Method for simulating standard exceeding of internal moisture of lithium ion battery and carrying out safety early warning by adopting characteristic signal

Abstract

The invention relates to the technical field of battery spontaneous heating out-of-control simulation, in particular to a method for simulating standard exceeding of moisture in a lithium ion battery and performing safety early warning by adopting a characteristic signal. The method comprises the following steps: providing a lithium ion battery sample of which the consistency meets the requirement; excessive moisture is controllably introduced into the battery to simulate the internal moisture exceeding state caused by explosion-proof valve breakage in the manufacturing process or in the use process; carrying out a simulation experiment, and respectively measuring the self-discharge rates of the control group battery and the experimental group battery; respectively measuring capacity differential curve envelope areas of the control group battery and the experimental group battery; marking the ratio of the self-discharge rate of the experimental group to the self-discharge rate of the control group as a, marking the ratio of the enveloping area of the experimental group to the enveloping area of the control group as c, and performing graded safety early warning according to the numerical value combination of a and c. According to the technical scheme, the thermal runaway phenomenon caused by the fact that the internal water content exceeds the standard in the production manufacturing and actual operation process of the battery can be rapidly and accurately simulated.

Description

Technical Field

[0001] This invention relates to the field of battery self-heating runaway simulation technology, specifically to a method for simulating excessive internal moisture in lithium-ion batteries and using characteristic signals for safety early warning. Background Technology

[0002] Throughout the entire lifecycle of lithium-ion batteries, from manufacturing to actual service use, excessive internal moisture levels are a frequent and serious concern. In the production process, inaccurate incoming material control can lead to raw materials carrying excessive moisture; lax humidity control in the manufacturing environment can also cause batteries to absorb moisture during production. Furthermore, the mechanical strength of the battery's explosion-proof valve is a crucial factor; design or manufacturing defects can increase the risk of excessive internal moisture.

[0003] When the water content inside a battery exceeds the standard, it triggers a series of serious side reactions. Chemical corrosion damages the electrode materials and electrolyte structure inside the battery, leading to a decrease in conductivity; interface failure hinders charge transfer within the battery, increasing internal resistance; and gas expansion increases internal pressure, compromising the battery's structural integrity. These side reactions interact, ultimately significantly reducing battery performance, such as capacity decay and reduced charge / discharge efficiency, while also greatly threatening battery safety, increasing the risk of battery malfunction or even explosion.

[0004] In the manufacturing process of lithium-ion batteries, strict control of the humidity in the manufacturing environment is crucial. However, due to the current level of environmental control in factories, even with a series of measures in place, it is still difficult to completely prevent a very small number of battery cells from having excessive internal moisture content.

[0005] If batteries with excessive internal moisture content fail to be detected during off-line testing, they will pose serious safety hazards once installed in electric vehicles. Excessive moisture causes severe volume expansion of the positive and negative electrode active materials. This expansion damages the battery's internal structure, causing individual battery cells to swell. The increased internal pressure further exacerbates the swelling, leading to a sharp decline in battery performance and a significantly increased risk of self-heating runaway. Self-heating runaway can cause a rapid rise in battery temperature, potentially resulting in fires, explosions, and other serious accidents, causing significant damage to passenger lives and the vehicle.

[0006] For prismatic and cylindrical battery cells, explosion-proof valves are typically designed on the surface of the battery casing to prevent the spread of high-temperature gases after thermal runaway. These valves are generally made of thin aluminum alloy sheets, chosen because of their ability to rupture under pressure and release internal gases. However, the mechanical strength of the aluminum alloy sheet is relatively low compared to the battery casing, making it a weak point in the battery enclosure.

[0007] In actual use, the explosion-proof valve may be subjected to external forces, such as impact or compression, or suffer corrosion damage, leading to its rupture. Once the explosion-proof valve ruptures, moisture inside the battery pack will enter the battery casing and eventually diffuse into the electrode plates, causing the moisture content of the electrode plates to exceed the standard. After long-term operation, the active materials of the positive and negative electrodes of the battery with excessive moisture will undergo severe volume expansion, leading to the swelling of individual battery cells. Ultimately, the battery may experience thermal runaway events such as smoke and fire, posing a serious threat to the safe operation of electric vehicles.

