Battery Active Pressure Relief Explosion-Proof Valve and Control Method Based on Sensor Linkage

Abstract

The present invention relates to the technical field of battery safety, and discloses a battery active pressure relief explosion-proof valve and a control method based on sensor linkage. The explosion-proof valve includes: a pressure relief film located between the battery cases and inside the battery cover plate, with a notch provided on the surface of the pressure relief film; a pressure sensor module disposed on the pressure relief film to monitor the internal pressure of the battery in real time; a braking 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 the pressure threshold, the braking module energizes the pressure relief film, thereby reducing the strength of the pressure relief film and accelerating the fracture of the notch area. The control method adjusts the pressure threshold in real time in combination with the battery usage situation and the battery health state. The present invention can reduce the pressure relief threshold and cost, shorten the response time, and meet the safety requirements of different batteries at different aging stages.

Description

Technical Field

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

[0002] In the prior art, the explosion-proof valves of batteries such as lithium batteries and sodium batteries mainly adopt metal indentation structures (such as aluminum foil indentation) or polymer films. Although these structures can achieve pressure relief, there are still some defects. On the one hand, the triggering pressure of the existing structures 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. The traditional indentation structure relies on mechanical fracture, the rupture time is long, and the response time is generally greater than 1 s, which cannot cope with the rapid pressure surge during thermal runaway. In addition to the deficiency in pressure relief effect, the structures of these existing active pressure relief schemes are also relatively complex, costly, difficult to miniaturize and integrate, and cannot be applied to various batteries. Summary of the Invention

[0003] Therefore, 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 meet the safety requirements of different batteries at different aging stages.

[0004] To solve the above technical problems, the present invention provides a battery active pressure relief explosion-proof valve based on sensor linkage, comprising:

[0005] A pressure relief film, located between the battery cases and inside the battery cover plate, and the surface of the pressure relief film is provided with indentations;

[0006] A pressure sensor module, arranged on the pressure relief film to monitor the internal pressure of the battery in real time;

[0007] A braking module, arranged at the indentations and connected to the pressure sensor module;

[0008] When the internal pressure of the battery monitored by the pressure sensor module reaches the pressure threshold, the braking module energizes the pressure relief film, thereby reducing the strength of the pressure relief film and accelerating the fracture of the indented area.

[0009] Further, the indentations cover the pressure relief film, and the braking module and the indentations are located on both sides of the pressure relief film.

[0010] Further, the pressure relief film is an organic film, the braking module is an electric heating wire, and the electric heating wire is embedded in the pressure relief film along the trajectory of the notch; the thickness of the organic film is 100μm - 300μm, and the base material of the organic film is polyimide or polyether ether ketone.

[0011] Further, the composition of the organic film includes a conductive additive, and the conductive additive is 1wt.% - 3wt.% of carbon nanotubes or graphene microflakes, or 0.1wt.% - 1wt.% of alloy particles.

[0012] Further, the particle size of the alloy particles is less than 5μm, and the melting point of the alloy particles is 80°C - 150°C.

[0013] Further, 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 braking module is a piezoelectric ceramic.

[0014] Further, the braking module includes a plurality of piezoelectric ceramic sheets, and the piezoelectric ceramic sheets are equidistantly distributed along the notch or are arranged at the thinnest part of the pressure relief film.

[0015] The present invention also provides a control method for a battery active pressure relief explosion-proof valve based on sensor linkage, including: when using the battery active pressure relief explosion-proof valve based on sensor linkage, adjusting the pressure threshold in real time in combination with the battery usage situation and the battery health status.

[0016] Further, the adjusting the pressure threshold in real time in combination with the battery usage situation and the battery health status is specifically:

[0017] Set the initial pressure threshold of the battery, and adjust the pressure threshold in real time in combination with the initial pressure threshold of the battery, the used time, the number of battery cycles, and the battery health status.

[0018] Further, when adjusting the pressure threshold in real time in combination with the initial pressure threshold of the battery, the used time, the number of battery cycles, and the battery health status, the calculation method of the pressure threshold adjusted in real time is:

[0019] P set = P set0 ×(1 + k t × t + k N × N cycle - k S ×(1 - SOH)),

[0020] Wherein, P set is the pressure threshold value for real-time adjustment, P set0 is the initial pressure threshold value of the battery, t is the service life of the battery in years, N cycle is the number of charge-discharge cycles of the battery, and SOH is the state of health of the battery. k t and k N and k S are the weight coefficients.

