Flexible pressure sensor for battery detection, preparation method and detection method

Abstract

The invention provides a flexible pressure sensor for battery detection, a preparation method and a detection method, and relates to the technical field of battery detection. The two sides of the flexible thin film layer are each provided with a non-nick area and a nick area, and the two sides of the flexible thin film layer are each coated with a pressure-sensitive material layer. In the process of mounting the composite structure to the electrode layer, when the pressure-sensitive layer is subjected to pre-pressure, the non-nick region is preferentially stressed relative to the nick region, so that the first pressure-sensitive material region corresponding to the non-nick region is deformed and the conductive network is changed; and when the battery swells, the second pressure-sensitive material region corresponding to the nick region is pressed to deform, so that an electric signal is changed. Through the ingenious structural design of the nick area, the pre-pressure is guided to mainly act on the non-nick area when the sensor is installed, and the nick area preferentially responds to deformation when the battery swells, so that the flexible pressure sensor keeps higher detection sensitivity in a large pre-pressure application scene.

Description

Technical Field

[0001] This invention relates to the field of battery testing technology, and in particular to a flexible pressure sensor, its preparation method, and a testing method for battery testing. Background Technology

[0002] With the widespread use of lithium batteries, especially large-capacity square lithium batteries, their safety has become an increasingly important concern. Battery bulging is often one of the early precursors to thermal runaway, and if not detected in time, it can easily lead to serious safety accidents. Therefore, early and reliable detection of battery bulging is of great significance. Attaching a flexible pressure sensor to the surface of the battery casing for real-time monitoring is a direct and effective technical means. However, this installation method not only results in poor integration between the flexible pressure sensor and the battery, but also faces a key technical challenge in practical applications: the pre-pressure problem. To ensure good contact between the flexible pressure sensor and the battery casing and to ensure timely response when the battery initially expands, the flexible pressure sensor usually needs to be subjected to a large initial pre-pressure during installation, such as by binding, clamping, or installing it in a compact battery module.

[0003] Most existing flexible pressure sensors are based on conductive composite materials, such as conductive rubber, conductive sponge, and conductive polymers. Their working principle is that under external force, the spacing between conductive particles decreases, the number of conductive pathways increases, and thus the sensor's resistance decreases. However, under the aforementioned large pre-pressure, the conductive network inside the sensor is often sufficiently compressed and tends to saturate. In this situation, when the battery slightly bulges, the resulting additional pressure increment is unlikely to significantly alter the conductive network structure, resulting in minimal resistance change. This leads to a sharp drop in sensitivity within the critical monitoring range of minute pressure changes under large pre-pressure conditions, and may even result in detection failure.

[0004] Therefore, there is an urgent need to design a flexible pressure sensor that can maintain high sensitivity to minute pressure changes even under high pre-stress conditions. Summary of the Invention

[0005] One objective of this invention is to provide a flexible pressure sensor for battery detection, addressing the technical problems of poor sensitivity and low integration in existing flexible pressure sensors under high pre-pressure conditions.

[0006] Another object of the present invention is to provide a method for fabricating the above-mentioned flexible pressure sensor.

[0007] Another object of the present invention is to provide a method for detecting battery bulging using the above-described flexible pressure sensor.

[0008] In particular, the present invention provides a flexible pressure sensor for battery detection, the flexible pressure sensor comprising an electrode layer and a composite structure, the composite structure comprising an adhesive layer and a pressure-sensitive layer, wherein the metal casing of the battery serves as the electrode layer of the flexible pressure sensor, and the pressure-sensitive layer is connected to the electrode layer through the adhesive layer; The pressure-sensitive layer includes a flexible thin film layer and a pressure-sensitive material layer. Both sides of the flexible thin film layer have non-marked areas and marked areas with a preset pattern. The pressure-sensitive material layer is coated on both sides of the flexible thin film layer. During the process of installing the composite structure onto the electrode layer, when the pressure-sensitive layer is subjected to pre-pressure, the non-marked area is preferentially subjected to force relative to the marked area, causing the first pressure-sensitive material area corresponding to the non-marked area to undergo major deformation and changes in the conductive network. When the battery bulges, the second pressure-sensitive material area corresponding to the etched area is deformed under pressure, thereby causing a change in the electrical signal.

