A carbon nanotube composite conductive agent with high conductivity and a preparation method thereof

Abstract

The present invention discloses a carbon nanotube composite conductive agent with high conductivity and a preparation method thereof. The preparation method comprises the following steps: 1) heating sodium borate decahydrate and sodium borate pentahydrate to complete melting under a water bath condition; 2) stirring the melted sodium borate decahydrate and sodium borate pentahydrate using a constant temperature magnetic stirrer, and then placing them in an ultrasonic cleaner for ultrasonic oscillation to obtain a sodium borate decahydrate / sodium borate pentahydrate eutectic salt; 3) heating the sodium borate decahydrate / sodium borate pentahydrate eutectic salt obtained in step 2) to melting, and adding single-walled carbon nanotubes, graphene, and methyl acetate; 4) stirring the mixture using a constant temperature magnetic stirrer, then placing it in an ultrasonic cleaner for ultrasonic oscillation, and then filtering and drying to obtain the carbon nanotube composite conductive agent. The carbon nanotube composite conductive agent prepared by the present invention not only meets the requirement of high conductivity, but also has good dispersibility and heat dissipation performance.

Description

Technical Field

[0001] The invention relates to the technical field of lithium ion battery materials, and in particular to a carbon nanotube composite conductive agent with high conductivity and a preparation method thereof. Background Art

[0002] Lithium-ion batteries are increasingly used in modern society, especially in mobile electronics and emerging electric vehicles. Lithium-ion batteries have the advantages of high specific energy and no memory effect. In recent years, they have been favored as a new energy source and have developed rapidly. With the continuous advancement of technology and the increasing attention to sustainable energy, the performance requirements for lithium-ion batteries are constantly increasing, especially in terms of fast charging performance and energy density.

[0003] Among them, conductive agent is an important component of lithium-ion battery. Although it occupies a small proportion, it greatly affects the performance of lithium-ion battery and plays an important role in improving battery cycle performance, capacity utilization, rate performance, etc. The primary function of conductive agent is to improve electronic conductivity. In order to ensure that the electrode has good charge and discharge performance, a certain amount of conductive agent is usually added when making the pole piece. It plays the role of collecting microcurrent between active materials and between active materials and current collectors to reduce the contact resistance of the electrode and accelerate the movement rate of electrons. In addition, conductive agent can also improve the processing of pole pieces, promote the infiltration of electrolyte into pole pieces, and effectively increase the migration rate of lithium ions in electrode materials and reduce polarization, thereby improving the charge and discharge efficiency of electrodes and the service life of lithium batteries.

[0004] In the prior art, the conductive agent of lithium-ion batteries is usually conductive graphite, acetylene black or carbon nanotubes. Acetylene black is a chain of spherical amorphous carbon particles and is currently the most widely used conductive agent. Its advantages are low price, easy production and application. However, in order to achieve the purpose of enhancing the mutual contact between the electrode active substances, the required amount of addition is large, which causes a decrease in the energy capacity of the electrode and limits the performance and application of lithium-ion batteries.

[0005] Compared with acetylene black, carbon nanotubes (CNTs) are linear one-dimensional carbonaceous materials with better electrical conductivity and superior mechanical properties. Since the addition amount of carbon nanotubes in the electrode is small, the reduction degree of the electrode energy capacity is reduced. However, the preparation cost of carbon nanotubes is high, which limits their application in actual industrial production. At the same time, metal catalysts remain in the carbon nanotube synthesis process. During the charge and discharge process at high potential of the battery, metal impurities are easily oxidized and precipitated on the surface of the negative electrode, resulting in internal micro-short circuit of the battery, serious self-discharge, and even safety accidents. In addition, the strong van der Waals force between carbon nanotubes makes it difficult to uniformly disperse in the active material, and it is easy to agglomerate, hindering the performance of electrical conductivity.

[0006] Therefore, in recent years' research, scholars have been committed to developing a carbon nanotube composite conductive agent with high electrical conductivity, low cost and good dispersibility. For example, some researchers have tried to compound carbon nanotubes with conductive polymers to reduce costs and improve electrical conductivity. However, despite some progress, the existing technology still has difficulty achieving an ideal balance between low cost and high performance.

