A high-strength heat-dissipating battery pack shell material and preparation method thereof

Abstract

The present invention relates to a high-strength heat-dissipating battery pack shell material and a preparation method thereof, belonging to the field of new energy vehicle technology. A polyurea buffer layer is sprayed onto the positive impact surface and the back impact surface of a high-strength heat-dissipating base material, which can reduce the deformation of the base material and enhance the impact resistance of the base material. The polyurea can avoid the formation of shear plugs on the positive impact surface and avoid the pore expansion effect on the back impact surface, thereby increasing the energy absorption capacity of the substrate. When the polyurea coating on the positive impact surface is impacted first, the base material is prevented from being subjected to local rigid impact, so that more parts of the base material participate in the deformation. Afterwards, the polyurea coating on the back impact surface has a larger strain. At this time, the polyurea is in a tensile state. On the one hand, it provides back support for the base material structure, so that the aluminum plate structure has a larger range of deformation participation and avoids stress concentration. On the other hand, it dissipates part of the impact energy through stretching, and improves the protection capability of the overall structure through the synergistic effect of the polyurea layers on the positive impact surface and the back impact surface.

Description

Technical Field

[0001] The present invention relates to a high-strength heat-dissipating battery pack shell material and a preparation method thereof, belonging to the technical field of new energy vehicles. Background Art

[0002] The automotive power battery pack is a core component and energy source for electric vehicles. It is also the largest component by mass in pure electric vehicles and has a significant impact on the vehicle's overall energy consumption. Electric vehicle power battery packs are typically located under the vehicle, and current automotive power batteries typically use lithium-ion batteries. Lithium-ion batteries can cause fires and explosions in the event of a collision. Therefore, automotive power battery packs should be placed in a safe area that is not susceptible to collision deformation and should not intrude into the driver's cabin in the event of a collision. When lithium-ion batteries are subjected to localized compression, they are prone to internal short circuits, leading to thermal runaway and fire. Because automotive power battery packs are typically installed under the vehicle chassis, underbody collisions are more likely to cause battery safety incidents. These include sharp objects piercing the battery pack (known as underbody penetration) and blunt objects such as curbs that continuously impact and penetrate the battery pack structure (known as underbody collisions). To mitigate the risks of short circuits and fires caused by underbody penetrations and underbody collisions during driving, the industry generally uses steel and aluminum plates as the base materials for battery pack protective structures. However, single-material protective structures struggle to achieve both battery crash safety and lightweight performance.

[0003] In view of the above-mentioned defects, the present invention aims to create a high-strength heat-dissipating battery pack shell material and a preparation method thereof, so as to make it more valuable for industrial use. Summary of the Invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide a high-strength heat-dissipating battery pack shell material and a preparation method thereof.

[0005] A high-strength heat-dissipating battery pack shell material of the present invention comprises a high-strength heat-dissipating base material and a polyurea buffer layer coated on its positive impact surface and back impact surface;

[0006] The polyurea buffer layer is formed by coating and curing the polyurea coating;

[0007] The polyurea coating comprises component A and component B;

[0008] The polyurea coating component A comprises 45 to 50 parts by weight of polyisocyanate and 50 to 75 parts by weight of polyether polyol;

[0009] The polyurea coating component B comprises, by weight, 18 to 50 parts of diethyltoluenediamine, 25 to 60 parts of amino-terminated polyether containing a propylene oxide main chain, 5 to 10 parts of silicon dioxide, 5 to 10 parts of layered graphite, and 5 to 15 parts of polydimethylsiloxane.

[0010] Furthermore, the thickness ratio of the polyurea buffer layer to the high-strength heat dissipation base material is 0.5 to 0.8.

[0011] Furthermore, the polyisocyanate is one or more of toluene diisocyanate, polymethylene diisocyanate, and polyphenyl polyisocyanate.

[0012] Furthermore, the polyether polyol is one or more of polyethylene glycol ether, polypropylene glycol ether, and polyglycerol ether.

[0013] A method for preparing a high-strength heat-dissipating battery pack shell material, the specific preparation steps are:

[0014] (1) Add polyisocyanate to a reaction kettle, fill it with nitrogen, stir it at a constant speed, heat it to 50-80°C, add polyether polyol dropwise to the kettle, and keep it warm while stirring. After the addition is complete, keep it warm at 60-90°C for 3 hours, cool it and discharge it to obtain component A;

[0015] (2) Grinding diethyltoluenediamine, amino-terminated polyether containing propylene oxide main chain, silica, layered graphite, and polydimethylsiloxane on a three-roll mill to a fineness of ≤45 μm, adding the ground slurry into a reactor, mixing uniformly, filtering with a 200-mesh sieve, and discharging to obtain component B;

[0016] (3) Component A and component B are metered, heated, and pressurized in a high-pressure spraying device with a fixed ratio of 1:1, mixed evenly through a spray gun, and then sprayed onto the positive impact surface and the back impact surface of the high-strength heat dissipation matrix material. The polyurea buffer layer is cured at rest to finally produce a high-strength heat dissipation battery pack shell material.

