Patent ID: 12199253

In the drawings, reference numbers may be reused to identify similar and/or identical elements.

DETAILED DESCRIPTION

Typically, thermal runaway propagation is prevented by employing barriers formed using thick layers of aerogel insulation. The aerogel insulation is not only expensive but the thickness of the aerogel insulation layers precludes the use of the barriers between every battery cell. Accordingly, the barriers are placed between two battery cells after every Nthbattery cell, where N is an integer typically greater than 3, which is insufficient to completely prevent thermal runaway propagation. A metallic heat sink/heat transfer plate is arranged adjacent to the barriers, which is relatively less effective for removing heat.

The present disclosure provides a heat removal system that prevents thermal runaway propagation using more compact and efficient material than aerogel insulation. The heat removal system provides both insulating and conducting properties. Specifically, the heat removal system prevents heat transfer between the battery cells by providing insulation between the battery cells. Additionally, the heat removal system conducts heat from the battery cells and transfers the conducted heat to a cooling plate attached to the heat removal system.

The heat removal system uses a stack of multiple thin conductive sheets placed between the battery cells. As explained below in detail, a thermal contact resistance provided by the stack between the battery cells provides a highly effective insulator in a through-plane direction (i.e., across the thickness of the stack and between the battery cells) while maintaining high in-plane conductivity (i.e., in a plane parallel to the length of the stack and parallel to the height of the battery cells). The thermal insulating properties are provided by the contact resistance across the thickness of the stack.

The contact resistance is created by stacking multiple sheets of a conducting material. When enough number of the conductive sheets are stacked, the sum of all the contact resistances becomes very high, simulating a highly effective insulator. However, because the sheets are highly conductive, the stack of the sheets still carries a significant amount of heat in the in-plane direction from the battery cell to the cooling plate. Furthermore, as explained below, the stack is constructed such that the stack has a relatively high contact resistance between the battery cells and a relatively low contact resistance where the stack is joined with the cooling plate/heat sink.

By using the stack of thin sheets, the heat removal system occupies a smaller area relative to the barriers formed using thick layers of aerogel insulation. The material used to form the heat removal system is less expensive than the aerogel insulation. Thus, the heat removal system provides better protection for neighboring battery cells against thermal runaway propagation relative to the barriers formed using thick layers of aerogel insulation.

More specifically, the heat removal system comprises a thermal barrier formed using a stack of thin sheets made of a highly conductive material. Non-limiting examples of the conductive material include metals, alloys, composites, and any combination thereof. First portions of the conductive sheets are stacked between the battery cells and have a relatively high surface roughness to increase a contact resistance between the conductive sheets. Second portions of the conductive sheets are stacked and connected to a heat sink and have a relatively low surface roughness to decrease the contact resistance between the conductive sheets. For example, the conductive sheets may be creased/wrinkled to reduce the contact area (i.e., to increase contact resistance) between the conductive sheets in the first portions when the conductive sheets are compressed between the battery cells. In the second portions, the contact area increases (i.e., contact resistance decreases) between the conductive sheets due to higher compression used between the heat sink and the cells than between the battery cells.

Optionally, the first portions of the conductive sheets may be coated with a thin thermally insulating layer. For example, the insulating layer may include an anodized coating. Alternatively, insulating sheets of a thermally insulating material may be placed in between the first portions of the conductive sheets at any interval. The insulating sheets may include a solid pattern or a pattern with holes.

The conductive sheets are made to conduct heat away from a first mass (e.g., a first battery cell) to a second mass (e.g., a heat sink or a cooling plate), while protecting a third mass (e.g., a second battery cell adjacent to the first battery cell) from heat generated by the first mass. The conductive sheets are compressed tightly together where the conductive sheets contact the second mass to promote heat transfer. Alternatively, the conductive sheets are welded together where the conductive sheets join the second mass to promote heat transfer. The conductive sheets may use a conductive paste where the conductive sheets are joined together with the second mass to promote heat transfer through the thickness of the conductive sheets at the location of the joint. The conductive sheets may be staggered where the conductive sheets join the second mass to promote heat transfer so that a portion of each conductive sheet contacts the second mass. The conductive sheets may be made up of multiple types of materials. Surface treatments can also be applied to the various portions of each individual conductive sheet. These and other features of the heat removal system of the present disclosure are described below in detail.

Throughout the present disclosure, a battery system is used only as an example to illustrate an application of the heat removal system. The heat removal system of the present disclosure can be used in any application where heat generated by one mass can adversely affect a neighboring mass, which in turn can cause a domino effect in other neighboring masses. The heat removal system of the present disclosure can be used to prevent similar heat propagation in any application.

