Battery cell pressure determination method, apparatus, battery, device, medium, and product

Abstract

This application provides a method, apparatus, battery, device, computer-readable storage medium, and computer program product for determining battery cell pressure. The method includes: acquiring current state data of a target battery cell during charging and discharging; and applying a corresponding pressure to the target battery cell based on the current state data. Since the pressure applied to the target battery cell is determined according to the current state data of the target battery cell, the accuracy of pressure determination can be ensured, and more precise pressure control can be achieved.

Description

Technical Field

[0001] This application relates to the field of vehicle technology, and in particular to a method, apparatus, battery, device, computer-readable storage medium, and computer program product for determining battery cell pressure. Background Technology

[0002] Currently, during the charging and discharging process of lithium-ion batteries, the positive and negative electrode active materials shrink and expand as lithium ions are extracted and inserted (the expansion rate of graphite negative electrodes can reach 10%, and that of silicon-based negative electrodes can reach 300%). Initially, the interfaces of the positive electrode, separator, and negative electrode are in close contact, but as the expansion gradually increases, pores gradually appear between the interfaces, increasing the contact resistance. At the same time, irregular interfaces can cause local lithium ion enrichment, thereby inducing the growth of lithium dendrites and deteriorating the battery's safety and cycle performance. Therefore, limiting cell expansion is crucial.

[0003] In related technologies, a constant pressure is applied to the battery cell to limit its expansion. However, this method is difficult to achieve precise pressure control and cannot ensure the performance of the battery cell. Summary of the Invention

[0004] This application provides a method, apparatus, battery, device, computer-readable storage medium, and computer program product for determining battery cell pressure.

[0005] The technical solution of this application embodiment is implemented as follows: This application provides a method for determining battery cell pressure, the method comprising: Acquire the current state data of the target battery cell during the charging and discharging process; Based on the current state data, a corresponding pressure is applied to the target battery cell.

[0006] This application provides a battery cell pressure determination device, the method comprising: The acquisition module is used to acquire the current status data of the target cell during the charging and discharging process; An application module is used to apply a corresponding application pressure to the target cell based on the current state data.

[0007] This application provides a battery including a battery cell, a shape memory alloy, and a casing encapsulating the battery cell and the shape memory alloy. The battery cell pressure is determined using the battery cell pressure determination method described above.

[0008] This application also provides a battery cell pressure determination device, including: a memory; a processor; and a computer program; wherein the computer program is stored in the memory and configured to be executed by the processor to implement the battery cell pressure determination method as described above.

[0009] This application also provides a computer-readable storage medium storing computer-executable instructions or computer programs, which, when executed by a processor, implement the cell pressure determination method described above.

[0010] This application also provides a computer program product, including computer-executable instructions or a computer program, which, when executed by a processor, can implement the cell pressure determination method described above.

[0011] The embodiments of this application have the following beneficial effects: In this embodiment, after obtaining the current state data of the target cell during the charging and discharging process, a corresponding pressure is applied to the target cell based on the current state data. It can be seen that the applied pressure determined in this application is not a constant pressure, but a dynamic pressure that is related to the current state data of the target cell during the charging and discharging process. That is, the applied pressure changes with the change of the current state data of the target cell. In this way, the accuracy of pressure determination can be ensured, more precise pressure control can be achieved, and the performance of the cell can be effectively ensured. Attached Figure Description

[0012] Figure 1 A schematic flowchart illustrating a method for determining battery cell pressure provided in an embodiment of this application; Figure 2 A flowchart illustrating another method for determining battery cell pressure provided in an embodiment of this application; Figure 3 This is a schematic diagram of a battery cell pressure determination device provided in an embodiment of this application; Figure 4 This is a schematic diagram of the battery cell pressure determination device provided in an embodiment of this application. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. The described embodiments should not be regarded as limitations on this application. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0014] In the following description, references are made to “some embodiments,” which describe a subset of all possible embodiments. However, it is understood that “some embodiments” may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0015] In the embodiments of this application, the terms "module" or "unit" refer to a computer program or part of a computer program that has a predetermined function and works with other related parts to achieve a predetermined goal, and can be implemented wholly or partially using software, hardware (such as processing circuitry or memory), or a combination thereof. Similarly, a processor (or multiple processors or memory) can be used to implement one or more modules or units. Furthermore, each module or unit can be part of an overall module or unit that includes the functionality of that module or unit.

[0016] Unless otherwise defined, all technical and scientific terms used in the embodiments of this application have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in the embodiments of this application is for the purpose of describing the embodiments of this application only and is not intended to limit this application.

[0017] Currently, during the charging and discharging process of lithium-ion batteries, the positive and negative electrode active materials shrink and expand as lithium ions are extracted and inserted (the expansion rate of graphite negative electrodes can be as high as 10%, and that of silicon-based negative electrodes can be as high as 300%). Initially, the interfaces of the positive electrode, separator, and negative electrode are in close contact, but as the expansion gradually increases, pores gradually appear between the interfaces, increasing the contact resistance. At the same time, irregular interfaces can cause local lithium ion enrichment, thereby inducing the growth of lithium dendrites and deteriorating the battery's safety and cycle performance.

[0018] In related technologies, a pre-tightening force is typically applied during the assembly process to ensure the flatness of the cell surface. Specifically, this is achieved by limiting the position using steel plates at both ends of the envelope, with the external restraint force transmitted through aerogel. The drawback of this approach is that the initial pre-tightening force is a constant pressure, which cannot be dynamically adjusted based on the expansion volume of the negative electrode during charging, making it difficult to achieve optimal performance. Furthermore, appropriate pressure can reduce the voids at the electrode-separator interface, lowering interfacial impedance; excessive pressure compresses the electrode pores (further reducing porosity), obstructing the electrolyte transport path, decreasing the lithium-ion diffusion coefficient, and affecting cell performance.

[0019] Based on the above technical problems, embodiments of this application provide a method, apparatus, battery, device, computer-readable storage medium, and computer program product for determining battery cell pressure.

