CN110635135B

CN110635135B - Conductive paste and preparation method thereof

Info

Publication number: CN110635135B
Application number: CN201910856863.1A
Authority: CN
Inventors: 杨树斌
Original assignee: Beihang University
Current assignee: Jinan Sanchuan New Material Technology Co ltd
Priority date: 2019-09-11
Filing date: 2019-09-11
Publication date: 2022-07-29
Anticipated expiration: 2039-09-11
Also published as: CN114976017A; CN114023968A; CN114023968B; CN110635135A; CN114976017B

Abstract

The invention discloses conductive paste and a preparation method thereof, wherein the conductive pasteThe components of the material comprise a conductive agent, micro-bubbles and liquid, wherein the conductive agent comprises graphene and/or carbon nano tubes, the particle size of the micro-bubbles is less than 100 mu m, and the concentration of the micro-bubbles is more than 10 ⁶ One per ml. The preparation method of the conductive paste comprises the following steps: forming gas-liquid mixed fluid by carrying out a gas-liquid dispersion method on liquid and gas; and adding the conductive agent into the gas-liquid mixed fluid to obtain the conductive slurry. The conductive paste obtained by the method can achieve the effect of uniformly dispersing the conductive agent under the condition of not adding or adding a little dispersant, is beneficial to transportation, storage and use of the conductive paste, and when the conductive paste is applied to the preparation process of a battery electrode, micro bubbles disappear in the drying process, no impurity is introduced, and the conductive property of the conductive agent can be better exerted.

Description

Conductive paste and preparation method thereof

Technical Field

The invention relates to the field of conductive materials, in particular to conductive paste for preparing an electrode of a battery and a preparation method thereof.

Background

Due to the characteristics of ultrahigh conductivity, ultrathin two-dimension, high chemical stability and the like, the graphene is widely favored on the conductive paste of the battery, and the graphene and the active substance can be in contact in a surface-point mode. Meanwhile, the carbon nano tube also has higher conductivity and can be contacted with the active substance in a line-point mode. Meanwhile, the composite conductive slurry containing graphene and carbon nano tubes can realize surface-line-point contact, greatly improve the conductivity of the whole electrode, and reduce the using amount of a conductive agent in the whole electrode, so that more active substances are used and are densely accumulated, and the mass specific capacity and the volume specific capacity of the battery are improved. However, graphene and carbon nanotubes have strong van der waals force and high specific surface area, and are easily agglomerated, stacked and even precipitated in the conductive paste, so that the storage and practical application of the conductive paste are greatly limited. In order to improve the stability of the conductive paste, it is generally necessary to add a large amount of a dispersant or an additive, which generally has no conductivity. Such composite slurry with a dispersant or additive seriously affects the contact of the conductive agent and the active material when it is practically applied to a battery electrode, thereby affecting the conductivity-enhancing effect thereof.

Disclosure of Invention

The invention provides conductive paste and a preparation method thereof, aiming at the technical problem that conductive paste of conductive agent graphene and carbon nano tubes is easy to agglomerate, stack and even precipitate. The conductive slurry is introduced with micro-bubbles, and the micro-bubbles can be spontaneously adsorbed around graphene sheets and/or carbon nanotubes under the high specific surface area adsorption effect of the conductive agent graphene and/or carbon nanotubes, so that the graphene and/or the carbon nanotubes can be uniformly and stably dispersed in the conductive slurry.

In one aspect, the conductive paste comprises a conductive agent, micro-bubbles and a liquid, wherein the conductive agent comprises graphene and/or carbon nano tubes, the particle size of the micro-bubbles is less than 100 μm, and the concentration of the micro-bubbles is more than 10 ⁶ Each/ml.

In some embodiments, the liquid comprises: water, N-methylpyrrolidone (NMP), N-Dimethylformamide (DMF), ethanol, Isopropanol (IPA), Methyl Ethyl Ketone (MEK), or toluene.

In some embodiments, the fine bubbles have a particle size in the range of 10nm to 10 μm.

In some embodiments, the fine bubbles have a particle size ranging from 100 nm to 300nm, and the concentration of the fine bubbles is between 10 ⁸ To 10 ⁹ One per ml.

In some embodiments, the types of gas in the micro-fine bubbles include: one or more of air, oxygen, nitrogen, argon, hydrogen, helium, or ozone.

In some embodiments, the conductive agent is present in an amount of 0.5 wt.% to 8 wt.%.

In some embodiments, the conductive agent comprises graphene and carbon nanotubes, wherein the mass ratio of graphene to carbon nanotubes is between 1: 10 to 1: between 0.1.

In another aspect, the present invention also includes a method of preparing a conductive paste, comprising the steps of:

forming gas-liquid mixed fluid by carrying out a gas-liquid dispersion method on liquid and gas;

adding a conductive agent into the gas-liquid mixed fluid, and stirring and/or ultrasonically treating to obtain conductive slurry;

wherein the gas-liquid mixed fluid contains fine bubblesThe particle diameter of the bubbles is less than 100 μm, and the concentration of the fine bubbles is more than 10 ⁶ One per ml.

