Patent Application
20160218336
The present disclosure relates generally to battery packaging arrangements, and more particularly to the consideration of one or more battery cells experiencing a thermal runaway condition.
Mobile and portable electronic products rely on a battery as a power source. The battery includes one or more battery cells assembled in a package that allows the battery cells to be recharged, and typically allows the battery to be removed from a device it is used to power. The battery plays a critical role in the form factor, size and weight of these electronic products.
The use of lithium ion batteries has grown in popularity due to advantages over other cell technologies such as high energy density and low rate of self-discharge. The high energy density allows lithium ion cells to be used in a variety of different applications ranging from portable electronic radios to electric vehicles while minimizing the overall weight and size of the system (device and battery) compared to more mature battery chemistries such as nickel-based rechargeable batteries (e.g. nickel-cadmium, nickel metal hydride).
Product designs incorporating lithium ion cells should take into account robustness and safe current, voltage, and temperature operating limits. As lithium ion cells continue to increase in energy density, upon a failure of a battery cell, there is a corresponding increase in the release of energy, at high temperatures, of battery cell material upon a catastrophic failure. The newer, higher energy density cells increase the potential danger of such a thermal runaway event. Thermal runaway refers to a situation where an increase in temperature changes the conditions in a way that causes a further increase in temperature, often leading to a destructive result. Thermal runaway of a single lithium ion cell can lead to a cascade of catastrophic cell failures in multi-cell packs.
Accordingly, it would be desirable to have an improved battery pack design which addresses the above issues while minimizing the impact on battery pack size and weight.
The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views, together with the detailed description below, are incorporated in and form part of the specification, and serve to further illustrate embodiments of concepts that include the claimed invention, and explain various principles and advantages of those embodiments.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.
Embodiments exemplified by the following discussion include a battery pack that is thermally protected against battery cell faults that cause thermal venting which can affect other battery components, including inducing similar faults in adjacent battery cells in some embodiments. The battery pack includes at least one battery cell having a pressure vent that is disposed in a barrier structure formed around at least one battery cell. The barrier structure is comprised of a thermally resistant material, and forms a vent channel in proximity to the pressure vent of the at least one battery cell. The battery pack further includes a housing in which at least one battery and barrier structure are disposed. The housing includes a housing wall that is configured to form a flow channel between the housing wall and the barrier structure from the vent channel of the barrier structure to a housing vent formed in the housing wall.
In a typical prior art battery pack, the battery cells are connected in series, anode to cathode, or in parallel combinations, and use identical cell geometries. As a result, the pressure vent of a given battery cell can be in close proximity to the container of the next battery cell in the series of battery cells. As a result, if a battery cell in a conventional arrangement vents, it can vent hot gas and material directly onto an adjacent battery cell, potentially cause that battery cell to likewise fail, leading to a thermal runaway condition of the battery.
The barrier structure 214 is assembled into a housing that has a housing wall 216. The housing wall 216 separates the inside of the housing from the outside of the housing, and is configured to form a flow channel 218, 220, respectively, between the housing wall 216 and the barrier structure 214 from the vent channel 207, 213 of the barrier structure 214 to a housing vent 222, 224 formed in the housing wall. Thus there is a separation 217, 219 between the housing wall 216 and the barrier structure 214. Upon a battery cell 202, 204 experiencing a fault condition and venting, the hot material will escape through the pressure vent 206 or 208 into a respective vent channel 207, 213, and continue along the respective contiguous flow channel 218, 220 in the direction of respective arrows 226, 228, where the volume of the flow channels 218, 220 allows relief of the pressure. Furthermore, the vented material can further escape out of the battery pack entirely through a respective housing vent 222, 224, as indicated by respective arrows 230, 232. The housing vents can simply be openings in the housing wall 216, or they can be mechanical sealed vent mechanisms that open upon pressure in the respective flow channel 218, 220 exceeding a pressure threshold (which is lower than the pressure threshold of the battery cell pressure vents 206, 208). In some embodiments the housing vents 222, 224 can be covered with a label on the outside of the housing wall 216 that obscures the housing vents 222, 224 from view. The volume of the flow channel allows expansion of the vented material, thereby cooling the vented material. Accordingly, the housing wall material does not necessarily have to withstand the same temperatures that can be withstood by the barrier structure, but in some embodiments the housing wall 216 can be formed with thermal barriers or shields in the area of the pressure vents 206, 208.
It will be appreciated by those skilled in the art that, as shown here in
As can be seen, the battery cells 308, 310 are physically isolated from each other. They will be electrically connected together, either in series or in parallel inside the battery pack 300 to provide voltage and current at battery contacts of the battery pack 300, as is known in the art. The barrier structure acts as both a thermal and electrical insulator, and can be formed in a variety of ways, including molding, machining, or assembly of parts.
The housing wall 414 is configured to be spaced away from the sides 444, 446 of the barrier structure 416, forming flow channels 418, 420 that are contiguous with vent channels 422, 424. Gasses and other materials that get vented out of the battery cells 402, 404, 406, 408, 410, 412 in the event of a fault expand into the vent and flow channels 418, 420, 422, 424, and can exit out of housing ports 448, 450. The housing is further configured to include a plurality of baffle walls 438 in the flow channels 418, 420. The baffle walls 438 alternate sides of the flow channels 418, 420 along the lengths of the flow channels 418, 420, and extend part-way across the flow channels 418, 420. The baffle walls 438 act to slow the escape of gasses out of the battery pack 400, and block solid material ejected from a venting battery cell so as to prevent solid matter from leaving the battery pack or potentially block a housing port 448, 450.
The embodiments provide the benefit of preventing a cascade or thermal runaway failure in a battery pack upon a fault condition occurring in one battery cell. Furthermore, in single cell embodiments, the use of a flow channel to allow expansion of venting gasses before they exit the battery pack in a directed manner can reduce the temperature of the venting gasses, therefore reduce the risk damage to nearby objects or injury to users.
In the foregoing specification, specific embodiments have been described. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present teachings.
The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims. The invention is defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims as issued.
Moreover in this document, relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” “has”, “having,” “includes”, “including,” “contains”, “containing” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises, has, includes, contains a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by “comprises . . . a”, “has . . . a”, “includes . . . a”, “contains . . . a” does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises, has, includes, contains the element. The terms “a” and “an” are defined as one or more unless explicitly stated otherwise herein. The terms “substantially”, “essentially”, “approximately”, “about” or any other version thereof, are defined as being close to as understood by one of ordinary skill in the art, and in one non-limiting embodiment the term is defined to be within 10%, in another embodiment within 5%, in another embodiment within 1% and in another embodiment within 0.5%. The term “coupled” as used herein is defined as connected, although not necessarily directly and not necessarily mechanically. A device or structure that is “configured” in a certain way is configured in at least that way, but may also be configured in ways that are not listed.
The Abstract of the Disclosure is provided to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, it can be seen that various features are grouped together in various embodiments for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separately claimed subject matter.
