Current collector for an electrochemical cell

A current collector for an electrochemical cell includes a member having an outer member and an inner member coupled to the outer member by a plurality of flexible arms configured to allow the inner member to move relative to the outer member.

BACKGROUND

The present application relates generally to the field of batteries and battery systems. More specifically, the present application relates to batteries and battery systems that may be used in vehicle applications to provide at least a portion of the motive power for the vehicle.

Vehicles using electric power for all or a portion of their motive power (e.g., electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and the like, collectively referred to as “electric vehicles”) may provide a number of advantages as compared to more traditional gas-powered vehicles using internal combustion engines. For example, electric vehicles may produce fewer undesirable emission products and may exhibit greater fuel efficiency as compared to vehicles using internal combustion engines (and, in some cases, such vehicles may eliminate the use of gasoline entirely, as is the case of certain types of PHEVs).

As electric vehicle technology continues to evolve, there is a need to provide improved power sources (e.g., battery systems or modules) for such vehicles. For example, it is desirable to increase the distance that such vehicles may travel without the need to recharge the batteries. It is also desirable to improve the performance of such batteries and to reduce the cost associated with the battery systems.

One area of improvement that continues to develop is in the area of battery chemistry. Early electric vehicle systems employed nickel-metal-hydride (NiMH) batteries as a propulsion source. Over time, different additives and modifications have improved the performance, reliability, and utility of NiMH batteries.

More recently, manufacturers have begun to develop lithium-ion batteries that may be used in electric vehicles. There are several advantages associated with using lithium-ion batteries for vehicle applications. For example, lithium-ion batteries have a higher charge density and specific power than NiMH batteries. Stated another way, lithium-ion batteries may be smaller than NiMH batteries while storing the same amount of charge, which may allow for weight and space savings in the electric vehicle (or, alternatively, this feature may allow manufacturers to provide a greater amount of power for the vehicle without increasing the weight of the vehicle or the space taken up by the battery system).

It is generally known that lithium-ion batteries perform differently than NiMH batteries and may present design and engineering challenges that differ from those presented with NiMH battery technology. For example, lithium-ion batteries may be more susceptible to variations in battery temperature than comparable NiMH batteries, and thus systems may be used to regulate the temperatures of the lithium-ion batteries during vehicle operation. The manufacture of lithium-ion batteries also presents challenges unique to this battery chemistry, and new methods and systems are being developed to address such challenges.

It would be desirable to provide an improved battery module and/or system for use in electric vehicles that addresses one or more challenges associated with NiMH and/or lithium-ion battery systems used in such vehicles. It also would be desirable to provide a battery module and/or system that includes any one or more of the advantageous features that will be apparent from a review of the present disclosure.

SUMMARY

One exemplary embodiment relates to a current collector for an electrochemical cell including a member having an outer member and an inner member coupled to the outer member by a plurality of flexible arms configured to allow the inner member to move relative to the outer member.

Another exemplary embodiment relates to flexible current collector for an electrochemical cell. The current collector includes an outer portion, and inner portion, and a plurality of connecting members. Each of the connecting members has a first end coupled to the outer portion and a second end coupled to the inner portion. The connecting members are configured to allow the inner portion to move relative to the outer portion.

Another exemplary embodiment relates to an electrochemical cell including a current collector including a member having an outer member and an inner member coupled to the outer member by a plurality of flexible arms configured to allow the inner member to move relative to the outer member.

DETAILED DESCRIPTION

FIG. 1is a perspective view of a vehicle10in the form of an automobile (e.g., a car) having a battery system20for providing all or a portion of the motive power for the vehicle10. Such a vehicle10can be an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), or other type of vehicle using electric power for propulsion (collectively referred to as “electric vehicles”).

Although the vehicle10is illustrated as a car inFIG. 1, the type of vehicle may differ according to other exemplary embodiments, all of which are intended to fall within the scope of the present disclosure. For example, the vehicle10may be a truck, bus, industrial vehicle, motorcycle, recreational vehicle, boat, or any other type of vehicle that may benefit from the use of electric power for all or a portion of its propulsion power.

Although the battery system20is illustrated inFIG. 1as being positioned in the trunk or rear of the vehicle, according to other exemplary embodiments, the location of the battery system20may differ. For example, the position of the battery system20may be selected based on the available space within a vehicle, the desired weight balance of the vehicle, the location of other components used with the battery system20(e.g., battery management systems, vents or cooling devices, etc.), and a variety of other considerations.

FIG. 2illustrates a cutaway schematic view of a vehicle11provided in the form of an HEV according to an exemplary embodiment. A battery system21is provided toward the rear of the vehicle11proximate a fuel tank12(the battery system21may be provided immediately adjacent the fuel tank12or may be provided in a separate compartment in the rear of the vehicle11(e.g., a trunk) or may be provided elsewhere in the vehicle11). An internal combustion engine14is provided for times when the vehicle11utilizes gasoline power to propel the vehicle11. An electric motor16, a power split device17, and a generator18are also provided as part of the vehicle drive system.

Such a vehicle11may be powered or driven by just the battery system21, by just the engine14, or by both the battery system21and the engine14. It should be noted that other types of vehicles and configurations for the vehicle drive system may be used according to other exemplary embodiments, and that the schematic illustration ofFIG. 2should not be considered to limit the scope of the subject matter described in the present application.

According to various exemplary embodiments, the size, shape, and location of the battery system21, the type of vehicle11, the type of vehicle technology (e.g., EV, HEV, PHEV, etc.), and the battery chemistry, among other features, may differ from those shown or described.

According to an exemplary embodiment, the battery system21includes a plurality of electrochemical batteries or cells. The battery system21may also include features or components for connecting the electrochemical cells to each other and/or to other components of the vehicle electrical system, and also for regulating the electrochemical cells and other features of the battery system21. For example, the battery system21may include features that are responsible for monitoring and controlling the electrical performance of the battery system21, managing the thermal behavior of the battery system21, containment and/or routing of effluent (e.g., gases that may be vented from an electrochemical cell through a vent), and other aspects of the battery system21.

