Method and system for evaluating heat resistance of solid-state lithium ion battery under voltage overcharge

Abstract

The invention discloses a method and a system for evaluating the heat resistance of a solid-state lithium ion battery under voltage overcharge, and relates to the field of battery performance evaluation. The method comprises the following steps: under the conditions of different environment temperatures and overcharge voltages, carrying out overcharge test on a solid-state lithium ion battery sample so as to enable the voltage of the solid-state lithium ion battery sample to reach a set value, keeping the voltage of the solid-state lithium ion battery sample unchanged, continuously carrying out overcharge treatment until the current of the solid-state lithium ion battery sample is abnormal, the overcharge test is completed; in the overcharge test process, voltage and current data and temperature data of the solid-state lithium ion battery sample are obtained in real time; determining the heating rate of the solid-state lithium ion battery sample based on the temperature data; generating a test result graph based on the voltage and current data, the temperature data and the heating rate; and obtaining an evaluation result based on the test result graph. According to the invention, accurate evaluation of the heat resistance of the solid-state lithium ion battery under voltage overcharge can be realized.

Description

Technical Field

[0001] The present application relates to the field of battery performance evaluation, and in particular to a method and system for evaluating the heat resistance of a solid-state lithium-ion battery under voltage overcharge. Background Art

[0002] Lithium-ion batteries have been widely used in portable devices, electrochemical energy storage, and new energy vehicles due to their small size, light weight, high energy density, and low self-discharge rate. With the promotion of liquid lithium-ion batteries in practical applications in the market, people have higher and higher requirements for the application of lithium-ion batteries. Not only do they require the electrochemical performance of lithium-ion batteries to meet market indicators, but they also require lithium-ion batteries to have better safety performance and not cause fires or explosions that threaten life safety. However, reality and various studies have shown that the activity of lithium ions and the high energy density characteristics of lithium-ion batteries will bring greater safety problems to batteries, and safety accidents such as combustion and explosion of lithium-ion batteries are also constantly occurring. Therefore, the safety of lithium-ion batteries has received great attention from both inside and outside the industry. At present, in the screening methods for various safety hazards of lithium-ion batteries, the inspection methods and standards used have always lagged behind the development of lithium-ion battery materials and technologies, and the evaluation methods and evaluation systems also need to be further improved and perfected to meet the requirements of lithium-ion battery safety performance evaluation.

[0003] Among them, overcharging (i.e. continuing to charge after the battery has reached a full state) is a common abuse phenomenon of lithium-ion batteries. When the overcharge reaches a certain voltage, the battery will fail, or even thermal runaway will occur, causing the battery surface temperature to be too high and burn, and eventually cause a serious fire. For liquid lithium-ion batteries, overcharging abuse is one of the main factors that cause battery combustion and fire. At present, there are many ways to study the thermal runaway of commercial liquid lithium-ion batteries during overcharging, and it is found that severe overcharging causes battery combustion and fires, which are mainly affected by parameters such as voltage, temperature and impedance. Some minor overcharging will only cause battery aging and failure problems, which are not easy to be found. Although it will not obviously cause combustion or eventually form a fire, there are still safety hazards.

[0004] Compared with liquid lithium-ion batteries, all-solid-state lithium-ion batteries have higher safety and energy density, flexible structure, and a wide operating temperature range. They have become a new generation of battery technology that breaks through the bottleneck of lithium-ion batteries. Therefore, solid-state lithium-ion batteries have been rapidly developed. However, all-solid-state lithium-ion batteries also have disadvantages such as low yield and poor cycle stability, which hinder their own development. Although all-solid-state lithium-ion batteries do not have the safety problems caused by conductive liquid leakage like liquid lithium-ion batteries, they also have thermal problems caused by overcharge abuse. There have been many studies and reports on the overcharge abuse of liquid lithium-ion batteries, but there are no reports on the research of solid-state battery structures under overcharge conditions. Summary of the invention

[0005] The purpose of the present application is to provide a method and system for evaluating the heat resistance of a solid-state lithium-ion battery under voltage overcharge, which can achieve accurate evaluation of the heat resistance of a solid-state lithium-ion battery under voltage overcharge.