[0008] Currently, thermal runaway caused by excessive internal water content in batteries during manufacturing and actual operation remains a relatively new and pressing issue in the new energy vehicle industry. In laboratory research, there is a lack of methods to quickly and accurately simulate this failure factor. Existing research methods may suffer from complex simulation processes, long cycles, and high costs, failing to meet the needs for rapid assessment and early warning of battery safety performance. Summary of the Invention

[0009] The purpose of this invention is to propose a method for simulating excessive internal moisture in lithium-ion batteries and using characteristic signals for safety warning. This technical solution can quickly and accurately simulate the thermal runaway phenomenon caused by excessive internal water content in batteries during production and actual operation.

[0010] To achieve the above objectives, in a first aspect, the present invention provides a method for simulating excessive internal moisture in a lithium-ion battery and using characteristic signals for safety early warning, comprising: Provide lithium-ion battery samples that meet the consistency requirements; Excessive moisture is introduced into the battery in a controlled manner to simulate the excessive internal moisture caused by the rupture of the explosion-proof valve during manufacturing or use. A simulation experiment was conducted to measure the self-discharge rate of the control group battery and the experimental group battery, respectively. The method for measuring the self-discharge rate was as follows: Charge the battery to 105% SOC at a 0.5C rate, let it stand for 2 hours, and continuously collect the open circuit voltage at time intervals of ≤10 minutes. Calculate the voltage drop rate per unit time as the self-discharge rate. The envelope areas of the capacity differential curves of the control group and the experimental group batteries were measured separately. The measurement method was as follows: At 25℃, the battery was charged and discharged at a rate of 0.01C within the ≥20% SOC range, and the capacity-voltage data were recorded. The curve was fitted using a ≥8th order quadratic polynomial, and the derivative was used to obtain the slope and voltage relationship curve of capacity versus voltage. The envelope area was obtained by integrating the curve within the same voltage range. The ratio of the self-discharge rate of the experimental group to that of the control group is denoted as a, and the ratio of the envelope area of ​​the experimental group to that of the control group is denoted as c. A graded safety warning is carried out based on the combination of the values ​​of a and c.

[0011] Beneficial effects of the basic scheme: The simulation method of this scheme can accurately reproduce the risk scenarios in actual battery applications, ensuring that the experimental data has practical reference value.

[0012] The method of moisture introduction is controllable, which can simulate two core risk sources: residual moisture in the manufacturing process and water ingress due to rupture of the explosion-proof valve during use, covering the problem of excessive moisture throughout the entire battery life cycle.

[0013] Using a control group and an experimental group for comparison can eliminate the interference of individual battery differences, making subsequent comparisons of data such as self-discharge rate and envelope area more convincing.

[0014] By using two monitoring indicators—self-discharge rate and capacity differential curve envelope area—the impact of excessive moisture can be accurately reflected from different dimensions, avoiding the limitations of a single indicator.

[0015] The method of charging the self-discharge rate to 105% SOC+ at intervals of ≤10min can amplify the voltage changes caused by internal side reactions (such as electrolyte decomposition and lithium metal deposition) due to excessive moisture, allowing even minor anomalies to be captured.

[0016] The capacity differential curve envelope area, through high-precision operation of 0.01C slow charge and discharge + ≥8th order polynomial fitting, can accurately reflect the damage of moisture to battery active materials and electrolyte interface (SEI film). The change in envelope area can directly correspond to the degree of degradation of the battery's internal structure.

[0017] Based on a combination of α-value (self-discharge rate ratio) and β-value (envelope area ratio), early warning systems can provide different levels of alerts according to the degree of risk, adapting to the safety management needs of different scenarios. Different levels can be defined based on the specific values ​​of α and β, enabling more precise early warnings.

[0018] As a feasible preferred option, the consistency requirements are: same model, capacity deviation ≤2%, and open circuit voltage difference ≤2% at 100% SOC.

[0019] As a feasible and preferred solution, in simulating excessive internal moisture during battery manufacturing, excess moisture is controllably introduced into the battery by injecting phase change material / water capsules or hydrated salt particles. The hydrated salt particles used are calcium chloride hexahydrate.

[0020] As a feasible preferred approach, a phase change material / water capsule is prepared using a phase change material with a phase change temperature of 40°C, comprising the following preparation steps: Weigh out an appropriate amount of phase change material and heat it to above its phase change temperature to melt it; Add the calculated amount of water to the molten phase change material and stir until homogeneous; The mixture is dripped into a cooling device to form spherical capsules; the cooling device is designed as a container with circulating cooling water to ensure rapid solidification of the capsules; Select capsules that are uniform in size and undamaged for later use.

