A method for detecting abnormal state of vehicle battery and battery management system

Abstract

The present invention discloses a method for detecting abnormal state of a vehicle battery, including setting a hydrogen adsorbent inside a battery cell of the vehicle battery, the hydrogen adsorbent absorbing hydrogen when the temperature is lower than a preset temperature and releasing hydrogen when the temperature is higher than a preset temperature; and during the operation of the vehicle battery, detecting the concentration of hydrogen in the gas overflowing from the pressure relief valve of the vehicle battery by a hydrogen sensor. The present invention sets a hydrogen adsorbent inside the battery cell, and in the early stage of thermal runaway of the battery, the hydrogen adsorbent adsorbs and accumulates the generated hydrogen; when the temperature is further increased, the hydrogen adsorbent releases the stored hydrogen, so that the hydrogen diffuses to the outside of the battery cell and is detected by the hydrogen sensor. By detecting the accumulated hydrogen generated in the early stage, the early thermal runaway of the battery can be detected more timely. Therefore, the present invention can judge the early stage of thermal runaway more quickly, and there is no need to modify the battery cell or implant a sensor inside.

Description

Technical Field

[0001] The present invention relates to the technical field of electric vehicles, and in particular to a method for detecting abnormal state of a vehicle battery and a battery management system. Background Art

[0002] Lithium batteries are widely used in various fields such as new energy vehicles, electrochemical energy storage, and digital appliances. In particular, their application in the field of new energy vehicles has promoted the rapid development of lithium battery technology. New energy vehicle power batteries have higher requirements for energy density, so it is necessary to improve the energy density of power batteries from multiple angles. Researchers have improved the energy density of power batteries by using highly active positive electrode materials, more compact battery cells and module structures, but this has put forward higher requirements on the safety performance of batteries, especially the problem of battery thermal runaway has received more and more attention. The causes of battery thermal runaway include: external short circuit, external high temperature and internal short circuit, among which thermal runaway caused by internal short circuit is the most common. Taking battery overcharge thermal runaway as an example, during normal charging, the lithium ions embedded in the negative electrode gradually become saturated; when slightly overcharged, the lithium ions cannot be embedded in the negative electrode and thus precipitate on the surface of the negative electrode to form dendrites; after further overcharging, the lithium dendrites further react with the electrolyte to make the internal temperature of the battery reach 90°C, resulting in the decomposition of the SEI film; when the internal temperature of the battery reaches 130°C, the battery separator dissolves to form a greater short circuit, further increasing the internal temperature of the battery until the electrolyte decomposes to produce a large amount of gas, leading to fire or even explosion accidents.

[0003] The prior art mainly detects the air pressure, temperature or concentration of characteristic gas outside the battery cell, and then determines whether thermal runaway occurs through threshold judgment by BMS. However, because heat and gas are generated inside the battery cell, when they are transferred to the outside of the battery cell and detected by the sensor, the thermal runaway of the battery has developed to the middle and late stages of electrolyte decomposition, and these detection data are easily interfered by external conditions, and it is difficult to set a suitable threshold to balance accuracy and sensitivity. CN116759682A detects the early stage of thermal runaway of the battery by detecting the hydrogen concentration in the external accommodating cavity of the battery cell. However, the hydrogen generation rate in the early stage of thermal runaway is very low, and it will continue to escape from the accommodating cavity. The hydrogen concentration near the sensor is difficult to reach the detection lower limit of the sensor, so it is impossible to detect and intervene in the early stage of thermal runaway. CN115472941A proposes a single-cell lithium battery implantable hydrogen detection device, which sets a sensor inside each battery cell and can accurately detect the hydrogen concentration in the battery cell. However, this solution requires the installation of a sensor in each battery cell and the modification of the battery cover, which is costly. Existing technologies cannot achieve both low cost and detection sensitivity.

[0004] Therefore, it is necessary to provide a method for detecting abnormal status of automotive batteries and a battery management system to solve the problem of difficult detection in the early stage of thermal runaway at a low cost. Summary of the invention

[0005] A first aspect of the present invention provides a method for detecting an abnormal state of a vehicle battery, comprising:

[0006] A hydrogen adsorbent is arranged inside a battery cell of a vehicle battery, wherein the hydrogen adsorbent absorbs hydrogen when the temperature is lower than a preset temperature and releases hydrogen when the temperature is higher than a preset temperature;

[0007] During the operation of the vehicle battery, the concentration of hydrogen in the gas overflowing from the pressure relief valve of the vehicle battery is detected by a hydrogen sensor.

