Method for evaluating valve opening risk of battery

Abstract

The invention provides a battery valve opening risk assessment method, which comprises: obtaining a gas production rate: infiltrating an electrode plate in an electrolyte, and detecting the gas production rate generated by a reaction between the electrode plate and the electrolyte at a test temperature; a battery corresponding to the electrode plate is selected, the battery comprises an anti-explosion valve, and the battery is subjected to a pressing test to obtain the valve opening pressure of the anti-explosion valve; and risk assessment: determining a corresponding gas production threshold value according to the obtained valve opening pressure, and comparing the gas production rate with the gas production threshold value to determine whether a valve opening risk exists in the battery corresponding to the electrode pole piece. By adopting the technical scheme, the accuracy and the reliability of detection are improved, the time and the economic cost are reduced, whether the valve opening risk exists in the battery or not can be quickly and accurately evaluated, and therefore battery products meeting the standard can be quickly screened and prepared within a short time.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and in particular relates to a method for assessing the risk of battery valve opening. Background Art

[0002] With the continuous development of batteries, users have put forward higher requirements for battery performance, such as battery capacity and cycle life. However, the premise of these performance improvements is that the safety performance of the battery must be guaranteed. Therefore, it is very important to study the safety performance of batteries under high temperature conditions, which is a necessary condition to ensure the safe and reliable use of batteries.

[0003] As the use environment changes, especially the temperature difference, the temperature of the battery surface will also fluctuate. For example, in the summer, the temperature inside a car that is exposed to the outside for a long time will continue to rise. Even if the outside temperature does not reach 60°C, the temperature on the surface of the car battery may approach or reach 60°C. Under high temperature conditions, the positive and negative electrode materials of the battery may react with the electrolyte to produce gas, causing the internal pressure to rise. If the pressure exceeds the set threshold of the explosion-proof valve, the gas may break through the explosion-proof valve and allow external air (containing oxygen) to enter the battery. The entry of oxygen may react violently with active materials such as lithium, causing thermal runaway, which may eventually cause the battery to catch fire or explode, causing serious safety problems. Therefore, it is crucial to ensure that the battery can maintain internal pressure within safe limits in all use environments to prevent abnormal opening of the explosion-proof valve.

[0004] The existing technology usually uses a pressure sensor to monitor whether there is a risk of the explosion-proof valve opening in a high-temperature environment. The sensor is connected to the inside of the battery through a pipe, that is, one end of the pipe is connected to the battery and the other end is connected to the sensor. However, this method has the following limitations:

[0005] First, the test temperature and test duration are limited. Most sensors cannot withstand a high temperature of 90°C. In a high temperature environment, the sensor material may age, thus affecting the accuracy of the test. In addition, even if the sensor can withstand a temperature of 60°C, the test time should not be too long. If the test time is too long, the stability of data acquisition may be affected, thereby reducing the accuracy of the test results.

[0006] Second, the scope of application is limited. This sensor testing method is only applicable to hard-shell (aluminum shell) batteries, such as square shell batteries, but not to soft-shell batteries, such as soft-pack batteries.

[0007] Third, the cost is high. Before using the pressure sensor for testing, the various performance characteristics of the battery must be fully tested to ensure that they meet the test standards. This preliminary preparation process itself is quite time-consuming. In addition, if the explosion-proof valve is triggered during the test, the battery needs to be improved accordingly. After that, the battery casing must be reinstalled, the installed battery must be connected to the sensor, and the performance test must be performed again before the test can continue. The process is complicated and the time cost is high. In addition, this testing method also increases the economic cost.

[0008] Fourthly, the detection accuracy is not enough. In practice, it is found that sometimes the pressure sensor does not show that the valve opening pressure has been reached, but the explosion-proof valve has been opened in advance. The reason for this phenomenon may be that the installation method or position of the pressure sensor is not accurate enough, making the measured pressure value lower than the actual internal pressure. This makes it impossible to guarantee the reliability of the test results, thereby limiting the effectiveness of the pressure sensor detection method in practical applications. Summary of the invention

[0009] The present invention provides the following technical solutions to solve the above technical problems.

[0010] The present invention provides a method for assessing the risk of battery valve opening, the method comprising:

[0011] Obtaining gas production: Immerse the electrode plate in the electrolyte and detect the gas production generated by the reaction between the electrode plate and the electrolyte at the test temperature;

[0012] Obtaining the valve opening pressure: Select a battery corresponding to the electrode plate, the battery having an explosion-proof valve, and perform a pressure test on the battery to obtain the valve opening pressure of the explosion-proof valve;

[0013] Risk assessment: Determine the corresponding gas production threshold value based on the obtained valve opening pressure, and compare the gas production amount and the gas production threshold value to determine whether the battery corresponding to the electrode plate has a valve opening risk.

[0014] The adoption of the above technical solution improves the accuracy and reliability of detection, reduces time and economic costs, and helps to quickly and accurately evaluate whether the battery has a valve opening risk, thereby helping to quickly screen and prepare battery products that meet the standards in a shorter period of time.

