Composite material battery shell and injection molding method thereof

Abstract

The invention discloses a composite material battery shell and an injection molding method thereof. The injection molding method comprises the following steps: providing a modified fiber with a nickel film layer and a first mixture comprising titanium dioxide-graphene core-shell particles and a fluorinated polyurethane prepolymer; uniformly mixing the modified fibers with the first mixture to obtain a second mixture, and injecting the second mixture into a forming mold with a gradient magnetic field through an injection molding method, so that the modified fibers are oriented and arranged to form a shell-like layered structure; the second mixture injected into the forming mold through an injection molding method is subjected to ultraviolet pre-curing and then subjected to thermocuring, the shell-like layered structure is locked, and a primary material is obtained; and cleaning the surface of the preliminary material, and performing atomic layer deposition on the surface of the preliminary material to obtain the composite material. Biological adhesion on the composite material is reduced through the first mixture, the mechanical property is improved through the modified fiber of the shell-like layered structure, virtuous cycle is achieved, and the service life of the composite material is prevented from being affected.

Description

Technical Field

[0001] The present invention relates to the field of battery preparation, and in particular to a composite material battery shell and an injection molding method thereof. Background Art

[0002] Composite materials are widely used in the manufacture of buoy battery shells due to their light weight, high strength and excellent corrosion resistance. These materials can provide good mechanical protection and ensure the long-term stable operation of the battery in the marine environment. The use of composite materials not only improves the overall performance of the buoy battery, but also effectively extends its service life, becoming an important choice in application fields such as marine monitoring and communications.

[0003] Composite materials are generally made into battery shells by injection molding, which can achieve efficient production and excellent mechanical strength. The injection molding method mixes the polymer matrix with the reinforcing material, heats and melts it, injects it into the mold, and cools and solidifies it to form the desired shape. The injection molding process ensures that the battery shell has excellent impact resistance and heat resistance, meeting the strict requirements of modern battery technology on material performance.

[0004] At present, when composite materials are used as battery shells for ocean buoys, the composite materials will face the problem of damage caused by biological attachment. The composite materials prepared by existing technologies are easily attached by organisms such as barnacles and algae when used. Biological attachment not only increases the surface roughness, but also accelerates the hydrolysis of the composite materials by secreting acidic metabolites. In addition, the mechanical stress caused by biological attachment will also lead to the generation and expansion of microcracks on the composite materials, further reducing the bending strength of the composite materials, thereby causing a significant decrease in the physical and chemical properties of the composite materials. After biological attachment, seawater corrosion will weaken the interface bonding between the resin and the glass fiber in the composite materials, thereby reducing the mechanical properties of the entire composite material. After the mechanical properties of the composite material are reduced, the service life is affected under the influence of the marine environment. The reduced mechanical properties of the composite material will also cause the battery shell to lose structural integrity under water pressure, increase the risk of leakage, and thus affect the electrical performance and safety of the battery.

[0005] Therefore, a composite material battery shell and an injection molding method thereof are proposed to solve the problem that the service life of the composite material in the above-mentioned marine environment is affected by biological attachment. Summary of the invention

[0006] The object of the present invention is to provide a composite material battery casing and an injection molding method thereof, so as to solve the problem that the service life of the composite material is affected by biological attachment in the marine environment.

[0007] To achieve this object, the present invention adopts the following technical solutions: A method for injection molding a composite material battery housing, the injection molding method comprising the following steps: Step S1, providing a modified fiber having a nickel film layer and a first mixture including titanium dioxide-graphene core-shell particles and a fluorinated polyurethane prepolymer; Step S2, uniformly mixing the modified fiber with the first mixture to obtain a second mixture, and injecting the second mixture into a molding mold with a gradient magnetic field by injection molding to orient the modified fiber to form a shell-like layered structure; Step S3, pre-curing the second mixture injected into the molding mold by the injection molding method by ultraviolet light, and then performing thermal curing to lock the shell-like layered structure to obtain a preliminary material; Step S4: cleaning the surface of the preliminary material and performing atomic layer deposition on the surface to obtain a composite material.

[0008] The modified fiber is obtained according to the following steps: Step S11, drying the glass fiber, and then placing the glass fiber in a radio frequency plasma treatment machine for treatment; Step S12, immersing the treated glass fiber in a buffer solution and shaking; Step S13: nickel is plated on the glass fiber by a magnetron sputtering coating machine to form a nickel film layer to obtain a modified fiber.

[0009] In the step S11, the drying temperature is 120-140° C., the time is 3.5-4 hours, the power of the RF plasma treatment machine is 180-200 W, the chamber pressure is 18-20 Pa, the treatment time is 10-15 minutes, and during the treatment, argon gas with a flow rate of 15-17 sccm is introduced into the RF plasma treatment machine; In the step S12, the oscillation time is 10-12h, the rotation speed is 120-200rpm, the buffer is a dopamine-Tris buffer, the dopamine-Tris buffer includes dopamine hydrochloride and Tris-HCl buffer, the mass percentage of dopamine hydrochloride in the dopamine-Tris buffer is 0.2-0.6%, and the rest is Tris-HCl buffer; In the step S13, the nickel film layer has a thickness of 180-200 nm and a magnetization intensity of 1-1.2 T.

