Battery pack

Abstract

The application discloses a battery pack. The battery pack comprises a shell assembly formed with a containing cavity, and an electric core module arranged in the containing cavity. The containing cavity is sealed and isolated from the external space of the shell assembly, and the containing cavity is filled with inert gas. The battery pack can improve the protection, heat dissipation and temperature uniformity of the battery pack structure.

Description

Technical Field

[0001] This application relates to the field of power tool technology, and more specifically to a battery pack. Background Technology

[0002] After evolving from manual to fuel-powered systems, most tools widely used in landscaping, construction, and other applications now utilize lithium-ion batteries for power. A key aspect of lithium-ion battery technology is safety, which encompasses both microscopic safety (related to the materials used in the cell's positive and negative electrodes) and macroscopic safety (affecting factors such as heat dissipation, compression, and drops). Improving the overall performance of the battery pack and enhancing its adaptability to harsh working conditions requires a comprehensive consideration of these factors.

[0003] This section provides background information related to this application, which is not necessarily prior art. Utility Model Content

[0004] One object of this application is to solve or at least mitigate some or all of the aforementioned problems. Therefore, one object of this application is to provide a battery pack.

[0005] To achieve the above objectives, this application adopts the following technical solution:

[0006] A battery pack includes: a housing assembly having a receiving cavity; and a cell module disposed within the receiving cavity; wherein the receiving cavity is sealed and isolated from the external space of the housing assembly, and is filled with an inert gas.

[0007] In some embodiments, the housing assembly includes a metal housing, and multiple metal housings are welded together.

[0008] In some embodiments, the housing assembly includes an aluminum alloy housing.

[0009] In some embodiments, the housing assembly includes a metal housing with a heat-dissipating coating on its outer wall.

[0010] In some embodiments, the housing assembly includes a plastic housing with an inner wall covered by a composite metal film.

[0011] In some embodiments, the battery pack further includes an explosion-proof device disposed on the housing assembly.

[0012] In some embodiments, the battery pack further includes an inflation device disposed on the housing assembly.

[0013] In some embodiments, the opening pressure of the explosion-proof device is greater than or equal to 10 kPa.

[0014] In some embodiments, the battery pack further includes a gas circulation device that drives an inert gas to flow within the containment cavity.

[0015] In some embodiments, a desiccant is also provided in the receiving cavity to absorb moisture within the receiving cavity.

[0016] In some embodiments, the desiccant within the containment cavity includes an irreversible desiccant.

[0017] A battery pack includes: a housing assembly having a receiving cavity; and a cell module disposed within the receiving cavity; wherein the receiving cavity is sealed and isolated from the external space of the housing assembly, and the thermal conductivity of the gas within the receiving cavity is greater than or equal to 0.03 W / m·℃.

[0018] In some embodiments, the thermal conductivity of the gas filling the cavity is greater than or equal to 0.03 W / m·℃ and less than or equal to 0.3 W / m·℃.

[0019] A battery pack includes: a housing assembly having a receiving cavity; and a cell module disposed within the receiving cavity; wherein the receiving cavity is sealed and isolated from the external space of the housing assembly, and the molecular weight of the gas inside the receiving cavity is less than the molecular weight of the air outside the receiving cavity.

[0020] In some embodiments, the molecular weight of the gas filling the cavity is less than or equal to 5 g / mol.

[0021] In some embodiments, the gas filling the cavity includes at least one of hydrogen, helium, and neon.

[0022] In some embodiments, a phase change material is also disposed within the cavity.

[0023] In some embodiments, the phase change material within the cavity includes at least one of paraffin and polyethylene glycol.

[0024] In some embodiments, the battery pack is detachably connected to the power tool to power the power tool after installation.

[0025] The advantage of this application lies in the comprehensive improvement of the battery pack's structural protection and heat dissipation performance. Attached Figure Description

[0026] Figure 1 This is a schematic diagram illustrating a battery pack and an electric tool powered by the battery pack according to one embodiment of this application;

[0027] Figure 2 This is a perspective view of a battery pack and its housing assembly and terminal assembly as shown in one embodiment of this application;

[0028] Figure 3 yes Figure 2The diagram shows the battery pack after the casing has been removed, including the cell modules and terminal assemblies.