In some embodiments, a gas-liquid mixing method comprises: the gas-liquid dispersion method includes: one or more of a mechanical shearing method, an ultrasonic cavitation method, a pressurized dissolved gas and gas release method, a microporous dispersed gas method, a jet aeration method, a gas floating pump gas production method or an electrolysis method.

In still another aspect, the present invention also includes the use of the above conductive paste for the preparation of an electrode for a battery.

Compared with the prior art, the invention has the beneficial technical effects that:

(1) the conductive paste obtained by the invention disperses the conductive agent (graphene and/or carbon nano tubes) into the liquid containing a large amount of micro bubbles, and the micro bubbles can be spontaneously adsorbed around the conductive agent through the adsorption effect of the graphene and the carbon nano tubes with high specific surface area. According to Stokes formula R = ρ gd ² μ 18 μ (ρ = density, g = acceleration of gravity, d = bubble diameter, μ = viscosity). The rising speed of small bubbles in the liquid is proportional to the square of the bubble diameter, and the smaller the diameter of the obtained fine bubbles, the longer the time of existence in water, the more stable. Since the fine bubbles have a small particle diameter and are much smaller in buoyancy than ordinary bubbles, the fine bubbles have a characteristic of being slow in rising speed in the liquid and being capable of existing for a long time in the liquid. When a large number of fine bubbles are dispersed around the conductive agent, the conductive agent can be uniformly and stably dispersed in the conductive paste. The effect of using no dispersant or additive or using a small amount of dispersant or additive is achieved.

(2) When the conductive paste obtained by the invention is used in the actual battery electrode preparation process, the conductive paste containing micro-bubbles is very easy to store, does not generate precipitates after being placed for months, and meets the requirement that the conductive paste needs to be placed for a period of time in storage and transportation. The problem that the existing graphene dispersion liquid can be used after being subjected to dispersion treatment is solved, and the graphene dispersion liquid can be directly used for preparing the electrode of the battery.

(3) The conductive paste does not contain a dispersing agent or an additive, micro bubbles contained in the conductive paste spontaneously disappear in the drying process of electrode preparation, no impurity is introduced, and the influence of the dispersing agent or the additive on the contact of a conductive agent and an active substance is avoided, so that the characteristic of high conductivity of graphene can be better played, and the electrochemical performance of the battery is remarkably improved.

Drawings

FIG. 1 is a schematic diagram of the steps of the conductive paste preparation process of the present invention;

FIG. 2 is a diagram illustrating the definition and classification of bubbles according to the bubble particle size in ISO 20480-1: 2017;

fig. 3 is a schematic view of an apparatus for preparing a gas-liquid mixed fluid by a gas floating pump gas production method according to an embodiment of the present invention.

Symbolic illustration in the drawings:

1 gas-liquid mixing pump; 2, a gas-liquid separation tank; 3, a water tank; 4, a gas releasing device; 5 a waterway valve; 6, a gas circuit valve; 7 a pressure valve; 8, a pressure gauge; 9 a water inlet pipeline a; 10 a water inlet pipeline b; 11 connecting pipelines; 12 water outlet pipeline; 13 an air inlet pipeline; 14 a gas line; s1 and S2.

Detailed Description

The technical solution of the present invention will be described below by way of specific examples. It is to be understood that one or more of the steps mentioned in the present invention does not exclude the presence of other methods or steps before or after the combined steps, or that other methods or steps may be inserted between the explicitly mentioned steps. It should also be understood that these examples are intended only to illustrate the invention and are not intended to limit the scope of the invention. Unless otherwise indicated, the numbering of the method steps is only for the purpose of identifying the method steps, and is not intended to limit the arrangement order of each method or the scope of the implementation of the present invention, and changes or modifications of the relative relationship thereof may be regarded as the scope of the implementation of the present invention without substantial technical change.

The raw materials and apparatuses used in the examples are not particularly limited in their sources, and may be purchased in the market or prepared according to a conventional method well known to those skilled in the art.

Example 1

The present embodiment provides a method for preparing conductive paste, the preparation steps of which are shown in fig. 1, and include steps S1 and S2:

s1: forming gas-liquid mixed fluid by carrying out a gas-liquid dispersion method on liquid and gas;

s2: and adding the conductive agent into the gas-liquid mixed fluid, and stirring and/or carrying out ultrasonic treatment to obtain the conductive slurry.

Wherein the conductive agent comprises graphene and/or carbon nanotubes; the liquid comprises one of water, N-methylpyrrolidone (NMP), N-Dimethylformamide (DMF), ethanol, Isopropanol (IPA), Methyl Ethyl Ketone (MEK) or toluene; the obtained gas-liquid mixed fluid contains fine bubbles with particle diameter less than 100 μm and concentration greater than 10 ⁶ Per ml; the type of gas in the micro-bubbles includes one or more of air, oxygen, nitrogen, argon, hydrogen, helium, or ozone.

