Method and device for identifying a safety boundary perturbation factor of a traction battery

Abstract

This invention provides a method and apparatus for identifying safety boundary disturbance factors of a power battery, comprising the following steps: S100: obtaining a first failure critical temperature of the power battery based on a first test device, the first test device including two first sub-cavities for positive or negative electrode plates of the power battery respectively, the two first sub-cavities being thermally insulated from each other and connected through one or more through holes for electrolyte exchange; S200: in response to a first deviation between the first failure critical temperature and the theoretical failure critical temperature exceeding a first threshold, determining that the safety boundary disturbance factor includes mass transfer; S300: obtaining a second failure critical temperature of the power battery based on a second test device, the second test device having a second sub-cavity for accommodating positive and negative electrode plates arranged in a stacked manner; S400: in response to a second deviation between the second failure critical temperature and the first failure critical temperature exceeding a second threshold, determining that the safety boundary disturbance factor includes heat transfer.

Description

Technical Field

[0001] The present invention relates to a method for identifying safety boundary disturbance factors of a power battery and an apparatus for performing such a method. Background Technology

[0002] Power batteries, such as lithium-ion batteries, are widely used in new energy vehicles. To meet the requirements of vehicle range, their energy density or number of modules is also increasing, which places higher demands on the thermal failure safety of power batteries.

[0003] Considering this, the power battery needs to operate below its safety boundary during vehicle operation; for example, the battery's operating temperature must be below a predetermined thermal safety boundary. However, thermal runaway in lithium-ion batteries is a complex chemical reaction, and the critical temperature for thermal failure is not fixed but influenced by numerous factors. In practical industrial applications, the thermal safety boundary of the power battery is stored in the processor as a fixed estimated or theoretical value, ignoring the fact that it can change due to environmental parameters or its own state parameters. Therefore, it is necessary to explore the factors that perturb the safety boundary of the power battery to provide more accurate guidance for thermal failure management strategies. Summary of the Invention

[0004] Depending on the specific aspects, the object of the present invention is to provide a method for identifying safety boundary disturbance factors of a power battery and an apparatus for performing such a method.

[0005] Furthermore, the present invention aims to solve or alleviate other technical problems existing in the prior art.

[0006] The present invention solves the above problems by providing a method, specifically comprising the following steps:

[0007] S100: Obtain the first failure critical temperature of the power battery based on the first test device, wherein the first test device includes two first sub-cavities for the positive electrode or negative electrode of the power battery, the two first sub-cavities are heat-insulated from each other and connected through one or more through holes for electrolyte exchange.

[0008] S200: In response to the first deviation between the first failure critical temperature and the theoretical failure critical temperature exceeding the first threshold, it is determined that the safety boundary disturbance factor includes mass transfer.

[0009] S300: Obtain the second failure critical temperature of the power battery based on the second test device, wherein the second test device has a second sub-cavity for accommodating positive and negative electrode sheets arranged in a stacked manner; and

[0010] S400: In response to the second deviation between the second failure critical temperature and the first failure critical temperature exceeding the second threshold, it is determined that the safety boundary disturbance factor includes heat transfer.

[0011] According to one aspect of the method of the present invention, step S100 includes the following sub-steps:

[0012] S110: Construct a first sample and a first comparison sample based on the first test device, wherein, in the first sample, the positive electrode and the negative electrode of the power battery are respectively housed in one of the corresponding first sub-cavities of the two first sub-cavities; in the first comparison sample, one of the positive electrode and the negative electrode is housed in one of the first sub-cavities of the two first sub-cavities;

[0013] S120: Perform a failure operation on the first sample and the first comparison sample, and record the failure critical temperature of the first sample as the first failure critical temperature, and record the failure critical temperature of the first comparison sample as the theoretical failure critical temperature.

[0014] According to one aspect of the method of the present invention, step S300 includes the following sub-steps:

[0015] S310: A second sample is prepared by placing the stacked assembly of the power battery in the second sub-cavity of the second test device, wherein the stacked assembly includes a positive electrode, a negative electrode, and a separator located between the positive electrode and the negative electrode arranged on top of each other.

[0016] S320: Perform a failure operation on the second sample and record the failure critical temperature of the second sample as the second failure critical temperature.

[0017] According to one aspect of the method of the present invention, the power battery is constructed as a stacked battery, wherein the first sub-cavity and / or the second sub-cavity are made of aluminum-plastic film.

[0018] According to one aspect of the invention, a method is proposed to apply an impact force or heat to a power battery housed in the first test device or the second test device to perform the failure operation.

[0019] According to one aspect of the present invention, during the failure operation, a temperature profile of the power battery is acquired and a failure critical temperature is obtained based on the temperature profile.

