Detection device and early warning system for internal pressure change of battery cell

Abstract

The utility model provides a detection device for internal pressure change of a battery cell, the battery cell comprises an explosion-proof valve or an explosion-proof sheet, and the explosion-proof valve or the explosion-proof sheet is arranged on a shell of the battery cell. When the internal pressure of the battery cell changes, the explosion-proof valve or the explosion-proof sheet deforms at first until the battery cell is broken due to overlarge internal pressure, and the detection device comprises an electrode sheet which is arranged above or on the side of the explosion-proof valve or the explosion-proof sheet, the sensing capacitor and the explosion-proof valve or the explosion-proof sheet form an inductive capacitor, and the deformation of the explosion-proof valve or the explosion-proof sheet is detected based on the capacitance change; and the detection circuit is connected to the electrode thin sheet through a connecting wire and is also connected to the anti-explosion valve or the anti-explosion sheet through a connecting wire. The utility model also provides a battery core internal pressure early warning system.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of battery detection, and in particular to a detection device and early warning system for internal pressure change of a battery cell. BACKGROUND

[0002] The root cause of thermal runaway of a battery cell is that the exothermic side reaction inside the battery cell leads to heat accumulation, and the rate of heat exchange outside the battery cell is less than the rate of heat accumulation, the temperature continues to rise until the ignition point temperature is reached, causing combustion and explosion.

[0003] In order to prevent the occurrence of thermal runaway accidents and avoid the imbalance of internal and external pressure of the battery cell, and considering that a large amount of toxic gas is generated instantaneously when the lithium battery catches fire, the gas needs to be discharged in a timely and directional manner.

[0004] Therefore, it is crucial to detect the internal pressure of the battery cell in advance and give an early warning before an accident occurs in the battery cell. CONTENT OF THE INVENTION

[0005] The present disclosure provides a detection device and early warning system for internal pressure change of a battery cell.

[0006] According to one aspect of the present disclosure, a detection device for internal pressure change of a battery cell is provided, the battery cell comprising a rupture disc or a rupture plate arranged on a housing of the battery cell, the rupture disc or the rupture plate first deforms until it breaks due to excessive internal pressure of the battery cell when the internal pressure of the battery cell changes, the detection device comprising: an electrode sheet arranged above or beside the rupture disc or the rupture plate, forming an induced capacitance with the rupture disc or the rupture plate and detecting deformation of the rupture disc or the rupture plate based on capacitance change; a detection circuit connected to the electrode sheet through a connecting line and also connected to the rupture disc or the rupture plate through a connecting line.

[0007] According to the detection device of at least one embodiment of the present disclosure, the electrode sheet is a multi-segment electrode sheet comprising a plurality of electrode segments, each electrode segment being physically separated and forming an induced capacitance with a different part of the rupture disc or the rupture plate to detect deformation of the different positions of the rupture disc or the rupture plate, and the detection circuit is a multi-channel detection circuit, each channel being connected to each electrode segment through a connecting line in a one-to-one correspondence.

[0008] According to the detection device of at least one embodiment of the present disclosure, each electrode segment maximizes the overlapping area with the rupture disc or the rupture plate.

[0009] According to the detection device of at least one embodiment of the present disclosure, the detection circuit is arranged on the outer surface of the battery cell and close to the tab of the battery cell.

[0010] According to the detection device of at least one embodiment of the present disclosure, the detection circuit is connected to the battery core tab through a connecting line to measure the battery impedance.

[0011] According to the detection device of at least one embodiment of the present disclosure, the detection circuit compares signals from multiple electrode segments, and eliminates the capacitance change caused by the environment according to the comparison of the signals.

[0012] According to the detection device of at least one embodiment of the present disclosure, the electrode sheet is arranged directly above the explosion-proof valve or the explosion-proof sheet, and the two ends of each electrode segment are fixed to the battery core tab or the shell of the battery core.

[0013] According to the detection device of at least one embodiment of the present disclosure, the electrode sheet is arranged on more than two sides of the explosion-proof valve or the explosion-proof sheet.

[0014] According to the detection device of at least one embodiment of the present disclosure, multiple electrode segments are arranged in a ring around the explosion-proof valve or the explosion-proof sheet.

[0015] According to the detection device of at least one embodiment of the present disclosure, the electrode sheet is arranged on the cover plate of the battery box, and after the cover plate is installed, the electrode sheet is located directly above the explosion-proof valve or the explosion-proof sheet in the battery box.

[0016] According to the detection device of at least one embodiment of the present disclosure, the detection circuit is connected with an environmental compensation capacitor, which is used to compensate the inherent induced capacitance between the electrode sheet and the explosion-proof valve or the explosion-proof sheet, so as to accurately sense the capacitance change between the electrode sheet and the explosion-proof valve or the explosion-proof sheet.

[0017] According to the detection device of at least one embodiment of the present disclosure, the detection circuit includes a capacitance-voltage conversion circuit and an analog-to-digital converter, the capacitance-voltage conversion circuit receives the signal of the induced capacitance and converts it into a voltage signal, and the analog-to-digital converter converts the voltage signal into a digital signal.

[0018] According to the detection device of at least one embodiment of the present disclosure, the detection circuit includes a capacitance-voltage conversion circuit and a demodulation and analog-to-digital conversion circuit, wherein the capacitance-voltage conversion circuit modulates the received signal of the induced capacitance into a voltage signal based on an external alternating current signal, and then demodulates and analog-to-digital converts through the demodulation and analog-to-digital conversion circuit, and finally converts into a digital signal.

[0019] According to the detection device of at least one embodiment of the present disclosure, the detection circuit includes a capacitance-frequency conversion circuit and a time-to-digital converter, the capacitance-frequency conversion circuit converts the signal of the induced capacitance into a frequency signal, and the time-to-digital converter converts the frequency signal into a digital signal.