Referring now toFIG. 3, an isometric view of an electrochemical cell24is shown according to an exemplary embodiment. A battery system (such as battery system20,21) includes a plurality of such electrochemical cells24(e.g., lithium-ion cells, nickel-metal-hydride cells, lithium polymer cells, etc., or other types of electrochemical cells now known or hereafter developed). According to an exemplary embodiment, the electrochemical cells24are generally cylindrical lithium-ion cells configured to store an electrical charge. According to other exemplary embodiments, the cells24could have other physical configurations (e.g., oval, prismatic, polygonal, etc.). The capacity, size, design, terminal configuration, and other features of the cells24may also differ from those shown according to other exemplary embodiments.

FIG. 4is a partial cross-sectional view of a cell24such as that shown inFIG. 3taken along line4-4inFIG. 3. According to an exemplary embodiment, the cell24includes a container or housing25, a cap or cover42, a bottom portion (not shown), and a cell element30. According to an exemplary embodiment, the housing25may be constructed from a conductive material such as a metal (e.g., aluminum or an aluminum alloy, copper or a copper alloy, etc.). According to an exemplary embodiment, the cell element30is a wound cell element. According to another exemplary embodiment, the cell element30may be a prismatic or oval cell element.

According to an exemplary embodiment, the cell element30includes at least one cathode or positive electrode36, at least one anode or negative electrode38, and one or more separators32,34. The separators32,34are provided intermediate or between the positive and negative electrodes36,38to electrically isolate the electrodes36,38from each other. According to an exemplary embodiment, the cell24includes an electrolyte (not shown). According to an exemplary embodiment, the electrolyte is provided in the housing25of the cell24through a fill hole41. After completion of filling the cell24with electrolyte, a fill plug (e.g., such as fill plug43as shown inFIGS. 28 and 29) may be provided in the fill hole41to seal the electrolyte inside the cell24.

The cell24also includes a negative current collector40and a positive current collector (not shown). The negative current collector40and the positive current collector are conductive members that are used to couple the electrodes36,38of the cell element30to the terminals26,28of the cell24. For example, the negative current collector40couples the negative electrode38to the negative terminal28(via a tab44) and the positive current collector couples the positive electrode36to the positive terminal26of the cell24(e.g., via the housing25). According to the exemplary embodiment shown inFIG. 4, the tab44of the negative current collector40has been at least partially folded or bent back over itself at least one time before being coupled to the negative terminal28. According to an exemplary embodiment, the current collectors are coupled to the electrodes with a welding operation (e.g., a laser welding operation).

According to an exemplary embodiment, the cell element30has a wound configuration in which the electrodes36,38and separators32,34are wound around a member or element provided in the form of a tube or mandrel50. Such a configuration may be referred to alternatively as a jelly roll configuration. Although the mandrel50is shown as being provided as having a generally cylindrical shape, according to other exemplary embodiments, the mandrel50may have a different configuration (e.g., it may have an oval or rectangular cross-sectional shape, etc.). It is noted that the cell element30, although shown as having a generally cylindrical shape, may also have a different configuration (e.g., it may have an oval, prismatic, rectangular, or other desired cross-sectional shape).

According to another exemplary embodiment, the electrochemical cell24may be a prismatic cell having prismatic or stacked cell elements (not shown). In such an embodiment, the positive and negative electrodes36,38are provided as plates that are stacked upon one another in an alternating fashion, with the separators32,34provided intermediate or between the positive and negative electrodes36,38to electrically isolate the electrodes36,38from each other.

According to an exemplary embodiment, the positive electrode36is offset from the negative electrode38in the axial direction as shown in the partial cross-sectional view shown inFIG. 5. Accordingly, at a first end of the cell element30, the wound positive electrode36will extend further than the negative electrode38, and at a second (opposite) end of the cell element30, the negative electrode38will extend further than the positive electrode36.

One advantageous feature of such a configuration is that current collectors may be connected to a specific electrode at one end of the cell24without contacting the opposite polarity electrode. For example, according to an exemplary embodiment, a negative current collector40(e.g., as shown inFIG. 4) may be connected to the exposed negative electrode38at one end of the cell element30and a positive current collector (not shown) may be connected to the exposed positive electrode36at the opposite end of the cell element30.

According to an exemplary embodiment, the negative current collector40electrically connects the negative electrode38to the negative terminal28of the cell24. The negative terminal28is insulated from the cover42of the housing25by an insulator45, as shown inFIG. 4. According to an exemplary embodiment, the positive current collector (not shown) electrically connects the positive electrode36to a bottom of the housing25. The housing25is electrically connected to the cover42(e.g., as shown inFIG. 4), which in turn is electrically connected to the positive terminal26.

FIGS. 6-7illustrate an exemplary embodiment of a wound cell element30(e.g., a jelly roll) in which electrodes36,38and separators32,34(not shown) are wound around a member or element provided in the form of a mandrel50(e.g., a body, center member, shaft, rod, tube etc.). According to an exemplary embodiment, an adhesive or tape48(e.g., as shown inFIG. 6) may be used to position an electrically-insulating wrap or film46(e.g., as shown inFIGS. 4 and 6) around the cell element30in order to at least partially electrically insulate the cell element30from the housing25. According to an exemplary embodiment, the film46is a polymide material such as is commercially available under the trade name Kapton® from E.I. du Pont de Nemours and Company.

According to an exemplary embodiment, the mandrel50is provided in the form of an elongated hollow tube52and is configured to allow gases from inside the electrochemical cell to flow from one end of the electrochemical cell (e.g., the top) to the other end of the electrochemical cell (e.g., the bottom). According to another exemplary embodiment, the mandrel50may be provided as a solid tube.

The mandrel50is illustrated, for example, inFIG. 7as being provided within the center of the cell element30. According to an exemplary embodiment, the mandrel50does not extend all the way to the very top and bottom of the cell element30. According to other exemplary embodiments, the mandrel50may extend all the way to the top and/or bottom of the cell element30.

Still referring toFIGS. 6-7, according to an exemplary embodiment, the mandrel50includes at least one (i.e., one or more) element or drive member60joined to an end of the hollow tube52. According to an exemplary embodiment, the drive members60are configured to electrically insulate the hollow tube52from the electrodes36,38. According to another exemplary embodiment, the hollow tube52may be provided in electrical contact with one of the electrodes while being electrically insulated from the other electrode. For example, according to an exemplary embodiment, the hollow tube52may be electrically coupled to the positive electrode36(or negative electrode38), while the hollow tube52is electrically isolated from the negative electrode38(or positive electrode36) by the drive member60.

