High polymer material for new energy automobile battery pack and preparation method of high polymer material

Abstract

The invention provides a high polymer material for a new energy automobile battery pack and a preparation method thereof.The preparation method comprises the steps that main chain polyether glycol and functional isocyanate are mixed according to a preset proportion, preliminary heating is conducted, and a polyurethane prepolymer is generated; adding a particle reinforcing agent into the polyurethane prepolymer while stirring for several times, and then adding a dynamic cross-linking agent to obtain a mixture; and heating the mixture to 80-100 DEG C, reducing the stirring speed to 500-1000 rpm, detecting the viscosity of the mixture until the viscosity reaches a preset viscosity range, stopping heating and stirring, and transferring the mixture into a mold for cooling to obtain the high polymer material for the new energy automobile battery pack. The material can automatically repair microcracks, prevent crack propagation and prolong the service life of the material.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy vehicle materials, and particularly relates to a polymer material for a new energy vehicle battery pack and a preparation method thereof. Background Art

[0002] The battery pack of a new energy vehicle is the core component of an electric vehicle, undertaking the key functions of storing and releasing electric energy. During the driving process of a new energy vehicle, it will be subjected to various vibrations and impacts such as uneven roads, acceleration, and braking. The battery pack contains a large amount of energy. If it is impacted and short-circuited or mechanically damaged, it may trigger thermal runaway, leading to fire or explosion.

[0003] In related technologies, a protective material made of high-strength plastic can absorb these forces and prevent the battery cells from shifting or cracking. In the event of a collision or other unexpected situations, the protective material can provide an additional protective layer for the battery pack, reducing the risk of damage. However, in daily use, multiple minor impacts will also affect the protective material, and microcracks are likely to appear. Microcracks will weaken the overall mechanical strength and toughness of the protective material, reduce its load-bearing capacity, and the microcracks will gradually expand under the action of stress and eventually develop into macroscopic cracks, presenting safety risks. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a polymer material for a new energy vehicle battery pack and a preparation method thereof, aiming to solve the problem of easy appearance of microcracks, resulting in an increased safety risk.

[0005] To solve the above problems, the present invention proposes a preparation method for a polymer material for a new energy vehicle battery pack, and the steps include: S1. Mix the main-chain polyether diol and the functionalized isocyanate in a preset ratio and perform preliminary heating to generate a polyurethane prepolymer, wherein the preliminary heating temperature is 60 - 70 °C and the heating time is 60 - 120 min; S2. Gradually stir and add the particulate reinforcing agent to the polyurethane prepolymer, and then add the dynamic crosslinking agent to obtain a mixture, wherein the stirring speed is 2000 - 3000 rpm and the stirring time is 30 - 60 min; S3. Heat the mixture to 80 - 100 °C, reduce the stirring speed to 500 - 1000 rpm, detect that the viscosity of the mixture reaches the preset viscosity range, stop heating and stirring, and transfer it to a mold for cooling to obtain the polymer material for a new energy vehicle battery pack.

[0006] In some embodiments of the present invention, the step S2 includes: S2.1. Determine the ratio and addition sequence of nano-silicon particles, micro-silicon particles, and nano-carbon particles to obtain the particulate reinforcing agent; S2.2. Add the particulate reinforcing agent to the polyurethane prepolymer in portions with stirring according to the determined addition sequence of the particulate reinforcing agent; S2.3. Add the dynamic crosslinking agent, and a mixture is obtained after stirring is completed.

[0007] In some embodiments of the present invention, the dynamic crosslinking agent includes at least one of a disulfide crosslinking agent, a furan / maleimide group crosslinking agent, an oxime alkane or a ketoxime crosslinking agent.

[0008] In some embodiments of the present invention, step S2.1 includes: Set the relevant parameters of the nano-silicon particles, micro-silicon particles, and nano-carbon particles, where the relevant parameters include the particle size, particle density, overall volume, and overall particle mass of the particles; Transfer the polyurethane prepolymer, nano-silicon particles, micro-silicon particles, and nano-carbon particles to a test container to obtain a test object, and apply an external stress to the test object; Calculate the bulk density and porosity of the test object; Determine whether the bulk density and porosity of the test object meet a preset numerical range; If so, determine the ratio and addition sequence of the nano-silicon particles, micro-silicon particles, and nano-carbon particles to obtain the particulate reinforcing agent; If not, adjust the ratio and addition sequence of the nano-silicon particles, micro-silicon particles, and nano-carbon particles and perform the step of calculating the bulk density and porosity of the test object.

[0009] In some embodiments of the present invention, the calculation formulas for the bulk density and porosity of the test object are: , , , , , , , , , , , , where, is the bulk density of the test object, is the number of particles of the nano-silicon particles, is the number of particles of the micro-silicon particles, is the number of particles of the nano-carbon particles, is the overall particle mass of the nano-silicon particles, is the overall particle mass of the micro-silicon particles, is the overall particle mass of the nano-carbon particles, is the particle density of nano-silicon particles, is the particle density of micro-silicon particles, is the particle density of nano-carbon particles, is the monomer volume of nano-silicon particle, is the monomer volume of micro-silicon particle, is the monomer volume of nano-carbon particle, is the shape factor of nano-silicon particles, is the shape factor of micro-silicon particles, is the shape factor of nano-carbon particles, is the particle size of nano-silicon particles, is the particle size of micro-silicon particles, is the particle size of nano-carbon particles, is the porosity of the test object, is the void volume of the test object, is the ideal packing volume of nano-silicon particles, is the ideal packing volume of micro-silicon particles, is the ideal packing volume of nano-carbon particles, and V is the overall volume of the test object.

