An adjustable pressure gas buffer heat insulation composite protection structure for power batteries and a preparation method thereof

Abstract

The application discloses a kind of adjustable pressure gas buffer heat-insulating composite protective structure for power battery and preparation method thereof.The protective structure is the symmetrical sandwich structure with flexible airtight gas buffer layer as center, heat-insulating composite barrier layer and high-strength fire-resistant heat-insulating shell layer are sequentially arranged on both sides of the gas buffer layer.The gas buffer layer is enclosed by high-temperature-resistant airtight flexible film material to form airtight cavity filled with gas medium, support structure is arranged between the inner walls of the cavity, and gas pressure regulating assembly comprising inflation interface, pressure detection interface and pressure relief interface is connected, so that the cavity generates reverse support force when compressed under pressure, and restores original shape by gas expansion when unloaded, so that the thickness of the protective structure and support pressure dynamically change with stress state.The application solves the problems of fixed structure, unadjustable buffering capacity and performance degradation after long-term compression of existing heat-insulating buffer materials, and considers high-temperature insulation, bearing, dynamic buffering and failure safety.

Description

Technical Field

[0001] This invention relates to the field of thermal safety protection and composite thermal insulation buffer structure technology for power batteries in new energy vehicles, specifically to an adjustable pressure gas buffer thermal insulation composite protection structure for power batteries and its preparation method. This invention can be applied to the fields of power battery packs for new energy vehicles, inter-cell thermal diffusion blocking structures, power battery module protection components, and high-temperature thermal runaway protection. Background Technology

[0002] As the energy density of power batteries for new energy vehicles continues to increase, higher requirements are placed on the thermal runaway protection of power batteries, particularly on the internal thermal insulation and buffering materials of the battery pack. Existing power battery packs typically incorporate thermal insulation and buffering materials between cells, between modules, or inside the battery pack casing to achieve functions such as heat diffusion blocking, mechanical buffering, and insulation protection. Currently, commonly used thermal insulation and buffering materials mainly include aerogel materials, foam materials, rubber elastic materials, and inorganic heat insulation boards.

[0003] In existing technologies, aerogel materials are widely used in the field of thermal protection for power batteries due to their low thermal conductivity, high temperature resistance, and lightweight properties. However, traditional aerogel materials mainly rely on their static structure to achieve thermal insulation, and their fixed structural shape cannot actively adjust to changes in volume, assembly pressure, and thermal expansion stress generated during battery operation. Under long-term compressive loads, the porous structure inside the aerogel is prone to compressive damage, leading to a reduction in material thickness and a decrease in thermal insulation performance. Furthermore, its elastic recovery ability is limited, making it difficult to independently meet mechanical buffering requirements.

[0004] Existing technologies also employ elastic materials such as silicone rubber, polyurethane foam, and EPDM rubber foam as buffer layers between battery cells. These materials rely on the compression deformation of the material itself for buffering, but their buffering capacity is limited by the material's elastic modulus and fatigue life. Long-term cyclic compression can easily lead to permanent compression deformation, gradually reducing the buffer gap. Furthermore, organic elastic materials are prone to thermal decomposition under high-temperature thermal runaway conditions, making it difficult to balance high-temperature insulation with long-term mechanical stability. Another approach uses rigid inorganic materials such as ceramic plates, mica plates, and metal insulation plates. While these materials have good temperature resistance, they are rigid, lack deformability, and cannot provide a continuous buffer space, easily leading to localized stress concentrations.

[0005] To address the aforementioned issues, existing technologies have further proposed incorporating inflatable and deflated airbag structures between battery cells. These airbags provide cushioning by altering the internal gas pressure, and are further divided into multiple air chambers, equipped with one-way valves and pressure relief valves, or fitted with pressure sensors, air pumps, and controllers to achieve active constant pressure. However, such gas buffer structures still present the following engineering challenges.

[0006] First, the gas path architecture cannot simultaneously meet the three requirements of independently setting pressure for each chamber, active pressure relief, and preventing cross-contamination. If each chamber is connected to a continuously connected common gas path via only one branch, the single check valve on that branch can only allow gas to flow in one direction: when the check valve is open towards the chamber, it can prevent other chambers from leaking gas back to the damaged chamber, but the chamber itself cannot exhaust gas through that branch, so active pressure relief cannot be achieved; if the check valve is removed or bidirectional flow is used to achieve pressure relief, then each chamber is connected to each other via the common gas path, which makes it impossible to maintain different initial pressures for a long time, and also impossible to block the back leakage of other chambers when a single chamber is damaged.

[0007] Secondly, using a single passive component such as a fusible alloy plug or a rupture disc cannot simultaneously perform two opposing actions: "cutting off the connection between the gas chamber and the common gas path" and "connecting to the exhaust channel outside the battery pack." When the fusible plug melts, its channel changes from closed to open; similarly, when the rupture disc opens, its channel changes from closed to open. Both can only achieve a single "from closed to open" action, not a "from open to closed" action on the gas supply channel. If only one type of component is used, either the gas chamber is cut off but has no exhaust path, or the gas chamber can exhaust but remains connected to the common gas path, causing the other gas chambers to lose pressure as well.

[0008] Third, the criterion of adjusting pressure and temperature according to the ideal gas relationship is not subject to any specific conditions. The practice of adjusting measured pressure based on a reference temperature can only eliminate the influence of temperature on pressure readings if both the volume of the gas chamber and the amount of gas within it remain constant. However, the volume of the gas chamber in a gas buffer structure changes with the expansion of the battery cell, and the amount of gas within the chamber also changes during inflation and deflation. Therefore, without specifying the detection period and incorporating volume information, this adjustment result cannot distinguish between the mechanical expansion of the battery cell and the thermal expansion of the gas.

[0009] Fourth, using only a rapid rate of pressure change as a criterion for sensor failure is unreliable. Vehicle collisions, localized mechanical impacts, and valve opening and closing actions can also cause rapid pressure changes. If these are not combined with displacement signals, valve status, and redundant sensor readings for joint judgment, it is easy to misjudge normal operating conditions as sensor failure, or to miss sensor failure altogether.

[0010] Fifth, using the compressive strength of a material as a criterion for determining whether a support participates in load-bearing is conceptually flawed. Compressive strength typically characterizes a material's failure index, while the timing of a support's participation in load-bearing depends on the contact gap between it and the opposing wall, and its load-bearing capacity depends on the plateau stress and ultimate compression during compression. Describing the load-bearing initiation point using a failure index is neither a reliable basis for design nor for verification.

[0011] Therefore, existing thermal insulation buffer materials and existing gas buffer structures for power batteries cannot yet meet the comprehensive protection requirements of power batteries under thermal runaway, high-pressure compression, and long-term cyclic conditions, while ensuring compatibility with independent pressure regulation and anti-cross-flow, a definite passive safety response under failure conditions, reliable identification of the pressure source, and testability and verification of load-bearing grading. Summary of the Invention

[0012] In view of the problems existing in the thermal protection materials of power batteries, such as fixed thermal insulation structure, unadjustable buffering capacity, performance degradation after long-term compression, and existing gas buffer structures with incompatible gas path architecture, lack of passive thermal safety measures, insufficient conditions for identifying pressure sources, unreliable fault diagnosis and unmeasurable load-bearing grading, the purpose of this invention is to provide an adjustable pressure gas buffer thermal insulation composite protection structure for power batteries and its preparation method.

[0013] To achieve the above objectives, the present invention adopts the following technical solution.

[0014] This invention provides an adjustable pressure gas buffer and heat insulation composite protection structure for power batteries. The protection structure is a symmetrical sandwich structure centered on a flexible sealed gas buffer layer. From the center to both sides, it includes the flexible sealed gas buffer layer, two heat insulation composite barrier layers respectively disposed on both sides of the flexible sealed gas buffer layer, and two high-strength fire-resistant heat insulation shell layers respectively disposed on the outside of the two heat insulation composite barrier layers.

