Lithium-ion battery assembly and battery expansion pressure detection method

Abstract

The present application provides a lithium-ion battery assembly and a battery expansion pressure detection method, which belongs to the field of lithium-ion battery technology. The lithium-ion battery assembly includes: at least two battery cells and an ion capacitive thin film sensor sandwiched between each two battery cells; the ion capacitive thin film sensor includes an ion membrane layer and an electrode array layer arranged under the ion membrane layer, at least one first electrode unit in the electrode array is pressed with the ion membrane layer to form at least one temperature sensing unit, and at least one second electrode unit is not pressed and contacted with the ion membrane layer to form at least one pressure sensing unit. The present application can improve the accuracy of battery expansion pressure calculation.

Description

Technical Field

[0001] The present application relates to the technical field of lithium-ion batteries, and in particular to a lithium-ion battery assembly and a battery expansion pressure detection method. Background Art

[0002] New energy vehicles and electrochemical energy storage are key supporting industries for the development of my country's major renewable energy transformation strategy. Battery safety issues are an important obstacle to the large-scale development of electrochemical energy storage systems (application scenarios). The traditional battery management system (BMS) estimates and manages the battery system by measuring the voltage of the single cell, the temperature of the module, and the current of the battery pack. However, the traditional BMS technology cannot provide effective early warning for sudden battery death.

[0003] Lithium-ion batteries are physical-electrochemical systems. Since stress and strain are closer to the essence of changes in the crystal structure inside the battery, measuring the expansion force of lithium-ion batteries during operation makes it easier to monitor the sudden death of batteries that was previously difficult to warn. Monitoring the expansion pressure through an ion capacitive film pressure sensor can quickly detect significant lithium deposition and gas production defects in the battery. It can also be used to estimate battery SOC and other states, making up for the difficulty in state estimation of LFP batteries due to the wide voltage platform.

[0004] The ion capacitive thin film pressure sensor is based on the piezoelectric effect and outputs the corresponding capacitance value. The expansion pressure inside the battery can be calculated through the output capacitance value. However, the ion capacitive thin film pressure sensor will be affected by the ambient temperature, such as Figure 1 As shown, it shows the influence of temperature fluctuation on the output capacitance value of the pressure sensor when a periodic fixed pressure is applied to the ion capacitive pressure sensor. It can be seen that at different temperatures, the capacitance values ​​output by the same pressure are different.

[0005] However, in the prior art, a separate temperature sensor and a capacitive pressure sensor are usually provided in the battery assembly to monitor the temperature and pressure of the battery assembly respectively. As a result, the battery expansion pressure calculated based on the capacitance value measured by the pressure sensor still has a certain deviation and cannot truly reflect the health status of the battery. Therefore, an improved technical solution is urgently needed to solve the above problem. Summary of the invention

[0006] The object of the present invention is to provide a lithium-ion battery assembly and a battery expansion pressure detection method to solve at least one of the above technical problems.

[0007] In a first aspect of the present application, a lithium-ion battery assembly is provided, the lithium-ion battery assembly comprising: at least two battery cells and an ion capacitive thin film sensor sandwiched between every two battery cells;

[0008] The ion capacitive thin film sensor includes an ion membrane layer and an electrode array layer arranged under the ion membrane layer, at least one first electrode unit in the electrode array is pressed together with the ion membrane layer to form at least one temperature sensing unit, and at least one second electrode unit is in non-pressed contact with the ion membrane layer to form at least one pressure sensing unit.

[0009] Optionally, the temperature sensing unit is formed by pressing the first electrode unit and the ion membrane layer together by hot pressing, ultrasonic welding or solution casting; and the electrode array layer is a planar interdigitated electrode layer.

[0010] Optionally, the temperature sensing unit and the pressure sensing unit have the same temperature influence factor representing the weight of the influence of temperature on the output capacitance value.

[0011] Optionally, each of the temperature sensing units and each of the pressure sensing units are circular or square; the at least one temperature sensing unit and the at least one pressure sensing unit together form a sensing unit array of m rows and n columns, where m and n are both positive integers greater than 1.

[0012] Optionally, in the ion capacitive thin film sensor, a first spacing between adjacent sensing units in a middle region is smaller than a second spacing between adjacent sensing units in an edge region.

[0013] Optionally, at least one temperature sensing unit and at least one pressure sensing unit are distributed in each array sub-area of ​​the ionic capacitive thin film sensor.

[0014] In a second aspect of the present application, a method for detecting battery expansion pressure is provided, the method being applied to the lithium-ion battery assembly described in any one of the embodiments of the present application, comprising:

[0015] Acquire a first capacitance value collected by the pressure sensing unit;

[0016] Acquire a second capacitance value collected by a temperature sensing unit adjacent to the pressure sensing unit;

[0017] The expansion pressure of the battery cell is calculated based on the first capacitance value and the second capacitance value.

[0018] Optionally, acquiring the second capacitance value collected by a temperature sensing unit adjacent to the pressure sensing unit includes: acquiring the second capacitance value collected by at least one temperature sensing unit that is separated from the pressure sensing unit by a first distance range.

[0019] Optionally, calculating the expansion pressure of the battery cell based on the first capacitance value and the second capacitance value includes:

[0020] Based on the ratio between the first capacitance value and the second capacitance value, obtaining a contact area percentage between the second electrode unit of the pressure sensing unit and the ion membrane layer;

[0021] A calibration value of the expansion pressure of the battery cell at a first position is calculated based on the contact area percentage and a proportional factor between the contact area percentage between the second electrode unit and the ion membrane layer and the applied pressure related to the ion capacitive thin film sensor, wherein the first position is a position in the battery cell corresponding to the pressure sensing unit.