[0010] In some embodiments of the present invention, the step S1 includes: S1.1. Stir the main-chain polyether diol at a low stirring speed of 50-100 rpm in an inert atmosphere at room temperature or 30-40 °C, and then slowly add the functionalized isocyanate; S1.2. Gradually heat to 60-70 °C at a rate of 3-5 °C / min, and at the same time increase the stirring rate to 100-300 rpm; S1.3. Keep at 60-70 °C for 60-120 min, and detect the content of the remaining isocyanate groups by infrared spectroscopy or isocyanate group titration. When the content of the remaining isocyanate groups reaches the ideal prepolymer content, a polyurethane prepolymer is obtained.

[0011] In some embodiments of the present invention, the step S3 includes: S3.1. Gradually heat the mixture to 80-100 °C at a rate of 2-5 °C / min, and reduce the stirring speed to the range of 500-1000 rpm; S3.2. Obtain the real-time viscosity of the mixture and judge whether the real-time viscosity of the mixture reaches the preset viscosity range; S3.3. If so, stop heating, slowly reduce the stirring rate to zero, and maintain a low-speed rotation with a stirring rate of 100 rpm for 1-2 min; S3.4. Transfer the mixture to a mold and let it stand at room temperature for 120 - 240 min. After surface treatment, a polymer material for a new energy vehicle battery pack is obtained.

[0012] In some embodiments of the present invention, in step S1, the main-chain polyether diol includes at least one of polytetramethylene ether glycol, polypropylene glycol, and polyethylene glycol, and the functionalized isocyanate includes at least one of modified toluene diisocyanate, modified diphenylmethane diisocyanate, and hexamethylene diisocyanate derivatives. The mass ratio of the main-chain polyether diol to the functionalized isocyanate is 100:30 - 80.

[0013] The present invention provides a polymer material for a new energy vehicle battery pack, which is made by the preparation method of the polymer material for a new energy vehicle battery pack as described above. By weight percentage, the polymer material for a new energy vehicle battery pack includes 60 - 80 parts of main-chain polyether diol, 15 - 30 parts of functionalized isocyanate, 1 - 5 parts of particulate reinforcing agent, and 0.5 - 5 parts of dynamic crosslinking agent; wherein, The main-chain polyether diol is used to provide flexibility; The functionalized isocyanate is used to provide groups that react with the main-chain polyether diol; The particulate reinforcing agent is used to enhance mechanical properties and impact resistance; The dynamic crosslinking agent is used to provide reversible crosslinking and self-healing functions.

[0014] Compared with the prior art, the preparation method of a polymer material for a new energy vehicle battery pack in the present invention has the beneficial effects that: After the particulate reinforcing agent is added to the polyurethane prepolymer, a structure with high packing density and low porosity is formed. The high packing density and low porosity reduce air bubbles, microcracks, and other defects inside the material, improving the overall structural integrity and impact resistance of the material. Then, the dynamic crosslinking agent is added to form a reversible or adjustable crosslinked structure. When damaged, the reversible bonds in the dynamic crosslinking agent can break and reform under specific conditions, automatically repairing microcracks, preventing crack propagation, and extending the material life. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic flow chart of a preparation method of a polymer material for a new energy vehicle battery pack in an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0017] Please refer to Figure 1 , the present invention provides a preparation method of a polymer material for a new energy vehicle battery pack, and the steps include: S1. Mix the main-chain polyether diol and the functionalized isocyanate in a preset ratio, and perform preliminary heating to generate a polyurethane prepolymer. Among them, the preliminary heating temperature is 60~70°C, and the heating time is 60~120 min.

[0018] Select a stainless-steel container with a jacket heating or heat preservation function and good sealing performance to prevent external moisture or oxygen from entering. It is internally equipped with a temperature sensor, a pressure indicator, etc. to ensure the visualization and safety of the process. An electronic scale or a mass flow meter can be used to quantify the main-chain polyether diol and the functionalized isocyanate to ensure the feeding accuracy.

[0019] By maintaining the temperature in the mild temperature range of 60~70°C, on the one hand, it allows sufficient time for the partial reaction of hydroxyl groups and isocyanate groups to form polyurethane chain segments of a certain length; on the other hand, it prevents the reaction from being too rapid or excessive. The prepolymer obtained in this way has relatively controllable molecular weight and viscosity, which is convenient for the preparation and processing of subsequent processes. At this stage, the reaction is not complete, but by controlling the time and temperature, a part of the –NCO groups are still retained in the system. When the temperature is higher or other additives (such as dynamic cross-linking agents, particulate reinforcing agents) are added later, these residual –NCO can further react with polyether diols or other functional groups to complete cross-linking or functional modification.

[0020] Specifically, step S1 includes: S1.1. Under an inert atmosphere at room temperature or 30~40°C, for example, it can be 30°C, 35°C, 40°C, perform low-speed stirring of the main-chain polyether diol at a stirring speed of 50~100 rpm, for example, it can be 50 rpm, 80 rpm, 100 rpm, and then slowly add the functionalized isocyanate.

[0021] Operating under nitrogen or other inert atmospheres can effectively prevent moisture and oxygen from entering, causing side reactions (such as the formation of biuret or foam) or oxidation problems, thus ensuring the stability of the activity of isocyanate groups.

[0022] In the temperature range of room temperature or 30~40°C, the reaction rate between isocyanate and polyether diol is relatively low. The main goal is to make preliminary contact and mix evenly, rather than rapid reaction. This avoids local high-temperature rapid reaction or sudden increase in viscosity when adding isocyanate, ensuring the subsequent operability of the system.

[0023] Low-speed stirring can gently agitate the relatively low-viscosity polyether diol first, reducing the entrainment of eddies or excessive bubbles. The slow addition of isocyanate can prevent excessive polymerization or local temperature rise from occurring instantaneously at the feeding point, thus forming a stable and uniform initial system, preparing for the subsequent heating reaction.