[0029] Figure 4 yes Figure 2 A cross-sectional view of the battery pack and its housing cavity shown;

[0030] Figure 5 yes Figure 2 A schematic diagram of the terminal assembly of the battery pack shown;

[0031] Figure 6 yes Figure 5 An exploded view of the terminal assembly of the battery pack shown.

[0032] Figure 7 yes Figure 6 A cross-sectional view of the connector of the battery pack terminal assembly;

[0033] Figure 8A This is an embodiment of the present application showing the thermal conductivity of helium under different conditions;

[0034] Figure 8B This is an embodiment of the present application showing the thermal conductivity of neon gas under different conditions;

[0035] Figure 8C This is the thermal conductivity of hydrogen under different conditions, as shown in one embodiment of this application.

[0036] Figure captions: 100, Battery pack; 200, Power tool; 10, Housing assembly; 11, Housing; 12, Receiving cavity; 13, Explosion-proof device; 15, Protective component; 20, Cell module; 21, Cell unit; 22, Cell bracket; 31, Terminal assembly; 311, Metal part; 311a, Limiting part; 311b, Connecting part; 312, Electrode; 313, Terminal base; 314, Connecting base; 314a, Contact layer with housing; 314b, Outer layer; 314c, Intermediate layer. Detailed Implementation

[0037] Before explaining any implementation of this application in detail, it should be understood that this application is not limited to its application to the structural details and component arrangements set forth in the following description or shown in the above drawings.

[0038] In this application, the terms "comprising," "including," "having," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0039] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this application generally indicates that the preceding and following related objects have an "and / or" relationship.

[0040] In this application, the terms "connection," "combination," "coupling," and "installation" can refer to direct connection, combination, coupling, or installation, or indirect connection, combination, coupling, or installation. For example, a direct connection refers to two parts or components being connected together without the need for an intermediary, while an indirect connection refers to two parts or components each being connected to at least one intermediary, with the connection achieved through the intermediary. Furthermore, "connection" and "coupling" are not limited to physical or mechanical connections or couplings, but can also include electrical connections or couplings.

[0041] In this application, those skilled in the art will understand that relative terms (e.g., “about,” “approximately,” “basically,” etc.) used in conjunction with quantities or conditions are to include the values ​​and have the meaning indicated by the context. For example, such relative terms may include at least the degree of error associated with the measurement of a particular value, tolerances associated with the particular value due to manufacturing, assembly, use, etc. Such terms should also be considered as disclosing a range defined by the absolute values ​​of the two endpoints. Relative terms may refer to a certain percentage (e.g., 1%, 5%, 10% or more) of the indicated value. Numerical values ​​not using relative terms should also be disclosed as specific values ​​with tolerances. Furthermore, “basically” when expressing relative angular relationships (e.g., substantially parallel, substantially perpendicular) may refer to a certain degree (e.g., 1 degree, 5 degrees, 10 degrees or more) added to or subtracted from the indicated angle.

[0042] In this application, those skilled in the art will understand that the function performed by a component can be performed by one component, multiple components, one part, or multiple parts. Similarly, the function performed by a part can also be performed by one part, one component, or a combination of multiple parts.

[0043] In this application, the directional terms "upper," "lower," "left," "right," "front," and "rear" are used to describe the orientation and positional relationships shown in the accompanying drawings and should not be construed as limiting the embodiments of this application. Furthermore, in the context, it should be understood that when an element is mentioned as being connected "upper" or "lower" to another element, it can be directly connected to the other element "upper" or "lower," or indirectly connected through an intermediate element. It should also be understood that directional terms such as upper side, lower side, left side, right side, front side, and rear side not only represent positive orientation but can also be understood as lateral orientation. For example, "below" can include directly below, lower left, lower right, lower front, and lower rear.

[0044] In this application, the terms "controller," "processor," "central processing unit," "CPU," and "MCU" are used interchangeably. When using the unit "controller," "processor," "central processing unit," "CPU," or "MCU" to perform a specific function, unless otherwise stated, these functions may be performed by a single or multiple of the aforementioned units.

[0045] In this application, the terms "device," "module," or "unit" are used to describe devices that can be implemented in hardware or software to perform a specific function.

[0046] In this application, the terms “calculation,” “judgment,” “control,” “determine,” “identify,” etc., refer to the operation and process of a computer system or similar electronic computing device (e.g., controller, processor, etc.).

