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AssigneeTexas Instruments Incorporated
InventorSteven K. Sullivan
Estimating the term…
A pressure actuated current interrupt device particularly useful for prismatic electrochemical cells has a cup-shaped member (12, 12′, 12″, 12′″, 12IV, 12V, 12VI) mounted on the cover of the cell and arranged to protrude into the interior of the cell. The cup-shaped member can be formed either as a separate member or as a portion of a layer of a composite cover. The cup-shaped member has a side wall (12b) in which stress is created by pressure generated in the cell which acts on the generally flat end wall (12a) of the cup-shaped member. A selected amount of pressure causes the side wall to catastrophically collapse with the configuration of the cup-shaped member being inverted to permanently break the electric current path with a cover mounted terminal. A composite cover (8iv, 8v) includes a membrane layer in which the cup-shaped member is formed and which can also include a pressure vent (12g).
Current interrupt apparatus for use with an electrochemical cell having a housing with an open end and comprising a cover having a support layer receivable in the open end co-extensive therewith to close the open end of the electrochemical cell, the electrochemical cell having a positive and a negative terminal, an aperture formed in the support layer, a membrane having at least a portion formed into a cup-shaped member having a generally flat end wall, the cup-shaped member having a side wall depending from the flat end wall extending along a length to a support portion, the support portion being attachable to the support layer with the cup-shaped member being in alignment with the aperture and with the side wall extending in a direction toward the interior of the housing and with the flat end wall generally lying in a plane parallel to a plane in which the cover lies, said membrane and the support layer forming a composite in which they are co-extensive with one another and with the open end of the electrochemical cell, an electrical current path formed between an electrode within the housing and one of the positive and negative terminals, the material of the membrane being chosen to have a selected material properties so that upon being subjected to a pressure level from within the housing above a predetermined level, the side wall will catastrophically collapse with the configuration of the cup-shaped member changing to an opposite, inverted configuration with the side wall extending in a direction away from the interior of the housing and with the flat end wall continuing to lie generally in a plane generally parallel to the plane in which the cover lies, the catastrophical collapse of the side wall interrupting the current path.
Current interrupt apparatus for use with an electrochemical cell having a housing formed with an open end and comprising a cover having a support layer receivable in the open end co-extensive therewith to close the open end of the electrochemical cell, the electrochemical cell having a positive and a negative terminal, an aperture formed in the support layer, a membrane having at least a portion formed into a cup-shaped member having a generally flat end wall, the cup-shaped shaped member having a side wall depending from the flat end wall extending along a length to a support portion, the support portion being attachable to the support layer with the cup-shaped member being in alignment with the aperture and with the side wall extending in a direction toward the interior of the housing and with the flat end wall generally lying in a plane parallel to a plane in which the cover lies, an electrical current path formed between an electrode! within the housing and one of the positive and negative terminals, one of the positive and negative terminals comprising an electrically conductive member having an outer, annular flange portion with an outer periphery and upper and lower opposed face surfaces, the apparatus further comprising an electrically conductive crimp ring and an electrically insulative sleeve, the support potion of the cup-shaped member being disposed about the outer periphery of the annular flange portion and being in contact with both the upper and lower opposed surfaces, the annular flange portion and support portion received in the electrically insulative sleeve and crimped to the crimp ring with the electrically insulative sleeve electrically separating the cup-shaped member and support member from the crimp ring and providing an elongated tortuous fluid seal path therebetween and the crimp ring being fixedly mounted to the cover in fluid sealed relation, the material of the membrane being chosen to have a selected material properties so that upon being subjected to a pressure level from within the housing above a predetermined level, the side wall will catastrophically collapse with the configuration of the cup-shaped member changing to an opposite, inverted configuration with the side wall extending in a direction away from the interior of the housing and with the flat end wall continuing to lie generally in a plane generally parallel to the plane in which the cover lies, the catastrophical collapse of the side wall interrupting the current path.