The conductive paste and the method for preparing the same according to the present invention will be further described by way of the following detailed examples, which should be construed as illustrating the technical idea of the present invention and not limiting the scope of the patented practice of the present invention.

Example 2

The embodiment provides a conductive paste, the components of which are composed of graphene, micro bubbles and water. Wherein the type of gas in the micro-bubbles is air. The preparation method comprises the steps 1) and 2):

step 1) forming gas-liquid mixed fluid by air and water through a gas-liquid dispersion method;

and 2) adding a certain mass of conductive agent graphene into the 1L of gas-liquid mixed fluid obtained in the step 1), and stirring and carrying out ultrasonic treatment to obtain conductive slurry.

The mass range of the added graphene is between 5g and 86g, and the mass fraction of the conductive agent in the correspondingly obtained conductive paste is between 0.5 wt.% and 8 wt.%. Preferably, the addition amount of the graphene is between 30g and 50g, the mass fraction of the conductive agent of the conductive paste is about 3 wt.% to 5 wt.%, and the conductive paste has a better viscosity in the concentration range.

Example 3

The embodiment provides a conductive paste, which comprises graphene, carbon nanotubes, micro bubbles and water. Wherein the type of gas in the micro-bubbles is air. The preparation method comprises the steps 1) and 2):

and step 2) adding a certain mass of conductive agents (graphene and carbon nano tubes) into the 1L of gas-liquid mixed fluid obtained in the step 1), and stirring to obtain conductive slurry.

The mass range of the added conductive agent (graphene and carbon nano tube) is 5 g-86 g, and the mass ratio of the graphene to the carbon nano tube is 1: 10-1: 0.1. Preferably, the mass of the conductive agent (of graphene and carbon nanotubes) is 30-50 g, and the mass ratio of graphene to carbon nanotubes is 1:1 to 1:0.5, and the conductive paste in this range has a better viscosity.

Example 4

The present embodiment provides a conductive paste, which comprises graphene, carbon nanotubes, carbon black, micro bubbles, and water. Wherein the type of gas in the micro-bubbles is air. The preparation method comprises the steps 1) and 2):

and 2) adding a certain mass of conductive agents (graphene, carbon nano tubes and carbon black) into the 1L of gas-liquid mixed fluid obtained in the step 1) in sequence according to a certain proportion, and performing ultrasonic treatment to obtain conductive slurry.

The mass range of the conductive agent (graphene, carbon nano tube and carbon black) is 5 g-80 g, the mass ratio of the graphene to the carbon nano tube is 1: 10-1: 0.1, and the mass ratio of the carbon black in the conductive agent is 50% -80%. Preferably, the mass of the conductive agent (graphene, carbon nano tube and carbon black) is 30-50 g, the mass ratio of the carbon black in the conductive agent is 60-70%, and the mass ratio of the graphene to the carbon nano tube is 1: 1.

Example 5

The embodiment provides a conductive paste, which comprises graphene, ultra-micro bubbles and water. Wherein the type of gas in the ultramicro bubbles is nitrogen, and the particle size of the ultramicro bubbles is less than 1 micron. The preparation method comprises the steps 1) and 2):

Step 1) forming gas-liquid mixed fluid by nitrogen and water through a gas-liquid dispersion method;

step 2) adding 40g of graphene into 1L of gas-liquid mixed fluid obtained in the step 1), and performing ultrasonic treatment to obtain conductive paste, wherein the mass fraction of a conductive agent in the conductive paste is about 4 wt.%.

Example 6

The embodiment provides a conductive paste, which comprises graphene, ultra-micro bubbles and ethanol. Wherein the type of gas in the micro-bubbles is nitrogen. The preparation method comprises the steps 1) and 2):

step 1) forming gas-liquid mixed fluid by nitrogen and ethanol through a gas-liquid dispersion method;

step 2) adding 5g of graphene into 1L of gas-liquid mixed fluid obtained in the step 1), and performing ultrasonic treatment to obtain conductive paste, wherein the mass fraction of the conductive agent in the conductive paste is about 0.5 wt.%.

Example 7

The embodiment provides a conductive paste, which comprises the components of carbon nano tubes, ultramicro bubbles and ethanol. Wherein the type of gas in the ultramicrobubbles is air. The preparation method comprises the steps 1) and 2):

step 1) forming gas-liquid mixed fluid by air and ethanol through a gas-liquid dispersion method;

step 2) adding 20g of carbon nanotubes into 1L of gas-liquid mixed fluid obtained in the step 1), stirring and performing ultrasonic treatment to obtain conductive paste, wherein the mass fraction of the conductive agent in the conductive paste is about 2 wt.%.

Example 8

The embodiment provides a conductive paste, which comprises the components of carbon nano tubes, carbon black, ultramicrobubbles and water. Wherein the type of gas in the ultramicrobubbles is air. The preparation method comprises the steps 1) and 2):

step 2), adding 88g of conductive agent (carbon nano tube and carbon black) into 1L of gas-liquid mixed fluid obtained in the step 1) according to a ratio, and performing ultrasonic treatment to obtain conductive slurry, wherein the mass fraction of the conductive agent in the conductive slurry is 8 wt.%.

