Ceramic sensor for monitoring internal state of battery and preparation method thereof

Abstract

The invention relates to a ceramic sensor for monitoring the internal state of a battery and a preparation method of the ceramic sensor. The ceramic sensor comprises a ceramic substrate with a cavity structure, a pressure sensitive element which is arranged in the ceramic substrate and comprises a cavity structure, and a temperature sensitive element which is arranged in a non-cavity structure area in the ceramic substrate, wherein the pressure sensitive element is a capacitive pressure sensitive element which is composed of a cavity structure, a first pressure sensitive electrode arranged on the upper surface of the cavity structure and a second pressure sensitive electrode arranged on the lower surface of the cavity structure, or the first pressure sensitive electrode and the second pressure sensitive electrode are arranged in the cavity structure. The pressure sensitive element is a piezoresistive pressure sensitive element which is composed of a cavity structure, a Wheatstone bridge and a piezoresistor, wherein the Wheatstone bridge and the piezoresistor are arranged on the inner surface of the cavity structure. The lithium battery internal state monitoring sensor overcomes the defects of an existing lithium battery internal state monitoring sensor in the aspects of high temperature resistance, corrosion resistance and high reliability, and a new scheme is provided for lithium battery internal state monitoring and similar harsh environment sensing.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery monitoring, and in particular relates to a ceramic sensor for monitoring the internal state of a battery and a preparation method thereof. Background Art

[0002] Lithium batteries, as energy storage devices with high energy density and excellent cycle performance, have achieved significant application and development in fields such as electric vehicles, portable electronic devices, and renewable energy storage systems. However, the lifespan and safety of lithium batteries remain key challenges in battery technology research. To ensure efficient battery system operation, extend battery life, and prevent potential safety issues, battery status monitoring technology has become crucial. Currently widely used battery management systems (BMS) typically only monitor the current, voltage, and temperature of the entire battery pack externally. When fault alarm thresholds are triggered, the time available for action is very limited. Monitoring internal battery parameters, on the other hand, provides a more accurate and real-time understanding of the electrochemical and mechanical changes within the battery, facilitating early warning and action. Furthermore, lithium dendrite growth within the battery can lead to internal short circuits, generating large amounts of flammable gases and heat, ultimately leading to fire and deflagration. This typically occurs first in the most severely degraded battery cell within the battery pack, further affecting the entire pack. Therefore, in situ monitoring of the internal operating parameters of individual battery cells is crucial for improving the real-time and accuracy of lithium battery thermal runaway warnings. To address these challenges, a number of new implantable sensor technologies have emerged in recent years to enable real-time and comprehensive monitoring of the internal state of battery cells. Among them, pressure and temperature sensors have attracted significant attention due to their high sensitivity to the physical and chemical processes within the battery. Temperature sensors can monitor temperature changes caused by electrochemical reactions and resistive heating during battery operation. Battery overheating can lead to electrolyte and SEI decomposition, potentially triggering thermal runaway. Therefore, monitoring internal battery temperature is crucial. During lithium battery operation, electrolyte decomposition and electrode side reactions inevitably produce gases such as carbon dioxide, carbon monoxide, methane, and hydrogen. Gas accumulation within the battery cell increases internal pressure and volume, potentially leading to cell rupture, leakage, and explosion. Pressure sensors can capture key information such as electrolyte expansion, structural deformation, and gas production. Therefore, monitoring internal battery pressure is crucial for early warning of thermal runaway and assessing battery health. Research has shown that incorporating simultaneous pressure and temperature monitoring into battery condition monitoring systems has the potential to provide more comprehensive and accurate status information.

[0003] Lithium battery internal condition monitoring requires sensors with a small size and high integration density. However, technical challenges include sensor resistance to electrolyte corrosion, sensor reliability, and high-temperature resistance. Currently, the battery internal temperature / pressure monitoring sensors that have received significant attention or are already in use include thin-film sensors based on organic substrates and electrodes, and fiber-optic sensors based on the diffraction principle. A small number of reports have also used MEMS sensors to monitor internal battery pressure and temperature. Thin-film sensors typically construct a Wheatstone bridge circuit on an organic substrate, leveraging thermal resistance and piezoresistive effects to sense temperature and pressure (e.g., patent publications CN117607712B and CN111896876B). Thin-film sensors have the advantages of being very small, having minimal impact on the battery during implantation, and using electrical signals for sensing, making them easy to integrate with conditioning circuits. However, the organic substrates they use cannot withstand the high temperatures experienced during thermal runaway, and decoupling temperature, pressure, and strain signals is challenging. MEMS sensors primarily integrate various silicon-based sensors in a modular fashion (e.g., patent number CN218824624U). These sensors offer the advantages of high integration and miniaturization. However, their use of silicon-based semiconductor materials limits their operating temperature range to 150°C, and their resistance to the corrosive environment within batteries is also a concern. They also face challenges such as difficulty withstanding the internal corrosive environment or the high temperatures that can cause thermal runaway. Fiber optic sensors, on the other hand, face difficulties with reliability and signal conditioning, hindering their widespread adoption. Preventing the effects of high temperatures, acidic corrosive environments, and sensor implantation within lithium batteries remains the greatest challenge in internal battery monitoring.

[0004] In contrast, ceramic-based sensors show unique potential. Among them, ceramic sensors have the characteristics of corrosion resistance and high temperature resistance, which makes them have the potential for internal monitoring of lithium batteries. However, most of the existing ceramic-based sensors use ceramic substrates such as alumina, which are prepared through cutting, sputtering electrodes, glass sealing, etc., and most of them are single temperature sensors or pressure sensors. Moreover, the internal space of the battery is very limited, and ceramic sensors that are too large cannot be implanted internally. Therefore, the biggest challenge currently faced is that ceramic sensors are generally difficult to integrate multiple parameters and difficult to prepare complex structures, which makes them difficult to miniaturize and integrate. In addition, lithium batteries used as power batteries also need to face scenarios such as vibration and collision. How to achieve a stable connection between ceramic sensors and batteries and achieve reliable implantation of sensors is also one of the problems to be solved by the present invention. Summary of the Invention

[0005] In view of the large-scale use of lithium batteries but the frequent occurrence of safety problems, there is a need for more timely, comprehensive and accurate monitoring of the status of lithium batteries. The purpose of the present invention is to provide a ceramic sensor for battery internal status monitoring based on multilayer ceramic technology and a preparation method thereof, so as to solve the shortcomings of existing lithium battery internal status monitoring sensors in high temperature resistance, corrosion resistance and high reliability, and provide a new solution for lithium battery internal status monitoring and similar harsh environment sensing.

