Battery pack and electric device

Abstract

The battery pack and the electric device are provided by the present disclosure, and relate to the technical field of batteries. The battery pack comprises a box body, the box body comprising a bottom plate and a surrounding frame connected to the bottom plate to form a containing cavity; a pressure relief valve arranged on the box body and communicated with the containing cavity; and a battery module accommodated in the containing cavity, the battery module comprising a plurality of arrayed batteries. The maximum exhaust capacity of a single pressure relief valve is Q1, the number of the pressure relief valves is n, and the peak gas production rate of a single battery is Qe, and the following conditions are met: n*Q1>Qe, and 0.1<= (n*Q1-Qe) / (n*Q1)<=0.7. According to the present disclosure, when any battery produces gas due to thermal runaway, the total exhaust capacity of the pressure relief valves is always greater than the peak gas production rate of a single battery. Thus, timely pressure relief of the box body pressure relief valve is achieved, and the high-temperature and high-pressure gas generated in the battery pack can be discharged in time, thereby preventing larger-scale thermal runaway.

Description

Technical Field

[0001] This disclosure relates to the field of battery technology, and in particular to a battery pack and an electrical device. Background Technology

[0002] When the explosion-proof valve of a single cell inside the battery pack opens, the high-temperature gas emitted by that cell accumulates inside the pack. A pressure relief valve on the casing allows for timely pressure release from inside the battery pack to the outside, expelling the high-temperature gas and reducing internal pressure. This prevents the risk of fire or explosion from adjacent cells or internal electrical connections. However, during use, the pressure relief valve may not open in time, causing the explosion-proof valve to open and emit flames, potentially leading to thermal runaway of the battery pack and other safety risks. Summary of the Invention

[0003] The purpose of this disclosure is to provide a battery pack that solves the technical problems in the prior art, enabling timely pressure relief by the pressure relief valve on the housing.

[0004] This disclosure provides a battery pack, including: The box body includes a bottom plate and a surrounding frame, the surrounding frame being connected to the bottom plate to enclose and form a receiving cavity; A pressure relief valve is installed on the frame of the housing and is connected to the receiving cavity. The pressure relief valve is used to open when the internal pressure of the battery pack reaches a certain level. A battery module is housed within the receiving cavity, the battery module comprising a plurality of batteries arranged in an array; Wherein, the maximum exhaust volume of a single pressure relief valve is Q1, in L / s, the number of pressure relief valves is n, and the peak gas production rate of a single battery is Qe, in L / s, satisfying: n×Q1>Qe, and 0.1≤(n×Q1-Qe) / (n×Q1)≤0.7.

[0005] Compared with existing technologies, this disclosure sets the maximum venting capacity of a single pressure relief valve to Q1, the number of pressure relief valves to n, and the peak gas generation rate of a single battery to Qe, ensuring that n × Q1 > Qe. This ensures that when any battery experiences thermal runaway and gas generation, the total venting capacity of the pressure relief valves is always greater than the peak gas generation rate of a single battery. This achieves timely pressure relief from the housing pressure relief valves, guaranteeing that the high-temperature, high-pressure gas generated inside the battery pack can be discharged promptly, preventing larger-scale thermal runaway.

[0006] Furthermore, by selecting the value of the formula (n×Q1-Qe) / (n×Q1) within a reasonable range of 0.1 to 0.7, the reliability of the battery pack's thermal runaway protection can be further improved. This ensures that when the battery experiences thermal runaway and releases high-temperature and high-pressure gas, the pressure relief valve has sufficient and abundant venting capacity. Multiple pressure relief valves can promptly and continuously release the gas before it accumulates to a dangerous level, reducing the possibility of thermal runaway spreading to adjacent batteries or other components, and improving the overall safety and stability of the battery pack. Attached Figure Description

[0007] Figure 1 This is a perspective view of a battery pack provided in an embodiment of this disclosure.

[0008] Figure 2 yes Figure 1 A perspective view of the battery pack provided in the Chinese embodiment from another direction.

[0009] Figure 3 yes Figure 1 A perspective view of the battery pack with the battery module hidden in the embodiment provided in the Chinese version.

[0010] Figure 4 yes Figure 1 A perspective view of the first frame of the battery pack provided in the Chinese embodiment.

[0011] Figure 5 yes Figure 4 A side view of the first border provided in the embodiment.

[0012] Figure 6 yes Figure 1 A perspective view of the battery pack pressure relief valve provided in the Chinese embodiment, which is located on the frame in one direction.

[0013] Figure 7 yes Figure 1 A perspective view of the battery pack pressure relief valve provided in the embodiment, located on the frame from another direction.

[0014] Figure 8 yes Figure 1 A perspective view of the pressure relief valve of the battery pack provided in the embodiment.

[0015] Figure 9 yes Figure 8 A perspective view of the pressure relief valve in the open state provided in the embodiment.

[0016] Figure 10 yes Figure 1 A perspective view of the battery pack and individual batteries assembled in the embodiment provided in the Chinese version.

[0017] Figure 11 yes Figure 1A partial cross-sectional view of the battery, first plate, and second plate of the battery pack provided in the Chinese embodiment, in their mating state.

[0018] Figure 12 yes Figure 1 A perspective view of a single cell in the battery pack provided in the embodiment.

[0019] Figure 13 yes Figure 12 A perspective view of the battery provided in the Chinese embodiment from another direction.

[0020] Explanation of reference numerals in the attached figures: 10. Box body; 11. Base plate; 111. First plate; 112. Second plate; 12. Frame; 121. First side frame; 122. Second side frame; 123. Cavity; 1231. First sub-cavity; 1232. Second sub-cavity; 124. First connecting hole; 125. Partition plate; 13. Receiving cavity; 14. Exhaust channel; 15. Connecting part; 20. Pressure relief valve; 201. First pressure relief valve; 202. Second pressure relief valve; 21. Valve seat; 211. Pressure relief through hole; 22. Valve cover; 23. Piston; 30. Battery; 31. First wall; 32. Explosion-proof valve. Detailed Implementation

[0021] The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this disclosure, and should not be construed as limiting this disclosure.

[0022] Individual cells are usually equipped with explosion-proof valves. When the internal pressure of the cell exceeds a set threshold, the explosion-proof valve opens to release the high-temperature and high-pressure gas and electrolyte generated inside the cell. The battery pack is also equipped with a pressure relief valve. By opening the pressure relief valve, the ejected material is discharged to the outside of the battery pack, thereby reducing the internal pressure and preventing thermal runaway of the entire battery pack.

[0023] Studies have found instances where the pressure relief valve of a single battery cell fails to release pressure even after the cell's explosion-proof valve is opened. The main reason for this failure is that the overall exhaust capacity of the pressure relief valve is insufficient to meet the gas generation rate during battery thermal runaway. Additionally, the pressure relief area, location, and number of pressure relief valves do not meet requirements. Consequently, the high-temperature flammable gas emitted from the battery cannot be quickly discharged from the pressure relief valve, leading to the accumulation of this gas inside the cell. This eventually causes the gas to ignite at high temperatures, resulting in an open flame when it is ejected from the pressure relief valve, posing an external safety risk and potentially triggering a chain reaction of thermal runaway in multiple batteries within the battery pack.

[0024] Therefore, embodiments of this disclosure provide a battery pack that enables timely pressure relief via the pressure relief valve of the housing. Specifically, refer to... Figures 1 to 13As shown, the battery pack includes a housing 10 and battery modules disposed within the housing 10.

[0025] The enclosure 10 is a closed or semi-closed structure made of materials such as metal and plastic. It serves as the physical carrier of the battery modules, and its design and manufacturing must meet the safety, reliability, and functionality requirements of the battery pack under different usage scenarios. The enclosure provides installation space for the battery modules, battery management system, cooling system, electrical connection components, etc., and through a reasonable structural design, fixes these components within the enclosure 10, ensuring they maintain a relatively stable position during battery pack operation and preventing damage or loosening of connections due to vibration, impact, or other factors. The enclosure 10 can be cast from materials such as steel plates or aluminum alloys, or made of lightweight materials such as glass fiber reinforced composite materials or carbon fiber reinforced composite materials. The shape of the enclosure 10 can be cylindrical, cuboid, cube, etc.