[0020] Figure 1 This is a flowchart illustrating a method for determining battery cell pressure provided in an embodiment of this application, as shown below. Figure 1 As shown, the method includes the following steps: Step 101: Obtain the current state data of the target cell during the charging and discharging process.

[0021] Here, the target cell refers to the cell whose pressure needs to be determined. The pressure refers to the external pressure of the target cell, also known as external pressure, which is used to limit the expansion of the cell.

[0022] In this embodiment of the application, the cell pressure determination method can be applied to the battery management system (BMS) in the battery. Here, the type of battery is not specifically limited. For example, the battery can be a lithium-ion battery, a nickel-cadmium battery, or other types of batteries.

[0023] For example, a battery may include one or more cells, i.e., at least one cell, and the target cell may be one of the at least one cells. The battery may be used in electric vehicles or other electronic devices, without specific limitations herein.

[0024] For example, the BMS is responsible for battery status monitoring and management to ensure the safe use of the battery during charging and discharging. In this embodiment, the BMS can obtain the current status data of the target cell during charging and discharging.

[0025] The current status data may include at least the current temperature, the current state of charge (SOC), and the current state of health (SOH).

[0026] For example, the battery generates a certain amount of heat during charging and discharging. The battery is also equipped with a temperature sensor to monitor the cell temperature in real time. After the temperature sensor detects the current temperature of the target cell, it sends the current temperature to the BMS. At this time, the BMS obtains the current temperature of the target cell during charging and discharging.

[0027] For example, SOC represents the remaining percentage of charge in a battery cell, typically expressed in 0-100%. SOH reflects the health condition or aging level of the battery cell, also typically expressed in 0-100%.

[0028] High SOC indicates that the battery cell is close to full charge, while low SOC indicates that the battery cell has a low charge level. Low SOH indicates that the battery cell is aging; the higher the value, the better the health condition, and the lower the value, the worse the health condition. SOH of 100% indicates that the battery cell is in a brand new state, also known as BOL (Beginning of Life), while SOH of less than 100% indicates that the battery cell is in an intermediate state, also known as XOL (Excess of Life).

[0029] In this embodiment of the application, considering that when the SOH of the battery cell drops below 80%, its battery life and performance will decrease significantly and it will no longer be suitable for continued use, the range of SOH values ​​corresponding to the battery cell, i.e., the SOH range, can be 100%-80%.

[0030] For example, since the current temperature, current SOC, and current SOH can comprehensively assess the cell's condition, obtaining this cell condition data can ensure the accurate determination of the pressure to be applied to the cell subsequently.

[0031] Step 102: Based on the current state data, apply the corresponding pressure to the target cell.

[0032] In this embodiment of the application, after obtaining the current state data of the target cell during the charging and discharging process according to the above steps, a corresponding pressure can be applied to the target cell based on the current state data; here, the applied pressure refers to the actual pressure applied to the target cell.

[0033] In some embodiments, applying a corresponding pressure to a target cell based on current state data may include: determining the total pressure to be applied to the target cell based at least on the current temperature, current SOC, and current SOH; obtaining the current pressure of the target cell; determining the application pressure based on the total pressure and the current pressure; and applying the corresponding application pressure to the target cell.

[0034] In this embodiment of the application, when the current state data includes the current temperature, current SOC and current SOH, the total pressure to be applied to the target cell can be determined based on the current temperature, current SOC and current SOH; here, the total pressure refers to the expected pressure that can ensure close contact between the electrodes and the separator of the target cell.

[0035] Furthermore, after determining the total pressure that needs to be applied to the target cell, the current pressure of the target cell can be obtained; and based on the total pressure and the current pressure, the applied pressure can be determined.

[0036] It should be noted that the current pressure is generated by the shape memory alloy (SMA) set on the outside of the target cell.

[0037] As can be seen, in this embodiment of the application, the applied pressure, i.e. the actual pressure, is determined by combining the current pressure generated by the SMA and the expected pressure of the target cell. This can improve the accuracy of pressure determination. By using the actual pressure to limit cell expansion, it can ensure that the positive electrode, separator, and negative electrode interfaces of the cell are always in close contact, thereby improving the safety performance and cycle performance of the battery.

[0038] In some embodiments, determining the total pressure based at least on the current temperature, current SOC, and current SOH may include: determining the target SOH segment where the current SOH is located, obtaining the corresponding pressure demand prediction model based on the target SOH segment; determining the total pressure based on the pressure demand prediction model, the current temperature, and the current SOC; the pressure demand prediction model characterizes the correspondence between temperature and SOC and pressure.

[0039] In this embodiment of the application, the SOH range of the test cell can be segmented in advance to obtain multiple different SOH segments; wherein, the multiple SOH segments include the target SOH segment; then, the pressure demand prediction model corresponding to the multiple SOH segments is determined.

[0040] Among them, the test cell refers to a cell that can be actually measured, and its parameter information is the same as that of the target cell, and the two are cells of the same type.

[0041] For example, as can be seen from the above, the SOH range corresponding to the battery cell can be 100%-80%; for example, the SOH range of the test battery cell can be segmented according to a set length. Here, the value of the set length is not specifically limited. For example, the set length can be 2% or 3%, etc. 2% will be used as an example for explanation below.

[0042] It is understandable that the SOH of the battery cell will gradually decrease as the cell is used. If the SOH range is 100%-80% and the set length is 2%, then the SOH range can be divided into 10 SOH segments. Correspondingly, 100%-98% is the first SOH segment, 98%-96% is the second SOH segment, and so on, until 82%-80% is the last SOH segment.

[0043] In this embodiment of the application, after obtaining the current SOH of the target cell, the target SOH segment where the current SOH is located can be determined by matching the current SOH with multiple SOH segments.

