with positive and negative electrode materials, and also easy to absorb electrolyte; four, easy Dispersion, easy to open and disperse in the process of preparing slurry for positive and negative electrode materials, and can be better mixed with positive and negative electrode materials; Fifth, high stability, can exist stably in the process of charging and discharging lithium-ion batteries, not It will react with the electrolyte and affect the cycle performance of the battery. The existing commercialized conductive agents are mainly carbon materials, mainly including conductive graphite, conductive carbon black, and carbon nanotubes. The above-mentioned conductive agents have their own advantages, but they do not have the above-mentioned characteristics that an excellent conductive agent should have. Can't meet the demand of conductive agent for power lithium ion battery, therefore, it is necessary to develop novel conductive agent.

Contents of the invention

The purpose of the present invention is to develop a novel Graphene/CNTs/Super-P composite conductive agent for a power lithium ion battery and a preparation method thereof.

At first, the present invention provides a kind of Graphene/CNTs/Super-P composite conducting agent, and its technical scheme is as follows:

A kind of Graphene/CNTs/Super-P composite conductive agent, described composite conductive agent is made up of Graphene, CNTs and Super-P; The mass percentage that Graphene occupies is 0.01%～30%; The mass percentage that CNTs occupies Mineral content is 0.01%~30%.

Preferably, the size of Graphene in the composite conductive agent is greater than 5 μm, and the number of layers is 5-7.

Preferably, the CNTs in the composite conductive agent have a length of 3 µm to 5 µm and a diameter of 50 nm to 70 nm.

Secondly, the present invention also provides a kind of above-mentioned composite conductive agent slurry, and its technical scheme is as follows:

A above-mentioned composite conductive agent slurry, including the above-mentioned composite conductive agent and a solvent; the percentage content of the composite conductive agent is ≤50%.

Preferably, the solvent is selected from secondary deionized water and N-methylpyrrolidone.

Preferably, the percentage content of the composite conductive agent is 10%.

Again, the present invention provides a kind of preparation method of Graphene/CNTs/Super-P composite conductive agent, the technical scheme adopted is as follows:

A kind of preparation method of Graphene/CNTs/Super-P composite conductive agent, comprises the steps:

(1) Mixing: Add graphene oxide slurry with a solid content of ≤50% into a single-layer glass reactor, add CNTs, Super-P and surfactants, stir mechanically for 25 minutes to 35 minutes, and then ultrasonically disperse for 20 minutes to 35 minutes. make it evenly mixed;

(2) Pulverization: Suction filter the mixed slurry in step (1), and dry it at 90°C to 110°C until the water content is ≤5%, and pulverize the dried solid with a pulverizer to make the pulverized particles The particle size is ≤74μm;

(3) Expansion: Heat the muffle furnace to raise the temperature to 200°C-450°C, quickly put the mixture particles pulverized in step (2) into the muffle furnace, puff them in the air for 3min-10min, then take them out quickly, and cool to room temperature;

(4) Reduction: place the mixture in step (3) in a tube furnace with an inert atmosphere at 1000°C, and heat-treat for 5 minutes to 15 minutes to obtain Graphene/CNTs/Super-P composite conductive agent powder;

In the preparation method of composite conductive agent of the present invention:

The graphene oxide slurry in step (1) is a product prepared by an oxidation-reduction reaction, and has been washed with water to be weakly acidic;

The water content in step (2) is controlled below 5% to prevent possible burning or explosion caused by water decomposition during puffing treatment;

The temperature of the puffing treatment in step (3) is preferably 200°C to 300°C, and the time is preferably 3 to 5 minutes, mainly to prevent damage to the raw materials that may be caused by excessive temperature;

The high temperature of 1000°C used in step (4) is to ensure that graphene oxide is reduced to graphene, and the inert atmosphere used is to ensure that Graphene, CNTs and Super-P are not burned.

Preferably, the surfactant in the step (1) is selected from any one of polyvinylpyrrolidone, sodium dodecylsulfonate and cetyltrimethylammonium chloride.

Preferably, the mass percentage of surfactant added in the step (1) is 0.01%-1% of the total mass of graphene oxide, carbon nanotubes and conductive carbon black.

