Battery active pressure relief explosion-proof valve based on sensor linkage and control method

Abstract

The invention relates to the technical field of battery safety, and discloses a battery active pressure relief explosion-proof valve based on sensor linkage and a control method, and the explosion-proof valve comprises a pressure relief film which is located between battery shells and on the inner side of a battery cover plate, and the surface of the pressure relief film is provided with nicks; the pressure sensor module is arranged on the pressure relief film and is used for monitoring the internal pressure of the battery in real time; the brake module is arranged at the nick and is connected with the pressure sensor module; when the pressure sensor module monitors that the internal pressure of the battery reaches a pressure threshold value, the braking module electrifies the pressure relief film, so that the strength of the pressure relief film is reduced, and breakage of the nick area is accelerated. According to the control method, the pressure threshold is adjusted in real time in combination with the battery use condition and the battery health state. The method can reduce the pressure relief threshold and cost, shortens the response time, and meets the safety requirements of different aging stages of different batteries.

Description

Technical Field

[0001] The present invention relates to the field of battery safety technology, and in particular to a battery active pressure relief explosion-proof valve based on sensor linkage and a control method. Background Art

[0002] In the prior art, explosion-proof valves for lithium batteries, sodium batteries and other batteries mainly use metal notch structures (such as aluminum foil notches) or polymer films. Although these structures can achieve pressure relief, they also have some defects. On the one hand, the trigger pressure of the existing structure is too high, and the pressure relief threshold is usually between 0.5 MPa and 2 MPa, which is difficult to meet the requirements of solid-state batteries, flexible batteries and new batteries for ultra-low pressure relief (usually less than 0.2 MPa); on the other hand, the response speed is slow, and the traditional notch structure relies on mechanical fracture, which has a long rupture time and a response time generally greater than 1s, and cannot cope with the rapid pressure surge at the moment of thermal runaway. In addition to the shortcomings in the pressure relief effect, the structure of these existing active pressure relief solutions is also relatively complex and costly, making them difficult to miniaturize and integrate, and cannot be applied to various batteries. Summary of the invention

[0003] To this end, the technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide a battery active pressure relief explosion-proof valve and control method based on sensor linkage, which can reduce the pressure relief threshold and cost, shorten the response time, and adapt to the safety requirements of different batteries at different aging stages.

[0004] In order to solve the above technical problems, the present invention provides a battery active pressure relief explosion-proof valve based on sensor linkage, comprising: A pressure relief film is located between the battery shells and inside the battery cover, and the surface of the pressure relief film is provided with notches; A pressure sensor module is arranged on the pressure relief film to monitor the internal pressure of the battery in real time; a brake module, disposed at the notch and connected to the pressure sensor module; When the internal pressure of the battery monitored by the pressure sensor module reaches a pressure threshold, the brake module supplies power to the pressure relief film, thereby reducing the strength of the pressure relief film and accelerating the fracture of the notched area.

[0005] Furthermore, the notch covers the pressure relief film, and the brake module and the notch are located on both sides of the pressure relief film.

[0006] Furthermore, the pressure relief film is an organic film, the brake module is a heating wire, and the heating wire is embedded in the pressure relief film along the track of the notch; the thickness of the organic film is 100μm~300μm, and the substrate of the organic film is polyimide or polyetheretherketone.

[0007] Furthermore, the composition of the organic film includes a conductive additive, and the conductive additive is 1wt.% to 3wt.% of carbon nanotubes or graphene microsheets, or 0.1wt.% to 1wt.% of alloy particles.

[0008] Furthermore, the particle size of the alloy particles is less than 5 μm, and the melting point of the alloy particles is 80° C. to 150° C.

[0009] Furthermore, the pressure relief film is a metal film, the metal film is a nickel-based alloy foil or a stainless steel film, and the material of the brake module is piezoelectric ceramics.

[0010] Furthermore, the braking module comprises a plurality of piezoelectric ceramic sheets, and the piezoelectric ceramic sheets are evenly distributed along the notches, or are arranged at the thinnest part of the pressure relief film.