[0010] The first mixture is obtained according to the following steps: Step S21, introducing nitrogen into the Grubbs catalyst, the fluorinated polyurethane prepolymer and the dynamic disulfide bond chain extender, and mixing and stirring to obtain a mixture A; Step S22, adding polyethersulfone toughened microspheres and nanoclay to the mixture A for ultrasonic dispersion to obtain a resin matrix; Step S23: adding titanium dioxide-graphene core-shell particles and microcapsules into a resin matrix, mixing and stirring to obtain a first mixture.

[0011] In step S21, the mass percentages of the Grubbs catalyst and the dynamic disulfide bond chain extender in the mixture are 0.5-1% and 6-8% respectively, and the rest is a fluorinated polyurethane prepolymer. The mixing and stirring speed is 500-700 rpm, the time is 2-2.5h, and the temperature is 60-70°C; In the step S22, the mass percentages of the polyethersulfone toughened microspheres and nanoclay in the resin matrix are 5-7% and 2-4% respectively, and the rest is mixture A. The ultrasonic dispersion power is 350-400W, the frequency is 40-60kHz, and the time is 1-2h; In the step S23, the mass percentages of the titanium dioxide-graphene core-shell particles and the microcapsules in the first mixture are 5-9% and 3-5% respectively, and the rest is a resin matrix. The mixing and stirring speed is 300-600 rpm and the time is 1.5-2h.

[0012] The modified fiber accounts for 55-60% by weight in the second mixture, and the rest is the first mixture; An outer electromagnetic coil and an inner electromagnetic coil are respectively arranged on the outer wall and inner cavity of the molding mold; after the second mixture is injected into the molding mold by injection molding, the outer electromagnetic coil is connected to a power source, and the current flows in a clockwise direction, so that the outer electromagnetic coil generates a toroidal magnetic field, driving the modified fibers to be arranged in a toroidal direction; after the inner electromagnetic coil is connected to a power source, the current flows in a radial direction, generating a radial magnetic field to assist the modified fiber support structure, and a gradient magnetic field that gradually weakens from the outside to the inside is formed through the toroidal magnetic field and the radial magnetic field distributed inside and outside, so that the modified fibers are oriented and arranged to form a shell-like layered structure.

[0013] The molding die is provided with a quartz glass window for allowing ultraviolet light to penetrate the second mixture. The ultraviolet light reacts with the fluorinated polyurethane prepolymer in the second mixture to pre-cure the second mixture. After the ultraviolet pre-curing is completed, the second mixture is subjected to three-stage thermal curing. After the thermal curing is completed, the shell-like layered structure is locked to obtain a preliminary material formed by injection molding.

[0014] The three-stage thermal curing is divided into the first stage thermal curing, the second stage thermal curing and the third stage thermal curing. The temperature of the first stage thermal curing is 45-55°C and the time is 0.5-1h, the temperature of the second stage thermal curing is 70-80°C and the time is 3-3.5h, and the temperature of the first stage thermal curing is 60-70°C and the time is 1-2h.

[0015] After cleaning the preliminary material formed by injection molding, the preliminary material is placed in an ALD reaction chamber for atomic layer deposition, and the ALD reaction chamber is evacuated to a base pressure of ≤0.1Pa, and then nitrogen plasma is introduced to clean the surface of the preliminary material and enhance the activity, followed by a trimethylaluminum pulse, and a first nitrogen purge is performed after the trimethylaluminum pulse is completed, and a water vapor pulse is performed after the first nitrogen purge is completed, and a second nitrogen purge is performed after the water vapor pulse is completed, and the above steps are repeated 200-220 times, and an aluminum oxide protective layer is deposited on the surface of the preliminary material to finally obtain a composite material; The deposition temperature is 150-180° C., the trimethylaluminum pulse time is 0.1-0.2 s, the first nitrogen purge time is 10-15 s, the water vapor pulse time is 0.1-0.2 s, and the second nitrogen purge time is 10-15 s.

[0016] A composite material battery shell is produced by the injection molding method of the composite material battery shell as described above.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. A composite battery shell and an injection molding method thereof of the present invention reduces biological attachment on the composite material and improves corrosion resistance through titanium dioxide-graphene core-shell particles and fluorinated polyurethane prepolymers in a first mixture, alleviates the hydrolysis of the composite material and the reduction of bending strength caused by biological attachment, and the titanium dioxide-graphene core-shell particles are excited by ultraviolet light to produce active oxygen during the injection molding and curing process of the composite material, which can reduce biological attachment, and the fluorine segments in the fluorinated polyurethane prepolymer improve the corrosion resistance of the composite material obtained by injection molding. At the same time, under the action of modified fibers that form a shell-like layered structure, the mechanical properties of the composite material are improved, the generation and expansion of microcracks are reduced, thereby reducing the anchoring points of biological attachment, and the composite material achieves a virtuous cycle under the cooperation of the first mixture and the modified fibers that form a shell-like layered structure, thereby avoiding the composite material The service life is affected by biological attachment.

[0018] 2. The present invention provides a composite material battery shell and an injection molding method thereof. When the first mixture is cured with modified fibers to form a composite material, the titanium dioxide-graphene core-shell particles in the first mixture cooperate with ultraviolet light in the subsequent curing process to produce active oxygen to destroy the microbial mucus layer, and cooperate with an aluminum oxide protective layer to reduce biological attachment.