[0009] Optionally, the depth of the etched region is 20%-80% of the thickness of the flexible thin film layer; The width of the etched area ranges from 50um to 200um.

[0010] Optionally, the preset pattern can be serpentine, grid-like, honeycomb-like, biomimetic spider web-like, or concentric ring-like.

[0011] Optionally, the flexible thin film layer has opposing first and second sides; The grooved area on the first side is symmetrically arranged with the grooved area on the second side.

[0012] Optionally, the two pressure-sensitive material layers are a first pressure-sensitive material layer and a second pressure-sensitive material layer, respectively; The adhesive layer includes a first adhesive layer and a second adhesive layer, wherein the first adhesive layer is disposed on the outside of the first pressure-sensitive material layer and the second adhesive layer is disposed on the outside of the second pressure-sensitive material layer; Each adhesive layer includes multiple adhesive structures with gaps between them, and is uniformly adhered to the corresponding pressure-sensitive material layer; Each of the aforementioned adhesive structures is strip-shaped, arc-shaped, or circular.

[0013] Optionally, each pressure-sensitive material layer is divided into multiple preset pressure-sensitive regions, each preset pressure-sensitive region corresponding to a different position of the battery, and each outputs an electrical signal separately.

[0014] Optionally, the battery includes a plurality of lithium battery modules stacked together, each of the lithium battery modules having the metal casing; The composite structure in which a flexible pressure sensor is installed between two adjacent lithium battery modules, wherein the surface of the metal casing of one lithium battery module serves as the first electrode layer of the flexible pressure sensor, and the surface of the metal casing of the other lithium battery module serves as the second electrode layer of the flexible pressure sensor.

[0015] In particular, the present invention also provides a method for fabricating a flexible pressure sensor, applicable to the aforementioned flexible pressure sensor, comprising the following steps: Provide a flexible film; Laser etching is used to form grooved areas with preset patterns on the upper and lower surfaces of the flexible film to obtain a flexible film layer. Pressure-sensitive carbon paste is coated onto the upper and lower surfaces of the flexible film layer, and then dried to form pressure-sensitive material layers on the upper and lower surfaces of the flexible film layer, respectively. At least two adhesive layers are respectively bonded to the outside of the two pressure-sensitive material layers to form the composite structure of the flexible pressure sensor; The composite structure is attached to the metal casing of the battery to obtain the flexible pressure sensor.

[0016] In particular, the present invention also provides a method for detecting battery bulging, using the aforementioned flexible pressure sensor, comprising the following steps: The first electrical signal of the first pressure-sensitive material layer and the second electrical signal of the second pressure-sensitive material layer are respectively acquired. The battery is determined to have bulged and the severity of the bulge based on the first and second electrical signals.

[0017] Optionally, in the step of determining whether the battery has bulged and the severity of the bulge based on the first electrical signal and the second electrical signal: When the first electrical signal changes and the second electrical signal does not change, it is determined that the lithium battery module on the first pressure-sensitive material layer side has a slight bulge, and the battery includes multiple lithium battery modules. When the first electrical signal remains unchanged but the second electrical signal changes, it is determined that the lithium battery module on the second pressure-sensitive material layer side has a slight bulge. When both the first and second electrical signals change, it is determined that the lithium battery module on the first pressure-sensitive material layer side or the lithium battery module on the second pressure-sensitive material layer side has experienced severe bulging.

[0018] This invention discloses a flexible pressure sensor comprising an electrode layer and a composite structure. The composite structure includes an adhesive layer and a pressure-sensitive layer. The metal casing of the battery serves as the electrode layer, and the pressure-sensitive layer is connected to the electrode layer via the adhesive layer. This technical solution utilizes the battery's metal casing as the electrode layer, eliminating the need for a separate electrode layer in traditional sensors. This improves the integration of the flexible pressure sensor with the battery, allowing the sensor to better adapt to the battery's shape and operating environment, and simplifying the sensor structure and manufacturing process. Similarly, the insulating layer and blue film in the middle of the battery can be replaced by the flexible pressure sensor, significantly reducing manufacturing costs.