Current interrupt apparatus for use with an electrochemical cell having a housing formed with an open end and comprising a cover having a support layer receivable in the open end co-extensive therewith to close the open end of the electrochemical cell, the electrochemical cell having a positive and a negative terminal, an aperture formed in the support layer, a membrane having a least a portion formed into a cup-shaped member having a generally flat end wall, the cup-shaped member having a side wall depending from the flat end wall extending along a length to a support portion, the support portion being attachable to the support layer with a cup-shaped member being in alignment with the aperture and with the side wall extending in a direction toward the interior of the housing and with the flat end wall generally lying in a plane parallel to a plane in which the cover lies, an electrical current path formed between an electrode within the housing and one of the positive and negative terminals, said cup-shaped membrane being formed of electrically conductive material and being part of the current path and further comprising an electrically conductive plate welded to the flat end wall on the side thereof facing the interior of the housing, the electrode being connected to the electrically conductive plate, the material of the membrane being chosen to have a selected material properties so that upon being subjected to a pressure level from within the housing above a predetermined level, the side wall will catastrophically collapse with the configuration of the cup-shaped member changing to an opposite, inverted configuration with the side wall extending in a direction away from the interior of the housing and with the flat end wall continuing to lie generally in a plane generally parallel to the plane in which the cover lies, the catastrophical collapse of the side wall breaking the weld between the flat end wall and the electrically conductive plate to interrupt the electric current path.
Current interrupt apparatus for use with an electrochemical cell having a housing formed with an open end and comprising a cover having the support layer receivable in the open end co-extensive therewith to close the open end of the electrochemical cell, the electrochemical cell having a positive and a negative terminal, an aperture formed in the support layer, a membrane having at least a portion formed into a cup-shaped member having a generally flat end wall, the cup-shaped member having a side wall depending from the flat end wall extending along a length to a support portion, the support portion being attachable to the support layer with the cup-shaped member being in alignment with the aperture and with the side wall extending in a direction toward the interior of the housing and with the flat end wall generally lying in a plane parallel to a plane in which the cover lies, an electrically conductive support member having an outer periphery and an opening therethrough, the support portion of the cup-shaped member received about the outer periphery of the support member, a terminal plate and an electrically insulative annular member received on the support member, an electrically insulative, flexible sealing sleeve within which the support of the cup-shaped member, the support member, terminal plate and insulative annular member are received and a crimp ring crimping the terminal plate, insulative annular member, support portion and support member together with the terminal plate electrically isolated from the support portion and support member, the crimp ring extending through the aperture and being hermetically attached to the cover, a movable electrical contact electrically connected to the terminal plate and normally biased into electrical engagement with the support member, an electrically insulative motion transfer member having a portion disposed adjacent to the flat end wall and being received through the opening in the support member and aligned with the movable contact, the motion transfer member transferring motion from the flat end wall to the movable contact upon catastrophic collapse of the side wall to move the movable contact permanently out of engagement with the support member, an electrical current path formed between an electrode within the housing and one of the positive and negative terminals, the material of the membrane being chosen to have a selected material properties so that upon being subjected to a pressure level from within the housing above a predetermined level, the side wall will catastrophically collapse with the configuration of the cup-shaped member changing to an opposite, inverted configuration with the side wall extending in a direction away from the interior of the housing and with the flat end wall continuing to lie generally in a plane generally parallel to the plane in which the cover lies, the catastrophical collapse of the side wall interrupting the current path.
Current interrupt apparatus for use with an electrochemical cell having a housing formed with an open end and comprising a cover having a support layer receivable in the open end co-extensive therewith to close the open end of the electrochemical cell the electrochemical cell having a positive and a negative terminal, an aperture formed in the support layer, a membrane having at least a portion formed into a cup-shaped member having a generally flat end wall, the cup-shaped member having a side wall depending from the flat end wall extending along a length to a support portion, the support portion being attachable to the support layer with the cup-shaped member being in alignment with the aperture and with the side wall extending in a direction toward the interior of the housing and with the flat end wall generally lying in a plane parallel to a plane in which the cover lies said support portion of the cup-shaped member being hermetically attached directly to the cover and the cover being crimped to and electrically isolated from the housing, an electrical current path formed between an electrode within the housing and one of the positive and negative terminals, the material of the membrane being chosen to have a selected material properties so that upon being subjected to a pressure level from within the housing above a predetermined level, the side wall will catastrophically collapse with the configuration of the cup-shaped member changing to an opposite, inverted configuration with the side wall extending in a direction away from the interior of the housing and with the flat end wall continuing to lie generally in a plane generally parallel to the plane in which the cover lies, the catastrophical collapse of the side wall interrupting the current path.
