Method and device for evaluating deformability of current collector in electrode, equipment, medium and program product

Abstract

The invention relates to a method and device for evaluating the deformation capacity of a current collector in an electrode, equipment, a medium and a program product, and the method comprises the steps: simulating the deformation process of the current collector due to the expansion of the electrode through a finite element simulation model of the current collector, and obtaining the deformation of different positions in the finite element simulation model; according to the stress-strain constitutive equation of the material used by the current collector and the deformation amount of different positions in the finite element simulation model, the maximum stress generated by the finite element simulation model is obtained, and the stress-strain constitutive equation represents the mathematical relationship between the stress and the strain of the material used by the current collector in the deformation process; and determining the deformability of the current collector according to the maximum stress generated by the finite element simulation model and the pre-tested fracture stress when the material used by the current collector is fractured, and representing the maximum deformation borne by the current collector in the working process of the electrode by the deformability. Therefore, the maximum deformation borne by the current collector in the working process of the electrode can be quickly evaluated at low cost.

Description

Technical Field

[0001] This disclosure relates to the field of batteries, and in particular to a method, apparatus, device, medium and procedure for evaluating the deformability of current collectors in electrodes. Background Technology

[0002] The lateral deformation mechanism of lithium batteries during charging and discharging and its impact on the structural failure of current collector foils have become key scientific issues restricting the cycle life and safety performance of high-energy-density batteries. During lithium-ion intercalation and deintercalation, negative electrode active materials, represented by graphite and silicon, undergo significant volume expansion (approximately 10% for graphite and over 300% for silicon). This anisotropic volume change, through the interfacial bonding between the active material and the metal current collector, generates mechanical stress in the large-plane direction (in-plane direction) of the electrode's layered structure. The current collector, which serves as the charge transport carrier in the electrode (usually made of copper / aluminum foil), is subjected to stress under the electrode expansion. When the local stress concentration exceeds the material's yield strength, plastic deformation occurs. Once the dynamic strain amplitude exceeds the fatigue limit of the current collector material, microcracks nucleate and propagate, ultimately leading to the current collector's fracture failure. This mechanical failure not only directly damages the electrode's conductive network, causing active material stripping and capacity decay, but may also trigger safety hazards such as internal short circuits.

[0003] Currently, the method for assessing the maximum deformation that a current collector can withstand during electrode operation is to conduct actual charging tests on lithium batteries. This method is time-consuming and costly, significantly extending the lithium battery development cycle. Therefore, how to quickly and efficiently help researchers assess the maximum deformation that a current collector can withstand to accelerate the lithium battery development process has become an urgent problem to be solved. Summary of the Invention

[0004] In view of this, this disclosure proposes a method, apparatus, device, medium and program product for evaluating the deformation capacity of current collectors in electrodes, which can quickly and cost-effectively evaluate the maximum deformation that current collectors can withstand during electrode operation, thereby helping to shorten the research and development cycle of lithium batteries.

[0005] According to one aspect of this disclosure, a method for evaluating the deformability of a current collector in an electrode is provided, comprising: simulating the deformation process of the current collector due to electrode expansion using a finite element simulation model of the current collector, and obtaining the deformation amount at different locations in the finite element simulation model; obtaining the maximum stress generated by the finite element simulation model based on the stress-strain constitutive equation of the material used in the current collector and the deformation amount at different locations in the finite element simulation model, wherein the stress-strain constitutive equation characterizes the mathematical relationship between stress and strain of the material used in the current collector during deformation; determining the deformability of the current collector based on the maximum stress generated by the finite element simulation model and the fracture stress when the material used in the current collector fractures (pre-tested), wherein the deformability characterizes the maximum deformation that the current collector can withstand during electrode operation.

[0006] In one possible implementation, the step of simulating the deformation process of the current collector due to electrode expansion using a finite element simulation model to obtain the deformation amount at different locations in the finite element simulation model includes: establishing a finite element simulation model of the current collector, which includes a weld equivalent boundary and a specified equivalent boundary. The weld equivalent boundary represents the boundary of the electrode tab weld in the current collector, and the specified equivalent boundary represents the two side boundaries in the deformation direction of the current collector due to electrode expansion; by applying fixed constraint boundary conditions to the weld equivalent boundary in the finite element simulation model and applying multiple displacement boundary conditions to the specified equivalent boundary, the deformation amount at different locations in the finite element simulation model under each displacement boundary condition is obtained. The deformation amount at different locations represents the displacement change at different locations, and the displacement boundary conditions are used to apply directional constraints to the two side boundaries of the specified equivalent boundary. The displacement to the outward; wherein, the step of obtaining the maximum stress generated by the finite element simulation model based on the stress-strain constitutive equation of the material used in the current collector and the deformation at different positions in the finite element simulation model includes: obtaining the stress-strain constitutive equation of the material used in the current collector, and determining the maximum stress generated by the finite element simulation model under each displacement boundary condition based on the stress-strain constitutive equation and the deformation at different positions in the finite element simulation model under each displacement boundary condition; wherein, the step of determining the deformation capacity of the current collector based on the maximum stress generated by the finite element simulation model and the fracture stress when the material used in the current collector fractures (pre-tested) includes: determining the deformation capacity of the current collector based on the maximum stress generated by the finite element simulation model under each displacement boundary condition and the fracture stress when the material used in the current collector fractures (pre-tested) in the multiple displacement boundary conditions.

[0007] In one possible implementation, obtaining the stress-strain constitutive equation of the material used in the current collector includes: obtaining the stress-strain curve of the material used in the current collector by performing a tensile test; determining the basic mechanical parameters of the material used in the current collector based on the stress-strain curve, the basic mechanical parameters including Young's modulus, initial yield stress, and fracture stress; and determining the stress-strain constitutive equation of the material used in the current collector based on the stress-strain curve and the basic mechanical parameters.

[0008] In one possible implementation, determining the basic mechanical parameters of the material used in the current collector based on the stress-strain curve includes: determining the Young's modulus of the material used in the current collector as the ratio between the increase in stress and the increase in strain in the elastic stage of the stress-strain curve; determining the stress corresponding to the intersection point between the extended linear portion of the elastic stage and the extended linear portion of the plastic stage of the stress-strain curve as the initial yield stress of the material used in the current collector; and determining the stress corresponding to the end of the plastic stage of the stress-strain curve as the fracture stress of the material used in the current collector.

[0009] In one possible implementation, the stress-strain constitutive equation is expressed as:

[0010] σ t =E·ε t

[0011] σ h =σ e ε total -σ y0

[0012] Where, σ t The stress ε represents the elastic stage. t Strain σ represents the elastic stage. h Represents the plastic stage at the initial yield stress σ y0 The added stress and total strain ε total The functional relationship, σ e The expression representing the stress-strain curve is given, where E is the Young's modulus.

[0013] In one possible implementation, establishing the finite element simulation model of the current collector includes: establishing the finite element simulation model of the current collector based on the size information of the current collector, the size information of the tabs in the current collector, the position information of the tabs in the current collector, and the size information of the solder joints in the tabs; wherein the finite element simulation model is further assigned the Young's modulus of the material used in the current collector, and the material used in the current collector includes foil.

[0014] In one possible implementation, determining the maximum stress generated by the finite element simulation model under each displacement boundary condition based on the stress-strain constitutive equation and the deformation at different locations in the finite element simulation model under each displacement boundary condition includes: determining the strain value at different locations in the finite element simulation model under each displacement boundary condition based on the deformation at different locations in the finite element simulation model under each displacement boundary condition and the original length of the finite element simulation model; determining the stress value at different locations in the finite element simulation model under each displacement boundary condition based on the strain value at different locations in the finite element simulation model under each displacement boundary condition using the stress-strain constitutive equation; and determining the maximum value among the stress values ​​at different locations in the finite element simulation model under each displacement boundary condition as the maximum stress generated by the finite element simulation model under each displacement boundary condition.