[0015] Optionally, the step of obtaining the gas production specifically includes: fully charging the battery, then disassembling the battery to obtain electrode plates, then immersing the electrode plates in an electrolyte, and detecting the gas production generated by the reaction of the electrode plates and the electrolyte at a test temperature.

[0016] Optionally, in the step of obtaining the gas production amount, the battery is fully charged in the following manner: the battery is constant-current charged at a charging current of 0.1C-1C to a cut-off voltage of 3.6V-4.4V, and then constant-voltage charged until the charging current drops to 0.05-0.1C.

[0017] Optionally, the electrode plates include a positive electrode plate and a negative electrode plate, and the gas production is the sum of the gas production generated by the positive electrode plate reacting with the electrolyte at the test temperature and the gas production generated by the negative electrode plate reacting with the electrolyte at the test temperature.

[0018] Optionally, the step of obtaining the gas production includes: independently immersing the positive electrode plate and the negative electrode plate in the electrolyte, and detecting the gas production generated by the reaction of the positive electrode plate and the electrolyte at a test temperature and the gas production generated by the reaction of the negative electrode plate and the electrolyte.

[0019] Optionally, the total number of electrode plates is 5-10 plates.

[0020] Optionally, in the step of obtaining the gas production, the amount of electrolyte used to soak the electrode plates is determined based on the product of the injection coefficient of the battery corresponding to the electrode plates and the capacity of each electrode plate, wherein the capacity of each electrode plate = the capacity of the battery corresponding to the electrode plate / the number of electrode plates.

[0021] Optionally, in the step of obtaining the gas production, the method of testing the gas production at the test temperature specifically includes: placing the electrode plate into an aluminum-plastic film bag, adding electrolyte, then vacuum sealing, and using the water displacement method to test the first volume of the aluminum-plastic film bag containing the electrode plate and electrolyte; then placing the aluminum-plastic film bag at the test temperature to react and produce gas; then taking it out, and using the water displacement method to test the second volume of the aluminum-plastic film bag containing electrolyte, electrode plate and gas production, wherein the difference between the second volume and the first volume is the gas production.

[0022] Optionally, in the step of obtaining the gas production, the test temperature is the highest temperature in the application scenario of the battery corresponding to the electrode plate or 1.1 to 1.8 times the highest temperature.

[0023] Optionally, the step of obtaining the valve opening pressure further includes placing a battery corresponding to the electrode plate at a test temperature, and then performing a pressure test on the battery to obtain the valve opening pressure of the explosion-proof valve. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A flow chart showing a method for assessing the risk of battery valve opening in one embodiment of the present invention is shown;

[0025] Figure 2 A schematic structural diagram of a pressing device in one embodiment of the present invention is shown. DETAILED DESCRIPTION

[0026] The following specific embodiments illustrate the implementation of the present invention, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Although the description of the present invention will be introduced in conjunction with the preferred embodiment, this does not mean that the features of this invention are limited to this implementation. On the contrary, the purpose of introducing the invention in conjunction with the implementation is to cover other options or modifications that may extend based on the claims of the present invention. In order to provide a deep understanding of the present invention, the following description will include many specific details. The present invention can also be implemented without using these details. In addition, in order to avoid confusion or blurring the focus of the present invention, some specific details will be omitted in the description. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0027] It should be noted that in this specification, similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings.

[0028] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0029] like Figure 1 As shown, the present invention provides a method for reducing the risk of battery valve opening, the method comprising:

[0030] Obtain gas production: Immerse the electrode plate in the electrolyte and detect the gas production generated by the reaction between the electrode plate and the electrolyte at the test temperature. The test temperature is set according to the actual test requirements. For example, if the valve opening risk of a battery made of the electrode plate at 50°C needs to be evaluated, the test temperature should be set to 50°C; if the valve opening risk of a battery made of the electrode plate at 60°C needs to be evaluated, the test temperature should be set to 60°C.

[0031] Obtaining the valve opening pressure: Select a battery corresponding to the above-mentioned electrode plate, the battery having an explosion-proof valve, and perform a pressure test on the battery to obtain the valve opening pressure of the explosion-proof valve (that is, to obtain the valve opening pressure of the explosion-proof valve of the battery made of the above-mentioned electrode plate).

[0032] Risk assessment: Determine the corresponding gas production threshold value based on the obtained valve opening pressure, and compare the gas production volume and the gas production threshold value to determine whether the battery corresponding to the above-mentioned electrode plate has a valve opening risk. Among them, the gas production threshold value can be the obtained valve opening pressure (that is, the valve opening pressure threshold value), or it can be a volume threshold value obtained by converting the valve opening pressure. The specific choice depends on the characterization method of the gas production volume. For example, if the gas production volume is measured in volume, then the valve opening pressure needs to be converted into an equivalent volume value for comparison. If the gas production volume is expressed in pressure, it can be directly compared with the valve opening pressure to determine whether there is a valve opening risk. During this process, if the measured gas production volume is greater than the equivalent volume converted by the valve opening pressure or the gas production pressure is greater than the valve opening pressure, it means that the battery corresponding to the above-mentioned electrode plate will open the valve at the test temperature; if the gas production volume is equal to the equivalent volume converted by the valve opening pressure or the gas production pressure is equal to the valve opening pressure, it means that the battery corresponding to the above-mentioned electrode plate has a valve opening risk at the test temperature; if the gas production volume is less than the equivalent volume value converted by the valve opening pressure and the gas production pressure is less than the valve opening pressure, it means that the battery corresponding to the above-mentioned electrode plate will not open the valve at the test temperature.