Current interrupt apparatus for use with an electrochemical cell having a housing formed with an open end and comprising a cover having a support layer receivable in the open end co-extensive therewith to close the open end of the electrochemical cell, the electrochemical cell having a positive and a negative terminal, an aperture formed in the support layer, a membrane having at least a portion formed into a cup-shaped member having a generally flat end wall, the cup-shaped member having a side wall depending from the flat end wall extending along a length to a support portion, the support portion being attachable to the support layer with the cup-shaped member being in alignment with the aperture and with the side wall extending in a direction toward the interior of the housing and with the flat end wall generally lying in a plane parallel to a plane in which the cover lies an electrical current path formed between an electrode within the housing and one of the positive and negative terminals, the material of the membrane being chosen to have a selected material properties and a generally circular groove of reduced thickness formed in the flat end wall of the cup-shaped member at a distance from the side wall to compensate for variations in the geometry and material properties of the cup-shaped member, so that upon being subjected to a pressure level from within the housing above a predetermined level, the side wall will catastrophically collapse with the configuration of the cup-shaped member changing to an opposite, inverted configuration with the side wall extending in a direction away from the interior of the housing and with the flat end wall continuing to lie generally in a plane generally parallel to the plane in which the cover lies due to such pressure level acting on the flat end wall creating stress in the side wall effectively through a moment arm, the catastrophical collapse of the side wall interrupting the current path.
Current interrupt apparatus for use with an electrochemical cell having a housing with a cover and having a cup-shaped member with a generally flat end wall and a side wall depending therefrom to support portion in which the cup-shaped member is mounted in an aperture formed in the cover and the side wall protrudes from the support portion into the interior of the housing to be exposed to fluid pressure generated in the housing which creates stress in the side wall effectively acting through a moment arm comprising the method steps of adjusting the effective length of the moment arm by choosing a radius between the flat end wall and the side wall to compensate for variations in geometry and material properties of the cup-shaped member.
In an electrochemical cell having a housing with a cover and having a cup-shaped member with a generally flat end wall and a side wall depending therefrom to a support portion in which the cup-shaped member is mounted in an aperture formed in the cover and the side wall protrudes from the support portion into the interior of the housing to be exposed to fluid pressure generated in the housing which creates stress in the side wall effectively acting through a moment arm comprising the method steps of adjusting the effective length of the moment arm by forming a generally circular groove of reduced thickness in the end wall adjacent to the side wall at a distance from the side wall selected to compensate for variations in geometry and material properties of the cup-shaped member.
Current interrupt apparatus for use with an electrochemical cell having a housing with a cover and having a positive and a negative terminal, the cover having an outer periphery and being a composite comprising a first support layer and a second membrane layer lying generally in a first plane and with each layer formed with an upstanding flange extending around the outer periphery for welding attachment with the housing with the membrane layer disposed between the support layer and the housing, the support having at least three apertures, the second membrane layer having an aperture aligned with the first aperture in the support layer, an electrically conductive rivet received through the first aperture in the support layer and the aperture in the membrane layer aligned with an electrically insulative sleeve between the rivet and the layers, the rivet having an externally exposed, relative to the housing, top portion and an internally exposed, relative to the housing, lower portion for connection to an electrical strap, the support layer having a second aperture in the support layer with the membrane layer extending across the second aperture, the membrane layer being formed with a coined portion aligned with the second aperture to serve as a pressure vent, a third aperture in the support layer, the membrane layer formed with a cup-shaped portion having a side wall extending downwardly from the plane to a generally flat end wall and aligned with the third aperture, the flat end wall lying in a plane parallel to the first plane, the material of the membrane being chosen to have selected material properties being chosen so that upon being subjected to a pressure level from within the housing above a predetermined level, the pressure will exceed the ultimate strength of the side wall material causing the side wall to catastrophically collapse with the configuration of the cup-shaped portion changing to an opposite, inverted configuration with at least a portion of the side wall extending in a direction away from the interior of the housing and with the flat end wall continuing to lie generally in a plane generally parallel to the first plane.
