Off-electric multi-mode thin film sensor and lithium battery

Abstract

The invention provides an ionizing multi-mode thin film sensor comprising an electrode layer which is provided with a first substrate layer and a plurality of interdigital electrode units which are arranged in a periodic array; the functional layer is provided with a second substrate layer and a sensitive film; the sensitive film is made of a flexible ionic polymer material, and the surface of the sensitive film is provided with a plurality of microstructure regions arranged at intervals; in the electrode layer, a part of the interdigital electrode units and a micro-structure area which is correspondingly arranged on the sensitive film form a pressure detection unit with a solid-gas-solid interface, and the rest of the interdigital electrode units and other areas except the micro-structure area on the sensitive film form a temperature detection unit with a solid-solid interface; the pressure detection units and the temperature detection units are alternately arranged at intervals. According to the invention, the influence of the temperature on the pressure is eliminated through in-situ decoupling, the adaptability of the film sensor in different environments is improved, and multi-mode detection of the pressure and the temperature is also realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pressure detection, in particular to a kind of off-electricity film sensor pressure detection technology. BACKGROUND

[0002] Lithium-ion battery (referred to as "lithium battery") as the core technology of efficient energy storage, plays a key role in electric vehicles, smart grid and distributed energy systems and other new energy applications. Battery state and safety detection is crucial for lithium battery, it not only ensures the safety of lithium battery in use, prevent overcharge, overdischarge and thermal runaway and other risks, but also effectively prolongs the battery life, optimizes performance, improves efficiency.

[0003] Due to the whole lithium battery system is complex electro-thermal-mechanical coupling inhomogeneous electrochemical reaction, lithium battery will produce local heat accumulation, stress concentration and electrochemical reaction rate difference during operation. These inhomogeneous phenomena may induce electrode material structure damage, electrolyte decomposition or electrode swelling and other failure mechanisms, ultimately affect the safety and cycle stability of lithium battery. Existing literature shows that there is a change in swelling pressure of lithium battery during charging and discharging, which is due to the lithium extraction and lithium intercalation process between the positive and negative electrodes of the battery, indicating that the change in swelling pressure of lithium battery is related to the internal electrochemical state of the battery. Battery state estimation and safety detection through mechanical signals can effectively solve the limitations and difficulties of the above-mentioned conventional methods, and studies have shown that the battery state (mainly including the state of charge (SOC) and the state of health (SOH)) has a stronger corresponding relationship with the mechanical signal, and the use of mechanical signal can realize early warning more than 500s than the traditional detection method.

[0004] At present, the swelling pressure detection of lithium battery is mainly realized by the film pressure sensor attached to the surface of the battery cell. Most of the film pressure sensors use high molecular materials to make sensitive materials. Due to the inherent characteristics of high molecular materials, they are sensitive to temperature changes. Therefore, on the one hand, the pressure signal output by the film pressure sensor is disturbed by the temperature of the environment, and will inevitably contain temperature signal and other interference components; on the other hand, due to the temperature response sensitive characteristics, it will also cause the output signal of the sensor to fluctuate, and the anti-interference ability is insufficient, which is not conducive to long-term and stable swelling pressure monitoring. SUMMARY

[0005] To solve the above problems, the present application provides an off-electricity multi-modal film sensor and a lithium battery, and the specific scheme includes the following aspects: The first aspect of the present application discloses an off-electricity multi-modal film sensor, comprising: an electrode layer having a first substrate layer and a plurality of periodically arrayed interdigital electrode units formed on the first substrate layer; a functional layer having a second substrate layer and a plurality of sensitive films formed on the second substrate layer; the sensitive films are flexible ionic polymer materials, and surfaces of the sensitive films are configured to have a plurality of microstructure regions arranged at intervals; the surfaces of the microstructure regions are configured to have a periodic array of repetitive micro-protrusion units; In the electrode layer, part of the interdigital electrode units and the microstructure regions arranged in direct correspondence on the sensitive films form pressure detection units having solid-gas-solid interfaces, and the remaining interdigital electrode units and other regions on the sensitive films form temperature detection units having solid-solid interfaces; the pressure detection units and the temperature detection units are arranged alternately at intervals.

[0006] The second aspect of the present application discloses an electrostatically driven multi-modal thin film sensor, comprising: an electrode layer having a first substrate layer and a plurality of interdigital electrode units arranged in a periodic array on the first substrate layer; a functional layer having a second substrate layer and a plurality of sensitive films formed on the second substrate layer and arranged in direct correspondence with the interdigital electrode units respectively; the sensitive films are flexible ionic polymer materials of the same kind, and surfaces of part of the sensitive films are configured to have a periodic array of repetitive micro-protrusion units; In the electrode layer, part of the interdigital electrode units and the sensitive films having the repetitive micro-protrusion units form pressure detection units having solid-gas-solid interfaces, and the remaining interdigital electrode units and the remaining sensitive films form temperature detection units having solid-solid interfaces; the pressure detection units and the temperature detection units are arranged alternately at intervals.

[0007] Optionally, the pressure detection units have the same geometric parameters; the temperature detection units have the same geometric parameters.

[0008] Optionally, the pressure detection units and the temperature detection units have the same geometric parameters.

[0009] Optionally, the array is any one of a rectangular array, a ring array, a staggered array, and a honeycomb lattice array.

[0010] Optionally, the top of the micro-protrusion unit is a planar or approximately planar structure.

