A lithium ion battery thermal runaway early warning method and system based on internal air pressure monitoring

Abstract

The application discloses a lithium ion battery thermal runaway early warning method and system based on internal air pressure monitoring, solves the technical problems of existing technology early warning lag and high false alarm rate, synchronously acquires real-time air pressure value and temperature value in the cell, obtains normalized air pressure value representing actual gas production through temperature compensation, calculates air pressure change rate and extracts air pressure curve curvature change inflection point, adopts normalized air pressure value and air pressure change rate dual condition combined triggering preliminary warning, and upgrades to confirmation warning after detecting the curvature change inflection point. The application also discloses a double-cavity differential pressure sensing structure and a two-stage early warning response mechanism. The application can issue early warning in advance of several minutes to several tens of minutes in the thermal runaway incubation period, completely eliminates temperature interference through double temperature compensation, greatly reduces the false alarm rate through three-stage progressive judgment logic, realizes the balance between safety and availability through the staged early warning mechanism, and can be widely applied in the fields of new energy vehicles, energy storage power stations and the like.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a method and system for early warning of thermal runaway in lithium-ion batteries based on internal air pressure monitoring. Background Technology

[0002] The large-scale application of lithium-ion batteries in new energy vehicles and energy storage power stations has led to frequent thermal runaway safety accidents. Existing thermal runaway early warning technologies mainly rely on monitoring external parameters such as temperature, voltage, and smoke, which have significant limitations: temperature monitoring suffers from heat conduction lag, providing warnings only a few seconds before thermal runaway occurs, severely insufficient emergency response time; voltage monitoring only reflects the overall state of the electrodes and cannot identify internal microscopic side reactions; smoke monitoring is a post-accident alarm. More critically, existing gas pressure monitoring solutions fail to effectively distinguish between gas expansion and contraction caused by temperature changes and gas production from abnormal chemical reactions. Normal charging and discharging temperature rises and ambient temperature fluctuations easily trigger false alarms, severely impacting system availability. Summary of the Invention

[0003] To overcome the shortcomings of existing technical solutions, this invention provides a method and system for early warning of thermal runaway in lithium-ion batteries based on internal air pressure monitoring, which can effectively solve the problems mentioned in the background technology.

[0004] The technical solution adopted by this invention to solve its technical problem is:

[0005] A method for early warning of thermal runaway in lithium-ion batteries based on internal air pressure monitoring includes the following steps:

[0006] Step S1: Obtain the real-time air pressure value inside the battery cell and simultaneously obtain the real-time temperature value of the battery cell.

[0007] Step S2: Based on the real-time temperature value, perform temperature compensation on the real-time gas pressure value to determine the normalized gas pressure value that characterizes the actual gas production inside the battery cell.

[0008] Step S3: Calculate the rate of change of the normalized pressure value within a preset time window, and extract the pressure curve features of the normalized pressure value changing with time. The pressure curve features include at least the inflection point of the pressure curvature change.

[0009] Step S4: When the normalized air pressure value exceeds a preset safety threshold and the air pressure change rate exceeds a preset safety change rate threshold, a preliminary warning signal is triggered.

[0010] Step S5: After the preliminary warning signal is triggered, if the inflection point of the air pressure curvature change is detected within a continuous monitoring cycle, it is determined that the battery cell is in the early stage of thermal runaway, and the preliminary warning signal is upgraded to a confirmed warning signal.

[0011] As a further description of the above technical solution, in step S1, the "acquiring of the real-time air pressure value inside the battery cell" is achieved through a dual-cavity differential pressure sensing structure, which includes:

[0012] A pressure chamber connected to the inside of the battery cell, and a reference chamber sealed with the same initial gas composition and pressure as the inside of the battery cell;

[0013] The differential pressure between the pressure chamber and the reference chamber is measured, and this differential pressure is directly used as the normalized gas pressure value after excluding the influence of temperature.

[0014] As a further description of the above technical solution, in steps S4 and S5, the steps of "triggering the preliminary warning signal" and "upgrading the preliminary warning signal to a confirmed warning signal" correspond to different response actions;

[0015] When the initial warning signal is triggered, the response actions should include at least increasing the sampling frequency of air pressure and temperature, and connecting the heat dissipation circuit to pre-cool the battery;

[0016] When the preliminary warning signal is upgraded to a confirmed warning signal, the response action includes at least disconnecting the main circuit switch of the battery and triggering an audible and visual alarm.

