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

Abstract

The invention 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 a multi-section type electrode sheet comprising a plurality of electrode sections, each electrode section is physically separated and is arranged above or on the side of the explosion-proof valve or the explosion-proof sheet, each electrode section and the explosion-proof valve or the explosion-proof sheet form an inductive capacitor, and deformation of different positions of the explosion-proof valve or the explosion-proof sheet is detected based on capacitance change; and the chip is a multi-channel chip, each channel is connected with each electrode section through a connecting line in a one-to-one correspondence manner, and the chip is also connected to an anti-explosion valve or an anti-explosion sheet through a connecting line. The invention 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 will be 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. SUMMARY

[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 burst valve or a burst disc, the burst valve or the burst disc being arranged on a housing of the battery cell and being 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, the detection device comprising: an electrode sheet, the electrode sheet being a multi-segment electrode sheet comprising a plurality of electrode segments, each electrode segment being physically separated and arranged above or aside the burst valve or the burst disc, each electrode segment forming an induction capacitance with the burst valve or the burst disc and detecting deformation of the burst valve or the burst disc at different positions based on capacitance change; a chip, the chip being a multi-channel chip, each channel being connected to each electrode segment through a connecting line in a one-to-one correspondence, and the chip being further connected to the burst valve or the burst disc through a connecting line.

[0007] According to the detection device of at least one embodiment of the present disclosure, the overlapping area of each electrode segment with the burst valve or the burst disc is maximized.

[0008] According to the detection device of at least one embodiment of the present disclosure, the chip is arranged on the outer surface of the battery cell and is close to the tab of the battery cell.

[0009] According to the detection device of at least one embodiment of the present disclosure, the chip is connected to the tab of the battery cell through a connecting line to measure the battery impedance.

[0010] The detection device according to at least one embodiment of the present disclosure compares signals from multiple electrode segments, and eliminates environmental capacitance changes according to the comparison of the signals.

[0011] The detection device according to at least one embodiment of the present disclosure is arranged above the explosion-proof valve or the explosion-proof sheet, and both ends of each electrode segment are fixed to the battery core tab or the battery core housing.

[0012] The detection device according to at least one embodiment of the present disclosure is arranged on more than two sides of the explosion-proof valve or the explosion-proof sheet.

[0013] The detection device according to at least one embodiment of the present disclosure is arranged in a ring shape around the explosion-proof valve or the explosion-proof sheet.

[0014] The detection device according to at least one embodiment of the present disclosure is arranged on the cover plate of the battery box, and after the cover plate is installed, the electrode sheet is arranged above the explosion-proof valve or the explosion-proof sheet in the battery box.

[0015] The detection device according to at least one embodiment of the present disclosure is connected with an environmental compensation capacitor, which is used to compensate the inherent inductive 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.

[0016] The detection device according to at least one embodiment of the present disclosure includes a capacitance-voltage conversion circuit and an analog-to-digital converter, the capacitance-voltage conversion circuit receives the signal of the inductive capacitance and converts it into a voltage signal, and the analog-to-digital converter converts the voltage signal into a digital signal.

[0017] The detection device according to at least one embodiment of the present disclosure includes a capacitance-voltage conversion circuit and a demodulation and analog-to-digital conversion circuit, the capacitance-voltage conversion circuit modulates the received signal of the inductive 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.

[0018] The detection device according to at least one embodiment of the present disclosure includes a capacitance-frequency conversion circuit and a time-to-digital converter, the capacitance-frequency conversion circuit converts the signal of the inductive capacitance into a frequency signal, and the time-to-digital converter converts the frequency signal into a digital signal.

[0019] The detection device according to at least one embodiment of the present disclosure includes a relaxation oscillator and a time-to-digital converter, the relaxation oscillator converts the signal of the inductive capacitance into a frequency signal, and the time-to-digital converter converts the frequency signal into a digital signal.