[0020] According to another aspect of the present invention, an apparatus for performing such a method is provided, comprising:

[0021] The first test device includes two first sub-cavities for accommodating the positive or negative electrode of the power battery, the two first sub-cavities being thermally insulated from each other and connected by one or more through holes for electrolyte exchange.

[0022] The second test device has a second sub-cavity for accommodating electrodes arranged in a stacked manner;

[0023] A failure device configured to perform a failure operation to cause thermal failure of a power battery housed in a first or second test device; and

[0024] A failure critical temperature acquisition device is configured to acquire the failure critical temperature of the power battery during failure operation.

[0025] According to another aspect of the invention, the power battery is constructed as a stacked battery, wherein the first sub-cavity and / or the second sub-cavity are formed by stamping aluminum-plastic film.

[0026] According to another aspect of the invention, the failure-causing device is configured as a stamping element for applying an impact force to a power battery housed in the first test device or the second test device; or the failure-causing device is configured as a heating element for heating a power battery housed in the first test device or the second test device.

[0027] According to another aspect of the present invention, the failure critical temperature acquisition device includes a temperature measuring element for acquiring a temperature curve of the power battery during failure operation and a processing element connected to the temperature measuring element for acquiring the failure critical temperature based on the temperature curve.

[0028] According to this disclosure, by exploring the disturbance factors of the safety boundary of power batteries, more accurate guidance can be provided for the thermal failure management strategy of power batteries. Attached Figure Description

[0029] Referring to the accompanying drawings, the above and other features of the present invention will become apparent, wherein,

[0030] Figures 1 to 3 The main steps of the method according to the present invention are shown;

[0031] Figure 4 A schematic diagram of a first sample including a power battery, constructed during the execution of the method is shown. Detailed Implementation

[0032] It is readily understood that, based on the technical solution of this invention, those skilled in the art can propose various interchangeable structural methods and implementations without altering the essential spirit of the invention. Therefore, the following detailed embodiments and accompanying drawings are merely illustrative examples of the technical solution of this invention and should not be considered as the entirety of the invention or as limitations or restrictions on the technical solution of this invention.

[0033] The directional terms such as up, down, left, right, front, back, front, back, top, and bottom mentioned or possibly used in this specification are defined relative to the structures shown in the accompanying drawings. These are relative concepts and may therefore vary depending on their location and usage. Therefore, these or other directional terms should not be interpreted as restrictive. Furthermore, the terms "first," "second," "third," and similar expressions are used for descriptive and distinguishing purposes only and should not be construed as indicating or implying the relative importance of the corresponding components.

[0034] refer to Figures 1 to 3 This invention illustrates a method for identifying safety boundary disturbance factors of a power battery. The concept of "safety boundary" introduced herein specifically refers to the "thermal safety boundary," which can be understood as the thermal safety boundary of the battery as a whole and the thermal safety boundary of its positive or negative electrode itself, wherein the thermal safety boundary of the battery as a whole depends simultaneously on the individual thermal safety boundaries of the positive and negative electrodes of the power battery. The safety boundary mentioned below can be understood as the safety boundary of the battery electrodes in the electrolyte or the safety boundary of the power battery as a whole. Here, disturbances to the safety boundary of the positive or negative electrode essentially reflect the impact on the battery as a whole.

[0035] In summary, this method mainly includes mass transfer and heat transfer determination processes. By exploring the disturbance factors of the power battery's safety boundary, it can provide relatively accurate guidance for the power battery's thermal failure management strategy. By distinguishing between mass transfer and heat transfer, the influencing factors of the thermal safety boundary can be more accurately controlled as a whole, and the design of the power battery can be improved in a targeted manner.

[0036] Here, the mass transfer determination process includes:

[0037] S100: Obtain the first critical failure temperature of the power battery based on the first test device;

[0038] S200: In response to the first deviation between the first failure critical temperature and the theoretical failure critical temperature exceeding the first threshold, it is determined that the safety boundary disturbance factor includes mass transfer.

[0039] Here, the first experimental device has a dual-cavity structure, such as in Figure 4As shown, it includes two first sub-chambers 100 and 200 that are spaced apart from each other, particularly thermally and electrically, and each first sub-chamber is used to accommodate a battery electrode of the same polarity. That is, the positive electrode 300 of the battery is accommodated in one of the first sub-chambers 100, and the negative electrode 400 of the battery is accommodated in the other first sub-chamber 200. It should be noted that the positive or negative electrode can be placed in the respective first sub-chamber as a single piece, or it can also be placed in the respective first sub-chamber in the form of a certain number of stacked pieces, in which case a separator is provided between adjacent electrodes of the same polarity.