[0017] Furthermore, the pressure of the spraying equipment is 55-70 kg / cm 2 The temperature is 60-71℃, the viscosity of components A and B in the spray gun mixing chamber is less than 200cps, and the dynamic pressure difference between components A and B during spraying is less than 14kg / cm 2 .

[0018] Furthermore, the preparation steps of the high-strength heat dissipation matrix material are:

[0019] (1) Weighing rice husks and placing them in a pyrolysis furnace, pyrolyzing them at 600-700°C for 1-2 hours under an argon atmosphere to obtain pyrolyzed rice husk ash, and then mixing the pyrolyzed rice husk ash and a 40% glucose solution in an equal mass ratio and ball milling them for 2-3 hours before discharging to obtain a ball milled product;

[0020] (2) drying the ball-milled product and placing it in a tubular furnace, heating it to 600-700°C in a nitrogen atmosphere, keeping it warm for 1-2 hours, and then transferring it to a vacuum sintering furnace, heating it to 1300-1400°C in a vacuum atmosphere, keeping it warm for 2-3 hours, and then heating it to 600-700°C in an air atmosphere after sintering. After continuing to sinter for 2-3 hours, the product was rinsed 3-5 times with 1 mol / L hydrofluoric acid to obtain spherical porous silicon carbide powder;

[0021] (3) taking, by weight, 2.0-13.0 parts of Al, 0.4-4.0 parts of Mn, 0.4-2.0 parts of Cu, 6.0-10.0 parts of Si, 0.5-7.0 parts of Zn, 0.5-2.0 parts of Mg, 0.5-1.0 parts of Cr, 0.8-3.0 parts of Ni, and 85-88 parts of Fe, placing the mixture in a medium frequency induction furnace, heating it to 1600° C., and melting it into molten steel;

[0022] (4) 8 to 8.5 parts of spherical porous silicon carbide powder are then loaded into a ladle, and the above molten steel is poured into the ladle to obtain a casting liquid, which is cast into a mold and naturally cooled to obtain a high-strength heat dissipation matrix material.

[0023] By means of the above solution, the present invention has at least the following advantages:

[0024] (1) With the increase of the thickness of the polyurea coating, the fracture displacement and the maximum impact load of the substrate increase. And the impact load that can be sustained is the highest in the range of 0.5 to 0.8. In the polyurea coating, the amino-terminated polyether containing the propylene oxide main chain has high reactivity with isocyanate, and the polyurea formation reaction can proceed smoothly without relying on the activation of the catalyst; and the introduction of the propylene oxide main chain can obtain a polyurea buffer layer with high elongation, low hardness and flexibility; the inorganic filler silica itself has excellent mechanical properties and can increase the overall impact strength of the polyurea coating. When the polyurea layer is impacted, the layered graphite filler will produce interlayer slippage to disperse the impact stress, further improving the impact resistance of the polyurea layer;

[0025] (2) The polyurea buffer layer is sprayed onto the positive impact surface and the back impact surface of the high-strength heat dissipation base material. The polyurea coating acts as an impact-resistant protective structure, which can reduce the deformation of the base material and enhance the impact resistance of the base material. The polyurea can avoid the formation of shear plugs on the positive impact surface and avoid the pore expansion effect on the back impact surface, thereby increasing the energy absorption capacity of the substrate. When the polyurea coating on the positive impact surface is impacted first, the base material is prevented from being subjected to local rigid impact, so that more parts of the base material participate in the deformation. Afterwards, the strain of the polyurea coating on the back impact surface is larger. At this time, the polyurea is in a tensile state. On the one hand, it provides back support for the base material structure, so that the aluminum plate structure participates in deformation in a larger range to avoid stress concentration. On the other hand, it dissipates part of the impact energy through stretching, and improves the protective capability of the overall structure through the synergistic effect of the polyurea layers on the positive impact surface and the back impact surface.

[0026] (3) The present invention first uses rice husk as raw material, crushes it and then pyrolyzes it to obtain pyrolyzed rice husk ash, and then uses rice husk ash and glucose as raw materials, adopts a simple mixing process, and prepares porous silicon carbide powder with good sphericity through carbonization, calcination and other steps, and adds it to the matrix raw material. In conjunction with the subsequent molten steel punching process, the molten steel churns, thereby exposing a large amount of gas contained in the internal gaps of the porous silicon carbide powder, forming bubbles on its surface. Combined with the light weight of the porous silicon carbide powder itself, it eventually floats to the surface of the matrix material to form raised silicon carbide protrusions. Due to the nano-silicon carbide It has high mechanical strength and can improve the mechanical strength of the base material. In addition, silicon carbide is a ceramic material with extremely high thermal conductivity. Its addition can significantly improve the heat dissipation performance of the base material surface. The protruding silicon carbide protrusions significantly increase the roughness of the base material surface, which can increase the physical anchoring strength between the polyurea coating and the base material and improve the overall bonding strength between the polyurea coating and the base material. The higher the bonding strength between the polyurea coating and the base material, the higher its stability and the higher the impact-absorbing performance, which can greatly improve the impact-resistant performance of the base material.