[0020] According to at least one embodiment of the present disclosure, the detection device, the detection circuit comprises a relaxation oscillator and a time-to-digital converter, the relaxation oscillator converts the signal of the sensing capacitor into a frequency signal, and the time-to-digital converter converts the frequency signal into a digital signal.

[0021] According to at least one embodiment of the present disclosure, the detection device, the detection circuit comprises a differential amplifier, a loop filter and a quantizer, the differential amplifier is used for differential measurement of the sensing capacitor and the reference capacitor, to obtain a differential signal, the loop filter is used for Σ-Δ modulation of the differential signal, to obtain a modulation signal, and the quantizer converts the modulation signal into a digital signal, wherein the digital signal is used to control switching of the external excitation voltage and the ground voltage of the reference capacitor.

[0022] According to at least one embodiment of the present disclosure, the detection device, the detection circuit comprises a differential amplifier, a quantizer and a successive approximation logic, the differential amplifier differentially measures the sensing capacitor and the reference capacitor array to obtain a differential signal, the quantizer converts the differential signal into a digital signal, and the successive approximation logic controls switching of the external excitation voltage and the ground voltage of each reference capacitor of the reference capacitor array based on the digital signal.

[0023] According to another aspect of the present disclosure, a battery cell internal pressure early warning system is provided, comprising:

[0024] The detection device for change of internal pressure of a battery cell according to any one of the above;

[0025] A judgment device determines the change of internal pressure of the battery according to the detection signal from the detection circuit, and in the case where the change of internal pressure exceeds a threshold value, an early warning is performed. BRIEF DESCRIPTION OF DRAWINGS

[0026] The accompanying drawings illustrate exemplary embodiments of the present disclosure and together with the general description of the disclosure given above, and the detailed description of the embodiments below, serve to explain the principles of the present disclosure. These drawings are included herewith and constitute a part of this specification.

[0027] Figure 1 is a schematic diagram of a detection device for change of internal pressure of a battery cell according to an embodiment of the present disclosure.

[0028] Figure 2 is a schematic diagram of a detection device for change of internal pressure of a battery cell according to an embodiment of the present disclosure.

[0029] Figure 3 is a schematic diagram of a detection device for change of internal pressure of a battery cell according to an embodiment of the present disclosure.

[0030] Figure 4 is a schematic diagram of a detection device for battery cell internal pressure change according to an embodiment of the present disclosure.

[0031] Figure 5 is a schematic diagram of a detection device for battery cell internal pressure change according to an embodiment of the present disclosure.

[0032] Figure 6 is a schematic diagram of a detection device for battery cell internal pressure change according to an embodiment of the present disclosure.

[0033] Figure 7 is a schematic diagram of a detection device for battery cell internal pressure change according to an embodiment of the present disclosure.

[0034] Figure 8 is a schematic diagram of a detection device for battery cell internal pressure change according to an embodiment of the present disclosure.

[0035] Figure 9 is a circuit structure diagram for capacitance detection according to an embodiment of the present disclosure.

[0036] Figure 10 is a circuit structure diagram for capacitance detection according to an embodiment of the present disclosure.

[0037] Figure 11 is a circuit structure diagram for capacitance detection according to an embodiment of the present disclosure.

[0038] Figure 12 is a circuit structure diagram for capacitance detection according to an embodiment of the present disclosure.

[0039] Figure 13 is a circuit structure diagram for capacitance detection according to an embodiment of the present disclosure.

[0040] Figure 14 is a circuit structure diagram for capacitance detection according to an embodiment of the present disclosure.

[0041] Figure 15 is a circuit structure diagram for capacitance detection according to an embodiment of the present disclosure.

[0042] Figure 16 is a block diagram of a pre-warning system according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0043] The present disclosure will be further described by way of illustration with reference to the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are merely illustrative and not limiting to the present disclosure. It is also to be understood that only parts of the present disclosure that are pertinent to the understanding of the present disclosure are shown in the drawings.

[0044] It should be noted that the embodiments and features of the embodiments in the present disclosure can be combined with each other without conflict. The technical solutions of the present disclosure will be described in detail below with reference to the drawings and in combination with the embodiments.

[0045] Unless otherwise specified, the exemplary embodiments / examples shown will be understood as providing exemplary features of various details that can implement the technical ideas of the present disclosure in practice. Therefore, unless otherwise specified, the features of various embodiments / examples can be additionally combined, separated, interchanged and / or rearranged without departing from the technical ideas of the present disclosure.

[0046] In the drawings, cross-hatching and / or shading are generally used to indicate that a portion of one component is positioned above another component. As such, unless otherwise specified, the presence of cross-hatching or shading is not a requirement of the claimed disclosure and does not convey or imply any preference or requirement for specific material, material properties, dimensions, proportions, commonality of components between illustrated examples, and / or any other characteristic, attribute, property, etc. of the components. In addition, in the drawings, the size and relative sizes of components can be exaggerated for clarity and / or descriptive purposes. When exemplary embodiments can be carried out in different ways, a specific process sequence can be performed in a different order than described. For example, two consecutively described processes can be performed at substantially the same time or in reverse order to the described sequence. In addition, the same reference numerals denote the same components.

[0047] When a component is referred to as being "on" or "over" another component, "connected to" or "coupled to" another component, it can be directly on, directly connected to, or directly coupled to the other component, or intervening components can be present. However, when a component is referred to as being "directly on", "directly connected to", or "directly coupled to" another component, there are no intervening components present. For this reason, the term "connected" can refer to a physical connection, an electrical connection, etc., with or without intervening components.