Finally, the present invention provides a method for preparing the above-mentioned composite conductive agent slurry, the specific scheme is as follows:

A preparation method of the above-mentioned composite conductive agent slurry, on the basis of preparing the above-mentioned composite conductive agent, also includes the following steps:

Add the Graphene/CNTs/Super-P composite conductive agent powder obtained in step (4) into the solvent with a solid content of ≤50%, and ultrasonically disperse for 8 minutes to 12 minutes to prepare Graphene/CNTs/Super-P composite conductive agent slurry material.

Principle of the present invention is:

Utilizing the excellent electrical conductivity of Graphene and CNTs and the microstructural properties of Graphene, CNTs, and Super-P, when used as a conductive agent, Graphene, CNTs, and Super-P exert a synergistic effect and can build efficient electrodes in the electrode sheet The conductive network can reach the maximum contact with the electrode active material, which can greatly improve the surface electronic conductivity of the electrode active material, so that the electrode active material can be charged and discharged quickly. Therefore, it is suitable as a conductive lithium-ion battery. Additives used.

The present invention has the following advantages: (1) Graphene oxide slurry is used as a raw material in the present invention. In this state, graphene oxide is in a well-dispersed state due to the solvent on its surface, and does not exist in a powder state. Due to the agglomeration phenomenon caused by the strong van der Waals force on the surface, it is beneficial to the composite with carbon nanotubes; (2) the large specific surface area of graphene, the high aspect ratio of carbon nanotubes and the small size of Super-P The particle size can build an efficient conductive network in the electrode sheet, realize the effective contact with the electrode active material to the greatest extent, improve its electronic conductivity, especially realize the fast charge and discharge performance of large current; (3) the present invention is in the air The puffing of raw materials and the reduction treatment of high-temperature inert atmosphere mainly have the following functions: A. Decompose the added surfactant, and the selected surfactant can be completely decomposed during heat treatment in air without residue; B. Remove oxidation The functional group on the surface or edge of graphene makes it be reduced into graphene in situ in the compound; C. Expansion treatment in the air makes the product fluffy and easy to disperse, which is convenient for its application in actual production; (4 ) The process of the present invention is simple and convenient, the energy consumption is small, and it is suitable for large-scale production.

Description of drawings

Figure 1 is a scanning electron microscope (SEM) image of Graphene/CNTs/Super-P composite conductive agent in Example 1 of the present invention;

2 is a scanning electron microscope (SEM) image of Graphene in Graphene/CNTs/Super-P composite conductive agent in Example 1 of the present invention;

3 is a transmission electron microscope (TEM) image of Graphene in Graphene/CNTs/Super-P composite conductive agent in Example 1 of the present invention;

4 is a scanning electron microscope (SEM) image of CNTs in Graphene/CNTs/Super-P composite conductive agent in Example 1 of the present invention;

5 is a transmission electron microscope (TEM) image of CNTs in Graphene/CNTs/Super-P composite conductive agent in Example 1 of the present invention;

6 is a scanning electron microscope (SEM) image of the Graphene/CNTs composite conductive agent in Comparative Example 1 of the present invention;

Figure 7 is a scanning electron microscope (SEM) image of the CNTs/Super-P composite conductive agent in Comparative Example 3 of the present invention;

Fig. 8 is the Graphene/CNTs/Super-P composite conductive agent in Example 1 of the present invention and the Graphene/CNTs composite conductive agent in Comparative Example 1, the Graphene/Super-P composite conductive agent in Comparative Example 2 and Comparative Example 3 Comparison of CNTs/Super-P composite conductive agent in improving the rate performance of lithium ion battery anode material (spinel lithium titanate—Li ₄ Ti ₅ O ₁₂ ).

detailed description

The present invention will be further described below in conjunction with the examples, and the protection scope of the present invention is not limited to the following description.

Embodiment 1. A kind of preparation method of Graphene/CNTs/Super-P composite conductive agent, its concrete steps are as follows:

(1) Mixing: Add 100g of graphene oxide slurry with a solid content of 10% into a single-layer glass reactor, add 5g of CNTs, 5g of Super-P and 0.2g of surfactant polyvinylpyrrolidone, mechanically stir for 30min, and then ultrasonically disperse 30min, make it mix evenly;

(2) Pulverization: Suction filter the mixed slurry in step (1), and dry it at 100°C until the water content is ≤5%, and pulverize the dried solid with a pulverizer so that the particle size of the pulverized particles is ≤74μm;

(3) Expansion: Heat the muffle furnace to raise the temperature to 300°C, quickly put the mixture particles pulverized in step (2) into the muffle furnace, puff them in the air for 5 minutes, take them out quickly, and cool to room temperature;

(4) Reduction: The mixture in step (3) was placed in a tube furnace at 1000°C in an inert atmosphere, and heat-treated for 10 minutes to obtain Graphene/CNTs/Super-P composite conductive agent powder.