[0026] The enclosure 10 includes a base plate 11 and a frame 12, with the frame 12 connected to the base plate 11 to enclose and form a receiving cavity 13. The frame 12 is the framework structure of the enclosure 10, serving to support, protect, and connect. The frame 12 can be formed by splicing multiple beams together. In one feasible embodiment, the frame 12 includes four sub-frames, which are joined end to end to form an enclosed space. This enclosed space is sealed by the cover and the base plate 11 to form the receiving cavity 13. The frame 12 can be made of various materials, such as aluminum alloy, copper alloy, steel, and plastic. The frame 12 can be rectangular, circular, polygonal, etc., and is not specifically limited. The interior of the frame 12 can be a solid structure or contain a cavity 123. The cavity 123 is formed directly during material extrusion molding, injection molding, etc., or formed by bending the sheet material constituting the frame 12. The frame 12 and the base plate 11 can be fixedly connected by bolts, riveting, welding, or drilling screws.

[0027] The base plate 11 is the main load-bearing component of the battery pack, typically referring to a structural component installed at the bottom of the battery pack, used to support and fix the battery modules, battery management system, cooling system, and other components inside the battery pack. The base plate 11 is located at the bottom of the frame, for example, by welding, riveting, or screwing. The base plate 11 can be made of various materials, such as high-strength materials like aluminum alloy, steel, and stainless steel. The base plate 11 can be rectangular, circular, polygonal, or a plate-like structure; its specific shape is not limited, and its dimensions are determined by the number of batteries 30 contained in the battery pack and the dimensions of the batteries 30.

[0028] The battery 30 and the base plate 11 are usually fixed by adhesive bonding, but other methods such as riveting, screwing, and welding can also be used.

[0029] Structural adhesive is used for bonding and fixing internal structural components of the battery pack. It possesses high strength, can withstand large loads, is resistant to aging, fatigue, and corrosion, and exhibits stable performance throughout its expected lifespan, thus improving the connection strength between the battery and the casing. The structural adhesive is made of an insulating material doped with a conductive medium. It can use insulating materials as the base material, i.e., non-conductive adhesives, such as epoxy resin, silicone rubber, and polyurethane. Structural adhesives can also be epoxy resin structural adhesives or polyurethane structural adhesives. They can be two-component epoxy resin structural adhesives, two-component acrylic structural adhesives, two-component polyurethane structural adhesives, or two-component silane structural adhesives.

[0030] A pressure relief valve 20 is installed on the housing 10. The pressure relief valve 20 is fixedly installed on the frame 12 of the housing 10 by means of bonding, screwing, riveting, welding, or interference fit. The pressure relief valve 20 is connected to the receiving cavity 13. The pressure relief valve 20 is a component that is actuated to release internal pressure or temperature when the internal pressure or temperature of the battery pack reaches a predetermined threshold. The pressure relief valve 20 is used to prevent the risk of explosion caused by abnormal conditions such as overheating or overcharging of the battery 30, ensuring the safe operation of the battery 30. When the battery 30 is working normally, the pressure relief valve 20 seals the housing to ensure normal battery operation; in the event of thermal runaway of the battery 30, the pressure relief valve 20 needs to activate its explosion-proof function in a timely manner to release internal gas and heat, thereby reducing the risk of explosion.

[0031] The pressure relief valve 20 works by establishing a regulating venting channel inside the housing assembly. When the pressure inside the housing assembly increases, the valve opens, allowing gas to be released from the housing assembly, thereby reducing the pressure.

[0032] The pressure relief valve 20 may include a housing, a valve cover, and a hinge structure. The pressure relief valve 20 may be made of metallic materials, such as aluminum, aluminum alloy, copper, copper alloy, iron, steel, stainless steel, titanium alloy, etc., or it may be made of flame-retardant polymer materials such as polyvinyl chloride, polyvinylidene chloride, fluoroplastics, etc.

[0033] When a large amount of high-temperature and high-pressure gas is generated in the containment cavity 13 due to thermal runaway of the battery 30, if the internal pressure of the containment cavity 13 exceeds the set threshold of the pressure relief valve 20, the pressure relief valve 20 will open to discharge the internal gas, thereby blocking the further spread of thermal runaway and improving the safety of the battery pack.

[0034] The battery module is housed within the receiving cavity 13. The battery module includes multiple arrayed batteries 30. Each battery 30 can store chemical energy and controllably convert chemical energy into electrical energy. In recyclable batteries, the active materials can be reactivated by charging after discharge for continued use. The battery includes a casing and battery cells disposed within the casing.

[0035] The battery 30 has an explosion-proof valve 32, which is a component or part that can be actuated to release the internal pressure or temperature when the internal pressure or temperature of the battery 30 reaches a predetermined threshold.

[0036] During the use of battery 30, explosion-proof valve 32 is mainly used to allow gas inside battery 30 to be discharged in order to reduce the internal pressure of battery 30 in order to prevent excessive increase in internal pressure of battery 30 and cause deformation or explosion.

[0037] The explosion-proof valve 32 is made of any material, including but not limited to aluminum, steel, alloys, etc. The shape of the explosion-proof valve 32 is not limited, such as square, oblong, elliptical, racetrack-shaped, etc. The type of explosion-proof valve 32 is not limited, such as a scored explosion-proof valve, which can be formed by stamping or laser etching.

[0038] The study found that the main reason why the pressure relief valve 20 failed to release pressure in time was that the overall exhaust volume of the pressure relief valve 20 did not meet the gas production rate when the battery thermal runaway occurred. At the same time, the pressure relief area of ​​the pressure relief valve 20 and the location and number of pressure relief valves 20 were unreasonable and did not take into account the gas production of the battery. This caused the gas produced by the battery to accumulate inside the box, triggering thermal runaway of multiple batteries. In addition, the pressure relief valve 20 carried an open flame after opening, causing severe thermal runaway of the battery pack.

[0039] To achieve timely pressure relief of the pressure relief valve 20, the maximum exhaust volume of a single pressure relief valve 20 is limited to Q1, with the unit being L / s. Q1 is the volume of gas that a single pressure relief valve 20 can discharge per unit time when it is fully open. The value of Q1 can be 6, 8, 10, 12, 14, 16, 18 or 20. The value can be one of the values ​​listed above or any value between 6 and 20.

[0040] The number of pressure relief valves 20 in the battery pack is n, where n is a positive integer. The size of n determines the total venting capacity of the battery pack. The value of n can be 1, 2, 3, 4, 5, 6, 7 or 8, and the specific values ​​can be those listed above.

[0041] The peak gas production rate of a single cell 30 is Qe, in L / s. Qe is the volume of high-temperature and high-pressure gas produced per unit time when a single cell 30 experiences thermal runaway. The value of Qe can be 10, 15, 20, 25, 30, 35, 40, 45 or 50. The value can be one of the values ​​listed above or any value between 10 and 50.

[0042] In the embodiments provided in this disclosure, n×Q1>Qe is controlled to ensure that the total venting capacity of the battery pack is always greater than the peak gas generation rate when a single battery 30 experiences thermal runaway. This enables the gas ejected from the battery 30 to be quickly vented when a single battery 30 experiences thermal runaway, preventing gas from accumulating in the containment cavity 13. At the same time, it prevents high-temperature gas from causing thermal runaway of adjacent batteries 30, thereby improving the safety and reliability of the battery pack.

[0043] Furthermore, 0.1 ≤ (n×Q1-Qe) / (n×Q1) ≤ 0.7, where n×Q1 is the total venting capacity that all pressure relief valves 20 of the battery pack can achieve at the same time; and Qe is the peak gas production rate of a single battery 30 under thermal runaway conditions. By limiting this formula to a preset value range, the reliability of the battery pack's thermal runaway protection is further improved. This ensures that when a battery 30 experiences thermal runaway and releases high-temperature, high-pressure gas, the pressure relief valves 20 have sufficient and abundant venting capacity. Multiple pressure relief valves 20 can promptly and continuously vent the gas before it accumulates to a dangerous level, reducing the possibility of thermal runaway spreading to adjacent batteries 30 or other components, and improving the overall safety and stability of the battery pack. Meanwhile, an excessively large total venting capacity provided by the pressure relief valve 20 means that too many openings need to be made on the housing 10 to correspond to the pressure relief valve 20, which will reduce the strength of the housing 10 itself. Installing too many or too large pressure relief valves 20 on the housing will also encroach on the placement space of other components in the battery pack. Furthermore, it may lead to a risk of sealing failure at the location where the pressure relief valve 20 is installed on the housing 10. The value of (n×Q1-Qe) / (n×Q1) can be 0.1, 0.11, 0.13, 0.15, 0.2, 0.25, 0.4, 0.5, 0.6, 0.7, or any value between 0.1 and 0.7.