[0008] The present invention sets a hydrogen adsorbent inside the battery cell of the vehicle battery, and the hydrogen adsorbent can reversibly combine with the hydrogen generated in the early stage of thermal runaway by physical adsorption or chemical adsorption. In the early stage of thermal runaway of the battery, when the temperature is lower than the preset temperature, the hydrogen adsorbent adsorbs the hydrogen generated at this time and accumulates it; when the temperature is further increased to be higher than the preset temperature, the hydrogen adsorbent releases the stored hydrogen, so that the hydrogen concentration inside the battery cell suddenly increases, so that the hydrogen diffuses to the outside of the battery cell and is detected by the hydrogen sensor, and the early battery thermal runaway can be detected more timely by accumulating the hydrogen generated in the early stage. Different from the prior art method of detecting the characteristic gas and temperature outside the battery cell, the present invention can detect the hydrogen changes inside the battery cell more quickly to judge the early stage of thermal runaway; in addition, the structure of the hydrogen adsorbent is simple, and there is no need for a complex circuit structure, nor is there a need to modify the battery cell or implant a sensor inside, so it has obvious cost advantages.

[0009] Furthermore, the preset temperature is 40-50°C. If the preset temperature is too low, hydrogen will be released during normal operation of the battery, even at room temperature, causing misjudgment; if the preset temperature is too high, such as 80°C, hydrogen may be released only in the middle and late stages of battery thermal runaway, thus failing to achieve early detection of battery thermal runaway.

[0010] Furthermore, the hydrogen adsorbent contains metals and / or alloys that can adsorb hydrogen. Metals / alloy materials that can adsorb hydrogen generally have good chemical stability, such as titanium, palladium, etc., which can adsorb and release hydrogen at a certain temperature and pressure.

[0011] Furthermore, the hydrogen adsorbent contains palladium and / or palladium alloy. Palladium can absorb hundreds of times the volume of hydrogen and is widely used in the detection and purification of hydrogen. Only a very small amount of palladium is needed to meet the demand. It hardly takes up the internal space of the battery cell and does not need to adjust the internal structure of the battery cell. Palladium is relatively stable at room temperature and will not react with the internal structure of the battery or dissolve in the electrolyte. It can be set in most areas inside the battery cell. Palladium alloy has a faster hydrogen adsorption efficiency. For example, the hydrogen adsorption efficiency of palladium-gold alloy is 40 times that of palladium metal. Palladium alloys have different hydrogen release temperatures, and different palladium alloys can be used according to the preset temperature.

[0012] Furthermore, the palladium alloy is a palladium-gold alloy. The palladium-gold alloy has stronger hydrogen adsorption performance and chemical stability.

[0013] Furthermore, the hydrogen adsorbent is disposed in a layered form on the inner surface of the battery cell. Specifically, the hydrogen adsorbent can be coated on the inner surface of the battery cell to form a coating, and the coating has a large specific surface area, so that when the coating located in this area reaches a preset temperature, the hydrogen adsorbent releases the hydrogen stored therein.

[0014] Furthermore, the battery cell includes an end cap, on which a pressure relief valve and a hydrogen sensor are arranged. Hydrogen generated in the battery cell is discharged through the pressure relief valve, and the hydrogen sensor is arranged on the end cap to directly detect the hydrogen discharged through the pressure relief valve.

[0015] Furthermore, the hydrogen adsorbent is arranged in a layered form on the inner surface of the end cap of the battery cell. Hydrogen has a low density and thus moves toward the end cap at the top of the battery cell. The hydrogen adsorbent is arranged in a layered form on the inner surface of the end cap of the battery cell to fully absorb hydrogen. The hydrogen sensor is located on the end cap. When hydrogen is released, it can quickly leave the interior of the battery cell through the pressure relief valve and be detected by the hydrogen sensor on the end cap.

[0016] Furthermore, the detection limit of the hydrogen sensor is 20-400ppm. If a hydrogen sensor with a detection limit that is too low is used, it is difficult to avoid being affected by the environmental background; if a hydrogen sensor with a detection limit that is too high is used, the hydrogen concentration that reaches the hydrogen sensor through the accumulation amplification of the hydrogen storage may still not reach the detection limit.

[0017] A second aspect of the present invention provides a battery management system, comprising a battery module, a thermal runaway detection module and a battery management module. The thermal runaway detection module executes the detection method as described above. The thermal runaway detection module detects thermal runaway information of the battery module and transmits it to the battery management module.