[0019] Furthermore, in this invention, the pressure-sensitive layer comprises a flexible thin film layer and a pressure-sensitive material layer. Both sides of the flexible thin film layer have non-marked areas and marked areas with a pre-defined pattern. The pressure-sensitive material layer is coated on both sides of the flexible thin film layer. During the process of installing the composite structure onto the electrode layer and applying pre-pressure, because the marked areas have lower structural stiffness, the non-marked areas preferentially bear the pre-pressure compared to the marked areas. This causes the first pressure-sensitive material area corresponding to the non-marked areas to undergo major deformation, resulting in a corresponding change in the conductive network. Therefore, the pressure-sensitive material layer as a whole can be prevented from entering a conductive network saturation state in its initial state. When the battery bulges during use, a non-perpendicular compressive force is generated. The second pressure-sensitive material area corresponding to the marked areas begins to be compressed and deformed, thereby causing a significant change in the electrical signal and achieving effective detection of battery bulging. The above technical solution, through the ingenious structural design of the etched area, guides the pre-pressure to act mainly on the non-etched area during the sensor installation stage, while making the etched area respond to deformation preferentially during the battery bulging stage. Thus, even in high pre-pressure application scenarios, it can still avoid premature saturation of the conductive network, and enable the flexible pressure sensor to maintain good linear response and high detection sensitivity to small pressure changes in battery bulging.

[0020] The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0021] The following sections will describe some specific embodiments of the invention in detail by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or portions. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings: Figure 1 This is a schematic structural diagram of a flexible pressure sensor according to an embodiment of the present invention; Figure 2 This is a schematic structural diagram of a flexible pressure sensor according to another embodiment of the present invention; Figure 3This is a schematic diagram of the grooved area according to an embodiment of the present invention; Figure 4 This is a schematic structural diagram of a pressure-sensitive material layer according to an embodiment of the present invention; Figure 5 This is a schematic structural diagram of a flexible thin film layer according to an embodiment of the present invention; Figure 6 This is a schematic structural diagram of a flexible thin film layer according to another embodiment of the present invention; Figure 7 This is a schematic structural diagram of a flexible thin film layer according to yet another embodiment of the present invention; Figure 8 This is a schematic structural diagram of a flexible thin film layer according to another embodiment of the present invention; Figure 9 This is a schematic structural diagram of an adhesive layer according to an embodiment of the present invention; Figure 10 This is a performance comparison chart between Example 1 and Comparative Example 1; Figure 11 This is a schematic flowchart of a method for manufacturing a flexible pressure sensor according to an embodiment of the present invention; Figure 12 This is a schematic flowchart of a battery bulging detection method according to an embodiment of the present invention.

[0022] Figure label: 100-Flexible pressure sensor, 10-Pressure-sensitive layer, 20-Composite structure, 30-Metal shell, 11-Flexible thin film layer, 12-Pressure-sensitive material layer, 21-Adhesive layer, 211-Adhesive structure, 212-Gap. Detailed Implementation

[0023] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0024] In the description of this invention, it should be understood that the terms "upper" and "lower" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0025] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature, that is, include one or more of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified. When a feature "includes or contains" one or more of the features it encompasses, unless otherwise specifically stated, this indicates that other features are not excluded and may be further included.

[0026] Unless otherwise expressly specified and limited, the terms "connection," "installation," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art should be able to understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0027] Unless otherwise specified, all terms (including technical and scientific terms) used in the description of this embodiment have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0028] Figure 1 This is a schematic structural diagram of a flexible pressure sensor 100 according to an embodiment of the present invention. Figure 2 This is a schematic structural diagram of a flexible pressure sensor 100 according to another embodiment of the present invention. Figure 3 This is a schematic diagram of the grooved area according to an embodiment of the present invention. Figures 1 to 3As shown, in a specific embodiment, the flexible pressure sensor 100 for battery detection includes an electrode layer and a composite structure 20. The composite structure 20 includes an adhesive layer 21 and a pressure-sensitive layer 10. The metal casing 30 of the battery serves as the electrode layer of the flexible pressure sensor 100, and the pressure-sensitive layer 10 is connected to the electrode layer through the adhesive layer 21. The pressure-sensitive layer 10 includes a flexible thin film layer 11 and a pressure-sensitive material layer 12. Both sides of the flexible thin film layer 11 have non-marked areas and marked areas with a preset pattern. The pressure-sensitive material layer 12 is coated on both sides of the flexible thin film layer 11. During the process of installing the composite structure 20 onto the electrode layer, when the pressure-sensitive layer 10 is subjected to pre-pressure, the non-marked areas are preferentially stressed compared to the marked areas, causing the first pressure-sensitive material area corresponding to the non-marked areas to undergo major deformation and changes in the conductive network. When the battery bulges, the second pressure-sensitive material area corresponding to the marked areas is deformed under pressure, thereby causing changes in the electrical signal. Here, the metal shell 30 is made of aluminum, and both the upper and lower surfaces of the metal shell 30 can serve as electrode layers. In other words, the composite structure 20 directly contacts the surface of the aluminum shell to form a flexible pressure sensor 100.

