A fire-retardant cover plate for a battery pack

Abstract

The application relates to the field of power batteries, in particular to a fireproof cover plate of a battery pack. From top to bottom, the fireproof cover plate comprises an upper structural layer, a functional interlayer and a lower heat insulation layer; the upper structural layer is made of a steel product, constitutes a main force-bearing part of an upper cover, provides structural rigidity and mechanical strength; the lower heat insulation layer is made of ceramic fiber felt or aerogel felt material, is attached to the inner side of the functional interlayer and serves as a redundant heat insulation barrier; the functional interlayer is integrally formed into a closed cavity through co-curing or welding process of the reinforcing ribs and the upper and lower skins; the upper cover adopts a multilayer composite structure, the safety performance of the battery system under extreme working conditions such as thermal runaway can be improved, and the passive inhibition of thermal shock and the active alarm are cooperatively protected.

Description

Technical Field

[0001] This application relates to the field of power batteries, specifically to a flame-retardant cover for a battery pack. Background Technology

[0002] Currently, the safety of the power battery pack, as the core energy storage unit of electric vehicles, especially its protection under extreme conditions such as thermal runaway, is one of the key factors restricting the industry's development. The battery pack cover, as the uppermost structural component of the system, traditionally primarily serves sealing and basic protection functions. Common existing technologies include using metal sheets such as steel or aluminum alloys. While these solutions offer good structural strength, they have inherent shortcomings in thermal management. The high thermal conductivity of metal materials means that when a battery cell experiences thermal runaway, heat can rapidly dissipate through the cover, potentially igniting surrounding components and posing a direct thermal threat to the passenger compartment.

[0003] To further improve thermal insulation performance, some composite material cover designs have emerged in existing technologies, such as structures combining glass fiber reinforced plastic with thermal insulation pads. While these designs slow down heat transfer to some extent, their function is relatively limited, typically providing only passive thermal insulation. The insulation layer in these structures is often simply superimposed on the load-bearing structural layer. Under thermal shock, the interfaces between these layers may fail due to mismatched coefficients of thermal expansion, affecting long-term reliability. More importantly, such passive structures cannot provide any form of early warning signal for thermal runaway events occurring within the battery pack. The battery management system can only indirectly determine the situation by monitoring cell voltage and temperature, which carries the risk of delayed or missed warnings, making it difficult to buy valuable emergency response time for drivers and passengers, and also failing to trigger system-level safety interlocking measures. Utility Model Content

[0004] The purpose of this application is to overcome at least one deficiency in the prior art and provide a flame-retardant cover for a battery pack. This cover employs a multi-layered composite structure, which can improve the safety performance of the battery system under extreme conditions such as thermal runaway, achieving synergistic protection through passive suppression of thermal shock and active warning.

[0005] To achieve the above objectives, this application discloses a flame-retardant cover for a battery pack, which includes, from top to bottom, an upper structural layer, a functional interlayer, and a lower heat insulation layer. The upper structural layer is made of steel and forms the main load-bearing part of the cover, providing structural rigidity and mechanical strength.

[0006] The lower insulation layer is made of ceramic fiber felt or aerogel felt and is attached to the inner side of the functional interlayer as a redundant insulation barrier to effectively block heat from being transferred to the outside.

[0007] The functional interlayer is formed by reinforcing ribs and upper and lower skins through co-curing or welding processes to create an integrated sealed cavity. The cavity is filled with a phase change working fluid with a high boiling point, high heat of vaporization, and electrical insulation properties, such as a fluorinated liquid.

[0008] At the highest point of the sealed cavity, at least one resettable pressure valve is installed. The mechanical actuating component of the pressure valve is coupled to a micro switch. The micro switch is connected in series to the hard-wired alarm circuit of the battery management system to form a normally closed or normally open contact for real-time status monitoring.

[0009] Furthermore, the opening pressure threshold of the pressure valve is lower than the pressure bearing limit of the upper cover structure but higher than the vapor pressure generated by the phase change working fluid under normal temperature fluctuations.

[0010] When thermal runaway occurs within the battery pack, the high temperature impacts the inner wall of the top cover, and heat is rapidly conducted to the functional interlayer. The phase change working fluid undergoes a liquid-to-gas phase change upon heating, absorbing a large amount of heat and thus slowing down the temperature rise on the back of the top cover. Simultaneously, the vaporization of the working fluid causes a sharp increase in pressure within the sealed cavity. When the pressure reaches a preset threshold, the pressure valve opens, and its mechanical displacement directly drives a microswitch to switch states, generating a jump electrical signal. This signal is instantly acquired by the battery management circuit through a hard-wired loop. Based on this signal, the circuit triggers the highest-priority fault alarm and executes predetermined safety measures, such as forcibly disconnecting the high-voltage circuit.

