Method and equipment for evaluating safety of preset battery

Abstract

The method for evaluating the safety of the preset battery comprises the following steps: respectively carrying out extrusion test on a preset positive plate and a preset negative plate, and recording first displacement data corresponding to the preset positive plate and second displacement data corresponding to the preset negative plate; determining a first compression ratio based on the first initial thickness and the first displacement data of the preset positive plate; determining a second compression ratio based on a second initial thickness and second displacement data of the preset negative plate; based on the first initial thickness and the second initial thickness, respectively determining the total thickness of positive electrode material layers of all preset positive electrode plates and the total thickness of negative electrode material layers of all preset negative electrode plates in the preset battery; estimating a target deformation rate corresponding to the preset battery based on the total thickness of the positive electrode material layer, the first compression ratio, the total thickness of the negative electrode material layer and the second compression ratio; and evaluating the safety of the preset battery based on the target deformation rate and the limit deformation rate. And based on the pre-estimated target deformation rate and the obtained limit deformation rate, realizing safety evaluation of the preset battery.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a method and device for evaluating the safety of a preset battery. Background Art

[0002] As the energy storage battery with the highest energy density at present, lithium-ion batteries are widely used in various power tools, electric vehicles and various portable devices. However, lithium-ion batteries also have some safety issues, such as thermal runaway of lithium-ion batteries caused by mechanical abuse. At this time, the deformation of lithium-ion batteries will cause damage to the pole pieces, diaphragms and other structural parts inside the battery cell, thereby causing internal short circuits. At present, the ways to evaluate such safety risks of batteries include: heavy object impact method and extrusion method, that is, to measure the battery cell by heavy object impact or extrusion method. However, these evaluation methods have lags and cannot make safety judgments at the beginning of product design.

[0003] After the battery design is finalized, the produced batteries are subjected to re-impact or extrusion tests. If the test fails, the battery design needs to be readjusted, which will cause immeasurable losses to the manufacturer. Therefore, how to effectively evaluate the safety of batteries before production is a technical problem that needs to be solved urgently. Summary of the invention

[0004] The main technical problem solved by the present invention is to achieve effective evaluation of the safety of batteries before producing the batteries.

[0005] According to a first aspect, an embodiment provides a method for evaluating the safety of a preset battery, wherein the preset battery includes a plurality of preset positive electrode sheets and a plurality of preset negative electrode sheets, and the method includes:

[0006] Performing an extrusion test on the preset positive electrode sheet and the preset negative electrode sheet respectively, and recording first displacement data corresponding to the preset positive electrode sheet and second displacement data corresponding to the preset negative electrode sheet;

[0007] Determine a first compression ratio of the preset positive electrode sheet based on a first initial thickness of the preset positive electrode sheet and the first displacement data; determine a second compression ratio of the preset negative electrode sheet based on a second initial thickness of the preset negative electrode sheet and the second displacement data;

[0008] Based on the first initial thickness of the preset positive electrode sheet and the second initial thickness of the preset negative electrode sheet, respectively determine the total thickness of the positive electrode material layers of all the preset positive electrode sheets in the preset battery and the total thickness of the negative electrode material layers of all the preset negative electrode sheets in the preset battery;

[0009] Based on the total thickness of the positive electrode material layer, the first compression ratio, the total thickness of the negative electrode material layer and the second compression ratio, estimating a target deformation rate corresponding to the extrusion test of the preset battery;

[0010] Obtain the limit deformation rate corresponding to the reference battery;

[0011] Based on the target deformation rate and the limit deformation rate, the safety of the preset battery is evaluated.

[0012] According to a second aspect, an embodiment provides a device for evaluating the safety of a preset battery, the device comprising:

[0013] An acquisition unit, used to acquire first displacement data obtained after a preset positive electrode sheet is subjected to an extrusion test, and second displacement data obtained after a preset negative electrode sheet is subjected to an extrusion test; and also used to acquire a limit deformation rate corresponding to a reference battery;

[0014] A processing unit, configured to determine a first compression ratio of the preset positive electrode sheet based on a first initial thickness of the preset positive electrode sheet and the first displacement data; determine a second compression ratio of the preset negative electrode sheet based on a second initial thickness of the preset negative electrode sheet and the second displacement data; determine a total thickness of positive electrode material layers of all preset positive electrode sheets in the preset battery and a total thickness of negative electrode material layers of all preset negative electrode sheets in the preset battery based on the first initial thickness of the preset positive electrode sheet and the second initial thickness of the preset negative electrode sheet; estimate a target deformation rate corresponding to an extrusion test of the preset battery based on the total thickness of the positive electrode material layer, the first compression ratio, the total thickness of the negative electrode material layer and the second compression ratio;

[0015] An evaluation unit is used to evaluate the safety of the preset battery based on the target deformation rate and the limit deformation rate.