FIGS.1A and1Bshow examples of a heat removal system100according to the present disclosure. InFIG.1A, a side cross-sectional view of the heat removal system100is shown. For example, the heat removal system100is installed in a battery module of which only two battery cells, a first battery cell102and a second battery cell104, are shown for illustrative purposes. Hereinafter, for convenience, the first and second battery cells102,104are simply called the cells102,104; and it is understood that the cells102,104are located in a battery module of a battery pack.

Suppose that the cell102is experiencing thermal runaway, and the cell104that is neighboring or adjacent to the cell102is functioning normally (i.e., the cell104is not generating an abnormal amount of heat). The heat removal system100conducts heat from the cell102and transfers the conducted heat to a heating sink (or a cooling plate)106. The heat removal system100prevents the heat from the cell102from flowing to the neighboring cell104and causing thermal runaway.

The heat removal system100comprises a plurality of sheets108-1,108-2,108-3, and108-4(collectively the sheets108) made of a thermally conductive material. Only four sheets108are shown for example only. Fewer or more than four sheets108can be used instead. The sheets108are made of a highly thermally conductive material. For example, the sheets108can be made of a metal or an alloy. Alternatively, the sheets can be made of a composite material. In some examples, one set of the sheets108can be made of a first conductive material (e.g., a metal), and another set of the sheets108can be made of a second conductive material (e.g., a composite material).

In some examples, at least one of the sheets108closest to the cell102(e.g., sheet108-1, or sheets108-1and108-2) can be made of a first conductive material, and the remaining sheets108can be made of a second conductive material having a higher thermal conductivity than the first conductive material. Many other permutations and combinations of conductive materials can be used to make the sheets108.

The sheets108are stacked together and are disposed between the two adjacent cells102,106. The sheets108include two portions: a first portion110of the sheets108is compressed between the cells102,104; and a second portion112of the sheets108is disposed and compressed between the heat sink106and the top of the cell102as shown. The first portion110of the sheets108extends from the bottom of the cells102,104to the top of the cells102,104. The first portion110of the sheets108is compressed between the cells102,104. The second portion112of the sheets108extends beyond the first portion110and is folded at about right angle over the top of the cell102as shown at111.

The first and second portions110,112are continuous; that is, the sheets108in the first and second portions110,112are simply folded to form the first and second portions110,112but are otherwise continuous. Alternatively, the first and second portions110,112can be two separate portions of the sheets108that are joined together at111. The first and second portions110,112of the sheets108are designated as such so that the different properties and structural details of the sheets108in the first and second portions110,112can be described by conveniently referencing the two portions.

The heat sink106, which includes a cooling plate, compresses the second portion112of the sheets108between the heat sink106and the top of the cell102(and may be another cell neighboring the cell102on the opposite side of the cell104, not shown). The heat sink106compresses the second portion112of the sheets108with a much greater force than the force with which the first portion110of the sheets108is compressed between the cells102,104. Alternatively, as shown inFIG.1B, the heat sink106may include two layers106-1and106-2, and the second portion112of the sheets108is compressed between the two layers106-1and106-2of the heat sink106. Note that the heat sink106can include a cooling or heating plate in a battery pack. Alternatively, a portion of the battery pack can serve as the heat sink106. Further, neighboring cells can also serve as the heat sink106.

InFIG.1A, in the first portion110, the sheets108provide a thermal contact resistance in a through-plane direction120(i.e., along a plane extending across the thickness of the sheets108in the first portion110between the cells102,104). The contact resistances of the sheets108connect in series. Depending on the number of the sheets108stacked and compressed together, a sum of all of the contact resistances of the sheets108in the first portion110becomes very high in proportion to the number of sheets108used. As a result, the first portion110of the sheets108functions like a highly effective thermal insulator that prevents heat from the cell102from transferring to the cell104. The insulating effect of the first portion110of the sheets108can be enhanced further by coating the sheets108in the first portion110with an insulating material or by using layers of an insulating material between the sheets108in the first portion110of the sheets108as described below in detail.

While the first portion110of the sheets108functions as a highly effective thermal insulator between the cells102,104, the sheets108themselves are made of a highly conductive material. Therefore, the sheets108maintain high conductivity in an in-plane direction122(i.e., in a plane parallel to the length of the stack of the sheets108and parallel to the height of the cells102,104). In general, the through-plane direction120can be called a horizontal direction, and the in-plane direction122, which is perpendicular to the through-plane direction120, can be called a vertical direction. The first portion110of the stack functions as a thermal insulator across a thickness of the first portion110of the stack (i.e., in the horizontal direction) and as a thermal conductor in a direction perpendicular to the thickness of the first portion110of the stack (i.e., in the vertical direction).

