Wide-temperature-range anti-attenuation battery pack and application thereof

Abstract

The invention belongs to the technical field of power batteries, and particularly relates to a wide-temperature-range anti-attenuation battery pack and application thereof. The wide-temperature-range anti-attenuation battery pack comprises a thermal management system and an intelligent battery management system which are connected with each other, the thermal management system comprises a shell assembly, a battery cell assembly and a heat-conducting glue layer; the shell assembly is connected with the battery cell assembly through the heat-conducting glue layer and is connected with a vehicle mounting seat through a buckle assembly; the shell assembly comprises a PTC heating film, a micro-channel liquid cooling plate and an aerogel heat insulation layer, and the PTC heating film, the micro-channel liquid cooling plate and the aerogel heat insulation layer are arranged in sequence; and the PTC heating film is connected with the battery cell assembly through the heat-conducting glue layer. The wide-temperature-range anti-attenuation battery pack can effectively solve the problem that in the prior art, the performance of a lithium battery becomes poor in low-temperature and high-temperature environments, the anti-attenuation performance of the battery pack can be improved, the cycle life of the battery pack is prolonged, and the product reliability is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power batteries, and particularly relates to a wide-temperature-range anti-degradation battery pack and application thereof. BACKGROUND

[0002] Due to the advantages of high energy density, good safety, light weight and long cycle life, lithium ion power batteries have been widely applied to energy storage systems in new energy vehicles. In particular in the field of electric vehicle energy storage, lithium ion power batteries have become the first choice of battery types. The existing lithium ion power batteries have a large decrease in battery pack cell activity and a 30%-50% decrease in charging and discharging efficiency in a low-temperature environment below-10 DEG C, which leads to poor starting performance of the vehicle, sharp reduction in vehicle mileage and failure to meet the use requirements in northern winter or high-altitude areas. When in a high-temperature environment above 45 DEG C, the failure risk of the battery pack thermal management system increases, which not only accelerates the aging of the cell, but also may cause safety problems such as bulging and liquid leakage, and is particularly not suitable for open-air operation scenes in southern summer, such as scenic sightseeing vehicles and factory forklifts. In addition, the existing battery pack is generally designed for general use, and is not optimized for the installation space, weight limit and vibration environment of electric low-speed vehicles, which causes inconvenience in installation and easy loosening during operation, affecting the use stability.

[0003] Therefore, it is urgent to develop a battery pack which can have a wide temperature range and effectively improve the anti-vibration and anti-degradation performance. SUMMARY

[0004] The application aims to provide a wide-temperature-range anti-degradation battery pack and a preparation method and application thereof. The wide-temperature-range anti-degradation battery pack can effectively solve the problems of poor performance of lithium batteries in low-temperature and high-temperature environments in the prior art, and can improve the anti-degradation performance of the battery pack, prolong the cycle life of the battery pack and improve the product reliability. At the same time, the battery pack structure is designed to be modular and splicable according to the scene characteristics of electric low-speed vehicles, such as small installation space, frequent vibration and limited weight, to solve the problems of general battery packs, such as inconvenient loading and unloading and loosening during operation.

[0005] In order to achieve the above-mentioned purpose, the application adopts the following technical scheme: a wide-temperature-range anti-degradation battery pack, comprising a thermal management system and an intelligent battery management system connected with each other. The thermal management system comprises a shell assembly, a cell assembly and a heat-conducting adhesive layer; the shell assembly is connected with the cell assembly through the heat-conducting adhesive layer and connected with a vehicle mounting seat through a buckle assembly. The shell assembly comprises a PTC heating film, a micro-channel liquid cooling plate and an aerogel thermal insulation layer, which are sequentially arranged; the PTC heating film is connected with the cell assembly through the heat-conducting adhesive layer.

[0006] The PTC heating film in the shell assembly in the application is attached to the electric core assembly through the heat-conducting adhesive layer, realizing rapid and uniform low-temperature self-starting heating; the micro-channel liquid cooling plate in the middle layer adopts an S-shaped flow channel design, conforms to the shell assembly, and realizes high-efficiency heat dissipation through cooling liquid circulation; the aerogel thermal insulation layer in the outer layer can effectively block the invasion of external environmental heat or the loss of internal heat.

[0007] Preferably, the electric core assembly comprises at least one electric core, the electric core adopts a regular hexagonal honeycomb arrangement, and a wave-shaped flexible nickel sheet is used for electrical connection between the electric cores; the height of the wave crest of the wave-shaped flexible nickel sheet, the height of the wave trough of the wave-shaped flexible nickel sheet, and the distance between the wave crest and the wave trough of the wave-shaped flexible nickel sheet are adapted to the boundary of the honeycomb structure formed by the electric cores.