[0011] The present invention also provides a battery active pressure relief explosion-proof valve control method based on sensor linkage, comprising: when using the battery active pressure relief explosion-proof valve based on sensor linkage, adjusting the pressure threshold in real time in combination with battery usage and battery health status.

[0012] Furthermore, the pressure threshold is adjusted in real time in combination with the battery usage and battery health status, specifically: Set the initial pressure threshold of the battery, and adjust the pressure threshold in real time based on the initial pressure threshold of the battery, usage time, number of battery cycles, and battery health status.

[0013] Furthermore, when the pressure threshold is adjusted in real time in combination with the initial pressure threshold of the battery, the usage time, the number of battery cycles, and the battery health status, the calculation method of the pressure threshold adjusted in real time is: P set = P set0 ×(1+ k t × t + k N × N cycle - k S ×(1-SOH)), in, P set For real-time adjustment of the pressure threshold, P set0 is the initial pressure threshold of the battery, t The battery life is N cycle is the number of cycles the battery has undergone, SOH is the battery health status,k t , k N , k S is the weight coefficient.

[0014] The above technical solution of the present invention has the following beneficial effects compared with the prior art: The present invention monitors the internal pressure of the battery through the pressure sensor module, which can reduce the error of the pressure release triggering pressure and effectively prevent the battery from entering a critical state of thermal runaway. Active pressure release can reduce irreversible damage inside the battery and extend the battery life. By adjusting the pressure threshold in real time, the safety requirements of different batteries at different aging stages can be met, the dependence on the accuracy of the mechanical structure can be reduced, and the cost can be effectively reduced. The linkage between the pressure sensor module and the brake module can achieve a millisecond response. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to make the contents of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings.

[0016] Figure 1 It is a structural schematic diagram of a battery active pressure relief and explosion-proof valve based on sensor linkage in a preferred embodiment of the present invention.

[0017] Figure 2 It is a top view of a battery active pressure relief explosion-proof valve based on sensor linkage in a preferred embodiment of the present invention.

[0018] Figure 3 Schematic diagram of different notch shapes on a battery active pressure relief and explosion-proof valve based on sensor linkage in a preferred embodiment of the present invention.

[0019] Figure 4 It is a partial cross-sectional view of the notch on the battery active pressure relief and explosion-proof valve based on sensor linkage in the preferred embodiment of the present invention.

[0020] Figure 5 The flowchart of the battery active pressure relief and explosion-proof valve control method based on sensor linkage in the preferred embodiment of the present invention.

[0021] Explanation of the reference numerals in the specification: 1. pressure relief film; 2. battery shell; 3. notch; 4. brake module; 41. piezoelectric ceramic sheet; 5. pressure sensor module. DETAILED DESCRIPTION

[0022] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention. Embodiment 1

[0023] Reference Figure 1 The battery active pressure relief explosion-proof valve based on sensor linkage shown in the figure includes: a pressure relief film 1, which is located between the battery shell 2 and the inner side of the battery cover, and the surface of the pressure relief film 1 is provided with a notch 3; the notch 3 can be engraved by laser, and the notch 3 is arranged toward the outside of the battery to prevent the electrolyte vapor inside the battery from corroding the notch 3. A pressure sensor module 5 is arranged on the pressure relief film 1 to monitor the internal pressure of the battery in real time; a brake module 4 is arranged at the notch 3 and connected to the pressure sensor module 5. When the internal pressure of the battery monitored by the pressure sensor module 5 reaches the pressure threshold, the brake module 4 energizes the pressure relief film 1, generates local mechanical stress through the inverse piezoelectric effect to reduce the local strength of the pressure relief film 1, and accelerates the fracture of the notch 3 area. The brake module 4 and the pressure sensor module 5 are connected through a control circuit, and the brake module 4 is activated when the internal pressure of the battery monitored by the pressure sensor module 5 is greater than the pressure threshold, and the brake module 4 energizes the pressure relief film 1 to reduce the local strength of the pressure relief film 1. After the strength of the pressure relief film 1 is weakened, the actual rupture pressure is reduced, and early pressure relief is achieved. After the pressure is released, the control circuit turns off the brake module 4 to avoid secondary risks caused by continuous heating.