[0029] This embodiment utilizes the battery's metal casing 30 as the electrode layer, eliminating the need for a separate electrode layer in traditional sensors. This improves the integration of the flexible pressure sensor 100 with the battery, allowing the flexible pressure sensor 100 to better adapt to the battery's shape and operating environment, and significantly reduces manufacturing costs. Furthermore, through the ingenious structural design of the etched area, pre-pressure is directed primarily to the non-etched area during sensor installation, while the etched area preferentially responds to deformation during battery bulging. This prevents premature saturation of the conductive network even under high pre-pressure applications, ensuring the flexible pressure sensor 100 maintains good linear response and high detection sensitivity to minute pressure changes during battery bulging.

[0030] In some embodiments, the pressure-sensitive material layer 12 is made of conductive nanomaterials such as carbon nanotubes and graphene.

[0031] In some embodiments, the depth of the etched region is 20%-80% of the thickness of the flexible thin film layer 11, for example, 20%, 30%, 40%, 50%, 60%, 70%, or 80%. This embodiment limits the depth of the etched region within the above range, ensuring that while forming an effective stress-guiding structure, the flexible thin film layer 11 still has sufficient remaining thickness to bear the pre-pressure load, ensuring stable support. This avoids the effective load-bearing capacity of the flexible thin film layer 11 being significantly reduced due to excessive etched depth, thus affecting its supporting role for the pressure-sensitive material layer 12. If the etched depth is too small, the weakening effect of the etched region on the local stiffness of the flexible thin film layer 11 is not significant. Under the action of pre-pressure and subsequent pressure changes, the stress difference between the etched and non-etched regions is insufficient, making it difficult to form effective stress concentration. This results in insignificant changes in the conductive network in the pressure-sensitive material layer 12, thereby reducing the response sensitivity of the flexible pressure sensor 100 to slight battery bulging.

[0032] In some embodiments, the width of the etched region ranges from 50µm to 200µm, for example, it can be 50µm, 80µm, 100µm, 120µm, 150µm, 180µm, or 200µm. This embodiment limits the width of the etched region within the above range, which can ensure that the flexible thin film layer 11 has sufficient support strength while forming a reasonable stress regulation structure. This allows the non-etched region to be preferentially stressed under pre-pressure, thereby inducing a significant change in the conductive network of the pressure-sensitive material under small pressure changes. This balances detection sensitivity and structural reliability, and is beneficial for achieving stable and accurate detection of battery bulging.

[0033] In some embodiments, the preset pattern is serpentine, grid-like, honeycomb-like, biomimetic spiderweb-like, or concentric ring-like. Here, a suitable notch pattern can be selected based on the expected pressure detection range and sensitivity requirements. For example, serpentine notches facilitate stress dispersion and guidance in a specific direction. Grid-like notches enable multi-directional stress response.

[0034] This embodiment allows for precise control of the sensitivity of the flexible pressure sensor 100 across different pressure ranges by designing different preset patterns, depths, and densities of the grooves. This adapts to the needs of different pre-pressures and different bulge detection sensitivities, demonstrating strong customization capabilities. Furthermore, this embodiment only adds a flexible thin film layer 11 with grooved areas to the traditional sensor structure, resulting in a simple structure, minimal cost increase, and easy integration into existing battery module designs.

[0035] In some embodiments, the density and / or depth of the grooves are gradually varied along a predetermined direction. This gradually varied groove structure introduces different deformation modes at different stress stages. For example, in lower pressure ranges, areas with shallower grooves or lower density deform preferentially, giving the sensor higher sensitivity to minute pressure changes; in higher pressure ranges, areas with deeper grooves or higher density gradually participate in deformation, thereby preventing premature saturation of the conductive network and maintaining the continuity and stability of the resistive response. Thus, the flexible pressure sensor 100 can achieve segmented optimized sensitivity response over a wide pressure range, improving its ability to detect battery bulging of varying degrees.

