Battery overcharge safety test method, electronic equipment and storage medium

Abstract

The invention relates to the technical field of battery testing, particularly provides a battery overcharge safety testing method, electronic equipment and a storage medium, and aims to solve the problem of testing the safety of a battery cell during overcharge efficiently at low cost. In order to achieve the purpose, the method comprises the steps that volt-ampere testing is carried out on a to-be-tested battery, and the testing voltage change process sequentially comprises a normal voltage stage and an overvoltage stage; the ratio of the first peak current density to the second peak current density is obtained, the first peak current density is the peak current density in the normal voltage stage, and the second peak current density is the peak current density in the overvoltage stage; and if the ratio is greater than a first preset threshold value, the to-be-tested battery passes the test preliminarily. Based on the method, the battery cell does not need to be assembled into a high-capacity lithium ion battery, and the overcharge safety test can still be accurately and reliably completed, so that the efficiency of testing the safety of the battery cell during overcharge is remarkably improved, and the test cost is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of battery testing, and particularly relates to a method for testing the overcharge safety of a battery, an electronic device, and a storage medium. Background Art

[0002] Lithium-ion batteries are widely used in fields such as portable electronic devices and electric vehicles due to their advantages of high energy density, long cycle life, high working voltage, fast charging speed, and low self-discharge.

[0003] In actual applications, when charging a lithium-ion battery, it is possible that the battery voltage exceeds the normal voltage (hereinafter described as overcharging), which may lead to a decline in the performance of the lithium-ion battery, damage, shortened life, and even explosion. Therefore, before putting the lithium-ion battery into an actual application scenario, it is necessary to test the safety of the lithium-ion battery during overcharging to ensure that the lithium-ion battery still has high safety under overcharging conditions.

[0004] Currently, in fields such as portable electronic devices and electric vehicles, the capacity requirements for lithium-ion batteries are relatively large. A lithium-ion battery assembled from one or a small number of small-capacity battery cells (hereinafter described as small cells) cannot meet the battery capacity requirements of the above-mentioned portable electronic devices, electric vehicles, etc. Therefore, usually, many small cells are assembled into a lithium-ion battery, which is equivalent to assembling multiple small cells into a large-capacity battery cell (hereinafter described as a large cell). The current conventional overcharge safety test method is to directly conduct an overcharge test on the above-mentioned lithium-ion battery (i.e., the battery finished product). Since the above-mentioned lithium-ion battery is a large cell, the test cost is relatively high and the efficiency is also relatively low.

[0005] Specifically, first, a lithium-ion battery is composed of many small cells, and the costs of these small cells accumulate, resulting in a higher battery cost of the lithium-ion battery itself, which is equivalent to increasing the test cost. Second, when conducting an overcharge test, it is necessary to first fully charge the capacity of the lithium-ion battery and then continue charging. Since the capacity of the lithium-ion battery is relatively large, the time required to fully charge the capacity will be relatively long, which is equivalent to increasing the test duration. In addition, during the overcharge process, it is necessary to monitor in real time whether the lithium-ion battery has abnormal situations such as temperature ignition, explosion, etc. If abnormal situations such as ignition or explosion occur, it indicates that the lithium-ion battery has failed the test. If these abnormal situations do not occur, it indicates that the lithium-ion battery has passed the test. During this process, due to the relatively large capacity of the lithium-ion battery, if the lithium-ion battery catches fire or explodes, it will pose a great danger to the test personnel. Therefore, it is necessary to set up a special protection device (such as an isolation device for the lithium-ion battery), which further increases the test cost.

[0006] Correspondingly, a new technical solution is needed in this field to solve the above problems. Summary of the Invention

[0007] In order to overcome the above defects, the present application is proposed to solve or at least partially solve the technical problem of efficiently and low - cost testing the safety of the battery cell during over - charging.

[0008] In a first aspect, a method for testing the over - charge safety of a battery is provided. The method includes:

[0009] Performing a volt - ampere test on the battery to be tested. The test voltage change process of the volt - ampere test sequentially includes a normal voltage stage and an over - voltage stage;

[0010] Obtaining the ratio of the first peak current density to the second peak current density; the first peak current density is the peak current density in the normal voltage stage, and the second peak current density is the peak current density in the over - voltage stage;

[0011] Comparing the ratio with a first preset threshold. If the ratio is greater than the first preset threshold, the battery to be tested preliminarily passes the test;

[0012] Wherein, the first preset threshold is greater than 1.