[0033] The above method provided by the present invention abandons the reliance on additional components such as pressure sensors, which avoids damage to the battery structure on the one hand, and also reduces the detection interference that may be caused by the sensor, thereby improving the accuracy and reliability of the detection. On the other hand, it eliminates the complicated steps of rolling the electrode plate into a complete battery and installing the shell and performing a comprehensive performance test on the battery to ensure compliance with the test standards. In addition, if it is found during the detection process that the battery made of the electrode plate has a valve opening risk, after the electrode plate or the electrolyte is optimized and adjusted, it is only necessary to continue to detect the gas production generated by the reaction of the optimized electrode plate and the electrolyte at the test temperature and the valve opening pressure of the explosion-proof valve of the battery made of the optimized electrode plate, and then compare the gas production threshold corresponding to the gas production and the valve opening pressure to directly determine whether the battery has a valve opening risk, without the need to re-install the shell and the battery performance test steps, which greatly simplifies the installation process, greatly shortens the detection cycle, improves the detection efficiency, and also reduces time and economic costs. On the other hand, since the detection object of the above technical solution of the present invention is the electrode plate, there are no specific restrictions on the type of battery, test temperature and test time. This means that the above scheme is not only applicable to various hard-shell and soft-shell batteries, but can also be tested at any set test temperature according to actual needs, and the test duration can be flexibly adjusted according to specific circumstances to obtain accurate gas production. This helps to quickly screen and prepare battery products that meet the standards in a short period of time.

[0034] Furthermore, in the above embodiment, the step of obtaining the gas production specifically includes: fully charging the battery, then disassembling the battery to obtain the electrode plate, then immersing the electrode plate in the electrolyte, and detecting the gas production generated by the reaction between the electrode plate and the electrolyte at the test temperature. By fully charging the battery in advance, the reaction activity inside the battery can be increased, thereby ensuring that the chemical reaction inside the battery is active, so that the gas production of the battery under normal use can be simulated in subsequent tests, so that the maximum gas production can be obtained at the test temperature. This can improve the reliability of the evaluation results.

[0035] Further, in the above embodiment, in the step of obtaining the gas production, the battery is fully charged in the following manner: the battery is charged to a cut-off voltage of 3.6V-4.4V with a charging current of 0.1C-1C, and then a constant voltage charge is performed until the charging current drops to 0.05-0.1C. In this way, the reaction activity inside the battery can be maximized, thereby ensuring that the maximum gas production is obtained, thereby ensuring the reliability of the evaluation. Specifically, during the charging process, the lithium ions of the positive electrode migrate to the negative electrode. The more the migration amount, the worse the structural stability of the negative electrode, and the higher the reaction activity. The charging scheme provided by the present invention can ensure that after the battery is fully charged, almost all of the lithium ions of the positive electrode migrate to the negative electrode. At this time, the activity of the negative electrode is significantly improved, the structural stability is reduced, and the positive electrode is enhanced due to the lack of lithium ions, and the structure becomes unstable. This state causes the reaction between the positive and negative electrodes and the electrolyte to be more intense under high temperature conditions, thereby generating more gas. Therefore, at the test temperature, the maximum gas production can be achieved. By comparing this maximum gas production with the gas production threshold, the reliability of the evaluation can be ensured.

[0036] Furthermore, in the above-mentioned embodiment, the electrode plates include a positive plate and a negative plate, and the gas production is the sum of the gas production generated by the reaction of the positive plate with the electrolyte at the test temperature and the gas production generated by the reaction of the negative plate with the electrolyte at the test temperature. Due to the different chemical properties of the positive and negative plates, the gas production of their reactions with the electrolyte at the test temperature is also different. Normally, the reaction between the positive electrode and the electrolyte is the main source of gas production. In order to accurately characterize the gas production of the entire plate inside the battery, this embodiment tests the gas production of the positive and negative plates, thereby ensuring that the measured gas production can truly reflect the gas production inside the battery. By then comparing the actual gas production with the gas production threshold, a more valuable reference evaluation result can be obtained.

[0037] Furthermore, in the above-mentioned embodiment, the step of obtaining the gas production includes: independently immersing the positive electrode plate and the negative electrode plate in the electrolyte, and detecting the gas production generated by the reaction of the positive electrode plate with the electrolyte and the gas production generated by the reaction of the negative electrode plate with the electrolyte at the test temperature. Then, the gas production generated by the reaction of the positive electrode plate with the electrolyte at the test temperature and the gas production generated by the reaction of the negative electrode plate with the electrolyte at the test temperature are added to obtain the final gas production. By testing the gas production of the positive and negative electrode plates separately, it is possible to accurately identify whether the positive electrode plate or the negative electrode plate causes the increase in gas production based on the difference in gas production, so that the plate can be optimized and improved in a targeted manner. This shortens the detection cycle, which helps to quickly manufacture batteries that meet the standards in a shorter period of time.