[0015] The high-strength fire-resistant and heat-insulating outer shell layer is made of high-temperature resistant rigid material, forming the load-bearing boundary of the protective structure to withstand external mechanical loads and high-temperature heat flow impacts during thermal runaway. The heat-insulating composite barrier layer is made of low thermal conductivity insulating material to reduce heat transfer to the flexible sealed gas buffer layer. The flexible sealed gas buffer layer is formed by a high-temperature resistant, airtight flexible membrane material enclosing a sealed gas cavity, which is filled with a gas medium. A support structure is provided within the sealed gas cavity, located between the inner walls on both sides of the sealed gas cavity, to limit the deformation range of the sealed gas cavity during pressure application to prevent local collapse of the sealed gas cavity. The flexible sealed gas buffer layer is connected to a pressure regulating component, which includes an inflation port, a pressure detection port, and a pressure relief port that communicate with the sealed gas cavity. The component is used to regulate the gas pressure in the sealed gas cavity to a preset pressure range, so that when the sealed gas cavity is subjected to an external compressive load, it is compressed, the internal gas pressure increases, and a reverse support force is generated. When the external compressive load decreases, the internal gas expands and pushes the flexible membrane material to restore its original shape, thereby making the thickness and support pressure of the protective structure dynamically change with the stress state.

[0016] By employing the aforementioned symmetrical sandwich structure, both sides of the flexible sealed gas buffer layer are covered by a thermally insulating composite barrier layer and a high-strength fire-resistant thermally insulating outer shell layer. When the protective structure is installed between two adjacent power battery cells, regardless of which cell experiences thermal runaway, the high-strength fire-resistant thermally insulating outer shell layer and the thermally insulating composite barrier layer on the side closer to the heat source can withstand the flame impact first and reduce the heat transfer rate, thereby preventing the flexible sealed gas buffer layer from directly bearing thermal shock and mechanical loads.

[0017] Preferably, the flexible sealed gas buffer layer is divided into multiple independent air chamber units by the partition structure. Each independent air chamber unit constitutes an independent pressure regulating unit and is connected to the air pressure regulating component, so that when any independent air chamber unit is locally compressed, only the gas in that independent air chamber unit is compressed and generates a reverse supporting force, while the other independent air chamber units maintain their original pressure state.

[0018] Preferably, the air pressure regulating component includes a miniature air pump, a common air supply line, a common pressure relief line, and an inflation branch, a pressure relief branch, and a pressure sensor, each corresponding to one of the independent air chamber units. One end of each inflation branch is connected to the corresponding independent air chamber unit, and the other end is connected to the common air supply line. The miniature air pump is connected to the common air supply line via the inflation interface. Each inflation branch is sequentially connected in series along the air supply direction with a zoned inflation valve, a flow-limiting orifice, and a check valve. The zoned inflation valve is a normally closed valve that closes upon power failure. The check valve's conduction direction is from the common air supply line to the corresponding independent air chamber unit. The flow area of ​​the flow-limiting orifice is smaller than the flow area of ​​the inflation branch. One end of each pressure relief branch is connected to the corresponding independent air chamber unit, and the other end is connected to the pressure relief interface via the common pressure relief line. Each pressure relief branch is equipped with a zoned pressure relief valve, which is a normally closed valve that closes upon power failure. Each pressure sensor detects the gas pressure within its corresponding independent gas chamber unit via the pressure detection interface.

[0019] The aforementioned gas path architecture serves to separate inflation and depressurization into two independent branches, allowing the unidirectional flow direction of the check valve to be dedicated solely to inflation without obstructing depressurization. This simultaneously satisfies the requirements of independent chamber pressure setting, active depressurization, and prevention of cross-contamination. Specifically, each independent chamber unit is gas-isolated when its zone inflation valve and zone depressurization valve are both closed, allowing it to be inflated to different initial gas pressures and maintained thereafter. During inflation, only the zone inflation valve of that chamber is opened, and gas enters that chamber unidirectionally via the common gas supply line and the check valve. During depressurization, only the zone depressurization valve of that chamber is opened, and gas exits via the depressurization branch without passing through the check valve. When any independent chamber unit is damaged, the corresponding check valve prevents other chambers from leaking gas back to the damaged chamber via the common gas supply line. Even if the zone inflation valve of that chamber is accidentally opened, its leakage flow is limited by the flow restrictor. Since both the zonal inflation valve and the zonal pressure relief valve are normally closed valves that close when power is off, each air chamber automatically remains sealed when the control system loses power, and the buffering capacity does not depend on the power supply.

[0020] Preferably, the protective structure further includes a heat-triggered isolation valve, a heat-triggered pressure relief component, and a discharge branch corresponding to each of the independent air chamber units. The heat-triggered isolation valve and the heat-triggered pressure relief component are two independent components. The heat-triggered isolation valve is disposed on the corresponding inflation branch and located between the check valve and the independent air chamber unit. The heat-triggered isolation valve includes a valve body, a fusible element, and a valve core subjected to the action of a pre-tightening component. At room temperature, the fusible element holds the valve core in the open position, thereby opening the inflation branch. When the temperature of the area where the heat-triggered isolation valve is located reaches the first operating temperature, the fusible element melts and releases the valve core. The valve core moves to the closed position under the action of the pre-tightening component, disconnecting the independent air chamber unit from the common air supply line. The thermally triggered pressure relief component is disposed on the corresponding discharge branch. One end of the discharge branch is connected to the independent air chamber unit, and the other end is connected to the safety exhaust manifold outside the power battery pack. The discharge branch does not pass through the partitioned inflation valve, the partitioned pressure relief valve, and the common pressure relief path. The thermally triggered pressure relief component includes a thermally sensitive rupture disc, which opens when the temperature in its area reaches the second operating temperature or when the gas pressure in the independent air chamber unit reaches the set rupture pressure.

[0021] The passive thermal safety function is separated into two independent components: a heat-triggered isolation valve and a heat-triggered pressure relief element. This is because fusible elements or rupture discs can only perform a single action from closed to open, and cannot simultaneously close the gas supply channel and open the discharge channel. In this invention, the closing action is completed by the heat-triggered isolation valve: after the fusible element melts, it loses its constraint on the valve core, and the valve core is driven to the closed position by the pre-tightening element, thereby converting the "solid-to-liquid transition of the fusible element" into the "open-to-close transition of the valve port"; the opening action is completed independently by the heat-triggered pressure relief element. The second action temperature is higher than the first action temperature, causing both to operate in the order of isolation first and discharge later, avoiding discharge before the chamber is disconnected from the common gas supply line, which would cause the other gas chambers to lose pressure simultaneously.

[0022] The first operating temperature is lower than the lowest of the following three values: the allowable operating temperature of the high-temperature resistant, airtight, flexible membrane material, the allowable operating temperature of the interlayer adhesive layer of the protective structure, and the allowable operating temperature of the valve body seal, with a set temperature margin maintained between these three values. The reason for not using the thermal decomposition temperature of the membrane material substrate as the sole reference is that the thermal decomposition temperature is usually significantly higher than the allowable operating temperatures of the edge sealing heat fusion layer, adhesive layer, and valve body seal. These components are the first to fail during the heating process of the entire gas circuit system. If the operating temperature is set solely based on the thermal decomposition temperature, the edge sealing or seal may have already failed before the passive components activate, resulting in uncontrolled leakage.

[0023] The discharge branch and the thermally triggered pressure relief device operate independently of electrical signals, ensuring that in the power-off state, each of the zone inflation valves and each of the zone pressure relief valves closes due to power failure, and each of the independent air chamber units remains sealed and maintains its buffering capacity; while the thermally triggered isolation valve and the thermally triggered pressure relief device can still operate passively according to temperature and pressure. Therefore, the protective structure has a definite safety response under three failure conditions: single-chamber failure, control system power failure, and localized thermal runaway.

[0024] Preferably, the protective structure further includes a pressure control module, which includes a controller, temperature sensors corresponding to each of the independent air chamber units, and displacement sensors for detecting the compression displacement of the protective structure along its thickness. The controller stores a calibrated volume model V(s) between the volume of the independent air chamber unit and the compression displacement, where s is the compression displacement and V(s) is the air chamber volume of the independent air chamber unit at that compression displacement. The controller calculates the equivalent quantity n′ only within a detection window, which is the time period during which the partition inflation valve and partition pressure relief valve corresponding to the independent air chamber unit are both closed, and the thermally triggered isolation valve and thermally triggered pressure relief component are not activated. The equivalent quantity is calculated using the following formula: n′=P·V(s) / T, where P is the measured pressure and T is the gas temperature expressed in absolute temperature.