[0008] The electric core in the application is cylindrical or square and arranged in a regular hexagonal honeycomb manner.

[0009] The wave-shaped flexible nickel sheet in the application has a wave-shaped structure, and the wave-shaped flexible nickel sheet can effectively absorb and dissipate vibration stress from vehicle operation in three-dimensional directions, fundamentally avoiding failure of the connection point due to fatigue.

[0010] The application innovatively selects a honeycomb-wave composite electric core connection structure, which can increase the energy density by 15%, improve the anti-vibration performance by 40%, and improve the installation adaptability by 60% in a limited space, perfectly matching the special use scenarios of compact space and frequent vibration of electric low-speed vehicles.

[0011] The electric core assembly in the application is embedded in a specially-made gradient heat-conducting adhesive layer, which ensures mechanical stability and optimizes the heat conduction path.

[0012] Preferably, the electric core comprises a positive electrode material, a negative electrode material, and an electrolyte; the positive electrode material comprises lithium iron phosphate; the negative electrode comprises graphite; and the electrolyte comprises an organic solvent, an additive, and a lithium salt.

[0013] Preferably, the mass fraction of the positive electrode material is 45%–55%, the mass fraction of the negative electrode material is 20%–28%, and the mass fraction of the electrolyte is 15%–22% based on the total mass of the electric core.

[0014] More preferably, the mass fraction of the positive electrode material is 48%–52%, the mass fraction of the negative electrode material is 22%–26%, and the mass fraction of the electrolyte is 17%–19% based on the total mass of the electric core.

[0015] Through extensive experimentation, the inventors discovered that the mass ratio of each component in a battery cell is crucial for achieving high performance across a wide temperature range. As the primary source and energy carrier of lithium ions, the positive electrode material's proportion below 45% leads to insufficient overall battery energy density; above 55%, it compresses the space between the negative electrode and electrolyte, causing lithium deposition on the negative electrode surface during high-rate charging, posing a safety hazard. Simultaneously, the proportion of the negative electrode material must maintain a reasonable capacity balance with the positive electrode material (i.e., the negative electrode / positive electrode capacity ratio, N / P ratio). This invention controls the N / P ratio between 1.05 and 1.15, ensuring sufficient negative electrode interface to receive lithium ions under low-temperature or fast-charging conditions, preventing lithium deposition, while also avoiding energy density loss caused by excessive negative electrode material. Furthermore, the electrolyte's proportion is key to achieving wide-temperature-range performance. When the electrolyte content is below 15%, the electrode pores cannot be fully wetted, leading to obstructed ion transport paths, especially at low temperatures where the internal resistance increases sharply. When the content is above 22%, it not only negatively impacts energy density, but also causes excessive free liquid electrolyte to participate in side reactions at high temperatures, accelerating capacity decay. This invention controls the electrolyte content within the range of 15%–22%, allowing the electrolyte to fully wet the porous electrode composed of lithium iron phosphate and graphite. Simultaneously, it exhibits synergistic effects with a specific ratio of organic solvent, maintaining high ionic conductivity and stable interfacial film formation capability even at extreme temperatures. The resulting cell achieves a discharge capacity retention rate of over 85% at -30℃, and a capacity retention rate exceeding 88% after 500 cycles at 60℃, achieving an optimal balance between high energy density and long cycle life over a wide temperature range.

[0016] Preferably, the content of the organic solvent in the electrolyte is 60-75 wt%, the content of the additive is 3-10 wt%, and the content of the lithium salt is 15-30 wt%.

[0017] Preferably, the organic solvent includes at least one of fluoroethylene carbonate (FEC) and propyl propionate (PP).

[0018] Preferably, the additive includes at least one of adiponitrile (AND) and propylene sulfate (PES).

[0019] Preferably, the lithium salt includes at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium trifluoromethanesulfonate, and lithium difluorosulfonylimide.

[0020] Preferably, the organic solvent comprises fluoroethylene carbonate and propyl propionate; the mass ratio of fluoroethylene carbonate to propyl propionate is 1:(3~5).

[0021] Through extensive experiments, the inventors discovered that controlling the mass ratio of fluoroethylene carbonate to propyl propionate within the range of 1:(3~5) enables the battery cell to form a stable, dense, and low-impedance SEI film on the negative electrode surface within an extreme temperature range of -30℃ to 60℃, thus forming a stable lithium-ion transport channel. At the same time, it ensures that the electrolyte has sufficiently high ionic conductivity and oxidation stability, thereby enabling the battery pack to have high charge and discharge efficiency in both low and high temperature environments. This effectively solves the industry problem of the rapid performance degradation of existing battery packs in extremely cold and hot environments.

