KR20130128163A - Smart composite for controlling heat conductivity - Google Patents

Abstract

The present invention relates to a smart composite for thermal conductivity control, and more particularly, to a smart composite for thermal conductivity control that can control thermal conductivity by using a volume change of phase-transfer spherical particles.
That is, the present invention uses a phase transition material in which a phase transition phenomenon occurs in a liquid / solid phase starting from the melting point, but the thermal conductivity path is easily changed by using a volume change of about 10 vol% or less at the phase transition of the phase transition material. It is to provide a smart composite material for thermal conductivity control that can actively control and improve the reliability while preventing stability and performance deterioration according to the operating temperature of batteries and electrical and electronic components.

Description

Smart composite for thermal conductivity control {SMART COMPOSITE FOR CONTROLLING HEAT CONDUCTIVITY}

The present invention relates to a smart composite for thermal conductivity control, and more particularly, to a smart composite for thermal conductivity control that can control thermal conductivity by using a volume change of phase-transfer spherical particles.

In general, the energy and output of Li-ion batteries are generally known to drop rapidly when the temperature drops below -10 ° C. In fact, at -40 ° C, the energy density is 5% of the energy compared with the environment at 20 ° C. It is reported that it delivers only 1.25% of the density (Ref, G. Nagasubramanian, J. Appl. Electrochem. 31 (2001) 99).

In addition, lithium-ion batteries can be discharged normally in a low temperature environment, but have been reported to be poorly charged (Ref, CK Huang, JS Sakamoto, J. Wolfenstine, S. Surampudi, J. Electrochem. Soc. 147 (2000) 2893; SS Zhang, K Xu, TR Jow, Electrochim. Acta 48 (2002) 241).

In addition, it has been reported that the deterioration of a lithium ion battery in a low temperature environment is caused by reduced ion conductivity of the electrolyte, low diffusion of lithium ions into graphite, and increased resistance of charge transfer at the interface between the electrolyte and the electrode. (Ref, SS Zhang, K Xu, TR Jow, J of Power Sources 115 (2003) 137).

In such a low temperature environment, a decrease in output and performance of the battery is the most serious problem. Therefore, in order to prevent the battery from degrading in a low temperature environment, a separate battery cell is maintained at an appropriate temperature (35 to 45 ° C.). Insulation is required.

On the other hand, even when the actual use environment (temperature) is a high temperature, the problem occurs in the electrical components and the battery, the stability of the thermal runaway (thermal runaway) of the battery (hot run) is a problem at high temperatures.

As the heat insulation is excellent, there is a problem of heat dissipation, and when the heat dissipation is excellent, the problem of heat insulation is caused by high thermal conductivity, so that electrical components including lithium ion batteries of hybrid and electric vehicles are actively in an environment requiring heat insulation and heat radiation. There is a problem that cannot be coped.

In order to solve this problem, when foam foam is applied as a heat insulating means to the battery, it can be expected to improve the low temperature performance. Accelerating congestion can be a factor, causing catastrophic damage to electrical components and batteries.

In addition, the method of increasing the capacity of the blower, which is an air cooling means to enhance the heat dissipation performance of the battery, or adopting a water cooling means, and constituting the battery housing with a heat insulating material for enhancing the thermal insulation performance, but this increases the weight There is a problem.

Therefore, in order to solve heat dissipation and heat insulation problems in automotive electronic and electronic parts, especially battery systems, development of smart housing materials that can actively control heat conduction according to the surrounding environment and achieve a light weight effect It is required.

As an example of a high heat dissipation material, the battery housing is composed of a composite material containing a filler having excellent thermal conductivity, but in order to reach a desired thermal conductivity target, the filler must be filled with a high content of 70 wt% or more, which is a composite material. It leads to a decrease in physical properties.

In addition, when manufacturing a battery housing or the like using a composite material containing a filler having excellent thermal conductivity, anisotropy of thermal conductivity is generated by the filler orientation in the injection direction.

More specifically, since the polymer composite resin containing the high thermal conductivity fillers developed for improving heat dissipation performance includes most of the plate- or fiber-type fillers, when injected into a battery case or the like, The filler is uniaxially oriented in the injection direction by the shearing force in the injection direction, which causes the anisotropy problem of the thermal conductivity. Therefore, the thermal conductivity in the injection direction is generally 1/3 to 1/4 level as compared to the thermal conductivity in the thickness direction. There is a very low disadvantage.

Therefore, for effective heat dissipation, a heat transfer path should be formed according to the shape and characteristics of the parts, and most of the housings for electrical appliances and batteries should be manufactured to have heat transfer path characteristics in the thickness direction to improve heat dissipation efficiency. .