[0007] This application aims to solve the above problems, improve the performance of the conductive agent for lithium-ion batteries, and reduce production costs. Specifically, this application needs to develop a carbon nanotube composite conductive agent with high electrical conductivity and its preparation method, aiming to comprehensively optimize the carbon nanotube composite conductive agent in terms of electrical conductivity, dispersibility, cost-effectiveness, etc. Summary of the Invention

[0008] The purpose of the present invention is to provide a carbon nanotube composite conductive agent with high electrical conductivity and its preparation method in view of the deficiencies of the prior art; the carbon nanotube composite conductive agent prepared by the present invention not only meets the requirements of high electrical conductivity, but also has good dispersibility and heat dissipation, so that it can more effectively improve the overall performance of lithium-ion batteries in practical applications.

[0009] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0010] A preparation method of a carbon nanotube composite conductive agent with high electrical conductivity includes the following steps:

[0011] 1) Heat sodium borate decahydrate and sodium borate pentahydrate with a mass ratio of 10:5 in a water bath at 90 - 100 °C for 10 - 30 min until completely melted;

[0012] 2) The melted sodium borate decahydrate and sodium borate pentahydrate are magnetically stirred at 85 °C at a speed of 130 - 150 r / min for 80 - 100 min using a constant temperature magnetic stirrer, and then placed in an ultrasonic cleaner for 1 - 2 h of ultrasonic oscillation in a water bath environment at 80 - 85 °C with a power of 120 - 130 W and an oscillation frequency of 40 - 50 kHz to obtain the sodium borate decahydrate / sodium borate pentahydrate eutectic salt;

[0013] 3) The sodium borate decahydrate / sodium borate pentahydrate eutectic salt obtained in step 2) is heated to melting in a water bath at 85 °C, and single-walled carbon nanotubes, graphene, and methyl acetate are added according to a mass ratio of 46:34:5;

[0014] 4) The mixture is magnetically stirred at 85 °C at a speed of 130 - 150 r / min for 1 h using a constant temperature magnetic stirrer, and then placed in an ultrasonic cleaner for 1 - 2 h of ultrasonic oscillation in a water bath environment at 100 °C with a power of 120 - 130 W and an oscillation frequency of 40 - 50 kHz, and then filtered and dried to obtain the composite conductive agent.

[0015] Preferably, in step 2), the phase change temperature of the sodium borate decahydrate / sodium borate pentahydrate eutectic salt is 55 °C, and the phase change latent heat is 240 J·g -1 。

[0016] Preferably, in step 3), 1 - 3 parts by weight of polyvinylpyrrolidone and boric acid are further added, wherein the mass ratio of polyvinylpyrrolidone to boric acid is (1 - 2):1.

[0017] Preferably, in step 3), 1 - 3 parts by weight of polythiophene and polyvinylpyrrolidone are further added, wherein the mass ratio of polythiophene to polyvinylpyrrolidone is 1:1.

[0018] Preferably, in step 3), 1 - 5 parts by weight of polydopamine and ethyl acetate are further added, wherein the mass ratio of polydopamine to ethyl acetate is 1:2.

[0019] Preferably, in step 4), an inert gas is introduced into the stirred mixture using a bubbler.

[0020] Preferably, in step 3), 1 - 3 parts by weight of a hydroxy compound are further added, and the hydroxy compound is ethanol or glycerol.

[0021] Preferably, in step 3), 1 - 3 parts by weight of a carboxyl compound are further added, and the carboxyl compound is acrylic acid or benzoic acid.

[0022] Preferably, in step 3), it further includes adding 1 to 3 parts by weight of a thiol-based compound, and the thiol-based compound is mercaptoacetic acid or methanethiol.

[0023] Preferably, in step 3), it further includes adding 1 to 3 parts by weight of nano-silica.

[0024] Preferably, in step 3), it further includes adding 1 to 5 parts by weight of nano-titanium oxide and tannic acid, wherein the mass ratio of nano-titanium oxide to tannic acid is 1:2.