Wherein the mass ratio of the carbon black in the conductive agent is 50-80%.

Example 9

The embodiment provides a conductive paste, which comprises the components of carbon nano tubes, ultramicro bubbles and water. Wherein the type of gas in the ultramicrobubbles is air. The preparation method comprises the steps 1) and 2):

step 2) adding 50g of carbon nanotubes into the 1L of gas-liquid mixed fluid obtained in the step 1), stirring and performing ultrasonic treatment to obtain conductive paste, wherein the mass fraction of the conductive agent in the conductive paste is 4.8 wt.%.

Example 10

The embodiment provides a conductive paste, which comprises the components of carbon nano tubes, ultramicro bubbles and ethanol. Wherein the type of gas in the ultra-micro bubbles is air. The preparation method comprises the steps 1) and 2):

step 2) adding 10g of carbon nano tubes into 1L of gas-liquid mixed fluid obtained in the step 1), and performing ultrasonic treatment to obtain conductive slurry, wherein the mass fraction of a conductive agent in the conductive slurry is 1 wt.%.

Example 11

The embodiment provides a conductive paste, which comprises graphene, ultra-micro bubbles, lignin and water. Wherein the type of gas in the ultramicrobubbles is air. The preparation method comprises the steps 1) and 2):

step 2) adding 50g of graphene and dispersant lignin into 1L of gas-liquid mixed fluid obtained in step 1), wherein the mass fraction of the conductive agent in the conductive slurry obtained after ultrasonic treatment is 4.8 wt.%. Wherein the mass ratio of the added graphene to the lignin is 50:1 to 100:1, namely the mass of the added lignin is between 0.5g and 1 g.

Example 12

The embodiment provides a conductive paste, which comprises the components of carbon nano tubes, ultramicro bubbles, sodium lignin sulfonate and water. Wherein the type of gas in the ultramicrobubbles is air. The preparation method comprises the steps 1) and 2):

step 2) adding 30g of carbon nano tube and dispersant sodium lignosulfonate into 1L of gas-liquid mixed fluid obtained in step 1), wherein the mass fraction of the conductive agent of the conductive slurry obtained after ultrasonic treatment is 2.9 wt.%. Wherein the mass ratio of the added carbon nano tube to the sodium lignosulfonate is 50:1 to 100:1, namely the mass of the added sodium lignosulfonate is between 1.6g and 3.3 g.

Example 13

The present embodiment provides an electroconductive paste whose composition is composed of graphene, fine bubbles, and NMP. Wherein the type of gas in the micro-bubbles is argon. The preparation method comprises the steps 1) and 2):

step 1) forming a gas-liquid mixed fluid by argon and NMP through a gas-liquid dispersion method;

and 2) adding a certain mass of graphene into the 1L of gas-liquid mixed fluid obtained in the step 1), and stirring and performing ultrasonic treatment to obtain the conductive slurry.

Example 14

The present embodiment provides a conductive paste, which comprises graphene, carbon nanotubes, microbubbles, and NMP. Wherein the type of gas in the micro-bubbles is argon. The preparation method comprises the steps 1) and 2):

and 2) adding graphene and carbon nanotubes with certain mass into the 1L of gas-liquid mixed fluid obtained in the step 1) according to a certain proportion, and stirring and carrying out ultrasonic treatment to obtain the conductive slurry.

Example 15

The mass concentration of the conductive paste can be configured according to requirements, and when the purpose of the conductive paste is preparation of a battery electrode material, the configured concentration is preferably 0.5-8 wt.%, wherein the mass ratio of the added graphene to the carbon nanotubes is in a range of 1:10 to 1:0.1, more preferably in a range of 1:2 to 1:0.5, and even more preferably in a range of 1: 1.

Example 16

The present example provides a conductive paste, which comprises graphene, carbon nanotubes, carbon black, fine bubbles, and NMP. Wherein the type of gas in the micro-bubbles is argon. The preparation method comprises the steps 1) and 2):

and 2) adding a certain mass of conductive agents (graphene, carbon nano tubes and carbon black) into the 1L of gas-liquid mixed fluid obtained in the step 1) according to a certain proportion, and stirring and carrying out ultrasonic treatment to obtain conductive slurry.

The mass concentration of the conductive paste can be configured according to requirements, wherein the mass ratio of the added graphene to the carbon nanotubes to the added carbon black is 2:1:1 or 1:1:1, and the mass concentration of the conductive agent (the graphene to the carbon nanotubes to the added carbon black) is 0.5-8 wt.%.

Example 17

The embodiment provides a conductive paste, which comprises graphene, carbon nanotubes, micro bubbles, IPA and water. Wherein the type of gas in the micro-bubbles is nitrogen. The preparation method comprises the steps 1) and 3):

step 1) mixing water and IPA according to a certain proportion to form a mixed solution;

step 2) forming gas-liquid mixed fluid by nitrogen and the mixed solution through a gas-liquid dispersion method;

And 3) adding a certain amount of graphene and carbon nanotubes into the certain amount of gas-liquid mixed fluid obtained in the step 1) according to the proportion of 1:0.1, and stirring and carrying out ultrasonic treatment to obtain the conductive slurry.

