Method for determining cell restraint gap, cell, battery pack and electric device

Abstract

The application provides a method for determining a cell restraint gap, a cell, a battery pack and a power utilization device, and solves the problem of long cycle and high cost consumption in the prior art by relying on the experience trial and error method to determine the restraint gap. The risk determination method comprises: obtaining a cell thickness of a to-be-restrained cell in a restraint direction that meets a preset requirement; and determining the restraint gap of the to-be-restrained cell according to the cell thickness through a preset nonlinear function relationship. The method establishes a preset nonlinear function relationship between the cell thickness and the restraint gap, so that under the premise of meeting the specific structure condition, the optimal restraint gap suitable for the cell can be quickly and accurately determined without relying on the traditional multi-gradient trial and error verification.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a method for determining the cell restraint gap, a cell, a battery pack, and an electrical device. Background Technology

[0002] During the capacity grading process of lithium-ion batteries, electrochemical side reactions occur in the electrolyte, generating gas. For cells with a stacked structure, especially blade cells, if there is a gap between the electrode assembly and the inner wall of the casing, the generated gas tends to accumulate at the interface, forming localized debonding areas, which appear as "black spots" during disassembly and observation. This defect not only leads to increased internal resistance and capacity loss but may also induce lithium plating, seriously affecting the battery's safety and cycle life.

[0003] To avoid the aforementioned problems, existing technologies typically apply external restraint pressure to the battery cells during the capacity testing process to ensure the electrode assembly adheres to the casing, expel gases, and maintain good interfacial contact. Currently, the method for determining the restraint gap (i.e., the set distance between the two pressure plates of the restraint fixture) mainly relies on trial and error: taking a batch of battery cells of the same model and performing capacity testing with different restraint gaps, then disassembling and observing the condition of the batch of battery cells, and selecting the restraint gap value with the best battery cell condition.

[0004] While relying on trial and error based on experience can indeed help select a suitable constraint gap, this method has a long verification cycle, which affects the battery production schedule. Furthermore, each verification requires a large number of cells, resulting in high costs. Different cell models may also need to be verified repeatedly, lacking versatility. Summary of the Invention

[0005] In view of this, the embodiments of this application aim to provide a method, a battery cell, a battery pack, and an electrical device for determining the cell restraint gap, so as to solve the problems of long cycle and high cost in the prior art, which relies on experience and trial and error to determine the restraint gap.

[0006] In a first aspect, embodiments of this application provide a method for determining the cell restraint gap, comprising: Obtain the cell thickness in the restraint direction of the cell to be restrained, which meets the preset requirements; Based on the cell thickness, the restraint gap of the cell to be restrained is determined by a preset nonlinear function relationship.

[0007] Optionally, the nonlinear functional relationship satisfies: H=-0.0503h 2 +2.5145h-10.802; Wherein, H represents the restraint gap of the battery cell to be restrained, and h represents the thickness of the battery cell; and / or, The manufacturing tolerance 'a' of the restraint gap satisfies: a ≤ 0.1 mm; and / or, The manufacturing tolerance b of the cell thickness satisfies: b≤0.1mm.

[0008] Optionally, the step of obtaining the cell thickness in the restraint direction of the cell to be restrained, which meets the preset requirements, includes: Obtain the battery cell to be constrained; Measure the shell wall thickness of the battery cell to be constrained in the constraining direction; Based on the relationship between the shell wall thickness and the preset wall thickness, determine whether the battery cell to be constrained meets the first preset requirement; Calculate the assembly ratio of the electrode group to the housing in the cell to be constrained; Based on the relationship between the assembly ratio and the preset assembly ratio, determine whether the battery cell to be constrained meets the second preset requirement; If the battery cell to be constrained simultaneously meets both the first preset requirement and the second preset requirement, then the battery cell to be constrained is determined to be a battery cell that meets the preset requirements. If the battery cell to be constrained does not meet the first preset requirement and / or the second preset requirement, then the battery cell to be constrained is determined to be a constrained battery cell that does not meet the preset requirements.

[0009] Optionally, the first preset requirement is: d≤D, where d represents the shell wall thickness, D represents the preset wall thickness, and D=0.4mm; The second preset requirement is: Q1≤q≤Q2, where q represents the assembly ratio, Q1 represents the minimum value of the preset assembly ratio, Q2 represents the maximum value of the preset assembly ratio, and Q1=90% and Q2=93%.