[0011] In summary, compared with existing technologies, this top cover achieves a balance between lightweight and high strength through a composite structure. Furthermore, by integrating passive thermal protection with active electrical alarms through the heat absorption and vaporization of the built-in phase change working fluid and the pressure triggering mechanism, it effectively improves the thermal safety redundancy and early warning reliability of the battery pack.

[0012] The beneficial effects listed above are not exhaustive of all advantages. Other potential beneficial effects and detailed technical implementation methods will be further disclosed in the embodiments or other descriptive sections of this application. Attached Figure Description

[0013] A better understanding of various aspects of this disclosure will be achieved by reading the following detailed description in conjunction with the accompanying drawings. The positions, dimensions, and extents of the structures shown in the drawings, etc., do not always represent actual positions, dimensions, and extents. In the drawings: Figure 1 This is a schematic diagram of the structure of one embodiment disclosed in this application.

[0014] Figure 2 This is a schematic diagram of the structure of one embodiment disclosed in this application from another perspective.

[0015] Figure 3 This is a schematic diagram of the internal structure of one embodiment disclosed in this application. Detailed Implementation

[0016] The present disclosure will now be described with reference to the accompanying drawings, which illustrate several embodiments of the present disclosure. However, it should be understood that the present disclosure can be presented in many different ways and is not limited to the embodiments described below; in fact, the embodiments described below are intended to make the disclosure more complete and to fully illustrate the scope of protection of the present disclosure to those skilled in the art. It should also be understood that the embodiments disclosed herein can be combined in various ways to provide further additional embodiments.

[0017] It should be understood that the same reference numerals denote the same elements in all the accompanying drawings. For clarity, the dimensions of certain features may be modified in the drawings.

[0018] It should be understood that the terminology used in this specification is for describing specific embodiments only and is not intended to limit this disclosure. All terms used in this specification (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. For the sake of brevity and / or clarity, techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail; however, where appropriate, such techniques, methods, and apparatus should be considered part of this specification.

[0019] Unless otherwise specified, the singular forms “a,” “the,” and “the” used in this specification include the plural forms. The terms “comprising,” “including,” and “containing” used in this specification indicate the presence of the claimed feature but do not exclude the presence of one or more other features. The term “and / or” used in this specification includes any and all combinations of one or more of the relevant listed items.

[0020] See attached document Figures 1 to 3 In this embodiment, the flame-retardant cover of the power battery pack adopts a multi-layer composite structure, consisting of an upper structural layer 1, a functional interlayer 2, and a lower heat insulation layer 3, which are fixedly connected to achieve integrated molding. Among them, the upper structural layer 1 serves as the main load-bearing component, providing overall rigid support. The functional interlayer 2 forms a sealed cavity filled with phase change working fluid and integrates a pressure sensing mechanism. The lower heat insulation layer 3 serves as a redundant thermal barrier to prevent heat from being transferred outward. Through the coordinated design of materials and structure, each functional layer jointly achieves the dual functions of passive thermal protection and active electrical alarm under thermal runaway conditions.

[0021] Specifically, the upper structural layer 1 is made of steel through a hot pressing process.

[0022] Furthermore, the functional interlayer 2 is formed into an integrated sealed cavity by co-curing the upper and lower panels with Z-shaped continuous reinforcing ribs. The cross-sectional height of the reinforcing ribs is 8.0 mm, the thickness of the rib plate is 1.2 mm, the center-to-center distance between adjacent reinforcing ribs is 25.0 mm, and the Z-shaped angle is 75°. The phase change working fluid filled inside the cavity is perfluoropolyether Galden HT-270, which has a boiling point of 270°C, a heat of vaporization of 88 kJ / kg, a viscosity of 45 cSt at 25°C, and a dielectric strength of 40 kV / 2.5 mm. The high boiling point of this working fluid ensures that it remains liquid and stable within the normal operating temperature range of the battery, while its high heat of vaporization provides effective thermal buffering during thermal shock.

[0023] Understandably, the continuous arrangement of the Z-shaped reinforcing ribs not only increases the bending stiffness of the cover plate by about 2.3 times, but the specific geometry of its internal cavity also increases the contact area between the phase change working fluid and the heat transfer inner wall by about 1.8 times, thereby significantly improving the heat exchange efficiency. Subsequently, the lower insulation layer 3 is made of high-purity alumina ceramic fiber felt with a density of 200±10 kg / m³ and a thickness of 2.0 mm. Its thermal conductivity at a high temperature of 800℃ is 0.11 W / (m·K). This layer is completely bonded to the lower skin of the functional interlayer 2 with a high-temperature resistant silicone adhesive with a thickness of 0.1 mm. The peel strength after bonding is not less than 2.5 N / mm.