[0011] Optionally, the micro-protrusion unit is a circular truncated cone, a prismatic truncated cone, a circular cylinder, a prismatic cylinder, or a hemispherical structure; preferably, the micro-protrusion unit is a circular truncated cone, a prismatic truncated cone, or a hemispherical structure.

[0012] Optionally, the flexible ionic polymer is any one of an ionic gel, an ionic rubber, and a polyionic polymer material.

[0013] Optionally, the ionic gel is selected from any one of polyvinyl alcohol-borate gel, polyacrylate-ionic liquid composite gel; the ionic rubber is selected from any one of polyurethane-based ionic rubber, styrene block copolymer-based ionic elastomer, siloxane-based ionic conductive elastomer; the polyionic polymer material is selected from any one of polystyrene sulfonate sodium, polyacrylic acid sodium, polyethyleneimine.

[0014] The third aspect of the present application discloses a distributed pressure detection method, based on the ionic multi-modal film sensor of the first aspect of the present application and any one of the optional solutions, the electrical signal output by the temperature detection unit is used to represent temperature change, the electrical signal output by the pressure detection unit is decoupled by the electrical signal output by the temperature detection unit and is used to represent pressure change, comprising: The temperature signal output by each pressure detection unit is calculated based on formula (1): (1); The pressure signal output by the temperature detection unit is calculated based on formula (2): (2); The real pressure of each pressure detection unit after decoupling is calculated based on formula (7): is expressed as: , (7); In the formula, represents the system error or noise in the pressure detection unit signal, represents the system error or noise in the temperature detection unit signal, and the function represents the fitting function obtained from the calibration experiment of the pressure detection unit, represents the fitting function obtained from the calibration experiment of the temperature detection unit, represents the mapping relationship of and , represents the mapping relationship of and n represents the number of temperature detection units around the pressure detection unit to be decoupled.

[0015] Optionally, the electrical signal output by the temperature detection unit is used to represent temperature change, and the electrical signal output by the pressure detection unit is decoupled by the electrical signal output by the temperature detection unit and is used to represent pressure change, wherein, The temperature signal output by the pressure detection unit is expressed as: (1); The pressure signal output by the temperature detection unit is expressed as: (2); the real pressure of the pressure detection unit after decoupling is expressed as: , In the formula, represents the system error or noise in the pressure detection unit signal, represents the system error or noise in the temperature detection unit signal, the function represents the fitting function obtained from the calibration experiment of the pressure detection unit, represents the fitting function obtained from the calibration experiment of the temperature detection unit, represents the mapping relationship of the pressure detection unit and the temperature detection unit, and T, the mapping relationship of is inversely deduced , represents the mapping relationship of the pressure detection unit and the temperature detection unit, represents the mapping relationship of the pressure detection unit and the temperature detection unit, n represents the number of equidistant temperature detection units around the pressure detection unit required for decoupling.

[0016] The third aspect of the present application discloses a lithium battery, comprising a battery cell, and the outer surface of the battery cell is integrated with the off-electric multi-modal thin film sensor according to the first aspect of the present application and any one of the optional solutions.

[0017] Optionally, the off-electric multi-modal thin film sensor is attached to the outer surface of the battery cell through the first base layer or the second base layer.

[0018] Optionally, the first base layer or the second base layer of the off-electric multi-modal thin film sensor is a packaging layer of the outer surface of the battery cell, and the packaging layer is an aluminum-plastic composite film or a polymer insulating film.

[0019] The present application has the following beneficial effects: (1) The thin film pressure sensor commonly used is mostly made of high molecular material as the sensitive material, and due to the inherent characteristics of the high molecular material, it is sensitive to temperature changes. The present application just takes advantage of this feature, combines the pressure and temperature double-sensitive mechanism of the "ion-electron" double electric layer, and through a special structure designed thin film sensor, skillfully uses the characteristics of the sensitive material, eliminates the influence of temperature on pressure through in-situ decoupling, not only improves the adaptability of the thin film sensor in different environments, realizes accurate pressure detection, and at the same time realizes accurate temperature detection.

[0020] (2) The off-electric multi-modal thin film sensor disclosed in the present application, based on the pressure and temperature double-sensitive mechanism of the "ion-electron" double electric layer, can provide high spatial resolution and high sensitivity real-time detection capability on two key variables of pressure and temperature, and realize multi-parameter detection of pressure and temperature.

[0021] (3) The microstructure of the sensitive film surface of the present application is optimized in the electrically isolated multi-modal thin film sensor, which can reduce the stress concentration at the top of the microstructure, effectively reduce the plastic deformation at the top under high pressure, and enable the thin film sensor to maintain structural stability under high pressure, improve the high repeatability of detection under high pressure, and be suitable for the needs of high pressure environment of the battery, and improve the service life of the thin film sensor.

[0022] (4) The electrically isolated multi-modal thin film sensor disclosed in the present application is based on the ultra-thin design of the pressure-temperature sensing structure integration, which can be attached to the surface of the battery cell, or directly use the outermost layer of the cell as the sensor base layer, realize integrated integration, and realize effective sensing and early warning of the complex electric-thermal-force state change in the battery through accurate detection of pressure-temperature multi-parameters. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 Fig. (a) and (b) are two schematic diagrams of detection unit arrangement, wherein 11 is a pressure detection unit, and 12 is a temperature detection unit.

[0024] Figure 2 Fig. is a structural schematic diagram of a multi-modal thin film sensor, wherein A is a pressure detection unit, B is a temperature detection unit, 1 is a base layer, 21 is an electrode unit corresponding to the pressure detection unit, 22 is an electrode unit corresponding to the temperature detection unit, and 3 is a sensitive film.

