CN115109568B - Graphene heating/radiating composite material for lithium battery of new energy automobile and preparation method - Google Patents

Abstract

The invention discloses a preparation method of a graphene heating/radiating composite material for a lithium battery of a new energy automobile, which comprises the following steps: s1: taking carbon fiber bundles and carrying out cobalt film deposition; s2: detecting magnetism of a cobalt film deposition end; s3: placing carbon fiber bundles into copper hydroxide/graphene oxide suspension, and performing ultrasonic dispersion to obtain a mixed solution; s4: carrying out multistage directional arrangement on the carbon fiber bundles in the mixed solution by a magnetic attraction arrangement device; s5: the mixed solution is subjected to a bidirectional freezing gradient and a freezing drying process to form a carbon fiber bundle-copper hydroxide/graphene oxide heat conduction material; s6: the carbon fiber bundles in the mixed solution are subjected to highly directional arrangement through multistage magnetic attraction arrangement to form the carbon fiber bundle-copper doped graphene heat conduction material, and the heat conduction coefficient of the product can be improved by more than 30%.

Description

Graphene heating/radiating composite material for lithium battery of new energy automobile and preparation method

Technical Field

The invention belongs to the technical field of new energy electric automobile accessories, and particularly relates to a graphene composite material for heating and radiating a lithium battery pack of a new energy automobile and a preparation method thereof.

Background

The lithium battery is an energy storage device commonly used for new energy electric vehicles in the prior art, the lithium ion battery technology can provide higher (3 times) energy density, size, weight and other aspects than a lead-acid chemical battery, but in the running process of the system, the motor can enable the engine in a stopped state to reach 3000r/min within hundreds of milliseconds under the driving of the battery pack, the engine is driven to re-ignite, the battery pack is in a high-rate discharge state, the heating value in the working process is very large, the discharge amount of the battery pack is directly influenced by the excessively high temperature, the stable running of the whole system is reduced, meanwhile, the excessively high temperature can cause thermal runaway of the battery pack, and the probability of ignition and explosion is increased, so that the lithium battery is required to dissipate heat; in addition, the low-temperature performance of the lithium battery is slightly poorer than that of batteries of other technical systems, the low temperature has influence on the anode and the cathode of lithium iron phosphate, electrolyte and the like, the electronic conductivity of the anode of the lithium iron phosphate is poorer, and polarization is easy to generate in a low-temperature environment, so that the capacity of the battery is reduced, and therefore, the temperature of a battery pack needs to be increased in the low-temperature environment; thus, there is a need for a high performance thermally conductive material that provides heat dissipation to lithium batteries.

At present, new high-performance heat conduction materials, represented by graphene, are actively searched, and new two-dimensional crystal materials are the focus of research in recent years due to the two-dimensional crystal structure and unique physical properties of the single-atom thickness. The graphene has outstanding heat conduction performance (5000W/(m.K)) and extraordinary specific surface area (2630 m 2/g), can be applied to some good technological performances such as solid surfaces, and is an ideal heat dissipation material. However, with reference to the problem of heat dissipation application of graphene, research on a preparation method and application skills of graphene is in a rapid development stage, and how to fully and reasonably utilize the high heat conductivity of graphene to successfully apply the graphene to the heat dissipation field is still a technical problem to be solved. Because the graphene is of a two-dimensional structure, the heat dissipation mode can only diffuse the heat emitted by the battery surface to surrounding materials in a horizontal mode, so that the heat dissipation effect of the materials is weakened to a certain extent; in addition, since graphene has a very large specific surface area, agglomeration is easy to occur, and when graphene is agglomerated and a composite material is polymerized during preparation, the performance of the material is greatly reduced.

Disclosure of Invention

The invention aims to provide a graphene heating/radiating composite material for a lithium battery of a new energy automobile and a preparation method thereof, so as to solve the problems in the prior art.

