Lithium-ion battery collision safety protection device based on negative Poisson's ratio metamaterial

Abstract

This invention relates to the field of lithium battery protection technology, and more particularly to a lithium battery collision safety protection device based on a negative Poisson's ratio metamaterial. The device includes a housing, a metamaterial separator, and vibration-damping foam; a situational awareness module for data acquisition; a protection strategy determination module for determining the protection strategy; an intrusion protection module for determining whether the resistance strength of the metamaterial separator is adequate based on the deformation synergy index, and for determining weak resistance areas based on dynamic compaction trajectories to adjust the magnetic field strength of these weak areas; a vibration suppression module for determining whether the vibration isolation capability of the protection device is adequate based on the pressure distribution entropy between the battery pack and the vibration-damping foam, and for adjusting the elongation of the hydraulic rod based on conditions where the vibration isolation capability of the protection device is inadequate; and a protection optimization module for optimizing a preset energy index based on conditions where the protection strategy is inadequate. This invention improves the adaptability of the protection strategy of the lithium battery protection device.

Description

Technical Field

[0001] This invention relates to the field of lithium battery protection technology, and in particular to a lithium battery collision safety protection device based on a negative Poisson's ratio metamaterial. Background Technology

[0002] With the rapid development of new energy vehicles, energy storage systems, and other fields, lithium batteries have been widely used due to their advantages such as high energy density and long cycle life. However, the safety protection issues under collision and impact conditions are becoming increasingly prominent. The instantaneous impact load generated by a collision can easily cause the lithium battery casing to crack and the cell to short-circuit, leading to serious risks such as thermal runaway, fire, and explosion. Long-term vibration can also exacerbate fatigue damage to the battery pack and protective components, further reducing safety redundancy. Existing lithium battery protection devices mostly use metal casings, ordinary foam, or traditional composite materials, which have drawbacks such as difficulty in balancing lightweight and protective performance, low impact energy dissipation efficiency, and inability to dynamically adapt to combined impact / vibration conditions: rigid metal casings are heavy and have poor buffering and energy absorption effects, easily transferring impact energy directly to the cell; ordinary flexible materials have weak intrusion resistance and are difficult to withstand high-intensity collisions; and traditional protective structures lack the ability to monitor and adapt to their own fatigue damage, and their protective effectiveness is prone to decay after long-term use. Against this backdrop, negative Poisson's ratio metamaterials with compressive radial expansion characteristics can achieve efficient dispersion and dissipation of impact energy with their unique mechanical properties, while also taking into account lightweight and structural stability. This provides a new path to solve the core pain point of lithium battery collision safety protection. Developing safety protection devices based on this material that are adapted to the complex working conditions of lithium batteries, have both rigid anti-intrusion and flexible vibration isolation functions, and can dynamically respond to damage states has become an urgent need in the industry.

[0003] Chinese Patent Application Publication No. CN119651018A discloses a protective device and a lithium battery pack, relating to the field of lithium battery pack technology. The protective device includes: a first housing having a first cavity inside, and the first housing having a first opening communicating with the first cavity on its side in a first direction, the first cavity being used to accommodate a battery body; an elastic component being disposed at the bottom of the first housing; a second housing having a second cavity inside, and the top of the second housing having a second opening communicating with the second cavity, the second cavity being used to accommodate the first housing and to close the second opening through the first housing; and two sets of adjustment components movably disposed on opposite sides of the second housing in a second direction, the adjustment ends of the adjustment components being located within the first cavity and cooperating with the first housing, for adjusting whether the first housing is fixed within the second cavity or removed from the second housing.

[0004] The existing technology still has the following problems: In the actual use scenarios of lithium battery protection devices, it is difficult to classify and process the external load. As a result, the protection device cannot dynamically match the corresponding protection and monitoring strategies according to key parameters such as collision impact intensity, vibration frequency characteristics, and duration of action. When the load is small, it is easy to waste energy and wear the metamaterial separator and vibration isolation foam due to over-activation of the rigid anti-intrusion mode. When the load is large and accompanied by long-period vibration characteristics, the lack of timely intervention will cause the cell displacement to exceed the range and resonance amplification, which will induce safety risks such as shell rupture, cell short circuit, and thermal runaway. At the same time, there is a lack of dynamic adjustment mechanism for metamaterial stiffness and foam damping that is compatible with load classification. As a result, it is difficult to balance the rigid anti-intrusion effect, flexible vibration isolation performance and lithium battery structural safety. Moreover, disordered switching of protection strategies can easily lead to increased residual deformation of metamaterials and shortened service life of foam. It cannot meet the use requirements of precise risk control and efficient adaptation of lithium battery protection devices in complex working conditions such as vehicle and energy storage. Summary of the Invention

[0005] To address this issue, the present invention provides a lithium battery collision safety protection device based on a negative Poisson's ratio metamaterial, which overcomes the problem of low adaptability of protection strategies in existing lithium battery protection devices.

