Flexible sensor for monitoring temperature and pressure of lithium battery and preparation method

Abstract

The invention relates to the technical field of flexible sensing monitoring, and discloses a flexible sensor for monitoring temperature and pressure of a lithium battery and a preparation method, the flexible sensor comprises a first flexible substrate layer, a second flexible substrate layer and an elastic layer arranged between the first flexible substrate layer and the second flexible substrate layer; the sensing circuit is attached to the first flexible substrate layer and is provided with a temperature sensing part and a pressure sensing part; a conductive substrate is attached to the second flexible substrate layer, an opening is formed in the elastic layer, and the conductive substrate, the elastic layer and the pressure sensing part form a pressing cavity. According to the flexible sensor for monitoring the temperature and the pressure of the lithium battery, the fitting degree between the sensor and a battery cell structure is effectively improved, signal noise generated by installation errors or structural stress is reduced, and high-precision detection of the temperature and the pressure at different areas in the battery is realized; and the measurement precision and stability of the sensor in the low-voltage initial response and high-voltage continuous monitoring process are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible sensing and monitoring, and in particular to a flexible sensor for monitoring the temperature and pressure of a lithium battery and a preparation method thereof. Background Art

[0002] In recent years, lithium-ion batteries, with their advantages of high energy density, long cycle life, and low self-discharge, have been widely used in new energy vehicles, large-scale energy storage systems, and consumer electronics. During battery operation, the coordinated control of temperature and pressure is a key prerequisite for ensuring safe and efficient battery operation. On the one hand, abnormal temperatures can accelerate the decomposition of the solid electrolyte interface membrane, triggering chain reactions such as electrolyte oxidation and heat generation, lithium dendrite growth, and ultimately thermal runaway. On the other hand, the insertion and extraction of lithium ions, gas side reactions, and mechanical expansion effects during the battery's charge and discharge processes can cause a sharp increase in internal pressure. Without timely monitoring and intervention, this can lead to battery shell rupture, electrolyte leakage, and even explosion.

[0003] Existing battery monitoring solutions usually attach sensors to the battery surface to collect data, and they mainly obtain information about the battery's exterior or surface. Due to the temperature gradient distribution and local non-uniform effects, the battery's external sensor monitoring method has certain limitations in terms of monitoring response speed and data accuracy. It cannot effectively obtain internal battery fault conditions, and cannot obtain internal battery temperature and pressure changes in the first place, resulting in a certain lag and data deviation in the battery monitoring data. Summary of the Invention

[0004] In response to one or more of the above-mentioned defects or improvement needs of the prior art, the present invention provides a flexible sensor for lithium battery temperature and pressure monitoring, which is used to solve the problems of hysteresis and data deviation in monitoring data of existing lithium battery monitoring sensors.

[0005] To achieve the above objectives, the present invention provides a flexible sensor for monitoring temperature and pressure of a lithium battery, comprising: a first flexible base layer and a second flexible base layer, wherein the first flexible base layer and the second flexible base layer form an accommodating cavity; an elastic layer, the elastic layer being disposed between the first flexible base layer and the second flexible base layer; a sensing circuit, the sensing circuit being attached to a side of the first flexible base layer facing the elastic layer, the sensing circuit comprising a temperature sensing portion and a pressure sensing portion; A conductive substrate is provided, wherein the conductive substrate and the pressure sensing portion are aligned along the thickness direction of the first flexible base layer and the second flexible base layer, the elastic layer is provided with an opening in a direction facing the conductive substrate and the pressure sensing portion, the conductive substrate, the elastic layer and the pressure sensing portion form a pressing cavity, and when the conductive substrate contacts the pressure sensing portion, the resistance value of the pressure sensing portion changes accordingly.

[0006] As a further improvement of the present invention, the sensing circuit is made by silver paste lead printing, the pressure sensing portion includes interdigital electrodes, and the conductive substrate is made by compounding elastic material and conductive filler.