In order to solve the technical problem, the technical scheme of the invention is as follows:

the preparation method of the graphene heating/radiating composite material for the lithium battery of the new energy automobile comprises the following steps:

s1: taking a carbon fiber bundle, wrapping a layer of aluminum foil on the carbon fiber bundle and exposing a bare end, and carrying out cobalt film deposition on the bare end by adopting pulse laser vapor deposition equipment;

s2: detecting magnetism of a cobalt film deposition end on the carbon fiber bundle; if the magnetism is insufficient, carrying out cobalt film deposition operation again, and if the magnetism meets the requirement, entering a step S3;

s3: preparing copper hydroxide/graphene oxide suspension; placing the carbon fiber bundles obtained in the step S2 into copper hydroxide/graphene oxide suspension, and performing ultrasonic dispersion to obtain a mixed solution;

s4: carrying out multistage directional arrangement on the carbon fiber bundles in the mixed solution by a magnetic attraction arrangement device; enabling the top ends of the carbon fiber bundles to penetrate out of the top surface of the mixed liquid after directional arrangement;

s5: the mixed solution is subjected to a bidirectional freezing gradient and a freezing drying process to form a carbon fiber bundle-copper hydroxide/graphene oxide heat conduction material;

s6: and reducing the carbon fiber bundle-copper doped graphene oxide heat conduction material at the heating temperature of 1000 ℃ in an argon protection environment to form the carbon fiber bundle-copper doped graphene heat conduction material.

Preferably, the length of the exposed end of the carbon fiber bundle is 1.5mm;

preferably, in the step S3, the mass ratio of the carbon fiber bundles to the copper hydroxide/graphene oxide is 1:16;

preferably, the method for preparing the copper hydroxide/graphene oxide suspension comprises the following steps:

dissolving graphene oxide in water, performing ultrasonic dispersion to obtain a graphene oxide suspension for later use, dripping sodium hydroxide into a copper nitrate solution to obtain liquid copper hydroxide, adding the copper hydroxide dissolved in water into the graphene oxide suspension under the stirring condition, performing ultrasonic vibration, and embedding the copper hydroxide into the graphene oxide through hydrogen bonds; a copper hydroxide/graphene oxide suspension is obtained.

Preferably, the molar ratio of graphene oxide to copper element is 1:1.6;

according to the invention, copper oxide/graphene oxide particles are adsorbed on the carbon fiber material, and graphene is uniformly adsorbed on the carbon fiber material after reduction, so that the excellent heat conduction performance of the graphene is matched with the continuous heat conduction path of the carbon fiber, and the heat conduction performance of the material is greatly improved; and the copper hydroxide is adopted to modify the graphene material, so that the graphene oxide has better hydrophilic property and is more uniformly dispersed, and the graphene oxide is adsorbed on the carbon fiber material.

Preferably, the magnetic attraction arrangement device comprises a plurality of electromagnet units which are connected in a telescopic sleeved mode, each electromagnet unit forms a working area, and the outer container is arranged on the working area; the outline of the electromagnet unit is overlapped with the outer edge of the working area, and each electromagnet unit is connected with an independent magnetic switch control system to form a multistage magnetic attraction arrangement area;

the method for directionally arranging the carbon fiber bundles in the mixed solution by the magnetic attraction arrangement device comprises the following substeps:

s41: starting an electromagnet unit positioned at the periphery, wherein the peripheral electromagnet unit adsorbs the carbon fiber bundles on the outer ring of the inner bottom surface of the container through magnetic force;

s42: stirring the mixed solution to separate carbon fiber bundles with insufficient magnetic attraction from the outer ring of the inner bottom surface of the container;

s43: lifting the electromagnet units in the middle to be on the same plane with the electromagnet units in the periphery, and starting the electromagnet units so that the detached carbon fiber bundles are re-adsorbed at the center of the inner bottom surface of the container;

s44: and continuing stirring the mixed solution to ensure that carbon fiber bundles with insufficient magnetic attraction in the mixed solution are separated from the inner bottom surface of the container and then are rearranged and adsorbed.

According to the invention, the carbon fiber bundles in the mixed solution are arranged in a highly directional array in advance through the magnetic attraction arrangement device, so that the heat conduction route of the heat conduction material is continuous from bottom to top, and the heat conduction performance of the material is greatly improved.

Preferably, the magnetic attraction arrangement device comprises a first-stage electromagnet unit, a second-stage electromagnet unit and a third-stage electromagnet unit which are formed in a sleeved arrangement, wherein each electromagnet unit correspondingly forms a first-stage magnetic attraction arrangement area, a second-stage magnetic attraction arrangement area and a third-stage magnetic attraction arrangement area from inside to outside on the bottom surface of a container for containing the mixed liquid, and the method for directionally arranging the carbon fiber bundles comprises the following sub-steps:

s411: starting a three-stage electromagnet unit, forming magnetic force in a three-stage magnetic attraction arrangement area, and adsorbing carbon fiber bundles in the three-stage magnetic attraction arrangement area on the inner bottom surface of the container;