[0048] For descriptive purposes, the disclosure can use spatially relative terms, such as "below," "beneath," "lower," "under," "above," "upper," "over," and the like, to describe the relative position of one component to another in the drawings. The spatially relative terms are intended to encompass different positions of the devices in use, operation, and / or manufacture in the drawings. For example, if a device in the drawings is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary term "below" can encompass both an orientation of above and below. The devices can be otherwise oriented (e.g., rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0049] The root cause of battery cell thermal runaway is that the exothermic side reaction inside the battery cell causes heat accumulation, the rate of heat exchange outside the battery cell is less than the rate of heat accumulation, the temperature continues to rise until the ignition point temperature is reached, causing combustion and explosion. In order to prevent the occurrence of thermal runaway accidents, avoid the imbalance of internal and external pressure of the battery cell, and at the same time consider that when the lithium battery catches fire, a large amount of toxic gas will be generated instantaneously, which needs to be discharged in time and directionally. The explosion-proof valve or the explosion-proof sheet as a passive safety protection measure for preventing thermal runaway of the battery system can achieve the above requirements of maintaining pressure balance and directional gas discharge.

[0050] At present, the pressure change in the battery cell can be detected by detecting the explosion-proof valve or the explosion-proof sheet. The following lists several detection methods currently used.

[0051] Resistance strain sensor: a sensor with resistance strain gauge as the conversion element. The resistance strain gauge is pasted on the surface of the explosion-proof valve or the explosion-proof sheet. Due to the deformation of the explosion-proof valve or the explosion-proof sheet, the surface is strained, thereby causing the resistance value of the resistance strain gauge to change. By measuring the change of the resistance, the size of the strain (or stress) is reflected.

[0052] Differential transformer sensor: using mutual inductance in electromagnetic induction, the measured displacement of the explosion-proof valve or the explosion-proof sheet is converted into the change of the mutual inductance of the coil.

[0053] Ultrasonic sensor: the deformation of the explosion-proof valve or the explosion-proof sheet is detected by the ultrasonic sensor.

[0054] Compared with other detection methods, the capacitive detection method has the advantages of non-contact, low power consumption and the like. In the present application, the inventors have made careful research and proposed the technical scheme of the present application. According to the technical scheme of the present application, the detection is more accurate and the influence of errors can be eliminated.

[0055] According to one embodiment of the present application, a device for detecting the change of internal pressure of a battery cell is proposed. The battery cell comprises a burst valve or a burst disc, which is arranged on the housing of the battery cell and is the first to deform until it breaks due to excessive internal pressure of the battery cell when the internal pressure of the battery cell changes. In the present application, an electrode foil is arranged to form a capacitive coupling with the burst valve or the burst disc. Both the electrode foil and the burst valve or the burst disc are made of metal material. When the burst valve or the burst disc deforms, the distance between the electrode foil and the burst valve or the burst disc changes, which accordingly causes the capacitance value of the coupling capacitance between them to change. In the present application, the deformation is detected by the change of the capacitance value, and thus the internal pressure of the battery cell is detected. For example, the capacitance value can be related to the distance between them, and thus to the internal pressure of the battery cell. The relationship can be recorded in a table by pre-measurement or fitted by pre-measurement. For this, the relationship will not be described herein, and the relationship can be referred to the related content in the prior art.

[0056] The device for detecting the change of internal pressure of a battery cell comprises an electrode foil. The number of the electrode foil can be one, and the electrode foil can be arranged above or beside the burst valve or the burst disc. The electrode foil and the burst valve or the burst disc can form an inductive capacitance, and the deformation of the burst valve or the burst disc is detected based on the change of the capacitance. Preferably, the electrode foil is a multi-segment electrode foil comprising a plurality of electrode segments. Each electrode segment is arranged above or beside the burst valve or the burst disc to form a distributed detection network. Each electrode segment is physically separated, i.e. physically spaced apart. Each electrode segment forms a coupling capacitance with the burst valve or the burst disc. That is, each electrode segment forms a coupling capacitance with a part of the burst valve or the burst disc, so that the deformation of the part of the burst valve or the burst disc can be detected when the coupling capacitance between each electrode segment and the part of the burst valve or the burst disc changes. That is, the electrode segments respectively detect the deformation of different positions of the burst valve or the burst disc. This design is not only suitable for static detection, but also can monitor the dynamic changes of the burst valve or the burst disc during operation in real time.

[0057] Specifically, each electrode segment acts as an independent sensing unit by forming a coupling capacitance with the burst valve or the burst disc. When the burst valve or the burst disc deforms due to pressure, temperature or other external factors, the distance or dielectric properties between the electrode segment and the burst valve or the burst disc will change, resulting in a corresponding fluctuation of the capacitance value. By analyzing these capacitance changes, the deformation position, degree and even deformation mode (e.g. local bulging, overall bending, etc.) of the burst valve or the burst disc, environmental interference, etc. can be accurately inferred. In addition, the system can combine a signal processing unit to convert the capacitance change data into a visual deformation distribution map, providing support for subsequent analysis and decision-making.

[0058] The detection principle based on capacitive coupling has the characteristic of fast response, so that the electrode sheet can capture the dynamic deformation of the explosion-proof valve or the explosion-proof sheet in real time. The multi-segment electrode sheet realizes partition detection through multiple independent electrode segments, which can more accurately locate the deformation area of the explosion-proof valve or the explosion-proof sheet compared with a single electrode design. This regional monitoring capability is particularly important for identifying local minor deformation, avoiding the problem of missing details due to overall detection.