[0010] Optionally, the step of calculating the assembly ratio of the electrode group to the housing in the cell to be constrained includes: Measure the cell thickness and electrode assembly thickness of the cell to be constrained in the constraining direction and record the cell thickness; Calculate the inner cavity width of the housing in the restraint direction based on the cell thickness and the housing wall thickness; The assembly ratio is calculated based on the inner cavity width and the electrode assembly thickness; and / or, The formula for calculating the assembly ratio is: q = L / N, where q represents the assembly ratio, L represents the electrode assembly thickness, and N represents the inner cavity width; The formula for calculating the inner cavity width N is: N = h - 2 × d, where h represents the cell thickness and d represents the shell wall thickness.

[0011] Optionally, after the step of determining that the battery cell to be constrained is a battery cell that meets the preset requirements if the battery cell to be constrained simultaneously meets both the first preset requirement and the second preset requirement, the method further includes: The cell thickness recorded when calculating the assembly ratio of the cell to be constrained, which meets the preset requirements.

[0012] Optionally, the cell thickness h of the cell to be constrained in the constraining direction, which meets the preset requirements, satisfies: 14mm≤h≤20mm.

[0013] Secondly, embodiments of this application provide a battery cell whose constraint gap is determined by the method for determining the battery cell constraint gap as described in the first aspect.

[0014] Thirdly, embodiments of this application provide a battery pack including at least one cell as described in the second aspect.

[0015] Fourthly, embodiments of this application provide an electrical appliance, including: Electricity-consuming entities; The battery pack as described in the third aspect is electrically connected to the power-consuming body.

[0016] The beneficial effects of the embodiments of this application are as follows: This application provides a method for determining the cell restraint gap, a cell, a battery pack, and electrical equipment. The method establishes a preset nonlinear functional relationship between the cell thickness and the restraint gap, enabling the rapid and accurate determination of the optimal restraint gap for a given cell without relying on traditional multi-gradient trial-and-error verification, provided specific structural conditions are met. This significantly shortens the process verification cycle for introducing new cell models into the capacity testing process, avoids substantial cell losses due to repeated disassembly and verification, and substantially reduces R&D and production costs. Simultaneously, since the restraint gap is objectively calculated using a functional relationship, the subjectivity and inconsistency of manual experience-based judgment are eliminated, improving the stability and repeatability of the restraint process. This effectively ensures the cell interface bonding quality, prevents the generation of black spot defects, and ultimately improves the yield, safety, and cycle life of battery products. Attached Figure Description

[0017] Figure 1 The diagram shown is a structural schematic of an electrical device provided in an embodiment of this application.

[0018] Figure 2 The diagram shown is a flowchart of the steps of a method for determining the cell restraint gap provided in an embodiment of this application.

[0019] Figure 3 The diagram shown is a flowchart of step S1 in a method for determining the cell restraint gap provided in an embodiment of this application.

[0020] Figure 4 The diagram shown is a flowchart of step S14 in a method for determining the cell restraint gap provided in an embodiment of this application.

[0021] Explanation of reference numerals in the attached figures: 100. Electrical equipment; 110. Main power supply unit; 110a. Battery compartment; 120. Battery pack. Detailed Implementation

[0022] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] Please see Figure 1 , Figure 1 This is a schematic diagram of an electrical device 100 provided in some embodiments of this application. Figure 1 In the illustrated embodiment, an electric vehicle is used as an example for illustrative purposes, and this should not be construed as a specific limitation of this application. In other embodiments, the electrical device 100 may also be a mobile phone, a laptop computer, a mobile charging station, or other similar devices.

[0024] Please continue reading. Figure 1 The electrical device 100 includes a power-consuming body 110 and a battery pack 120. The battery pack 120 is fixed to the power-consuming body 110 and electrically connected to the power-consuming components of the power-consuming body 110 to supply power to the power-consuming components of the power-consuming body 110. Specifically, the power-consuming body 110 may have a battery compartment 110a, and the battery pack 120 is fixed inside the battery compartment 110a.