[0006] To achieve the above objectives, the present invention provides a lithium battery collision safety protection device based on a negative Poisson's ratio metamaterial, comprising: The housing includes a cavity for accommodating the battery pack; A metamaterial partition is disposed in the cavity and is movably connected to the inner wall of the shell via several hydraulic rods; Vibration-damping foam is fixedly installed on the surface of the metamaterial separator and adhered to the outer surface of the battery pack; The situational awareness module includes several acceleration sensors for real-time monitoring of the impact energy acting on the protective device, and a strain sensor array for real-time monitoring of the strain of the metamaterial partition and the strain stress distribution of the foam. The protection strategy determination module is used to determine whether the protection strategy of the protection device is a rigid intrusion protection strategy or a flexible vibration suppression strategy based on the comparison between the energy index of the external impact and the preset energy index. An intrusion protection module, in response to the determination result of the rigid intrusion protection strategy, determines whether the resistance strength of the metamaterial partition is qualified based on the deformation synergy index of the metamaterial partition, and determines the weak resistance strength area based on the dynamic compaction trajectory of the metamaterial partition according to the condition that the resistance strength of the metamaterial partition is unqualified, so as to adjust the magnetic field strength of the weak resistance strength area. The vibration suppression module, in response to the determination result of the flexible vibration suppression strategy, determines whether the vibration isolation capability of the protective device is qualified based on the pressure distribution entropy between the battery pack and the vibration isolation foam, and adjusts the elongation of the hydraulic rod based on the condition that the vibration isolation capability of the protective device is unqualified. The protection optimization module is used to determine whether the protection strategy is qualified based on the cumulative damage of the battery pack, and to optimize the preset energy index based on the condition that the protection strategy is unqualified.

[0007] Furthermore, the protection strategy determination module determines the protection strategy as a rigid intrusion protection strategy based on the comparison result that the energy index is greater than the preset energy index.

[0008] Furthermore, the protection strategy determination module determines the protection strategy as a flexible vibration suppression strategy based on the comparison result of the energy index being less than or equal to the preset energy index.

[0009] Furthermore, the intrusion protection module determines the ratio of the radial deformation uniformity coefficient to the axial deformation uniformity coefficient of the metamaterial partition as the deformation synergy index.

[0010] Furthermore, the intrusion protection module determines that the resistance strength of the metamaterial partition is unqualified based on the comparison result of whether the deformation synergy index is greater than the second preset synergy index or less than the first preset synergy index.

[0011] Furthermore, under the condition that the resistance strength of the metamaterial partition is unqualified, the intrusion protection module determines the corresponding position where the vertical distance between the dynamic compaction trajectory and the ideal compaction trajectory is greater than the preset distance as the weak resistance area based on the overlap and alignment result of the dynamic compaction trajectory of the metamaterial partition compaction process and the retrieved ideal compaction trajectory.

[0012] Furthermore, under the condition of determining the weak resistance area, the intrusion protection module sets several strength adjustment coefficients based on the relative difference between the preset spacing and the vertical spacing, and the comparison result with the preset relative difference, to increase the magnetic field strength of the weak resistance area.

[0013] Furthermore, the vibration suppression module determines that the vibration isolation capability of the protective device is unqualified based on the comparison result that the pressure distribution entropy between the battery pack and the vibration isolation foam is greater than the preset distribution entropy, and sets several length adjustment coefficients to increase the elongation of the hydraulic rod based on the comparison result that the pressure amplitude between the battery pack and the vibration isolation foam is greater than the preset amplitude.

[0014] Furthermore, the protection optimization module determines that the protection strategy is unqualified based on the comparison result that the cumulative damage degree of the battery pack is greater than the preset damage degree.

[0015] Furthermore, when the rigid intrusion protection strategy fails, the protection optimization module reduces the preset energy index by using an exponential correction coefficient based on the comparison result between the damage difference between the cumulative damage degree and the preset damage degree and the preset difference. When the flexible vibration suppression strategy fails, the protection optimization module increases the preset energy index by an exponential optimization coefficient based on the comparison result between the damage difference between the cumulative damage degree and the preset damage degree and the preset difference.