[0038] Further, in the above-mentioned embodiment, in the step of obtaining the gas production, the test method of the gas production at the test temperature specifically includes: placing the electrode pole piece in an aluminum-plastic film bag, adding an electrolyte, and then vacuum sealing, and using a water displacement method to test the first volume of the aluminum-plastic film bag containing the electrode pole piece and the electrolyte; then placing the aluminum-plastic film bag at the test temperature to react and produce gas; then taking it out, and using a water displacement method to test the second volume of the aluminum-plastic film bag containing the electrolyte, the electrode pole piece and the gas production, wherein the difference between the second volume and the first volume is the gas production. The aluminum-plastic film bag has good isolation performance, which can effectively isolate the electrode pole piece from the external environment, prevent moisture and other gas components in the air from reacting with the electrolyte or the electrode pole piece, thereby ensuring the accuracy of the test. At the same time, the aluminum-plastic film bag has good temperature resistance, which can adapt to certain temperature changes, and will not deform or break at the test temperature, ensuring that the test can be carried out under different test temperature conditions. In the water displacement method, the water used can be at room temperature or adjusted to the same temperature as the test temperature. In particular, in order to reduce the influence of temperature differences on volume measurement, the temperature of the water used is the same as the test temperature. By adopting the above technical solution, the gas production test can be completed quickly and accurately.

[0039] Furthermore, in the above-mentioned embodiment, the total number of electrode plates is 5-10. When the water displacement method is used to determine the gas production, if the number of electrode plates is too small, the amount of gas produced may be small, resulting in the test data being not significant enough and difficult to accurately judge. On the contrary, if the number of electrode plates is too large, more gas will be produced. Since the instrument for measuring gas volume (such as a measuring cylinder or a gas volume meter) usually has a certain range of measurement accuracy, if the volume of gas produced exceeds the optimal measurement range of the instrument, it may cause a large measurement error, thereby affecting the accuracy of the test results. To this end, controlling the number of electrode plates within the range of 5 to 10 pieces can effectively improve the accuracy of the test and improve the reliability of the evaluation.

[0040] Furthermore, in the above embodiment, in the step of obtaining the gas production, the amount of electrolyte that soaks the electrode plate is determined based on the product of the injection coefficient of the battery corresponding to the electrode plate and the capacity of each electrode plate, wherein the capacity of each electrode plate = the capacity of the battery corresponding to the electrode plate / the number of electrode plates. For example, assuming that the capacity of the battery is 100Ah, and it contains 10 positive electrode plates and 10 negative electrode plates, then the capacity of a single positive electrode is 5Ah. The injection coefficient of the battery often has an empirical value (related to the specifications of the battery). For example, the injection coefficient of the ternary battery is 2.2g / Ah, from which it can be calculated that the injection amount of a single positive electrode plate is 11g. The present invention determines the amount of electrolyte that wets the electrode plates according to the product of the liquid injection coefficient of the battery corresponding to the electrode plates and the capacity of each electrode plate. This can not only accurately determine the amount of electrolyte required to wet the electrode plates, but also effectively simulate the conditions of the battery in a real working environment, thereby more accurately reflecting the gas production behavior of the battery in actual applications, thereby ensuring that the subsequent gas production is consistent with the situation in the real environment.

[0041] In order to further explore the valve opening risk of batteries made of electrode plates under normal working conditions, the test temperature can be set to the operating temperature of the battery corresponding to the electrode plate (that is, the battery made of the electrode plate) in its application scenario. For example, if the operating temperature is 40°C, the test temperature is also set to 40°C. Further, in order to more comprehensively evaluate the performance of the battery in a high temperature environment, the test temperature can also be selected as the highest temperature in the application scenario of the battery corresponding to (matching) the electrode plate or 1.1 to 1.8 times the highest temperature. Specifically, in the application scenario of automotive batteries, in summer, although the operating temperature of the battery is only 40°C (that is, the outside temperature), the surface temperature of the battery may reach up to 60°C. Therefore, when testing the gas production, the test temperature can be selected as 60°C or a temperature in the temperature range of 66°C to 108°C (that is, 1.1 times to 1.8 times the highest temperature) as the test temperature. Among them, setting the test temperature to the highest temperature can ensure the reliability of the evaluation results. Selecting a temperature as the test temperature between 1.1 and 1.8 times the maximum temperature can not only provide a certain safety redundancy, but also significantly shorten the test cycle, thereby accelerating the development process of qualified batteries. Specifically, the gas production characteristics of the battery change with increasing temperature (the gas production rate increases with increasing temperature, but the gas production tends to stabilize after reaching a certain inflection point). Therefore, in order to speed up the evaluation process and obtain results in advance, an accelerated aging test (selecting a test temperature within the range of 1.1 to 1.8 times the above-mentioned maximum temperature for testing) can be used to simulate the long-term aging effect of the battery at a lower temperature. For example, when the maximum temperature is 60°C, the test temperature can be carried out in the temperature range of 66°C to 102°C. In order to evaluate whether the battery will open the valve after being stored at 60°C for 300 days, the electrode plate can be subjected to a 60-day gas production test and the gas production can be detected at a test temperature of 70°C, or a 10-day gas production test can be carried out at a test temperature of 90°C and the gas production can be detected. This not only ensures the reliability of the evaluation, but also significantly shortens the testing cycle, allowing qualified batteries to be developed in a shorter time.

