A method, device, computer equipment and storage medium for assessing the risk of physical short circuit of a battery cell

Abstract

The present application provides a method for assessing the risk of physical short circuits in battery cells. The method fits the first functional relationship between the pressure on the diaphragm and the size of the foreign matter, and then fits the second functional relationship corresponding to different sharpness, and tests the relationship between the diaphragm pressure and the force with a more stringent acupuncture experiment. By combining the first functional relationship with the second functional relationship, the force can be associated with the size of the foreign matter to obtain a third functional relationship. A fourth functional relationship is established for diaphragms with different degrees of aging, and then a set of third functional relationships and fourth functional relationships corresponding to the most ideal and worst working conditions are combined to obtain a functional relationship between the critical size and critical sharpness of the foreign matter, so that the upper and lower boundaries of the foreign matter size can be selected when the sharpness is determined, which is helpful to take corresponding measures according to different ranges in each link of battery production, use and quality control to prevent short circuit risks.

Description

Technical Field

[0001] The present application relates to the field of battery safety technology, and in particular to a method, device, computer equipment and storage medium for assessing the risk of physical short circuit of a battery cell. Background Art

[0002] The safety of batteries has attracted much attention. The presence of foreign matter in raw materials or during the production process can cause battery safety risks. The main metal foreign matter is copper, iron, and stainless steel. These foreign matter mainly appear in the process of raw material synthesis, hardware knife cutting, and welding slag splashing. When foreign matter physically pierces or dissolves to form dendrites, it may pierce the diaphragm and cause a short circuit. With the use of battery cells, the risk of short circuit is also changing. In order to improve the quality and safety performance of battery cells, there is an urgent need for a method to evaluate the physical short circuit risk of battery cells over a certain life cycle to determine the risk of foreign matter (insoluble) piercing the diaphragm inside the battery cell for a long time. Summary of the invention

[0003] The purpose of this application is to solve at least one of the above-mentioned technical defects, and in particular to provide a solution that can determine the physical short circuit risk of a battery cell within a certain life cycle.

[0004] In a first aspect, the present application provides a method for assessing the risk of physical short circuit of a battery cell, comprising:

[0005] Based on the results of the first experiment, a first functional relationship is obtained by fitting; the first functional relationship is the relationship between the pressure on the diaphragm and the size of the insoluble foreign matter in the battery cell under the set preload;

[0006] Based on the results of the second experiment, multiple sets of second functional relationships are fitted; the second functional relationship corresponds to the set sharpness one by one, and the second functional relationship is the relationship between the force and the pressure on the diaphragm when the outer surface of the battery cell is acted upon by a needle-shaped object with a corresponding set sharpness under a set preload;

[0007] The first functional relationship is combined with each second functional relationship to obtain a third functional relationship corresponding to each set sharpness; the third functional relationship is the relationship between the size of the insoluble foreign matter and the force acting on the diaphragm under the set preload force of the battery cell;

[0008] Based on the results of the third experiment, multiple sets of fourth functional relationships are fitted; the fourth functional relationship corresponds to the set aging degree one by one, and the fourth functional relationship is the relationship between the sharpness of the needle-like object acting on the diaphragm and the force required for the needle-like object to pierce the diaphragm when the battery cell is opened to the diaphragm layer and a diaphragm corresponding to the set aging degree is selected;

[0009] The third functional relationship with the smallest set sharpness and the fourth functional relationship with the smallest set aging degree are combined to obtain an upper limit short-circuit relationship, and the third functional relationship with the largest set sharpness and the fourth functional relationship with the largest set aging degree are combined to obtain a lower limit short-circuit relationship; both the upper limit short-circuit relationship and the lower limit short-circuit relationship reflect the relationship between the critical size and critical sharpness of the insoluble foreign matter;

[0010] The target sharpness is input into the upper short-circuit relationship and the lower short-circuit relationship to determine the control range of the insoluble foreign matter.

[0011] In one embodiment, inputting the target sharpness into the upper short-circuit relationship and the lower short-circuit relationship to determine the control range of the insoluble foreign matter includes: inputting the target sharpness into the upper short-circuit relationship to obtain a first critical size, and inputting the target sharpness into the lower short-circuit relationship to obtain a second critical size;

[0012] The range larger than the first critical size is determined as the immediate short circuit range, the range between the first critical size and the second critical size is determined as the delayed short circuit range, and the range smaller than the second critical size is determined as the safety range.

[0013] In one embodiment, based on the result of the first experiment, fitting the first functional relationship includes:

[0014] The battery cell is opened to the inner layer area of ​​the negative electrode layer, and a plurality of insoluble foreign objects of different sizes are placed and pressure-sensitive paper is set;

[0015] Restoring the battery cell to a bare battery cell state, applying a clamping force of a set pre-tightening force magnitude to the battery cell, and maintaining the first set time length;

[0016] The pressure-sensitive paper is taken out, and the pressure corresponding to each insoluble foreign body is determined according to the pressure-sensitive paper to obtain a plurality of first data points;

[0017] A first functional relationship is obtained by fitting each first data point.

[0018] In one embodiment, based on the results of the second experiment, multiple sets of second functional relationships are fitted, including:

[0019] For any set sharpness, a pressure-sensitive paper is placed on the outer surface of the cell, and a clamping force of the set preload magnitude is applied to the cell;

[0020] Using needle-shaped objects with currently set sharpness to act on the outer surface of the battery cell with different forces;

[0021] Record the magnitude of each force, and determine the pressure at the action position according to the pressure-sensitive paper to obtain a plurality of second data points;

[0022] A second functional relationship corresponding to the currently set sharpness is obtained by fitting the second data points.

[0023] In one embodiment, based on the results of the third experiment, multiple sets of fourth functional relationships are fitted, including:

[0024] For any set aging degree, open the battery cell to the diaphragm layer and select the diaphragm with the current set aging degree;

[0025] Using needles with different sharpness to act on the diaphragm with gradually increasing force until the needle pierces the diaphragm, recording the magnitude of the force during piercing, and obtaining a plurality of third data points;

[0026] A fourth functional relationship corresponding to the currently set aging degree is obtained by fitting the third data points.

[0027] In one embodiment, the third experiment further includes:

[0028] Use a multimeter to connect the needle-shaped object and the negative electrode layer of the battery cell respectively;

[0029] When the multimeter shows that the needle-like object is conductive to the negative electrode layer of the battery cell, it is determined that the needle-like object has pierced the diaphragm.