[0006] A first aspect of the present invention provides a ceramic sensor, comprising: Ceramic substrate with cavity structure, A pressure sensitive element having a cavity structure provided in a ceramic substrate, and A temperature sensitive element provided in a non-cavity structure area of the ceramic substrate; The pressure sensitive element is a capacitive pressure sensitive element consisting of a cavity structure, a first pressure sensitive electrode provided on the upper surface of the cavity structure, and a second pressure sensitive electrode provided on the lower surface of the cavity structure. Alternatively, the pressure sensitive element is a piezoresistive pressure sensitive element consisting of a cavity structure, a Wheatstone bridge and a piezoresistor arranged on the inner surface of the cavity structure.

[0007] This invention creatively produces a highly integrated ceramic-based integrated pressure and temperature sensor. The pressure-sensitive element in this ceramic sensor is integrally formed within the cavity structure of the ceramic substrate, with both the pressure-sensitive element and the temperature sensor electrodes embedded within the ceramic substrate. This sensor exhibits excellent corrosion and high-temperature resistance, withstanding the long-term corrosion from the electrolyte environment within batteries (such as lithium batteries) and temperatures ranging from -50°C to 200°C. Furthermore, this ceramic sensor boasts a high level of integration, integrating dual-parameter pressure and temperature sensing, and centrally outputting both pressure and temperature signals.

[0008] Preferably, when the pressure sensitive element is a capacitive pressure sensitive element, the upper surface and the lower surface of the cavity structure are parallel.

[0009] Preferably, the ceramic sensor further comprises a plurality of metal through-hole electrodes; the metal through-hole electrodes are electrically connected to the pressure sensitive element and the temperature sensitive element respectively.

[0010] More preferably, when the pressure sensitive element is a capacitive pressure sensitive element, the number of the metal through-hole electrodes is at least 5, preferably 5 to 8; Alternatively, when the pressure sensitive element is a piezoresistive pressure sensitive element, the number of the metal through-hole electrodes is at least 6, preferably 5 to 8.

[0011] More preferably, the metal through-hole electrodes are electrically connected to the pressure-sensitive element and the temperature-sensitive element respectively through a plurality of internal wiring electrodes provided in the ceramic substrate; and / or, the ceramic sensor further comprises a lead electrode electrically connected to the metal through-hole electrodes. The ceramic substrate of the present invention has internally embedded metal wiring (metal through-hole electrodes and internal wiring electrodes), which functions to transmit and aggregate the signals of the pressure- and temperature-sensitive elements to the external electrodes on the surface of the substrate, facilitating signal acquisition and further processing. The metal wiring can be multi-layered as needed, and the layers are connected by metal through-holes filled with metal. The metal wiring is embedded in the ceramic substrate through a multi-layer ceramic process and is integrally sintered at 850-900°C with the pressure / temperature-sensitive elements, the ceramic substrate, and the metal external electrodes. Preferably, the material of the metal wiring inside the ceramic substrate can be an electrode material selected from at least one of gold, silver, copper, nickel, tungsten, molybdenum, platinum, etc., or a combination thereof.

[0012] Preferably, a metal electrode layer is provided on the lower surface of the ceramic substrate with the cavity structure; preferably, the thickness of the metal electrode layer is at least 1000 nm. The metal electrode layer (or metal external electrode) is sintered integrally with the ceramic substrate and the pressure / temperature sensor using multilayer ceramic technology. The metal external electrode can be used for welding leads. The number of welding leads ranges from 5 to 8, depending on the sensor principle. The size, shape, and position of the metal external electrode can be adjusted based on the signal acquisition method and assembly method. The size, shape, and position of the metal external electrode for integration with the cover plate can be adjusted based on the assembly method. The metal external electrode can be made of metals such as gold, silver, copper, nickel, tungsten, molybdenum, and platinum, or alloys such as silver-palladium and Kovar. The metal electrode layer in the ceramic sensor of the present invention can be subsequently integrated with a battery cover plate (e.g., a lithium battery cover plate), providing a secure and reliable structure that minimizes the effects of vibration and impact on the battery.

[0013] Preferably, the thickness (or height) of the cavity structure is 5 to 200 microns; and / or, an average distance between the upper surface of the cavity structure and the upper surface of the ceramic substrate having the cavity structure is 200 to 400 micrometers; and / or, an average distance between the lower surface of the cavity structure and the lower surface of the ceramic substrate having the cavity structure is ≥800 μm; Preferably, the cavity structure is cylindrical or rectangular; more preferably, when the cavity structure is cylindrical, the diameter of the cavity structure is at least 5 mm; more preferably, when the cavity structure is rectangular, the length of the cavity structure is at least 4 mm and the width is at least 4 mm.

[0014] Preferably, the ceramic substrate with a cavity structure is made of a HTCC high-temperature co-fired ceramic material with a co-firing temperature greater than 950° C. and / or a LTCC low-temperature co-fired ceramic material with a co-firing temperature less than or equal to 950° C.

[0015] Preferably, the Wheatstone bridge is a balanced bridge or an unbalanced bridge; the material of the varistor is at least one of gold, silver, copper, ruthenium dioxide, ruthenate, or a combination thereof.

[0016] Preferably, the temperature-sensitive element and the pressure-sensitive element are vertically staggered. Preferably, the temperature-sensitive element is arranged in a non-cavity structure area above the upper surface of the cavity structure. More preferably, the average distance between the temperature-sensitive element and the upper surface of the ceramic substrate with the cavity structure is ≤15μm, and most preferably 5-15μm. And / or, the temperature-sensitive element is a positive temperature coefficient thermistor or a negative temperature coefficient thermistor. Preferably, the temperature-sensitive element should be arranged as close to the upper surface of the ceramic substrate as possible (preferably ≤15μm) to reduce the time it takes for the internal battery temperature to be transmitted to the temperature-sensitive element, thereby significantly reducing the response time. However, in order to reduce the impact of the high-temperature corrosive environment inside the battery on the temperature-sensitive element and meet the requirements of the multilayer ceramic preparation process, the distance between the temperature-sensitive element and the upper surface of the ceramic substrate with the cavity structure must be controlled to be no less than 5μm.