[0047] With the development of lithium battery technology, its application in various industries has become more widespread. A major focus in the design process is safety, which includes both cell-level and battery pack-level safety. This requires improving cell safety performance through improvements in positive and negative electrode materials, as well as battery pack safety performance through improvements in heat dissipation, temperature uniformity, and drop resistance. In general, these factors are interconnected, requiring a comprehensive consideration of multiple aspects to achieve a better overall effect. A key aspect of the optimization process is thermal design. Currently, most battery pack technologies for power tools employ air cooling or natural cooling solutions. This can be achieved by creating ventilation holes on the battery pack casing for natural heat dissipation or by combining air cooling with fans. Some solutions also utilize vapor deposition technology to improve heat dissipation. In other industries, such as electric vehicle battery packs, air cooling or liquid cooling solutions are also commonly used. Traditional solutions have limited effectiveness, while some solutions involving new technologies are complex and costly. Therefore, there is a need to design a battery pack solution that is highly feasible and comprehensively improves related performance.

[0048] The battery pack solution proposed in this application will be described in detail below with reference to specific embodiments and accompanying drawings.

[0049] This application primarily provides a battery pack 100 with improved safety performance, featuring comprehensive improvements in structural protection and heat dissipation. The battery pack 100 can be detached from and connected to a power tool 200, providing power to the power tool 200. Some parameters are designed to meet the operating conditions of the power tool 200. (Reference) Figure 1 The power tool 200 powered by the battery pack 100 of this application can be of various types, including but not limited to... Figure 1The illustrated tools include a ride-on lawnmower 200a, an electric drill 200b, a chainsaw 200c, a lawn mower 200d, a blower 200e, and an all-terrain vehicle 200f. In some embodiments, the power tool 200 powered by the battery pack 100 of this application may include handheld tools, such as a pruning shearer or a circular saw. In some embodiments, the power tool 200 powered by the battery pack 100 of this application may include benchtop tools, such as a miter saw or a metal cutter. In some embodiments, the power tool 200 powered by the battery pack 100 of this application may include push tools or ride-on tools, such as a push lawnmower, a push snowplow, or a ride-on lawnmower or a stand-up lawnmower. In some embodiments, the power tool 200 powered by the battery pack 100 of this application may include outdoor wheeled tools, such as a farm vehicle or a golf cart. In some embodiments, the power tool 200 receiving power from the battery pack 100 of this application may include robotic tools, such as lawnmowers and snowplows. Alternatively, in some embodiments, the power tool 200 may be garden tools, such as pruning machines, hair dryers, lawnmowers, and mowers. In some embodiments, the power tool 200 may be decorating tools, such as screwdrivers, nail guns, glue guns, sanders, and circular saws. In some embodiments, the power tool 200 may be cleaning tools, such as hair dryers, snowplows, and washing machines. In some embodiments, the power tool 200 may be sawing tools, such as reciprocating saws, jigsaws, circular saws, and chainsaws. In some embodiments, the power tool 200 may be fastening tools, such as electric drills, screwdrivers, and hammer drills. In some embodiments, the power tool 200 may be grinding tools, such as angle grinders and sanders. In some embodiments, the power tool 200 may also be other tools, such as lights and fans. It is understandable that, provided that the characteristics are not contradictory, there may be other types of power tools 200 that receive power from the battery pack 100 of this application that have not been shown above. The aforementioned power tools 200 generally have a battery pack 100 mounting part that can be detachably connected to the battery pack 100. The location and specific structure of the battery pack 100 mounting part may differ between different power tools 200, and the structure of different power tools 200 themselves is also different, which will not be elaborated here.

[0050] refer to Figures 2 to 7 The battery pack 100 includes a housing assembly 10 and a cell module 20. The housing assembly 10 forms a receiving cavity 12, and the cell module 20 is disposed in the receiving cavity 12. The receiving cavity 12 is sealed, and the space inside the cavity is isolated from the external space of the housing assembly 10. The sealed receiving cavity 12 is filled with a specific gas, which has a better heat dissipation and temperature equalization effect on the module inside the cavity of the battery pack 100 than air.

[0051] The battery module 20 may include one or more battery cells 21, each capable of storing electrical energy. The specific number of battery cells 21 within the battery pack 100 can be adjusted within a certain range. In some embodiments, the battery cell 21 may be a cylindrical battery, a prismatic battery, or a pouch battery. In some embodiments, the battery cell 21 may be a unitab battery, a bitab battery, or a omnitab battery. In some embodiments, the battery cell 21 may be a lithium iron phosphate cell or a ternary lithium battery. In some embodiments, the battery cell 21 may also be a sodium-ion cell. In some embodiments, the characteristics of the multiple battery cells 21 within the battery pack 100 may be different or partially different.