[0020] The detection device according to at least one embodiment of the present disclosure, the chip comprises a differential amplifier, a loop filter and a quantizer, the differential amplifier is used for differential measurement of the inductive capacitance and the reference capacitance, to obtain a differential signal, the loop filter is used for sigma-delta modulation of the differential signal, to obtain a modulated signal, and the quantizer converts the modulated signal into a digital signal, wherein the digital signal is used to control the switching of the external excitation voltage and the ground voltage of the reference capacitance.

[0021] The detection device according to at least one embodiment of the present disclosure, the chip comprises a differential amplifier, a loop filter and a quantizer, the differential amplifier is used for differential measurement of the inductive capacitance and the reference capacitance, to obtain a differential signal, the loop filter is used for sigma-delta modulation of the differential signal, to obtain a modulated signal, and the quantizer converts the modulated signal into a digital signal, wherein the digital signal is used to control the switching of the external excitation voltage and the ground voltage of the reference capacitance.

[0022] According to another aspect of the present disclosure, a battery cell internal pressure early warning system is provided, comprising: The detection device for the change of the internal pressure of the battery cell according to any one of the above; A judgment device determines the change of the internal pressure of the battery according to the detection signal from the chip, and in the case that the change of the internal pressure exceeds a threshold value, an early warning is performed. BRIEF DESCRIPTION OF DRAWINGS

[0023] 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.

[0024] Figure 1 is a schematic diagram of a detection device for the change of the internal pressure of the battery cell according to an embodiment of the present disclosure.

[0025] Figure 2 is a schematic diagram of a detection device for the change of the internal pressure of the battery cell according to an embodiment of the present disclosure.

[0026] Figure 3 is a schematic diagram of a detection device for the change of the internal pressure of the battery cell according to an embodiment of the present disclosure.

[0027] Figure 4 is a schematic diagram of a detection device for the change of the internal pressure of the battery cell according to an embodiment of the present disclosure.

[0028] Figure 5 is a schematic diagram of a detection device for the change of the internal pressure of the battery cell according to an embodiment of the present disclosure.

[0029] Figure 6 is a schematic diagram of a detection device for battery cell internal pressure change according to an embodiment of the present disclosure.

[0030] Figure 7 is a schematic diagram of a detection device for battery cell internal pressure change according to an embodiment of the present disclosure.

[0031] Figure 8 is a schematic diagram of a detection device for battery cell internal pressure change according to an embodiment of the present disclosure.

[0032] Figure 9 is a circuit structure diagram for capacitance detection according to an embodiment of the present disclosure.

[0033] Figure 10 is a circuit structure diagram for capacitance detection according to an embodiment of the present disclosure.

[0034] Figure 11 is a circuit structure diagram for capacitance detection according to an embodiment of the present disclosure.

[0035] Figure 12 is a circuit structure diagram for capacitance detection according to an embodiment of the present disclosure.

[0036] Figure 13 is a circuit structure diagram for capacitance detection according to an embodiment of the present disclosure.

[0037] Figure 14 is a circuit structure diagram for capacitance detection according to an embodiment of the present disclosure.

[0038] Figure 15 is a circuit structure diagram for capacitance detection according to an embodiment of the present disclosure.

[0039] Figure 16 is a block diagram of a pre-warning system according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0040] The present disclosure will be described in further detail below with reference to the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the related content, and not to limit the present disclosure. In addition, it should be noted that only parts related to the present disclosure are shown in the drawings for ease of description.

[0041] It should be noted that the embodiments and features in the embodiments of 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.

[0042] Unless otherwise stated, the exemplary implementations / examples shown will be understood to provide exemplary features of various details that can be implemented in practice to embody the technological concepts of the present disclosure. Accordingly, features of the various implementations / examples can additionally be combined, separated, interchanged, and / or rearranged, unless otherwise stated, without departing from the technological concepts of the present disclosure.