[0019] 3. A composite material battery shell and its injection molding method of the present invention can absorb impact energy through the special structure of polyethersulfone toughened microspheres, so that the impact toughness of the prepared composite material is improved. Under the gradient magnetic field orientation, the distribution of the modified fibers reduces stress concentration and the fatigue life is obtained. In addition, the lamellar structure of nanoclay can also block crack propagation to ensure the bending strength of the prepared composite material, making the composite material suitable for marine environment.

[0020] 4. The present invention provides a composite material battery shell and an injection molding method thereof. By orienting the modified fibers in a gradient magnetic field, the thermal expansion coefficient of the obtained composite material can be reduced, thereby avoiding the risk of stratification caused by the temperature difference between day and night. In addition, the oriented modified fibers form a conductive continuous network under the action of the nickel film layer, which improves the shielding efficiency of the prepared composite material, thereby improving the shielding effect on the internal structure of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0022] The structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with the technology. They are not used to limit the conditions under which the present invention can be implemented, and therefore have no substantive technical significance. Any structural modification, change in proportion or adjustment of size shall still fall within the scope of the technical contents disclosed in the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0023] Figure 1 It is a flowchart of the injection molding method of the present invention. DETAILED DESCRIPTION

[0024] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] In the description of the present invention, it should be understood that the terms "upper", "lower", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. It should be noted that when a component is considered to be "connected" to another component, it may be directly connected to the other component or there may be a centrally arranged component at the same time.

[0026] Embodiment 1: See also Figure 1 In this embodiment, a composite material battery shell injection molding method is provided, and the injection molding method comprises the following steps: Step S1, providing a modified fiber having a nickel film layer and a first mixture including titanium dioxide-graphene core-shell particles and a fluorinated polyurethane prepolymer; It should be noted that the modified fiber has good magnetic field responsiveness and interface bonding strength through the nickel film layer, which provides a basis for subsequent orientation arrangement. The prepared first mixture lays a chemical and physical foundation for the subsequent long-life application of composite materials in the marine environment.

[0027] The modified fiber is obtained according to the following steps: Step S11, drying the glass fiber, and then placing the glass fiber in a radio frequency plasma treatment machine for treatment; In step S11, the drying temperature is 120-140° C., the time is 3.5-4 hours, the power of the RF plasma treatment machine is 180-200 W, the chamber pressure is 18-20 Pa, the treatment time is 10-15 minutes, and during the treatment, argon gas with a flow rate of 15-17 sccm is introduced into the RF plasma treatment machine; Preferably, in step S11, the drying temperature is 120°C, the time is 4 hours, the power of the RF plasma processor is 200W, the chamber pressure is 20Pa, the processing time is 10 minutes, and during the processing, argon gas with a flow rate of 15 sccm is introduced into the RF plasma processor.

[0028] It should be noted that drying the glass fiber can remove moisture and volatile organic matter adsorbed on the surface of the glass fiber, avoiding residual moisture that may cause uneven subsequent plasma treatment, so as to ensure the stability of subsequent treatment.

[0029] Step S12, immersing the treated glass fiber in a buffer solution and shaking; In step S12, the oscillation time is 10-12h, the rotation speed is 120-200rpm, the buffer is dopamine-Tris buffer, the dopamine-Tris buffer includes dopamine hydrochloride and Tris-HCl buffer, the mass percentage of dopamine hydrochloride in the dopamine-Tris buffer is 0.2-0.6%, and the rest is Tris-HCl buffer; preferably, the oscillation time is 12h, the rotation speed is 120rpm; the mass percentage of dopamine hydrochloride in the dopamine-Tris buffer is 0.2%, and the rest is Tris-HCl buffer.

[0030] It should be noted that when the glass fiber is subjected to plasma treatment, argon plasma bombards the surface of the glass fiber, generating amino groups and hydroxyl groups on its surface, thereby increasing the surface energy of the glass fiber. Subsequently, when the glass fiber is oscillated in a buffer solution, it reacts with the buffer solution to form a polydopamine coating on the surface of the glass fiber. The polydopamine coating is then formed through covalent bonds with the amino groups and hydroxyl groups on the surface of the glass fiber to form a stable physical adsorption bond, thereby enhancing the interfacial shear strength and interfacial bonding force of the glass fiber.

[0031] Specifically, the pH value of the dopamine-Tris buffer is 8.5. When the glass fiber and the dopamine-Tris buffer are mixed and oscillated, the catechol structure in the dopamine-Tris buffer is oxidized to o-benzoquinone, and o-benzoquinone forms a cross-linked network through Michael addition or Schiff base reaction or amino and hydroxyl groups on the surface of the glass fiber. The cross-linked product is gradually deposited on the surface of the glass fiber to form a dense and highly adhesive polydopamine coating.

[0032] It should be emphasized that the polydopamine coating on the glass fiber is both hydrophilic and chemically active, which can provide binding sites for subsequent nickel plating on the glass fiber and facilitate subsequent mixing with the second mixture.

[0033] In addition, the enhanced interfacial shear force of the glass fiber can allow the glass fiber to withstand greater orientation stress in the subsequent gradient magnetic field and avoid arrangement deviation. At the same time, the enhanced interfacial shear force of the glass fiber can also improve the mechanical properties of the prepared composite material and enhance the impact resistance of the prepared composite material.