[0025] The principle and conditions for the criterion are as follows: From the ideal gas law PV=nRT, we can obtain n=PV / (RT), that is, P·V / T is proportional to the amount of gas in the cavity, n. Therefore, P·V / T is an invariant only when the amount of gas in the cavity is constant. The detection window is set precisely to meet this premise—when both the zone filling valve and the zone pressure relief valve are closed and the passive components are not activated, the gas cavity neither intakes nor exhausts gas, and the amount of gas remains constant; at the same time, since the volume of the gas cavity changes with the expansion of the battery cell, the compression displacement measured by the displacement sensor must be introduced and the current volume V(s) must be calculated according to the calibrated volume model in order to separate the volume change from the pressure change. In contrast, the practice of only converting pressure according to the reference temperature without introducing volume information does not hold true when the gas cavity is compressed.

[0026] Based on the above-mentioned calculated values, the controller distinguishes the state of the independent gas chamber unit as follows: When the calculated value n′ remains constant while the compression displacement s increases, it indicates that the gas volume has decreased without any increase or decrease, and this is determined to be mechanical compression caused by the expansion of the power battery cell; when the calculated value n′ remains constant, the compression displacement s remains unchanged, and the measured pressure P increases synchronously with the gas temperature T, it is determined to be gas thermal expansion rather than cell expansion, and the controller does not perform a pressure relief action; when the calculated value n′ continuously decreases within the detection window, it indicates that the amount of gas in the chamber has decreased under conditions where neither the valve is open nor is it under pressure, and this is determined to be a leak in the independent gas chamber unit, and an airtightness failure alarm signal is output. The controller performs control in three states: normal pre-tightening state, expansion compensation state, and thermal runaway protection state.

[0027] Preferably, each of the independent air chamber units is equipped with a first pressure sensor and a second pressure sensor that are independent of each other. The controller determines sensor failure based on four criteria: sensor mutual calibration, physical upper limit verification, valve status verification, and impact condition identification, rather than solely relying on the pressure change rate. Furthermore, it outputs a corresponding fault signal only when at least two of the four criteria simultaneously point to the same conclusion. Its function is as follows: collisions and local impacts can simultaneously cause abrupt changes in pressure and compression displacement, and valve opening and closing can cause a step change in pressure; both can produce pressure change rates similar to sensor failure. By introducing redundant sensor readings, displacement signals, and valve status, the above conditions can be identified and eliminated by "synchronous displacement change" and "valve in action state," respectively, thereby reducing false positives and false negatives.

[0028] Preferably, the support structure is a compressible support frame disposed within the sealed air cavity, the compressible support frame comprising a plurality of high-temperature resistant elastic supports spaced apart along the inner wall surface of the sealed air cavity; the protective structure further comprises a mechanical limiting stop disposed between the two layers of the high-strength fire-resistant and heat-insulating outer shell. A first contact gap g1 exists between the top of each high-temperature resistant elastic support and the opposing inner wall surface of the sealed air cavity, and a second contact gap g2 exists between the mechanical limiting stop and its opposing high-strength fire-resistant and heat-insulating outer shell, wherein g1 is less than g2.

[0029] The pressure-displacement characteristics of the protective structure along its thickness direction form three sequentially connected segments: The first segment is a gas-bearing segment where the compression displacement s is less than g1. The initial stiffness of this segment is determined by the initial gas pressure of the sealed air chamber and the relationship between the air chamber volume and the compression displacement. It has low stiffness and can fully absorb the reversible breathing deformation during the charging and discharging process of the battery cell. The second segment is a gas and frame co-bearing segment where the compression displacement s is between g1 and g2. In this segment, the high-temperature resistant elastic support body contacts the relative inner wall surface and enters its platform deformation range, providing platform stress σp. The stiffness is increased, which can suppress the continuous displacement caused by the irreversible expansion of the battery cell. σp is greater than the gas support pressure of the sealed air chamber at the upper limit of the preset pressure range, and the compression amount of the high-temperature resistant elastic support body when the compression displacement reaches g2 does not exceed its ultimate compression amount εmax. The third segment is a mechanical stop bearing segment after the compression displacement s reaches g2. The mechanical limit stop bears the load and restricts the protective structure from continuing to compress, so that the minimum gap between adjacent battery cells is maintained. Even if the air chamber leaks, the displacement constraint will not be lost.

[0030] The contact gap, initial stiffness, plateau stress, and ultimate compression are used to describe the load-bearing capacity of the three sections, rather than the compressive strength of the support, because compressive strength characterizes the failure index of the material and has no corresponding relationship with the timing when the support begins to participate in the load-bearing. When the support participates in the load-bearing is entirely determined by the first contact gap g1, the supporting force it provides in the load-bearing section is determined by the plateau stress σp, and its available stroke is determined by the ultimate compression εmax. All of these parameters can be directly measured from the pressure-displacement curve of the protective structure, and therefore can be used for both design and verification. Since the displacement constraint during the large deformation stage is provided by mechanical limit stops, the working pressure of the air chamber does not need to be increased to a level that the sealing edge and air passage components cannot withstand.

[0031] Preferably, the initial gas pressure of each independent air chamber unit is set according to a zone pressure mapping relationship. The zone pressure mapping relationship is determined by the expansion amount in the thickness direction of the battery cell in the bonding area corresponding to the independent air chamber unit. The expansion amount is taken from the measured expansion displacement of the battery cell or the finite element calculation result of the expansion deformation of the battery cell, and the initial gas pressure is negatively correlated with the expansion amount. The high-temperature resistant airtight flexible membrane material is a multi-layer composite membrane, which includes, from the outside to the inside, a high-temperature resistant protective layer, an airtight barrier layer, a fiber reinforcement layer, and a thermoplastic fusible seal layer. The sealing edge of the sealed air chamber and the partition rib are formed by fusing two opposing thermoplastic fusible seal layers. The function of setting the thermoplastic fusible seal layer is to provide a fusible connection medium for hot-press welding: polyimide film and some fluororubber and silicone rubber composite films are non-thermoplastic or cross-linked systems. Their bodies do not produce a melt that can be fused together when heated, and it is difficult to form a reliable seal by heating and pressurizing alone.

[0032] Regarding the preset pressure range, it should be noted that the working pressure of the sealed air chamber is limited by the combined strength of the sealing edge, the strength of the membrane material, and the pressure-bearing capacity of the air circuit components. The separation force acting on the wall of the sealed air chamber is equal to the product of the air chamber pressure and the projected area of ​​the air chamber. This invention, by setting mechanical limit stops and a compressible support frame to bear the load during the large deformation stage, makes displacement constraint no longer dependent on increasing the air chamber pressure. Therefore, the working pressure of the sealed air chamber is preferably 0.1–1.5 MPa, and its upper limit should be determined by sealing edge and air circuit pressure-bearing tests while retaining a safety factor. It should be noted that the 3–6 MPa external compressive load borne by the high-strength fire-resistant and heat-insulating outer shell refers to the surface pressure borne by the outer shell as a surface support structure, which is a different stress object from the internal working pressure of the sealed air chamber and should not be confused with it.

[0033] The present invention also provides a method for preparing the above-mentioned adjustable pressure gas buffer heat insulation composite protective structure for power batteries, comprising seven steps: molding to obtain an outer shell layer, dispersing to obtain a heat insulation composite barrier layer, partition sealing to obtain a multi-cavity gas buffer layer, gas path integration, cavity-by-cavity leak detection, symmetrical layering and composite, and calibration and partitioned gas filling. See the specific embodiments for details.

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

[0035] First, the present invention adopts a symmetrical sandwich structure with a flexible sealed gas buffer layer as the center, so that both sides of the gas buffer layer are provided with a heat-insulating composite barrier layer and a high-strength fire-resistant heat-insulating outer shell layer. No matter which side of the battery cell experiences thermal runaway, the gas buffer layer will not directly bear the flame impact and mechanical load.

[0036] Secondly, this invention separates inflation and depressurization into two independent branches, so that the one-way conduction direction of the check valve is dedicated to the inflation direction. Thus, in the same structure, it can simultaneously achieve independent pressure setting of each chamber, active depressurization, and prevention of cross-flow, solving the problem of conflicting requirements under the single branch single check valve architecture.

[0037] Third, the present invention splits the passive thermal safety function into two independent components: a thermally triggered isolation valve and a thermally triggered pressure relief component. It uses a fusible element in conjunction with a pre-tightening component to convert the "solid to liquid" state into the "open to closed" state of the valve port, thereby realizing the two-step action of first cutting off the gas supply and then discharging to the outside of the package, which cannot be accomplished by a single passive component. Moreover, the discharge branch bypasses all electrically controlled valves and can still operate when power is lost.