[0017] A second aspect of the present invention provides a method for preparing a ceramic sensor, the method comprising the following steps: (1) punching the multilayer green ceramic tape, wherein the punching process includes preparing through holes required for metal through-hole electrodes and / or macroholes required for cavity structures; (2) Printing a first pressure-sensitive electrode, a second pressure-sensitive electrode, a temperature-sensitive element, a metal electrode layer, or constructing a Wheatstone bridge and a varistor on the inner surface of the cavity structure on a plurality of green ceramic tapes having only through holes; (3) laminating and cutting the green ceramic strip obtained in step (1) and the green ceramic strip obtained in step (2) according to the internal structure sequence of the above-mentioned ceramic sensor to obtain a green body; (4) The obtained green body is co-fired to obtain the ceramic sensor.

[0018] The present invention innovatively uses multilayer ceramic technology to prepare an integrated pressure / temperature sensor. The present invention uniquely designs pressure-sensitive and temperature-sensitive elements embedded within a ceramic substrate, and sinters them integrally with the ceramic substrate with embedded circuits (metal through-hole electrodes and internal line electrodes). Ceramic sensors offer significantly superior high-temperature resistance, corrosion resistance, and reliability to thin-film or silicon-based semiconductor sensors, making them a new option for battery internal status monitoring sensors. The multilayer ceramic technology used in the present invention is a manufacturing technology that combines traditional ceramic process technologies such as ceramic powder processing, tape casting, and ceramic sintering, with component design and electronic component process technologies such as electromagnetic field simulation, drilling, electrode wiring, and lamination. It can be divided into high-temperature co-fired ceramics (HTCC, sintering temperature > 950°C) and low-temperature co-fired ceramics (LTCC, sintering temperature ≤ 950°C). It can co-fire ceramics with metal electrodes, perform multi-layer wiring and inter-layer via metal interconnection, and prepare ceramic substrates, devices or functional modules with complex structures and high integration. It has the advantages of flexible structural design and three-dimensional integration, while retaining the inherent high temperature resistance, corrosion resistance and high reliability of ceramics. It has demonstrated unique advantages in the preparation of integrated sensors for harsh environments.

[0019] Preferably, after the drilling process, the through-holes are filled with metal electrode slurry to obtain metal through-hole electrodes. Preferably, the temperature sensitive element should be arranged as close to the ceramic surface as possible to reduce the increase in response time caused by the time required for temperature conduction.

[0020] Preferably, the thickness of the green tape is 50 μm to 200 μm. Preferably, when the green tape is an HTCC green tape, the co-firing temperature is greater than 950° C.; when the green tape is an LTCC green tape, the co-firing temperature is less than or equal to 950° C.

[0021] The temperature-sensitive element of the present invention comprises a temperature-sensitive element fabricated using a multilayer ceramic process (e.g., a thick-film electrode as the sensitive portion). With the green ceramic tape of the temperature-sensitive element positioned at the top, facing away from the cavity structure, a thinner layer of green ceramic tape (e.g., ≤20 μm, for example, 8-20 μm) is preferably applied to the surface of the temperature-sensitive element. This allows the temperature-sensitive element to be embedded within the ceramic substrate during subsequent sintering, providing corrosion protection while minimizing response time. Its resistance and sensitivity can be adjusted based on the shape of the thick-film electrode. The thick-film electrode is co-fired with the multilayer ceramic film and ceramic substrate at 850-900°C. The electrode material of the temperature-sensitive element can be metals such as platinum, copper, and titanium, or materials such as NTC and PTC. The present invention utilizes lamination of non-macroporous regions to achieve embedded temperature-sensitive electrodes. However, the green ceramic sheet used for the internal electrode is relatively thick (130 μm). Direct use of this sheet would result in the temperature-sensitive element being embedded too deeply. This would increase the response time of the temperature sensor due to the time required for temperature conduction, thus reducing performance. If the thickness of the green ceramic sheet is too low, it is difficult to prepare a uniform and flat green ceramic sheet, and the ultra-thin green ceramic sheet is difficult to be laminated with other green ceramics, which seriously affects the complete coverage of the temperature sensitive components during the integrated sintering process, resulting in the risk of exposing the temperature sensitive components.

[0022] A third aspect of the present invention provides the use of the aforementioned ceramic sensor for monitoring the internal state of a battery, preferably a lithium battery. This invention innovatively utilizes multilayer ceramic technology to fabricate an integrated pressure / temperature sensor for monitoring the internal state of a lithium battery. The sensor is integrated with the lithium battery cover, resulting in a highly compact and reliable structure.

[0023] The fourth aspect of the present invention provides a battery cell with internal state monitorable, comprising: a battery cell, and the above-mentioned ceramic sensor provided inside the battery cell. Preferably, the ceramic sensor is provided on the inner side of the cover of the battery cell. More preferably, the battery is a lithium battery. Most preferably, the ceramic sensor and the battery cover are connected in a fixed or detachable manner, and preferably, the fixed connection is co-firing, bonding or eutectic welding. Among them, the integration method of the lithium battery internal state monitoring sensor and the lithium battery cover includes but is not limited to co-firing, bonding, eutectic welding, etc.; the signal lead-out method of the lithium battery internal state monitoring sensor includes but is not limited to cover punching pins, flexible wiring, wireless signals, etc.

[0024] The present invention provides a battery pack comprising a battery module comprising a plurality of battery cells with monitorable internal states, wherein the plurality of battery cells with monitorable internal states are connected in series, in parallel, or in series-parallel.