[0024] The score 3 extends over the pressure relief film 1. The shape of the score 3 can be as follows: Figure 2 The ring shown can also be Figure 3 Middle (a), Figure 3 The straight line shown in (b) can also be Figure 3 The notch 3 may be in different shapes such as the arc shape shown in (c), and the notch 3 may cover the entire surface area of ​​the pressure relief film 1. In this embodiment, a high-safety sodium ion battery is selected as the test object. Under the size of the high-safety sodium ion battery, the length of the notch 3 is designed to be 5 mm to 50 mm.

[0025] In this embodiment, the pressure sensor module 5 is a micro-electro-mechanical system (MEMS) integrated with a pressure sensor. The pressure sensor module 5 has a measuring range of 0 MPa to 0.2 MPa and an accuracy of ±0.005 MPa.

[0026] In this embodiment, the pressure relief film 1 may be an organic film or a metal film. The organic film may be a polyimide (PI) film, a polyetheretherketone (PEEK) film, etc., and the metal film may be a nickel-based alloy foil, a stainless steel film, etc. Figure 4 As shown, the braking module 4 and the notch 3 are located on both sides of the pressure relief film 1, and the braking module 4 is a micro heating wire or is made of piezoelectric ceramics.

[0027] When the pressure relief film 1 is an organic film, it is generally used in conjunction with the thermal braking of the micro-heating wire. In this embodiment, in order to improve the response speed of the pressure relief module, the thickness of the organic film is set to 100μm~300μm, and the composition of the organic film is modified, and a conductive additive is added to the composition. The composition of the organic film is specifically as follows: the substrate is polyimide or polyetheretherketone, and the conductive additive is 1wt.%~3wt.% of carbon nanotubes (CNT) or graphene microsheets, or 0.1wt.%~1wt.% of low-melting-point alloy particles. The carbon nanotubes or graphene microsheets are evenly distributed to form a conductive network, and the Joule heat effect is significant when power is turned on; the particle size of the low-melting-point alloy (such as Bi-based alloy, Sn-based alloy) particles is <5μm, the melting point is 80°C~150°C, and the material is melted and weakened after power is turned on. When power is turned on, the local temperature of the pressure relief film 1 can rise to above 150°C within 5 ms, and the strength of the notch 3 area decreases by 50%~70%. The pressure relief film 1 maintains high mechanical strength (tensile strength>100 MPa) under normal conditions.

[0028] When the pressure relief film 1 is an organic film, the heating wire is embedded in the pressure relief film 1 along the track of the notch 3. In this embodiment, an annular notch 3 is laser-etched on the pressure relief film 1 with a thickness of 200 μm, and the depth of the notch 3 is 60% of the thickness of the pressure relief film 1. The embedded heating wire is a nickel-chromium heating wire with a diameter of 50 μm to 100 μm, and the resistance value is designed to be 10Ω to 20 Ω. The notch 3 is heated by the Joule effect. The heating temperature of the heating wire is 80℃ to 120℃ and the duration is 50 ms to 200 ms. The internal pressure of the battery is monitored by the MEMS pressure sensor. When the pressure value is greater than the set value, the heating wire is started to heat, which can reduce the strength of the pressure relief film 1 by 30% to 50%. When the material of the pressure relief film 1 is polyimide, the specific tensile strength can be reduced from 200 MPa to 100 MPa. When the high-safety sodium ion battery in this embodiment is tested, the pressure relief film 1 ruptures at 0.17 MPa, and the response time is less than 200 ms.

[0029] When the pressure relief film 1 is a metal film, it is generally used in conjunction with a mechanical brake of a piezoelectric ceramic. By optimizing and improving the layout of the notches 3, the brake module 4, and the pressure sensor module 5 on the pressure relief film 1, the response speed of the pressure relief film 1 is improved. Figure 2 Taking the annular notch 3 in the example, the depth of notch 3 is set to 40μm ~55μm, and the brake module 4 includes 6 PZT-5H piezoelectric ceramic sheets 41, which are evenly distributed along the circumference of notch 3, and each sheet has a size of 5×5×2 mm³. The piezoelectric ceramic sheet 41 is bonded to the edge of the metal film by conductive silver glue, and the electrode lead is integrated into the drive circuit. When the piezoelectric ceramic sheet 41 is energized, radial tension is generated, which acts evenly around the notch 3, increasing the circumferential stress concentration factor by 2~3 times and accelerating crack propagation.