[0016] Compared with existing technologies, the advantages of this invention lie in its ability to determine the energy index of the external load by real-time monitoring of the impact acceleration, impact duration, and strain distribution of the metamaterial separator acting on the protective device. This allows for the determination of whether the protection strategy should be rigid intrusion protection or flexible vibration suppression, thereby ensuring the safety of the battery pack under different impact scenarios. The energy index integrates impact acceleration, frequency, and period to accurately quantify the intrusion risk of the load. If the energy index exceeds a preset threshold, a rigid intrusion protection strategy is triggered, enhancing resistance through the negative Poisson bit of the metamaterial separator and the controllable viscosity of the magnetofluid. If the energy index is below the threshold, a flexible vibration suppression strategy is triggered, absorbing vibration energy through the elastic deformation of the vibration-damping foam. This dynamic strategy switching avoids structural damage and safety risks to the battery pack caused by insufficient protection under rigid intrusion loads, and also prevents energy waste and ineffective material loss caused by excessive protection under flexible vibration scenarios, thus improving the adaptability of the lithium battery protection device's protection strategy.

[0017] Furthermore, this invention determines the resistance strength of the metamaterial separator by using its deformation synergy index to optimize the rigid intrusion protection effect. The deformation synergy index reflects the uniformity of axial and radial deformation of the metamaterial separator under impact load. If the index deviates from the acceptable range, it indicates that some cells have failed prematurely, resulting in a decrease in resistance strength. In this case, weak resistance areas are identified based on dynamic compaction trajectories, and the magnetic field strength in these areas is adjusted to enhance the magnetohydrodynamic viscosity, thereby restoring the overall uniformity of resistance strength. Simultaneously, the vibration isolation capability is determined by the pressure distribution entropy between the battery pack and the vibration isolation foam. If the pressure distribution entropy is too high, it indicates uneven pressure distribution, local overload or insufficient deformation of the vibration isolation foam, and a decrease in vibration isolation efficiency. In this case, the elongation of the hydraulic rod is adjusted to improve the uniformity of pressure distribution, ensuring that the vibration isolation foam dissipates energy synergistically and effectively suppresses vibration transmission. This precise adjustment based on real-time monitoring avoids local stress concentration or vibration isolation failure caused by uneven resistance strength, thereby improving the adaptability of the protection strategy of the lithium battery protection device.

[0018] Furthermore, this invention evaluates the long-term effectiveness of the protection strategy by assessing the cumulative damage level of the battery pack to optimize the preset energy index. The cumulative damage level is calculated based on the proportion of failed cells in the metamaterial separator or the failed area of ​​the vibration-damping foam. If the damage level exceeds a preset threshold, it indicates that the current protection strategy may lead to accelerated material fatigue. When the rigid intrusion protection strategy is inadequate, the preset energy index is lowered to trigger rigid protection earlier, reducing further impact of high-impact loads on the damaged separator. When the flexible vibration suppression strategy is inadequate, the preset energy index is raised to delay the system's switch to rigid protection, avoiding over-protection that exacerbates fatigue damage to the vibration-damping foam. This adaptive optimization ensures that the protection device remains highly efficient during long-term use, effectively suppressing mechanical damage, fretting wear, and aging of the battery pack while ensuring its operational stability and lifespan, thereby improving the adaptability of the lithium battery protection strategy. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of a lithium battery collision safety protection device based on a negative Poisson's ratio metamaterial according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the metamaterial partition structure according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the concave cell structure of the metamaterial partition in an embodiment of the present invention; Figure 4 This is a structural block diagram of a lithium battery collision safety protection device based on a negative Poisson's ratio metamaterial, according to an embodiment of the present invention. In the diagram: 1. Shell, 11. Cover plate, 12. Cavity, 13. Circumferential sidewall, 2. Metamaterial partition, 21. Inward-facing cell, 22. Miniature electromagnetic coil, 23. Magnetofluid, 3. Vibration-damping foam, 4. Hydraulic rod. Detailed Implementation

[0020] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0021] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0022] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0023] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0024] Please see Figures 1-4 As shown, Figure 1 This is a schematic diagram of the structure of a lithium battery collision safety protection device based on a negative Poisson's ratio metamaterial according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the metamaterial partition structure according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the concave cell structure of the metamaterial partition in an embodiment of the present invention; Figure 4 This is a structural block diagram of a lithium battery collision safety protection device based on a negative Poisson's ratio metamaterial, according to an embodiment of the present invention.