[0015] In one possible implementation, the total displacement change imposed by different displacement boundary conditions is different, and the total displacement change characterizes the change in the total length of the finite element simulation model after the displacement boundary conditions are applied compared to the original length; wherein, determining the deformation capacity of the current collector based on the maximum stress generated by the finite element simulation model under each of the multiple displacement boundary conditions and the fracture stress of the material used in the current collector when it fractures as previously tested, includes: selecting a target displacement boundary condition from the multiple displacement boundary conditions when the maximum stress reaches the fracture stress; and determining the total displacement change imposed by the target displacement boundary condition as the maximum deformation of the current collector when it fractures during electrode operation.

[0016] According to another aspect of this disclosure, a device for evaluating the deformation capacity of a current collector in an electrode is provided, comprising: a simulation module for simulating the deformation process of the current collector due to electrode expansion using a finite element simulation model of the current collector, and obtaining the deformation amount at different locations in the finite element simulation model; a stress determination module for obtaining the maximum stress generated by the finite element simulation model based on the stress-strain constitutive equation of the material used in the current collector and the deformation amount at different locations in the finite element simulation model, wherein the stress-strain constitutive equation characterizes the mathematical relationship between stress and strain of the material used in the current collector during deformation; and a deformation determination module for determining the deformation capacity of the current collector based on the maximum stress generated by the finite element simulation model and the fracture stress when the material used in the current collector fractures (pre-tested), wherein the deformation capacity characterizes the maximum deformation amount that the current collector can withstand during electrode operation.

[0017] According to another aspect of this disclosure, an electronic device is provided, including a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the above-described method.

[0018] According to another aspect of this disclosure, a non-volatile computer-readable storage medium is provided, on which a computer program is stored, which, when executed by a processor, implements the steps of the above-described method.

[0019] According to another aspect of this disclosure, a computer program product is provided, including a computer program or a non-volatile computer-readable storage medium carrying the computer program, wherein the computer program, when executed by a processor, implements the steps of the above-described method.

[0020] According to various aspects of this disclosure, by using a finite element simulation model of the current collector to simulate the deformation process of the current collector due to electrode expansion, the deformation amount at different locations can be obtained. Combined with the stress-strain constitutive equation of the material used in the current collector, the maximum stress generated by the finite element simulation model can be calculated, which is equivalent to obtaining the maximum stress generated by the current collector during the actual deformation process. Therefore, based on the obtained maximum stress generated by the current collector and the fracture stress of the material used in the current collector, the maximum deformation amount that the current collector can withstand can be quickly evaluated, that is, the maximum deformation amount (i.e., the critical displacement) when the current collector does not break (i.e., reaches the failure criterion and is about to break). This replaces the traditional time-consuming and laborious physical charging test, and realizes a rapid and low-cost evaluation of the maximum deformation amount that the current collector can withstand during the electrode operation process, which is conducive to shortening the research and development cycle of lithium batteries.

[0021] Other features and aspects of this disclosure will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0022] The accompanying drawings, which are included in and form part of this specification, illustrate exemplary embodiments, features, and aspects of this disclosure together with the specification and serve to explain the principles of this disclosure.

[0023] Figure 1 A flowchart is shown for a method for evaluating the deformation capacity of a current collector in an electrode according to an embodiment of the present disclosure.

[0024] Figure 2 A schematic diagram of a finite element simulation model of a current collector according to an embodiment of the present disclosure is shown.

[0025] Figure 3 This diagram illustrates the application of boundary conditions to a finite element simulation model of a current collector according to an embodiment of the present disclosure.

[0026] Figure 4A schematic diagram of a stress-strain curve according to an embodiment of the present disclosure is shown.

[0027] Figure 5 A block diagram of an electrode current collector deformation assessment apparatus according to an embodiment of the present disclosure is shown.

[0028] Figure 6 A block diagram of an electronic device according to an embodiment of the present disclosure is shown. Detailed Implementation

[0029] Various exemplary embodiments, features, and aspects of this disclosure will now be described in detail with reference to the accompanying drawings. The same reference numerals in the drawings denote elements that have the same or similar functions. Although various aspects of the embodiments are shown in the drawings, they are not necessarily drawn to scale unless specifically indicated otherwise.

[0030] As used herein, the terms “comprising,” “including,” “having,” or variations thereof are open-ended and include one or more of the stated features, integrals, elements, steps, components, or functions, but do not exclude the presence or addition of one or more other features, integrals, elements, steps, components, functions, or groups thereof.

[0031] When an element is referred to as “connected,” “coupled,” “responding,” or a variation thereof relative to another element, it may be directly connected, coupled, or responding to another element, or there may be an intermediate element present.

[0032] Although the terms first, second, third, etc., may be used herein to describe various elements / operations, these elements / operations should not be limited by these terms. These terms are only used to distinguish one element / operation from another. Therefore, without departing from the teachings of the inventive concept, a first element / operation in some embodiments may be referred to as a second element / operation in other embodiments.

[0033] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0034] Furthermore, to better illustrate this disclosure, numerous specific details are set forth in the following detailed description. Those skilled in the art will understand that this disclosure can be practiced without certain specific details. In some instances, methods, means, components, and circuits well known to those skilled in the art have not been described in detail in order to highlight the main points of this disclosure.

[0035] As mentioned above, the current method for evaluating the maximum deformation that the current collector in an electrode can withstand is through lithium battery charging tests. This method is time-consuming and costly, significantly extending the lithium battery R&D cycle. To help researchers quickly screen current collectors and accelerate the lithium battery R&D process, this disclosure provides a method for evaluating the deformation capacity of the current collector in an electrode. By establishing a finite element simulation model of the current collector, simulating the actual situation of the current collector during use, fixed boundary conditions are applied at the tab solder joint, and different displacement boundary conditions are applied at the deformation boundary of the current collector. By evaluating the critical displacement in the model that does not cause fracture, the maximum deformation that the current collector can withstand is obtained. In other words, the evaluation method proposed in this disclosure can quickly and cost-effectively obtain the maximum deformation that the current collector foil can withstand, effectively avoiding the resource waste caused by traditional trial-and-error methods and accelerating the lithium battery R&D process.

[0036] In practical applications, the current collector deformation capability evaluation method in the electrodes of this disclosure can be deployed on various terminal devices through software or hardware modifications. The terminal devices involved in this disclosure can refer to devices with wireless and / or wired connection functions. Wireless connection means that they can connect to other devices via Wi-Fi, Bluetooth, or other wireless methods. The terminal devices involved in this disclosure can also communicate with other devices via wired connection. The terminal devices involved in this disclosure can be touchscreen, non-touchscreen, or screenless. Touchscreen devices can be controlled by clicking or swiping on the display screen using fingers or styluses. Non-touchscreen devices can connect to input devices such as mice, keyboards, and touch panels to control the terminal device. Screenless devices can be, for example, screenless Bluetooth speakers. For example, the terminal devices in this application can include, but are not limited to, user equipment (UE), mobile devices, user terminals, terminals, handheld devices, tablets, laptops, PDAs, and computing devices.

[0037] The method for evaluating the deformation capability of the current collector in the electrode according to the embodiments of this disclosure can also be deployed on a server. This server can be located in the cloud or locally, and can be a physical device or a virtual device, such as a virtual machine or container, with wireless communication capabilities. These wireless communication capabilities can be configured in the server's chip (system) or other components. It can refer to a device with wireless connectivity, meaning it can connect to other servers or terminal devices via wireless connection methods such as Wi-Fi or Bluetooth. The server involved in the embodiments of this disclosure can also have wired communication capabilities. For example, the server can receive evaluation requests sent by terminal devices, execute the evaluation method of the embodiments of this disclosure, obtain the evaluated deformation capability of the current collector, and return it to the terminal device so that the evaluated deformation capability of the current collector can be displayed to the user on the terminal device.

[0038] Figure 1 A flowchart illustrating a method for evaluating the deformability of a current collector in an electrode according to an embodiment of the present disclosure is shown. Figure 1 As shown, the method includes steps S11 to S13.

[0039] Step S11: Use the finite element simulation model of the current collector to simulate the deformation process of the current collector due to electrode expansion, and obtain the deformation amount at different locations in the finite element simulation model.

