Lithium ion battery pack with safety protection structure for electric vehicle

Abstract

The invention discloses an electric vehicle lithium ion battery pack with a safety protection structure, the electric vehicle lithium ion battery pack comprises a protection shell and a battery pack mounted in the protection shell, the battery pack comprises a first battery unit and a second battery unit arranged around the first battery unit; inserting grooves are formed in the periphery of the first battery unit, and inserting plates capable of being inserted into the inserting grooves are arranged on the side face, facing the first battery unit, of each second battery unit; the protection shell comprises a shell body, a containing cavity is formed in the shell body, a safety protection structure is arranged in the containing cavity, the safety protection structure comprises a first panel, a second panel and an energy absorption buffer structure arranged between the first panel and the second panel, the energy absorption buffer structure is composed of a plurality of columns and curved-surface blades, the adjacent columns are distributed in parallel at equal intervals, and the curved-surface blades are arranged on the first panel and the second panel. The curved-surface blades are connected and surround the column body. Compared with the prior art, the problems that an existing lithium ion battery pack for the electric vehicle is inconvenient to disassemble and assemble and poor in safety protection effect are effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy batteries, and in particular to a lithium-ion battery pack for electric vehicles with a safety protection structure. Background Art

[0002] With the increasing popularity of electric vehicles, especially electric two-wheelers, lithium-ion battery packs, as their core power source, have become increasingly important. Their performance and safety directly impact the user experience and market acceptance of electric vehicles. However, existing lithium-ion battery packs for electric vehicles have exposed numerous issues in practical applications that require urgent resolution.

[0003] First, traditional lithium-ion battery packs for electric vehicles typically utilize a monolithic design, with battery cells often secured together through welding or complex bolting. This design necessitates disassembly of the entire battery pack when a battery cell fails and requires replacement, potentially requiring specialized technicians. This significantly increases maintenance costs and time. For the average user, this complex maintenance process degrades the user experience and shortens the battery's lifespan, as users may postpone necessary maintenance.

[0004] Secondly, the protection design of existing electric vehicle lithium-ion battery packs is generally inadequate. Electric two-wheelers are often subjected to vibration, impact, and even collisions and falls during operation. In these situations, if the battery pack lacks an effective protective structure, it can easily damage the battery cells. Battery damage not only affects performance but, more seriously, can cause safety issues such as battery short circuits, overheating, and even fires and explosions.

[0005] Furthermore, existing battery packs often lack adequate heat dissipation, making them susceptible to overheating in high-temperature environments or under high loads. Overheating accelerates battery aging, reduces capacity and cycle life, and in severe cases can trigger thermal runaway, leading to safety incidents. Battery temperature management is particularly critical in applications such as electric two-wheelers, which are exposed to a wide range of environmental conditions.

[0006] Therefore, developing a lithium-ion battery pack for electric vehicles that combines convenient disassembly and assembly, effective protection, and excellent thermal management functions is of great significance to improving the safety of electric vehicles, extending battery life, and improving user experience. Summary of the Invention

[0007] The main purpose of the present disclosure is to provide a lithium-ion battery pack for electric vehicles with a safety protection structure, so as to solve the problems of inconvenient disassembly and assembly and poor safety protection effect of existing lithium-ion battery packs for electric vehicles.

[0008] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] A lithium-ion battery pack for an electric vehicle with a safety protection structure includes a protective shell and a battery pack mounted within the protective shell. The battery pack includes a first battery cell and second battery cells arranged around the first battery cell. The battery pack is arranged in a cross-shaped structure, with the first battery cell located at the center of the cross-shaped structure and the second battery cells arranged along four sides of the cross-shaped structure.

[0010] The first battery unit is provided with plug-in slots on all four sides, and each second battery unit is provided with a plug-in board on the side facing the first battery unit that can be plugged into the plug-in slot. The first battery unit and the second battery unit are plug-in-matched and connected through the plug-in slot and the plug-in board. The first battery unit and the second battery unit are electrically connected via a conductive sheet.

[0011] The protective shell includes a shell, a accommodating cavity is provided in the shell, a safety protection structure is provided in the accommodating cavity, the safety protection structure includes a first panel, a second panel and an energy absorption buffer structure arranged between the first panel and the second panel, the energy absorption buffer structure is composed of a plurality of columns and curved blades, adjacent columns are distributed in parallel at equal intervals, and the curved blades are connected and surround the columns.

[0012] Preferably, the cross-section of the shell is a cross-shaped structure, and the internal space is divided into five independent areas, each area is used to accommodate a group of battery cells, and a reinforcement block is provided between adjacent outer side walls of the shell, and the cross-section of the reinforcement block is triangular.

[0013] Preferably, the plug-in slot and the plug-in plate are both extended longitudinally and are in a T-shaped structure.

[0014] Preferably, the column is a hollow column, the interior of the column is uniformly filled with polyacrylamide polymer, the curved blades are in the shape of plant leaves, and are composed of continuous minimal curved surfaces; and the outer surface of the column is adjacent to the curved blades.

[0015] Preferably, the minimal surface extends and expands in an orderly manner in the three-dimensional direction, and its surface equation is A=cos(2x)·sin(y)+cos(2y)·sin(z)+cos(z)·sin(3x), wherein x, y, and z are the three-dimensional coordinates of space, and A is the displacement of the surface blade along the normal direction.

[0016] Preferably, the inner radius of the cylinder is 15-25 mm, the thickness of the cylinder and the curved blade is 1.0-2.5 mm, and the length of the curved blade in the x, y and z directions is 4π.

[0017] Preferably, the column and the curved blades are made of aluminum alloy.

[0018] Preferably, the surface of the plug board of the second battery unit is coated with a heat-absorbing flame-retardant coating with a thickness of 1-10 mm.

[0019] Preferably, the heat-absorbing flame-retardant coating is prepared by mixing the following components, applying the mixture to the surface of the plugboard, and then drying the mixture. The components include, by weight:

[0020] 30-40 parts of ammonium dihydrogen phosphate

[0021] 20-30 parts of sodium bicarbonate

[0022] 15-25 parts of melamine

[0023] 10-20 parts polyurethane prepolymer

[0024] 5-10 parts of nano titanium dioxide

[0025] 8-15 parts expandable graphite

[0026] 40-80 parts of organic solvent.

[0027] Preferably, the organic solvent is selected from at least one of dimethyl sulfoxide, propylene glycol methyl ether acetate, cyclohexanone and N-methylpyrrolidone.