[0022] Optionally, the calculating the expansion pressure of the battery cell based on the first capacitance value and the second capacitance value further includes:

[0023] The calibrated value of the expansion pressure of the battery cell at the second position is calculated based on the calibrated value of the expansion pressure at at least one first position adjacent to the second position, the second position being a position in the battery cell corresponding to the temperature sensing unit.

[0024] The lithium-ion battery assembly and battery expansion pressure detection method in the present application form an isomorphic thin film pressure sensing unit and a thin film temperature sensing unit through an ion capacitive thin film sensor, and are placed in the interlayer between two battery cells at the same time; the pressure sensing unit will be affected by both temperature and pressure, and although the temperature sensor is sandwiched in the interlayer, because its electrode unit has been pressed together with the ion membrane layer, it is no longer affected by force but only by temperature, and is insensitive to mechanical changes. Therefore, the lithium-ion battery assembly in the present application can accurately measure the temperature of the battery assembly through the sensing capacitance value of the temperature sensing unit on the one hand, and correct the sensing capacitance value of the pressure sensing unit according to the sensing capacitance value of the temperature sensing unit on the other hand, thereby eliminating the influence of temperature on the sensing capacitance value of the pressure sensor and improving the accuracy of pressure measurement in the battery assembly. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope of the present application.

[0026] Figure 1 A schematic diagram of the effect of temperature on the output signal of an ion capacitive pressure sensor in one embodiment;

[0027] Figure 2 A schematic diagram of the structure of a lithium-ion battery assembly in one embodiment;

[0028] Figure 3 A schematic diagram of the structure of an ion capacitive thin film sensor in one embodiment;

[0029] Figure 4 Schematic diagram of a flow chart of a battery expansion pressure detection method in one embodiment.

[0030] Explanation of the accompanying drawings: 10, ion capacitive thin film sensor; 20, battery cell; 30, support plate; 40, locking baffle; 50, locking column; 60, acquisition board; 70, fixing frame; 80, locking nut; 11, pressure sensing unit; 12, temperature sensing unit; 13, sensing unit wiring group; 15, array sub-area; 61, connecting terminal. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0032] All terms (including technical and scientific terms) used in this application have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used here should be interpreted as having a meaning consistent with the context of this specification, and should not be interpreted in an idealized or overly rigid manner.

[0033] For example, the terms "first", "second", etc. used in this application are only used to distinguish similar objects and to differentiate the first object from another object, rather than to describe a specific order or sequence, and cannot be understood as indicating or implying relative importance.

[0034] The present application proposes a lithium-ion battery assembly, which includes: at least two battery cells and a thin film sensor. The thin film sensor is sandwiched between every two battery cells (or "battery cells"), and is used to measure the temperature and pressure of any one of the two battery cells. The thin film sensor can be an ion capacitive thin film sensor, which has the ability to measure temperature and pressure simultaneously.

[0035] Specifically, a lithium-ion battery assembly may include multiple battery cells, each of which is stacked in series or in parallel, and together with an ion capacitive thin film sensor and other related components (such as the shell covering the battery cell, etc.) forms a lithium-ion battery assembly. Among them, an ion capacitive thin film sensor is sandwiched between each two adjacent battery cells, and the battery cells at both ends of the battery assembly are also provided with corresponding ion capacitive thin film sensors on the side of the battery cell close to the end of the battery assembly, so that the pressure and temperature of the end surface can be measured.

[0036] like Figure 2 As shown, the lithium-ion battery assembly may include a plurality of battery cells 20 , a plurality of ion capacitive film sensors 10 , a support plate 30 , a locking baffle 40 , a locking column 50 , a fixing frame 70 , a collection plate 60 and a locking nut 80 .

[0037] Among them, an ion capacitive thin film sensor 10 and a support plate 30 are sandwiched between each two adjacent battery cells 20. The support plate 30 is used to support the ion capacitive thin film sensor. Corresponding support plates 30 and locking baffles 40 are also provided at the head and tail ends of the battery assembly. The edge of the support plate 30 and the edge of the locking baffle 40 are provided with multiple through holes. The number of locking holes 50 is the same as the number of through holes of a single support plate 30 and a single locking baffle 40. It can pass through one of the through holes on each support plate 30 and each locking baffle 40, and the relevant battery cells 20 and ion capacitive thin film sensors 10 are fixed by locking nuts and components such as a fixing frame 70 and a collection board 60 on one side of the battery cell 20. The collection board 60 is provided with a connecting terminal 61 at the interlayer between each two adjacent battery cells 20, so as to facilitate the collection of the output signal of the ion capacitive thin film sensor 10 from the connecting terminal.

[0038] The ion capacitive thin film sensor comprises an ion membrane layer and an electrode array layer arranged under the ion membrane layer, at least one first electrode unit in the electrode array is pressed together with the ion membrane layer to form at least one temperature sensing unit, and at least one second electrode unit is in non-pressed contact with the ion membrane layer to form at least one pressure sensing unit.

[0039] Combination Figure 3 FIG. 1 is a schematic diagram of the structure of an ion capacitive thin film sensor 10 in an embodiment. The ion capacitive thin film sensor may be a sensor array formed by a plurality of sensing units, each of which may be a pressure sensing unit 11 or a temperature sensing unit 12.

[0040] The ion capacitive thin film sensor is composed of an ion membrane layer located at the upper layer and an electrode array layer located at the lower layer. The electrode array layer includes a plurality of electrode units arranged in an array below the ion membrane layer.

[0041] The ion membrane layer is made of a polymer material with ion conductivity (such as polymer electrolyte, ion exchange membrane, etc.). This material can allow ions to migrate inside the membrane layer under the action of an electric field, thereby achieving a capacitive effect. The electrode array layer is arranged below the ion membrane layer to form a capacitive structure with the ion membrane layer.