On the other hand, as a material for maintaining the proper temperature of the battery, a phase change material is used that absorbs heat when the temperature rises and releases heat when the temperature falls, so that the internal temperature of the battery can be properly maintained. The disadvantage is that no effective heat exchange rate between the materials is achieved.

The present invention has been made in order to solve the conventional problems as described above, using a phase transition material in which the phase transition phenomenon occurs in the liquid / solid phase from the melting point, the volume change of about 10 vol% or less during the phase transition of the phase transition material By making it easy to change the heat conduction path, it is possible to actively control the heat conduction, and to control the heat conduction to improve the reliability while preventing stability and performance deterioration according to the operating temperature of the battery and electrical and electronic parts. The purpose is to provide smart composites.

One embodiment of the present invention for achieving the above object is: a core made of a phase change material that changes the volume of expansion or contraction according to temperature changes, a shell made of an elastic material surrounding the phase change material, and the surface of the shell A hybrid phase-transition particle having a core shell structure composed of a high thermal conductivity filler to be coated so as to control the thermal conductivity by itself; A thermally conductive pouch member for encapsulating the hybrid phase transition particles together with a thermally conductive medium; It provides a smart composite material for thermal conductivity control, characterized in that consisting of.

In one embodiment of the present invention, the core of the hybrid phase change particle is a phase change material that changes in volume based on the melting point, characterized in that it is adopted as lauric acid (lauric acid) or nonadecane (nonadecane).

In one embodiment of the present invention, the hybrid phase change particle shell is characterized in that it is adopted as an elastomeric material having an elastic force surrounding the core surface.

In one embodiment of the present invention, the high thermal conductivity filler is characterized in that any one selected from graphite, carbon nanotubes, carbon fiber, high conductivity carbon black, boron nitride, aluminum nitride.

In one embodiment of the present invention, the thermally conductive pouch member includes: an upper plate and a lower plate of aluminum material spaced up and down; An epoxy plate disposed vertically between the upper plate and the lower plate to form a plurality of filling spaces; Epoxy cover that is covered on the side of the space between the upper plate and the lower plate; .

In addition, the heat conduction medium is characterized in that the dynamic viscosity is changed to ethylene glycol or propylene glycol is changed in accordance with the ambient temperature changes.

In particular, when the core is changed from a solid phase to a liquid phase and the volume increases, the shell expands outward to increase the contact area between the shell and at the same time to make side contact between the shells.

Another embodiment of the present invention for achieving the above object is: a phase transition material in which a high thermal conductivity filler is dispersed in a phase transition material that undergoes a volume change of expansion or contraction according to temperature change, and is directly filled in a filling space of a thermally conductive pouch material. It provides a smart composite material for thermal conductivity control.

In another embodiment of the present invention, the phase change material is characterized in that it is adopted as lauric acid (lauric acid) or nonadecane (nonadecane), the high thermal conductivity filler is graphite, carbon nanotubes, carbon fiber, high conductivity carbon It is characterized in that any one selected from black, boron nitride, aluminum nitride.

In another embodiment of the present invention, the thermally conductive pouch member comprises: a top plate and a bottom plate of aluminum material spaced up and down, and an epoxy cover that is covered on the side of the space between the top plate and the bottom plate, one filling An upper plate and a lower plate made of aluminum or spaced up and down spaced apart from each other, and an epoxy plate formed vertically between the upper plate and the lower plate to form a plurality of filling spaces, and a space between the upper plate and the lower plate. It is characterized by consisting of a cover made of epoxy to be covered on the side of the.

Through the above-mentioned means for solving the problems, the present invention provides the following effects.

The present invention provides a hybrid phase change particle composed of a core made of a phase change material that undergoes a volume change of expansion or contraction according to temperature change, a shell made of an elastic material surrounding the phase change material, and a high thermal conductivity filler coated on the surface of the shell. It is intended to provide a smart composite material for thermal conductivity control filled in a thermally conductive pouch member together with a thermally conductive medium material, and by applying it as a case material of a housing or a battery module of an electrical and electronic component, thermal insulation and heat dissipation effect can be simultaneously obtained.

That is, when the phase transition material is phase-transformed into the liquid or solid phase based on the melting point, the thermal conductivity can be actively controlled using the volume change, and accordingly, the stability and performance according to the operating temperature of the battery such as electric and electronic parts The problem of degradation can be fundamentally solved.

In other words, when heat generation occurs due to the operation of a battery including an electrical and electronic component or an increase in the ambient temperature, the thermal conductivity of the composite material of the present invention is increased, thereby showing an efficient heat dissipation effect. The thermal insulator function essentially prevents the low temperature performance of the component.