[0016] According to a method for evaluating the safety of a preset battery in the above embodiment, a target deformation rate corresponding to the preset battery is estimated by obtaining the total thickness of the positive electrode material layer, the first compression ratio, the total thickness of the negative electrode material layer and the second compression ratio of the preset battery; then, the safety of the preset battery is evaluated by comparing the target deformation rate with the limit deformation rate corresponding to the reference battery, thereby achieving the purpose of effectively evaluating the safety of the battery before producing the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of a flow chart of a method for evaluating the safety of a preset battery provided in this embodiment;

[0018] Figure 2A schematic diagram of a flow chart for determining a preset first compression ratio of a positive electrode sheet and a preset second compression ratio of a negative electrode sheet provided in this embodiment;

[0019] Figure 3 This is a structural block diagram of a device for evaluating the safety of a preset battery provided in this embodiment. DETAILED DESCRIPTION

[0020] The present invention is further described in detail below by specific embodiments in conjunction with the accompanying drawings. Wherein similar elements in different embodiments adopt associated similar element numbers. In the following embodiments, many detailed descriptions are for making the present application better understood. However, those skilled in the art can easily recognize that some features can be omitted in different situations, or can be replaced by other elements, materials, methods. In some cases, some operations related to the present application are not shown or described in the specification, this is to avoid the core part of the present application being overwhelmed by too much description, and for those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations according to the description in the specification and the general technical knowledge in the art.

[0021] In addition, the features, operations or characteristics described in the specification can be combined in any appropriate manner to form various implementations. At the same time, the steps or actions in the method description can also be interchanged or adjusted in a manner that is obvious to those skilled in the art. Therefore, the various sequences in the specification and the drawings are only for the purpose of clearly describing a certain embodiment and are not meant to be a required sequence, unless otherwise specified that a certain sequence must be followed.

[0022] The serial numbers of the components in this document, such as "first", "second", etc., are only used to distinguish the objects described and do not have any order or technical meaning. The "connection" and "coupling" mentioned in this application, unless otherwise specified, include direct and indirect connections (couplings).

[0023] At present, lithium-ion batteries have the following safety issues: thermal runaway of lithium-ion batteries caused by mechanical abuse. Deformation of lithium-ion batteries will cause damage to the pole pieces, diaphragms and other structural parts inside the battery cell, which will cause internal short circuits. At present, there are two ways to evaluate such safety risks of batteries: heavy impact and extrusion, that is, to measure the battery cell by heavy impact or extrusion. However, these evaluation methods have lags, and they cannot make safety judgments at the beginning of product design, and their accuracy is very low.

[0024] Based on this, the solution of the present invention is proposed. In the embodiment of the present invention, an external force is applied to the preset positive / negative electrode sheet by an extrusion device, and the displacement data of the preset positive / negative electrode sheet is read by a displacement acquisition device; the deformation of the preset positive / negative electrode sheet is further obtained; the total thickness of the electrode sheet material layer in the winding core is obtained by designing a preset battery; the target deformation of the designed winding core is calculated by the deformation of the preset positive / negative electrode sheet and the total thickness of the electrode sheet material layer. The limit deformation X corresponding to the reference battery is obtained by re-punching / extruding the reference battery cell. 1 , and compared with the target deformation X of the designed core, if X<X 1 , it can be determined that the designed core (preset battery) can pass the heavy object impact, extrusion and other tests. This method does not rely on the actual test results of the actual battery cell to make a judgment, and can quickly and accurately judge the safety of the preset battery in the early stage of core design. The following is a detailed description of this through some embodiments.

[0025] Example 1, please refer to Figure 1 , Figure 1 is a flow chart of a method for evaluating the safety of a preset battery provided in this embodiment. Figure 1 As shown, the method specifically includes the following steps 101-106:

[0026] Step 101 : performing compression tests on a preset positive electrode sheet and a preset negative electrode sheet respectively, and recording first displacement data corresponding to the preset positive electrode sheet and second displacement data corresponding to the preset negative electrode sheet.

[0027] Here, a plurality of preset positive electrode sheets and a plurality of preset negative electrode sheets belong to the electrode sheet composition of a preset battery. The preset battery may be any type of battery. Exemplarily, the preset battery may be a lithium-ion battery or a nickel-chromium battery, and the present application does not impose any limitation on this. The following description will be made using a lithium-ion battery as an example. The preset battery may be a battery in the design stage, that is, the specifications of its preset positive electrode sheet and preset negative electrode sheet are known.

[0028] It should be noted that the extrusion pressure in the extrusion test can be any value of the extrusion pressure; the extrusion speed can be any value of the extrusion speed.

[0029] In practical applications, the extrusion test standard in the national standard can be selected to perform an extrusion test on the above-mentioned preset battery, wherein the extrusion force corresponding to the extrusion test standard can be 13KN, and the extrusion speed corresponding to the extrusion test standard can be 0.1mm / s.

[0030] Here, the surface density parameters, compaction density parameters and thickness parameters of multiple preset positive electrode sheets are all the same; the surface density parameters, compaction density parameters and thickness parameters of multiple preset negative electrode sheets are all the same.