[0042] The electrode array layer includes multiple electrode units, which are arranged in a specific manner. The electrode array layer is usually made of conductive materials, such as metals with good conductivity and chemical stability (such as copper, silver, gold, etc.), conductive polymers or carbon materials, etc., to adapt to the harsh working environment of the battery assembly. The electrode array layer and the ion membrane layer together form a capacitor structure for monitoring the temperature and pressure changes of the battery assembly.

[0043] Part of the electrode units (referred to as the first electrode units) are pressed together with the ion membrane layer area covered above them, and the other part of the electrode units (referred to as the second electrode units) are not pressed together with the ion membrane layer area above them. The pressed electrode units and the corresponding ion membrane layer area no longer have microstructure features, forming a corresponding temperature sensing unit; while the unpressed electrode units and the corresponding ion membrane layer area still retain the original microstructure features, forming a corresponding pressure sensing unit.

[0044] The first electrode unit and the ion membrane layer are pressed together to form a temperature sensing unit, so that the electrode unit and the ion membrane layer form good contact, which is not affected by pressure but only by temperature, so that the temperature change of the battery assembly can be monitored by the capacitance effect. When the temperature of the battery assembly rises, the capacitance value between the ion membrane layer and the electrode unit will change, and by measuring this change, real-time monitoring of the temperature can be achieved.

[0045] The second electrode unit and the ion membrane layer are not pressed into contact to form a pressure sensing unit. This non-pressed structure allows a certain gap between the electrode unit and the ion membrane layer, so that the capacitive effect can be used to monitor the pressure change of the battery assembly. When the expansion pressure is generated on the surface of the battery assembly, the gap and contact area between the electrode unit and the ion membrane layer will change, and the flexible ion film dielectric layer will deform, causing the capacitance of the electrode unit to change, thereby converting the expansion pressure inside the electronic component into a sensing capacitance value. However, since the sensing capacitance value of the pressure sensing unit is also affected by temperature at the same time, there will be a certain error in measuring pressure only by the sensing capacitance value of the pressure sensing unit. Since the sensing capacitance values ​​of the isomorphic pressure sensing unit and the temperature sensing unit are affected by the same temperature, the present application corrects the sensing capacitance value of the pressure sensing unit by the sensing capacitance value of the temperature sensor, so that the expansion pressure distribution of the battery assembly can be measured more accurately.

[0046] The arrangement of the sensing units formed by the pressure sensing unit and the temperature sensing unit in the ion capacitive thin film sensor can be flexibly adjusted according to actual needs and designs (for example, according to the shape, size and monitoring requirements of the battery component, etc.), and the arrangement can be linear arrangement, matrix arrangement (or grid arrangement), ring arrangement or other arbitrary irregular arrangement.

[0047] The ion capacitive thin film sensor in this application forms an isomorphic thin film pressure sensing unit and a thin film temperature sensing unit, which are placed in the interlayer between two battery cells at the same time. The pressure sensing unit will be affected by both temperature and pressure, and measure the mechanical characteristics of the corresponding position on the surface of the battery cell; and although the temperature sensor is sandwiched in the interlayer, because its electrode unit has been pressed together with the ion membrane layer, it is no longer affected by force but only by temperature, and is insensitive to mechanical changes.

[0048] Therefore, the lithium-ion battery assembly in the present application can accurately measure the temperature of the battery cells in the battery assembly through the sensing capacitance of the temperature sensing unit, and correct the sensing capacitance of the pressure sensing unit according to the sensing capacitance of the temperature sensing unit, thereby improving the accuracy of the pressure measurement in the battery assembly. The lithium-ion battery assembly in the present application can be widely used in electric vehicles, energy storage systems, portable electronic devices and other fields. By integrating ion capacitive thin film sensors, real-time monitoring and early warning of the temperature and pressure of the battery assembly can be achieved, improving the safety and reliability of the battery assembly.

[0049] In one embodiment, the temperature sensing unit is formed by pressing the first electrode unit and the ion membrane layer together by hot pressing, ultrasonic welding or solution casting; the ion membrane layer is an ionizing thin film layer with a microstructure; and the electrode array layer is a planar interdigitated electrode layer.

[0050] In this embodiment, before the ion membrane layer and the first electrode unit are pressed together, the ion membrane layer and the first electrode unit and other related materials may be pretreated first. The pretreatment may include one or more of cleaning, impurity removal, and deoxidation of the materials.

[0051] For the hot pressing method, a hot pressing device that provides uniform and controllable heating temperature and pressure can be used to press the ion membrane layer and the first electrode unit. During the pressing process, the ion membrane layer and the first electrode unit can be aligned according to a predetermined position, and then placed in a mold of the hot pressing device, and the heating temperature and pressure are adjusted to an appropriate range for pressing. The pressing time is determined according to the characteristics of the material and the required pressing strength. The pressed ion membrane layer and the first electrode unit are removed from the mold, and necessary cooling and curing treatment is performed to ensure the stability and reliability of the pressed part.

[0052] The temperature sensing unit is formed by pressing the first electrode unit and the ion membrane layer together by heat pressing, which can ensure a close connection between the two and improve the overall strength and stability of the temperature sensing unit.

[0053] For the ultrasonic welding method, an ultrasonic welding device with appropriate frequency and amplitude can be selected, and the welding parameters can be set according to the material properties of the ion membrane layer and the first electrode unit. During the welding process, the ion membrane layer and the first electrode unit are aligned and placed in the fixture of the ultrasonic welding device. Start the welding equipment, and the energy generated by the ultrasonic vibration will cause the two to generate friction heat at the contact surface and fuse with each other. After the welding is completed, the pressed ion membrane layer and the first electrode unit are subjected to necessary inspections, such as appearance inspection, resistance test, etc., to ensure that the welding quality meets the requirements. If necessary, the welding parameters can be fine-tuned to optimize the welding effect.