[0025] This invention provides a lithium battery collision safety protection device based on a negative Poisson's ratio metamaterial, comprising: The housing 1 includes a cover plate 11, a bottom plate, a circumferential sidewall 13, and a cavity 12 formed by the circumferential sidewall 13 and the bottom plate for accommodating a battery pack, wherein the bottom plate and the circumferential sidewall 13 are an integrated rigid enclosure structure. The metamaterial partition 2 is disposed in the cavity 12 and is movably connected to the inner wall of the shell 1 by a number of hydraulic rods 4. It includes a number of concave cell structures 21 embedded with micro electromagnetic coils 22 and a number of pores filled with magnetofluid 23. Vibration-damping foam 3 is fixedly installed on the surface of the metamaterial separator 2 and is attached to the outer surface of the battery pack; The situational awareness module includes several acceleration sensors for real-time monitoring of the impact acceleration and impact duration acting on the protective device, and a strain sensor array for real-time monitoring of the strain of the metamaterial partition 2 and the strain stress distribution of the foam. The protection strategy determination module is used to determine whether the protection strategy of the protection device is a rigid intrusion protection strategy or a flexible vibration suppression strategy based on the comparison result between the impact energy index and the preset energy index. An intrusion protection module, in response to the determination result of the rigid intrusion protection strategy, determines whether the resistance strength of the metamaterial partition 2 is qualified based on the deformation synergy index of the metamaterial partition 2, and determines the weak resistance strength area based on the dynamic compaction trajectory of the metamaterial partition 2 according to the condition that the resistance strength of the metamaterial partition 2 is unqualified, so as to adjust the magnetic field strength of the weak resistance strength area. The vibration suppression module, in response to the determination result of the flexible vibration suppression strategy, determines whether the vibration isolation capability of the protective device is qualified based on the pressure distribution entropy between the battery pack and the vibration isolation foam 3, and adjusts the elongation of the hydraulic rod 4 based on the condition that the vibration isolation capability of the protective device is unqualified. The protection optimization module is used to determine whether the protection strategy is qualified based on the cumulative damage of the battery pack, and to optimize the preset energy index based on the condition that the protection strategy is unqualified.

[0026] Specifically, the acceleration sensor is a miniature triaxial piezoelectric acceleration sensor, wherein one sensor is arranged at each of the four corners of the bottom and top of the protective device, and one sensor is arranged on each of the four sides, which are rigidly connected to the housing 1 of the protective device by means of thread fixing or adhesive bonding, as not shown in the figure.

[0027] Specifically, the strain sensor array used to monitor the metamaterial partition 2 uses foil strain gauges and adopts a composite grid of "well" shape and ring shape. A strain gauge is arranged every 15-20 mm along the length and width of the metamaterial partition 2, which is not shown in the figure.

[0028] Specifically, the strain sensor array used to monitor the vibration isolation foam 3 uses flexible piezoelectric sensors, and several flexible piezoelectric sensors are evenly distributed along the interface between the battery pack and the vibration isolation foam 3, which are not shown in the figure.

[0029] Specifically, the metamaterial partition 2 is made of a negative Poisson's ratio metamaterial. The pores of the metamaterial partition 2 are filled with a magnetic fluid 23, and micro electromagnetic coils 22 are embedded in the cell structure of the metamaterial partition 2, which are distributed alternately with the pores. Each coil corresponds to a region, and the magnetic field strength of the region can be controlled by an independent circuit. When there is no magnetic field, the magnetic fluid 23 is a low-viscosity fluid. When a magnetic field is applied, the magnetic particles, usually micron-sized ferromagnetic materials, change from random distribution to chain or columnar structure arranged along the direction of the magnetic field. This causes the viscosity of the magnetic fluid 23 to increase by 2 to 3 orders of magnitude within milliseconds, forming a solid-like state, thereby changing the relative density of the metamaterial.

[0030] Specifically, the vibration-damping foam 3 is EVA foam.

[0031] Specifically, the protection strategy determination module determines the protection strategy as a rigid intrusion protection strategy based on the comparison result that the energy index is greater than the preset energy index; The protection strategy determination module determines the protection strategy as a flexible vibration suppression strategy based on the comparison result that the energy index is less than or equal to the preset energy index.

[0032] Specifically, the preset energy index range is set to [90, 110], and in this embodiment of the invention, 100 is preferred.

[0033] Specifically, the energy index is a weighted sum of the impact acceleration coefficient, impact frequency coefficient, and impact period coefficient. The impact acceleration coefficient is the ratio of the peak impact acceleration to the critical acceleration reference value for rigid intrusion damage to the battery pack, with a weighting coefficient of 0.8. The impact frequency coefficient is the ratio of the impact frequency to the critical frequency reference value for rigid intrusion damage to the battery pack, with a weighting coefficient of 0.1. The impact period coefficient is the ratio of the impact period to the critical period reference value, with a weighting coefficient of 0.1. The critical acceleration reference value is 5g, where g is the acceleration due to gravity; the critical frequency reference value is 200Hz; and the critical period reference value is 0.005s.