[0027] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention. DETAILED DESCRIPTION

[0028] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0029] A high-strength heat-dissipating battery pack shell material according to a preferred embodiment of the present invention comprises a high-strength heat-dissipating base material and a polyurea buffer layer coated on its positive impact surface and back impact surface;

[0030] The thickness ratio of the polyurea buffer layer to the high-strength heat dissipation base material is 0.5 to 0.8. As the thickness of the polyurea coating increases, the substrate fracture displacement and maximum impact load both increase. The highest impact load can be sustained within the range of 0.5 to 0.8.

[0031] The polyurea buffer layer is formed by coating and curing the polyurea coating;

[0032] The polyurea coating comprises component A and component B;

[0033] The polyurea coating component A comprises, by weight, 45 to 50 parts of polyisocyanate and 50 to 75 parts of polyether polyol; the polyurea coating component B comprises, by weight, 18 to 50 parts of diethyltoluenediamine, 25 to 60 parts of amino-terminated polyether containing a propylene oxide main chain, 5 to 10 parts of silicon dioxide, 5 to 10 parts of layered graphite, and 5 to 15 parts of polydimethylsiloxane;

[0034] The amino-terminated polyether containing a propylene oxide backbone has high reactivity with isocyanate, and the polyurea formation reaction can proceed smoothly without relying on the activation of a catalyst. In addition, the introduction of the propylene oxide backbone can produce a polyurea buffer layer with high elongation, low hardness, and flexibility.

[0035] The inorganic filler silica itself has excellent mechanical properties and can increase the overall impact strength of the polyurea coating. The layered graphite filler will produce interlayer slippage when the polyurea layer is impacted to disperse the impact stress, further improving the impact resistance of the polyurea layer.

[0036] The polyisocyanate is one or more of toluene diisocyanate, polymethylene diisocyanate, and polyphenyl polyisocyanate;

[0037] The polyether polyol is one or more of polyethylene glycol ether, polypropylene glycol ether, and polyglycerol ether;

[0038] The preparation steps of component A of the polyurea coating are as follows: adding polyisocyanate to a reaction kettle, filling it with nitrogen, stirring at a constant speed, heating it to 50-80°C, adding polyether polyol dropwise to the kettle, stirring and keeping it warm, and after the addition is complete, keeping it warm at 60-90°C for 3 hours, cooling and discharging the material to obtain component A;

[0039] The preparation steps of component B of the polyurea coating are as follows: grinding diethyltoluenediamine, amino-terminated polyether containing propylene oxide main chain, silicon dioxide, layered graphite, and polydimethylsiloxane on a three-roll mill to a fineness of ≤45 μm, adding the ground slurry into a reactor, mixing evenly, filtering with a 200-mesh sieve, and then discharging to obtain component B;

[0040] The preparation steps of the polyurea buffer layer are as follows: component A and component B are measured, heated, and pressurized in a high-pressure spraying device at a fixed ratio of 1:1, mixed evenly through a spray gun, and then sprayed onto the positive impact surface and the back impact surface of the high-strength heat dissipation base material, and allowed to stand and solidify to obtain the polyurea buffer layer.

[0041] The pressure of the spraying equipment is 55-70 kg / cm 2 The temperature is 60-71℃, the viscosity of components A and B in the spray gun mixing chamber is less than 200cps, and the dynamic pressure difference between components A and B during spraying is less than 14kg / cm 2 .

[0042] The polyurea buffer layer is sprayed onto the positive impact surface and the back impact surface of the high-strength heat dissipation base material. The polyurea coating serves as an impact-resistant protective structure, which can reduce the deformation of the base material and enhance the impact resistance of the base material. The polyurea can avoid the formation of shear plugs on the positive impact surface and avoid the pore expansion effect and increase the energy absorption capacity of the substrate on the back impact surface. When the polyurea coating on the positive impact surface is impacted first, the base material is prevented from being subjected to local rigid impact, so that more parts of the base material participate in the deformation. Afterwards, the strain of the polyurea coating on the back impact surface is larger. At this time, the polyurea is in a tensile state. On the one hand, it provides back support for the base material structure, so that the aluminum plate structure has a larger range of deformation and avoids stress concentration. On the other hand, it dissipates part of the impact energy through stretching, and improves the protection capability of the overall structure through the synergistic effect of the polyurea layers on the positive impact surface and the back impact surface.