[0013] In a technical solution of the above - mentioned method for testing the over - charge safety of a battery, the first peak current density is obtained by the following method:

[0014] Obtaining the volt - ampere curve of the battery to be tested during the volt - ampere test. The volt - ampere curve represents the process of the current density of the battery to be tested changing with the test voltage;

[0015] Obtaining the first test voltage range corresponding to the normal voltage stage;

[0016] According to the volt - ampere curve, obtaining the maximum current density of the battery to be tested within the first test voltage range;

[0017] According to the maximum current density, obtaining the first peak current density.

[0018] In a technical solution of the above - mentioned method for testing the over - charge safety of a battery, the second peak current density is obtained by the following method:

[0019] Obtaining the volt - ampere curve of the battery to be tested during the volt - ampere test. The volt - ampere curve represents the process of the current density of the battery to be tested changing with the test voltage;

[0020] Obtaining the second test voltage range corresponding to the over - voltage stage;

[0021] Obtain the maximum current density of the battery under test within the second test voltage range according to the volt-ampere curve;

[0022] Obtain the second peak current density according to the maximum current density.

[0023] In a technical solution of the above test method for the overcharge safety of the battery, the positive electrode material of the battery under test is lithium iron phosphate, the negative electrode material is graphite, and the first preset threshold is 20.

[0024] In a technical solution of the above test method for the overcharge safety of the battery, the method includes:

[0025] Obtain the gas generated by the battery under test during the overvoltage stage;

[0026] If the composition of the gas meets the preset safety conditions, the battery under test finally passes the test.

[0027] In a technical solution of the above test method for the overcharge safety of the battery, the composition of the gas includes combustible gas, and the preset safety condition is that the proportion of the combustible gas in the total amount of the gas is less than the second preset threshold.

[0028] In a technical solution of the above test method for the overcharge safety of the battery, the positive electrode material of the battery under test is lithium iron phosphate, the negative electrode material is graphite, and the second preset threshold is 0.1.

[0029] In a technical solution of the above test method for the overcharge safety of the battery, the battery under test is any one of a button cell, a soft-pack battery, and a single-chip battery.

[0030] In a second aspect, there is provided an electronic device, which includes at least one processor; and a memory communicatively connected to the at least one processor; wherein, a computer program is stored in the memory, and when the computer program is executed by the at least one processor, the method described in any one of the technical solutions of the above test method for the overcharge safety of the battery is implemented.

[0031] In a third aspect, there is provided a computer-readable storage medium, which stores multiple program codes, and the program codes are adapted to be loaded and run by a processor to execute the method described in any one of the technical solutions of the above test method for the overcharge safety of the battery.

[0032] One or more of the above technical solutions of the present application have at least one or more of the following beneficial effects:

[0033] In the technical solution of implementing the test method for battery overcharge safety provided by this application, a volt-ampere test can be performed on the battery to be tested. The test voltage change process of the volt-ampere test sequentially includes a normal voltage stage and an overvoltage stage; obtain the ratio of the first peak current density to the second peak current density, where the first peak current density is the peak current density in the normal voltage stage, and the second peak current density is the peak current density in the overvoltage stage; compare the ratio with a first preset threshold. If the ratio is greater than the first preset threshold, the battery to be tested preliminarily passes the test, where the first preset threshold is greater than 1.

[0034] If the above ratio is greater than the first preset threshold, it indicates that the gap between the first and second peak current densities is relatively large and the first peak current density is greater than the second peak current density. That is to say, the electrochemical reaction intensities of the battery to be tested in the normal voltage stage and the overvoltage stage are quite different, and the electrochemical reaction intensity in the overvoltage stage is less than that in the normal voltage stage. Based on this, it can be determined that the electrochemical reaction of the battery to be tested in the overvoltage stage is not intense. If the battery to be tested is overcharged for a long time, the possibility of thermal runaway is also relatively small. Therefore, it can be determined that the battery to be tested has high safety during overcharging and has passed the battery overcharge safety test.

[0035] When it is necessary to perform an overcharge test on a large-capacity lithium-ion battery (a large-capacity battery cell assembled from many small battery cells), only the small battery cells used in the lithium-ion battery need to be obtained, and a volt-ampere test is performed on one small battery cell or a small-capacity battery (a lithium-ion battery assembled from a small number of small battery cells), and the volt-ampere test data is used to evaluate whether this small battery cell or small-capacity battery passes the overcharge safety test. If this small battery cell or small-capacity battery passes the test, then it can be determined that the entire lithium-ion battery will also pass the test. Since there is no need to assemble a large number of small battery cells into a battery, the battery cost will be reduced, which is equivalent to reducing the test cost; in addition, the capacity of the small battery cell or small-capacity battery is relatively small. Even if a fire or explosion occurs during the test, the danger will not be relatively high, and there is no need to set up a special protection device, which further reduces the test cost.