[0028] Preferably, the shell includes an outer shell and an inner shell, the inner shell is arranged in the outer shell and forms the accommodating cavity with the outer shell, and the safety protection structure is arranged in the accommodating cavity.

[0029] Preferably, a plurality of support columns are provided between the outer shell and the inner shell, and the support columns are made of shape memory alloy.

[0030] Preferably, the first battery unit and the second battery unit both include a battery core and a thermal management layer covering the battery core, and the thermal management layer includes a phase change material.

[0031] Preferably, the thermal management layer includes a low-temperature resistant phase change material and a high-temperature resistant phase change material, the phase change temperature of the low-temperature resistant phase change material is -10°C to -20°C, and the phase change temperature of the high-temperature resistant phase change material is 55°C to 65°C.

[0032] Preferably, the low-temperature resistant phase change material comprises the following components in parts by weight: 30-40 parts of polyethylene glycol 400, 15-25 parts of octadecylamine ethoxylate, 10-20 parts of 1-bromodecane, 5-10 parts of graphene quantum dots, 3-7 parts of alumina nanofibers, and 2-5 parts of multi-walled carbon nanotubes;

[0033] The high-temperature resistant phase change material comprises the following components in parts by weight: 35-45 parts of stearylethanolamine, 25-35 parts of myristic acid, 10-15 parts of cross-linked polyvinyl alcohol, 5-10 parts of graphene aerogel, 3-8 parts of hollow carbon nanospheres, and 2-5 parts of aluminum nitride nanosheets.

[0034] Compared with the prior art, the present invention has at least the following beneficial effects:

[0035] 1) The battery pack designed in this invention utilizes a plug-in structure, with the first and second battery cells plugged into and connected to the plug-in board via a plug-in slot. This design allows the battery cells to be individually removed and replaced, greatly simplifying the maintenance process and improving assembly and disassembly efficiency. When a battery cell fails, only that specific cell needs to be replaced, eliminating the need to replace the entire battery pack. This saves costs and reduces maintenance time, making operation more convenient and efficient. This design is particularly well-suited for the daily maintenance needs of electric two-wheelers, allowing even ordinary users to easily complete battery replacement and maintenance tasks. This modular design also facilitates standardized production and maintenance, further reducing costs.

[0036] 2) The battery pack of the present invention is arranged in a cross-shaped structure, with the first battery cell located at the center of the cross-shaped structure and the second battery cells arranged along the four directions of the cross-shaped structure. The advantages of this arrangement are as follows: a) Optimizing the current path: The cross-shaped arrangement makes the current flow path inside the battery pack more balanced and shorter. The first battery cell at the center serves as an energy collection point, which can minimize the difference in current path length introduced from all directions and reduce the efficiency loss caused by internal resistance imbalance. b) Enhancing heat dissipation performance: The cross-shaped arrangement significantly improves the thermal management effect inside the battery pack. Since each second battery cell is directly connected to the first battery cell in the center and extends outward to the edge of the shell, a natural heat diffusion channel is formed. This structure allows heat to diffuse evenly from the center to the surrounding areas, avoiding hot spot concentration. The temperature difference inside the battery pack can be controlled within 5°C. c) Enhancing structural stability: The cross-shaped arrangement forms a mutually supporting system in the mechanical structure, which gives the battery pack better integrity and rigidity. When the battery pack is subjected to external impact, the force can be evenly dispersed along the four directions of the cross-shaped structure, reducing stress concentration and improving overall impact resistance. d) Optimize battery management: The cross-shaped arrangement facilitates the implementation of a zoning management strategy. The first battery cell in the center can integrate the core control unit of the battery management system (BMS), while the second battery cells in the four directions can be respectively equipped with temperature sensors and voltage monitoring points to form four independent management areas. This layout makes the distribution of monitoring points more reasonable and the data collection more comprehensive, improves the accuracy and response speed of fault detection, and enhances the intelligence level of the battery management system. e) Facilitate disassembly and maintenance: The cross-shaped arrangement is perfectly combined with the plug-in design of the present invention. Plug-in slots are set around the first battery cell in the center, which are connected to the plug-in boards of the second battery cells in the four directions. This layout makes plug-in and unplugging operations more intuitive and convenient. Users can clearly identify the position and connection relationship of each battery cell, significantly reducing the risk of misoperation and improving the efficiency of maintenance and replacement. Maintenance personnel only need to operate in any direction of the cross to complete the disassembly or replacement of the battery cells in the corresponding area.

[0037] 3) The protective shell of the present invention is equipped with a unique safety protection structure, which includes a first panel, a second panel, and an energy-absorbing buffer structure. The energy-absorbing buffer structure adopts a combined design of a column and curved blades, and the column is filled with polymer. This design significantly improves the impact resistance of the battery pack. When the battery pack is subjected to external impact, this structure can effectively absorb and disperse the impact energy, protecting the internal battery cells from damage. Especially when the electric two-wheeled vehicle experiences vibration, collision, or even falls, this protective structure can provide comprehensive protection, greatly improving the safety and reliability of the battery pack.

[0038] 4) The energy-absorbing and cushioning structure of this invention utilizes an innovative combination of columns and curved blades. The curved blades are composed of a continuous series of minimally curved surfaces. This design not only provides excellent cushioning performance but also maximizes energy absorption and protection within a confined space. When the first and second panels are subjected to pressure, the blades undergo uniform and significant deformation, enabling stress transfer, thereby reducing the concentrated force on the columns and preventing sudden structural failure.

[0039] 5) The present invention features a rational overall structural design, which not only solves the problem of inconvenient battery pack assembly and disassembly, but also enhances the battery pack's safety and protection capabilities. Furthermore, its compact structure makes it suitable for installation on electric two-wheeled vehicles with limited space. This innovative design effectively extends the battery pack's service life and improves the reliability and safety of electric two-wheeled vehicles, thus contributing to the widespread adoption and application of electric two-wheeled vehicles. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is one of the structural schematic diagrams of a lithium-ion battery pack in one embodiment of the present invention;

[0041] Figure 2 This is a second structural diagram of a lithium-ion battery pack in one embodiment of the present invention;

[0042] Figure 3 is an exploded view of the structure of a lithium-ion battery pack in one embodiment of the present invention;

[0043] Figure 4 is a cross-sectional view of a lithium-ion battery pack in one embodiment of the present invention;

[0044] Figure 5 is a cross-sectional view of a protective shell in one embodiment of the present invention;

[0045] Figure 6 Schematic diagram of the safety protection structure in one embodiment of the present invention.