[0043] The preparation steps of the high-strength heat dissipation base material are as follows:

[0044] (1) Weighing rice husks and placing them in a pyrolysis furnace, pyrolyzing them at 600-700°C for 1-2 hours under an argon atmosphere to obtain pyrolyzed rice husk ash, and then mixing the pyrolyzed rice husk ash and a 40% glucose solution in an equal mass ratio and ball milling them for 2-3 hours before discharging to obtain a ball milled product;

[0045] (2) drying the ball-milled product and placing it in a tubular furnace, heating it to 600-700°C in a nitrogen atmosphere, keeping it warm for 1-2 hours, and then transferring it to a vacuum sintering furnace, heating it to 1300-1400°C in a vacuum atmosphere, keeping it warm for 2-3 hours, and then heating it to 600-700°C in an air atmosphere after sintering. After continuing to sinter for 2-3 hours, the product was rinsed 3-5 times with 1 mol / L hydrofluoric acid to obtain spherical porous silicon carbide powder;

[0046] (3) taking, by weight, 2.0-13.0 parts of Al, 0.4-4.0 parts of Mn, 0.4-2.0 parts of Cu, 6.0-10.0 parts of Si, 0.5-7.0 parts of Zn, 0.5-2.0 parts of Mg, 0.5-1.0 parts of Cr, 0.8-3.0 parts of Ni, and 85-88 parts of Fe, placing the mixture in a medium frequency induction furnace, heating it to 1600° C., and melting it into molten steel;

[0047] (4) 8 to 8.5 parts of spherical porous silicon carbide powder are then loaded into a ladle, and the above molten steel is poured into the ladle to obtain a casting liquid, which is cast into a mold and naturally cooled to obtain a high-strength heat dissipation matrix material.

[0048] The present invention first uses rice husk as raw material, crushes it and then pyrolyzes it to obtain pyrolyzed rice husk ash, then uses rice husk ash and glucose as raw materials, adopts a simple mixing process, and prepares porous silicon carbide powder with good sphericity through carbonization, calcination and other steps, adds it to the matrix raw material, cooperates with the subsequent molten steel punching process, and the molten steel churns, so that a large amount of gas contained in the internal gaps of the porous silicon carbide powder is exposed, forming bubbles on its surface, combined with the light weight of the porous silicon carbide powder itself, and finally floats to the surface of the matrix material to form raised silicon carbide protrusions. Due to the nano-silicon carbide itself High mechanical strength can improve the mechanical strength of the base material by itself. In addition, silicon carbide is a ceramic material with extremely high thermal conductivity. Its addition can significantly improve the heat dissipation performance of the base material surface. Moreover, the protruding silicon carbide protrusions significantly increase the roughness of the base material surface, which can increase the physical anchoring strength between the polyurea coating and the base material and improve the overall bonding strength between the polyurea coating and the base material. The higher the bonding strength between the polyurea coating and the base material, the higher its stability and the higher the impact-absorbing performance, which can greatly improve the impact-resistant performance of the base material.

[0049] Example 1

[0050] A high-strength heat-dissipating battery pack shell material, comprising a high-strength heat-dissipating base material and a polyurea buffer layer coated on its positive impact surface and back impact surface;

[0051] The thickness ratio of the polyurea buffer layer to the high-strength heat dissipation base material is 0.5;

[0052] The polyurea buffer layer is formed by coating and curing the polyurea coating;

[0053] The polyurea coating comprises component A and component B;

[0054] The polyurea coating component A comprises, by weight, 45 parts of polyisocyanate and 50 parts of polyether polyol; the polyurea coating component B comprises, by weight, 18 parts of diethyltoluenediamine, 25 parts of amino-terminated polyether containing a propylene oxide main chain, 5 parts of silicon dioxide, 5 parts of layered graphite, and 5 parts of polydimethylsiloxane;

[0055] The polyisocyanate is toluene diisocyanate;

[0056] The polyether polyol is polyethylene glycol ether;

[0057] The preparation steps of component A of the polyurea coating are as follows: adding polyisocyanate to a reaction kettle, filling it with nitrogen, stirring at a constant speed, heating it to 50°C, adding polyether polyol dropwise to the kettle, stirring and keeping it warm, and after the addition is completed, keeping it warm at 60°C for 3 hours, cooling and discharging the material to obtain component A;

[0058] The preparation steps of component B of the polyurea coating are as follows: grinding diethyltoluenediamine, amino-terminated polyether containing propylene oxide main chain, silicon dioxide, layered graphite, and polydimethylsiloxane on a three-roll mill to a fineness of ≤45 μm, adding the ground slurry into a reactor, mixing evenly, filtering with a 200-mesh sieve, and then discharging to obtain component B;

[0059] The preparation steps of the polyurea buffer layer are as follows: component A and component B are measured, heated, and pressurized in a high-pressure spraying device at a fixed ratio of 1:1, mixed evenly through a spray gun, and then sprayed onto the positive impact surface and the back impact surface of the high-strength heat dissipation base material, and allowed to stand and solidify to obtain the polyurea buffer layer.

[0060] The pressure of the spraying equipment is 55kg / cm 2 The temperature is 60℃, the viscosity of components A and B in the spray gun mixing chamber is less than 200cps, and the dynamic pressure difference between components A and B during spraying is less than 14kg / cm 2 .