[0022] The inventors tested the performance of battery cells prepared with a mass ratio of ethylene fluorocarbonate to propyl propionate of 1:(3~5). The ionic conductivity measured at -30℃ ranged from 0.51 to 0.55 mS / cm, and the 500-cycle capacity retention rate measured at 60℃ ranged from 84% to 88%. The battery cells with the ethylene fluorocarbonate to propyl propionate mass ratio of 1:4 exhibited the best performance. When the ethylene fluorocarbonate to propyl propionate mass ratio was 1:2, the ionic conductivity measured at -30℃ was 0.35 mS / cm, and the 500-cycle capacity retention rate measured at 60℃ was 72%. When the ethylene fluorocarbonate to propyl propionate mass ratio was 1:6, the ionic conductivity measured at -30℃ was 0.40 mS / cm, and the 500-cycle capacity retention rate measured at 60℃ was 70%. This indicates that when the mass ratio of fluoroethylene carbonate to propyl propionate in the selected organic solvent is 1:(3~5), a high-performance equilibrium over a wide temperature range can be achieved.

[0023] The methods used in this invention to measure ionic conductivity at -30°C and to test capacity retention after 500 cycles at 60°C are both common methods in the field.

[0024] Preferably, the additive includes adiponitrile and propylene sulfate; the mass ratio of adiponitrile to propylene sulfate is (2.5~3.5):(0.8~1.2). When the mass ratio of adiponitrile to propylene sulfate in the additive is inappropriate, the cycle life of the final battery pack is significantly reduced, and the resulting SEI film has a loose structure, is easily decomposed at high temperatures, and cannot adapt to a wide temperature range.

[0025] More preferably, the mass ratio of adiponitrile to propylene sulfate is 3:1. At a mass ratio of approximately 3:1, adiponitrile and propylene sulfate can construct a "rigid-flexible" synergistic composite SEI film at the negative electrode interface (especially in lithium iron phosphate / graphite systems), thereby achieving a wide-temperature-range protection effect that cannot be achieved by a single additive.

[0026] Preferably, the lithium salt comprises lithium hexafluorophosphate, lithium difluorophosphate, and lithium bis(fluorosulfonyl)imide. The mass ratio of lithium hexafluorophosphate, lithium difluorophosphate, and lithium bis(fluorosulfonyl)imide is (8~10):(2~3):(3~5).

[0027] More preferably, the mass ratio of lithium hexafluorophosphate, lithium difluorophosphate, and lithium difluorosulfonylimide is 9:2.5:4.

[0028] The present invention employs a ternary composite lithium salt system of LiPF6, LiPO2F2, and LiFSI, which combines high ionic conductivity, interfacial stability, and high temperature resistance.

[0029] Preferably, the thermally conductive adhesive layer comprises silicone rubber and a thermally conductive filler; the thermally conductive filler comprises boron nitride and graphene; the mass ratio of boron nitride to graphene is 1:(0.5~2).

[0030] More preferably, the mass ratio of boron nitride to graphene is 1:(0.8~1.5).

[0031] Preferably, the thermally conductive adhesive layer is distributed in a vertical gradient within the thermal management system.

[0032] Preferably, the thermally conductive adhesive layer is distributed as follows: Near the battery cell side: the mass ratio of boron nitride to graphene is 1:0.8; the boron nitride content is slightly higher, forming a "thermal insulation layer"; Intermediate transition layer: The mass ratio of boron nitride to graphene is 1:1; it can effectively balance heat conduction. Near the shell: the mass ratio of boron nitride to graphene is 1:1.2; the graphene content is slightly higher, forming a "heat dissipation layer".

[0033] This invention, through the vertical gradient distribution of the thermally conductive adhesive layer in the thermal management system, enables the manufactured battery pack to achieve the following: at low temperatures (<-10℃), boron nitride dominates the phonon conduction path, increasing the thermal resistance at the graphene interface, resulting in an overall thermal conductivity ≤0.5 W / m·K, forming a "thermal barrier" and exhibiting heat preservation characteristics, which is beneficial for heat retention at low temperatures. Even at extreme low temperatures of -30℃, the capacity retention rate remains above 82%, and the charge / discharge efficiency exceeds 85%. At high temperatures (>45℃), the electronic thermal conductivity mechanism of graphene is activated, forming a three-dimensional thermally conductive network, and the thermal conductivity jumps to ≥2.5 W / m·K, automatically enhancing thermal conductivity and facilitating the removal of high-temperature heat. Ultimately, this achieves a cycle life improvement of over 50% in high-temperature environments. By using a filler concentration gradient, temperature-responsive self-regulation of thermal conductivity is achieved, breaking through the limitations of traditional materials with a "single thermal conduction direction."