[0034] In addition, after step S12 is completed, the glass fiber needs to be removed by rinsing with deionized water for multiple times and vacuum drying at 60° C. for 2 h.

[0035] It is known that unreacted oxidation byproducts and physically adsorbed impurities on the glass fiber can be removed by cleaning to prevent residues from interfering with subsequent nickel plating. Vacuum drying can also make the polydopamine coating more thoroughly cross-linked and improve solvent resistance.

[0036] Step S13: nickel is plated on the glass fiber by a magnetron sputtering coating machine to form a nickel film layer to obtain a modified fiber.

[0037] In step S13, the nickel film layer has a thickness of 180-200 nm and a magnetization intensity of 1-1.2 T. Preferably, the nickel film layer has a thickness of 200 nm and a magnetization intensity of 1.2 T.

[0038] It should be noted that by nickel plating the glass fiber, the glass fiber can respond to the external magnetic field, so that the glass fiber can be oriented and arranged under the action of the external magnetic field when the subsequent second mixture is poured and solidified, so that the mechanical properties, thermal stability and functional characteristics of the prepared composite material are enhanced; at the same time, the nickel film layer formed by nickel plating is formed on the polydopamine coating, and the two can prevent the nickel film layer from falling off after chemical bonding.

[0039] In addition, after the nickel plating is completed, the modified fiber can be subjected to an annealing treatment at a temperature of 200° C. for 1 hour.

[0040] It is known that the high-speed deposition of nickel atoms during sputtering will cause lattice distortion and residual stress. Annealing repairs defects through atomic diffusion and reduces the risk of peeling of the coating layer. Annealing can also promote the interface diffusion between the nickel film layer and the polydopamine coating to improve the chemical bonding effect. After annealing of the coating layer, the nickel grain size is increased, the coercive force is reduced, the magnetic response sensitivity is improved, and the subsequent magnetic field orientation stability is ensured.

[0041] The first mixture is obtained according to the following steps: Step S21, introducing nitrogen into the Grubbs catalyst, the fluorinated polyurethane prepolymer and the dynamic disulfide bond chain extender, and mixing and stirring to obtain a mixture A; In step S21, the mass percentages of Grubbs catalyst and dynamic disulfide bond extender in the mixture are 0.5-1% and 6-8% respectively, and the rest is fluorinated polyurethane prepolymer, and the mixing and stirring speed is 500-700 rpm, the time is 2-2.5 hours, and the temperature is 60-70°C; Preferably, in step S21, the mass percentages of Grubbs catalyst and dynamic disulfide bond extender in the mixture are 0.5% and 6% respectively, the rest is fluorinated polyurethane prepolymer, the mixing and stirring speed is 500 rpm, the time is 2 hours, and the temperature is 60°C; It should be noted that the dynamic disulfide bonds in the dynamic disulfide chain extender can be reversibly broken / recombined in a high temperature environment or under ultraviolet light, which can give the first mixture obtained subsequently self-healing ability. The fluorine segments in the fluorinated polyurethane prepolymer can reduce the surface energy of the first mixture and improve its corrosion resistance, thereby reducing the corrosion of the subsequently prepared composite material by biological attachment and the marine environment. Therefore, the functionality of the composite material prepared according to the first mixture is improved.

[0042] It should be emphasized that the mixing and stirring temperature of 60°C can reduce the viscosity during mixing, ensure the uniform dispersion of the dynamic disulfide bond chain extender, and the passage of nitrogen during mixing and stirring can also prevent the dynamic disulfide bond from oxidative failure.

[0043] Step S22, adding polyethersulfone toughened microspheres and nanoclay to the mixture A for ultrasonic dispersion to obtain a resin matrix; In step S22, the mass percentages of polyethersulfone toughened microspheres and nanoclay in the resin matrix are 5-7% and 2-4% respectively, the rest is mixture A, and the ultrasonic dispersion power is 350-400W, the frequency is 40-60kHz, and the time is 1-2h; Preferably, in step S22, the mass percentages of polyethersulfone toughened microspheres and nanoclay in the resin matrix are 5% and 2% respectively, the rest is mixture A, and the ultrasonic dispersion power is 400W, the frequency is 40kHz, and the time is 1h; It should be noted that the special structure of polyethersulfone toughened microspheres allows the resulting resin matrix to absorb impact energy to prevent crack propagation, thereby improving the mechanical properties of the composite material and reducing the anchor points for biological attachment. At the same time, nanoclay can also allow the resin matrix to form a lamellar structure to extend the seawater penetration path of the composite material and enhance the functionality of the composite material.

[0044] It is understandable that the gaps and depressions in the cracks increase the surface roughness, making it easier for organisms such as barnacles and algae to fix themselves by secreting adhesive substances; at the same time, organic debris and nutrients are easily accumulated inside the cracks, attracting microorganisms to gather and form biofilms, further accelerating corrosion and adhesion and diffusion.

[0045] Step S23: adding titanium dioxide-graphene core-shell particles and microcapsules into a resin matrix, mixing and stirring to obtain a first mixture.