[0040] The two first sub-chambers of this first test device are made of heat-insulating material to prevent significant heat exchange between the two first sub-chambers during the test. For example, in the design scheme of a power battery as a stacked battery, in order to better simulate the operating environment of the power battery, the two first sub-chambers are stamped from aluminum-plastic film with insulating and heat-insulating properties. A sealed cavity is formed by sealing the aluminum-plastic film using a hot-pressing process. This seal (in) Figure 4 (Illustrated schematically by a section line) For example, as shown in the diagram Figure 4 As shown, it is located between the edges of the two first sub-cavities and between the two first sub-chambers to isolate them from heat transfer.

[0041] There is also a through hole in the sealing area between these two first sub-cavities (see details). Figure 4 This allows for electrolyte exchange between the two first sub-chambers. The size and number of these through-holes can be selected based on the experimental accuracy, i.e., the size and number of the through-holes are designed such that heat transfer caused by electrolyte exchange is negligible while meeting the experimental accuracy requirements. In a preferred embodiment, the through-holes are designed to be as small as possible while ensuring electrolyte exchange.

[0042] In this mass transfer determination process, there is essentially no heat transfer between the positive and negative electrodes; only mass transfer occurs. This mass transfer involves the exchange of substances generated at these two electrodes (specifically, between the electrode and the electrolyte). For example, before the battery experiences overall thermal failure, byproducts generated from the chemical reaction at the negative electrode diffuse with the electrolyte to the positive electrode, thus affecting its thermal safety boundary. That is, it causes a deviation between the actual and theoretical critical failure temperatures of the positive electrode. Here, the byproducts, through the mass transfer effect of the electrolyte, can be considered as a disturbance factor to the electrode safety boundary. If this method identifies that the mass transfer between the positive and negative electrodes affects the battery safety boundary, then in practical applications, this can be used to adjust the safety boundary stored in the battery control system, or the safety boundary of the power battery can be adjusted in real time based on power battery monitoring data (e.g., operating temperature) to further ensure the safety of the power battery. This will be further explained below.

[0043] It should be noted that the mass transfer effect of the side reaction products of the negative electrode mentioned above is merely an example and should not be interpreted in a restrictive manner. Furthermore, the description of it can be easily adapted to the mass transfer effect of the side reaction products of the positive electrode.

[0044] Optionally, the mass transfer determination process can be, but is not limited to, based on comparative experiments. In a feasible embodiment, step S100 above includes the following sub-steps:

[0045] First, in sub-step S110, a first sample and a first comparison sample are constructed based on the first test device. In the first sample, a positive or negative electrode (and optionally a separator between electrodes of the same polarity in a stacked configuration) is contained in one of the first sub-cavities; while a negative or positive electrode of opposite polarity is contained in the other of the first sub-cavities. In contrast, in the first comparison sample, the positive or negative electrode to be tested is contained only in one of the first sub-cavities (optionally, a separator is also present). For example, to identify disturbances to the safety boundary of the positive electrode, in the first sample, the positive and negative electrodes each occupy one of the first sub-cavities; in the first comparison sample, a positive electrode or optionally a separator is contained in one of the first sub-cavities, while only electrolyte is present in the other first sub-cavity.

[0046] Specifically, when creating the sample, the power battery is first pretreated at a suitable charge / discharge rate to ensure it is in a state of charge. For example, in a lithium-ion battery design, the power battery can be charged to approximately 100% SOC at a rate of 0.33C, so that the positive electrode is in a delithiated state and the negative electrode is in a lithium-intercalated state. Next, in a dry environment, the positive and negative electrodes, or optionally a separator, of the power battery in this state of charge are obtained and placed in the dual-cavity structure according to the above requirements. Then, electrolyte is injected into the two first sub-cavities, and the two first sub-cavities are evacuated and sealed.

[0047] Next, in step S120, a failure operation is performed on the first sample and the first comparison sample, and the failure critical temperature (i.e., safety boundary) of the power battery, especially its electrode and electrolyte, is obtained. On one hand, thermal failure of the electrode can be induced by heating these two samples. That is, in the apparatus used to perform such a method, the failure-inducing device includes a heating element. Specifically, during the failure operation, the real-time temperature curve of the power battery can be measured using a temperature sensing element, and the failure critical temperature can be obtained manually or using a corresponding processing element based on the temperature curve. For example, using the processing element, the point with the largest rate of change in the temperature curve (i.e., the point where the slope of the temperature curve suddenly increases the fastest) is taken as the thermal failure point, and the temperature of this thermal failure point is the failure critical temperature. This temperature sensing element can be implemented as a non-contact temperature sensing element. Furthermore, considering the gas caused by battery thermal failure, it is also possible to determine whether the power battery contained therein, especially its electrode, has undergone thermal failure by observing the state changes of these two samples. This can be achieved using a pressure sensor or a combination of an image acquisition device and a corresponding processing unit, which will not be elaborated further. On the other hand, thermal failure of the electrode can be induced by applying an impact force to the prepared sample; that is, the aforementioned failure-inducing device includes a stamping element. During this process, the temperature of the power battery electrode and its critical failure temperature can also be obtained using the aforementioned temperature measuring element or image acquisition device.