According to an exemplary embodiment, the drive members60are formed from an electrically-insulating material such as a polymeric material or other suitable material (e.g., a plastic resin) and the hollow tube52is formed from an electrically (and thermally) conductive material such as a metallic material or other suitable material (e.g., aluminum or aluminum alloy). According to another exemplary embodiment, the drive members60are formed from an electrically (and thermally) conductive material such as a metallic material or other suitable material (e.g., aluminum or aluminum alloy) and the hollow tube52is formed from an electrically-insulating material such as a polymeric material or other suitable material (e.g., a plastic resin). According to another exemplary embodiment, both the drive members60and the hollow tube52are formed from an electrically-insulating material such as a polymeric material or other suitable material (e.g., a plastic resin).

One advantageous feature of the mandrels50as described above is that the drive members60coupled to the hollow tube52keep the positive and negative electrodes36,38electrically separated from each other. Additionally, when the hollow tube52of the mandrel50is formed from a relatively low cost material (e.g., a drawn aluminum tube or extruded aluminum tube), the mandrel50may have a lower cost as compared to other mandrels in which the entire assembly is made of a polymeric material.

According to other exemplary embodiments, other configurations of the cell element30may be used that do not include the mandrel50or the drive members60(e.g., a prismatic cell element). Additionally, while the cell24inFIGS. 4 and 6is shown according to an exemplary embodiment as having the exposed negative electrode38proximate to the top of the cell24and the exposed positive electrode36proximate to the bottom of the cell24, according to other exemplary embodiments, the orientation of the cell element30(and thus the positions of the current collectors) may be reversed. Additionally, according to other exemplary embodiments, the terminals26,28of the cell24may be provided on opposite ends of the cell24(e.g., a negative terminal28may be provided on the top of the cell24and a positive terminal26may be provided on the bottom of the cell24).

Referring now toFIGS. 8-9A, a member or element provided in the form of a current collector or collector plate140is shown according to an exemplary embodiment. According to an exemplary embodiment, the current collector140is provided in the form of a generally flat member with a plurality of legs or extensions142and an extension or tab144(formed, e.g., by a stamping operation, a laser cutting operation, etc.). According to an exemplary embodiment, the current collector140may be formed from a material having a thickness of between approximately 1 and 2 millimeters, but may have a greater or lesser thickness according other exemplary embodiments. According to various exemplary embodiments, the current collector140may be formed from any of a wide variety of conductive materials such as aluminum or an aluminum alloy (e.g., for a positive current collector), copper or a copper alloy (e.g., for a negative current collector), nickel-plated copper or an alloy thereof, etc.

As shown, the legs142are configured to extend across one end of the cell element30to contact the edge of the exposed electrode (e.g., the negative electrode38). According to another exemplary embodiment, the legs142may extend only partially across the end of the cell element30. While three legs142are shown in the exemplary embodiment ofFIGS. 8-9A, according to other exemplary embodiments, the current collector140may have a greater or lesser number of legs142.

As shown inFIG. 9A, according to an exemplary embodiment, the extension or tab144is configured to be folded away from the cell element30and at least partially back over the main body141of the current collector140. The tab144is configured to be coupled to the housing of the cell or to a terminal of the cell to create a conductive path between the electrode and the housing or terminal (e.g., similar to that shown inFIG. 4). According to another exemplary embodiment, the tab144may be folded or bent at least partially over itself multiple times (e.g., similar to that shown inFIG. 4). The tab144provides a substantially flexible connection between the electrode of the cell element30and the terminal or housing and allows the cell element30to move relative to the terminal or housing if required.

As best seen inFIG. 8, the ends of the legs142may include a rounded or curved shape to complement the perimeter of the cell element30. According to other exemplary embodiments, the legs142(including the ends of the legs) may have other shapes and/or sizes. According to an exemplary embodiment, the legs142of the current collector are separated from one another by an Angle A of approximately 120 degrees. According to other exemplary embodiments, the legs142may be separated from one another by a greater or smaller angle.

According to an exemplary embodiment, the current collector140may be coupled to the electrode with a welding operation (e.g., a laser welding operation) along the legs142of the current collector140(e.g., such as along weld lines146as shown inFIG. 8). As such, the welding occurs radially with respect to the end of the cell element30. This allows for more efficient current flow from the electrode of the cell element30to the current collector140, because the edge of the wound electrode is coupled (e.g., welded) to the current collector140(via the legs142) multiple times. Additionally, radial welds on a wound cell element (such as shown inFIG. 9) allow the weld to occur substantially perpendicular to the edge of the electrode, providing for better weld control and repeatability of the weld from one cell to the next. According to an exemplary embodiment, the welding of the current collector140to the electrode is done prior to the folding of the tab144, but may occur at a different time according to other exemplary embodiments.

Referring now toFIGS. 10-12B, a current collector240is shown according to another exemplary embodiment. The current collector240is similar to the current collector140ofFIGS. 8-9, except the current collector240ofFIGS. 10-12Bis formed as a relatively narrow elongated strip of material (to allow for the efficient use of material). According to an exemplary embodiment, the current collector240may be formed from a material having a thickness of between approximately 1 and 2 millimeters, but may have a greater or lesser thickness according other exemplary embodiments. According to various exemplary embodiments, the current collector240may be formed from any of a wide variety of conductive materials such as aluminum or an aluminum alloy (e.g., for a positive current collector), copper or a copper alloy (e.g., for a negative current collector), nickel-plated copper or an alloy thereof, etc.

The legs242are formed (e.g., by a stamping operation, a laser cutting operation, etc.) by a series of generally parallel cuts at one end of the strip of material in a longitudinal direction. To form the current collector240, according to an exemplary embodiment, the outer legs242are folded or otherwise manipulated outward at an angle (seeFIG. 12) of approximately 120 degrees from one another. According to other exemplary embodiments, the outer legs may be folded at an angle that is greater or smaller than 120 degrees.

According to an exemplary embodiment, the legs242of the current collector240are configured to extend across the end of the electrode of the cell element30to contact the edge of the exposed electrode (e.g., the negative electrode or the positive electrode). According to another exemplary embodiment, the legs242may extend only partially across the end of the wound electrode. While three legs242are shown in the exemplary embodiment ofFIGS. 10-12, according to other exemplary embodiments, the current collector240may have a greater or lesser number of legs.