[0038] Fourth, the present invention changes the operating temperature reference of the passive component from the thermal decomposition temperature of the membrane material to the lowest value among the allowable operating temperatures of the membrane material, the adhesive layer and the valve body seal, while retaining a margin, so that the passive component operates before the weakest link in the system, avoiding uncontrolled leakage before operation.

[0039] Fifth, the present invention uses the converted quantity n′=P·V(s) / T as the criterion and limits its calculation to the detection window in which both electronically controlled valves are closed and the passive components are not activated. At the same time, a displacement sensor and a calibration volume model are introduced to ensure that the conditions for the criterion are fully met, thereby reliably distinguishing between mechanical expansion of the battery cell, thermal expansion of the gas and leakage of the gas cavity.

[0040] Sixth, this invention uses four criteria—sensor cross-calibration, physical upper limit verification, valve status verification, and impact condition identification—to jointly determine sensor failure, and requires at least two criteria to point to the same conclusion, thus overcoming the problem of misjudging collisions, impacts, and valve actions as sensor failure when relying solely on the pressure change rate.

[0041] Seventh, the present invention describes the three-stage load bearing using the first contact gap, the second contact gap, the initial stiffness, the platform stress, and the ultimate compression. All of the above parameters can be determined by the pressure-displacement curve, thus transforming the load bearing classification from an unverifiable material failure index into a designable and verifiable structural parameter. Attached Figure Description

[0042] Figure 1 This is a schematic cross-sectional view of the adjustable pressure gas buffer heat insulation composite protection structure for power batteries described in this invention.

[0043] Figure 2 This is a schematic diagram of the working principle of the protective structure described in this invention, wherein (a) is the initial pre-inflated state, (b) is the pressure state of the cell expansion and compression, and (c) is the automatic recovery state after the pressure is released.

[0044] Figure 3 This is a schematic diagram of the flexible sealed gas buffer layer of the present invention when it adopts a multi-cavity independent structure;

[0045] Figure 4 This is a schematic diagram showing the connection relationship of the partitioned gas path and pressure control module described in this invention;

[0046] Figure 5 This is a cross-sectional schematic diagram of the thermally triggered isolation valve and thermally triggered pressure relief component described in this invention, wherein (a) is the initial state at room temperature, and (b) is the operating state after reaching the operating temperature;

[0047] Figure 6 This is a schematic diagram of the pressure-displacement characteristics and three-section load-bearing capacity of the protective structure along the thickness direction described in this invention;

[0048] Figure 7 This is a flowchart illustrating the preparation method of the adjustable pressure gas buffer heat insulation composite protective structure for power batteries according to the present invention.

[0049] In the diagram: 1-High-strength fire-resistant and heat-insulating outer shell layer; 2-Heat-insulating composite barrier layer; 3-Flexible sealed gas buffer layer; 31-Sealed gas cavity; 32-High-temperature resistant airtight flexible membrane material; 33-Partition structure; 34-Independent gas cavity unit; 35-High-temperature resistant sliding layer; 4-Support structure; 41-High-temperature resistant elastic support; 42-Mechanical limit stop; 5-Pressure regulating component; 51-Inflation interface; 52-Pressure detection interface; 53-Pressure relief interface; 54-Inflation branch; 55-Pressure relief branch; 56-Emission branch; 57-Common gas supply line; 58-Common pressure relief circuit; 59-Miniature air pump; 61-Sectional inflation valve; 62-Sectional pressure relief valve; 63-Flow limiting orifice; 64-Check valve; 65-Thermal-triggered isolation valve; 651-Valve body; 652-Fuse element; 653-Valve core; 654-Pre-tightening component; 66-Thermal-triggered pressure relief component; 661-Thermal-sensitive rupture disc; 7-Pressure control module; 71-First pressure sensor; 72-Second pressure sensor; 73-Temperature sensor; 74-Displacement sensor; 75-Controller; 8-Safety exhaust manifold; 9-Power battery cell. Detailed Implementation

[0050] The present invention will be further described below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited to the following embodiments. Those skilled in the art can adjust the material composition, structural dimensions, and control methods according to actual application needs without departing from the technical concept of the present invention, and all equivalent substitutions made should fall within the scope of protection of the present invention.

[0051] like Figure 1 As shown, this invention provides an adjustable pressure gas buffer and heat insulation composite protective structure for power batteries. It is a symmetrical sandwich structure centered on a flexible sealed gas buffer layer 3. From the center outwards, it consists of the flexible sealed gas buffer layer 3, heat insulation composite barrier layers 2 on either side, and a high-strength fire-resistant heat insulation outer shell layer 1 located outside the two heat insulation composite barrier layers 2. The flexible sealed gas buffer layer 3 is connected to a pressure regulating component 5. A support structure 4 is provided within the sealed gas cavity 31, and a high-temperature resistant sliding layer 35 is provided between the flexible membrane material 32 and the heat insulation composite barrier layer 2. In use, the protective structure is installed between two adjacent power battery cells 9, or between power battery modules, or on the inner wall of the power battery pack casing.

[0052] The sealed air chamber 31 is divided into multiple independent air chamber units 34 along the contact surface with the power battery cell 9 by the partition structure 33. Each independent air chamber unit 34 is a part of the sealed air chamber 31, and adjacent independent air chamber units 34 are isolated by the air passage of the partition structure 33. The description of the sealed air chamber 31 in the following text also applies to each independent air chamber unit 34 when the partition structure 33 is provided.

[0053] The function of the high-temperature resistant sliding layer 35 is as follows: During the inflation, depressurization, and compression and recovery processes of the sealed air cavity 31, the high-temperature resistant airtight flexible membrane 32 undergoes reciprocating expansion and contraction deformation along the bonding surface direction. If the high-temperature resistant airtight flexible membrane 32 is directly bonded to the thermal insulation composite barrier layer 2, this expansion and contraction deformation will act on the interlayer adhesive layer in a shearing manner, which is prone to fatigue cracking and interlayer delamination after long-term cycling. After setting the high-temperature resistant sliding layer 35, the opposing surfaces of the flexible sealed gas buffer layer 3 and the thermal insulation composite barrier layer 2 can slide relative to each other, and the above-mentioned shearing deformation is no longer transmitted to the interlayer adhesive layer. The high-temperature resistant sliding layer 35 can also withstand the high temperature under thermal runaway conditions without melting and sticking, thereby ensuring that the cyclic deformation of the flexible sealed gas buffer layer 3 is not constrained by the interlayer while maintaining the bonding of each layer.

[0054] like Figure 2 As shown, in the initial pre-inflated state, the sealed air chamber 31 maintains a preset pressure, providing a stable pre-tightening force and buffer gap for the battery cell 9; when the battery cell 9 expands and is squeezed, the sealed air chamber 31 is compressed, the internal gas volume decreases and the pressure increases, thereby generating a reverse support force and absorbing the mechanical stress generated by the change in battery cell volume; when the external pressure is released, the gas expansion pushes the flexible membrane 32 to restore its original shape, realizing a cyclic elastic recovery.

[0055] Example 1

[0056] This embodiment describes the fabrication of a symmetrical sandwich structure adjustable pressure gas buffer thermal insulation composite protective structure for power batteries. The fabrication process is as follows: Figure 7 As shown.

[0057] Step S1: Prepare the high-strength, fire-resistant, and heat-insulating outer shell layer 1. An alumina fiber-reinforced ceramic composite material is used, wherein the alumina fiber content is 50 wt%, the silica fiber content is 30 wt%, and the high-temperature resistant inorganic binder content is 20 wt%. After uniform mixing, it is molded at a molding temperature of 180℃, a pressure of 5 MPa, and a holding time of 40 min. Two layers are prepared, each with a thickness of 1 mm.

[0058] Step S2: Prepare the thermal insulation composite barrier layer 2. It is formed by combining silica aerogel and high-temperature resistant thermal insulation adhesive, wherein the silica aerogel has a mass fraction of 30 wt% and the high-temperature resistant thermal insulation adhesive has a mass fraction of 70 wt%. The mixture is processed using a high-speed dispersion device at a dispersion speed of 1200 r / min for a dispersion time of 30 min. After uniform dispersion, it is coated onto the inner surface of the two high-strength fire-resistant thermal insulation outer shell layers 1 and cured to form a single layer with a thickness of 0.5 mm.