[0021] The above technical solution of the present invention has the following beneficial effects compared with the prior art:

[0022] By monitoring the internal pressure of the battery through the pressure sensor module, the present invention can reduce the error of the pressure relief trigger pressure, effectively avoid the battery entering the critical state of thermal runaway, reduce the irreversible damage inside the battery through active pressure relief, and extend the service life of the battery. By adjusting the pressure threshold value in real time, it can adapt to the safety requirements of different batteries in different aging stages, reduce the dependence on the mechanical structure accuracy, and effectively reduce the cost. Through the linkage of the pressure sensor module and the braking module, a millisecond-level response can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to make the content of the present invention easier to be clearly understood, the present invention will be further described in detail below according to the specific embodiments of the present invention and in conjunction with the drawings.

[0024] Figure 1 is a schematic structural diagram of the active pressure relief explosion-proof valve of the battery based on sensor linkage in the preferred embodiment of the present invention.

[0025] Figure 2 is a top view of the active pressure relief explosion-proof valve of the battery based on sensor linkage in the preferred embodiment of the present invention.

[0026] Figure 3 is a schematic diagram of different notch shapes on the active pressure relief explosion-proof valve of the battery based on sensor linkage in the preferred embodiment of the present invention.

[0027] Figure 4 is a partial sectional view of the notch on the active pressure relief explosion-proof valve of the battery based on sensor linkage in the preferred embodiment of the present invention.

[0028] Figure 5 is a flowchart of the control method of the active pressure relief explosion-proof valve of the battery based on sensor linkage in the preferred embodiment of the present invention.

[0029] 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

[0030] 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

[0031] 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.

[0032] 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.

[0033] 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.

[0034] In this embodiment, the pressure relief film 1 can be an organic film or a metal film. The organic film can be a polyimide (PI) film, a polyether ether ketone (PEEK) film, etc., and the metal film can be a nickel-based alloy foil, a stainless steel film, etc. As Figure 4 shown, the braking module 4 and the notch 3 are located on both sides of the pressure relief film 1. The braking module 4 is a micro electrothermal wire or a piezoelectric ceramic material.

[0035] When the pressure relief film 1 is an organic film, it is generally used in combination with the thermal braking of the micro electrothermal 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 100 μm to 300 μm, and the composition of the organic film is modified by adding a conductive additive. The specific composition of the organic film is: the base material is polyimide or polyether ether ketone, and the conductive additive is 1 wt.% to 3 wt.% of carbon nanotubes (CNTs) or graphene microflakes, or 0.1 wt.% to 1 wt.% of low melting point alloy particles. The carbon nanotubes or graphene microflakes are evenly distributed to form a conductive network, and the Joule heat effect is significant when energized; the particle size of the low melting point alloy (such as Bi-based alloy, Sn-based alloy) particles is <5 μm, and the melting point is 80°C to 150°C. After energization, the material is melted and weakened. When energized, the local temperature of the pressure relief film 1 can rise above 150°C within 5 ms, and the strength of the notch 3 area decreases by 50% to 70%. The pressure relief film 1 maintains high mechanical strength (tensile strength > 100 MPa) under normal conditions.

[0036] When the pressure relief film 1 is an organic film, the electrothermal wire is embedded in the pressure relief film 1 along the trajectory 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 electrothermal wire is a nickel-chromium electrothermal wire with a diameter of 50 μm to 100 μm, and the resistance value is designed to be 10 Ω to 20 Ω. The notch 3 is heated by the Joule effect. The heating temperature of the electrothermal wire during operation is 80°C to 120°C, and the duration is 50 ms to 200 ms. The internal pressure of the battery is monitored by a MEMS pressure sensor. When the pressure value is greater than the set value, the electrothermal 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 testing with the high-safety sodium ion battery in this embodiment, the pressure relief film 1 ruptures at 0.17 MPa, and the response time is less than 200 ms.