[0044] For example, after segmenting the SOH range of the test cell to obtain multiple SOH segments, the pressure demand prediction model corresponding to each of the multiple SOH segments will be further determined. The determination process will be explained later. That is, after determining the target SOH segment where the current SOH is located, the corresponding pressure demand prediction model can be obtained based on the target SOH segment, which is used to determine the pressure required by the cell, i.e., the total pressure. Here, the pressure demand prediction model represents the correspondence between temperature and SOC and pressure.

[0045] It is understandable that different SOH segments can reflect different aging degrees of the battery cell. In the embodiments of this application, by setting different pressure demand prediction models for different SOH segments, the reliability of the pressure demand prediction model can be effectively improved.

[0046] For example, after obtaining the pressure demand prediction model corresponding to the target SOH segment, the total pressure can be determined based on the pressure demand prediction model, the current temperature of the target cell, and the current SOC.

[0047] As can be seen, in this embodiment of the application, the pressure demand prediction model can be uniquely determined based on the target SOH segment where the current SOH of the battery cell is located. That is, the pressure demand prediction model can reflect different aging degrees of the battery cell. Using this pressure demand prediction model to determine the total pressure can effectively improve the accuracy of the total pressure determination.

[0048] In some embodiments, determining the pressure demand prediction model corresponding to multiple SOH segments may include: for each SOH segment, obtaining the measured state data of the test cell at the endpoint of the SOH segment; and determining the pressure demand prediction model corresponding to each SOH segment based on the measured state data.

[0049] Here, the measured state data may include at least multiple measured temperatures, multiple measured SOCs, and multiple measured expansion amounts. It should be noted that, since the battery cell includes a positive electrode and a negative electrode, the expansion amount involved in this application embodiment refers to the cumulative value of the positive electrode expansion amount and the negative electrode expansion amount.

[0050] Here, we take multiple SOH segments, including 10 SOH segments such as 100%-98%, 98%-96%, ... 82%-80%, as an example for explanation; in the embodiments of this application, the measured state data of the test cell at the endpoint of the SOH segment can be obtained for each SOH segment.

[0051] It should be noted that if different SOH segments include overlapping endpoints, then only one measured state data acquisition is needed, and there is no need to acquire it repeatedly. For example, for the 100%-98% segment, the endpoints include 100% and 98%, and for the 98%-96% segment, the endpoints include 98% and 96%. In this case, the measured state data for the 98% endpoint only needs to be acquired once. In this case, the measured state data for the 100%, 98%, and 96% endpoints are obtained directly from actual measurements.

[0052] For example, after obtaining the measured state data of each SOH segment endpoint, the pressure demand prediction model corresponding to each SOH segment can be determined based on the measured state data.

[0053] For example, when the measured state data of the test cell is obtained at 100% SOH, the pressure demand prediction model corresponding to the 100%-98% segment can be determined based on the measured state data; similarly, when the measured state data of the test cell is obtained at 98% SOH, the pressure demand prediction model corresponding to the 98%-96% segment can be determined based on the measured state data.

[0054] For example, as can be seen from the above, the measured state data of each SOH segment endpoint can include multiple measured temperatures and multiple measured SOCs. That is, the measured temperature and measured SOCs are known values. At this time, it is only necessary to determine the pressure corresponding to each measured expansion to obtain the correspondence between the measured temperature and measured SOCs and the pressure, and then obtain the pressure demand prediction model corresponding to each SOH segment.

[0055] For example, the pressure corresponding to the measured expansion amount refers to the pressure required to maintain the contact between the electrode and the diaphragm of the test cell under the measured expansion amount, that is, the pressure that needs to be applied to the test cell, which is positively correlated with the expansion amount; the pressure determination equation characterizing the relationship between the expansion amount and the pressure can be established according to elasticity, as shown in formula (1): P = Eeff * △h total / h0 (1) Here, P represents the pressure corresponding to the measured expansion amount, △h total = △h negative electrode + △h positive electrode, which represents the expansion amount of the tested cell, △h negative electrode represents the expansion amount of the negative electrode, and △h positive electrode represents the expansion amount of the positive electrode; Eeff represents the equivalent elastic modulus of the electrode and separator composite (which can be determined experimentally, with a reference value of 1-5 MPa); h0 represents the initial thickness of the electrode.

[0056] Furthermore, after obtaining the pressure determination equation, the pressure corresponding to each measured expansion at each endpoint of the SOH segment can be determined using this equation. At this point, a pressure demand prediction model for each SOH segment can be constructed based on each measured temperature, each measured SOC, and the corresponding determined pressure at each endpoint of the SOH segment.

[0057] For example, the pressure demand prediction model characterizes the correspondence between temperature, SOC, and pressure. The pressure demand prediction model can be expressed as P = Lookup(SOC, T). Here, SOC represents one of the measured SOCs, T represents one of the measured temperatures, and P represents the pressure corresponding to the measured temperature and measured SOC. SOC and T are the inputs, and P is the output.

[0058] As can be seen from the embodiments of this application, by pre-processing each of the multiple SOH segments as described above, a pressure demand prediction model corresponding to each SOH segment is obtained and saved for later retrieval. Thus, in subsequent practical applications, once the target SOH segment where the current SOH is located is determined, the corresponding pressure demand prediction model can be quickly obtained directly based on that target SOH segment for subsequent processing, ensuring data processing efficiency.

[0059] In this embodiment of the application, after obtaining the pressure demand prediction model corresponding to the target SOH segment, the total pressure to be applied to the target cell can be determined based on the pressure demand prediction model, the current temperature, and the current SOC.

[0060] For example, the pressure demand forecasting model may include a first equation and a second equation; determining the total pressure based on the pressure demand forecasting model, the current temperature, and the current state of pressure (SOC) may include: using the first equation to calculate the current SOC at the current temperature to obtain the current expansion amount; and using the second equation to calculate the current expansion amount to obtain the total pressure.

[0061] Among them, the first equation is also called the expansion amount determination equation, which characterizes the relationship between SOC and expansion amount; the second equation is also called the pressure determination equation, which characterizes the relationship between expansion amount and pressure, as shown in the above formula (1).