[0046] In the figure: 1. Protective shell; 11. Reinforcement block; 12. Safety protection structure; 121. First panel; 122. Second panel; 123. Column; 124. Curved blade; 2. First battery unit; 21. Plug-in slot; 3. Second battery unit; 31. Plug-in board; 32. Heat-absorbing flame-retardant coating. DETAILED DESCRIPTION

[0047] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0048] Please see the attached Figures 1 to 6 This embodiment provides a lithium-ion battery pack for electric vehicles with a safety protection structure, including a protective shell 1 and a battery pack installed in the protective shell 1. The battery pack includes a first battery cell 2 and second battery cells 3 arranged around the first battery cell 2. The battery pack is arranged in a cross-shaped structure, with the first battery cell 2 located at the center of the cross-shaped structure and the second battery cells 3 arranged along the four directions of the cross-shaped structure.

[0049] The first battery unit 2 is provided with insertion slots 21 on all sides. Each second battery unit 3 is provided with an insertion board 31 that can be inserted into the insertion slot 21 on the side facing the first battery unit 2. The first battery unit 2 and the second battery unit 3 are plugged and connected through the insertion slots 21 and the insertion board 31. The battery units are connected in series or in parallel through conductive sheets.

[0050] The protective shell 1 includes a shell, a accommodating cavity is provided in the shell, and a safety protection structure 12 is provided in the accommodating cavity. The safety protection structure 12 includes a first panel 121, a second panel 122 and an energy absorption and buffering structure arranged between the first panel 121 and the second panel 122. The energy absorption and buffering structure is composed of a plurality of columns 123 and curved blades 124. The adjacent columns 123 are distributed in parallel at equal intervals, and the curved blades 124 are connected and surround the columns 123.

[0051] Through the above design, the present invention realizes convenient disassembly and assembly and efficient maintenance of the battery unit, while providing excellent safety protection performance, effectively solving the problems of inconvenient disassembly and assembly and poor protection performance of existing lithium-ion battery packs for electric vehicles.

[0052] In one embodiment of the present invention, the cross-section of the shell is a cross-shaped structure, and the internal space is divided into five independent areas, each area is used to accommodate a group of battery cells, and a reinforcement block 11 is provided between adjacent outer walls of the shell, and the cross-section of the reinforcement block 11 is triangular; preferably, the reinforcement block 11 and the shell are an integrally formed structure.

[0053] Among them, the structural design of the shell has the following advantages:

[0054] 1) Enhanced Structural Strength: The cross-shaped structure offers excellent mechanical resistance to bending and torsion, providing increased structural strength while maintaining lightweight. During operation, especially on uneven surfaces, the battery pack of an electric two-wheeled vehicle is subject to multi-directional vibration and impact. The cross-shaped structure can more effectively withstand and disperse these stresses, reducing the risk of structural deformation and damage.

[0055] 2) Optimized Space Utilization: The cross-shaped design rationally divides the internal space into five independent zones, each accommodating a group of battery cells. This layout ensures more uniform temperature distribution within the battery pack, avoiding heat concentration and improving heat dissipation efficiency and battery performance. Furthermore, this zoning design facilitates maintenance and management. If a battery problem in one area arises, it can be addressed independently without affecting other areas.

[0056] 3) Enhanced impact resistance: Reinforcement blocks 11 between adjacent outer walls provide additional support, significantly improving the overall rigidity and impact resistance of the housing. Made from high-strength composite materials, these blocks effectively disperse and absorb impact energy when the housing is subjected to external forces, preventing the impact from being directly transmitted to the internal battery cells.

[0057] 4) Improved heat dissipation: The cross-shaped structure increases the housing's surface area, facilitating heat dissipation. Furthermore, the spaces between the reinforcement blocks 11 serve as natural convection channels, promoting heat dissipation. In high-temperature environments or high-load operating conditions, this design more effectively maintains the battery pack's optimal operating temperature, extending battery life.

[0058] In one embodiment of the present invention, the plug slot 21 and the plug plate 31 are both arranged to extend longitudinally and are both T-shaped. The T-shaped structure design provides a larger contact area and stronger mechanical support, ensuring the stability and reliability of the connection between the battery cells. This design not only enhances the strength of the connection, but also facilitates the insertion and removal of the battery cells. The user only needs to apply force in the vertical direction to complete the disassembly and assembly without the need for special tools, which greatly simplifies the maintenance process and ensures that the connection is both firm and reliable and easy to operate. The T-shaped structure is made of aluminum alloy or high-strength engineering plastic, which has good mechanical strength and durability.

[0059] In one embodiment of the present invention, the conductive sheet includes a copper foil conductive sheet and an insulating protective layer, and the insulating protective layer is made of polyimide material; one end of the conductive sheet is connected to the positive or negative electrode of the first battery unit 2, and the other end is connected to the corresponding negative or positive electrode of the second battery unit 3, forming a series or parallel structure. The connection method of the conductive sheet is separated from the plug-in structure, so that when disassembling the battery unit, the user only needs to disconnect the conductive sheet and then pull out the plug board to complete the disassembly of the battery unit, which is simple and convenient to operate. Preferably, the connection method of the conductive sheet adopts a quick connector. This connector adopts an elastic metal contact sheet design, so that the connection and disconnection operations can be easily completed without the use of tools; at the same time, the outside of the connector is wrapped with insulating material to prevent the risk of short circuit; in order to enhance the reliability of the connection, the connection adopts a self-locking design, which will not loosen or disconnect even if the electric vehicle is subjected to vibration during driving.

[0060] In one embodiment of the present invention, the cylinder 123 is a hollow cylinder 123, and the interior of the cylinder 123 is uniformly filled with polyacrylamide (PAM) polymer. The curved blade 124 is in the shape of a plant leaf and is composed of continuous minimal curved surfaces; and the outer surface of the cylinder 123 is adjacent to the curved blade 124. This biomimetic design is inspired by the structure of plant leaves in nature and can produce uniform deformation when subjected to force, effectively dispersing and absorbing impact energy. The hollow design further reduces the weight of the structure while providing space for the filling material, enhancing the overall energy absorption effect. In addition, the polyacrylamide polymer has excellent viscoelasticity and can effectively absorb mechanical energy. When the cylinder 123 is subjected to pressure, the polyacrylamide filled inside can deform and absorb a large amount of energy, thereby providing better cushioning and protection effects. The polymer also has good chemical stability and durability, ensuring that the battery pack can maintain good protection performance during long-term use.