[0036] In this embodiment, a laser etching process is used to form a pre-defined patterned etched area on the flexible thin film layer 11. These patterns divide the flexible thin film layer 11 into multiple independent islands or lobes, forming stress guiding channels. When the flexible pressure sensor 100 is subjected to a large pre-pressure, a new and controllable deformation mode is artificially created, thereby avoiding the saturation of the conductive network and ensuring that it can still produce a significant resistance response to the pressure increment under a large pre-pressure background.

[0037] In some embodiments, the flexible thin film layer 11 has a first side and a second side opposite to each other, with the grooved regions on the first side and the grooved regions on the second side arranged symmetrically. In other embodiments, the grooved regions on both sides may also be designed to be arranged asymmetrically.

[0038] Figure 4 This is a schematic structural diagram of the pressure-sensitive material layer 12 according to an embodiment of the present invention, as shown below. Figure 4 As shown, in some embodiments, each pressure-sensitive material layer 12 is divided into multiple preset pressure-sensitive regions, each preset pressure-sensitive region corresponding to a different position of the battery, and outputs an electrical signal separately.

[0039] In some embodiments, the number of preset pressure-sensitive regions is seven. A first preset pressure-sensitive region is located in the middle of the pressure-sensitive material layer 12. A second preset pressure-sensitive region is located above the first preset pressure-sensitive region, and a third preset pressure-sensitive region is located below the first preset pressure-sensitive region. A fourth preset pressure-sensitive region and a fifth preset pressure-sensitive region are located at the upper left and upper right corners of the second preset pressure-sensitive region, respectively. A sixth preset pressure-sensitive region and a seventh preset pressure-sensitive region are located at the lower left and lower right corners of the third preset pressure-sensitive region, respectively. This embodiment, by setting multiple preset pressure-sensitive regions, can obtain the force conditions at different locations of the battery, thereby determining the bulging area of ​​the battery. In other embodiments, the number of preset pressure-sensitive regions can also be designed according to actual needs, for example, it can be six, eight, or ten, etc.

[0040] In some embodiments, the battery includes multiple lithium battery modules stacked together, each lithium battery module having the metal casing 30. A composite structure 20 with a flexible pressure sensor 100 is installed between two adjacent lithium battery modules, wherein the surface of the metal casing 30 of one lithium battery module serves as the first electrode layer of the flexible pressure sensor 100, and the surface of the metal casing 30 of the other lithium battery module serves as the second electrode layer of the flexible pressure sensor 100. This is equivalent to having a flexible pressure sensor 100 between each two adjacent lithium battery modules, thereby enabling the detection of bulging in a single lithium battery module.

[0041] This embodiment eliminates the need for separate electrode layer materials, such as the PET / PI substrate and conductive layer, found in traditional flexible pressure sensors 100, and also simplifies the related fabrication processes, thereby simplifying the sensor structure and production process. Similarly, the insulating layer and blue film in the middle of the lithium battery can be replaced by the flexible pressure sensor 100, significantly reducing manufacturing costs. Furthermore, this embodiment avoids the obstruction of pressure transmission by the electrode layer substrate film, such as PET / PI, and the adhesive layer 21 between the electrode layer and the pressure-sensitive layer 10, as found in traditional sensors. The minute deformations caused by the bulging of the lithium battery can be transmitted more directly and efficiently to the pressure-sensitive layer 10, reducing signal loss and thus improving the sensor's sensitivity to bulging signals.

[0042] Figure 5 This is a schematic structural diagram of a flexible thin film layer 11 according to an embodiment of the present invention. Figure 5 As shown, the preset pattern formed by the etched area of ​​the flexible thin film layer 11 can be designed according to the corresponding preset pressure-sensitive area, and different preset patterns can be set at the positions corresponding to different preset pressure-sensitive areas.

[0043] Figure 6 This is a schematic structural diagram of the flexible thin film layer 11 according to another embodiment of the present invention. Figure 7 This is a schematic structural diagram of the flexible thin film layer 11 according to yet another embodiment of the present invention. Figure 8 This is a schematic structural diagram of the flexible thin film layer 11 according to another embodiment of the present invention. Figure 6 , Figure 7 and Figure 8 As shown, the preset pattern formed by the etched area of ​​the flexible thin film layer 11 can be the same, for example, it can be honeycomb, grid, etc.