[0036] When performing the volt-ampere test, as long as it is ensured that the test stage includes a normal voltage stage and an overvoltage stage, the data of these two stages can be used to evaluate whether the small battery cell or small-capacity battery passes the overcharge safety test. It is not necessary to first fully charge the battery capacity and then continuously charge it as in the conventional test method, and monitor the battery situation during the continuous charging process. Compared with the conventional test method, the test efficiency is significantly improved. Description of the Drawings

[0037] With reference to the accompanying drawings, the disclosure of the present application will become more readily understandable. It is easily understood by those skilled in the art that these drawings are only for illustrative purposes and are not intended to limit the scope of protection of the present application. Among them:

[0038] Figure 1 is a schematic diagram of the main step flow of a test method for battery overcharge safety according to an embodiment of the present application;

[0039] Figure 2 is a schematic diagram of the main step flow of obtaining the first peak current density of a battery under test in the normal voltage stage according to an embodiment of the present application;

[0040] Figure 3 is a schematic diagram of the volt-ampere curves of three coin cells according to an embodiment of the present application;

[0041] Figure 4 is a schematic diagram of the volt-ampere curves of three soft-pack batteries according to an embodiment of the present application;

[0042] Figure 5 is a schematic diagram of the main step flow of obtaining the second peak current density of a battery under test in the overvoltage stage according to an embodiment of the present application;

[0043] Figure 6 is a schematic diagram of the proportion of combustible gas and non-combustible gas according to an embodiment of the present application;

[0044] Figure 7 is a schematic diagram of the main structure of an electronic device according to an embodiment of the present application.

[0045] Reference numerals:

[0046] 11: Memory; 12: Processor. Detailed embodiments

[0047] Some embodiments of the present application will be described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principle of the present application and are not intended to limit the scope of protection of the present application.

[0048] In the description of the present application, a "processor" may include hardware, software, or a combination of both. A processor may be a central processing unit, a microprocessor, an image processor, a digital signal processor, or any other suitable processor. The processor has data and / or signal processing functions. The processor may be implemented in software, in hardware, or in a combination of both. A computer-readable storage medium includes any suitable medium for storing program code, such as a magnetic disk, a hard disk, an optical disk, a flash memory, a read-only memory, a random access memory, and so on.

[0049] The embodiments of the test method for battery overcharge safety provided by the present application will be described below.

[0050] Refer to the attached Figure 1 Figure 1 It is a schematic diagram of the main step flow of the test method for battery overcharge safety according to an embodiment of the present application. As Figure 1 shown, the test method for battery overcharge safety in the embodiments of the present application mainly includes the following steps S101 to step S103.

[0051] Step S101: Perform a volt-ampere test on the battery to be tested. The test voltage change process of the volt-ampere test sequentially includes a normal voltage stage and an overvoltage stage.

[0052] The test voltage is the voltage applied across the battery, and the test voltage can also be understood as the open-circuit voltage.

[0053] The principle of the volt-ampere test is to set the range of the test voltage and the scan rate, and based on the range of the test voltage, perform a forward scan or a reverse scan on the battery according to the scan rate, and obtain the current density of the battery during the scan. The forward scan means starting from the starting voltage value of the test voltage, and gradually increasing the voltage value of the test voltage according to the scan rate until the voltage value reaches the termination voltage value of the test voltage; the reverse scan means starting from the termination voltage value of the test voltage, and gradually decreasing the voltage value of the test voltage according to the scan rate until the voltage value reaches the starting voltage value of the test voltage.

[0054] In this embodiment, the range of the test voltage is divided into two sub-ranges: a normal voltage stage and an overvoltage stage. The test voltage within the normal voltage stage is determined according to the voltage (hereinafter described as the normal voltage) range used during the normal charging of the battery to be tested, and the test voltage within the overvoltage stage is determined according to the voltage (hereinafter described as the overvoltage) range used during the overcharging of the battery to be tested.

[0055] Different types of batteries may have different normal voltages and overvoltages. When obtaining the normal voltage and overvoltage of the battery to be tested, the type of the battery to be tested can be determined first, and then the normal voltage and overvoltage of this type of battery can be queried. For example, if the battery to be tested is a lithium iron phosphate button battery, the normal voltage that can be queried according to this battery type is 2.0 - 3.65V, and the overvoltage is 5.5V. Based on this, the test voltage in the normal voltage stage can be 2.0 - 3.65V, and the test voltage in the overvoltage stage can be 3.66V - 5.5V.

[0056] A large-capacity lithium-ion battery can be composed of multiple small-capacity battery cells (hereinafter described as small cells), such as large-capacity lithium-ion batteries used in fields such as portable electronic devices and electric vehicles. The battery to be tested can be a lithium-ion battery assembled from one or a small number of the above-mentioned small cells. In some embodiments, the battery to be tested can be any one of a button cell, a soft-pack battery, and a single-cell battery.