As shown inFIG. 12A, according to one exemplary embodiment, the outer legs242may be bent or folded under the main body241of the current collector240such that the outer legs242are substantially parallel to the inner leg242. As shown inFIG. 12B, according to another exemplary embodiment, the outer legs242may be bent or folded under the main body241of the current collector240such that the outer legs242are at an angle with respect to the plane of the main body241(e.g., such as Angle B as shown inFIG. 13A). Additionally, as shown inFIG. 12B, the inner leg242may be bent or folded towards the cell element30such that the inner leg242is at an angle with respect to the plane of the main body241(e.g., such as Angle B as shown inFIG. 13A). According to an exemplary embodiment, the inner leg242may be bent or folded before, after, or consecutively with the bending or folding of the outer legs242.

The current collector240may be coupled to the electrode with a welding operation (e.g., a laser welding operation) along the legs242of the current collector240(e.g., such as along weld lines246as shown inFIG. 12). As such, the welding occurs radially with respect to the edge of the electrode of the cell element30. Similarly to as stated above, radial welding allows for more efficient current flow from the electrode of the cell element30to the current collector240, and for better weld control and repeatability of the weld from one cell to the next. According to an exemplary embodiment, the welding of the current collector240to the electrode is done prior to the folding of the tab244, but may occur at a different time according to other exemplary embodiments.

The current collector240also includes an extension or tab244that is configured to be folded away from the cell element30and/or at least partially back over the main body241of the current collector240(e.g., such as shown inFIGS. 13A and 13B). The tab244is configured to be coupled to the housing of the cell or to a terminal of the cell to create a conductive path between the electrode and the housing or terminal (e.g., similar to that as shown inFIG. 4). According to another exemplary embodiment, the tab244may be folded or bent at least partially over itself multiple times (e.g., similar to that as shown inFIG. 4). The tab244provides a substantially flexible connection between the electrode and the terminal or housing and allows the cell element30to move relative to the terminal or housing.

Referring toFIGS. 13A and 13B, the inner leg242of the current collector240may be at an angle with respect to the plane of the tab244, shown as Angle B (for clarity, the outer legs242are not shown). It is noted that the legs142of the current collector140(e.g., as shown inFIGS. 8-9A) may also be at an angle with respect to the plane of the tab (e.g., such as shown inFIGS. 13A and 13B). For clarity, only the current collector240is discussed below, although one of ordinary skill in the art would know that the embodiment discussed below may also apply to the embodiment shown inFIGS. 8-9Aor other embodiments not discussed.

Referring toFIGS. 13A and 13B, Angle B is chosen so that the legs242of the current collector240bend or crush the edge or side of the electrode (e.g., the negative electrode38) as the legs242make contact with the edge of the electrode as the legs242are brought down to contact the edge of the electrode (see, e.g.,FIG. 13B). Because the electrodes of the cell element30are wound, each of the electrodes will have multiple portions extending from the edge of each electrode. The legs242of the current collector240may then be coupled to the multiple portions of the edge of the electrode by a welding operation (e.g., a laser welding operation).

The multiple portions of the edge of the electrode are bent or crushed so that they contact one another to create a substantially continuous surface. The substantially continuous surface allows for better control of the penetration of the weld. By controlling the penetration of the weld, a stronger, higher quality, and more repeatable weld may be formed than is possible with an electrode that hasn't been deformed (e.g., an electrode that hasn't had the multiple portions of the edge of the electrode bent to touch one another). The tab244of the current collector240is then coupled to the housing of the cell or to the terminal of the cell to create a conductive path between the electrode and the housing or terminal.

To create a high quality and repeatable weld between the current collector240and the electrode, it is desirable for the legs242of the current collector240to contact as many of the multiple portions of the edge of the electrode as possible. According to an exemplary embodiment, Angle B is between approximately 0 degrees and 30 degrees, but may have an angle that is greater or smaller according to other exemplary embodiments. According to a particular exemplary embodiment, Angle B is between approximately 15 and 25 degrees. According to another particular exemplary embodiment, Angle B is approximately 20 degrees.

Referring now toFIGS. 14-17, a member or element provided in the form of a current collector or collector plate340is shown according to another exemplary embodiment. According to one exemplary embodiment, the current collector340is provided as a disc-like member that includes one or more projections, ridges, or protrusions342that extend along one side of the current collector340. The protrusions342of the current collector340have corresponding grooves, valleys, troughs, depressions, etc. on the opposite side of the current collector340. According to other exemplary embodiments, the protrusions342may not have corresponding grooves, valleys, troughs, depressions, etc. on the opposite side of the current collector340. According to one exemplary embodiment, the protrusions342are configured to crush or compress the multiple portions of the edge of the exposed electrode (e.g., the positive electrode36) at an end of the cell element30so that the multiple portions contact one another (e.g., as shown inFIG. 18B).

The current collector340may be formed (e.g., extruded, stamped, etc.) such that one or more protrusions342, shown as generally V-shaped ridges, extend from a surface of the current collector340. According to an exemplary embodiment, a tip or edge of the protrusions342may have a pointed profile. According to another exemplary embodiment, the tip or edge of the protrusions342may have a rounded profile. According to other exemplary embodiments, the protrusions342may extend all the way across the current collector340(e.g., as shown inFIG. 14) or may extend only partially across the current collector340.

According to another exemplary embodiment, the current collector340may substantially match the size and shape of the end of the cell element30. According to other exemplary embodiments, the current collector340may be provided in other shapes and/or sizes (e.g., the current collector340may cover only a portion of the end of the cell element30). According to an exemplary embodiment, the current collector340may be formed from a material having a thickness of between approximately 1 and 2 millimeters, but may have a greater or lesser thickness according other exemplary embodiments. According to various exemplary embodiments, the current collector340may be formed from any of a wide variety of conductive materials such as aluminum or an aluminum alloy (e.g., for a positive current collector), copper or a copper alloy (e.g., for a negative current collector), nickel-plated copper or an alloy thereof, etc.

The current collector340is coupled to the exposed edge of an electrode (e.g., the positive electrode36) of the cell element30with a welding operation (e.g., a laser welding operation). According to an exemplary embodiment, the current collector340is welded to the electrode along the protrusions342of the current collector340(e.g., such as along weld lines346as shown inFIG. 14).