1 and 2 is a schematic diagram showing a hybrid phase transition particle of the smart composite for thermal conductivity control according to an embodiment of the present invention,
Figure 3 is a schematic diagram showing a thermal conductive pouch member of the smart composite for thermal conductivity control according to an embodiment of the present invention,
Figure 4 is a schematic diagram illustrating a thermal control mechanism of the smart composite for thermal conductivity control according to an embodiment of the present invention,
5 and 6 is a schematic diagram showing a smart composite for thermal conductivity control according to another embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The present invention is a kind of smart material that can be actively controlled the thermal conductivity of the material according to the ambient temperature, it is applied to the housing of the electrical and electronic components, in particular the housing or case material of the battery module, showing excellent heat dissipation performance under heat conditions The company aims to provide smart composites for thermal conductivity control to maintain the proper temperature through thermal insulation in low temperature environments.

To this end, the smart composite for thermal conductivity control according to an embodiment of the present invention, as shown in Figures 1 to 3 attached, the core shell to adjust the thermal conductivity by itself while changing the volume of expansion or contraction according to the temperature change And a thermally conductive pouch member which encapsulates the particles of the structure (hereinafter referred to as hybrid phase transition particles) and the coreshell structure together with a thermally conductive medium material.

The core 12 of the hybrid phase change particle 10 is adopted as a phase change material (PCM) that changes volume based on a melting point, and various materials can be selected according to a temperature required by an applied thermal control system. For example, lauric acid, nonadecane can be used.

The shell 14 wrapped on the surface of the core 12 of the hybrid phase transition particle 10 is an elastomeric material having an elastic force that encapsulates the core material like a capsule and expands or contracts according to a change in the volume ratio of the core material. Is adopted.

In particular, the surface of the shell 14 is coated with a high thermal conductivity filler (16).

That is, any one selected from graphite, carbon nanotubes, carbon fibers, highly conductive carbon black, boron nitride, and aluminum nitride is coated on the surface of the shell made of elastomer material as a high thermal conductivity filler.

At this time, the size of the high thermal conductivity filler 16 should be selected to an optimal size so that it can be easily coated on the surface of the shell, such as microcapsules, for example, if the shell is a particle size of 50 ~ 100 micrometers The conductive filler should be used for plate particles of 5 to 20 micrometers.

The thermally conductive pouch member 20 is made of an aluminum-based composite material that completely seals the hybrid phase change particle 10.

More specifically, the thermally conductive pouch member 20 is disposed between the upper plate 21 and the lower plate 22 made of aluminum having high thermal conductivity spaced up and down, and the space between the upper plate 21 and the lower plate 22 is It is formed of a plurality of filling spaces (24) partitioned by a partition plate 23 made of epoxy material of low thermal conductivity (about 0.2 ~ 0.3 W / mK), the side of the space between the upper plate 21 and the lower plate 22 Epoxy cover 25 is also made of a structure that is integrally attached to the side.

Accordingly, the thermally conductive pouch member 20 has an upper plate 21 and a lower plate 22 made of aluminum having high thermal conductivity along the thickness direction, so that the thermal conductivity can be easily made in the thickness direction, while the longitudinal direction is in the longitudinal direction. Accordingly, since the plate and the cover of the epoxy material having a low thermal conductivity exist, the thermal conductivity is not easily made in the longitudinal direction.

At this time, the above-mentioned hybrid phase transition particles are filled together with the thermally conductive medium 26 in each filling space 24 of the thermally conductive pouch member 20.

The thermally conductive medium 26 has a function of increasing the thermal insulation properties at low temperature, and the thermal conductivity is very low at 0.3 W / mK or less, which is advantageous for the expression of thermal insulation properties and dynamic viscosity due to heat transferred when the ambient temperature rises. It is preferable to use a material having a low viscosity, and as an example, an extremely low ethylene glycol (EG) or propylene glycol (PG) may be used as the thermal conductivity is 0.258 W / mK.

In order to provide fluidity even at a low temperature of 0 ° C. or less, the thermally conductive medium may be mixed with propylene glycol (PG) or ethylene glycol (EG) as water or another solvent.

More specifically, when the ethylene glycol is mixed with water, and generally mixed at 60:40 (ethylene glycol: water), the freezing point becomes -50 to -55 ° C and the boiling point at the same time. ) Becomes 120 ℃ and it is placed in general electrical components and use temperature environment, and dynamic viscosity is 35.0 ~ 40.0 [cP] around -17 ~ -20 ℃, Fluidity is adjustable.