[0025] Beneficial effects of the present invention: 1. This invention integrates the temperature sensor and the pressure sensor into one for the first time, making it compact and capable of multi-parameter sensing. In addition, the ceramic sensor is made of ceramic material on the outside, which can play a role in corrosion resistance. 2. The present invention integrates the ceramic sensor as a whole with the lithium battery cover, reducing the impact of sensor implantation on the lithium battery and improving the reliability of the sensor and battery integration; 3. The present invention aggregates the internal circuit electrodes of the temperature and pressure sensitive elements into a plurality of metal through-hole electrodes to facilitate wiring and sensor signal extraction; 4. The present invention uses multilayer ceramic technology, which allows for flexible adjustment of materials and structural design to suit different working conditions and requirements. Furthermore, the process is simple and the cost is low. Specifically, the output signal, range, and accuracy of the pressure and temperature sensitive elements can be flexibly adjusted through material selection and structural design. 5. The size and shape of the ceramic sensor of the present invention can be flexibly designed according to the structure and size of the battery cover, and its integration with the battery cover is diverse and can be selected according to different assembly and performance requirements, and has wide applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the structure of a ceramic sensor based on multilayer ceramic technology; Figure 2 This is a schematic diagram of the structural disassembly of a ceramic sensor based on multilayer ceramic technology; Figure 3 Schematic diagram of the raw ceramic chip, pressure / temperature sensitive element and surface electrode pattern; Figure 4 Schematic diagram of the integrated ceramic sensor and lithium battery cover; Figure 5 This is a temperature sensitivity test graph of the ceramic sensor prepared in Example 1, where the horizontal axis is temperature (Temperature) / °C, and the vertical axis is the change in resistance (ΔResistance) / Ω based on the resistance value at 0°C; Figure 6 This is a pressure sensitivity response test graph of the ceramic sensor prepared in Example 1, where the horizontal axis is pressure (Pressure) / MPa and the vertical axis is capacitance (Capacity) / pF; Figure 7 This is a photo of the ceramic sensor of the present invention after being immersed in electrolyte. DETAILED DESCRIPTION

[0027] The present invention will be further described below through the following embodiments. It should be understood that the following embodiments are only used to illustrate the present invention and not to limit the present invention. Unless otherwise defined, the technical terms or scientific terms used in the present invention should have the common meanings understood by people with ordinary skills in the field to which the present invention belongs. For example, the "first", "second", "third" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, "one" or "a layer" and similar words do not indicate a quantity limit, but rather indicate the presence of at least one. "Connect" or similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Electrical connection", "electrical connection", "electrical connection", such connections are usually achieved using wires, leads, electrodes, plugs, sockets, connectors, plugs or other electrical connection elements. Electrical connections can be temporary, such as plug-in connections, or permanent, such as solder connections. Directional descriptions such as "up", "down", "left", "right", "upper left", "upper right", "lower left", "lower right", "horizontal", and "vertical" are only used to express relative position relationships. When the absolute position of the described object changes, the relative position relationship will also change accordingly.

[0028] In one embodiment of the present invention, a ceramic sensor (or multilayer ceramic sensor) is a pressure / temperature integrated sensor based on multilayer ceramic technology, comprising: a ceramic substrate having a cavity structure, a pressure-sensitive element having a cavity structure provided in the ceramic substrate, a temperature-sensitive element embedded in the ceramic substrate, and an optional metal outer electrode layer (for welding leads or integrating with the battery cover, preferably integrated with the hard-shell lithium battery cover to monitor the internal state of the lithium battery). The pressure-sensitive element has a cavity structure within the ceramic substrate prepared by a multilayer ceramic process, and its sensing principle can be capacitive or piezoresistive. Furthermore, the temperature-sensitive element is embedded in the non-cavity structure area of the ceramic substrate, and is preferably offset vertically from the pressure-sensitive element.

[0029] In one embodiment of the present invention, the capacitive pressure sensor is fabricated by fabricating a cavity parallel plate capacitor within a ceramic substrate. When subjected to pressure, the ceramic deforms, reducing the spacing between the parallel plate capacitors and causing a change in capacitance. Its capacitance and sensitivity to pressure can be adjusted based on the plate area, spacing between the plates, and thickness of the movable plate. The electrode materials of the cavity parallel plate capacitor can be gold, silver, copper, or other materials.

[0030] In one embodiment of the present invention, a piezoresistive pressure sensor constructs a Wheatstone bridge and a varistor on the inner surface of a ceramic cavity. When subjected to pressure, the ceramic cavity diaphragm strains, causing the varistor to change, resulting in a change in the bridge output voltage. Its resistance and sensitivity can be adjusted based on the shape and size of the varistor electrodes and the thickness of the cavity diaphragm. The Wheatstone bridge can use a balanced or unbalanced bridge output, and the varistor electrode material can be made of metals such as gold, silver, and copper, or materials such as ruthenium dioxide and ruthenate.

[0031] In one embodiment of the present invention, the ceramic sensor's pressure and temperature sensors are embedded within the ceramic substrate, offering excellent corrosion and high-temperature resistance, capable of withstanding the long-term corrosion of the battery's internal electrolyte environment and temperatures ranging from -50°C to 200°C. The ceramic sensor boasts a high level of integration, integrating dual-parameter pressure and temperature sensing, centrally routing signals, and integrating with the lithium battery cover, resulting in a secure and reliable structure that minimizes impact on the battery.

[0032] In one embodiment of the present invention, the structure of the ceramic sensor for monitoring the internal state of the lithium battery is as follows: Figure 1-2 As shown, the device comprises: a ceramic substrate 1, a temperature-sensitive element (e.g., a temperature-sensitive electrode) 2, a first pressure-sensitive electrode 3, a second pressure-sensitive electrode 4, multiple internal wiring electrodes 5, multiple metal through-hole electrodes 6, multiple lead-out electrodes 7, and a metal electrode layer (i.e., metal external electrode) 8 for integration with the cover plate. The first pressure-sensitive electrode 3 and the second pressure-sensitive electrode 4 must be vertically aligned and overlapped. Preferably, the signals of the pressure-sensitive element and the temperature-sensitive element are uniformly led out to six lead electrodes on the surface for wire bonding.