[0042] The evaluation method in each of the above-mentioned embodiments provided by the present invention is flexibly applicable to a variety of test temperatures, so that during the evaluation process, once it is found that the battery corresponding to the electrode plate has a valve opening risk, the electrode plate or electrolyte can be improved in a targeted manner. This improvement can be achieved by designing multiple groups of experiments, such as preparing multiple aluminum-plastic film bags to perform gas production tests on multiple groups of improved electrolytes or electrode plates, and testing them separately at different test temperatures. In this way, the evaluation results can be obtained more quickly. Compared with the traditional method of using pressure sensors to test batteries one by one, the method of the present invention significantly reduces the time required for subsequent testing, thereby accelerating the development process of qualified battery products.

[0043] Furthermore, in the above embodiment, the step of obtaining the valve opening pressure also includes placing a battery matching the electrode plate at a test temperature, and then performing a pressure test on the battery to obtain the valve opening pressure of the explosion-proof valve. Considering that the electrode material may fatigue when the battery is under high temperature conditions for a long time, the explosion-proof valve may open when the preset pressure value is not reached. To this end, the battery can be placed at a test temperature of an actual application scenario for a period of time, and then the battery can be pressure tested to obtain the valve opening pressure. The valve opening pressure thus obtained is closer to the actual working condition of the battery, thereby being able to provide more accurate and reliable valve opening pressure data, thereby improving the reliability of the evaluation.

[0044] Furthermore, the battery in each of the above embodiments is a lithium battery. Lithium-ion batteries have the advantages of high platform voltage and high energy density, and have become a current research hotspot, and are widely used in energy storage, electric vehicles and other fields. Among them, the positive electrode materials mainly include: one or more of lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMn2O4), lithium iron phosphate (LiFePO4), ternary materials (lithium nickel cobalt manganese oxide (NCM) and lithium nickel cobalt aluminum oxide (NCA)). The negative electrode materials mainly include: one or more of artificial graphite, natural graphite, silicon-carbon negative electrode, silicon-oxygen negative electrode and the like.

[0045] The present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings.

[0046] Example 1

[0047] Obtain gas production: Charge the battery at a constant current of 0.33C to a cut-off voltage of 4.25V, and then charge at a constant voltage until the charging current drops to 0.05C to obtain a fully charged Li 0.5 Ni 0.8 Co 0.1 Mn 0.1 O2 / graphite full battery, and then disassemble the battery in the glove box to obtain 62 lithium-free LiNi 0.5 Co 0.2 Mn 0.3 O2 positive electrode sheet and 63 fully lithium-embedded graphite negative electrode sheets.

[0048] Put 5 dried delithiation positive electrode sheets into an aluminum-plastic film bag, add 6.94g of electrolyte (the battery filling coefficient is 2.15, the battery capacity is 80Ah, and the amount of electrolyte is determined according to the product of the battery filling coefficient corresponding to the electrode sheet and the capacity of each electrode sheet), and then vacuum seal it, and use the water displacement method to test the first volume of the aluminum-plastic film bag containing the electrode sheet and the electrolyte, and the first volume is 45ml; then place the aluminum-plastic film bag at a test temperature of 90°C to react and produce gas (the test temperature is the highest temperature in the application scenario of the battery corresponding to the electrode sheet); take it out after 10 days, and use the water displacement method to test the second volume of the aluminum-plastic film bag containing the electrolyte, electrode sheet and gas production, and the second volume is 265ml, so the gas production is 220ml.

[0049] Put 5 dried fully lithium-embedded negative electrode sheets into an aluminum-plastic film bag, add 6.94g of electrolyte (the battery's filling coefficient is 2.15, the battery's capacity is 80Ah, and the amount of electrolyte is determined based on the product of the battery's filling coefficient corresponding to the electrode sheet and the capacity of each electrode sheet), then vacuum seal the bag, and use the water displacement method to test the first volume of the aluminum-plastic film bag containing the electrode sheet and the electrolyte, and the first volume is 45ml; then place the aluminum-plastic film bag at a test temperature of 90°C to react and produce gas; take it out after 10 days, and use the water displacement method to test the second volume of the aluminum-plastic film bag containing the electrolyte, the electrode sheet and the gas production, and the second volume is 60ml, so the gas production is 15ml.

[0050] It can be concluded that the gas production of the full battery is 2.9L (220 / 5*62+15 / 5*63=2.9L).

[0051] Get the valve opening pressure: Take five fully charged Li 0.5 Ni 0.8 Co 0.1 Mn 0.1 The O2 / graphite full cell was placed at a test temperature of 90°C for 10 days and then Figure 2 The pressure test device 1 shown performs a pressure test on the battery to obtain the opening pressure of the explosion-proof valve, and the test result is 0.56Mpa. (The pressure test method is: drill a hole on the battery 2, install the air pipe 5 into the hole, and then use AB glue to fix the position where the air pipe 5 is connected to the aluminum shell (of the battery 2), use the clamp 3 to fix the battery 2, and then connect the other end of the air pipe 5 to the inert gas bottle in the control cabinet 4, and continue to inflate the battery 2 through the pressure valve in the control cabinet 4 until the explosion-proof valve opens, and detect the opening pressure through the monitor 6 on the pressure test device 1.)