[0040] Step S12: Based on the stress-strain constitutive equation of the material used in the current collector and the deformation at different locations in the finite element simulation model, the maximum stress generated by the finite element simulation model is obtained. The stress-strain constitutive equation characterizes the mathematical relationship between stress and strain of the material used in the current collector during the deformation process.

[0041] Step S13: Determine the deformation capacity of the current collector based on the maximum stress generated by the finite element simulation model and the fracture stress of the material used in the current collector when it fractures, wherein the deformation capacity characterizes the maximum amount of deformation that the current collector can withstand during the operation of the electrode.

[0042] It should be understood that the embodiments of this disclosure do not limit the shape, size and material of the current collector to be evaluated for deformation capability. The current collector in the electrode is usually made of foil, for example, copper foil is used for the current collector in the negative electrode and aluminum foil is used for the current collector in the positive electrode, etc. The embodiments of this disclosure do not limit this.

[0043] In practical applications, open-source finite element analysis software in this field, such as Code-aster software, can be used to establish a finite element simulation model of the current collector based on its actual size and to perform simulation analysis on the finite element simulation model. For example, based on the actual deformation process and actual constraints of the current collector, corresponding displacement boundary conditions and constraint boundary conditions can be applied to the finite element simulation model to simulate the deformation process of the current collector due to electrode expansion. At the same time, the simulation analysis capabilities of the finite element analysis software can be used to obtain the deformation amount at different positions in the finite element simulation model during the deformation process. This disclosure does not limit this aspect. Optionally, in step S11, the deformation amount at different positions in the finite element simulation model can be obtained by applying fixed constraint boundary conditions to the weld equivalent boundary in the finite element simulation model and applying specified displacement boundary conditions to the specified equivalent boundary. The weld equivalent boundary represents the boundary of the electrode tab weld in the current collector, and the specified equivalent boundary represents the two sides of the deformation direction of the current collector due to electrode expansion. The displacement boundary condition is used to apply outward displacement to the two sides of the specified equivalent boundary, and the fixed constraint boundary condition is used to fix the weld equivalent boundary in the finite element simulation model. It should be understood that the embodiments disclosed herein do not impose any restrictions on the modeling and analysis processes of the finite element simulation model, as long as the simulation deformation process and the deformation amount can be determined.

[0044] In step S12, the material used for the current collector can be designed according to actual needs. For example, if the current collector is usually made of foil, the stress-strain curve of the material can be obtained by conducting a tensile test on the material, thereby obtaining the basic mechanical parameters of the material. Considering that the deformation of the current collector as the electrode expands includes both elastic and plastic deformation stages, the stress-strain constitutive equation of the material used for the current collector is constructed based on the basic mechanical parameters and the stress-strain curve. Of course, those skilled in the art can also use other methods in the art to establish the stress-strain constitutive equation of the material used for the current collector, and this embodiment does not limit this.

[0045] In step S12, based on the deformation at different locations in the finite element simulation model and the original length of the finite element model, the strain values ​​at different locations in the finite element simulation model can be determined. Then, using the stress-strain constitutive equation, the stress values ​​at different locations in the finite element simulation model can be determined based on the strain values. Finally, the maximum stress value among the stress values ​​at different locations in the finite element simulation model is determined as the maximum stress generated by the finite element simulation model, which is equivalent to obtaining the maximum stress generated by the current collector. It should be understood that the location of the maximum stress in the current collector is highly likely to be the location where the current collector fractures.

[0046] Furthermore, in step S13, it can be determined whether the maximum stress generated by the finite element simulation model reaches the fracture stress of the material used in the current collector when it fractures as previously tested. If the maximum stress generated by the finite element simulation model reaches the fracture stress, it means that the current collector begins to fracture under the displacement boundary conditions applied during the above deformation process. The maximum stress reaching the fracture stress can include the maximum stress being the same as the fracture stress or the difference between the maximum stress and the fracture stress being within a specified error range. Then, the total displacement change applied by the displacement boundary conditions when the maximum stress reaches the fracture stress can be determined as the maximum deformation of the current collector when it fractures during the electrode operation. Alternatively, the length change of the finite element simulation model when the maximum stress reaches the fracture stress during the deformation process can be taken as the maximum deformation of the current collector when it fractures. The total displacement change can characterize the length change of the total length of the finite element simulation model after applying the displacement boundary conditions compared to the original length. The length change can be understood as the length change of the finite element simulation model when the maximum stress reaches the fracture stress compared to the original length of the finite element simulation model. The original length of the finite element simulation model is also the original length of the current collector.

[0047] It should be understood that if the maximum stress generated by the finite element simulation model does not reach the fracture stress, different displacement boundary conditions can be applied to the finite element simulation model (for example, increasing the total displacement change generated by the displacement boundary conditions, i.e., the length change), and the maximum stress can be recalculated according to the above steps S11 to S13 to determine whether the fracture stress has been reached, until the maximum stress reaches the fracture stress, thereby obtaining the maximum deformation of the current collector when the electrode breaks during operation.

[0048] In practical applications, users can also specify the total displacement change applied by the displacement boundary conditions (i.e., the maximum allowable deformation of the current collector). Steps S11 to S13 above are used to test whether the current collector will fracture under this maximum deformation (i.e., the given displacement boundary conditions). Specifically, in step S11, the deformation process of the current collector due to electrode expansion can be simulated using the finite element simulation model of the current collector under the specified displacement boundary conditions. The deformation at different locations in the finite element simulation model under the specified displacement boundary conditions is obtained. Then, in step S12, based on the stress-strain constitutive equation of the material used in the current collector and the deformation at different locations in the finite element simulation model under the specified displacement boundary conditions, the maximum stress generated by the finite element simulation model under the specified displacement boundary conditions is obtained. Furthermore, in step S13, if the maximum stress generated by the finite element simulation model under the specified displacement boundary conditions does not reach the fracture stress, it means that the current collector will not fracture under the maximum allowable deformation (i.e., the total displacement change applied by the specified displacement boundary conditions). In this case, the maximum allowable deformation of the current collector can also be used as the deformation capacity of the current collector. This embodiment of the present disclosure does not limit this.

[0049] According to the method of this disclosure, by using the finite element simulation model of the current collector to simulate the deformation process of the current collector due to electrode expansion, the deformation amount at different positions can be obtained by combining the stress-strain constitutive equation of the material used in the current collector. The maximum stress generated by the finite element simulation model can be calculated, which is equivalent to obtaining the maximum stress generated by the current collector during the actual deformation process. Therefore, based on the obtained maximum stress generated by the current collector and the fracture stress of the material used in the current collector, the maximum deformation amount that the current collector can withstand can be quickly evaluated, that is, the maximum deformation amount (i.e., the critical displacement) when the current collector does not break (i.e., reaches the failure criterion and is about to break). This replaces the traditional time-consuming and laborious physical charging test, and realizes a rapid and low-cost evaluation of the maximum deformation amount that the current collector can withstand during the electrode operation process, which is conducive to shortening the research and development cycle of lithium batteries.

[0050] As described above, the deformation process of the current collector due to electrode expansion can be simulated by applying corresponding displacement boundary conditions to the finite element simulation model according to the actual deformation process of the current collector. In order to make the finite element simulation model more accurately simulate the deformation process of the current collector and improve the evaluation efficiency of deformation capacity, in one possible implementation, in step S11, the deformation process of the current collector due to electrode expansion is simulated using the finite element simulation model of the current collector to obtain the deformation amount at different positions in the finite element simulation model, which may include:

[0051] Step S111: Establish a finite element simulation model of the current collector. The finite element simulation model includes a weld equivalent boundary and a specified equivalent boundary. The weld equivalent boundary represents the boundary of the electrode weld in the current collector, and the specified equivalent boundary represents the two sides of the current collector in the deformation direction caused by the electrode expansion.

[0052] Step S112: By applying fixed constraint boundary conditions to the weld equivalent boundary in the finite element simulation model and applying multiple displacement boundary conditions to the specified equivalent boundary, the deformation amount at different positions in the finite element simulation model under each displacement boundary condition is obtained. The deformation amount at different positions represents the displacement change at different positions. The displacement boundary conditions are used to apply outward displacement to the two sides of the specified equivalent boundary.