[0052] In some embodiments, taking a cylindrical battery as an example, the diameter of the cell unit 21 is greater than or equal to 1.8 cm, for example, 1.85 cm, 2.1 cm, or 2.5 cm. In some embodiments, the height of the cell unit 21 is greater than or equal to 60 cm, for example, 65 cm or 70 cm. The cell units 21 are not completely isolated from each other. If some cell units 21 experience thermal runaway during the operation of the battery pack 100, adjacent cell units 21 will be affected, leading to safety accidents such as heat spread, fire, and explosion. Therefore, the importance of heat dissipation and temperature uniformity in the battery pack 100 is evident.

[0053] Following on from the previous text, the key feature of the battery pack 100 in this application is the sealing of the casing and the filling of it with a specific gas. The following text will explain the sealing and gas aspects separately, but it is understandable that these two features work synergistically.

[0054] The housing assembly 10 of the battery pack 100 constitutes the main body of the battery pack 100's exterior. At least one receiving cavity 12 can be formed inside, which is sealed to isolate it from the external space. The housing assembly 10 may include multiple housings 11, which together form the receiving cavity 12. Specifically, the housing assembly 10 may include a main housing and a cover plate. The main housing has a groove, and the cover plate closes the groove of the main housing to form the sealed receiving cavity 12. Ideally, the sealing of the receiving cavity 12 requires that the sealing performance not be compromised during the joining of the separate housing components to prevent air leakage, and that the housing material itself has good resistance to the permeation of small molecule gases. With the overall pack sealed through the housing assembly, the sealing requirements for the circuit board, cell end faces, and connecting pieces can be reduced or eliminated, thereby ensuring battery pack safety in a low-cost and simple manner.

[0055] In some embodiments, the housing assembly 10 includes one or more metal housings 11, which can be welded together to form the sealed receiving cavity 12 described above. That is, a sealed space inside the housing can be formed by welding the closed shells and the gaps between the shells. For example, the main shell and the cover plate can be made of the same metal material to facilitate welding. In some embodiments, the metal housing 11 can be an aluminum alloy shell, or it can be a copper alloy shell, and the average thickness of the metal housing 11 is approximately 1 mm. In some embodiments, when multiple metal housings 11 are welded to form the receiving cavity 12, the welding material and the base material can be the same type of metal material, or at least the welding material at the welding position is the same as the base material. In other embodiments, the housing assembly 10 may also include one or more plastic housings 11, and the inner wall of the plastic housing 11 can be covered with a metal film such as a composite aluminum-plastic film, and the average thickness of the metal film is about 20 μm.

[0056] In some embodiments, a heat dissipation coating is provided on the outer wall of the battery pack 100 housing assembly 10, thereby further improving the heat radiation capability of the metal housing 11 and better exchanging the heat transferred to the housing with the outside air.

[0057] One purpose of this application in using the aforementioned metal casing or plastic casing with an inner aluminum film is to utilize the excellent thermal conductivity of metal and the low permeability of metal. The former can effectively transfer the heat from the inside of the casing to the outside by the gas inside the casing, improving the heat exchange between the inside and outside of the casing, while the latter can ensure the airtightness of the cavity space, preventing the gas inside the casing from leaking or seeping out. In addition, the metal casing also has good structural strength and is not prone to breakage, damage, or disintegration, thereby providing better protection for the battery cell inside the casing.

[0058] In some embodiments, the battery pack 100 further includes an explosion-proof device 13. Specifically, the explosion-proof device 13 may include an explosion-proof valve, which opens when the internal gas pressure exceeds a set upper limit, partially expelling the gas inside the casing to restore or reduce the internal gas pressure, thereby preventing accidents such as explosions. The explosion-proof device 13 is disposed on the casing assembly 10, generally on the upper casing assembly 10 such as a cover plate. In some embodiments, the explosion-proof device 13 may be disposed on the aforementioned metal casing 11. Because the material properties of the explosion-proof device 13 are similar to those of the metal casing 11, it is easier to implement than to install the explosion-proof device 13 on the plastic casing 11, and issues such as installation, sealing, and sensitivity are easier to resolve. In some embodiments, the aforementioned explosion-proof valve may be made of a metal material such as aluminum alloy, and it may also be welded to the metal casing 11. The metal casing 11 may be made of the same metal material as the explosion-proof valve. In some embodiments, the opening pressure of the explosion-proof device 13 is greater than or equal to 10 kPa. That is, if the gas pressure in the sealed cavity 12 exceeds 10 kPa, the explosion-proof device 13 will open to release the gas in the cavity.