The following is the preparation of composite conductive agent paste:

On the basis of the preparation of the above-mentioned composite conductive agent, take 10 g of the Graphene/CNTs/Super-P composite conductive agent powder prepared in step (4) and add it to 90 g of secondary deionized water, and ultrasonically disperse it for 10 minutes to obtain the solid content It is 10% water-based Graphene/CNTs/Super-P composite conductive agent slurry.

The scanning electron microscope (SEM) image of a Graphene/CNTs/Super-P composite conductive agent obtained in this example is shown in Figure 1. It can be observed that Graphene, CNTs and Super-P are more uniformly composited together, and can also be It was observed that the Graphene/CNTs/Super-P composite conductive agent was loose and porous, indicating that it would be easy to disperse in practical applications.

The scanning electron microscope (SEM) image of Graphene in a Graphene/CNTs/Super-P composite conductive agent obtained in this example is shown in Figure 2. It can be observed that Graphene shows a brighter luster under the field emission electron microscope, indicating that The prepared Graphene has excellent electronic conductivity. In addition, it can also be observed that the size of Graphene is larger than 5 µm.

A transmission electron microscope (TEM) image of Graphene in a Graphene/CNTs/Super-P composite conductive agent obtained in this example is shown in Figure 3. It can be observed that the prepared Graphene is oligolayer graphene with a layer number of 7 layer or so.

A scanning electron microscope (SEM) image of CNTs in a Graphene/CNTs/Super-P composite conductive agent obtained in this example is shown in Figure 4. It can be observed that the prepared CNTs have a higher aspect ratio, and the length 3µm ~5µm.

The transmission electron microscope (TEM) image of CNTs in a Graphene/CNTs/Super-P composite conductive agent obtained in this example is shown in Figure 5. It can be observed that the diameter of the prepared CNTs is 50 nm to 70 nm.

The following are the experimental test steps:

a) Preparation of electrode sheets: The active material Li ₄ Ti ₅ O ₁₂ (anode material for lithium-ion batteries—spinel lithium titanate), conductive agent, and binder LA132 were mixed in a weight ratio of 90:5:5. Proportionally mixed and uniformly ground in an agate mortar to make an electrode slurry, and then evenly coated on an aluminum foil, dried in a vacuum oven at 80°C for 12 hours to make an electrode sheet, in which the active material loading is greater than 3.0 mg/cm ² .

b) Coin cell assembly and rate performance test: use the CR2032 coin cell model, use a metal lithium sheet as the counter electrode, the diaphragm type is Celgard2400, and the electrolyte is 1mol/L LiPF6/EC:DEC:DMC (1: 1:1 volume ratio), assembled into a button battery. The rate performance was tested by constant current charge and discharge at room temperature. The test voltage range was 3.0 V to 1.0 V, and the test current was expressed as 0.2 C, 0.5 C, 1.0 C, 3.0 C, 5.0 C and 10.0 C in terms of rate.

3) Experimental results: As shown in Figure 8, the Graphene/CNTs/Super-P composite conductive agent exhibited the best performance in improving the rate performance of Li ₄ Ti ₅ O ₁₂ , and Li ₄ Ti ₅ O ₁₂ at 0.2 C The discharge specific capacity is as high as 163 mAh/g at 1.0 C, 156 mAh/g at 1.0 C, 147 mAh/g at 3.0 C, and 138 mAh/g at 5.0 C. The specific discharge capacity is still as high as 130 mAh/g at a rate of 10.0 C. Graphene/CNTs/Super _- P composite conductive agent is better than Graphene/ _CNTs composite conductive agent (comparative example ₁ ), better than Graphene/Super-P composite conductive agent (comparative example 2) and better than CNTs/Super-P composite conductive agent (comparative example 3).