[0021] As a feasible and preferred solution, simulating excessive internal moisture during battery manufacturing, the battery treatment and moisture implantation include the following steps: The selected lithium-ion battery is discharged until the SOC reaches 0%; the discharge process is carried out under constant current and constant voltage conditions to ensure that the battery is completely discharged. The external encapsulation of the battery is damaged in the dry, inert atmosphere of the glove box; The prepared phase change material / water capsule is implanted into a specific location in the battery using a syringe. The implanted battery is then repackaged.

[0022] As a feasible preferred option, the implantation location can be selected between the positive electrode and the septum, between the negative electrode and the septum, 1 cm below the positive electrode tab, 1 cm below the negative electrode tab, or the center of the large surface.

[0023] As a feasible and preferred approach, to simulate excessive internal moisture during battery manufacturing, the simulation experiment includes the following steps: The encapsulated battery is then transferred into a temperature chamber, and the ambient temperature of the temperature chamber is set to be at least 5°C higher than the phase change temperature of the phase change material. This allows moisture to escape from the packaging and fully combine or react with the target material inside the battery. The rate of temperature rise in the battery is controlled at 1℃ / min to control the rate of reaction between moisture and the electrolyte inside the battery. To simulate extreme conditions, such as the reaction between moisture and lithium dendrites on the negative electrode, the battery was first controlled to undergo at least 3 discharge and charge cycles at 0°C, with the current rate not exceeding 0.5C; when the battery SOC was 100%, it was switched to a 45°C environment and left to stand for at least 5 hours. Adjust the temperature chamber to 25°C to allow the battery to return to a stable state.

[0024] As a feasible and preferred solution, in simulating a situation where excessive internal moisture occurs due to a ruptured explosion-proof valve during battery use, the moisture injection method includes the following steps: The battery, after being injected with water, was placed in a high-temperature environment chamber, and the temperature of the environment chamber was set to 45℃. The battery should undergo at least three charge-discharge cycles with a current rate not exceeding 1C. Adjust the temperature chamber to 25°C to allow the battery to return to a stable state.

[0025] As a feasible and preferred approach, the simulation experiment for a battery experiencing excessive internal moisture due to a ruptured explosion-proof valve includes the following steps: The battery, after being injected with water, was placed in a high-temperature environment chamber, and the temperature of the environment chamber was set to 45℃. Perform at least three charge-discharge cycles on the battery, with a current rate not exceeding 1C, to ensure that the injected water diffuses evenly inside the battery. Adjust the temperature chamber to 25°C to allow the battery to return to a stable state.

[0026] As a feasible and preferred solution, the graded security early warning method is as follows: When a≥1.2 and c<0.8, a level 2 self-heating runaway alarm is issued; When a ≥ 1.5, a level three self-heating runaway alarm is issued; When a ≥ 1.2 but does not meet the conditions for a level 2 or 3 alarm, a level 1 self-heating runaway alarm will be issued. Attached Figure Description

[0027] Figure 1 This is a logical schematic diagram of Embodiment 1 of the present invention.

[0028] Figure 2 This is a logical schematic diagram of Embodiment 2 of the present invention. Detailed Implementation

[0029] To make the technical solution and advantages of this application clearer, the technical solution of the present invention will be further described in detail below with reference to the accompanying drawings. It is understood that the specific embodiments described herein are only some embodiments of the present invention, and are only used to explain this application, not to limit it. It should be noted that the technical features or combinations of technical features described in the following embodiments should not be considered isolated; they can be combined with each other to achieve better technical effects. The same reference numerals appearing in the accompanying drawings of the following embodiments represent the same features or components, and can be applied to different embodiments.

[0030] Furthermore, unless otherwise defined, the technical or scientific terms used in this invention description shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains.

[0031] The present invention will now be described in further detail with reference to the accompanying drawings.

[0032] Example 1: Simulating excessive internal moisture during battery manufacturing, referring to... Figure 1 .

[0033] Step S100A, Material and Equipment Preparation, includes: For phase change materials, select those with a phase change temperature of 40℃, such as paraffin-based materials, to prevent moisture leakage during operation.

[0034] Hydrated salt particles, preferably calcium chloride hexahydrate, have a dehydration temperature that matches the battery's operating temperature range.

[0035] For lithium-ion batteries, samples were selected based on the same model, capacity deviation within 2%, and OCV difference within 2% under 100% SOC conditions.

[0036] The glove box, with its dry, inert atmosphere, is used for battery disassembly and reassembly.

[0037] A temperature chamber allows for precise temperature control, simulating the reaction of a battery at different temperatures.