For example, when the temperature of the heat conduction medium material is increased to 90 ~ 95 ℃ the dynamic viscosity is lowered to 0.8 ~ 1.0 [cP], it is possible to control the fluidity according to the temperature of the heat conduction medium material.

When the viscosity of the thermally conductive medium 26 is lowered by the heat transferred from the surroundings, its fluidity is increased, so that the degree of freedom of the volume change of the hybrid phase-transition particles 10 embedded with the thermally conductive medium 26 is increased. Will increase.

Therefore, when the ambient temperature rises above the melting point of the core 12 of the hybrid phase transition particle 10, that is, the melting point of the phase transition material, the core 12 is liquefied and absorbs heat from the surroundings, thereby preventing heat from the external environment. A primary heat dissipation effect can be obtained.

In addition, when the core 12 changes from the solid phase to the liquid phase and the volume thereof is increased to about 10 vol% or less, a secondary heat dissipation effect can be obtained as follows.

First, when the core 12 changes from a solid phase to a liquid phase and its volume increases to about 10 vol% or less, the shell 14 made of an expandable and shrinkable elastomer material as shown in FIG. In the expansion direction), thereby increasing the contact area between the shell 14 and the shell 14.

More specifically, when the shell 14 is inflated, the contact between the high thermal conductivity fillers 16 coated on the surface of the shell becomes a side contact at the point contact (side contact), the shell ( The area of contact between the shell 14 and the shell 14 is increased.

At this time, the connectivity between the micro particles of the high thermal conductivity fillers 16 coated on the surface of each shell 14 is increased, so that the high thermal conductivity fillers 16 coated on each shell 14 are three-dimensional network. (Network) form a heat conduction path, so it is possible to obtain a thermal conductivity improvement effect.

Therefore, the heat generated around one side is moved to the other side along the heat transfer path formed as described above, thereby obtaining a secondary heat dissipation effect.

On the other hand, when the ambient temperature is lowered, the dynamic viscosity of the thermally conductive medium material is increased, and thus, the hybrid phase transition particle 10 filled in each of the filling spaces 24 of the thermally conductive pouch member 20 together with the thermally conductive medium material 26. Fixing is performed, and together with this, the core of the hybrid phase transition particle falls below the melting point, thereby solidifying.

When the ambient temperature falls below the core melting point of the hybrid phase transition particle, that is, the melting point of the phase transition material, the core solidifies and releases the heat absorbed from the surroundings, and the released heat is transferred to the system (eg, the electronics). It is delivered to the battery (including, etc.) to obtain a primary thermal insulation effect that the heating action.

In addition, when the core 12 of the hybrid phase-transition particle 10 is phase-reduced to a solid phase and the volume thereof is reduced, the shell 14 made of the elastomer material contracts inward, thereby reducing the contact area between the shell and the shell. In addition, the contact between the high thermal conductivity fillers 16 coated on the surface of the shell 14 is converted from side contact to point contact, resulting in an increase in the interface resistance of the heat transfer path. Thermal conductivity is sharply lowered.

As the thermal conductivity is lowered, the composite material of the present invention has an insulating function to insulate the thermal energy of the system from the external environment, thereby preventing performance and stability deterioration due to the temperature drop of the system. Can contribute.

Here, referring to Figures 4 and 5 attached to the smart composite for thermal conductivity control according to another embodiment of the present invention.

Smart composite for thermal conductivity control according to another embodiment of the present invention, as shown in Figure 4, includes a thermal conductive pouch member forming a filling space.

More specifically, the thermally conductive pouch member is composed of a top plate and a bottom plate made of aluminum having high thermal conductivity spaced up and down, and an epoxy cover forming a side plate between the top plate and the bottom plate, and filling one inside thereof. Space is formed.

In particular, the filling phase of the thermally conductive pouch member is filled with a phase change material in which a high thermal conductivity filler is dispersed in a liquid phase transition material having a volume change based on the melting point as described above.

Therefore, when the phase change material solidifies below the melting point, the volume is reduced to form a gap at the interface between the top plate and the phase change material, so that an air layer is formed, thereby obtaining an insulation effect from the outside due to the air layer, whereas the melting point is higher than the melting point. When liquefied in the volume is increased to be in contact with the upper plate and the lower plate to function to heat the heat inside.

At this time, if too many high thermal conductive fillers are dispersed in the phase transition material, there is no volume difference due to the phase transition effect, and thus, an air layer is not formed. If too little is added, the effective phase transition phenomenon is not effective because the thermal conductivity is low. To distribute.