[0017] As a further description of the above technical solution, in step S3, the step of "extracting the pressure curve features of the normalized pressure value changing with time" further includes:

[0018] Step S6: During the continuous monitoring period, analyze the second derivative of the pressure curve to identify the inflection point of the pressure curvature change from a gradual rising stage to a rapid rising stage, caused by the rapid decomposition of the electrode material inside the cell or the violent vaporization of the electrolyte.

[0019] As a further description of the above technical solution, the "acquisition of real-time air pressure value inside the battery cell" is achieved by an air pressure sensor integrated on the battery cell casing and directly connected to the gas phase space inside the battery cell.

[0020] A lithium-ion battery thermal runaway early warning system based on internal air pressure monitoring, and a method for early warning of thermal runaway in lithium-ion batteries, the system comprising:

[0021] The air pressure sensing unit is used to directly detect and output the real-time air pressure value inside the battery cell;

[0022] Temperature sensing unit, used to detect and output the real-time temperature value of the battery cell;

[0023] The data processing and control unit is electrically connected to the air pressure sensing unit and the temperature sensing unit, respectively, and is configured as follows:

[0024] Receive the real-time air pressure value and the real-time temperature value;

[0025] A temperature compensation algorithm is executed to convert the real-time air pressure value into a normalized air pressure value;

[0026] Calculate the rate of change of the normalized pressure value and the inflection point of the pressure curvature change;

[0027] Based on preset logical rules, the system sequentially determines whether the preliminary warning conditions and the confirmed warning conditions are met, and generates the corresponding warning signals.

[0028] The early warning execution unit is electrically connected to the data processing and control unit and is used to receive and execute the protective action corresponding to the early warning signal.

[0029] As a further description of the above technical solution, the air pressure sensing unit is a gauge pressure type MEMS air pressure sensor, which is connected to the pressure relief area of ​​the cell explosion-proof valve or a dedicated airtight interface on the cell cover through an internal cavity, so as to realize non-invasive or semi-invasive direct measurement of the air pressure inside the cell.

[0030] As a further description of the above technical solution, the data processing and control unit stores a pressure-temperature compensation model, which is used to convert the real-time pressure to a normalized pressure value at the same reference temperature based on the real-time temperature, thereby eliminating the interference of pressure rise caused by normal charging and discharging temperature rise on the early warning logic.

[0031] As a further description of the above technical solution, the early warning execution unit includes a first-level response module and a second-level response module;

[0032] The first-level response module is used to trigger enhanced thermal management actions upon receiving a preliminary warning signal;

[0033] The second-level response module is used to trigger power failure protection and alarm actions when a confirmation warning signal is received.

[0034] As a further description of the above technical solution, the thermal management enhancement actions triggered by the first-level response module include activating the liquid cooling plate, the air-cooled fan, or switching to a low-power operation strategy.

[0035] The power failure protection and alarm actions triggered by the second-level response module include sending a circuit breaker command to the battery management system to disconnect the main positive or main negative contactor, and driving the alarm indicator light or buzzer to work.

[0036] Compared with the prior art, the beneficial effects of the present invention are:

[0037] The present invention provides a method and system for early warning of thermal runaway in lithium-ion batteries based on internal air pressure monitoring, which has at least one of the following beneficial effects during use:

[0038] First, by directly monitoring the internal air pressure of the battery cell, the earliest characteristic of thermal runaway, the early warning time is increased by an order of magnitude compared to traditional temperature monitoring solutions, which can buy several minutes to tens of minutes of valuable time for emergency response, fundamentally solving the industry pain point of lagging early warning in existing technologies.

[0039] Secondly, a dual temperature compensation mechanism combining hardware differential pressure compensation and software model compensation is adopted, which completely eliminates the interference of normal charging and discharging temperature rise and ambient temperature fluctuations on air pressure monitoring, and significantly reduces the probability of false alarms.

[0040] Furthermore, the constructed three-level progressive judgment logic of normalized air pressure value, air pressure change rate, and curvature change inflection point comprehensively depicts the thermal runaway development process from three dimensions: quantity, speed, and quality, significantly improving the accuracy of early warning.