[0030] In one embodiment, the diaphragm with a set aging degree includes a diaphragm in an initial state and at least one diaphragm stored at a set temperature for a set period of time.

[0031] In a second aspect, the present application provides a battery cell physical short circuit risk assessment device, comprising:

[0032] A first fitting module is used to fit a first functional relationship based on the result of the first experiment; the first functional relationship is the relationship between the pressure on the diaphragm and the size of the insoluble foreign matter in the battery cell under a set preload;

[0033] The second fitting module is used to fit multiple sets of second functional relationships based on the results of the second experiment; the second functional relationship corresponds to the set sharpness one by one, and the second functional relationship is the relationship between the force and the pressure on the diaphragm when the outer surface of the battery cell is acted upon by a needle-shaped object with a corresponding set sharpness under the set preload force;

[0034] The first analytical module is used to combine the first functional relationship with each second functional relationship to obtain a third functional relationship corresponding to each set sharpness; the third functional relationship is the relationship between the size of the insoluble foreign matter and the force acting on the diaphragm under the set preload of the battery cell;

[0035] A third fitting module is used to fit multiple sets of fourth functional relationships based on the results of the third experiment; the fourth functional relationship corresponds to the set aging degree one by one, and the fourth functional relationship is the relationship between the sharpness of the needle-like object acting on the diaphragm and the force required for the needle-like object to pierce the diaphragm when the battery cell is opened to the diaphragm layer and a diaphragm corresponding to the set aging degree is selected;

[0036] The second analytical module is used to combine the third functional relationship with the minimum set sharpness with the fourth functional relationship with the minimum set aging degree to obtain an upper limit short-circuit relationship, and combine the third functional relationship with the maximum set sharpness with the fourth functional relationship with the maximum set aging degree to obtain a lower limit short-circuit relationship; both the upper limit short-circuit relationship and the lower limit short-circuit relationship reflect the relationship between the critical size and critical sharpness of the insoluble foreign matter;

[0037] The control and analysis module is used to input the target sharpness into the upper short-circuit relationship and the lower short-circuit relationship to determine the range of the insoluble foreign matter.

[0038] In a third aspect, the present application provides a computer device comprising one or more processors and a memory, wherein the memory stores computer-readable instructions, and when the computer-readable instructions are executed by one or more processors, the steps of the battery cell physical short circuit risk assessment method in any of the above-mentioned embodiments are executed.

[0039] In a fourth aspect, the present application provides a storage medium storing computer-readable instructions. When the computer-readable instructions are executed by one or more processors, the one or more processors execute the steps of the battery cell physical short circuit risk assessment method in any of the above-mentioned embodiments.

[0040] It can be seen from the above technical solutions that the embodiments of the present application have the following advantages:

[0041] Based on the physical short circuit risk assessment method of the battery cell in this embodiment, the first functional relationship between the pressure on the diaphragm and the size of the foreign body is fitted, and then the second functional relationship corresponding to different sharpness is fitted respectively, and the relationship between the pressure and the force of the diaphragm is tested by a more stringent acupuncture experiment. The first functional relationship and the second functional relationship are combined to establish a correlation between the force and the size of the foreign body, and a third functional relationship is obtained. In order to change the diaphragm according to the life cycle of the battery cell, a fourth functional relationship is established for the diaphragms with different aging degrees, and the relationship between the critical piercing force and the sharpness of the foreign body under the corresponding aging degree is obtained. Finally, a set of third functional relationships and fourth functional relationships corresponding to the most ideal and worst working conditions are combined to obtain the functional relationship between the critical size and critical sharpness of the foreign body, so that the control range of insoluble foreign bodies can be selected when the sharpness is determined, which is helpful to take corresponding measures according to different ranges in the production, use and quality control of batteries, prevent short circuit risks in advance, ensure the safety and stability of battery use, and improve the overall quality and performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0043] Figure 1 A schematic diagram of a flow chart of a method for assessing the risk of physical short circuit of a battery cell provided in one embodiment of the present application;

[0044] Figure 2 A schematic diagram of an upper limit short circuit relationship and a lower limit short circuit relationship in one embodiment of the present application;

[0045] Figure 3 This is a schematic diagram of a process for fitting a first functional relationship in one embodiment of the present application;

[0046] Figure 4 This is a schematic diagram of a first functional relationship in one embodiment of the present application;

[0047] Figure 5 This is a schematic diagram of a process for fitting a second functional relationship in one embodiment of the present application;

[0048] Figure 6 A schematic diagram of a second functional relationship in one embodiment of the present application;

[0049] Figure 7 This is a schematic diagram of a flow chart of fitting a fourth functional relationship in one embodiment of the present application;

[0050] Figure 8 A schematic diagram of a fourth functional relationship in one embodiment of the present application;

[0051] Fig. 9 An internal structure diagram of a computer device provided for one embodiment of the present application. DETAILED DESCRIPTION

[0052] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0053] See also Figure 1 The present application provides a method for assessing the risk of physical short circuit of a battery cell, comprising steps S102 to S114.

[0054] S102: Based on the result of the first experiment, a first functional relationship is obtained by fitting. The first functional relationship is the relationship between the pressure on the diaphragm and the size of the insoluble foreign matter in the battery cell under the set preload.

[0055] It can be understood that the battery cell includes a positive electrode layer, a negative electrode layer, and a diaphragm, which are formed by winding or laminating the positive electrode layer, the negative electrode layer and the diaphragm. The diaphragm is used to isolate the positive electrode layer and the negative electrode layer to keep them insulated. Insoluble foreign matter inside the battery cell may pierce the diaphragm under the action of internal expansion force or external pressure, destroying the insulation state, resulting in a physical short circuit. When there are insoluble foreign matter inside the battery cell, these foreign matter will squeeze the diaphragm, thereby changing the pressure on the diaphragm. The magnitude of the pressure is closely related to the size of the foreign matter. Larger foreign matter will cause greater pressure on the diaphragm under the same conditions. The first functional relationship is fitted based on the first experiment in order to quantify the change law between the size of the insoluble foreign matter in the battery cell and the pressure on the diaphragm. The first functional relationship can specifically be a quantitative relationship with the pressure on the diaphragm as the independent variable and the size of the insoluble foreign matter as the dependent variable. The first experiment here is carried out on a battery cell with a set preload applied. By applying the set preload, the expansion force during the charging and discharging process of the battery cell can be simulated to simulate the effect of the size of different insoluble foreign matter on the surface pressure under normal working conditions.