Example 18

The embodiment provides a conductive paste, which comprises graphene, carbon nanotubes, microbubbles and DMF. Wherein the type of gas in the ultra-micro bubbles is helium. The preparation method comprises the steps 1) and 2):

step 1) helium and DMF form gas-liquid mixed fluid by a gas-liquid dispersion method;

and 2) adding a certain mass of graphene and carbon nanotubes into a certain amount of gas-liquid mixed fluid obtained in the step 1) according to a ratio of 1:10, and stirring and carrying out ultrasonic treatment to obtain the conductive slurry.

Example 19

The embodiment provides a conductive paste, which comprises graphene, carbon nanotubes, microbubbles and MEK. Wherein the type of gas in the ultra-micro bubbles is argon. The preparation method comprises the steps 1) and 2):

step 1) forming a gas-liquid mixed fluid by argon and MEK through a gas-liquid dispersion method;

and 2) adding a certain mass of graphene and carbon nanotubes into 1L of gas-liquid mixed fluid obtained in the step 1) according to a ratio of 1:1, and stirring and carrying out ultrasonic treatment to obtain the conductive slurry.

Example 20

The embodiment provides a conductive paste, which comprises graphene, carbon nanotubes, ultramicrobubbles and toluene. Wherein the type of gas in the ultra-micro bubbles is argon. The preparation method comprises the steps 1) and 2):

and 2) adding a certain mass of graphene and carbon nanotubes into 1L of gas-liquid mixed fluid obtained in the step 1) according to a ratio of 1:0.5, and stirring and carrying out ultrasonic treatment to obtain the conductive slurry.

In order to illustrate the preparation method of the conductive paste of the present invention, in examples 2 to 20, only the amount of 1L of the gas-liquid mixed fluid is used for illustration, and in the actual production configuration process, the mass concentration of the conductive paste can be configured as required, and any amount of the gas-liquid mixed fluid is selected to obtain the mass concentration of the conductive paste of 0.5 to 8 wt.%. When the conductive paste is used for preparing a battery electrode material, the concentration of the conductive paste is preferably 3 to 5 wt.%. At this concentration, the conductive paste shows the best viscosity performance (the viscosity ranges from 2000 mPa s to 3000 mPa s, the test adopts a rotary viscometer with a number 4 rotor, and the torque is 40 to 60N m), when the conductive agent in the conductive paste is a graphene and carbon nanotube composite conductive material, the mass ratio of graphene to carbon nanotubes is between 1:10 and 1:0.1, and when the conductive paste is used for preparing a battery electrode material, the mass ratio of graphene to carbon nanotubes is preferably between 1:2 and 1: 0.5.

Graphene belongs to a typical two-dimensional material, while carbon nanotubes belong to a typical one-dimensional material, when the mixture of graphene and carbon nanotubes is used as a conductive agent, a surface-line-point conductive network can be formed, and compared with conductive slurry of a single-component conductive agent, the conductive slurry of the composite-component conductive agent has better conductivity under the condition of the same mass content of the conductive agent, so that the conductivity of the material can be improved; under the condition of the same conductive performance, the mass content of the composite conductive agent in the conductive paste is lower, and the cost can be saved.

The Micro-bubbles are defined according to the bubble particle size in the international Micro-bubble standard ISO 20480-1:2017, and as shown in FIG. 2, the Micro-bubbles (Fine bubbles) with the bubble particle size smaller than 100 μm, the Micro-bubbles (Micro bubbles) with the bubble particle size between 1 and 100 μm, and the ultra-Micro-bubbles (ultra Fine bubbles) with the bubble particle size smaller than 1 μm are adopted. The concept of the fine bubbles in the present invention is consistent with this standard, and refers to bubbles having a bubble particle diameter of less than 100 μm. The present invention utilizes the characteristic that the smaller the diameter of the fine bubbles, the more stable the fine bubbles exist in water for a longer time. More preferably, the fine bubbles in the conductive paste of the present invention are ultra fine bubbles having a particle size of less than 1 μm. The size and concentration of the bubbles can be tested by a Marvens Nanosight NS500 or IZON qNano nanometer particle size analysis device. The particle size value of the fine bubbles or the ultra-fine bubbles in the present invention means a particle size value of D50 (D50 is a particle size of 50% in cumulative distribution of particles, and is also called a median diameter or a median particle size).

At present, the technology for generating micro bubbles in liquid is more mature, and the gas-liquid dispersion method mainly comprises the following steps according to the generation principle of the micro bubbles:

(1) a pressurized dissolved air release method: the gas is forcibly dissolved in the liquid by pressurization to form a supersaturated state, and then the gas is released again by depressurization to generate a large number of microbubbles whose size and strength depend on various conditions under which the air is released and the surface tension of the water.