[0041] Furthermore, the two-tiered early warning mechanism enables differentiated responses between preliminary and confirmed early warnings, ensuring safety while avoiding over-protection that could interfere with normal use. Finally, the system architecture of this invention is complete and highly modular, allowing for easy integration into existing battery management systems, and it has broad prospects for industrial application. Attached Figure Description

[0042] Figure 1 This is a first cross-sectional schematic diagram of the integrated structure of a dual-cavity differential pressure sensor for a lithium-ion battery thermal runaway early warning system based on internal air pressure monitoring, according to the present invention.

[0043] Figure 2 This is a second cross-sectional schematic diagram of the integrated structure of a dual-cavity differential pressure sensor for a lithium-ion battery thermal runaway early warning system based on internal air pressure monitoring, according to the present invention.

[0044] Figure 3 This is a schematic diagram of the overall architecture of a lithium-ion battery thermal runaway early warning system based on internal air pressure monitoring according to the present invention.

[0045] Figure 4 This is the main flowchart of a lithium-ion battery thermal runaway early warning method based on internal air pressure monitoring according to the present invention.

[0046] Figure 5 This is a schematic diagram comparing the differential pressure (normalized pressure) curve characteristics of a lithium-ion battery thermal runaway early warning method based on internal air pressure monitoring, according to the present invention.

[0047] Numbering on the map:

[0048] 1. Cell housing; 2. Cell explosion-proof valve; 3. Airtight interface; 4. Dual-chamber differential pressure sensing structure; 5. Pressure chamber; 6. Reference chamber. Detailed Implementation

[0049] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] like Figure 1-5 As shown, this invention provides a method for early warning of thermal runaway in lithium-ion batteries based on internal air pressure monitoring, comprising the following steps:

[0051] Step S1: Obtain the real-time air pressure value inside the battery cell and simultaneously obtain the real-time temperature value of the battery cell.

[0052] Before thermal runaway occurs, a series of side reactions take place inside the lithium-ion battery in this embodiment, including SEI film decomposition, cathode material decomposition, and electrolyte decomposition. These reactions all generate a large amount of gas, leading to an increase in internal gas pressure within the cell. Simultaneously, changes in battery temperature cause thermal expansion and contraction of the gas, affecting the gas pressure measurement. Therefore, simultaneously acquiring real-time internal gas pressure and temperature values ​​provides the raw data foundation for subsequent data processing.

[0053] Step S2: Based on the real-time temperature value, perform temperature compensation on the real-time gas pressure value to determine the normalized gas pressure value that characterizes the actual gas production inside the battery cell.

[0054] The internal gas pressure change of the battery cell in this embodiment consists of two parts: one is the thermal expansion and contraction of gas caused by temperature changes (temperature effect), and the other is the increase in the amount of substance caused by gas production from internal chemical reactions (gas production effect). Through a temperature compensation algorithm, the gas pressure values ​​measured at different temperatures are converted to the gas pressure values ​​at a unified reference temperature, eliminating the interference of temperature changes on the gas pressure measurement, and obtaining a normalized gas pressure value that only reflects the actual gas production inside the battery cell.

[0055] Step S3: Calculate the rate of change of the normalized pressure value within a preset time window, and extract the pressure curve features of the normalized pressure value changing with time. The pressure curve features include at least the inflection point of the pressure curvature change.

[0056] In this embodiment, the pressure changes during the thermal runaway development process exhibit distinct phased characteristics: a slow increase in pressure during the incubation period, an accelerated increase during the triggering period, and a sharp increase during the outbreak period. By calculating the rate of change of pressure (first derivative) within a preset time window, the speed of pressure increase can be quantified; by extracting the inflection point of the curvature change of the pressure curve (the critical point where the second derivative changes from positive to negative or vice versa), the turning point from slow to rapid thermal runaway can be identified. The inflection point of the pressure curvature change corresponds to the critical moment when the internal side reactions of the battery cell transform from slow to a chain-like self-accelerating reaction.

[0057] Step S4: When the normalized air pressure value exceeds a preset safety threshold and the air pressure change rate exceeds a preset safety change rate threshold, a preliminary warning signal is triggered.