[0031] It should be noted that the surface density parameter, compaction density parameter and thickness parameter of each preset positive electrode sheet may be the same as or different from the surface density parameter, compaction density parameter and thickness parameter of each preset negative electrode sheet, and this application does not impose any limitation on this.

[0032] It should be noted that the first displacement data corresponding to the preset positive electrode sheet can represent the deformation data of the preset positive electrode sheet after the extrusion test; the second displacement data corresponding to the preset negative electrode sheet can represent the deformation data of the preset negative electrode sheet after the extrusion test.

[0033] Step 102: Determine a first compression ratio of the preset positive electrode sheet based on a first initial thickness and first displacement data of the preset positive electrode sheet; and determine a second compression ratio of the preset negative electrode sheet based on a second initial thickness and second displacement data of the preset negative electrode sheet.

[0034] It should be noted that the first initial thickness of the preset positive electrode sheet can represent the thickness of the preset positive electrode sheet without the extrusion test. The second initial thickness of the preset negative electrode sheet can represent the thickness of the preset negative electrode sheet without the extrusion test.

[0035] It should be noted that the first compression ratio of the preset positive electrode sheet can represent the degree of compression of the preset positive electrode sheet after the compression test; the second compression ratio of the preset negative electrode sheet can represent the degree of compression of the preset negative electrode sheet after the compression test.

[0036] In practical applications, the first compression ratio of the preset positive electrode sheet can be determined according to the following formula:

[0037] Y 正 =L 正 / T 正 (1)

[0038] In formula (1), Y 正 is the first compression ratio of the preset positive electrode; L 正 is the first displacement data of the preset positive electrode; T 正 It is the first initial thickness of the preset positive electrode sheet.

[0039] In practical applications, the second compression ratio of the preset negative electrode sheet can be determined according to the following formula:

[0040] Y 负 =L 负 / T 负 (2)

[0041] In formula (2), Y 负 is the second compression ratio of the preset negative electrode sheet; L 负 is the second displacement data of the preset negative electrode sheet; T 负It is the second initial thickness of the preset negative electrode sheet.

[0042] Step 103: Based on the first initial thickness of the preset positive electrode sheet and the second initial thickness of the preset negative electrode sheet, determine the total thickness of the positive electrode material layers of all preset positive electrode sheets in the preset battery and the total thickness of the negative electrode material layers of all preset negative electrode sheets in the preset battery.

[0043] Here, when determining the total thickness of the positive electrode material layer of all preset positive electrode sheets in the preset battery and the total thickness of the negative electrode material layer of all preset negative electrode sheets in the preset battery, the diaphragm thickness parameters, battery cell diameter parameters, assembly ratio parameters and steel shell wall thickness parameters corresponding to the preset battery can be obtained (for batteries in the design stage, these parameters are known); based on the first initial thickness, the second initial thickness and the diaphragm thickness parameters, the first material layer proportion of the preset positive electrode sheet in the battery cell structure and the second material layer proportion of the preset negative electrode sheet in the battery cell structure are determined respectively; based on the first material layer proportion, battery cell diameter parameters, assembly ratio parameters and steel shell wall thickness parameters, the total thickness of the positive electrode material layer of all preset positive electrode sheets in the preset battery is determined (as calculated); based on the second material layer proportion, battery cell diameter parameters, assembly ratio parameters and steel shell wall thickness parameters, the total thickness of the negative electrode material layer of all preset negative electrode sheets in the preset battery is determined (as calculated).

[0044] In practical applications, the lithium-ion battery unit structure is composed of 1 positive electrode sheet + 1 separator + 1 negative electrode sheet + 1 separator. After winding based on the lithium-ion battery unit structure, the corresponding battery cell of the lithium-ion battery can be formed.

[0045] It should be noted that the membrane thickness parameter corresponding to the preset battery can represent the thickness corresponding to one membrane layer in the preset battery unit structure. For example, the membrane thickness corresponding to the lithium-ion battery is the thickness corresponding to two membrane layers in the lithium-ion battery unit structure.

[0046] It should be noted that the cell diameter parameter corresponding to the preset battery can represent the cell diameter corresponding to the preset battery that has not been subjected to the extrusion test, that is, the diameter parameter corresponding to the cell formed after winding based on the preset battery unit structure. Exemplarily, the cell diameter corresponding to the lithium-ion battery is the cell diameter corresponding to the lithium-ion battery that has not been subjected to the extrusion test.

[0047] It should be noted that the assembly ratio parameter corresponding to the preset battery can characterize the ratio of the diameter of the battery cell after all preset positive plates, all preset negative plates and all diaphragms are wound to the inner diameter of the steel shell.

[0048] It should be noted that the steel shell wall thickness parameter corresponding to the preset battery can represent the thickness of the steel shell that wraps the preset battery cell. For example, the steel shell wall thickness corresponding to the lithium-ion battery is the thickness of the steel shell that wraps the lithium-ion battery cell.