[0062] For example, before using the pressure demand prediction model to determine the total pressure corresponding to the target cell, it can be determined whether the first equation corresponding to the target SOH segment needs to be modified based on the current SOH of the target cell.

[0063] For example, it can be determined whether the first equation corresponding to the target SOH segment needs to be modified by determining whether the current SOH is the endpoint of the target SOH segment. Here, the endpoint of the target SOH segment can include any segment endpoint other than the initial state endpoint, i.e., the segment endpoint of 100%. If it is determined that the current SOH is the endpoint of the target SOH segment, then it is determined that the first equation corresponding to the target SOH segment needs to be modified. For example, if the current SOH is 98% and the target SOH segment is the 98%-96% segment, i.e., the current SOH is the endpoint of the target SOH segment, then the first equation corresponding to the 100%-98% segment needs to be modified. At this time, the pressure demand prediction model corresponding to the endpoint of the target SOH segment can be queried directly based on the current temperature and current SOC of the target cell to obtain the current pressure that needs to be applied to the target cell. This is because the pressure has been determined in advance based on the measured state data of the test cell.

[0064] For example, if it is determined that the current SOH is not an endpoint of the target SOH segment, that is, a point inside the target SOH segment, then it is determined that there is no need to modify the first equation corresponding to the target SOH segment; for example, if the current SOH is 99%, and the target SOH segment is the 100%-98% segment, that is, the current SOH is not an endpoint of the target SOH segment, then there is no need to modify the first equation corresponding to the 100%-98% segment. The following is an example of the modification process.

[0065] In some embodiments, the above method may further include: using measured state data of the test cell at the endpoint of the target SOH segment to correct the first equation corresponding to the target SOH segment, thereby obtaining the corrected first equation; accordingly, using the first equation to calculate the current SOC at the current temperature to obtain the current expansion amount, which may include: using the corrected first equation to calculate the current SOC at the current temperature to obtain the current expansion amount.

[0066] In this embodiment of the application, when it is determined that the first equation corresponding to the target SOH segment needs to be corrected based on the current SOH, the measured state data of the test cell at the endpoint of the target SOH segment can be used to correct the first equation corresponding to the target SOH segment to obtain the corrected first equation; the corrected first equation is used to determine the current expansion amount corresponding to the current SOC; and then, the second equation is used to determine the total pressure corresponding to the current expansion amount.

[0067] Considering that the SOH of the battery cell will gradually decrease during use, in this embodiment of the application, if the current SOH of the target battery cell is 98% and the target SOH segment is 98%-96%, the measured state data of the test cell when the SOH is 98% can be used to correct the first equation corresponding to the target SOH segment, and then the corrected first equation can be used to determine the current expansion amount corresponding to the SOH of 98%. Similarly, if the current SOH of the target battery cell is 96% and the target SOH segment is 96%-94%, the measured state data of the test cell when the SOH is 96% can be used to first correct the first equation corresponding to the target SOH segment, and then the corrected first equation can be used to determine the current expansion amount corresponding to the current SOC. The following explanation will be based on the current SOH of 98%.

[0068] As can be seen in this embodiment, for the target SOH segment endpoint in the intermediate state, when the measured state data of the cell at the target SOH segment endpoint is obtained, the model parameters can be continuously corrected based on the measured state data. Subsequently, the required pressure of the cell can be determined based on the corrected model, that is, the adaptive determination of the required pressure of the cell can be achieved.

[0069] It should be noted that the expansion amount and SOC have a nonlinear relationship. The first equation characterizing the relationship between the expansion amount and SOC can be established in advance through experimental measurements and simulations. This equation is an empirical equation, as shown in formulas (2) to (4): △h negative electrode = k1*SOC + k2*SOC^2 (2) △h positive electrode = k3 * SOC (3) △h total = △h negative pole + △h positive pole (4) Here, Δhnegative represents the expansion amount of the negative electrode, and Δhpositive represents the expansion amount of the positive electrode. The values ​​of k1, k2, and k3 in the first equation are related to the positive and negative electrode materials of the tested battery cell. For example, if the negative electrode material is a silicon-doped system, then k1 = 1.6 and k2 = 0.8; if the positive electrode material is NCM811, then k3 = 0.03. NCM811 refers to a positive electrode material composed of nickel, cobalt, and manganese in a ratio of 8:1:1. In this embodiment, modifying the first equation refers to modifying the parameters k1, k2, and k3 of the first equation based on measured state data.

[0070] In this embodiment of the application, if the current SOH of the target cell is determined to be 98%, the measured state data of the test cell when the SOH is 98% is used to correct k1, k2, and k3 in the first equation corresponding to the 100%-98% segment, so as to obtain the corrected first equation. Subsequently, the corrected first equation can be used to determine the current expansion amount corresponding to the current SOC when the current SOH of the target cell is 98%.

[0071] Furthermore, after determining the current expansion amount corresponding to the current SOC, the second equation, namely the above formula (1), can be used to calculate the total pressure corresponding to the current expansion amount, and thus obtain the total pressure corresponding to the current expansion amount.

[0072] Understandably, since the cell expansion is related to the cell temperature and the cell state of charge (SOC), the current expansion obtained by calculating the current temperature and current SOC using the first equation can accurately reflect the real-time deformation state of the cell; by calculating the current expansion using the second equation, the total pressure that needs to be applied to the target cell can be accurately determined.

[0073] In some embodiments, the pressure demand forecasting model may further include a third process, and the above method may further include: after obtaining the current expansion amount, using the third process to correct the current expansion amount to obtain the corrected expansion amount; accordingly, using the second equation to calculate the current expansion amount to obtain the total pressure, including: using the second equation to calculate the corrected expansion amount to obtain the total pressure.

[0074] Here, the third equation, also known as the expansion correction equation, characterizes the correspondence between the expansion amount before and after the correction.