[0025] In addition, the present invention also provides a carbon nanotube composite conductive agent with high electrical conductivity, which is prepared by the preparation method of the carbon nanotube composite conductive agent with high electrical conductivity as described above.

[0026] Compared with the prior art, the present invention has at least the following beneficial effects:

[0027] 1) By adding sodium borate decahydrate and sodium borate pentahydrate in this application, a phase change heat dissipation material with a phase change temperature of 55 °C and a phase change latent heat of 240 J·g -1 can be obtained, so that the composite conductive agent has good heat dissipation performance. Applying it to the lithium-ion battery electrode sheet can effectively improve the heat dissipation effect of the electrode sheet and the lithium battery.

[0028] 2) By adding graphene in this application, graphene is an allotrope of carbon nanotubes, and its chemical structure is similar to that of carbon nanotubes. The sp2 hybridized carbon atoms can generate many delocalized π electrons, which combine with carbon nanotubes through π-π interaction to separate carbon nanotubes from each other, improving the dispersion effect of carbon nanotubes; moreover, graphene has a very high specific surface area and conductivity, which can further improve the conductivity and stability of the composite conductive agent; in addition, graphene also has a relatively high thermal conductivity coefficient, which can meet the rapid diffusion of heat in the composite conductive agent, making the temperature of the phase change material more uniform and absorbing more heat.

[0029] 3) In the preparation process of this application, by using water bath heating, constant temperature magnetic stirring and ultrasonic oscillation, and controlling the corresponding condition parameters, the strong adsorption force of carbon nanotube aggregates can be overcome and the entangled bonding state of carbon nanotube long fibers can be destroyed, so that the carbon nanotube aggregates are dispersed.

[0030] 4) By adding methyl acetate in this application, on the one hand, as a dispersant, it can have a good dispersion effect on the conductive agent mixture and stabilize the dispersion state of carbon nanotubes; on the other hand, it can be used as a foaming agent, which will thermally decompose to generate bubbles during the stirring process of the mixture. During the rising process of the bubbles, the dispersion effect of the mixture is further improved, and it can also make the conductive agent mixture form a pore structure, further improving the heat dissipation effect. Detailed implementation manners

[0031] To make the technical solutions and advantages of the present invention clearer, the following will, in conjunction with specific embodiments, clearly and completely describe the technical solutions of the present invention. Obviously, the described embodiments are some, rather than all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0032] According to a first aspect of the present invention, a method for preparing a carbon nanotube composite conductive agent with high electrical conductivity is provided, comprising the following steps:

[0033] 1) Heating sodium borate decahydrate and sodium borate pentahydrate with a mass ratio of 10:5 in a water bath at 90 - 100 °C for 10 - 30 min until completely melted;

[0034] 2) Using a constant temperature magnetic stirrer to magnetically stir the melted sodium borate decahydrate and sodium borate pentahydrate at 85 °C at a speed of 130 - 150 r / min for 80 - 100 min, and then placing them in an ultrasonic cleaner to perform ultrasonic oscillation for 1 - 2 h in a water bath environment at 80 - 85 °C with a power of 120 - 130 W and an oscillation frequency of 40 - 50 kHz to obtain a eutectic salt of sodium borate decahydrate / sodium borate pentahydrate;

[0035] 3) Heating the eutectic salt of sodium borate decahydrate / sodium borate pentahydrate obtained in step 2) to melt in a water bath at 85 °C, and adding single-walled carbon nanotubes, graphene, and methyl acetate in a mass ratio of 46:34:5;

[0036] 4) Using a constant temperature magnetic stirrer to magnetically stir the mixture at 85 °C at a speed of 130 - 150 r / min for 1 h, and then placing it in an ultrasonic cleaner to perform ultrasonic oscillation for 1 - 2 h in a water bath environment at 100 °C with a power of 120 - 130 W and an oscillation frequency of 40 - 50 kHz, and then filtering and drying to obtain the composite conductive agent.