[0058] A dual-condition joint judgment mechanism is adopted to trigger the initial warning. A single threshold judgment is prone to false alarms: if only the absolute value of the gas pressure exceeds the threshold, it may be due to the gas pressure balance after normal charging is completed; if only the rate of change of the gas pressure exceeds the threshold, it may be due to a temporary external disturbance. Only when the normalized gas pressure value exceeds the safety threshold and the rate of change of the gas pressure also exceeds the safety rate of change threshold, does it indicate that there is indeed a continuous abnormal gas production inside the battery cell, triggering the initial warning.

[0059] Step S5: After the preliminary warning signal is triggered, if the inflection point of the air pressure curvature change is detected within a continuous monitoring cycle, it is determined that the battery cell is in the early stage of thermal runaway, and the preliminary warning signal is upgraded to a confirmed warning signal.

[0060] The inflection point of pressure curvature change is a hallmark of the early stages of thermal runaway, corresponding to the critical point where internal reactions transition from quantitative to qualitative change. Detecting this inflection point within a continuous monitoring period eliminates misjudgments caused by transient interference, confirming that the thermal runaway process has irreversibly begun. At this point, the warning is upgraded to ensure its accuracy and reliability.

[0061] Compared to traditional temperature monitoring and early warning systems, this method, through internal air pressure monitoring, can identify anomalies during the thermal runaway incubation period, buying valuable time for emergency response. Employing a three-level progressive judgment logic, it filters out interference from normal operating conditions and instantaneous noise at each level, resulting in a significantly higher early warning accuracy than single-parameter judgment methods. By obtaining a normalized air pressure value through temperature compensation, the influence of non-fault factors such as normal battery charging and discharging temperature rise and ambient temperature changes on air pressure monitoring is eliminated, ensuring that the early warning logic is only sensitive to abnormal gas production. The tiered mechanism of step-by-step and confirmed early warnings ensures safety while avoiding unnecessary downtime and panic. Identifying inflection points in air pressure curvature changes allows for accurate determination of the early irreversible stage of thermal runaway. The inflection point detection mechanism within the continuous monitoring cycle effectively eliminates false signals caused by electromagnetic interference, sensor noise, and instantaneous vibrations, resulting in high early warning reliability.

[0062] Furthermore, in step S1, the "acquisition of the real-time air pressure value inside the battery cell" is achieved through a dual-cavity differential pressure sensing structure 4, which includes:

[0063] The pressure chamber 5 is connected to the inside of the battery cell, and the reference chamber 6 is sealed with the same initial gas composition and pressure as the inside of the battery cell;

[0064] The differential pressure between the pressure chamber 5 and the reference chamber 6 is measured, and this differential pressure is directly used as the normalized gas pressure value after excluding the influence of temperature.

[0065] Pressure chamber 5 is directly connected to the inside of the battery cell, and its pressure changes synchronously with the internal pressure and temperature of the battery cell. Reference chamber 6 is a sealed structure, containing gas with the same composition and pressure as the battery cell in its initial state, and its pressure changes only with the ambient temperature. Since the two chambers are in the same temperature field, the effect of temperature changes on the pressure in both chambers is exactly the same.

[0066] According to the differential pressure calculation formula ΔP=P_pressure_cavity5-P_reference_cavity6, the temperature effects cancel each other out, and the differential pressure value directly reflects the gas pressure increment caused by the gas production due to chemical reaction inside the battery cell, that is, the normalized gas pressure value.

[0067] It features high differential pressure compensation accuracy, eliminates the need to wait for temperature sampling and software calculation, directly outputs the normalized pressure value as the differential pressure signal, shortens the warning response delay, has good operational stability, and has a long maintenance cycle.

[0068] Furthermore, in steps S4 and S5, the steps of "triggering a preliminary warning signal" and "upgrading the preliminary warning signal to a confirmed warning signal" correspond to different response actions.

[0069] When the initial warning signal is triggered, the response actions should include at least increasing the sampling frequency of air pressure and temperature, and connecting the heat dissipation circuit to pre-cool the battery;

[0070] When the preliminary warning signal is upgraded to a confirmed warning signal, the response action includes at least disconnecting the main circuit switch of the battery and triggering an audible and visual alarm.