[0030] In addition to being evenly distributed along the notch 3, the piezoelectric ceramic sheet 41 can also be set at the thinnest part of the pressure relief film 1. In this embodiment, on the pressure relief film 1 of 316L stainless steel with a thickness of 100μm, the piezoelectric ceramic sheet 41 is mounted on the back of the notch 3. The internal pressure of the battery is monitored by a MEMS pressure sensor. When the pressure value is greater than the set value, a pulse voltage of 50V~100V is applied to the piezoelectric ceramic sheet 41 to generate local shear stress. The piezoelectric ceramic sheet 41 generates a pressure of 1MPa~10MPa when working. When the high-safety sodium ion battery in this embodiment is tested, the pressure relief film 1 breaks at 0.16MPa, and the mechanical energy conversion efficiency is increased by 15% compared with that when using a heating wire. Embodiment 2

[0031] like Figure 5 As shown, a battery active pressure relief explosion-proof valve control method based on sensor linkage is used. When the battery active pressure relief explosion-proof valve based on sensor linkage in Example 1 is used, the pressure threshold is adjusted in real time in combination with the battery usage and battery health status.

[0032] The internal pressure of the battery changes differently at different SOH stages. At the beginning of life (BOL), the electrode structure of the new battery is stable, the electrolyte decomposition and gas production are less, and the pressure relief pressure is only for thermal runaway caused by thermal abuse or mechanical abuse. During thermal runaway, the pressure rises slowly and the peak is low. At this time, setting a certain pressure relief pressure threshold (such as 0.15 MPa) can reduce false triggering. As the battery runs, the electrochemical system is no longer stable, such as the electrolyte decomposition intensifies, the active material pulverizes, and the gas production increases; and the thermal runaway reaction is more intense, and the internal pressure may reach a dangerous value faster. At this time, a lower pressure setting is required to avoid danger. At the same time, the increase in the number of cycles will cause the physical structure of the battery to age. For example, the internal resistance of the electrode material increases due to the volume effect, resulting in internal heat accumulation, which may also increase the internal pressure. However, based on the characteristics of the membrane itself, as the service life increases, the aging of the membrane material may reduce its mechanical strength, making it easier to rupture under the same pressure. At this time, the pressure relief pressure of the membrane needs to be increased. If the initial pressure relief pressure of 0.15 MPa is still used, pressure relief may occur during normal battery operation. Therefore, the pressure relief pressure threshold is not constant during the entire life cycle of the battery. The pressure relief pressure threshold needs to be adjusted (increased) according to the actual operating conditions to avoid unnecessary battery failure.

[0033] Therefore, in this embodiment, the pressure threshold is adjusted in real time in combination with the battery usage and battery health status. Specifically, the initial pressure threshold of the battery is set, and the pressure threshold is adjusted in real time in combination with the initial pressure threshold of the battery, usage time, number of battery cycles, and battery health status throughout the battery life cycle.

[0034] In this embodiment, when the pressure threshold is adjusted in real time in combination with the initial pressure threshold of the battery, the usage time, the number of battery cycles, and the battery health status, the calculation method of the pressure threshold adjusted in real time is: P set = P set0 ×(1+ k t × t + k N × N cycle - k S ×(1-SOH)), in, P set For real-time adjustment of the pressure threshold, P set0 is the initial pressure threshold, t The battery life is N cycle SOH is the battery health status, which is determined by the battery management system (BMS). The SOH value ranges from 0 to 1, where 1 means the battery is brand new and 0 means the battery is scrapped. k t , k N , k S The weight coefficient is calibrated by experiment. When the same high-safety sodium ion battery as in Example 1 is used in this embodiment, k t =0.1, k N =0.000024, k S = 0.8. The service life has a positive effect on the pressure threshold, so the material aging needs to increase the pressure setting compensation strength; the number of cycles also has a positive effect on the pressure threshold, so the electrode structure degradation needs to be partially compensated; the reduction of SOH has a negative effect on the pressure threshold, and the capacity attenuation leads to increased gas production, so the pressure setting needs to be reduced.