[0059] According to a further embodiment of the present disclosure, the detection device for internal pressure change of the battery cell can further comprise a detection circuit. The detection circuit can be connected with the electrode sheet and the explosion-proof valve or the explosion-proof sheet through the connecting lines, for obtaining a physical quantity reflecting the change of the capacitance, so as to determine the deformation amount of the explosion-proof valve or the explosion-proof sheet. In the case of a multi-segment electrode sheet, the detection circuit can be a multi-channel detection circuit. The multi-channel detection circuit refers to integrating multiple detection channels on a single detection circuit, which can simultaneously or independently process multiple signals. In the present application, a suitable multi-channel detection circuit can be selected, or an integrated detection circuit with the following circuit can be used. Each channel of the multi-channel detection circuit is connected with each electrode segment through the connecting line one by one, and each channel is connected to the explosion-proof valve or the explosion-proof sheet. In this way, each channel detects the change of the capacitance value of the coupling capacitance between each electrode segment and the explosion-proof valve or the explosion-proof sheet, respectively. In the preferred embodiment of the present application, the detection circuit can be arranged on the outer surface of the battery cell, and arranged at a position close to the tab of the battery cell. The tab of the battery cell is the metal lead of the positive and negative electrodes of the battery cell, which is directly connected to the internal electrode (anode and cathode) of the battery cell, and can be connected with the detection circuit. The detection circuit applies an electrical signal through the tab and measures the response signal. For example, the detection circuit applies a known alternating signal to the battery cell through the tab, and collects the response signal. The impedance characteristics of the battery cell are measured through the collected response signal. For the measurement of impedance, reference can be made to the content of the prior art, which will not be described herein.

[0060] When the internal pressure of the battery cell changes, the explosion-proof valve or explosion-proof plate will deform. Once the internal pressure of the battery cell reaches a preset limit, the explosion-proof valve or explosion-proof plate will open to relieve pressure. Monitoring the internal pressure changes of the battery cell before it reaches the limit and before the explosion-proof valve or explosion-proof plate opens is crucial. By monitoring the internal pressure changes of the battery cell, early warning can be provided, allowing for intervention before thermal runaway occurs. In this application, a coupling capacitance is formed between the electrode sheet and the explosion-proof valve or explosion-proof plate. When the explosion-proof valve or explosion-proof plate deforms, the distance between them changes, and the coupling capacitance value also changes. By detecting this change in coupling capacitance value, internal pressure monitoring can be achieved, further enabling early warning. In various embodiments, those skilled in the art should understand that the electrode sheet and the explosion-proof valve or explosion-proof plate should be insulated.

[0061] Figure 1 A schematic diagram of a detection device for changes in internal pressure of a battery cell, according to an embodiment of the present disclosure, is shown. Figure 1 As shown, an explosion-proof valve or explosion-proof disc 120 is provided on the housing 110 of the battery cell. The explosion-proof valve or explosion-proof disc 120 is made of metal. A metal electrode sheet 130 is positioned directly above the explosion-proof valve or explosion-proof disc 120. Although in Figure 1 Only one motor plate is shown, but electrode plates can be provided. Each electrode plate can extend in the lateral direction of the explosion-proof valve or explosion-proof plate 130, or in the longitudinal direction. For example... Figure 1 As shown, each electrode sheet can be formed directly above the explosion-proof valve or explosion-proof sheet 130 via a support strip 150. The two ends of the support strip 150 can be attached to the tabs on both sides of the battery cell.

[0062] The detection circuit 140 is disposed on the housing 110 of the battery cell and is located close to the battery cell tab. As described above, the detection circuit can be used to detect the battery cell impedance. Although not shown in the figure, the detection circuit 140 is connected to the electrode sheet, the explosion-proof valve or explosion-proof sheet and the battery cell tab via connecting wires, thereby realizing the measurement of capacitance and impedance.

[0063] Figure 2 It shows Figure 1 A schematic diagram illustrating the measurement principle of an embodiment. (As shown...) Figure 2As shown, an induction capacitance is formed between the explosion-proof valve or rupture disc 120 and the electrode sheet 130. The explosion-proof valve or rupture disc 120 and the electrode sheet 130 are connected to the detection circuit 140 through connecting wires. The detection circuit 140 is used to collect the induction capacitance formed by the explosion-proof valve or rupture disc 120 and the electrode sheet 130. When the internal pressure of the battery cell changes, the explosion-proof valve or rupture disc 120 deforms, and the induction capacitance between the two changes. The change in the internal pressure of the battery cell is obtained through the change in the induction capacitance.

[0064] In this embodiment, the electrode sheet is installed directly above the explosion-proof valve or rupture disc, so that the overlapping area between the electrode sheet and the explosion-proof valve or rupture disc is maximized, the induction capacitance between the two is maximized, and the test will be more sensitive. However, it will use additional electrode fixing materials, the installation is more complex and the signal collection is more complex.

[0065] Figure 3 A schematic diagram of a detection device for internal pressure changes of a battery cell according to another embodiment of the present disclosure is shown. The battery usually has several battery cells formed, each battery cell is contained in a battery box, and the battery box has a cover plate. In Figure 3 In the embodiment, the electrode sheet 330 can be installed on the cover plate 370. The cover plate 340 covers the battery box, and the electrode sheet 330 can be above the explosion-proof valve or rupture disc 320. In addition, the detection circuit can be provided on the shell 310 of the battery cell and located near the battery cell tab 350. In this case, the detection circuit can be connected to the explosion-proof valve or rupture disc, the electrode sheet through connecting wires, so as to collect the signal generated by the coupling capacitance of the two, so as to measure the deformation of the explosion-proof valve or rupture disc, and further obtain the internal pressure change of the battery cell. The number of electrode sheets corresponding to each explosion-proof valve or rupture disc can be two or more, forming multiple electrode segments. Each electrode segment is physically separated and capacitively coupled with the explosion-proof valve or rupture disc. By detecting the capacitance change of each electrode segment, the deformation of the explosion-proof valve or rupture disc at different positions can be detected. Similarly, the detection circuit is a multi-channel detection circuit, each channel is connected to each electrode segment through a connecting wire one by one. In addition, the detection circuit can also be connected to the battery cell tab through the connecting wire, so as to measure the impedance of the battery cell.

[0066] According to Figure 3In the embodiment, the electrode sheet is attached to the cover plate, without changing the structure of the battery cell, and the maximum overlap area design can improve the amplitude of the capacitance signal.

[0067] In the embodiment, the electrode sheet is attached to the cover plate, without changing the structure of the battery cell, and the maximum overlap area design can improve the amplitude of the capacitance signal.