[0053] As can be seen, the current collector has a tab protruding from its long side. The tab is usually welded to fix the tab and the current collector. The welded area can be called a weld mark. Therefore, the above-mentioned finite element simulation model of the current collector can be established by: establishing the finite element simulation model of the current collector based on the size information of the current collector (i.e., length and width), the size information of the tab in the current collector (length and width of the tab, chamfer radius at the connection between the tab and the current collector), the position information of the tab in the current collector (e.g., the distance between the tab and the left side of the current collector), and the size information of the weld mark in the tab (e.g., the length and width of the weld mark).

[0054] For example, Figure 2 A schematic diagram of a finite element simulation model of a current collector is shown, as follows. Figure 2 As shown, the simulation model displays the equivalent current collector 21, the equivalent electrode tab 22, and the equivalent solder mark 23. Then, the four boundaries of the equivalent solder mark 23 in the finite element simulation model can be used as the equivalent boundary of the solder mark, and the two sides of the equivalent current collector in the deformation direction caused by the electrode expansion (usually the two short side boundaries of the current collector, such as boundary ab and boundary cb of the two short sides in the figure) can be used as the specified equivalent boundary.

[0055] It is known that the tab solder joints can be considered fixed and immovable during the operation of a lithium battery. Therefore, fixed boundary conditions are applied to the tab solder joints. These fixed boundary conditions are used to fix the equivalent boundaries of the solder joints in the finite element simulation model to simulate the fixed position of the tab solder joints in actual operation. During lithium battery operation, electrode expansion causes deformation of the current collector towards the shorter sides. Therefore, displacement boundary conditions are used to apply outward displacement to the two sides of the specified equivalent boundaries. Other boundaries besides the equivalent boundaries of the solder joints and the specified equivalent boundaries can be free. These free boundaries will not have boundary conditions applied, thus more accurately simulating the deformation process of the current collector due to electrode expansion in actual operation. For example, Figure 3A schematic diagram illustrating the application of boundary conditions to a finite element simulation model of a current collector is shown, as follows: Figure 3 As shown, the equivalent boundary of the solder mark is subject to a fixed boundary (i.e., a fixed constraint boundary condition). The equivalent boundaries ab and cb are respectively subject to different outward displacement boundaries. The outward direction means that the direction is from the inside of the current collector to the outside of the current collector, which simulates the deformation direction of the current collector due to the force of electrode expansion.

[0056] The total displacement change varies depending on the applied displacement boundary conditions. This total displacement change characterizes the change in the total length of the finite element simulation model after applying displacement boundary conditions compared to its original length; it can also be called the total deformation. The original length can be understood as the length of the two boundaries of the specified equivalent boundary before the application of displacement boundary conditions (before deformation), which is the original length of the current collector in the deformation direction (usually the length of the longer side of the current collector, e.g., ...). Figure 2 The length of the middle boundary (bd), or in other words, the total displacement change can be the sum of the displacements applied to the two boundaries in the specified equivalent boundary, such as... Figure 3 The sum of the displacements applied to the middle boundary ab and the boundary cd. It should be understood that the single displacement boundary condition in this disclosure includes the displacements applied to each of the two sides of the specified equivalent boundary; therefore, under the same displacement boundary condition, the magnitudes of the displacements applied to each of the two sides of the specified equivalent boundary can be different (e.g., ...). Figure 3 If a displacement of 0.5 mm can be applied to the middle boundary ab, and a displacement of 0.3 mm can be applied to the boundary cd, then the total displacement change is 0.8 mm. Of course, they can also be the same (e.g., Figure 3 The middle boundary ab and boundary cd can each be subjected to a displacement of 0.4 mm, but this disclosure does not limit the scope of the embodiments.

[0057] As described above, a finite element simulation model of the current collector can be established using finite element analysis software. Then, within the finite element analysis software, fixed constraint boundary conditions can be applied to the equivalent boundary of the weld, and displacement boundary conditions can be applied to specified equivalent boundaries. Furthermore, the analysis capabilities of the finite element analysis software itself can be utilized to obtain the deformation at different locations in the finite element simulation model under each displacement boundary condition. It should be understood that this disclosure does not limit the analysis process of deformation at different locations in the finite element simulation model using finite element analysis software, as long as the deformation at different locations in the finite element simulation model under each displacement boundary condition can be obtained.

[0058] In practical applications, for example, multiple displacement boundary conditions can be applied to a specified equivalent boundary in ascending order of total displacement change to obtain the deformation at different locations in the finite element simulation model under each displacement boundary condition. It should be understood that applying displacement to the finite element simulation model of the current collector will cause deformation. Constraints at different locations will lead to different deformation distributions at different locations within the model. Therefore, different locations in the finite element simulation model will produce different deformation amounts (i.e., the displacement change of different points in the finite element simulation model compared to their original positions). Furthermore, the deformation amounts at different locations in the finite element simulation model will also differ under different displacement boundary conditions. By applying multiple displacement boundary conditions, the deformation distribution of the finite element simulation model under different displacement boundary conditions can be obtained, which is beneficial for more effectively obtaining the maximum stress at which fracture stress is reached, thereby improving the efficiency of deformation capacity assessment.

[0059] Based on the deformation at different locations in the finite element simulation model under each of the various displacement boundary conditions obtained through steps S111 to S112 above, in one possible implementation, in step S12, the maximum stress generated by the finite element simulation model is obtained according to the stress-strain constitutive equation of the material used for the current collector and the deformation at different locations in the finite element simulation model, including:

[0060] Step S121: Obtain the stress-strain constitutive equation of the material used for the current collector;

[0061] Step S122: Based on the stress-strain constitutive equation and the deformation at different locations in the finite element simulation model under each displacement boundary condition, determine the maximum stress generated by the finite element simulation model under each displacement boundary condition.

[0062] As described above, the stress-strain constitutive equation characterizes the mathematical relationship between stress and strain in the material used for the current collector during deformation. The material used for the current collector can be designed according to actual needs. The stress-strain curve of the material used for the current collector can be obtained by conducting tensile tests, thereby obtaining the basic mechanical parameters of the material. Considering that the deformation process of the current collector with the expansion of the electrode includes both elastic and plastic deformation stages, the stress-strain constitutive equation of the material used for the current collector is constructed. In one possible implementation, obtaining the stress-strain constitutive equation of the material used for the current collector in step S121 may include:

[0063] The stress-strain curve of the material used in the current collector was obtained by conducting tensile tests on the material.

[0064] The basic mechanical parameters of the material used for the current collector are determined based on the stress-strain curve. The basic mechanical parameters include Young's modulus, initial yield stress, and fracture stress.

[0065] Based on the stress-strain curves and basic mechanical parameters, the stress-strain constitutive equations of the materials used in the current collector are determined.

[0066] It should be understood that the present disclosure does not limit the tensile test process of the material used in the current collector, as long as the stress-strain curve of the material used in the current collector can be obtained. The stress-strain curve describes the stress magnitude of the material used in the current collector under different strains during the tensile process.

[0067] The determination of the basic mechanical parameters of the material used in the current collector based on the stress-strain curve includes: determining the Young's modulus of the material used in the current collector as the ratio between the increase in stress and the increase in strain in the elastic stage of the stress-strain curve; determining the stress corresponding to the intersection point between the extension of the linear portion of the elastic stage and the extension of the linear portion of the plastic stage of the stress-strain curve as the initial yield stress of the material used in the current collector; and determining the stress corresponding to the end of the plastic stage of the stress-strain curve as the fracture stress of the material used in the current collector.

[0068] For example, Figure 4 A schematic diagram of a stress-strain curve is shown, such as... Figure 4 As shown, Δσ elastic Δε represents the increase in stress during the elastic phase of the stress-strain curve obtained from a tensile test. elastic The stress-strain curve obtained from the tensile test represents the increase in strain during the elastic phase. The coordinates of the intersection point between the extended linear portion of the elastic phase and the extended linear portion of the plastic phase in the stress-strain curve are (x1, y1), and the stress corresponding to this intersection point is y1. The coordinates of the end of the plastic phase in the stress-strain curve are (x2, y2), and the stress at coordinates (x2, y2) is y2. It should be understood that using the above-mentioned stress-strain curve to determine the basic mechanical parameters of the material is one possible implementation method provided by the embodiments of this disclosure. This method can quickly obtain the basic mechanical parameters of the material. In fact, those skilled in the art can use any known experimental testing method in the art to test the basic mechanical parameters of the material used in the current collector, and the embodiments of this disclosure do not limit this.