[0006] To achieve the above objectives, this application provides the following solutions:

[0007] In a first aspect, the present application provides a method for evaluating the heat resistance of a solid-state lithium-ion battery under voltage overcharge, comprising:

[0008] Under different ambient temperatures and different overcharge voltages, the solid-state lithium-ion battery samples are overcharged to make the voltage of the solid-state lithium-ion battery samples reach the set value; an incubator is used to provide the ambient temperature;

[0009] When the voltage of the solid-state lithium-ion battery sample reaches the set value, the voltage of the solid-state lithium-ion battery sample is kept unchanged, and the overcharge process is continuously performed until the current of the solid-state lithium-ion battery sample becomes abnormal, and the overcharge test is completed;

[0010] During the overcharge test of the solid-state lithium-ion battery sample, the voltage, current and temperature data of the solid-state lithium-ion battery sample are obtained in real time;

[0011] Determining a heating rate of the solid-state lithium-ion battery sample based on the temperature data;

[0012] Generate a test result graph based on the voltage and current data, the temperature data, and the heating rate;

[0013] Based on the test result graph, an evaluation result of the heat resistance of the solid-state lithium-ion battery under voltage overcharge is obtained.

[0014] Optionally, during the overcharge test of the solid-state lithium-ion battery sample, the solid-state lithium-ion battery sample is charged with a constant current according to a set charge and discharge rate so that the voltage of the solid-state lithium-ion battery sample reaches a set value.

[0015] Optionally, the set charge and discharge rate is a 2C charge and discharge rate; C represents the capacity of the solid-state lithium-ion battery sample.

[0016] Optionally, an overcharge test is performed on the solid-state lithium-ion battery sample under different ambient temperatures and different overcharge voltage conditions so that the voltage of the solid-state lithium-ion battery sample reaches a set value, including:

[0017] The solid-state lithium-ion battery samples of the same batch are numbered to obtain a first battery sample, a second battery sample, and a third battery sample;

[0018] Under a first ambient temperature, performing a heat preservation treatment on the first battery sample until the temperature of the first battery sample reaches the first ambient temperature, and then performing an overcharge test on the first battery sample so that the voltage of the first battery sample reaches a first set value;

[0019] At a first ambient temperature, performing a heat preservation treatment on the second battery sample until the temperature of the second battery sample reaches the first ambient temperature, and then performing an overcharge test on the second battery sample so that the voltage of the second battery sample reaches a second set value;

[0020] At a second ambient temperature, the third battery sample is subjected to a heat preservation treatment until the temperature of the third battery sample reaches the second ambient temperature, and then an overcharge test is performed on the third battery sample to make the voltage of the third battery sample reach a first set value.

[0021] Optionally, the first ambient temperature is 25°C; the second ambient temperature is 40°C.

[0022] Optionally, the first set value is 6.4V; the second set value is 8V.

[0023] Optionally, the current abnormality of the solid-state lithium-ion battery sample means that the current of the solid-state lithium-ion battery sample reaches a cut-off current.

[0024] Optionally, the cut-off current is set to 0.5A.

[0025] In a second aspect, the present application provides a system for evaluating the heat resistance of a solid-state lithium-ion battery under voltage overcharge, comprising:

[0026] An insulated box, used to provide an environmental temperature for overcharge testing of solid-state lithium-ion battery samples;

[0027] Multi-channel temperature measuring instrument, used to collect temperature data of solid-state lithium-ion battery samples in real time during overcharge test;

[0028] Voltage and current tester, used to collect voltage and current data of solid-state lithium-ion battery samples in real time during overcharge testing;

[0029] The processor is connected to the multi-channel temperature measuring instrument and the voltage and current tester respectively, and is used to execute the evaluation method provided above based on the temperature data and the voltage and current data to complete the evaluation of the heat resistance of the solid-state lithium-ion battery sample under voltage overcharge.

[0030] Optionally, the multi-channel temperature measuring instrument includes a plurality of temperature probes; each temperature probe is placed on the surface of the solid-state lithium-ion battery sample.

