Secondary batteries with improved safety

Abstract

The disclosed invention relates to a secondary battery, and in one example, includes a venting device that opens when the pressure inside the case exceeds a first set value, the venting device includes a rupture disk having a rupture portion that ruptures at the first set value, and a heat absorbing porous member is provided on at least one of the upstream and downstream sides of the rupture disk.

Description

[Technical Field]

[0001] The present invention relates to a secondary battery, and more particularly to a secondary battery that can delay or suppress structural collapse of the secondary battery even when thermal runaway occurs in the secondary battery.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0092176, filed on July 26, 2022, and all contents disclosed in the documents of said Korean patent application are incorporated herein by reference. [Background technology]

[0003] Unlike primary batteries, secondary batteries are rechargeable and have been the subject of much research and development in recent years due to their potential for miniaturization and large capacity. Demand for secondary batteries as an energy source is rapidly increasing due to the increasing technological development and demand for mobile devices, as well as the emergence of electric vehicles and energy storage systems in response to modern demands for environmental protection.

[0004] Secondary batteries are classified into coin-type batteries, cylindrical batteries, prismatic batteries, and pouch-type batteries depending on the shape of the battery case. The electrode assembly installed inside the battery case of a secondary battery is a power generating element that can be charged and discharged and is made up of a laminated structure of electrodes and a separator.

[0005] Since secondary batteries are required to be used continuously for long periods of time, it is necessary to effectively control the heat generated during the charging and discharging process.If secondary batteries are not cooled smoothly, a positive feedback chain reaction will occur in which a rise in temperature causes an increase in current, and the increase in current causes another rise in temperature, ultimately leading to a catastrophic state of thermal runaway.

[0006] When thermal runaway occurs in a secondary battery, the temperature and pressure rise together, and if the temperature and pressure rise to a level that exceeds the secondary battery's heat and pressure resistance, the secondary battery's structure will collapse as a result. When the structure collapses, a large amount of air is supplied inside the secondary battery, causing a fire or explosion that grows uncontrollably and spreads to the surrounding area, resulting in an accident that causes great damage.

[0007] To prevent such structural collapse of secondary batteries, secondary batteries, especially cylindrical and prismatic batteries, are often equipped with a venting device, which acts as a kind of safety valve that breaks to release pressure when the pressure inside the secondary battery exceeds a certain level.

[0008] However, current venting devices do not have the function of preventing flame propagation even when they release gas and relieve pressure. For example, there is a risk of flames erupting along with strong gases through the venting device, leading to an external fire. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Korean Patent Publication No. 2017-0014309 (Published February 8, 2017) Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention aims to improve the safety of secondary batteries by enabling a venting device to not only release pressure inside the secondary battery by discharging gas but also prevent flame discharge.

[0011] However, the technical problems that the present invention aims to solve are not limited to the above-mentioned problems, and other problems not mentioned will be clearly understood by those skilled in the art from the description of the invention described below. [Means for solving the problem]

[0012] The present invention relates to a secondary battery, and in one example, the secondary battery includes a venting device that opens when the pressure inside the case exceeds a first set value, and the venting device includes a rupture disk having a rupture portion that ruptures at the first set value, and a heat-absorbing porous member is provided at least either upstream or downstream of the rupture disk.

[0013] In one embodiment of the present invention, the heat absorbing porous member is located outside the rupture area of ​​the rupture part.

[0014] The heat-absorbing porous member may be a member made of a plurality of layers of pleated metal ribbon wound into a ring shape, or may be a member made of a metal mesh net.

[0015] The heat absorbing porous member is located downstream of the rupture disk, and can be released to the outside of the venting device when a pressure of a second set value exceeding the first set value acts on the heat absorbing porous member for a predetermined time.

[0016] For example, the heat absorbing porous member can be detached from the venting device when an internal pressure of 3 atmospheres or more is maintained for 1 second or more.