[0061] The preparation steps of the high-strength heat dissipation base material are as follows:

[0062] (1) Weighing rice husks and placing them in a pyrolysis furnace, pyrolyzing them at 600°C for 1 h under an argon atmosphere, and obtaining pyrolyzed rice husk ash. The pyrolyzed rice husk ash and a 40% glucose solution were mixed in equal weight ratios and ball-milled for 2 h before discharging to obtain a ball-milled product.

[0063] (2) The ball-milled product was dried and placed in a tubular furnace, heated to 600°C in a nitrogen atmosphere, kept warm for 1 hour, and then transferred to a vacuum sintering furnace. In a vacuum atmosphere, the temperature was raised to 1300°C, and the temperature was kept warm for 2 hours. After the sintering was completed, the product was heated to 600°C in an air atmosphere, and sintered for another 2 hours. The product was then rinsed three times with 1 mol / L hydrofluoric acid to obtain spherical porous silicon carbide powder.

[0064] (3) 2.0 parts of Al, 0.4 parts of Mn, 0.4 parts of Cu, 6.0 parts of Si, 0.5 parts of Zn, 0.5 parts of Mg, 0.5 parts of Cr, 0.8 parts of Ni, and 85 parts of Fe were taken in a medium frequency induction furnace, heated to 1600°C, and smelted into molten steel;

[0065] (4) Then, 8 parts of spherical porous silicon carbide powder are placed in a ladle, and the above molten steel is poured into the ladle to obtain a casting liquid, which is cast into a mold and naturally cooled to obtain a high-strength heat dissipation matrix material.

[0066] Example 2

[0067] A high-strength heat-dissipating battery pack shell material, comprising a high-strength heat-dissipating base material and a polyurea buffer layer coated on its positive impact surface and back impact surface;

[0068] The thickness ratio of the polyurea buffer layer to the high-strength heat dissipation base material is 0.65;

[0069] The polyurea buffer layer is formed by coating and curing the polyurea coating;

[0070] The polyurea coating comprises component A and component B;

[0071] The polyurea coating component A comprises, by weight, 48 parts of polyisocyanate and 65 parts of polyether polyol; the polyurea coating component B comprises, by weight, 35 parts of diethyltoluenediamine, 45 parts of amino-terminated polyether containing a propylene oxide main chain, 8 parts of silicon dioxide, 8 parts of layered graphite, and 10 parts of polydimethylsiloxane;

[0072] The polyisocyanate is polymethylene diisocyanate;

[0073] The polyether polyol is polypropylene glycol ether;

[0074] The preparation steps of component A of the polyurea coating are as follows: adding polyisocyanate to a reaction kettle, filling it with nitrogen, stirring at a constant speed, heating it to 65°C, adding polyether polyol dropwise to the kettle, stirring and keeping it warm, and after the addition is completed, keeping it warm at 75°C for 3 hours, cooling and discharging the material to obtain component A;

[0075] The preparation steps of component B of the polyurea coating are as follows: grinding diethyltoluenediamine, amino-terminated polyether containing propylene oxide main chain, silicon dioxide, layered graphite, and polydimethylsiloxane on a three-roll mill to a fineness of ≤45 μm, adding the ground slurry into a reactor, mixing evenly, filtering with a 200-mesh sieve, and then discharging to obtain component B;

[0076] The preparation steps of the polyurea buffer layer are as follows: component A and component B are measured, heated, and pressurized in a high-pressure spraying device at a fixed ratio of 1:1, mixed evenly through a spray gun, and then sprayed onto the positive impact surface and the back impact surface of the high-strength heat dissipation base material, and allowed to stand and solidify to obtain the polyurea buffer layer.

[0077] The pressure of the spraying equipment is 60kg / cm 2 The temperature is 65℃, the viscosity of components A and B in the spray gun mixing chamber is less than 200cps, and the dynamic pressure difference between components A and B during spraying is less than 14kg / cm 2 .

[0078] The preparation steps of the high-strength heat dissipation base material are as follows:

[0079] (1) Weighing rice husks and placing them in a pyrolysis furnace, pyrolyzing them at 650°C for 1 h under an argon atmosphere to obtain pyrolyzed rice husk ash, and then mixing the pyrolyzed rice husk ash and a 40% glucose solution in an equal mass ratio and ball milling them for 2 h to obtain a ball-milled product;

[0080] (2) The ball-milled product was dried and placed in a tube furnace, heated to 650°C in a nitrogen atmosphere, kept warm for 2 hours, and then transferred to a vacuum sintering furnace. In a vacuum atmosphere, the temperature was raised to 1350°C and kept warm for 2 hours. After sintering, the product was heated to 650°C in an air atmosphere and continued to be sintered for 3 hours. The product was then rinsed five times with 1 mol / L hydrofluoric acid to obtain spherical porous silicon carbide powder.

[0081] (3) 6.5 parts of Al, 2.0 parts of Mn, 1.5 parts of Cu, 8.0 parts of Si, 3.5 parts of Zn, 1.5 parts of Mg, 0.8 parts of Cr, 1.5 parts of Ni, and 87 parts of Fe were taken in a medium frequency induction furnace, heated to 1600°C, and smelted into molten steel;

[0082] (4) 8.3 parts of spherical porous silicon carbide powder are then placed in a ladle, and the above molten steel is poured into the ladle to obtain a casting liquid, which is cast into a mold and naturally cooled to obtain a high-strength heat dissipation matrix material.