[0018] The thermal runaway detection module of the battery management system of the present invention implements a method for detecting abnormal states of vehicle batteries. A hydrogen adsorbent is arranged inside the battery cells of the battery module. In the early stage of thermal runaway of the battery, the hydrogen adsorbent adsorbs and accumulates the hydrogen generated at this time. When the temperature is further increased to be higher than the preset temperature, the hydrogen adsorbent releases the stored hydrogen, causing the hydrogen concentration inside the battery cell to increase suddenly, thereby causing the hydrogen to diffuse to the outside of the battery cell and be detected by the hydrogen sensor. The thermal runaway detection module will detect the early thermal runaway information and transmit it to the battery management module. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 FIG. 4 is a schematic diagram of the structure of a battery management system according to an embodiment of the present invention.

[0020] Figure 2 The figure is a flow chart of a method for detecting abnormal state of a vehicle battery according to an embodiment. DETAILED DESCRIPTION

[0021] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are given in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0022] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. In the description of the present application, the meaning of "several" is at least one, such as one, two, etc., unless otherwise clearly and specifically defined.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present application belongs. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0024] In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0025] In this application, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are deemed to be continuous and include the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0026] like Figure 1 As shown, the present invention provides a battery management system in one embodiment, including a battery module 100, a thermal runaway detection module 200 and a battery management module 300. The thermal runaway detection module 200 transmits thermal runaway information of the battery module 100 to the battery management module 300. The thermal runaway detection module 200 can perform a method for detecting abnormal states of vehicle batteries. Specifically, by setting a hydrogen adsorbent inside the battery cell of the battery module 100, in the early stage of thermal runaway of the battery, the hydrogen adsorbent adsorbs the hydrogen generated at this time and accumulates it; when the temperature is further increased to be higher than the preset temperature, the hydrogen adsorbent releases the stored hydrogen, so that the hydrogen concentration inside the battery cell suddenly increases, so that the hydrogen diffuses to the outside of the battery cell and is detected by the hydrogen sensor. When the battery management module 300 receives the thermal runaway information output by the thermal runaway detection module 200, it can adjust the battery module 100, including disconnecting the charging circuit of the battery module 100 and starting the physical cooling device to cool the battery module 100, because the thermal runaway detection module 200 can timely determine whether the battery is in the early stage of thermal runaway, so the above measures can be used to prevent the rapid development of thermal runaway of the battery module 100. In this application, the battery can also be called a battery pack, and the battery cell can also be called a battery cell.

[0027] like Figure 2 As shown, in one embodiment, the present invention provides a method for detecting an abnormal state of a vehicle battery, comprising:

[0028] S1. During the assembly process of the vehicle battery, a palladium-gold alloy coating is provided on the inner surface of the end cover of the battery cell and a hydrogen sensor is provided on the outer surface of the end cover, and the vehicle battery is assembled into a battery module and installed in an electric vehicle for operation;

[0029] S2. During the operation of the vehicle battery, the concentration of hydrogen in the gas overflowing from the pressure relief valve is detected by a hydrogen sensor.

[0030] In this embodiment, a palladium-gold alloy (the mass ratio of gold to palladium in the palladium-gold alloy is 1:20) coating is used as a hydrogen adsorbent. Palladium metal or other conventional palladium alloy materials can also be used to prepare the coating. The palladium-gold alloy is fixed to the inner surface of the battery end cap by an inert organic binder. The inner surface of the battery end cap refers to the surface of the end cap facing the winding core, and the outer surface of the end cap refers to the surface of the end cap facing away from the winding core. The palladium-gold alloy used in this embodiment can adsorb a large amount of hydrogen at a preset temperature of 40°C, and its adsorption performance for hydrogen is greatly reduced when the temperature reaches the preset temperature of 40°C, so that it can release the adsorbed hydrogen, so that the hydrogen concentration inside the battery cell suddenly increases, so that the hydrogen diffuses to the outside of the battery cell and is detected by the hydrogen sensor. By accumulating the hydrogen generated in the early stage, the early thermal runaway of the battery can be detected more timely. The palladium-gold alloy coating of this embodiment can be applied to the existing battery structure and can detect the small amount of hydrogen generated in the battery cell in the early stage of thermal runaway without modification or adding complex circuits. In other embodiments, palladium-gold alloy materials with different gold contents or other palladium alloy materials can be used according to different preset temperature requirements. The preset temperature is preferably between 40 and 50°C, and can be any value of, but not limited to, 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C, and 50°C; if the preset temperature is too low, hydrogen will be released during normal operation of the battery, even at room temperature, causing misjudgment; if the preset temperature is too high, such as 80°C, hydrogen release may occur in the middle and late stages of thermal runaway of the battery, thereby failing to detect early thermal runaway of the battery.