[0069] It should be understood that, given any stress-strain curve, the aforementioned Δσ can be determined from the stress-strain curve. elastic , Δε elastic Information from (x1, y1) and (x2, y2), in this embodiment of the disclosure regarding Δσ elastic , Δε elastic The method of determining (x1, y1) and (x2, y2) is not restricted.

[0070] The formula for calculating the Young's modulus E of the material used for the current collector can be expressed as formula (1):

[0071]

[0072] In practical applications, to reduce the computation time of the model, the stress-strain curve obtained from the tensile test can be simplified. By extending the linear portions of the elastic and plastic stages of the stress-strain curve respectively, the intersection point (x1, y1) is the transition point between the elastic and plastic stages. The coordinates of the end of the plastic stage of the stress-strain curve can be obtained as (x2, y2). Therefore, the stress y1 at the intersection point (x1, y1) can be determined as the initial yield stress σ. y0 The stress y2 at the coordinate point (x2, y2) at the end of the plastic stage is determined as the fracture stress. Simultaneously, based on (x1, y1) and (x2, y2), the mathematical expression for the stress-strain curve shown in formula (2) can also be obtained:

[0073]

[0074] Where x represents arbitrary strain, σ e The stress represents any strain. It should be understood that the mathematical expression of the stress-strain curve shown in formula (2) is a simplified expression of the stress-strain curve provided by the embodiments of this disclosure. In fact, those skilled in the art can construct complex expressions of the stress-strain curve according to their needs to truly express the functional relationship represented by the stress-strain curve. The embodiments of this disclosure do not limit this.

[0075] For example, based on the above Young's modulus E and initial yield stress σ y0 And the expression for the stress-strain curve σ e The stress-strain constitutive equations shown in equations (3-1) and (3-2) can be constructed as follows:

[0076] σ t =E·ε t (3-1)

[0077] σ h =σ e ε total -σ y0 (3-2)

[0078] Where, σ t ε represents the stress in the elastic stage of a material. t The strain representing the elastic stage of a material (i.e., elastic strain), σ h Represents the initial yield stress σ of the material during the plastic stage. y0The added stress and total strain ε total The functional relationship (which can be called the hardening function), σ e The expression representing the stress-strain curve is given, where E is Young's modulus. The total strain can be understood as the strain resulting from the combined action of the elastic and plastic stages, or as the strain during the plastic stage. It should be understood that the above stress-strain constitutive equation and its establishment process are one possible implementation provided by the embodiments of this disclosure. In fact, those skilled in the art can use any known technical means to establish the stress-strain constitutive equation for the material used in the current collector, and this disclosure does not limit such implementation.

[0079] In practical applications, considering that finite element analysis software may internally require separating the plastic strain and elastic strain from the total strain to determine whether the plastic stage has been reached before calculating the Mises stress, etc., the aforementioned hardening function σ h It can also be expressed as: Where, ε p Representing the equivalent plastic strain, its calculation formula is: σ m Representing the Mises stress, the calculation formula is: σ1, σ2, and σ3 are the three principal stresses. It is known that finite element analysis software can calculate Mises stress by default, and this embodiment does not limit the calculation process for Mises stress.

[0080] Based on the above stress-strain constitutive equation, in step S122, determining the maximum stress generated by the finite element simulation model under each displacement boundary condition, according to the stress-strain constitutive equation and the deformation at different locations in the finite element simulation model under each displacement boundary condition, may include:

[0081] Based on the deformation at different locations in the finite element simulation model under each displacement boundary condition and the original length of the finite element simulation model, the strain value at different locations in the finite element simulation model under each displacement boundary condition is determined; where the original length of the finite element simulation model represents the original length between the two boundaries in the specified equivalent boundary (that is, the original length of the current collector before deformation).

[0082] By using the stress-strain constitutive equation and the strain values ​​at different locations in the finite element simulation model under each displacement boundary condition, the stress values ​​at different locations in the finite element simulation model under each displacement boundary condition are determined.

[0083] The maximum stress value at different locations in the finite element simulation model under each displacement boundary condition is determined as the maximum stress generated by the finite element simulation model under each displacement boundary condition.

[0084] It is known that there is a certain physical relationship between strain and displacement change. By measuring displacement change, the strain magnitude can be estimated. In elastic materials, the actual deformation can be obtained by multiplying the strain by the original length. Therefore, given the deformation (i.e., displacement change, or length change at different locations after material deformation) and the original length of the finite element simulation model at different locations, the strain value ε at different locations can be calculated using formula (4): Where ΔL represents the deformation at different locations, and L0 represents the original length.

[0085] It is understandable that after displacement is applied to the finite element simulation model (i.e., the current collector), deformation will occur. Constraints at different locations will cause different deformation distributions at different locations in the finite element simulation model. Different deformation distributions can be calculated using the above formula (4) to obtain the strain values ​​at different locations. Then, the strain values ​​at different locations can be substituted into the stress-strain constitutive equations shown in the above formulas (3-1) and (3-2) to calculate the stress values ​​at different locations. The obtained stress value results are the result of the combined action of deformation and constraint, which can effectively evaluate the maximum stress generated by the finite element simulation model under different displacement boundary conditions, which is equivalent to evaluating the maximum stress that the current collector can withstand.

[0086] It should be understood that knowing the strain values ​​at different locations allows us to determine whether the deformation at those locations is in the elastic or plastic stage. For example, if the strain value at a certain location falls within the range of 0 ≤ x ≤ x1, it indicates that the deformation at that location is in the elastic stage. We can then substitute this strain value into the elastic stage constitutive equation in formula (3-1) to obtain the stress value at that location. If the strain value at a certain location falls within the range of x1 ≤ x ≤ x2, it indicates that the deformation at that location is in the plastic stage, and the strain value at that location is equivalent to ε. total Then, the strain value at that location can be substituted into the plastic stage constitutive equation of formula (3-2) to obtain the stress value at that location. Thus, the stress values ​​at different locations (i.e., different points) in the finite element simulation model can be calculated. The maximum stress value among these different locations can then be selected as the maximum stress generated by the finite element simulation model under the current displacement boundary condition. Similarly, the maximum stress generated by the finite element simulation model under each of various displacement boundary conditions can be calculated.

[0087] Based on the maximum stress generated by the finite element simulation model under each of the various displacement boundary conditions obtained in steps S121 to S122, in one possible implementation, in step S13, the deformation capacity of the current collector is determined according to the maximum stress generated by the finite element simulation model and the fracture stress of the material used in the current collector when it fractures as previously tested. This includes: determining the deformation capacity of the current collector according to the maximum stress generated by the finite element simulation model under each of the various displacement boundary conditions and the fracture stress of the material used in the current collector when it fractures as previously tested. The deformation capacity characterizes the maximum amount of deformation that the current collector can withstand during electrode operation.

[0088] As mentioned above, the total displacement change varies depending on the displacement boundary conditions. The total displacement change characterizes the change in the total length of the finite element simulation model after applying the displacement boundary conditions compared to its original length; it can also be understood as the overall length change or the total deformation. Therefore, determining the deformation capacity of the current collector based on the maximum stress generated by the finite element simulation model under each of the various displacement boundary conditions and the pre-tested fracture stress of the material used in the current collector during electrode operation can include: selecting the target displacement boundary condition from the various displacement boundary conditions where the maximum stress reaches the fracture stress; and determining the total displacement change applied by the target displacement boundary condition as the maximum deformation of the current collector when it fractures during electrode operation.