[0033] In one embodiment of the present invention, the sensing principle of the ceramic sensor is as follows: (1) The pressure sensitive element can be a capacitive pressure sensitive element or a piezoresistive pressure sensitive element. The capacitive pressure sensitive element forms a closed cavity parallel plate capacitor by preparing a first pressure sensitive electrode 3 and a second pressure sensitive electrode 4 on the upper and lower surfaces of the cavity structure inside the ceramic substrate. When subjected to pressure, the ceramic deforms, the distance between the parallel plate capacitors decreases, resulting in a change in capacitance, and the pressure value can be obtained by measuring the capacitance value. (2) The piezoresistive pressure sensitive element constructs a Wheatstone bridge and a piezoresistor at a position on the inner surface of the cavity structure of the ceramic substrate 1 (for example, the position of the first pressure sensitive electrode 3 or the second pressure sensitive electrode 4). When subjected to pressure, the ceramic cavity diaphragm generates strain, causing the piezoresistor to change, resulting in a change in the bridge output voltage. The temperature sensitive element adopts the resistive principle, and a thick film electrode 2 is prepared by multilayer ceramic technology, and a layer such as is covered on the surface of the thick film electrode 2. Figure 2The multilayer ceramic material shown in Figure 1 allows the thick film electrode 2 to be buried inside the ceramic substrate, which plays an anti-corrosion role. When the temperature changes, the resistance value of the thick film electrode 2 will change accordingly, and the temperature change can be monitored by measuring the resistance value. The electrode material of the temperature sensitive element can be a metal such as platinum, copper, titanium, or a material such as NTC, PTC, etc. The signals of the pressure sensitive element and the temperature sensitive element are aggregated to one end of the ceramic sensor through the metal circuit shown in the internal circuit electrode 5, and then connected to the lead electrode 7 on the surface of the ceramic sensor through the metal through-hole shown in Figure 6 to realize the aggregation and export of the signal. The temperature and pressure changes can be calculated through external circuit processing. Figure 2 The middle metal outer electrode 8 is a metal outer electrode reserved for integration with the battery cover. Depending on different integration methods such as eutectic welding and co-firing, its material can be metals or alloys such as gold, silver, and copper.

[0034] In one embodiment of the present invention, the electrode shape and size of the pressure-sensitive and temperature-sensitive elements can be optimized based on the required range and sensitivity. For temperature-sensitive elements, when thick-film electrodes are used, the larger the overall area of the thick-film electrode 2, the faster the response time. For scenarios requiring high sensitivity but a narrow range, the electrode line width should be reduced and the length increased; for scenarios requiring a wide range, the electrode line width should be increased. For pressure-sensitive elements, the larger the area of the first and second pressure-sensitive electrodes 3 and 4, the higher the sensitivity. The thicker the elastic diaphragm, the greater the range. The elastic diaphragm refers to the portion of the ceramic substrate above the cavity. When subjected to pressure, it undergoes elastic deformation, bending, causing a change in the height (or thickness) of the cavity structure, which in turn changes the capacitance and other sensor signals. The average distance between the upper surface of the cavity structure and the upper surface of the ceramic substrate containing the cavity structure is controlled to be between 200 and 400 microns. If the thickness between the upper surface of the cavity structure and the upper surface of the ceramic substrate containing the cavity structure is too large, deformation is minimal or even nonexistent under the same pressure, resulting in reduced sensitivity. If the thickness between the upper surface of the cavity structure and the upper surface of the ceramic substrate having the cavity structure is too small, the cavity structure may be easily deformed, cracked, or collapsed during subsequent sintering of corresponding green ceramic sheets.

[0035] In one embodiment of the present invention, green ceramic tapes (also known as green ceramic sheets, ceramic green ceramic sheets, etc.) are made of HTCC high-temperature co-fired ceramic materials with a co-firing temperature greater than 950°C and / or LTCC low-temperature co-fired ceramic materials with a co-firing temperature less than 950°C. Each green ceramic tape has a thickness of 50 μm to 200 μm.

[0036] In one embodiment of the present invention, holes are drilled into the surface of a multilayer green tape, including through-holes for electrical connectivity between layers and macropores for forming the cavity structure of the pressure sensor. The through-holes are then filled with a metal electrode slurry to form a ceramic green tape with electrode through-holes. Preferably, the through-hole diameter can be 100 to 200 microns (e.g., 100, 120, 150, 180, 200 microns, etc.).

[0037] In one embodiment of the present invention, the patterns of the electrodes for the pressure / temperature sensor and the metal external electrodes for soldering are screen-printed on the surface of the through-hole-filled green ceramic tape. Specifically, the temperature sensor 2 (thick film electrode 2), the first pressure-sensitive electrode 3, the second pressure-sensitive electrode 4, multiple internal wiring electrodes 5, multiple metal through-hole electrodes 6, multiple lead external electrodes 7, and the metal electrode layer (i.e., metal external electrode) 8 for soldering and integration with the cover plate are screen-printed onto the surface of the multilayer ceramic green sheet using a metal or sensitive paste. The metal through-hole electrodes 6 are formed by drilling holes in the green sheet and then filling them with metal electrode paste. The cavity structure of the pressure sensor is formed by drilling holes (large holes) in the green sheet and then laminating them with a complete green sheet. The layer of multilayer ceramic material covering the surface of the temperature sensor is preferably a green sheet that is thinner than the other layers (≤20μm). Preferably, when printing the temperature sensitive element, the position of the temperature sensitive element on the green ceramic sheet is controlled to be vertically offset from the position of the first pressure sensitive electrode (or second pressure sensitive electrode, or Wheatstone bridge and piezoresistor) on the green ceramic sheet. For example, the schematic diagram of the punching process of the multilayer ceramic green ceramic sheet and the printing pattern of each electrode is as follows: Figure 3 As shown, Figure 3 In the middle, a is a thin layer of raw porcelain covering the surface of the temperature sensitive element; Figure 3 Middle b is a layer of green ceramic sheet with through holes and macropores used to form a cavity structure; Figure 3 In the figure, "c" represents several layers of green ceramic sheets with through-holes. When using LTCC materials to make ceramic sensors, silver electrodes (all electrodes except the temperature-sensitive electrode) can be used. Preferably, when using HTCC materials to make ceramic sensors, platinum electrodes (all electrodes except the temperature-sensitive electrode) can be used.