[0017] According to an embodiment, a rupture protrusion protruding from the inner surface of the venting device may be provided on the downstream side of the heat absorbing porous member, and the rupture protrusion may rupture when the pressure of the second set value acts for a predetermined period of time.

[0018] Here, the heat absorbing porous member may be made of a heat-resistant stainless steel material.

[0019] According to another embodiment of the present invention, the heat absorbing porous member is located downstream of the rupture disk, and when the temperature of the venting gas rises above the boundary temperature and acts for a predetermined time, it can be melted and removed from the venting device.

[0020] For example, the heat absorbing porous member may be melted and removed from the venting device when the temperature of the venting gas rises to 500° C. or more and acts for 5 seconds or more.

[0021] Here, the heat absorbing porous member may be made of an aluminum material or an aluminum alloy material.

[0022] The aluminum material may include at least one of 1060 and 1100 aluminum.

[0023] The aluminum alloy material may include at least one of aluminum alloys such as 2011, 2014, 2017, 2024, 3003, 4032, 5052, 5056, 5083, 6061, 6N01, 6063, 7003, 7075, and 7N01. [Effects of the Invention]

[0024] In the secondary battery of the present invention having the above-described configuration, when the pressure inside the case rises excessively to the extent that it exceeds the first set value, the rupture disk of the venting device opens to discharge gas, thereby preventing the secondary battery from collapsing. In addition, the heat-absorbing porous member absorbs the heat from the high-temperature gas and flame, lowering the temperature to below the ignition point, thereby providing a dual safety function of preventing the risk of fire.

[0025] In addition, in the secondary battery of the present invention, in a dangerous situation where a large amount of particles accumulate in the heat absorbing porous member, preventing gas discharge and causing an excessive rise in internal pressure, the heat absorbing porous member is configured to detach from the venting device, thereby preventing rapid flame spread due to structural collapse of the secondary battery, and thereby further improving the safety of the secondary battery.

[0026] However, the technical effects that can be obtained by the present invention are not limited to the effects described above, and other effects not mentioned can be clearly understood by those skilled in the art from the description of the invention described below.

[0027] The following drawings attached to this specification illustrate preferred embodiments of the present invention and, together with the detailed description of the invention described below, serve to further understand the technical concept of the present invention, and therefore the present invention should not be interpreted as being limited solely to the matters depicted in such drawings. [Brief explanation of the drawings]

[0028] [Figure 1] 1 is a diagram illustrating a secondary battery according to the present invention. [Figure 2] 1 is a cross-sectional view of a venting device for a secondary battery according to an embodiment of the present invention. [Figure 3] 1 is a diagram illustrating an example of a heat absorbing porous member; [Figure 4] 1 is a diagram illustrating an example of a heat absorbing porous member; [Figure 5] 3 is a diagram illustrating the operation of the venting device of FIG. 2. [Figure 6] 3 is a view illustrating another embodiment of the venting device of FIG. 2. [Figure 7] 10 illustrates an embodiment in which a heat absorbing porous member separates from a venting device when overpressure is applied. [Figure 8] 10 illustrates an embodiment in which the heat absorbing porous member is removed from the venting device when subjected to excessive temperatures. DETAILED DESCRIPTION OF THE INVENTION

[0029] Because the present invention can be modified in various ways and can have various embodiments, specific embodiments will be described in detail below.

[0030] However, this is not intended to limit the invention to any particular embodiment, but is understood to include all modifications, equivalents, or alternatives falling within the spirit and scope of the invention.

[0031] In the present invention, the terms "comprise" and "have" are intended to specify the presence of features, numbers, steps, operations, components, parts or combinations thereof described in the specification, and are understood as not precluding the presence or possible addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

[0032] Furthermore, in the present invention, when a layer, film, region, plate, or other portion is described as being "on" another portion, this includes not only the case where it is "directly on" the other portion, but also the case where there is another portion therebetween. Conversely, when a layer, film, region, plate, or other portion is described as being "under" the other portion, this includes not only the case where it is "directly under" the other portion, but also the case where there is another portion therebetween. Furthermore, in this application, being "located on" can include not only the case where it is located at the top, but also the case where it is located at the bottom.