[0035] The present invention can be applied to scenes such as cylindrical and square sodium batteries. When selecting a high-safety sodium ion battery, the thermal stability of the positive and negative active materials of the battery is greater than 900°C, and there is no side reaction of CEI and SEI between the electrolyte and the positive and negative active materials, which completely avoids the stage where a large amount of gas is generated due to the reaction between the positive and negative electrodes and the electrolyte, causing the internal pressure of the battery to rise sharply. The high-safety battery valve only needs to release the electrolyte that is gasified due to high temperature. However, the pressure relief pressure of the pressure relief structure of the conventional battery is too large to be applied to the high-safety battery. In order to ensure safety in use, the battery active pressure relief explosion-proof valve based on sensor linkage in this embodiment is applied to the high-safety battery. The test measured that the pressure relief pressure of the explosion-proof valve is 0.12 MPa ~ 0.4 MPa, which is effectively reduced compared to the existing 0.5 MPa ~ 2 MPa. Thereby, the active linkage of pressure detection and pressure relief is realized, the response speed is fast, and it will not be triggered by mistake at high temperature.

[0036] Compared with the prior art, the present invention has the following advantages: 1. The internal pressure of the battery is monitored by a MEMS pressure sensor. When the pressure value is greater than the set value, the pressure relief process is started. The area where the notch 3 is located is not simply destroyed by the internal pressure. The control accuracy depends on the accuracy of the MEMS pressure sensor monitoring the pressure. In this embodiment, the accuracy of the MEMS pressure sensor is 0.005 MPa. Combined with the deviation of the subsequent power-on step, the pressure relief trigger pressure error can be controlled within ±0.02 MPa.

[0037] 2. The pressure error when the battery enters the critical state of thermal runaway is usually greater than 0.2 MPa. Therefore, the present invention can effectively prevent the battery from entering the critical state of thermal runaway.

[0038] 3. Active pressure relief reduces irreversible damage inside the battery and increases the battery’s cycle life by 10-15%.

[0039] 4. The MEMS pressure sensor and the micro-heating wire are directly integrated on the surface of the film, with a total thickness of less than 0.5 mm. It is compatible with the existing battery packaging process and does not require high-precision machining. The component cost is at least 60% lower than that of existing solenoid valves and other solutions.

[0040] 5. Through the linkage between MEMS pressure sensor and BMS, the pressure threshold can be adjusted in real time to meet the safety requirements of different batteries at different aging stages. At the same time, it can reduce the dependence on mechanical structure accuracy and effectively reduce costs.

[0041] 6. The linkage between the MEMS pressure sensor and the brake module 4 can achieve millisecond-level response, which significantly improves safety compared to traditional mechanical valves (response time > 1 second).

[0042] In order to further illustrate the beneficial effects of the present invention, firstly, organic films with different thicknesses and different conductive additives are tested, and the corresponding pressure relief pressure and response time results are shown in Table 1.

[0043] Table 1 Comparison of the test results of pressure relief pressure and response time corresponding to different organic films

[0044]

[0045] It can be seen from Table 1 that when the composition formula of the organic film in this embodiment is used, the pressure relief pressure can be effectively reduced and the response time can be shortened.

[0046] Next, an aluminum-plastic film notched pressure relief valve in the prior art (for the specific structure, see the explosion-proof valve in paragraphs

[0075] to

[0079] of the specific embodiment of patent publication number CN108428836A) is selected as a comparative example for comparative testing. The comparative example tests the pressure relief pressure through a helium pressurization valve, and records the response time (the time difference between the pressure value reaching the threshold and the moment of pressure relief) through a high-speed camera. The sensor-linked active pressure relief explosion-proof valve for batteries using the organic film and heating wire in Example 1 and the method in Example 2 are used as Scheme 1, and the sensor-linked active pressure relief explosion-proof valve for batteries using the metal film and piezoelectric ceramic sheet 41 in Example 1 and the method in Example 2 are used as Scheme 2. Scheme 1, Scheme 2 and the comparative example are all set on a high-safety sodium ion battery for testing, and the measured pressure relief pressure and response time results are shown in Table 2.