[0037] First of all, in this application, by adding sodium borate decahydrate and sodium borate pentahydrate, a phase change heat dissipation material with a phase change temperature of 55 °C and a phase change latent heat of 240 J·g -1 can be obtained, so that the composite conductive agent has good heat dissipation performance. Applying it to the lithium-ion battery electrode sheet can effectively improve the heat dissipation effect of the electrode sheet and the lithium battery.

[0038] Secondly, in the present application, by adding graphene, which has a very high specific surface area and conductivity, the conductivity and stability of the composite conductive agent can be further improved; moreover, graphene has a high thermal conductivity coefficient, which can meet the rapid diffusion of heat within the composite conductive agent, making the temperature of the phase change material more uniform and absorbing more heat.

[0039] Thirdly, in the present application, by adding methyl acetate, on the one hand, as a dispersant, it can have a good dispersing effect on the conductive agent mixture and stabilize the dispersed state of carbon nanotubes; on the other hand, it can be used as a foaming agent, which will thermally decompose to generate bubbles during the mixing process of the mixture. During the rising process of the bubbles, the dispersing effect of the mixture can be further improved, and moreover, it can make the conductive agent mixture form a pore structure, further improving the heat dissipation effect.

[0040] In addition, during the preparation process of the present application, by adopting water bath heating, constant temperature magnetic stirring and ultrasonic oscillation, and controlling the corresponding condition parameters, the strong adsorption force of carbon nanotube aggregates can be overcome and the entangled bonding state of carbon nanotube long fibers can be destroyed, so that the carbon nanotube aggregates are dispersed.

[0041] In an embodiment according to the present application, in step 2), the phase change temperature of the sodium borate decahydrate / sodium borate pentahydrate eutectic salt is 55 °C, and the phase change latent heat is 240 J·g -1 . Both the phase change temperature and the phase change latent heat of the phase change heat dissipation material are important parameters affecting the heat dissipation performance. The phase change heat dissipation material can absorb or release a large amount of heat near the phase change temperature, which helps to transfer the heat out quickly. Therefore, appropriate phase change temperature and phase change latent heat are crucial.

[0042] In an embodiment according to the present application, in step 3), it also includes adding 1 to 3 parts by weight of polyvinylpyrrolidone and boric acid, wherein the mass ratio of polyvinylpyrrolidone to boric acid is (1 to 2):1. Among them, polyvinylpyrrolidone is an excellent dispersant. By adding polyvinylpyrrolidone, the dispersing effect of carbon nanotubes can be improved; since polyvinylpyrrolidone can form a stable layer compatible with the interface of carbon nanotubes on the surface, the re-aggregation of carbon nanotubes can be prevented and the dispersion stability can be improved. Adding boric acid is on the one hand because it can form a mutually compatible system with polyvinylpyrrolidone and enhance the thermal stability of polyvinylpyrrolidone; on the other hand, introducing boric acid into graphene and carbon nanotubes can increase the hole concentration, thereby making the material become P-type and improving its conductivity and stability.

[0043] In one embodiment according to the present application, in step 3), 1 to 3 parts by weight of polythiophene and polyvinylpyrrolidone are further added, wherein the mass ratio of polythiophene to polyvinylpyrrolidone is 1:1. Among them, polythiophene contains thiophene groups, and is adsorbed on the surface of carbon nanotubes in a coiled manner through π-π conjugation, which can effectively disperse and stabilize carbon nanotubes; moreover, the main chain of polythiophene has a high π electron cloud density, so it has a high electrical conductivity, which can improve the overall electrical conductivity of carbon nanotubes, thereby improving the performance of the composite conductive agent. And polyvinylpyrrolidone has good heat resistance, acid and alkali resistance, and the ketone groups on its molecules can form weak interactions with carbon nanotubes, making it better dispersed in carbon nanotubes. At the same time, polyvinylpyrrolidone itself has a certain thermal conductivity, which can improve the thermal conductivity of the composite conductive agent. Therefore, in this embodiment, both polythiophene and polyvinylpyrrolidone are added, which can further improve the dispersibility and heat dissipation of the composite conductive agent while increasing the electrical conductivity of the composite conductive agent.