[0043] The use of cross-hatching and / or shading in the drawings is generally used to make the boundaries and regions of adjacent components more clearly understood. As such, unless specifically stated otherwise, the presence of cross-hatching or shading in a drawing is not a requirement for the presence of a particular material, material property, dimension, ratio, commonality between components shown in the exemplary implementations / examples, and / or any other characteristic, attribute, property, etc. of a component. Moreover, the size and relative sizes of components shown in the drawings can be exaggerated for clarity and / or descriptive purposes. When exemplary implementations / examples can be practiced differently, a particular sequence of processing steps can be performed in a different order than described. For example, two consecutively described processing steps can be performed at substantially the same time or in the reverse order of the order described. Furthermore, like reference numerals are used to denote like components throughout the drawings.

[0044] 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 one or more 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. To that end, the term “connected” can refer to a physical or electrical connection, whether or not with intervening components.

[0045] For descriptive purposes, the present disclosure can use spatial or relative terms, such as “below,” “lower,” “below,” “low,” “above,” “upper,” “on,” “higher,” and “side” (e.g., as in “sidewall”), to describe the relationship between one component and another component as shown in the drawings. The spatial or relative terms are intended to encompass different orientations of the device in use, operation, and / or manufacture in addition to the orientation depicted in the drawings. For example, if the device in the drawings is turned over, a component described as “below” or “beneath” other components or features would then be oriented “above” the other components or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. Moreover, the device can be otherwise oriented (e.g., rotated 90 degrees or at other orientations) and the spatial or relative descriptors used herein interpreted accordingly.

[0046] The root cause of battery cell thermal runaway is that the exothermic side reaction inside the battery cell leads to 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 and avoid the imbalance of internal and external pressure of the battery cell, while considering that lithium batteries will instantaneously produce a large amount of toxic gas when on fire, it is necessary to timely and directionally release the gas. The explosion-proof valve or explosion-proof sheet as a passive safety protection measure for the battery system to prevent thermal runaway can achieve the above requirements of maintaining pressure balance and directionally releasing gas.

[0047] Currently, the pressure change in the battery cell can be detected by detecting the explosion-proof valve or explosion-proof sheet. The following lists several detection methods currently used.

[0048] 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 explosion-proof sheet. Due to the deformation of the explosion-proof valve or explosion-proof sheet, the surface is strained, thereby causing the resistance of the resistance strain gauge to change. By measuring the change of resistance, the size of strain (or stress) is reflected.

[0049] Differential transformer sensor: using mutual inductance in electromagnetic induction, the measured displacement of the explosion-proof valve or explosion-proof sheet is converted into the change of mutual inductance of the coil.

[0050] Ultrasonic sensor: the deformation of the explosion-proof valve or explosion-proof sheet is detected by the ultrasonic sensor.

[0051] 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.

[0052] 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 accordingly, which causes the capacitance value of the coupling capacitor 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.

[0053] The device for detecting the change of internal pressure of a battery cell comprises an electrode foil. The electrode foil is a multi-segment electrode foil comprising a plurality of electrode segments. Each electrode segment is arranged above or aside the burst valve or the burst disc, forming a distributed detection network. Each electrode segment is physically separated, i.e. physically spaced apart. Each electrode segment forms a coupling capacitor with the burst valve or the burst disc. That is, each electrode segment forms a coupling capacitor with a part of the burst valve or the burst disc, so that the deformation of a part of the burst valve or the burst disc can be detected when the coupling capacitor between each electrode segment and the part of the burst valve or the burst disc changes. That is, the electrode segments detect the deformation of different positions of the burst valve or the burst disc respectively. 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.

[0054] Specifically, each electrode segment acts as an independent sensing unit by forming a coupling capacitor 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 (such as 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.