[0007] As a further improvement of the present invention, when the flexible sensor for monitoring temperature and pressure of a lithium battery is at a first pressure, the conductive substrate is not in contact with the pressure sensing portion, and the pressure sensing portion is in an unloaded state; When the flexible sensor for monitoring temperature and pressure of a lithium battery is at a second pressure, the conductive substrate is in partial contact with the pressure sensing portion, and the resistance of the pressure sensing portion changes linearly with the contact area between the conductive substrate and the pressure sensing portion; When the flexible sensor for monitoring the temperature and pressure of a lithium battery is at a third pressure, the conductive substrate is in contact with the pressure sensing part, the pressure sensing part deforms as the pressure changes, the conductive network formed by the conductive filler in the conductive substrate is reconstructed, and the conductive substrate and the pressure sensing part form a stable connection.

[0008] As a further improvement of the present invention, the elastic material in the conductive substrate includes one or more of PDMS, PI, TPU or epoxy resin; The conductive filler includes one or more of carbon black, carbon nanotubes, graphene, and nano-conductive metal materials.

[0009] As a further improvement of the present invention, the temperature sensing portion is formed by a magnetron sputtering process, and the temperature sensing portion is made of platinum metal.

[0010] As a further improvement of the present invention, the elastic layer has a groove on the outer side along the plane direction, and the groove is filled with electrolyte corrosion-resistant glue.

[0011] The present application also includes a method for preparing a flexible sensor for monitoring temperature and pressure of a lithium battery, which comprises the following steps: S1, selecting two polyimide films as the first flexible base layer and the second flexible base layer, respectively, cleaning and drying the two polyimide films to remove residual impurities on the surfaces of the polyimide films; S2, preparing a metal mask for the temperature sensing portion, and preparing a temperature sensing portion of platinum metal on the first flexible substrate layer by a magnetron sputtering process; S3, adding the conductive polymer composite material to an organic solvent, stirring to obtain a printing slurry, adding a conductive filler to the organic solvent, ultrasonically obtaining a suspension, and mixing the suspension with the printing slurry to obtain a conductive polymer composite material slurry; S4. Screen-printing silver paste leads and interdigitated electrodes serving as pressure sensing portions on the first flexible substrate layer, connecting the pressure sensing portion and the temperature sensing portion to the silver paste leads, respectively; screen-printing a conductive polymer composite material slurry on the second substrate layer, and heating and curing the slurry to obtain a conductive substrate; S5. Cut the PET elastic film as the elastic layer, use release paper to adhere to both sides of the PET elastic film, and apply electrolyte corrosion-resistant glue circumferentially on the plane of the PET elastic film; use release paper to bond the PET elastic film to the first flexible base layer and the second flexible base layer respectively to obtain a flexible sensor for lithium battery temperature and pressure monitoring.

[0012] As a further improvement of the present invention, the magnetron sputtering gas pressure of the magnetron sputtering process in step S2 is 0.2Pa~0.6Pa, the sputtering power is 80w~160w, the sputtering time is 15min~35min, and the thickness of the platinum metal is 60nm~200nm.

[0013] As a further improvement of the present invention, the step S2 further includes an annealing process after the temperature sensing portion of the platinum metal is prepared by the magnetron sputtering process, and the platinum metal is annealed at 200° C. to 300° C.

[0014] As a further improvement of the present invention, the organic solvent in step S3 includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide.

[0015] The above-mentioned improved technical features can be combined with each other as long as they do not conflict with each other.