[0044] In one embodiment according to the present application, in step 3), 1 to 5 parts by weight of polydopamine and ethyl acetate are further added, wherein the mass ratio of polydopamine to ethyl acetate is 1:2. Among them, polydopamine has a strong π-π interaction with carbon nanotubes, forms an effective and stable coating layer on the surface of carbon nanotubes, and uses the amino or hydroxyl groups on the surface of polydopamine to form covalent bonds with the hydroxyl or amino groups of the ethyl acetate solution, thereby improving the dispersibility of carbon nanotubes.

[0045] In one embodiment according to the present application, in step 4), an inert gas is further introduced into the stirred mixture by using a bubbler. By introducing bubbles externally, that is, introducing an inert gas by using a bubbler, some aggregations in the mixture can be broken, achieving a better dispersion effect.

[0046] In one embodiment according to the present application, in step 3), 1 to 3 parts by weight of a hydroxyl compound are further added, and the hydroxyl compound is ethanol or glycerol. By introducing the hydroxyl compound, it can be used to modify the surface of carbon nanotubes, enabling carbon nanotubes to be well dispersed in a polar environment. This is because the hydroxyl compound has a good affinity for carbon nanotubes, can form surface forces, improves the stability of carbon nanotubes in a polar environment, and thus makes the dispersion effect of carbon nanotubes better.

[0047] In one embodiment according to the present application, in step 3), 1 to 3 parts by weight of a carboxyl compound are further added, and the carboxyl compound is acrylic acid or benzoic acid. By introducing the carboxyl compound, it can be used to modify the surface of carbon nanotubes, and can form interactions with the surface of the nanotubes through their carboxyl groups, preventing the re-aggregation of nanotubes during mixing and improving their dispersibility.

[0048] In an embodiment according to the present application, in step 3), it further includes adding a mercapto compound with a weight fraction of 1 to 3 parts, and the mercapto compound is mercaptoacetic acid or methanethiol. By forming a chemical bond (S-C bond) between the mercapto group and the surface of the carbon nanotubes, the lyophilicity and dispersibility of the carbon nanotubes are further enhanced; preferably, mercaptoacetic acid is used. Mercaptoacetic acid is a compound with both a mercapto group and a carboxyl group. It not only has strong reducibility, but also its sulfur atom forms a chemical bond with the carbon nanotubes, thereby improving the stability of the nanotubes and the electrical conductivity after treatment.

[0049] In an embodiment according to the present application, in step 3), it further includes adding nano-silica with a weight fraction of 1 to 3 parts. Among them, due to the charge transfer interaction between silica and single-walled carbon nanotubes, silica can be well adsorbed on the surface of single-walled carbon nanotubes, thereby generating effective charges on the surface of single-walled carbon nanotubes, thus improving the dispersibility and stability of the carbon nanotubes.

[0050] In an embodiment according to the present application, in step 3), it further includes adding nano-titanium oxide and tannic acid with a weight fraction of 1 to 5 parts, wherein the mass ratio of nano-titanium oxide to tannic acid is 1:2. Although inorganic nanoparticles such as silica have good dispersion effects, their dispersibility will change with the aging time. Stable metal particles are prone to charge transfer interaction with carbon nanotubes and have good affinity for carbon nanotubes. In this embodiment, titanium metal ions and tannic acid form a stable metal-polyphenol coordination structure by wrapping on the surface of carbon nanotubes through π-π interaction, further improving the electrical conductivity, dispersibility and thermal stability of the carbon nanotubes.

[0051] According to the second aspect of the present invention, the present invention also provides a carbon nanotube composite conductive agent with high electrical conductivity, which is prepared by the above-mentioned preparation method of the carbon nanotube composite conductive agent with high electrical conductivity.

[0052] The following will further illustrate the present application with specific embodiments.