[0033] The present invention relates to a secondary battery, and in one example, the secondary battery includes a venting device that opens when the pressure inside the case exceeds a first set value, and the venting device includes a rupture disk having a rupture portion that ruptures at the first set value, and a heat-absorbing porous member is provided at least either upstream or downstream of the rupture disk.

[0034] As described above, the secondary battery of the present invention is provided with a venting device, and the venting device is also provided with a heat-absorbing porous member. Thus, when the pressure inside the case rises excessively to a level exceeding a first set value, the rupture disk of the venting device opens to discharge gas, thereby preventing structural collapse of the secondary battery, and the heat-absorbing porous member absorbs heat from the high-temperature gas flame and lowers the temperature to a level below the ignition point, thereby preventing the risk of fire.

[0035] Hereinafter, specific embodiments of the secondary battery according to the present invention will be described in detail with reference to the accompanying drawings. For reference, directions such as front-back, up-down, left-right, and right-left used in the following description are intended to facilitate understanding of the invention, and unless otherwise specified, directions shown in the drawings are used as the basis.

[0036] (First embodiment) Figure 1 is a diagram illustrating a secondary battery 10 according to the present invention. The diagram exemplarily illustrated in Figure 1 is a bidirectional secondary battery 10 in which positive and negative electrode terminals 110 are separately disposed on both sides of a case 100, and a venting device 200 is located on the top surface of the case 100. The bidirectional secondary battery 10 of Figure 1 is just one example, and the main configuration of the present invention can be applied to various secondary batteries, including unidirectional secondary batteries.

[0037] The secondary battery 10 of the present invention includes a venting device 200, which is a safety means that releases pressure when the pressure inside the secondary battery 10 exceeds a specific level, i.e., when the pressure inside the case 100 exceeds a first set value, thereby relieving the pressure that has built up inside. Figure 2 is a cross-sectional view of the venting device 200 of the secondary battery 10 according to the first embodiment of the present invention, and the venting device 200 includes a rupture disk 210.

[0038] The rupture disk 210 is a thin plate-like member, and has a notched rupture portion 212 formed on its surface. The rupture disk 210 seals the secondary battery 10, but when the internal pressure of the case 100 increases, the pressure causes tensile deformation throughout the thin rupture disk 210, causing the weak rupture portion 212 to break and release the internal pressure of the case 100.

[0039] The venting device 200 is useful for releasing gas to relieve excessive internal pressure that affects the structural safety of the secondary battery 10, but if a fire breaks out inside the secondary battery 10, the flame may erupt along with the strong gas, posing a risk of an external fire. In order to prevent flames from erupting through the venting device 200, the present invention provides a heat-absorbing porous member 220 inside the venting device 200 at least either upstream or downstream of the rupture disk 210.

[0040] The heat absorbing porous member 220 is a metal structure having a large number of small holes, and in the present invention, the heat absorbing porous member 220 performs filtering and flame quenching functions.

[0041] When the rupture disk 210 ruptures due to an internal pressure increase caused by thermal runaway in the venting device 200, high-temperature gas and particles are ejected. The filtering function of the heat absorbing porous member 220 acts on high-temperature particles, filtering out high-temperature particles with large diameters. In particular, high-temperature particles exceeding a certain size can act as an ignition source for an external fire, so filtering by the heat absorbing porous member 220 can effectively eliminate the cause of external ignition.

[0042] In addition, the heat-absorbing porous member 220 absorbs heat generated from the burning gas mixture and dissipates it to the surrounding area, thereby lowering the combustion temperature of the surrounding gas so that it does not rise to its spontaneous ignition temperature. This is because the high-temperature gas absorbs heat from the porous structure of the metal material as it passes through the heat-absorbing porous member 220. Therefore, a flame generated by thermal runaway in the secondary battery 10 absorbs so much heat as it passes through the heat-absorbing porous member 220 in the venting device 200 that the flame can no longer be sustained. This prevents heat propagation, which spreads the thermal runaway phenomenon to other surrounding secondary batteries, and prevents external fires.