[0034] Preferably, the preparation of the thermally conductive adhesive layer includes the steps of: injecting silicone containing boron nitride and graphene into the gap between the battery cell and the housing assembly, curing it to form a thermally conductive adhesive layer with a continuous concentration gradient in the vertical direction.

[0035] Preferably, the curing process employs a stepped temperature increase procedure, specifically pre-curing at 40℃~60℃ for 30~90 minutes, followed by final curing at 80℃~100℃ for 60~120 minutes.

[0036] This invention controls the curing temperature and time during the preparation of the thermally conductive adhesive layer, and utilizes the sedimentation and self-assembly behavior of fillers under gravity and temperature fields to obtain a thermally conductive adhesive layer with a continuous concentration gradient in the vertical direction.

[0037] Preferably, the method for preparing the housing assembly includes the following steps: in a mold, a PTC heating film, a microchannel liquid cooling plate, and an aerogel prepreg are sequentially laid, and an epoxy resin interface agent is sprayed; then, a modified epoxy resin is injected using a vacuum-assisted resin transfer molding method, heated, and cured, so that the three heterogeneous materials form an integrated structure with a strong interface bond and minimal thermal resistance, thereby obtaining the housing assembly.

[0038] Preferably, the microchannel liquid cooling plate is an aluminum plate pre-impregnated with epoxy resin, which is pre-cured at 80°C for 30 minutes to a semi-cured state.

[0039] Preferably, the aerogel prepreg is a composite of hydrophobic silica aerogel powder, chopped carbon fibers, and a phenolic epoxy resin carrier; wherein the mass fraction of the hydrophobic silica aerogel powder is 60%~80%, the mass fraction of the chopped carbon fibers is 5%~15%, and the remainder is the phenolic epoxy resin carrier.

[0040] Preferably, the hydrophobic silica aerogel powder has a particle size distribution of 10-100 μm and a contact angle greater than 130°. Selecting hydrophobic silica aerogel powder with a specific particle size range and contact angle range ensures that it maintains excellent thermal insulation performance and structural stability even in humid environments.

[0041] Preferably, the epoxy resin interface agent includes at least one of aminosilane coupling agent, nano-alumina particles, and bisphenol A type epoxy resin.

[0042] Preferably, the epoxy resin interface agent comprises an aminosilane coupling agent, nano-alumina particles, and bisphenol A type epoxy resin; the mass fraction of the nano-alumina particles is 3% to 8%, the mass fraction of the aminosilane coupling agent is 5% to 15%, and the balance is bisphenol A type epoxy resin.

[0043] The aminosilane coupling agent used in this invention can be γ-aminopropyltriethoxysilane (KH550).

[0044] The epoxy resin interface agent of the present invention is prepared by mixing the components.

[0045] Preferably, the modified epoxy resin comprises the following components in parts by weight: 100 parts epoxy resin matrix, 15-25 parts modifier, 30-35 parts curing agent, 40-60 parts thermally conductive filler, and 0.5-1 parts catalyst.

[0046] Preferably, the epoxy resin matrix comprises a mixture of bisphenol A type epoxy resin (such as E-51) and hydrogenated bisphenol A epoxy resin in a mass ratio of 7:3.

[0047] The modifier may be a carboxyl-terminated liquid fluororubber-polyethersulfone block copolymer.

[0048] The curing agent can be a phosphorus-containing spirocyclic diamine curing agent.

[0049] The thermally conductive filler can be a composite of aluminum nitride nanowires modified with silane coupling agent KH-560 and spherical alumina, with a mass ratio of 1:4, wherein the particle size of the spherical alumina is 1~5μm.

[0050] The catalyst can be a microencapsulated imidazole latent catalyst. The outer shell is a thermoplastic polyester that melts and releases the active ingredient at temperatures above 90°C.

[0051] Preferably, the preparation method of the modified epoxy resin includes the following steps: heating the epoxy resin matrix to 80±5℃, slowly adding the modifier under high-speed shear (speed >2000 rpm), and continuing shearing for 1 hour to form a homogeneous and transparent premix; slowly adding the thermally conductive filler to the premix in three portions, and stirring and degassing with a planetary vacuum mixer after each addition until a composite material with suitable viscosity and uniform filler dispersion is formed; lowering the system temperature to below 50℃, adding the curing agent and catalyst in sequence, stirring and mixing evenly at medium and low speeds, and immediately discharging, sealing and storing to obtain the modified epoxy resin.