(2) Gas production method of gas floating pump: the impeller assembly is directly adopted to directly dissipate air to generate micro bubbles, or pressure dissolved air and impeller air dissipation are combined, and meanwhile three processes of gas-liquid mixing, pressurization dissolved air and decompression air release are completed in one pump, so that the bubble generation efficiency is improved.

(3) High-speed rotary cutting method: the hollow part of the gas-liquid two-phase inlet device rotates, the gas forms a negative pressure gas shaft at the central shaft due to specific gravity difference, the gas of the negative pressure gas shaft is cut off to be micro-bubbles when passing through a gap between the external liquid and the internal high-speed rotating liquid, a large amount of micro-bubbles can be rapidly generated, and the uniformity of the bubble concentration is good.

(3) Jet aeration: the fine bubbles are generated mainly by a jet aerator. The jet aerator has small nozzle diameter and high flow speed, and the liquid flow can form partial vacuum after entering the air chamber. At this time, the gas may enter the gas chamber through the suction pipe to be mixed with the liquid. After passing through the mixing tube and the diffuser tube, fine bubbles are formed in the liquid.

(4) Microporous dispersed gas method: the microporous medium is relatively simple in a mode that a microporous structure formed by sintering certain media such as metallurgical powder, ceramic or plastic mixed with a proper binder at a high temperature cuts gas into fine bubbles by utilizing micropores when compressed gas passes through the microporous medium, and the smaller the pore diameter of the microporous medium, the narrower the distribution, and the smaller the particle size of the formed bubbles, the more concentrated the distribution.

(5) Ultrasonic cavitation method: the liquid generates negative pressure through ultrasonic cavitation, the gas originally dissolved in the liquid is released in the form of micro bubbles, the control of bubble destruction can be realized, and the liquid has better prospect in the application aspect of bubble precise control.

(6) Mechanical shearing method: the gas is generally drawn into a swirling water stream by a pump, and the vortex is then collapsed to crush the bubbles, which are then discharged as fine bubbles through an outlet nozzle.

(7) An electrolytic method: the main principle is that micro-nano bubbles are generated on positive and negative electrode plates by means of water electrolysis of electrodes. The diameter of the micro-bubbles generated by the method is usually 20-60 mu m, the size controllability is good, and the method has the corresponding defects of high energy consumption, low bubble yield and the like.

The particle size range of 10nm to 100 μm and the particle size concentration of the micro-bubbles of 10 can be obtained by the micro-bubble generating equipment in the prior art ⁶ To 10 ⁹ The volume of the gas-liquid mixed fluid per ml contains micro bubbles. In the invention, the higher the concentration of the micro-bubbles and the smaller the particle size, the better the dispersion effect of the graphene and/or the carbon nano tube in the conductive slurry is obtained. Further, it has been found that when the particle size of the fine bubbles is less than 100nm, the particle size of the bubbles in the obtained gas-liquid mixed fluid changes with the lapse of the standing time and gradually stabilizes in the range of 100nm to 300 nm. Therefore, the present embodiment provides a preferable condition for the gas-liquid mixed fluid, that is, the particle size of the micro-bubbles is 100nm to 300nm, concentration of micro-bubbles of 10 order ⁸ ~10 ⁹ On the order of one/ml.

Example 21

This embodiment provides a method for preparing a gas-liquid mixed fluid by a gas floating pump gas production method, in which a liquid is water and a gas phase is air, for example, to describe the gas-liquid dispersion method. The preparation device is shown in fig. 3 and comprises a dissolved air pump 1, an air-liquid mixing tank 2, a container 3, a releaser 4 and the like. The water inlet pipeline 9 and the air inlet pipeline 13 are respectively connected with a water inlet and an air inlet of the dissolved air pump 1, a water outlet of the dissolved air pump 1 is connected with the gas-liquid mixing tank 2 through a connecting pipeline 11, the tail end of a water outlet pipeline 12 of the gas-liquid mixing tank 2 is connected with the air releaser 4, the air releaser 4 is placed inside the container 3 and is submerged below the water surface in the water making process, and the water outlet pipeline 12 is also connected with a pressure gauge 8 and a pressure valve 7. One end of the water inlet pipeline 10 is communicated with the water inlet pipeline 9, and the position of the communication point is between the valve 5 and the water inlet of the dissolved air pump 1. The other end of the water inlet line 10 is inside the container 3 and is also below the water surface during the water production process.