[0068] Figure 4 A schematic diagram of a detection device for the internal pressure change of a battery cell according to another embodiment of the present disclosure is shown, Figure 5 A schematic diagram of the coupling capacitance between the electrode sheet and the explosion-proof valve or explosion-proof sheet is shown. In the embodiment, the electrode sheet 430 is arranged at the side of the explosion-proof valve or explosion-proof sheet 420. Although one electrode sheet is shown in the figure, multiple electrode sheets can be arranged to form multiple electrode segments. The electrode sheet 430 is arranged at the side of the explosion-proof valve or explosion-proof sheet 420 and fixed to the battery cell housing 410. In this way, the electrode sheet forms a coupling capacitance with the explosion-proof valve or explosion-proof sheet. Similarly, when the explosion-proof valve or explosion-proof sheet deforms, the distance between the electrode sheet and the explosion-proof valve or explosion-proof sheet changes, and thus the capacitance between them also changes. By detecting the change in capacitance, the change in the internal pressure of the battery cell can be obtained.

[0069] In the embodiment in the present application, the electrode sheet arranged at the side of the explosion-proof valve or explosion-proof sheet can be multiple segments, i.e. multiple electrode sheets are arranged around the side of the explosion-proof valve or explosion-proof sheet. Each electrode sheet forms a coupling capacitance with a portion of the explosion-proof valve or explosion-proof sheet. Then, the signals of each electrode sheet and the signals of the explosion-proof valve or explosion-proof sheet are collected by a multi-channel detection circuit, so as to obtain the coupling capacitance between each electrode sheet and the explosion-proof valve or explosion-proof sheet.

[0070] In the embodiment of the side installation, although the installation is simple, the overlap area between each electrode sheet and the explosion-proof valve or explosion-proof sheet is small, and the sensitivity of the capacitance measurement is poor. In order to solve this problem, the upper end of each electrode sheet can be inclined to the upper side of the explosion-proof valve or explosion-proof sheet, i.e. each electrode sheet is installed in an inclined direction, so as to maximize the overlap area between the electrode sheet and the explosion-proof valve or explosion-proof sheet.

[0071] Figure 6 A schematic diagram of a detection device for internal pressure change of a battery cell according to yet another embodiment of the present disclosure is shown. In this embodiment, the electrode sheet 630 is arranged in a ring shape, i.e. around the explosion-proof valve or rupture disc 620. A portion of each electrode sheet is attached to the housing of the battery cell, and the inner portion is located above the explosion-proof valve or rupture disc 620. In addition, the electrode sheet can be composed of two portions. The portion attached to the housing of the battery cell is made of a non-metallic material, which cannot form an induced capacitance with the explosion-proof valve or rupture disc made of a metallic material. The portion of the electrode sheet above the explosion-proof valve or rupture disc is made of a metallic material, which can form an induced capacitance with the explosion-proof valve or rupture disc made of a metallic material. This approach can also be used for other embodiments of the present disclosure. Figure 6 Figure 6 In the above embodiment, four electrode segments are shown, and thus a four-channel detection circuit can be configured, each channel being connected to an electrode segment via a connecting line, so as to achieve acquisition of signals of the four electrode segments. In addition, four channels are also connected to the explosion-proof valve or rupture disc, e.g. at positions corresponding to the four electrode segments. As shown above, the detection circuit can be arranged near the tab 650 of the battery cell, so as to achieve measurement of the impedance of the battery cell.

[0072] Figure 7 A schematic diagram of a detection device for internal pressure change of a battery cell according to one embodiment of the present disclosure is shown. In this embodiment, two electrode sheets 730 are arranged on the side, and are arranged on both sides of the explosion-proof valve or rupture disc 720. Of course, more electrode sheets can be arranged to increase the resolution of the measurement. For example Figure 7 The electrode sheets can also be arranged on the upper and lower sides, or the two electrode sheets 730 can be arranged in two segments, or three or more segments, etc.

[0073] Figure 8 A schematic diagram of a detection device for internal pressure change of a battery cell according to one embodiment of the present disclosure is shown. In this embodiment, multi-segment electrode sheets 830 are arranged directly above the explosion-proof valve or rupture disc 820. Four electrode sheets are shown in the diagram, and of course more or two or more electrode sheets can be arranged. The two ends of each electrode sheet can be fixed to the housing of the battery cell, and the portion of the electrode sheet above the explosion-proof valve or rupture disc forms an induced capacitance with the explosion-proof valve or rupture disc. As an example, each electrode sheet can be divided into a non-metallic portion and a metallic portion. The portion above the explosion-proof valve or rupture disc is the portion made of a metallic material, as the metallic portion. The portion not above the explosion-proof valve or rupture disc is the portion made of a non-metallic material, as the non-metallic portion.

[0074] Figure 8 ​The two ends of each electrode sheet can be attached to the shell of the battery core, or can be arranged in a U shape, with the two ends fixed to the shell of the battery core.

[0075] Those skilled in the art can understand that not only the distance between the explosion-proof valve or explosion-proof sheet and the electrode sheet affects the induced capacitance between them, but also other environmental factors, such as moisture, can affect the induced capacitance. When the humidity changes, the dielectric constant of the medium between the explosion-proof valve or explosion-proof sheet and the electrode sheet will be affected, thereby affecting the capacitance value of the induced capacitance. In this application, these effects are referred to as environmental effects, and the measurement errors caused by environmental effects are referred to as environmental errors.

[0076] In this application, the influence of environmental errors on measurement can be effectively eliminated by using a multi-section electrode sheet. As described above, when measuring the explosion-proof valve or explosion-proof sheet using a multi-section electrode sheet, each electrode section corresponds to a part of the explosion-proof valve or explosion-proof sheet. When a certain part of the explosion-proof valve or explosion-proof sheet deforms while other parts do not deform, there is a difference between the induced capacitance of the deformed part and the induced capacitance of the non-deformed part. At this time, the induced capacitance of the non-deformed part can be measured as the measurement capacitance reference value under the current environment. The induced capacitance of the deformed part is compared with the measurement capacitance reference value, and the change in capacitance value caused by deformation can be accurately obtained without the influence of the current environment. In this way, the non-deformed part compensates for the influence of environmental errors on the entire test system.