[0016] In general, the above technical solutions conceived by the present invention have the following beneficial effects compared with the prior art: (1) The flexible sensor for monitoring the temperature and pressure of a lithium battery of the present invention adopts a flexible material as the sensor body, which makes it possible to make the sensor directly inside the lithium battery, and sets a temperature sensing part and a pressure sensing part on the sensing circuit, thereby realizing the internal temperature and pressure monitoring of the lithium battery, improving the accuracy of the temperature and pressure monitoring of the lithium battery, and reducing the problems of lag and deviation in the existing battery monitoring data; secondly, the flexible sensor for monitoring the temperature and pressure of a lithium battery in the present application is set inside the lithium battery, and the present application sets an elastic layer inside the sensor, and forms a pressing cavity structure through the elastic layer, the pressure sensing part and the conductive substrate, so that the conductive substrate does not directly contact the pressure sensing part. When the lithium battery vibrates or is slightly squeezed due to external operation, the pressure sensing part is in an unloaded state, avoiding the static drift caused by the deformation of the flexible substrate layer, ensuring the accuracy of pressure sensing, and realizing accurate monitoring of the operating status of the lithium battery.

[0017] (2) The flexible sensor for monitoring temperature and pressure of lithium batteries of the present invention controls the parameters of the two flexible base layers, the elastic layer, the interdigitated electrodes, and the conductive substrate, and combines the cavity structure of the elastic layer to achieve stable embedding in the narrow space inside the lithium battery while ensuring the sensitivity and response speed of the sensor temperature and pressure test. The flexible sensor for monitoring temperature and pressure of lithium batteries in this application effectively improves the fit between the sensor and the battery cell structure, reduces the signal noise generated by installation errors or structural stress, achieves high-precision detection of temperature and pressure in different areas inside the battery, and improves the measurement accuracy and stability of the sensor during low-pressure initial response and high-pressure continuous monitoring. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 1 is a schematic diagram of the overall structure of a flexible sensor for monitoring temperature and pressure of a lithium battery in an embodiment of the present invention; Figure 2 1 is a flow chart of a method for preparing a flexible sensor for monitoring temperature and pressure of a lithium battery according to an embodiment of the present invention; Figure 3 Schematic diagram of the preparation process of a flexible sensor for monitoring temperature and pressure of a lithium battery according to an embodiment of the present invention; Figure 4 is a SEM image of platinum metal in an embodiment of the present invention; Figure 5 This is a temperature test diagram of the temperature sensing portion in an embodiment of the present invention; Figure 6 2 is a pressure test diagram of the pressure sensing part in an embodiment of the present invention.

[0018] In all the drawings, the same reference numerals represent the same technical features, specifically: 1. Second flexible base layer; 2. Elastic layer; 3. Conductive substrate; 4. Temperature sensing part; 5. Pressure sensing part. DETAILED DESCRIPTION

[0019] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to illustrate the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0020] In the description of the present invention, it should be understood that, unless otherwise specified, the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as limiting the present invention.

[0021] Furthermore, unless otherwise specified, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Thus, a feature specified as "first" or "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specified.

[0022] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediate medium; internal communication between two components, or interaction between two components, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0023] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0024] Example: See Figures 1 to 6 The flexible sensor for monitoring temperature and pressure of a lithium battery in a preferred embodiment of the present invention includes a first flexible substrate layer and a second flexible substrate layer 1, wherein the first flexible substrate layer and the second flexible substrate layer 1 form an accommodating cavity; an elastic layer 2, which is arranged between the first flexible substrate layer and the second flexible substrate layer 1; and a sensing circuit, which is attached to the side of the first flexible substrate layer facing the elastic layer 2 and has a temperature sensing portion 4 and a pressure sensing portion 5; a conductive substrate 3, wherein the conductive substrate 3 and the pressure sensing portion 5 are aligned and compensated along the thickness direction of the first flexible substrate layer and the second flexible substrate layer 1, and the elastic layer 2 has an opening in the direction opposite to the conductive substrate 3 and the pressure sensing portion 5, so that the conductive substrate 3, the elastic layer 2 and the pressure sensing portion 5 form a pressing cavity. When the substrate contacts the pressure sensing portion 5, the resistance value of the pressure sensing portion 5 changes accordingly.