s412: stirring the mixed solution to enable carbon fiber bundles with insufficient magnetic attraction in the mixed solution to be separated from a three-stage magnetic attraction arrangement area on the inner bottom surface of the container;

s413: starting the secondary electromagnet unit, rising to the same plane as the tertiary electromagnet unit, and forming magnetic force in the secondary magnetic attraction arrangement area to adsorb the detached carbon fiber bundles in the secondary magnetic attraction arrangement area of the inner bottom surface of the container;

s414: stirring the mixed solution to enable carbon fiber bundles with insufficient magnetic attraction in the mixed solution to be separated from a three-stage magnetic attraction arrangement area and a two-stage arrangement area on the inner bottom surface of the container;

s415: the primary electromagnet unit is started and rises to the same plane with the secondary electromagnet unit, magnetic force is formed in the primary magnetic attraction arrangement area to attract the separated carbon fiber bundles in the primary magnetic attraction arrangement area of the inner bottom surface of the container, and then a carbon fiber bundle array which is uniformly distributed is formed.

Preferably, the three-stage electromagnet unit comprises an outer ring iron core, the outer ring iron core is of a hollow structure, a first coil winding area is formed on the surface of the outer ring iron core, a first coil is wound in the first coil winding area, and a first shell is arranged outside the first coil winding area; the secondary electromagnet unit comprises an inner ring iron core, the inner ring iron core is of a hollow structure, a second coil winding area is formed on the surface of the inner ring iron core, a second coil is wound in the second coil winding area, and a second shell is arranged outside the second coil winding area; the second shell is slidably connected in the outer ring iron core through the first sliding component; the primary electromagnet unit comprises a central iron core, a third coil winding area is formed on the surface of the central iron core, a third coil is wound in the third coil winding area, and a third shell is arranged outside the third coil winding area; the third shell is slidably connected in the second shell through a second sliding assembly; the first coil, the second coil and the third coil are connected with a magnetic switch control system.

Preferably, the magnetic switch control system comprises a power supply, a switch, a transformer and a diode which are electrically connected with the electromagnet unit, and the diode is arranged on the circuit of the electromagnet, so that after the power supply is powered off, the induced current can be blocked through the diode, the magnetism of the electromagnet is immediately disappeared, the demagnetizing efficiency of the electromagnet is improved, and the influence on the next working period is avoided.

The invention also aims to provide the graphene heating/radiating composite material prepared by the method.

The technical scheme has the beneficial effects that:

according to the invention, the carbon fiber bundles in the mixed solution are subjected to highly directional arrangement through the multistage magnetic arrangement, so that a continuous heat conduction route is formed from the bottom to the top of the heat conduction material, and compared with the existing directional arrangement technology, the carbon fiber bundles are more stable and more uniform through the multistage magnetic arrangement mode, and the heat conduction coefficient of the product can be improved by more than 30%; the heat conduction performance of the graphene heat conduction material is greatly improved; in addition, compared with the graphene heat conduction material prepared from unmodified graphene oxide, the copper hydroxide modified graphene material is adopted, so that the graphene oxide has better hydrophilic performance and is more uniformly dispersed, further, the graphene oxide can be more uniformly adsorbed on the surface of the carbon fiber, and the heat conduction coefficient of a reduced product can be improved by more than 45%.

Drawings

FIG. 1 is a schematic view of the structure of a multi-stage magnetic attraction alignment area according to embodiment 1 of the present invention;

FIG. 2 is a cross-sectional view of a magnetic attraction arrangement of the present invention;

Detailed Description

In order to further explain the technical solution of the present invention, the present invention will be described in detail by means of specific examples, as shown in fig. 1-2.

Example 1

The preparation method of the graphene heating/radiating composite material for the lithium battery of the new energy automobile comprises the following steps:

s1: cutting the carbon fiber bundles into required sizes by using a cutter, wrapping a layer of aluminum foil on the carbon fiber bundles and exposing a bare end, taking the bare end upwards as a matrix, taking high-purity cobalt (99%) as a target material, and carrying out cobalt film deposition on the bare end by using pulse laser vapor deposition equipment; in the embodiment, the pulse frequency is 4Hz, and the background air pressure is 5Pa; the length of the exposed end of the carbon fiber bundle is 0.5mm;

s2: performing magnetic attraction on the carbon fiber bundles by adopting a magnet to detect whether the cobalt film is uniformly deposited on the exposed ends, or checking the color of the exposed ends by adopting an amplifying device, wherein the deposited exposed ends of the cobalt film are silver gray to detect whether the cobalt film is uniformly deposited, and entering a step S3 after the detection is finished;