[0055] 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 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 explosion-proof sheet compared to 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. According to a further embodiment of the present disclosure, the detection device for internal pressure change of the battery cell can further include a chip, wherein the chip can be a multi-channel chip. The multi-channel chip refers to integrating multiple detection channels on a single chip, which can simultaneously or independently process multiple signals. In the present application, a suitable multi-channel chip can be selected, and an integrated chip with the following circuit can also be used. Each channel of the multi-channel chip is connected to each electrode segment through a connecting line in a one-to-one correspondence, and each channel is connected to the explosion-proof valve or explosion-proof sheet. In this way, each channel detects the change in the capacitance value of the coupling capacitance between each electrode segment and the explosion-proof valve or explosion-proof sheet, respectively. In the preferred embodiment of the present application, the chip can be arranged on the outer surface of the battery cell and 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 electrodes (anode and cathode) of the battery cell and can be connected to the chip. The chip applies an electrical signal through the tab and measures the response signal. For example, the chip 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 by the collected response signal. For the measurement of impedance, reference can be made to the prior art, which will not be described here.

[0056] When the internal pressure of the battery cell changes, the explosion-proof valve or explosion-proof sheet will deform. When the internal pressure of the battery cell reaches a preset limit, the explosion-proof valve or explosion-proof sheet will be opened to achieve the purpose of pressure relief. In order to prevent the battery cell from reaching the limit value of the internal pressure before the explosion-proof valve or explosion-proof sheet is opened, it is also crucial to monitor the internal pressure change of the battery cell before the explosion-proof valve or explosion-proof sheet is opened. By monitoring the internal pressure change of the battery cell, the pressure change inside the battery cell can be known in advance, so that early warning can be made. Thus, intervention can be made in advance before the battery cell experiences thermal runaway. In the present application, the coupling capacitance is formed between the electrode sheet and the explosion-proof valve or explosion-proof sheet. 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 the coupling capacitance value between them also changes. By detecting the change in the coupling capacitance value, the internal pressure can be monitored, and further early warning can be achieved. In various embodiments, those skilled in the art should understand that the electrode sheet and the explosion-proof valve or explosion-proof sheet should be insulated.

[0057] Figure 1FIG. 1 is a schematic diagram of a device for detecting changes in pressure inside a battery cell according to an embodiment of the present disclosure. Figure 1 As shown, the battery cell housing 110 is provided with an explosion-proof valve or explosion-proof disc 120. The explosion-proof valve or explosion-proof disc 120 is made of metal material. The metal electrode sheet 130 is provided just above the explosion-proof valve or explosion-proof disc 120. Figure 1 Only one motor sheet is shown in the figure, but electrode sheets may be provided. Each electrode sheet may extend in the transverse direction of the explosion-proof valve or explosion-proof disk 130, or in the longitudinal direction of the explosion-proof valve or explosion-proof disk. Figure 1 As shown, each electrode sheet can be made directly above the explosion-proof valve or explosion-proof disk 130 through a support bar 150. The two ends of the support bar 150 can be placed on the tabs on both sides of the battery core.

[0058] Chip 140 is mounted on the battery cell housing 110 and positioned adjacent to the cell tabs. As described above, the chip can be used to detect the cell's impedance. Although not shown, chip 140 is connected to the electrode sheet, explosion-proof valve or disc, and cell tabs via connecting wires, enabling capacitance and impedance measurements.

[0059] Figure 2 Shown Figure 1 The measurement principle diagram of the embodiment. Figure 2 As shown, an inductive capacitance is formed between the explosion-proof valve or disk 120 and the electrode sheet 130. These two components are connected to a chip 140 via a connecting wire. Chip 140 is used to detect the inductive capacitance formed by these two components. When the internal pressure of the battery cell changes and the explosion-proof valve or disk 120 deforms, the inductive capacitance between them changes. This change in capacitance is used to determine the internal pressure of the battery cell.

[0060] In this embodiment, the electrode sheet is installed directly above the explosion-proof valve or disk, maximizing the overlap between the electrode sheet and the explosion-proof valve or disk. This maximizes the inductive capacitance between the two, resulting in a more sensitive test. However, this requires additional electrode fixing material, making installation and signal acquisition more complex.