[0056] S104, based on the results of the second experiment, multiple sets of second functional relationships are fitted. The second functional relationship corresponds to the set sharpness one by one, and the second functional relationship is the relationship between the force and the pressure on the diaphragm when the outer surface of the battery cell is acted upon by a needle-shaped object with a corresponding set sharpness under the set preload force.

[0057] It can be understood that the sharpness in this embodiment is a quantitative index for measuring needle-like objects, which can comprehensively consider factors such as the needle angle, arc length and contact area with the diaphragm of the needle-like object. In order to facilitate the experiment, the diameter of the needle-like object can also be used directly to reflect the size of the sharpness. The smaller the diameter, the greater the sharpness. In order to utilize the effect of the needle-like equivalent foreign body on the diaphragm, the selected needle-like diameter should be of the same order of magnitude as the size of the foreign body targeted by the experiment. For example, if the size of the foreign body is 100μm, the diameter of the needle-like object should also be selected in this order of magnitude, such as 50 / 100 / 150 / 200μm. The second experiment here is carried out on the battery cell with a set preload. By applying the set preload, the expansion force during the charging and discharging process of the battery cell can be simulated to simulate the effect of the surface pressure caused by needle-like objects of different sharpness on the diaphragm under the change of force under normal working conditions. For each set sharpness, a second experiment is required, and the relationship between the force and the pressure on the diaphragm under the action of the steel needle of this sharpness can be observed. Specifically, the second functional relationship may be a quantitative relationship in which the force applied by the needle-shaped object is the independent variable and the pressure applied to the diaphragm is the dependent variable.

[0058] In this embodiment, the needle-like object is used to apply force from the surface of the battery cell mainly because: on the one hand, the contact area between the needle tip of the needle-like object and the battery cell is smaller than the contact area of ​​the foreign object, and the needle tip of the needle-like object is sharper than the foreign object. Using the needle tip of the needle-like object to simulate the foreign object is a more stringent experimental condition, which can replace the foreign object placed inside the battery cell for testing, ensuring that the test results are accurate and reliable. On the other hand, it is easier and more direct to control the size of the force from the outside, which facilitates the experiment.

[0059] S106, the first functional relationship is combined with each second functional relationship to obtain a third functional relationship corresponding to each set sharpness. The third functional relationship is the relationship between the size of the insoluble foreign matter and the force acting on the diaphragm under the set preload force of the battery cell.

[0060] It can be understood that the first functional relationship reveals the influence of the size of foreign matter in the battery cell on the diaphragm pressure, while the second functional relationship reflects the relationship between the force and the diaphragm pressure under the action of a needle-shaped object with a set sharpness. If the first functional relationship is in the form of R=f1(p) (where p represents the pressure on the diaphragm and R represents the size of the foreign matter), the second functional relationship corresponding to a certain set sharpness is p=f2(F) (where p represents the pressure on the diaphragm and F represents the force), the pressure on the diaphragm in the first and second functional relationships represents the same physical quantity, so they can be combined as R=f1(f2(F)), that is, a third functional relationship can be obtained. The third functional relationship is a quantitative relationship with the force as the independent variable and the size of the insoluble foreign matter as the dependent variable. Although the force here is not directly applied to the diaphragm, since the electrode layers of the battery cell have a weak effect on the force dissipation, and the external acupuncture is a more stringent experimental condition, the third functional relationship can be equivalent to the quantitative relationship between the size of the insoluble foreign matter and the local force on the diaphragm under a set preload environment.

[0061] S108, based on the results of the third experiment, multiple sets of fourth functional relationships are fitted. The fourth functional relationship corresponds to the set aging degree one by one, and the fourth functional relationship is the relationship between the sharpness of the needle-like object acting on the diaphragm and the force required for the needle-like object to pierce the diaphragm when the battery cell is opened to the diaphragm layer and a diaphragm corresponding to the set aging degree is selected.

[0062] It can be understood that the degree of aging is a state description that reflects the change in the performance of the diaphragm in the battery cell as the use time, the number of charge and discharge cycles and other factors change. During long-term use, the diaphragm will be affected by factors such as electrolyte erosion, temperature changes, and repeated internal stress, resulting in the gradual deterioration of its physical and chemical properties. The higher the degree of aging, the weaker its ability to resist puncture and deformation. This experiment uses diaphragms with different degrees of aging to simulate different conditions of the battery cell within a certain life cycle. The third experiment in this embodiment is to directly test the puncture resistance of diaphragms with different degrees of aging to foreign objects of various sharpness. The diaphragm structure with a high degree of aging becomes relatively fragile, and only a needle-like object with a smaller sharpness can pierce it with a smaller force; while the diaphragm with a low degree of aging is relatively more resistant to puncture, and a sharper needle-like object or a greater force is required to pierce it. The fourth functional relationship corresponding to a variety of set aging degrees is tested by the third experiment, that is, to find out the inherent connection between the sharpness of the needle-like object and the force required to pierce the diaphragm under different degrees of aging. Specifically, the fourth functional relationship may be a quantitative relationship in which the sharpness of the needle-like object is the independent variable and the force required for piercing the diaphragm is the dependent variable.

[0063] S110, the third functional relationship with the minimum set sharpness and the fourth functional relationship with the minimum set aging degree are combined to obtain an upper limit short-circuit relationship, and the third functional relationship with the maximum set sharpness and the fourth functional relationship with the maximum set aging degree are combined to obtain a lower limit short-circuit relationship. Both the upper limit short-circuit relationship and the lower limit short-circuit relationship reflect the relationship between the critical size and critical sharpness of the insoluble foreign matter.

[0064] It can be understood that the fourth functional relationship is the dividing line that distinguishes whether the diaphragm is punctured. Starting from the point on the fourth functional relationship, keeping the sharpness unchanged and increasing the force will mean that the diaphragm is punctured, and reducing the sharpness means that the diaphragm is not punctured. Therefore, the actual force and actual sharpness of the foreign matter in the battery cell are quantified into a coordinate point. If the coordinate point is located in the area above the fourth functional relationship, it means that the battery cell has a physical short circuit risk, and there is no risk below. However, the fourth functional relationship is related to the force. It is difficult to directly test the force that the diaphragm is subjected to during the actual production and use of the battery cell, so it is difficult to directly rely on the fourth functional relationship to determine the physical short circuit risk status of the battery cell. However, the third functional relationship obtained in step S108 of this embodiment is related to the applied force and the size of the insoluble foreign matter, and the size of the insoluble foreign matter can be measured and controlled. As long as the size of the insoluble foreign matter is determined, the magnitude of the applied force on the diaphragm can be inferred based on the third functional relationship. Further assuming the sharpness of the insoluble foreign matter, a data point consisting of the size and sharpness of the insoluble foreign matter can be obtained. Based on the positional relationship between the data point and the fourth functional relationship, it can be determined whether the battery cell has a risk of physical short circuit.