Deionized water is used as a water source, and air is used as an air source. When fine bubble water is prepared, the gas circuit valve 6 is closed, the valve 5 and the pressure valve 7 are opened, the dissolved air pump 1 is opened, deionized water enters the dissolved air pump 1 through the water inlet pipeline 9, and air enters the dissolved air pump 1 through the gas circuit pipeline 13. Air and deionized water are fully mixed in the dissolved air pump to form gas-liquid mixed fluid, the gas-liquid mixed fluid enters the gas-liquid mixing tank 2 through the connecting pipeline 11, and the gas-liquid mixed fluid is sprayed into the container 3 through the releaser 4 after passing through the water outlet pipeline 12. When the water surface in the container 3 rises and the inlet ends of the releaser 4 and the water inlet pipeline 10 in the container 3 are submerged below the water surface, the valve 5 is closed, the water in the container 3 enters the dissolved air pump 1 through the water inlet pipeline 10, and the gas-liquid mixed water in the container 3 is subjected to a circulating dissolved air releasing process. The water amount in the container 3 is 40L, and the circulating dissolved air is released for 10min to obtain the fine bubble water taking the air as the air source.

In this embodiment, when the gas line 13 is connected to a nitrogen gas source, the fine nitrogen bubble water can be prepared without changing other operation methods. Similarly, the type of gas source connected to the gas line 13 is changed, such as oxygen, nitrogen, argon, helium, carbon dioxide, ozone, hydrogen, and the like. Can respectively prepare the fine bubble water containing different gas source types. These bubble water can also be used for the preparation of the conductive paste of the present invention. By the same principle, a gas-liquid mixed fluid containing fine bubbles can be obtained by replacing the liquid type with NMP, MEK, DMF, ethanol, toluene, IPA, or the like.

The gas production method of the gas floating pump of the embodiment can be used for preparing the gas floating pump with the particle size range of 10nm to 10 mu m and the concentration range of 10 ⁶ To 10 ⁹ Micro-bubbles of the order of one/ml.

It should be noted that this example only provides a method of gas-liquid dispersion, and gas-liquid mixed fluid containing fine bubbles obtained by other methods can be used for preparing conductive paste according to the present invention.

Example 22

The embodiment provides application of the conductive paste in preparation of a lithium ion battery positive pole piece. The selected conductive paste comprises graphene, carbon nano tubes, ultramicro bubbles and NMP, wherein the mass content of the mixture of the graphene and the carbon nano tubes is 4 wt.%, the mass ratio of the carbon nano tubes to the graphene is 1:1, and the type of gas in the micro bubbles is argon. In this embodiment, graphene and carbon nanotubes are used as the conductive agent.

In this example, the positive electrode material was lithium cobaltate (LiCoO) ₂ ) The application of the conductive paste in the preparation of the positive pole piece of the lithium ion battery is illustrated by way of example. 950 parts of positive electrode material LiCoO according to the mass ratio ₂ 375 parts of conductive slurry and 35 parts of polyvinylidene fluoride (PVDF) binder are uniformly mixed to prepare the anode slurry. Coating the anode slurry on an aluminum foil with the thickness of 20 mu m, and controlling the density of the two sides of the anode to be 0.037g/cm ² And then carrying out vacuum drying at 120 ℃ for 12h, and then placing the positive pole piece on a roller press for rolling, wherein the thickness of the positive pole piece is controlled to be 0.13-0.14 mm. And cutting according to the design size to obtain the lithium ion battery anode piece.

And pairing the obtained positive pole piece with the corresponding negative pole piece, separating the positive pole piece and the corresponding negative pole piece by using a diaphragm, and filling electrolyte into the battery. A lithium ion battery is obtained.

The lithium ion battery cathode material can also be replaced by other lithium ion battery usable cathode materials, including but not limited to: olivine-structured LiMPO ₄ (M = Co, Ni, Mn, Fe, etc.), spinel-structured LiMn ₂ O ₄ LiMO of laminated structure ₂ (M = Co, Ni, Mn, etc.), ternary cathode material (LiNi) ₁ - _x - _y Co _x Mn _y O ₂ ) Compounds such as sulfur, elemental sulfur, and the like.

Example 23

The embodiment provides application of the conductive paste in preparation of a lithium ion battery negative electrode plate. The selected conductive paste comprises graphene, carbon nano tubes, carbon black, ultramicro bubbles and water, wherein the graphene, the carbon nano tubes and the carbon black are used as conductive agents, the mass content of the conductive agents is 5wt.%, the mass ratio of the graphene to the carbon nano tubes to the carbon black is 1:0.5:0.5, and the type of gas in the micro bubbles is argon.

In the embodiment, the application of the conductive paste in the preparation of the negative electrode plate of the lithium ion battery is described by taking the negative electrode material graphite as an example. Mixing 950 parts of graphite, 200 parts of conductive slurry, 15 parts of sodium carboxymethylcellulose and 25 parts of styrene butadiene rubber according to a mass ratio, and adjusting by taking deionized water as a liquid to prepare cathode slurry. Coating the negative electrode slurry on a copper foil with the thickness of 9 microns, drying for 8 hours at the temperature of 120 ℃ in vacuum, rolling on a roller press, and cutting according to the design size to obtain the negative electrode plate of the lithium ion battery.

And pairing the obtained negative pole piece with the corresponding positive pole piece, separating the negative pole piece and the corresponding positive pole piece by using a diaphragm, and filling electrolyte into the battery. A lithium ion battery is obtained.