[0059] Step S3: Prepare the flexible, airtight gas buffer layer 3 by partition sealing molding. The high-temperature resistant, airtight flexible membrane material 32 is a four-layer composite membrane, consisting of a 0.15mm thick polyimide film as a high-temperature protective layer, a 0.02mm thick aluminum foil as an airtight barrier layer, a 0.15mm thick aramid fiber fabric layer as a fiber reinforcement layer, and a 0.08mm thick perfluoroethylene propylene copolymer film as a thermoplastic fusible sealing layer, with a total thickness of 0.4mm. Two composite membranes are stacked together with the fusible sealing layers facing each other. After the supporting structure 4 is in place, the edge sealing and partition ribs are simultaneously hot-pressed and welded according to the predetermined air cavity partitioning pattern. The hot-pressing temperature is set within the range higher than the melting temperature of the perfluoroethylene propylene copolymer but lower than the upper limit of the polyimide temperature resistance. The hot-pressing pressure is 0.5MPa, the holding time is 60s, the edge sealing width is 8mm, and the partition rib width is 5mm. The free thickness of the airtight cavity 31 is 3mm.

[0060] Step S4, gas path integration. (e.g.) Figure 4 As shown, each independent air chamber unit 34 is equipped with an inflation branch 54, a pressure relief branch 55, and a discharge branch 56. One end of the inflation branch 54 is connected to the common air supply line 57, and the other end is connected to the corresponding independent air chamber unit 34. Along the air supply direction, a partition inflation valve 61, a flow restrictor 63, a check valve 64, and a thermally triggered isolation valve 65 are sequentially installed on it. A miniature air pump 59 is connected to the common air supply line 57 via an inflation interface 51. A partition pressure relief valve 62 is installed on the pressure relief branch 55 and then connected to the pressure relief interface 53 via a common pressure relief line 58. A thermally triggered pressure relief component 66 is installed on the discharge branch 56, bypassing the partition inflation valve 61, the partition pressure relief valve 62, and the common pressure relief line 58 before connecting to the safety exhaust manifold 8 outside the power battery pack. Both the partition inflation valve 61 and the partition pressure relief valve 62 are normally closed solenoid valves that close upon power failure. Each independent air chamber unit 34 is equipped with a first pressure sensor 71 and a second pressure sensor 72 via a pressure detection interface 52.

[0061] Step S5, chamber-by-chamber leak detection. With the partition inflation valve 61 and partition pressure relief valve 62 corresponding to the other independent air chamber units 34 closed, nitrogen is individually injected into the tested independent air chamber unit 34 through the inflation branch 54 to the leak detection pressure and the pressure is maintained in each chamber for no less than 24 hours. The pressure drop rate of the chamber is measured. At the same time, the pressure of adjacent independent air chamber units 34 is monitored to determine the effectiveness of the air path isolation of the partition rib. Products with a pressure drop rate exceeding the set value or with isolation failure are rejected.

[0062] Step S6: Centered on the flexible sealed gas buffer layer 3, heat-insulating composite barrier layer 2 and high-strength fire-resistant heat-insulating outer shell layer 1 are sequentially stacked on both sides. The layers are bonded with high-temperature heat-insulating adhesive. A 0.1mm thick polytetrafluoroethylene glass fiber composite cloth is set between the opposite surfaces of the flexible sealed gas buffer layer 3 and the heat-insulating composite barrier layer 2 as a high-temperature resistant sliding layer 35. At the same time, a mechanical limiting stop 42 is installed between the two high-strength fire-resistant heat-insulating outer shell layers 1 to obtain a symmetrical sandwich structure.

[0063] Step S7, Calibration and Inflation. The protective structure is compressed and the pressure-displacement curve is recorded. The calibration volume model V(s) between the volume and compression displacement of the independent air chamber unit 34, as well as the first contact gap g1 and the second contact gap g2, are calibrated. Then, according to the partition pressure mapping relationship, the inflation valves 61 of each partition are opened respectively, and the pressure of each independent air chamber unit 34 is adjusted to its own initial gas pressure before the partition inflation valves 61 are closed.

[0064] The protective structure obtained in this embodiment has the following layer sequence and thickness along the thickness direction: 1mm high-strength fire-resistant and heat-insulating outer shell layer + 0.5mm heat-insulating composite barrier layer + 0.1mm high-temperature resistant sliding layer + 3mm flexible sealed gas buffer layer (including 0.4mm upper and lower membrane materials, and 2.2mm net air cavity space) + 0.1mm high-temperature resistant sliding layer + 0.5mm heat-insulating composite barrier layer + 1mm high-strength fire-resistant and heat-insulating outer shell layer, with a total free thickness of 6.2mm.

[0065] Example 2

[0066] This embodiment further incorporates a passive thermal safety component and a pressure control module based on Embodiment 1, while the remaining structure and manufacturing process are the same as in Embodiment 1.

[0067] like Figure 5 As shown, the heat-triggered isolation valve 65 includes a valve body 651, a fusible element 652, a valve core 653, and a preload element 654. At room temperature, the fusible element 652 holds the valve core 653 in place. Figure 5 In the open position shown in (a), the inflation branch 54 is connected via the valve port; when the temperature in this area reaches the first operating temperature, the fusible element 652 melts and releases the valve core 653, which moves under the action of the preload member 654 (a compression spring is used in this embodiment) to... Figure 5 In the closed position shown in (b), the valve port is closed, and the independent gas chamber unit 34 is disconnected from the common gas supply line 57. The heat-triggered pressure relief element 66 includes a heat-sensitive rupture disc 661, which opens when the temperature in the area reaches the second operating temperature or when the gas pressure in the chamber reaches the set burst pressure, such as... Figure 5 As shown in (b), the gas in this cavity is discharged to the safety exhaust manifold 8 via the exhaust branch 56.

[0068] The first operating temperature is determined as follows: The allowable operating temperature of the high-temperature resistant, airtight flexible membrane material 32 (based on the melting temperature of its thermoplastic fusible sealant), the allowable operating temperature of the interlayer adhesive layer, and the allowable operating temperature of the valve body 651's seal are measured respectively. The lowest value among these three is taken, and then the set temperature margin is subtracted from this lowest value to obtain the first operating temperature. The second operating temperature is set to a value higher than the first operating temperature, causing the heat-triggered isolation valve 65 to operate before the heat-triggered pressure relief component 66. The specific values ​​of the above allowable operating temperatures and temperature margins should be determined based on the measured temperature resistance data of the selected membrane material, adhesive layer, and seal.

[0069] The pressure control module 7 includes a controller 75, a temperature sensor 73, and a displacement sensor 74, and is connected to a first pressure sensor 71, a second pressure sensor 72, a partitioned inflation valve 61, a partitioned pressure relief valve 62, and a micro air pump 59. The controller 75 stores a calibration volume model V(s). The controller 75 calculates the equivalent quantity n′=P·V(s) / T only within a detection window, where the partitioned inflation valve 61 and partitioned pressure relief valve 62 of the cavity are both closed, and the thermally triggered isolation valve 65 and thermally triggered pressure relief component 66 are not activated.

[0070] The controller 75 determines the following: when n′ is constant and the compression displacement s increases, it is determined that the cell is expanding; when n′ is constant, s is unchanged, and the measured pressure P increases synchronously with the temperature T, it is determined that the gas is expanding due to heat, and no pressure relief is performed; when n′ continuously decreases within the detection window, it is determined that the cavity is leaking and an alarm is triggered. The controller 75 performs control in three states: in the normal pre-tightening state, the partition inflation valve 61 is opened to replenish pressure to the pre-tightening target pressure and then closed; in the expansion compensation state, when the compression displacement s exceeds the expansion judgment threshold, the partition pressure relief valve 62 is opened to release gas and then closed; in the thermal runaway protection state, when the temperature T exceeds the thermal runaway judgment threshold, the micro air pump 59 is stopped to inflate and the target pressure is reduced to increase the compressible stroke.

[0071] Furthermore, the controller 75 determines sensor failure based on four criteria: If the difference between the readings of the first pressure sensor 71 and the second pressure sensor 72 exceeds the cross-calibration threshold, one of them is deemed to be faulty, and the value consistent with the trend of n′ is taken as the valid value; if the rate of change of any pressure sensor reading exceeds the upper limit of the pressure change rate calculated by the calibrated volumetric model based on the rate of change of displacement and temperature, and neither displacement nor temperature has changed accordingly, the sensor is deemed to be faulty; before determination, the opening and closing states of the partition inflation valve 61 and the partition pressure relief valve 62 are read to rule out pressure changes caused by valve action; if the rate of change of pressure exceeds the limit and the displacement sensor 74 simultaneously detects a sudden change in compression displacement, it is determined to be due to external mechanical impact rather than sensor failure. A fault signal is output only when at least two criteria point to the same conclusion.