[0065] Since both the third functional relationship and the fourth functional relationship are related to the applied force, with the applied force as a bridge, the third functional relationship and the fourth functional relationship can be combined to obtain a dividing line for distinguishing whether there is a risk of physical short circuit. As in the above example, the third functional relationship can be expressed in the form of a mathematical expression of R=f1(f2(F)), and the fourth functional relationship can be F=f3(S) (where S represents sharpness and F represents applied force). The third functional relationship and the fourth functional relationship can be combined to obtain R=f1(f2(f3(S))), which becomes a quantitative relationship in which the critical sharpness when the diaphragm is pierced is the independent variable and the critical size of the insoluble foreign matter is the dependent variable. Furthermore, this embodiment needs to select a set of third functional relationships and fourth functional relationships corresponding to the two most extreme working conditions from multiple third functional relationships and fourth functional relationships for combination.

[0066] Specifically, the battery cell has the strongest puncture resistance under the most ideal working conditions, and the critical value under the most ideal working conditions represents the upper limit of the battery cell's puncture resistance. In the actual use scenario of the battery cell, the best situation is that the sharpness of the foreign matter inside the battery cell is as low as possible, and the aging degree of the diaphragm is also at the lowest level, that is, the diaphragm still maintains a good performance state. Setting the minimum sharpness means that the ability of foreign matter to damage the diaphragm is relatively weak, and the minimum aging degree means that the diaphragm's own structural integrity, strength and other performance are in the best state, and it can better withstand possible external destructive factors. Therefore, for the most ideal working conditions, the third function relationship with the minimum sharpness and the fourth function relationship with the minimum aging degree will be selected to be combined, and the upper limit short-circuit relationship will be obtained.

[0067] The upper limit short circuit relationship obtained by combining the fourth function relationship with the minimum sharpness and the third function relationship with the minimum aging degree is actually describing the critical correspondence between factors such as foreign body size and sharpness under ideal conditions. It is equivalent to defining a dangerous boundary of foreign body-related situations that the battery cell can tolerate under the most ideal conditions. As long as the actual situation exceeds the range defined by the upper limit short circuit relationship, it means that the battery cell has entered the risk area of ​​short circuit.

[0068] The battery cell has the weakest puncture resistance under the worst working conditions, and the critical value under the worst working conditions represents the lower limit of the battery cell's puncture resistance. In the actual use scenario of the battery cell, the worst case scenario is that the foreign matter inside the battery cell is the sharpest, and at the same time, the aging degree of the diaphragm is at the highest level, that is, the performance state of the diaphragm has decayed. Setting the sharpness to the maximum means that the ability of foreign matter to damage the diaphragm is relatively the strongest, and the maximum aging degree means that the structure of the diaphragm itself is the most fragile. Therefore, for the most ideal working conditions, the third function relationship with the maximum sharpness and the fourth function relationship with the maximum aging degree will be selected together, and the result will be a lower limit short-circuit relationship.

[0069] The lower limit short circuit relationship is obtained by combining the fourth function relationship with the maximum sharpness and the third function relationship with the maximum aging degree. This relationship shows the critical correspondence between factors such as foreign body size and sharpness under harsh conditions. It is equivalent to defining a safety boundary where the battery cell can still maintain under the worst conditions. As long as the actual situation is within the range defined by this lower limit short circuit relationship, it means that the battery cell is still in a relatively safe state. The upper limit short circuit relationship and the lower limit short circuit relationship can be referred to Figure 2 , Figure 2 The lower limit short-circuit relationship in is obtained under the condition that the sharpness is set to a maximum of 50 μm and the separator is stored at 60° C. for 14 days. Figure 2The upper limit short-circuit relationship is obtained under the condition that the minimum sharpness is set to 200μm and the diaphragm is in the BOL (Beginning of Life) state.

[0070] S112, inputting the target sharpness into the upper limit short circuit relationship and the lower limit short circuit relationship to determine the control range of the insoluble foreign matter.

[0071] Specifically, the target sharpness is input into the upper short-circuit relationship to obtain the first critical size, and the target sharpness is input into the lower short-circuit relationship to obtain the second critical size. The range greater than the first critical size is determined as the immediate short-circuit range, the range between the first critical size and the second critical size is determined as the delayed short-circuit range, and the range less than the second critical size is determined as the safety range. The control range includes the immediate short-circuit range, the delayed short-circuit range and the safety range. The first critical size and the second critical size corresponding to each target sharpness are determined, so that the size of the insoluble foreign matter can be determined according to each target sharpness to achieve the control of the foreign matter.

[0072] It can be understood that the target sharpness is the specific sharpness targeted during physical short circuit analysis. This value can be determined based on factors such as the actual battery cell application scenario and possible foreign matter. For example, for a specific model of battery, a typical target sharpness can be determined by analyzing the characteristics of foreign matter that may be mixed into its production environment and use environment. Figure 2 As shown, Figure 2In the above, the diameter of the insoluble foreign matter is used to reflect the sharpness, and the height of the insoluble foreign matter is used to reflect the size. It is worth mentioning that the larger the diameter, the smaller the sharpness, which is somewhat different from the expression of other positive correspondences. The diameter mainly refers to the length of the cross section of the insoluble foreign matter parallel to the diaphragm, and the height mainly refers to the distance perpendicular to the diaphragm. When the target sharpness is input into the upper short-circuit relationship, it is actually based on this specific sharpness to explore the maximum size of the insoluble foreign matter that the battery cell can tolerate under this sharpness, that is, the first critical size. Once the size of the foreign matter exceeds this value, according to the control range of the short-circuit area and the safe area defined earlier, the battery cell will enter the risk range of immediate short circuit. The second critical size obtained by inputting the target sharpness into the lower short-circuit relationship means that under the same sharpness conditions, when the size of the foreign matter is less than this value, the battery cell is in a safe state and will not cause a short circuit due to this foreign matter. The range between these two critical dimensions is a transition state, that is, the delayed short-circuit range, which means that although the risk of short circuit caused by foreign matter will gradually increase with the aging of the diaphragm, that is, with the passage of time and changes in the internal conditions of the battery cell, the presence of the foreign matter will cause the battery cell to gradually develop into a short circuit. In the actual production and use process, as long as the sharpness to be analyzed is determined, the puncture resistance of the diaphragm in a certain life cycle can be analyzed based on the three determined numerical ranges, so that corresponding control regulations can be formulated during production and use. For example, when the first critical dimension obtained when the target sharpness is 0 is 130μm, and the second critical dimension is 110μm, then in the production control process, it can be set to control the flow of foreign matter above 110μm into the market to improve the safety and reliability of the battery cell.