[0038] In one embodiment of the present invention, a green porcelain tape printed with electrodes and a green porcelain tape with large holes are stacked together in sequence, and the vias and patterns of each green porcelain tape are aligned. By controlling the stacking conditions and sequence, an internal cavity is prepared without using a sacrificial layer for filling, and the green porcelain tapes are fully bonded to each other to form a green porcelain block. Preferably, the axial pressure of the stacking can be 10-15 MPa, the stacking temperature can be 55-60°C, and the stacking time can be 10-20 seconds. Preferably, during the stacking process, the thickness of the cavity structure is preferably controlled to be 5-200 microns. The cavity structure needs to have a certain thickness to reserve space for the deformation of the elastic ceramic diaphragm after being subjected to pressure. The smaller the cavity thickness, the higher the sensitivity of the sensor, but a thickness that is too small is difficult to prepare and is prone to collapse and deformation during the co-firing process, resulting in sensor preparation failure. Excessive thickness will reduce the sensitivity of the sensor.

[0039] In a preferred embodiment of the present invention, during the lamination process, the green ceramic sheet printed with the temperature-sensitive element and the green ceramic sheet printed with the first pressure-sensitive electrode (or the green ceramic sheet printed with the second pressure-sensitive electrode, or the green ceramic sheet printed with the Wheatstone bridge and piezoresistor) are separated by one or more (e.g., one, two, or three) green ceramic sheets containing only through-holes, thereby physically isolating the pressure-sensitive element from the temperature-sensitive element. For example, the temperature-sensitive element can be positioned to the upper left, lower left, upper right, or lower right of the cavity structure. Positioning the temperature-sensitive element directly above or below the cavity structure will interfere with the pressure-sensitive element. Furthermore, the temperature-sensitive element should be as close to the surface of the ceramic substrate as possible to reduce response time. Specifically, the average distance between the temperature-sensitive element and the top surface of the ceramic substrate with the cavity structure should be ≤15 μm, preferably 5–15 μm.

[0040] In one embodiment of the present invention, the laminated blocks are placed on a cutting machine and cut into individual sensor green sheets along the printed cutting lines.

[0041] In one embodiment of the present invention, the cut green bodies are neatly placed on a setter plate and placed in a high-temperature furnace for sintering according to multi-layer ceramic co-firing conditions to complete the preparation of a ceramic sensor for detecting the internal state of a lithium battery. Preferably, when LTCC materials are used for preparation, the co-firing temperature can be 850°C to 900°C, and the co-firing time can be 10 to 30 minutes. Preferably, when HTCC materials are used for preparation, the co-firing temperature can be 1400°C to 1600°C, and the co-firing time can be 30 to 120 minutes.

[0042] In one embodiment of the present invention, the ceramic sensor and the battery cover are assembled and the signal is led out according to the aforementioned integration method, and the signal reading circuit is connected to complete the sensor calibration and battery assembly. Specifically, the assembly diagram of the ceramic sensor and the battery cover is as follows: Figure 4 As shown, 9 is the sensor, 10 is the injection hole on the lithium battery cover, 11 is the main body of the lithium battery cover, and 12 is the positive and negative terminals of the lithium battery. The ceramic sensor can be integrated on one side of the lithium battery injection hole, or different ceramic sensors can be integrated on both sides, or a hole can be punched in the center of the ceramic sensor so that it can be inserted through the lithium battery injection hole and integrated into the main body of the cover. The lithium battery cover is usually made of metal, and the sensor can be integrated with it by bonding, eutectic welding, co-firing, etc.

[0043] The following examples are further given to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention all fall within the scope of protection of the present invention. The specific process parameters and the like in the following examples are only examples within a suitable range, that is, those skilled in the art can make selections within a suitable range through the description herein, and are not limited to the specific numerical values exemplified below.

[0044] Example 1: The preparation of a lithium battery status monitoring ceramic sensor that uses a platinum resistor as a temperature sensitive element, provides a capacitive pressure sensitive element with an 8mm diameter cylindrical cavity structure, and leads the signal with a pin. The sensor is bonded and integrated with the battery cover, and includes the following steps: (1) According to the designed drilling positions, holes are drilled on the surface of the multilayer ceramic raw material (thickness 0.13 mm), including through holes with a diameter of 200 microns and cavity holes (or macropores) with a diameter of 8 mm, and the through holes are filled with silver electrode paste. Then, the platinum electrode paste is printed on the surface of the raw ceramic sheet according to the electrode pattern of the temperature sensitive element using the screen printing process; the silver electrode paste is printed on the surface of the raw ceramic sheet with through holes according to the patterns of the first pressure sensitive electrode and the second pressure sensitive electrode of the pressure sensitive element respectively; the silver palladium gold electrode paste is printed on the surface of the raw ceramic sheet with through holes according to the lead external electrode pattern, and then placed in a 70°C oven to dry for 20 minutes for use;

[0045] (2) Use the printed green ceramic sheets for step-by-step lamination. First, place a thin green ceramic sheet (thickness of 15 μm), a green ceramic sheet with a printed temperature-sensitive element, and a green ceramic sheet with a printed first pressure-sensitive electrode or second pressure-sensitive electrode on a pressure-sensitive element on a laminating machine for alignment and lamination (wherein the temperature-sensitive element and the pressure-sensitive element are offset in the vertical direction). The lamination temperature is 65°C, the lamination pressure is 10 MPa, and the lamination time is 20 s to obtain component 1. Then, place a green ceramic sheet with a cavity hole, a green ceramic sheet with a printed pressure-sensitive lower electrode, 5 green ceramic sheets with through-hole electrodes, and a green ceramic sheet with a printed surface electrode on a laminating machine for alignment and lamination. The lamination temperature is 65°C, the lamination pressure is 10 MPa, and the lamination time is 20 s to obtain component 2. Finally, place component 1 and component 2 on a laminating machine for lamination. The lamination temperature is 65°C, the lamination pressure is 3 MPa, and the lamination time is 10 s to obtain a ceramic sensor blank.