[0052] Preferably, the heating is a stepped heating, which includes the following steps: heating at 70~90℃ for 1~3 hours, heating at 110~130℃ for 2~5 hours, heating again, and heating at 140~160℃ for 1~2 hours.

[0053] This invention employs a stepped heating method during the fabrication of the housing assembly. This ensures sufficient mechanical strength in the matrix material and allows the PTC heating film, microchannel liquid cooling plate, and aerogel insulation layer to covalently bond through an interfacial agent, achieving a robust interfacial bond, minimizing interlayer thermal resistance, and endowing the housing assembly with higher dimensional stability, heat resistance, and fatigue resistance to adapt to the vibration environment and wide-temperature thermal cycling of vehicle operation. The resulting housing assembly exhibits an interlayer peel strength exceeding 50 N / cm.

[0054] More preferably, the stepped heating includes the following steps: heating at 80°C for 2 hours, heating at 120°C for 3 hours, heating again, and heating at 150°C for 1 hour.

[0055] The vacuum-assisted resin transfer molding method described in this invention is a conventional method in the art.

[0056] In this invention, the three-layer structure of the housing assembly, consisting of a PTC heating film, a microchannel liquid cooling plate, and an aerogel insulation layer, is formed through a co-curing process, integrating the heating circuit and cooling channels onto the same thin substrate.

[0057] Preferably, the intelligent battery management system integrates a multi-parameter sensor network. The intelligent battery management system is used to monitor the voltage, temperature and internal resistance changes of each cell in the battery cell assembly in real time, and adjusts the thermal management system based on an intelligent algorithm of ambient temperature and battery status. When the temperature is low, the PTC heating film is activated for graded heating, and when the temperature is high, the microchannel liquid cooling plate is activated to ensure that the battery cell assembly is always in the optimal operating temperature range.

[0058] Preferably, the multiple wide-temperature-range anti-ageing battery packs are connected using a combination of magnetic positioning and mechanical locking. This supports rapid parallel expansion of multiple battery packs.

[0059] The magnetic positioning and mechanical locking described in this invention are conventional connection methods in the art.

[0060] Preferably, the wide-temperature-range anti-degradation battery pack further includes a modular splicing interface; the modular splicing interface is equipped with an intelligent identification circuit, which can automatically identify the number of the wide-temperature-range anti-degradation battery packs and adjust the parameters of the intelligent battery management system to realize plug-and-play capacity expansion functionality.

[0061] This invention addresses the challenges of limited installation space, frequent vibrations, and limited load-bearing capacity in low-speed electric vehicles by designing a modular and connectable battery pack structure. This solves the problems of inconvenient removal and loose operation associated with general-purpose battery packs.

[0062] The present invention also claims protection for the application of the wide-temperature-range anti-degradation battery pack in a low-speed electric vehicle.

[0063] Preferably, the electric low-speed vehicle includes electric golf carts, forklifts, sightseeing vehicles, low-speed delivery vehicles, etc.

[0064] Compared with the prior art, the present invention has the following beneficial effects: (1) The PTC heating film, microchannel liquid cooling plate and aerogel insulation layer in the shell assembly of the present invention realize the triple thermal management function of "active heating + active cooling + passive insulation".

[0065] (2) In this invention, through the synergistic effect between the thermally conductive adhesive layer and the shell components that can achieve temperature self-adaptation, the battery pack obtained can still maintain a capacity retention rate of more than 82% and a charge-discharge efficiency of more than 85% at an extreme low temperature of -30℃; and the cycle life is improved by more than 50% at a high temperature of 60℃, which completely solves the industry problem of the rapid performance degradation of existing battery packs in cold and hot environments.

[0066] (3) The wide temperature range anti-degradation battery pack of the present invention is based on a smart battery management system (BMS) to realize the leap from "passive response" to "active prediction" in thermal management strategy, and keeps the internal temperature difference of the battery pack within ±2.5℃, significantly delaying battery degradation and keeping the performance consistency error of mass-produced battery packs within 5%. Detailed Implementation

[0067] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0068] Unless otherwise specified, the experimental methods used in the examples and comparative examples are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0069] Example 1 A wide-temperature-range anti-degradation battery pack includes a thermal management system and a smart battery management system (BMS) connected together. The thermal management system includes a housing assembly, a battery cell assembly, and a thermally conductive adhesive layer; the housing assembly is connected to the battery cell assembly through the thermally conductive adhesive layer and to a vehicle mounting bracket through a snap-fit ​​assembly; The housing assembly includes a PTC heating film, a microchannel liquid cooling plate, and an aerogel insulation layer, which are arranged sequentially from the inside to the outside. The PTC heating film is connected to the battery cell assembly through the thermally conductive adhesive layer.