[0034] Specifically, external loads acting on battery packs can be categorized into high-amplitude, short-duration, and highly invasive rigid intrusive loads, such as collisions and punctures, and medium-amplitude, periodic, and continuous flexible vibration loads, such as road bumps and equipment vibrations. The former causes structural impact fatigue and intrusive damage, while the latter leads to fretting wear and material aging accumulation, corresponding to two differentiated protection logics: rigid blocking and energy absorption, and vibration attenuation and displacement suppression. The energy index, through dimensionless processing, integrates three core parameters: peak impact acceleration (characterizing load intensity), impact frequency (characterizing load rhythm), and impact period (characterizing load duration). After weighting and calibration, these parameters can accurately quantify the load. Assigning intrusion risk level and vibration characteristics together is more effective at avoiding misjudgments than relying on a single parameter. For example, high-frequency, medium-acceleration vibration may be misjudged as rigid intrusion, and low-frequency, high-acceleration impact may be misjudged as flexible vibration. Meanwhile, the preset threshold of the energy index is calibrated through battery pack damage criticality experiments, clearly defining the boundary between the two types of loads. This allows for real-time, dynamic switching of protection strategies, avoiding battery pack structural damage and safety risks caused by insufficient protection under rigid intrusion loads, while also preventing energy waste and ineffective loss of protective materials due to over-protection in flexible vibration scenarios. Ultimately, this ensures that the protective device adapts to external load characteristics in the optimal way, maximizing the battery pack's damage resistance, operational stability, and service life.

[0035] Specifically, the intrusion protection module determines the ratio of the radial deformation uniformity coefficient to the axial deformation uniformity coefficient of the metamaterial partition 2 as the deformation synergy index. The radial deformation uniformity coefficient is the coefficient of variation of the radial deformation of the metamaterial partition 2 when subjected to impact, and the axial deformation uniformity coefficient is the coefficient of variation of the axial deformation of the metamaterial partition 2 when subjected to impact. The specific determination process includes: The axial force-bearing surfaces of the upper and lower surfaces along the vibration / impact load direction and the radial force-bearing surfaces of the side surfaces perpendicular to the load direction of the metamaterial partition 2 are divided into several grids. The division method is that the number of grids on a single surface is ≥20, and the grid density of stress concentration areas such as corners and dense cells is twice that of ordinary areas. The deformation displacement of each grid is synchronously collected by the strain sensor array at the instant of impact. The axial deformation displacement is the vertical distance between the grid center point along the load direction (axial direction) and the original position plane, and the radial deformation displacement is the horizontal distance between the grid center point along the load direction (radial direction) and the original position plane. Calculate the coefficient of variation of deformation displacement of all grids along the axial direction, and define the coefficient of variation as the axial / radial deformation uniformity coefficient.

[0036] Specifically, the intrusion protection module determines that the resistance strength of the metamaterial partition 2 is unqualified based on the comparison result that the deformation synergy index is greater than the second preset synergy index or less than the first preset synergy index; The intrusion protection module determines that the resistance strength of the metamaterial partition 2 is qualified based on the comparison result that the phase change synergy index is less than or equal to the second preset synergy index and greater than or equal to the first preset synergy index.

[0037] Specifically, the first preset synergy index is 0.8, and the second preset synergy index is 1.2.

[0038] Specifically, the resistance strength of a concave structure with a negative Poisson's ratio is not the load-bearing capacity in a single direction, but depends on the synergistic effect of axial compression and radial expansion. The uniformity of axial deformation ensures uniform load transfer and avoids local stress concentration that could lead to cell cracking. The uniformity of radial deformation enhances the axial load-bearing stability through lateral constraints, preventing the overall structure from collapsing. The synergistic matching of the two is a prerequisite for the concave cells 21 to be simultaneously stressed and dissipate energy in synergy. Once the ratio deviates from this range, it indicates that some cells have failed prematurely, and the overall resistance strength will inevitably decrease.

[0039] Specifically, under the condition that the resistance strength of the metamaterial partition 2 is unqualified, the intrusion protection module constructs a dynamic compaction trajectory of the metamaterial partition 2 compaction process based on the real-time deformation displacement data of each grid of the metamaterial partition 2 collected by the strain sensor array. The horizontal axis of the trajectory is the time dimension, and the vertical axis is the real-time compaction displacement of each grid along the impact / vibration load direction. The ideal compaction trajectory is retrieved and aligned with the time axis as a unified reference. The vertical distance between the dynamic compaction trajectory and the ideal compaction trajectory is calculated at the same time point and the same grid position after alignment. The vertical distance is compared with a preset distance. Based on the comparison result that the vertical distance is greater than the preset distance, the corresponding position is determined as a weak resistance strength area.

[0040] Specifically, the ideal compaction trajectory is the time-compaction displacement standard trajectory calibrated by multiple sets of impact tests when the resistance strength of the metamaterial partition 2 is qualified.