[0054] Ultrasonic welding can achieve fast and precise welding, ensuring close bonding between the first electrode unit and the ion membrane layer to form a temperature sensing unit while avoiding thermal damage to the material.

[0055] For the solution casting method, a solvent that can dissolve the ion membrane material and is compatible with the surface of the first electrode unit can be selected first; then the ion membrane material (such as Nafion membrane powder) is added to the selected solvent, and fully dissolved by stirring or heating to form a uniform solution. The temperature and stirring speed need to be controlled during the dissolution process to ensure the completeness of the dissolution and the stability of the solution.

[0056] According to the characteristics of the ion membrane material and the required thickness, the concentration of the solute in the solution is adjusted; some additives such as surfactants, cross-linking agents, etc. are added to the solution as needed to improve the properties of the solution or enhance the performance of the membrane layer; the prepared solution is filtered to remove insoluble matter or impurities, and the bubbles in the solution are removed by degassing to ensure the purity and smoothness of the solution during casting.

[0057] Before casting, the surface of the first electrode unit is pretreated, such as cleaning, drying and activation, to ensure good bonding with the solution; after the pretreatment, the solution is evenly coated on the first electrode unit by drip coating, scraping, spin coating or spraying. After the casting is completed, the electrode unit coated with the solution is placed in a ventilated or heated environment to allow the solvent to evaporate gradually. After the solvent is completely evaporated, the film layer can be cured, such as by heating or ultraviolet irradiation, to enhance its structure and performance.

[0058] Through the above detailed solution casting process, it is possible to ensure that the first electrode unit of the temperature sensing unit is well bonded with the ion membrane layer, and at the same time obtain a temperature sensing unit with excellent temperature sensitivity and electrochemical performance.

[0059] The ion membrane layer in the present application is an ion-type flexible film layer with microstructures, and these microstructures can be in the shape of nanopores, microchannels, microprotrusions, etc. These microstructures can increase the surface area of ​​the ion membrane layer, improve the ion conduction efficiency, and help improve the capacitance effect. The specific structure and preparation method of the ion membrane layer can refer to the introduction in patents CN119060476A and CN119060387A, which will not be repeated here. The microstructure of the ion membrane layer contributes to the efficient transmission of ions and improves the performance of the battery.

[0060] The planar interdigitated electrode layer is an interdigitated circuit prepared on a flexible circuit board. The electrode units are arranged in a planar form, and an interdigitated structure is formed between adjacent electrode units. This structure can increase the contact area between the electrode units, improve the capacitance effect, and help achieve more accurate monitoring. The planar interdigitated electrode layer can be prepared on the substrate material by micro-machining techniques such as photolithography and etching to form electrode units and interdigitated structures with the desired shape. Then, conductive materials are deposited on the electrode units by electroplating, chemical deposition, etc. to form a complete planar interdigitated electrode layer.

[0061] In one embodiment, the temperature sensing unit and the pressure sensing unit have the same temperature influence factor representing the influence weight of temperature on the output capacitance value.

[0062] Among them, the output signals of the temperature sensing unit and the pressure sensing unit are both capacitance values. The design of the two sensing units makes the change of their capacitance values ​​have a specific relationship with the temperature, that is, the temperature influence factor, and the temperature influence factors that characterize the weight of the influence of temperature on the output capacitance value are the same for both. This means that when the temperature changes, the capacitance value changes of the two sensing units will be affected to the same extent, which facilitates subsequent data processing and calibration, and can more easily eliminate the influence of temperature on the measurement results, thereby obtaining more accurate temperature and pressure values.

[0063] In one embodiment, the battery assembly further includes a plurality of collectors and a daisy chain bus. Each collector is electrically connected to a corresponding ion capacitive thin film sensor sandwiched between every two battery cells, and is used to collect a first capacitance value output by a pressure sensing unit and a second capacitance value output by a temperature sensing unit in the ion capacitive thin film sensor, and the plurality of collectors are interconnected via a daisy chain communication interface.

[0064] Specifically, the collector selects one of the array channels of the ion capacitive thin film sensor through a multiplexer, and connects it to the capacitance-pressure conversion circuit to collect the output capacitance value. Since the temperature sensing unit and the pressure sensing unit are composed of the same electrode form and material, the collection method of the two is the same. The output capacitance value of the temperature sensing unit is only affected by temperature, while the output capacitance value of the pressure sensor is affected by both temperature and pressure because it retains the original microstructure. The capacitance-pressure conversion circuit can refer to the introduction of the prior art CN118961004B, CN118961003B, etc., which will not be repeated here.

[0065] Multiple collectors are connected to each other through a daisy chain communication interface. One collector is used as the master node, and the other collectors are used as slave nodes, which are connected in sequence to form a communication link. The daisy chain communication interface can be a wired interface (such as RS-485, CAN bus, etc.) or a wireless interface (such as Zigbee, LoRa, etc.).

[0066] For each collector, there are two groups of input and output data channels, one of which is connected to the upstream collector, and the other is connected to the downstream collector, thus forming a chain structure. The beginning and end of the chain structure are connected to the BMS system, which sends communication requests and reads communication instructions. When the daisy chain bus is working, each collector receives the upstream data, adds its own data, and forwards it to the downstream. The collected temperature / pressure / voltage and other data can be transmitted and summarized through the daisy chain.