[0070] The buckle assembly described in this embodiment can be any conventional buckle or other parts in the art.

[0071] The battery cell assembly includes at least one battery cell, which is cylindrical or square and arranged in a regular hexagonal honeycomb pattern. The battery cells are electrically connected to each other using a corrugated flexible nickel sheet. The height of the crests, the height of the troughs, and the spacing between the crests and troughs of the corrugated flexible nickel sheet are adapted to the boundary of the honeycomb structure formed by the battery cells.

[0072] The battery cell includes a positive electrode material, a negative electrode material, and an electrolyte; the positive electrode material includes lithium iron phosphate; the negative electrode includes graphite. Based on the total mass of the battery cell, the positive electrode material accounts for 45%–55% of the mass, the negative electrode material accounts for 20%–28% of the mass, and the electrolyte accounts for 15%–22% of the mass. The electrolyte comprises an organic solvent, an additive, and a lithium salt; the organic solvent content is 60-75 wt%, the additive content is 3-10 wt%, and the lithium salt content is 15-30 wt%. The organic solvent includes fluoroethylene carbonate and propyl propionate; the mass ratio of fluoroethylene carbonate to propyl propionate is 1:(3~5). The additives include adiponitrile and propylene sulfate; the mass ratio of adiponitrile to propylene sulfate is (2.5~3.5):(0.8~1.2).

[0073] The lithium salt includes lithium hexafluorophosphate, lithium difluorophosphate and lithium difluorosulfonylimide; the mass ratio of lithium hexafluorophosphate, lithium difluorophosphate and lithium difluorosulfonylimide is (8~10):(2~3):(3~5).

[0074] The thermally conductive adhesive layer comprises silicone rubber and thermally conductive filler; the thermally conductive filler comprises boron nitride and graphene; the mass ratio of boron nitride to graphene is 1:(0.8~1.5).

[0075] The thermally conductive adhesive layer is distributed in a vertical gradient within the thermal management system; the distribution of the thermally conductive adhesive layer is as follows: Near the cell side: the mass ratio of boron nitride to graphene is 1:0.8; Intermediate transition layer: the mass ratio of boron nitride to graphene is 1:1; Near the shell side: the mass ratio of boron nitride to graphene is 1:1.2.

[0076] The preparation of the thermally conductive adhesive layer includes the following steps: injecting silicone containing boron nitride and graphene into the gap between the battery cell and the housing assembly, curing it, and utilizing the sedimentation and self-assembly behavior of the filler under the gravitational and temperature fields to form a thermally conductive adhesive layer with a continuous concentration gradient in the vertical direction. The curing process employs a stepped temperature increase procedure, specifically pre-curing at 40℃~60℃ for 30~90 minutes, followed by final curing at 80℃~100℃ for 60~120 minutes.

[0077] The method for preparing the shell assembly includes the following steps: in a mold, a PTC heating film, a microchannel liquid cooling plate, and an aerogel prepreg are laid in sequence, and an epoxy resin interface agent is sprayed on; then, a modified epoxy resin is injected using a vacuum-assisted resin transfer molding method, heated, and cured, so that the three heterogeneous materials form an integrated structure with a strong interface bond and minimal thermal resistance, thereby obtaining the shell assembly.

[0078] The microchannel liquid cooling plate is an aluminum plate pre-impregnated with epoxy resin, which is pre-cured at 80°C for 30 minutes to a semi-cured state.

[0079] The aerogel prepreg is composed of hydrophobic silica aerogel powder, chopped carbon fibers, and a phenolic epoxy resin carrier; wherein the mass fraction of the hydrophobic silica aerogel powder is 60%~80%, the mass fraction of the chopped carbon fibers is 5%~15%, and the remainder is the phenolic epoxy resin carrier.

[0080] The hydrophobic silica aerogel powder has a particle size distribution of 10-100 μm and a contact angle greater than 130°.

[0081] The epoxy resin interface agent comprises an aminosilane coupling agent, nano-alumina particles, and bisphenol A type epoxy resin; the mass fraction of the nano-alumina particles is 3% to 8%, the mass fraction of the aminosilane coupling agent is 5% to 15%, and the balance is bisphenol A type epoxy resin.

[0082] In this embodiment, the epoxy resin interface agent is prepared by mixing the various components.

[0083] In this embodiment, the modified epoxy resin comprises the following components in parts by weight: 100 parts epoxy resin matrix, 15-25 parts modifier, 30-35 parts curing agent, 40-60 parts thermally conductive filler, and 0.5-1 parts catalyst.

[0084] The epoxy resin matrix comprises a mixture of bisphenol A type epoxy resin (such as E-51) and hydrogenated bisphenol A epoxy resin in a mass ratio of 7:3.