s3: preparing a copper hydroxide/graphene oxide suspension: dissolving graphene oxide in water, performing ultrasonic dispersion to obtain graphene oxide suspension for later use, and dripping sodium hydroxide into a copper nitrate solution in a molar ratio of 1:1, reacting for 45min to obtain liquid copper hydroxide, adding the copper hydroxide dissolved in water into the graphene oxide suspension under the stirring condition, and ensuring that the molar ratio of graphene oxide to copper element is 1:1.2, stirring at room temperature for 24 hours, and carrying out ultrasonic vibration; obtaining copper hydroxide/graphene oxide suspension; the graphene oxide contains a large number of polar oxygen-containing functional groups, has the characteristics of good hydrophilicity and mechanical property, and is combined with copper hydroxide containing hydroxyl through hydrogen bonds, so that the hydrophilicity of the graphene oxide is improved, and the dispersion is more stable. Placing the carbon fiber bundles obtained in the step S2 into copper hydroxide/graphene oxide suspension, and performing ultrasonic dispersion to obtain a mixed solution, wherein the mass ratio of the carbon fiber bundles to the copper hydroxide/graphene oxide is 1:11;

s4: adding the mixed solution into a bidirectional freezing mold, and carrying out multistage directional arrangement on carbon fiber bundles in the mixed solution by a magnetic attraction arrangement device; enabling the top ends of the carbon fiber bundles to penetrate out of the top surface of the mixed liquid after directional arrangement;

the magnetic attraction arrangement device comprises a first-stage electromagnet unit, a second-stage electromagnet unit and a third-stage electromagnet unit which are formed in a sleeved arrangement mode, wherein each electromagnet unit correspondingly forms a first-stage magnetic attraction arrangement region, a second-stage magnetic attraction arrangement region and a third-stage magnetic attraction arrangement region from inside to outside on the bottom surface of a container for containing mixed liquid, and the method for directionally arranging the carbon fiber bundles comprises the following sub-steps: s411: starting a three-stage electromagnet unit, forming magnetic force in the three-stage magnetic attraction arrangement area to adsorb the carbon fiber bundles in the three-stage magnetic attraction arrangement area on the inner bottom surface of the container, wherein the pressurizing voltage is 14.5V, and the next step is carried out after the duration time is 10 seconds; s412: stirring the mixed solution to enable carbon fiber bundles with insufficient magnetic attraction in the mixed solution to be separated from a three-stage magnetic attraction arrangement area on the inner bottom surface of the container; s413: starting the secondary electromagnet unit, rising to the same plane as the tertiary electromagnet unit, and forming magnetic force in the secondary magnetic attraction arrangement area to adsorb the detached carbon fiber bundles in the secondary magnetic attraction arrangement area of the inner bottom surface of the container; at this time, the pressurized voltage was 15.5V for 10 seconds before the next step was performed; s414: stirring the mixed solution to enable carbon fiber bundles with insufficient magnetic attraction in the mixed solution to be separated from a three-stage magnetic attraction arrangement area and a two-stage arrangement area on the inner bottom surface of the container; s415: starting the primary electromagnet unit, rising to the same plane as the primary electromagnet unit, forming magnetic force in the primary magnetic attraction arrangement area to adsorb the separated carbon fiber bundles in the primary magnetic attraction arrangement area of the inner bottom surface of the container, wherein the pressurizing voltage is 16.5V, and the duration time is 10S, so that a uniformly arranged carbon fiber bundle array is formed, and performing step S5.

S5: the mixed solution is subjected to a bidirectional freezing gradient and a freezing drying process to form a carbon fiber bundle-copper hydroxide/graphene oxide heat conduction material; the specific method comprises the following steps: pouring the mixture into a bidirectional freezing mould, freezing the mixture for 6 hours at the temperature of minus 70 ℃, and then performing vacuum freeze drying (the vacuum degree is 0.1-2 Pa, and the drying time is 72 hours) to obtain the composite material;

s6: and in an argon protection environment, heating at 1000 ℃ for 7 hours, and reducing the carbon fiber bundle-copper doped graphene oxide heat conduction material to form the carbon fiber bundle-copper doped graphene heat conduction material.