[0057] Step S102: Obtain the ratio of the first peak current density to the second peak current density.

[0058] The first peak current density can be understood as the maximum current density of the battery to be tested in the normal voltage stage. In the normal voltage stage, the current density of the battery to be tested can be detected, and the maximum current density can be obtained from the detection results at the end of the normal voltage stage.

[0059] The second peak current density can be understood as the maximum current density in the overvoltage stage. In the overvoltage stage, the current density of the battery to be tested can be detected, and the maximum current density can be obtained from the detection results at the end of the overvoltage stage.

[0060] The above ratio is the result of dividing the first peak current density by the second peak current density.

[0061] Step S103: Compare the ratio with a first preset threshold, and determine the test result according to the comparison result.

[0062] If the above ratio is greater than the first preset threshold, the battery to be tested initially passes the test, and the battery to be tested has a certain degree of safety during overcharging; otherwise, the battery to be tested fails the test, and the battery to be tested has poor safety during overcharging. Among them, the first preset threshold is greater than 1.

[0063] Specifically, the magnitude of the peak current density during the volt-ampere test can represent the intensity of the electrochemical reaction (oxidation reaction or reduction reaction) occurring in the battery. Based on this, it can be determined that the first peak current density represents the intensity of the electrochemical reaction of the battery to be tested in the normal voltage stage (i.e., the electrochemical reaction intensity during normal charging), and the second peak current density represents the intensity of the electrochemical reaction of the battery to be tested in the overvoltage stage (i.e., the electrochemical reaction intensity during overcharging).

[0064] If the above ratio is greater than the first preset threshold, it indicates that the difference between the first and second peak current densities is relatively large and the first peak current density is greater than the second peak current density. That is to say, the difference in the electrochemical reaction intensity of the battery under test between the normal voltage stage and the overvoltage stage is relatively large, and the electrochemical reaction intensity in the overvoltage stage is less than that in the normal voltage stage. Based on this, it can be determined that the electrochemical reaction of the battery under test is not intense in the overvoltage stage. If the battery under test is overcharged for a long time, the possibility of thermal runaway is also relatively small. Therefore, it can be determined that the battery under test has high safety during overcharging and passes the battery overcharge safety test.

[0065] If the above ratio is less than or equal to the first preset threshold, it indicates that the difference between the first and second peak current densities is relatively small. That is to say, the difference in the electrochemical reaction intensity of the battery under test between the normal voltage stage and the overvoltage stage is relatively small and they are relatively close. Based on this, it can be determined that the electrochemical reaction of the battery under test is relatively intense in the overvoltage stage. If the battery under test is overcharged for a long time, the possibility of thermal runaway is also relatively large and it may even explode. Therefore, it can be determined that the safety of the test battery during overcharging is poor and it fails the battery overcharge safety test.

[0066] When setting the value of the first preset threshold, those skilled in the art can perform voltammetry tests on multiple batteries to obtain the above ratios of each battery respectively. Then overcharge these batteries and record which batteries will experience thermal runaway or explosion, and set the value of the first preset threshold based on the above ratios of these batteries. For example, select the smallest ratio from the above ratios of these batteries and set the value of the first preset threshold according to this smallest ratio. For instance, set the value of the first preset threshold to this smallest ratio.

[0067] In some embodiments, the positive electrode material of the battery to be tested is lithium iron phosphate, the negative electrode material is graphite, and the electrolyte can be a conventional electrolyte applied to lithium iron phosphate batteries. For example, the electrolyte of model TC-8087 produced by Tianci Materials Company can be used. In this embodiment, for the above-mentioned battery to be tested, the first preset threshold is set to 20. The method for determining the first preset threshold will be described below. Specifically, using lithium iron phosphate as the positive electrode material, graphite as the negative electrode material, and adopting the same conventional electrolyte applied to lithium iron phosphate batteries, 20 batteries to be tested, LFP-1 to LFP-20, are prepared. Voltammetric tests are performed on the 20 batteries to be tested respectively. The test voltage change process of the voltammetric test sequentially includes a normal voltage stage and an overvoltage stage. The test voltage range of the normal voltage stage is 2.0 - 3.75V, and the test voltage range of the overvoltage stage is 4.7 - 4.9V. During the overcharge in the voltammetric test, the first peak current density (i.e., the maximum current density in the normal voltage stage) and the second peak current density (i.e., the maximum current density in the overvoltage stage) of each battery to be tested are obtained respectively, and the ratio of the first and second peak current densities corresponding to each battery to be tested is calculated. In addition, during the voltammetric test, it is also monitored whether each battery to be tested passes the overcharge test. If the battery to be tested meets the passing conditions of the overcharge test (such as no thermal runaway and no fire or explosion), it is determined that the test battery passes the overcharge test; if the battery to be tested does not meet the passing conditions of the overcharge test (such as thermal runaway or fire or explosion), it is determined that the test battery fails the overcharge test. In addition, during the voltammetric test, the proportion of alkane gases generated by each battery to be tested is also monitored. This proportion refers to the proportion of alkane gases in the total amount of gases generated by the battery to be tested. Specifically, the above test results are shown in Table 1 below.