[0025] Figure 3 Fig. is a structural change schematic diagram of a pressure detection unit and a temperature detection unit under the action of external force; wherein A is a pressure detection unit, B is a temperature detection unit, 1 is a base layer, 21 is an electrode unit corresponding to the pressure detection unit, 22 is an electrode unit corresponding to the temperature detection unit, and 3 is a sensitive film.

[0026] Figure 4 Fig. is a structural change schematic diagram of different microstructures before and after pressure.

[0027] Figure 5 Fig. is a repetitive pressure test curve schematic diagram under high pressure environment, wherein ADM represents signal amplitude. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0029] In the description of the present application, if the terms indicating the orientation or positional relationship such as "upper", "lower", "inner", "outer", "top", "bottom" and the like appear, they are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, if the terms such as "first", "second" and the like appear, they are used to distinguish similar objects, and do not necessarily be used to describe a particular order or relative importance. For those skilled in the art, the specific meaning of the above terms in the present application can be understood in combination with the specific circumstances. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, but can include other elements not clearly listed or inherent to these products or devices.

[0030] The embodiment of the present application proposes a multi-modal thin film sensor (referred to as "sensor" for short), which can be designed into an array type sensing structure and includes a plurality of periodically arrayed detection units. The array form of the detection units can be a common array form such as a rectangular array, a ring array, a staggered array or a honeycomb lattice array. The detection units at least include two kinds of pressure detection units or temperature detection units, and the pressure detection units and the temperature detection units are alternately and spacedly arranged.

[0031] It is worth noting that the pressure detection units or the temperature detection units are arranged in an alternating manner, which is beneficial to in-situ decoupling on the one hand and can also realize distributed detection of temperature and pressure on the other hand. Since it is necessary to realize in-situ rejection of the influence of temperature on pressure, it is necessary to accurately obtain the influence of temperature on the pressure detection point as much as possible, that is, the temperature detection unit needs to be as close as possible to the pressure detection unit which needs to be decoupled to avoid the influence of uneven temperature distribution on detection accuracy, and therefore the temperature detection unit is usually arranged adjacent to the pressure detection unit for detecting the influence of temperature. In addition, the alternating arrangement of the temperature detection units and the pressure detection units can also realize distributed detection of temperature and pressure signals.

[0032] It is also noted that the geometric parameters of the temperature detection units and the pressure detection units in the sensor do not require consistency, as long as the materials of the sensitive films are the same, the geometric parameters of all the temperature detection units are consistent, and the geometric parameters of all the pressure detection units are consistent. The geometric parameters include shape and size, that is, the temperature detection units and the pressure detection units can be the same shape but different sizes, or different shapes but the same area, or different shapes and different sizes, and the present application does not limit this. However, as a preferred scheme, the temperature detection units and the pressure detection units can be designed to have the same geometric parameters in appearance to facilitate manufacturing and decoupling calculation.

[0033] As Figure 1As shown, in one embodiment, the pressure detection units 11 and the temperature detection units 12 are all regular triangular structures of the same size and arranged in a honeycomb lattice array. In another embodiment, the pressure detection units 11 and the temperature detection units 12 are all rectangular structures and arranged in a rectangular array.

[0034] Both the pressure detection units and the temperature detection units are composed of an electrode layer and a functional layer, and are of a double-layer interdigital electrode structure. The functional layer substrate and the electrode substrate can be made of the same material or different materials, for example, polyethylene terephthalate (PET), polyimide (PI), polypropylene (PP), cast polypropylene (CPP), polydimethylsiloxane (PDMS), etc. The thickness of the polymer flexible material is usually 50-150 um.

[0035] The electrode layer includes an electrode substrate and a plurality of periodically arrayed interdigital electrode units formed on the electrode substrate. The interdigital electrode units can be made of copper, silver or other metal materials.

[0036] It is worth noting that in the present application, all the interdigital electrode units have the same shape and size (finger width, pitch, length) and are periodically arrayed. The overall arrangement of the detection units is determined by the arrangement of the interdigital electrode units in the electrode layer. The interdigital electrode units in the electrode layer are not functionally distinguished, and whether they are used for pressure detection or temperature detection is determined by the sensitive film used therewith.

[0037] As for the size of each detection unit and the pitch (i.e. the arrangement period) of adjacent detection units, the overall arrangement should be as dense as possible, and the coverage area should be as large as possible. However, due to the precision and cost of additive manufacturing process, in the commonly used solution, for example, in a rectangular array, the detection units are square or rhombic with a side length of 8-10 mm, or circular with a diameter of 8-10 mm, and the pitch of adjacent detection units is 3-5 mm.

[0038] The functional layer includes a functional layer substrate and a sensitive film formed on the substrate. The sensitive film can be made of flexible ionomer, ion rubber, polyion high polymer material, etc. These flexible ionomers can provide stable ion conduction paths by introducing charged groups, and have excellent ion conductivity and mechanical flexibility. It can be understood that the surface of the lithium battery expands non-uniformly, and therefore the use of flexible materials has better ductility and adaptability, and the detection effect will be better.

[0039] The ion gel can be selected from polyvinyl alcohol-borate gel, polyacrylate-ion liquid composite gel and the like; the ion rubber can be selected from polyurethane-based ion rubber (such as PU-LiTFSI composite), styrene block copolymer-based ion elastomer (such as SEBS-IL), siloxane-based ion conductive elastomer (such as PDMS-EMIMTFSI composite) and the like; and the polyion polymer material can be selected from polystyrene sulfonate sodium (PSS), polyacrylic acid sodium (PAA-Na) and polyethyleneimine and the like.