[0044] The flexible pressure sensor 100 of this embodiment can maintain good linear response and high sensitivity within a large pressure range, such as 0-1MPa, solving the problem that traditional flexible pressure sensors 100 are prone to conductive network saturation and sharp decrease in sensitivity under high pre-pressure.

[0045] Figure 9This is a schematic structural diagram of the adhesive layer 21 according to an embodiment of the present invention. Figure 9 As shown, and see Figure 1 and Figure 2 In some embodiments, the two pressure-sensitive material layers 12 are a first pressure-sensitive material layer and a second pressure-sensitive material layer, respectively. The adhesive layer 21 includes a first adhesive layer and a second adhesive layer, with the first adhesive layer disposed outside the first pressure-sensitive material layer and the second adhesive layer disposed outside the second pressure-sensitive material layer. Each adhesive layer 21 includes multiple adhesive structures 211, with gaps 212 between the multiple adhesive structures 211, and they are uniformly adhered to the corresponding pressure-sensitive material layer 12. Each adhesive structure 211 is strip-shaped, arc-shaped, or circular.

[0046] In this embodiment, the adhesive layer 21 adopts a discrete adhesive structure composed of multiple spaced adhesive structures 211. On the one hand, the gaps 212 formed between adjacent adhesive structures 211 reduce the overall stiffness of the adhesive layer 21 in pressure transmission, allowing the small deformations caused by the lithium battery bulge to bypass the large-area damping of the adhesive layer 21 and be transmitted more directly to the pressure-sensitive layer 10. This effectively reduces energy attenuation during deformation transmission and improves the detection sensitivity and response accuracy of the flexible pressure sensor 100 for battery bulges. On the other hand, the gaps 212 formed between the adhesive structures 211 constitute air-permeable channels. During sensor compression or deformation, this facilitates timely balancing of the air pressure difference inside and outside the flexible pressure sensor 100, avoiding measurement drift or hysteresis caused by air stagnation or local negative pressure. This improves the stability and repeatability of the sensor during long-term monitoring.

[0047] The following provides specific embodiments and comparative examples for illustration: Example 1: The flexible pressure sensor 100 includes an electrode layer and a composite structure 20. The composite structure 20 includes an adhesive layer 21 and a pressure-sensitive layer 10. The metal casing 30 of the battery serves as the electrode layer of the flexible pressure sensor 100, and the pressure-sensitive layer 10 is connected to the electrode layer through the adhesive layer 21. The pressure-sensitive layer 10 includes a flexible thin film layer 11 and two pressure-sensitive material layers 12. The flexible thin film layer 11 has a non-marked area and a marked area with a preset pattern. The pressure-sensitive material layers 12 are coated on both sides of the flexible thin film layer 11. During the process of installing the composite structure 20 onto the electrode layer, when the pressure-sensitive layer 10 is subjected to pre-pressure, the non-marked area is preferentially stressed compared to the marked area, causing the first pressure-sensitive material area corresponding to the non-marked area to undergo major deformation and changes in the conductive network. When the battery bulges, the second pressure-sensitive material area corresponding to the marked area is deformed under pressure, thereby causing a change in the electrical signal.

[0048] Comparative Example 1: The only difference between Comparative Example 1 and Example 1 is that: The flexible pressure sensor 100 has an independent electrode layer, instead of the metal casing 30 of the battery serving as the electrode layer. Furthermore, there are no etched areas on the flexible thin film layer 11.

[0049] Figure 10 This is a performance comparison chart between Example 1 and Comparative Example 1. For example... Figure 10 As shown, the tests indicate that, based on a pre-pressure of 0.5 MPa, applying a pressure increment of 0.02 MPa to simulate battery bulging, the resistance change rate of the flexible pressure sensor 100 in Example 1 still reaches over 3%, while the resistance change rate of the non-marked sensor in Comparative Example 1 is less than 0.2% under the same conditions. This demonstrates that Example 1 has higher sensitivity than Comparative Example 1.