[0024] Preferably, a resettable pressure valve 4 is installed at the geometrically highest point of the sealed cavity of the functional interlayer 2. The valve body adopts a spring-loaded 316L stainless steel ball valve structure, and the valve seat material is polytetrafluoroethylene filled with graphite. The preload of the spring is set by a precision adjusting screw, so that the opening pressure threshold of the pressure valve 4 is 0.45±0.02 MPa. This threshold is carefully designed to be lower than the pressure bearing limit of the cover structure to ensure structural safety, and higher than the safety margin of 0.25 MPa saturated vapor pressure generated by the phase change working fluid at an ambient temperature of 120°C. The top of the valve stem of the pressure valve 4 is rigidly coupled to a 15 mm long phosphor bronze lever-type trigger arm. The end of the trigger arm maintains an initial gap of 0.5±0.1 mm with the actuation button of the micro switch. This gap design is optimized to avoid false triggering caused by normal vehicle vibration and to ensure timely transmission of displacement when the valve core moves. The micro switch is a single-pole double-throw switch with IP67 protection rating. Its normally closed contact is connected in series to the hard-wired alarm circuit of the battery management system. The circuit is powered by 12V DC and includes the digital input port of the main control board and a 1 kΩ / 0.5W current-limiting resistor in series. This circuit design is a conventional technology in the field, but its mechanical coupling with the pressure valve to form a complete signal triggering chain is the key innovation of this invention.

[0025] When thermal runaway occurs inside the battery pack, high-temperature flames or hot air currents directly impact the lower surface of the cover plate. Heat is rapidly conducted to the phase change working fluid through the lower insulation layer 3 and the lower skin of the functional interlayer 2. Thermal runaway tests conducted according to GB / T 31467.3-2015 standard show that under the condition that a single cell releases approximately 100 kJ of heat during thermal runaway, the vaporization process of the phase change working fluid can maintain the outer surface temperature of the upper structural layer 1 below 180°C for 120 seconds, while the comparative sample without this design exceeds 300°C within 60 seconds. At the same time, the continuous vaporization of the working fluid causes the pressure inside the sealed cavity to rise linearly at a rate of approximately 0.1 MPa / s. When the pressure inside the cavity reaches the preset threshold of 0.45 MPa, the valve core of the pressure valve 4 generates an axial displacement of 3.2 mm, and drives a microswitch through a lever arm to complete the contact switching within 15 milliseconds, generating a transition signal from high level (12V) to low level (0V) transmitted to the battery management system. Based on this, the battery management system captures the signal via a hardware interrupt and immediately triggers the highest-priority fault handling procedure. This includes driving the high-voltage contactor to disconnect the main circuit within 100 milliseconds, activating the red warning icon on the instrument panel, and sending a highest-priority alarm message to the vehicle controller via the CAN bus. Ultimately, the composite cover, through a synergistic mechanism of phase change heat absorption and pressure triggering, achieves early warning of thermal runaway while maintaining structural integrity. The pressure valve automatically resets when the internal pressure drops to 0.35 MPa, and the microswitch also returns to its initial state. This recoverable characteristic allows the protection system to be reused after a single triggering, significantly improving the product's economy and maintenance convenience. Testing has shown that this pressure sensing system can withstand multiple cycles of operation while maintaining stable performance.

[0026] While exemplary embodiments of this disclosure have been described, those skilled in the art will understand that various changes and modifications can be made to the exemplary embodiments of this disclosure without departing from the spirit and scope thereof. Therefore, all changes and modifications are included within the scope of protection of this disclosure as defined by the claims. This disclosure is defined by the appended claims, and equivalents of those claims are also included.

Claims

1. A flame-retardant cover for a battery pack, characterized in that, The structure comprises, from top to bottom, an upper structural layer, a functional interlayer, and a lower insulation layer. The upper structural layer, made of steel, forms the main load-bearing component of the cover, providing structural rigidity and mechanical strength. The lower insulation layer, made of ceramic fiber felt or aerogel felt, is attached to the inner side of the functional interlayer as a redundant insulation barrier. The functional interlayer consists of reinforcing ribs and upper and lower skins, forming an integrated sealed cavity through co-curing or welding processes. This cavity is filled with a phase change working fluid. At the highest point of the sealed cavity, at least one resettable pressure valve is installed. The opening pressure threshold of the pressure valve is lower than the pressure bearing limit of the upper cover structure but higher than the vapor pressure generated by the phase change working fluid under normal temperature fluctuations.

2. The flame-retardant cover plate for a battery pack as described in claim 1, characterized in that, The mechanical actuating component of the pressure valve is coupled to a micro switch; the micro switch is connected in series in the hard-wired alarm circuit of the battery management circuit to form a normally closed or normally open contact for real-time status monitoring.

Images