[0046] (3) The ceramic sensor blank was placed in a high-temperature electric furnace, heated at a rate of 1.5°C / min to 450°C, and kept at that temperature for 120 minutes to completely remove organic matter from the multilayer ceramic raw material. The temperature was then heated at a rate of 10°C / min to 850°C, and kept at that temperature for 30 minutes to sinter the ceramic sensor sample. In the obtained ceramic sensor, the thickness of the cavity structure was 40 microns and the diameter was 680 microns. The average distance between the temperature sensitive element and the upper surface of the ceramic substrate with the cavity structure was 11 μm, the average distance between the upper surface of the cavity structure and the upper surface of the ceramic substrate with the cavity structure was 200 microns, and the average distance between the lower surface of the cavity structure and the lower surface of the ceramic substrate with the cavity structure was 800 microns.

[0047] (4) First, prepare 6 pins on the battery cover according to the assembly position. Their positions correspond to the positions of the sensor lead electrodes, so as to lead the sensor signal to the outside of the battery and connect it to the signal processing circuit. Apply inorganic adhesive on one side of the sensor surface electrode, then stick it to the assembly position and clamp it with a fixture. Place it in a 150℃ oven for 2 hours to complete the bonding and curing, and obtain a sensor sample integrated with the lithium battery cover.

[0048] (5) Connect the signal conditioning circuit and perform sensor calibration, and write the parameters into the circuit microcontroller to complete the preparation of the ceramic sensor for lithium battery monitoring.

[0049] Example 2: The preparation of a ceramic sensor for lithium battery status monitoring using an NTC temperature sensitive element, a 5mm diameter piezoresistive pressure sensitive element, a flexible wiring signal output, and eutectic welding integrated with a battery cover includes the following steps: (1) According to the designed drilling positions, holes are drilled on the surface of the multilayer ceramic raw material (thickness 0.13 mm), including through holes with a diameter of 200 microns and cavity holes (or macropores) with a diameter of 5 mm, and the through holes are filled with silver electrode paste. Then, the NTC paste is printed on the surface of the raw material according to the electrode pattern of the temperature sensitive element using the screen printing process; the silver electrode paste is printed on the surface of the raw material with through holes according to the Wheatstone bridge pattern of the pressure sensitive element and the piezoresistive paste is printed on the surface of the raw material with through holes according to the pattern of the lead and welding external electrode; the silver palladium gold electrode paste is printed on the surface of the same raw material with through holes, and then placed in a 70℃ oven to dry for 20 minutes for use;

[0050] (2) Use the printed green ceramic sheets for lamination. Place a thin green ceramic sheet (thickness of 15 μm), a green ceramic sheet with printed NTC temperature sensitive elements, a green ceramic sheet with printed Wheatstone bridge and varistor, a green ceramic sheet with a cavity hole, 5 green ceramic sheets with through-hole electrodes, and a green ceramic sheet with printed surface metal external electrodes on a laminating machine for alignment and lamination (wherein the temperature sensitive element and the pressure sensitive element are offset in the vertical direction). The lamination temperature is 65 ° C, the lamination pressure is 10 MPa, and the lamination time is 20 s to obtain a ceramic sensor blank. (3) The ceramic sensor blank was placed in a high-temperature electric furnace, heated at a rate of 1.5°C / min to 450°C, and kept at that temperature for 120 minutes to completely remove organic matter from the multilayer ceramic green sheet material. The temperature was then heated at a rate of 10°C / min to 850°C, and kept at that temperature for 30 minutes to sinter the ceramic sensor sample. In the obtained ceramic sensor, the thickness of the cavity structure was 50 microns and the diameter was 420 microns. The average distance between the temperature sensitive element and the upper surface of the ceramic substrate with the cavity structure was 11 μm, the average distance between the upper surface of the cavity structure and the upper surface of the ceramic substrate with the cavity structure was 200 microns, and the average distance between the lower surface of the cavity structure and the lower surface of the ceramic substrate with the cavity structure was 800 microns.

[0051] (4) First, cut a slit on the battery cover according to the assembly position, insert the flexible cable and seal it by extrusion. Its position corresponds to the position of the sensor lead electrode to lead the sensor signal to the outside of the battery and connect it to the signal processing circuit. Weld the cable terminal on the inside of the battery cover to the lead electrode on the surface of the sensor by ultrasonic welding or soldering. Then, sandwich the eutectic welding piece between the welding electrode on the surface of the sensor and the lithium battery cover. After adjusting the assembly position, use a clamp to clamp and tighten it. Place it in an electric furnace and slowly heat it to 300℃. Keep it warm for 5 minutes to complete the welding. Then, obtain a sensor sample integrated with the lithium battery cover.

[0052] (5) Connect the signal conditioning circuit and perform sensor calibration, and write the parameters into the circuit microcontroller to complete the preparation of the ceramic sensor for lithium battery monitoring.

[0053] Temperature-response time curve test: The LTCC pressure / temperature integrated sensitive element test platform includes an air pressure controller, a sealed test chamber, a silicone oil constant temperature bath, a signal acquisition circuit, and a high-precision resistance meter.

[0054] When testing the response of the temperature sensitive element in the ceramic sensor obtained in Example 1, the sensitive element in the ceramic sensor was connected to a high-precision resistance meter and then placed in a silicone oil thermostat with a set temperature. After 10 minutes of heat preservation, the resistance reading was read and the data was recorded. The standard temperature was provided by a strictly calibrated thermostat, the test range was -40℃~150℃, and the detection step was 5℃. The temperature sensitivity test data is shown in the figure below. Figure 5 As shown in the figure, T1, T2, T3, T4, T5 and T6 represent 6 temperature sensitive elements with different electrode widths and lengths. The sensitivity of the optimal sample T1 reaches 0.33Ω / ℃.

[0055] Pressure sensitivity test: Pressure sensitive element response test: Place the ceramic sensor prepared in Example 1 into a sealed test chamber, connect the output air pipe of the air pressure controller to the test chamber, connect the signal reading circuit and start the test. The air pressure controller provides standard air pressure, sets the detection range to 0~1MPa apparent pressure, and the detection step length to 100KPa. Perform three pressurization-depressurization cycles and record the data. Calculate the average value of the three tests (subtract the capacitance value at 0 pressure from the capacitance value at maximum pressure, and then divide by the change in pressure, i.e. 1MPa, or 1000kPa). The measurement curve is as follows: Figure 6 As shown, the average sensitivity of the ceramic sensor of Example 1 is 14.42 fF / kPa.