[0044] In one feasible implementation, when n≥2, that is, when the number of pressure relief valves 20 is not less than two, the limiting relationship satisfies: (n×Q1-Qe) / (n×Q1)≥0.12. At least two pressure relief valves 20 work together, ensuring that the overall venting capacity of the battery pack's pressure relief valves 20 has sufficient venting margin in the event of thermal runaway of the battery 30, thus preventing rapid gas accumulation within the housing 10 due to insufficient venting capacity.

[0045] By setting multiple pressure relief valves 20, the total exhaust capacity can be improved. Multiple pressure relief valves 20 can open simultaneously to exhaust gas, quickly forming an efficient exhaust channel to continuously discharge high-temperature and high-pressure gas, further ensuring the stability of the pressure relief process. On the other hand, it can ensure that even if one pressure relief valve 20 fails to open, the remaining pressure relief valves 20 can still function, ensuring that the total exhaust capacity meets the requirements.

[0046] As those skilled in the art will understand, the mass energy density of battery 30 is a parameter measuring the amount of electrical energy stored per unit mass of battery 30. A higher mass energy density indicates that battery 30 integrates more active material per unit mass, resulting in stronger energy storage capacity. However, it also leads to a faster gas generation rate and a larger gas generation volume during thermal runaway. The formula for the mass energy density of battery 30 is "Mass Energy Density = Battery Capacity / Battery Mass". The battery capacity is tested according to GB / T31486-2024, and the battery mass is measured using a balance or electronic scale.

[0047] In the embodiments provided in this disclosure, for the high-energy-density battery 30, the internal gas generation rate of the battery 30 is relatively large. When the mass energy density of the battery 30 is ≥200Wh / kg, the number of pressure relief valves 20 is limited to n≥2. That is, at least two pressure relief valves 20 are configured. Through the coordinated work of multiple pressure relief valves 20, the total venting capacity of the battery pack is improved, and high-temperature and high-pressure gases can be discharged more quickly, ensuring that the venting capacity of the pressure relief valves 20 of the battery 30 can exceed the gas generation rate of the high-energy-density battery 30. At the same time, by setting multiple pressure relief valves 20, which are distributed on the housing 10, the thermal runaway gas generation of a certain battery 30 can be responded to in a timely manner, further reducing the possibility of thermal runaway propagation. At least two pressure relief valves 20 can be set on one frame 12, or at least two pressure relief valves 20 can be set on two adjacent frames 12 to increase the venting rate of the pressure relief valves 20. The size of the pressure relief valves 20 or the size of the first connecting hole 124 on the frame 12 can also be increased to achieve rapid pressure relief.

[0048] In one feasible implementation, refer to Figure 1 as well as Figure 2 As shown, the frame 12 includes a first frame 121 and a second frame 122 connected to each other. The first frame 121 and the second frame 122 are arranged adjacent to each other and are located on two adjacent sides of the frame 12. They can be arranged perpendicularly or at an angle other than 90°. The angle is preferably 80-160°.

[0049] The length of the first frame 121 is greater than the length of the second frame 122, forming a cuboid structure. The longer the first frame 121, the more batteries 30 it can support. The ratio of the length of the first frame 121 to the length of the second frame 122 is K, satisfying 0.5 ≤ K < 1. The value of K can be 0.5, 0.6, 0.7, 0.8, 0.9, or 1, specifically any of the values ​​listed above, or any value between 0.5 and 1. Preferably, the pressure relief valve 20 is located on the first frame 121.

[0050] First, the longer first frame 121 provides ample space for the arrangement of the pressure relief valve 20. The pressure relief valve 20 can be evenly distributed according to the exhaust demand, avoiding problems such as concentrated exhaust paths and mutual interference caused by insufficient installation space.

[0051] Secondly, the first frame 121 usually corresponds to the side of the vehicle, and the second frame 122 is usually located in the corresponding position of the electrical compartment of the battery pack. The battery pack box includes the battery compartment and the electrical compartment, which are separated by a beam. The pressure relief valve 20 is set in the first frame 121. The first frame 121 is not connected to the electrical compartment and can be set away from the electrical compartment of the battery pack. This can effectively avoid the electrical components in the electrical compartment (electrical components refer to electronic components used to electrically connect with the battery cells to cooperate with the battery cells to work. Electrical components include current acquisition units, battery management units, pre-charge resistors, fuses, wiring harnesses, etc.), avoid the high temperature and high pressure gas during pressure relief from causing excessive heat to the electrical components, and reduce the risk of damage and short circuit of electrical components.

[0052] Furthermore, along the length of the first frame 121, the minimum distance between the pressure relief valve 20 and the center line of the first frame 121 is less than or equal to 500 mm. The center line of the first frame 121 is a symmetrical reference line along the length direction. Limiting the position of the pressure relief valve 20 to a certain value range close to the center line can prevent the pressure relief valve 20 from being too close to the two ends or edges of the first frame 121, ensuring that the pressure relief valve 20 covers as much of the gas-generating area as possible.

[0053] Furthermore, with a limit of (n×Q1-Qe) / (n×Q1)≥0.15, the first frame 121 with a larger length has a longer pressure relief path, making it difficult for the battery 30 to reach the pressure relief valve 20 quickly after the valve is opened. This avoids the batteries at both ends reaching the pressure relief valve 20 at unequal distances, as the thermal runaway of the battery 30 is unpredictable, and any battery 30 in the battery pack may experience thermal runaway. The above settings can ensure a uniform pressure relief path. At the same time, the pressure relief valve 20 of the housing is set at the center point of the first frame 121 to ensure the structural strength of the pressure relief valve 20 and prevent abnormal opening.

[0054] When the battery 30 experiences thermal runaway and generates high-temperature and high-pressure gas, the gas inside the housing 10 will diffuse in all directions. The pressure relief valve 20, which is located near the center line of the first frame 121, can respond to the exhaust demand more promptly, ensuring that the high-temperature and high-pressure gas in different locations inside the housing 10 can quickly reach the pressure relief valve 20 and be discharged, thereby improving the overall pressure relief efficiency.

[0055] When thermal runaway occurs inside the battery pack, generating high-temperature, high-pressure gas, the gas diffuses in all directions within the containment cavity 13. To respond to the gas pressure in different areas, the internal pressure can be rapidly released from multiple directions. In one feasible embodiment, pressure relief valves 20 are provided on both the first frame 121 and the second frame 122. Specifically, refer to... Figures 1 to 3 As shown, the pressure relief valve 20 includes a first pressure relief valve 201 disposed on the first frame 121 and a second pressure relief valve 202 disposed on the second frame 122.

[0056] The first pressure relief valve 201 is arranged on the longer first frame 121, which can release the pressure in the long side direction of the housing 10. The second pressure relief valve 202 is arranged on the shorter second frame 122, which can release the pressure in the short side direction of the housing 10. Thus, pressure relief channels can be formed on different sides of the housing 10, forming a multi-directional pressure relief arrangement structure and improving the overall pressure relief efficiency.

[0057] Furthermore, the distance between the first pressure relief valve 201 and the second pressure relief valve 202 is between 300mm and 2000mm. The distance can be 300mm, 500mm, 700mm, 1000mm, 1300mm, 1500mm, 1700mm, or 2000mm, and can be any value between 300mm and 2000mm, specifically the values ​​listed above.

[0058] This distance is the distance from the first pressure relief valve 201 to the second pressure relief valve 202. Setting this distance within a preset range can improve the pressure relief uniformity and response speed of the pressure relief valve 20, while ensuring the structural strength of the housing 10.

[0059] If this spacing is too small, the first pressure relief valve 201 and the second pressure relief valve 202 will be too close together, causing the first connecting holes 124 in the corresponding area on the frame 12 to be too concentrated. This weakens the structural strength and rigidity of the housing 10, making the frame 12 prone to deformation or cracking under internal pressure impact or external vibration. Furthermore, the first pressure relief valve 201 and the second pressure relief valve 202 are too far from the center lines of the first frame 121 and the second frame 122, respectively, affecting the smoothness of exhaust and reducing the overall pressure relief efficiency.

[0060] If this gap is too large, the high-temperature and high-pressure gas generated in the central area between the first pressure relief valve 201 and the second pressure relief valve 202 cannot reach the first pressure relief valve 201 or the second pressure relief valve 202 in time, causing the gas to accumulate locally and preventing multiple pressure relief valves 20 from opening at the same time, thus increasing the risk of thermal runaway.