[0068] Table 1

[0069]

[0070]

[0071] As can be seen from Table 1 above, the batteries to be tested, LEP-2 and LFP-4, fail the overcharge test, and the remaining 18 batteries to be tested pass the overcharge test. The "ratio of the first and second peak current densities" of these 18 batteries to be tested is greater than 20, which indicates that when the "ratio of the first and second peak current densities" is greater than 20, the safety level of the battery to be tested is relatively high. Therefore, the first preset threshold can be set to 20.

[0072] Based on the method described in the above steps S101 to S103, the safety test of overcharging can be accurately and reliably completed by using the peak current density in the voltammetric test.

[0073] Next, the embodiments of the test method for the overcharge safety of the battery provided in this application will be further described.

[0074] 1. Description of the method for obtaining the first peak current density.

[0075] In some embodiments of this application, the first peak current density of the battery to be tested in the normal voltage stage can be obtained through Figure 2 the following steps S201 to S204 shown below.

[0076] Step S201: Obtain the volt-ampere curve of the battery to be tested during the volt-ampere test. The volt-ampere curve represents the process in which the current density of the battery to be tested changes with the test voltage.

[0077] The abscissa of the volt-ampere curve is the test voltage, and the ordinate is the current density.

[0078] Step S202: Obtain the first test voltage range corresponding to the normal voltage stage.

[0079] According to the description of the foregoing step S102, this application divides the range of the test voltage into two sub-ranges: the normal voltage stage and the overvoltage stage. The first test voltage range is the sub-range representing the normal voltage stage.

[0080] Step S203: According to the volt-ampere curve, obtain the maximum current density of the battery to be tested within the first test voltage range.

[0081] Specifically, according to the volt-ampere curve, obtain the current density corresponding to each test voltage within the first test voltage range, and select the maximum current density from these current densities.

[0082] Step S204: According to the maximum current density, obtain the first peak current density.

[0083] Specifically, the maximum current density can be used as the first peak current density.

[0084] Next, in combination with the attached Figure 3 and the attached Figure 4 the method for obtaining the first peak current density will be described.

[0085] Referring to the attached Figure 3 , prepare three lithium iron phosphate button cells LFP-1, LFP-2, and LFP-3. Figure 3 The three curves in Figure 3As shown, the first peak current densities of LFP-1, LFP-2, and LFP-3 in the normal voltage stage are 0.01 A / cm 2 , 0.00526 A / cm 2 , and 0.008 A / cm 2 .

[0086] Refer to the appendix Figure 4 , and prepare three soft-pack batteries LFP-1, LFP-2, and LFP-3 of lithium iron phosphate. The model of lithium iron phosphate in the soft-pack battery is different from that in the button battery shown Figure 3 . Figure 4 The three curves in Figure 4 respectively represent the volt-ampere curves of LFP-1, LFP-2, and LFP-3 during the volt-ampere test. The test voltage in the normal voltage stage can be 2.0 - 3.75 V, and the test voltage in the overvoltage stage can be 4.7 V - 4.9 V. The scanning rate is 0.1 mV / s. As shown 2 , the first peak current densities of LFP-1, LFP-2, and LFP-3 in the normal voltage stage are 3.51 A / cm 2 , 3.078 A / cm 2 , and 3.0225 A / cm

[0087] Based on the method described in the above steps S201 to S204, the first peak current density of the battery to be tested can be quickly and accurately obtained by using the volt-ampere curve.

[0088] II. Explain the method for obtaining the second peak current density.

[0089] In some embodiments of the present application, the second peak current density of the battery to be tested in the overvoltage stage can be obtained through the following steps S301 to S304 shown Figure 5 .

[0090] Step S301: Obtain the volt-ampere curve of the battery to be tested during the volt-ampere test. The volt-ampere curve represents the process of the current density of the battery to be tested changing with the test voltage.

[0091] The abscissa of the volt-ampere curve is the test voltage, and the ordinate is the current density.

[0092] Step S302: Obtain the second test voltage range corresponding to the overvoltage stage.

[0093] According to the description of the foregoing step S102, the present application divides the range of the test voltage into two sub-ranges: the normal voltage stage and the overvoltage stage. The second test voltage range is the sub-range representing the overvoltage stage.