[0025] The flexible sensor for monitoring the temperature and pressure of a lithium battery in the present application adopts a flexible material as the sensor body, which makes it possible to make the sensor directly inside the lithium battery, and arranges a temperature sensing part 4 and a pressure sensing part 5 on the sensing circuit, thereby realizing the internal temperature and pressure monitoring of the lithium battery, improving the accuracy of the temperature and pressure monitoring of the lithium battery, and reducing the problems of lag and deviation in the existing battery monitoring data; secondly, the flexible sensor for monitoring the temperature and pressure of a lithium battery in the present application is arranged inside the lithium battery, and the present application arranges an elastic layer 2 inside the sensor, and forms a pressing cavity structure through the elastic layer 2, the pressure sensing part 5 and the conductive substrate 3, so that the conductive substrate 3 is not in direct contact with the pressure sensing part 5. When the lithium battery vibrates or is slightly squeezed due to external operation, the pressure sensing part 5 is in a no-load state, avoiding the static drift caused by the deformation of the flexible substrate layer, ensuring the accuracy of pressure sensing, and realizing accurate monitoring of the operating status of the lithium battery.

[0026] It's worth noting that the first and second flexible substrate layers 1 in this application represent the two sides of the flexible sensor. During use, there's no top or bottom surface. For ease of distinction, this application refers to the base structure during sensor fabrication as the first flexible substrate layer, and the top closed structure as the second flexible substrate layer 1. Furthermore, the first and second flexible substrate layers 1 are made of PET (polyethylene terephthalate), a material that can operate normally in temperatures between -200°C and 300°C and exhibits high insulation properties and low dielectric loss. PET does not affect the proper operation of the lithium battery and ensures stable operation of the flexible sensor's internal components. Furthermore, the sensor circuit in this application passes through the bonded boundary between the first and second flexible substrate layers 1 and connects to external data receivers and a power source to ensure signal reception and stable operation.

[0027] Furthermore, as an optional embodiment of the present invention, the sensing circuit in the present application is made of silver paste lead printing, and the pressure sensing part 5 includes a forked electrode, and the conductive substrate 3 is made of a composite of elastic material and conductive filler. Specifically, the pressure sensing part 5 in the present application is a forked electrode, and the forked electrode is a forked structure as a whole, with gaps between the forked structures. The conductive substrate 3 is a composite of elastic material and conductive filler. During the force extrusion process, the conductive substrate 3 is deformed and extruded as a whole, and the conductive network composed of the conductive filler is correspondingly reconstructed, and the ability of carriers to pass through the energy barrier is enhanced. The sensing circuit forms a stable transmission line at the pressure sensing part 5, realizing stable monitoring of the pressure in the extrusion stage, thereby forming a wide range pressure response mechanism of no-load-contact-extrusion.

[0028] Specifically, as an optional embodiment of the present invention, when the flexible sensor for monitoring the temperature and pressure of a lithium battery in the present application is at a first pressure, the conductive substrate 3 and the pressure sensing portion 5 are not in contact, and the pressure sensing portion 5 is in an unloaded state; when the flexible sensor for monitoring the temperature and pressure of a lithium battery is at a second pressure, the conductive substrate 3 and the pressure sensing portion 5 are partially in contact, and the resistance of the pressure sensing portion 5 changes linearly with the contact area between the conductive substrate 3 and the pressure sensing portion 5; when the flexible sensor for monitoring the temperature and pressure of a lithium battery is at a third pressure, the conductive substrate 3 and the pressure sensing portion 5 are in contact, the pressure sensing portion 5 deforms with the pressure change, the conductive network formed by the conductive filler in the conductive substrate 3 is reconstructed, and the conductive substrate 3 and the pressure sensing portion 5 form a stable connection. Here, the first pressure, the second pressure, and the third pressure are all range values. Optionally, the first pressure is 0-10 kPa, the second pressure is 10-40 kPa, and the third pressure is 40-120 kPa.