[0025] The battery pack 120 may include a mounting shell and at least one battery cell. The mounting shell has a first inner cavity for receiving the battery cell, thereby sealing the battery cell within the first inner cavity. In this embodiment, multiple battery cells are provided, and multiple battery cells can form multiple battery modules. The battery modules are disposed in the first inner cavity and fixed relative to the mounting shell. The mounting shell can protect the battery cells, preventing external forces from causing vibration and impact that could damage the battery cells. The mounting shell can be a metal structural component or a plastic structural component.

[0026] A battery cell is the most basic electrochemical unit, capable of storing and releasing electrical energy. A battery cell can be a blade battery cell or another type requiring a confinement process, where the wall thickness of the confinement casing is no greater than 0.4 mm.

[0027] In the battery pack 120, there are multiple battery cells. These cells can be electrically connected in series, in parallel, or in a mixed configuration. A mixed configuration means that the electrical connections in multiple electrode groups involve both series and parallel connections, which can be designed according to the power requirements of the electrical device 100. In some other embodiments, the battery pack 120 may contain only one battery cell.

[0028] The battery cell includes a housing, a top cover, and electrode assemblies. The housing has a receiving cavity and a first opening communicating with the receiving cavity. The receiving cavity is used to receive the electrode assemblies and electrolyte. The first opening is used to house the electrode assemblies within the receiving cavity. The top cover is connected to the housing and seals the first opening.

[0029] The housing can be generally rectangular in shape, so that the electrode assembly is also generally rectangular. The housing can be a metal housing. In some examples, the housing can be an aluminum alloy housing to make the housing lighter, which is beneficial for the lightweighting of the electrode assembly and thus the overall lightweighting of the electrical equipment. In other examples, the housing can also be a stainless steel housing, a titanium alloy housing, etc., to make the housing stronger, which in turn makes the electrode assembly stronger and more resistant to puncture and vibration damage. In other embodiments, the housing can also be cylindrical, irregularly shaped, etc.

[0030] The electrode assembly is disposed within a receiving cavity and immersed in an electrolyte. The electrode assembly includes a positive electrode (not shown), a negative electrode (not shown), and a separator (not shown). The positive electrode can be formed from a positive current collector and a positive active material coated on the current collector. In some examples, the positive current collector can be aluminum foil, and the positive active material can be lithium cobalt oxide (LCO), ternary materials (NCM / NCA), lithium iron phosphate (LFP), etc. Based on this, the electrode assembly also includes a positive electrode tab (not shown), which is connected to the positive electrode and electrically conductive. Specifically, the positive electrode tab can be fixed to the positive current collector by welding or integrally formed with the positive current collector.

[0031] The negative electrode sheet can be formed from a negative current collector and a negative active material coated on the negative current collector. In some examples, the negative current collector can be copper foil, and the negative active material can be graphite, silicon-carbon composite material, etc. Based on this, the electrode assembly also includes a negative electrode tab (not shown in the figure), which is connected to the negative electrode sheet and is electrically conductive. The negative electrode tab and the positive electrode tab are used to electrically connect the electrode assembly to the circuit. Specifically, the negative electrode tab can be fixed to the negative current collector by welding, or it can be integrally formed with the negative current collector.

[0032] A separator is placed between the positive and negative electrode plates to isolate them and prevent short circuits. The separator can be made of porous polyethylene (PE) or polypropylene (PP), etc.

[0033] In the manufacturing process of lithium-ion batteries, especially blade cells with a stacked structure, the capacity grading stage inevitably involves the generation of gas from electrolyte side reactions. If there is a gap between the electrode assembly and the inner wall of the casing, the gas can easily accumulate at the interface, forming localized debonding, which manifests as visible "black spots" upon disassembly. This not only causes increased internal resistance and capacity loss but may also induce lithium plating, seriously threatening battery safety and cycle life. To suppress this defect, the industry generally applies external restraint during capacity grading, adjusting the degree of cell compression by controlling the gap between the two pressure plates of the restraint fixture. However, the setting of the restraint gap is extremely sensitive: if the gap is too large, the gas cannot be discharged, resulting in black spots; if the gap is too small, permanent indentations may form on the casing, or even trigger the safety valve due to a sudden increase in internal pressure. The current technology for determining the constraint gap mainly relies on multi-gradient trial and error verification: for each new battery cell, several gap levels need to be set based on its measured thickness. After small-batch capacity testing, the interface and appearance are disassembled and evaluated, and then the optimal value is selected. This process not only takes up to several weeks and seriously slows down the pace of new product introduction, but also consumes dozens to hundreds of battery cells for each verification, which is costly. It is difficult to reuse them between different models. In addition, the judgment criteria rely on human experience, resulting in poor consistency.