[0024] S1.2. Gradually heat to 60 - 70°C at a rate of 3 - 5°C / min. For example, it can be 3°C / min, 4°C / min, 5°C / min, and heat to 60°C, 65°C, 70°C. At the same time, increase the stirring rate to 100 - 300 rpm. For example, it can be 100 rpm, 200 rpm, 300 rpm.

[0025] Progressive temperature increase ensures a uniform temperature rise in the reaction kettle or mixing container, avoiding excessive reactions or side reactions caused by instantaneous local high temperatures. The heat generated by the exothermic reaction during this process can be more effectively removed by the jacket or cooling system, reducing the sudden increase in viscosity or non-uniform reaction caused by too fast heat release.

[0026] As the temperature rises, the viscosity of the system gradually increases. It is necessary to appropriately increase the stirring speed to maintain the uniform mixing and heat transfer of the materials. If some polymer chain segments have been formed in the early stage, increasing the stirring speed can prevent them from depositing or stratifying, ensuring the overall consistency of the subsequent reaction.

[0027] S1.3. Maintain at 60 - 70°C for 60 - 120 min. For example, 60°C, 65°C, 70°C, 60 min, 80 min, 120 min. Detect the remaining isocyanate group content by infrared spectroscopy or isocyanate group titration. When the remaining isocyanate group content reaches the ideal prepolymer content, a polyurethane prepolymer is obtained.

[0028] Maintaining for a certain period in a relatively mild temperature range allows the addition reaction between –OH and –NCO to form prepolymer chain segments of a certain length. At the same time, it avoids over-reaction and retains some –NCO without completely exhausting –NCO at this stage. The moderately retained –NCO groups will provide active sites for subsequent cross-linking or modification.

[0029] By detecting the –NCO absorption peak through infrared spectroscopy or measuring the remaining –NCO content using chemical titration methods, it is possible to timely judge whether the prepolymerization reaction has reached the preset target. When the detection result shows that the isocyanate content is in the ideal range, heating can be stopped to obtain a polyurethane prepolymer with controllable viscosity and molecular structure. The value range of the ideal prepolymer content is approximately between 1 - 7% (weight percentage). For relatively flexible prepolymers, the –NCO content can be around 1 - 3%. If a higher cross-linking density or more reaction activity is desired in the future, the –NCO content can be increased to 4 - 7%.

[0030] In the infrared spectrum, the isocyanate group (–NCO) has a characteristic absorption peak at around 2260–2270 cm⁻¹. As the reaction progresses, the intensity of this peak gradually weakens. By comparing the change in the intensity of this peak with a reference peak (such as other absorption peaks like C=O, C–H, etc.) or with the change in the peak intensity of a standard sample, the remaining –NCO content can be quantitatively or semi-quantitatively inferred. Take a small amount of sample from the reaction kettle or mixing kettle (preferably under an inert atmosphere to avoid the sample absorbing water or oxidizing). If the viscosity is high, it can be appropriately diluted with a solvent (a solvent that does not react with NCO, such as dry chloroform or tetrahydrofuran), and then drop-coated or pressed into a tablet on an infrared spectrometer. Use an FTIR instrument to scan the sample and pay attention to the absorption peak intensity in the 2260–2270 cm⁻¹ region. If multiple groups of samples with known NCO contents have been prepared beforehand, a corresponding relationship between the peak intensity (or peak area) and NCO% can be established, thereby accurately calculating the NCO content. Or by comparing the ratio change of the internal standard peak (such as C=O) and the NCO peak, it can be inferred whether the remaining NCO content reaches the target.

[0031] The isocyanate group (NCO) can undergo a quantitative reaction in the presence of specific reagents (such as di-n-butylamine or di-isopropylamine), and the excess amine can be titrated back with an acid, thereby calculating the percentage content of –NCO in the sample. Commonly used reagents include di-n-butylamine combined with an indicator (such as bromocresol green), or using a standard hydrochloric acid solution for back-titration, etc. Accurately weigh a small amount (such as 0.5–1.0 g) of the prepolymer sample into a conical flask.

[0032] Add an excess of amine solution, such as di-n-butylamine solution (known concentration), to make the –NCO group react quantitatively with the amine to form a urea derivative. It is often necessary to stir in a solvent (such as toluene, tetrahydrofuran, etc.) for a period of time (it can be heated or at room temperature) to ensure a complete reaction. Titrate the remaining unreacted amine with a standard acid solution (such as hydrochloric acid), and use an indicator or pH meter to detect the end point. Based on the difference between the remaining amine amount and the initial amine amount, the amount of –NCO in the sample can be obtained, and then converted into a weight percentage.

[0033] This prepolymer has a moderate viscosity and contains a certain amount of active groups, which can be fully combined with other components (such as dynamic cross-linking agents, flame retardants, particulate reinforcing agents, etc.) for a secondary reaction or modification, obtaining a stable intermediate within a controllable time and temperature, which is beneficial for storage, transportation, or the next process.

[0034] The main-chain polyether diol includes at least one of polytetramethylene ether glycol, polypropylene glycol, and polyethylene glycol, and the functionalized isocyanate includes at least one of modified toluene diisocyanate, modified diphenylmethane diisocyanate, and hexamethylene diisocyanate derivatives. The mass ratio of the main-chain polyether diol to the functionalized isocyanate is 100:30–80.