[0061] In the embodiments provided in this disclosure, reference is made to Figure 4 , Figure 5 as well as Figure 7 As shown, a cavity 123 is formed within the frame 12. The cavity 123 includes a first cavity formed within the first frame 121 and a second cavity formed within the second frame 122. The first cavity and the second cavity are connected, making the frame 12 a hollow frame structure. The first cavity is connected to the receiving cavity 13 and the first pressure relief valve 201. The second cavity is connected to the receiving cavity 13 and the second pressure relief valve 202, forming a passage and constituting a gas pressure relief path. A first connecting hole 124 is provided on the side of the frame 12 facing outwards. The pressure relief valve 20 is disposed on the first connecting hole 124, and the pressure relief valve 20 is disposed at least partially through the first connecting hole 124 and is sealed to the first connecting hole 124. A second connecting hole is provided on the side of the frame 12 facing the receiving cavity 13, and the second connecting hole is connected to the receiving cavity 13.

[0062] When the battery 30 inside the housing 10 experiences thermal runaway and generates high-temperature and high-pressure gas, the gas in the containment cavity 13 will enter the cavity 123 inside the frame 12 through the first connecting hole 124. After being guided by the first cavity and the second cavity, the gas flows evenly to the first pressure relief valve 201 and the second pressure relief valve 202. Both the first pressure relief valve 201 and the second pressure relief valve 202 can effectively perform the pressure relief function.

[0063] In one feasible implementation, the width of the cavity 123 is between 15mm and 20mm. The value can be 15mm, 16mm, 17mm, 18mm, 19mm, or 20mm; it can specifically be one of the values ​​listed above, or any value between 15mm and 20mm. Limiting the width of the cavity 123 to a preset range allows for smooth gas flow within the cavity 123 while maintaining the structural strength and rigidity of the frame 12.

[0064] If the width of cavity 123 is too small, the high-temperature and high-pressure gas will not be able to flow quickly and smoothly through cavity 123 to pressure relief valve 20, resulting in a delayed pressure relief response of pressure relief valve 20. This makes it difficult to meet the instantaneous gas generation and diversion requirements when battery 30 is thermally runaway, increasing the risk of internal pressure accumulation.

[0065] If the cavity 123 is too wide, it will reduce the structural strength and rigidity of the frame 12, reduce the frame 12's resistance to external impacts, and the frame 12 is prone to deformation under vibration or impact conditions, affecting the safety and reliability of the overall battery pack structure.

[0066] In one feasible implementation, refer to Figure 7As shown, a partition plate 125 is provided inside the frame 12. Along the direction perpendicular to the bottom plate 11, the cavity 123 is divided into a first sub-cavity 1231 and a second sub-cavity 1232 by the partition plate 125. The pressure relief valve 20 is connected to the first sub-cavity 1231 but not connected to the second sub-cavity 1232. The dimension of the first sub-cavity 1231 along the direction perpendicular to the bottom plate 11 is larger than the dimension of the second sub-cavity 1232 along the same direction perpendicular to the bottom plate 11. This allows the first sub-cavity 1231 to have a larger flow cross-section and a larger receiving cavity, while the second sub-cavity 1232 maintains a smaller vertical dimension.

[0067] The first sub-cavity 1231 serves as a channel for the ejected material during thermal runaway. It is specifically designed for venting and guiding the pressure relief valve 20. When the battery 30 experiences thermal runaway and generates high-temperature, high-pressure gas and debris, the ejected material only flows into the first sub-cavity 1231, which is connected to the pressure relief valve 20. The second sub-cavity 1232 does not participate in the transmission of ejected material. The second sub-cavity 1232 can be used independently for wiring or structural reinforcement, achieving lightweighting and compactness while ensuring the overall structural strength of the frame 12.

[0068] Furthermore, the area of ​​the first connecting hole 124 determines the size of the gas flow cross-section and the local structural strength of the frame 12. Therefore, the area of ​​the first connecting hole 124 is limited to 490 mm². 2 -3847mm 2 Between. The value can be 490mm. 2 700mm 2 1000mm 2 1500mm 2 2000mm 2 2500mm 2 3000mm 2 3500mm 2 Or 3847mm 2 The value can be one of the values ​​listed above, or it can be 490mm. 2 -3847mm 2 Any value between the given values. Limiting the area of ​​the first connecting hole 124 to a preset range ensures both smooth gas flow and sufficient structural strength of the frame 12 at the location of the first connecting hole 124.

[0069] If the area of ​​the first connecting hole 124 is too small, the flow cross section of gas between the cavity 123 and the pressure relief valve 20 will be insufficient, the gas flow resistance will increase, and the high temperature and high pressure gas will not be able to flow quickly through the first connecting hole 124 to the pressure relief valve 20. This will make it difficult to meet the instantaneous exhaust demand when the battery 30 thermally runs away, thereby increasing the risk of pressure accumulation inside the housing 10.

[0070] If the area of ​​the first connecting hole 124 is too large, it will reduce the structural strength and rigidity of the frame 12, reduce the frame 12's resistance to external impacts, and the frame 12 is prone to deformation under vibration or impact conditions, affecting the safety and reliability of the overall battery pack structure.

[0071] In the embodiments provided in this disclosure, reference is made to Figure 8 and Figure 9 As shown, the pressure relief valve 20 can be a piston pressure relief valve as shown in the figure. Figure 8 This is a schematic diagram showing the pressure relief valve in the closed position. Figure 9 This is a schematic diagram showing the pressure relief valve in its open state. The pressure relief valve 20 includes a valve seat portion 21, which is used to fix it to the housing 10. The connection method includes, but is not limited to, screwing, riveting, snap-fitting, welding, and bonding. The valve seat portion 21 is provided with a pressure relief through hole 211 that passes through the valve seat portion 21. When the pressure relief through hole 211 is open, it is used to discharge gas inside the housing. It also includes a valve cover portion 22 and a piston portion 23. The piston portion 23 is fixedly connected to the valve seat portion 21, and the valve cover portion 22 is slidably connected to the piston portion 23, so that the valve cover portion 22 is movably disposed in the pressure relief through hole 211 and blocks the pressure relief through hole 211. In non-pressure relief conditions, the piston portion 23, under the pull of the piston portion 23, abuts against the valve seat portion 21 and blocks the pressure relief through hole 211. During pressure relief operation, the internal air pressure of the battery pack pushes the valve cover 22 to slide open outwards, exposing the pressure relief through hole 211, which then releases pressure. In the embodiments provided in this disclosure, reference is made to... Figure 10 as well as Figure 11 As shown, the base plate 11 has a split structure, comprising a first plate 111 and a second plate 112. The first plate 111 is closer to the battery module than the second plate 112, and the battery module is supported on the first plate 111. A predetermined gap of a certain height is formed between the first plate 111 and the second plate 112, thereby forming an exhaust channel 14, which is connected to the pressure relief valve 20. The exhaust channel 14 is the discharge path for high-temperature ejected materials when the battery 30 experiences thermal runaway. When the battery 30 experiences thermal runaway, the explosion-proof valve 32 ejects a large amount of high-temperature and high-pressure gas and metal fragments. These ejected materials are guided to the pressure relief valve 20 through the exhaust channel 14, thereby quickly releasing the internal pressure of the battery 30 and preventing more severe thermal runaway.

[0072] Furthermore, along the direction perpendicular to the base plate 11, the distance between the first plate 111 and the second plate 112 is between 6mm and 12mm. The value can be 6mm, 7mm, 8mm, 9mm, 10mm, 11mm or 12mm, and can be any value between 6mm and 12mm, as listed above.

[0073] If this interval is too small, the height of the flow section of the exhaust channel 14 between the first plate 111 and the second plate 112 will be too small. When the battery 30 thermally runs away, the high-temperature and high-pressure gas and metal debris ejected by the explosion-proof valve 32 cannot be quickly and smoothly guided to the pressure relief valve 20, which will easily block the exhaust channel 14, causing the internal pressure to be released in time and increasing the risk of cascading thermal runaway of adjacent batteries 30.

[0074] If this gap is too large, the height of the exhaust channel 14 between the first plate 111 and the second plate 112 will be too large, which will reduce the space utilization of the battery pack, which is not conducive to the compact design of the battery pack, and will also reduce the overall structural strength of the base plate 11.