[0071] In the initial warning stage, thermal runaway is still in its early stages and the risk level is low. At this time, increasing the sampling frequency can monitor data change trends more intensively and ensure that no key features are missed. Connecting the heat dissipation circuit for pre-cooling can suppress the temperature rise and slow down the side reaction rate, which may nip thermal runaway in the bud.

[0072] Once the early warning stage is confirmed, thermal runaway has entered an irreversible early stage of development, posing a high risk. At this point, decisive measures must be taken: disconnect the main circuit switch to cut off energy input and prevent the electrochemical reaction from continuing; trigger audible and visual alarms to notify relevant personnel to handle the situation promptly and prevent the accident from escalating.

[0073] Furthermore, in step S3, the step of "extracting the pressure curve features of the normalized pressure value changing with time" also includes:

[0074] Step S6: During the continuous monitoring period, analyze the second derivative of the pressure curve to identify the inflection point of the pressure curvature change from a gradual rising stage to a rapid rising stage, caused by the rapid decomposition of the electrode material inside the cell or the violent vaporization of the electrolyte.

[0075] The first derivative of the pressure curve reflects the rate of pressure increase, while the second derivative reflects the rate of change of that rate, i.e., acceleration. Before thermal runaway occurs, the rate of side reactions inside the battery cell gradually increases, and the acceleration of the pressure increase increases. When a critical point is reached, the electrode material rapidly decomposes or the electrolyte violently vaporizes, resulting in an exponential increase in gas production. The pressure curve changes from "upward convex" (positive second derivative, increasing acceleration) to "downward convex" (second derivative changes from positive to negative, the rate itself has reached an extremely high value). This turning point is the inflection point of curvature change. This key characteristic can be accurately identified by continuously monitoring the change in the sign of the second derivative over a period of time.

[0076] To further explain, the "acquisition of real-time air pressure value inside the battery cell" is achieved through an air pressure sensor integrated on the battery cell housing 1 and directly connected to the gas phase space inside the battery cell.

[0077] The pressure sensor is integrated into the cell housing 1 and directly connected to the internal gas phase space. The sensor's measuring surface directly contacts the gas inside the cell, avoiding problems such as pressure transmission lag, pipeline leakage, and gas adsorption caused by long gas guide pipes. The gas phase space is the area where gas first accumulates inside the cell; measuring here allows for immediate detection of pressure changes without propagation delay.

[0078] A lithium-ion battery thermal runaway early warning system based on internal air pressure monitoring, and a method for early warning of lithium-ion battery thermal runaway, the system comprising:

[0079] The air pressure sensing unit is used to directly detect and output the real-time air pressure value inside the battery cell;

[0080] Temperature sensing unit, used to detect and output the real-time temperature value of the battery cell;

[0081] The data processing and control unit is electrically connected to the air pressure sensing unit and the temperature sensing unit, respectively, and is configured as follows:

[0082] Receive the real-time air pressure value and the real-time temperature value;

[0083] A temperature compensation algorithm is executed to convert the real-time air pressure value into a normalized air pressure value;

[0084] Calculate the rate of change of the normalized pressure value and the inflection point of the pressure curvature change;

[0085] Based on preset logical rules, the system sequentially determines whether the preliminary warning conditions and the confirmed warning conditions are met, and generates the corresponding warning signals.

[0086] The early warning execution unit is electrically connected to the data processing and control unit and is used to receive and execute the protective action corresponding to the early warning signal.

[0087] The air pressure sensing unit, as the front-end sensing layer, converts the physical quantity of air pressure inside the battery cell into an electrical signal output; the temperature sensing unit simultaneously collects temperature data; the data processing and control unit, as the core computing layer, executes algorithms such as temperature compensation, feature extraction, and logical judgment. The early warning execution unit, as the execution layer, completes specific protective actions according to control commands, realizing full automation of the thermal runaway early warning process. From sensing to execution, the entire chain is covered, and the entire early warning process can be completed without human intervention, demonstrating a high degree of automation.

[0088] Furthermore, the pressure sensing unit is a gauge pressure type MEMS pressure sensor, which is connected to the pressure relief area of ​​the cell explosion-proof valve 2 or a dedicated airtight interface 3 on the cell cover through an internal cavity, so as to realize non-invasive or semi-invasive direct measurement of the internal pressure of the cell.