Embodiment 2. A kind of preparation method of Graphene/CNTs/Super-P composite conductive agent, its concrete steps are as follows:

(1) Mixing: Add 100g of graphene oxide slurry with a solid content of 20% into a single-layer glass reactor, add 10g of CNTs, 10g of Super-P and 0.4g of surfactant polyvinylpyrrolidone, mechanically stir for 30min, and then ultrasonically disperse 30min, make it mix evenly;

(2) Pulverization: Suction filter the mixed slurry in step (1), and dry it at 100°C until the water content is ≤5%, and pulverize the dried solid with a pulverizer so that the particle size of the pulverized particles is ≤74μm;

(3) Expansion: Heat the muffle furnace to raise the temperature to 300°C, quickly put the mixture particles pulverized in step (2) into the muffle furnace, puff them in the air for 5 minutes, take them out quickly, and cool to room temperature;

(4) Reduction: The mixture in step (3) was placed in a tube furnace at 1000°C in an inert atmosphere, and heat-treated for 10 minutes to obtain Graphene/CNTs/Super-P composite conductive agent powder.

The following is the preparation of composite conductive agent paste:

On the basis of the preparation of the above-mentioned composite conductive agent, 5 g of the Graphene/CNTs/Super-P composite conductive agent powder prepared in step (4) was added to 95 g of N-methylpyrrolidone, and ultrasonically dispersed for 10 minutes to obtain a solid Oily Graphene/CNTs/Super-P composite conductive agent slurry with a content of 5%.

With reference to the test procedure of Example 1, the experimental results: the discharge specific capacity of Li ₄ Ti ₅ O ₁₂ at 0.2 C is as high as 161mAh/g, the discharge specific capacity at 1.0 C is 154 mAh/g, and the discharge specific capacity at 3.0 C is 145 mAh/g, the discharge specific capacity at 5.0 C is 136 mAh/g, even at a high rate of 10.0 C, the discharge specific capacity is still as high as 131 mAh/g.

Embodiment 3. A kind of preparation method of Graphene/CNTs/Super-P composite conductive agent, its concrete steps are as follows:

(1) Mixing: Add 100g of graphene oxide slurry with a solid content of 5% into a single-layer glass reactor, add 2.5g of CNTs, 2.5g of Super-P and 0.1g of surfactant polyvinylpyrrolidone, stir mechanically for 30min, and then Ultrasonic dispersion for 30 minutes to make it evenly mixed;

(2) Pulverization: Suction filter the mixed slurry in step (1), and dry it at 100°C until the water content is ≤5%, and pulverize the dried solid with a pulverizer so that the particle size of the pulverized particles is ≤74μm;

(3) Expansion: Heat the muffle furnace to raise the temperature to 300°C, quickly put the mixture particles pulverized in step (2) into the muffle furnace, puff them in the air for 5 minutes, take them out quickly, and cool to room temperature;

(4) Reduction: The mixture in step (3) was placed in a tube furnace at 1000°C in an inert atmosphere, and heat-treated for 10 minutes to obtain Graphene/CNTs/Super-P composite conductive agent powder.

The following is the preparation of composite conductive agent paste:

On the basis of the preparation of the above-mentioned composite conductive agent, 1 g of the Graphene/CNTs/Super-P composite conductive agent powder prepared in step (4) was added to 99 g of N-methylpyrrolidone, and ultrasonically dispersed for 10 minutes to obtain a solid Oily Graphene/CNTs/Super-P composite conductive agent slurry with a content of 1%.

With reference to the test procedure of Example 1, the experimental results: Li ₄ Ti ₅ O ₁₂ has a discharge specific capacity of 164mAh/g at 0.2 C, a discharge specific capacity of 158 mAh/g at 1.0 C, and a discharge specific capacity of 3.0 C of 147 mAh/g, the discharge specific capacity at 5.0 C is 139 mAh/g, even at a high rate of 10.0 C, the discharge specific capacity is still as high as 134 mAh/g.

Embodiment 4. A kind of preparation method of Graphene/CNTs/Super-P composite conducting agent, its concrete steps are as follows:

(1) Mixing: Add 100g of graphene oxide slurry with a solid content of 10% into a single-layer glass reactor, add 15g of CNTs, 15g of Super-P and 0.4g of surfactant cetyltrimethylammonium chloride, mechanically Stir for 30 minutes, then ultrasonically disperse for 30 minutes to make it evenly mixed;

(2) Pulverization: Suction filter the mixed slurry in step (1), and dry it at 100°C until the water content is ≤5%, and pulverize the dried solid with a pulverizer so that the particle size of the pulverized particles is ≤74μm;

(3) Expansion: Heat the muffle furnace to raise the temperature to 300°C, quickly put the mixture particles pulverized in step (2) into the muffle furnace, puff them in the air for 5 minutes, take them out quickly, and cool to room temperature;

(4) Reduction: The mixture in step (3) was placed in a tube furnace at 1000°C in an inert atmosphere, and heat-treated for 10 minutes to obtain Graphene/CNTs/Super-P composite conductive agent powder.