[0083] Example 3

[0084] A high-strength heat-dissipating battery pack shell material, comprising a high-strength heat-dissipating base material and a polyurea buffer layer coated on its positive impact surface and back impact surface;

[0085] The thickness ratio of the polyurea buffer layer to the high-strength heat dissipation base material is 0.8;

[0086] The polyurea buffer layer is formed by coating and curing the polyurea coating;

[0087] The polyurea coating comprises component A and component B;

[0088] The polyurea coating component A comprises, by weight, 50 parts of polyisocyanate and 75 parts of polyether polyol; the polyurea coating component B comprises, by weight, 50 parts of diethyltoluenediamine, 60 parts of amino-terminated polyether containing a propylene oxide main chain, 10 parts of silicon dioxide, 10 parts of layered graphite, and 15 parts of polydimethylsiloxane;

[0089] The polyisocyanate is polyphenyl polyisocyanate;

[0090] The polyether polyol is polyglycerol ether;

[0091] The preparation steps of component A of the polyurea coating are as follows: adding polyisocyanate to a reaction kettle, filling it with nitrogen, stirring at a constant speed, heating it to 80°C, adding polyether polyol dropwise to the kettle, stirring and keeping it warm, and after the addition is completed, keeping it warm at 90°C for 3 hours, cooling and discharging the material to obtain component A;

[0092] The preparation steps of component B of the polyurea coating are as follows: grinding diethyltoluenediamine, amino-terminated polyether containing propylene oxide main chain, silicon dioxide, layered graphite, and polydimethylsiloxane on a three-roll mill to a fineness of ≤45 μm, adding the ground slurry into a reactor, mixing evenly, filtering with a 200-mesh sieve, and then discharging to obtain component B;

[0093] The preparation steps of the polyurea buffer layer are as follows: component A and component B are measured, heated, and pressurized in a high-pressure spraying device at a fixed ratio of 1:1, mixed evenly through a spray gun, and then sprayed onto the positive impact surface and the back impact surface of the high-strength heat dissipation base material, and allowed to stand and solidify to obtain the polyurea buffer layer.

[0094] The pressure of the spraying equipment is 70kg / cm 2 The temperature is 71℃, the viscosity of components A and B in the spray gun mixing chamber is less than 200cps, and the dynamic pressure difference between components A and B during spraying is less than 14kg / cm 2 .

[0095] The preparation steps of the high-strength heat dissipation base material are as follows:

[0096] (1) Weighing rice husks and placing them in a pyrolysis furnace, pyrolyzing them at 700°C for 2 h under an argon atmosphere, and obtaining pyrolyzed rice husk ash. The pyrolyzed rice husk ash and a 40% glucose solution were mixed in equal weight ratios and ball-milled for 3 h before discharging to obtain a ball-milled product.

[0097] (2) The ball-milled product was dried and placed in a tubular furnace, heated to 700°C in a nitrogen atmosphere, kept warm for 2 hours, and then transferred to a vacuum sintering furnace. In a vacuum atmosphere, the temperature was raised to 1400°C and kept warm for 3 hours. After sintering, the product was heated to 700°C in an air atmosphere and continued to be sintered for 3 hours. The product was then rinsed five times with 1 mol / L hydrofluoric acid to obtain spherical porous silicon carbide powder.

[0098] (3) 13.0 parts of Al, 4.0 parts of Mn, 2.0 parts of Cu, 10.0 parts of Si, 7.0 parts of Zn, 2.0 parts of Mg, 1.0 parts of Cr, 3.0 parts of Ni, and 88 parts of Fe were taken in a medium frequency induction furnace, heated to 1600° C., and smelted into molten steel;

[0099] (4) 8.5 parts of spherical porous silicon carbide powder are then loaded into a ladle, and the above molten steel is poured into the ladle to obtain a casting liquid, which is cast into a mold and naturally cooled to obtain a high-strength heat dissipation matrix material.

[0100] Control Example

[0101] Comparative Example 1: The preparation method of this comparative example is basically the same as that of Example 1 of the present invention, except that the polyurea coating is applied only on the positive impact surface of the substrate material. The other steps remain unchanged, and a high-strength heat-dissipating battery pack shell material is also prepared;

[0102] Comparative Example 2: The preparation method of this comparative example is basically the same as that of Example 1 of the present invention, except that the polyurea coating is applied only on the back impact surface of the substrate material. The other steps remain unchanged, and a high-strength heat-dissipating battery pack shell material is also prepared;

[0103] Comparative Example 3: The preparation method of this comparative example is basically the same as that of Example 1 of the present invention, except that the polyurea coating is not applied to the surface of the base material. The other steps remain unchanged, and a high-strength heat-dissipating battery pack shell material is also prepared;

[0104] Comparative Example 4: The preparation method of this comparative example is basically the same as that of Example 1 of the present invention, except that ordinary solid silicon carbide particles are used instead of the porous silicon carbide particles of the present invention during the preparation of the base material. The other steps remain unchanged, and a high-strength, heat-dissipating battery pack shell material is also prepared.