[0053] Example 1

[0054] A preparation method of a carbon nanotube composite conductive agent with high electrical conductivity includes the following steps:

[0055] 1) Heating sodium borate decahydrate and sodium borate pentahydrate with a mass ratio of 10:5 in a 90 °C water bath for 20 min until completely melted;

[0056] 2) The melted sodium borate decahydrate and sodium borate pentahydrate were magnetically stirred at 85 °C at a speed of 140 r / min for 90 min using a constant-temperature magnetic stirrer, and then placed in an ultrasonic cleaner for 2 h of ultrasonic oscillation in a water bath environment at 85 °C with a power of 125 W and an oscillation frequency of 45 kHz to obtain the sodium borate decahydrate / sodium borate pentahydrate eutectic salt;

[0057] 3) The sodium borate decahydrate / sodium borate pentahydrate eutectic salt obtained in step 2) was heated to melting under the condition of an 85 °C water bath, and single-walled carbon nanotubes, graphene, and methyl acetate were added according to a mass ratio of 46:34:5;

[0058] 4) The mixture was magnetically stirred at 85 °C at a speed of 140 r / min for 1 h using a constant-temperature magnetic stirrer, and then placed in an ultrasonic cleaner for 2 h of ultrasonic oscillation in a water bath environment at 100 °C with a power of 125 W and an oscillation frequency of 45 kHz, and then filtered and dried to obtain the composite conductive agent.

[0059] Example 2

[0060] Different from Example 1, in step 3), 3 parts by weight of polyvinylpyrrolidone and boric acid were further added, and the mass ratio of polyvinylpyrrolidone to boric acid was 2:1.

[0061] Other operations are the same as those in Example 1 and will not be elaborated here.

[0062] Example 3

[0063] Different from Example 1, in step 3), 2 parts by weight of polythiophene and polyvinylpyrrolidone were further added, and the mass ratio of polythiophene to polyvinylpyrrolidone was 1:1.

[0064] Other operations are the same as those in Example 1 and will not be elaborated here.

[0065] Example 4

[0066] Different from Example 1, in step 3), 3 parts by weight of polydopamine and ethyl acetate were further added, and the mass ratio of polydopamine to ethyl acetate was 1:2.

[0067] Other operations are the same as those in Example 1 and will not be elaborated here.

[0068] Example 5

[0069] Different from Example 1, in step 4), helium gas was introduced into the stirred mixture using a bubbler.

[0070] Other operations are the same as those in Example 1 and will not be elaborated here.

[0071] Example 6

[0072] Different from Example 1, in step 3), it further includes adding 2 parts by weight of a hydroxyl compound, and the hydroxyl compound is ethanol.

[0073] The others are the same as in Example 1 and will not be elaborated here.

[0074] Example 7

[0075] Different from Example 1, in step 3), it further includes adding 2 parts by weight of a carboxyl compound, and the carboxyl compound is benzoic acid.

[0076] The others are the same as in Example 1 and will not be elaborated here.

[0077] Example 8

[0078] Different from Example 1, in step 3), it further includes adding 2 parts by weight of a thiol group compound, and the thiol group compound is methanethiol.

[0079] The others are the same as in Example 1 and will not be elaborated here.

[0080] Example 9

[0081] Different from Example 1, in step 3), it further includes adding 2 parts by weight of a thiol group compound, and the thiol group compound is mercaptoacetic acid.

[0082] The others are the same as in Example 1 and will not be elaborated here.

[0083] Example 10

[0084] Different from Example 1, in step 3), it further includes adding 2 parts by weight of nano-silica.

[0085] The others are the same as in Example 1 and will not be elaborated here.

[0086] Example 11

[0087] Different from Example 1, in step 3), it further includes adding 3 parts by weight of nano-titanium oxide and tannic acid, wherein the mass ratio of nano-titanium oxide to tannic acid is 1:2.

[0088] The others are the same as in Example 1 and will not be elaborated here.

[0089] Comparative Example 1

[0090] Different from Example 1, in this comparative example, the conductive agent is carbon nanotubes.

[0091] Comparative Example 2

[0092] Different from Example 1, in this comparative example, the conductive agent is a mixture of carbon nanotubes and polyaniline.

[0093] The conductive agents prepared in Examples 1-11 and Comparative Examples 1-2 were respectively made into negative electrode sheets and lithium-ion batteries for electrochemical performance testing, and the test results are shown in Table 1.