[0046] In step S23, the mass percentages of titanium dioxide-graphene core-shell particles and microcapsules in the first mixture are 5-9% and 3-5% respectively, and the rest is a resin matrix. The mixing and stirring speed is 300-600 rpm and the time is 1.5-2h; Preferably, in step S23, the mass percentages of titanium dioxide-graphene core-shell particles and microcapsules in the first mixture are 5% and 3% respectively, the rest is a resin matrix, and the mixing and stirring speed is 300 rpm and the time is 1.5 h; It should be noted that the titanium dioxide-graphene core-shell particles generate electron-hole pairs under the excitation of the cured ultraviolet light, which react with the H 2 O / O 2The reaction generates active oxygen, which can destroy microbial cell membranes, inhibit microbial metabolism and reproduction, and reduce biofilm formation. Barnacles must first attach to the surface of the composite material by secreting mucus proteins. Active oxygen can destroy the mucus layer formed by barnacles and prevent barnacles from anchoring, thereby reducing barnacle attachment. At the same time, the acidic metabolites secreted by microbial cell membranes during metabolism and reproduction will accelerate the corrosion of composite materials. The corrosion rate can be effectively reduced by inhibiting biofilm.

[0047] It should also be emphasized that the composite material is prepared by the first mixture, and a continuous conductive network can be formed under the action of the graphene core in the titanium dioxide-graphene core-shell particles, thereby reducing the surface resistance of the composite material, achieving electrostatic dissipation, and preventing the adsorption of microorganisms due to static electricity; the titanium dioxide-graphene core-shell particles are a core-shell structure composite material formed by titanium dioxide nanoparticles and graphene, and its core structure is that titanium dioxide nanoparticles are uniformly loaded on the surface of the graphene sheet to form a tight interface bonding.

[0048] It is known that when crack extension stress appears in the composite material, the microcapsule will rupture, releasing the dicyclopentadiene core material, and reacting with the Grubbs catalyst in the resin matrix to generate polydicyclopentadiene to fill the deep cracks. By filling the cracks, the anchor points for biological attachment are reduced, and the corrosion and delamination of the composite material accelerated by seawater penetration, which reduces the mechanical properties, is avoided. When cracks appear on the composite material, repair is automatically triggered without human intervention. At the same time, the dynamic reorganization of the dynamic disulfide bonds in the dynamic disulfide chain extender can also fill the surface cracks caused by crack extension stress, thereby achieving double repair.

[0049] Furthermore, when the first mixture is mixed and stirred, it is necessary to stir it in an environment with a vacuum degree of 0.5 kPa.

[0050] It is understandable that the vacuum environment can eliminate bubbles in the first mixture to avoid the composite material from forming excessively large pores due to bubbles after molding, thereby reducing the mechanical properties and corrosion resistance of the composite material.

[0051] It should also be noted that through the synergy of titanium dioxide-graphene core-shell particles and microcapsules, active oxygen can reduce biological attachment while triggering dynamic disulfide bond recombination and polydicyclopentadiene filling to deeply repair microcracks, thereby resisting the synergistic damage of biology and corrosion in all directions and improving the comprehensive performance of the composite material.

[0052] Step S2, uniformly mixing the modified fiber with the first mixture to obtain a second mixture, and injecting the second mixture into a molding mold with a gradient magnetic field by injection molding to orient the modified fiber to form a shell-like layered structure; It should be noted that the modified fibers in the second mixture injected into the molding mold by the injection molding method are oriented and arranged through the gradient magnetic field, so that the modified fibers are transformed from the original chaotic distribution into a shell-like layered structure, thereby improving the mechanical properties of the obtained composite material; the natural shell structure is composed of multiple layers of fibers or layers arranged alternately in a specific direction (such as circumferential and radial directions), and has the characteristics of high strength, high toughness, and crack deflection.

[0053] Specifically, when the modified fiber is mixed with the first mixture, it is necessary to stir at a speed of 200 rpm for 30 minutes in an environment of vacuum degree of 0.1 kPa to eliminate bubbles and reduce the porosity of the prepared composite material to improve bending strength, reduce stress concentration, and delay crack propagation; the mass percentage of the modified fiber in the second mixture is 55-60%, and the rest is the first mixture; preferably, the mass percentage of the modified fiber in the second mixture is 58%, and the rest is the first mixture.

[0054] It should be noted that an outer electromagnetic coil and an inner electromagnetic coil are respectively arranged on the outer wall and the inner cavity of the molding mold; after the second mixture is injected into the molding mold by injection molding, after the outer electromagnetic coil is connected to a power source, the current flows in a clockwise direction, causing the outer electromagnetic coil to generate a toroidal magnetic field, driving the modified fibers to be arranged in a toroidal direction; after the inner electromagnetic coil is connected to a power source, the current flows radially to generate a radial magnetic field, assisting the modified fiber support structure, and forming a gradient magnetic field that gradually weakens from the outside to the inside through the toroidal magnetic field and the radial magnetic field distributed inside and outside, so that the modified fibers can be oriented and arranged to form a shell-like layered structure; specifically, the outer electromagnetic coil generates a toroidal magnetic field of 0.8T, and the inner electromagnetic coil generates a radial magnetic field of 0.3T.

[0055] It should also be noted that after the outer electromagnetic coil and the inner electromagnetic coil are connected to a power source, the modified fiber generates a magnetic torque under the action of the magnetic field, and the magnetic torque drives the modified fiber to rotate to the direction of the magnetic field, and finally arranged along the magnetic field lines; specifically, the strong annular magnetic field generated by the outer electromagnetic coil causes the modified fiber to be highly annularly arranged, thereby improving the circumferential tensile strength, and the weak radial magnetic field generated by the inner electromagnetic coil causes part of the modified fiber to be radially distributed to form a supporting structure.