[0072] Example 3

[0073] This embodiment further implements multi-cavity partitioned pressure mapping and three-segment load-bearing design based on embodiment 2, while the remaining structure and manufacturing process are the same as in embodiment 2.

[0074] like Figure 3 As shown, the flexible sealed gas buffer layer 3 is divided by the partition structure 33 into six independent gas chamber units 34 arranged in a three-row, two-column array along the bonding surface. The zone pressure mapping is determined as follows: First, for the matching square battery cell, the expansion amount of the battery cell along the thickness direction of each region of the bonding surface during the charge and discharge cycle is measured using a displacement sensor array, or the expansion deformation finite element model of the battery cell is established to calculate the above expansion amount distribution; then, the initial gas pressure is determined according to the expansion amount of the corresponding region of each independent gas chamber unit 34, and the initial gas pressure is negatively correlated with the expansion amount, that is, the region with larger expansion amount takes a lower initial pressure to obtain a larger compressible stroke, and the region with smaller expansion amount takes a higher initial pressure to provide sufficient preload. Since the zone inflation valve 61 and zone pressure relief valve 62 of each chamber are normally closed valves, each chamber is isolated from each other after inflation and can maintain different initial pressures for a long time.

[0075] like Figure 6 As shown, the three-section load-bearing structure is designed as follows: the support structure 4 adopts a compressible support frame, including multiple high-temperature resistant elastic supports 41 arranged at intervals along the inner wall of the sealed air cavity 31. In this embodiment, ceramic fiber reinforced silicone rubber columnar bodies are used; a first contact gap g1 is left between the top of the high-temperature resistant elastic support 41 and the relative inner wall of the sealed air cavity 31; the mechanical limiting stop 42 is set between the two high-strength fire-resistant heat-insulating outer shell layers 1, and a second contact gap g2 is left between it and the relative high-strength fire-resistant heat-insulating outer shell layer 1, and g1 is less than g2.

[0076] Therefore, when the compression displacement s is less than g1, the high-temperature resistant elastic support 41 has not yet contacted the inner wall surface and is supported solely by the gas. The initial stiffness of this section is determined by the relationship between the initial gas pressure and the volume of the gas cavity with displacement, resulting in low stiffness. When s is between g1 and g2, the high-temperature resistant elastic support 41 contacts the inner wall surface and enters the platform deformation range, providing platform stress σp, which is jointly supported by the gas and the frame, increasing stiffness. When s reaches g2, the mechanical limit stop 42 contacts the outer shell layer 1 and bears the load, limiting further compression. During design, σp should be greater than the gas support pressure at the preset pressure upper limit of the gas cavity to ensure that the frame can effectively participate in the load-bearing in the second section; and the compression of the high-temperature resistant elastic support 41 when s reaches g2 should not exceed its ultimate compression εmax to avoid the frame being compacted before the stop contacts. g1, g2, initial stiffness, σp, and εmax are all determined by the pressure-displacement curve of this protective structure.

[0077] Comparative Example 1: No gas buffer structure. The symmetrical thermal insulation sandwich structure of Example 1 is adopted, but the internal sealed air cavity is eliminated, and only the cavity structure is retained, so it is impossible to use gas compression to generate reverse support force.

[0078] Comparative Example 2: Rubber Elastic Cushioning Structure. Traditional silicone rubber material is used to replace the flexible, sealed gas cushioning layer. The cushioning capacity is determined by the material's elastic modulus, and the supporting force cannot be changed through external adjustment. Furthermore, permanent compression deformation occurs after long-term cyclic compression.

[0079] Comparative Example 3: Single-branch, single-check-valve gas path. Each independent gas chamber unit is connected to a continuously connected common gas path via only one branch, and a check valve is installed on this branch facing the gas chamber. Although this structure can prevent other gas chambers from leaking back to the damaged gas chamber, each gas chamber cannot exhaust gas through this branch, and active pressure relief cannot be achieved; if a bidirectional flow is used, the gas chambers are connected to each other through the common gas path, and it is impossible to maintain different initial pressures for a long time.

[0080] Comparative Example 4: Single passive element. A fusible alloy plug is placed only between each independent gas chamber unit and the common gas path. After the element melts, the channel it is in changes from closed to open, making it impossible to close the gas supply channel. Therefore, while the chamber is being heated and venting gas, it is still connected to the common gas path, causing the other gas chambers to lose pressure.

[0081] Comparative Example 5: Temperature-Pressure Conversion without Limiting the Detection Window. The sensor configuration of Example 2 is used, but a displacement sensor is not set, and the detection window is not limited; the measured pressure is directly converted from the reference temperature. When the gas chamber is compressed due to the expansion of the battery cell, or during the inflation / deflation process, the conversion result is affected by both volume changes and quantity changes, making it impossible to distinguish between the mechanical expansion of the battery cell and the thermal expansion of the gas.

[0082] Comparative Example 6: Sensor failure is determined solely by the rate of pressure change. The controller from Example 2 is used, but sensor failure is determined only by whether the rate of pressure change exceeds the limit, without introducing redundant sensors, displacement signals, or valve status. In the event of a vehicle collision, localized impact, or valve opening / closing, this criterion may misjudge normal operating conditions as sensor failure.

[0083] Performance testing methods

[0084] To verify the overall performance of the protective structure described in this invention, the above embodiments and comparative examples can be evaluated according to the following test methods. The test conditions and evaluation indicators are given in the following test methods; the specific test results should be based on the test records of the actual prototype.

[0085] (1) Determination of pressure-displacement curve. The protective structure was subjected to quasi-static compression using a universal testing machine, and the pressure-displacement curve was recorded. The first contact gap g1 and the second contact gap g2 were read from the three abrupt change points of the curve, respectively. The initial stiffness, plateau stress σp and ultimate compression εmax were determined by the slope of each segment and the stress level of the plateau segment, and used to verify the design values.

[0086] (2) Independent pressure regulation and anti-cross-flow test of each chamber. Each independent chamber unit was filled to a different initial pressure and its zonal filling valve and zonal pressure relief valve were closed. The pressure of each chamber was recorded while maintaining the pressure. Then, any chamber was punctured and the leakage rate of that chamber and the pressure maintenance of the other chambers were recorded and compared with Comparative Example 3.

[0087] (3) Active pressure relief test. With the check valve in the direction of the gas chamber, open the pressure relief valve of any chamber, record the pressure drop process of the chamber, verify the exhaust capacity of the pressure relief branch, and compare with Comparative Example 3.

[0088] (4) Passive thermal safety test. Apply a heating load to the area corresponding to any independent air chamber unit, and record the operating temperature and timing of the thermally triggered isolation valve, the operating temperature and timing of the thermally triggered pressure relief component, the discharge path, and the pressure maintenance of the remaining chambers to verify the action sequence of isolation before discharge, and compare it with Comparative Example 4. At the same time, repeat the above test under the condition of power disconnection to verify that each chamber remains sealed and the passive components can still operate when power is lost.

[0089] (5) Pressure source identification test. Three types of excitations were applied: mechanical compression load, overall temperature rise load, and artificial micro-leakage. The measured pressure P, gas temperature T, compression displacement s, and equivalent value n′ were recorded in the detection window to verify the controller's identification results of cell expansion, gas thermal expansion and gas cavity leakage, and compared with Comparative Example 5.

[0090] (6) Fault diagnosis test. Simulate three working conditions: single-channel sensor drift, valve action and external mechanical impact. Record the output of four criteria and the final judgment result to verify the false judgment rate and false negative rate, and compare with Comparative Example 6.

[0091] (7) Pressure and thermal protection test. The flexible sealed gas buffer layer after partition sealing is subjected to a pressure increase test. The pressure of the gas cavity is increased step by step until the sealing edge, membrane material or gas interface fails. The failure pressure and failure location are recorded to determine the upper limit of the preset pressure range. The protective structure is placed in a heat source environment of 800-1400℃ for 10-30 minutes using the high temperature thermal shock method, and the temperature rise curve of the cold surface is recorded.

[0092] (8) Cyclic reliability test. The protective structure was subjected to repeated compression and alternating hot and cold treatments using a pressure cycling and temperature cycling coupling method. The thickness change rate, pressure retention rate of each cavity, and interlayer bonding state were recorded.