Further, the second portion112of the sheets108does not include any insulating coating or insulating material between the sheets108. Instead, the sheets108in the second portion112are connected to the heat sink106in one or more ways described below to reduce contact resistance between the sheets108in the second portion112and to enhance heat transfer between the sheets108in the second portion112and the heat sink106. Accordingly, the sheets108provide a lower thermal contact resistance in the second portion112of the stack than in the first portion110of the stack. The heat conducted from the cell102by the sheets108in the first portion110is readily transferred from the sheets108in the second portion112to the heat sink106.

Optionally, the sheets108may be coated with an insulating material. For example, the sheets108may be coated with the insulating material or a material that can increase the contact resistance of the sheets108only in the first portion110of the stack. The sheets108in the second portion112of the stack are not coated with the insulating material. Alternatively, a plurality of layers114-1,114-2, and114-3(collectively the layers114) of an insulating material can be disposed between the sheets108in the first portion110. The layers114are not disposed between the sheets108in the second portion112. The sheets108in the second portion112of the stack may be coated with materials that reduce contact resistance of the sheets108in the second portion112of the stack.

The presence of the insulating material (coating or the layers114) in the first portion110of the sheets108further increases the contact resistance of the sheets108in the first portion110, which in turn prevents heat transfer from the cell102to the cell104. The absence of the insulating material (coating or the layers114) in the second portion112of the sheets108and optional use of a coating that reduces contact resistance of the sheets108in the second portion112allow heat conducted by the sheets108from the cell102to be readily transferred to the heat sink106. Note that while the layers114are shown between every pair of the sheets108in the first portion110, the layers114can be disposed in any other manner. The coating and the layers114are shown and described in further detail with reference toFIGS.4and5.

FIG.2is similar toFIG.1Aexcept thatFIG.2shows an additional heat sink130at the bottom of the cells102(Cell1),104(Cell2). The heat sink130is parallel to the heat sink106, both of which are parallel to the through-plane direction120. InFIG.2, the sheets108include a third portion132that is structurally similar to the second portion112in all respects. Therefore, the third portion132of the sheets108is not described in further detail for brevity. The third portion132transfers heat conducted by the first portion110of the sheets108from the cell102to the heat sink130in the same manner as the second portion112of the sheets108transfers the heat conducted by the first portion110of the sheets108from the cell102to the heat sink106as described above. Note that as shown inFIG.1B, the heat sink130may also include two layers, and the third portion132can be compressed between the two layers of the heat sink130. Further, the heat sink130can also include a cooling or heating plate in a battery pack. Alternatively, a portion of the battery pack can serve as the heat sink130. Further, neighboring cells can also serve as the heat sink130.

FIGS.3A and3Bshow different ways in which the sheets108in the second portion112can be connected to each other and to the heat sink106. InFIGS.3A and3B, partial side cross-sectional views of the heat removal system100are shown without the cells102,104. The cells102,104are omitted to focus on the different ways in which the sheets108in the second portion112can be connected to each other and to the heat sink106.

Note that the sheets108in the third portion132(shown inFIG.2) can be connected to each other and to the heat sink130(shown inFIG.2) in the same manner. InFIGS.3A and3B, the layers114are shown for completeness. The layers114can be arranged differently or omitted altogether as already described above. Further, the description of other features such as surface treatment and surface roughness of the sheets108in the first and second portions110,112provided elsewhere applies equally to the elements shown and described below with reference toFIGS.3A and3B.

InFIG.3A, in the second portion112, the sheets108are arranged in a staggered manner as shown. In the staggered or staircase-like arrangement shown, at least a portion of each of the sheets108in the second portion112is connected to the heat sink106. In addition, all of the sheets108in the second portion112contact each other. As already described above, the sheets108in the second portion112are neither coated with nor separated by any insulating material. Instead, as described below, the sheets108in the second portion112may have a surface roughness less than that of the sheets108in the first portion110. As a result, the contact resistance of the sheets108in the second portion112is much less than the contact resistance of the sheets108in the first portion110. The layered manner of arranging the sheets108shortens the path for heat transfer in the through-plane direction120for more of the sheets108in the second portion112. Therefore, the sheets108in the second portion112readily transfer the heat, which is conducted from the cell102by the sheets108in the first portion110, to the heat sink106.