[0061] Wherein, the preparation method of polyacrylamide polymer is as follows:

[0062] 1) Add 400 ml of deionized water to the reaction vessel and introduce nitrogen gas for 10 minutes to remove dissolved oxygen;

[0063] 2) Add 40g of acrylamide monomer and stir until completely dissolved;

[0064] 3) Add 0.8 g of N,N'-methylenebisacrylamide as a cross-linking agent and continue stirring for 15 minutes;

[0065] 4) Add 0.2 g of ammonium persulfate as an initiator and stir for 5 minutes;

[0066] 5) Add 0.05 g of N,N,N',N'-tetramethylethylenediamine as a catalyst and stir rapidly;

[0067] 6) Pour the mixed solution into the pre-prepared column 123 and let it stand at room temperature for 4 hours to complete the polymerization reaction;

[0068] 7) Drying the polymer-filled column 123 at 60° C. for 12 hours to remove excess moisture;

[0069] 8) Cooling to room temperature to obtain a column 123 filled with polyacrylamide polymer.

[0070] In one embodiment according to the present invention, the minimal surface extends and expands in an orderly manner in three dimensions, and its surface equation is A = cos(2x)·sin(y)+cos(2y)·sin(z)+cos(z)·sin(3x), where x, y, and z are the three-dimensional coordinates of space, respectively, in radians (rad), and A is the displacement of the curved blade 124 along the normal direction, in millimeters (mm). This mathematically defined curved surface structure has good space filling properties and mechanical properties, can evenly distribute stress in all directions, and avoid structural failure caused by stress concentration. By precisely controlling the shape of the curved surface, the energy absorption performance and space utilization of the structure can be optimized.

[0071] Furthermore, the surface equation employed in this invention incorporates a combination of trigonometric functions of varying frequencies, making the surface structure more complex and uniform, enabling uniform stress distribution and energy absorption in a wider range of directions. Numerical simulation results demonstrate that the curved surface structure of this invention achieves improved energy absorption efficiency under conditions of equal volume and mass, exhibiting more stable mechanical properties, particularly under multi-directional impacts.

[0072] In one embodiment of the present invention, the inner radius of column 123 is 15-25 mm, preferably 20 mm; the thickness of column 123 and curved blade 124 is 1.0-2.5 mm, preferably 1.8 mm; and the length of curved blade 124 in the x, y, and z directions is 4π. These specific dimensional parameters are derived through mechanical analysis and optimization, maximizing energy absorption and space utilization while ensuring structural strength. The entire energy-absorbing buffer structure accounts for approximately 5-8% of the total weight of the battery pack, meeting lightweight design requirements.

[0073] In one embodiment of the present invention, the column 123 and curved blades 124 are made of aluminum alloy. Aluminum alloy has advantages such as low density, high specific strength, and good processability, making it suitable for manufacturing lightweight structural components with excellent mechanical properties. Furthermore, aluminum alloy has excellent thermal conductivity, which helps conduct and dissipate heat within the battery pack, further improving battery pack safety.

[0074] The preferred aluminum alloy used in this invention is 7075-T6 aluminum alloy, whose main chemical composition (by weight percentage) is: aluminum (Al) approximately 87.1-91.4%, zinc (Zn) 5.1-6.1%, magnesium (Mg) 2.1-2.9%, copper (Cu) 1.2-2.0%, chromium (Cr) 0.18-0.28%, and the remainder are trace elements. This high-strength aluminum alloy has a tensile strength of up to 570 MPa and a yield strength of approximately 500 MPa. It has excellent mechanical properties and a low density (approximately 2.81 g / cm³), making it particularly suitable for structural parts requiring high strength and lightweighting. In addition, this alloy has excellent corrosion resistance and fatigue resistance, ensuring long-term and stable protection in various operating environments of electric vehicles.

[0075] In another embodiment of the present invention, the column 123 and the curved blades 124 can be made of different materials, such as aluminum alloy for the column 123 and titanium alloy or carbon fiber composite for the curved blades 124, to further optimize the mechanical properties and weight of the structure. When the curved blades 124 are made of carbon fiber composite, the composite material has a formula of 60% carbon fiber (T700 grade) + 40% epoxy resin matrix. This formula can provide excellent specific strength and toughness while maintaining a low density of approximately 1.6g / cm³.

[0076] The safety protection structure 12 can be manufactured using advanced manufacturing technology. The specific manufacturing method is as follows:

[0077] 1) Digital modeling: Based on the design parameters and the surface equation A = cos(2x)·sin(y) + cos(2y)·sin(z) + cos(z)·sin(3x), a precise three-dimensional model of the column 123 and the curved blade 124 is established using CAD software (such as SOLIDWORKS or CATIA);

[0078] 2) Material preparation: Prepare appropriate 7075-T6 aluminum alloy sheet or aluminum alloy powder;

[0079] 3) Manufacturing process selection:

[0080] a. Metal 3D printing technology (Selective Laser Melting SLM or Direct Metal Laser Sintering DMLS):

[0081] i. Spread the aluminum alloy powder evenly on the printing platform, and control the layer thickness to 0.05-0.1mm;

[0082] ii. Use a high-power laser with a power of 400-1000W to melt the aluminum alloy powder according to the outline of the digital model;

[0083] iii. Lower the printing platform by one layer thickness, apply another layer of powder, and repeat the above steps;

[0084] iv. After the entire structure is printed, remove the unmelted powder material;

[0085] b. Advanced CNC machining (for mass production):

[0086] i using a 5-axis CNC machine tool cutting from an aluminum alloy sheet cylinder 123;

[0087] ii. The curved blade 124 is manufactured using precision mold forming technology. The mold is made of high-hardness steel with an accuracy controlled within ±0.05mm;

[0088] iii. Assemble the column 123 and the curved blade 124 by laser welding (power 300-500W) or high-precision mechanical connection (micro bolts or snaps);

[0089] 4) Polymer filling:

[0090] i. The prepared polyacrylamide solution is accurately injected into the hollow column through a syringe pump, and the injection pressure is controlled at 0.2-0.3MPa;

[0091] ii. Curing in a controlled environment at a temperature of 25±2°C and a relative humidity of 50±5% for 4-6 hours;

[0092] iii. Use a vacuum chamber at -0.08 MPa negative pressure for 15-20 minutes to remove bubbles;

[0093] 5) Surface treatment:

[0094] i. Anodize the entire structure in a 15-20% sulfuric acid solution at a current density of 1.5-2.0 A / dm 2 , treat at 20±2℃ for 30-40 minutes to form an oxide layer with a thickness of 15-20μm;

[0095] ii. Apply a PTFE-based protective coating with a thickness of 10-15 μm and cure at 120°C for 30 minutes to enhance weather resistance and chemical corrosion resistance;

[0096] 6) Quality inspection:

[0097] i. Use high-precision X-ray computed tomography (CT) equipment to check the internal structural integrity with a resolution of not less than 50μm;

[0098] ii. Conduct standardized drop weight impact tests at 15-20J energy to verify energy absorption performance;

[0099] iii. Use a three-dimensional coordinate measuring machine to measure key dimensions, and control the tolerance within ±0.1mm to ensure that it meets the design requirements.