[0059] In some embodiments, the battery pack 100 further includes an inflation device disposed on the housing assembly 10. Specifically, an inflation hole can be provided on the housing and used with an air nozzle, rubber stopper, etc., to realize the inflation device without damaging the seal of the space inside the receiving cavity 12. In some embodiments, the inflation device and the explosion-proof device 13 can be integrated into a single device. When using the inflation device to fill or replenish the receiving cavity 12 of the battery pack 100 with an inert gas, small molecule gas, or high thermal conductivity gas (described below), in one alternative embodiment, the inflation device is disposed on the cover plate of the housing assembly 10. The battery pack 100 can be inverted and the receiving cavity 12 can be filled with gas through the inflation device. The filled gas will rise in the cavity, and the non-filled gas will sink. Once the overflow gas is detected to be of the type of filled gas, the gas filling or replenishment is completed.

[0060] In some embodiments, the housing assembly 10 further includes a protective member 15, which can be installed in locations where the battery pack 100 is prone to impact damage or is near critical components when dropped. Specifically, the protective member 15 can be installed on the edges or corners of the battery pack 100 housing, and can be provided only on the outer wall or inner wall of the housing, or on both the inner and outer walls of the housing. The material of the protective member 15 can be composite soft rubber, etc., and the protective member 15 can be injection molded onto the housing. In some embodiments, the above-mentioned protective member 15 is installed near the edges and / or corners of the metal housing 11 to improve the structural strength of the housing assembly 10 while providing cushioning, further enhancing the protection of the battery pack 100.

[0061] Following the preceding text, the cell module 20 may further include a cell support 22 outside the cell unit 21. The cell support 22 can support at least part of the cell module 20 or cell unit 21, and can also protect and limit the cell module 20 or cell unit 21. In some embodiments, compared with existing solutions, by utilizing the good thermal conductivity of the gas in the receiving cavity 12 of the battery pack 100, the maximum distance between the cell support 22 and the housing assembly 10 can be reduced to a certain extent.

[0062] The battery pack 100 also includes a terminal assembly 31, which includes at least a power terminal and a communication terminal. The power terminal includes a positive terminal and a negative terminal, capable of interfacing with terminals on an electrical device such as a power tool 200 for power transmission between them. The communication terminal also interfacing with terminals on the same device for data transmission. To enable power and data transmission between the battery pack 100 and external devices such as the power tool 200, the terminal assembly 31 is partially located outside the housing assembly 10 and partially located inside the housing assembly 10. In the case where the battery pack 100 requires the housing assembly 10 to be sealed, the terminal assembly 31 must be stably mounted on the housing assembly 10 without compromising the sealing of the housing cavity 12. In other words, the portion of the terminal assembly 31 located outside the housing cavity 12 of the housing assembly 10 is sealed to the housing assembly 10. In some embodiments, the terminal assembly 31 includes a connecting body and the aforementioned terminals electrically connected to an external device, both of which are at least partially located outside the housing 11. The connecting body can support the aforementioned terminals and fix them to the housing 11. Wherein, if the contact portion between the connecting body and the terminal is made of metal, it needs to be insulated; if the contact portion between the connecting body and the housing 11 is made of metal, they can be welded together. Furthermore, after fixing the connecting body and the terminals to the housing 11 by welding, injection molding can be used to strengthen the support, fixation, and gap sealing between the housing 11, the terminals, and the connecting body.

[0063] like Figures 5 to 7 As shown, in some embodiments, the charging and discharging current of the cell module 20 inside the battery pack 100 cavity, as well as the data signals of the controller, communication module, etc. on the circuit board, can be led out through a metal part 311 penetrating the housing 11. The metal part 311 is made of conductive material such as copper, and its main body can be rod-shaped, for example, it can be a terminal post leading out of the housing. One end of the metal part 311 inside the housing 11 cavity 12 can have a limiting part 311a. The limiting part 311a can be connected to the cell connecting piece and other components of the cell module 20 inside the cavity, and the cross section of the limiting part along the axial direction is larger than the cross section of the main body to prevent the terminal assembly 31 from detaching from the housing 11 during the insertion and removal process. The other end of the metal part 311 outside the cavity is a connecting part 311b connected to the electrode 312. The metal part 311 combined with the connected electrode 312 can form the battery pack terminal. In addition, a terminal seat 313 for guiding the insertion and removal of the terminal is generally provided outside the terminal electrode 312, which can be made of plastic.