[0073] Based on the physical short circuit risk assessment method of the battery cell in this embodiment, the first functional relationship between the pressure on the diaphragm and the size of the foreign body is first fitted, and then the second functional relationship corresponding to different sharpness is fitted respectively, and the relationship between the pressure on the diaphragm and the force is tested by a more stringent acupuncture experiment. The first functional relationship and the second functional relationship are combined to establish a correlation between the force and the size of the foreign body. In order to establish a correlation between the critical puncture force and the sharpness of the foreign body under the corresponding aging degree according to the changes in the diaphragm during the life cycle of the battery cell. Finally, a set of third functional relationships and fourth functional relationships corresponding to the most ideal and worst working conditions are combined to obtain the functional relationship between the critical size and critical sharpness of the foreign body, so that the upper and lower boundaries of the foreign body size can be selected when the sharpness is determined, which is helpful to take corresponding measures according to different ranges in each link of battery production, use and quality control, prevent short circuit risks in advance, ensure the safety and stability of battery use, and improve the overall quality and performance.

[0074] In one embodiment, see Figure 3 Based on the result of the first experiment, fitting to obtain a first functional relationship includes steps S302 to S308.

[0075] S302, opening the battery cell to the inner layer area of ​​the negative electrode layer, placing a plurality of insoluble foreign objects of different sizes and setting pressure-sensitive paper.

[0076] It can be understood that the battery cell is generally made by a winding process. The negative electrode layers will overlap each other during the winding process. The inner layer area of ​​the negative electrode layer refers to the spatial range close to the inside of the battery cell and at a deeper position of the negative electrode layer. The reason for choosing this area for operation is that it can better simulate the environment in which foreign matter actually exists inside the battery cell and affects components such as the diaphragm. In a specific embodiment, the core can be opened to the fifth circle of the negative electrode layer. Insoluble foreign matter usually refers to foreign impurities that will not dissolve in the normal electrolyte environment of the battery cell and always exist in solid form, such as tiny metal particles mixed in during the production process. In the first experiment, it can be stainless steel particles. Foreign matter of different sizes will exert different pressures on the diaphragm due to different factors such as the contact area with the surrounding area and its own weight. Placing multiple insoluble foreign matter of different sizes can collect multiple data points required for fitting in one experiment, thereby improving experimental efficiency.

[0077] In a specific embodiment, multiple insoluble foreign bodies can be selected according to a set size gradient. The set size gradient refers to a pre-planned, regularly changing range and interval of foreign body size changes. The set size gradient can be 50 μm, and the size of the insoluble foreign bodies finally placed can include 50 / 100 / 150 / 200 μm. By setting a size gradient to select foreign bodies, it is possible to explore the quantitative relationship between this size change and pressure change in detail and in an orderly manner, laying the foundation for accurately fitting a reliable functional relationship. During the preparation process, it should be ensured that the shape and material of each foreign body are uniform. Except for the variable of size, other characteristics should be kept the same as much as possible to ensure the scientificity and accuracy of the experiment. These foreign bodies can be evenly placed in the corresponding positions of the inner layer area of ​​the negative electrode layer according to a certain layout and spacing. At the same time, the pressure-sensitive paper is properly attached near the position where the foreign body may exert pressure on it to ensure that the pressure-sensitive paper can fully and accurately receive the pressure applied by the foreign body.

[0078] In order to facilitate the detection of the pressure on the diaphragm, pressure-sensitive paper is used in this embodiment. Pressure-sensitive paper is a special material, and its structure is generally two layers, one layer of microcapsules wrapped with dyes, which burst when under pressure, and the other layer of dyes, which are exposed to form traces after the absorption microcapsules burst for observation. By comparing with the standard color card, the pressure at the contact position with the insoluble foreign matter can be determined.

[0079] S304, restoring the battery cell to a bare battery cell state, applying a clamping force of a set pre-tightening force magnitude to the battery cell, and maintaining the clamping force for a first set time period.

[0080] It can be understood that the bare cell state refers to the state in which only the key components such as the core positive electrode layer, negative electrode layer, and diaphragm are retained after the external packaging, protective shell and other auxiliary structures of the cell are removed. The winding structure of the cell was opened in step S302, so it needs to be restored in this step, so that the cell body can be operated and external force can be applied more directly, and it is also convenient to simulate the actual force environment of the cell. The application of preload can be achieved by clamping the cell with a perforated plywood, and the preset preload can be 25kN. The first set duration refers to the length of time that the clamping force is applied. The purpose of setting a certain duration is to allow the pressure of foreign matter on the pressure-sensitive paper inside the cell to be fully and stably displayed under the action of a stable preload, so as to ensure that the measured pressure data is reliable and can reflect the actual situation. The first set duration can be 2 minutes.

[0081] S306, taking out the pressure-sensitive paper, and determining the pressure corresponding to each insoluble foreign matter based on the pressure-sensitive paper, to obtain a plurality of first data points.

[0082] It can be understood that pressure-sensitive paper is a key medium for obtaining data on the pressure generated by insoluble foreign matter inside the battery cell. Each insoluble foreign matter will leave a mark at the corresponding position of the inductive paper under the action of the preload force. By comparing with the standard colorimetric card, the magnitude of the pressure caused by each insoluble foreign matter can be determined. Each first data point is composed of the size of the insoluble foreign matter and the magnitude of the pressure caused by it.

[0083] S308: Obtain a first functional relationship by fitting according to each first data point.

[0084] It is understandable that since we have obtained multiple first data points through the previous steps, these data points reflect the pressure corresponding to insoluble foreign matter of different sizes, but they are discrete and isolated data, and it is difficult to directly see the overall rules and trends from them. However, through the fitting method, using mathematical tools and algorithms, such as common linear fitting, polynomial fitting, etc., according to the distribution characteristics of the data points, to find a suitable function form, so that this function curve can be as close as possible to all data points, that is, to minimize the error between the law described by the function and the actual measured data. The first functional relationship obtained in this way can be used as a general regular expression for subsequent theoretical analysis and practical applications. Figure 4 The figure shows a schematic diagram of the first functional relationship obtained by linear fitting, in which the height of the insoluble foreign matter represents the size of the insoluble foreign matter.