[0049] Here, when determining the proportion of the first material layer of the preset positive electrode sheet in the battery cell structure and the proportion of the second material layer of the preset negative electrode sheet in the battery cell structure, the first initial thickness, the second initial thickness and the sum of the two diaphragm thickness parameters can be determined; the ratio of the first initial thickness to the sum is determined as the proportion of the first material layer of the preset positive electrode sheet in the battery cell structure; the ratio of the second initial thickness to the sum is determined as the proportion of the second material layer of the preset negative electrode sheet in the battery cell structure.

[0050] In practical applications, the proportion of the first material layer of the preset positive electrode sheet in the battery cell structure can be determined according to the following formula:

[0051] P 正 = T 正 / (T 正 + T 负 +q*2) (3)

[0052] In formula (3), P 正 is the proportion of the first material layer; q is the membrane thickness parameter.

[0053] In practical applications, the proportion of the second material layer of the preset negative electrode sheet in the battery cell structure can be determined according to the following formula:

[0054] P 负 = T 负 / (T 正 + T 负 +q*2) (4)

[0055] In formula (4), P 负 is the proportion of the second material layer; q is the membrane thickness parameter.

[0056] Here, when determining the total thickness of the positive electrode material layer of all preset positive electrode sheets in a preset battery and the total thickness of the negative electrode material layer of all preset negative electrode sheets, the difference between the battery cell diameter parameter and the two steel shell wall thickness parameters can be determined; the product of the difference, the proportion of the first material layer and the assembly ratio parameter is determined as the total thickness of the positive electrode material layer of all preset positive electrode sheets in the preset battery; the product of the difference, the proportion of the second material layer and the assembly ratio parameter is determined as the total thickness of the negative electrode material layer of all preset negative electrode sheets in the preset battery.

[0057] In practical applications, the total thickness of the positive electrode material layer of all the preset positive electrode sheets in the preset battery can be determined according to the following formula:

[0058] W 正 =(D - g*2)*m * P 正 (5)

[0059] In formula (5), W 正is the total thickness of the positive electrode material layer; D is the core diameter parameter; g is the steel shell wall thickness parameter; m is the assembly ratio parameter; P 正 The proportion of the first material layer.

[0060] In practical applications, the total thickness of the negative electrode material layer of all preset negative electrode sheets in a preset battery can be determined according to the following formula:

[0061] W 负 =(D - g*2)*m * P 负 (6)

[0062] In formula (6), W 负 is the total thickness of the negative electrode material layer; D is the core diameter parameter; g is the steel shell wall thickness parameter; m is the assembly ratio parameter; P 负 The proportion of the second material layer.

[0063] Step 104: based on the total thickness of the positive electrode material layer, the first compression ratio, the total thickness of the negative electrode material layer and the second compression ratio, estimate the target deformation rate corresponding to the compression test of the preset battery.

[0064] Here, when estimating the target deformation rate corresponding to the extrusion test of the preset battery, the target deformation rate corresponding to the extrusion test of the preset battery can be estimated according to the following formula based on the total thickness of the positive electrode material layer, the first compression ratio, the total thickness of the negative electrode material layer and the second compression ratio:

[0065] X=(W 正 * Y 正 + W 负 * Y 负 ) / (W 正 + W 负 ) (7)

[0066] In formula (7), X is the target deformation rate; W 正 is the total thickness of the positive electrode material layer; W 负 is the total thickness of the negative electrode material layer; Y 正 is the first compression ratio of the preset positive electrode; Y 负 It is the second compression ratio of the preset negative electrode sheet.

[0067] Step 105: Obtain the limit deformation rate corresponding to the reference battery.

[0068] Here, when obtaining the limit deformation rate corresponding to the reference battery, the reference cell diameter parameters and winding needle diameter parameters corresponding to the reference battery can be obtained; the reference battery is subjected to an extrusion test within a preset limit time, and the cell diameter deformation parameters corresponding to the reference battery are recorded; based on the reference cell diameter parameters, the winding needle diameter parameters and the cell diameter deformation parameters, the limit deformation rate corresponding to the reference battery is determined.

[0069] It should be noted that the reference cell diameter parameter corresponding to the reference battery can characterize the diameter of the cell formed after winding based on the reference battery unit structure. In practical applications, the reference battery can be discharged at a small rate to an empty state, and the initial diameter corresponding to the empty reference cell, i.e., the reference cell diameter parameter, can be recorded.

[0070] It should be noted that the winding needle diameter parameter corresponding to the reference battery can represent the diameter corresponding to the center hole of the reference battery cell.

[0071] It should be noted that the reference battery and the preset battery can be batteries of the same model in the same system, or batteries of different models in the same system. This application does not impose any limitation on this.

[0072] In practical applications, the limit deformation rate corresponding to the reference battery can be determined according to the following formula:

[0073] X 1 =(D 1 -D 2 -D 3 ) / (D 1 -D 3 ) (8)

[0074] In formula (8), X 1 is the limiting deformation rate; D 1 is the reference cell diameter parameter; D 2 is the cell diameter deformation parameter; D 3 It is the winding needle diameter parameter.