[0038] A high-precision voltmeter used to measure the open-circuit voltage of a battery.

[0039] Syringe for precise injection of phase change material / water capsules or hydrated salt particles.

[0040] Step S200A, preparing phase change material / water capsules, includes: Step S201A: Weigh an appropriate amount of phase change material and heat it to above its phase change temperature to melt it.

[0041] Step S202A: Add the calculated amount of water to the molten phase change material and stir until homogeneous.

[0042] For example, to prepare a phase change material / water capsule with a water content of 5%, add 5g of water to every 100g of phase change material.

[0043] In step S203A, the mixture is dripped into a cooling device to form spherical capsules. The cooling device can be designed as a container with circulating cooling water to ensure rapid solidification of the capsules.

[0044] Step S204A: Select capsules that are uniform in size and undamaged for later use.

[0045] Step S300A, battery treatment and moisture implantation, includes: Step S301A: Discharge the selected lithium-ion battery until the SOC reaches 0%. The discharge process is carried out under constant current and constant voltage conditions to ensure that the battery is completely discharged.

[0046] Step S302A: In a dry, inert atmosphere within a glove box, use precision tools to break the battery's external encapsulation, such as the aluminum casing or aluminum-plastic film. Care must be taken during this process to avoid damaging the battery's internal structure.

[0047] Step S303A: Use a syringe to implant the prepared phase change material / water capsule into a specific location in the battery. Depending on the research needs, the implantation location can be between the positive electrode and the separator, between the negative electrode and the separator, 1 cm below the positive electrode tab, 1 cm below the negative electrode tab, or at the center of the large surface area.

[0048] Step S305A involves resealing the implanted battery. The sealing material must be compatible with the original battery's sealing material to ensure a tight seal. The sealing process is completed inside a glove box to prevent moisture from re-entering.

[0049] Step S400, simulation test, including: Step S401A: Transfer the packaged battery into a temperature chamber, setting the ambient temperature to 45°C, which is at least 5°C higher than the phase change temperature of the phase change material. This allows moisture to escape from the packaging and fully combine or react with the target substances inside the battery.

[0050] Step S402A: Control the rate of increase of battery temperature to 1℃ / min (or 2℃ / min or 4℃ / min as needed) to control the rate of reaction between moisture and the electrolyte inside the battery.

[0051] Step S403A, to simulate extreme conditions, such as the reaction between moisture and lithium dendrites on the negative electrode, first control the battery to undergo at least 3 discharge and charge cycles at 0°C, with the current rate not exceeding 0.5C. When the battery SOC is 100%, switch to a 45°C environment and let it stand for at least 5 hours.

[0052] Step S404A: Adjust the temperature of the temperature chamber to 25°C to restore the battery to a stable state.

[0053] Step S500, Characteristic Signal Testing and Safety Warning, includes: Step S501A: Screen samples with good consistency and divide them into a control group (samples without modification) and an experimental group (samples with modified internal water content).

[0054] Step S502A involves testing the self-discharge rate characteristic signal of the batteries in the experimental and control groups at an ambient temperature of 25°C. Specifically, the batteries are charged to 105% SOC using a 0.5C current rate. After resting for 2 hours, the open-circuit voltage is measured every 10 minutes using a voltmeter, and the voltage change rate is calculated as the self-discharge rate.

[0055] Step S503A: After obtaining the self-discharge rates of the control group and the experimental group, take their relative proportion (defined as a), including: When a reaches 1.2, it is defined as a level 1 alarm for self-heating runaway; when a reaches 1.2 and the envelope area b of the capacity differential curve is less than 0.8, it is defined as a level 2 alarm for self-heating runaway; when a reaches 1.5, it is defined as a level 3 alarm for self-heating runaway.

[0056] Step S504A involves testing the capacity differential curve envelope area characteristic signal of the battery, including: At an ambient temperature of 25°C, the battery is subjected to charge and discharge cycles at a rate of 0.01C within a specific SOC range (at least greater than 20%).

[0057] After obtaining the relationship between capacity and voltage during the charging process, a second-order polynomial of order 8 or higher is used to fit the curve. After differentiation, the slope and voltage relationship between capacity and voltage are established, and the envelope area characteristic signal of the capacity differential curve is obtained by integration.

[0058] The relative ratio of the experimental group to the control group (defined as c) is used for battery safety warning.

[0059] Example 2: Simulating excessive moisture content due to the rupture of the explosion-proof valve during battery use, referring to... Figure 2 .