[0037] When the pressure relief film 1 is a metal film, it is generally used in combination with the mechanical braking of the piezoelectric ceramic. By optimizing the layout of the notch 3, the braking 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. In this embodiment, Figure 2Taking the annular notch 3 in [the relevant context] as an example, the depth of the notch 3 is set to be 40 μm to 55 μm. The braking module 4 includes 6 PZT-5H piezoelectric ceramic sheets 41, which are evenly distributed circumferentially along the notch 3. Each sheet has a size of 5×5×2 mm³. The piezoelectric ceramic sheets 41 are bonded to the edge of the metal film through conductive silver paste, and the electrode leads are integrated into the drive circuit. After the piezoelectric ceramic sheets 41 are energized, they generate radial tensile forces, which act uniformly around the notch 3, increasing the circumferential stress concentration factor by 2 to 3 times and accelerating the crack propagation.

[0038] In addition to being evenly distributed along the notch 3, the piezoelectric ceramic sheets 41 can also be arranged at the thinnest part of the pressure relief film 1. In this embodiment, on the 316L stainless steel pressure relief film 1 with a thickness of 100 μm, the piezoelectric ceramic sheets 41 are mounted on the back of the notch 3. The internal pressure of the battery is monitored by the MEMS pressure sensor. When the pressure value is greater than the set value, a pulsed voltage of 50V to 100V is applied to the piezoelectric ceramic sheets 41 to generate local shear stress, and the piezoelectric ceramic sheets 41 generate a pressure of 1MPa to 10 MPa during operation. When testing the high-safety sodium-ion battery in this embodiment, the pressure relief film 1 ruptures at 0.16MPa, and the mechanical energy conversion efficiency is increased by 15% compared with that when using the heating wire. Embodiment 2

[0039] As Figure 5 shown, a control method for the battery active pressure relief and explosion-proof valve based on sensor linkage. When using the battery active pressure relief and explosion-proof valve based on sensor linkage in Embodiment 1, the pressure threshold is adjusted in real time in combination with the battery usage situation and the battery health state.

[0040] 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.

[0041] 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.

[0042] 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:

[0043] P set = P set0 ×(1+ k t × t + k N × N cycle - k S ×(1-SOH)),

[0044] in, P set For real-time adjustment of the pressure threshold, P set0 is the initial pressure threshold, t The battery life isN cycle Let \(N\) be the number of charge-discharge cycles of the battery, and SOH be the state of health of the battery. SOH is measured by the Battery Management System (BMS), and the value of SOH ranges from 0 to 1, where 1 represents a brand-new battery and 0 represents a scrapped battery. k t 、 k N 、 k S Let \(k_1\), \(k_2\), and \(k_3\) be the weight coefficients calibrated through experiments. When using the same high-safety sodium-ion battery as in Embodiment 1 in this embodiment, k t \(k_1 = 0.1\), k N \(k_2 = 0.000024\), k S = \(k_3 = 0.8\). The service life has a positive impact on the pressure threshold, so the pressure setting compensation intensity needs to be increased due to material aging; the number of cycles also has a positive impact on the pressure threshold, so partial compensation is required for electrode structure deterioration; the decrease in SOH has a negative impact on the pressure threshold, and the gas generation increases due to capacity attenuation, so the pressure setting needs to be reduced.

[0045] The present invention can be applied to scenarios 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, completely avoiding the stage of a large amount of gas accumulation caused by the reaction between the positive and negative electrodes and the electrolyte, resulting in a sharp rise in the internal pressure of the battery. The high-safety battery only needs to release the electrolyte vaporized due to high temperature when the valve is opened. However, the pressure relief pressure of the pressure relief structure of the conventional battery is too high to be applicable to this high-safety battery. To ensure safety in use, the battery active pressure relief explosion-proof valve based on sensor linkage in this embodiment is applied to this high-safety battery. The measured pressure relief pressure of the explosion-proof valve is 0.12 MPa to 0.4 MPa, which effectively reduces compared with the existing 0.5 MPa to 2 MPa. Thus, active linkage of pressure detection and pressure relief is achieved, with a fast response speed and no false triggering at high temperatures.

[0046] The advantages of the present invention compared with the prior art are:

[0047] 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. Instead of simply relying on the internal pressure to damage the area where the notch 3 is located, the control accuracy depends on the accuracy of the pressure monitored by the MEMS pressure sensor. In this embodiment, the accuracy of the MEMS pressure sensor is 0.005 MPa. Combining with the deviation of the subsequent power-on steps, the pressure relief trigger pressure error can be controlled within ±0.02 MPa.