[0056] It should be emphasized that the modified fibers are oriented to form a shell-like layered structure by forming an alternating arrangement of the modified fibers and the first mixture. When cracks appear in the composite material, the cracks are forced to deflect in a circuitous manner during expansion, which significantly absorbs impact energy and improves the fracture toughness of the composite material. At the same time, under the enhanced interfacial bonding force of the modified fibers, interlaminar delamination is effectively inhibited, the bending strength is improved, and the mechanical properties of the composite material are improved.

[0057] It can be known that after the modified fibers are oriented, the circumferential tensile strength and impact toughness of the formed composite materials can be improved and stress concentration can be reduced. At the same time, the oriented arrangement of the modified fibers can also reduce the thermal expansion coefficient of the obtained composite materials and reduce the risk of delamination caused by thermal cycles. In addition, the oriented modified fibers form a conductive continuous network under the action of the nickel film layer, which improves the shielding efficiency of the prepared composite materials, thereby improving the shielding effect on the internal structure of the battery.

[0058] It is understandable that the composite material's thermal expansion coefficient is reduced, reducing the risk of delamination caused by thermal cycles. It can also avoid the composite material as a battery shell in a marine environment. Due to the temperature difference between day and night, the battery shell will repeatedly expand and contract. Seawater penetrates between layers through microcracks, causing delamination under thermal stress and reducing the compression strength.

[0059] Step S3, pre-curing the second mixture injected into the molding mold by the injection molding method by ultraviolet light, and then performing thermal curing to lock the shell-like layered structure to obtain a preliminary material; It should be noted that a quartz glass window is provided on the molding mold for ultraviolet light to penetrate the second mixture. The ultraviolet light reacts with the fluorinated polyurethane prepolymer in the second mixture to form a pre-cured second mixture. The ultraviolet light also simultaneously activates the titanium dioxide-graphene core-shell particles to produce active oxygen, so that the surface of the obtained composite material can reduce biological attachment. After the ultraviolet pre-curing is completed, the second mixture is subjected to three-stage thermal curing. During the thermal curing, the second mixture is initially gelled to lock the shell-like layered structure formed by the oriented arrangement of the modified fibers. After cross-linking is completed, the second mixture gradually becomes a preliminary material with improved mechanical strength. Finally, the dynamic disulfide bonds are reorganized to repair the defects caused by thermal stress during thermal curing, release residual stress, and improve stability to obtain a preliminary material formed by injection molding.

[0060] It should be emphasized that the fluorinated polyurethane prepolymer has acrylate end groups. The acrylate end groups, as photosensitive groups, can react ultraviolet light with the fluorinated polyurethane prepolymer to generate active free radicals. The active free radicals trigger the opening of the double bonds of the acrylate end groups, and free radical polymerization and cross-linking occur to form a pre-cure; the three-stage thermal curing is divided into the first stage thermal curing, the second stage thermal curing, and the third stage thermal curing. The temperature of the first stage thermal curing is 45-55°C and the time is 0.5-1h, the temperature of the second stage thermal curing is 70-80°C and the time is 3-3.5h, and the temperature of the first stage thermal curing is 60-70°C and the time is 1-2h; preferably, the three-stage thermal curing is divided into the first stage thermal curing, the second stage thermal curing, and the third stage thermal curing. The temperature of the first stage thermal curing is 50°C and the time is 1h, the temperature of the second stage thermal curing is 80°C and the time is 3h, and the temperature of the first stage thermal curing is 60°C and the time is 2h.

[0061] Step S4: cleaning the surface of the preliminary material and performing atomic layer deposition on the surface to obtain a composite material.

[0062] Specifically, after the preliminary material formed by injection molding is cleaned, it is placed in an ALD reaction chamber for atomic layer deposition, and the ALD reaction chamber is evacuated to a basic pressure of ≤0.1Pa, and then nitrogen plasma is introduced to clean the surface of the preliminary material and enhance the activity, followed by a trimethylaluminum pulse, and a first nitrogen purge is performed after the trimethylaluminum pulse is completed, and a water vapor pulse is performed after the first nitrogen purge is completed, and a second nitrogen purge is performed after the water vapor pulse is completed, and the above steps are repeated 200-220 times, and an aluminum oxide protective layer is deposited on the surface of the preliminary material to finally obtain a composite material; preferably, the above steps are repeated 200 times.

[0063] It should be emphasized that the deposition temperature is 150-180°C, and the trimethylaluminum pulse time is 0.1-0.2s. The trimethylaluminum pulse can chemically adsorb the dimethylaluminum group on the surface of the preliminary material, and then the first nitrogen purge of 10-15s can remove the unadsorbed trimethylaluminum and reaction by-products on the preliminary material; the water vapor pulse time is 0.1-0.2s, and the water vapor pulse can oxidize the dimethylaluminum group attached to the surface of the preliminary material due to the trimethylaluminum pulse, and then the second nitrogen purge of 10-15s can remove the residual water vapor and by-products on the surface of the preliminary material; the deposition temperature is 150°C, the trimethylaluminum pulse time is 0.1s, the first nitrogen purge time is 10s, the water vapor pulse time is 0.1s, and the second nitrogen purge time is 10s.