[0031] According to the specific embodiments provided in this application, this application has the following technical effects:

[0032] The present application provides a method and system for evaluating the heat resistance of a solid-state lithium-ion battery under voltage overcharge. The method performs an overcharge test on a solid-state lithium-ion battery sample under different ambient temperatures and overcharge voltages, and acquires voltage, current and temperature data of the solid-state lithium-ion battery sample in real time. Then, a test result graph is generated based on the voltage, current data, temperature data and a heating rate determined by the temperature data, so as to achieve an accurate evaluation of the heat resistance of the solid-state lithium-ion battery under voltage overcharge. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 A schematic flow chart of a method for evaluating the heat resistance of a solid-state lithium-ion battery under voltage overcharge provided in one embodiment of the present application;

[0035] Figure 2 A schematic diagram of a test framework for the heat resistance of a solid-state lithium-ion battery under voltage overcharge provided in one embodiment of the present application;

[0036] Figure 3 A temperature-time relationship diagram of a temperature measurement point when the test temperature is 25°C and the overcharge voltage is 6.4V provided in an embodiment of the present application;

[0037] Figure 4 A graph showing changes in test voltage and current when the test temperature is 25°C and the overcharge voltage is 6.4V provided in an embodiment of the present application;

[0038] Figure 5A graph showing the relationship between the heating rate and time of a temperature measuring point when the test temperature is 25°C and the overcharge voltage is 6.4V provided in an embodiment of the present application;

[0039] Figure 6 A temperature-time relationship diagram of a temperature measurement point when the test temperature is 25°C and the overcharge voltage is 8V provided in an embodiment of the present application;

[0040] Figure 7 A graph showing the change in test voltage and current when the test temperature is 25°C and the overcharge voltage is 8V provided in an embodiment of the present application;

[0041] Figure 8 A graph showing the relationship between the heating rate and time of a temperature measuring point when the test temperature is 25°C and the overcharge voltage is 8V provided in an embodiment of the present application;

[0042] Fig. 9 A temperature-time relationship diagram of a temperature measurement point when the test temperature is 40°C and the overcharge voltage is 6.4V provided in an embodiment of the present application;

[0043] Fig.10 A graph showing changes in test voltage and current when the test temperature is 40°C and the overcharge voltage is 6.4V provided in an embodiment of the present application;

[0044] Fig.11 A graph showing the relationship between the heating rate of a temperature measuring point and time when the test temperature is 40° C. and the overcharge voltage is 6.4V provided in an embodiment of the present application. DETAILED DESCRIPTION

[0045] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0046] According to the overcharge and abuse of liquid lithium-ion batteries, this application conducts a new experimental design to investigate and evaluate the thermal effect and safety of solid-state lithium-ion batteries under voltage overcharge conditions, thereby improving the performance of solid-state lithium-ion batteries and promoting their application.

[0047] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0048] In an exemplary embodiment, the present application provides a method for evaluating the heat resistance of a solid-state lithium-ion battery under voltage overcharge, such as Figure 1 As shown, the method includes:

[0049] Step 100: Under different ambient temperatures and different overcharge voltages, an overcharge test is performed on the solid-state lithium-ion battery sample to make the voltage of the solid-state lithium-ion battery sample reach a set value. An incubator is used to provide the ambient temperature.

[0050] Step 101: When the voltage of the solid-state lithium-ion battery sample reaches a set value, the voltage of the solid-state lithium-ion battery sample is kept unchanged, and the overcharge process is continuously performed until the current of the solid-state lithium-ion battery sample becomes abnormal, and the overcharge test is completed.

[0051] Step 102: During the overcharge test of the solid-state lithium-ion battery sample, voltage, current data and temperature data of the solid-state lithium-ion battery sample are acquired in real time.

[0052] Step 103: Determine the heating rate of the solid-state lithium-ion battery sample based on the temperature data.

[0053] Step 104: Generate a test result graph based on the voltage and current data, the temperature data, and the heating rate.

[0054] Step 105: obtaining an evaluation result of the heat resistance of the solid-state lithium-ion battery under voltage overcharge based on the test result graph.

[0055] In another exemplary embodiment of the present application, during the overcharge test of the solid-state lithium-ion battery sample, the solid-state lithium-ion battery sample is charged with a constant current according to a set charge and discharge rate so that the voltage of the solid-state lithium-ion battery sample reaches a set value. For example, the charge and discharge rate is set to a 2C charge and discharge rate. C represents the capacity of the solid-state lithium-ion battery sample.

[0056] In another exemplary embodiment of the present application, an overcharge test is performed on a solid-state lithium-ion battery sample under different ambient temperatures and different overcharge voltages so that the voltage of the solid-state lithium-ion battery sample reaches a set value, including:

[0057] The solid-state lithium-ion battery samples of the same batch are numbered to obtain a first battery sample, a second battery sample and a third battery sample.