[0100] The aforementioned manufacturing process allows for the precise realization of complex curved blade 124 structures while maintaining overall structural integrity and performance stability. Metal 3D printing technology, in particular, enables the creation of complex geometric shapes difficult to achieve using traditional machining methods during an integrated molding process, making it ideally suited for the energy-absorbing and cushioning structures of the present invention.

[0101] In one embodiment of the present invention, the surface of the connector board 31 of the second battery cell 3 is coated with a heat-absorbing, flame-retardant coating 32 with a thickness of 1-10 mm, preferably 3-5 mm. This coating 32, another innovative feature of the present invention, effectively absorbs heat and prevents fire from spreading when the battery overheats, thereby addressing the issue of thermal runaway in battery cells under extreme conditions.

[0102] The reason for choosing a coating thickness of 1-10mm is that a coating that is too thin (e.g., <1mm) will not provide sufficient heat absorption and flame retardancy, while a coating that is too thick (e.g., >10mm) may excessively increase volume and weight, and may also affect plug-in functionality. Thermal simulation analysis and fire testing have shown that a thickness range of 1-10mm provides the best balance between thermal protection and space utilization, with a thickness of approximately 3-5mm performing best in most applications.

[0103] In one embodiment of the present invention, the heat-absorbing flame-retardant coating 32 is prepared by mixing the following components, applying the mixture to the surface of the plugboard 31, and then drying the mixture. The components include, by weight:

[0104] 30-40 parts of ammonium dihydrogen phosphate

[0105] 20-30 parts of sodium bicarbonate

[0106] 15-25 parts of melamine

[0107] 10-20 parts polyurethane prepolymer

[0108] 5-10 parts of nano titanium dioxide

[0109] 8-15 parts expandable graphite

[0110] 40-80 parts of organic solvent.

[0111] The organic solvent is selected from at least one of dimethyl sulfoxide, propylene glycol methyl ether acetate, cyclohexanone, and N-methylpyrrolidone. The organic solvent is primarily used as a dispersion medium during the preparation process and is largely evaporated after curing. However, a small amount (≤5 wt%) of the solvent remains to provide the coating with a certain degree of flexibility, preventing cracking caused by vibration or temperature fluctuations during battery pack use.

[0112] Among them, the heat-absorbing flame-retardant coating 32 formula design has multiple synergistic protection mechanisms:

[0113] 1) Multi-level heat absorption protection: Ammonium dihydrogen phosphate decomposes and absorbs heat at 150-200℃, and sodium bicarbonate decomposes at 120-150℃ to release carbon dioxide and absorb a large amount of heat, forming a two-level temperature protection barrier;

[0114] 2) Gas barrier effect: Carbon dioxide generated by the thermal decomposition of sodium bicarbonate and nitrogen generated by the decomposition of melamine form an inert gas protective layer at high temperatures, reducing oxygen concentration and inhibiting combustion;

[0115] 3) Carbonization flame retardant mechanism: Melamine and ammonium dihydrogen phosphate form a high-temperature resistant cross-linked network structure at high temperatures, generating a dense PN flame retardant carbonized layer that blocks heat transfer and oxygen diffusion;

[0116] 4) Nano-enhancement effect: Nano-titanium dioxide acts as a catalyst to promote the formation of a denser carbonized layer, while improving the mechanical strength and thermal stability of the coating;

[0117] 5) Expansion insulation mechanism: expandable graphite expands dozens of times at high temperatures to form a porous and fluffy insulation layer, effectively isolating heat conduction;

[0118] 6) Bonding and curing mechanism: Polyurethane prepolymer provides excellent bonding properties and flexibility, ensuring that the coating is not easy to fall off or crack during battery use.

[0119] The coating demonstrated excellent performance in lithium-ion battery thermal runaway tests, reducing the heat diffusion rate by approximately 70% and effectively delaying heat spread by 10-15 minutes, providing users with ample time to escape and extinguish fires.

[0120] The preparation method of the heat-absorbing flame-retardant coating 32 is as follows:

[0121] 1) Preparation of organic solvent: Select an appropriate organic solvent or solvent mixture. In this embodiment, dimethyl sulfoxide and propylene glycol monomethyl ether acetate are mixed in a volume ratio of 3:1.

[0122] 2) Preparation of suspension:

[0123] a. Grind ammonium dihydrogen phosphate to an average particle size of less than 50 μm;

[0124] b. Grinding the sodium bicarbonate to an average particle size of less than 30 μm;

[0125] c. The powder is mixed with melamine, nano-titanium dioxide and expandable graphite according to the formula ratio;

[0126] d. The mixed powder was added to an organic solvent and dispersed using a high-speed disperser at 3000 rpm for 30 minutes to form a uniform suspension;

[0127] 3) Prepolymer preparation:

[0128] a. In another container, 4,4'-diphenylmethane diisocyanate (MDI) and polyether polyol were mixed in an NCO / OH equivalent ratio of 1.2:1;

[0129] b. Under nitrogen protection, the reaction was stirred at 45 ° C oil bath temperature for 2 hours at a stirring speed of 250-300 rpm;

[0130] c. Use infrared spectroscopy to monitor the NCO group content and ensure that it is within ±5% of the theoretical value;

[0131] 4) Coating preparation:

[0132] a. Slowly add the prepared prepolymer to the suspension at a rate of 3-5g / min while maintaining medium stirring speed (500-700rpm) and mix well;

[0133] b. Add dimethylolpropionic acid (0.5-1.0wt%) as a crosslinking agent and dibutyltin dilaurate (0.1-0.3wt%) as a catalyst and continue stirring for 15 minutes;

[0134] c. The coating material is applied to the surface of the plug board 31 by spraying, brushing or dipping;

[0135] d. Curing in a constant temperature and humidity chamber at 60°C and 50% relative humidity for 24 hours;

[0136] e. Carry out post-processing and quality inspection to ensure the coating thickness is uniform and free of bubbles and cracks.

[0137] After completing the above steps, a uniform and dense heat-absorbing flame-retardant coating 32 is formed on the surface of the plug board 31, with a thickness controlled within the range of 1-10 mm. This coating has good adhesion and is not easy to fall off. It also has a certain degree of flexibility to adapt to the slight deformation of the battery pack during use.