[0064] The terminal assembly 31 also includes a connector 314, which has a through hole through which metal parts such as poles can pass. The gap between the pole and the through hole can be filled by components such as rubber rings, bushings, and gaskets to maintain a seal and to insulate the connector 314, which is made of a portion of metal material. The connector 314 or a portion of the connector 314 can be made of metal material and can be welded to the metal housing 11, which can be made of the same metal material or a different metal material, to fix the terminal assembly 31 on the housing assembly 10 and keep the receiving cavity 13 sealed. In some embodiments, the connector 314 can be flat and have a multi-layer structure. The outermost layer 314a that is in contact with the housing 11 can be made of metal material, and the outermost layer 314b can be made of insulating material. Further, an intermediate layer 314c made of insulating and flame-retardant material can also be provided. In addition, a similar layered structure can also be provided inside the cavity. The pole can penetrate the above-mentioned multiple layers and the sealing of the receiving cavity 12 and the insulation between the pole and the metal material layers of the connector 314 can be maintained by components such as bushings fitted on the pole.

[0065] In some embodiments, the battery pack 100 also includes MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) devices. These MOSFET devices can assist in the safe monitoring of charging and discharging of the battery pack 100. For example, in discharge mode, the MOSFET devices can identify the connection of electrical equipment such as the power tool 200. If the device is identified, the battery pack 100 is allowed to discharge; otherwise, it is prohibited. During device operation, the MOSFET devices also generate heat, which may exacerbate the heat dissipation problem of the battery pack 100. Therefore, many battery packs 100 in the current related technologies do not include MOSFET devices with the aforementioned functions. However, the battery pack 100 of this application can effectively improve the heat dissipation and temperature uniformity of the battery pack 100 by sealing the metal housing 11 with a specific gas, making it possible to install MOSFET devices. In some embodiments, the MOSFET devices can be arranged close to the metal housing 11, thereby making the metal housing 11 equivalent to a large heat sink. In some embodiments, a heat dissipation coating can also be provided on the outer wall of the metal housing 11, such as an aluminum shell, to enhance heat radiation. Similarly, other power components that generate a lot of heat within the battery pack 100 can also be placed close to the metal casing 11 of the battery pack 100, but attention should be paid to the insulation between the two.

[0066] As mentioned above, this application fills the housing cavity 12 with gas, which reduces the overall weight of the package compared to some liquid cooling solutions, and is similar in weight to some conventional solutions.

[0067] The sealed cavity 12 is filled with a specific gas. This specific gas is used to equalize the temperature of each cell unit 21 in the cell module 20 within the cavity and to transfer heat from various locations within the cavity to the housing assembly 10 and then to the outside of the housing. In this application, the gas filled in the sealed cavity 12 may, in one case, be an inert gas with stable chemical properties, unlikely to react chemically with other substances within the cavity, and thus posing no threat to the safety of the cell units 21. It is understood that the inert gas required in the cavity 12 does not include some highly reactive isotopes or synthetic gases. In some embodiments, the inert gas filled in the sealed cavity 12 includes at least one of helium and neon, that is, it may be helium, neon, or a mixture of helium and neon, or it may be further mixed with other types of inert gases.

[0068] In this application, the gas filling the sealed cavity can, in another case, be a gas with a molecular weight smaller than that of the air outside the cavity. The thermal conductivity of a gas is negatively correlated with its molecular weight; the gas with a smaller molecular weight inside the cavity has better thermal conductivity than air, thus better serving the heat dissipation and temperature equalization of the components such as the battery cell unit 21 inside the cavity. The molecular weight of air is generally considered to be about 29, that is, the molecular weight of the gas inside the battery pack 100 casing cavity is less than 29, but it is not excluded that the molecular weight of air as a mixed gas may be higher or lower than 29 depending on the composition. In some embodiments, the gas can be at least one of hydrogen, helium, and neon, wherein the molecular weight of hydrogen is 2, the molecular weight of helium is 4, and the molecular weight of neon is 20. That is, the gas can be hydrogen, helium, or neon, or a mixture of any two of hydrogen, helium, and neon, or a mixture of all three, or other types of gases can be mixed in. In some embodiments, the gas filling the sealed cavity 12 has a molecular weight of less than or equal to 5. For example, it can be at least one of hydrogen and neon, or the proportions of hydrogen, helium, and neon in the mixed gas can be adjusted.