[0075] In practical applications, the extrusion equipment can perform an extrusion test on the reference battery according to the extrusion test standard in the national standard, and record the surface temperature of the reference battery. When the temperature rise rate of three consecutive temperature data in the surface temperature data of the reference battery exceeds 1°C / s, or the reference battery fails, catches fire, or explodes, the extrusion test is terminated and the preset limit time t is recorded. Here, the preset limit time t can represent the duration corresponding to the difference between the end time of the extrusion test and the start time of the extrusion test. After the reference battery is extruded within the preset limit time t, the corresponding cell diameter of the reference battery after extrusion, that is, the cell diameter deformation parameter, can be obtained.

[0076] Step 106: Evaluate the safety of the preset battery based on the target deformation rate and the limit deformation rate.

[0077] Here, when evaluating the safety of a preset battery, when the target deformation rate is less than the limit deformation rate, the preset battery is determined to be qualified; when the target deformation rate is greater than or equal to the limit deformation rate, the preset battery is determined to be unqualified.

[0078] It should be noted that when the target deformation rate is less than the limit deformation rate, it means that under the same extrusion test conditions, the maximum deformation produced by the designed preset battery is smaller than the maximum deformation produced by the reference battery. It also means that the preset battery is less likely to fail, catch fire, explode or produce continuous temperature rise than the reference battery.

[0079] It should be noted that when the target deformation rate is greater than the limit deformation rate, it means that under the same extrusion test conditions, the maximum deformation produced by the designed preset battery is greater than the maximum deformation produced by the reference battery. It also means that the preset battery is more likely to fail, catch fire, explode, or produce continuous temperature rise than the reference battery.

[0080] A method for evaluating the safety of a preset battery provided in an embodiment of the present application comprises performing an extrusion test on a preset positive electrode sheet and a preset negative electrode sheet, respectively, recording first displacement data corresponding to the preset positive electrode sheet and second displacement data corresponding to the preset negative electrode sheet; determining a first compression ratio based on a first initial thickness and the first displacement data of the preset positive electrode sheet; determining a second compression ratio based on a second initial thickness and the second displacement data of the preset negative electrode sheet; determining a total thickness of positive electrode material layers of all preset positive electrode sheets and a total thickness of negative electrode material layers of all preset negative electrode sheets in the preset battery based on the first initial thickness and the second initial thickness; estimating a target deformation rate corresponding to the preset battery based on the total thickness of the positive electrode material layer, the first compression ratio, the total thickness of the negative electrode material layer and the second compression ratio; and evaluating the safety of the preset battery based on the target deformation rate and the limit deformation rate. By obtaining the total thickness of the positive electrode material layer, the first compression ratio, the total thickness of the negative electrode material layer and the second compression ratio of the preset battery, the target deformation rate corresponding to the preset battery is estimated; then, by comparing the target deformation rate with the limit deformation rate corresponding to the reference battery, the safety of the preset battery is evaluated, thereby achieving the purpose of effectively evaluating the safety of the battery before producing the battery.

[0081] Example 2, please refer to Figure 2 , Figure 2 is a flow chart of determining a first compression ratio of a preset positive electrode sheet and a second compression ratio of a preset negative electrode sheet provided in this embodiment, such as Figure 2 As shown, a compression test is performed on a preset positive electrode sheet and a preset negative electrode sheet respectively, and first displacement data corresponding to the preset positive electrode sheet and second displacement data corresponding to the preset negative electrode sheet are recorded; a first compression ratio of the preset positive electrode sheet is determined based on a first initial thickness of the preset positive electrode sheet and the first displacement data; and a second compression ratio of the preset negative electrode sheet is determined based on a second initial thickness of the preset negative electrode sheet and the second displacement data, specifically including the following steps 201-203:

[0082] Step 201 , respectively perform compression tests on a preset first number of preset positive electrode sheets and a preset second number of preset negative electrode sheets, and record first total displacement data corresponding to the preset first number of preset positive electrode sheets and second total displacement data corresponding to the preset second number of preset negative electrode sheets.

[0083] It should be noted that the preset positive electrode sheet and the preset negative electrode sheet of the preset battery are relatively thin (micrometer level). In order to avoid the influence of the gap between the electrode sheets, the multi-layer preset positive electrode sheet and the multi-layer preset negative electrode sheet can be pre-pressed separately and then subjected to extrusion test.

[0084] In practical applications, the preset first number of preset positive electrode sheets and the preset second number of preset negative electrode sheets can be pre-pressed to eliminate the gaps between the electrode sheets, and then the pre-pressed multi-layer preset positive electrode sheets and the multi-layer preset negative electrode sheets can be extruded respectively using the extrusion test standard in the national standard to obtain the first total displacement data corresponding to the preset first number of preset positive electrode sheets and the second total displacement data corresponding to the preset second number of preset negative electrode sheets.