[0048] 2. The pressure error of the battery in 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.

[0049] 3. Active pressure relief reduces the irreversible damage inside the battery, increasing the cycle life of the battery by 10 - 15%.

[0050] 4. The MEMS pressure sensor and the micro electrothermal wire are directly integrated on the film surface, with a total thickness of less than 0.5 mm. It can be compatible with the existing battery packaging process, without high-precision machining. The component cost is at least 60% lower than the existing solutions such as solenoid valves.

[0051] 5. Through the linkage between the MEMS pressure sensor and the 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 the accuracy of the mechanical structure and effectively reduce the cost.

[0052] 6. The linkage between the MEMS pressure sensor and the braking module 4 can achieve a millisecond-level response, significantly improving the safety compared with traditional mechanical valves (response time > 1 second).

[0053] To further illustrate the beneficial effects of the present invention, experiments are first conducted on organic films with different thicknesses and different conductive additives. The corresponding pressure relief pressures and response times are shown in Table 1.

[0054] Table 1 Comparison table of test results of pressure relief pressures and response times corresponding to different organic films

[0055]

[0056] As can be seen from Table 1, when using the component formula of the organic film in this embodiment, the pressure relief pressure can be effectively reduced and the response time can be shortened.

[0057] Next, select a kind of aluminum-plastic film scoring pressure relief valve in the prior art (for the specific structure, see the explosion-proof valve in paragraphs

[0075] to

[0079] of the specific implementation manner of patent publication number CN108428836A) as a comparative example for comparative tests. This comparative example tests the pressure relief pressure through a helium gas pressure valve and records the response time (the time difference between when the pressure value reaches the threshold and the instant when pressure relief occurs) through a high-speed camera. Take the battery active pressure relief explosion-proof valve based on sensor linkage using the organic film and the heating wire in Example 1 and simultaneously using the method in Example 2 as Scheme 1, and take the battery active pressure relief explosion-proof valve based on sensor linkage using the metal film and the piezoelectric ceramic sheet 41 in Example 1 and simultaneously using the method in Example 2 as Scheme 2. Set Scheme 1, Scheme 2, and the comparative example on a high-safety sodium ion battery for testing, and the test results of the pressure relief pressure and the response time are shown in Table 2.

[0058] Table 2 Comparison table of test results of Scheme 1, Scheme 2, and the comparative example

[0059]

[0060] It can also be seen from Table 2 that the present invention can effectively reduce the pressure relief pressure and shorten the response time.

[0061] Obviously, the above embodiments are merely examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or variations can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or variations derived therefrom are still within the protection scope of the present invention.

Claims

1. An active pressure relief explosion-proof valve for a battery based on sensor linkage, characterized in that, Comprising: A pressure relief film, located between battery cases and inside the battery cover plate, with indentations provided on the surface of the pressure relief film; A pressure sensor module, disposed on the pressure relief film to monitor the internal pressure of the battery in real time; A braking module, disposed at the indentations and connected to the pressure sensor module; When the internal pressure of the battery monitored by the pressure sensor module reaches the pressure threshold, the braking module energizes the pressure relief film, thereby reducing the strength of the pressure relief film and accelerating the fracture of the indented area; Set the initial pressure threshold of the battery, and adjust the pressure threshold in real time in combination with the initial pressure threshold of the battery, the used 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)), Among them, P set is the pressure threshold adjusted in real time, P set0 is the initial pressure threshold of the battery, t is the number of years the battery has been used, N cycle is the number of cycles the battery has undergone, SOH is the battery health state, k t , k N , k S are weighting coefficients.

2. The battery active pressure relief explosion-proof valve based on sensor linkage according to claim 1, wherein: The indentations cover the pressure relief film, and the braking module and the indentations 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, characterized in that: The pressure relief film is an organic film, the braking module is an electrothermal wire, and the electrothermal wire is embedded in the pressure relief film along the trajectory of the indentation; the thickness of the organic film is 100μm - 300μm, and the substrate of the organic film is polyimide or polyether ether ketone.

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

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

6. The battery active pressure relief explosion-proof valve based on sensor linkage according to claim 1, wherein: 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 braking module is a piezoelectric ceramic.

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

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