[0058] At a first ambient temperature (eg, 25° C.), the first battery sample is subjected to a heat preservation treatment until the temperature of the first battery sample reaches the first ambient temperature, and then an overcharge test is performed on the first battery sample to make the voltage of the first battery sample reach a first set value (eg, 6.4V).

[0059] At the first ambient temperature, the second battery sample is subjected to a heat preservation treatment until the temperature of the second battery sample reaches the first ambient temperature, and then an overcharge test is performed on the second battery sample to make the voltage of the second battery sample reach a second set value (eg, 8V).

[0060] At a second ambient temperature (eg, 40° C.), the third battery sample is subjected to a heat preservation treatment until the temperature of the third battery sample reaches the second ambient temperature, and then an overcharge test is performed on the third battery sample to make the voltage of the third battery sample reach a first set value.

[0061] In another exemplary embodiment of the present application, the abnormal current of the solid-state lithium-ion battery sample means that the current of the solid-state lithium-ion battery sample reaches the cut-off current. For example, the cut-off current is set to 0.5 A. That is, when the current decreases to 0.5 A, the overcharge test of the solid-state lithium-ion battery sample ends.

[0062] Based on the same inventive concept, the embodiment of the present application also provides a system for implementing the above-mentioned method for evaluating the heat resistance of solid-state lithium-ion batteries under voltage overcharge. The implementation scheme for solving the problem provided by the system is similar to the implementation scheme recorded in the above-mentioned method, so the specific limitations in one or more system embodiments provided below can refer to the above-mentioned limitations on the method for evaluating the heat resistance of solid-state lithium-ion batteries under voltage overcharge, and will not be repeated here.

[0063] In an exemplary embodiment, the present application provides a system for evaluating the heat resistance of a solid-state lithium-ion battery under voltage overcharge, such as Figure 2 As shown, the system includes:

[0064] The incubator (not shown) is used to provide an ambient temperature for overcharge testing of solid-state lithium-ion battery samples.

[0065] Multi-channel temperature measuring instrument, used to collect temperature data of solid-state lithium-ion battery samples in real time during overcharge test.

[0066] The voltage and current tester (not shown in the figure) is used to collect the voltage and current data of the solid-state lithium-ion battery sample in real time during the overcharge test.

[0067] The processor is connected to the multi-channel temperature measuring instrument and the voltage and current tester respectively, and is used to execute the evaluation method provided above based on the temperature data and the voltage and current data to complete the evaluation of the heat resistance of the solid-state lithium-ion battery sample under voltage overcharge.

[0068] As an optional embodiment, the multi-channel temperature measuring instrument includes a plurality of temperature probes. Each temperature probe is placed on the surface of the solid-state lithium-ion battery sample. For example, Figure 2 As shown, 7 temperature probes are set, and correspondingly there will be 7 temperature measurement points in the solid-state lithium-ion battery sample.

[0069] In another exemplary embodiment of the present application, a lithium iron phosphate battery, a representative all-solid-state lithium-ion battery, is selected, and the evaluation method and evaluation system provided by the present application are used to perform overcharge test operations on the lithium iron phosphate battery under different overcharge voltage conditions, and the relevant thermal effect problems are evaluated according to the temperature change of the surface temperature of the test battery sample. Based on this, the overcharge test process provided in this embodiment includes:

[0070] (1) The lithium iron phosphate battery samples of the same batch are numbered, and the specific test conditions of each lithium iron phosphate battery sample are shown in Table 1.

[0071] (2) Set the incubator at 25°C and keep warm for 20 minutes.

[0072] (3) Place the #I lithium iron phosphate battery sample in a constant temperature box at 25°C for insulation, so that the temperature of the #I lithium iron phosphate battery sample is consistent with the temperature of the insulation box. The surface temperature of the #I lithium iron phosphate battery sample can be tested to determine whether it is consistent with the temperature of the insulation box.

[0073] (4) Perform an overcharge test on the #I lithium iron phosphate battery sample by charging at a constant current rate of 2C until the voltage of the #I lithium iron phosphate battery sample reaches 6.4V.

[0074] (5) Use a multi-channel thermometer to collect temperature at seven temperature measurement points of the #I lithium iron phosphate battery sample.