[0085] In one embodiment, see Figure 5Based on the results of the second experiment, multiple sets of second functional relationships are fitted, including steps S502 to S508.

[0086] S502, for any set sharpness, placing pressure-sensitive paper on the outer surface of the battery cell, and applying a clamping force of a set pre-tightening force magnitude to the battery cell.

[0087] It can be understood that placing the pressure-sensitive paper on the outer surface of the battery cell and applying a clamping force of a set preload is mainly to prepare for the accurate measurement of pressure when the needle-like object acts later. The pressure-sensitive paper needs to fit tightly to the outer surface of the battery cell, so that when the needle-like object applies force, it can sense the pressure change in a timely and accurate manner and reflect the pressure value. The preload is set because there is a certain stress environment inside the battery cell during normal use, and setting the preload can simulate the existence of this stress. It can also be achieved by clamping the battery cell with a plywood with holes.

[0088] S504 , using a needle-shaped object with a currently set sharpness to act on the outer surface of the battery cell with forces of different magnitudes.

[0089] S506, recording the magnitude of each force, and determining the pressure at the action position according to the pressure-sensitive paper to obtain a plurality of second data points.

[0090] It can be understood that steps S502 to S508 are respectively implemented for a needle-like object with a set sharpness, and the currently set sharpness is the current sharpness. You can use a professional mechanical testing device, such as a high-precision pressure application device (tensile machine), to install the needle-like object on the force-applying end of the device. It is best to ensure that the axis of the needle-like object is perpendicular to the outer surface of the battery cell, so that the force can be evenly applied to the surface of the battery cell, avoiding uneven pressure distribution due to angle deviation and affecting the experimental results. Then, starting from a smaller force, gradually increase the force size according to a certain increment. Each time the force is applied, it must be maintained for a period of time (such as a few seconds) to allow the pressure to be stably transmitted and accurately sensed by the pressure-sensitive paper, and then replace the pressure-sensitive paper and perform the next application of different forces. During the whole process, carefully observe the state changes of the battery cell and the pressure-sensitive paper to ensure that the experiment is carried out safely and orderly. At the same time, record the size of the force applied each time to prepare for the subsequent acquisition of accurate data. The recorded force magnitude and the corresponding pressure value are taken as a set of data, and the data obtained under each different force action are recorded in this way in turn to ensure that multiple complete and accurate second data points are obtained.

[0091] S508: Obtain a second functional relationship corresponding to the currently set sharpness by fitting the second data points.

[0092] It can be understood that what is obtained through the previous experimental steps are just isolated and discrete second data points. Although these data points record the correspondence between the force and the pressure, it is difficult to directly see the overall and general laws and trends from them. However, through the fitting method, using mathematical tools and algorithms, such as common linear fitting, polynomial fitting, etc., according to the distribution characteristics of these data points, to find a suitable function form, so that this function curve can be as close as possible to all data points, that is, to minimize the error between the law described by the function and the actual measured data. The second function relationship obtained in this way can be used as a general law expression for subsequent theoretical analysis and practical applications. Figure 6 The figure shows a schematic diagram of three second function relationships obtained by linear fitting, and the three second function relationships are obtained based on steel needles with diameters of 100 / 150 / 200 μm, respectively.

[0093] In one embodiment, see Figure 7 Based on the results of the third experiment, multiple sets of fourth functional relationships are fitted, including steps S702 to S706.

[0094] S702, for any set aging degree, the battery cell is opened to the diaphragm layer, and a diaphragm with the current set aging degree is selected.

[0095] It can be understood that steps S702 to S706 are respectively implemented for a diaphragm with a set aging degree. For any set aging degree, the battery cell is opened to the diaphragm layer and a diaphragm with a corresponding aging degree is selected. The purpose is to conduct subsequent puncture experiments on the diaphragm in a specific aging state, so as to accurately explore the changes in the puncture resistance performance of the diaphragm under the aging degree.

[0096] Specifically, the corresponding diaphragm samples should be prepared according to the pre-set aging level classification standards. In order to better simulate the life cycle of the battery cell, the aging level is set to include the diaphragm in the initial state (BOL) and at least one diaphragm stored at a set temperature for a set time. Specifically, the battery in the BOL state can be kept at 60°C for 7 days and 14 days to obtain two diaphragm samples with set aging levels. Other accelerated aging experiments can also be used to simulate diaphragms with different aging levels. Then, select the appropriate battery cell sample, use professional disassembly tools, and carefully open the battery cell. During the operation, pay attention to avoid unnecessary damage to other parts of the battery cell and the diaphragm itself, and open it accurately to the diaphragm layer to expose the diaphragm completely. Then, from the prepared diaphragm samples marked with the corresponding set aging level, select the diaphragm that meets the current experimental requirements and replace it with the original diaphragm in the battery cell to ensure that it is installed in place and fits well with other parts of the battery cell.

[0097] S704, using needles with different sharpness to act on the diaphragm with gradually increasing force until the needle pierces the diaphragm, recording the magnitude of the force during piercing, and obtaining a plurality of third data points.

[0098] It can be understood that in this step, a needle with one sharpness is used and needles with different sharpness are used to act on the diaphragm with gradually increasing force until the diaphragm is pierced and the magnitude of the force when pierced is recorded, and the sharpness of the current needle and the corresponding force magnitude are used as a third data point, and then another needle with another sharpness is replaced and repeated to obtain another third data point. After obtaining multiple groups of third data points, the third experiment for the currently set aging degree is completed, and these third data points can be used to fit the fourth functional relationship corresponding to the currently set aging degree.

[0099] In order to determine whether the needle-like object has pierced the diaphragm, in a specific embodiment, a multimeter is used to connect the needle-like object and the negative electrode layer of the battery cell respectively. When the multimeter reflects that the needle-like object is conductive with the negative electrode layer of the battery cell, it is determined that the needle-like object has pierced the diaphragm, and the negative electrode layer is adjacent to the diaphragm with the currently set aging degree, so as to improve the detection accuracy. In order to simplify the method, the outermost diaphragm of the battery cell can be opened, and the diaphragm with the currently set aging degree can be set directly on the outermost negative electrode layer, and the positive electrode of the multimeter is connected to the needle-like object, and the negative electrode is connected to the outermost negative electrode layer. Under normal circumstances, the positive electrode layer and the negative electrode layer inside the battery cell are separated by a diaphragm, and the diaphragm plays an insulating role to prevent the positive and negative electrode layers from directly contacting to form a short circuit. At this time, if a multimeter is used to connect the needle-like object and the negative electrode layer of the battery cell, the circuit is in a disconnected state, and the multimeter cannot detect the current path, and it will not display conduction. However, when the needle-like object exerts force on the diaphragm and pierces the diaphragm in the experiment, the insulation function of the diaphragm is destroyed, forming a closed current path, and the multimeter can detect the formation of this path, thereby displaying the conduction state. In this way, we can use the multimeter to intuitively and accurately determine whether the needle-like object has successfully pierced the diaphragm during the experiment.