[0035] When the mass ratio of the two is in the range of 100:30 to 80, the appropriate isocyanate content can be selected within this range according to requirements (such as higher toughness or higher hardness) to obtain a moderate crosslinking density and mechanical strength, taking into account processability and final performance. At the low-end ratio (such as 100:30), the isocyanate content is relatively low, and the overall crosslinking degree of the system is relatively low, making the material softer, more elastic, and more ductile; at the high-end ratio (such as 100:80), the isocyanate content is high, which can form more crosslinking points, significantly improving the hardness, impact resistance, high-temperature resistance, or wear resistance of the material, but the elasticity and flexibility may be relatively reduced. Fine-tuning can be done within this ratio range for different applications to achieve the transformation from a soft elastomer to a high-rigidity structural material.

[0036] S2. Gradually add the particulate reinforcing agent to the polyurethane prepolymer with stirring, and then add the dynamic crosslinking agent to obtain a mixture, where the stirring speed is 2000 - 3000 rpm and the stirring time is 30 - 60 min.

[0037] The particulate reinforcing agent is added in portions to the polyurethane prepolymer and stirred at high speed to form a uniform nano-reinforcement network inside the material, effectively improving the mechanical properties. First, ensure that the nanoparticles are fully dispersed to avoid premature reaction of the dynamic crosslinking agent or a sharp increase in viscosity leading to poor dispersion; then introduce the dynamic crosslinking agent to undergo partial reversible crosslinking with the residual NCO groups or other active sites. On the one hand, the dispersion effect of the nanoparticles is retained, and on the other hand, stepwise control is achieved in the formulation to reduce the risk of side reactions or competing reactions.

[0038] Specifically, step S2 includes: S2.1. Determine the ratio and addition sequence of nano-silicon particles, micro-silicon particles, and nano-carbon particles to obtain the particulate reinforcing agent.

[0039] By reasonably matching nano-silicon, micro-silicon, and nano-carbon particles, the mutual filling or bridging effect of multi-scale particles can be achieved, making the internal structure of the material more dense and reducing the porosity. Enhanced effects are obtained at both the micro and nano levels, improving properties such as tensile strength, impact resistance, and fatigue resistance. Designing the particle size distribution and addition sequence in an orderly manner can reduce the risk of agglomeration and achieve overall uniform dispersion.

[0040] Through experimental or empirical design, first determine the reasonable addition sequence and respective ratios, and then the stirring intensity and duration can be targeted controlled during the subsequent dispersion process to reduce energy consumption and the tendency of agglomeration, allowing each type of particle to complete preliminary dispersion or wetting respectively under the corresponding stirring time and conditions, laying a good foundation for the final composite reinforcement. By adding in stages, the fillers with different particle sizes / morphologies can play the best reinforcing role, avoiding uneven performance caused by the first-arrival-first-adhesion or local high concentration.

[0041] Step S2.1 includes: Set the relevant parameters of nano - silicon particles, micro - silicon particles, and nano - carbon particles. Among them, the relevant parameters include particle size, particle density, overall volume, and particle mass.

[0042] By selecting silicon particles (nano - scale and micro - scale) and nano - carbon particles with different particle sizes, the material properties can be enhanced at multiple scales. Nano - silicon particles provide the enhancement effect of a high surface area, micro - silicon particles fill the voids between nano - particles, and nano - carbon particles improve the mechanical strength of the material. Reasonably select the density of each type of particle to ensure that the particles can be evenly distributed during the mixing process, avoiding sedimentation or floating caused by density differences.

[0043] By setting the overall volume and mass, ensure the accurate distribution of the particulate reinforcing agent in the polyurethane prepolymer, avoiding excess or deficiency, and ensuring the consistency of material properties. A reasonable volume - to - mass ratio helps the particulate reinforcing agent to be evenly dispersed in the matrix, improving the overall mechanical properties and durability of the material. Presetting the parameters of each type of particle provides a clear basis for subsequent sequential addition and stirring operations, improving the repeatability and stability of the process. By setting specific parameters such as particle size and density, the bulk density and porosity of the material can be predicted at the initial stage, guiding subsequent process optimization.

[0044] Transfer the polyurethane prepolymer, nano - silicon particles, micro - silicon particles, and nano - carbon particles to a test container to obtain a test object, and apply an external stress to the test object.

[0045] Through precise weighing and controlling the transfer process, ensure that each component is mixed in the preset ratio, avoiding performance inconsistencies caused by mixing ratio deviations. Use an inert atmosphere or a vacuum environment during the transfer process to prevent side reactions of isocyanate groups caused by moisture and oxygen, ensuring the activity of the prepolymer. Following the set addition sequence (such as adding nano - silicon particles first, then micro - silicon particles, and finally nano - carbon particles) helps the uniform dispersion of various particles in the matrix, avoiding local agglomeration. Transfer various particles in batches, combined with appropriate stirring operations, to ensure the uniform distribution of the particulate reinforcing agent in the prepolymer, improving the overall performance of the material. Maintain an appropriate temperature and an inert atmosphere during the transfer process to prevent unnecessary reactions of isocyanate groups due to environmental changes, ensuring the controllability of subsequent dynamic cross - linking reactions.

[0046] Calculate the bulk density and porosity of the test object.