[0138] In one embodiment of the present invention, the housing includes an outer shell and an inner shell. The inner shell is disposed within the outer shell, forming a cavity therebetween. The safety protection structure 12 is disposed within the cavity. This double-layer housing design further enhances the protection of the battery pack. The outer shell provides the first line of defense, while the inner shell forms the second line of defense. The cavity between the two houses the safety protection structure 12, forming a multi-layer protection system.

[0139] The outer shell is made of high-strength engineering plastic ABS / PC, aluminum alloy, or steel, with a thickness of 3-5mm, offering excellent mechanical strength and impact resistance. The inner shell can be made of flame-retardant PA66, aluminum alloy, or steel, with a thickness of 2-3mm, offering excellent heat resistance and flame retardancy. The width of the cavity between the two shells is greater than the thickness of the safety protection structure 12, providing sufficient space for it.

[0140] Preferably, the housing is manufactured using an injection molding process, with the mold made of P20 mold steel and the mold surface mirror-polished to Ra ≤ 0.2 μm. The injection molding parameters are as follows: barrel temperature 230-250°C (outer shell) and 270-290°C (inner shell), mold temperature 80-90°C, injection pressure 90-110 MPa, holding time 15-20 seconds, cooling time 25-30 seconds, and the entire injection molding cycle is approximately 45-55 seconds. The molded housing undergoes dimensional inspection and airtightness testing to ensure it meets design requirements.

[0141] In one embodiment according to the present invention, multiple support columns are provided between the outer and inner shells, and these columns are made of shape-memory alloy. These support columns not only provide structural support between the outer and inner shells but also exhibit intelligent responsiveness. When the battery pack is subjected to a strong impact, the shape-memory alloy columns undergo controllable deformation to absorb the impact energy. After the impact subsides, the shape-memory alloy returns to its original shape, maintaining the integrity of the support structure. This design enhances the battery pack's impact resistance and is particularly suitable for use in electric two-wheeled vehicle applications, which are subject to frequent vibrations and collisions.

[0142] The support columns are made of a shape memory alloy called nickel-titanium alloy (Nitinol), whose main components are approximately 55.8wt% nickel (Ni) and 44.2wt% titanium (Ti), with a phase transition temperature designed to be 35-45°C. The diameter of the support columns is 3-5mm, and the length is adjusted according to the spacing between the outer and inner shells. Each battery pack has 20-30 support columns evenly distributed inside to ensure sufficient support and cushioning capacity in all directions.

[0143] The manufacturing method of the support column is as follows:

[0144] 1) Alloy preparation: High-purity nickel (99.9%) and titanium (99.8%) were melted into alloy ingots in a predetermined ratio (Ni:Ti = 55.8:44.2 wt%) using vacuum induction melting. The melting was carried out in a vacuum of better than 5×10 -3 Pa environment, with the highest temperature reaching 1500℃ to ensure uniform alloy composition;

[0145] 2) Hot working: The alloy ingot is heated to 850-950℃ and processed into bars with a diameter of 6-8mm by hot forging and hot rolling under inert gas protection. The strain rate is controlled at 0.1-0.5s during the hot working process. -1 range to prevent excessive deformation and hardening of the material;

[0146] 3) Cold working: The bar is processed step by step to the required diameter (3-5mm) through the cold drawing process. The deformation rate of each cold drawing is controlled at 10-15% to avoid material cracking. During the cold working process, an intermediate annealing treatment (700℃, 30 minutes) is performed to restore the plasticity of the material.

[0147] 4) Shape setting: The processed rod is cut into the required length (8-15 mm), kept at 500-550 ° C for 30 minutes while applying the mold constraint of the required shape, and then water quenched to room temperature to fix the shape memory effect;

[0148] 5) Deformation training: The alloy was subjected to 5-10 cycles of deformation-recovery training. The specific method is to deform the support pillar by 5% at room temperature, then heat it to 60-70°C to restore it to its original shape, and repeat this process to stabilize the material's shape memory properties. After training, the material exhibits more stable and predictable shape memory behavior, with deformation recovery rate increased to over 95%;

[0149] 6) Surface treatment: Improve surface finish and corrosion resistance through electrochemical polishing (in a mixed solution of nitric acid: hydrofluoric acid: glycerol = 3:1:6, current density 0.2-0.3A / cm², treatment for 3-5 minutes) and passivation treatment (immersion in 30% nitric acid for 30 minutes);

[0150] 7) Installation and Fixing: The processed shape memory alloy support column is fixed to the preset position between the outer shell and inner shell using a special connector. The connector is made of high-strength nylon material and has a snap-on structure that allows for quick installation and removal, facilitating maintenance and replacement.

[0151] In one embodiment of the present invention, the first and second battery cells 2 and 3 each include multiple battery cells and a thermal management layer surrounding the cells. The thermal management layer comprises a phase change material. Phase change materials can absorb or release large amounts of heat energy within a specific temperature range, effectively regulating the battery's operating temperature and preventing overheating or overcooling from impacting battery performance and lifespan. This thermal management solution requires no additional energy input and is a passive temperature control system with high reliability and low maintenance costs.

[0152] Each battery unit contains 4-16 high-energy-density lithium-ion cells, connected in parallel or in a series-parallel hybrid to meet voltage and capacity requirements. A 2-4mm gap is left between the cells to accommodate the thermal management layer and facilitate heat dissipation. The thermal management layer is 2-4mm thick and covers the outer surface of each cell.

[0153] In one embodiment of the present invention, the thermal management layer includes a low-temperature-resistant phase-change material (PCM) and a high-temperature-resistant PCM. The PCM transitions between -10°C and -20°C, preferably around -15°C; the high-temperature-resistant PCM transitions between 55°C and 65°C, preferably around 60°C. This dual-phase-change temperature design enables the battery pack to operate stably over a wide temperature range, effectively addressing the problem of lithium-ion batteries experiencing a sharp drop in performance at extreme temperatures.

[0154] The selection of -10°C to -20°C as the low-temperature phase transition point is based on the low-temperature performance characteristics of lithium-ion batteries: when temperatures fall below -10°C, the viscosity of the electrolyte inside the battery increases significantly, lithium ion migration slows, internal resistance rises sharply, and both output power and capacity drop significantly. By releasing heat within this temperature range, the battery is kept in a more optimal operating state. Similarly, the high-temperature phase transition point of 55°C to 65°C was carefully chosen: the optimal operating temperature for lithium-ion batteries is approximately 15-35°C. When temperatures exceed 45°C, battery aging accelerates, and temperatures above 60°C pose safety risks. By absorbing heat within this temperature range, the battery is prevented from overheating, extending its lifespan and improving safety.