[0069] It should be noted that the molecular weights mentioned above refer to molecular mass, which is the sum of the atomic weights of all the atoms that make up the gas molecule. When there are no units, this is a relative molecular weight; the value remains the same when converted to absolute molecular weight. The unit is g / mol. For example, the molecular weight of the gas filling the sealed cavity 12 is less than or equal to 5 g / mol. Furthermore, the molecular weights of the gases mentioned above are all expressed as integers. Of course, more precise methods can also be used; for example, the molecular weight of hydrogen can be recorded as 2.016, and the molecular weight of air can be recorded as 28.959.

[0070] In another instance, the gas filling the sealed cavity in this application can be a gas with high thermal conductivity, having a thermal conductivity greater than or equal to 0.03 W / m·℃, while the thermal conductivity of air at room temperature and pressure is approximately 0.025 W / m·℃. Optionally, in some embodiments, the gas filling the receiving cavity 12 of the battery pack 100 has a thermal conductivity greater than or equal to 0.03 W / m·℃ and less than or equal to 0.3 W / m·℃. In some embodiments, the thermal conductivity of the gas filling the sealed cavity is greater than or equal to 0.04 W / m·℃ and less than or equal to 0.10 W / m·℃. In some embodiments, the thermal conductivity of the gas filling the sealed cavity is greater than or equal to 0.04 W / m·℃ and less than or equal to 0.08 W / m·℃. In some embodiments, the thermal conductivity of the gas filling the sealed cavity is greater than or equal to 0.10 W / m·℃ and less than or equal to 0.20 W / m·℃. In some embodiments, the thermal conductivity of the gas filling the sealed cavity is greater than or equal to 0.15 W / m·℃ and less than or equal to 0.25 W / m·℃. In some embodiments, the gas can be at least one of hydrogen, helium, and neon, wherein the thermal conductivity of hydrogen at room temperature and pressure is approximately 0.18 W / m·℃, the thermal conductivity of helium at room temperature and pressure is approximately 0.15 W / m·℃, and the thermal conductivity of neon at room temperature and pressure is approximately 0.048 W / m·℃. The gas can be hydrogen, helium, neon, or a mixture of any two of hydrogen, helium, and neon, or a mixture of all three, or other types of gases can be mixed in.

[0071] It is understandable that, influenced by the external environment and the operating conditions of the power tool 200, the actual temperature of the battery pack 100 is not constant. Since the pressure of a given mass of gas, with a constant volume, is positively correlated with its temperature, the gas pre-filled in the sealed cavity 12 of the battery pack 100 naturally corresponds to a pressure variation range within a temperature variation range. Relevant data can be obtained by querying or calculating based on the volume of the sealed cavity 12 of the battery pack 100, the composition of the filled gas, and the temperature of the battery pack 100. Refer to Table 1 below. Figures 8A to 8C , Figures 8A to 8C The thermal conductivity of helium, hydrogen, and neon under different conditions is shown. Taking helium as an example, under isochoric conditions, the thermal conductivity of the gas inside the cavity is approximately 0.138 W / m·℃ to 0.167 W / m·℃ in the range of -20℃ to 60℃. Taking neon as an example, under isochoric conditions, the thermal conductivity of the gas inside the cavity is approximately 0.043 W / m·℃ to 0.053 W / m·℃ in the range of -20℃ to 60℃. Taking hydrogen as an example, under isochoric conditions, the thermal conductivity of the gas inside the cavity is approximately 0.163 W / m·℃ to 0.203 W / m·℃ in the range of -20℃ to 60℃.

[0072]

[0073] Table 1

[0074] In one embodiment, the gas filled in the sealed cavity in this application includes hydrogen. Hydrogen is a commonly used gas in industry and has good thermal conductivity. It is lightweight and a reducing gas that is not prone to oxidation. At the same time, hydrogen has good arc-quenching ability and can improve the insulation condition in the cavity 12. Filling the sealed cavity 12 of the battery pack 100 in this application with hydrogen or a mixture of hydrogen is an excellent choice.