[0085] The modifier may be a carboxyl-terminated liquid fluororubber-polyethersulfone block copolymer.

[0086] The curing agent can be a phosphorus-containing spirocyclic diamine curing agent.

[0087] The thermally conductive filler can be a composite of aluminum nitride nanowires modified with silane coupling agent KH-560 and spherical alumina, with a mass ratio of 1:4, wherein the particle size of the spherical alumina is 1~5μm.

[0088] The catalyst may be a microencapsulated imidazole latent catalyst.

[0089] In this embodiment, the preparation method of the modified epoxy resin includes the following steps: heating the epoxy resin matrix to 80±5℃, slowly adding the modifier under high-speed shear (speed >2000 rpm), and continuing shearing for 1 hour to form a homogeneous and transparent premix. The thermally conductive filler is slowly added to the premix in three portions, and after each addition, a planetary vacuum mixer is used to stir and degas until a composite material with suitable viscosity and uniform filler dispersion is formed. The system temperature is lowered to below 50℃, and the curing agent and catalyst are added sequentially. After mixing evenly at medium and low speeds, the mixture is immediately discharged, sealed, and stored to obtain the modified epoxy resin.

[0090] The heating is a stepped heating, which includes the following steps: heating at 70~90℃ for 1~3 hours, heating at 110~130℃ for 2~5 hours, heating again, and heating at 140~160℃ for 1~2 hours.

[0091] The vacuum-assisted resin transfer molding method described in this embodiment is a conventional method in the art.

[0092] The intelligent battery management system (BMS) integrates a multi-parameter sensor network. The intelligent battery management system is used to monitor the voltage, temperature and internal resistance changes of each cell in the battery cell assembly in real time, and adjusts the thermal management system based on an intelligent algorithm of ambient temperature and battery status. When the temperature is low, the PTC heating film is activated for graded heating, and when the temperature is high, the microchannel liquid cooling plate is activated to ensure that the battery cell assembly is always in the optimal operating temperature range.

[0093] Multiple of the aforementioned wide-temperature-range anti-age battery packs are connected using a combination of magnetic positioning and mechanical locking.

[0094] The wide-temperature-range anti-degradation battery pack also includes a modular splicing interface. The modular splicing interface is equipped with an intelligent identification circuit, which can automatically identify the number of the wide-temperature-range anti-degradation battery packs and adjust the parameters of the intelligent battery management system to realize plug-and-play capacity expansion functionality.

[0095] The modular splicing interface incorporates an intelligent identification circuit that automatically identifies the number of battery packs connected in parallel in the system using a combination of a two-wire serial bus and resistor address encoding. When multiple battery packs are physically connected through the modular interface, the intelligent identification circuit applies a constant reference voltage to the bus and reads the total current value on the bus. According to Ohm's law, the total system resistance is inversely proportional to the number of connected packs. By comparing and decoding the measured total resistance value with the resistor address codes of each battery pack pre-stored in the main control BMS, the circuit can accurately calculate the actual number of battery packs (N) in the current system.

[0096] After accurately identifying the number of packs (N), the main control intelligent battery management system (BMS) will automatically adjust the following key operating parameters to achieve seamless capacity expansion: (1) Capacity parameter: Reset the total available capacity of the system (Ah) to N × the rated capacity of a single battery pack.

[0097] (2) Current limit: The maximum charge and discharge current limit of the system is synchronously adjusted to N × a single battery pack.

[0098] (3) Safety current limit to ensure that each battery pack operates with equal current.

[0099] (4) SOC calibration: Based on the expanded total capacity, the state of charge (SOC) of the entire battery system is recalibrated to achieve accurate updates of the power display.

[0100] (5) Allocate the total available power of PTC heating and liquid cooling according to the number of packages to ensure that each package can still obtain balanced and effective thermal management support when multiple packages work together. The closed loop of "identification-calculation-adjustment" enables the system to achieve plug-and-play and collaborative management from single package to multiple packages, and finally completes the smooth and safe expansion of capacity.

[0101] Working process: When the intelligent battery management system detects a low-temperature environment, the BMS activates the PTC heating film, while simultaneously maintaining uniform heat distribution through the low thermal conductivity of the gradient thermally conductive adhesive layer. In high-temperature environments, the microchannel liquid cooling plate is activated, and combined with the high thermal conductivity of the thermally conductive adhesive layer, heat dissipation is rapid, ensuring that the temperature gradient of the battery cell does not exceed 3°C. Throughout the process, the honeycomb structure in the battery cell assembly effectively suppresses cell expansion, and the flexible connections absorb mechanical stress, thereby achieving high-performance and stable output over a wide temperature range.