[0075] (6) Maintaining the voltage of 6.4 V, continue to overcharge the #I lithium iron phosphate battery sample until the voltage or current of the #I lithium iron phosphate battery sample becomes abnormal, for example, when the current decreases to 0.5 A, the test is terminated.

[0076] (7) Place the #II lithium iron phosphate battery in a constant temperature box at an ambient temperature of 25°C so that the temperature of the #II lithium iron phosphate battery sample is consistent with the temperature of the incubator.

[0077] (8) After applying an overcharge voltage of 8.0 V at a charging rate of 2C to the #II lithium iron phosphate battery, perform the same operations as the above steps (4) to (6) to complete the test of the #II lithium iron phosphate battery under 8V overcharge conditions.

[0078] (9) Raise and maintain the ambient temperature of the #III lithium iron phosphate battery at 40°C, perform the same operations as steps (4) to (6) above, and complete the test of the #III lithium iron phosphate battery under 6.4V overcharge conditions.

[0079] (10) Collect the temperature field data and voltage and current data of #I, #II, and #III lithium iron phosphate batteries during overcharge testing.

[0080] (11) Based on the collected temperature field data and voltage and current data, graphs were drawn with time as the horizontal axis and temperature (°C), voltage (V), current (A) and heating rate (°C / s) as the vertical axis, respectively, to obtain the following: Figures 3 to 11 The test result graph is shown.

[0081] Table 1 Specific test conditions for each lithium iron phosphate battery sample

[0082]

[0083] (12) Based on the test result graph, the evaluation results of the heat resistance of the solid-state lithium-ion battery under voltage overcharge are obtained. Among them:

[0084] Under the conditions of ambient temperature of 25℃ and voltage of 6.4V, during the overcharge test of #I lithium iron phosphate battery sample, the temperature change of 7 temperature measuring points showed a volcanic relationship with the increase of time (such as Figure 3 As shown in Table 2). The temperature changes relatively smoothly from the beginning of the test to time t0, and rises sharply from t0 to t1, reaching the maximum temperature at t1. From t1 to t2, the temperature drops sharply again, and then after reaching t2, the temperature changes with time and enters a stable state again. During the entire test phase, the highest temperature of the #I lithium iron phosphate battery sample occurs at temperature measurement point 2, reaching 79.7°C (as shown in Table 2). Figure 4 It can be seen that during the overcharge test, when the time reached 2265s, the voltage just rose to 6.4V and the current began to drop to 9.9A, and then as the test time increased, the current continued to drop to 0.5A. In terms of the changes in voltage and current, it can be found that when the voltage reaches the overcharge voltage of 6.4V, the current begins to drop significantly. At this time, the battery sample can no longer reach the output stage of stable current, that is, the internal thermal failure of the battery system caused by overcharging begins. As the failure progresses, the battery temperature gradually rises to the highest temperature, and then begins to drop until it reaches 0.5A. This drop process is the complete failure process during the test, and the failure time is maintained at 1037s. In this way, the highest temperature on the battery surface also occurs during the failure process, and most importantly, when the voltage reaches 6.4V, the current begins to drop, indicating that the battery begins to enter the failure process. Figure 5 It shows the relationship between the heating rate and time of the seven temperature measuring points, where the heating rate is derived from the temperature change of each temperature measuring point with respect to time. When the temperature rise rate of the liquid battery is greater than 1°C / s, the battery is judged to be in thermal runaway. The highest temperature rise rate of the solid-state battery sample in the test is 0.142°C / s. When the solid-state battery sample (i.e., the #I lithium iron phosphate battery sample) is overcharged at an ambient temperature of 25°C and a voltage of 6.4V, the battery does not reach a thermal runaway state during the entire process.