[0094] Step S303: Obtain the maximum current density of the battery under test within the second test voltage range according to the volt-ampere curve.

[0095] Specifically, obtain the current density corresponding to each test voltage within the second test voltage range according to the volt-ampere curve, and select the maximum current density from these current densities.

[0096] Step S304: Obtain the second peak current density according to the maximum current density.

[0097] Specifically, the maximum current density can be used as the second peak current density.

[0098] Refer to the appendix Figure 3 again. As Figure 3 shown, the second peak current densities of LFP-1, LFP-2, and LFP-3 in the overvoltage stage are 0.0004 A / cm 2 , 0.00085 A / cm 2 , and 0.0004 A / cm 2 , respectively.

[0099] Refer to the appendix Figure 4 again. As Figure 4 shown, the second peak current densities of LFP-1, LFP-2, and LFP-3 in the overvoltage stage are 0.1398 A / cm 2 , 2.235 A / cm 2 , and 0.13955 A / cm 2 , respectively.

[0100] Based on the method described in the above steps S1031 to S1034, the second peak current density of the battery under test can be quickly and accurately obtained by using the volt-ampere curve.

[0101] Next, the preliminary test results of the battery under test will be described in conjunction with Figure 3 the appendix Figure 4 and the appendix

[0102] In the example shown in the appendix Figure 3 , the first peak current density, the second peak current density, and the ratio of the button cells LFP-1, LFP-2, and LFP-3 are shown in Table 2 below.

[0103] Table 2

[0104] LFP-1 LFP-2 LFP-3 Normal voltage stage <![CDATA[0.01A / cm 2 > <![CDATA[0.00526 A / cm 2 > <![CDATA[0.008A / cm 2 > Overvoltage stage <![CDATA[0.0004 A / cm 2 > <![CDATA[0.00085 A / cm 2 > <![CDATA[0.0004 A / cm 2 > Ratio 25 6 20

[0105] In this embodiment, the first preset threshold is 20. The first ratios of LFP-1 and LFP-3 are both greater than 20. Therefore, LFP-1 and LFP-3 have initially passed the overcharge safety test; the first ratio of LFP-2 is less than 20. Therefore, LFP-2 has not passed the overcharge safety test. The overcharge tests are performed on LFP-1, LFP-2, and LFP-3 to verify the above test results. After the overcharge tests, it is confirmed that LFP-2 has experienced thermal runaway and explosion, while LFP-1 and LFP-3 have not experienced thermal runaway and explosion. It can be seen that the method provided by this application can accurately test the safety of the battery during overcharge.

[0106] In the attached Figure 4 In the example shown, the first peak current density, the second peak current density, and the first ratio of the pouch cells LFP-1, LFP-2, and LFP-3 are shown in Table 3 below.

[0107] Table 3

[0108] LFP-1 LFP-2 LFP-3 Normal voltage stage <![CDATA[3.51 A / cm 2 > <![CDATA[3.078 A / cm 2 > <![CDATA[3.0225 A / cm 2 > Overvoltage stage <![CDATA[0.1398A / cm 2 > <![CDATA[2.235 A / cm 2 > <![CDATA[0.13955 A / cm 2 > Ratio 25.11 1.38 21.65

[0109] In this embodiment, the first preset threshold is 20. The first ratios of LFP-1 and LFP-3 are both greater than 20. Therefore, LFP-1 and LFP-3 have initially passed the overcharge safety test; the first ratio of LFP-2 is less than 20. Therefore, LFP-2 has not passed the overcharge safety test.

[0110] Next, the embodiments of the method for testing the overcharge safety of the battery provided by this application will be further described.

[0111] In some embodiments according to this application, if the battery to be tested is a pouch cell or a single cell, when it is determined that the battery to be tested has initially passed the overcharge safety test, the following steps S401 to S402 can be used to determine whether the battery to be tested finally passes the test.

[0112] Step S401: Obtain the gas generated by the battery to be tested during the overvoltage stage.

[0113] Step S402: If the composition of the gas meets the preset safety conditions, the battery to be tested finally passes the test; if the composition of the gas does not meet the preset safety conditions, the battery to be tested finally fails the test.

[0114] Specifically, an explosion may occur when the battery undergoes thermal runaway. The reason for the explosion is that the battery generates flammable gas. When the concentration of the flammable gas is relatively high and the battery temperature is also relatively high, an explosion may occur. Based on this, a safety condition for the gas composition is set. If the gas composition generated by the battery meets this safety condition, it indicates that the flammable gas in the gas is within the safe range and will not cause the battery to explode. Therefore, it can be determined that the battery under test finally passes the overcharge safety test. If this safety condition is not met, it indicates that the flammable gas in the gas is not within the safe range and may cause the battery to explode. Therefore, even if it is preliminarily determined that the battery under test passes the overcharge safety test based on the peak current density, since the battery may explode, it is still determined that the battery under test finally fails the overcharge safety test.