[0077] Suppose that in a battery core of a new energy vehicle, the size of the explosion-proof valve or explosion-proof sheet is 50mm x 50mm, and the electrode sheet installed above the battery cover plate is divided into four independent electrode sections (each section has an area of 25mm x 25mm), labeled as Seg1, Seg2, Seg3, and Seg4. The detection circuit measures the capacitance values C1, C2, C3, and C4 between the four electrode sections and the explosion-proof valve or explosion-proof sheet through multi-channel design. Under the initial condition, the internal pressure of the battery core is normal, and the explosion-proof valve or explosion-proof sheet does not deform, at which time the same four initial capacitances C1=C2=C3=C4 can be obtained.

[0078] If the internal pressure of the battery cell changes, the region of the explosion-proof valve or explosion-proof sheet corresponding to Seg1 expands and deforms, for example, bulges, while other regions do not deform. The sensing capacitance of Seg1 will change, C1 becomes C1', while C2, C3, C4 do not change. However, if the environment changes, the environmental error will affect the measured capacitance. For example, the environmental temperature rises or the humidity changes, causing the measured values of all electrode segments to change due to changes in the node constant. However, if the sensing capacitances of three of the four independent electrode segments are the same or substantially the same, it is determined that even if the sensing capacitances of the three electrode segments change, the change is caused by the change in the environmental temperature. The change in the sensing capacitance of the other electrode segment is significantly different from the changes in the sensing capacitances of the three electrode segments, and it can be determined that the change in the sensing capacitance of the other electrode segment is caused by deformation. Finally, the change in the sensing capacitance of the other electrode segment can be calibrated by the changes in the sensing capacitances of the three electrode segments, thereby eliminating the influence of environmental error. In addition, the capacitance change caused by environmental error is usually less than 5% of the reference value. In this application, a change of less than 5% of the reference value is not considered to be a capacitance change caused by deformation. Only a change greater than 5% of the reference value is a capacitance change caused by deformation. For example, under initial conditions, C1, C2, C3, and C4 are all 22.13 pF. In the actual environment, C2, C3, and C4 are all 23.24 pF, and the change is less than 5%, so it can be considered that the changes in C2, C3, and C4 are not caused by deformation. If the capacitance value of C1 in the actual environment is 25.82 pF, it is obvious that the change is greater than 5%. The change in C1 is affected by deformation. For C1, the capacitance change value affected by the environment can be obtained from C2, C3, and C4, which is 23.24 pF-22.13 pF=1.23 pF. The capacitance change value of C1 is 25.82 pF-22.13 pF=3.69 pF. Among them, the capacitance value change of C1 affected by deformation will be 3.69 pF-1.23 pF=2.46 pF. Then according to 2.46 pF, the corresponding pressure increment of 0.08 MPa can be obtained by table lookup or other methods. Obviously, the multi-segment electrode sheet of the present disclosure can effectively cope with environmental interference and ensure the reliability of deformation monitoring.

[0079] Alternatively, in the embodiments disclosed herein, the entire electrode sheet can also be disposed above or to the side of the explosion-proof valve or explosion-proof sheet. Those skilled in the art can implement this technical solution based on the above description; however, this solution cannot cope with environmental interference. In this case, an environmental compensation capacitor needs to be introduced. This will be described in detail below. The environmental compensation capacitor compensates for the inherent induced capacitance between the electrode sheet and the explosion-proof valve or explosion-proof sheet, thereby accurately sensing the capacitance change between the electrode sheet and the explosion-proof valve or explosion-proof sheet. The inherent induced capacitance can be considered as the induced capacitance generated between the two under a fixed environment. For example, the inherent induced capacitance formed under a certain distance and a certain medium.

[0080] In this application, in order to measure the induced capacitance, the capacitance can be converted into voltage and then measured directly using an ADC (digital-to-analog converter). Figure 9 An embodiment according to this disclosure is shown in the figure. Figure 9 The sensing capacitor Cx is connected to the CVC (capacitor-to-voltage converter), and the process of converting the sensing capacitor into a voltage is achieved based on the reference capacitor Cref connected to the CVC. VDD is used to provide excitation and power to the sensing capacitor. The converted voltage is input to the ADC and outputs a digital signal.

[0081] In addition, it can also be like Figure 10 As shown, during the process of converting capacitance to voltage, modulation is achieved through modulation provided by VEXC (alternating current signal), and then demodulation is realized in the demodulation & ADC circuit (demodulation circuit and analog-to-digital converter). This method will obtain better and more accurate results. The specific methods of demodulation and modulation are existing technologies and will not be elaborated in this article.

[0082] The following will address... Figure 9 The specific implementation method is provided in the way that, such as Figure 11 As shown. In Figure 11 The environmental compensation capacitor is shown. This capacitor can be used or not used in the case of multi-segment electrode sheets. Using the environmental compensation capacitor will result in more accurate compensation.

[0083] While this application focuses on a multi-segment electrode sheet approach, those skilled in the art can use a single electrode sheet for measurement. However, this approach requires an additional environmental compensation capacitor. Figure 9 As shown. In Figure 9 The diagram illustrates converting capacitance into a voltage signal, which is then tested using a high-precision ADC. Figure 9The voltage excitation is applied to the deformation-induced capacitance Cx to obtain the charge, and then the charge is transferred to the capacitor voltage conversion circuit (charge amplifier) to obtain the voltage output Vout, Vout=VDD*Cx / Cref. Where Vout is the output of the capacitor conversion voltage circuit, connected to the ADC, VDD is the excitation voltage. Cx is the induced voltage between the electrode sheet and the explosion-proof valve or explosion-proof sheet, and Cref is the reference voltage.