Meanwhile, as shown in FIG. 5 to which the thermally conductive pouch member is attached, the upper and lower plates made of aluminum having high thermal conductivity are spaced up and down, and the space between the upper and lower plates is low thermal conductivity (about 0.2 to 0.3 W). / mK) is formed of a plurality of filling spaces partitioned by an epoxy plate of the epoxy material, it is also possible to use a structure in which the cover of the epoxy material is integrally attached to the side of the space between the upper plate and the lower plate.

Of course, the phase transition material in which the high thermal conductivity fillers are dispersed in a liquid phase transition material having a volume change based on the melting point in each filling space is filled.

Similarly, when the phase change material is solidified below the melting point, the volume is reduced and a gap is generated at the interface between the top plate and the phase change material, thereby forming an air layer, thereby obtaining an insulation effect from the outside due to the air layer, whereas the melting point is higher than the melting point. When liquefied in the volume is increased to be in contact with the upper plate and the lower plate to function to heat the heat inside.

10: hybrid phase transition particle
12: Core
14: shell
16: high thermal conductivity filler
20: thermally conductive pouch member
21: top plate
22: Lower plate
23: plate
24: filling space
25: cover
26: heat conducting medium

Claims (11)

Core 12 made of a phase change material that changes the volume of expansion or contraction according to temperature change, a shell 14 made of an elastic material surrounding the phase change material, and a high thermal conductivity filler coated on the surface of the shell 14 ( 16 and a hybrid phase-transition particle 10 having a core-shell structure configured to self-regulate thermal conductivity;
A thermally conductive pouch member 20 for encapsulating the hybrid phase transition particles 10 together with a thermally conductive medium 26;
Smart composite material for thermal conductivity control, characterized in that consisting of.
The method according to claim 1,
The core 12 of the hybrid phase transition particle 10 is a phase change material having a volume change based on a melting point, and is characterized in that it is selected as lauric acid or nonadecane. .
The method according to claim 1,
The shell 14 of the hybrid phase transition particle 10 is a smart composite material for thermal conductivity control, characterized in that it is adopted as an elastomeric material having an elastic force surrounding the surface of the core (12).
The method according to claim 1,
The high thermal conductivity filler 16 is thermal conductivity control smart composite, characterized in that any one selected from graphite, carbon nanotubes, carbon fibers, high conductivity carbon black, boron nitride, aluminum nitride.
The method according to claim 1,
The thermally conductive pouch member 20 is:
An upper plate 21 and a lower plate 22 made of aluminum spaced apart from each other up and down;
An epoxy plate (23) disposed vertically between the upper plate (21) and the lower plate (22) to form a plurality of filling spaces (24);
Epoxy cover 25 is covered on the side of the space between the upper plate 21 and the lower plate 22;
Smart composite material for thermal conductivity control, characterized in that consisting of.
The method according to claim 1,
The thermally conductive medium material 26 is a smart composite for thermal conductivity control, characterized in that the dynamic viscosity is changed to ethylene glycol or propylene glycol in accordance with the change in ambient temperature.
The method according to claim 1,
When the core 12 changes from a solid phase to a liquid phase and increases in volume, the shell 14 expands outward to increase the contact area between the shell 14 and the shell 14 and at the same time the surface contact between the shells 14. Smart composite for thermal conductivity control, characterized in that the (side contact) is made.
Thermal conductivity, characterized in that the phase-transfer material in which the high thermal conductivity filler 16 is dispersed in the phase-transfer material that changes the volume of expansion or contraction in accordance with the temperature change in the filling space 24 of the thermally conductive pouch material 10 directly. Smart composite for control.
The method according to claim 8,
The phase change material is a smart composite for thermal conductivity control, characterized in that it is adopted as lauric acid or nonadecane.
The method according to claim 8,
The high thermal conductivity filler 16 is thermal conductivity control smart composite, characterized in that any one selected from graphite, carbon nanotubes, carbon fibers, high conductivity carbon black, boron nitride, aluminum nitride.
The method according to claim 8,
The thermally conductive pouch member 20 is:
It is composed of an upper plate 21 and a lower plate 22 made of aluminum spaced apart up and down, and an epoxy cover 25 covered on the side of the space between the upper plate 21 and the lower plate 22. Is adopted as a structure having a space 24, or
Epoxy plate 23 which is vertically disposed between the upper plate 21 and the lower plate 22 of the aluminum material and spaced up and down and the upper plate 21 and the lower plate 22 to form a plurality of filling space 24 And a cover 25 made of epoxy, which is covered on the side of the space between the upper plate 21 and the lower plate 22.

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