[0050] Figure 11 This is a schematic flowchart illustrating a method for fabricating a flexible pressure sensor 100 according to an embodiment of the present invention. Figure 11 As shown, in a specific embodiment, the method for fabricating the flexible pressure sensor 100 is applied to the flexible pressure sensor 100 of any of the above embodiments, and the fabrication method includes the following steps: Step S11: Provide a flexible film; Step S12: A pre-defined patterned etching region is formed on the upper and lower surfaces of the flexible thin film by laser etching process to obtain the flexible thin film layer 11. Step S13: Pressure-sensitive carbon paste is coated onto the upper and lower surfaces of the flexible film layer 11, and then dried to form pressure-sensitive material layers 12 on the upper and lower surfaces of the flexible film layer 11, respectively. Step S14: At least two adhesive layers 21 are respectively bonded to the outside of the two pressure-sensitive material layers 12 to form a composite structure 20 of the flexible pressure sensor 100. In step S15, the composite structure 20 is attached to the metal casing 30 of the battery to obtain the flexible pressure sensor 100.

[0051] In step S11, the flexible film is a PI film.

[0052] In step S12, the parameters of laser etching, such as wavelength, power, and scanning speed, can be optimized according to the required etching depth, width, and pattern. Laser etching offers high precision and good consistency, enabling the batch fabrication of flexible thin film layers 11 with identical microstructures, thus ensuring the consistency and stability of the flexible pressure sensor 100's performance.

[0053] In some embodiments, a UV laser cutter is used to etch a grid pattern with a depth of 30 μm, a line width of 50 μm, and a spacing of 2 mm on the upper and lower surfaces of the PI film. Afterwards, ethanol is used to wipe away the carbonized material on the surface etched areas, which can improve the adhesion between the PI film and the pressure-sensitive material.

[0054] In step S13, the material is dried at 150°C, and the thickness of the pressure-sensitive material layer 12 is 200 μm.

[0055] In step S14, multiple patterned double-sided adhesive layers 21 are die-cut out and attached to both sides of the pressure-sensitive material layer 12 respectively.

[0056] In step S15, the composite structure 20 with adhesive layer 21 is attached to the aluminum shell of a 100Ah square lithium iron phosphate battery and installed in the lithium battery module to withstand a pre-pressure of about 0.5MPa.

[0057] Figure 12 This is a schematic flowchart of a battery bulging detection method according to an embodiment of the present invention. Figure 12 As shown, in one specific embodiment, the battery bulge detection method uses the flexible pressure sensor 100 of any of the above embodiments, and the detection method includes the following steps: Step S21: Obtain the first electrical signal of the first pressure-sensitive material layer 12 and the second electrical signal of the second pressure-sensitive material layer 12 respectively; Step S22: Determine whether the battery has bulged and the severity of the bulge based on the first and second electrical signals.

[0058] In some embodiments, in step S22: When the first electrical signal changes and the second electrical signal does not change, it is determined that the lithium battery module on the first pressure-sensitive material layer 12 side has a slight bulge. The battery includes multiple lithium battery modules. When the first electrical signal does not change but the second electrical signal changes, it is determined that the lithium battery module on the second pressure-sensitive material layer 12 has a slight bulge. When both the first and second electrical signals change, it is determined that the lithium battery module on the first pressure-sensitive material layer 12 side or the lithium battery module on the second pressure-sensitive material layer 12 side has experienced severe bulging.

[0059] Here, changes in the electrical signal include, but are not limited to, at least one of the following: 1. The resistance value exceeds a preset threshold; 2. The rate of change of resistance exceeds a preset rate of change threshold; 3. The electrical signal exhibits a continuous changing trend within a preset time window.

[0060] This embodiment compares and analyzes the electrical signals of the first and second varistor material layers 12 to determine which side of the battery or the corresponding lithium battery module the bulge occurs on, improving the accuracy of fault location. Furthermore, a change in the electrical signal on one side indicates a minor bulge; a change in the electrical signals on both sides indicates a severe bulge, thus providing a tiered early warning system for the battery management system.

[0061] Therefore, those skilled in the art should recognize that although numerous exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications conforming to the principles of the present invention can be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Thus, the scope of the present invention should be understood and construed as covering all such other variations or modifications.