[0047] The calculation formulas for the bulk density and porosity of the test object are: , , , , , , , , , , , , where is the bulk density of the test substance, is the number of particles of nano-silicon particles, is the number of particles of micro-silicon particles, is the number of particles of nano-carbon particles, is the total mass of the microparticles of nano-silicon particles, is the total mass of the microparticles of micro-silicon particles, is the total mass of the microparticles of nano-carbon particles, is the microparticle density of nano-silicon particles, is the microparticle density of micro-silicon particles, is the microparticle density of nano-carbon particles, is the monomer volume of the microparticles of nano-silicon particles, is the monomer volume of the microparticles of micro-silicon particles, is the monomer volume of the microparticles of nano-carbon particles, is the shape factor of nano-silicon particles, is the shape factor of micro-silicon particles, is the shape factor of nano-carbon particles. When S = 1, it is an ideal sphere, and S > 1 or S < 1 indicates the degree of deviation from spherical shape. is the particle size of the microparticles of nano-silicon particles, is the particle size of the microparticles of micro-silicon particles, is the particle size of the microparticles of nano-carbon particles, is the porosity of the test substance, is the void volume of the test substance, is the ideal packing volume of nano-silicon particles, is the ideal packing volume of micro-silicon particles, is the ideal packing volume of nano-carbon particles, and V is the total volume of the test substance. 、 、 and V can be measured, 、 、 are the inherent parameters of the microparticles. Using microparticles produced by different manufacturers, they have different densities.

[0048] Among them, the particle size of the nano-silicon particles is 10 - 100 nm, the particle size of the micro-silicon particles is 1 - 10 μm, and the particle size of the nano-carbon particles is 10 - 100 nm. The shape factor S of the nano-silicon particles can be 0.85 - 1.0. The nano-silicon particles usually exhibit a near-spherical shape, so their shape factor is relatively high, close to 1.0. The high shape factor helps the particles to be evenly dispersed in the polymer matrix, improving the mechanical properties and thermal stability of the material, and contributing to the improvement of the surface smoothness and transparency of the material, which is suitable for application scenarios requiring high uniformity and stability. The shape factor S of the micro-silicon particles can be 0.6 - 0.8. Due to their larger size, the shape of the micro-silicon particles is relatively more irregular and the shape factor is lower. The lower shape factor helps to fill the gaps between the nano-silicon particles in the polymer matrix, improving the density and impact resistance of the material, and contributing to the improvement of the crack propagation resistance and overall mechanical strength of the material.

[0049] The nano-carbon particles include two forms: carbon black and graphene. The shape factor S of the carbon black can be 0.7 - 0.9. The shape of the carbon black particles is relatively regular and the shape factor is relatively high, which helps to improve the conductivity and mechanical strength of the material. The high shape factor helps to be evenly dispersed in the polymer matrix, avoiding agglomeration and ensuring the consistency of the material properties, and is widely used to enhance the mechanical properties and ultraviolet resistance of polymers.

[0050] The shape factor of graphene can be 0.5 - 0.8. As a two-dimensional material, the shape factor of graphene depends on the shape and size of its sheets and is usually described by other parameters (such as the number of layers, defect density). It provides excellent electrical conductivity, thermal conductivity and mechanical strengthening effects, and is suitable for high-performance composite materials. It forms a conductive network in the material and at the same time realizes self-healing ability through dynamic crosslinking agents, improving the comprehensive properties of the material.

[0051] In the test object, the polyurethane prepolymer is approximately a fluid without voids. The bulk density and porosity of the whole test object can be obtained by calculating the voids between the aggregated particles.

[0052] Judge whether the bulk density and porosity of the test object meet the preset numerical ranges. Among them, the preset numerical range of the bulk density is 1.2 - 1.5 g / cm³, and the preset numerical range of the porosity is 10% - 20%.

[0053] If so, determine the proportion and addition order of the nano-silicon particles, micro-silicon particles and nano-carbon particles to obtain the particulate enhancer.

[0054] If not, adjust the proportion and addition order of the nano-silicon particles, micro-silicon particles and nano-carbon particles and perform the steps of calculating the bulk density and porosity of the test object.

[0055] Add in stages according to the particle size and shape of different particulate reinforcements to optimize the dispersion effect. For example, first add micron silicon particles, then add nano silicon particles and nano carbon particles to ensure that various particles are evenly dispersed and effectively fill the voids. By optimizing the addition sequence, the interfacial bonding force between the particulate reinforcement and the polyurethane matrix is enhanced, improving the overall mechanical properties and durability of the material.

[0056] Calculated by mass percentage, nano silicon particles: micron silicon particles: nano carbon particles = 5 - 20%: 10 - 30%: 5 - 15%.

[0057] In another embodiment, calculate the uniformity index and dispersion degree of the test substance.

[0058] Among them, the calculation formula for the uniformity index is , is the uniformity index, is the minimum particle size of the test substance, is the maximum particle size of the test substance. Obtain the particle size distribution data of the particles in the sample using a particle size analyzer (such as a laser particle size analyzer, scanning electron microscope (SEM), etc.). When UI is close to 1, the particle sizes are uniform, and the particulate reinforcement is evenly dispersed in the matrix, which helps to improve the mechanical properties and stability of the material. When UI is low, the particle size distribution is wide, resulting in an excess or deficiency of the reinforcement in local areas, affecting the overall performance and consistency of the material.

[0059] The calculation formula for the dispersion degree is , where D is the dispersion degree, is the standard deviation of the particle size, is the average particle size, , is the total number of particles, is the particle size of the i-th particle, which can be obtained by a particle size analyzer. With a low dispersion degree, the particle size distribution is concentrated, and the reinforcement is evenly dispersed in the matrix, which helps to improve the mechanical properties and consistency of the material. With a high dispersion degree, the particle size distribution is wide, which may lead to non-uniform material properties and affect the overall quality and stability.

[0060] Judge whether the uniformity index and dispersion degree of the test substance meet the preset numerical range. Among them, the preset numerical range for the uniformity index is greater than or equal to 0.8, and the preset numerical range for the dispersion degree is less than or equal to 0.2.

[0061] If so, determine the ratio and addition sequence of nano silicon particles, micron silicon particles, and nano carbon particles to obtain the particulate reinforcement.

[0062] If not, adjust the ratio and addition sequence of nano silicon particles, micron silicon particles, and nano carbon particles and perform the steps of calculating the uniformity index and dispersion degree of the test substance.