[0075] In one feasible implementation, refer to Figure 10 as well as Figure 11 As shown, a connecting portion 15 is provided on the first plate 111. Along a direction perpendicular to the base plate 11, the explosion-proof valve 32 at least partially corresponds to the connecting portion 15. The connecting portion 15 is a through hole, thus providing a pressure relief channel for the explosion-proof valve 32 of the battery 30. When the battery 30 experiences thermal runaway, the explosion-proof valve 32 ejects a large amount of high-temperature, high-pressure gas. This ejected gas is discharged from the connecting portion 15 into the exhaust channel 14 between the first plate 111 and the second plate 112, thereby quickly releasing the internal pressure of the battery 30 and preventing more severe thermal runaway. The exhaust channel 14 provides a separate exhaust path in the battery pack, reducing the risk of crosstalk with other components and allowing for faster extraction of gas ejected from the battery during thermal runaway from the explosion-proof valve, thus improving safety. Along the direction perpendicular to the base plate 11, the height of the exhaust channel 14 between the first plate 111 and the second plate 112 ranges from 6mm to 20mm, for example, 6mm, 8mm, 10mm, 12mm, 15mm, 18mm, 20mm, or any value between 6mm and 20mm.

[0076] Along the direction perpendicular to the base plate 11, the explosion-proof valve 32 corresponds at least partially to the connecting part 15. When the explosion-proof valve 32 is opened, at least part of the ejected high-temperature and high-pressure gas, electrolyte and other ejected materials can be directly discharged through the connecting part 15 below, shortening the pressure relief path, avoiding the continuous increase of internal pressure of the battery pack, and also reducing the thermal impact of ejected materials from a single battery 30 on other adjacent batteries 30, avoiding larger-scale thermal runaway, and further improving the overall safety performance of the battery pack.

[0077] The battery casing also includes an electrolyte, which is liquid and used to transport active ions, such as Li ions. It requires a liquid material that can conduct ions while isolating electrons. The electrolyte consists of solvents, electrolyte salts, additives, and other chemical substances. Solvents can be carbonates, carboxylic acid esters, or ethers, electrolyte salts can be lithium salts, sodium salts, or zinc salts, and additives can be vinylene carbonate, fluoroethylene carbonate, propylene sulfite, vinyl sulfite, etc. Electrolyte salts include lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate, lithium perchlorate, lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(oxalateborate), etc.

[0078] The electrolyte can be prepared by mixing different organic solvents, then dissolving the thoroughly dried lithium salt in the mixed organic solvents to prepare an electrolyte with a concentration of 1 mol / L.

[0079] a) The lithium salt is selected from at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP), and the concentration of lithium salt in the electrolyte is 0.5 mol / L - 2.5 mol / L.

[0080] (b) The solvent is selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone, acetonitrile, dimethyl glycol ether (DME), dimethyl propylene glycol ether (PGME), and tetrahydrofuran.

[0081] c) The additives can be negative electrode film-forming additives, positive electrode film-forming additives, or additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, additives that improve battery low-temperature performance, etc.

[0082] Specifically, positive electrode film-forming additives include: anisole derivatives, polymeric monomers (such as xylene and phenylcyclohexane), and boron / nitrogen heterocyclic compounds (such as LiBOB).

[0083] Negative electrode film-forming additives: vinylene carbonate (VC), fluoroethylene carbonate (FEC), vinyl ethylene carbonate (VEC), 1,3-propanesulfonate lactone (1,3-PS), vinyl sulfite (ES), and vinyl sulfate (DTD).

[0084] To suppress gas generation within the battery, lithium bisfluorosulfonylimide (LiFSI) can be added as an electrolyte salt. This electrolyte can improve the ion transport rate between the positive and negative electrodes, ensuring the battery's charge and discharge rates. The amount of LiFSI added is between 0.2 mol / L and 2 mol / L, for example, 0.2 mol / L, 0.4 mol / L, 0.6 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.2 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.8 mol / L, 2.0 mol / L, or any value between 0.2 mol / L and 2 mol / L. When LiFSI is used as a small amount of additive (usually mixed with LiPF6), it can suppress gas generation and improve battery performance. A small amount of LiFSI can also help optimize the composition and structure of the solid electrolyte interphase (SEI) film between the electrode and the electrolyte. It can promote the formation of a denser and more stable SEI film, which effectively isolates the electrolyte from direct contact with the electrode, thereby suppressing side reactions and gas generation. However, if LiFSI is used as the main lithium salt of the electrolyte or its content is very high, the gas generation problem of the battery becomes very prominent. LiFSI decomposes at high temperatures and produces gases such as nitrogen. Due to the extremely high bond energy of nitrogen molecules, its formation process releases a large amount of heat, which in turn exacerbates the decomposition of the electrolyte and gas generation. Preferably, (n×Q1-Qe) / (n×Q1)≥0.13 can ensure that the problem of untimely pressure relief caused by the increased gas generation of the battery is not addressed when a higher content of LiFSI is selected.

[0085] The test method for the amount of LiFSI added is as follows: Lithium salt and inorganic salt additive content Step 1) Collecting Electrolyte: If the electrolyte of the test object is in the battery, use a battery charging and discharging device to discharge the battery under test. Discharge conditions: current 0.3C, cutoff lower limit voltage (determine the lower limit voltage according to the specific system, where lithium iron phosphate LFP - upper limit voltage 3.65V, lower limit voltage 2.5V; nickel cobalt manganese ternary NCM - upper limit voltage 4.25V, lower limit voltage 2.5V; lithium manganese iron phosphate LFMP - upper limit voltage 4.25V, lower limit voltage 2.5V; lithium nickel manganese oxide - upper limit voltage 4.8V, lower limit voltage 3.5V). After recording the battery number / barcode, disassemble the battery in a glove box (H2O≤0.1ppm, O2≤0.1ppm) to collect the electrolyte. There are three methods for collecting the electrolyte: After opening the battery cover, ① if there is free electrolyte, use a pipette to collect the electrolyte into a 5mL sample tube and seal it with sealing glue to prevent electrolyte leakage. ② If there is no free electrolyte, a hydraulic press (Beijing Heng'ao Technology Co., Ltd. FY-30 hydraulic press) can be used to continuously pressurize until free electrolyte appears. Collect the electrolyte into a sample tube and seal it. ③ Add an appropriate amount of dichloromethane extractant to the battery and record the dichloromethane content. After adding dichloromethane, put the battery into an aluminum-plastic bag and seal it with a heat sealer. Transfer it to an ultrasonic oscillator and oscillate for 12 hours to allow the electrolyte and dichloromethane in the electrode to mix thoroughly. Then, use a pipette to draw the mixture of dichloromethane and electrolyte into a 5mL sample tube and seal the sample tube with sealing tape. If the electrolyte of the test object is a finished product, the component content can be determined directly by standard GC-MS spectrum comparison without the need for electrolyte collection.

[0086] 2) After filtering out solid suspended matter from the collected electrolyte sample, transfer 0.2 g of the above organic solution to a centrifuge tube containing approximately 19.8 g of ultrapure water. Shake vigorously to ensure the lithium salt (e.g., LiPF6) reacts fully with the water, dissociating the anion to be tested (e.g., ...). The sample solution was filtered using an aqueous syringe filter (0.22 or 0.45 μm pore size), placed in an IC-specific sample vial, and tested using an IC to obtain an IC spectrum. The obtained IC spectrum was compared with the standard spectrum in the IC database (the IC database contains spectra of all ionic substances) to confirm the type of lithium salt (the matching degree between the standard curve and the sample curve of the electrolyte to be tested is ≥98%). Then, the content of the corresponding lithium salt / inorganic salt additive was determined based on the peak area of ​​the anion to be tested in the electrolyte to be tested.

[0087] Furthermore, along the direction perpendicular to the base plate 11, the orthographic projection of the explosion-proof valve 32 falls entirely within the connecting portion 15. This ensures that the connecting portion 15 completely covers the entire explosion-proof valve 32. When the explosion-proof valve 32 is open, the entire pressure relief opening formed is directly above the connecting portion 15, allowing the ejected material to completely enter the connecting portion 15. This reduces the lateral diffusion of the ejected material within the exhaust channel 14 and lowers the possibility of thermal runaway spreading to adjacent batteries 30.