[0052] Risk assessment: Calculate the volume threshold corresponding to the valve opening pressure based on the valve opening pressure (the volume of the battery casing is always 0.65L), and the result is 3.6L (0.56Mpa*0.65 / 101.325Kma=3.6L). Since the gas production of 2.9L<3.6L, there is no valve opening risk for the battery corresponding to the electrode plate. In view of the fact that the volume threshold of 3.6L obtained by the pressure test is significantly higher than the gas production of 2.9L of the electrode, the gas production accounts for 80.6%, indicating that there is still 19.4% gas production redundancy before the battery valve opens. Therefore, the battery corresponding to this electrode is a qualified battery.

[0053] Example 2

[0054] Obtain gas production: Charge the battery at a constant current of 0.33C to a cut-off voltage of 4.35V, and then charge at a constant voltage until the charging current drops to 0.05C to obtain a fully charged LiNi 0.8 Co 0.1 Mn 0.1 O2 / graphite full battery, and then disassemble the battery in the glove box to obtain 62 lithium-free LiNi 0.8 Co 0.1 Mn 0.1 O2 positive electrode sheet and 63 fully lithium-embedded graphite negative electrode sheets.

[0055] Put 5 dried delithiation positive electrode sheets into an aluminum-plastic film bag, add 6.94g electrolyte (the battery filling coefficient is 2.15, the battery capacity is 80Ah, and the amount of electrolyte is determined according to the product of the battery filling coefficient corresponding to the electrode sheet and the capacity of each electrode sheet), then vacuum seal, and use the water displacement method to test the first volume of the aluminum-plastic film bag containing the electrode sheet and the electrolyte, and the first volume is 56ml; then place the aluminum-plastic film bag at a test temperature of 90°C to react and produce gas; take it out after 10 days, and use the water displacement method to test the second volume of the aluminum-plastic film bag containing the electrolyte, the electrode sheet and the gas production, and the second volume is 346ml, so the gas production is 290ml.

[0056] Put 5 dried fully lithium-embedded negative electrode sheets into an aluminum-plastic film bag, add 6.94g of electrolyte (the battery's filling coefficient is 2.15, the battery's capacity is 80Ah, and the amount of electrolyte is determined based on the product of the battery's filling coefficient corresponding to the electrode sheet and the capacity of each electrode sheet), then vacuum seal the bag, and use the water displacement method to test the first volume of the aluminum-plastic film bag containing the electrode sheet and the electrolyte, and the first volume is 56ml; then place the aluminum-plastic film bag at a test temperature of 90°C to react and produce gas; take it out after 10 days, and use the water displacement method to test the second volume of the aluminum-plastic film bag containing the electrolyte, the electrode sheet and the gas production, and the second volume is 71ml, so the gas production is 15ml.

[0057] It can be concluded that the gas production of the full battery is 3.79L (290 / 5*62+15 / 5*63=3.79L).

[0058] Get the valve opening pressure: Take five fully charged LiNi 0.8 Co 0.1 Mn 0.1 The O2 / graphite full cell was placed at a test temperature of 90°C for 10 days and then Figure 1 The pressure test device shown in the figure performs a pressure test on the battery at 90 degrees to obtain the opening pressure of the explosion-proof valve, and the test result is 0.55Mpa. (The pressure test method is the same as that in Example 1)

[0059] Risk assessment: The volume threshold corresponding to the valve opening pressure is calculated based on the valve opening pressure (the volume of the battery housing is always 0.65L), and the result is 3.53L (0.55Mpa*0.65 / 101.325Kma=3.53L). Since the gas production volume is 3.79L>3.53L, the battery corresponding to the electrode plate will open the valve at the test temperature. The battery corresponding to the electrode plate is an unqualified battery.

[0060] Example 3

[0061] Obtain gas production: Charge the battery at a constant current of 0.33C to a cut-off voltage of 4.35V, and then charge at a constant voltage until the charging current drops to 0.05C to obtain a fully charged LiNi 0.8 Co 0.1 Mn 0.1 O2 / graphite full battery, and then disassemble the battery in the glove box to obtain 62 lithium-free LiNi 0.8 Co 0.1 Mn 0.1 O2 positive electrode sheet and 63 fully lithium-embedded graphite negative electrode sheets.

[0062] Put 5 dried delithiation positive electrode sheets into an aluminum-plastic film bag, add 6.94g electrolyte (the battery filling coefficient is 2.15, the battery capacity is 80Ah, and the amount of electrolyte is determined according to the product of the battery filling coefficient corresponding to the electrode sheet and the capacity of each electrode sheet), then vacuum seal, and use the water displacement method to test the first volume of the aluminum-plastic film bag containing the electrode sheet and the electrolyte, and the first volume is 56ml; then place the aluminum-plastic film bag at a test temperature of 90°C to react and produce gas; take it out after 10 days, and use the water displacement method to test the second volume of the aluminum-plastic film bag containing the electrolyte, the electrode sheet and the gas production, and the second volume is 346ml, so the gas production is 290ml.