[0061] Figure 3 A schematic diagram of a device for detecting changes in pressure inside a battery cell according to another embodiment of the present disclosure is shown. A battery is generally formed of several battery cells, each of which is housed in a battery box, and the battery box has a cover. Figure 3In the embodiment of the application, the electrode sheet 330 can be installed on the cover plate 370. The cover plate 370 covers the battery box, and the electrode sheet 330 can be above the explosion-proof valve or rupture disc 320. In addition, the chip can be arranged on the shell 310 of the battery core and located close to the battery core tab 350. In this case, the chip can be connected with the explosion-proof valve or rupture disc and the electrode sheet through the connecting wire, 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 core. The number of electrode sheets corresponding to each explosion-proof valve or rupture disc can be two or more, forming a plurality of electrode segments. Each electrode segment is physically separated and forms a capacitive coupling 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 chip is a multi-channel chip, and each channel is connected with each electrode segment through the connecting wire in a one-to-one correspondence. In addition, the chip can also be connected to the battery core tab through the connecting wire, so as to measure the battery core impedance.

[0062] According to Figure 3 In the embodiment of the application, the electrode sheet 330 can be installed on the cover plate 370. The cover plate 370 covers the battery box, and the electrode sheet 330 can be above the explosion-proof valve or rupture disc 320. In addition, the chip can be arranged on the shell 310 of the battery core and located close to the battery core tab 350. In this case, the chip can be connected with the explosion-proof valve or rupture disc and the electrode sheet through the connecting wire, 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 core. The number of electrode sheets corresponding to each explosion-proof valve or rupture disc can be two or more, forming a plurality of electrode segments. Each electrode segment is physically separated and forms a capacitive coupling 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 chip is a multi-channel chip, and each channel is connected with each electrode segment through the connecting wire in a one-to-one correspondence. In addition, the chip can also be connected to the battery core tab through the connecting wire, so as to measure the battery core impedance.

[0063] In the embodiment of the application, the electrode sheet 330 can be installed on the cover plate 370. The cover plate 370 covers the battery box, and the electrode sheet 330 can be above the explosion-proof valve or rupture disc 320. In addition, the chip can be arranged on the shell 310 of the battery core and located close to the battery core tab 350. In this case, the chip can be connected with the explosion-proof valve or rupture disc and the electrode sheet through the connecting wire, 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 core. The number of electrode sheets corresponding to each explosion-proof valve or rupture disc can be two or more, forming a plurality of electrode segments. Each electrode segment is physically separated and forms a capacitive coupling 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 chip is a multi-channel chip, and each channel is connected with each electrode segment through the connecting wire in a one-to-one correspondence. In addition, the chip can also be connected to the battery core tab through the connecting wire, so as to measure the battery core impedance.

[0064] Figure 4 A schematic diagram of a detection device for internal pressure change of a battery core according to another embodiment of the present disclosure is shown, Figure 5A schematic diagram of the induced capacitance between the electrode sheet and the explosion-proof valve or explosion-proof sheet is shown. In this embodiment, the electrode sheet 430 is disposed on 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 disposed to form multiple electrode segments. The electrode sheet 430 is disposed at the side of the explosion-proof valve or explosion-proof sheet 420 and is 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 the two also changes. By detecting this capacitance change, the change in the internal pressure of the battery cell is obtained.

[0065] In the embodiments of the present application, the electrode sheet disposed on the side of the explosion-proof valve or explosion-proof sheet can be multiple segments, i.e., multiple electrode sheets are installed 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 chip, and thus the induced capacitance between each electrode sheet and the explosion-proof valve or explosion-proof sheet is obtained.