[0063] Add large particles first and then small particles. First add micron silicon particles to form a preliminary filling network, and then add nano silicon particles and nano carbon particles to fill the gaps between micron particles. Reduce the agglomeration of nano particles, improve the overall dispersibility and filling efficiency, reduce the porosity, and increase the packing density.

[0064] Add nano particles first and then large particles. The nano particles are first dispersed in the matrix to form a microscopic reinforcement network, and then micron particles are added to effectively fill the gaps between the nano particles. Optimize the multi-scale filling structure and improve the comprehensive mechanical properties and density of the material.

[0065] Increase the proportion of nano silicon particles and nano carbon particles to improve UI and reduce D. Appropriately reduce the proportion of micron silicon particles to avoid increased brittleness of the material caused by overfilling.

[0066] S2.2. According to the determined addition sequence of the particulate reinforcing agent, add the particulate reinforcing agent to the polyurethane prepolymer in batches with stirring.

[0067] S2.3. Add a dynamic crosslinking agent and obtain a mixture after stirring is completed.

[0068] The dynamic crosslinking agent includes at least one of a disulfide crosslinking agent, a furan / maleimide group crosslinking agent, an oxime alkane or a ketoxime crosslinking agent. The dynamic crosslinking agent refers to a chemical substance that can form a reversible or adjustable crosslinked structure under certain conditions (such as temperature, light, chemical environment, etc.). These crosslinked structures can not only enhance the mechanical properties of the polyurethane material, but also endow the material with advanced properties such as self-healing ability, reversibility and adaptability.

[0069] The reversible bonds (such as disulfide bonds, Diels-Alder bonds, etc.) in the dynamic crosslinking agent can break and reform through external stimuli (such as heating, light, etc.) when the material is damaged, repairing cracks or damages in the material. Significantly extend the service life of the material, reduce the performance attenuation and failure caused by microcracks, and improve the reliability and durability of the material.

[0070] The dynamic crosslinking agent can form and break crosslinking points under specific conditions, making the crosslinked network of the material reversible and adjustable. Endow the material with repeatable processability and recyclability, facilitating repair or reprocessing after use, and meeting the requirements of environmental protection and sustainable development. The dynamic crosslinked structure can adjust its crosslinking density and network structure according to environmental changes (such as temperature, humidity, stress, etc.). Improve the performance of the material in different working environments, such as enhancing the crosslinking density at high temperature to improve heat resistance; adjusting the network structure under stress to improve impact resistance and toughness.

[0071] Dynamic cross-linking agents improve the tensile strength, elastic modulus and fatigue resistance of materials by forming an efficient cross-linking network, making the materials exhibit higher strength and better toughness when subjected to repeated stress or impact, and adapting to the high-load working environment of new energy vehicle battery packs.

[0072] The dynamic cross-linking structure can be stable at high temperatures, providing additional thermal stability, improving the stability and performance of the material under high temperature working conditions, extending the service life, and preventing performance degradation caused by thermal deformation or decomposition.

[0073] S3, heating the mixture to 80-100°C, reducing the stirring speed to 500-1000rpm, detecting the viscosity of the mixture until it reaches a preset viscosity range, stopping heating and stirring, transferring the mixture to a mold for cooling, and obtaining a polymer material for a new energy vehicle battery pack.

[0074] By heating to 80~100℃ and controlling the stirring speed, the chemical reaction in the polyurethane prepolymer is ensured to proceed to a predetermined degree, forming a high-quality cross-linked network and improving the mechanical properties and thermal stability of the material. By real-time monitoring and controlling the viscosity of the mixture, the material is ensured to strike a balance between appropriate fluidity and processability to prevent the subsequent molding and material properties from being affected by excessive or low viscosity. The mixture with appropriate viscosity is quickly transferred to the mold for cooling to ensure the material's accurate shape and uniform internal structure, reduce processing defects, and improve the quality and performance of the final product. The resulting polymer material not only has excellent mechanical strength and toughness, but also has good self-healing and durability, meeting the strict requirements of new energy vehicle battery packs for high-performance materials.

[0075] S3.1. Gradually heat the mixture to 80-100°C at a rate of 2-5°C / min and reduce the stirring speed to 500-1000 rpm.

[0076] Gradually heating ensures that the reaction temperature rises slowly, avoiding excessive reaction rate due to sudden temperature rise, preventing excessive cross-linking or decomposition. Ensure that the polyurethane chain segments grow evenly, avoid excessive cross-linking in local areas, and ensure the uniformity of the material and the stability of mechanical properties.

[0077] As the temperature rises, the viscosity of the system gradually increases. Reducing the stirring speed to 500-1000rpm can adapt to the viscosity change and avoid excessive shearing caused by high speed. Maintain the uniformity and stability of the mixture, prevent polymer chain breakage or bubble formation due to high shear force, and ensure the smooth progress of the reaction.

[0078] Slow heating helps to distribute heat more evenly, avoid local overheating of the reactor, reduce heat accumulation during the reaction, reduce the risk of side reactions, and improve the overall quality and performance of the material.

[0079] S3.2. Obtain the real-time viscosity of the mixture and determine whether the real-time viscosity of the mixture reaches the preset viscosity range. Continuously obtain the viscosity data of the mixture through an on-line viscometer or other real-time measurement devices. Compare the real-time measured viscosity with the preset target viscosity range to determine whether the requirements are met. The change in viscosity reflects the degree of extension and crosslinking of the polymer chains. Real-time monitoring of viscosity can intuitively understand the progress of the reaction. Ensure that the polyurethane system reaches the predetermined crosslinking degree and molecular weight, avoid overreaction or underreaction, and ensure the stable performance of the final material. By setting and monitoring the target viscosity range, the reaction can be terminated in time when it reaches the optimal state. Prevent the material from having too high viscosity, difficult processing or deteriorated performance due to excessive crosslinking; avoid the mechanical properties of the material not meeting the standards due to insufficient crosslinking.