[0040] In combination with Figure 2 As shown in the figure, for the pressure detection unit, a microstructure needs to be prepared on the surface of the region corresponding to the sensitive film, forming a plurality of independent microstructure regions, so that a cavity is formed between the sensitive film and the electrode at the position of the pressure detection unit, thereby forming a solid-gas-solid interface (referred to as "solid-gas-solid interface"). With the change of pressure, the contact area between the sensitive film and the electrode changes.

[0041] In combination with Figure 2 As shown in the figure, for the temperature detection unit, the functional layer and the electrode layer are in direct contact. Since the surface of the region corresponding to the sensitive film of the temperature detection unit is a flat interface, the sensitive material and the electrode are in close contact, forming a solid-solid interface (referred to as "solid-solid interface"). As can be seen, the surface of the sensitive film is actually composed of a plurality of arrayed microstructure regions and flat regions (i.e., planar structures) outside the microstructure regions. When the external pressure changes, the contact area between the sensitive film and the electrode does not change.

[0042] After the electrode layer and the functional layer are prepared, the functional layer is fixed on the surface of the electrode layer by external packaging, for example, using double-sided tape to attach the four sides of the functional layer to the electrode layer. In the finally formed multi-modal thin film sensor, the temperature detection unit is not sensitive to pressure, but temperature changes will affect the ion migration rate, conductivity and the like in the sensitive film, so this part only responds to temperature changes.

[0043] It is worth noting that in the above embodiment, the sensitive film is a whole film formed on the substrate layer, and the region corresponding to the pressure detection unit in the sensitive film is prepared with a microstructure. In another optional embodiment, the sensitive film can also be a plurality of independent units, i.e., each pressure detection unit has a relatively independent sensitive film, and the surface of this part of the sensitive film has a microstructure. Correspondingly, the temperature detection unit also has a plurality of relatively independent sensitive films, and the surface of this part of the sensitive film is a flat structure. In this embodiment, screen printing, coating, inkjet printing, dip coating and the like can be used to directly prepare the corresponding sensitive film on the interdigital electrode unit. After preparation, the substrate layer is attached to the surface of the electrode layer by double-sided tape. As can be seen, in the present application, the sensitive film can be a whole film or a plurality of independent films.

[0044] It is worth mentioning that the swelling force detection of lithium battery is crucial for mechanical stability evaluation, and the temperature of lithium battery is directly related to thermal safety. Synchronous temperature monitoring is a double guarantee for preventing thermal runaway and optimizing thermal management, but traditional thin film pressure sensors can usually only measure single pressure data. Due to the development trend of small or lightweight design of lithium battery, the requirements for the size and installation space of lithium battery are extremely strict, so it is difficult to integrate other types of sensors on the surface of the battery cell, which limits the comprehensive evaluation of the overall state of the battery, and it is difficult to obtain multi-dimensional information related to the safety and performance of the battery in real time.

[0045] At present, in the monitoring of battery thermal management, the detected tab temperature is usually taken as the actual temperature of the lithium battery. However, this method has obvious defects. On the one hand, the tab temperature is a metal conductive tab extending from the positive and negative current collectors, located on the outside of the battery cell, so its position is not the dominant area of electrochemical reaction. On the other hand, the temperature change signal of the battery cell needs to be transmitted through heat conduction to reach the tab, resulting in strong response hysteresis and difficulty in timely reflecting early signs of local thermal runaway. In addition, the tab temperature also has non-negligible heat loss and signal attenuation during heat conduction, further limiting its detection accuracy and response speed.

[0046] In the overall design of the device, the temperature detection unit and the pressure detection unit are prepared at the same time using the same material system, only with structural differences. When pressed, the pressure detection unit changes the contact area between the microstructure area and the electrode under the action of pressure due to the existence of the microstructure. In the temperature detection unit, the contact area between the sensitive film and the electrode does not change with the change of pressure. The surface of the sensitive film, the corresponding area of the temperature detection unit remains flat to improve the specificity and stability of the temperature response; the corresponding area of the pressure detection unit constructs a microstructure to regulate the contact area and the change of capacitance, realizing high-sensitivity pressure response. The present application realizes regional differentiation molding through the microstructure area of the surface of the functional layer, providing a multi-modal and high-integration sensing function basis for the device. Moreover, the temperature detection unit attached to the surface of the battery cell can directly detect the temperature of the battery cell surface, which well overcomes the problems of low detection accuracy and slow response speed caused by tab temperature detection.

[0047] It should be particularly pointed out that the thin film sensor provided by the present application is based on the principle of electric double layer, under the action of external pressure, the electric double layer capacitance changes significantly, the nanoscale spacing between the charge layers (the effective spacing between the charge layers during the formation of the electric double layer capacitance is usually in the nanoscale), so that the sensor has ultra-high sensitivity. Therefore, under the action of external pressure, the contact area of the sensitive material and the electrode will change, which also causes the capacitance of the sensor to change significantly, so that the sensor has strong sensitivity for pressure detection, and the output capacitance is also high, and it also has high anti-interference ability. At the same time, the temperature change will also affect the ion mobility, dielectric constant, conductivity and other characteristics of the electric double layer material, and has high sensitivity to the electric double layer capacitance. Therefore, the sensor also has high sensitivity for temperature detection.