[0066] In the side-mounted embodiment, although it is simple to install, the overlapping area between each electrode sheet and the explosion-proof valve or explosion-proof sheet is small, and the sensitivity angle of the capacitance measurement. In order to combine this problem, the upper end of each electrode sheet can be tilted above the explosion-proof valve or explosion-proof sheet, i.e., each electrode sheet is installed in a tilted direction, so that the overlapping area of the electrode sheet and the explosion-proof valve or explosion-proof sheet is maximized.

[0067] Figure 6 A schematic diagram of a detection device for the internal pressure change of a battery cell according to still another embodiment of the present disclosure is shown. In the Figure 6 In the embodiment, the electrode sheet 630 is annularly disposed, i.e., it is installed around the top of the explosion-proof valve or explosion-proof sheet 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 explosion-proof sheet 620. In addition, the electrode sheet can be composed of two parts. The part 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 explosion-proof sheet made of a metallic material. The portion of the electrode sheet above the explosion-proof valve or explosion-proof sheet is made of a metallic material, and this portion made of a metallic material can form an induced capacitance with the explosion-proof valve or explosion-proof sheet made of a metallic material. In addition, this method can also be used for other embodiments of the present disclosure. In the Figure 6Four electrode segments are shown in the figure, so the chip can be configured with four channels, each connected to an electrode segment through a connecting line, so as to realize the collection of signals of the four electrode segments, and the other four channels are also connected to the explosion-proof valves or explosion-proof sheets, for example, can be connected to the positions corresponding to the four electrode segments. As shown above, the chip can be arranged near the battery core tab 650 to realize the measurement of the battery core impedance.

[0068] Figure 7 A schematic diagram of a detection device for internal pressure changes of a battery core according to an embodiment of the present disclosure is shown. In this embodiment, two electrode sheets 730 are arranged on the side, and the two electrode sheets 730 are arranged on the two sides of the explosion-proof valve or explosion-proof sheet 720. Of course, more electrode sheets can also be arranged to increase the resolution of the measurement. For example Figure 7 The upper and lower sides of the explosion-proof valve or explosion-proof sheet 720 can also be provided with electrode sheets, or the two electrode sheets 730 can be arranged in two or more segments.

[0069] Figure 8 A schematic diagram of a detection device for internal pressure changes of a battery core according to an embodiment of the present disclosure is shown. In this embodiment, multi-segment electrode sheets 830 are arranged directly above the explosion-proof valve or explosion-proof sheet 820. Four electrode sheets are shown in the figure, 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 battery core shell, and the part of the electrode sheet above the explosion-proof valve or explosion-proof sheet forms an induced capacitance with the explosion-proof valve or explosion-proof sheet. As an example, each electrode sheet can be divided into a non-metallic part and a metallic part. The part above the explosion-proof valve or explosion-proof sheet is formed by a metallic material as a metallic part. The part not above the explosion-proof valve or explosion-proof sheet is formed by a non-metallic material as a non-metallic part.

[0070] 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 shape with two ends fixed to the shell of the battery core.

[0071] 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, it will affect the dielectric constant of the medium between the explosion-proof valve or explosion-proof sheet and the electrode sheet, 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.

[0072] In the present application, the influence of environmental errors on measurement can be effectively eliminated by using a multi-segment electrode sheet. As described above, when a multi-segment electrode sheet is used to measure the explosion-proof valve or explosion-proof sheet, each electrode segment 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 measurement value of the non-deformed part can be used 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.

[0073] Suppose that the size of the explosion-proof valve or explosion-proof sheet in a battery core of a new energy vehicle is 50mm x 50mm, and the electrode sheet installed above the battery cover plate is divided into four independent electrode segments (each segment has an area of 25mm x 25mm), labeled as Seg1, Seg2, Seg3, and Seg4. The chip measures the capacitance values C1, C2, C3, and C4 between the four electrode segments and the explosion-proof valve or explosion-proof sheet through a 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 can be obtained, i.e., C1 = C2 = C3 = C4.