[0034] To address this, embodiments of this application propose a method for determining the cell restraint gap. This method is also applied to the cell described in any of the foregoing embodiments to help the cell determine its required restraint gap. Please refer to... Figure 2 The method includes steps S1 and S2, as follows: S1. Obtain the cell thickness in the restraint direction of the cell to be restrained, which meets the preset requirements.

[0035] The suitability of the battery cell to be processed is assessed to confirm that it belongs to the type of battery cell to which this method is applicable—namely, a stacked structure battery cell with a relatively thin shell wall and an assembly ratio within a specific window range (e.g., a blade battery cell or a thin-walled square battery cell conforming to the VDA / MEB standard). Under this premise, the cell thickness in the restraint direction is obtained. This thickness can be a theoretical design value or a measured value obtained through online measurement equipment. The key is that it can accurately reflect the overall dimensional characteristics of the battery cell in the pressure direction.

[0036] S2. Based on the cell thickness, determine the restraint gap of the cell to be restrained through a preset nonlinear function relationship.

[0037] The obtained cell thickness is substituted into a pre-calibrated nonlinear function relationship. This function relationship is obtained through systematic experiments and data fitting on the capacity testing performance of a large number of similar cells under different restraint gaps (including interface black spots, shell indentations, internal pressure states, etc.). It can accurately map the inherent law between cell thickness and optimal restraint gap. The calculated restraint gap value serves as the basis for setting the closing distance between the two pressure plates of the restraint fixture, and is used to guide the mechanical restraint operation in the subsequent capacity testing process.

[0038] Therefore, the method adopted in this application abandons the traditional cyclical verification mode of "testing, disassembling, judging, and adjusting," transforming the determination of the constraint gap from experience-driven to model-driven. On the one hand, since multi-gradient small-batch trial production and manual disassembly are not required, the verification cycle for introducing cell models into the capacity grading process is significantly shortened, typically from several weeks to a single calculation. On the other hand, it avoids the consumption of a large number of cells during the verification process, effectively reducing R&D and trial production costs. More importantly, the constraint gap is objectively output by a functional relationship, eliminating the subjective bias of human judgment, ensuring a high degree of consistency in constraint parameters between different batches and production lines. This stabilizes the interface bonding quality between the electrode assembly and the casing, effectively suppresses the generation of black spot defects, and improves the internal resistance consistency, safety, and long-term cycle performance of the cell.

[0039] In some embodiments, the nonlinear functional relationship satisfies: H=-0.0503h 2 +2.5145h-10.802; Where H represents the restraint gap of the battery cell to be restrained, and h represents the thickness of the battery cell. Both H and h are in millimeters.

[0040] This functional relationship is not derived theoretically, but rather is an empirical model obtained through data fitting after conducting systematic constraint verification experiments on multiple typical blade battery cells (including various models of L4 and L6 sizes). Specifically, for each battery cell, given its casing thickness, at least three gradient constraint gaps (with a step size typically of 0.2 mm) are set. After capacity testing, the interface black spots, casing indentations, and internal pressure are evaluated through disassembly to select the constraint gap value with the best overall performance. The casing thickness of each battery cell and its corresponding optimal constraint gap are paired, and a quadratic polynomial regression analysis is performed to finally determine the functional expression with the above coefficients accurate to four decimal places.

[0041] In practical applications, this formula can be directly embedded into the production line MES system or the control unit of the restraint equipment. Once the shell thickness h of a certain batch of battery cells is determined, the system automatically substitutes it into the formula to calculate H≈14.76mm, and sets the fixture stroke accordingly.

[0042] Furthermore, to ensure the reliability of the calculation results and the robustness of the process, this embodiment further proposes control requirements for the manufacturing tolerances of relevant dimensions: the manufacturing tolerance a of the restraint gap H satisfies: a≤0.1mm, that is, the manufacturing tolerance a does not exceed 0.1mm. The manufacturing tolerance b of the cell thickness h satisfies: b≤0.1mm, that is, the manufacturing tolerance b also does not exceed 0.1mm.