[0048] For the pressure detection unit, the microstructure on the surface of the functional layer is in contact with the electrode in the conventional state, and the microstructure does not deform. But under the action of external pressure, the microstructure deforms, causing the whole sensitive film to reversibly compress, and at the same time, the contact area between the microstructure on the surface and the electrode below changes significantly. The microstructure is specifically composed of a plurality of repetitive micro-protrusion units, that is, the shape and size of each micro-protrusion unit are consistent. And these micro-protrusion units are arranged in a periodic array. Under the action of pressure, the contact area between the micro-protrusion units in the microstructure and the electrode increases, which promotes the increase of the local capacitance, thereby causing the change of the electric signal output by the sensor.

[0049] As a preferred scheme, the geometric morphology of the micro-protrusion unit can be a circular truncated cone, a prismatic truncated cone, a prism, a cylinder, a hemisphere and the like. The adoption of these structures makes the top of the micro-protrusion unit be a plane (the top surface corresponding to the circular truncated cone, the prismatic truncated cone, the prism and the cylinder) or an approximately plane (the arc surface of the hemisphere). Under the action of external pressure, the contact area between the microstructure on the surface of the sensitive film and the electrode will be dynamically adjusted with the change of pressure, thereby causing the change of the capacitance signal. It should be noted that the hemisphere referred to by the present application includes not only the standard hemisphere whose thickness from the top to the bottom is equal to the radius of the hemisphere, but also the approximate hemisphere whose thickness from the top to the bottom is less than the radius of the sphere.

[0050] It is worth mentioning that sharp structures such as pyramids or cones have extremely small initial contact areas, and the contact area increases rapidly under pressure, which is prone to stress concentration and irreversible deformation, resulting in nonlinear response curves and poor repeatability. Microstructures of different morphologies can change their contact areas during loading, but the controllability, linearity and repeatability of their change behaviors differ significantly. Among them, the top surface of the round table shape, the prism table shape and the hemisphere shape structure has a flat structure at the top, and when pressed, it can realize a uniform fitting process from the center to the outside, and the contact area gradually expands with the pressure, the change process is smooth, linear and predictable, and the repeatability is better, and it shows better structural stability and deformation consistency during multiple loading-unloading cycles, which helps to improve the durability and signal repeatability of the sensor, and is suitable for building high-sensitivity and high-stability pressure sensors. The contact area of the cylinder and the prism will also change during loading, but the change rate is usually slow, and the contact behavior is greatly affected by the boundary effect, and the stability and sensitivity are not as good as the round table, prism and hemisphere structure. Therefore, the application preferably uses round table shape, prism table shape and hemisphere shape microstructure as the basic structure of the micro-protrusion unit, which can effectively regulate the electrode contact area and has excellent structural stability and deformation consistency, maintains the high repeatability of the electrical signal output in multiple loading-unloading cycles, and significantly improves the device performance and long-term use reliability.

[0051] In one specific embodiment, the micro-protrusion unit is selected as a round table shape structure, the bottom diameter of the round table shape structure is 100-500 um, the top diameter is 20-200 um, the height is 50-300 um, and the distance (i.e. period) between adjacent round table shape structures is controlled at 100-600 um. The thickness of the electrode layer is 100-150 um, the thickness of the functional layer is 50-100 um, and the overall thickness is 150-250 um.

[0052] The preparation of the surface microstructure of the functional layer can be based on the required geometric morphology and material properties, and a variety of micro-nano processing techniques can be selected to obtain a high-repeatability, regularly arranged and functional integrated micro-protrusion structure array. Common methods include 3D printing, photoetching-reverse mold replication and local imprinting reconstruction, etc.

[0053] In which, by using 3D printing technology, combining with the preset geometric model and functional slurry, the regular structure with specific topography and size parameters of flat or gentle slope top can be directly constructed on the flexible substrate, especially suitable for circular truncated cone microstructure. The photoetching-reverse mold replication process can realize large-area and high-consistency microstructure array replication by patterning the microstructure template in the photoresist layer and then copying and transferring the elastic material (such as PDMS), which is suitable for batch manufacturing of small microstructures with uniform features. For the primary microstructure with sharp features (such as cone, pyramid, etc.) on the top, further secondary reconstruction methods such as hot pressing or mechanical imprinting can be used to shape the sharp end region into a flat top structure by applying directional pressure to the local area with a prefabricated planar template, so as to improve the stability and loading repeatability of the electrode contact.

[0054] To realize the differential design of local microstructure and flat area in the sensitive film, the present application adopts a regionally selective preparation strategy. Taking photoetching-reverse mold replication and 3D printing as an example, during the patterning and reverse molding or printing process, pattern mask, limited printing area or local coating are used to form microstructure only in the pressure detection area, while the temperature detection area remains as a continuous flat surface without pattern. For the whole piece of pre-processed sensitive material, local pressure imprinting technology can also be used to flatten the specified area (temperature sensing area) on the existing microstructure surface, so as to realize the accurate coexistence of microstructure and flat area on the same piece of material. The above method has the advantages of strong process universality, high processing precision and good structure consistency, and is suitable for the integrated construction of flexible multi-modal sensors.