[0043] 3 and 4 are diagrams illustrating examples of a heat absorbing porous member 220. The heat absorbing porous member 220 of FIG. 3 is a member in which a corrugated metal ribbon is wound into a ring shape to form multiple layers, and the corrugated metal ribbon forms multiple voids. The heat absorbing porous member 220 of FIG. 4 is a member made of a metal mesh net, i.e., a member made of a metal net with a sieve pattern that forms multiple small holes. Here, it can be said that it is preferable for the metal mesh net to have a complex porous structure formed by stacking multiple thin nets.

[0044] 5 is a diagram illustrating the operation of the venting device 200 equipped with the heat absorbing porous member 220. When the internal pressure of the secondary battery 10 increases, tensile deformation occurs throughout the rupture disk 210, causing the weak rupture portion 212 to rupture and release venting gas to the outside. This relieves the excessive internal pressure in the case 100.

[0045] And, the heat absorption porous member 220 is arranged downstream of the broken rupture disk 210. Here, the heat absorption porous member 220 is located outside the rupture range of the rupture portion 212, so that it does not hinder the operation of the rupture disk 210.

[0046] The numerous holes formed in the heat absorbing porous member 220 along the venting channel perform filtering and flame quenching functions. The filtering function of the heat absorbing porous member 220 filters out large high-temperature particles that could act as an ignition source for an external fire, and also performs a flame quenching function by absorbing the heat generated from the gas mixture and dissipating it to the surrounding area, thereby lowering the temperature below the combustion point and preventing the outbreak of flames.

[0047] Figure 6 is a drawing showing another embodiment of the venting device 200 of Figure 2, and the venting device 200 of Figure 2 is arranged downstream of the rupture disk 210, and the venting device 200 of Figure 2 is arranged downstream of the heat absorbing porous member 220. On the other hand, the venting device 200 of Figure 6 is arranged upstream of the rupture disk 210, and the heat absorbing porous member 220 is arranged upstream and downstream of the rupture disk 210, although not shown in the drawing. Alternatively, the heat absorbing porous member 220 can be arranged upstream and downstream of the rupture disk 210, respectively. In other words, as long as it does not adversely affect the operation of the rupture disk 210, the position and number of the heat absorbing porous member 220 can be freely designed.

[0048] Meanwhile, the heat-absorbing porous member 220 may be made of a heat-resistant stainless steel material that can withstand high-temperature flames. In one example, the heat-resistant stainless steel may be a ferritic stainless steel alloy such as X10CrAlSi7, X10CrAl13, X10CrAl18, or X18CrN28, an austenitic stainless steel alloy such as X15CrNiSi20-12, X15CrNiSi25-20, X15CrNiSi25-21, or X12CrNiTi18-10, or a nickel-chromium stainless steel alloy such as NiCr15Fe, NiCr23Fe, NiCr22Mo9Nb, NiCr21Mo, or NiCr28FeSiCe.

[0049] However, if a large amount of particles accumulate in the heat absorbing porous member 220 due to the filtering function of the heat absorbing porous member 220, the venting device 200 may be clogged, hindering or blocking the external discharge of the venting gas. If the venting device 200 is clogged and loses its original function, the internal pressure of the secondary battery 10 may rise again, which may cause the structure of the secondary battery 10 to collapse.

[0050] FIG. 7 illustrates an embodiment for preventing clogging of the venting device 200 by the heat absorbing porous member 220. The venting device 200 of FIG. 7 prevents the worst case scenario of the secondary battery 10 collapsing due to the heat absorbing porous member 220 being separated from the venting device 200 when excessive pressure is applied.

[0051] In the embodiment of Fig. 7, the heat absorption porous member 220 is located downstream of the rupture disk 210, so that the heat absorption porous member 220 can be separated from the venting device 200 without being obstructed.Then, the outer surface of the rupture disk 210 is provided with a breaking protrusion 240, which breaks when the pressure of the second set value that exceeds the first set value that the rupture disk 210 bursts acts for a predetermined time.