[0084] By controlling switches q1 and q3, it can be selected whether the environmental compensation capacitor Coff or the deformation-induced capacitance Cx is connected to the circuit. When measurement is needed, q3 is closed and q1 is opened, so that the deformation-induced capacitance Cx is connected to the voltage source VDD and is excited by voltage. When Cx is excited by voltage, the capacitance value changes due to deformation, and the corresponding amount of charge is generated. Switch q24 controls whether the charge is transferred to the charge amplifier (capacitor voltage conversion). When q24 is closed, the generated charge is transferred from Cx to the input of the charge amplifier. After the charge amplifier receives the charge from Cx, it converts it into a voltage output (Vout). This process uses a reference capacitor Cref to determine the charge-to-voltage ratio. Specifically, the charge amplifier adjusts its output voltage Vout=VDDxCref according to the ratio of Cx and Cref. In actual operation, in order to eliminate the influence of environmental capacitance on the measurement result, first close q1 and q24, so that the environmental compensation capacitor Coff receives the same voltage excitation, and its charge is also transferred to the charge amplifier. This step ensures that when measuring the change of the deformation-induced capacitance Cx, the influence of the environmental capacitance can be effectively eliminated.

[0085] The common-mode voltage Vcm is connected to the inverting input of the charge amplifier through switches q13 and q24, providing a stable reference point to help stabilize the working state of the charge amplifier and avoid problems caused by DC offset. The MOS capacitor MosCap is used for filtering and stabilizing the voltage at some nodes in the circuit, helping to maintain the stability of the circuit.

[0086] Although the multi-section electrode sheet in the present application can not use the environmental compensation capacitor, the environmental compensation capacitor can also be used. The specific reason is that sometimes the capacitance change caused by environmental error may be greater than the capacitance change caused by deformation. If the environmental capacitance is not compensated, the charge amplifier needs to have a very large conversion capacitance, which will result in a too large detection circuit area, so a reverse excitation environmental capacitance compensation circuit (adjustable in size) is placed at the input of the charge amplifier. In addition, the capacitance test circuit containing the environmental capacitance compensation circuit only measures the capacitance change caused by deformation, thereby obtaining higher sensitivity and smaller detection circuit area.

[0087] In addition, the capacitance can be converted into frequency and then output digitally during the measurement of the induced capacitance. Figure 12 A capacitance conversion circuit is shown for one embodiment. In the conversion circuit, the induced capacitance Cx and the reference capacitance Cref are connected to a CFC (capacitance frequency conversion circuit), which can be implemented using known circuits. The converted frequency signal output by the CFC circuit is input to a TDC (time-to-digital converter), which outputs a converted digital signal. The TDC can be implemented using known circuits or detection circuits. Fref is the reference frequency. Figure 13 A capacitance conversion circuit is shown for another embodiment. In the conversion circuit, the induced capacitance Cx is converted into a frequency signal by a relaxation oscillator, which can be implemented using known circuits or detection circuits. The output converted frequency signal is then input to a TDC (time-to-digital converter), which outputs a converted digital signal. The TDC can be implemented using known circuits or detection circuits. In Figure 13 In one embodiment, the measured capacitance (induced capacitance) is used to construct an oscillator, the frequency of which is related to the measured capacitance. The frequency of the oscillator output signal is quantized using a TDC, thereby obtaining the capacitance value. VEXC is the external excitation voltage.

[0088] In addition, the capacitance can be directly converted into a digital output. Figure 14 A capacitance detection circuit block diagram based on a Σ-Δ (Sigma-Delta) analog-to-digital converter is shown. The induced capacitance Cx changes with the deformation of the explosion-proof valve or diaphragm, and the reference capacitance Cref provides a reference value for differential measurement. The external excitation voltage VEXC can be an alternating current signal applied to Cx and Cref. A differential amplifier is used to compare the charge difference generated by Cx and Cref. The loop filter implements the integration and filtering functions of the Σ-Δ modulator, which can be an integrator or a multi-stage filter. The quantizer converts the output of the loop filter into a digital signal (bitstream), such as a 1-bit bitstream. The bitstream controls the switching of the external excitation voltage VEXC and the ground voltage VGND through a feedback path, forming a closed loop. In Figure 14 In one embodiment, the loop filter and quantizer can be implemented using known circuits. Figure 14 An implementation of a capacitance-to-voltage converter based on a SAR ADC is shown. The capacitances of the induced capacitance Cx and the reference capacitance array Cref are connected to the external excitation voltage VEXC and the ground voltage VGND through switches. The reference capacitance array is composed of a capacitance array including the most significant bit capacitance MSB and the least significant bit capacitance LSB. The capacitance-to-voltage conversion is similar to that of the Σ-Δ ADC, but the SAR ADC does not require a loop filter and quantizer. Figure 13The embodiments of the SAR ADC are the same, the quantizer outputs digital signals, and the SAR Logic (Successive Approximation Logic Controller) is connected to the output of the quantizer to control the excitation of the reference capacitor array according to the output of the quantizer, that is, the connection state of each capacitor in the reference capacitor array, which has achieved the purpose of successive approximation. For the specific implementation of this SAR ADC, please refer to the prior art, which will not be described here.

[0089] Figure 15 A battery cell internal pressure early warning system according to one embodiment of the present disclosure is shown. As shown, the early warning system can include a detection device of battery cell internal pressure change as described above; and a determination device. The determination device determines the internal pressure change of the battery cell according to the detection signal from the detection circuit, and in the case that the internal pressure change exceeds a threshold value, an early warning is performed.

[0090] In the description of the present specification, the description of the terms "one embodiment / way", "some embodiments / ways", "example", "specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment / way or example are included in at least one embodiment / way or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment / way or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments / ways or examples. In addition, the skilled in the art can combine and combine the different embodiments / ways or examples described in the present specification and the features of the different embodiments / ways or examples without contradiction.