[0093] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural modifications made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A composite protective structure for power batteries with adjustable pressure gas buffering and heat insulation, characterized in that, The protective structure is a symmetrical sandwich structure centered on a flexible sealed gas buffer layer. From the center to both sides, it includes the flexible sealed gas buffer layer, two heat-insulating composite barrier layers respectively disposed on both sides of the flexible sealed gas buffer layer, and two high-strength fire-resistant heat-insulating outer shell layers respectively disposed on the outside of the two heat-insulating composite barrier layers. The high-strength fire-resistant and heat-insulating outer shell layer is made of high-temperature resistant rigid material, which constitutes the load-bearing boundary of the protective structure and is used to withstand external mechanical loads and high-temperature heat flow impacts during thermal runaway. The thermal insulation composite barrier layer is made of a low thermal conductivity insulation material to reduce the transfer of heat to the flexible sealed gas buffer layer. The flexible sealed gas buffer layer is formed by enclosing a sealed air cavity with a high-temperature resistant, airtight, flexible membrane material. The sealed air cavity is filled with a gas medium, and a support structure is provided inside the sealed air cavity. The support structure is located between the inner walls on both sides of the sealed air cavity and is used to limit the deformation range of the sealed air cavity during the process of being pressurized to avoid local collapse of the sealed air cavity. The flexible sealed gas buffer layer is connected to a pressure regulating component, which includes an inflation port, a pressure detection port, and a pressure relief port that communicate with the sealed gas cavity. The component is used to regulate the gas pressure in the sealed gas cavity to a preset pressure range, so that when the sealed gas cavity is subjected to an external compressive load, it is compressed, the internal gas pressure increases, and a reverse support force is generated. When the external compressive load decreases, the internal gas expands and pushes the flexible membrane material to restore its original shape, thereby making the thickness and support pressure of the protective structure dynamically change with the stress state.

2. The adjustable pressure gas buffer heat insulation composite protection structure for power batteries according to claim 1, characterized in that, The flexible sealed gas buffer layer is divided into multiple independent air chamber units by the partition structure. Each independent air chamber unit constitutes an independent pressure regulating unit and is connected to the air pressure regulating component. When any independent air chamber unit is locally compressed, only the gas in that independent air chamber unit is compressed and generates a reverse supporting force, while the other independent air chamber units maintain their original pressure state.

3. The adjustable pressure gas buffer heat insulation composite protection structure for power batteries according to claim 2, characterized in that, The air pressure regulating component includes a miniature air pump, a common air supply circuit, a common pressure relief circuit, and an inflation branch, a pressure relief branch, and a pressure sensor that correspond one-to-one with each of the independent air chamber units. One end of each inflation branch is connected to the corresponding independent air chamber unit, and the other end is connected to the common air supply line. The micro air pump is connected to the common air supply line via the inflation interface. Each inflation branch is provided with a partition inflation valve, a flow limiting orifice, and a check valve in series along the air supply direction. The partition inflation valve is a normally closed valve that closes when power is off. The flow direction of the check valve is from the common air supply line to the corresponding independent air chamber unit. The flow area of ​​the flow limiting orifice is smaller than the flow area of ​​the inflation branch. One end of each of the pressure relief branches is connected to the corresponding independent air chamber unit, and the other end is connected to the pressure relief interface via the common pressure relief path. Each of the pressure relief branches is equipped with a partition pressure relief valve, which is a normally closed valve that closes when power is off. Each of the pressure sensors detects the gas pressure in the corresponding independent air chamber unit via the pressure detection interface; Each independent air chamber unit is gas-isolated from the others when both its partition inflation valve and partition pressure relief valve are closed, allowing each independent air chamber unit to be inflated to different initial gas pressures and to maintain those initial gas pressures. When any independent air chamber unit is damaged, the check valve corresponding to that independent air chamber unit prevents the other independent air chamber units from leaking gas in reverse to the damaged independent air chamber unit through the common gas supply line, and the flow limiting orifice limits the leakage flow of that independent air chamber unit when its partition inflation valve is open.

4. The adjustable pressure gas buffer heat insulation composite protection structure for power batteries according to claim 3, characterized in that, The protective structure also includes a thermally triggered isolation valve, a thermally triggered pressure relief component, and a discharge branch corresponding to each of the independent air chamber units. The thermally triggered isolation valve and the thermally triggered pressure relief component are two independent components. The heat-triggered isolation valve is disposed on the corresponding inflation branch and located between the check valve and the independent air chamber unit. The heat-triggered isolation valve includes a valve body, a fusible element, and a valve core subjected to the action of a pre-tightening element. At room temperature, the fusible element holds the valve core in the open position, thereby opening the inflation branch. When the temperature of the area where the heat-triggered isolation valve is located reaches the first operating temperature, the fusible element melts and releases the valve core. The valve core moves to the closed position under the action of the pre-tightening element, disconnecting the independent air chamber unit from the common air supply line. The heat-triggered pressure relief component is disposed on the corresponding discharge branch. One end of the discharge branch is connected to the independent air chamber unit, and the other end is connected to the safety exhaust manifold outside the power battery pack. The discharge branch does not pass through the partitioned inflation valve, the partitioned pressure relief valve, or the common pressure relief path. The heat-triggered pressure relief component includes a heat-sensitive rupture disc. The heat-sensitive rupture disc opens when the temperature of its area reaches the second operating temperature or when the gas pressure in the independent air chamber unit reaches the set rupture pressure, so that the gas in the independent air chamber unit is discharged to the safety exhaust manifold through the discharge branch. The set burst pressure is higher than the highest pressure that the sealed gas chamber can reach under all operating conditions where the temperature is lower than the first operating temperature, and a pressure margin is maintained. The second operating temperature is higher than the first operating temperature, thereby ensuring that the thermally triggered pressure relief component does not open before the thermally triggered isolation valve, so that the thermally triggered isolation valve operates before the thermally triggered pressure relief component, that is, first cuts off the connection between the independent gas chamber unit and the common gas supply circuit, and then discharges the gas in the independent gas chamber unit to the safety exhaust manifold. The first operating temperature is lower than the lowest of the following three values: the allowable operating temperature of the high-temperature resistant airtight flexible membrane material, the allowable operating temperature of the interlayer adhesive layer of the protective structure, and the allowable operating temperature of the valve body seal, and a set temperature margin is maintained between the first operating temperature and the lowest value. The discharge branch and the heat-triggered pressure relief component do not rely on electrical signals to operate, so that when the protective structure is de-energized: each of the partition inflation valves and each of the partition pressure relief valves closes due to power failure, each of the independent air chamber units remains sealed and maintains buffering capacity; while the heat-triggered isolation valve and the heat-triggered pressure relief component can still operate passively according to temperature and pressure.

5. The adjustable pressure gas buffer heat insulation composite protection structure for power batteries according to claim 4, characterized in that, It also includes a pressure control module, which includes a controller and temperature sensors and displacement sensors corresponding to each of the independent air chamber units. Each displacement sensor detects the local compression displacement s of the area where the corresponding independent air chamber unit is located along the thickness direction of the protective structure. The controller stores a calibration volume model V(s) of the air chamber volume of each independent air chamber unit as s changes. The controller calculates the equivalent value n′ only within the detection window according to n′=P·V(s) / T. The detection window is the time period during which the partitioned inflation valve and the partitioned pressure relief valve of the independent air chamber unit are both closed, and the thermally triggered isolation valve and the thermally triggered pressure relief component are not activated. P is the measured pressure, and T is the gas temperature expressed in absolute temperature. When n′ is constant and s increases, it is determined to be mechanical compression caused by cell expansion. When n′ is constant, s is unchanged, and P increases synchronously with T, it is determined to be gas thermal expansion and no pressure relief is performed. When n′ continues to decrease, it is determined to be leakage of the independent air chamber unit and an alarm is triggered. The controller performs control in three states: in the normal pre-tightening state, the partition inflation valve is opened to replenish pressure to the pre-tightening target pressure and then closed; in the expansion compensation state, when s exceeds the expansion judgment threshold, the partition pressure relief valve is opened to release pressure to the pre-tightening target pressure and then closed; in the thermal runaway protection state, when T exceeds the thermal runaway judgment threshold, inflation is stopped and the target pressure is reduced to below the pre-tightening target pressure.