The following is the preparation of composite conductive agent paste:

On the basis of the preparation of the above-mentioned composite conductive agent, take 20g of the Graphene/CNTs/Super-P composite conductive agent powder prepared in step (4) and add it to 80g of secondary deionized water, and ultrasonically disperse it for 10min to obtain the solid content It is 20% water-based Graphene/CNTs/Super-P composite conductive agent slurry.

With reference to the test procedure of Example 1, the experimental results: Li ₄ Ti ₅ O ₁₂ has a discharge specific capacity of up to 160mAh/g at 0.2 C, a discharge specific capacity of 151 mAh/g at 1.0 C, and a discharge specific capacity of 3.0 C of 140 mAh/g, the discharge specific capacity at 5.0 C is 132 mAh/g, even at a high rate of 10.0 C, the discharge specific capacity is still as high as 127 mAh/g.

Embodiment 5. A kind of preparation method of Graphene/CNTs/Super-P composite conductive agent, its concrete steps are as follows:

(1) Mixing: Add 100g of graphene oxide slurry with a solid content of 5% into a single-layer glass reactor, add 15g of CNTs, 20g of Super-P and 0.4g of surfactant polyvinylpyrrolidone, stir mechanically for 30min, and then ultrasonically disperse 30min, make it mix evenly;

(2) Pulverization: Suction filter the mixed slurry in step (1), and dry it at 100°C until the water content is ≤5%, and pulverize the dried solid with a pulverizer so that the particle size of the pulverized particles is ≤74μm;

(3) Expansion: Heat the muffle furnace to raise the temperature to 300°C, quickly put the mixture particles pulverized in step (2) into the muffle furnace, puff them in the air for 5 minutes, take them out quickly, and cool to room temperature;

(4) Reduction: The mixture in step (3) was placed in a tube furnace at 1000°C in an inert atmosphere, and heat-treated for 10 minutes to obtain Graphene/CNTs/Super-P composite conductive agent powder.

The following is the preparation of composite conductive agent paste:

On the basis of the preparation of the above-mentioned composite conductive agent, take 5g of the Graphene/CNTs/Super-P composite conductive agent powder prepared in step (4) and add it to 95g of secondary deionized water, and ultrasonically disperse it for 10min to obtain the solid content It is 5% water-based Graphene/CNTs/Super-P composite conductive agent slurry.

With reference to the test procedure of Example 1, the experimental results: Li ₄ Ti ₅ O ₁₂ has a discharge specific capacity of 162 mAh/g at 0.2 C, a discharge specific capacity of 152 mAh/g at 1.0 C, and a discharge specific capacity of 3.0 C of 142 mAh/g, the discharge specific capacity at 5.0 C is 133 mAh/g, even at a high rate of 10.0 C, the discharge specific capacity is still as high as 130 mAh/g.

Embodiment 6. A kind of preparation method of Graphene/CNTs/Super-P composite conductive agent, its concrete steps are as follows:

(1) Mixing: Add 100g of graphene oxide slurry with a solid content of 1% into a single-layer glass reactor, add 9g of CNTs, 40g of Super-P and 0.1g of surfactant polyvinylpyrrolidone, stir mechanically for 30min, and then ultrasonically disperse 30min, make it mix evenly;

(2) Pulverization: Suction filter the mixed slurry in step (1), and dry it at 100°C until the water content is ≤5%, and pulverize the dried solid with a pulverizer so that the particle size of the pulverized particles is ≤74μm;

(3) Expansion: Heat the muffle furnace to raise the temperature to 300°C, quickly put the mixture particles pulverized in step (2) into the muffle furnace, puff them in the air for 5 minutes, take them out quickly, and cool to room temperature;

(4) Reduction: place the mixture in step (3) in a tube furnace with an inert atmosphere at 1000°C, and heat-treat for 10 minutes to obtain Graphene/CNTs/Super-P composite conductive agent powder;

The following is the preparation of composite conductive agent paste:

On the basis of the preparation of the above-mentioned composite conductive agent, 5 g of the Graphene/CNTs/Super-P composite conductive agent powder prepared in step (4) was added to 45 g of N-methylpyrrolidone, and ultrasonically dispersed for 10 minutes to obtain a solid Oily Graphene/CNTs/Super-P composite conductive agent slurry with a content of 10%.