The lithium ion battery cathode material can also be replaced by other lithium ion battery usable cathode materials, including but not limited to: carbon material, transition metal oxide material (e.g. Fe) ₃ O ₄ 、Co ₃ O ₄ Etc.), transition metal sulfides (MoS) ₂ FeS, etc.), tin-based oxides (e.g., SnO ₂ Etc.), silicon materials, alloy materials, etc.

Example 24

The embodiment provides an application of the conductive paste in the preparation of lead-acid battery negative electrode lead paste. The conductive paste comprises the components of graphene, ultramicro bubbles and water, wherein the mass concentration of the graphene is 4wt.%, the gas in the bubbles is air, and the graphene is a finished product prepared by a commercially available liquid phase stripping method.

Lead powder, fibers, acetylene black, barium sulfate and sulfuric acid are mixed according to the mass ratio of 100: 0.1: 0.5: 0.8: 9, adding the conductive paste prepared by the method to obtain the lead plaster, and controlling the mass content of the graphene in the lead plaster to be 0.05%, 0.1%, 0.2%, 0.5% and 1% respectively. Adding a certain amount of deionized water to control the apparent density of the lead paste to be 4.0 +/-0.5 g/cm ³ 。

Coating the obtained lead plaster on a negative plate grid, curing to obtain a raw negative electrode, assembling the lead-acid batteries with different specifications by using a commercial raw positive electrode and glass fiber cotton as a diaphragm, and filling the lead-acid batteries with the filling density of 1.325g/cm ³ The sulfuric acid aqueous solution is used as electrolyte, and the lead-acid battery containing graphene is obtained by performing internal formation on the battery.

The conductive paste provided by the invention has the beneficial effects that the conductive paste contains a large amount of micro-bubbles, and the micro-bubbles can be spontaneously adsorbed around graphene sheets and carbon nanotubes under the adsorption action of the high specific surface area of the graphene and the carbon nanotubes, so that the graphene and the carbon nanotubes can be uniformly and stably dispersed in the conductive paste. The effect of using no dispersant or additive or using a small amount of dispersant or additive is achieved. The stably-dispersed conductive paste is very easy to store, does not precipitate after being placed for months, avoids the problem that the existing conductive paste can be used after being subjected to dispersion treatment before use, can be directly used for preparing the electrode of the battery, and the micro-bubbles disappear spontaneously in the drying process of electrode preparation without introducing any impurities, so that the characteristics of high conductivity of graphene and carbon nano tubes can be better exerted, and the electrical property of the battery is remarkably improved.

The type of gas in the fine bubbles is preferably air from the viewpoint of easy availability and cost. However, in the preparation of an organic battery electrode, in order to avoid oxidation generation due to introduction of an oxygen component into the electrode, the type of gas is selected from nitrogen, argon or helium, and argon is preferred.

Examples 22 to 24 show the use of the conductive paste of the present invention in the preparation of electrodes in batteries, and the conductive paste of the present invention as a conductive liquid product can also be applied to other fields, such as plastics, additives in rubber synthesis, and the like.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and should not be taken as limiting the scope of the present invention, but rather, all equivalent variations on the spirit of the present invention are within the scope of the present invention.

Claims

1. The preparation method of the conductive paste is characterized by comprising the following steps:

adding a conductive agent into the gas-liquid mixed fluid to carry out stirring and/or ultrasonic treatment to obtain the conductive slurry;

wherein the conductive agent is graphene and/or carbon nanotubes;

the gas-liquid mixed fluid contains micro-bubbles, the particle size of the micro-bubbles is less than 100 mu m, and the concentration of the micro-bubbles is more than 10 ⁶ Per ml, the fine bubbles are used for dispersing the conductive agent.

2. The method for producing conductive paste according to claim 1, wherein the gas-liquid dispersion method comprises: one or more of a mechanical shearing method, an ultrasonic cavitation method, a pressurized dissolved gas and gas release method, a microporous dispersed gas method, a jet aeration method, a gas floating pump gas production method or an electrolysis method.

3. The production method according to claim 1, wherein the mass content of the conductive agent is 0.5 wt.% to 8 wt.%.

4. The method according to claim 1, wherein the conductive agent is graphene and carbon nanotubes, and the mass ratio of the graphene to the carbon nanotubes is 1: 10 to 1: between 0.1.

5. The method of claim 1, wherein the liquid comprises: water, N-methylpyrrolidone, N-dimethylformamide, ethanol, isopropanol, butanone or toluene.

6. The method according to claim 1, wherein the fine bubbles have a particle size ranging from 100nm to 300nm and a concentration of 10 ⁸ To 10 ⁹ One per ml.

7. The production method according to claim 1, wherein the types of gas in the fine bubbles include: one or more of air, oxygen, nitrogen, argon, hydrogen, helium, or ozone.

8. The production method according to claim 1, wherein the fine bubbles have a particle size in a range of 10nm to 10 μm.

9. Use of the conductive paste obtained by the production method according to any one of claims 1 to 8 for the production of an electrode for a battery.