[0155] In one embodiment of the present invention, the low-temperature resistant phase change material comprises the following components in parts by weight: 30-40 parts of polyethylene glycol 400, 15-25 parts of octadecylamine ethoxylate, 10-20 parts of 1-bromodecane, 5-10 parts of graphene quantum dots, 3-7 parts of alumina nanofibers, and 2-5 parts of multi-walled carbon nanotubes.

[0156] Among them, the low-temperature resistant phase change material has multiple functional characteristics:

[0157] 1) Precise phase transition temperature control: Polyethylene glycol 400 and octadecylamine ethoxylate form a eutectic system, which can accurately control the phase transition temperature within the range of -10°C to -20°C;

[0158] 2) Enhanced latent heat of phase change: 1-Bromodecane acts as a phase change temperature regulator, increasing the latent heat of phase change of the material and improving the heat storage / release capacity per unit volume;

[0159] 3) Thermal Conductive Network Construction: Graphene quantum dots, alumina nanofibers, and multi-walled carbon nanotubes construct a three-dimensional thermal conductive network, significantly improving the thermal conductivity of the material and accelerating heat transfer;

[0160] 4) Optimized cyclic stability: The synergistic effect of multiple components improves the cyclic stability of the material, maintaining stable phase change properties even after hundreds of temperature cycles;

[0161] 5) Anti-supercooling performance: Graphene quantum dots act as efficient nucleating agents, suppressing the supercooling phenomenon of phase change materials and ensuring timely heat release at the target temperature.

[0162] The preparation method of the low-temperature resistant phase change material is as follows:

[0163] 1) Heat polyethylene glycol 400 to 60°C and stir until completely melted;

[0164] 2) adding octadecylamine ethoxylate and stirring until uniformly mixed;

[0165] 3) 1-bromodecane was heated to 40° C. and then slowly added to the above mixture, and stirred for 30 minutes using a high-speed stirrer (2000-2500 rpm);

[0166] 4) Graphene quantum dots, alumina nanofibers, and multi-walled carbon nanotubes were dispersed in a small amount of ethanol and ultrasonically treated (power 300 W, frequency 40 kHz) for 20 minutes to form a uniform suspension;

[0167] 5) Add the suspension dropwise to the above mixture while maintaining high-speed stirring (2500-3000 rpm) to ensure uniform dispersion of the nanomaterials;

[0168] 6) Use a vacuum degasser to remove air bubbles from the mixture;

[0169] 7) Pour the mixture into a pre-prepared mold and cool and solidify at -5°C;

[0170] 8) The solidified material is taken out from the mold and cut into desired shapes and sizes to obtain a low-temperature resistant phase change material layer.

[0171] In one embodiment of the present invention, the high-temperature-resistant phase-change material comprises the following components by weight: 35-45 parts stearylethanolamine, 25-35 parts myristic acid, 10-15 parts cross-linked polyvinyl alcohol, 5-10 parts graphene aerogel, 3-8 parts hollow carbon nanospheres, and 2-5 parts aluminum nitride nanosheets. This combination provides efficient high-temperature phase-change performance, rapidly absorbing heat when the battery temperature is too high, preventing thermal runaway.

[0172] Among them, the high temperature resistant phase change material has multiple functional characteristics:

[0173] 1) High-temperature phase change system: A mixture of stearylethanolamine and myristic acid provides precise high-temperature phase change characteristics, with the phase change temperature adjustable within the range of 55-65°C;

[0174] 2) Shape stabilization: Cross-linked polyvinyl alcohol forms a three-dimensional network structure, preventing leakage of the phase change material in the liquid state and providing shape stability;

[0175] 3) Multi-level thermal conductivity enhancement: Graphene aerogel, hollow carbon nanospheres and aluminum nitride nanosheets form a multi-scale thermal conductivity network, increasing thermal conductivity by 5-8 times;

[0176] 4) Thermal stress buffering: Hollow carbon nanospheres provide microscopic expansion space, relieving thermal expansion stress and extending the service life of the material;

[0177] 5) Improved thermal stability: Aluminum nitride nanosheets improve the thermal stability of the material, preventing performance degradation under long-term high temperature conditions.

[0178] The preparation method of the high temperature resistant phase change material is as follows:

[0179] 1) Mix stearylethanolamine and myristic acid in proportion, melt at 90° C., and stir until completely mixed;

[0180] 2) In another container, dissolve cross-linked polyvinyl alcohol in an appropriate amount of a water / ethanol mixed solvent, heat to 80°C, and stir until a homogeneous solution is formed;

[0181] 3) Graphene aerogel, hollow carbon nanospheres, and aluminum nitride nanosheets were mixed in proportion and ultrasonically dispersed in isopropyl alcohol for 30 minutes;

[0182] 4) Slowly add the solution in step 2 to the molten mixture in step 1 and stir at high speed for 15 minutes;

[0183] 5) While continuing to stir, slowly add the nanomaterial suspension in step 3;

[0184] 6) Add borax (0.5-1 wt%) as a crosslinking agent and continue stirring for 10 minutes;

[0185] 7) Pour the mixture into a preheated mold and keep it at 90°C for 2 hours to complete the crosslinking process;

[0186] 8) Cool naturally to room temperature, demould, and cut into desired shapes and sizes to obtain a high-temperature resistant phase change material layer.

[0187] When installing the prepared thermal management layer into the battery cell, the surface of the battery cell is first cleaned to remove oil and dust; then a layer of thermal conductive silicone grease (thickness of about 0.1-0.2mm) is applied to ensure good thermal contact; finally, the thermal management layer is wrapped around the outer surface of the battery cell and fixed with tape.

[0188] The working principle and effects of the present invention are as follows:

[0189] In daily use, the first battery cell 2 and the second battery cell 3 in the battery pack are securely connected via the socket 21 and the socket plate 31, forming a complete power system. When a battery cell fails and needs to be replaced, the user simply unplugs the corresponding battery cell from the socket and inserts a new one. The entire process is simple and quick, requiring no specialized tools or skills. The cross-shaped arrangement of the battery pack optimizes the current path and heat distribution, resulting in higher efficiency and more uniform temperature distribution. The central first battery cell 2 serves as the connecting hub, while the surrounding second battery cells 3 are arranged in four directions, forming a structure with efficient space utilization. This design also improves the mechanical stability of the battery pack, enabling it to better cope with various usage environments.