[0056] Corrosion resistance test: The ceramic sensor prepared in Example 1-2 was immersed in lithium battery electrolyte (the main component of lithium battery electrolyte is lithium hexafluorophosphate, and the solvent is dimethyl phosphate DMC) at room temperature (25°C) for 16 days and then disassembled (as shown in Figure 1). Figure 7 The test results, shown in Table 1, show that the mass and resistance remained essentially unchanged before and after immersion. Specifically, the ceramic sensor's mass changed by no more than ±0.5wt%, and its resistance changed by no more than ±1.0%. This slight increase in mass is likely due to a very small amount of electrolyte adhering to the ceramic sensor surface. The change in resistance is attributed to the change in air temperature before and after the test.

[0057] Table 1 shows the changes in mass and resistance of the ceramic sensor before and after immersion: .

[0058] Among them, sample No. 1 represents the ceramic sensor prepared in Example 1 Device Sample No. 2 represents the ceramic sensor prepared in Example 1. Device , Sample No. 3 represents the ceramic sensor prepared in Example 1.

Claims

1. A ceramic sensor, characterized in that: The ceramic sensor comprises: Ceramic substrate with cavity structure, A pressure sensitive element having a cavity structure provided in a ceramic substrate, and A temperature sensitive element provided in a non-cavity structure area of the ceramic substrate; The pressure sensitive element is a capacitive pressure sensitive element consisting of a cavity structure, a first pressure sensitive electrode provided on the upper surface of the cavity structure, and a second pressure sensitive electrode provided on the lower surface of the cavity structure. Alternatively, the pressure sensitive element is a piezoresistive pressure sensitive element consisting of a cavity structure, a Wheatstone bridge and a piezoresistor arranged on the inner surface of the cavity structure.

2. The ceramic sensor according to claim 1, characterized in that When the pressure sensitive element is a capacitive pressure sensitive element, the upper surface and the lower surface of the cavity structure are parallel.

3. The ceramic sensor according to claim 1, characterized in that The ceramic sensor further comprises a plurality of metal through-hole electrodes; the metal through-hole electrodes are electrically connected to the pressure sensitive element and the temperature sensitive element respectively.

4. The ceramic sensor according to claim 3, characterized in that When the pressure sensitive element is a capacitive pressure sensitive element, the number of the metal through-hole electrodes is at least 5, preferably 5 to 8; Alternatively, when the pressure sensitive element is a piezoresistive pressure sensitive element, the number of the metal through-hole electrodes is at least 6, preferably 5 to 8.

5. The ceramic sensor according to claim 3 or 4, characterized in that: The metal through-hole electrodes are electrically connected to the pressure sensitive element and the temperature sensitive element respectively through a plurality of internal line electrodes provided in the ceramic substrate; And / or, the ceramic sensor further includes a lead electrode electrically connected to the metal through-hole electrode.

6. The ceramic sensor according to any one of claims 1 to 5, characterized in that A metal electrode layer is further provided on the lower surface of the ceramic substrate having the cavity structure; preferably, the thickness of the metal electrode layer is at least 1000 nm.

7. The ceramic sensor according to any one of claims 1 to 6, characterized in that The thickness of the cavity structure is 5 to 200 microns; and / or, an average distance between the upper surface of the cavity structure and the upper surface of the ceramic substrate having the cavity structure is 200 to 400 micrometers; and / or, an average distance between the lower surface of the cavity structure and the lower surface of the ceramic substrate having the cavity structure is ≥800 μm; Preferably, the cavity structure is cylindrical or rectangular; More preferably, when the cavity structure is cylindrical, the diameter of the cavity structure is at least 5 mm; More preferably, when the cavity structure is in a rectangular parallelepiped shape, the length of the cavity structure is at least 4 mm and the width is at least 4 mm.

8. The ceramic sensor according to any one of claims 1 to 7, characterized in that: The temperature sensitive element and the pressure sensitive element are staggered in the vertical direction; preferably, the temperature sensitive element is arranged in a non-cavity structure area above the upper surface of the cavity structure; more preferably, the average distance between the temperature sensitive element and the upper surface of the ceramic substrate having the cavity structure is ≤15 μm, and most preferably 5-15 μm; And / or, the temperature sensitive element is a positive temperature coefficient thermistor or a negative temperature coefficient thermistor.

9. A method for preparing a ceramic sensor, characterized in that: The preparation method comprises the following steps: (1) punching the multilayer green ceramic tape, wherein the punching process includes preparing through holes required for metal through-hole electrodes and / or macroholes required for cavity structures; (2) Printing a first pressure-sensitive electrode, a second pressure-sensitive electrode, a temperature-sensitive element, a metal electrode layer, or constructing a Wheatstone bridge and a varistor on the inner surface of the cavity structure on a plurality of green ceramic tapes having only through holes; (3) laminating and cutting the green ceramic strip obtained in step (1) and the green ceramic strip obtained in step (2) in the order of the internal structure of the ceramic sensor according to any one of claims 1 to 8 to obtain a green body; (4) The obtained green body is co-fired to obtain the ceramic sensor.

10. The preparation method according to claim 9, characterized in that After the punching process, the through-holes are filled with metal electrode slurry to obtain metal through-hole electrodes.

11. Use of the ceramic sensor according to any one of claims 1 to 8 in monitoring the internal state of a battery.

12. A battery cell with a monitorable internal state, characterized in that: include: A battery cell, and the ceramic sensor according to any one of claims 1 to 8 arranged inside the battery cell.

13. The battery cell with internal state monitorable according to claim 11, characterized in that: The ceramic sensor is arranged on the inner side of the cover plate of the battery unit; preferably, the battery unit is a lithium battery unit.

14. A battery pack, characterized in that: include: A battery module composed of a plurality of battery cells with monitorable internal states as claimed in claim 12 or 13.

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