[0085] It should be noted that the preset first number and the preset second number can be the same or different, and this application does not impose any limitation on this. In practical applications, the preset first number and the preset second number are both 30.

[0086] Step 202: determine a first total initial thickness of a preset first number of preset positive electrode sheets based on a preset first number and a first initial thickness of a preset positive electrode sheet; and determine a second total initial thickness of a preset second number of preset negative electrode sheets based on a preset second number and a second initial thickness of a preset negative electrode sheet.

[0087] It should be noted that the first total initial thickness of the preset first number of preset positive electrode sheets may represent the thickness corresponding to the first initial thickness of the preset first number of preset positive electrode sheets.

[0088] It should be noted that the second total initial thickness of the preset second number of preset negative electrode sheets may represent the thickness corresponding to the second initial thickness of the preset second number of preset negative electrode sheets.

[0089] Step 203: Determine a first compression ratio of a preset positive electrode sheet based on the first total initial thickness and the first total displacement data; and determine a second compression ratio of a preset negative electrode sheet based on the second total initial thickness and the second total displacement data.

[0090] In practical applications, the first compression ratio of the preset positive electrode sheet can be determined according to the following formula:

[0091] Y' 正 =L' 正 / (T 正 *n 1 ) (9)

[0092] In formula (9), Y' 正 is a first compression ratio of a preset first number of preset positive electrode sheets; L' 正 is the first total displacement data; T 正 is the first initial thickness of the preset positive electrode sheet; n 1 is the preset first quantity.

[0093] In practical applications, the second compression ratio of the preset negative electrode sheet can be determined according to the following formula:

[0094] Y' 负 =L' 负 / (T 负 *n 2 ) (10)

[0095] In formula (10), Y' 负 is a second compression ratio of a preset second number of preset negative electrode sheets; L' 负 is the second total displacement data; T 负 is the second initial thickness of the preset negative electrode sheet; n 2 is the preset second quantity.

[0096] In the embodiment of the present application, by stacking multiple layers of preset pole pieces and then performing extrusion measurement, the influence of the pole piece gap can be effectively avoided, and inaccurate measurement results caused by thin pole pieces can also be avoided.

[0097] The present invention also provides a device for evaluating the safety of a preset battery, such as Figure 3 The structure block diagram of a device for evaluating the safety of a preset battery is shown. The device 30 includes an acquisition unit 301, a processing unit 302 and an evaluation unit 303:

[0098] The acquisition unit 301 is used to acquire the first displacement data obtained after the preset positive electrode sheet is subjected to the compression test, and the second displacement data obtained after the preset negative electrode sheet is subjected to the compression test; and is also used to acquire the limit deformation rate corresponding to the reference battery. That is, it is used to execute the above steps 101 and 105. The specific process is shown in the above steps 101 and 105, which will not be described in detail here.

[0099] The processing unit 302 is used to determine the first compression ratio of the preset positive electrode sheet based on the first initial thickness and the first displacement data of the preset positive electrode sheet; determine the second compression ratio of the preset negative electrode sheet based on the second initial thickness and the second displacement data of the preset negative electrode sheet; determine the total thickness of the positive electrode material layer of all preset positive electrode sheets in the preset battery and the total thickness of the negative electrode material layer of all preset negative electrode sheets in the preset battery based on the first initial thickness of the preset positive electrode sheet and the second initial thickness of the preset negative electrode sheet; estimate the target deformation rate corresponding to the extrusion test of the preset battery based on the total thickness of the positive electrode material layer, the first compression ratio, the total thickness of the negative electrode material layer and the second compression ratio. That is, it is used to execute the above steps 102-104. The specific process is shown in the above steps 102-104, which will not be repeated here.

[0100] The evaluation unit 303 is used to evaluate the safety of the preset battery based on the target deformation rate and the limit deformation rate. The evaluation unit 303 can be connected to a display to display the safety evaluation result of the preset battery on the display. The specific process is shown in the above step 106 and will not be repeated here.

[0101] An embodiment of the present application provides a device for evaluating the safety of a preset battery, including an acquisition unit for acquiring first displacement data obtained after a preset positive electrode sheet is subjected to an extrusion test, and second displacement data obtained after a preset negative electrode sheet is subjected to an extrusion test; and also for acquiring a limit deformation rate corresponding to a reference battery; a processing unit for determining a first compression ratio of a preset positive electrode sheet based on a first initial thickness of the preset positive electrode sheet and the first displacement data; determining a second compression ratio of a preset negative electrode sheet based on a second initial thickness of the preset negative electrode sheet and the second displacement data; determining a total thickness of positive electrode material layers of all preset positive electrode sheets in the preset battery and a total thickness of negative electrode material layers of all preset negative electrode sheets in the preset battery based on the first initial thickness of the preset positive electrode sheet and the second initial thickness of the preset negative electrode sheet, respectively; estimating a target deformation rate corresponding to an extrusion test of the preset battery based on the total thickness of the positive electrode material layer, the first compression ratio, the total thickness of the negative electrode material layer and the second compression ratio; and an evaluation unit for evaluating the safety of the preset battery based on the target deformation rate and the limit deformation rate. By obtaining the total thickness of the positive electrode material layer, the first compression ratio, the total thickness of the negative electrode material layer and the second compression ratio of the preset battery, the target deformation rate corresponding to the preset battery is estimated; then, by comparing the target deformation rate with the limit deformation rate corresponding to the reference battery, the safety of the preset battery is evaluated, thereby achieving the purpose of effectively evaluating the safety of the battery before producing the battery.