Specific: the three-stage electromagnet unit comprises an outer ring iron core 100, the outer ring iron core is of a hollow structure, a first coil winding area 101 is formed on the surface of the outer ring iron core, a first coil 102 is wound in the first coil winding area, and a first shell 103 is arranged outside the first coil winding area; the secondary electromagnet unit comprises an inner ring iron core 104, the inner ring iron core is of a hollow structure, a second coil winding area 105 is formed on the surface of the inner ring iron core, a second coil 106 is wound in the second coil winding area, and a second shell 107 is arranged outside the second coil winding area; the second shell is slidably connected in the outer ring iron core through a first sliding component (a first cylinder 108); the primary electromagnet unit comprises a central iron core 109, a third coil winding area 110 is formed on the surface of the central iron core, a third coil 111 is wound in the third coil winding area, and a third shell 112 is arranged outside the third coil winding area; the third housing is slidably coupled within the second housing by a second slide assembly (second cylinder 113); the first cylinder and the second cylinder respectively push the secondary electromagnet unit and the electromagnet unit to move up and down, wherein the first shell, the second shell and the third shell are made of ceramic materials; the first coil, the second coil and the third coil are connected with a magnetic switch control system. The switch control system is formed by assembling commercially available components, and is not described in detail herein.

Example 2

The difference from example 1 is that: in the step S3, the mol ratio of graphene oxide to copper element is 1:1.4;

example 3

The difference from example 1 is that: in the step S3, the mol ratio of graphene oxide to copper element is 1:1.6;

example 4

The difference from example 1 is that: in the step S3, the mol ratio of graphene oxide to copper element is 1:1.8;

example 5

The difference from example 3 is that: the mass ratio of the carbon fiber bundles to the copper hydroxide/graphene oxide is 1:14;

example 6

The difference from example 3 is that: the mass ratio of the carbon fiber bundles to the copper hydroxide/graphene oxide is 1:16;

example 7

The difference from example 3 is that: the mass ratio of the carbon fiber bundles to the copper hydroxide/graphene oxide is 1:18;

example 8

The difference from example 6 is that: in step S4, the magnetic attraction arrangement device includes a first-stage electromagnet unit and a second-stage electromagnet unit which are formed in a sleeved arrangement, each electromagnet unit correspondingly forms a first-stage magnetic attraction arrangement area and a second-stage magnetic attraction arrangement area from inside to outside on the bottom surface of a container for containing the mixed liquid, and the method for directionally arranging the carbon fiber bundles includes the following sub-steps: s411: starting a secondary electromagnet unit, forming magnetic force in a secondary magnetic attraction arrangement area, and adsorbing carbon fiber bundles in the secondary magnetic attraction arrangement area on the inner bottom surface of the container; s412: stirring the mixed solution to enable carbon fiber bundles with insufficient magnetic attraction in the mixed solution to be separated from a secondary magnetic attraction arrangement area of the inner bottom surface of the container; s413: starting a primary electromagnet unit, forming magnetic force in the primary magnetic attraction arrangement area to adsorb the separated carbon fiber bundles in the primary magnetic attraction arrangement area on the inner bottom surface of the container, and then forming a uniformly arranged carbon fiber bundle array.

Example 9

The difference from example 6 is that: in step S4, the magnetic attraction and arrangement device includes a first-stage electromagnet unit, a second-stage electromagnet unit, a third-stage electromagnet unit and a fourth-stage electromagnet unit which are formed in a sleeved arrangement, each electromagnet unit correspondingly forms a first-stage magnetic attraction and arrangement area, a second-stage magnetic attraction and arrangement area, a third-stage magnetic attraction and arrangement area and a fourth-stage electromagnet unit from inside to outside on the bottom surface of a container for containing the mixed liquid, and the method for directionally arranging the carbon fiber bundles includes the following sub-steps: s411: starting a four-stage electromagnet unit, forming magnetic force in a four-stage magnetic attraction arrangement area, and adsorbing carbon fiber bundles in the four-stage magnetic attraction arrangement area on the inner bottom surface of the container; s412: stirring the mixed solution to enable carbon fiber bundles with insufficient magnetic attraction in the mixed solution to be separated from a four-stage magnetic attraction arrangement area on the inner bottom surface of the container; s413: starting a three-stage electromagnet unit, forming magnetic force in a three-stage magnetic attraction arrangement area, and adsorbing carbon fiber bundles in the three-stage magnetic attraction arrangement area on the inner bottom surface of the container; s414: stirring the mixed solution to enable carbon fiber bundles with insufficient magnetic attraction in the mixed solution to be separated from a three-stage magnetic attraction arrangement area on the inner bottom surface of the container; s415: starting a secondary electromagnet unit, forming magnetic force in a secondary magnetic attraction arrangement area, and adsorbing the separated carbon fiber bundles in the secondary magnetic attraction arrangement area of the inner bottom surface of the container; s416: stirring the mixed solution to enable carbon fiber bundles with insufficient magnetic attraction in the mixed solution to be separated from a three-stage magnetic attraction arrangement area and a two-stage arrangement area on the inner bottom surface of the container; s417: starting a primary electromagnet unit, forming magnetic force in the primary magnetic attraction arrangement area to adsorb the separated carbon fiber bundles in the primary magnetic attraction arrangement area on the inner bottom surface of the container, and then forming a uniformly arranged carbon fiber bundle array.