[0029] Optionally, there are multiple temperature sensing parts 4 and pressure sensing parts 5 in the present application, so that the flexible sensor for monitoring the temperature and pressure of the lithium battery can test the temperature and pressure of different parts of the lithium battery.

[0030] Furthermore, as an optional embodiment of the present invention, the elastic material in the conductive substrate 3 of the present application includes one or more of PDMS (polydimethylsiloxane), PI (polyimide), TPU (thermoplastic polyurethane), or epoxy resin; and the conductive filler includes one or more of carbon black, carbon nanotubes, graphene, and nano-conductive metal materials. Specifically, PDMS, PI, TPU, or epoxy resin have excellent thermal insulation, electrical insulation, corrosion resistance, and mechanical properties, while carbon black, carbon nanotubes, graphene, and nano-conductive metal materials have good conductivity, low percolation concentration, and low cost. A low percolation concentration means that only a small amount of conductive filler is required to achieve conductivity and avoids material hardening or brittleness caused by excessive conductive filler concentration, thus allowing the conductive substrate 3 to possess the elasticity, stretchability, and flexibility of the elastic material matrix.

[0031] Furthermore, as an optional embodiment of the present invention, the temperature sensing portion 4 in the present application is formed by a magnetron sputtering process, and the temperature sensing portion 4 is made of platinum metal. The temperature sensing principle is based on the fact that the thermal vibration of atoms in the metal lattice is enhanced due to the temperature rise, and when the temperature rises, the position vibration of the metal atoms in its lattice becomes more intense, which significantly increases the scattering encountered by free electrons during movement, reduces the average free motion distance of electrons, and thus increases the resistivity, resulting in inaccurate temperature monitoring by the temperature sensing portion 4. Platinum metal has good heat resistance and can work stably at high temperatures. The resistance value below 400°C changes strictly linearly with temperature. At the same time, after the platinum metal is formed by the magnetron sputtering process, the present application also includes a high-temperature annealing process. After the high-temperature annealing process, the defects of the platinum metal are reduced, the grains grow, and its resistivity can be reduced, so as to obtain a uniform and dense platinum metal film with good grain structure, thereby achieving high-precision temperature detection.

[0032] Furthermore, as an optional embodiment of the present invention, the elastic layer 2 in this application has a groove along its outer side in the planar direction, and the groove is filled with electrolyte-resistant glue. The elastic layer 2 is interposed between the first flexible substrate layer and the second flexible substrate layer 1. By filling the groove with electrolyte-resistant glue, the bonding area between the first and second flexible substrate layers 1 is protected from corrosion in the lithium battery electrolyte environment, ensuring the stable operation of the flexible sensor. The elastic layer 2 in this application has a thin sheet-like structure, and the outer side of the elastic layer 2 along the planar direction is the circumferential outer edge of the plane of the elastic layer 2.

[0033] Furthermore, the present application also includes a flexible sensor for monitoring temperature and pressure of a lithium battery, which is used to prepare the flexible sensor for monitoring temperature and pressure of a lithium battery, comprising the following steps: S1, selecting two polyimide films as the first flexible base layer and the second flexible base layer 1 respectively, cleaning and drying the two polyimide films to remove residual impurities on the surfaces of the polyimide films; S2, making a metal mask for the temperature sensing portion 4, and preparing the temperature sensing portion 4 of platinum metal on the first flexible substrate layer by a magnetron sputtering process; S3, adding the conductive polymer composite material to an organic solvent and stirring to obtain a printing slurry; adding the conductive filler to the organic solution and ultrasonically obtaining a suspension, mixing the suspension with the printing slurry and stirring to obtain a conductive polymer composite material slurry; S4. Screen-print silver paste leads and interdigital electrodes serving as the pressure sensing portion 5 on the first flexible substrate layer, and connect the pressure sensing portion 5 and the temperature sensing portion 4 to the silver paste leads, respectively. Screen-print a conductive polymer composite material slurry on the second substrate layer, heat and cure, and obtain a conductive substrate 3. S5. Cut the PET elastic film as the elastic layer 2, use release paper to adhere to both sides of the PET elastic film, and apply electrolyte corrosion-resistant glue circumferentially on the plane of the PET elastic film; use release paper to bond the PET elastic film to the first flexible base layer and the second flexible base layer 1 respectively to obtain a flexible sensor for lithium battery temperature and pressure monitoring.