[0089] It should be understood that the maximum deformation that the current collector can withstand during electrode operation can be interpreted as the maximum deformation at which the current collector does not fracture or begins to fracture during electrode operation. This means that when the actual deformation of the current collector due to electrode expansion reaches or exceeds this maximum deformation, the current collector begins to fracture. The total displacement change applied by different displacement boundary conditions can characterize the total deformation of the current collector under different displacement boundary conditions. When the maximum stress in the finite element simulation model under a certain displacement boundary condition reaches the fracture stress, it indicates that the current collector begins to fracture under that displacement boundary condition. Therefore, the total displacement change applied by the target displacement boundary condition when the maximum stress reaches the fracture stress can be determined as the maximum deformation of the current collector when it fractures during electrode operation, thus achieving the evaluation of the current collector's deformation capacity. Optionally, a target displacement boundary condition where the difference between the maximum stress and the fracture stress is within a specified error range can be selected from multiple displacement boundary conditions. The total displacement change applied by this target displacement boundary condition can then be determined as the maximum deformation of the current collector when it fractures during electrode operation. This can be customized according to the user's actual needs, and this embodiment does not limit this.

[0090] According to the deformation capacity assessment method of the current collector according to the embodiments of this disclosure, by establishing a finite element simulation model of the current collector, applying fixed constraints on the equivalent boundary of the electrode tab and applying various outward displacement boundary conditions on both sides of the equivalent boundary in the deformation direction, the actual deformation process of the current collector due to electrode expansion during use can be effectively simulated. By combining the deformation amount at different positions obtained by simulating the actual deformation process of the current collector through the finite element simulation model with the stress-strain constitutive equation of the material used in the current collector, the maximum stress under different displacement boundary conditions can be calculated. Thus, based on the maximum stress and fracture stress under different displacement boundary conditions, the maximum deformation amount that the current collector can withstand can be quickly and accurately assessed, that is, the maximum deformation amount (i.e., the critical displacement) when the current collector does not break (i.e., reaches the failure criterion and is about to break). This replaces the traditional time-consuming and laborious physical charging test, and realizes a rapid and low-cost assessment of the maximum deformation amount that the current collector can withstand during electrode operation, which is conducive to shortening the research and development cycle of lithium batteries.

[0091] This disclosure provides a computer simulation-based method for evaluating the deformation capacity of current collectors. The core of this method lies in establishing a digital simulation model of the current collector, applying fixed constraints at the tab solder joint, and applying displacement boundary conditions at the current collector boundary to simulate the actual deformation process. The simulation calculates the critical displacement at which the current collector does not fracture (or reaches the failure criterion), thus quickly and cost-effectively replacing the traditional time-consuming and labor-intensive physical charging test, enabling rapid evaluation and screening of the maximum deformation capacity of the current collector. This method and its specific implementation (including the establishment of the current collector model and the setting of boundary conditions) are the core innovative points sought to be protected, aiming to accelerate the lithium battery research and development process.

[0092] For example, based on the current collector deformation capacity evaluation method proposed in the above-described embodiments of this disclosure, this disclosure uses the current collector of negative electrode copper foil material as an example to evaluate the deformation capacity. Specifically, the stress-strain curve of the negative electrode copper foil material is obtained through tensile testing; the stress-strain curve is processed to obtain the Young's modulus and stress-strain formula of the negative electrode copper foil material; stress-strain constitutive equations for the elastic deformation stage and the plastic deformation stage are constructed; and a finite element simulation model is established according to the actual size of the lithium battery foil material. In this model, the length and width of the negative electrode current collector are 140 mm and 70 mm, the length and width of the tab are 35 mm and 12 mm, the distance between the tab and the left side of the current collector is 14 mm, the chamfer radius of the tab is 1.2 mm, and the length and width of the solder mark are 28 mm and 3.5 mm, respectively. The Young's modulus of the foil is calculated to be 25 GPa from the elastic stage of the stress-strain curve. The intersection point (x1, y1) obtained by extending the linear part of the elastic stage and the linear part of the plastic stage of the curve is (0.012, 300 MPa), that is, the yield stress of the material is 300 [MPa]. The coordinate point (x2, y2) at the end of the plastic stage of the stress-strain curve is (0.1, 350 MPa), that is, the stress when the negative electrode copper foil material fractures is 350 [MPa]. Thus, the expression of the stress-strain curve of the negative electrode copper foil material can be obtained as formula (5):

[0093]

[0094] Furthermore, the stress-strain constitutive equations for the negative electrode copper foil material can be obtained as formulas (6-1) and (6-2):

[0095] σ t =25[GPa]·ε t (6-1)

[0096]

[0097] Then, by applying fixed constraint boundary conditions at the four boundaries of the equivalent electrode tab in the model, and applying different specified displacement boundary conditions at the two sides of the short side of the equivalent current collector in the model, while leaving other boundaries free, the simulation results shown in Table 1 can be output to evaluate the maximum stress caused by deformation, and thus evaluate the deformation that the foil can withstand, that is, to evaluate the maximum amount of deformation that the current collector can withstand.

[0098] Table 1 Simulation results of the embodiments

[0099] Total deformation / mm Maximum stress / MPa 0.8 302 1.2 311 1.45 325 1.63 351 1.85 368

[0100] The stress-strain curve of the negative electrode copper foil material shows that the stress at which the negative electrode copper foil material fractures is 350 MPa. The maximum deformation of the aforementioned negative electrode copper foil material during lithium battery operation can be the total deformation of 1.63 mm corresponding to the maximum stress of 351 MPa. Of course, various displacement boundary conditions can be resampled between 1.45 mm and 1.63 mm to re-evaluate according to the evaluation method of this embodiment to obtain a total deformation (i.e., total displacement change) closer to the fracture stress of 350 MPa as the maximum deformation that the negative electrode copper foil material can withstand. This embodiment does not limit this. It should be understood that the total deformation under various displacement boundary conditions shown in Table 1 above are some possible implementations provided by this embodiment. In fact, the intervals between the total deformations indicated by various displacement boundary conditions during simulation can be more dense, and this embodiment does not limit this.

[0101] Therefore, the deformation capacity evaluation method for current collectors provided in this embodiment of the present disclosure can quickly evaluate the critical displacement in the current collector simulation model without fracture by establishing a finite element simulation model of the current collector, simulating the actual deformation of the current collector during use, applying fixed boundary conditions at the electrode tab solder joint, and applying different displacement boundary conditions at the current collector boundary. This allows for the rapid evaluation of the maximum deformation that the current collector can withstand, effectively avoiding the resource waste caused by traditional trial and error methods and accelerating the lithium battery research and development process.

[0102] Figure 5 A block diagram of an electrode current collector deformation capacity evaluation device according to an embodiment of the present disclosure is shown, as follows: Figure 5 As shown, the device includes:

[0103] The simulation module 511 is used to simulate the deformation process of the current collector due to electrode expansion using the finite element simulation model of the current collector, and to obtain the deformation amount at different positions in the finite element simulation model.

[0104] The stress determination module 512 is used to obtain the maximum stress generated by the finite element simulation model based on the stress-strain constitutive equation of the material used in the current collector and the deformation at different positions in the finite element simulation model. The stress-strain constitutive equation characterizes the mathematical relationship between stress and strain of the material used in the current collector during the deformation process.

[0105] The deformation determination module 513 is used to determine the deformation capacity of the current collector based on the maximum stress generated by the finite element simulation model and the fracture stress when the material used for the current collector fractures as tested in advance. The deformation capacity characterizes the maximum amount of deformation that the current collector can withstand during electrode operation.

[0106] In one possible implementation, the step of simulating the deformation process of the current collector due to electrode expansion using a finite element simulation model to obtain the deformation amount at different locations in the finite element simulation model includes: establishing a finite element simulation model of the current collector, which includes a weld equivalent boundary and a specified equivalent boundary. The weld equivalent boundary represents the boundary of the electrode tab weld in the current collector, and the specified equivalent boundary represents the two side boundaries in the deformation direction of the current collector due to electrode expansion; by applying fixed constraint boundary conditions to the weld equivalent boundary in the finite element simulation model and applying multiple displacement boundary conditions to the specified equivalent boundary, the deformation amount at different locations in the finite element simulation model under each displacement boundary condition is obtained. The deformation amount at different locations represents the displacement change at different locations, and the displacement boundary conditions are used to apply outward displacement to the two side boundaries in the specified equivalent boundary.