[0088] In the embodiments provided in this disclosure, the ratio of the area of ​​the explosion-proof valve 32 to the area of ​​the first wall 31 is between 0.008 and 0.3. The value can be 0.008, 0.02, 0.05, 0.1, 0.15, 0.2, 0.25, or 0.3, specifically the values ​​listed above, or any value between 0.008 and 0.3. This ensures both the timely pressure relief capability of the battery 30 and sufficient structural strength of the first wall 31 to prevent abnormal opening of the pressure relief valve 20.

[0089] If this ratio is too small, the opening area formed by the explosion-proof valve 32 will be insufficient, the exhaust rate will be slowed down, and the pressure will not be released in time, causing the internal pressure of the battery 30 to continue to rise, increasing the risk of the battery 30 rupturing from the side and causing a larger-scale thermal runaway.

[0090] If this ratio is too large, the weak area caused by the explosion-proof valve 32 will be too large, which will excessively weaken the structural strength of the first wall 31. The first wall 31 is prone to deformation under vibration or impact conditions, which will lead to the abnormal opening of the explosion-proof valve 32.

[0091] Furthermore, when battery 30 is a ternary lithium battery, due to its higher energy density, the gas production during thermal runaway is more intense and faster. Therefore, the area of ​​the explosion-proof valve 32 needs to be increased, limiting the ratio of its area to the area of ​​the first wall 31 to between 0.02 and 0.3. The value can be 0.02, 0.05, 0.1, 0.15, 0.2, 0.25, or 0.3, specifically the values ​​listed above, or any value between 0.02 and 0.3. This ensures that battery 30 has sufficient pressure relief capacity to quickly release the high-temperature, high-pressure gas generated during thermal runaway.

[0092] In one feasible implementation, when the thickness of the battery 30 is ≤35mm, the battery 30 has a flat structure. When multiple batteries 30 are arranged in an array, their large faces face each other, thus achieving a denser arrangement within the battery pack and improving the overall energy density of the battery pack. Under this structural arrangement, the constraint expression satisfies (n×Q1-Qe) / (n×Q1)>0.12. This improves the overall pressure relief capacity of the battery pack, avoids exacerbating the risk of thermal runaway propagation due to an increase in the number of batteries 30, and improves the safety and stability of the battery pack. Preferably, (n×Q1-Qe) / (n×Q1)≤0.7. In the battery pack, when the battery insulation and battery pack pressure relief rate meet the requirements, generally only one battery will experience thermal runaway at the same time, and in extreme cases, multiple batteries will not experience simultaneous thermal runaway. Therefore, the requirement for the battery pack pressure relief rate does not need to be too high. If the upper limit is exceeded, too many pressure relief valves 20 will lead to a decrease in the strength of the housing 10 on which they are installed, increase the number of processes in the overall battery pack production, and increase costs. The optimal value is (n×Q1-Qe) / (n×Q1)≤0.5, which allows for further control over the size and number of pressure relief valves 20.

[0093] In one feasible implementation, when the thickness of the battery 30 is ≥60mm (e.g., 60mm, 62mm, 64mm, 65mm, 70mm, 80mm, 100mm, or a value between two of these), the volume of a single battery is large, the total amount of active material in the cell is large, and the gas production is greater. In the event of thermal runaway, the gas production of a single battery is large, and because the area of ​​the explosion-proof valve that can be installed on the battery is limited, the venting rate of the larger battery itself will be affected, easily causing the battery temperature to rise rapidly, which may ignite the high-temperature, high-pressure flammable ejecta. Therefore, it is necessary to further increase the venting efficiency of the battery pack itself, making (n×Q1-Qe) / (n×Q1) ≥0.17, reducing the accumulation of flammable gas inside the battery pack, reducing the possibility of open flame when the battery pack is depressurized, and ensuring safety in use. When the battery thickness is less than 60mm (e.g., 20mm, 25mm, 30mm, 40mm, 50mm, 55mm, 59mm or any two of the above values), the gas production of the battery will not be too large, so the requirement for the total exhaust volume of the explosion-proof valve is relatively low.

[0094] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0095] Test method for peak gas production rate of a single battery at 30°C: For the test of the peak gas production rate of a single battery at 30, refer to the test method provided in "Appendix 2-1: Test method for opening pressure of thermal runaway relief valve of power battery (draft for comments)" in the "Letter from China Association of Automobile Manufacturers on soliciting opinions on two group standards including "Test method for thermal runaway gas production of power battery products for electric vehicles".

[0096] To control the peak gas production rate of a single battery at 30%, when the positive electrode active material remains constant, the method can be achieved by adjusting the compaction density of the positive electrode sheet (the compaction density range of the positive electrode sheet is 2.4 g / cm³). 3 -3.8g / cm 3 For example, 2.4 g / cm³ 3 2.5g / cm 3 2.7g / cm 3 2.8g / cm 3 3.0g / cm 3 3.2g / cm 3 3.3g / cm 3 3.5g / cm 3 3.7g / cm 3 3.8g / cm 3 It can also be 2.4 g / cm³. 3 -3.8g / cm 3 The amount of gas produced by the battery during thermal runaway can be adjusted by varying the compaction density (any value between these two values). A higher compaction density results in a greater amount of gas produced during thermal runaway under the same state of charge; conversely, a lower compaction density results in a smaller amount of gas produced during thermal runaway under the same state of charge. The amount of gas produced can also be adjusted by changing the type of positive electrode active material, such as lithium iron phosphate or lithium nickel cobalt manganese oxide. For lithium nickel cobalt manganese oxide ternary materials, adjusting the molar ratio of nickel in the lithium nickel cobalt manganese oxide can also regulate the amount of gas produced by the battery cell during thermal runaway. The chemical formula of lithium nickel cobalt manganese oxide ternary materials is LiNi. x Co y Mn z M d O2, where 0 < x < 1, 0 < y < 1, 0 ≤ z < 1, 0 ≤ d < 1, and x + y + z + d = 1. The molar content of nickel in the total transition metal elements ranges from 20% to 90% (e.g., 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or any value between 20% and 90%). The higher the molar percentage of nickel in lithium nickel cobalt manganese oxide, the greater the gas production during thermal runaway of the battery cell, and vice versa. For the same capacity and state of charge, the gas production of a battery cell with lithium nickel cobalt manganese oxide as the positive electrode active material is greater than that with lithium iron phosphate as the positive electrode active material.

[0097] The test method for compacted density is as follows: Step 1) Pretreatment: Discharge the battery at 0.33C to the lower limit voltage (determine the lower limit voltage according to the specific system, where lithium iron phosphate (LFP) has an upper limit voltage of 3.65V and a lower limit voltage of 2.5V; nickel cobalt manganese ternary NCM has an upper limit voltage of 4.25V and a lower limit voltage of 2.5V; lithium manganese iron phosphate (LFMP) has an upper limit voltage of 4.25V and a lower limit voltage of 2.5V; and lithium nickel manganese oxide has an upper limit voltage of 4.8V and a lower limit voltage of 3.5V). Take the empty battery, disassemble the electrode, soak the electrode in dimethyl carbonate (DMC) solution for 4 hours, and then take it out and let it dry.

[0098] Step 2) Use a punching machine to punch the pre-treated positive electrode sheet into circular pieces of a fixed area, denoted as S0 (unit: cm). 2 Take three circular plates as parallel samples, and weigh each of the three plates using an electronic balance. Record the average mass as M1 (in g). Measure the thickness of the active material layer (i.e., the total thickness minus the current collector) in each of the three plates using a micrometer, and record the average mass as B (in cm). Finally, add a suitable amount of deionized water to each of the three plates, gently wipe away the coating with lint-free paper to expose the copper foil, and let stand at room temperature (or dry) for 10 minutes. After the copper foil is dry, weigh each of the three copper foils, record the average mass as M0 (in g), and calculate the compaction density of the positive electrode plate using the following formula: A = (M1 - M0) / (B × S0). Test method for the maximum discharge capacity of a single pressure relief valve 20.

[0099] The pressure relief valve 20 is fixed to the sealing test chamber by a clamp, and a flow meter is installed on one side of the pressure relief valve 20 in the opening direction to collect the flow rate of the pressure relief valve 20 in real time. One side of the pressure relief valve 20 in the opening direction faces the outside of the sealing test chamber, and the other side faces the inside of the sealing test chamber. A pressure sensor is installed inside the sealing chamber to collect the gas pressure inside the sealing chamber in real time.