[0034] Furthermore, as an optional embodiment of the present invention, the magnetron sputtering gas pressure of the magnetron sputtering process in step S2 of the present application is 0.2Pa~0.6Pa, the sputtering power is 80w~160w, the sputtering time is 15min~35min, and the obtained platinum metal thickness is 60nm~200nm.

[0035] Furthermore, as an optional embodiment of the present invention, the temperature sensing part 4 of the platinum metal prepared by the magnetron sputtering process in step S2 of the present application also includes an annealing process, so that the platinum metal is annealed at 200°C~300°C, and the annealing time is 0.5~3h.

[0036] Furthermore, as an optional embodiment of the present invention, the organic solvent in step S3 of the present application includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide. These solvents can dissolve the elastic material, disperse the conductive filler, and adjust the viscosity of the slurry to facilitate screen printing.

[0037] The preparation method of the flexible sensor for lithium battery temperature and pressure monitoring in the present application adopts a magnetron sputtering process to prepare the platinum metal temperature sensing part 4, so that the chemical inertness and the linearity of the resistance change with temperature of the temperature sensing part 4 are significantly better than those of traditional thermocouples and thermistors, achieving high measurement accuracy of the sensor in the range of 0~150℃; secondly, the present application adopts a screen printing process to prepare silver paste leads and interdigitated electrodes, and cooperates with the opening structure of the elastic layer 2 to separate the interdigitated electrodes from the conductive substrate 3, so that the pressure sensing part 5 and the conductive substrate 3 have no contact current at zero load, eliminating the static drift of the sensing parameters caused by the deformation of the two flexible base layers when the lithium battery is shaken, thereby ensuring the stability of the pressure detection parameters; at the same time, in the high-voltage stage, the conductive substrate 3 is squeezed and deformed as a whole, the conductive network composed of the conductive filler is reconstructed, the ability of the carriers to pass through the energy barrier is enhanced, and the sensing pressure is stably detected.

[0038] At the same time, the present application combines the magnetron sputtering process with the screen printing process. Through the design of the magnetron sputtering-annealing-printing-drying steps, the incompatibility between the annealing temperature and the drying temperature, as well as the process problem that the sputtering mask cannot be completely fitted with the substrate, are solved. Specifically, the present application combines the magnetron sputtering process with the screen printing process for the first time. In order to improve the internal defects of the platinum metal film and reduce the resistivity of the platinum metal, the platinum metal after magnetron sputtering needs to be annealed. The present application lowers the platinum metal annealing process temperature and correspondingly extends the annealing time; so that the screen printing process after the platinum metal preparation is not affected. The conventional annealing process temperature is in the range of 300~400℃, while the heating and curing temperature of the silver paste lead and the conductive substrate 3 is around 100℃. This causes the silver paste lead to crack when the silver paste lead is prepared after the annealing process. Therefore, the present application adaptively adjusts the platinum metal annealing temperature and annealing time to ensure the stable formation of the platinum metal, silver paste lead, interdigital electrode, and conductive substrate 3. Secondly, in the conventional flexible sensor preparation process, silver paste wires are usually prepared first, and then connected to other sensing components through the silver paste wires; for this application, this application combines magnetron sputtering with screen printing technology. The thickness of the silver paste wires is usually around 10μm, and the thickness of the mask used for platinum metal preparation is around 100μm. After the silver paste wires are prepared first, the mask is covered on the surface of the flexible substrate layer. The mask cannot be attached to the surface of the flexible substrate layer, and a gap will be generated between the mask and the silver paste wires, resulting in deviations in the shape and size of the platinum metal preparation, affecting the platinum metal's accurate perception of temperature. Therefore, this application adjusts the overall sensor preparation process accordingly, preferentially preparing platinum metal at a set position on the flexible substrate layer, and then forming silver paste wires, interdigitated electrodes, and a conductive substrate 3 through a screen printing process to ensure the preparation accuracy of each component inside the sensor.