[0048] Here, the failure critical temperature corresponding to the first sample obtained through the above method is recorded as the first failure critical temperature, and correspondingly, the failure critical temperature corresponding to the first comparative sample is recorded as the theoretical failure critical temperature. If the first failure critical temperature is less than the theoretical failure critical temperature, it is determined that the mass transfer effect of the by-reaction products of the negative electrode sheet promotes the thermal failure of the positive electrode sheet. Based on this, appropriate additives can be added to the electrolyte of the power battery to reduce or preferably prevent the mass transfer effect of the by-reaction products. If the first failure critical temperature is greater than the theoretical failure critical temperature, it is determined that the mass transfer effect of the by-reaction products of the negative electrode sheet inhibits the thermal failure of the positive electrode sheet. If these two are basically equal, it is proven that the mass transfer effect of the by-reaction products of the negative electrode sheet has no effect on the thermal failure of the positive electrode sheet. In addition, in practical applications, the (thermal) safety boundary of the power battery can be dynamically adjusted according to the battery's operating state, such as the temperature of the electrode sheet.

[0049] In addition, it should be noted that the theoretical failure critical temperature mentioned in sub-step S120 is not necessarily obtained from the first comparative sample; it can be a predetermined theoretical value.

[0050] Furthermore, the heat transfer determination process according to the method of the present invention can be designed similarly to the mass transfer process described above, but the two differ in the design of the second test device. Specifically, the heat transfer determination process includes the following steps:

[0051] S300: Obtain the second critical failure temperature of the power battery based on the second test device; and

[0052] S400: In response to the second deviation between the second failure critical temperature and the first failure critical temperature exceeding the second threshold, it is determined that the safety boundary disturbance factor includes heat transfer.

[0053] It should be noted that, in order to enhance the heat transfer process between the positive and negative electrodes, in the second sample, the stack of positive and negative electrodes and the separator between them is placed in a second sub-cavity. This second sub-cavity differs from the aforementioned dual-cavity structure in that it lacks an intermediate sealing region.

[0054] Here, in step S300, a second sample is first constructed by placing the stacked group of power batteries in the second sub-cavity of the second test device (i.e., sub-step S310); then, a failure operation is performed on the second sample, and the failure critical temperature of the second sample is recorded as the second failure critical temperature (i.e., sub-step S320).

[0055] If the second critical failure temperature is lower than the first critical failure temperature measured during the mass transfer determination process, then the heat transfer effect is determined to promote the thermal failure of the positive electrode. In this case, a flame retardant can be added to the electrolyte of the power battery to suppress the heat transfer between the positive and negative electrodes. If the second critical failure temperature is higher than the first critical failure temperature, then the heat transfer effect is determined to inhibit the thermal failure of the positive electrode, which is more advantageous for practical applications. If the second critical failure temperature is substantially equal to the first critical failure temperature or the deviation between the two meets the requirements, then the heat transfer effect is determined to have no effect on the thermal failure of the positive electrode.

[0056] Here, the mass transfer effect determination process and the heat transfer effect determination process can be explored qualitatively. Of course, in order to achieve more accurate thermal management of the power battery, it can also be explored quantitatively. For example, its disturbance effect can be classified into levels, and the thermal management design scheme of the power battery can be improved based on these levels in practical applications.

[0057] Furthermore, the present invention relates to an apparatus capable of performing a method for identifying safety boundary disturbance factors of a power battery. Specifically, the apparatus includes a first test device, a second test device, a failure-inducing device, and a failure critical temperature acquisition device, wherein the first and second test devices are referable to the above description of the method to be performed. The failure-inducing device is configured to perform a failure operation to cause thermal failure of the power battery housed in the first and second test devices; the failure critical temperature acquisition device is configured to acquire the failure critical temperature of the power battery during the failure operation.

[0058] In an optional embodiment, the failure-causing device is configured as a stamping element for applying an impact force to a power battery housed in the first test device or the second test device to simulate a power battery failure caused by a collision during driving.