[0080] Real-time viscosity monitoring provides accurate process control data, ensuring the consistency of each batch of materials in key parameters. Improve the quality consistency of the final product and ensure the reliability and stability of the materials required for new energy vehicle battery packs.

[0081] Through real-time data feedback, process parameters such as temperature and stirring rate can be dynamically adjusted according to the actual reaction conditions. Achieve the optimization of process parameters, improve production efficiency and material properties.

[0082] S3.3. If so, stop heating, slowly reduce the stirring rate to zero, and maintain a low-speed rotation of 100 rpm for 1 - 2 minutes.

[0083] After the viscosity of the mixture reaches the preset range, immediately stop heating, slowly reduce the stirring rate from 500 - 1000 rpm to zero, and continue to stir at a low speed of 100 rpm for 1 - 2 minutes in the final stage.

[0084] After stopping heating, the reaction temperature no longer rises, fixing the current reaction progress and crosslinking degree, preventing the reaction from continuing, ensuring that the crosslinking degree and molecular structure of the material remain in the predetermined state, and avoiding performance fluctuations. Slowly reducing the stirring rate and maintaining low-speed stirring helps to gradually release the stress in the system and promote the escape of bubbles. Reduce the stress concentration and bubble content inside the material, improve the uniformity and mechanical properties of the material, and avoid defects during the molding process. Slowly reducing the stirring rate avoids breaking or degrading the polymer chains due to high shear forces. Maintain the integrity of the polyurethane segments to ensure that the material has good toughness and elasticity. Terminate the reaction under suitable stirring conditions to ensure that the mixture has appropriate fluidity and viscosity, facilitating transfer to the mold. Improve the smoothness and efficiency of the molding process, ensure uniform filling of the material in the mold, and obtain high-quality molded products.

[0085] S3.4. Transfer the mixture to a mold and leave it at room temperature for 120 - 240 min. After surface treatment, a polymer material for new energy vehicle battery packs is obtained.

[0086] Quickly transfer the mixture that has reached the preset viscosity to a pre-prepared mold, leave it at room temperature for 120 - 240 minutes to complete curing and crosslinking, and perform necessary surface treatments such as deburring, edge trimming, or polishing to obtain the final product.

[0087] Quickly transfer the mixture with suitable viscosity and fluidity to the mold, ensuring uniform filling of the material in the mold and precisely replicating the shape and dimensions of the mold. Obtain a polymer material with precise dimensions and consistent shape, meeting the design specifications and performance requirements of new energy vehicle battery packs.

[0088] Leave it at room temperature, and the crosslinking reaction of the polyurethane system continues in a stable environment to form a stable three-dimensional network structure. Improve the mechanical strength, heat resistance, and durability of the material, ensuring its stability and reliability in practical applications.

[0089] Perform surface treatments such as removing burrs introduced during the processing, trimming irregular edges, or surface polishing. Improve the appearance quality of the material, reduce surface defects, and avoid stress concentration or other performance problems caused by surface unevenness during use. Natural cooling and curing in the mold help eliminate air bubbles, delamination, and other internal defects in the material. Improve the overall structural integrity and mechanical properties of the material, ensuring its reliability in high-load and high-stress environments. By leaving it in the mold for a certain time for natural cooling, ensure that the temperature inside the material gradually decreases and the crosslinking network is stabilized. Reduce internal stress and deformation, improve the structural integrity and mechanical properties of the material, and ensure the stability and reliability of the final product. Through the precise molding and curing process, the molecular chains of the polyurethane material are rearranged and the crosslinking network is stabilized, forming a high-performance three-dimensional structure. The final material has high strength, high toughness, impact resistance, and good self-healing properties, suitable for the high-demand application scenarios of new energy vehicle battery packs.

[0090] Regarding the specific shape of the mold, based on the specific shape of the new energy vehicle battery pack, a specific snap structure or other locking structures can be designed to form a space for placing the new energy vehicle battery pack inside. In the above preparation process, the specific structures and usage methods of the mechanical devices, equipment, and instruments used are known to those skilled in the art and will not be elaborated here.

[0091] The present invention provides a polymer material for a new energy vehicle battery pack. By weight percentage, the polymer material for the new energy vehicle battery pack comprises 60-80 parts of main-chain polyether diol, 15-30 parts of functionalized isocyanate, 1-5 parts of particulate reinforcing agent, and 0.5-5 parts of dynamic crosslinking agent; wherein, The main-chain polyether diol is used to provide flexibility; The functionalized isocyanate is used to provide groups that react with the main-chain polyether diol; The particulate reinforcing agent is used to enhance mechanical properties and impact resistance; The dynamic crosslinking agent is used to provide reversible crosslinking and self-healing functions.

[0092] The equipment, devices and other mechanical structures used in all embodiments of the present invention are known to those skilled in the art, and the specific usage methods and working principles will not be elaborated herein.

[0093] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a polymer material for a new energy vehicle battery pack, characterized in that: The steps include: S1. Main chain polyether diol and functionalized isocyanate are mixed in a preset ratio and preliminarily heated to generate a polyurethane prepolymer, wherein the preliminarily heating temperature is 60-70° C. and the heating time is 60-120 min; S2, adding a particulate reinforcing agent to the polyurethane prepolymer in batches while stirring, and then adding a dynamic crosslinking agent to obtain a mixture, wherein the stirring speed is 2000-3000 rpm, and the stirring time is 30-60 min; S3, heating the mixture to 80-100° C., reducing the stirring speed to 500-1000 rpm, detecting that the viscosity of the mixture reaches a preset viscosity range, stopping heating and stirring, transferring the mixture to a mold for cooling, and obtaining a polymer material for a new energy vehicle battery pack.