[0041] Specifically, the intrusion protection module, upon determining a region with weak resistance, sets several strength adjustment coefficients based on the relative difference between the preset spacing and the vertical spacing, and the comparison result with the preset relative difference, to increase the magnetic field strength of the region with weak resistance.

[0042] Specifically, the intrusion prevention module determines to increase the magnetic field strength by a first intensity adjustment coefficient based on a comparison result where the relative difference is greater than the preset relative difference; The intrusion prevention module determines to increase the magnetic field strength by a second intensity adjustment coefficient based on the comparison result that the relative difference is less than or equal to the preset relative difference.

[0043] Specifically, the preset spacing is set to a range of [0.01mm, 0.05mm], preferably 0.03mm in this embodiment; the preset relative difference is set to a range of [10%, 30%], preferably 15% in this embodiment; the first intensity adjustment coefficient is set to a range of [1.3, 1.6], preferably 1.4 in this embodiment; and the second intensity adjustment coefficient is set to a range of [1.1, 1.2], preferably 1.15 in this embodiment.

[0044] Understandably, the overall magnetic field strength of the metamaterial partition 2 is pre-set under the intrusion protection strategy. When the resistance strength of the metamaterial partition 2 is unqualified, the magnetic field strength at the corresponding position is adjusted in a targeted manner. The selected strength adjustment coefficient is multiplied by the overall magnetic field strength, and the product is the adjusted magnetic field strength, so as to ensure the uniformity of the overall resistance strength of the metamaterial partition 2.

[0045] Specifically, the vibration suppression module determines that the vibration isolation capability of the protective device is unqualified based on the comparison result that the pressure distribution entropy between the battery pack and the vibration isolation foam 3 is greater than the preset distribution entropy; The vibration isolation capability of the protective device is determined to be qualified if the comparison result of the pressure distribution entropy of the vibration suppression module being less than or equal to the preset distribution entropy.

[0046] Specifically, the vibration suppression module calculates the pressure distribution entropy using the Shannon entropy formula based on the normalized values ​​of several monitored pressures and the average monitored pressure of the pressure sensor array. This is existing technology and will not be elaborated further. The ratio of the calculated result to the maximum entropy value when the pressure at all monitoring points is completely uniform is determined as the pressure distribution entropy.

[0047] Specifically, the preset distribution entropy is set to a range of [0.7, 0.8], and preferably 0.76 in this embodiment of the invention.

[0048] Specifically, the vibration isolation principle of vibration-damping foam 3 is to absorb and dissipate vibration energy through elastic deformation, reducing energy transfer to the battery pack. When the pressure is uniform, all areas of vibration-damping foam 3 undergo synchronous elastic deformation with consistent deformation amplitude, forming a synergistic energy dissipation effect. Vibration energy is evenly distributed across the entire contact surface, significantly reducing the vibration amplitude transferred to the battery pack. When the pressure is uneven, local areas bear excessive pressure, causing the vibration-damping foam 3 to be over-compressed or even exceed its elastic limit. This area loses its effective energy dissipation capacity, and vibration energy directly penetrates the concentrated area. Simultaneously, areas with insufficient pressure do not deform enough and cannot participate in energy dissipation, resulting in a significant decrease in overall vibration isolation efficiency. Pressure distribution entropy can precisely quantify this uniformity. The closer the entropy value is to 1, the more uniform the pressure distribution, and the better the vibration isolation capability of vibration-damping foam 3. The further the entropy value is from 1, the more concentrated the pressure is locally, and the worse the vibration isolation capability of vibration-damping foam 3.

[0049] Specifically, when the vibration suppression module determines that the vibration isolation capability of the protective device is unqualified, it determines to increase the elongation of the hydraulic rod 4 by a first length adjustment coefficient based on the comparison result that the pressure amplitude between the battery pack and the vibration isolation foam 3 is greater than the preset amplitude. The vibration suppression module determines to increase the elongation of the hydraulic rod 4 by using a second length adjustment coefficient based on the comparison result that the pressure amplitude between the battery pack and the vibration isolation foam 3 is less than or equal to the preset amplitude.

[0050] Specifically, the pressure amplitude is the difference between the maximum and minimum pressure between the battery pack and the vibration-damping foam 3. The preset amplitude range is set to [15kPa, 30kPa], and preferably 20kPa in this embodiment of the invention. The first length adjustment coefficient range is set to [1.05, 1.1], and preferably 1.07 in this embodiment of the invention. The second length adjustment coefficient range is set to [1.11, 1.2], and preferably 1.15 in this embodiment of the invention.