[0055] Since the same sensitive material and interdigital electrode unit with the same geometric parameters (i.e. uniform shape and size) are used, the capacitance response of the pressure detection unit and the temperature detection unit is affected by temperature and the degree of influence is basically the same, so the signal measured by the temperature detection unit can compensate the signal output by the pressure detection unit, reducing the influence of the change of the electrical properties of the sensitive material on the accuracy of pressure sensing. The output of the temperature detection unit can be used as a reference signal to evaluate the influence of environmental temperature change on the electrical properties (such as dielectric constant, ion mobility, etc.) of the sensitive material in real time, so as to dynamically compensate the temperature interference component in the output of the pressure detection unit. This self-compensation mechanism does not require additional materials or structures, and only through the adjacent temperature unit can realize in-situ calibration, effectively reducing the influence of the fluctuation of the intrinsic electrical properties of the sensitive material on the pressure sensing accuracy, and improving the reliability and measurement consistency of the system in complex thermal environment.

[0056] The pressure detection unit and the temperature detection unit output independent capacitance signals. The temperature detection unit has a flat surface corresponding to the sensitive film region and the sensitive material directly contacts the electrode. The contact area between the functional material and the electrode does not change under external force. Therefore, the temperature detection unit is not affected by mechanical stress and does not respond to external pressure changes. The output capacitance change is only related to temperature, and thus can be used as a reference for temperature changes.

[0057] The pressure detection unit is made of sensitive material, and its electrical properties fluctuate with changes in ambient temperature, resulting in the inevitable superposition of temperature response components in the output signal of the pressure detection unit. Therefore, although the pressure detection unit is mainly used to sense external pressure, its output signal is still affected by changes in electrical properties caused by temperature. The temperature detection unit eliminates the pressure response mechanism in its structure and is only sensitive to temperature changes. Therefore, the output capacitance change of the temperature detection unit can be considered as a pure response of the material to temperature. Based on this characteristic, the output signal of the temperature detection unit can be used as a reference input to compensate and correct the capacitance drift caused by temperature in the pressure detection unit, thereby decoupling the true pressure response signal. It can be understood that the geometric parameters of the temperature detection unit and the pressure detection unit are not necessarily consistent, but since the materials of the sensitive films are the same, the relationship between temperature and pressure can be known through calibration.

[0058] To effectively decouple the pressure and temperature signals, a multi-point calibration experiment can be performed under specific environmental conditions. The experiment is performed in a constant temperature control environment, and multiple representative temperature points (for example, 25°C, 35°C, 45°C, 55°C, etc.) are selected. At each temperature condition, a series of known pressures (for example, from 0 to 1.5 MPa in stages) are applied in turn, and the capacitance response values of the pressure detection unit and the temperature detection unit are recorded synchronously. By establishing a complete capacitance response matrix in the two-dimensional temperature-pressure parameter space, the influence trend of temperature on the pressure response curve can be revealed.

[0059] During the experiment, the temperature can be controlled by a thermostat or a hot table system, and the pressure loading can be performed by a static weight loading system, a piezoelectric loading platform, or a standard material testing machine to ensure the accuracy and repeatability of data acquisition. Through multivariate fitting analysis (such as quadratic polynomial, polynomial regression, or neural network fitting) of the multiple sets of capacitance-temperature-pressure data obtained from the experiment, a mathematical relationship model (referred to as a "calibration model") describing the joint response of capacitance change to temperature and pressure can be constructed. The calibration model can be used as a basis for dynamic compensation in actual use to extract the influence of temperature interference on the output of the pressure detection unit, and to compensate the pressure response signal according to the real-time acquired temperature signal in actual application, to eliminate the capacitance drift caused by temperature changes, thereby extracting the effective signal component corresponding to the pressure change and realizing independent sensing of pressure and temperature.

[0060] Specifically, a specific pressure is applied to the distributed sensor, placed at a specific temperature, and then each detection unit is calculated respectively. The real-time collected temperature signal can be input into the calibration model to predict the interference amount of temperature on pressure detection, and the interference signal can be removed from the original signal of the pressure detection unit, so as to realize temperature compensation and independent decoupling of pressure response. The calibration model effectively improves the signal stability and response accuracy of the sensor in the multi-physical field coupling environment through the decoupling and compensation mechanism, and is especially suitable for flexible sensing application scenarios with complex temperature control or significant thermal-mechanical interaction.

[0061] It can be understood that the compensation mechanism is one of the effective methods to realize the decoupling mechanism. Here, the pressure and temperature jointly affect the capacitance signal, the temperature component is obtained through the temperature detection unit, and then it is removed from the output signal of the pressure detection unit. Essentially, the signal decoupling of temperature and pressure is realized through compensation.

[0062] The present application utilizes the pressure-temperature dual-sensitive mechanism of the "ion-electron" double electric layer, and through different sensing structure designs, the temperature detection unit measures the electrical properties of the ion material in real time and brings it into the pressure detection unit, so as to reduce the influence of the change of the electrical properties of the ion material caused by temperature change on the pressure signal output, and realize accurate pressure-temperature dual-mode detection through in-situ compensation.

[0063] In the present application, the pressure detection unit and the temperature detection unit use the same sensitive material, and the capacitance responses of the pressure detection unit and the temperature detection unit are both affected by temperature, and the temperature response effects are basically the same. Under different known temperatures T and pressures P, the response models of the pressure detection unit and the temperature detection unit are constructed respectively.

[0064] The actual capacitance signal output by each pressure detection unit Affected by pressure and temperature, it is represented as follows: (1) The capacitance signal output by each temperature detection unit Affected only by temperature, it is represented as follows: (2) In actual use, by collecting and data pairs, the real pressure is solved by decoupling the pressure. That is, the temperature part in is corrected by .