2. The method for preparing a polymer material for a new energy vehicle battery pack according to claim 1, characterized in that: The step S2 comprises: S2.1, determining the ratio and order of addition of nano silicon particles, micro silicon particles and nano carbon particles to obtain a particle enhancer; S2.2, according to the determined order of adding the particulate reinforcing agent, adding the particulate reinforcing agent to the polyurethane prepolymer in batches with stirring; S2.3, adding the dynamic cross-linking agent, and stirring to obtain a mixture.

3. The method for preparing a polymer material for a new energy vehicle battery pack according to claim 1 or 2, characterized in that: The dynamic cross-linking agent includes at least one of a disulfide bond cross-linking agent, a furan / maleimide group cross-linking agent, an oxime or a ketoxime cross-linking agent.

4. The method for preparing a polymer material for a new energy vehicle battery pack according to claim 1, characterized in that: The step S2.1 comprises: Setting relevant parameters of nano silicon particles, micro silicon particles and nano carbon particles, wherein the relevant parameters include particle size, particle density, overall volume and overall mass of particles; Transferring the polyurethane prepolymer, nano silicon particles, micron silicon particles and nano carbon particles into a test container to obtain a test object, and applying external stress to the test object; Calculating the bulk density and void ratio of the test object; Determine whether the bulk density and porosity of the test object meet the preset value range; If yes, then determine the ratio and order of addition of nano silicon particles, micro silicon particles and nano carbon particles to obtain a particulate reinforcing agent; If not, the ratio and the order of addition of the nano-silicon particles, micron-silicon particles and nano-carbon particles are adjusted and the step of calculating the packing density and the porosity of the test object is performed.

5. The method for preparing a polymer material for a new energy vehicle battery pack according to claim 4, characterized in that: The calculation formulas for the bulk density and porosity of the test object are: , , , , , , , , , , , ,in, is the bulk density of the test object, is the number of nano-silicon particles, is the number of micron silicon particles, is the number of nanocarbon particles, is the total mass of nano-silicon particles, is the total mass of micron silicon particles, is the total mass of the nanocarbon particles, is the particle density of nano-silicon particles, is the particle density of micron silicon particles, is the particle density of nanocarbon particles, is the volume of the nano-silicon particle monomer, is the volume of the micron silicon particle monomer, is the volume of the nanocarbon particle monomer, is the shape factor of the nano-silicon particles, is the shape factor of the micron silicon particle, is the shape factor of the nanocarbon particles, is the particle size of nano silicon particles, is the particle size of micrometer silicon particles, is the particle size of nanocarbon particles, is the porosity of the test object, is the void volume of the test object, is the ideal stacking volume of nano-silicon particles, is the ideal packing volume of micron silicon particles, is the ideal stacking volume of nanocarbon particles, and V is the overall volume of the test object.

6. The method for preparing a polymer material for a new energy vehicle battery pack according to claim 1, characterized in that: The step S1 comprises: S1.

1. At room temperature or in an inert atmosphere at 30-40°C, stir the main chain polyether diol at a low speed of 50-100 rpm, and then slowly add the functionalized isocyanate; S1.2, gradually heat to 60-70°C at a rate of 3-5°C / min, while increasing the stirring rate to 100-300 rpm; S1.3, maintaining the temperature at 60-70°C for 60-120 minutes, detecting the remaining isocyanate group content by infrared spectroscopy or isocyanate group titration, and obtaining a polyurethane prepolymer when the remaining isocyanate group content reaches the ideal prepolymer content.

7. The method for preparing a polymer material for a new energy vehicle battery pack according to claim 1, characterized in that: The step S3 comprises: S3.

1. Gradually heat the mixture to 80-100°C at a rate of 2-5°C / min, and reduce the stirring speed to 500-1000 rpm; S3.2, obtaining the real-time viscosity of the mixture, and determining whether the real-time viscosity of the mixture reaches a preset viscosity range; S3.

3. If yes, stop heating, slowly reduce the stirring rate to zero, and maintain a low speed of 100 rpm for 1 to 2 minutes; S3.4, transferring the mixture to a mold, placing it at room temperature for 120 to 240 minutes, and performing surface treatment to obtain a polymer material for a new energy vehicle battery pack.

8. The method for preparing a polymer material for a new energy vehicle battery pack according to claim 1, characterized in that: In step S1, the main chain polyether diol includes at least one of polytetramethylene ether glycol, polypropylene glycol, and polyethylene glycol, the functionalized isocyanate includes at least one of modified toluene diisocyanate, modified diphenylmethane diisocyanate, and a hexamethylene diisocyanate derivative, and the mass ratio of the main chain polyether diol to the functionalized isocyanate is 100:30~80.

9. A polymer material for a new energy vehicle battery pack, characterized in that: The polymer material for a new energy vehicle battery pack is prepared by the method for preparing the polymer material for a new energy vehicle battery pack according to any one of claims 1 to 8, wherein the polymer material for a new energy vehicle battery pack comprises 60 to 80 parts of a main chain polyether diol, 15 to 30 parts of a functionalized isocyanate, 1 to 5 parts of a particle enhancer, and 0.5 to 5 parts of a dynamic crosslinking agent in terms of percentage; wherein, The main chain polyether diol is used to provide flexibility; The functionalized isocyanate is used to provide a group that reacts with the main chain polyether diol; The microparticle reinforcing agent is used to enhance mechanical properties and impact resistance; The dynamic cross-linking agent is used to provide reversible cross-linking and self-healing functions.

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