[0067] When the BMS system sends a communication request, the first collector receives the request, adds the data it has collected to the request, and then forwards it to the downstream collector. The downstream collector receives the data from the upstream in turn, adds its own data, and then forwards it to the next collector until the data reaches the end of the chain structure. The last collector sends the data back to the BMS system, which summarizes and processes the received data.

[0068] like Figure 3 As shown, the ion capacitive thin film sensor 10 is further provided with a sensor unit wiring group 13, one end of which is independently connected to each pressure sensing unit 11 and the temperature sensing unit 12, and the other end is connected to the collector. Specifically, the other end of the sensor unit wiring group 13 is electrically connected to the collector via a connection terminal 61.

[0069] The collector can accurately collect the output signal of the sensor unit and eliminate the influence of temperature on the pressure measurement result through the calibration process, so as to obtain more accurate pressure data; multiple collectors are interconnected by using a daisy chain bus, which greatly simplifies the wiring inside the battery assembly and improves the communication efficiency; by increasing the number of collectors or changing the configuration of the collector, the monitoring function of the battery assembly can be easily expanded to meet different application scenarios and needs; the daisy chain bus structure enables each collector to receive upstream data and forward it to downstream, enhancing the fault tolerance and reliability of the system.

[0070] In one embodiment, the shape of each temperature sensing unit and each pressure sensing unit can be any suitable shape and size, and the shape and size of each temperature sensing unit and pressure sensing unit can be the same or different, for example, they can be round or square. The sensing units in the ionic capacitive thin film sensor can form a matrix, for example, an m×n matrix, that is, at least one temperature sensing unit and at least one pressure sensing unit together form a sensing unit array of m rows and n columns, and m and n are both positive integers greater than 1. ij represents the sensor unit at the i-th row and j-th column in the m×n sensor unit array. ij It may be a temperature sensing unit or a pressure sensing unit.

[0071] for example Figure 3 As shown, an 8×9 sensing unit array is formed, and each sensing unit (including temperature sensing units and pressure sensing units) is a square of the same size. The temperature sensing units and the pressure sensing units can be staggered and distributed at various positions in the array. Figure 3 T 22 , T 25 , T 28 , T 52 , T 55 , T58 , T 82 , T 85 , T 88 All are temperature sensing units, and the rest are pressure sensing units. It is understandable that the temperature sensing units and pressure sensing units can also have any other suitable position distribution. By forming an array distribution, it is convenient to measure the temperature and pressure at different positions of the battery cell, so as to obtain the temperature and pressure distribution at different positions of the battery cell.

[0072] Optionally, the relationship between the number of temperature sensing units and the number of pressure sensing units in the ion capacitive thin film sensor may not be limited. For example, the number of temperature sensing units may be less than or equal to the number of pressure sensing units, or may be greater than the number of pressure sensing units. For example, in the ion capacitive thin film sensor, the sensing units T where i is an odd number and j is also an odd number, and i is an even number and j is also an even number are ij As the pressure sensing unit, the remaining sensing units are all used as temperature sensing units, so that the pressure sensing units and the temperature sensing units in the ion capacitive thin film sensor are evenly distributed.

[0073] There is a certain distance between adjacent sensing units (including temperature sensing units and pressure sensing units) to avoid interference between each other. The distances between adjacent sensing units can be the same or different. The distance between two adjacent sensing units can be the distance between the center points of the two sensing units, or the minimum distance between the edges of the two sensing units. For example Figure 3 As shown, each square sensing unit is evenly distributed in the ion capacitive thin film sensor, and the distances between adjacent sensing units are the same.

[0074] In one embodiment, the ion capacitive thin film sensor is configured such that the sensing units in the middle region are densely distributed, while the sensing units in the edge region are sparsely distributed. This distribution design helps provide more intensive monitoring in areas where the temperature and pressure changes more drastically inside the battery assembly.

[0075] Specifically, in the ion capacitive thin film sensor, a first spacing between adjacent sensing units in the middle region is smaller than a second spacing between adjacent sensing units in the edge region, and the sensing units include a temperature sensing unit and a pressure sensing unit.

[0076] In one embodiment, at least one temperature sensing unit and at least one pressure sensing unit are distributed in each array sub-region of the ion capacitive thin film sensor, there is no intersection in each array sub-region, and the number of temperature sensing units in the ion capacitive thin film sensor is less than the number of pressure sensing units.

[0077] In this embodiment, the sensing unit array formed by the ion capacitive thin film sensor can be divided into regions to form a plurality of array sub-regions 15. The region size of each array sub-region can be the same or different. There is no intersection between the array sub-regions, and the union formed by all array sub-regions is all the regions of the sensing unit array. For each divided array sub-region, a certain number of temperature sensing units and pressure sensing units are contained therein.

[0078] like Figure 3 As shown, the ion capacitive thin film sensor can be divided into array sub-areas according to 3×3 or 2×3 sensor unit sub-arrays to form an 8×9 sensor unit array. Array sub-areas 15 corresponding to 9 sensor unit sub-arrays are formed, of which the 6 array sub-areas 15 in the first two rows are 3×3 sensor unit sub-arrays, and the 3 array sub-areas 15 in the last row are 2×3 sensor unit sub-arrays. There is one temperature sensor unit in each sensor unit sub-array (array sub-area), and the rest are pressure sensors. Specifically, the temperature sensor unit in the 3×3 sensor unit sub-array is located in the middle of the corresponding sub-array; the temperature sensor unit in the 2×3 sensor unit sub-array is located at the corresponding 2nd row and 2nd column.