[0075] In some embodiments, the battery pack 100 further includes a gas circulation device. Specifically, the gas circulation device or at least a portion of the gas circulation device may be disposed within the aforementioned receiving cavity 12. The device may include a fan and airflow guiding structures, which can drive the gas (inert gas, low molecular weight gas or high thermal conductivity gas) described above to flow within the sealed receiving cavity 12, thereby further enhancing the heat dissipation and temperature equalization effect of the gas in the cavity on components such as the cell unit 21.

[0076] In some embodiments, a desiccant is also provided in the sealed receiving cavity 12 of the battery pack 100 to adsorb moisture inside the cavity and keep the sealed space inside the cavity dry. In some embodiments, the desiccant may be an irreversible desiccant or at least partially an irreversible desiccant to prevent repeated vaporization-liquefaction processes inside the cavity.

[0077] In some embodiments, the polar end face, electrical connection piece, circuit board or other electrical connection of the cell unit 21 inside the battery pack 100 can be further sealed with sealant or other sealing treatments. That is, on the basis of sealing the outer shell, the key modules inside are further sealed to further ensure the waterproof, insulation and other safety performance of the battery pack 100.

[0078] In some embodiments, a phase change material is further disposed within the sealed cavity 12 of the battery pack 100. This phase change material can contact at least a portion of the cell module 20 or cell unit 21. For example, it can fill the space between the housing assembly 10 and the cell support 22, or it can be disposed in other locations. The phase change material within the cavity can absorb latent heat through its own change in state to improve the heat dissipation and temperature uniformity of the battery pack 100. One problem in related technologies is avoiding leakage after the phase change material undergoes a state change. The sealed cavity 12 of the battery pack 100 in this application precisely addresses this problem. Combining the phase change material with the battery pack 100 solution in this application can further improve the heat dissipation and temperature uniformity of the battery pack 100. In some embodiments, the aforementioned phase change material may include at least one of graphite and polyethylene glycol.

[0079] The foregoing has shown and described the basic principles, main features, and advantages of this application. Those skilled in the art should understand that the above embodiments do not limit this application in any way, and all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of this application.

Claims

1. A battery pack, comprising: The housing assembly has a receiving cavity; The battery cell module is disposed within the receiving cavity; The feature is that the receiving cavity is sealed and isolated from the external space of the housing assembly, and the receiving cavity is filled with inert gas.

2. The battery pack according to claim 1, characterized in that, The housing assembly includes a metal housing, and multiple metal housings are welded together.

3. The battery pack according to claim 2, characterized in that, The housing assembly includes an aluminum alloy housing.

4. The battery pack according to claim 1, characterized in that, The housing assembly includes a metal housing with a heat dissipation coating on its outer wall, and / or the housing assembly includes a plastic housing with a composite metal film attached to its inner wall.

5. The battery pack according to claim 1, characterized in that, The battery pack also includes an explosion-proof device, which is disposed on the housing assembly; the opening pressure of the explosion-proof device is greater than or equal to 10 kPa.

6. The battery pack according to claim 1, characterized in that, The battery pack also includes a gas circulation device that drives the inert gas to flow within the containment cavity.

7. The battery pack according to claim 1, characterized in that, The cavity is also equipped with a desiccant to absorb moisture within it.

8. A battery pack, comprising: The housing assembly has a receiving cavity; The battery cell module is disposed within the receiving cavity; The feature is that the receiving cavity is sealed and isolated from the external space of the housing assembly, and the thermal conductivity of the gas in the receiving cavity is greater than or equal to 0.03 W / m·℃.

9. A battery pack, comprising: The housing assembly has a receiving cavity; The battery cell module is disposed within the receiving cavity; The feature is that the receiving cavity is sealed and isolated from the external space of the housing assembly, and the molecular weight of the gas inside the receiving cavity is less than the molecular weight of the air outside the receiving cavity.

10. The battery pack according to claim 9, characterized in that, The molecular weight of the gas filling the cavity is less than or equal to 5 g / mol.

11. The battery pack according to claim 9, characterized in that, The gas filling the cavity includes at least one of hydrogen, helium, and neon.

12. The battery pack according to claim 9, characterized in that, The cavity contains a phase change material.

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