[0105] Comparative Example 5: The preparation method of this comparative example is basically the same as that of Example 1 of the present invention, except that the base material is prepared by directly casting the molten steel without using the molten steel ladle process. The other steps remain unchanged, and a high-strength heat-dissipating battery pack shell material is also prepared;

[0106] Comparative Example 6: The preparation method of this comparative example is basically the same as that of Example 1 of the present invention, except that porous silicon carbide particles are not added during the preparation of the base material. Other steps remain unchanged, and a high-strength, heat-dissipating battery pack shell material is also prepared;

[0107] The performance tests were performed on Examples 1-3 of the present invention and Comparative Examples 1-5, and the test results are shown in Table 1:

[0108] Detection method:

[0109] Maximum impact load: The penetration of the impact head into the specimen and the impact load applied by the impact head. The impact head displacement is captured by a high-speed camera using a DIC algorithm, while the impact load is measured by a force sensor located above the impact head. The impact head compresses the square plate at a speed of 0.6 mm / min, and the average test duration is 35 minutes.

[0110] Heat dissipation: The battery shell material prepared by the present invention is used to coat a lithium battery. The operating temperature of the lithium battery is measured from the time the heat generated by the lithium battery during charge and discharge reaches 45°C to the time it lasts for 20 minutes. The lower the operating temperature, the better the heat dissipation.

[0111] Table 1 Performance test results

[0112] Test items Maximum impact load (kN) Heat dissipation (℃) Example 1 27.36 31 Example 2 27.56 30 Example 3 27.42 32 Comparative Example 1 17.38 33 Comparative Example 2 17.50 34 Comparative Example 3 14.35 31 Comparative Example 4 23.81 40 Comparative Example 5 23.50 42 Comparative Example 6 22.31 39

[0113] It can be seen from the test data in the above table that the battery pack shell materials prepared in Examples 1 to 3 of the present invention have excellent impact resistance and heat dissipation performance, and the performance of Example 2 is the best. This proves that the technical solution of the present application is highly feasible, and that as the thickness of the polyurea coating increases, the substrate fracture displacement and maximum impact load both increase. And the highest impact load can be sustained in the range of 0.5 to 0.8. In the polyurea coating, the terminal amino polyether containing a propylene oxide main chain has high reactivity with isocyanate, and the polyurea formation reaction can proceed smoothly without relying on the activation of the catalyst; and the introduction of the propylene oxide main chain can obtain a polyurea buffer layer with high elongation, low hardness, and flexibility; the inorganic filler silica itself has excellent mechanical properties and can increase the overall impact strength of the polyurea coating, and the layered graphite filler will produce interlayer slippage to disperse the impact stress when the polyurea layer is impacted, thereby further improving the impact resistance of the polyurea layer;

[0114] Then, the test results of the control examples 1-3 of the present invention are compared with those of Example 1. It can be seen that the impact resistance of the control examples 1-3 is significantly reduced, and the reduction in the control example 3 is the largest. This proves that the polyurea buffer layer is sprayed onto the positive impact surface and the back impact surface of the high-strength heat dissipation substrate material. The polyurea coating serves as an impact-resistant protective structure, which can reduce the deformation of the substrate material and enhance the impact resistance of the substrate material. The polyurea can avoid the formation of shear plugs on the impact surface and avoid the pore expansion effect and increase the energy absorption capacity of the substrate on the back impact surface. When the polyurea coating on the impact surface is impacted first, the substrate material is prevented from being subjected to local rigid impact, so that more parts of the substrate material participate in the deformation. Afterwards, the strain of the polyurea coating on the back impact surface is larger. At this time, the polyurea is in a tensile state. On the one hand, it provides back support for the substrate material structure, so that the aluminum plate structure has a larger range of deformation and avoids stress concentration. On the other hand, it dissipates part of the impact energy through stretching, and improves the protection capability of the overall structure through the synergistic effect of the polyurea layers on the impact surface and the back impact surface.

[0115] Finally, the test results of the control examples 4-6 of the present invention are compared with those of Example 1. It can be seen that the impact resistance and heat dissipation of the control examples 4-6 are significantly reduced. This proves that the present invention first uses rice husk as raw material, crushes it and then pyrolyzes it to obtain pyrolyzed rice husk ash, and then uses rice husk ash and glucose as raw materials, adopts a simple mixing process, and prepares porous silicon carbide powder with good sphericity through carbonization, calcination and other steps, adds it to the matrix raw material, and cooperates with the subsequent molten steel punching process. The molten steel churns, thereby exposing a large amount of gas contained in the internal gaps of the porous silicon carbide powder, forming bubbles on its surface, and finally floating to the surface of the porous silicon carbide powder. Raised silicon carbide protrusions are formed on the surface of the base material. Since nano-silicon carbide itself has high mechanical strength, it can improve the mechanical strength of the base material. In addition, silicon carbide is a ceramic material with extremely high thermal conductivity. Its addition can significantly improve the heat dissipation performance of the base material surface. Moreover, the raised silicon carbide protrusions significantly increase the roughness of the base material surface, which can increase the physical anchoring strength between the polyurea coating and the base material and improve the overall bonding strength between the polyurea coating and the base material. The higher the bonding strength between the polyurea coating and the base material, the higher its stability and the higher the impact-absorbing performance, thereby greatly improving the impact-resistant performance of the base material.