[0075] It is understandable that batteries will age during use. For example, when the positive electrode material is NCM, lattice distortion and microcracks may occur during use; when the negative electrode material is graphite or silicon-carbon, the solid electrolyte interface (SEI) film may thicken and the particles may pulverize. The first equation mentioned above does not take aging factors into account when calculating the current expansion amount, which may lead to the final pressure not being accurate enough.

[0076] To address the aforementioned issues, embodiments of this application can utilize a third-party program to correct the current expansion amount, thereby obtaining a corrected expansion amount. In this way, the corrected expansion amount can be calculated using the second equation to obtain the total pressure.

[0077] For example, the third process may include a positive electrode expansion correction equation and a negative electrode expansion correction equation, as shown in Equation (5) and Equation (6), respectively.

[0078] The corrected equation for positive electrode expansion is: △hpositive_XOL=△hpositive_BOL*( (5) in, The aging coefficient is related to factors such as the positive electrode material of the battery cell, and is not specifically limited here. SOH is the current SOH of the target battery cell, Δh_positive_XOL is the corrected positive electrode expansion amount, and Δh_positive_BOL is the positive electrode expansion amount before correction.

[0079] The corrected equation for negative electrode expansion is: △h_negative_XOL=△h_negative_BOL*( (6) in, The attenuation coefficient is related to factors such as the negative electrode material of the battery cell, and is not specifically limited here. SOH is the current SOH of the target battery cell, Δh_negative_XOL is the corrected negative electrode expansion amount, and Δh_negative_BOL is the negative electrode expansion amount before correction.

[0080] For example, when calculating the current expansion amount using the first equation described above, if it is determined that the current SOH of the target cell is not the endpoint of the target SOH segment, for example, if the current SOH is 99% or 97%, then the current expansion amount is corrected; furthermore, after obtaining the corrected expansion amount, the corrected expansion amount can be calculated using the second equation described above to obtain the total pressure.

[0081] According to the above formula, the expansion correction equation uses the current SOH of the target cell to determine the correction coefficient. )and( The current expansion amount obtained through the first equation is corrected using a correction coefficient. Since SOH reflects the aging degree of the battery, the expansion amount of the positive electrode material will increase as SOH decreases during use, while the expansion amount of the negative electrode material will decrease as SOH decreases. Therefore, correcting the current expansion amount using the current SOH of the target cell can further ensure the accuracy of pressure determination.

[0082] In this embodiment of the application, after obtaining the total pressure corresponding to the target cell according to the above steps, the current pressure of the target cell can be obtained, and then the applied pressure can be determined based on the total pressure and the current pressure of the target cell.

[0083] In some embodiments, obtaining the current pressure of the target cell may include: obtaining the current recovery stress of the shape memory alloy and determining the current recovery stress as the current pressure of the target cell.

[0084] In this embodiment of the application, the battery includes not only at least one cell, but also a shape memory alloy disposed on the outside of each cell; that is, a shape memory alloy (SMA) is disposed on the outside of the target cell.

[0085] Here, the type of SMA is not specifically limited. For example, it can be a nickel-titanium alloy, a copper-nickel alloy, or other types of shape memory alloy.

[0086] It should be noted that SMA exhibits thermo-induced phase transition (TIC) characteristics and shape memory effect. The TIC characteristic refers to the fact that SMA is in the martensitic phase at low temperatures, where its crystal structure has high plasticity and is easily deformed by external forces; at this point, SMA is in a "soft state" and can undergo significant deformation (strain up to 8%) under external stress. At high temperatures, SMA is in the austenitic phase, its crystal structure recovers high symmetry, the material hardens, and recovery stress is generated. The shape memory effect refers to the fact that SMA attempts to recover its original shape when subjected to external forces; if this deformation process is constrained, it will generate extremely high recovery stress (over 500 MPa for Ni-Ti alloys). Because SMA can recover its original shape under temperature changes, by placing SMA outside the battery cell, SMA can apply pressure to the battery cell to compensate for the expansion caused by temperature changes, limiting the cell expansion and ensuring tight contact between interfaces.

[0087] Exemplarily, the overall action mechanism of the SMA is as follows: during the charging and discharging process of the cell, the temperature of the cell continuously rises, and the expansion amount gradually increases at the same time. When the phase transition temperature is reached, the SMA starts to function, applies external pressure for compensation, limits the expansion of the cell, and ensures close contact between interfaces; that is, the temperature of the cell triggers the phase transition of the SMA, so that the SMA attempts to restore its original shape. If restricted by an external structure (such as the cell packaging shell), an active contraction force is generated, that is, the current recovery stress of the SMA; the process of determining the current recovery stress is exemplarily described below.

[0088] Exemplarily, the current recovery stress of the SMA ( -recovery) is related to its pre-strain ( _pre), ambient temperature (Tsma) and phase transition state. Here, the pre-strain ( _pre) and the ambient temperature (Tsma) can be obtained by measurement, and the current recovery stress ( -recovery) can be approximately expressed by a modified Brinson model, as shown in Formula (7) to Formula (9).

[0089] When Tsma<Ms, -recovery=0; (7) Ms<Tsma<Af, -recovery=Ea*( _pre- Tsma) / (1+v); (8) Tsma>Af, -recovery=Ea* _pre; (9) Wherein, Ms is the martensitic phase transformation start temperature; Af is the austenitic phase transformation end temperature; Ea is the elastic modulus of the austenitic phase, and the values of Ms, Af and Ea are related to the material of the SMA, which are not specifically limited herein; Tsma is the phase transformation strain related to the ambient temperature; v is the Poisson's ratio, whose value is related to the SMA material. If the SMA is a Ni-Ti-Cu alloy, the value is about 0.3.

[0090] It can be seen that in the embodiments of the present application, the actual pressure applied to the target cell is determined jointly according to the recovery stress generated by the SMA and the total pressure corresponding to the target cell, which can improve the accuracy of the actual pressure. Using the actual pressure to limit the expansion of the cell can ensure that the interfaces among the positive electrode, the separator and the negative electrode of the cell are always in close contact, and improve the safety performance and cycle performance of the battery.