[0115] In some embodiments, the gas generated by the battery under test during the overvoltage stage can be divided into two types: flammable gas and non-flammable gas, and the preset safety condition is set to that the proportion of the flammable gas in the total gas generated by the battery is less than a second preset threshold.

[0116] Specifically, if the proportion of the flammable gas is less than the second preset threshold, it indicates that the content of the flammable gas is relatively small and the content of the non-flammable gas is relatively large, which is relatively safe. Even if the battery temperature is relatively high, an explosion will not occur. If the proportion of the flammable gas is greater than or equal to the second preset threshold, it indicates that the content of the flammable gas is relatively large and is relatively dangerous. If the battery temperature is relatively high, an explosion will easily occur.

[0117] When setting the value of the second preset threshold, those skilled in the art can conduct overcharge tests on multiple batteries, collect the gases generated by each battery, and record which batteries will not explode. Then, set the value of the second preset threshold according to the proportion of the flammable gas in these batteries. For example, select the largest one from the proportions of the flammable gas in these batteries and set the value of the second preset threshold according to this largest proportion. For instance, set the value of the second preset threshold to this largest proportion.

[0118] In some embodiments, the positive electrode material of the battery to be tested is lithium iron phosphate, the negative electrode material is graphite, and the electrolyte can be a conventional electrolyte applied to lithium iron phosphate batteries. For example, the electrolyte of model TC-8087 produced by Tianci Materials Company can be used. In this embodiment, for the above-mentioned battery to be tested, the second preset threshold is set to 0.1. Among them, the battery to be tested in this embodiment is the same as the battery to be tested provided in some embodiments of the foregoing step S103 (that is, the battery to be tested in the foregoing step S103 with lithium iron phosphate as the positive electrode material, graphite as the negative electrode material, and a conventional electrolyte applied to lithium iron phosphate batteries). The method for determining the second preset threshold is similar to the method for determining the first preset threshold in the foregoing step S103, and the value of the second preset threshold can also be determined by using the test results shown in Table 1 above. Specifically, according to Table 1, it can be seen that the batteries to be tested LEP-2 and LFP-4 failed the overcharge test, and the remaining 18 batteries to be tested passed the overcharge test. Among these 18 batteries to be tested that passed the overcharge test, the proportion of alkane gases in 17 batteries to be tested is less than 10%, that is, the proportion of alkane gases in at least 90% of the batteries to be tested is less than 10%. This indicates that when the proportion of alkane gases is less than 10%, the safety level of the battery to be tested is relatively high. Therefore, the second preset threshold is set to 0.1.

[0119] The following will be described in conjunction with Figure 6 , the gas component test of the battery to be tested.

[0120] Refer to the appendix Figure 6 , three lithium iron phosphate soft-pack batteries LFP-1, LFP-2, and LFP-3 are prepared. The combustible gases include alkane gases and hydrogen, and the non-combustible gas is carbon dioxide. As Figure 6 shown, the proportion of alkane gases generated by LFP-2 in the total amount of gases generated by LFP-2 reaches more than 45%, and hydrogen also reaches more than 45%, so that the proportion of combustible gases generated by LFP-2 reaches more than 90%, and the proportion is very high. If the second preset threshold is 0.1, then it can be determined that LFP-2 finally fails the overcharge safety test.

[0121] Based on the methods described in the above steps S401 to S402, when assembling the battery cells into soft-pack batteries or single-cell batteries, after the battery initially passes the overcharge safety test, the gas generated by the battery can be used for secondary testing to ensure the reliability of the test results. In addition, if the battery cells are assembled into button cells, due to the limitation of the structure of button cells, it is difficult to collect gases. Therefore, if the battery to be tested is a button cell, if it is determined that the battery to be tested initially passes the overcharge safety test by using the peak current density, then it is not necessary to use the gas generated by the battery for secondary testing, and it can be finally determined that it has passed the overcharge safety test.

[0122] It should be noted that although the above embodiments describe the various steps in a specific order, those skilled in the art can understand that, in order to achieve the effects of the present application, it is not necessary for different steps to be executed in such an order. They can be executed simultaneously (in parallel) or in other orders, and these adjusted solutions are equivalent technical solutions to the technical solutions described in the present application, and thus will also fall within the protection scope of the present application.