[0065] Since the pressure detection unit and the temperature detection unit use the same sensitive material and have similar temperature response characteristics, the output of the temperature detection unit It can be used to estimate the current ambient temperature T: (3) It should be noted that the temperature sensing unit selected here is usually the one closest to the pressure sensing unit that needs to be decoupled. When there are multiple temperature sensing units within the same distance, the ambient temperature T required to decouple the pressure sensing unit can be the average of the output signals of these multiple equidistant temperature sensing units. Therefore, the current ambient temperature T may be the output signal of a single temperature sensing unit, or it may be the average of the output signals of multiple temperature sensing units, expressed as: (4) Assuming there are n temperature sensing units equidistant from the pressure sensing unit requiring decoupling, the current ambient temperature output by the i-th temperature sensing unit... It is expressed as follows: in, , (5) Furthermore, by using equations (1) and (2) and combining them with real-time compensation for temperature interference in the pressure detection unit signal caused by ambient temperature T, the decoupled true pressure is obtained. It is expressed as follows: (6) Right now: (7) If there are multiple temperature detection units within the same distance, the decoupled actual pressure It is expressed as follows: In the above formula, This indicates systematic error or noise in the pressure detection unit signal. The function represents the systematic error or noise in the temperature detection unit signal. This represents the fitting function obtained from the calibration experiment of the pressure detection unit. This represents the fitting function obtained from the calibration experiment of the temperature detection unit. Indicates that from known And the reverse deduction of 𝑇 The mapping relationship, Indicates that from known The mapping relationship of 𝑇 can be deduced by reverse deduction.

[0066] The output capacitance of the pressure detection unit was collected under different known temperature and pressure conditions. Build The response model. In practical applications, the output of the pressure detection unit measured in real time is used. Value and temperature detection unit output The current real pressure is obtained by backstepping the model , that is, to realize pressure decoupling detection under temperature interference compensation.

[0067] The multi-modal thin film sensor attached to the surface of the lithium battery can respond to the pressure change in the charging and discharging process of the lithium battery through the pressure detection unit therein. The multi-modal thin film sensor attached to the surface of the lithium battery can also respond to the temperature change in the charging and discharging process through the integrated temperature detection unit, such as temperature rise of overcharging and overdischarging, temperature rapid change of thermal runaway, etc. Among them, the temperature detection unit is not sensitive to pressure because its sensitive film is a flat structure without microstructure design. The temperature change will affect the ion migration rate, electrical conductivity, etc., and only respond to the temperature change. The pressure detection unit, under the action of external pressure, forms a double-layer capacitor with ions and electrons, which changes significantly, and at the same time, the capacitance value will also be affected by temperature change. Therefore, the present application can decouple the temperature influence part in the pressure detection unit output signal by in-situ compensation, so as to realize accurate detection of temperature and pressure multi-parameters.

[0068] Due to the pressure change of up to MPa level in the charging and discharging, thermal runaway and other processes of the lithium battery, the repeatability of the sensor itself is the key to ensure accurate testing and long-term stable use under such high pressure. Therefore, the present application further improves the top of the microstructure in the sensitive film to a flat structure or an approximate flat structure, which can prevent excessive stress from concentrating on the tip under high pressure, causing plastic deformation of the sensitive material.

[0069] As shown in Figure 5 , the sensor shows excellent repeatability under high pressure environment. The pressure response curves of multiple loadings are almost completely coincided, which shows that the output results are highly consistent under the same pressure. After calibration, the sensor can realize high-precision pressure measurement, and will not produce obvious deviation due to the difference of the device itself, so as to ensure the accuracy of the detection results, and can provide stable and reliable signal support for long-term monitoring of the battery under high pressure environment.

[0070] The lithium battery to which the multi-modal thin film sensor can be applied includes but is not limited to soft package type, square shell type and cylindrical type. When applied, the multi-modal thin film sensor can be directly attached to the surface of the lithium battery through double-sided adhesive, and specifically, the electrode layer substrate side or the functional layer substrate side can be bonded to the surface of the battery cell of the lithium battery.

[0071] In other embodiments, the multi-modal thin film sensor can also be prepared directly on the outermost packaging layer of the lithium battery, taking the outermost packaging layer of the cell in the lithium battery as a component structure of the sensor. For soft package batteries, the packaging layer is an aluminum plastic composite film, and the outermost layer of square shell and cylindrical batteries is usually an insulating film (usually a polymer material) wrapped on the metal shell. Whether the packaging layer is an aluminum plastic composite film or an insulating film, it can be used as the substrate of the sensor. Specifically, the sensitive material can be printed on the packaging layer by printing and a microstructure region is prepared, and then the electrode layer prepared separately is attached to the sensitive material; or the interdigital electrode unit can be printed on the packaging layer, and the packaging layer is used as the substrate of the electrode layer, and then the functional layer is attached to the electrode.

[0072] It should be noted that for the pressure detection unit, a cavity needs to be reserved between the functional layer and the electrode layer; for the temperature detection unit, a cavity does not need to be reserved between the functional layer and the electrode layer. When bonding, the sensitive film of the pressure detection unit and the temperature detection unit are aligned with the respective interdigital electrode units, and the edge is attached using double-sided adhesive, avoiding contact of the double-sided adhesive with the electrode area.

[0073] Based on this, the embodiment of the present application also provides a lithium battery integrated with a multi-modal thin film sensor, which comprises a cell and a multi-modal thin film sensor formed on the surface of the cell or adhered to the surface of the cell. The specific structure of the multi-modal thin film sensor and the integration mode thereof with the cell can be referred to the above description.