[0031] In this embodiment, a palladium-gold alloy coating is arranged on the inner surface of the battery end cap. On the one hand, the flow law of hydrogen is taken into account, and the adsorption efficiency of hydrogen can be improved; on the other hand, when the palladium-gold alloy coating releases hydrogen at 40°C or above, the released hydrogen can quickly flow out from the pressure relief valve on the end cap, reducing the loss of hydrogen diffusion inside the battery. In this embodiment, the hydrogen sensor is arranged on the outer surface of the end cap, further shortening the path of the hydrogen flowing out of the pressure relief valve to reach the hydrogen sensor, so that the concentration of hydrogen in the gas overflowing from the pressure relief valve can be more accurately detected. In addition, since the palladium-gold alloy has good chemical stability and corrosion resistance, it will not interfere with the normal operation of the battery, nor will it be corroded by the electrolyte. Therefore, when it is not suitable to arrange the palladium-gold alloy on the battery end cap, the palladium-gold alloy coating can also be arranged at other positions on the inner surface of the battery cell. Specifically, in this embodiment, the vehicle battery is a 18650 lithium iron phosphate battery, and other cylindrical batteries or square batteries can also be used. The positive electrode material of the battery is not limited to lithium iron phosphate, and lithium nickel cobalt manganese oxide, lithium-rich manganese base, lithium iron manganese phosphate, lithium manganese oxide, etc. can also be used. Specifically, the detection limit of the hydrogen sensor is 20-400ppm. If a hydrogen sensor with a detection limit that is too low is used, it is difficult to avoid being affected by the environmental background; if a hydrogen sensor with a detection limit that is too high is used, the hydrogen concentration that reaches the hydrogen sensor through the cumulative amplification of the hydrogen storage device may still not reach the detection limit. In this embodiment, the battery management system is subjected to an overcharge experiment. When the charging voltage reaches 3.6V, the negative electrode of the electrode is close to saturation, and the hydrogen sensor does not detect the change in hydrogen concentration at this time. With the increase of the charging voltage, the temperature of the battery surface is 30°C, which is within the normal temperature range of the battery. However, the hydrogen sensor detects that the hydrogen concentration increases rapidly and then decreases to undetected. At this time, it can be judged that the battery has experienced early thermal runaway. The battery is continuously charged. At this time, the temperature of the battery surface reaches 40°C, and the hydrogen sensor detects that the hydrogen concentration changes and continues to increase again. At this time, the thermal runaway of the battery has reached the middle and late stages. Therefore, it can be explained that the battery management system of this embodiment can more quickly judge that the battery has entered the early stage of thermal runaway. When the hydrogen adsorbent releases hydrogen, the hydrogen concentration range detected by the hydrogen sensor is between 300-2000 ppm, so the hydrogen sensor in this embodiment is preferably a palladium alloy hydrogen sensor, and its detection range is 200 ppm-10%.

[0032] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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.

[0033] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for detecting abnormal state of a vehicle battery, characterized in that: include: A hydrogen adsorbent is arranged inside a battery cell of a vehicle battery, wherein the hydrogen adsorbent absorbs hydrogen when the temperature is lower than a preset temperature and releases hydrogen when the temperature is higher than a preset temperature, wherein the battery cell comprises an end cap, wherein a pressure relief valve and a hydrogen sensor are arranged on the end cap, and the hydrogen adsorbent is arranged in a layered form on the inner surface of the end cap of the battery cell; During the operation of the vehicle battery, the concentration of hydrogen in the gas leaking out of the pressure relief valve of the vehicle battery is detected by a hydrogen sensor.

2. The method for detecting abnormal state of a vehicle battery according to claim 1, characterized in that: The preset temperature is 40-50°C.

3. The method for detecting abnormal state of a vehicle battery according to claim 1, characterized in that: The hydrogen adsorbent includes a metal and / or an alloy capable of adsorbing hydrogen.

4. The method for detecting abnormal state of a vehicle battery according to claim 1, characterized in that: The hydrogen adsorbent comprises palladium and / or a palladium alloy.

5. The method for detecting abnormal state of a vehicle battery according to claim 4, characterized in that: The palladium alloy is a palladium-gold alloy.

6. The method for detecting abnormal state of a vehicle battery according to claim 1, characterized in that: The lower detection limit of the hydrogen sensor is 20-400 ppm.

7. A battery management system, characterized in that: It comprises a battery module, a thermal runaway detection module and a battery management module, wherein the thermal runaway detection module executes the detection method according to any one of claims 1 to 6, and the thermal runaway detection module detects thermal runaway information of the battery module and transmits it to the battery management module.

Images