With reference to the test procedure of Example 1, the experimental results: the discharge specific capacity of Li ₄ Ti ₅ O ₁₂ at 0.2 C is as high as 163mAh/g, the discharge specific capacity at 1.0 C is 152 mAh/g, and the discharge specific capacity at 3.0 C is 143 mAh/g, the discharge specific capacity at 5.0 C is 133 mAh/g, even at a high rate of 10.0 C, the discharge specific capacity is still as high as 134 mAh/g.

Embodiment 7. A kind of preparation method of Graphene/CNTs/Super-P composite conductive agent, its concrete steps are as follows:

(1) Mixing: Add 100g of graphene oxide slurry with a solid content of 9% into a single-layer glass reactor, add 1g of CNTs, 40g of Super-P and 0.1g of surfactant sodium dodecylsulfonate, and stir mechanically for 30min. Then ultrasonically disperse for 30 minutes to make it evenly mixed;

(2) Pulverization: Suction filter the mixed slurry in step (1), and dry it at 100°C until the water content is ≤5%, and pulverize the dried solid with a pulverizer so that the particle size of the pulverized particles is ≤74μm;

(3) Expansion: Heat the muffle furnace to raise the temperature to 300°C, quickly put the mixture particles pulverized in step (2) into the muffle furnace, puff them in the air for 5 minutes, take them out quickly, and cool to room temperature;

(4) Reduction: The mixture in step (3) was placed in a tube furnace at 1000°C in an inert atmosphere, and heat-treated for 10 minutes to obtain Graphene/CNTs/Super-P composite conductive agent powder.

The following is the preparation of composite conductive agent paste:

On the basis of the preparation of the above-mentioned composite conductive agent, take 5g of the Graphene/CNTs/Super-P composite conductive agent powder prepared in step (4) and add it to 45g of secondary deionized water, and ultrasonically disperse for 10min to obtain the solid content It is 10% water-based Graphene/CNTs/Super-P composite conductive agent slurry.

With reference to the test procedure of Example 1, the experimental results: the discharge specific capacity of Li ₄ Ti ₅ O ₁₂ at 0.2 C is as high as 163mAh/g, the discharge specific capacity at 1.0 C is 152 mAh/g, and the discharge specific capacity at 3.0 C is 141 mAh/g, the discharge specific capacity at 5.0 C is 132 mAh/g, even at a high rate of 10.0 C, the discharge specific capacity is still as high as 129 mAh/g.

Embodiment 8. A kind of preparation method of Graphene/CNTs/Super-P composite conductive agent, its concrete steps are as follows:

(1) Mixing: Add 100g of graphene oxide slurry with a solid content of 5% into a single-layer glass reactor, add 5g of CNTs, 1g of Super-P and 0.1g of surfactant polyvinylpyrrolidone, stir mechanically for 30min, and then ultrasonically disperse 30min, make it mix evenly;

(2) Pulverization: Suction filter the mixed slurry in step (1), and dry it at 100°C until the water content is ≤5%, and pulverize the dried solid with a pulverizer so that the particle size of the pulverized particles is ≤74μm;

(3) Expansion: Heat the muffle furnace to raise the temperature to 300°C, quickly put the mixture particles pulverized in step (2) into the muffle furnace, puff them in the air for 5 minutes, take them out quickly, and cool to room temperature;

(4) Reduction: The mixture in step (3) was placed in a tube furnace at 1000°C in an inert atmosphere, and heat-treated for 10 minutes to obtain Graphene/CNTs/Super-P composite conductive agent powder.

The following is the preparation of composite conductive agent paste:

On the basis of the preparation of the above-mentioned composite conductive agent, 5 g of the Graphene/CNTs/Super-P composite conductive agent powder prepared in step (4) was added to 45 g of N-methylpyrrolidone, and ultrasonically dispersed for 10 minutes to obtain a solid Oily Graphene/CNTs/Super-P composite conductive agent slurry with a content of 10%.

With reference to the test procedure of Example 1, the experimental results: the discharge specific capacity of Li ₄ Ti ₅ O ₁₂ at 0.2 C is as high as 163mAh/g, the discharge specific capacity at 1.0 C is 154 mAh/g, and the discharge specific capacity at 3.0 C is 144 mAh/g, the discharge specific capacity at 5.0 C is 138 mAh/g, even at a high rate of 10.0 C, the discharge specific capacity is still as high as 134mAh/g.