[0091] In addition, the terms "first", "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise specifically limited.

[0092] Those skilled in the art should understand that the above embodiments are only for the purpose of clearly illustrating the present disclosure, and are not intended to limit the scope of the present disclosure. Based on the above disclosure, other changes or modifications can also be made by those skilled in the art, and these changes or modifications are still within the scope of the present disclosure.

Claims

1. A device for detecting pressure changes inside a battery cell, characterized in that, The battery cell includes an explosion-proof valve or explosion-proof plate, which is disposed on the housing of the battery cell. When the internal pressure of the battery cell changes, the explosion-proof valve or explosion-proof plate will deform first until it ruptures due to excessive internal pressure. The detection device includes: Electrode sheet, the electrode sheet is arranged above or to the side of the explosion-proof valve or explosion-proof sheet, forming an inductive capacitance with the explosion-proof valve or explosion-proof sheet and detecting the deformation of the explosion-proof valve or explosion-proof sheet based on the capacitance change; The detection circuit is connected to the electrode sheet via a connecting wire, and also to the explosion-proof valve or explosion-proof sheet via a connecting wire.

2. The detection device as claimed in claim 1, wherein the electrode sheet is a multi-segment electrode sheet comprising multiple electrode segments, each electrode segment being physically separated and forming an inductive capacitance with different parts of the explosion-proof valve or explosion-proof sheet to detect the deformation of the different parts of the explosion-proof valve or explosion-proof sheet, and the detection circuit is a multi-channel detection circuit, each channel being connected to each electrode segment in a one-to-one correspondence via a connecting line.

3. The detection device as described in claim 2, characterized in that, The overlap area between each electrode segment and the explosion-proof valve or explosion-proof plate is maximized.

4. The detection device as described in claim 2, characterized in that, The detection circuit is located on the outer surface of the battery cell and close to the battery cell tab.

5. The detection device as described in claim 4, characterized in that, The detection circuit is connected to the battery cell tabs via a connecting wire to measure the battery impedance.

6. The detection device as described in claim 2, characterized in that, The detection circuit compares signals from multiple electrode segments and eliminates capacitance changes caused by the environment based on the signal comparison.

7. The detection device as described in claim 2, characterized in that, The electrode sheet is positioned directly above the explosion-proof valve or explosion-proof sheet, and both ends of each electrode segment are fixed to the battery cell tab or the battery cell housing.

8. The detection device as described in claim 2, characterized in that, The electrode sheet is disposed on two or more sides of the explosion-proof valve or explosion-proof sheet.

9. The detection device as described in claim 2, characterized in that, Multiple electrode segments are arranged in a ring around the explosion-proof valve or explosion-proof plate.

10. The detection device as described in claim 2, characterized in that, The electrode sheet is mounted on the cover plate of the battery box. After the cover plate is installed, the electrode sheet is located directly above the explosion-proof valve or explosion-proof plate in the battery box.

11. The detection device as described in claim 2, characterized in that, The detection circuit is connected to an environmental compensation capacitor to compensate for the inherent induced capacitance between the electrode sheet and the explosion-proof valve or explosion-proof sheet, thereby accurately sensing the capacitance change between the electrode sheet and the explosion-proof valve or explosion-proof sheet.

12. The detection device according to any one of claims 1 to 11, characterized in that, The detection circuit includes a capacitor voltage conversion circuit and an analog-to-digital converter. The capacitor voltage conversion circuit receives the signal from the sensing capacitor and converts it into a voltage signal. The analog-to-digital converter converts the voltage signal into a digital signal.

13. The detection device according to any one of claims 1 to 11, characterized in that, The detection circuit includes a capacitor voltage conversion circuit and a demodulation and analog-to-digital conversion circuit. The capacitor voltage conversion circuit modulates the received signal from the sensing capacitor into a voltage signal based on an external AC signal, and then performs demodulation and analog-to-digital conversion through the demodulation and analog-to-digital conversion circuit to finally convert it into a digital signal.

14. The detection device according to any one of claims 1 to 11, characterized in that, The detection circuit includes a capacitor-frequency conversion circuit and a time-to-digital converter. The capacitor-frequency conversion circuit converts the signal from the sensing capacitor into a frequency signal, and the time-to-digital converter converts the frequency signal into a digital signal.

15. The detection device according to any one of claims 1 to 11, characterized in that, The detection circuit includes a relaxation oscillator and a time-to-digital converter. The relaxation oscillator converts the signal from the sensing capacitor into a frequency signal, and the time-to-digital converter converts the frequency signal into a digital signal.

16. The detection apparatus according to any one of claims 1 to 11, characterized in that, The detection circuit includes a differential amplifier, a loop filter, and a quantizer. The differential amplifier is used to perform differential measurements on the sensing capacitor and the reference capacitor to obtain a differential signal. The loop filter is used to perform Σ-Δ modulation on the differential signal to obtain a modulated signal. The quantizer converts the modulated signal into a digital signal, wherein the digital signal is used to control the switching between the external excitation voltage and the ground voltage of the reference capacitor.

17. The detection apparatus according to any one of claims 1 to 11, characterized in that, The detection circuit includes a differential amplifier, a quantizer, and a successive approximation logic unit. The differential amplifier performs differential measurements on the sensing capacitor and the reference capacitor array to obtain a differential signal. The quantizer converts the differential signal into a digital signal, and the successive approximation logic unit controls the switching of the external excitation voltage and ground voltage of each reference capacitor in the reference capacitor array based on the digital signal.

18. A battery cell internal pressure early warning system, characterized in that, include: The device for detecting changes in internal pressure of a battery cell as described in any one of claims 1 to 17; The judgment device determines the internal pressure change of the battery based on the detection signal from the detection circuit, and issues an early warning if the internal pressure change exceeds a threshold.

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