Further, a thermally conductive paste may be used between the heat sink106and the portions of the sheets108in the second portion112that contact the heat sink106. The thermally conductive paste further enhances the heat transfer from the sheets108in the second portion112to the heat sink106.

InFIG.3B, the sheets108in the second portion112are joined (e.g., welded) together as shown at134. The joint134, that is the location where the sheets108in the second portion112are joined or welded together, is connected to the heat sink106. The joint134provides a zone of very high thermal conductivity along the through-plane direction120in which to transfer heat to the heat sink106. Further, a conductive paste may be used between the joint134and the heat sink106to further enhance the heat transfer from the sheets108in the second portion112to the heat sink106.

FIG.4shows an example of one of the sheets108(hereinafter the sheet108). Specifically,FIG.4shows a front view of the sheet108and also shows a cross-sectional view of the sheet108taken along the line A-A, which is seen inFIGS.1A-3B. In the front view, the dimensions d and h respectively denote the depth and height of the cells102,104, of which the height his shown inFIGS.1A-2.

The sheet108has a first portion110that is disposed between the cells102,104. The sheet108has a second portion112that is disposed between the heat sink106and the cell102. The sheet108is folded at111at about right angle to form the first and second portions110,112. These portions are already described above as respective portions of the sheets108stacked together. Various surface treatments of these portions are now described in further detail. The description provided with reference toFIG.1Aapplies to all of the sheets108shown and described above with reference toFIGS.1A-3B. Further, while a third portion132of the sheet108is not shown, it is to be understood that the third portion132of the sheet108is identical to the first portion110of the sheet108.

The first portion110of the sheet108may be treated in a manner to increase the surface roughness and to increase the thermal contact resistance. The second portion112of the sheet108may be treated in a manner to decrease the surface roughness and to decrease the thermal contact resistance. Surface roughness can be increased in many ways. For example, to increase surface roughness, the first portion110of the sheet108can be brushed, wrinkled, or creased. To decrease surface roughness, the second portion112of the sheet108may be smooth (or less rough than the first portion110).

To further increase the thermal contact resistance, instead of or in addition to wrinkling, the first portion110of the sheet108may be treated using a surface treatment. For example, the first portion110of the sheet108may be coated with a thin layer of an insulating material. For example, the thin layer may include an anodized coating. The second portion112of the sheet108is not coated using such a surface treatment. Instead, a conductive paste may be used to join the second portion112of the sheet108to the heat sink106to enhance heat transfer from the second portion112of the sheet108to the heat sink106.

InFIG.4, the difference in roughness between the first and second portions110,112of the sheet108and the presence and absence of the coating on the first and second portions110,112of the sheet108are shown using two different types of shading. A line denoted by reference numeral111shown between the two types of shading (i.e., between the first and second portions110,112of the sheet108) represents the fold111where the sheet108is folded at about right angle to form the first and second portions110,112of the sheet108. Further, while only one side of the sheet108is shown, it is understood that the other side of the sheet108, which is not shown, may be identical or similar to the side shown inFIG.4.

FIG.5shows an example of the layer114of insulating material shown inFIGS.1A-3B. Specifically,FIG.5shows a front view of the layer114and also shows a cross-sectional view of the layer114taken along the line B-B, which is seen inFIGS.1A-3B. In the front view, the dimensions d and h respectively denote the depth and height of the cells102,104, of which the height h is shown inFIGS.1A-2.

For example, the layer114can comprise a mesh of an insulating material. For example, the layer114comprise fiber glass. For example, the layer114can comprise a thin sheet of any thermally insulating material. The thin sheet may be solid or porous (i.e., can include air pockets). The thin sheet can include any regular or irregular pattern of holes.

Note that the layer114is optional. The layer114can be used between every pair of the sheets108in the first portion110. The layer114can be between any of the sheets108in the first portion110used using any regular or irregular pattern. The layer114can be used instead of or in addition to the thin coating of an insulating material applied to the sheets108in the first portion110. The layer114is not used in the second portion112.

Throughout the present disclosure, references have been made to insulating and conductive materials. The insulating and conductive properties of these materials are to be understood in the context of the ability or inability of these materials to conduct and transfer heat. An insulating material is to be understood as being thermally insulating, and a thermally conductive material is to be understood as being thermally conductive.

The foregoing description is merely illustrative in nature and is not intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims.

It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure. Further, although each of the embodiments is described above as having certain features, any one or more of those features described with respect to any embodiment of the disclosure can be implemented in and/or combined with features of any of the other embodiments, even if that combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and permutations of one or more embodiments with one another remain within the scope of this disclosure.