Referring toFIGS. 18A-18B, the protrusions342of the current collector340are configured to crush, bend, or otherwise deform the multiple portions of the exposed edge of the positive electrode36when the current collector340is coupled to the cell element30. The protrusions342cause the multiple portions of the edge of the electrode to contact each other to create a substantially continuous surface. The substantially continuous surface allows for better control of the penetration of the weld. By controlling the penetration of the weld, a stronger, higher quality, and more repeatable weld may be formed than is possible with an electrode that has not been deformed.

A surface344of the current collector340is then coupled to the housing of the cell or to the terminal to create a conductive path between the electrode and the housing or terminal. According to an exemplary embodiment, the surface344may include a hole or aperture348(e.g., as shown inFIG. 17) that is generally aligned with the center of the cell element30.

Referring now toFIGS. 19 and 19A, a member or element provided in the form of a current collector or collector plate440is shown according to another exemplary embodiment. The current collector440may be formed by a stamping operation (e.g., from a sheet metal material). According to an exemplary embodiment, the current collector440may be formed from a material having a thickness of between approximately 1 and 2 millimeters, but may have a greater or lesser thickness according other exemplary embodiments. According to various exemplary embodiments, the current collector440may be formed from any of a wide variety of conductive materials such as aluminum or an aluminum alloy (e.g., for a positive current collector), copper or a copper alloy (e.g., for a negative current collector), nickel-plated copper or an alloy thereof, etc.

According to an exemplary embodiment, the current collector440includes one or more lower portions442that are configured to be coupled to an electrode (e.g., the positive electrode36). The current collector440also includes one or more upper portions444that are configured to be coupled to the housing of the cell or to the terminal of the cell to create a conductive path between the electrode and the housing or terminal. According to the exemplary embodiment shown inFIG. 19, the current collector440includes four lower portions442and four upper portions444. According to other exemplary embodiments, the current collector440may have greater or fewer upper and/or lower portions.

According to an exemplary embodiment, each of the lower portions442are connected to the upper portion by a member shown as a sidewall or shoulder450. As shown inFIG. 19, the shoulders450may have a generally rounded profile and may smoothly transition from the lower portion442to the upper portion444. According to another exemplary embodiment, each of the lower portions442includes at least one projection or protrusion452.

According to an exemplary embodiment, the current collector440is coupled to exposed portions of the edge of the positive electrode36by a welding operation (e.g., a laser welding operation) along the lower portions442of the current collector440(e.g., such as along weld lines446as shown inFIG. 19A). According to one exemplary embodiment, the lower portions442may contact, bend, or deform the exposed portions of the edge of the electrode36prior to welding (e.g., similar to that as shown inFIG. 18B). According to another exemplary embodiment, the exposed portions of the edge of the electrode36may be deformed prior to coupling the current collector440to the electrode36. The current collector440may then be coupled to the cell housing or a terminal with another welding operation along the upper portions444of the current collector440.

Referring now toFIGS. 20 and 20A, a member or element provided in the form of a current collector or collector plate540is shown according to another exemplary embodiment. The current collector540may be formed by a stamping operation (e.g., from a sheet metal material). According to an exemplary embodiment, the current collector540may be formed from a material having a thickness of between approximately 1 and 2 millimeters, but may have a greater or lesser thickness according other exemplary embodiments. According to various exemplary embodiments, the current collector540may be formed from any of a wide variety of conductive materials such as aluminum or an aluminum alloy (e.g., for a positive current collector), copper or a copper alloy (e.g., for a negative current collector), nickel-plated copper or an alloy thereof, etc.

According to an exemplary embodiment, the current collector540includes one or more lower portions542that are configured to be coupled to an electrode (e.g., the positive electrode36). The current collector540also includes one or more upper portions544that are configured to be coupled to the housing of the cell or to the terminal of the cell to create a conductive path between the electrode and the housing or terminal. According to the exemplary embodiment shown inFIG. 20, the current collector540includes four lower portions542and four upper portions544. According to other exemplary embodiments, the current collector540may have greater or fewer upper and/or lower portions. According to an exemplary embodiment, an opening or aperture548is included in the current collector540. The aperture548has a central axis that is generally aligned with the central axis of the cell element30.

According to an exemplary embodiment, each of the lower portions542are connected to the upper portion by a member shown as a sidewall or shoulder550. As shown inFIG. 20, the shoulders550may have a generally rounded profile and may smoothly transition from the lower portion542to the upper portion544. According to another exemplary embodiment, each of the lower portions542extends to the perimeter of the cell element30, while the upper portions544extend only partially across the cell element30. According to various exemplary embodiments, the lower portions542and/or upper portions544may have other configurations (e.g., the lower portions542may extend only partially across the end of the cell element, the upper portions544may extend all the way across the end of the cell element, etc.)

According to an exemplary embodiment, the current collector540is coupled to exposed portions of the edge of the positive electrode36by a welding operation (e.g., a laser welding operation) along the lower portions542of the current collector540(e.g., such as along weld lines546as shown inFIG. 20A). According to one exemplary embodiment, the lower portions542may contact, bend, or deform the exposed portions of the edge of the electrode36prior to welding (e.g., similar to that as shown inFIG. 18B). According to another exemplary embodiment, the exposed portions of the edge of the electrode36may be deformed prior to coupling the current collector540to the electrode36. The current collector540may then be coupled to the cell housing or a terminal with another welding operation along the upper portions544of the current collector540.

Referring now toFIG. 21, a member or element provided in the form of a current collector or collector plate640is shown according to an exemplary embodiment. The current collector640may be formed from a stamping process, a laser cutting process, or other suitable process. According to an exemplary embodiment, the current collector640may be formed from a material having a thickness of between approximately 1 and 2 millimeters, but may have a greater or lesser thickness according other exemplary embodiments. According to various exemplary embodiments, the current collector640may be formed from any of a wide variety of conductive materials such as aluminum or an aluminum alloy (e.g., for a positive current collector), copper or a copper alloy (e.g., for a negative current collector), nickel-plated copper or an alloy thereof, etc.

As shown inFIG. 21, the current collector640includes a first or outer member648that is connected to a second or inner member644by a plurality of members or arms642. As shown inFIG. 21, the outer member648is connected to the inner member644by four arms642. According to other exemplary embodiments, the outer member648may be connected to the inner member644by a greater or lesser number of arms having the same or different configuration as shown inFIG. 21.