[0064] It can be known that the alumina protective layer on the composite material, due to its low surface energy and combined with micro-nano structure, further reduces biological attachment. At the same time, the deposited alumina protective layer forms a dense layer, which effectively isolates the seawater and avoids the corrosion of the composite material by seawater. The alumina protective layer can make the composite material have a higher surface hardness, resist barnacle drilling, and increase the service life of the composite material.

[0065] It is understandable that after the composite material is obtained in step S4, the composite material can be used as a battery shell without further processing.

[0066] Embodiment 2: A composite material battery shell in this embodiment is manufactured by the injection molding method of the composite material battery shell in Example 1.

[0067] The performance test of a composite material battery shell and a composite material battery shell made by the injection molding method according to the present invention is as follows: Performance tests include biological adhesion test, mechanical property test, corrosion resistance test and fatigue life test.

[0068] Table 1: Biological adhesion test of the composite battery shell (treatment group) and the ordinary battery shell (control group) The biological attachment test is as follows: the sensor is placed in artificial seawater, inoculated with marine Chlorella solution, the measurement frequency is fixed as the sensitive frequency, the change of the sensor impedance value over time is measured, and the attachment of Chlorella on the electrode at any time is expressed by the cell index to obtain the biological attachment of the treatment group and the control group; According to the test data in Table 1, the number of biological attachments in the treatment group is much lower than that in the control group; Table 2: Mechanical properties test of composite battery shell (treatment group) and ordinary battery shell (control group) The mechanical property test is as follows: the treatment group and the control group are subjected to a tensile test by a fixture, and the force-displacement curves of the two during the tensile process are recorded to obtain the tensile strength data of the two; the treatment group and the control group are subjected to a vibration fatigue evaluation method to obtain the bending strength data of the two; the treatment group and the control group are subjected to an impact toughness test by a mechanical detection device with a built-in impact mechanism to obtain the impact toughness data of the two; according to the test data in Table 2, the tensile strength of the treatment group is increased by about 33% compared with that of the control group, the bending strength of the treatment group is increased by about 33% compared with that of the control group, and the impact toughness of the treatment group is increased by about 67% compared with that of the control group; Table 3: Corrosion resistance test of the composite battery shell (treatment group) and the ordinary battery shell (control group) The corrosion resistance test is as follows: according to the marine environment where the battery shell is located, the sample and the reference electrode are fixed at the corresponding position on the sample rack and connected to the corrosion monitoring and detection module through a wire, and the propeller speed, water bath temperature, illumination time, environmental humidity, liquid level fluctuation cycle and erosion intensity and time of the corrosion test module are determined according to the simulated sea area characteristics, and the control module is used to automatically open or close different functional components to simulate the marine environment, so as to simulate the corrosion resistance test of the sample in the simulated marine environment; according to the test data in Table 3, it is known that the corrosion rate of the treatment group is significantly lower than that of the control group; Table 4: Fatigue life test of composite battery shell (treatment group) and ordinary battery shell (control group) The fatigue life test is as follows: the fatigue life data of the treatment group and the control group are predicted through environmental aging data and finite element simulation to obtain the fatigue life data of the two; according to the test data in Table 4, it is known that the fatigue life of the treatment group is increased by about 67%.

[0069] From the above description, it can be known that the titanium dioxide-graphene core-shell particles and fluorinated polyurethane prepolymer in the first mixture reduce biological attachment on the composite material and improve corrosion resistance, alleviate the hydrolysis of the composite material and the reduction of bending strength caused by biological attachment, and the titanium dioxide-graphene core-shell particles are excited by ultraviolet light to produce active oxygen during the injection molding and curing process of the composite material, which can reduce biological attachment, and the fluorine segments in the fluorinated polyurethane prepolymer improve the corrosion resistance of the composite material obtained by injection molding. At the same time, under the action of modified fibers that form a shell-like layered structure, the mechanical properties of the composite material are improved, and the generation and expansion of microcracks are reduced, thereby reducing the anchoring points of biological attachment. The composite material achieves a virtuous cycle under the cooperation of the first mixture and the modified fibers that form a shell-like layered structure, thereby avoiding the service life of the composite material being affected by biological attachment.

[0070] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for injection molding a composite material battery housing, characterized in that: The injection molding method comprises the following steps: Step S1, providing a modified fiber having a nickel film layer and a first mixture including titanium dioxide-graphene core-shell particles and a fluorinated polyurethane prepolymer; Step S2, uniformly mixing the modified fiber with the first mixture to obtain a second mixture, and injecting the second mixture into a molding mold with a gradient magnetic field by injection molding to orient the modified fiber to form a shell-like layered structure; Step S3, pre-curing the second mixture injected into the molding mold by the injection molding method by ultraviolet light, and then performing thermal curing to lock the shell-like layered structure to obtain a preliminary material; Step S4: cleaning the surface of the preliminary material and performing atomic layer deposition on the surface to obtain a composite material.

2. The injection molding method of a composite material battery housing according to claim 1, characterized in that: The modified fiber is obtained according to the following steps: Step S11, drying the glass fiber, and then placing the glass fiber in a radio frequency plasma treatment machine for treatment; Step S12, immersing the treated glass fiber in a buffer solution and shaking; Step S13: nickel is plated on the glass fiber by a magnetron sputtering coating machine to form a nickel film layer to obtain a modified fiber.