[0074] If the internal pressure of the battery cell changes, the area of the explosion-proof valve or explosion-proof sheet corresponding to Seg1 expands and deforms, for example, bulges, while other areas do not deform. The sensing capacitance of Seg1 will increase, 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 the 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 the environmental error. In addition, the capacitance change caused by the environmental error is usually less than 5% of the reference value. In the present 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.

[0075] In addition, in the embodiments of the present disclosure, the entire electrode sheet can also be set above or to the side of the explosion-proof valve or explosion-proof disk. For this technical solution, those skilled in the art can implement it according to the above description, but this solution cannot cope with environmental interference. At this time, it is necessary to introduce an environmental compensation capacitor. 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 disk, thereby accurately sensing the capacitance change between the electrode sheet and the explosion-proof valve or explosion-proof disk. The inherent induced capacitance can be considered as the induced capacitance generated between the two in a fixed environment. For example, the inherent induced capacitance formed under a certain distance and in a certain medium.

[0076] In this application, in order to measure the inductive capacitance, the capacitance may be converted into a voltage and then directly measured using an ADC (digital-to-analog converter). Figure 9 An embodiment according to the present disclosure is shown in FIG. Figure 9 As described above, the sensing capacitor Cx is connected to CVC (capacitance-to-voltage circuit), and the sensing capacitance is converted into a voltage based on the reference capacitor Cref connected to CVC. VDD is used to provide excitation and power to the sensing capacitor. The converted voltage is input to the ADC, which then outputs a digital signal.

[0077] In addition, you can also Figure 10 As shown in the figure, during the conversion of capacitance into voltage, modulation is performed using the modulation provided by VEXC (AC signal), and then demodulated in the demodulation & ADC circuit (demodulation circuit and analog-to-digital converter). This approach will achieve more accurate results. The specific methods of demodulation and modulation are existing technologies and will not be detailed in this article.

[0078] The following will target Figure 9 Provide specific implementation methods, such as Figure 11 As shown. Figure 11 The environmental compensation capacitor is shown in FIG. In the case of a multi-segment electrode sheet, the environmental compensation capacitor can be used or not. When the environmental compensation capacitor is used, the compensation result will be more accurate.

[0079] In this application, although the multi-segment electrode sheet method is mainly introduced, those skilled in the art can also use a single electrode sheet to perform measurements. However, the problem with this method is that it requires an additional environmental compensation capacitor. Figure 9 As shown. Figure 9 The figure shows how to convert capacitance into voltage signal and then use high-precision ADC to test the voltage signal. 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.

[0080] 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.

[0081] 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 certain nodes in the circuit, helping to maintain the stability of the circuit.

[0082] 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 chip 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 chip area.

[0083] 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 is input to a TDC (time-to-digital converter), which outputs a converted digital signal. The TDC can be implemented using known circuits or chips. 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 chips. The converted frequency signal output 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 chips. 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 by a TDC to obtain the capacitance value. VEXC is the external excitation voltage.

[0084] 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 this 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 capacitances of Cx and Cref are compared by a comparator, which can be implemented using known circuits or chips. The output of the comparator is input to a digital-to-analog converter (DAC), which can be implemented using known circuits or chips. The output of the DAC is input to a SAR ADC, which can be implemented using known circuits or chips. The output of the SAR ADC is a digital signal representing the capacitance value of Cx. 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.

[0085] 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 judgment device. The judgment device determines the internal pressure change of the battery cell according to the detection signal from the chip, and in the case that the internal pressure change exceeds the threshold value, an early warning is performed.

[0086] 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.

[0087] 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.

[0088] 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. Other changes or modifications can be made on the basis of the above disclosure, and these changes or modifications are still within the scope of the present disclosure.