Spatial and functional relationships between elements (for example, between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including “connected,” “engaged,” “coupled,” “adjacent,” “next to,” “on top of,” “above,” “below,” and “disposed.” Unless explicitly described as being “direct,” when a relationship between first and second elements is described in the above disclosure, that relationship can be a direct relationship where no other intervening elements are present between the first and second elements, but can also be an indirect relationship where one or more intervening elements are present (either spatially or functionally) between the first and second elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean “at least one of A, at least one of B, and at least one of C.”

In the figures, the direction of an arrow, as indicated by the arrowhead, generally demonstrates the flow of information (such as data or instructions) that is of interest to the illustration. For example, when element A and element B exchange a variety of information but information transmitted from element A to element B is relevant to the illustration, the arrow may point from element A to element B. This unidirectional arrow does not imply that no other information is transmitted from element B to element A. Further, for information sent from element A to element B, element B may send requests for, or receipt acknowledgements of, the information to element A.

In this application, including the definitions below, the term “module” or the term “controller” may be replaced with the term “circuit.” The term “module” may refer to, be part of, or include: an Application Specific Integrated Circuit (ASIC); a digital, analog, or mixed analog/digital discrete circuit; a digital, analog, or mixed analog/digital integrated circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor circuit (shared, dedicated, or group) that executes code; a memory circuit (shared, dedicated, or group) that stores code executed by the processor circuit; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip.

The module may include one or more interface circuits. In some examples, the interface circuits may include wired or wireless interfaces that are connected to a local area network (LAN), the Internet, a wide area network (WAN), or combinations thereof. The functionality of any given module of the present disclosure may be distributed among multiple modules that are connected via interface circuits. For example, multiple modules may allow load balancing.

The term code, as used above, may include software, firmware, and/or microcode, and may refer to programs, routines, functions, classes, data structures, and/or objects. The term shared processor circuit encompasses a single processor circuit that executes some or all code from multiple modules. The term group processor circuit encompasses a processor circuit that, in combination with additional processor circuits, executes some or all code from one or more modules. References to multiple processor circuits encompass multiple processor circuits on discrete dies, multiple processor circuits on a single die, multiple cores of a single processor circuit, multiple threads of a single processor circuit, or a combination of the above. The term shared memory circuit encompasses a single memory circuit that stores some or all code from multiple modules. The term group memory circuit encompasses a memory circuit that, in combination with additional memories, stores some or all code from one or more modules.

The term memory circuit is a subset of the term computer-readable medium. The term computer-readable medium, as used herein, does not encompass transitory electrical or electromagnetic signals propagating through a medium (such as on a carrier wave); the term computer-readable medium may therefore be considered tangible and non-transitory. Non-limiting examples of a non-transitory, tangible computer-readable medium are nonvolatile memory circuits (such as a flash memory circuit, an erasable programmable read-only memory circuit, or a mask read-only memory circuit), volatile memory circuits (such as a static random access memory circuit or a dynamic random access memory circuit), magnetic storage media (such as an analog or digital magnetic tape or a hard disk drive), and optical storage media (such as a CD, a DVD, or a Blu-ray Disc).

The apparatuses and methods described in this application may be partially or fully implemented by a special purpose computer created by configuring a general purpose computer to execute one or more particular functions embodied in computer programs. The functional blocks, flowchart components, and other elements described above serve as software specifications, which can be translated into the computer programs by the routine work of a skilled technician or programmer.

The computer programs include processor-executable instructions that are stored on at least one non-transitory, tangible computer-readable medium. The computer programs may also include or rely on stored data. The computer programs may encompass a basic input/output system (BIOS) that interacts with hardware of the special purpose computer, device drivers that interact with particular devices of the special purpose computer, one or more operating systems, user applications, background services, background applications, etc.

The computer programs may include: (i) descriptive text to be parsed, such as HTML (hypertext markup language), XML (extensible markup language), or JSON (JavaScript Object Notation) (ii) assembly code, (iii) object code generated from source code by a compiler, (iv) source code for execution by an interpreter, (v) source code for compilation and execution by a just-in-time compiler, etc. As examples only, source code may be written using syntax from languages including C, C++, C#, Objective-C, Swift, Haskell, Go, SQL, R, Lisp, Java®, Fortran, Perl, Pascal, Curl, OCaml, Javascript®, HTML5 (Hypertext Markup Language 5th revision), Ada, ASP (Active Server Pages), PHP (PHP: Hypertext Preprocessor), Scala, Eiffel, Smalltalk, Erlang, Ruby, Flash®, Visual Basic®, Lua, MATLAB, SIMULINK, and Python®.