According to the exemplary embodiment shown inFIG. 21, the outer member648is provided in the form of a ring or ring-like structure. In the embodiment shown, a perimeter of the outer member648substantially matches/aligns with the perimeter of the cell element30. Also according to the exemplary embodiment shown inFIG. 21, the inner member644has a generally circular shape.

According to the exemplary embodiment shown inFIG. 21, each of the plurality of arms642includes a first portion connected to the outer member648and a second portion connected to a member or extension650. The extension650connects the arm642to the inner member644. As shown inFIG. 21, the first portion of each of the arms642extends out from the outer member648in a generally perpendicular direction (i.e., the first portion extends generally perpendicular out from the outer member648). According to an exemplary embodiment, the extension650extends out from each of the arms642at a point between first and second ends of the arms642(e.g., at an approximate midpoint between the first and second ends of the arms642). According to an exemplary embodiment, the inner member644can move relative to the outer member648because of the flexibility of the arms642and/or the extensions650.

According to an exemplary embodiment, the arms642and/or the outer member648are coupled (e.g., by laser welding) to and edge of an electrode of the cell element30(e.g., such as along weld lines646as shown inFIGS. 21 and 24C) and the inner member644is coupled (e.g., by laser welding) to a portion of the housing of the cell or a terminal of the cell (e.g., such as along weld lines658as shown inFIG. 24C). According to an exemplary embodiment, the welding of the arms642is performed radially across the edge of the electrode of the cell element30(e.g., as shown inFIG. 21). According to another exemplary embodiment, the inner member644is coupled to the edge of the electrode of the cell element30and the arms642and/or the outer member648are coupled to the housing or the terminal.

According to an exemplary embodiment, the geometry of the outer member648, arms642, extensions650, and inner member644define a plurality of apertures or slots. These apertures or slots allow the current collector640to substantially flex (e.g., move, bend, deflect, etc.) if required (e.g., when a vent deploys from the bottom of the housing). For example, as shown inFIG. 24B, the inner member644is configured to flex with respect to the outer member648when the vent70deploys from the end of the cell24.

Having a flexible current collector allows for increased length of the cell element inside the housing (e.g., to maximize the power capacity of the cell). The flexible current collector also allows the cell element to remain substantially fixed during deployment of a vent. The flexible current collector also helps to isolate the vent from shock and vibration during handling and assembly and during use of the cell.

Referring now toFIG. 22, a current collector740is shown according to another exemplary embodiment. The current collector740is provided with similar but slightly different geometry than that of the current collector640shown inFIG. 21. The current collector740may be formed from a stamping process, a laser cutting process, or other suitable process. According to an exemplary embodiment, the current collector740may be formed from a material having a thickness of between approximately 1 and 2 millimeters, but may have a greater or lesser thickness according other exemplary embodiments. According to various exemplary embodiments, the current collector740may be formed from any of a wide variety of conductive materials such as aluminum or an aluminum alloy (e.g., for a positive current collector), copper or a copper alloy (e.g., for a negative current collector), nickel-plated copper or an alloy thereof, etc.

As shown inFIG. 22, the current collector740includes a first or outer member748that is connected to a second or inner member744by a plurality of members or arms742. As shown inFIG. 22, the outer member748is connected to the inner member744by four arms742. According to other exemplary embodiments, the outer member748may be connected to the inner member744by a greater or lesser number of arms.

According to the exemplary embodiment shown inFIG. 22, the outer member748is provided in the form of a ring or ring-like structure. According to an exemplary embodiment, a perimeter of the outer member748substantially matches/aligns with a perimeter of the cell element. According to the exemplary embodiment shown inFIG. 22, the inner member744has a generally circular shape.

According to the exemplary embodiment shown inFIG. 22, each of the plurality of arms742includes a first portion connected to the outer member748and a second portion connected to a member or extension750. The extension750connects the arm742to the inner member744. As shown inFIG. 22, the first portion of each of the arms742extends out from the outer member748in a generally perpendicular direction (i.e., the first portion extends generally perpendicular out from the outer member748). According to an exemplary embodiment, the extension750extends out from each of the arms742at a point between first and second ends of the arms742(e.g., at a point near the first end of the arms742). According to an exemplary embodiment, the inner member744can move relative to the outer member748because of the flexibility of the arms742and/or the extensions750.

According to an exemplary embodiment, the arms742and/or the outer member748are coupled (e.g., by laser welding) to an edge of an electrode of the cell element and the inner member744is coupled (e.g., by laser welding) to a portion of the housing of the cell or a terminal of the cell. According to an exemplary embodiment, the welding of the arms742is performed radially across the end of the cell element. According to another exemplary embodiment, the inner member744is coupled to the edge of the electrode of the cell element and the arms742and/or the outer member748are coupled to the housing or the terminal.

According to an exemplary embodiment, the geometry of the outer member748, arms742, extensions750, and inner member744define a plurality of apertures or slots. These apertures or slots allow the current collector740to substantially flex (e.g., move, bend, deflect, etc.) if required (e.g., when a vent deploys from the bottom of the housing). For example, the inner member744is configured to flex with respect to the outer member748(or vice-versa).

Referring now toFIG. 23, a current collector840is shown according to another exemplary embodiment. The current collector840may be formed from a stamping process, a laser cutting process, or other suitable process. According to an exemplary embodiment, the current collector840may be formed from a material having a thickness of between approximately 1 and 2 millimeters, but may have a greater or lesser thickness according other exemplary embodiments. According to various exemplary embodiments, the current collector840may be formed from any of a wide variety of conductive materials such as aluminum or an aluminum alloy (e.g., for a positive current collector), copper or a copper alloy (e.g., for a negative current collector), nickel-plated copper or an alloy thereof, etc.

As shown inFIG. 23, the current collector840includes a first or outer member848that is connected to a second or inner member844. As shown inFIG. 23, there are two outer members848that are connected to the inner member844. According to other exemplary embodiments, there may be a greater or lesser number of outer members848. According to an exemplary embodiment, each of the outer members848are connected to a member or element shown as an arm842that in turn is connected to the inner member844. According to the exemplary embodiment shown inFIG. 23, the outer member848is provided in the form of an enlarged portion of outer arm842.