Claims

1. A device for detecting changes in internal pressure of a battery cell, characterized in that: The battery core includes an explosion-proof valve or explosion-proof disk, which is provided on the battery core housing. When the internal pressure of the battery core changes, the explosion-proof valve or explosion-proof disk first deforms until it ruptures due to excessive internal pressure of the battery core. The detection device includes: An electrode sheet, wherein the electrode sheet is a multi-segment electrode sheet including a plurality of electrode segments, each electrode segment being physically separated and arranged above or to the side of the explosion-proof valve or explosion-proof disk, each electrode segment forming an inductive capacitance with the explosion-proof valve or explosion-proof disk and detecting deformation of different positions of the explosion-proof valve or explosion-proof disk based on capacitance changes; The chip is a multi-channel chip, each channel is connected to each electrode segment through a connecting wire in a one-to-one correspondence, and the chip is also connected to an explosion-proof valve or explosion-proof disk through a connecting wire.

2. The detection device according to claim 1, wherein The overlapping area between each electrode segment and the explosion-proof valve or explosion-proof disk is maximized.

3. The detection device according to claim 1, wherein The chip is arranged on the outer surface of the battery core and is close to the battery core tab.

4. The detection device according to claim 3, wherein The chip is connected to the battery cell tabs via connecting wires to measure the battery impedance.

5. The detection device according to claim 1, wherein The chip compares signals from multiple electrode segments and eliminates capacitance changes caused by the environment based on the signal comparison.

6. The detection device according to claim 1, wherein Optionally, the electrode sheet is arranged just above the explosion-proof valve or explosion-proof disk, and both ends of each electrode segment are fixed to the battery core tabs or the battery core shell. Optionally, the electrode sheets are arranged on two or more sides of the explosion-proof valve or explosion-proof disk. Optionally, a plurality of electrode segments are arranged in a ring around the explosion-proof valve or explosion-proof disk. Optionally, the electrode sheet is arranged on the cover of the battery box. After the cover is installed, the electrode sheet is located directly above the explosion-proof valve or explosion-proof disk in the battery box. Optionally, the chip is connected to an environmental compensation capacitor for compensating for the inherent inductive capacitance between the electrode sheet and the explosion-proof valve or explosion-proof disk, thereby accurately sensing the capacitance change between the electrode sheet and the explosion-proof valve or explosion-proof disk.

7. The detection device according to any one of claims 1 to 6, characterized in that Optionally, the chip includes a capacitance-to-voltage conversion circuit and an analog-to-digital converter, wherein the capacitance-to-voltage conversion circuit receives the signal of the sensing capacitor and converts it into a voltage signal, and the analog-to-digital converter converts the voltage signal into a digital signal. Optionally, the chip includes a capacitor-voltage conversion circuit and a demodulation and analog-to-digital conversion circuit, wherein the capacitor-voltage conversion circuit modulates the received signal of the inductive capacitor into a voltage signal based on an external AC signal, and then demodulates and converts the signal through the demodulation and analog-to-digital conversion circuit, and finally converts it into a digital signal.

8. The detection device according to any one of claims 1 to 6, characterized in that Optionally, the chip includes a capacitance-frequency conversion circuit and a time-to-digital converter, wherein the capacitance-frequency conversion circuit converts the signal of the inductive capacitance into a frequency signal, and the time-to-digital converter converts the frequency signal into a digital signal. Optionally, the chip includes a relaxation oscillator and a time-to-digital converter, wherein 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.

9. The detection device according to any one of claims 1 to 6, characterized in that: Optionally, the chip includes a differential amplifier, a loop filter, and a quantizer. The differential amplifier is used to perform differential measurement 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 of the external excitation voltage and the ground voltage of the reference capacitor. Optionally, the chip includes a differential amplifier, a quantizer and a successive approximation logic, the differential amplifier performs differential measurement 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 controls the switching of the external excitation voltage and the ground voltage of each reference capacitor of the reference capacitor array based on the digital signal.

10. A battery cell internal pressure warning system, characterized in that: include: The device for detecting changes in internal pressure of a battery cell according to any one of claims 1 to 9; The judgment device determines the internal pressure change of the battery according to the detection signal from the chip, and issues an early warning when the internal pressure change exceeds a threshold.

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