[0085] Table 2 Maximum temperature and corresponding time data of test #I lithium iron phosphate battery sample under overcharge voltage and ambient temperature

[0086]

[0087] Keep the temperature at 25℃, increase the overcharge voltage to 8.0V, and continue to perform overcharge test on #II lithium iron phosphate battery sample. Figure 6 As shown in Table 2, the 7 temperature measurement points also experienced the volcanic relationship of the #II lithium iron phosphate battery sample, and then gradually became stable as the temperature dropped. The highest temperature of the #II lithium iron phosphate battery sample during the entire test phase occurred at temperature measurement point 4, reaching 92.4°C (as shown in Table 2). Figure 7 It can be seen that when the test time reaches 2340s, the voltage just rises to 8.0V and the current begins to drop to 9.8A, which means that the #II lithium iron phosphate battery sample also begins to fail. Then, as the test time increases, the current continues to drop to 0.5A, and the failure test phase is completed. The failure process takes 6550s. Therefore, as the overcharge voltage increases, the battery failure time is longer. Figure 8 Among them, the highest heating rate of the solid-state battery sample is 0.143℃ / s, and the #II lithium iron phosphate battery sample did not show thermal runaway during the 8.0V overcharge voltage test at 25℃.

[0088] Considering that the ambient temperature of battery use is not necessarily limited to room temperature (25°C), the temperature in some areas can reach 40°C, so the voltage overcharge evaluation of #III lithium iron phosphate battery samples was carried out at 40°C. Fig. 9 As shown in Table 2, the 7 temperature measurement points also experienced the volcanic relationship between the #I lithium iron phosphate battery sample and the #II lithium iron phosphate battery sample, and then slowly became stable as the temperature dropped. The highest temperature of the #III lithium iron phosphate battery sample during the entire test phase occurred at temperature measurement point 4, reaching 72.1°C (as shown in Table 2). When the battery temperature was kept at 40°C, as the time increased to 2327s, the voltage just rose to 6.4V (as shown in Table 2). Fig.10 As shown in the figure, the current begins to drop to 9.9A, indicating that the battery failure begins. As time continues to increase, the current continues to drop to 0.5A, and the failure stage is completed, with a total time consumption of 8893s. In this way, as the ambient temperature increases, the failure time of the #III lithium iron phosphate battery sample is longer than that of the #I lithium iron phosphate battery sample at the same overcharge voltage. In addition, from Fig.11 It can be obtained that the maximum heating rate of the #III lithium iron phosphate battery sample is only 0.090℃ / s, so it can be determined that the #III lithium iron phosphate battery sample has not experienced thermal runaway.

[0089] According to the above test description, when the ambient temperature is 25℃, after two overcharge voltage tests (6.4V and 8.0V), the surface of the battery sample will be bulged or swollen, and no fire, combustion or explosion was found in the test. Similarly, when the battery temperature rises to 40℃, the overcharge voltage is maintained at 6.4V, and after testing, it is found that the surface of the battery sample also has bulges or swelling, and no fire, combustion or explosion was found in the test.

[0090] Taking the control test as a comparative example, if the reaction temperature is 20℃~45℃, a test plan corresponding to a reaction temperature outside the range of 20℃~45℃ can be provided, and the overcharge voltage of the battery can also be studied at an ambient temperature of 40℃.

[0091] In summary, the solution provided by this application first examines the thermal temperature changes of the battery surface and the current supply failure of the solid-state lithium-ion battery under an overcharge voltage of 6.4V under ambient temperature (25°C). Then, the overcharge voltage is maintained at 6.4V, the ambient temperature of the battery is increased to 40°C (matching the temperature in some areas), and the battery overcharge abuse condition is continued to be investigated. Finally, considering the same ambient temperature (25°C) condition, the overcharge voltage is increased to 8.0V to see the impact of the increase in overcharge voltage on the solid-state battery. In general, this application couples the temperature and overcharge voltage to evaluate the temperature changes and failure conditions of solid-state lithium-ion batteries, which can explain in more detail the use of solid-state lithium-ion batteries under extreme conditions of abuse.

[0092] In addition, the thermal effect and safety of solid-state lithium-ion batteries can be investigated by maintaining the overcharge voltage at a higher ambient temperature. If experimental conditions are feasible, a larger overcharge voltage (such as 10V, 20V, 30V, etc.) can also be used for testing.