[0043] It should be noted that the manufacturing tolerances a and b are not arbitrarily set, but are derived from sensitivity analysis: when the cell thickness h fluctuates by no more than 0.1 mm, the change in the restraint gap H is about 0.02 mm to 0.03 mm, which is much smaller than the gap tolerance allowed by the restraint process. The gap tolerance is usually ±0.1 mm. Therefore, within this tolerance range, the restraint gap H value output by the formula can still effectively ensure that there are no black spots on the interface and no damage to the shell.

[0044] Please see Figure 3 In some embodiments, the step of obtaining the cell thickness in the restraint direction of the cell to be restrained, which meets the preset requirements, further includes steps S11 to S17. Specifically: S11. Obtain the battery cell to be constrained.

[0045] S12. Measure the shell wall thickness of the battery cell to be constrained in the constraining direction.

[0046] Steps S11 and S12 are as follows: First, take the battery cell to be processed as the object; then, measure the thickness of the shell wall on one side of the battery cell in the restraint direction (usually the thickness direction of the battery cell). This value can be obtained by using a micrometer, laser thickness gauge or online visual inspection system.

[0047] S13. Based on the relationship between the shell wall thickness and the preset wall thickness, determine whether the cell to be constrained meets the first preset requirement.

[0048] Next, the measured shell wall thickness is compared with a preset wall thickness threshold. If it does not exceed the threshold, the cell is determined to meet the first preset requirement; otherwise, it does not.

[0049] S14. Calculate the assembly ratio of the electrode group and the casing in the cell to be constrained.

[0050] At the same time, it is also necessary to calculate the assembly ratio of the battery cell, which refers to the assembly ratio between the electrode assembly installed in the housing and the width of the housing in the restraining direction.

[0051] Further, please refer to Figure 4 The step of calculating the assembly ratio of the electrode group to the casing in the cell to be constrained further includes steps S141 to S143. Specifically: S141. Measure and record the cell thickness and electrode group thickness of the cell to be constrained in the constraining direction.

[0052] First, for the acquired battery cell to be constrained, its overall cell thickness and the thickness of the internal electrode assembly after hot pressing are simultaneously measured in the constraining direction. The measured cell thickness is recorded, and this value will be used later to calculate the inner cavity width. This cell thickness is equivalent to the width of the cell shell in the constraining direction.

[0053] S142. Calculate the inner cavity width of the casing in the restraint direction based on the cell thickness and casing wall thickness.

[0054] Subsequently, based on the previously measured thickness of the shell wall on one side, the effective width of the inner cavity in this direction was calculated according to geometric relationships. Since the shell is a symmetrical structure, the inner cavity width is equal to the total thickness of the cell minus the sum of the thicknesses of the shell walls on both sides, that is, calculated according to the formula N=h−2×d, where h is the thickness of the cell and d is the thickness of the shell wall on one side.

[0055] S143. Calculate the assembly ratio based on the inner cavity width and the electrode assembly thickness.

[0056] Further dividing the electrode assembly thickness L by the inner cavity width N yields the assembly ratio q, calculated as q = L / N. This ratio accurately reflects the tightness of the electrode assembly within the housing cavity and is a core criterion for determining whether the battery cell falls within the applicable window of this application.

[0057] Step S14 uses the total cell thickness and the measured shell wall thickness to derive the inner cavity width, avoiding errors caused by directly measuring the narrow inner cavity; while the electrode assembly thickness is taken from the state after hot pressing and shaping, which is closer to the actual physical form during capacity testing. Through this series of quantitative calculations based on measured data, the determination of the assembly ratio no longer relies on empirical estimation or simple reference to design theoretical values, but is based on actual structural parameters, significantly improving the accuracy of screening.

[0058] S15. Based on the relationship between the assembly ratio and the preset assembly ratio, determine whether the battery cell to be constrained meets the second preset requirement.

[0059] The assembly ratio is compared with a preset assembly ratio range. If it falls within the range, the second preset requirement is determined to be met.

[0060] S16. If the battery cell to be restrained simultaneously meets the first preset requirement and the second preset requirement, then the battery cell to be restrained is determined to be a battery cell that meets the preset requirements.

[0061] S17. If the battery cell to be restrained does not meet the first preset requirement and / or the second preset requirement, then the battery cell to be restrained is determined to be a restrained battery cell that does not meet the preset requirements.