[0051] Understandably, the core issue of substandard vibration isolation capability lies in localized pressure concentration and insufficient pressure in certain areas, rather than an overall pressure exceeding or falling short of the standard. Increasing the elongation of the hydraulic rod 4 essentially pushes the vibration-damping foam 3 slightly towards the battery pack side. This allows areas where the foam 3 is not in full contact and thus lacks sufficient pressure to receive effective pressure, reducing pressure differences between areas. For areas with concentrated pressure, since the foam 3 is already under some compression, the pressure increase from the slight elongation of the hydraulic rod 4 is limited and will not exceed the elastic limit. Instead, it can increase the overall pressure, making the deformation of the foam 3 more uniform and raising the pressure distribution entropy to within the acceptable range. Therefore, when the pressure amplitude is too high, the local pressure is close to the elastic limit of the foam 3. Only a slight increase in the elongation of the hydraulic rod 4 is needed to fine-tune the pressure distribution rather than a significant increase in pressure, avoiding localized overload. When the pressure amplitude is low, the overall pressure is too low, and insufficient deformation of the foam 3 leads to uneven distribution. In this case, the elongation needs to be appropriately increased to raise the overall pressure, promoting full contact of the foam 3 and improving uniformity.

[0052] Specifically, the protection optimization module determines that the protection strategy is unqualified based on the comparison result that the cumulative damage degree of the battery pack is greater than the preset damage degree; The protection optimization module determines the protection strategy to be qualified based on the comparison result that the cumulative damage degree is less than or equal to the preset damage degree.

[0053] Specifically, the cumulative damage is determined according to the protection strategy. For a rigid intrusion protection strategy, the cumulative damage is the percentage of the number of failed concave cells 21 in the metamaterial partition 2 to the total number of concave cells 21. For a flexible vibration suppression strategy, the cumulative damage is the percentage of the failed area of ​​the vibration isolation foam 3 to the total area of ​​the vibration isolation foam 3.

[0054] Specifically, the preset damage level is set to a range of [20%, 40%], and in this embodiment of the invention, 30% is preferred.

[0055] Specifically, when the rigid intrusion protection strategy fails, the protection optimization module reduces the preset energy index by using an exponential correction coefficient based on the comparison result between the damage difference between the cumulative damage degree and the preset damage degree and the preset difference. When the flexible vibration suppression strategy fails, the protection optimization module increases the preset energy index by an exponential optimization coefficient based on the comparison result between the damage difference between the cumulative damage degree and the preset damage degree and the preset difference.

[0056] Specifically, the preset difference is set to a range of [5%, 10%], and preferably 8% in this embodiment of the invention.

[0057] Specifically, when the rigid intrusion protection strategy fails, the protection optimization module determines to reduce the preset energy index by a first index correction coefficient based on the comparison result that the damage difference is greater than the preset difference. Based on the comparison result that the damage difference is less than or equal to the preset difference, the preset energy index is determined to be reduced by the second index correction coefficient.

[0058] Specifically, when the flexible vibration suppression strategy fails, the protection optimization module determines to increase the preset energy index by a first index optimization coefficient based on the comparison result that the damage difference is greater than the preset difference. Based on the comparison result that the damage difference is less than or equal to the preset difference, the preset energy index is increased by the second index optimization coefficient.

[0059] Specifically, the first index correction coefficient is 0.92, the second index correction coefficient is 0.95, the first index optimization coefficient is 1.05, and the second index optimization coefficient is 1.03.

[0060] Understandably, when the rigid protection strategy fails, the preset energy index should be lowered to allow the system to trigger rigid protection earlier, reducing the impact of high impact loads on the already damaged partition. When the flexible vibration protection strategy fails, the preset energy index should be raised to allow the system to switch to rigid protection later, avoiding over-protection that could exacerbate fatigue damage to the vibration isolation foam 3.