[0091] For example, after obtaining the current pressure of the target cell according to the above formula, determining the applied pressure based on the total pressure and the current pressure may include: determining a first pressure deviation between the current pressure and the total pressure; if the first pressure deviation does not meet the target conditions, adjusting the current pressure so that a second pressure deviation between the adjusted pressure and the total pressure meets the target conditions; the applied pressure includes the adjusted pressure.

[0092] For example, the current pressure of the target cell refers to the pressure that can currently be applied to the target cell to make the electrodes and the separator in contact; by subtracting the current pressure from the total pressure, the first pressure deviation between the current pressure and the total pressure can be obtained.

[0093] Here, the target condition refers to a pressure deviation that is less than or equal to a set value. It can be understood that if the first pressure deviation meets the target condition (i.e., the first pressure deviation is less than or equal to the set value), it means the current pressure and the total pressure are relatively close. In other words, the current pressure, i.e., the current recovery stress generated by the SMA, can compensate for the external pressure required by the battery cell during charging and discharging. In this case, the current recovery stress generated by the SMA can be directly determined as the actual pressure applied to the target battery cell, and the entire process does not require adjustment of the recovery stress. Conversely, if the first pressure deviation does not meet the target condition (i.e., the first pressure deviation is greater than the set value), it means the current recovery stress and the total pressure differ significantly. In this case, the current recovery stress generated by the SMA is insufficient to compensate for the external pressure required by the battery cell during charging and discharging. In this case, the current recovery stress can be adjusted so that the second pressure deviation between the adjusted recovery stress and the total pressure meets the target condition.

[0094] It can be seen that when the current recovery stress and total pressure are significantly different, by adjusting the current recovery stress, the adjusted recovery stress and total pressure can be made closer, ensuring that the positive electrode, separator, and negative electrode interfaces of the battery cell are always in close contact, thus achieving a better pressure compensation effect.

[0095] In some embodiments, adjusting the current pressure when the first pressure deviation does not meet the target condition may include: generating a compensation pressure signal based on the first pressure deviation when the first pressure deviation does not meet the target condition; inputting the compensation pressure signal to the piezoelectric ceramic, causing the piezoelectric ceramic to generate a deformation based on the compensation pressure signal, the deformation being used to adjust the current pressure.

[0096] In this embodiment of the application, a piezoelectric ceramic is also disposed outside the target cell. When the first pressure deviation does not meet the target conditions, the BMS can generate a compensation pressure signal based on the first pressure deviation and input the compensation pressure signal to the piezoelectric ceramic, so that the piezoelectric ceramic generates deformation according to the compensation pressure signal; the deformation is used to adjust the recovery stress.

[0097] As can be seen from the above, when the current pressure, i.e., the current recovery stress provided by SAM, is insufficient to compensate for the external pressure required by the cell during charging and discharging, i.e., the total pressure, the pressure deviation caused by SMA aging and design deficiencies can be compensated by adjusting the recovery stress through piezoelectric ceramics, so as to cover the application needs of the entire life cycle of the cell.

[0098] For example, besides adjusting the recovery stress through piezoelectric ceramics to compensate for pressure deviation, other methods can also be used to compensate for pressure deviation, which are not specifically limited here. For instance, pressure deviation compensation can be achieved by pre-optimizing the SMA material. Specifically, the phase transition temperature of the SMA can be broadened by element doping, such as Ni-Ti-Cu alloy, which can broaden the phase transition temperature to 30℃-60℃. In addition, as mentioned above, there is a correlation between ambient temperature and current recovery stress. Therefore, the current recovery stress can also be adjusted by controlling the water cooling strategy through BMS to adjust the ambient temperature. That is, pressure deviation compensation can also be achieved by adjusting the temperature.

[0099] For example, SMA can also perform regional gradient design based on the actual expansion distribution of the target cell. That is, SMAs of different materials are used in areas with large expansion and areas with small expansion to provide the pressure required by the cell, thereby achieving a better pressure compensation effect.

[0100] To facilitate understanding, the following will be combined with Figure 2 For further explanation, please refer to [link / reference]. Figure 2 A pressure demand prediction model for each SOH segment is pre-established through experimental measurements and simulations. This model includes a first equation characterizing the relationship between expansion and SOC, a second equation characterizing the relationship between expansion and pressure, and a third equation characterizing the relationship between expansion and pressure before and after correction. During the actual charging and discharging process of the target cell, if the pressure demand prediction model for the target cell at the current SOH is unavailable, the first equation in the pressure demand prediction model corresponding to the target SOH segment can be corrected based on the current SOH of the target cell. The corrected first equation is then used to determine the current expansion of the target cell. Considering the cyclic aging state of the cell, after obtaining the current expansion, the third equation can be used to correct the current expansion to obtain the corrected expansion. Then, the total pressure corresponding to the corrected expansion is determined using the second equation in the pressure demand prediction model corresponding to the target SOH segment. Figure 2The external pressure of the battery cell is further determined; the pressure deviation between the external pressure of the battery cell and the current pressure, i.e. the current recovery stress generated by the SMA, is further determined. When the pressure deviation does not meet the target conditions, the BMS generates a compensation pressure signal based on the pressure deviation and inputs the compensation pressure signal to the piezoelectric ceramic, so that the piezoelectric ceramic generates deformation according to the compensation pressure signal. This deformation is used to adjust the recovery stress. Finally, the adjusted recovery stress is close to the total pressure. In this way, it can be ensured that the positive electrode, separator and negative electrode interface of the battery cell are always in close contact, and a good pressure compensation effect is achieved.

[0101] It should be noted that the above process has been described in the foregoing embodiments, and will not be repeated here to avoid repetition.

[0102] It can be seen that the cell pressure determination method provided in this application embodiment can adaptively adjust the external pressure throughout the entire life cycle of the cell; while ensuring that the dynamics do not deteriorate, it ensures the contact and flatness between interfaces, suppresses the formation of lithium dendrites, and improves the battery safety performance and cycle performance.