[0100] S706: Obtain a fourth functional relationship corresponding to the currently set aging degree by fitting the third data points.

[0101] It can be understood that what is obtained through the previous experimental steps are only many discrete third data points. Although these data record the correspondence between the sharpness of the needle and the force required to pierce the diaphragm, they are isolated and it is difficult to directly see the overall, general laws and trends from them. For example, as the sharpness of the needle changes linearly, the force required to pierce the diaphragm changes according to what law. It is not clear whether it is a linear relationship, a quadratic function relationship, or other more complex relationships. However, through the fitting method, with the help of mathematical tools and algorithms, such as common linear fitting, polynomial fitting, etc., according to the distribution characteristics of the data points, we look for a suitable function form, so that this function curve can be as close as possible to all data points, that is, to minimize the error between the law described by the function and the actual measured data. The fourth functional relationship obtained in this way can be used as a general law expression for subsequent theoretical analysis and practical applications. Figure 8 The figure shows the puncture force obtained by testing the diaphragm in the initial state with a needle diameter reflecting the sharpness, using 50 / 100 / 200 μm steel needles, and fitting the fourth function relationship using a quadratic function based on these data points.

[0102] In a second aspect, the present application provides a battery cell physical short circuit risk assessment device, including a first fitting module, a second fitting module, a first analysis module, a third fitting module, a second analysis module, a critical determination module and a range division module.

[0103] The first fitting module is used to fit a first functional relationship based on the result of the first experiment. The first functional relationship is the relationship between the pressure on the diaphragm and the size of the insoluble foreign matter in the battery cell under a set preload.

[0104] The second fitting module is used to fit multiple sets of second functional relationships based on the results of the second experiment. The second functional relationship corresponds to the set sharpness one by one, and the second functional relationship is the relationship between the force and the pressure on the diaphragm when the outer surface of the battery cell is acted upon by a needle-shaped object with a corresponding set sharpness under the set preload.

[0105] The first analytical module is used to combine the first functional relationship with each second functional relationship to obtain a third functional relationship corresponding to each set sharpness. The third functional relationship is the relationship between the size of the insoluble foreign matter and the force acting on the diaphragm under the set preload of the battery cell.

[0106] The third fitting module is used to fit multiple sets of fourth functional relationships based on the results of the third experiment. The fourth functional relationship corresponds to the set aging degree one by one. The fourth functional relationship is the relationship between the sharpness of the needle-like object acting on the diaphragm and the force required for the needle-like object to pierce the diaphragm when the battery cell is opened to the diaphragm layer and the diaphragm corresponding to the set aging degree is selected.

[0107] The second analytical module is used to combine the third functional relationship with the minimum set sharpness with the fourth functional relationship with the minimum set aging degree to obtain an upper limit short-circuit relationship, and combine the third functional relationship with the maximum set sharpness with the fourth functional relationship with the maximum set aging degree to obtain a lower limit short-circuit relationship. Both the upper limit short-circuit relationship and the lower limit short-circuit relationship reflect the relationship between the critical size and critical sharpness of the insoluble foreign matter.

[0108] The management and control analysis module is used to input the target sharpness into the upper limit short circuit relationship and the lower limit short circuit relationship to determine the range of the insoluble foreign matter.

[0109] For the specific limitations of the battery cell physical short circuit risk assessment device, please refer to the limitations of the battery cell physical short circuit risk assessment method mentioned above, which will not be repeated here. The various modules in the above-mentioned viewpoint sorting device can be implemented in whole or in part through software, hardware and their combination. The above-mentioned modules can be embedded in or independent of the processor in the computer device in the form of hardware, or can be stored in the memory in the computer device in the form of software, so that the processor can call and execute the operations corresponding to the above modules. It should be noted that the division of modules in the embodiment of the present application is schematic and is only a logical function division. There may be other division methods in actual implementation.

[0110] The present application provides a computer device, including one or more processors and a memory, wherein the memory stores computer-readable instructions, and when the computer-readable instructions are executed by the one or more processors, the steps of the battery cell physical short circuit risk assessment method in any of the above embodiments are executed.

[0111] Indicatively, Fig. 9 As shown, Fig. 9 A schematic diagram of the internal structure of a computer device provided in an embodiment of the present application. Fig. 9 The computer device 900 includes a processing component 902, which further includes one or more processors, and a memory resource represented by a memory 901, for storing instructions executable by the processing component 902, such as an application. The application stored in the memory 901 may include one or more modules, each corresponding to a set of instructions. In addition, the processing component 902 is configured to execute instructions to perform the steps of the battery cell physical short circuit risk assessment method of any of the above embodiments.

[0112] The computer device 900 may further include a power supply component 903 configured to perform power management of the computer device 900 , a wired or wireless model interface 904 configured to connect the computer device 900 to the model, and an input / output (I / O) interface 905 .

[0113] The present application provides a storage medium, in which computer-readable instructions are stored. When the computer-readable instructions are executed by one or more processors, the one or more processors execute the steps of the battery cell physical short circuit risk assessment method in any of the above embodiments.

[0114] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0115] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The various embodiments can be combined as needed, and the same or similar parts can refer to each other.