6. The adjustable pressure gas buffer heat insulation composite protection structure for power batteries according to claim 5, characterized in that, Each independent air chamber unit is equipped with a first pressure sensor and a second pressure sensor that are independent of each other. The controller determines the sensor failure based on the following four criteria, and outputs a fault signal only when at least two of them point to the same conclusion: (1) When the difference between the two readings exceeds the mutual calibration threshold, one of them is determined to be faulty, and the one that matches the trend of the calculated quantity n′ is taken as the valid value; (2) When the rate of change of the reading exceeds the upper limit of the pressure change rate calculated from the rate of change of s and T according to the calibration volume model, and the readings of the displacement sensor and the temperature sensor do not change accordingly, the pressure sensor is determined to be faulty; (3) Before the determination, the opening and closing status of the partition air filling valve and the partition pressure relief valve is read to exclude the pressure change caused by the valve action; (4) When the rate of change of the reading exceeds the upper limit and the displacement sensor detects a sudden change in displacement, it is determined to be an external mechanical impact rather than a sensor failure, and the two valves are kept closed.

7. The adjustable pressure gas buffer heat insulation composite protection structure for power batteries according to claim 1, characterized in that, The support structure is a compressible support frame disposed within the sealed air cavity, comprising multiple high-temperature resistant elastic supports arranged at intervals along the inner wall of the sealed air cavity, with the support direction consistent with the thickness direction of the protective structure; the protective structure also includes a mechanical limiting stop disposed between the two layers of the high-strength fire-resistant and heat-insulating outer shell. There is a first contact gap g1 between the top of the high-temperature resistant elastic support and the inner wall of the sealed air cavity, and a second contact gap g2 between the mechanical limiting stop and the opposite high-strength fire-resistant and heat-insulating outer shell layer, where g1 is less than g2. This causes the pressure-displacement characteristics of the protective structure along the thickness direction to form three segments: when the compression displacement s is less than g1, it is borne solely by the gas medium; when s is between g1 and g2, the high-temperature resistant elastic support enters the platform deformation range and provides platform stress σp, sharing the load with the gas medium; after s reaches g2, it is borne by the mechanical limiting stop and further compression is restricted. The σp is greater than the gas support pressure of the sealed air chamber at the upper limit of the preset pressure range, and the compression of the high-temperature resistant elastic support body when s reaches g2 does not exceed its ultimate compression εmax; g1, g2, σp and εmax are determined by the pressure-displacement curve of the protective structure.

8. The adjustable pressure gas buffer heat insulation composite protection structure for power batteries according to claim 2, characterized in that, The partition structure is a partition rib formed by hot-press welding of the high-temperature resistant, airtight, flexible membrane material; each of the independent air chamber units is arranged in an array along the contact surface with the power battery cell, and its initial gas pressure is set according to the partition pressure mapping relationship. This relationship is determined by the expansion amount in the cell thickness direction of the contact surface area corresponding to each of the independent air chamber units. The expansion amount is taken from the measured results of the expansion displacement of the cell or the finite element calculation results of the expansion deformation, and the initial gas pressure is negatively correlated with the expansion amount. The high-temperature resistant, airtight, flexible membrane material is a multi-layer composite membrane, comprising, from the outside in, a high-temperature resistant protective layer, an airtight barrier layer, a fiber reinforcement layer, and a thermoplastic fusible seal layer. The melting temperature of the thermoplastic fusible seal layer is lower than the upper temperature limit of the high-temperature resistant protective layer. The sealing edge of the sealed air cavity and the partition rib are formed by fusing two opposing thermoplastic fusible seal layers. The total thickness of the multi-layer composite membrane is 0.1–1.5 mm. A high-temperature resistant sliding layer is provided between the opposing surfaces of the flexible airtight gas buffer layer and the heat-insulating composite barrier layer. The thickness of a single high-strength fire-resistant heat-insulating outer shell layer is 0.5–5 mm, and the thickness of a single heat-insulating composite barrier layer is 0.2–5 mm. The gas medium is one of nitrogen, argon, and carbon dioxide, or a mixture thereof. The preset pressure range is 0.1–1.5 MPa.

9. A method for preparing an adjustable pressure gas buffer and heat insulation composite protective structure for power batteries, wherein the protective structure is a symmetrical sandwich structure centered on a flexible sealed gas buffer layer, comprising, from the center to both sides, the flexible sealed gas buffer layer, two heat insulation composite barrier layers respectively disposed on both sides thereon, and two high-strength fire-resistant heat insulation outer shell layers respectively disposed outside the two heat insulation composite barrier layers, wherein the flexible sealed gas buffer layer is formed by a high-temperature resistant airtight flexible membrane material to form a sealed gas cavity and is divided into multiple independent gas cavity units by a partition structure, and a support structure is provided inside the sealed gas cavity, characterized in that... The preparation method includes the following steps: S1. After mixing the raw materials of high-temperature resistant rigid materials, the mixture is molded to obtain two layers of high-strength fire-resistant and heat-insulating outer shell. S2. Mix and disperse the low thermal conductivity insulation material with the high temperature resistant insulation adhesive evenly, and then form a two-layer thermal insulation composite barrier layer. S3, Partition sealing molding: The high-temperature resistant airtight flexible membrane material is a multi-layer composite membrane with a thermoplastic fusible seal layer on the inner surface. Two pieces of the multi-layer composite membrane are stacked with their respective thermoplastic fusible seal layers facing each other. After the support structure is in place, the two stacked membrane materials are simultaneously sealed with hot-press welding and partition rib hot-press welding according to the predetermined air cavity partition pattern, so that the thermoplastic fusible seal layers are fused together at one time to form multiple independent air cavity units that are isolated from each other by air path. S4. Gas Path Integration: Each independent gas chamber unit is equipped with an inflation branch, a pressure relief branch, and a discharge branch; on the inflation branch, a zoned inflation valve, a flow restrictor, a check valve, and a thermally triggered isolation valve are sequentially installed along the gas supply direction, and the inflation branch merges into a common gas supply line; on the pressure relief branch, a zoned pressure relief valve is installed and then merges into a common pressure relief line; on the discharge branch, a thermally triggered pressure relief component is installed and bypasses the zoned inflation valve, the zoned pressure relief valve, and the common pressure relief line before connecting to the external safety exhaust manifold of the power battery pack; both the zoned inflation valve and the zoned pressure relief valve are normally closed valves that close upon power failure. S5. Cavity-by-cavity leak detection: With the partition inflation valve and partition pressure relief valve corresponding to the other independent air cavity units closed, gas medium is individually injected into the independent air cavity unit under test through the inflation branch to the leak detection pressure and pressure is maintained in each cavity. The pressure drop rate of the independent air cavity unit is measured, and the pressure of the adjacent independent air cavity units is monitored to determine the air path isolation effectiveness of the partition rib. Products with a pressure drop rate exceeding the set value or isolation failure are rejected. S6. With the flexible sealed gas buffer layer as the center, the heat insulation composite barrier layer and the high-strength fire-resistant heat insulation shell layer are stacked and bonded to both sides in sequence, and a mechanical limiting stop is installed between the two layers of the high-strength fire-resistant heat insulation shell layer to obtain a symmetrical sandwich structure. S7. Calibration and inflation: The protective structure is compressed and the pressure-displacement curve is recorded. The calibration volume model between the volume of the independent air chamber unit and the compression displacement is calibrated, as well as the first contact gap between the support structure and the inner wall of the sealed air chamber and the second contact gap between the mechanical limit stop and the high-strength fire-resistant heat-insulating outer shell layer. Then, according to the partition pressure mapping relationship, the inflation valves of each partition are opened respectively. The gas pressure of each independent air chamber unit is adjusted to its initial gas pressure and then the partition inflation valves are closed to obtain the adjustable pressure gas buffer heat insulation composite protective structure for power batteries.

10. The preparation method according to claim 9, characterized in that, In step S1, the molding temperature is 150–220℃, the pressure is 3–8 MPa, and the holding time is 20–60 min. In step S2, the dispersion speed is 800–1800 r / min, and the time is 15–45 min. In step S3, the hot-press welding temperature is higher than the melting temperature of the thermoplastic fusible seal layer and lower than the allowable operating temperature of the other layers in the multilayer composite film. The pressure is 0.2–1.0 MPa, the holding time is 10–120 s, and the sealing width is greater than the width of the partition rib. In step S4, the operating temperature of the heat-triggered isolation valve is lower than the lowest of the melting temperature of the thermoplastic fusible seal layer, the allowable operating temperature of the interlayer adhesive layer and the valve body seal, and a temperature margin is retained. The operating temperature of the heat-triggered pressure relief component is higher than the operating temperature of the heat-triggered isolation valve. In step S5, the leak detection pressure is not lower than the initial gas pressure, and the chamber pressure holding time is not less than 24 h.

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