[0107] The step of obtaining the maximum stress generated by the finite element simulation model based on the stress-strain constitutive equation of the material used in the current collector and the deformation at different locations in the finite element simulation model includes: obtaining the stress-strain constitutive equation of the material used in the current collector, and determining the maximum stress generated by the finite element simulation model under each displacement boundary condition based on the stress-strain constitutive equation and the deformation at different locations in the finite element simulation model under each displacement boundary condition.

[0108] The step of determining the deformation capacity of the current collector based on the maximum stress generated by the finite element simulation model and the fracture stress of the material used in the current collector when it fractures (previously tested) includes: determining the deformation capacity of the current collector based on the maximum stress generated by the finite element simulation model under each of the multiple displacement boundary conditions and the fracture stress of the material used in the current collector when it fractures (previously tested).

[0109] In one possible implementation, obtaining the stress-strain constitutive equation of the material used in the current collector includes: obtaining the stress-strain curve of the material used in the current collector by performing a tensile test; determining the basic mechanical parameters of the material used in the current collector based on the stress-strain curve, the basic mechanical parameters including Young's modulus, initial yield stress, and fracture stress; and determining the stress-strain constitutive equation of the material used in the current collector based on the stress-strain curve and the basic mechanical parameters.

[0110] In one possible implementation, determining the basic mechanical parameters of the material used in the current collector based on the stress-strain curve includes: determining the Young's modulus of the material used in the current collector as the ratio between the increase in stress and the increase in strain in the elastic stage of the stress-strain curve; determining the stress corresponding to the intersection point between the extended linear portion of the elastic stage and the extended linear portion of the plastic stage of the stress-strain curve as the initial yield stress of the material used in the current collector; and determining the stress corresponding to the end of the plastic stage of the stress-strain curve as the fracture stress of the material used in the current collector.

[0111] In one possible implementation, the stress-strain constitutive equation is expressed as:

[0112] σ t =E·ε t

[0113] σ h =σ e ε total -σ y0

[0114] Where, σ t The stress ε represents the elastic stage. t Strain σ represents the elastic stage. h Represents the plastic stage at the initial yield stress σ y0 The added stress and total strain ε total The functional relationship, σ e The expression representing the stress-strain curve is given, where E is the Young's modulus.

[0115] In one possible implementation, establishing the finite element simulation model of the current collector includes: establishing the finite element simulation model of the current collector based on the size information of the current collector, the size information of the tabs in the current collector, the position information of the tabs in the current collector, and the size information of the solder joints in the tabs; wherein the finite element simulation model is further assigned the Young's modulus of the material used in the current collector, and the material used in the current collector includes foil.

[0116] In one possible implementation, determining the maximum stress generated by the finite element simulation model under each displacement boundary condition based on the stress-strain constitutive equation and the deformation at different locations in the finite element simulation model under each displacement boundary condition includes: determining the strain value at different locations in the finite element simulation model under each displacement boundary condition based on the deformation at different locations in the finite element simulation model under each displacement boundary condition and the original length of the finite element simulation model; determining the stress value at different locations in the finite element simulation model under each displacement boundary condition based on the strain value at different locations in the finite element simulation model under each displacement boundary condition using the stress-strain constitutive equation; and determining the maximum value among the stress values ​​at different locations in the finite element simulation model under each displacement boundary condition as the maximum stress generated by the finite element simulation model under each displacement boundary condition.

[0117] In one possible implementation, the total displacement change imposed by different displacement boundary conditions is different, and the total displacement change characterizes the change in the total length of the finite element simulation model after the displacement boundary conditions are applied compared to the original length; wherein, determining the deformation capacity of the current collector based on the maximum stress generated by the finite element simulation model under each of the multiple displacement boundary conditions and the fracture stress of the material used in the current collector when it fractures as previously tested, includes: selecting a target displacement boundary condition from the multiple displacement boundary conditions when the maximum stress reaches the fracture stress; and determining the total displacement change imposed by the target displacement boundary condition as the maximum deformation of the current collector when it fractures during electrode operation.

[0118] According to the apparatus of this disclosure, by using a finite element simulation model of the current collector to simulate the deformation process of the current collector due to electrode expansion, the deformation at different locations can be calculated by combining the stress-strain constitutive equation of the material used in the current collector. This is equivalent to obtaining the maximum stress generated by the current collector during the actual deformation process. Therefore, based on the obtained maximum stress generated by the current collector and the fracture stress of the material used in the current collector, the maximum deformation that the current collector can withstand can be quickly assessed, that is, the maximum deformation (critical displacement) when the current collector does not break (i.e., reaches the failure criterion and is about to break). This replaces the traditional time-consuming and laborious physical charging test, and realizes a rapid and low-cost assessment of the maximum deformation that the current collector can withstand during electrode operation, thereby helping to shorten the research and development cycle of lithium batteries.

[0119] In some embodiments, the functions or modules of the apparatus provided in this disclosure can be used to perform the methods described in the above method embodiments. The specific implementation can be referred to the description of the above method embodiments, and for the sake of brevity, it will not be repeated here.

[0120] This disclosure also provides an electronic device, including a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the above method.

[0121] This disclosure also provides a non-volatile computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the steps of the above-described method.

[0122] This disclosure also provides a computer program product, including a computer program or a non-volatile computer-readable storage medium carrying the computer program, wherein the computer program, when executed by a processor, implements the steps of the above method.

[0123] Figure 6 A block diagram of an electronic device 1900 according to an embodiment of the present disclosure is shown. For example, device 1900 may be provided as a server or terminal device. (Refer to...) Figure 6 The apparatus 1900 includes a processing component 1922, which further includes one or more processors, and memory resources represented by memory 1932 for storing instructions, such as application programs, that can be executed by the processing component 1922. The application programs stored in memory 1932 may include one or more modules, each corresponding to a set of instructions. Furthermore, the processing component 1922 is configured to execute instructions to perform the methods described above.

[0124] Device 1900 may also include a power supply component 1926 configured to perform power management of device 1900, a wired or wireless network interface 1950 configured to connect device 1900 to a network, and an input / output interface 1958 (I / O interface). Device 1900 can operate on an operating system, such as Windows Server, stored in memory 1932. TM macOS X TM Unix TM Linux TM FreeBSD TM Or similar.

[0125] In an exemplary embodiment, a non-volatile computer-readable storage medium is also provided, such as a memory 1932 including computer program instructions that can be executed by a processing component 1922 of the device 1900 to perform the above-described method.

[0126] Computer-readable storage media can be tangible devices capable of holding and storing programs / instructions used by instruction execution devices. Computer-readable storage media can be, for example—but not limited to—electrical storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of computer-readable storage media include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, such as punch cards or recessed protrusions storing instructions thereon, and any suitable combination of the foregoing. The computer-readable storage media used herein are not to be construed as transient signals themselves, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., light pulses through fiber optic cables), or electrical signals transmitted through wires.

[0127] The computer program (or computer-readable program instructions) described herein can be downloaded from a computer-readable storage medium to various computing / processing devices, or downloaded via a network, such as the Internet, local area network, wide area network, and / or wireless network, to an external computer or external storage device. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards them to the computer-readable storage medium in the respective computing / processing device.

[0128] The computer program (or computer program instructions) used to perform the operations of this disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, status setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, etc., and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving remote computers, the remote computer may be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, electronic circuits, such as programmable logic circuits, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), are personalized by utilizing state information of computer-readable program instructions. These electronic circuits can execute computer-readable program instructions to implement various aspects of this disclosure.

[0129] Various aspects of this disclosure are described herein with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this disclosure. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer-readable program instructions.

[0130] These computer-readable program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus to produce a machine such that, when executed by the processor of the computer or other programmable data processing apparatus, they create means for implementing the functions / actions specified in one or more blocks of the flowchart and / or block diagram. These computer-readable program instructions can also be stored in a computer-readable storage medium that causes a computer, programmable data processing apparatus, and / or other device to operate in a particular manner; thus, the computer-readable medium storing the instructions comprises an article of manufacture that includes instructions for implementing aspects of the functions / actions specified in one or more blocks of the flowchart and / or block diagram.