[0102] Those skilled in the art will appreciate that all or part of the functions of the various methods in the above-mentioned embodiments can be implemented by hardware or by computer programs. When all or part of the functions in the above-mentioned embodiments are implemented by computer programs, the program can be stored in a computer-readable storage medium, and the storage medium can include: read-only memory, random access memory, disk, optical disk, hard disk, etc., and the program is executed by a computer to implement the above-mentioned functions. For example, the program is stored in the memory of the device, and when the program in the memory is executed by the processor, all or part of the above-mentioned functions can be implemented. In addition, when all or part of the functions in the above-mentioned embodiments are implemented by computer programs, the program can also be stored in a storage medium such as a server, another computer, disk, optical disk, flash disk or mobile hard disk, and can be downloaded or copied and saved in the memory of the local device, or the system of the local device is updated, and when the program in the memory is executed by the processor, all or part of the functions in the above-mentioned embodiments can be implemented.

[0103] The above specific examples are used to illustrate the present invention, which is only used to help understand the present invention and is not intended to limit the present invention. For those skilled in the art, according to the idea of ​​the present invention, some simple deductions, modifications or substitutions can be made.

Claims

1. A method for evaluating the safety of a preset battery, characterized in that: The preset battery includes a plurality of preset positive plates and a plurality of preset negative plates, and the method includes: Performing an extrusion test on the preset positive electrode sheet and the preset negative electrode sheet respectively, and recording first displacement data corresponding to the preset positive electrode sheet and second displacement data corresponding to the preset negative electrode sheet; Determine a first compression ratio of the preset positive electrode sheet based on a first initial thickness of the preset positive electrode sheet and the first displacement data; determine a second compression ratio of the preset negative electrode sheet based on a second initial thickness of the preset negative electrode sheet and the second displacement data; Based on the first initial thickness of the preset positive electrode sheet and the second initial thickness of the preset negative electrode sheet, respectively determine the total thickness of the positive electrode material layers of all the preset positive electrode sheets in the preset battery and the total thickness of the negative electrode material layers of all the preset negative electrode sheets in the preset battery; Based on the total thickness of the positive electrode material layer, the first compression ratio, the total thickness of the negative electrode material layer and the second compression ratio, estimating a target deformation rate corresponding to the extrusion test of the preset battery; Obtain the limit deformation rate corresponding to the reference battery; Based on the target deformation rate and the limit deformation rate, the safety of the preset battery is evaluated.

2. The method according to claim 1, characterized in that The surface density parameters, compaction density parameters and thickness parameters of the plurality of preset positive electrode sheets are all the same; the surface density parameters, compaction density parameters and thickness parameters of the plurality of preset negative electrode sheets are all the same.

3. The method according to claim 1 or 2, characterized in that The method of determining the total thickness of the positive electrode material layers of all the preset positive electrode sheets in the preset battery and the total thickness of the negative electrode material layers of all the preset negative electrode sheets in the preset battery based on the first initial thickness of the preset positive electrode sheet and the second initial thickness of the preset negative electrode sheet respectively comprises: Obtaining the diaphragm thickness parameter, cell diameter parameter, assembly ratio parameter, and steel shell wall thickness parameter corresponding to the preset battery; Based on the first initial thickness, the second initial thickness and the separator thickness parameter, respectively determining a first material layer proportion of the preset positive electrode sheet in the battery cell structure and a second material layer proportion of the preset negative electrode sheet in the battery cell structure; Based on the first material layer ratio, the battery cell diameter parameter, the assembly ratio parameter and the steel shell wall thickness parameter, the total thickness of the positive electrode material layer of all preset positive electrode sheets in the preset battery is determined; based on the second material layer ratio, the battery cell diameter parameter, the assembly ratio parameter and the steel shell wall thickness parameter, the total thickness of the negative electrode material layer of all preset negative electrode sheets in the preset battery is determined.

4. The method according to claim 3, characterized in that The determining, based on the first initial thickness, the second initial thickness and the separator thickness parameter, respectively a first material layer proportion of the preset positive electrode sheet in the battery cell structure and a second material layer proportion of the preset negative electrode sheet in the battery cell structure, comprises: Determining the first initial thickness, the second initial thickness, and a sum of two membrane thickness parameters; Determine the ratio of the first initial thickness to the sum value as the proportion of the first material layer of the preset positive electrode sheet in the battery unit structure; The ratio of the second initial thickness to the sum value is determined as the proportion of the second material layer of the preset negative electrode sheet in the battery unit structure.