[0074] Further, in order to verify the repeatability performance of the multi-modal thin film sensor provided by the present application in a high pressure environment, a test platform based on a static weight type force standard machine is used to perform multiple loading-unloading cycle tests on the device, the loading pressure range covers the 0-1.5 MPa interval that may occur in the working process of the lithium battery, and the pressure-capacitance response curve is recorded in real time.

[0075] The test results are shown in Figure 4 As shown in the figure, during multiple loading processes in a high pressure environment, the capacitance change curve of the decoupled pressure signal output by the sensor is highly coincident, and the fluctuation amplitude is less than ±2%, and the repeatability is better than 1.5%. This shows that the multi-modal thin film sensor provided by the present application has good structural stability and electrical response consistency, and the sensor structure design significantly improves the stability and repeatability requirements of the output signal. Especially based on the design of the special morphology of the microstructure, the signal repeatability under high pressure conditions meets the demand of the stability and repeatability of the sensor for high pressure state monitoring in the battery module.

[0076] Finally, it should be noted that, although the embodiments of the present application are described above in conjunction with the drawings, the present application is not limited to the above-described specific embodiments and application fields, and the above-described specific embodiments are merely illustrative and instructive, but not restrictive. Those skilled in the art can make many forms under the guidance of the present specification without departing from the scope of the claims of the present application, and these all belong to the protection of the present application.

Claims

1. An electroded multi-modal thin film sensor, characterized in that, The electrode layer has a first substrate layer and a plurality of periodically arrayed interdigital electrode units formed on the first substrate layer. The functional layer has a second substrate layer and a plurality of sensitive films formed on the second substrate layer and arranged in correspondence with the interdigital electrode units; the sensitive films are made of the same flexible ionomer material, and the surface of part of the sensitive films is structured with periodically arrayed repetitive micro-protrusion units. In the electrode layer, part of the interdigital electrode units and the sensitive films with the repetitive micro-protrusion units form pressure detection units with solid-gas-solid interfaces, and the remaining interdigital electrode units and the remaining sensitive films form temperature detection units with solid-solid interfaces; the pressure detection units and the temperature detection units are alternately and periodically arranged. The pressure detection units have the same geometric parameters; the temperature detection units have the same geometric parameters.

2. An electroded multi-modal thin film sensor, characterized in that, The pressure detection units and the temperature detection units have the same geometric parameters. The array is any one of a rectangular array, a ring array, a staggered array, and a honeycomb lattice array. The top of the micro-protrusion unit is a planar or approximately planar structure. The micro-protrusion unit is a circular truncated cone, a prismatic truncated cone, a circular cylinder, a prismatic cylinder, or a hemispherical structure; preferably, a circular truncated cone, a prismatic truncated cone, or a hemispherical structure.

3. The electrokinetic multi-modal thin film sensor of claim 1 or 2, wherein, The flexible ionomer is any one of an ionogel, an ionomer, and a polyion polymer material.

4. The electrokinetic multi-modal thin film sensor of claim 1 or 2, wherein, The ionogel is any one of a polyvinyl alcohol-borate gel and a polyacrylate-ionic liquid composite gel; the ionomer is any one of a polyurethane-based ionomer, a styrene block copolymer-based ion elastomer, and a siloxane-based ion conductive elastomer; and the polyion polymer material is any one of polystyrene sulfonate, polyacrylic acid sodium, and polyethyleneimine.

5. The electrokinetic multi-modal thin film sensor of claim 1 or 2, wherein, The ionically flexible multi-modal thin film sensor according to any one of claims 1 to 9, wherein the electrical signal output by the temperature detection unit is used to represent temperature change, and the electrical signal output by the pressure detection unit is decoupled from the electrical signal output by the temperature detection unit and used to represent pressure change, wherein, 6. The electrokinetic multi-modal thin film sensor of claim 1 or 2, wherein, The temperature signal output by each pressure detection unit is calculated based on formula (1):

7. The electroded multi-modal thin film sensor of claim 6, wherein, The pressure signal output by each temperature detection unit is calculated based on formula (2):

8. The electrokinetic multi-modal thin film sensor of claim 1 or 2, wherein, ​ 9. The electroded multi-modal thin film sensor of claim 8, wherein, ​ 10. A distributed pressure detection method, characterized by, ​ ​ （1）； ​ （2）； The real pressure of each pressure detection unit after decoupling is calculated based on formula (7) is represented as: ， （7）； wherein, represents the system error or noise in the pressure detection unit signal, represents the system error or noise in the temperature detection unit signal, function represents the fitting function obtained from the calibration experiment of the pressure detection unit, represents the fitting function obtained from the calibration experiment of the temperature detection unit, represents the mapping relationship of and represents the mapping relationship of represents the mapping relationship of and n represents the number of temperature detection units around the pressure detection unit which are required to be decoupled.

11. A lithium battery comprising a cell, characterized in that, The outer surface of the battery cell is integrated with the electroded multi-modal thin film sensor according to any one of claims 1 to 9; the electroded multi-modal thin film sensor is attached to the outer surface of the battery cell through the first base layer or the second base layer.

12. The lithium battery of claim 11, wherein the lithium metal anode is coated with a layer of lithium phosphorus oxynitride. The first base layer or the second base layer of the electroded multi-modal thin film sensor is a packaging layer of the outer surface of the battery cell, and the packaging layer is an aluminum-plastic composite film or a polymer insulating film.

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