[0062] It should be noted that only when both of the above two judgment results are "satisfied" will the battery cell be finally confirmed as the object to which this application applies, that is, "a battery cell to be constrained that meets the preset requirements"; if either condition is not met, it will be classified as an inapplicable object and will not enter the subsequent function calculation process.

[0063] Since the functional relationship between the constraint gap and the cell structural parameters is calibrated under specific boundary conditions, once the cell exceeds this boundary (e.g., the casing is too thick leading to excessive rigidity, or the assembly ratio is too high resulting in no expansion margin for the electrode assembly), the gap value output by the original function will no longer be suitable, easily causing defects such as black spots or casing damage. By setting dual admission conditions before calculation, mismatched cells can be effectively intercepted, avoiding batch quality problems caused by misuse.

[0064] In some embodiments, the first preset requirement is: d ≤ D, where d represents the shell wall thickness, D represents the preset wall thickness, and D = 0.4 mm. The determination of D equal to 0.4 mm stems from research on the mechanical response of cells with different shell wall thicknesses during the restraint process: when the thickness of a single shell wall exceeds 0.4 mm, the shell rigidity is significantly enhanced, and the electrode assembly struggles to release stress through minute deformation during gas expansion. Even with appropriate restraint force, gas easily lingers at the interface, forming black spots. Cells with a wall thickness less than or equal to 0.4 mm possess sufficient flexibility, effectively conforming to the electrode assembly under external restraint without becoming unstable and deformed due to excessive thinness. Therefore, setting 0.4 mm as the upper limit ensures that the cell maintains both good interface response and structural integrity during the restraint process.

[0065] The second preset requirement is: Q1≤q≤Q2, where q represents the assembly ratio, Q1 represents the minimum value of the preset assembly ratio, and Q2 represents the maximum value of the preset assembly ratio, with Q1=90% and Q2=93%. When the assembly ratio is below 90%, there is a large gap between the electrode assembly and the inner wall of the casing. Even with the optimal restraint gap calculated using the method of this application, the gas generated during the capacity separation process cannot be completely discharged, leading to frequent black spot defects. When the assembly ratio is above 93%, the electrode assembly is in a highly compressed state. After the gas is generated during capacity separation, the internal pressure rises rapidly. If restraint is applied again, the internal pressure is very likely to exceed the safety valve opening threshold, causing the cell to depressurize and fail. Only when the assembly ratio is between 90% and 93%, such as a cell with an assembly ratio of 92%, can the functional relationship disclosed in the foregoing embodiments be applied.

[0066] In some embodiments, after the step of determining that the battery cell to be constrained is a battery cell that meets the preset requirements if the battery cell to be constrained simultaneously meets the first preset requirement and the second preset requirement, the method further includes: S16a. Obtain the cell thickness recorded when calculating the assembly ratio of the cell to be constrained, which meets the preset requirements.

[0067] After determining whether the battery cell meets the preset requirements, if the cell is confirmed to be suitable, the calculation of the restraint gap must proceed. It is important to note that the cell thickness used here is not a remeasurement, but rather directly uses the cell thickness data that was simultaneously acquired and recorded during the aforementioned assembly ratio calculation. Specifically, while measuring the electrode thickness to calculate the assembly ratio, the system or operator has already measured the overall thickness of the same cell in the restraint direction and stored or marked this value. When the determination result is "meets the preset requirements," the corresponding cell thickness value is extracted from this record and used as the input parameter for subsequent calculation of the restraint gap using a nonlinear function relationship.

[0068] By setting step S16a, on the one hand, the redundancy and potential errors caused by repeatedly measuring the thickness of the same cell in a short period of time are avoided, especially in automated production lines where multiple positioning or clamping may introduce positional deviations; on the other hand, it ensures that the cell thickness data on which the assembly ratio calculation and the restraint gap calculation are based are completely consistent, eliminating logical contradictions caused by the difference between the two measurements.

[0069] In some embodiments, the cell thickness h of the cell to be constrained in the constraining direction satisfies the preset requirements: 14mm≤h≤20mm.