[0061] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A lithium battery collision safety protection device based on a negative Poisson's ratio metamaterial, characterized in that, include: The housing includes a cavity for accommodating the battery pack; The metamaterial partition, which is disposed in the cavity and is movably connected to the inner wall of the shell through several hydraulic rods, includes several concave cell structures made of negative Poisson's ratio metamaterial with embedded micro electromagnetic coils and several pores filled with magnetic fluid; Vibration-damping foam is fixedly installed on the surface of the metamaterial separator and adhered to the outer surface of the battery pack; The situational awareness module includes several acceleration sensors for real-time monitoring of the impact energy acting on the protective device, and a strain sensor array for real-time monitoring of the strain of the metamaterial partition and the strain stress distribution of the foam. The protection strategy determination module is used to determine whether the protection strategy of the protection device is a rigid intrusion protection strategy or a flexible vibration suppression strategy based on the comparison result between the energy index of the external impact and the preset energy index. The energy index is a weighted sum of the impact acceleration coefficient, the impact frequency coefficient and the impact period coefficient. An intrusion protection module, responding to the determination result of the rigid intrusion protection strategy, determines whether the resistance strength of the metamaterial partition is qualified based on the deformation synergy index of the metamaterial partition. Based on the condition that the resistance strength of the metamaterial partition is unqualified, it identifies a weak resistance strength region according to the dynamic compaction trajectory of the metamaterial partition and adjusts the magnetic field strength of the weak resistance strength region. The deformation synergy index is the ratio of the radial deformation uniformity coefficient to the axial deformation uniformity coefficient of the metamaterial partition. The radial deformation uniformity coefficient is the coefficient of variation of the radial deformation of the metamaterial partition when subjected to impact, and the axial deformation uniformity coefficient is the coefficient of variation of the axial deformation of the metamaterial partition when subjected to impact. The vibration suppression module, in response to the determination result of the flexible vibration suppression strategy, determines whether the vibration isolation capability of the protective device is qualified based on the pressure distribution entropy between the battery pack and the vibration isolation foam, and adjusts the elongation of the hydraulic rod based on the condition that the vibration isolation capability of the protective device is unqualified. The pressure distribution entropy is the ratio of the result calculated by Shannon entropy formula based on the normalized value of several monitoring pressures and the average value of the monitoring pressure collected by the pressure sensor array to the maximum entropy value when the pressure at the monitoring point is uniform. The protection optimization module is used to determine whether the protection strategy is qualified based on the cumulative damage level of the battery pack, and to optimize the preset energy index based on the condition that the protection strategy is unqualified, wherein the cumulative damage level is determined according to the protection strategy. For rigid intrusion protection strategies, the cumulative damage is defined as the percentage of failed concave cells in the metamaterial partition relative to the total number of concave cells. For flexible vibration suppression strategies, the cumulative damage is the percentage of the failure area of ​​the vibration isolation foam to the total area of ​​the vibration isolation foam.

2. The lithium battery collision safety protection device based on a negative Poisson's ratio metamaterial according to claim 1, characterized in that, The protection strategy determination module determines the protection strategy as a rigid intrusion protection strategy based on the comparison result that the energy index is greater than the preset energy index.

3. The lithium battery collision safety protection device based on a negative Poisson's ratio metamaterial according to claim 2, characterized in that, The protection strategy determination module determines the protection strategy as a flexible vibration suppression strategy based on the comparison result that the energy index is less than or equal to the preset energy index.

4. The lithium battery collision safety protection device based on a negative Poisson's ratio metamaterial according to claim 3, characterized in that, The intrusion protection module determines that the resistance strength of the metamaterial partition is unqualified based on the comparison result that the deformation synergy index is greater than the second preset synergy index or less than the first preset synergy index.

5. The lithium battery collision safety protection device based on a negative Poisson's ratio metamaterial according to claim 4, characterized in that, Under the condition that the resistance strength of the metamaterial partition is unqualified, the intrusion protection module determines the corresponding position where the vertical distance between the dynamic compaction trajectory and the ideal compaction trajectory is greater than the preset distance as the weak resistance strength area based on the overlap and alignment result of the dynamic compaction trajectory of the metamaterial partition compaction process and the retrieved ideal compaction trajectory.

6. The lithium battery collision safety protection device based on a negative Poisson's ratio metamaterial according to claim 5, characterized in that, Under the condition of determining the weak resistance area, the intrusion protection module sets several strength adjustment coefficients based on the relative difference between the preset spacing and the vertical spacing, and the comparison result with the preset relative difference, to increase the magnetic field strength of the weak resistance area.

7. The lithium battery collision safety protection device based on a negative Poisson's ratio metamaterial according to claim 6, characterized in that, The vibration suppression module determines that the vibration isolation capability of the protective device is unqualified based on the comparison result that the pressure distribution entropy between the battery pack and the vibration isolation foam is greater than the preset distribution entropy, and sets several length adjustment coefficients to increase the elongation of the hydraulic rod based on the comparison result of the pressure amplitude between the battery pack and the vibration isolation foam and the preset amplitude.

8. The lithium battery collision safety protection device based on a negative Poisson's ratio metamaterial according to claim 7, characterized in that, The protection optimization module determines that the protection strategy is unqualified based on the comparison result that the cumulative damage degree of the battery pack is greater than the preset damage degree.

9. The lithium battery collision safety protection device based on a negative Poisson's ratio metamaterial according to claim 8, characterized in that, When the rigid intrusion protection strategy fails, the protection optimization module reduces the preset energy index by using an exponential correction coefficient based on the comparison result between the damage difference between the cumulative damage degree and the preset damage degree and the preset difference. When the flexible vibration suppression strategy fails, the protection optimization module increases the preset energy index by an exponential optimization coefficient based on the comparison result between the damage difference between the cumulative damage degree and the preset damage degree and the preset difference.

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