[0039] Furthermore, the present application controls the parameters of the two flexible base layers, the elastic layer 2, the interdigitated electrodes, and the conductive substrate 3, and combines the cavity structure of the elastic layer 2 to achieve stable embedding in the narrow space inside the lithium battery while ensuring the sensitivity and response speed of the sensor temperature and pressure test. The flexible sensor for lithium battery temperature and pressure monitoring in the present application effectively improves the fit between the sensor and the cell structure, reduces the signal noise generated by installation errors or structural stress, achieves high-precision detection of temperature and pressure in different areas inside the battery, and improves the measurement accuracy and stability of the sensor during low-pressure initial response and high-pressure continuous monitoring.

[0040] Further, based on the preparation method of the flexible sensor for monitoring temperature and pressure of lithium battery in this application, the SEM image of the temperature sensing part 4 of the prepared platinum metal is as follows: Figure 4 As shown in the figure, it can be seen that the surface of the platinum metal film is dense and has no obvious defects; the temperature test diagram of the temperature sensing part 4 in this application is as shown in FIG. Figure 5 As shown, it can be seen that the temperature sensing portion 4 in this application has a linear change in resistance with temperature within a wide temperature range (20°C~90°C). The change in resistance of the temperature sensing portion 4 can stably reflect the temperature change of the external lithium battery, thereby achieving accurate temperature measurement. The pressure side view of the pressure sensing portion 5 in this application is shown in FIG. Figure 6 As shown, it can be seen that the pressure sensing unit 5 is in an unloaded state within the range of 0-10 kPa, and the shaking of the lithium battery during operation will not cause false alarms from the pressure sensing unit 5; the pressure sensing unit 5 changes linearly within the range of 10-40 kPa, which can accurately reflect the changes in the internal pressure of the lithium battery and realize the monitoring of the lithium battery operation status; and the pressure sensing unit 5 basically maintains a linear relationship within the range of 40-120 kPa, which can basically reflect the internal working conditions of the lithium battery. At the same time, lithium batteries of different sizes and capacities generate different pressures during the charging and discharging process. The present application can adjust the thickness of the two flexible base layers and the elastic layer 2 accordingly to change the pressure sensing range of the pressure sensing unit 5 to meet the monitoring needs of different lithium batteries.

[0041] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A flexible sensor for monitoring temperature and pressure of a lithium battery, characterized in that: include: a first flexible base layer and a second flexible base layer, wherein the first flexible base layer and the second flexible base layer form an accommodating cavity; an elastic layer, the elastic layer being disposed between the first flexible base layer and the second flexible base layer; a sensing circuit, the sensing circuit being attached to a side of the first flexible base layer facing the elastic layer, the sensing circuit comprising a temperature sensing portion and a pressure sensing portion; A conductive substrate is provided, wherein the conductive substrate and the pressure sensing portion are aligned along the thickness direction of the first flexible base layer and the second flexible base layer, the elastic layer is provided with an opening in a direction facing the conductive substrate and the pressure sensing portion, the conductive substrate, the elastic layer and the pressure sensing portion form a pressing cavity, and when the conductive substrate contacts the pressure sensing portion, the resistance value of the pressure sensing portion changes accordingly.

2. The flexible sensor for monitoring temperature and pressure of a lithium battery according to claim 1, characterized in that: The sensing circuit is made by silver paste lead printing, the pressure sensing part includes interdigital electrodes, and the conductive substrate is made by compounding elastic material and conductive filler.