[0060] Step S100B, Material and Equipment Preparation, includes: A syringe used for precise injection of water.

[0061] The high-temperature resistant sealant can maintain the airtightness of the water injection hole for at least 1 hour at ambient temperatures above 500℃.

[0062] For lithium-ion batteries, samples were selected based on the same model, capacity deviation within 2%, and OCV difference within 2% under 100% SOC conditions.

[0063] High-temperature environmental chambers allow for precise temperature control, simulating battery reactions at high temperatures.

[0064] A high-precision voltmeter used to measure the open-circuit voltage of a battery.

[0065] Step S200B, moisture injection, includes: Step S201B: Place the battery after it has been injected with water in a high-temperature environment chamber and set the temperature of the environment chamber to 45°C.

[0066] Step S202B: Perform at least 3 charge-discharge cycles on the battery, with a current rate not exceeding 1C, to ensure that the injected water diffuses evenly inside the battery.

[0067] Step S203B: Adjust the temperature of the temperature chamber to 25°C to restore the battery to a stable state.

[0068] Step S300B, simulation experiment, includes: Step S301B: Place the battery after it has been injected with water in a high-temperature environment chamber and set the temperature of the environment chamber to 45°C.

[0069] Step S302B: Perform at least 3 charge-discharge cycles on the battery, with a current rate not exceeding 1C, so that the injected water diffuses evenly inside the battery.

[0070] Step S303B: Adjust the temperature of the temperature chamber to 25°C to restore the battery to a stable state.

[0071] Step S400B, Characteristic Signal Testing and Safety Warning, uses the same method as simulating excessive internal moisture during battery manufacturing. By testing the characteristic signals of self-discharge rate and capacity differential curve envelope area, a graded alarm for battery safety is achieved.

[0072] This application also provides a system for simulating excessive internal moisture in lithium-ion batteries and using characteristic signals for safety warnings, which utilizes the aforementioned method for simulating excessive internal moisture in lithium-ion batteries and using characteristic signals for safety warnings.

[0073] The present invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor of an electronic device, can implement the steps of the method described above for simulating excessive internal moisture in a lithium-ion battery and using characteristic signals for safety warning.

[0074] Those skilled in the art will understand that implementing all or part of the process in a method for simulating excessive internal moisture in a lithium-ion battery and using characteristic signals for safety warning can be accomplished by a computer program instructing related hardware. The program can be stored in a non-volatile computer-readable storage medium. When executed, the program can include the processes of various embodiments of a method for simulating excessive internal moisture in a lithium-ion battery and using characteristic signals for safety warning. Any references to memory, storage, databases, or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in a variety of forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), dual data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), RAMbus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

[0075] The above content is merely an embodiment of the present invention. Commonly known structures and characteristics of the solutions are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all prior art in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can improve and implement this solution based on the guidance provided in this application and their own capabilities. Some typical well-known structures or systems should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for simulating excessive internal moisture in lithium-ion batteries and using characteristic signals for safety early warning, characterized in that, include: Provide lithium-ion battery samples that meet the consistency requirements; Excessive moisture is introduced into the battery in a controlled manner to simulate the excessive internal moisture caused by the rupture of the explosion-proof valve during manufacturing or use. A simulation experiment was conducted to measure the self-discharge rate of the control group battery and the experimental group battery, respectively. The method for determining the self-discharge rate is as follows: Charge the battery to 105% SOC at a 0.5C rate, let it stand for 2 hours, and continuously collect the open circuit voltage at time intervals of ≤10 minutes. Calculate the voltage drop rate per unit time as the self-discharge rate. The envelope areas of the capacity differential curves of the control group and the experimental group batteries were measured separately. The measurement method was as follows: At 25℃, the battery was charged and discharged at a rate of 0.01C within the ≥20% SOC range, and the capacity-voltage data were recorded. The curve was fitted using a ≥8th order quadratic polynomial, and the derivative was used to obtain the slope and voltage relationship curve of capacity versus voltage. The envelope area was obtained by integrating the curve within the same voltage range. The ratio of the self-discharge rate of the experimental group to that of the control group is denoted as a, and the ratio of the envelope area of ​​the experimental group to that of the control group is denoted as c. A graded safety warning is carried out based on the combination of the values ​​of a and c.

2. The method for simulating excessive internal moisture in a lithium-ion battery and using characteristic signals for safety early warning, as described in claim 1, is characterized in that: The consistency requirements are: same model, capacity deviation ≤2%, and open circuit voltage difference ≤2% under 100% SOC state.