As shown inFIG. 23, each of the arms842includes an outer portion850and an inner portion852. According to an exemplary embodiment, an outer portion850of the arm842substantially matches/aligns with a perimeter of the cell element. As shown inFIG. 23, each of the inner portions852of the arms842double back along at least a portion of the outer portion850of the arms842before connecting to the inner member844.

According to an exemplary embodiment, the outer portion850of the arms842and/or the outer members848are coupled (e.g., by laser welding) to an edge of an electrode of the cell element and the inner member844is coupled (e.g., by laser welding) to a portion of the housing of the cell or to a terminal of the cell. According to another exemplary embodiment, the inner member844is coupled to the edge of an electrode of the cell element and the outer portion850of the arms842and/or the outer member848are coupled to the housing or the terminal.

According to an exemplary embodiment, the geometry of the outer members848, arms842, and inner member844define a plurality of apertures or slots. These apertures or slots allow the current collector840to substantially flex (e.g., move, bend, deflect, etc.) if required (e.g., when a vent deploys from the bottom of the housing). For example, the inner member844is configured to flex with respect to the outer member848(or vice-versa).

Referring now toFIGS. 24A-24D, according to an exemplary embodiment, the cell24includes a vent70. The vent70is configured to allow gases and/or effluent to exit the cell24once the pressure inside the cell24reaches a predetermined amount (e.g., during a rise in cell temperature). When the vent70deploys (e.g., activates, opens, separates, etc.), the gases and/or effluent inside the cell24exit the cell24in order to lower the pressure inside the cell24(e.g., as represented by arrows76shown inFIG. 24B). According to an exemplary embodiment, the vent70acts as a safety device for the cell24during a high pressure occurrence.

According to an exemplary embodiment, the vent70is located in the bottom or bottom portion of the housing25. According to other exemplary embodiments, the vent70may be located elsewhere (e.g., such as in the lid or cover of the cell). According to another exemplary embodiment, the vent70may be located in a cover or bottom that is a separate component from the housing25that in turn is coupled to the housing25(e.g., by a welding operation).

According to an exemplary embodiment, the bottom of the housing25may include a ridge, projection, or ring of material74(e.g., as shown inFIGS. 24A and 24B) to prevent fracture of the vent70during handling and/or assembly of the cell24. The ring of material74provides for a clearance space between the vent70and a surface that the cell24is set upon. According to an exemplary embodiment, the clearance space is configured to prevent the vent70from being accidentally bumped (and deployed) during handling and/or assembly of the cell24.

As shown inFIG. 24A, the vent70includes at least one annular fracture groove72(e.g., ring, trough, pressure point, fracture point, fracture ring, etc.). According to an exemplary embodiment, the annular fracture groove72has a V-shaped bottom and is configured to break away (i.e., separate) from the bottom of the housing25when the vent70deploys. According to other exemplary embodiments, the bottom of the annular fracture groove72may have another shape (e.g., rounded shape, curved shape, U-shape, etc.).

As stated earlier, the vent70is configured to deploy once the pressure inside the cell24reaches a pre-determined amount. When the vent70deploys, the annular fracture groove72fractures and separates the vent70from the rest of the bottom of the housing25, allowing the internal gases and/or effluent to escape the cell (e.g., as shown inFIG. 24B). By having the vent70separate from the bottom of the housing25, the vent70acts as a current interrupt or current disconnect device. This is because the separation of the vent70from the bottom of the housing25disrupts the flow of current from the cell element30(through the positive current collector640) to the housing25. In this way, the vent70acts not only as an over-pressure safety device, but also as a current disconnect device. In order to help insulate the cell element30and the current collector640from the housing25, the insulative wrap46may include an extension47provided between the current collector640and the bottom of the housing25.

According to an exemplary embodiment, the vent70(e.g., the annular fracture groove72) is formed by tooling located external the housing25. The tooling tolerance is only affected by one side of the tool, allowing for a more consistent annular fracture groove72, resulting in a more consistent and repeatable opening of the vent70. The depth, shape, and size of the fracture groove72may be easily modified simply by changing the tooling. Additionally, the vent70is easy to clean and inspect since the vent70(and annular fracture groove72) is located on an external side of the housing25.

According to one exemplary embodiment, the cell element30does not move during deployment of the vent70(i.e., the cell element remains stationary). According to such exemplary embodiments, flexible current collectors may be utilized (e.g., such as the current collector640shown in FIGS.21and24A-C, the current collector740shown inFIG. 22, or the current collector840shown inFIG. 23). According to other exemplary embodiments, the cell element30may move in order to help deploy the vent70(e.g., by “pushing” or “punching” the current collector through the vent). According to such exemplary embodiments, non-flexible current collectors may be utilized (e.g., such as the current collector340shown inFIGS. 14-17, the current collector440shown inFIG. 19, or the current collector540shown inFIG. 20.).

Referring now toFIG. 24D, a housing125for an electrochemical cell is shown according to another exemplary embodiment. The housing125includes a vent170provided in a bottom portion of the housing125. According to other exemplary embodiments, the vent170may be provided elsewhere (e.g., such as in the lid or cover of the cell). According to another exemplary embodiment, the vent170may be located in a cover or bottom that is a separate component from the housing125that in turn is coupled to the housing125(e.g., by a welding operation).

According to an exemplary embodiment, the bottom of the housing125may include a ridge, projection, or ring of material174to prevent fracture of the vent170during handling and/or assembly of the cell. The ring of material174provides for a clearance space between the vent170and a surface that the cell is set upon. According to an exemplary embodiment, the clearance space is configured to prevent the vent170from being accidentally bumped (and deployed) during handling and/or assembly of the cell.

As shown inFIG. 24D, the vent170includes at least one annular fracture groove172(e.g., ring, trough, pressure point, fracture point, fracture ring, etc.). According to an exemplary embodiment, the annular fracture groove172has a V-shaped bottom and is configured to break away (i.e., separate) from the bottom of the housing125when the vent170deploys. According to other exemplary embodiments, the bottom of the annular fracture groove172may have another shape (e.g., rounded shape, curved shape, U-shape, etc.).

Referring now toFIGS. 25-29, a member or element provided in the form of a current collector or collector plate940is shown according to an exemplary embodiment. As shown best inFIG. 29, the current collector940is used to conductively couple an end of the electrode (e.g., the negative electrode38) of the cell element30to a terminal (e.g., the negative terminal28).