Claims

1. A flexible pressure sensor for battery detection, characterized in that, The flexible pressure sensor includes an electrode layer and a composite structure. The composite structure includes an adhesive layer and a pressure-sensitive layer. The metal casing of the battery serves as the electrode layer of the flexible pressure sensor, and the pressure-sensitive layer is connected to the electrode layer through the adhesive layer. The pressure-sensitive layer includes a flexible thin film layer and a pressure-sensitive material layer. Both sides of the flexible thin film layer have non-marked areas and marked areas with a preset pattern. The pressure-sensitive material layer is coated on both sides of the flexible thin film layer. During the process of installing the composite structure onto the electrode layer, when the pressure-sensitive layer is subjected to pre-pressure, the non-marked area is preferentially subjected to force relative to the marked area, causing the first pressure-sensitive material area corresponding to the non-marked area to undergo major deformation and changes in the conductive network. When the battery bulges, the second pressure-sensitive material area corresponding to the etched area is deformed under pressure, thereby causing a change in the electrical signal.

2. The flexible pressure sensor according to claim 1, characterized in that, The depth of the etched area is 20%-80% of the thickness of the flexible thin film layer; The width of the etched area ranges from 50um to 200um.

3. The flexible pressure sensor according to claim 2, characterized in that, The preset pattern can be snake-shaped, grid-shaped, honeycomb-shaped, biomimetic spider web-shaped, or concentric ring-shaped.

4. The flexible pressure sensor according to claim 3, characterized in that, The flexible thin film layer has a first side and a second side opposite to each other; The grooved area on the first side is symmetrically arranged with the grooved area on the second side.

5. The flexible pressure sensor according to claim 4, characterized in that, The two pressure-sensitive material layers are a first pressure-sensitive material layer and a second pressure-sensitive material layer, respectively. The adhesive layer includes a first adhesive layer and a second adhesive layer, wherein the first adhesive layer is disposed on the outside of the first pressure-sensitive material layer and the second adhesive layer is disposed on the outside of the second pressure-sensitive material layer; Each adhesive layer includes multiple adhesive structures with gaps between them, and is uniformly adhered to the corresponding pressure-sensitive material layer; Each of the aforementioned adhesive structures is strip-shaped, arc-shaped, or circular.

6. The flexible pressure sensor according to any one of claims 1-5, characterized in that, Each pressure-sensitive material layer is divided into multiple preset pressure-sensitive regions, each preset pressure-sensitive region corresponding to a different position of the battery, and each outputs an electrical signal independently.

7. The flexible pressure sensor according to any one of claims 1-5, characterized in that, The battery includes multiple lithium battery modules stacked together, each of which has the metal casing. The composite structure in which a flexible pressure sensor is installed between two adjacent lithium battery modules, wherein the surface of the metal casing of one lithium battery module serves as the first electrode layer of the flexible pressure sensor, and the surface of the metal casing of the other lithium battery module serves as the second electrode layer of the flexible pressure sensor.

8. A method for fabricating a flexible pressure sensor, applied to the flexible pressure sensor as described in any one of claims 1-7, characterized in that, Includes the following steps: Provide a flexible film; Laser etching is used to form grooved areas with preset patterns on the upper and lower surfaces of the flexible film to obtain a flexible film layer. Pressure-sensitive carbon paste is coated onto the upper and lower surfaces of the flexible film layer, and then dried to form pressure-sensitive material layers on the upper and lower surfaces of the flexible film layer, respectively. At least two adhesive layers are respectively bonded to the outside of the two pressure-sensitive material layers to form the composite structure of the flexible pressure sensor; The composite structure is attached to the metal casing of the battery to obtain the flexible pressure sensor.

9. A method for detecting battery bulging, using a flexible pressure sensor as described in any one of claims 1-7, characterized in that, Includes the following steps: The first electrical signal of the first pressure-sensitive material layer and the second electrical signal of the second pressure-sensitive material layer are respectively acquired. The battery is determined to have bulged and the severity of the bulge based on the first and second electrical signals.

10. The detection method according to claim 9, characterized in that, In the step of determining whether the battery has bulged and the severity of the bulge based on the first electrical signal and the second electrical signal: When the first electrical signal changes and the second electrical signal does not change, it is determined that the lithium battery module on the first pressure-sensitive material layer side has a slight bulge, and the battery includes multiple lithium battery modules. When the first electrical signal remains unchanged but the second electrical signal changes, it is determined that the lithium battery module on the second pressure-sensitive material layer side has a slight bulge. When both the first and second electrical signals change, it is determined that the lithium battery module on the first pressure-sensitive material layer side or the lithium battery module on the second pressure-sensitive material layer side has experienced severe bulging.

Images