[0063] Put 5 dried fully lithium-embedded negative electrode sheets into an aluminum-plastic film bag, add 6.94g of electrolyte (the battery's filling coefficient is 2.15, the battery's capacity is 80Ah, and the amount of electrolyte is determined based on the product of the battery's filling coefficient corresponding to the electrode sheet and the capacity of each electrode sheet), then vacuum seal the bag, and use the water displacement method to test the first volume of the aluminum-plastic film bag containing the electrode sheet and the electrolyte, and the first volume is 56ml; then place the aluminum-plastic film bag at a test temperature of 90°C to react and produce gas; take it out after 10 days, and use the water displacement method to test the second volume of the aluminum-plastic film bag containing the electrolyte, the electrode sheet and the gas production, and the second volume is 71ml, so the gas production is 15ml.

[0064] It can be concluded that the gas production of the full battery is 3.79L (290 / 5*62+15 / 5*63=3.79L).

[0065] Get the valve opening pressure: Take five fully charged LiNi 0.8 Co 0.1 Mn 0.1 O2 / graphite full battery, then directly adopt Figure 1 The pressure test device shown performs a pressure test on the battery at room temperature to obtain the opening pressure of the explosion-proof valve. The test result is 0.8Mpa (i.e., the pressure design value of the explosion-proof valve). (The pressure test method is the same as that in Example 1)

[0066] Risk assessment: The volume threshold corresponding to the valve opening pressure is calculated based on the valve opening pressure (the volume of the battery housing is always 0.65L), and the result is 5.13L (0.8Mpa*0.65 / 101.325Kma=5.13L). Since the gas production is 3.79L<5.13L, the battery corresponding to the electrode plate will not open the valve at the test temperature. The battery corresponding to the electrode plate is a qualified battery.

[0067] Example 4

[0068] Obtain gas production: Charge the battery at a constant current of 0.33C to a cut-off voltage of 4.35V, and then charge at a constant voltage until the charging current drops to 0.05C to obtain a fully charged LiNi 0.8 Co 0.1 Mn 0.1 O2 / graphite full battery, and then disassemble the battery in the glove box to obtain 62 lithium-free LiNi 0.8 Co 0.1 Mn 0.1 O2 positive electrode sheet and 63 fully lithium-embedded graphite negative electrode sheets.

[0069] Five dried delithiation positive electrode sheets and six negative electrode sheets were placed in an aluminum-plastic film bag, separated by a diaphragm, and 13.88 g of electrolyte was added (the battery filling coefficient was 2.15, the battery capacity was 80 Ah, and the amount of electrolyte was determined according to the product of the battery filling coefficient corresponding to the electrode sheet and the capacity of each electrode sheet). The bag was then vacuum sealed and the first volume of the aluminum-plastic film bag containing the electrode sheet and the electrolyte was tested by the water displacement method, and the first volume was 115 ml. The aluminum-plastic film bag was then placed at a test temperature of 90°C to react and produce gas. The bag was taken out after 10 days, and the second volume of the aluminum-plastic film bag containing the electrolyte, the electrode sheet and the gas production was tested by the water displacement method, and the second volume was 425 ml. Therefore, the gas production was 310 ml.

[0070] It can be concluded that the gas production of the full battery is 3.8L (310 / 5*62=3.8L).

[0071] Get the valve opening pressure: Take five fully charged LiNi 0.8 Co 0.1 Mn 0.1 O2 / graphite full battery, then directly adopt Figure 1 The pressure test device shown performs a pressure test on the battery at room temperature to obtain the opening pressure of the explosion-proof valve. The test result is 0.8Mpa (i.e., the pressure design value of the explosion-proof valve). (The pressure test method is the same as that in Example 1)

[0072] Risk assessment: The volume threshold corresponding to the valve opening pressure is calculated based on the valve opening pressure (the volume of the battery casing is always 0.65L), and the result is 5.13L (0.8Mpa*0.65 / 101.325Kma=5.13L).

[0073] Since the gas production is 3.8L<5.13L, the battery corresponding to the electrode plate will not open the valve at the test temperature. The battery corresponding to the electrode plate is a qualified battery.

[0074] According to the above-mentioned embodiments 1-4, the battery valve opening risk assessment method provided by the present invention can quickly and accurately assess whether the battery corresponding to the electrode plate has a valve opening risk, which helps to quickly screen and prepare battery products that meet the standards in a relatively short period of time.