[0103] Based on the same technical concept, this application provides a schematic diagram of a battery cell pressure determination device, which can realize the battery cell pressure determination method provided in the foregoing embodiments; as Figure 3 As shown, the cell pressure determining device 2 includes: The acquisition module 200 is used to acquire the current status data of the target battery cell during the charging and discharging process; The application module 201 is used to apply the corresponding application pressure to the target cell based on the current state data.

[0104] In some embodiments, the current status data includes at least the current temperature, current SOC, and current SOH.

[0105] In some embodiments, the applying module 201 is further configured to: The total pressure that needs to be applied to the target cell should be determined based at least on the current temperature, current SOC, and current SOH. Obtain the current pressure of the target battery cell; Determine the applied pressure based on the total pressure and the current pressure; Apply the corresponding pressure to the target cell.

[0106] In some embodiments, the applying module 201 is further configured to: Determine the target SOH segment where the current SOH is located, and obtain the corresponding pressure demand prediction model based on the target SOH segment; The total pressure is determined based on the pressure demand forecasting model, the current temperature, and the current state of pressure (SOC). The pressure demand forecasting model represents the correspondence between temperature, SOC, and pressure.

[0107] In some embodiments, the pressure demand prediction model includes a first equation and a second equation, and the application module 201 is further configured to: The current SOC at the current temperature is calculated using the first equation to obtain the current expansion amount; the first equation characterizes the relationship between SOC and expansion amount. The total pressure is obtained by calculating the current expansion using the second equation; the second equation characterizes the relationship between expansion and pressure.

[0108] In some embodiments, the above-described apparatus further includes a correction module, which is configured to: Using the measured state data of the test cell at the endpoint of the target SOH segment, the first equation corresponding to the target SOH segment is corrected to obtain the corrected first equation; In some embodiments, the applying module 201 is further configured to: The current SOC at the current temperature is calculated using the modified first equation to obtain the current expansion.

[0109] In some embodiments, the stress demand forecasting model further includes a third-party process, a correction module, and is further configured to: After obtaining the current expansion amount, a third process is used to correct the current expansion amount to obtain the corrected expansion amount; the third process represents the correspondence between the expansion amount before and after the correction. In some embodiments, the applying module 201 is further configured to: The total pressure is obtained by calculating the corrected expansion using the second equation.

[0110] In some embodiments, the above-described apparatus further includes a determining module, which is configured to: The SOH range of the test cell is segmented to obtain multiple SOH segments; the multiple SOH segments include the target SOH segment; Determine the pressure demand prediction model corresponding to multiple SOH segments.

[0111] In some embodiments, the determining module is further configured to: For each SOH segment, the measured state data of the test cell at the endpoint of the SOH segment are obtained; Based on measured state data, a pressure demand prediction model corresponding to each SOH segment is determined.

[0112] In some embodiments, a shape memory alloy is disposed on the outside of the target cell, and the application module 201 is further configured to: Obtain the current recovery stress of the shape memory alloy and determine the current pressure of the target cell.

[0113] In some embodiments, the applying module 201 is further configured to: Determine the first pressure deviation between the total pressure and the current pressure; When the first pressure deviation does not meet the target condition, the current pressure is adjusted so that the second pressure deviation between the adjusted pressure and the total pressure meets the target condition; the applied pressure includes the adjusted pressure.

[0114] In some embodiments, a piezoelectric ceramic is further disposed on the exterior of the target cell, and the application module 201 is further configured to: When the first pressure deviation does not meet the target conditions, a compensation pressure signal is generated based on the first pressure deviation. A compensation pressure signal is input to the piezoelectric ceramic, causing the piezoelectric ceramic to generate deformation according to the compensation pressure signal; the deformation is used to adjust the current pressure.

[0115] For the above-described apparatus embodiments, since they are basically similar to the method embodiments, the relevant parts can be referred to the corresponding descriptions of the method embodiments. To avoid repetition, they will not be repeated here.

[0116] In practical applications, the aforementioned acquisition module 200, application module 201, correction module, and determination module can all be implemented by a processor located in the seat control device. The processor can be at least one of the following: Application-Specific Integrated Circuit (ASIC), Digital Signal Processor (DSP), Digital Signal Processing Device (DSPD), Programmable Logic Device (PLD), Field Programmable Gate Array (FPGA), Central Processing Unit (CPU), controller, microcontroller, and microprocessor.

[0117] Based on the foregoing embodiments, this application also provides a battery, including a battery cell, a shape memory alloy, and a casing for encapsulating the battery cell and the shape memory alloy. The battery cell pressure is determined using the previously described battery cell pressure determination method.

[0118] For example, the battery also includes aerogel, and the shape memory alloy and aerogel are integrally disposed inside the housing.

[0119] Understandably, the outer surface of the battery cell contains aerogel, whose main functions include heat insulation and fire protection. By integrating SMA with aerogel in a unified design, the space utilization and integration of the battery can be improved.

[0120] Figure 4 This is a schematic diagram of the structure of the cell pressure determination device provided in the embodiments of this application, as shown below. Figure 4 As shown, the cell pressure determination device 3 may include a processor 301 and a memory 302; wherein, the memory 302 is used to store computer-executable instructions; the processor 301 is used to implement the cell pressure determination method as described above when executing the computer-executable instructions or computer programs stored in the memory 302.

[0121] Based on the foregoing embodiments, this application also provides a vehicle, which includes the aforementioned cell pressure determining device or the aforementioned cell pressure determining equipment. Based on the foregoing embodiments, this application also provides a computer-readable storage medium storing computer-executable instructions or a computer program, which, when executed by a processor, implements the aforementioned cell pressure determining method.

[0122] Based on the foregoing embodiments, this application also provides a computer program product, including computer-executable instructions or a computer program, which, when executed by a processor, can realize the aforementioned cell pressure determination method.