Example 10

The difference from example 6 is that: the length of the exposed end of the carbon fiber bundle is 1mm;

example 11

The difference from example 6 is that: the length of the exposed end of the carbon fiber bundle is 1.5mm;

example 12

The difference from example 6 is that: the length of the exposed end of the carbon fiber bundle is 1.8mm;

comparative example 1

In this example, the magnetic attraction arrangement device is not used to perform directional arrangement on the carbon fiber bundles in the mixed solution, and the method includes the following steps: preparing a copper hydroxide/graphene oxide suspension: dissolving graphene oxide in water, performing ultrasonic dispersion to obtain graphene oxide suspension for later use, and dripping sodium hydroxide into a copper nitrate solution in a molar ratio of 1:1, reacting for 45min to obtain liquid copper hydroxide, adding the copper hydroxide dissolved in water into the graphene oxide suspension under the stirring condition, and ensuring that the molar ratio of graphene oxide to copper element is 1:1.6, stirring at room temperature for 24 hours, and carrying out ultrasonic vibration; obtaining copper hydroxide/graphene oxide suspension; the graphene oxide contains a large number of polar oxygen-containing functional groups, has the characteristics of good hydrophilicity and mechanical property, and is combined with copper hydroxide containing hydroxyl through hydrogen bonds, so that the hydrophilicity of the graphene oxide is improved, and the dispersion is more stable for later use; placing carbon fiber bundles into copper hydroxide/graphene oxide suspension, and performing ultrasonic dispersion to obtain a mixed solution, wherein the mass ratio of the carbon fiber bundles to the copper hydroxide/graphene oxide is 1:16; adding the mixed solution into a bidirectional freezing mould; the mixed solution is subjected to a bidirectional freezing gradient and a freezing drying process to form a carbon fiber bundle-copper hydroxide/graphene oxide heat conduction material; the specific method comprises the following steps: pouring the mixture into a bidirectional freezing mould, freezing the mixture for 6 hours at the temperature of minus 70 ℃, and then performing vacuum freeze drying (the vacuum degree is 0.1-2 Pa, and the drying time is 72 hours) to obtain the composite material; and in an argon protection environment, heating at 1000 ℃ for 7 hours, and reducing the carbon fiber bundle-copper doped graphene oxide heat conduction material to form the carbon fiber bundle-copper doped graphene heat conduction material.

Comparative example 2

In this example, the magnetic attraction arrangement device is not adopted, copper hydroxide doping is not performed on the graphene suspension, and the directional arrangement is performed on the carbon fiber bundles in the mixed solution, including the following steps:

preparing graphene oxide suspension: dissolving graphene oxide in water, and performing ultrasonic dispersion to obtain graphene oxide suspension for later use; placing carbon fiber bundles into copper hydroxide/graphene oxide suspension, and performing ultrasonic dispersion to obtain a mixed solution, wherein the mass ratio of the carbon fiber bundles to the copper hydroxide/graphene oxide is 1:16; adding the mixed solution into a bidirectional freezing mould; the mixed solution is subjected to a bidirectional freezing gradient and a freezing drying process to form a carbon fiber bundle-copper hydroxide/graphene oxide heat conduction material; the specific method comprises the following steps: pouring the mixture into a bidirectional freezing mould, freezing the mixture for 6 hours at the temperature of minus 70 ℃, and then performing vacuum freeze drying (the vacuum degree is 0.1-2 Pa, and the drying time is 72 hours) to obtain the composite material; and in an argon protection environment, heating at 1000 ℃ for 7 hours, and reducing the carbon fiber bundle-copper doped graphene oxide heat conduction material to form the carbon fiber bundle-copper doped graphene heat conduction material.