[0094] Table 1

[0095]

[0096] From the test results in the above table, it can be seen that the carbon nanotube composite conductive agent prepared in this application has a high conductivity, and the heat dissipation performance and high-temperature cycle performance of the lithium-ion battery and its electrode sheet prepared using the composite conductive agent of this application have been effectively improved.

[0097] Among them, by comparing Example 1 with Comparative Examples 1-2, it can be seen that the conductivity, heat dissipation performance, and high-temperature cycle performance of the composite conductive agent prepared in this application are significantly better than the existing carbon nanotube conductive agent, and are also better than the composite conductive agent formed by the mixture of existing carbon nanotubes and conductive polymers. It shows that the composite conductive agent prepared by the present application through the magnetic stirring, ultrasonic dispersion, and bubble mixing of phase change materials, graphene, methyl acetate, etc. with carbon nanotubes has good dispersibility and electrochemical characteristics.

[0098] Among them, by comparing Examples 1-11, it can be seen that by further adding polyvinylpyrrolidone and boric acid, polythiophene and polyvinylpyrrolidone, polydopamine and ethyl acetate, hydroxy compounds, carboxyl compounds, mercapto compounds, nano-silica, nano-titanium oxide, and tannic acid to the carbon nanotube composite conductive agent, the conductivity, heat dissipation performance, and high-temperature cycle performance of the composite conductive agent can be further improved; among them, when adding polyvinylpyrrolidone and boric acid, polythiophene and polyvinylpyrrolidone, mercaptoacetic acid, or nano-titanium oxide and tannic acid, the improvement of its electrochemical performance is particularly obvious, indicating that when adding the above substances, it can better interact with carbon nanotubes, thereby being able to more effectively improve the dispersion effect and thermal stability of carbon nanotubes.

[0099] According to the disclosure and teachings of the above specification, those skilled in the art to which the present invention pertains can also make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the above specific embodiments, and any obvious improvements, substitutions, or variations made by those skilled in the art on the basis of the present invention all fall within the protection scope of the present invention. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present invention.

Claims

1. A preparation method of a carbon nanotube composite conductive agent with high conductivity, characterized in that, It includes the following steps: 1) Heat sodium borate decahydrate and sodium borate pentahydrate with a mass ratio of 10:5 in a water bath at 90 - 100 °C for 10 - 30 min until completely melted; 2) Use a thermostatic magnetic stirrer to magnetically stir the melted sodium borate decahydrate and sodium borate pentahydrate at 85 °C at a speed of 130 - 150 r / min for 80 - 100 min, and then place it in an ultrasonic cleaner to perform ultrasonic oscillation for 1 - 2 h in a water bath environment at 80 - 85 °C with a power of 120 - 130 W and an oscillation frequency of 40 - 50 kHz to obtain the sodium borate decahydrate / sodium borate pentahydrate eutectic salt; 3) Heat the sodium borate decahydrate / sodium borate pentahydrate eutectic salt obtained in step 2) to melting in a water bath at 85 °C, and add single-walled carbon nanotubes, graphene, and methyl acetate in a mass ratio of 46:34:5; 4) Use a thermostatic magnetic stirrer to magnetically stir the mixture at 85 °C at a speed of 130 - 150 r / min for 1 h, and then place it in an ultrasonic cleaner to perform ultrasonic oscillation for 1 - 2 h in a water bath environment at 100 °C with a power of 120 - 130 W and an oscillation frequency of 40 - 50 kHz, and then filter and dry to obtain the composite conductive agent.

2. The preparation method of the carbon nanotube composite conductive agent with high conductivity according to claim 1, characterized in that: In step 2), the phase change temperature of the sodium borate decahydrate / sodium borate pentahydrate eutectic salt is 55 °C, and the latent heat of phase change is 240 J•g -1 .

3. The preparation method of the carbon nanotube composite conductive agent with high conductivity according to claim 1, characterized in that: In step 4), it also includes introducing an inert gas into the stirred mixture using a bubbler.

4. A carbon nanotube composite conductive agent with high conductivity, characterized in that: It is obtained by the preparation method of the carbon nanotube composite conductive agent with high conductivity described in any one of claims 1 to 3.

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