[0075] Comparing Example 2 and Example 3, it can be seen that the valve opening pressure of the battery corresponding to the electrode plate of Example 2 is significantly lower than the valve opening pressure of the battery corresponding to the electrode plate of Example 3, which makes the battery corresponding to the electrode plate evaluated in Example 2 have a valve opening risk, while the battery corresponding to the electrode plate evaluated in Example 3 does not have a valve opening risk. The reason for the two evaluation results is that when the battery is under high temperature conditions for a long time, fatigue may occur in the explosion-proof valve, resulting in the actual valve opening pressure of the explosion-proof valve being lower than the preset valve opening pressure (the design value of the valve opening pressure). In order to more accurately explore whether the battery has a valve opening risk at the test temperature, it is best to adopt the method provided in Example 2: first place the battery corresponding to the electrode plate at the test temperature, and then perform a pressure test on the battery to obtain the actual valve opening pressure of the explosion-proof valve, thereby ensuring the reliability of the evaluation.

[0076] Comparing Example 2 and Example 4, it can be seen that since Example 2 places the positive electrode sheet and the negative electrode sheet separately in the electrolyte to test their gas production at a preset temperature, it is possible to quickly identify that the positive electrode sheet causes the increase in gas production based on the difference in gas production, and then the positive electrode sheet or electrolyte can be optimized and improved, and the test can be continued. The test can be achieved by designing multiple groups of experiments, such as preparing multiple aluminum-plastic film bags to simultaneously test the gas production of multiple groups of improved electrolytes or electrode sheets, and testing them separately at different test temperatures. In this way, the evaluation results can be obtained more quickly, which helps to quickly screen and prepare battery products that meet the standards in a relatively short period of time.

[0077] Although the present invention has been illustrated and described with reference to certain preferred embodiments of the present invention, it should be understood by those skilled in the art that the above is a further detailed description of the present invention in conjunction with specific embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. Those skilled in the art may make various changes in form and details, including making several simple deductions or substitutions, without departing from the spirit and scope of the present invention.

Claims

1. A method for assessing the risk of battery valve opening, characterized in that: include: Obtaining gas production: immersing the electrode plate in the electrolyte, and detecting the gas production generated by the reaction between the electrode plate and the electrolyte at the test temperature; Obtaining the valve opening pressure: selecting a battery corresponding to the electrode plate, the battery having an explosion-proof valve, and performing a pressure test on the battery to obtain the valve opening pressure of the explosion-proof valve; Risk assessment: determining a corresponding gas production threshold value according to the obtained valve opening pressure, and comparing the gas production amount with the gas production threshold value to determine whether the battery corresponding to the electrode plate has a valve opening risk.

2. The battery valve opening risk assessment method according to claim 1, characterized in that: The step of obtaining the gas production specifically includes: fully charging the battery, then disassembling the battery to obtain the electrode plate, then immersing the electrode plate in the electrolyte, and detecting the gas production generated by the reaction between the electrode plate and the electrolyte at a test temperature.

3. The method for assessing battery valve opening risk according to claim 2, characterized in that: In the step of obtaining the gas production, the battery is fully charged in the following manner: the battery is constant-current charged at a charging current of 0.1C-1C to a cut-off voltage of 3.6V-4.4V, and then constant-voltage charged until the charging current drops to 0.05-0.1C.

4. The battery valve opening risk assessment method according to claim 1, characterized in that: The electrode plates include a positive electrode plate and a negative electrode plate, and the gas production is the sum of the gas production generated by the positive electrode plate reacting with the electrolyte at the test temperature and the gas production generated by the negative electrode plate reacting with the electrolyte at the test temperature.

5. The battery valve opening risk assessment method according to claim 4, characterized in that: The step of obtaining the gas production comprises: independently immersing the positive electrode plate and the negative electrode plate in the electrolyte, and detecting the gas production generated by the reaction of the positive electrode plate with the electrolyte and the gas production generated by the reaction of the negative electrode plate with the electrolyte at a test temperature.

6. The method for assessing battery valve opening risk according to claim 1, characterized in that: The total number of the electrode plates is 5-10.

7. The battery valve opening risk assessment method according to claim 1, characterized in that: In the step of obtaining the gas production, the amount of the electrolyte that soaks the electrode plates is determined based on the product of the injection coefficient of the battery corresponding to the electrode plates and the capacity of each electrode plate, wherein the capacity of each electrode plate = the capacity of the battery corresponding to the electrode plate / the number of electrode plates.

8. The battery valve opening risk assessment method according to claim 1, characterized in that: In the step of obtaining the gas production, the method of testing the gas production at the test temperature specifically includes: placing the electrode plate into an aluminum-plastic film bag, adding an electrolyte, then vacuum-sealing it, and using a water displacement method to test the first volume of the aluminum-plastic film bag containing the electrode plate and the electrolyte; then placing the aluminum-plastic film bag at the test temperature to react and produce gas; then taking it out, and using a water displacement method to test the second volume of the aluminum-plastic film bag containing the electrolyte, the electrode plate and the gas production, wherein the difference between the second volume and the first volume is the gas production.

9. The battery valve opening risk assessment method according to claim 1, characterized in that: In the step of obtaining the gas production, the test temperature is the highest temperature in the application scenario of the battery corresponding to the electrode plate or 1.1 to 1.8 times the highest temperature.

10. The battery valve opening risk assessment method according to claim 1, characterized in that: The step of obtaining the valve opening pressure also includes placing a battery corresponding to the electrode plate at the test temperature, and then performing a pressure test on the battery to obtain the valve opening pressure of the explosion-proof valve.

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