Experimental results: the products of examples 1-9, and comparative examples 1-2 were tested for thermal conductivity along the length of the carbon fiber;

thermal conductivity the thermal conductivity of the high thermal conductivity graphene heat sink material was tested using a C-THERM TCI instrument using ASTM D7984 standard.

The test results are shown in Table 1.

TABLE 1

As can be seen from table 1, after the carbon fiber bundles in the mixed solution are subjected to multi-stage directional arrangement by the magnetic attraction arrangement device, the thermal conductivity of the prepared carbon fiber bundle-copper doped graphene thermal conductive material can be improved by more than 30%; the heat conduction performance of the graphene heat conduction material is greatly improved; in addition, compared with the graphene heat conduction material prepared from unmodified graphene oxide, the heat conduction coefficient of the graphene heat conduction material can be improved by more than 45%;

as shown in comparative examples 1 to 4, as the molar ratio of graphene oxide to copper element is reduced, the thermal conductivity of the product is increased and then reduced, and the optimal molar ratio of graphene oxide to copper element is 1:1.6, under the condition, the heat conductivity coefficient of the product is maximum;

comparative example 3, examples 5-7, demonstrate that the reduction in the mass ratio of carbon fiber bundles to copper hydroxide/graphene oxide, with the increase in the product thermal conductivity followed by the decrease, demonstrates an optimal mass ratio of carbon fiber bundles to copper hydroxide/graphene oxide of 1:16;

in comparative example 6 and examples 8 to 9, it is known that the thermal conductivity of the four-stage electromagnet units is not significantly improved compared with that of the three-stage electromagnet units, because the dispersion properties of the four-stage electromagnet units and the three-stage electromagnet units on the carbon fibers are not greatly different, and therefore, the three-stage electromagnet units are adopted as the optimal magnetic attraction device to orient the carbon fibers.

Comparative example 6, examples 10-11, shows that as the length of the exposed end of the carbon fiber bundle increases, the thermal conductivity of the product increases and then decreases; the reason is that the exposed ends of the carbon fiber bundles are too short, the magnetic attraction force is insufficient, the dispersion is uneven, if the exposed ends are too long, the magnetic force is too large, and when the tail ends of the carbon fiber bundles are mutually attracted, the carbon fiber bundles are not easy to separate and rearrange, so that the overall arrangement effect of the product is affected;

comparing comparative example 1 with comparative example 2, it is known that doping the graphene suspension with copper hydroxide can improve the hydrophilic performance of the graphene suspension, further improve the dispersion uniformity of the graphene suspension, and enable the graphene suspension to be uniformly attached to the surface of the carbon fiber, and the heat conductivity coefficient of the graphene suspension can be improved by more than 10%, so that the heat conductivity of the graphene suspension is improved.

Claims (8)

1. The preparation method of the graphene heating/radiating composite material for the lithium battery of the new energy automobile is characterized by comprising the following steps of: the method comprises the following steps:

s1: taking a carbon fiber bundle, wrapping a layer of aluminum foil on the carbon fiber bundle and exposing a bare end, and carrying out cobalt film deposition on the bare end by adopting pulse laser vapor deposition equipment;

s2: detecting magnetism of a cobalt film deposition end on the carbon fiber bundle; if the magnetism is insufficient, carrying out cobalt film deposition operation again, and if the magnetism meets the requirement, entering a step S3;

s3: preparing copper hydroxide/graphene oxide suspension; placing the carbon fiber bundles obtained in the step S2 into copper hydroxide/graphene oxide suspension, and performing ultrasonic dispersion to obtain a mixed solution;

s4: carrying out multistage directional arrangement on the carbon fiber bundles in the mixed solution by a magnetic attraction arrangement device; enabling the top ends of the carbon fiber bundles to penetrate out of the top surface of the mixed liquid after directional arrangement;

s5: the mixed solution is subjected to a bidirectional freezing gradient and a freezing drying process to form a carbon fiber bundle-copper hydroxide/graphene oxide heat conduction material;

s6: and reducing the carbon fiber bundle-copper doped graphene oxide heat conduction material at the heating temperature of 1000 ℃ in an argon protection environment to form the carbon fiber bundle-copper doped graphene heat conduction material.

2. The preparation method of the graphene heating/radiating composite material for the lithium battery of the new energy automobile, which is disclosed in claim 1, is characterized in that: the length of the exposed end of the carbon fiber bundle is 1.5mm.