Comparative example 1. a kind of preparation method of Graphene/CNTs composite conductive agent, its concrete steps are as follows:

(1) Mixing: Add 100g of graphene oxide slurry with a solid content of 5% into a single-layer glass reactor, add 5g of CNTs and 0.1g of surfactant polyvinylpyrrolidone, stir mechanically for 30min, and then ultrasonically disperse for 30min to make it mix Uniform;

(2) Pulverization: Suction filter the mixed slurry in step (1), and dry it at 100°C until the water content is ≤5%, and pulverize the dried solid with a pulverizer so that the particle size of the pulverized particles is ≤74μm;

(3) Expansion: Heat the muffle furnace to raise the temperature to 300°C, quickly put the mixture particles pulverized in step (2) into the muffle furnace, puff them in the air for 5 minutes, take them out quickly, and cool to room temperature;

(4) Reduction: place the mixture in step (3) in a tube furnace with an inert atmosphere at 1000°C, and heat-treat for 10 minutes to obtain Graphene/CNTs composite conductive agent powder;

The following is the preparation of composite conductive agent paste:

On the basis of the preparation of the above-mentioned composite conductive agent, 5 g of the Graphene/CNTs composite conductive agent powder prepared in step (4) was added to 45 g of secondary deionized water, and ultrasonically dispersed for 10 minutes to obtain a solid content of 10%. Water-based Graphene/CNTs composite conductive agent slurry.

A scanning electron microscope (SEM) image of a Graphene/CNTs composite conductive agent obtained in this comparative example is shown in FIG. 6 , and it can be observed that Graphene and CNTs are relatively uniformly composited together. Nevertheless, compared with the Graphene/CNTs/Super-P composite conductive agent in Example 1, the Graphene/CNTs composite conductive agent has poor ability to construct an efficient conductive network.

With reference to the test procedure of Example 1, the experimental results: As shown in Figure 8, the discharge specific capacity of Li ₄ Ti ₅ O ₁₂ at 0.2 C is 159 mAh/g, and the discharge specific capacity at 1.0 C is 152 mAh/g, 3.0 The discharge specific capacity of C is 148 mAh/g, and the discharge specific capacity of 5.0C is 138 mAh/g. Even at a high rate of 10.0 C, the discharge specific capacity is still as high as 126 mAh/g.

Comparative example 2. a kind of preparation method of Graphene/Super-P composite conductive agent, its concrete steps are as follows:

(1) Mixing: Add 100g of graphene oxide slurry with a solid content of 5% into a single-layer glass reactor, add 5g of Super-P and 0.05g of surfactant sodium dodecylsulfonate, stir mechanically for 30min, and then sonicate Disperse for 30 minutes to make it evenly mixed;

(2) Pulverization: Suction filter the mixed slurry in step (1), and dry it at 100°C until the water content is ≤5%, and pulverize the dried solid with a pulverizer so that the particle size of the pulverized particles is ≤74μm;

(3) Expansion: Heat the muffle furnace to raise the temperature to 300°C, quickly put the mixture particles pulverized in step (2) into the muffle furnace, puff them in the air for 5 minutes, take them out quickly, and cool to room temperature;

(4) Reduction: The mixture in step (3) was placed in a tube furnace at 1000°C in an inert atmosphere, and heat-treated for 10 minutes to obtain Graphene/CNTs composite conductive agent powder.

The following is the preparation of composite conductive agent paste:

On the basis of the preparation of the above-mentioned composite conductive agent, take 1 g of the Graphene/Super-P composite conductive agent powder prepared in step (4) and add it to 49 g of N-methylpyrrolidone, and ultrasonically disperse it for 10 minutes to obtain a solid content of 2% oily Graphene/Super-P composite conductive agent paste.

With reference to the test procedure of Example 1, the experimental results: As shown in Figure 8, the discharge specific capacity of Li ₄ Ti ₅ O ₁₂ at 0.2 C is 150 mAh/g, and the discharge specific capacity at 1.0 C is 137 mAh/g, 3.0 The discharge specific capacity of C is 91 mAh/g, and the discharge specific capacity of 5.0 C is 80 mAh/g. Even at a high rate of 10.0 C, the discharge specific capacity is still as high as 71 mAh/g.