The current collector940may be formed from a stamping process, a laser cutting process, or other suitable process. According to an exemplary embodiment, the current collector940may be formed from a material having a thickness of between approximately 1 and 2 millimeters, but may have a greater or lesser thickness according other exemplary embodiments. According to various exemplary embodiments, the current collector940may be formed from any of a wide variety of conductive materials such as aluminum or an aluminum alloy (e.g., for a positive current collector), copper or a copper alloy (e.g., for a negative current collector), nickel-plated copper or an alloy thereof, etc.

Referring toFIGS. 26-27, the current collector940is provided in the form of a generally flat member having a main body942. Extending out from one end of the main body942is at least one tab or extension944(shown inFIG. 27as at least partially folded over the main body942). According to an exemplary embodiment, the tab944is at least partially folded over the main body942multiple times (e.g., similar to the tab44shown inFIG. 4). According to an exemplary embodiment, the main body942includes a hole or aperture950(e.g., as shown inFIG. 26). The aperture950may be provided as generally aligned with the center of the cell element30.

According to an exemplary embodiment, the tab944is configured to be coupled to a terminal (e.g., the negative terminal) of the cell (e.g., by laser welding). The tab944provides a substantially flexible connection between the electrode of the cell element and the terminal and allows the cell element to move relative to the terminal or housing if required.

According to an exemplary embodiment, the current collector940also includes a plurality of members or extensions shown as arms948that are configured to project or extend out from the main body942of the current collector940. The arms948, along with the main body942of the current collector940, extend out across one end of the cell element30(e.g., to contact the edge of the negative electrode38such as shown inFIG. 25). According to another exemplary embodiment, the arms948and main body942of the current collector940may extend only partially across the end of the cell element30. While two arms948are shown in the exemplary embodiment ofFIGS. 25-29, according to other exemplary embodiments, the current collector940may have a greater or lesser number of arms948.

As best seen inFIG. 25, the outer edge of the arms948may include a rounded or curved shape to complement the perimeter of the cell element30. According to other exemplary embodiments, the arms948(including the ends of the arms) may have other shapes and/or sizes. The current collector940may be coupled to the electrode38with a welding operation (e.g., a laser welding operation) along the arms948and main body942of the current collector940.

According to an exemplary embodiment, radial welds are used (e.g., such as along weld lines946as shown inFIG. 25) to couple the current collector940to the electrode38. According to one exemplary embodiment, the radial welds extend from the center of the main body942out to the outer edges of the main body942and arms948. According to other exemplary embodiments, the welds (radial or otherwise) may be formed differently. According to an exemplary embodiment, the welding of the current collector940to the electrode is done prior to the folding of the tab944, but may occur at a different time according to other exemplary embodiments.

The use of radial welds (i.e., welds that are radial with respect to the edge of the electrode of the cell element30) allows for more efficient current flow from the electrode of the cell element30to the current collector940in that all of the portions of the edge of the wound electrode are coupled (e.g., welded) to the current collector940(via the arms948and the main body942). Additionally, radial welds on a wound cell element (such as shown inFIG. 25) allow the weld to occur substantially perpendicular to the edge of the electrode, providing for better weld control and repeatability of the weld from one cell to the next.

While the current collectors ofFIGS. 8-13Band25-29are generally shown as being coupled to a negative electrode, according to other exemplary embodiments they may be coupled to a positive electrode. Likewise, while the current collectors ofFIGS. 14-24Care generally shown as coupled to a positive electrode, according to other exemplary embodiments they may be coupled to a negative electrode. Furthermore, while the current collectors shown inFIGS. 8-29are configured for use with wound cell elements, according to another exemplary embodiment, the current collectors may also be used with a series of flat plates (e.g., prismatic cells) or other cell configurations.

According to various exemplary embodiments, the current collectors shown inFIGS. 8-29may be formed from a relatively thin sheet of conductive material (e.g., by a stamping operation, a laser cutting operation, etc.) or may be formed by an extrusion process. According to various exemplary embodiments, the current collectors may be substantially rigid or may include a flexible or pliable portion (such as, e.g., the tabs shown inFIGS. 8-13and25-29or the arms shown inFIGS. 21-23).

Referring now toFIG. 30, an assembly process used to make a battery or electrochemical cell is shown according to an exemplary embodiment. In a first step1010, the separators and electrodes are wound around the mandrel to form the cell element in a jelly roll configuration. In a second step1020A/1020B, the positive and negative current collectors are electrically or conductively coupled (e.g., by a welding operation such as laser welding) to the positive and negative electrode ends of the jelly roll, respectively. According to various exemplary embodiments, the step1020A may occur before, after, or concurrent with the step1020B.

In a third step1030, the jelly roll is inserted into the cell housing. In a fourth step1040, the positive current collector is electrically or conductively coupled (e.g., by a welding operation) to the base of the cell housing. In a fifth step1050, the negative current collector is electrically or conductively coupled (e.g., by a welding operation) to the insulated terminal of the cap of the cell. In a sixth step1060, the cap of the cell is coupled to the housing of the cell (e.g., by a welding operation).

According to an exemplary embodiment, a current collector or plate for an electrochemical cell includes a member having a first surface and a second surface opposite the first surface. The second surface comprises at least one projection. The member is configured to be coupled to an electrode of the cell, the electrode having a wound configuration. The at least one projection is configured to engage an offset edge of the electrode so that the member can be welded to the cell.

Another embodiment of the invention relates to a current collector or plate for an electrochemical cell including a member. The member includes a main body and at least two legs extending out from a first end of the body. The legs are configured to engage an offset edge of a wound electrode of the cell so that the member can be welded to the cell.

One embodiment of the invention relates to a substantially flexible current collector for an electrochemical cell. The current collector includes a plurality of members coupled to a cell element and an inner ring coupled to a bottom of a housing.

Another embodiment of the invention relates to a current collector for an electrochemical cell. The current collector includes a main body and at least one arm extending out from a first end of the main body. The main body and the at least one arm are configured to be conductively coupled to a cell element. The current collector also includes a member extending out from the main body, the member being singularly folded partially over the main body. An end of the member is configured to be conductively coupled a terminal of the cell.