[0123] In some embodiments, the computer-readable storage medium may be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), flash memory, magnetic surface memory, optical disc, or a compact disc read-only memory (CD-ROM), etc.; or it may be a variety of devices including one or any combination of the above-mentioned memories.

[0124] In some embodiments, computer-executable instructions may take the form of programs, software, software modules, scripts, or code, written in any form of programming language (including compiled or interpreted languages, or declarative or procedural languages), and may be deployed in any form, including as stand-alone programs or as modules, components, subroutines, or other units suitable for use in a computing environment.

[0125] As an example, computer-executable instructions may, but do not necessarily, correspond to files in a file system. They may be stored as part of a file that holds other programs or data, for example, in one or more scripts in a Hyper Text Markup Language (HTML) document, in a single file dedicated to the program in question, or in multiple co-located files (e.g., a file that stores one or more modules, subroutines, or code sections).

Claims

1. A method for determining cell pressure, characterized in that, The method further includes: Acquire the current state data of the target battery cell during the charging and discharging process; Based on the current state data, a corresponding pressure is applied to the target battery cell.

2. The method according to claim 1, characterized in that, The current status data includes at least the current temperature, current SOC, and current SOH.

3. The method according to claim 2, characterized in that, The step of applying corresponding pressure to the target battery cell based on the current state data includes: The total pressure that needs to be applied to the target cell is determined based at least on the current temperature, the current state of charge (SOC), and the current state of oxygen (SOH). Obtain the current pressure of the target battery cell; The applied pressure is determined based on the total pressure and the current pressure; Apply the corresponding pressure to the target battery cell.

4. The method according to claim 3, characterized in that, The determination of the total pressure to be applied to the target cell, based at least on the current temperature, the current state of charge (SOC), and the current state of oxygen (SOH), includes: Determine the target SOH segment where the current SOH is located, and obtain the corresponding pressure demand prediction model based on the target SOH segment; The total pressure is determined based on the pressure demand prediction model, the current temperature, and the current state of pressure (SOC); the pressure demand prediction model represents the correspondence between temperature, SOC, and pressure.

5. The method according to claim 4, characterized in that, The pressure demand prediction model includes a first equation and a second equation. Determining the total pressure based on the pressure demand prediction model, the current temperature, and the current state of charge (SOC) includes: The current SOC at the current temperature is calculated using the first equation to obtain the current expansion amount; the first equation characterizes the relationship between SOC and expansion amount. The total pressure is obtained by calculating the current expansion amount using the second equation; the second equation characterizes the relationship between expansion amount and pressure.

6. The method according to claim 5, characterized in that, The method further includes: Using the measured state data of the test cell at the endpoint of the target SOH segment, the first equation corresponding to the target SOH segment is corrected to obtain the corrected first equation; The step of calculating the current SOC at the current temperature using the first equation to obtain the current expansion includes: The current SOC at the current temperature is calculated using the modified first equation to obtain the current expansion amount.

7. The method according to claim 5 or 6, characterized in that, The pressure demand forecasting model also includes a third-party process, and the method further includes: After obtaining the current expansion amount, the third-party program is used to correct the current expansion amount to obtain the corrected expansion amount; the third-party program represents the correspondence between the expansion amount before and after the correction. The step of calculating the total pressure using the second equation to determine the current expansion amount includes: The total pressure is obtained by calculating the corrected expansion using the second equation.

8. The method according to any one of claims 4-6, characterized in that, The method further includes: The SOH range of the test cell is segmented to obtain multiple SOH segments; the multiple SOH segments include the target SOH segment; Determine the pressure demand prediction model corresponding to the multiple SOH segments.

9. The method according to claim 8, characterized in that, The step of determining the pressure demand prediction model corresponding to the multiple SOH segments includes: For each SOH segment, the measured state data of the test cell at the endpoint of the SOH segment are obtained; Based on the measured state data, a pressure demand prediction model corresponding to each SOH segment is determined.

10. The method according to claim 3, characterized in that, The target battery cell is externally disposed of with a shape memory alloy, and the step of obtaining the current pressure of the target battery cell includes: The current recovery stress of the shape memory alloy is obtained, and the current recovery stress is determined as the current pressure of the target cell.

11. The method according to any one of claims 3-6 and 9-10, characterized in that, Determining the applied pressure based on the total pressure and the current pressure includes: Determine a first pressure deviation between the total pressure and the current pressure; When the first pressure deviation does not meet the target condition, the current pressure is adjusted so that the second pressure deviation between the adjusted pressure and the total pressure meets the target condition; the applied pressure includes the adjusted pressure.

12. The method according to claim 11, characterized in that, The target battery cell is further provided with a piezoelectric ceramic. Adjusting the current pressure when the first pressure deviation does not meet the target conditions includes: When the first pressure deviation does not meet the target condition, a compensation pressure signal is generated based on the first pressure deviation; The compensation pressure signal is input to the piezoelectric ceramic, causing the piezoelectric ceramic to generate deformation according to the compensation pressure signal; the deformation is used to adjust the current pressure.

13. A cell pressure determining device, characterized in that, The device includes: The acquisition module is used to acquire the current status data of the target cell during the charging and discharging process; An application module is used to apply a corresponding application pressure to the target cell based on the current state data.

14. A battery, characterized in that, The battery includes a battery cell, a shape memory alloy, and a casing encapsulating the battery cell and the shape memory alloy, wherein the battery cell in the battery is pressure determined using the battery cell pressure determination method described in claims 1-12.

15. The battery according to claim 14, characterized in that, The battery also includes aerogel, and the shape memory alloy and the aerogel are integrally disposed inside the housing.

16. A device for determining cell pressure, characterized in that, The method is characterized by comprising: a memory; a processor; and a computer program; wherein the computer program is stored in the memory and configured to be executed by the processor to implement the cell pressure determination method as described in any one of claims 1-12.

17. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the computer program implements the cell pressure determination method as described in any one of claims 1-12.

18. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the cell pressure determination method according to any one of claims 1-12.

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