5. The method according to claim 3, characterized in that The determining the total thickness of the positive electrode material layers of all the preset positive electrode sheets in the preset battery based on the first material layer ratio, the battery core diameter parameter, the assembly ratio parameter and the steel shell wall thickness parameter comprises: Determine the difference between the battery core diameter parameter and the two steel shell wall thickness parameters; The product of the difference, the first material layer proportion and the assembly ratio parameter is determined as the total thickness of the positive electrode material layers of all the preset positive electrode sheets in the preset battery; The product of the difference, the proportion of the second material layer and the assembly ratio parameter is determined as the total thickness of the negative electrode material layers of all preset negative electrode sheets in the preset battery.

6. The method according to claim 4 or 5, characterized in that The estimating a target deformation rate corresponding to the extrusion test of the preset battery based on the total thickness of the positive electrode material layer, the first compression ratio, the total thickness of the negative electrode material layer and the second compression ratio includes: Based on the total thickness of the positive electrode material layer, the first compression ratio, the total thickness of the negative electrode material layer and the second compression ratio, the target deformation rate corresponding to the extrusion test of the preset battery is estimated according to the following formula: X=( W 正 * Y 正 + W 负 * Y 负 ) / ( W 正 + W 负 ) (1) In formula (1), X is the target deformation rate; W 正 is the total thickness of the positive electrode material layer; Y 正 is the first compression ratio; W 负 is the total thickness of the negative electrode material layer; Y 负 is the second compression ratio.

7. The method according to claim 1, characterized in that The extrusion test is performed on the preset positive electrode sheet and the preset negative electrode sheet respectively, and the first displacement data corresponding to the preset positive electrode sheet and the second displacement data corresponding to the preset negative electrode sheet are recorded; Determining a first compression ratio of the preset positive electrode sheet based on a first initial thickness of the preset positive electrode sheet and the first displacement data; Determining a second compression ratio of the preset negative electrode sheet based on the second initial thickness of the preset negative electrode sheet and the second displacement data includes: Performing compression tests on a preset first number of preset positive electrode sheets and a preset second number of preset negative electrode sheets respectively, and recording first total displacement data corresponding to the preset first number of preset positive electrode sheets and second total displacement data corresponding to the preset second number of preset negative electrode sheets; Determine a first total initial thickness of the preset first number of preset positive electrode sheets based on the preset first number and the first initial thickness of the preset positive electrode sheets; determine a second total initial thickness of the preset second number of preset negative electrode sheets based on the preset second number and the second initial thickness of the preset negative electrode sheets; Based on the first total initial thickness and the first total displacement data, a first compression ratio of the preset positive electrode sheet is determined; based on the second total initial thickness and the second total displacement data, a second compression ratio of the preset negative electrode sheet is determined.

8. The method according to claim 1, characterized in that The obtaining of the limit deformation rate corresponding to the reference battery includes: Obtaining a reference cell diameter parameter and a winding needle diameter parameter corresponding to the reference battery; Performing an extrusion test on the reference battery within a preset limit time, and recording the cell diameter deformation parameters corresponding to the reference battery; Based on the reference cell diameter parameter, the winding needle diameter parameter and the cell diameter deformation parameter, the limit deformation rate corresponding to the reference battery is determined.

9. The method according to claim 1, characterized in that The evaluating the safety of the preset battery based on the target deformation rate and the limit deformation rate includes: When the target deformation rate is less than the limit deformation rate, determining that the preset battery is qualified; When the target deformation rate is greater than or equal to the limit deformation rate, it is determined that the preset battery is unqualified.

10. A device for evaluating the safety of a preset battery, characterized in that: The device comprises: An acquisition unit, used to acquire first displacement data obtained after a preset positive electrode sheet is subjected to an extrusion test, and second displacement data obtained after a preset negative electrode sheet is subjected to an extrusion test; and also used to acquire a limit deformation rate corresponding to a reference battery; A processing unit, configured to determine a first compression ratio of the preset positive electrode sheet based on a first initial thickness of the preset positive electrode sheet and the first displacement data; determine a second compression ratio of the preset negative electrode sheet based on a second initial thickness of the preset negative electrode sheet and the second displacement data; determine a total thickness of positive electrode material layers of all preset positive electrode sheets in the preset battery and a total thickness of negative electrode material layers of all preset negative electrode sheets in the preset battery based on the first initial thickness of the preset positive electrode sheet and the second initial thickness of the preset negative electrode sheet; estimate a target deformation rate corresponding to an extrusion test of the preset battery based on the total thickness of the positive electrode material layer, the first compression ratio, the total thickness of the negative electrode material layer and the second compression ratio; An evaluation unit is used to evaluate the safety of the preset battery based on the target deformation rate and the limit deformation rate.

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