[0047] Table 2 Comparison of experimental results of Scheme 1, Scheme 2 and Comparative Example

[0048]

[0049] It can also be seen from Table 2 that the present invention can effectively reduce the pressure relief pressure and shorten the response time.

[0050] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A battery active pressure relief explosion-proof valve based on sensor linkage, characterized in that: include: A pressure relief film is located between the battery shells and inside the battery cover, and the surface of the pressure relief film is provided with notches; A pressure sensor module is arranged on the pressure relief film to monitor the internal pressure of the battery in real time; a brake module, disposed at the notch and connected to the pressure sensor module; When the internal pressure of the battery monitored by the pressure sensor module reaches a pressure threshold, the brake module supplies power to the pressure relief film, thereby reducing the strength of the pressure relief film and accelerating the fracture of the notched area.

2. The battery active pressure relief explosion-proof valve based on sensor linkage according to claim 1 is characterized in that: The notch covers the pressure relief film, and the brake module and the notch are located on both sides of the pressure relief film.

3. The battery active pressure relief explosion-proof valve based on sensor linkage according to claim 1 is characterized in that: The pressure relief film is an organic film, the brake module is a heating wire, and the heating wire is embedded in the pressure relief film along the track of the notch; the thickness of the organic film is 100μm~300μm, and the substrate of the organic film is polyimide or polyetheretherketone.

4. The battery active pressure relief explosion-proof valve based on sensor linkage according to claim 3 is characterized in that: The organic film comprises a conductive additive, wherein the conductive additive is 1 wt.% to 3 wt.% of carbon nanotubes or graphene microsheets, or 0.1 wt.% to 1 wt.% of alloy particles.

5. The battery active pressure relief explosion-proof valve based on sensor linkage according to claim 4 is characterized in that: The particle size of the alloy particles is less than 5 μm, and the melting point of the alloy particles is 80° C. to 150° C.

6. The battery active pressure relief explosion-proof valve based on sensor linkage according to claim 1 is characterized in that: The pressure relief film is a metal film, the metal film is a nickel-based alloy foil or a stainless steel film, and the material of the brake module is piezoelectric ceramics.

7. The battery active pressure relief explosion-proof valve based on sensor linkage according to claim 6 is characterized in that: The braking module includes a plurality of piezoelectric ceramic sheets, and the piezoelectric ceramic sheets are distributed equidistantly along the notches, or are arranged at the thinnest part of the pressure relief film.

8. A battery active pressure relief explosion-proof valve control method based on sensor linkage, characterized in that: When using the battery active pressure relief explosion-proof valve based on sensor linkage as described in any one of claims 1 to 7, the pressure threshold is adjusted in real time in combination with the battery usage and battery health status.

9. The battery active pressure relief explosion-proof valve control method based on sensor linkage according to claim 8 is characterized in that: The real-time adjustment of the pressure threshold value in combination with the battery usage and the battery health status is specifically as follows: Set the initial pressure threshold of the battery, and adjust the pressure threshold in real time based on the initial pressure threshold of the battery, usage time, number of battery cycles, and battery health status.

10. The battery active pressure relief explosion-proof valve control method based on sensor linkage according to claim 9 is characterized in that: When the pressure threshold is adjusted in real time in combination with the initial pressure threshold of the battery, the usage time, the number of battery cycles, and the battery health status, the calculation method of the pressure threshold adjusted in real time is: P set = P set0 ×(1+ k t × t + k N × N cycle - k S ×(1-SOH)), in, P set For real-time adjustment of the pressure threshold, P set0 is the initial pressure threshold of the battery, t The battery life is N cycle is the number of cycles the battery has undergone, SOH is the battery health status, k t , k N , k S is the weight coefficient.

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