[0100] At room temperature (20°C), use clean, dry compressed air or nitrogen to pressurize the inside of the sealed chamber 10. The pressurization rate is controlled to be ≤10kPa / s. Record the pressure-time curve in real time. After the pressure relief valve 20 is opened, continue to pressurize until the pressure value inside the chamber 10 remains unchanged for more than 30 seconds in the pressure-time curve. Then stop pressurizing and maintain this pressure output for 1 minute.

[0101] Take 30 seconds from the period during which the pressure is maintained and read the value △V recorded by the flow meter during this period. The maximum discharge capacity of a single pressure relief valve 20 is △V / △t, where △t = 30s, and the unit is L / s.

[0102] The maximum discharge capacity of the pressure relief valve 20 can be adjusted by changing the opening end face area of ​​the pressure relief valve, the opening distance of the cover plate of the pressure relief valve, and the size of the hollow cavity in the frame on which the pressure relief valve is fixed.

[0103] The method for regulating the maximum discharge volume of a single pressure relief valve 20 includes adjusting the diameter of the pressure relief through-hole 211 of the single pressure relief valve 20 (the diameter range of the pressure relief through-hole 211 is 30mm-80mm, such as 30mm, 32mm, 35mm, 40mm, 45mm, 50mm, 55mm, 60mm, 65mm, 70mm, 75mm, 80mm, or any value between 30mm and 80mm). The smaller the diameter of the pressure relief through-hole 211, the more the maximum discharge volume of the single pressure relief valve 20 is constrained by the channel size, resulting in a smaller discharge volume; however, if the diameter of the pressure relief through-hole 211 is too large, it will also require a larger hole to be made on the housing to install the pressure relief valve 20, which will lead to a decrease in the structural strength of the housing. In addition, the maximum exhaust volume can be controlled by adjusting the opening distance of the valve cover 22 (the opening distance of the valve cover 22 is in the range of 5-25mm, such as 5mm, 7mm, 9mm, 10mm, 12mm, 15mm, 17mm, 20mm, 22mm, 25mm, or any value between 5-25mm), that is, the stroke of the piston 23. If the opening distance is too small, the opening for pressure relief will be too small, and the pressure relief will be too slow; if the opening distance is too large, the overall length of the piston 23 will be too large, which will affect the installation of the pressure relief valve.

[0104] Measurement methods for dimensions, area, etc. Use measuring instruments such as micrometers or calipers to measure parameters such as length, width, distance, and thickness. The area is calculated from the measured parameters such as length, width, distance, and thickness.

[0105] Battery pack manufacturing (1) Preparation of the positive electrode: The prepared positive electrode active material, conductive agent (e.g., acetylene black), and binder (e.g., PVDF) are mixed, and solvent NMP is added. The mixture is stirred under vacuum until the system is homogeneous to obtain a positive electrode slurry. The positive electrode slurry is uniformly coated on both surfaces of the positive electrode current collector foil, dried at room temperature, and then transferred to an oven for further drying. The positive electrode sheet is then obtained by rolling and slitting.

[0106] Specifically, the mass ratio of positive electrode active material: conductive agent: binder satisfies (92-98): (4-1): (4-1).

[0107] (2) Preparation of negative electrode: The negative electrode active material, conductive agent (e.g., acetylene black), thickener (e.g., carboxymethyl cellulose (CMC)), and binder (e.g., styrene-butadiene rubber (SBR)) are mixed, and deionized water is added as a solvent. The mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector foil, air-dried at room temperature, and then transferred to an oven for further drying. Finally, the negative electrode sheet is obtained by rolling and slitting.

[0108] Specifically, the ratio of negative electrode active material: conductive agent: thickener: binder satisfies (90-96): (4-2): (2-1): (4-1).

[0109] (3) Preparation of electrolyte: Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0110] (4) Preparation of the diaphragm: Polyethylene film is selected as the diaphragm.

[0111] (5) Preparation of lithium-ion battery 30: The positive electrode sheet, separator, and negative electrode sheet are stacked in sequence and formed into a bare cell by winding or stacking. The bare cell is placed in the casing of battery 30, which is a square casing, and an explosion-proof valve 32 is installed on the cover plate of battery 30. Battery 30 is dried, electrolyte is injected, and after encapsulation, settling, formation, and volume adjustment, lithium-ion battery 30 is obtained.

[0112] In the selection of materials for the battery 30, this application may also select other materials, not limited to the materials limited by the above preparation method. The positive electrode active material may be selected from one or more lithium-containing positive electrode active materials, including lithium iron phosphate, ternary materials containing nickel, cobalt and manganese, and lithium manganese iron phosphate; the negative electrode active material may be selected from one or more negative electrode active main materials, such as artificial graphite, natural graphite, silicon carbide, silicon oxide, and lithium titanate.

[0113] The conductive agent includes, but is not limited to, one or more combinations of graphite, superconducting carbon, carbon black (such as acetylene black, Ketjen black, Super P, etc.), carbon nanotubes, graphene, and carbon nanofibers.

[0114] The adhesive includes, but is not limited to, one or more combinations of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, carboxymethyl chitosan, etc.

[0115] The solvent can be deionized water, NMP (N-methylpyrrolidone), alcohol, ether, ketone or other types of pyrrolidone, etc.

[0116] The positive electrode current collector foil can be a metal foil or a composite current collector. For example, as a metal foil, it can be made of stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel, or titanium with a silver-plated surface. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0117] The negative electrode current collector foil can be made of stainless steel, copper, aluminum, nickel, carbon electrodes, or titanium, and can be surface-plated with silver. Composite current collectors may include a polymer base layer and a metal layer. Composite current collectors can be formed by forming metal materials (aluminum, aluminum alloys, copper, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on a polymer base material (such as polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0118] (6) Preparation of the battery pack: Multiple batteries 30 are connected in series and parallel through conductive busbars to form a battery module, and the battery pack housing 10 is manufactured. The housing 10 consists of a base plate 11, a frame 12 and a cover. The base plate 11 and the frame 12 are sealed and connected by a flow drill screw. The batteries 30 are glued and fixed to the base plate 11 with structural adhesive. The cover and the frame 12 are sealed and connected by rivets to form a battery pack.

[0119] The busbar is used to electrically connect the terminals (current output terminals of battery 30) of at least two batteries 30 to enable series or parallel connection of multiple battery cells 30. Materials include metals or alloys such as copper, aluminum, nickel, tungsten, and manganese, or copper-aluminum composite materials, which possess excellent electrical conductivity.

[0120] The bottom plate 11, frame 12 and lid of the box body 10 can be made of steel, copper alloy, aluminum alloy and other materials, formed by casting, stamping and extrusion. They can also be made of lightweight materials, such as plastics, resins (common resins can be polyphenylene sulfide resin PPS, polyphenylene sulfide resin PPO, polypropylene resin PP and other materials), glass fiber reinforced composite materials, carbon fiber reinforced composite materials, graphite fiber reinforced composite materials and so on.

[0121] The methods of fixing the base plate 11 to the frame 12, and the methods of fixing the box cover to the frame 12, also include welding, screwing, riveting, etc.

[0122] The testing method is as follows: Test Method 1: Number of open flames appearing when the battery pack is depressurized Following the above-described battery pack preparation method, 50 battery packs are prepared, each containing 100 batteries 30. A heating element is placed on the large side of the casing of one battery 30 at the same location in each battery pack. A pressure relief valve 20, corresponding to those in the embodiments and comparative examples, is provided on the frame of the battery pack housing 10.

[0123] Then, following steps (1) to (5) in the above battery pack preparation method, 20 corresponding batteries 30 are produced as reference batteries 30. The peak gas production rate of each reference battery 30 is measured according to the above battery 30 peak gas production rate test method, and the average value is taken as the peak gas production rate Qe of the group of batteries 30.

[0124] The battery pack is charged at a constant current rate of 1C until the voltage of battery 30 in the battery pack reaches the upper limit voltage. Then, it is switched to constant voltage charging until the current of battery 30 drops to 0.05C. After standing for 30 minutes, battery 30 is heated at the maximum power of the heating element. When thermal runaway occurs, the triggering is stopped and the heating element is turned off. During the thermal runaway process, the pressure relief valve 20 of the battery pack is observed to confirm whether it emits an open flame. For each embodiment and comparative example, if more than 2 battery packs out of the corresponding 50 battery packs show an open flame, it is recorded as unqualified; if 1 or 2 battery packs show an open flame, it is recorded as qualified; if no battery pack shows an open flame, it is recorded as good.