3. The method for simulating excessive internal moisture in a lithium-ion battery and using characteristic signals for safety early warning, as described in claim 1, is characterized in that... In simulating excessive internal moisture during battery manufacturing, excess moisture is introduced into the battery in a controlled manner by injecting phase change material / water capsules or hydrated salt particles. The hydrated salt particles used are calcium chloride hexahydrate.

4. The method for simulating excessive internal moisture in a lithium-ion battery and using characteristic signals for safety early warning, as described in claim 3, is characterized in that... The phase change material / water capsule was prepared by selecting a phase change material with a phase change temperature of 40℃, including the following preparation steps: Weigh out an appropriate amount of phase change material and heat it to above its phase change temperature to melt it; Add the calculated amount of water to the molten phase change material and stir until homogeneous; The mixture is dripped into a cooling device to form spherical capsules; the cooling device is designed as a container with circulating cooling water to ensure rapid solidification of the capsules; Select capsules that are uniform in size and undamaged for later use.

5. The method for simulating excessive internal moisture in a lithium-ion battery and using characteristic signals for safety early warning, as described in claim 1, is characterized in that... In simulating excessive internal moisture during battery manufacturing, battery treatment and moisture implantation include the following steps: The selected lithium-ion battery is discharged until the SOC reaches 0%; the discharge process is carried out under constant current and constant voltage conditions to ensure that the battery is completely discharged. The external encapsulation of the battery is damaged in the dry, inert atmosphere of the glove box; The prepared phase change material / water capsule is implanted into a specific location in the battery using a syringe. The implanted battery is then repackaged.

6. The method for simulating excessive internal moisture in a lithium-ion battery and using characteristic signals for safety early warning, as described in claim 1, is characterized in that... The implantation sites can be selected between the positive electrode and the septum, between the negative electrode and the septum, 1 cm below the positive electrode ear, 1 cm below the negative electrode ear, or the center of the large surface area.

7. The method for simulating excessive internal moisture in a lithium-ion battery and using characteristic signals for safety early warning, as described in claim 1, is characterized in that... The simulation experiment, which simulates excessive internal moisture during battery manufacturing, includes the following steps: The encapsulated battery is then transferred into a temperature chamber, and the ambient temperature of the temperature chamber is set at least 5°C higher than the phase change temperature of the phase change material. This allows moisture to escape from the packaging and fully combine or react with the target material inside the battery. The rate of temperature rise in the battery is controlled at 1℃ / min to control the rate of reaction between moisture and the electrolyte inside the battery. To simulate extreme conditions, such as the reaction between moisture and lithium dendrites on the negative electrode, the battery was first controlled to undergo at least 3 discharge and charge cycles at 0°C, with the current rate not exceeding 0.5C; when the battery SOC was 100%, it was switched to a 45°C environment and left to stand for at least 5 hours. Adjust the temperature chamber to 25°C to allow the battery to return to a stable state.

8. The method for simulating excessive internal moisture in a lithium-ion battery and using characteristic signals for safety early warning, as described in claim 1, is characterized in that... In simulating a battery's internal moisture exceeding the standard due to a ruptured explosion-proof valve during use, the moisture injection method includes the following steps: The battery, after being injected with water, was placed in a high-temperature environment chamber, and the temperature of the environment chamber was set to 45℃. The battery should undergo at least three charge-discharge cycles with a current rate not exceeding 1C. Adjust the temperature chamber to 25°C to allow the battery to return to a stable state.

9. The method for simulating excessive internal moisture in a lithium-ion battery and using characteristic signals for safety early warning, as described in claim 1, is characterized in that... The simulation experiment, which addresses the issue of excessive internal moisture in a battery due to a ruptured explosion-proof valve, includes the following steps: The battery, after being injected with water, was placed in a high-temperature environment chamber, and the temperature of the environment chamber was set to 45℃. Perform at least three charge-discharge cycles on the battery, with a current rate not exceeding 1C, to ensure that the injected water diffuses evenly inside the battery. Adjust the temperature chamber to 25°C to allow the battery to return to a stable state.

10. A method for simulating excessive internal moisture in a lithium-ion battery and using characteristic signals for safety early warning, characterized in that... The tiered safety early warning system is as follows: When a≥1.2 and c<0.8, a level 2 self-heating runaway alarm is issued; When a ≥ 1.5, a level three self-heating runaway alarm is issued; When a ≥ 1.2 but does not meet the conditions for a level 2 or 3 alarm, a level 1 self-heating runaway alarm will be issued.

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