[0052] The breaking protrusion 240 located downstream of the heat absorbing porous member 220 maintains its shape while pressure less than the second set value is applied, thereby supporting the heat absorbing porous member 220 so that it does not fall out of the venting device 200 due to the gas pressure.

[0053] However, when a pressure equal to or greater than the second set value is applied to the heat absorbing porous member 220, the fracture notch 242 formed at the base of the fracture protrusion 240 gradually deforms, and when the time during which the pressure equal to or greater than the second set value is applied reaches a predetermined time, the fracture protrusion 240 completely deforms or fractures, thereby losing its support for the heat absorbing porous member 220. As a result, the heat absorbing porous member 220 is pushed out of the venting device 200 by the gas pressure.

[0054] Here, when pressure equal to or greater than the second set value acts on the heat absorbing porous member 220, this includes cases where a large amount of particles accumulate in the heat absorbing porous member 220, significantly reducing breathability and causing the internal pressure to rise, as well as cases where thermal runaway progresses rapidly and the internal pressure increases so much that it reaches the second set value.

[0055] In this way, when the internal pressure of the secondary battery 10 rises to the extent that it reaches the second set value, priority must be given to preventing the rapid spread of flames due to structural collapse of the secondary battery 10, rather than maintaining the filtering and flame-extinguishing functions of the heat absorbing porous member 220. For this reason, the embodiment of Fig. 7 is configured to promote the flow of venting gas by removing the heat absorbing porous member 220 from the venting device 200 when the pressure of the second set value acts for a predetermined time.

[0056] The conditions for the heat absorbing porous member 220 to detach from the venting device 200 are set by the design of the fracture protrusion 240, for example, the strength of the fracture notch 242, and it is preferable to set it so that the heat absorbing porous member 220 will detach when an internal pressure of 3 atmospheres or more is maintained for 1 second or more.

[0057] (Second embodiment) The embodiment shown in FIG. 7 includes a configuration for removing the heat absorbing porous member 220, which acts as a flow obstacle, from the venting device 200 in response to an excessive increase in the internal pressure of the secondary battery 10.

[0058] On the other hand, the second embodiment of the present invention includes a configuration in which the heat absorption porous member 220 is removed from the venting device 200 in response to the temperature inside the secondary battery 10. That is, from the aspect of removing the heat absorption porous member 220, the first embodiment can be said to be a pressure-responsive type, and the second embodiment can be said to be a temperature-responsive type.

[0059] 8 illustrates a second embodiment in which the heat absorbing porous member 220 is removed from the venting device 200 when an excessive temperature occurs. Similar to the first embodiment, the heat absorbing porous member 220 is located downstream of the rupture disk 210, but the heat absorbing porous member 220 in the second embodiment is fixed in position by a conventional support protrusion 230 that does not have a breaking structure such as a breaking notch 242. Instead, the heat absorbing porous member 220 is made of a different material.

[0060] The heat absorbing porous member 220 in the second embodiment is made of a metal material that melts at least a portion of itself when the temperature of the venting gas rises above the boundary temperature and acts for a predetermined time, causing it to be removed from the venting device 200. In other words, in the second embodiment, the heat absorbing porous member 220 itself melts and deforms due to the abnormally high temperature of the venting gas, causing it to lose its supporting force. As a result, the heat absorbing porous member 220 is pushed out of the venting device 200 by the pressure of the venting gas.

[0061] In a preferred embodiment, the heat absorbing porous member 220 may melt and be removed from the venting device 200 when the temperature of the venting gas rises to 500°C or higher for 5 seconds or more. Correspondingly, the heat absorbing porous member 220 of the second embodiment may be made of a single metal or alloy having a melting point in the range of approximately 470 to 660°C.

[0062] Considering various conditions such as a melting point of around 500°C, high thermal conductivity for fast response to temperature, and workability that is advantageous for forming a porous structure, it can be said that the heat absorbing porous member 220 is preferably made of aluminum or an aluminum alloy material.