3. The preparation method of the graphene heating/radiating composite material for the lithium battery of the new energy automobile, which is disclosed in claim 1, is characterized in that: in the step S3, the mass ratio of the carbon fiber bundles to the copper hydroxide/graphene oxide is 1:16.

4. the preparation method of the graphene heating/radiating composite material for the lithium battery of the new energy automobile, which is disclosed in claim 1, is characterized in that: the method for preparing the copper hydroxide/graphene oxide suspension comprises the following steps:

dissolving graphene oxide in water, performing ultrasonic dispersion to obtain a graphene oxide suspension for later use, dripping sodium hydroxide into a copper nitrate solution to obtain liquid copper hydroxide, adding the copper hydroxide dissolved in water into the graphene oxide suspension under the stirring condition, performing ultrasonic vibration, and embedding the copper hydroxide into the graphene oxide through hydrogen bonds; a copper hydroxide/graphene oxide suspension is obtained.

5. The preparation method of the graphene heating/radiating composite material for the lithium battery of the new energy automobile, which is disclosed in claim 4, is characterized in that: the molar ratio of graphene oxide to copper element is 1:1.6.

6. the preparation method of the graphene heating/radiating composite material for the lithium battery of the new energy automobile, which is disclosed in claim 1, is characterized in that: the magnetic attraction arrangement device comprises a plurality of electromagnet units which are connected in a telescopic sleeving manner, each electromagnet unit forms a working area, and the outer container is arranged on the working area; the outline of the electromagnet unit is overlapped with the outer edge of the working area, and each electromagnet unit is connected with an independent magnetic switch control system to form a multistage magnetic attraction arrangement area;

the method for directionally arranging the carbon fiber bundles in the mixed solution by the magnetic attraction arrangement device comprises the following substeps:

s41: starting an electromagnet unit positioned at the periphery, wherein the peripheral electromagnet unit adsorbs the carbon fiber bundles on the outer ring of the inner bottom surface of the container through magnetic force;

s42: stirring the mixed solution to separate carbon fiber bundles with insufficient magnetic attraction from the outer ring of the inner bottom surface of the container;

s43: lifting the electromagnet units in the middle to be on the same plane with the electromagnet units in the periphery, and starting the electromagnet units so that the detached carbon fiber bundles are re-adsorbed at the center of the inner bottom surface of the container;

s44: and continuing stirring the mixed solution to ensure that carbon fiber bundles with insufficient magnetic attraction in the mixed solution are separated from the inner bottom surface of the container and then are rearranged and adsorbed.

7. The preparation method of the graphene heating/radiating composite material for the lithium battery of the new energy automobile, which is disclosed in claim 6, is characterized in that: the magnetic attraction arrangement device comprises a first-stage electromagnet unit, a second-stage electromagnet unit and a third-stage electromagnet unit which are formed in a sleeved arrangement mode, wherein each electromagnet unit correspondingly forms a first-stage magnetic attraction arrangement region, a second-stage magnetic attraction arrangement region and a third-stage magnetic attraction arrangement region from inside to outside on the bottom surface of a container for containing mixed liquid, and the method for directionally arranging the carbon fiber bundles comprises the following sub-steps:

s411: starting a three-stage electromagnet unit, forming magnetic force in a three-stage magnetic attraction arrangement area, and adsorbing carbon fiber bundles in the three-stage magnetic attraction arrangement area on the inner bottom surface of the container;

s412: stirring the mixed solution to enable carbon fiber bundles with insufficient magnetic attraction in the mixed solution to be separated from a three-stage magnetic attraction arrangement area on the inner bottom surface of the container;

s413: starting the secondary electromagnet unit, rising to the same plane as the tertiary electromagnet unit, and forming magnetic force in the secondary magnetic attraction arrangement area to adsorb the detached carbon fiber bundles in the secondary magnetic attraction arrangement area of the inner bottom surface of the container;

s414: stirring the mixed solution to enable carbon fiber bundles with insufficient magnetic attraction in the mixed solution to be separated from a three-stage magnetic attraction arrangement area and a two-stage arrangement area on the inner bottom surface of the container;

s415: the primary electromagnet unit is started and rises to the same plane with the secondary electromagnet unit, magnetic force is formed in the primary magnetic attraction arrangement area to attract the separated carbon fiber bundles in the primary magnetic attraction arrangement area of the inner bottom surface of the container, and then a carbon fiber bundle array which is uniformly distributed is formed.

8. The graphene heating/radiating composite material for the lithium battery of the new energy automobile is characterized in that: a method of manufacture according to any one of claims 1 to 7.

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