[0079] Furthermore, the positions of the pressure sensing units and the temperature sensing units are distributed so that there is at least one temperature sensing unit within the first distance range of any pressure sensing unit, and the first distance range can be any appropriate distance set. For example, it can be three times the length of the pressure sensing unit. Through such a setting, each pressure sensing unit can correct the first capacitance value of its sensed output based on the second capacitance value measured by the temperature sensing unit within the first distance range, so as to accurately obtain the expansion pressure inside the battery assembly.

[0080] In one embodiment, Figure 4 As shown, a method for detecting battery expansion pressure is provided, the method comprising:

[0081] Step 410: Acquire a first capacitance value collected by a pressure sensing unit.

[0082] Step 420: Acquire a second capacitance value collected by a temperature sensing unit adjacent to the pressure sensing unit.

[0083] Step 430 : Calculate the expansion pressure of the battery cell based on the first capacitance value and the second capacitance value.

[0084] The battery expansion pressure detection method in the present application can be applied to the lithium-ion battery assembly in any of the above embodiments.

[0085] The signals output by the pressure sensing unit and the temperature sensing unit are both capacitance values. The signal output by each pressure sensing unit is recorded as the first capacitance value, and the signal output by each temperature sensing unit is recorded as the second capacitance value. The battery assembly or related BMS and other systems can obtain the signals output by each pressure sensing unit and temperature sensing unit in the ion capacitive film sensor.

[0086] Specifically, based on the characteristics of the above-mentioned temperature sensing unit and pressure sensing unit, since the first capacitance value is affected by both the temperature and pressure of the resistance component, and the second capacitance value is only affected by the temperature of the battery component, on the basis that the two have the same temperature influence factor, based on the positional relationship between the temperature sensing unit and the pressure sensing unit, the first capacitance value can be corrected in combination with the second capacitance value collected by the temperature sensing unit adjacent to the pressure sensing unit, so that the expansion pressure of the battery cell in the battery component can be accurately obtained, and the expansion pressure can be the calibration value described below.

[0087] The temperature sensing unit adjacent to the pressure sensing unit may be the temperature sensing unit closest to the temperature sensing unit, or any one or more temperature sensing units within a preset distance range, which may be any appropriate range.

[0088] In one embodiment, step 420 includes: acquiring a second capacitance value collected by at least one temperature sensing unit that is spaced apart from the pressure sensing unit within a first distance range.

[0089] In this embodiment, the pressure sensing units and temperature sensing units are distributed at different positions of the battery cells, and each pressure sensing unit and temperature sensing unit can reflect the expansion pressure and temperature of the corresponding battery cell at the corresponding position.

[0090] The first distance range can be any suitable distance range, and by presetting the position distribution of the sensing units in the ion capacitive film sensor, any pressure sensing unit can have at least one temperature sensing unit within its first distance range.

[0091] For example, the first distance range is set to 3 times the length of the pressure sensing unit. Figure 3 The pressure sensing unit T 33 The temperature sensing unit matched with the pressure sensing unit (ie, the distance between the pressure sensing unit and the pressure sensing unit is within the first distance range) includes T 22 , T 25 , T 52 , T 55 Total 4; pressure sensing unit T 19 The matching temperature sensing unit includes T 281 in total. When there are multiple matching temperature sensing units, the first capacitance value can be corrected based on the second capacitance value output by any temperature sensing unit among all the matching temperature sensing units, or the first capacitance value can be corrected based on the second capacitance value output by the closest temperature sensing unit, or the first capacitance value can be corrected based on the average value of the second capacitance values ​​output by all the matching temperature sensing units.

[0092] In one embodiment, step 430 includes: calculating the expansion pressure of a battery cell in the battery assembly at a first position corresponding to the pressure sensing unit based on the first capacitance value and a second capacitance value collected by at least one temperature sensing unit within a first distance range, wherein the first position is a position in the battery cell corresponding to the pressure sensing unit.

[0093] Similarly, the battery cells can be divided into regions according to the position distribution of the sensor units in the corresponding ion capacitive thin film sensors. The battery cells can be divided into multiple regions, each region corresponds to one or more sensor units, and there is no intersection between the regions. The corresponding sensor units can be temperature sensor units and / or pressure sensor units. For example, the number of divided regions is the same as the number of sensor units, and each region corresponds to a sensor unit. Taking the above m×n sensor unit array as an example, the battery cells can be divided into m×n regions, with S ij represents the area of ​​the i-th row and j-th column on the battery cell, then area S ij The corresponding sensing unit is sensing unit T ij , T ij Represents the sensor unit of the i-th row and j-th column in the m×n sensor unit array. It can be understood that some areas correspond to temperature sensors and other areas correspond to pressure sensors. Taking the signal output by the pressure sensor x as an example, the first capacitance value is the first position corresponding to the area (or the position within the area) of the pressure sensor x; taking the signal output by the temperature sensor y as an example, the second capacitance value is the second position corresponding to the area (or the position within the area) of the temperature sensor y.

[0094] Specifically, based on the second capacitance value measured by one or more temperature sensing units at a position adjacent to the pressure sensing unit (i.e., the interval distance from the pressure sensing unit is within a first distance range), the first capacitance value sensed individually by the pressure sensing unit is corrected to obtain a calibration value of the expansion pressure, and the calibration value is used as the expansion pressure at the position corresponding to the pressure sensing unit (i.e., the first position) in the battery cell.

[0095] In one embodiment, step 430 includes: obtaining the contact area percentage between the second electrode unit of the pressure sensing unit and the ion membrane layer based on the ratio between the first capacitance value and the second capacitance value; and calculating a calibration value of the expansion pressure of the battery cell at the first position based on the contact area percentage and a proportional factor between the contact area percentage between the second electrode unit and the ion membrane layer and the applied pressure related to the ion capacitive film sensor.