[0116] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A high-strength heat-dissipating battery pack shell material, characterized by: It includes a high-strength heat dissipation base material and a polyurea buffer layer coated on its positive impact surface and back impact surface; The polyurea buffer layer is formed by coating and curing the polyurea coating; The polyurea coating comprises component A and component B; The polyurea coating component A comprises 45 to 50 parts by weight of polyisocyanate and 50 to 75 parts by weight of polyether polyol; The polyurea coating component B comprises, by weight, 18 to 50 parts of diethyltoluenediamine, 25 to 60 parts of amino-terminated polyether containing a propylene oxide main chain, 5 to 10 parts of silicon dioxide, 5 to 10 parts of layered graphite, and 5 to 15 parts of polydimethylsiloxane; The thickness ratio of the polyurea buffer layer to the high-strength heat dissipation base material is 0.5 to 0.8; The preparation steps of the high-strength heat dissipation base material are as follows: (1) Weighing rice husks and placing them in a pyrolysis furnace, pyrolyzing them at 600-700°C for 1-2 hours under an argon atmosphere to obtain pyrolyzed rice husk ash, and then mixing the pyrolyzed rice husk ash and a 40% glucose solution in an equal mass ratio and ball milling them for 2-3 hours before discharging to obtain a ball milled product; (2) drying the ball-milled product and placing it in a tubular furnace, heating it to 600-700°C in a nitrogen atmosphere, keeping it warm for 1-2 hours, and then transferring it to a vacuum sintering furnace, heating it to 1300-1400°C in a vacuum atmosphere, keeping it warm for 2-3 hours, and then heating it to 600-700°C in an air atmosphere after sintering. After continuing to sinter for 2-3 hours, the product was rinsed 3-5 times with 1 mol / L hydrofluoric acid to obtain spherical porous silicon carbide powder; (3) taking, by weight, 2.0-13.0 parts of Al, 0.4-4.0 parts of Mn, 0.4-2.0 parts of Cu, 6.0-10.0 parts of Si, 0.5-7.0 parts of Zn, 0.5-2.0 parts of Mg, 0.5-1.0 parts of Cr, 0.8-3.0 parts of Ni, and 85-88 parts of Fe, placing the mixture in a medium frequency induction furnace, heating it to 1600° C., and melting it into molten steel; (4) 8 to 8.5 parts of spherical porous silicon carbide powder are then loaded into a ladle, and the above molten steel is poured into the ladle to obtain a casting liquid, which is cast into a mold and naturally cooled to obtain a high-strength heat dissipation matrix material.

2. The high-strength heat-dissipating battery pack shell material according to claim 1, characterized in that: The polyisocyanate is one or more of toluene diisocyanate, polymethylene diisocyanate, and polyphenyl polyisocyanate.

3. The high-strength heat-dissipating battery pack shell material according to claim 1, characterized in that: The polyether polyol is one or more of polyethylene glycol ether, polypropylene glycol ether and polyglycerol ether.

4. The method for preparing a high-strength heat dissipation battery pack shell material according to claim 1, characterized in that The specific preparation steps are: (1) Add polyisocyanate to a reaction kettle, fill it with nitrogen, stir it at a constant speed, heat it to 50-80°C, add polyether polyol dropwise to the kettle, and keep it warm while stirring. After the addition is complete, keep it warm at 60-90°C for 3 hours, cool it and discharge it to obtain component A; (2) grinding diethyltoluenediamine, amino-terminated polyether containing propylene oxide main chain, silica, layered graphite, and polydimethylsiloxane on a three-roll mill to a fineness of ≤45 μm, adding the ground slurry into a reactor, mixing uniformly, filtering with a 200-mesh sieve, and discharging to obtain component B; (3) Component A and component B are metered, heated, and pressurized in a high-pressure spraying device with a fixed ratio of 1:1, mixed evenly through a spray gun, and then sprayed onto the positive impact surface and the back impact surface of the high-strength heat dissipation matrix material. The polyurea buffer layer is cured at rest to finally produce a high-strength heat dissipation battery pack shell material.

5. The method for preparing a high-strength heat-dissipating battery pack shell material according to claim 4, characterized in that: The pressure of the spraying equipment is 55-70 kg / cm 2 The temperature is 60-71℃, the viscosity of components A and B in the spray gun mixing chamber is less than 200cps, and the dynamic pressure difference between components A and B during spraying is less than 14kg / cm 2 .