[0070] When the cell thickness is less than 14 mm, the overall rigidity of the casing is relatively low, making it prone to unexpected bending or local collapse during the restraint process. Even with accurate gap calculations, it is still difficult to maintain a uniform fit. When the thickness exceeds 20 mm, the number of electrode layers increases significantly, leading to increased complexity in gas production and internal resistance distribution. The original function relationship suffers from prediction bias because it does not cover data for such thick cells, resulting in restraint gaps that are too large or too small, which in turn causes black spots or indentations. In contrast, for cells in the 14 mm to 20 mm range, such as a 17 mm cell, the structural characteristics and gas production behavior are highly consistent with the samples used in the modeling, and the restraint gap output by the function can accurately match actual requirements.

[0071] In practice, the condition of 14mm≤h≤20mm can be used as the third screening criterion for cell access, together with the wall thickness not greater than 0.4 mm and the assembly ratio between 90% and 93%, to form a complete applicability judgment system.

[0072] For example, to establish a method for determining the restraint gap applicable to a specific type of battery cell, this application first verifies the restraint parameters of several typical battery cells through systematic experiments, and fits a reliable functional relationship based on the verification results. In specific implementation, five blade battery cells, including CL23, CL08, CL33, CL34, and CL04, were selected as experimental subjects. Their shell thicknesses range from 14.4 mm to 17.7 mm, all meeting the structural conditions of a wall thickness not exceeding 0.4 mm and an assembly ratio within the range of 90% to 93%. For each battery cell, a unified restraint procedure was adopted: the battery cell was placed in a standard restraint tray, and restraint force was applied using equipment or a torque wrench. While controlling the restraint stroke, the restraint force was monitored in real time to ensure that the restraint force did not exceed 4000N to prevent shell deformation or safety valve opening. The restraint gap was set with three gradients in 0.2 mm increments; for example, the CL23 battery cell was tested at 14.0 mm, 14.2 mm, and 14.4 mm respectively. After capacity testing, each group of samples was comprehensively evaluated.

[0073] The evaluation included three aspects: first, disassembling and observing the interface between the electrode and the separator to determine the gas venting effect; second, visually and tactilely inspecting the aluminum shell surface for permanent indentations to assess the appearance yield; and third, monitoring the changes in internal pressure during capacity testing. If an abnormal increase in internal pressure caused the safety valve to open, it was considered a serious failure. Based on these three indicators, the optimal restraint gap value for each cell was selected. Subsequently, nonlinear regression analysis was performed on the five sets of data points for "shell thickness h" and "optimal restraint gap H". After multiple fitting comparisons, the quadratic polynomial function was finally determined: H = -0.0503h. 2 +2.5145h-10.802 can describe the mapping relationship between the two with high confidence. This formula serves as the core calculation model of this application, used for the rapid determination of the restraint gap in subsequent similar battery cells. It should be noted that in actual production line applications, after setting the restraint gap, it is also necessary to use vernier calipers to randomly check the actual gap of 3 to 5 channels in the restraint tray to ensure that its deviation from the target value does not exceed 0.1mm, in order to verify the execution accuracy of the equipment.

[0074] The experimental verification results for various batteries are as follows: First, five blade-type battery cells—CL23, CL08, CL33, CL34, and CL04—were selected as experimental subjects. The lengths of CL23 and CL08 cells were 400mm, while the lengths of CL33, CL34, and CL04 cells were 600mm. The cell thickness, or rather the width of the casing in the constraint direction, was 14.4mm for CL23, 14.5mm for CL08, 15mm for CL33, 17.7mm for CL34, and 14.6mm for CL04.

[0075] Then, three gradient restraint gaps were set for each type of cell, with a gradient step size of 0.2mm for all five cell types. Specifically, the gradient restraint gaps for CL23 cells are 14mm, 14.2mm, and 14.4mm; for CL08 cells, they are 13.9mm, 14.1mm, and 14.3mm; for CL33 cells, they are 14.6mm, 14.8mm, and 15mm; for CL34 cells, they are 17.2mm, 17.4mm, and 17.6mm; and for CL04 cells, they are 14.5mm, 14.7mm, and 14.9mm.

[0076] Constraint verification was performed on each gradient of each cell. The verification results showed that for the CL23 cell, indentations appeared on the casing when the constraint gap was 14mm; black spots appeared at the electrode interface when the constraint gap was 14.4mm; and when the constraint gap was 14.2mm, the casing of the CL23 cell was in good condition, the electrode interface showed almost no black spots, and the internal pressure change of the cell was normal. Therefore, the optimal constraint gap for the CL23 cell was determined to be 14.2mm. Similarly, the optimal constraint gaps for the CL08 cell were determined to be 14.1mm, for the CL33 cell 14.8mm, for the CL34 cell 17.4mm, and for the CL04 cell 14.7mm.