[0102] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A wide temperature range, anti-fading battery pack, characterized in that, The application relates to a battery pack with a wide temperature range and anti-attenuation, which comprises a connected thermal management system and an intelligent battery management system. The thermal management system comprises a shell assembly, an electric core assembly and a heat-conducting adhesive layer; the shell assembly is connected with the electric core assembly through the heat-conducting adhesive layer and is connected with a vehicle mounting seat through a buckle assembly. The shell assembly comprises a PTC heating film, a micro-channel liquid cooling plate and an aerogel thermal insulation layer, and the PTC heating film, the micro-channel liquid cooling plate and the aerogel thermal insulation layer are sequentially arranged; the PTC heating film is connected with the electric core assembly through the heat-conducting adhesive layer.

2. The wide temperature range, attenuation resistant battery pack of claim 1, wherein, The electric core assembly comprises at least one electric core, the electric core adopts a regular hexagonal honeycomb arrangement, and the electric cores are electrically connected through wave-shaped flexible nickel sheets; the height of the wave crest of the wave-shaped flexible nickel sheet, the height of the wave trough of the wave-shaped flexible nickel sheet and the interval between the wave crest and the wave trough of the wave-shaped flexible nickel sheet are matched with the boundary of the honeycomb structure formed by the electric cores.

3. The wide temperature range, anti-fading battery pack of claim 2, wherein, The electric core comprises a positive electrode material, a negative electrode material and an electrolyte; the positive electrode material comprises lithium iron phosphate; the negative electrode comprises graphite; and the electrolyte comprises an organic solvent, an additive and a lithium salt. The content of the organic solvent in the electrolyte is 60-75 wt%, the content of the additive is 3-10 wt%, and the content of the lithium salt is 15-30 wt%. The organic solvent comprises at least one of fluoroethylene carbonate and propyl propionate. The additive comprises at least one of adiponitrile and propylene sulfate. The lithium salt comprises at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium trifluoromethyl sulfonate and lithium bisfluorosulfonimide.

4. The wide temperature range, attenuation resistant battery pack of claim 3, wherein, The organic solvent comprises fluoroethylene carbonate and propyl propionate; and the mass ratio of the fluoroethylene carbonate to the propyl propionate is 1: (3-5).

5. The wide temperature range, attenuation resistant battery pack of claim 1, wherein, The heat-conducting adhesive layer comprises silicone rubber and heat-conducting fillers; the heat-conducting fillers comprise boron nitride and graphene; and the mass ratio of the boron nitride to the graphene is 1: (0.5-2). The heat-conducting adhesive layer is vertically gradiently distributed in the thermal management system. The distribution of the heat-conducting adhesive layer is as follows: Close to the electric core side: the mass ratio of the boron nitride to the graphene is 1:0.8; The middle transition layer: the mass ratio of the boron nitride to the graphene is 1:1; Close to the shell side: the mass ratio of the boron nitride to the graphene is 1:1.

2.

6. The wide temperature range, attenuation resistant battery pack of claim 1, wherein, The preparation method of the shell assembly comprises the following steps: in a mold, sequentially laying a PTC heating film, a micro-channel liquid cooling plate, aerogel prepreg and spraying an epoxy resin interface agent; then injecting modified epoxy resin by using a vacuum-assisted resin transfer molding method, stepwise heating, curing and obtaining the shell assembly.

7. The wide temperature range, attenuation resistant battery pack of claim 1, wherein, The intelligent battery management system integrates a multi-parameter sensing network; the intelligent battery management system is used for monitoring the voltage, temperature and internal resistance changes of each electric core in the electric core assembly in real time and adjusting the thermal management system based on an intelligent algorithm of the environmental temperature and the battery state, so that the PTC heating film is started for step-by-step heating in low temperature and the micro-channel liquid cooling plate is activated in high temperature, and the electric core assembly is ensured to be always in an optimal working temperature range.

8. The wide temperature range, attenuation resistant battery pack of claim 1, wherein, A plurality of the wide-temperature-range anti-attenuation battery packs are connected in a composite mode of magnetic attraction positioning and mechanical locking.

9. The wide temperature range, attenuation resistant battery pack of claim 1, wherein, The wide-temperature-range anti-attenuation battery pack further comprises a modular splicing interface; the modular splicing interface is provided with an intelligent identification circuit, which can automatically identify the number of the wide-temperature-range anti-attenuation battery pack and adjust the parameters of the intelligent battery management system.

10. Application of the wide-temperature-range anti-attenuation battery pack according to any one of claims 1-9 to an electric low-speed vehicle.