[0116] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for assessing the risk of physical short circuit of a battery cell, characterized in that: include: Based on the results of the first experiment, a first functional relationship is obtained by fitting; The first functional relationship is the relationship between the pressure on the diaphragm and the size of the insoluble foreign matter in the battery cell under the set preload; Based on the results of the second experiment, multiple sets of second functional relationships are obtained by fitting; the second functional relationships correspond to the set sharpness one by one, and the second functional relationship is the relationship between the force and the pressure on the diaphragm when the outer surface of the battery cell is acted upon by a needle-shaped object corresponding to the set sharpness under the set preload force; The first functional relationship is combined with each of the second functional relationships to obtain a third functional relationship corresponding to each of the set sharpnesses; the third functional relationship is the relationship between the size of the insoluble foreign matter and the force acting on the diaphragm under the set preload force of the battery cell; Based on the results of the third experiment, multiple groups of fourth functional relationships are fitted; the fourth functional relationships correspond to the set aging degrees one by one, and the fourth functional relationship is the relationship between the sharpness of the needle-like object acting on the diaphragm and the force required for the needle-like object to pierce the diaphragm when the battery cell is opened to the diaphragm layer and a diaphragm corresponding to the set aging degree is selected; The third functional relationship with the minimum set sharpness and the fourth functional relationship with the minimum set aging degree are combined to obtain an upper limit short-circuit relationship, and the third functional relationship with the maximum set sharpness and the fourth functional relationship with the maximum set aging degree are combined to obtain a lower limit short-circuit relationship; the upper limit short-circuit relationship and the lower limit short-circuit relationship both reflect the relationship between the critical size and critical sharpness of the insoluble foreign matter; The target sharpness is input into the upper limit short circuit relationship and the lower limit short circuit relationship to determine the control range of the insoluble foreign matter.

2. The method for assessing the risk of physical short circuit of a battery cell according to claim 1, characterized in that: The step of inputting the target sharpness into the upper limit short circuit relationship and the lower limit short circuit relationship to determine the control range of the insoluble foreign matter includes: Inputting the target sharpness into the upper short-circuit relationship to obtain a first critical dimension, and inputting the target sharpness into the lower short-circuit relationship to obtain a second critical dimension; A range larger than the first critical dimension is determined as an immediate short circuit range, a range between the first critical dimension and the second critical dimension is determined as a delayed short circuit range, and a range smaller than the second critical dimension is determined as a safety range.

3. The method for assessing the risk of physical short circuit of a battery cell according to claim 1, characterized in that: The fitting of the first functional relationship based on the result of the first experiment includes: Opening the battery cell to the inner layer area of ​​the negative electrode layer, placing a plurality of insoluble foreign matter of different sizes and setting pressure-sensitive paper; Restoring the battery cell to a bare battery cell state, applying a clamping force of the set pre-tightening force magnitude to the battery cell, and maintaining the first set time length; The pressure-sensitive paper is taken out, and the pressure corresponding to each of the insoluble foreign matter is determined according to the pressure-sensitive paper to obtain a plurality of first data points; The first functional relationship is obtained by fitting the first data points.

4. The method for assessing the risk of physical short circuit of a battery cell according to claim 1, characterized in that: Based on the results of the second experiment, multiple sets of second functional relationships are obtained by fitting, including: For any of the set sharpness, a pressure-sensitive paper is placed on the outer surface of the battery cell, and a clamping force of the set preload force is applied to the battery cell; Using needle-shaped objects with the currently set sharpness to act on the outer surface of the battery cell with different forces; Recording the magnitude of each force, and determining the pressure at the action position according to the pressure-sensitive paper, to obtain a plurality of second data points; The second functional relationship corresponding to the current set sharpness is obtained by fitting each of the second data points.

5. The method for assessing the risk of physical short circuit of a battery cell according to claim 1, characterized in that: Based on the results of the third experiment, multiple sets of fourth functional relationships are obtained by fitting, including: For any of the set aging degrees, the battery cell is opened to the diaphragm layer, and a diaphragm with the current set aging degree is selected; Using needles with different sharpness to act on the diaphragm with gradually increasing force until the needle pierces the diaphragm, recording the magnitude of the force during piercing, and obtaining a plurality of third data points; The fourth functional relationship corresponding to the current set aging degree is obtained by fitting the third data points.

6. The method for assessing the risk of physical short circuit of a battery cell according to claim 5, characterized in that: The third experiment also includes: Use a multimeter to connect the needle-shaped object and the negative electrode layer of the battery cell respectively; When the multimeter reflects that the needle-shaped object is in conduction with the negative electrode layer of the battery cell, it is determined that the needle-shaped object has pierced the diaphragm.

7. The method for assessing the risk of physical short circuit of a battery cell according to claim 1, characterized in that: The diaphragm with a set aging degree includes a diaphragm in an initial state and at least one diaphragm stored at a set temperature for a set period of time.

8. A battery cell physical short circuit risk assessment device, characterized in that: include: A first fitting module, used for fitting a first functional relationship based on the result of the first experiment; The first functional relationship is the relationship between the pressure on the diaphragm and the size of the insoluble foreign matter in the battery cell under the set preload; A second fitting module is used to fit multiple sets of second functional relationships based on the results of the second experiment; the second functional relationships correspond to the set sharpness one by one, and the second functional relationship is the relationship between the force and the pressure on the diaphragm when the outer surface of the battery cell is acted upon by a needle-shaped object corresponding to the set sharpness under the set preload force; A first analytical module is used to combine the first functional relationship with each of the second functional relationships to obtain a third functional relationship corresponding to each of the set sharpnesses; the third functional relationship is the relationship between the size of the insoluble foreign matter and the force acting on the diaphragm under the set preload force of the battery cell; A third fitting module is used to fit multiple groups of fourth functional relationships based on the results of the third experiment; the fourth functional relationships correspond to the set aging degrees one by one, and the fourth functional relationship is the relationship between the sharpness of the needle-like object acting on the diaphragm and the force required for the needle-like object to pierce the diaphragm when the battery cell is opened to the diaphragm layer and a diaphragm corresponding to the set aging degree is selected; The second analytical module is used to combine the third functional relationship with the minimum set sharpness with the fourth functional relationship with the minimum set aging degree to obtain an upper limit short-circuit relationship, and combine the third functional relationship with the maximum set sharpness with the fourth functional relationship with the maximum set aging degree to obtain a lower limit short-circuit relationship; the upper limit short-circuit relationship and the lower limit short-circuit relationship both reflect the relationship between the critical size and critical sharpness of the insoluble foreign matter; The control and analysis module is used to input the target sharpness into the upper short-circuit relationship and the lower short-circuit relationship to determine the range of the insoluble foreign matter.

9. A computer device, characterized in that: The method comprises one or more processors and a memory, wherein the memory stores computer-readable instructions, and when the computer-readable instructions are executed by the one or more processors, the steps of the method for assessing the risk of physical short circuit of a battery cell as described in any one of claims 1 to 7 are executed.

10. A storage medium, characterized in that: The storage medium stores computer-readable instructions, and when the computer-readable instructions are executed by one or more processors, the one or more processors execute the steps of the battery cell physical short circuit risk assessment method as described in any one of claims 1 to 7.

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