[0123] Those skilled in the art can understand that all or part of the processes in the method of the above-mentioned embodiment of the present application can also be completed by instructing relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by a processor, the steps of the above-mentioned method embodiments can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in the form of source code, object code, executable file or some intermediate forms, etc. The computer-readable storage medium can include: any entity or device, medium, USB flash drive, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory, random access memory, electrical carrier signal, telecommunication signal, and software distribution medium that can carry the computer program code, etc.

[0124] Another aspect of the present application also provides a computer-readable storage medium.

[0125] In an embodiment of a computer-readable storage medium according to the present application, the computer-readable storage medium can be configured to store a program for executing the battery overcharge safety test method of the above-mentioned method embodiment. The program can be loaded and run by a processor to implement the battery overcharge safety test method. For the sake of convenience of description, only the parts related to the embodiments of the present application are shown. For the specific technical details not disclosed, please refer to the method part of the embodiments of the present application. The computer-readable storage medium can be a storage device formed by various electronic devices. Optionally, the computer-readable storage medium in the embodiments of the present application is a non-transitory computer-readable storage medium.

[0126] Another aspect of the present application also provides an electronic device.

[0127] In an embodiment of an electronic device according to the present application, the electronic device can include at least one processor; and a memory communicatively connected to at least one processor; wherein, a computer program is stored in the memory, and when the computer program is executed by at least one processor, the method described in any of the above embodiments is implemented. Refer to the attached Figure 7 , Figure 7 Exemplarily, it is shown that the memory 11 and the processor 12 are communicatively connected through a bus.

[0128] In some embodiments of the present application, the electronic device described in the present application may be, but is not limited to, desktop, laptop, handheld computer, notebook computer, vehicle-mounted device, ultra-mobile personal computer (UMPC), netbook, personal digital assistant (PDA), etc., and the embodiments of the present application do not limit this.

[0129] So far, the technical solution of the present application has been described in conjunction with one embodiment shown in the drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present application is obviously not limited to these specific embodiments. Without departing from the principle of the present application, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present application.

Claims

1. A test method for the overcharge safety of a battery, characterized in that The method includes: Performing a volt-ampere test on the battery to be tested, where the test voltage change process of the volt-ampere test sequentially includes a normal voltage stage and an overvoltage stage; Obtaining the ratio of the first peak current density to the second peak current density; the first peak current density is the peak current density in the normal voltage stage, and the second peak current density is the peak current density in the overvoltage stage; Comparing the ratio with a first preset threshold. If the ratio is greater than the first preset threshold, the battery to be tested preliminarily passes the test; Wherein, the first preset threshold is greater than 1.

2. The method according to claim 1, wherein The first peak current density is obtained by the following method: Obtaining the volt-ampere curve of the battery to be tested during the volt-ampere test, where the volt-ampere curve represents the process of the current density of the battery to be tested changing with the test voltage; Obtaining the first test voltage range corresponding to the normal voltage stage; According to the volt-ampere curve, obtaining the maximum current density of the battery to be tested within the first test voltage range; According to the maximum current density, obtaining the first peak current density.

3. The method according to claim 1, wherein The second peak current density is obtained by the following method: Obtaining the volt-ampere curve of the battery to be tested during the volt-ampere test, where the volt-ampere curve represents the process of the current density of the battery to be tested changing with the test voltage; Obtaining the second test voltage range corresponding to the overvoltage stage; According to the volt-ampere curve, obtaining the maximum current density of the battery to be tested within the second test voltage range; According to the maximum current density, obtaining the second peak current density.

4. The method according to claim 1, wherein The positive electrode material of the battery to be tested is lithium iron phosphate, the negative electrode material is graphite, and the first preset threshold is 20.

5. The method according to claim 1, characterized in that, The method includes: Obtaining the gas generated by the battery to be tested during the overvoltage stage; If the composition of the gas meets the preset safety conditions, the battery to be tested finally passes the test.

6. The method according to claim 5, wherein The composition of the gas includes combustible gas, and the preset safety condition is that the proportion of the combustible gas in the total amount of the gas is less than a second preset threshold.

7. The method according to claim 6, wherein The positive electrode material of the battery to be tested is lithium iron phosphate, the negative electrode material is graphite, and the second preset threshold is 0.

1.

8. The method according to claim 1, wherein The battery to be tested is any one of a button cell, a soft package battery, and a single cell.

9. An electronic device, characterized in that, Includes: At least one processor; And a memory communicatively connected to the at least one processor; Wherein, a computer program is stored in the memory, and when the computer program is executed by the at least one processor, it implements the test method for battery overcharge safety described in any one of claims 1 to 8.

10. A computer-readable storage medium storing multiple program codes, characterized in that, The program code is adapted to be loaded and run by a processor to execute the test method for battery overcharge safety described in any one of claims 1 to 8.

Images