[0096] The first capacitance value is denoted as the first capacitance value Cp, the second capacitance value is denoted as the second capacitance value Ct, and the output value (first capacitance value Cp) of the pressure sensing unit is proportional to the contact area between the ionization membrane (ion membrane) with the microstructure and the electrode unit multiplied by the capacitance value per unit area. In mathematical expression, the first capacitance value Cp can be expressed as the following formula 1:

[0097] (Formula 1).

[0098] in, represents the output capacitance value of the pressure sensing unit, that is, the first capacitance value; is the contact area between the electrode unit of the pressure sensing unit and the ion membrane; represents the contact area correlation coefficient, which is a fixed value; Indicates the capacitance per unit area; The temperature influence factor is an empirical value that represents the weight of the influence of temperature on the output capacitance value of the pressure sensing unit.

[0099] The capacitance per unit area is affected by temperature. When the surface temperature of the battery cell to which the sensor unit contacts changes, the capacitance per unit area changes as follows: Then the above formula 1 can be changed into the following formula 2:

[0100] (Formula 2).

[0101] When the ionizing film is pressed onto the electrode surface by hot pressing / ultrasonic welding and other technologies, it loses its microstructure and becomes a temperature sensing unit. The contact area between the film and the electrode unit is the maximum contact area. And no longer changes, the output capacitance value is only affected by temperature. The second capacitance value Ct output by the temperature sensing unit can be expressed as:

[0102] (Formula 3).

[0103] in, represents the output capacitance value of the temperature sensing unit, that is, the second capacitance value; is the maximum contact area between the ionizing membrane and the electrode unit (total electrode surface area); represents the correlation coefficient of the contact area, which is a fixed value; Indicates the capacitance per unit area affected by temperature changes.

[0104] Divide Formula 2 by Formula 3 to get the output capacitance of the pressure sensing unit. Divide by the output capacitance of the temperature sensing unit (i.e., the ratio between the first capacitance value and the second capacitance value ), and the contact area between the ionized film and the electrode of the pressure sensing unit is obtained. Total electrode surface area Percentage / (i.e. the contact area percentage between the second electrode unit of the pressure sensing unit and the ion membrane layer). That is, the following formula 4 is obtained:

[0105] (Formula 4).

[0106] This percentage is affected by the external pressure, the stiffness coefficient of the ionizing film and the electrode material, and the surface microstructure. Among them, since the stiffness coefficient of the ionizing film and the electrode material, and the surface microstructure can be measured and calibrated in advance and are almost unchanged (approximately linear), it can be concluded that the above percentage is approximately proportional to the external pressure borne by the pressure sensing unit. The linear relationship is shown in the following formula 5:

[0107] (Formula 5).

[0108] It represents the proportionality factor between the contact area percentage and the applied pressure, which can be obtained through calibration; Indicating the applied pressure of the pressure sensing unit, that is, the calibration value of the expansion pressure at the position (that is, the first position) corresponding to the pressure sensing unit. In one embodiment, before step 430, it can also include: obtaining a proportional factor between the contact area percentage between the second electrode unit and the ion membrane layer and the applied pressure related to the ion capacitive thin film sensor.

[0109] As shown in Formula 5 above, the proportional factor of the ion capacitive thin film sensor is obtained by calibration. Under the premise of , then the value of the external pressure (i.e. the calibration value of the expansion pressure) can be calculated, that is .

[0110] In one embodiment, the calibration value of the expansion pressure of the battery cell at the first position is calculated based on the contact area percentage and the proportionality factor between the contact area percentage between the second electrode unit and the ion membrane layer and the applied pressure related to the ion capacitive thin film sensor, including: according to the above formula A calibrated value P of the expansion pressure at the first position is calculated.

[0111] In one embodiment, step 430 further includes: calculating a calibration value of the expansion pressure of the battery cell at a second position based on a calibration value of the expansion pressure at at least one first position adjacent to the second position, wherein the second position is a position in the battery cell corresponding to the temperature sensing unit.

[0112] The calibrated value of the expansion pressure at the second location may be obtained from a calibrated value corresponding to a pressure sensing unit adjacent to the temperature sensing unit.

[0113] For the expansion pressure at the second position, after the calibration values ​​corresponding to each pressure sensing unit are calculated according to the above formula 5, the calibration value of the expansion pressure at the second position is calculated based on the calibration values ​​of one or more adjacent pressure sensing units of the temperature sensing unit corresponding to the second position. For example, the multiple calibration values ​​can be weighted and summed to obtain a value as the calibration value of the expansion pressure at the second position.

[0114] Specifically, when there are multiple pressure sensing units adjacent to the temperature sensing unit, the calibration value corresponding to one of the pressure sensing units can be selected as the calibration value of the expansion pressure at the second position, and the calibration values ​​corresponding to each adjacent pressure sensing unit can be weighted averaged to obtain the obtained value as the calibration value of the expansion pressure at the second position. The weights of each pressure sensing unit can be the same or different. For example, it can be set to 1 / w, where w represents the number of adjacent pressure sensing units. Alternatively, the weight can be determined based on the distance between each adjacent pressure sensing unit and the second position, and the closer the distance, the greater the weight.

[0115] For example, if Figure 3 As shown, when the sensing unit corresponding to the second position is Figure 3 The temperature sensing unit T 22 When, and T 22 The adjacent pressure sensing unit includes T 21 , T 23 , T 12 , T 32 There are 4 in total. After calculating the calibration value of the expansion pressure corresponding to each pressure sensing unit, the calibration values ​​of the four pressure sensing units are weighted averaged to obtain the calibration value of the expansion pressure at the second position. The weights corresponding to the four pressure sensing units can all be 0.25.