[0089] MEMS pressure sensors are characterized by small size, high accuracy, and fast response. The gauge pressure measurement method eliminates the influence of atmospheric pressure changes compared to absolute pressure measurement. By connecting the inner cavity to the pressure relief area of ​​the explosion-proof valve or the dedicated airtight interface 3, non-invasive (using the existing explosion-proof valve structure) or semi-invasive (dedicated interface) measurement can be achieved, which not only ensures the directness of the measurement, but also avoids the risk of damaging the battery cell sealing structure by making additional holes in the battery cell housing 1.

[0090] The data processing and control unit of the lithium-ion battery thermal runaway early warning system stores a pressure-temperature compensation model. This model is used to convert the real-time pressure to a normalized pressure value at the same reference temperature based on the real-time temperature, thereby eliminating the interference of pressure rise caused by normal charging and discharging temperature rise on the early warning logic.

[0091] This model includes a pressure correction coefficient matrix for different temperatures. Based on the ideal gas law and actual gas correction factors, it can convert real-time pressure measured at any temperature to an equivalent pressure value at a standard reference temperature (e.g., 25°C), a value that depends only on the amount of gas. Through this model, the pressure rise caused by Joule heating during normal charging and discharging is completely compensated for, and the warning logic is only sensitive to abnormal gas production.

[0092] The early warning execution unit for lithium-ion battery thermal runaway early warning includes a first-level response module and a second-level response module.

[0093] The first-level response module is used to trigger enhanced thermal management actions upon receiving a preliminary warning signal;

[0094] The second-level response module is used to trigger power failure protection and alarm actions when a confirmation warning signal is received.

[0095] The first-level response module provides initial warnings for low-risk situations and executes non-destructive thermal management enhancement actions; the second-level response module provides confirmed warnings for high-risk situations and executes protective power-off and alarm actions. The two modules are configured and triggered independently, ensuring both gentle handling in low-risk situations and decisive protection in high-risk situations, achieving an optimal balance between safety and availability.

[0096] The thermal runaway warning of lithium-ion batteries triggers enhanced thermal management actions by the first-level response module, including activating the liquid cooling plate, air-cooled fan, or switching to a low-power operation strategy.

[0097] The power failure protection and alarm actions triggered by the second-level response module include sending a circuit breaker command to the battery management system to disconnect the main positive or main negative contactor, and driving the alarm indicator light or buzzer to work.

[0098] The first-level response works by simultaneously increasing heat dissipation and reducing heat generation through two aspects: activating liquid cooling plates and air-cooled fans to enhance heat dissipation, or limiting power through the BMS to reduce heat generation. This suppresses temperature rise and slows down the rate of side reactions. The second-level response disconnects the main contactor to cut off the electrochemical circuit, stopping energy input at its source, and simultaneously notifies personnel through audible and visual warnings.

[0099] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for early warning of thermal runaway in lithium-ion batteries based on internal air pressure monitoring, characterized in that, Includes the following steps: Step S1: Obtain the real-time air pressure value inside the battery cell and simultaneously obtain the real-time temperature value of the battery cell. Step S2: Based on the real-time temperature value, perform temperature compensation on the real-time gas pressure value to determine the normalized gas pressure value that characterizes the actual gas production inside the battery cell. Step S3: Calculate the rate of change of the normalized pressure value within a preset time window, and extract the pressure curve features of the normalized pressure value changing with time. The pressure curve features include at least the inflection point of the pressure curvature change. Step S4: When the normalized air pressure value exceeds a preset safety threshold and the air pressure change rate exceeds a preset safety change rate threshold, a preliminary warning signal is triggered. Step S5: After the preliminary warning signal is triggered, if the inflection point of the air pressure curvature change is detected within a continuous monitoring cycle, it is determined that the battery cell is in the early stage of thermal runaway, and the preliminary warning signal is upgraded to a confirmed warning signal.