[0093] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0094] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A method for evaluating the heat resistance of a solid-state lithium-ion battery under voltage overcharge, characterized in that: The evaluation method of the heat resistance of the solid-state lithium-ion battery under voltage overcharge includes: Under different ambient temperatures and different overcharge voltages, the solid-state lithium-ion battery samples are overcharged to make the voltage of the solid-state lithium-ion battery samples reach the set value; an incubator is used to provide the ambient temperature; When the voltage of the solid-state lithium-ion battery sample reaches the set value, the voltage of the solid-state lithium-ion battery sample is kept unchanged, and the overcharge process is continuously performed until the current of the solid-state lithium-ion battery sample becomes abnormal, and the overcharge test is completed; During the overcharge test of the solid-state lithium-ion battery sample, the voltage, current and temperature data of the solid-state lithium-ion battery sample are obtained in real time; Determining a heating rate of the solid-state lithium-ion battery sample based on the temperature data; Generate a test result graph based on the voltage and current data, the temperature data, and the heating rate; Based on the test result graph, an evaluation result of the heat resistance of the solid-state lithium-ion battery under voltage overcharge is obtained.

2. The method for evaluating the heat resistance of a solid-state lithium-ion battery under voltage overcharge according to claim 1, characterized in that: During the overcharge test of the solid-state lithium-ion battery sample, the solid-state lithium-ion battery sample is charged with a constant current according to a set charge and discharge rate so that the voltage of the solid-state lithium-ion battery sample reaches a set value.

3. The method for evaluating the heat resistance of a solid-state lithium-ion battery under voltage overcharge according to claim 2, characterized in that: The set charge and discharge rate is a 2C charge and discharge rate; C represents the capacity of the solid-state lithium-ion battery sample.

4. The method for evaluating the heat resistance of a solid-state lithium-ion battery under voltage overcharge according to claim 1, characterized in that: Under different ambient temperatures and different overcharge voltage conditions, the solid-state lithium-ion battery samples are overcharged to make the voltage of the solid-state lithium-ion battery samples reach the set value, including: The solid-state lithium-ion battery samples of the same batch are numbered to obtain a first battery sample, a second battery sample, and a third battery sample; Under a first ambient temperature, performing a heat preservation treatment on the first battery sample until the temperature of the first battery sample reaches the first ambient temperature, and then performing an overcharge test on the first battery sample so that the voltage of the first battery sample reaches a first set value; At a first ambient temperature, performing a heat preservation treatment on the second battery sample until the temperature of the second battery sample reaches the first ambient temperature, and then performing an overcharge test on the second battery sample so that the voltage of the second battery sample reaches a second set value; At a second ambient temperature, the third battery sample is subjected to a heat preservation treatment until the temperature of the third battery sample reaches the second ambient temperature, and then an overcharge test is performed on the third battery sample to make the voltage of the third battery sample reach a first set value.

5. The method for evaluating the heat resistance of a solid-state lithium-ion battery under voltage overcharge according to claim 4, characterized in that: The first ambient temperature is 25°C; the second ambient temperature is 40°C.

6. The method for evaluating the heat resistance of a solid-state lithium-ion battery under voltage overcharge according to claim 4, characterized in that: The first set value is 6.4V; the second set value is 8V.

7. The method for evaluating the heat resistance of a solid-state lithium-ion battery under voltage overcharge according to claim 1, characterized in that: The abnormal current of the solid-state lithium-ion battery sample means that the current of the solid-state lithium-ion battery sample reaches the cut-off current.

8. The method for evaluating the heat resistance of a solid-state lithium-ion battery under voltage overcharge according to claim 7, characterized in that: The cut-off current is set to 0.5A.

9. A system for evaluating the heat resistance of a solid-state lithium-ion battery under voltage overcharge, characterized in that: The evaluation system for the heat resistance of the solid-state lithium-ion battery under voltage overcharge includes: An insulated box, used to provide an environmental temperature for overcharge testing of solid-state lithium-ion battery samples; Multi-channel temperature measuring instrument, used to collect temperature data of solid-state lithium-ion battery samples in real time during overcharge test; Voltage and current tester, used to collect voltage and current data of solid-state lithium-ion battery samples in real time during overcharge testing; The processor is connected to the multi-channel temperature meter and the voltage and current tester respectively, and is used to execute the evaluation method as described in any one of claims 1 to 8 based on the temperature data and the voltage and current data to complete the evaluation of the heat resistance of the solid-state lithium-ion battery sample under voltage overcharge.

10. The evaluation system for heat resistance of solid-state lithium-ion batteries under voltage overcharge according to claim 9, characterized in that: The multi-channel temperature measuring instrument includes a plurality of temperature probes; each temperature probe is placed on the surface of the solid-state lithium-ion battery sample.

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