[0059] In another feasible embodiment, the failure device includes a heating element or optionally an associated component (e.g., a temperature controller), wherein the heating element is used to heat the power battery housed in the first or second test device.

[0060] In one feasible embodiment, the failure critical temperature acquisition device includes a temperature measuring element for acquiring the temperature curve of the power battery during failure operation and a processing element connected to the temperature measuring element for acquiring the failure critical temperature based on the temperature curve, such as a computer-based processing unit.

[0061] It should be noted that the description of the apparatus according to the invention can also be referenced to the description of the method according to the invention, which will not be repeated here.

[0062] It should be understood that all the above preferred embodiments are exemplary and not restrictive, and various modifications or variations made by those skilled in the art to the specific embodiments described above under the concept of the present invention should be within the legal protection scope of the present invention.

Claims

1. A method for identifying safety boundary disturbance factors of a power battery, characterized in that, Includes the following steps: S100: Obtain the first failure critical temperature of the power battery based on the first test device, wherein the first test device includes two first sub-cavities for the positive electrode or negative electrode of the power battery, the two first sub-cavities are heat-insulated from each other and connected through one or more through holes for electrolyte exchange. S200: In response to the first deviation between the first failure critical temperature and the theoretical failure critical temperature exceeding the first threshold, it is determined that the safety boundary disturbance factor includes mass transfer. S300: Obtain the second failure critical temperature of the power battery based on the second test device, wherein the second test device has a second sub-cavity for accommodating positive and negative electrode sheets arranged in a stacked manner; and S400: In response to the second deviation between the second failure critical temperature and the first failure critical temperature exceeding the second threshold, it is determined that the safety boundary disturbance factor includes heat transfer.

2. The method according to claim 1, characterized in that, Step S100 includes the following sub-steps: S110: Construct a first sample and a first comparison sample based on the first test device, wherein, in the first sample, the positive electrode and the negative electrode of the power battery are respectively housed in one of the corresponding first sub-cavities of the two first sub-cavities; in the first comparison sample, one of the positive electrode and the negative electrode is housed in one of the first sub-cavities of the two first sub-cavities; S120: Perform a failure operation on the first sample and the first comparison sample, and record the failure critical temperature of the first sample as the first failure critical temperature, and record the failure critical temperature of the first comparison sample as the theoretical failure critical temperature.

3. The method according to claim 1, characterized in that, Step S300 includes the following sub-steps: S310: A second sample is constructed by placing a stack of power batteries in the second sub-cavity of the second test device, wherein the stack includes positive electrode plates, negative electrode plates and a separator located between the positive electrode plates and the negative electrode plates arranged on top of each other. S320: Perform a failure operation on the second sample and record the failure critical temperature of the second sample as the second failure critical temperature.

4. The method according to any one of claims 1 to 3, characterized in that, The power battery is constructed as a stacked battery, and the first sub-cavity and / or the second sub-cavity are made of aluminum-plastic film.

5. The method according to claim 2 or 3, characterized in that, An impact force or heat is applied to the power battery housed in the first test device or the second test device to perform the failure operation.

6. The method according to claim 2 or 3, characterized in that, During the failure operation, the temperature profile of the power battery is acquired, and the critical failure temperature is obtained based on the temperature profile.

7. A device for identifying safety boundary disturbance factors of a power battery, characterized in that, It can be used to perform the method according to any one of claims 1 to 6, the apparatus comprising: The first test device includes two first sub-cavities for accommodating the positive or negative electrode of the power battery, the two first sub-cavities being thermally insulated from each other and connected by one or more through holes for electrolyte exchange. The second test device has a second sub-cavity for accommodating positive and negative electrode plates arranged in a stacked manner; A failure device configured to perform a failure operation to cause thermal failure of a power battery housed in a first or second test device; and A failure critical temperature acquisition device is configured to acquire the failure critical temperature of the power battery during failure operation.

8. The apparatus according to claim 7, characterized in that, The power battery is constructed as a stacked battery, and the first sub-cavity and / or the second sub-cavity are formed by stamping aluminum-plastic film.

9. The apparatus according to claim 7, characterized in that, The failure-causing device is constructed as a stamping element to apply an impact force to the power battery housed in the first test device or the second test device; or the failure-causing device is constructed as a heating element to heat the power battery housed in the first test device or the second test device.

10. The apparatus according to any one of claims 7 to 9, characterized in that, The failure critical temperature acquisition device includes a temperature measuring element for acquiring the temperature curve of the power battery during failure operation, and a processing element connected to the temperature measuring element for acquiring the failure critical temperature based on the temperature curve.

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