[0190] When an electric vehicle encounters vibrations, collisions, or other impacts during driving, the external force first acts on the protective shell 1, which is then absorbed by the first panel 121 or second panel 122 of the safety protection structure 12. The curved blades 124 in the safety protection structure 12 deform evenly, dispersing the impact force and transmitting it to the column 123. The polyacrylamide polymer filling the column 123 further absorbs energy, preventing the impact force from being directly transmitted to the battery cells, thereby protecting the battery pack from damage. Furthermore, the shell's cross-shaped structure and reinforcement blocks 11 further enhance the overall impact resistance. When subjected to external forces, the structure effectively disperses stress and protects the internal battery pack.

[0191] In environments with large temperature fluctuations, the phase-change material in the thermal management system within the battery cell automatically adjusts to the temperature: in low-temperature environments, the low-temperature-resistant phase-change material releases heat to keep the battery temperature within a certain range; in high-temperature environments or when operating under high loads, the high-temperature-resistant phase-change material absorbs excess heat to prevent overheating. This intelligent temperature management system significantly improves battery performance and lifespan in various environments.

[0192] If an extreme situation occurs and the battery temperature rises sharply, the heat-absorbing flame-retardant coating 32 on the plug-in board 31 will begin to work, absorbing a large amount of heat and releasing inert gas, reducing the concentration of surrounding combustible gases, effectively preventing the spread of fire and the occurrence of thermal runaway, and providing users with higher safety protection.

[0193] In summary, the lithium-ion battery pack for electric vehicles provided by the present invention, which has a safety protection structure 12 and is easy to disassemble and assemble, comprehensively solves the problems of inconvenient disassembly and assembly and poor safety protection effect existing in existing lithium-ion battery packs for electric vehicles through innovative structural design and material application, significantly improves the safety, convenience and reliability of electric vehicles, especially electric two-wheeled vehicles, and has broad application prospects.

[0194] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0195] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to the specific embodiments described. Obviously, many modifications and variations are possible based on the content of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A lithium-ion battery pack for electric vehicles with a safety protection structure, characterized in that: A battery pack comprising a protective shell and a battery pack mounted in the protective shell, the battery pack comprising a first battery cell and second battery cells arranged around the first battery cell; the battery pack is arranged in a cross-shaped structure, the first battery cell is located at the center of the cross-shaped structure, and the second battery cells are arranged along four directions of the cross-shaped structure; The first battery unit is provided with plug-in slots on all four sides, and each second battery unit is provided with a plug-in board that can be plugged into the plug-in slot on the side facing the first battery unit, and the first battery unit and the second battery unit are plug-in-matched and connected through the plug-in slot and the plug-in board; The protective shell includes a shell, a accommodating cavity is provided in the shell, a safety protection structure is provided in the accommodating cavity, the safety protection structure includes a first panel, a second panel and an energy absorption buffer structure arranged between the first panel and the second panel, the energy absorption buffer structure is composed of a plurality of columns and curved blades, adjacent columns are distributed in parallel at equal intervals, and the curved blades are connected and surround the columns.

2. The lithium-ion battery pack for electric vehicles with a safety protection structure according to claim 1, characterized in that: The cross section of the shell is a cross-shaped structure, and the internal space is divided into five independent areas, each area is used to accommodate a group of battery cells, and reinforcement blocks are provided between adjacent outer side walls of the shell, and the cross section of the reinforcement blocks is triangular.

3. The lithium-ion battery pack for electric vehicles with a safety protection structure according to claim 1, characterized in that: The plug-in slot and the plug-in plate are both extended longitudinally and are in a T-shaped structure.

4. The lithium-ion battery pack for electric vehicles with a safety protection structure according to claim 1, characterized in that: The column is a hollow column, and the interior of the column is uniformly filled with polyacrylamide polymer; the curved blades are in the shape of plant leaves and are composed of continuous minimal curved surfaces; and the outer surface of the column is adjacent to the curved blades.

5. The lithium-ion battery pack for electric vehicles with a safety protection structure according to claim 4, characterized in that: The minimal surface extends and expands in an orderly manner in the three-dimensional direction, and its surface equation is A=cos(2x)·sin(y)+cos(2y)·sin(z)+cos(z)·sin(3x), where x, y, and z are the three-dimensional coordinates of space, and A is the displacement of the surface blade along the normal direction.

6. The lithium-ion battery pack for electric vehicles with a safety protection structure according to claim 1, characterized in that: The surface of the plug board of the second battery unit is coated with a heat-absorbing flame-retardant coating with a thickness of 1-10 mm; The heat-absorbing flame-retardant coating comprises the following components in parts by weight: 30-40 parts of ammonium dihydrogen phosphate 20-30 parts of sodium bicarbonate 15-25 parts of melamine 10-20 parts polyurethane prepolymer 5-10 parts of nano titanium dioxide 8-15 parts expandable graphite 40-80 parts of organic solvent.

7. The lithium-ion battery pack for electric vehicles with a safety protection structure according to claim 1, characterized in that: The shell includes an outer shell and an inner shell. The inner shell is arranged in the outer shell and forms the accommodating cavity with the outer shell. The safety protection structure is arranged in the accommodating cavity.

8. The lithium-ion battery pack for electric vehicles with a safety protection structure according to claim 7, characterized in that: A plurality of support columns are provided between the outer shell and the inner shell, and the support columns are made of shape memory alloy.

9. The lithium-ion battery pack for electric vehicles with a safety protection structure according to claim 1, characterized in that: The first battery unit and the second battery unit both include multiple battery cells and a thermal management layer covering the battery cells. The thermal management layer includes a low-temperature resistant phase change material and a high-temperature resistant phase change material. The phase change temperature of the low-temperature resistant phase change material is -10°C to -20°C, and the phase change temperature of the high-temperature resistant phase change material is 55°C to 65°C.

10. The lithium-ion battery pack for electric vehicles with a safety protection structure according to claim 9, characterized in that: The low-temperature resistant phase change material comprises the following components in parts by weight: 30-40 parts of polyethylene glycol 400, 15-25 parts of octadecylamine ethoxylate, 10-20 parts of 1-bromodecane, 5-10 parts of graphene quantum dots, 3-7 parts of alumina nanofibers, and 2-5 parts of multi-walled carbon nanotubes; The high-temperature resistant phase change material comprises the following components in parts by weight: 35-45 parts of stearylethanolamine, 25-35 parts of myristic acid, 10-15 parts of cross-linked polyvinyl alcohol, 5-10 parts of graphene aerogel, 3-8 parts of hollow carbon nanospheres, and 2-5 parts of aluminum nitride nanosheets.

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