2. The lithium-ion battery thermal runaway early warning method based on internal air pressure monitoring according to claim 1, characterized in that, In step S1, the "acquiring of the real-time air pressure value inside the battery cell" is achieved through a dual-chamber differential pressure sensing structure, which includes: A pressure chamber connected to the inside of the battery cell, and a reference chamber sealed with the same initial gas composition and pressure as the inside of the battery cell; The differential pressure between the pressure chamber and the reference chamber is measured, and this differential pressure is directly used as the normalized gas pressure value after excluding the influence of temperature.

3. The lithium-ion battery thermal runaway early warning method based on internal air pressure monitoring according to claim 1, characterized in that, In steps S4 and S5, the steps of "triggering a preliminary warning signal" and "upgrading the preliminary warning signal to a confirmed warning signal" correspond to different response actions. When the initial warning signal is triggered, the response actions should include at least increasing the sampling frequency of air pressure and temperature, and connecting the heat dissipation circuit to pre-cool the battery; When the preliminary warning signal is upgraded to a confirmed warning signal, the response action includes at least disconnecting the main circuit switch of the battery and triggering an audible and visual alarm.

4. The lithium-ion battery thermal runaway early warning method based on internal air pressure monitoring according to claim 1, characterized in that, In step S3, the step of "extracting the pressure curve features of the normalized pressure value changing with time" further includes: Step S6: During the continuous monitoring period, analyze the second derivative of the pressure curve to identify the inflection point of the pressure curvature change from a gradual rising stage to a rapid rising stage, caused by the rapid decomposition of the electrode material inside the cell or the violent vaporization of the electrolyte.

5. The lithium-ion battery thermal runaway early warning method based on internal air pressure monitoring according to claim 1, characterized in that, The "acquisition of real-time air pressure value inside the battery cell" is achieved through an air pressure sensor integrated on the battery cell casing and directly connected to the gas phase space inside the battery cell.

6. A lithium-ion battery thermal runaway early warning system based on internal air pressure monitoring, characterized in that, The system comprising the method of any one of claims 1 to 5, wherein the method is: The air pressure sensing unit is used to directly detect and output the real-time air pressure value inside the battery cell; Temperature sensing unit, used to detect and output the real-time temperature value of the battery cell; The data processing and control unit is electrically connected to the air pressure sensing unit and the temperature sensing unit, respectively, and is configured as follows: Receive the real-time air pressure value and the real-time temperature value; A temperature compensation algorithm is executed to convert the real-time air pressure value into a normalized air pressure value; Calculate the rate of change of the normalized pressure value and the inflection point of the pressure curvature change; Based on preset logical rules, the system sequentially determines whether the preliminary warning conditions and the confirmed warning conditions are met, and generates the corresponding warning signals. The early warning execution unit is electrically connected to the data processing and control unit and is used to receive and execute the protective action corresponding to the early warning signal.

7. The lithium-ion battery thermal runaway early warning system based on internal air pressure monitoring according to claim 6, characterized in that, The pressure sensing unit is a gauge pressure type MEMS pressure sensor, which is connected to the pressure relief area of ​​the cell explosion-proof valve or a dedicated airtight interface on the cell cover through an internal cavity, so as to realize non-invasive or semi-invasive direct measurement of the internal pressure of the cell.

8. The lithium-ion battery thermal runaway early warning system based on internal air pressure monitoring according to claim 6, characterized in that, The data processing and control unit stores a pressure-temperature compensation model, which is used to convert the real-time pressure to a normalized pressure value at the same reference temperature based on the real-time temperature, thereby eliminating the interference of pressure rise caused by normal charging and discharging temperature rise on the early warning logic.

9. The lithium-ion battery thermal runaway early warning system based on internal air pressure monitoring according to claim 6, characterized in that, The early warning execution unit includes a first-level response module and a second-level response module; The first-level response module is used to trigger enhanced thermal management actions upon receiving a preliminary warning signal; The second-level response module is used to trigger power failure protection and alarm actions when a confirmation warning signal is received.

10. The lithium-ion battery thermal runaway early warning system based on internal air pressure monitoring according to claim 9, characterized in that, The enhanced thermal management actions triggered by the first-level response module include activating the liquid cooling plate, air-cooled fan, or switching to a low-power operation strategy; The power failure protection and alarm actions triggered by the second-level response module include sending a circuit breaker command to the battery management system to disconnect the main positive or main negative contactor, and driving the alarm indicator light or buzzer to work.

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