3. The injection molding method of a composite material battery housing according to claim 2, characterized in that: In the step S11, the drying temperature is 120-140° C., the time is 3.5-4 hours, the power of the RF plasma treatment machine is 180-200 W, the chamber pressure is 18-20 Pa, the treatment time is 10-15 minutes, and during the treatment, argon gas with a flow rate of 15-17 sccm is introduced into the RF plasma treatment machine; In the step S12, the oscillation time is 10-12h, the rotation speed is 120-200rpm, the buffer is a dopamine-Tris buffer, the dopamine-Tris buffer includes dopamine hydrochloride and Tris-HCl buffer, the mass percentage of dopamine hydrochloride in the dopamine-Tris buffer is 0.2-0.6%, and the rest is Tris-HCl buffer; In the step S13, the thickness of the nickel film layer is 180-200 nm, and the magnetization intensity is 1-1.2 T.

4. The injection molding method of a composite material battery housing according to claim 1, characterized in that: The first mixture is obtained according to the following steps: Step S21, introducing nitrogen into the Grubbs catalyst, the fluorinated polyurethane prepolymer and the dynamic disulfide bond chain extender, and mixing and stirring to obtain a mixture A; Step S22, adding polyethersulfone toughened microspheres and nanoclay to the mixture A for ultrasonic dispersion to obtain a resin matrix; Step S23: adding titanium dioxide-graphene core-shell particles and microcapsules into a resin matrix, mixing and stirring to obtain a first mixture.

5. The injection molding method of a composite material battery housing according to claim 4, characterized in that: In step S21, the mass percentages of the Grubbs catalyst and the dynamic disulfide bond chain extender in the mixture are 0.5-1% and 6-8% respectively, and the rest is a fluorinated polyurethane prepolymer. The mixing and stirring speed is 500-700 rpm, the time is 2-2.5h, and the temperature is 60-70°C; In the step S22, the mass percentages of the polyethersulfone toughened microspheres and nanoclay in the resin matrix are 5-7% and 2-4% respectively, and the rest is mixture A. The ultrasonic dispersion power is 350-400W, the frequency is 40-60kHz, and the time is 1-2h; In the step S23, the mass percentages of the titanium dioxide-graphene core-shell particles and the microcapsules in the first mixture are 5-9% and 3-5% respectively, and the rest is a resin matrix. The mixing and stirring speed is 300-600 rpm and the time is 1.5-2h.

6. The injection molding method of a composite material battery housing according to claim 1, characterized in that: The modified fiber accounts for 55-60% by weight in the second mixture, and the rest is the first mixture; An outer electromagnetic coil and an inner electromagnetic coil are respectively arranged on the outer wall and inner cavity of the molding mold; after the second mixture is injected into the molding mold by injection molding, the outer electromagnetic coil is connected to a power source, and the current flows in a clockwise direction, so that the outer electromagnetic coil generates a toroidal magnetic field, driving the modified fibers to be arranged in a toroidal direction; after the inner electromagnetic coil is connected to a power source, the current flows in a radial direction, generating a radial magnetic field to assist the modified fiber support structure, and a gradient magnetic field that gradually weakens from the outside to the inside is formed through the toroidal magnetic field and the radial magnetic field distributed inside and outside, so that the modified fibers are oriented and arranged to form a shell-like layered structure.

7. The injection molding method of a composite material battery housing according to claim 1, characterized in that: The molding die is provided with a quartz glass window for allowing ultraviolet light to penetrate the second mixture. The ultraviolet light reacts with the fluorinated polyurethane prepolymer in the second mixture to pre-cure the second mixture. After the ultraviolet pre-curing is completed, the second mixture is subjected to three-stage thermal curing. After the thermal curing is completed, the shell-like layered structure is locked to obtain a preliminary material formed by injection molding.

8. The injection molding method of a composite material battery casing according to claim 7, characterized in that: The three-stage thermal curing is divided into the first stage thermal curing, the second stage thermal curing and the third stage thermal curing. The temperature of the first stage thermal curing is 45-55°C and the time is 0.5-1h, the temperature of the second stage thermal curing is 70-80°C and the time is 3-3.5h, and the temperature of the first stage thermal curing is 60-70°C and the time is 1-2h.

9. The injection molding method of a composite material battery casing according to claim 1, characterized in that: After cleaning the preliminary material formed by injection molding, the preliminary material is placed in an ALD reaction chamber for atomic layer deposition, and the ALD reaction chamber is evacuated to a base pressure of ≤0.1Pa, and then nitrogen plasma is introduced to clean the surface of the preliminary material and enhance the activity, followed by a trimethylaluminum pulse, and a first nitrogen purge is performed after the trimethylaluminum pulse is completed, and a water vapor pulse is performed after the first nitrogen purge is completed, and a second nitrogen purge is performed after the water vapor pulse is completed, and the above steps are repeated 200-220 times, and an aluminum oxide protective layer is deposited on the surface of the preliminary material to finally obtain a composite material; The deposition temperature is 150-180° C., the trimethylaluminum pulse time is 0.1-0.2 s, the first nitrogen purge time is 10-15 s, the water vapor pulse time is 0.1-0.2 s, and the second nitrogen purge time is 10-15 s.

10. A composite material battery casing, characterized in that: The composite material battery shell is manufactured by the injection molding method as described in claims 1 to 9.

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