3. The flexible sensor for monitoring temperature and pressure of a lithium battery according to claim 2, characterized in that: When the flexible sensor for monitoring temperature and pressure of a lithium battery is at a first pressure, the conductive substrate is not in contact with the pressure sensing portion, and the pressure sensing portion is in an unloaded state; When the flexible sensor for monitoring temperature and pressure of a lithium battery is at a second pressure, the conductive substrate is in partial contact with the pressure sensing portion, and the resistance of the pressure sensing portion changes linearly with the contact area between the conductive substrate and the pressure sensing portion; When the flexible sensor for monitoring the temperature and pressure of a lithium battery is at a third pressure, the conductive substrate is in contact with the pressure sensing part, the pressure sensing part deforms as the pressure changes, the conductive network formed by the conductive filler in the conductive substrate is reconstructed, and the conductive substrate and the pressure sensing part form a stable connection.

4. The flexible sensor for monitoring temperature and pressure of a lithium battery according to claim 2, characterized in that: The elastic material in the conductive substrate includes one or more of PDMS, PI, TPU or epoxy resin; The conductive filler includes one or more of carbon black, carbon nanotubes, graphene, and nano-conductive metal materials.

5. The flexible sensor for monitoring temperature and pressure of a lithium battery according to claim 1, characterized in that: The temperature sensing portion is formed by adopting a magnetron sputtering process, and the temperature sensing portion is made of platinum metal.

6. The flexible sensor for monitoring temperature and pressure of a lithium battery according to claim 1, characterized in that: The elastic layer has a groove on the outer side along the plane direction, and the groove is filled with electrolyte corrosion-resistant glue.

7. A method for preparing a flexible sensor for monitoring temperature and pressure of a lithium battery, characterized in that: The steps include: S1, selecting two polyimide films as the first flexible base layer and the second flexible base layer, respectively, cleaning and drying the two polyimide films to remove residual impurities on the surfaces of the polyimide films; S2, preparing a metal mask for the temperature sensing portion, and preparing a temperature sensing portion of platinum metal on the first flexible substrate layer by a magnetron sputtering process; S3, adding the conductive polymer composite material to an organic solvent and stirring to obtain a printing slurry; Adding a conductive filler to an organic solution, ultrasonically obtaining a suspension, and mixing the suspension with a printing slurry to obtain a conductive polymer composite material slurry; S4. Screen-printing silver paste leads and interdigitated electrodes serving as pressure sensing portions on the first flexible substrate layer, connecting the pressure sensing portion and the temperature sensing portion to the silver paste leads, respectively; screen-printing a conductive polymer composite material slurry on the second substrate layer, and heating and curing the slurry to obtain a conductive substrate; S5. Cut the PET elastic film as the elastic layer, use release paper to adhere to both sides of the PET elastic film, and apply electrolyte corrosion-resistant glue circumferentially on the plane of the PET elastic film; use release paper to bond the PET elastic film to the first flexible base layer and the second flexible base layer respectively to obtain a flexible sensor for lithium battery temperature and pressure monitoring.

8. The method for preparing a flexible sensor for monitoring temperature and pressure of a lithium battery according to claim 7, characterized in that: In the magnetron sputtering process in step S2, the magnetron sputtering gas pressure is 0.2 Pa to 0.6 Pa, the sputtering power is 80 W to 160 W, the sputtering time is 15 min to 35 min, and the thickness of the platinum metal is 60 nm to 200 nm.

9. The method for preparing a flexible sensor for monitoring temperature and pressure of a lithium battery according to claim 7, wherein: After the temperature sensing portion of the platinum metal is prepared by the magnetron sputtering process in step S2, an annealing process is also included, and the platinum metal is annealed at 200° C. to 300° C.

10. The method for preparing a flexible sensor for monitoring temperature and pressure of a lithium battery according to claim 7, wherein: The organic solvent in step S3 includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide.

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