[0125] For different systems, the upper and lower voltage limits of a single 30-volt battery need to be adjusted accordingly: Lithium iron phosphate (LFP) - upper limit voltage 3.65V, lower limit voltage 2.5V; Nickel-cobalt-manganese ternary NCM - upper limit voltage 4.25V, lower limit voltage 2.5V; Lithium manganese iron phosphate (LFMP) - upper limit voltage 4.25V, lower limit voltage 2.5V; Lithium nickel manganese oxide - upper limit voltage 4.8V, lower limit voltage 3.5V.

[0126] According to the test results in Table 1 above, combined with Examples 1-18, when the formula value of (n×Q1-Qe) / (n×Q1) satisfies (n×Q1-Qe) / (n×Q1)≥0.1, the pressure relief valve 20 has sufficient and abundant venting capacity. Multiple pressure relief valves 20 can timely and continuously discharge gas before the gas accumulates to a dangerous level, reducing the possibility of thermal runaway spreading to adjacent batteries 30 or other components, and improving the overall safety and stability of the battery pack. The test showed that the number of open flames when the battery pack was depressurized met the preset requirements.

[0127] In Comparative Examples 1 to 4, the formula value of (n×Q1-Qe) / (n×Q1) is less than 0.1, which does not meet the gas generation rate during battery thermal runaway. Furthermore, the pressure relief area, location, and number of pressure relief valves 20 are unreasonable and not comprehensively considered in relation to the battery's gas generation. This leads to the accumulation of gas inside the casing, triggering thermal runaway in multiple batteries. When the pressure relief valves 20 open, they carry open flames, causing external thermal runaway of the battery pack. Testing showed that the number of open flames appearing during battery pack pressure relief did not meet the preset requirements.

[0128] Secondly, this disclosure provides an electrical device that may include the aforementioned battery pack.

[0129] Battery packs can serve as operating power for electrical equipment or as driving power for electrical equipment, replacing or partially replacing fuel or natural gas to provide driving power for vehicles. By way of example only, electrical equipment can be, but is not limited to, vehicles, ships, aircraft, household appliances, and industrial equipment. For example, vehicles can be passenger cars, trucks, construction vehicles, etc.

[0130] In addition, electrical equipment can also be used for the storage, conversion, and release of recyclable electrical energy.

[0131] The above description, based on the embodiments shown in the figures, details the structure, features, and effects of this disclosure. The above description is only a preferred embodiment of this disclosure, but this disclosure does not limit the scope of implementation to what is shown in the figures. Any changes made in accordance with the concept of this disclosure, or modifications to equivalent embodiments with equivalent changes, that do not exceed the spirit covered by the specification and figures, should be within the protection scope of this disclosure.

Claims

1. A battery pack, characterized in that, include: The box body includes a bottom plate and a surrounding frame, the surrounding frame being connected to the bottom plate to enclose and form a receiving cavity; A pressure relief valve is installed on the frame of the housing and is connected to the receiving cavity. The pressure relief valve is used to open when the internal pressure of the battery pack reaches a certain level. A battery module is housed within the receiving cavity, the battery module comprising a plurality of batteries arranged in an array; Wherein, the maximum exhaust volume of a single pressure relief valve is Q1, in L / s, the number of pressure relief valves is n, and the peak gas production rate of a single battery is Qe, in L / s, satisfying: n×Q1>Qe, and 0.1≤(n×Q1-Qe) / (n×Q1)≤0.

7.

2. The battery pack according to claim 1, characterized in that, When n≥2, (n×Q1-Qe) / (n×Q1)≥0.

12.

3. The battery pack according to claim 1, characterized in that, When the mass energy density of the battery is ≥200Wh / kg, n≥2.

4. The battery pack according to claim 1, characterized in that, The frame includes a first frame and a second frame connected to each other. The first frame and the second frame are arranged adjacent to each other. The length of the first frame is greater than the length of the second frame. The pressure relief valve is disposed on the first frame.

5. The battery pack according to claim 4, characterized in that, Along the length of the first frame, the minimum distance between the pressure relief valve and the center line of the first frame is less than or equal to 500 mm.

6. The battery pack according to claim 4, characterized in that, (n×Q1-Qe) / (n×Q1)≥0.

15.

7. The battery pack according to claim 1, characterized in that, The frame includes a first frame and a second frame connected to each other, the length of the first frame being greater than the length of the second frame, and the pressure relief valve includes a first pressure relief valve disposed on the first frame and a second pressure relief valve disposed on the second frame.

8. The battery pack according to claim 7, characterized in that, The distance between the first pressure relief valve and the second pressure relief valve is between 300mm and 2000mm.

9. The battery pack according to claim 7, characterized in that, A cavity is formed within the frame, the cavity including a first cavity formed within the first frame and a second cavity formed within the second frame, the first cavity and the second cavity being connected, and the first cavity being connected to the receiving cavity and the first pressure relief valve, and the second cavity being connected to the receiving cavity and the second pressure relief valve.

10. The battery pack according to claim 9, characterized in that, The width of the cavity is between 15mm and 30mm.

11. The battery pack according to claim 10, characterized in that, The enclosure is provided with a partition plate. Along the direction perpendicular to the bottom plate, the cavity is divided into a first sub-cavity and a second sub-cavity by the partition plate. The pressure relief valve is connected to the first sub-cavity but not connected to the second sub-cavity. The dimension of the first sub-cavity along the direction perpendicular to the bottom plate is larger than the dimension of the second sub-cavity along the direction perpendicular to the bottom plate.

12. The battery pack according to any one of claims 1-9, characterized in that, A first connecting hole is formed on the outer wall of the enclosure at the connection point of the pressure relief valve. The pressure relief valve is at least partially inserted through the first connecting hole and is sealed to the first connecting hole. The area of ​​the first connecting hole is 490 mm². 2 -3847mm 2 between.

13. The battery pack according to any one of claims 1-9, characterized in that, The base plate includes a first plate and a second plate. The first plate is closer to the battery module than the second plate. The battery module is supported on the first plate. An exhaust channel is formed between the first plate and the second plate. The exhaust channel is connected to the pressure relief valve.

14. The battery pack according to claim 13, characterized in that, Along a direction perpendicular to the base plate, the distance between the first plate and the second plate is between 6mm and 12mm.

15. The battery pack according to claim 13, characterized in that, The battery has a first wall on the side facing the first plate, and an explosion-proof valve is provided on the first wall. A connecting portion is provided on the first plate, and the explosion-proof valve at least partially corresponds to the connecting portion along a direction perpendicular to the base plate.

16. The battery pack according to claim 15, characterized in that, Along a direction perpendicular to the base plate, the orthographic projection of the explosion-proof valve falls entirely within the connecting portion.

17. The battery pack according to claim 15, characterized in that, The ratio of the area of ​​the explosion-proof valve to the area of ​​the first wall is between 0.008 and 0.

3.

18. The battery pack according to claim 15, characterized in that, When the battery is a ternary lithium battery, the ratio of the area of ​​the explosion-proof valve to the area of ​​the first wall is between 0.02 and 0.

3.

19. The battery pack according to claim 15, characterized in that, When the thickness of the battery is ≤35mm, (n×Q1-Qe) / (n×Q1)>0.

12.

20. The battery pack according to claim 13, characterized in that, (n×Q1-Qe) / (n×Q1)≤0.

7.

21. The battery pack according to claim 13, characterized in that, (n×Q1-Qe) / (n×Q1)≤0.

5.

22. The battery pack according to any one of claims 1-9, characterized in that, When the thickness of the battery is ≥60mm, (n×Q1-Qe) / (n×Q1)≥0.

17.

23. The battery pack according to any one of claims 1-9, characterized in that, The battery includes a casing, a cell housed within the casing, and an electrolyte. The electrolyte contains additives, including one or more of vinylene carbonate, fluoroethylene carbonate, propylene sulfite, or vinyl sulfite.

24. The battery pack according to any one of claims 1-9, characterized in that, The battery includes a casing, a cell housed within the casing, and an electrolyte, wherein the electrolyte contains lithium bis(fluorosulfonyl)imide (LiFSI) at an addition amount of 0.2 mol / L to 2 mol / L.

25. The battery pack according to claim 24, characterized in that, (n×Q1-Qe) / (n×Q1)≥0.

13.

26. An electrical appliance, characterized in that, Includes the battery pack according to any one of claims 1-25.

Images