[0077] By verifying the results through experiments, the following functional relationship can be fitted: H=-0.0503h 2 +2.5145h-10.802. By utilizing this functional relationship, the constraint gap of the battery cell that meets the preset conditions can be quickly determined, reducing the time and cost consumed by gradient verification.

[0078] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications or equivalent substitutions made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for determining the cell restraint gap, characterized in that, include: Obtain the cell thickness in the restraint direction of the cell to be restrained, which meets the preset requirements; Based on the cell thickness, the restraint gap of the cell to be restrained is determined by a preset nonlinear function relationship.

2. The method according to claim 1, characterized in that, The nonlinear functional relationship satisfies: H=-0.0503h 2 +2.5145h-10.802; Wherein, H represents the restraint gap of the battery cell to be restrained, and h represents the thickness of the battery cell; and / or, The manufacturing tolerance 'a' of the restraint gap satisfies: a ≤ 0.1 mm; and / or, The manufacturing tolerance b of the cell thickness satisfies: b≤0.1mm.

3. The method according to claim 1, characterized in that, The step of obtaining the cell thickness in the restraint direction of the cell to be restrained, which meets the preset requirements, includes: Obtain the battery cell to be constrained; Measure the shell wall thickness of the battery cell to be constrained in the constraining direction; Based on the relationship between the shell wall thickness and the preset wall thickness, determine whether the battery cell to be constrained meets the first preset requirement; Calculate the assembly ratio of the electrode group to the housing in the cell to be constrained; Based on the relationship between the assembly ratio and the preset assembly ratio, determine whether the battery cell to be constrained meets the second preset requirement; If the battery cell to be constrained simultaneously meets both the first preset requirement and the second preset requirement, then the battery cell to be constrained is determined to be a battery cell that meets the preset requirements. If the battery cell to be constrained does not meet the first preset requirement and / or the second preset requirement, then the battery cell to be constrained is determined to be a constrained battery cell that does not meet the preset requirements.

4. The method according to claim 3, characterized in that, The first preset requirement is: d≤D, where d represents the shell wall thickness, D represents the preset wall thickness, and D=0.4mm; The second preset requirement is: Q1≤q≤Q2, where q represents the assembly ratio, Q1 represents the minimum value of the preset assembly ratio, Q2 represents the maximum value of the preset assembly ratio, and Q1=90% and Q2=93%.

5. The method according to claim 3, characterized in that, The step of calculating the assembly ratio of the electrode group to the housing in the cell to be constrained includes: Measure the cell thickness and electrode assembly thickness of the cell to be constrained in the constraining direction and record the cell thickness; Calculate the inner cavity width of the housing in the restraint direction based on the cell thickness and the housing wall thickness; The assembly ratio is calculated based on the inner cavity width and the electrode assembly thickness; and / or, The formula for calculating the assembly ratio is: q = L / N, where q represents the assembly ratio, L represents the electrode assembly thickness, and N represents the inner cavity width; The formula for calculating the inner cavity width N is: N = h - 2 × d, where h represents the cell thickness and d represents the shell wall thickness.

6. The method according to claim 5, characterized in that, After the step of determining that the battery cell to be constrained is a battery cell that meets the preset requirements if the battery cell to be constrained simultaneously meets both the first preset requirement and the second preset requirement, the method further includes: Obtain the cell thickness recorded when calculating the assembly ratio of the cell to be constrained, which meets the preset requirements.

7. The method according to any one of claims 1-6, characterized in that, The cell thickness h of the cell to be constrained in the constraining direction satisfies the preset requirements as follows: 14mm≤h≤20mm.

8. A battery cell, characterized in that, The cell restraint gap is determined by the method for determining the cell restraint gap as described in any one of claims 1 to 7.

9. A battery pack, characterized in that, It includes at least one battery cell as described in claim 8.

10. An electrical appliance, characterized in that, include: Electricity-consuming entities; The battery pack as described in claim 9 is electrically connected to the power-consuming body.

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