[0116] The battery expansion pressure detection method in the present application uses an isomorphic temperature sensor and pressure sensor array formed by an ion-type thin film, and uses the capacitance value sensed by the temperature sensor array to calibrate the capacitance value of the pressure sensor array, thereby obtaining a more accurate pressure value on the surface of the battery cell, thereby realizing the measurement and detection of multi-point temperature and pressure of the battery.

[0117] In one embodiment, after step 430 , the method further includes: determining a health status of the battery assembly based on the swelling pressure.

[0118] In this embodiment, after the expansion pressure at each position of the battery cell is obtained, the health status of the corresponding battery cell and battery assembly can be detected based on the expansion pressure. For example, it can be determined whether the expansion pressure is normal based on the working status of the battery cell or battery assembly. When there is an abnormality, a corresponding warning message is triggered. The specific health status detection method is not repeated here.

[0119] By performing health status analysis based on the measured expansion pressure, an effective early warning of sudden battery death can be given.

[0120] The lithium-ion battery assembly and battery expansion pressure detection method in the present application form an isomorphic thin film pressure sensing unit and a thin film temperature sensing unit through an ion capacitive thin film sensor, and are placed in the interlayer between two battery cells at the same time; the pressure sensing unit will be affected by both temperature and pressure, and although the temperature sensor is sandwiched in the interlayer, because its electrode unit has been pressed together with the ion membrane layer, it is no longer affected by force but only by temperature, and is insensitive to mechanical changes. Therefore, the lithium-ion battery assembly in the present application can accurately measure the temperature of the battery assembly through the sensing capacitance value of the temperature sensing unit on the one hand, and correct the sensing capacitance value of the pressure sensing unit according to the sensing capacitance value of the temperature sensing unit on the other hand, thereby eliminating the influence of temperature on the sensing capacitance value of the pressure sensor and improving the accuracy of pressure measurement in the battery assembly.

[0121] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

[0122] In addition, those skilled in the art will appreciate that, although some embodiments herein include certain features included in other embodiments but not other features, the combination of features of different embodiments is meant to be within the scope of the present application and form different embodiments. For example, all of the above embodiments may be used in any combination. The information disclosed in this background technology section is intended only to deepen the understanding of the overall background technology of the present application and should not be regarded as an admission or in any form to imply that the information constitutes prior art known to those skilled in the art.

Claims

1. A lithium-ion battery assembly, characterized in that: The lithium-ion battery assembly comprises: At least two battery cells and an ion capacitive thin film sensor sandwiched between every two battery cells; The ion capacitive thin film sensor includes an ion membrane layer and an electrode array layer arranged under the ion membrane layer, at least one first electrode unit in the electrode array is pressed together with the ion membrane layer to form at least one temperature sensing unit, and at least one second electrode unit is in non-pressed contact with the ion membrane layer to form at least one pressure sensing unit. The output signals of the temperature sensing unit and the pressure sensing unit are both capacitance values, and the temperature sensing unit and the pressure sensing unit have the same temperature influence factor that characterizes the weight of the influence of temperature on the output capacitance value.

2. The lithium-ion battery assembly according to claim 1, characterized in that: The temperature sensing unit is formed by pressing the first electrode unit and the ion membrane layer together by hot pressing, ultrasonic welding or solution casting; and the electrode array layer is a planar interdigitated electrode layer.

3. The lithium-ion battery assembly according to any one of claims 1 to 2, characterized in that: Each of the temperature sensing units and each of the pressure sensing units are circular or square; the at least one temperature sensing unit and the at least one pressure sensing unit together form a sensing unit array of m rows and n columns, where m and n are both positive integers greater than 1.

4. The lithium-ion battery assembly according to any one of claims 1 to 2, characterized in that: In the ion capacitive thin film sensor, a first distance between adjacent sensing units in a middle region is smaller than a second distance between adjacent sensing units in an edge region.

5. The lithium-ion battery assembly according to any one of claims 1 to 2, characterized in that: At least one temperature sensing unit and at least one pressure sensing unit are distributed in each array sub-area of ​​the ion capacitive thin film sensor.

6. A method for detecting battery expansion pressure, characterized in that: The method is applied to the lithium-ion battery assembly according to any one of claims 1 to 5, comprising: Acquire a first capacitance value collected by the pressure sensing unit; Acquire a second capacitance value collected by a temperature sensing unit adjacent to the pressure sensing unit; The expansion pressure of the battery cell is calculated based on the first capacitance value and the second capacitance value.

7. The battery expansion pressure detection method according to claim 6, characterized in that: The acquiring of the second capacitance value collected by the temperature sensing unit adjacent to the pressure sensing unit includes: acquiring the second capacitance value collected by at least one temperature sensing unit that is spaced within a first distance range from the pressure sensing unit.

8. The battery expansion pressure detection method according to any one of claims 6 or 7, characterized in that: The calculating the expansion pressure of the battery cell based on the first capacitance value and the second capacitance value includes: Based on the ratio between the first capacitance value and the second capacitance value, obtaining a contact area percentage between the second electrode unit of the pressure sensing unit and the ion membrane layer; A calibration value of the expansion pressure of the battery cell at a first position is calculated based on the contact area percentage and a proportional factor between the contact area percentage between the second electrode unit and the ion membrane layer and the applied pressure related to the ion capacitive thin film sensor, wherein the first position is a position in the battery cell corresponding to the pressure sensing unit.

9. The battery expansion pressure detection method according to claim 8, characterized in that: The step of calculating the expansion pressure of the battery cell based on the first capacitance value and the second capacitance value further includes: The calibrated value of the expansion pressure of the battery cell at the second position is calculated based on the calibrated value of the expansion pressure at at least one first position adjacent to the second position, the second position being a position in the battery cell corresponding to the temperature sensing unit.

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