[0131] Computer-readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable data processing apparatus, or other device to produce a computer-implemented process, thereby causing the instructions executed on the computer, other programmable data processing apparatus, or other device to perform the functions / actions specified in one or more boxes of a flowchart and / or block diagram.

[0132] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present disclosure. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of an instruction containing one or more executable instructions for implementing a specified logical function. In some alternative implementations, the functions marked in the blocks may occur in a different order than those shown in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, may be implemented using a dedicated hardware-based system that performs the specified function or action, or using a combination of dedicated hardware and computer instructions.

[0133] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method of evaluating the deformation capability of a current collector in an electrode, characterized by, The method comprises the following steps: simulate the deformation process of the current collector caused by the expansion of the electrode by using a finite element simulation model of the current collector, to obtain the deformation amount at different positions in the finite element simulation model; obtain the maximum stress generated by the finite element simulation model according to the stress-strain constitutive equation of the material used by the current collector and the deformation amount at different positions in the finite element simulation model, wherein the stress-strain constitutive equation represents the mathematical relationship between stress and strain of the material used by the current collector in the deformation process; determine the deformation capacity of the current collector according to the maximum stress generated by the finite element simulation model and the fracture stress of the material used by the current collector when the material is fractured, which is tested in advance, wherein the deformation capacity represents the maximum deformation amount that the current collector can withstand in the working process of the electrode.

2. The method of claim 1, wherein, The step of simulating the deformation process of the current collector caused by the expansion of the electrode by using a finite element simulation model of the current collector, to obtain the deformation amount at different positions in the finite element simulation model, comprises the following steps: establish a finite element simulation model of the current collector, wherein the finite element simulation model comprises a welding mark equivalent boundary and a specified equivalent boundary, the welding mark equivalent boundary represents the boundary of the tab welding mark in the current collector, and the specified equivalent boundary represents the two side boundaries in the deformation direction of the current collector caused by the expansion of the electrode; obtain the deformation amount at different positions in the finite element simulation model under each displacement boundary condition by applying a fixed constraint boundary condition to the welding mark equivalent boundary in the finite element simulation model and applying a plurality of displacement boundary conditions to the specified equivalent boundary, respectively, wherein the displacement boundary condition is used to apply a displacement outwardly to the two side boundaries in the specified equivalent boundary, and the deformation amount at different positions represents the displacement change amount at different positions; wherein the step of obtaining the maximum stress generated by the finite element simulation model according to the stress-strain constitutive equation of the material used by the current collector and the deformation amount at different positions in the finite element simulation model comprises the following steps: obtaining the stress-strain constitutive equation of the material used by the current collector, and determining the maximum stress generated by the finite element simulation model under each displacement boundary condition according to the stress-strain constitutive equation and the deformation amount at different positions in the finite element simulation model under each displacement boundary condition; wherein the step of determining the deformation capacity of the current collector according to the maximum stress generated by the finite element simulation model and the fracture stress of the material used by the current collector when the material is fractured, which is tested in advance, comprises the following steps: determining the deformation capacity of the current collector according to the maximum stress generated by the finite element simulation model under each displacement boundary condition and the fracture stress of the material used by the current collector when the material is fractured, which is tested in advance.

3. The method of claim 2, wherein, The step of obtaining the stress-strain constitutive equation of the material used by the current collector comprises the following steps: obtain the stress-strain curve of the material used by the current collector by performing a tensile test on the material; determine the basic mechanical parameters of the material used by the current collector based on the stress-strain curve, wherein the basic mechanical parameters comprise Young's modulus, initial yield stress and fracture stress; determine a stress-strain constitutive equation of the material of the current collector based on the stress-strain curve and the basic mechanical parameters.

4. The method of claim 3, wherein, The determining the basic mechanical parameters of the material of the current collector based on the stress-strain curve comprises: determining a Young's modulus of the material of the current collector as a ratio between an increase in stress in the elastic stage of the stress-strain curve and an increase in strain in the elastic stage of the stress-strain curve; determining an initial yield stress of the material of the current collector as a stress corresponding to an intersection between a linear portion of the elastic stage of the stress-strain curve and an extended line of a linear portion of the plastic stage of the stress-strain curve; determining a fracture stress of the material of the current collector as a stress corresponding to an end of the plastic stage of the stress-strain curve.

5. The method according to claim 3 or 4, characterized in that, The stress-strain constitutive equation is expressed as: σ t = E ε t σ h = σ e ε total -σ y0 Where, σ t The stress ε represents the elastic stage. t Strain σ represents the elastic stage. h Represents the plastic stage at the initial yield stress σ y0 The added stress and total strain ε total The functional relationship, σ e The expression representing the stress-strain curve is given, where E is the Young's modulus.

6. The method according to any one of claims 2 to 4, characterized in that, The establishing the finite element simulation model of the current collector comprises: establishing the finite element simulation model of the current collector according to size information of the current collector, size information of tabs in the current collector, position information of the tabs in the current collector, and size information of welding marks in the tabs; wherein the finite element simulation model is further assigned with the Young's modulus of the material of the current collector, and the material of the current collector comprises a foil.

7. The method according to any one of claims 2 to 4, characterized in that, The determining the maximum stress generated by the finite element simulation model under each displacement boundary condition based on the stress-strain constitutive equation and deformation amounts of different positions in the finite element simulation model under each displacement boundary condition comprises: determining strain values of different positions in the finite element simulation model under each displacement boundary condition based on deformation amounts of different positions in the finite element simulation model under each displacement boundary condition and an original length of the finite element simulation model; determining stress values of different positions in the finite element simulation model under each displacement boundary condition by using the stress-strain constitutive equation according to the strain values of different positions in the finite element simulation model under each displacement boundary condition; determining the maximum stress generated by the finite element simulation model under each displacement boundary condition as a maximum value among the stress values of different positions in the finite element simulation model under each displacement boundary condition.

8. The method according to any one of claims 2 to 4, characterized in that, The total displacement variation amount applied by different displacement boundary conditions is different, and the total displacement variation amount represents a length variation amount of a total length of the finite element simulation model after the displacement boundary condition is applied relative to an original length; wherein the determining the deformation capability of the current collector based on the maximum stress generated by the finite element simulation model under each displacement boundary condition in the plurality of displacement boundary conditions and the fracture stress of the material of the current collector when the material is fractured, which is tested in advance, comprises: selecting a target displacement boundary condition in which the maximum stress reaches the fracture stress from the plurality of displacement boundary conditions; determining a maximum deformation amount of the current collector when the current collector is fractured in an electrode working process as a total displacement variation amount applied by the target displacement boundary condition.

9. An electrode current collector deformability evaluation device, characterized by, comprises: The simulation module is configured to simulate a deformation process of the current collector due to electrode expansion by using a finite element simulation model of the current collector, and obtain deformation amounts at different positions in the finite element simulation model; The stress determination module is configured to obtain a maximum stress generated by the finite element simulation model according to a stress-strain constitutive equation of a material used by the current collector and the deformation amounts at different positions in the finite element simulation model, the stress-strain constitutive equation representing a mathematical relationship between stress and strain of the material used by the current collector in the deformation process; The deformation evaluation module is configured to determine a deformation capacity of the current collector according to the maximum stress generated by the finite element simulation model and a fracture stress of the material used by the current collector when the material is fractured, which is tested in advance, the deformation capacity representing a maximum deformation amount that can be borne by the current collector in an electrode working process.

10. An electronic device comprising a memory, a processor, and a computer program stored on the memory, wherein the computer program, when executed by the processor, is arranged to perform the method of any one of claims 1 to 9. The processor executes the computer program to implement the steps of the method in any one of claims 1 to 8.

11. A non-transitory computer readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to implement the steps of the method in any one of claims 1 to 8.

12. A computer program product comprising a computer program or a non-transitory computer-readable storage medium bearing a computer program, characterized in that, The computer program is executed by the processor to implement the steps of the method in any one of claims 1 to 8.

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