[0063] For example, aluminum materials meeting these conditions may include 1060 and / or 1100 aluminum.

[0064] The aluminum alloy material that is not pure aluminum may include at least one of aluminum alloys 2011, 2014, 2017, 2024, 3003, 4032, 5052, 5056, 5083, 6061, 6N01, 6063, 7003, 7075, and 7N01.

[0065] Here, the pressure-responsive first embodiment and the temperature-responsive second embodiment can be implemented independently of each other, but they can also be combined as compatible embodiments. That is, by combining the configuration of the fracture protrusion 240 included in the first embodiment with the heat-absorbing porous member 220 with a specific melting point of the second embodiment, it is possible to configure it to respond to both excessive pressure and temperature caused by thermal runaway, which will be obvious to those skilled in the art from the contents disclosed in this specification.

[0066] The present invention has been described in more detail above with reference to the drawings and embodiments, etc. However, the configurations shown in the drawings or embodiments in this specification are merely one embodiment of the present invention and do not represent all of the technical ideas of the present invention, and therefore, at the time of filing this application, there may be various equivalents and modifications that can replace them. [Explanation of symbols]

[0067] 10: Secondary battery 100:Case 110: Electrode terminal 200: Venting equipment 210: Rupture Disc 212:Rupture part 220: Heat absorbing porous member 230: Support protrusion 240: Fracture protrusion 242:Fracture notch

Claims

1. A secondary battery including a venting device that opens when the pressure inside the case exceeds a first set value, The venting device is A rupture disk having a rupture portion formed therein that ruptures at the first set value, A heat absorbing porous member is provided downstream of the rupture disk; The heat absorbing porous member is The secondary battery is released to the outside of the venting device when a pressure of a second set value exceeding the first set value acts on the secondary battery for a predetermined period of time.

2. A secondary battery including a venting device that opens when the pressure inside the case exceeds a first set value, The venting device is A rupture disk having a rupture portion formed therein that ruptures at the first set value, A heat absorbing porous member is provided downstream of the rupture disk; The heat absorbing porous member is A secondary battery in which the temperature of the venting gas rises above a threshold temperature and acts for a predetermined time, the secondary battery melts and is removed from the venting device.

3. The heat absorbing porous member is The secondary battery according to claim 1 or 2, wherein the rupture part is located outside the rupture range.

4. The heat absorbing porous member is 3. The secondary battery according to claim 1, wherein the pleated metal ribbon is wound into a ring shape to form a plurality of layers.

5. The heat absorbing porous member is 3. The secondary battery according to claim 1, wherein the member is made of a metal mesh.

6. The heat absorbing porous member is The secondary battery according to claim 1 , which is detached from the venting device when an internal pressure of 3 atmospheres or more is maintained for 1 second or more.

7. a breaking protrusion formed on the downstream side of the heat absorbing porous member and protruding from the inner surface of the venting device; The secondary battery according to claim 1 , wherein the rupture protrusion ruptures when the pressure of the second set value acts on the rupture protrusion for a predetermined period of time.

8. The secondary battery according to claim 1 , wherein the heat absorbing porous member is made of a heat-resistant stainless steel material.

9. The heat absorbing porous member is 3. The secondary battery according to claim 2, wherein the venting gas melts and is removed from the venting device when the temperature of the venting gas rises to 500[deg.] C. or higher and acts for 5 seconds or more.

10. 10. The secondary battery according to claim 9, wherein the heat absorbing porous member is made of an aluminum material or an aluminum alloy material.

11. The secondary battery according to claim 10 , wherein the aluminum material includes at least one of 1060 and 1100 aluminum.

12. 11. The secondary battery according to claim 10, wherein the aluminum alloy material includes at least one of aluminum alloys 2011, 2014, 2017, 2024, 3003, 4032, 5052, 5056, 5083, 6061, 6N01, 6063, 7003, 7075, and 7N01.

Images