Comparative example 3. a kind of preparation method of CNTs/Super-P composite conductive agent, its concrete steps are as follows:

(1) Mixing: Add 5g of CNTs into a single-layer glass reactor, add 95g of secondary deionized water, then add 5g of Super-P and 0.05g of surfactant cetyltrimethylammonium chloride, stir mechanically for 30min, Then ultrasonically disperse for 30 minutes to make it evenly mixed;

(2) Pulverization: Suction filter the mixed slurry in step (1), and dry it at 100°C until the water content is ≤5%, and pulverize the dried solid with a pulverizer so that the particle size of the pulverized particles is ≤74μm;

(3) Expansion: Heat the muffle furnace to raise the temperature to 300°C, quickly put the mixture particles pulverized in step (2) into the muffle furnace, puff them in the air for 5 minutes, take them out quickly, and cool to room temperature;

(4) Reduction: place the mixture in step (3) in a tube furnace with an inert atmosphere at 1000°C, and heat-treat for 10 minutes to obtain Graphene/CNTs composite conductive agent powder;

The following is the preparation of composite conductive agent paste:

On the basis of the preparation of the above-mentioned composite conductive agent, take 1 g of the CNTs/Super-P composite conductive agent powder prepared in step (4) and add it to 49 g of secondary deionized water, and ultrasonically disperse it for 10 minutes to obtain a solid content of 2 % water-based CNTs/Super-P composite conductive agent slurry.

A scanning electron microscope (SEM) image of a CNTs/Super-P composite conductive agent obtained in this comparative example is shown in FIG. 8 . It can be observed that CNTs and Super-P are not more uniformly composited together. It shows that without in-situ compounding with graphene oxide slurry, it is difficult to achieve more uniform compounding.

Referring to the test procedure of Example 1, the experimental results: As shown in Figure 8, the discharge specific capacity of Li ₄ Ti ₅ O ₁₂ at 0.2 C is 157 mAh/g, and the discharge specific capacity at 1.0 C is 145 mAh/g, The discharge specific capacity is 125 mAh/g at 3.0 C, and 117 mAh/g at 5.0 C. Even at a high rate of 10.0 C, the discharge specific capacity is still as high as 105 mAh/g.

Claims (5)

1. a kind of preparation method of Graphene/CNTs/Super-P combined conductive agents, it is characterised in that comprise the steps：

（1）Mixing：The graphene oxide slurry of solid content≤50% is added in single-glass reactor, CNTs, Super- is added P and surfactant, mechanical agitation 25min～35min, then ultrasonic disperse 20min～35min again so as to be well mixed；

（2）Crush：By step（1）In mixed slurry suction filtration and in the drying of 90 DEG C～110 DEG C environment, be dried to water content≤5%, The solid of drying is crushed with pulverizer, particle diameter≤74 μm of pulverized particles are made；

（3）It is expanded：Heating muffle stove so as to be warming up to 200 DEG C～450 DEG C, by step（2）The compound particles of middle crushing are fast Speed is put in Muffle furnace, takes out rapidly, be cooled to normal temperature in air after expanding treatment 3min～10min；

（4）Reduction：By step（3）In mixture be placed on 1000 DEG C, in the tube furnace of inert atmosphere, heat treatment 5min～ 15min, obtains Graphene/CNTs/Super-P combined conductive agent powders.

2. the preparation method of combined conductive agent according to claim 1, it is characterised in that the step（1）Live on middle surface Property agent selected from polyvinylpyrrolidone, dodecyl sodium sulfate, hexadecyltrimethylammonium chloride any one.

3. the preparation method of combined conductive agent according to claim 1, it is characterised in that the step（1）Live on middle surface Property agent add mass percent for graphene oxide, CNT and conductive black gross mass 0.01%～1%.

4. a kind of preparation method of combined conductive agent slurry, it is characterised in that prepare the combined conductive agent in claim 1 On the basis of, also comprise the steps：

By the step（4）In the Graphene/CNTs/Super-P combined conductive agent powders that obtain be added in solvent, admittedly contain Amount≤50%, ultrasonic disperse 8min～12min, are obtained Graphene/CNTs/Super-P combined conductive agent slurries.

5. the preparation method of combined conductive agent slurry according to claim 4, it is characterised in that the solvent is selected from secondary Deionized water, 1-METHYLPYRROLIDONE.