Apparatus for use with an electrochemical cell having a housing with a cover and having a positive and a negative terminal, the cover having an outer periphery and being a composite comprising a first support layer and a second membrane layer lying generally in a first plane and with each layer formed with an upstanding flange extending around the outer periphery for welding attachment with the housing with the membrane layer disposed between the support layer and the housing, the support having at least two apertures, the second membrane layer having an aperture aligned with the first aperture in the support layer, an electrically conductive rivet received through the first aperture in the support layer and the aperture in the membrane layer aligned with an electrically insulative sleeve between the rivet and the layers, the rivet having an externally exposed, relative to the housing, top portion and an internally exposed, relative to the housing, lower portion for connection to an electrical strap, the support layer having a second aperture in the support layer with the membrane layer extending across the second aperture, the membrane layer being formed with a coined portion aligned with the second aperture to serve as a pressure vent.
Dependencies are inferred from the claim text.
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From the US filing history. Foreign family members aren’t listed.
Arrangements for facilitating escape of gases: non-re-sealable arrangements
Characterised by the methods of assembling casings with lids: by welding, brazing or soldering
Means for preventing undesired use or discharge: devices or arrangements for the interruption of current
Non-re-sealable arrangements: in the form of rupturable membranes or weakened parts, e.g. pierced with the aid of a sharp member
Term ended 13 May 2019 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
This invention relates generally to electrochemical cells and more particularly to current interrupt apparatus for use with prismatic electrochemical cells responsive to selected adverse conditions.
Electrochemical cells, especially high energy density cells such as those in which lithium is an active material, are subject to leakage or rupture as a result of various abusive treatment, which in turn, can cause damage to a device which is powered by the cell or to the surrounding environment. Such cells are sealed to prevent egress of electrolyte solvent and ingress of moisture from the exterior environment. When a cell is overcharged, self-heating occurs during the charging procedure. Examples of abusive treatment include charging at too rapid a rate, overcharging above a specified maximum voltage or discharging below a specified minimum cell voltage which can lead to an increase in temperature and/or pressure. In the case of cells utilizing lithium, should the temperature exceed a certain point an exothermic reaction begins which leads to overheating and causes a build-up in pressure which may result in expulsion of electrolyte from the cell.
It is known for commercially available cylindrical lithium ion electrochemical cells to incorporate a pressure driven current interrupt device to terminate current flow under adverse charge or discharge conditions. Typically, a thin metallic diaphragm, e.g., formed of aluminum, mounted in a header of the cell and exposed to pressure generated in the cell is attached to a pressure plate at the central axis, as by laser or ultrasonic welding, with an electrical insulator sandwiched therebetween. As pressure increases stress is created at the welded interface with the weld joint fracturing at a selected pressure range allowing the diaphragm to translate away from the plate to permanently open the electric circuit and terminate current flow. In some designs, the diaphragm is formed with a reduced thickness portion, e.g., a C-shaped groove extending along the peripheral edge of the diaphragm so that the diaphragm ruptures at a calibrated predetermined pressure to allow controlled venting of pressurized electrolyte. A current interrupt device of this type is shown in U.S. Pat. No. 5,691,073.
The present invention will be more fully understood and appreciated from the following description taken in conjunction with the drawings in which:
FIG. 1a is a perspective view of a typical cylindrical electrochemical cell and FIG. 1b is a perspective view of a prismatic cell incorporating a current interrupt device made in accordance with several embodiments of the invention;
FIG. 2 is a cross sectional view of the top portion of the FIG. 1b cell including a header mounting the current interrupt device made in accordance with a first embodiment of the invention;
With reference to FIG. 1a, a typical cylindrical electrochemical cell 2 is shown. Since the end faces of cell 2 are circular, essentially the entire area can be used to accommodate an appropriate safety mechanism such as those shown in copending U.S. Provisional Application Ser. No. 60/071, 557, filed Jan, 15, 1998 or U.S. Pat. No. 5,691,073, referenced supra. Such safety mechanisms are characterized in having a flexible diaphragm exposed to the fluid within the cell which bulges upon a selected increase in pressure creating sufficient stress to fracture a welded joint of the diaphragm and a pressure plate and to provide sufficient translation to break a current path, either directly or through a motion transfer member. With respect to a prismatic electrochemical cell such as cell 4 shown in FIG. 1b, the working diameter available for a diaphragm is limited by the thickness of the cell so that insufficient translational movement is obtainable in small prismatic cells to effectively use the teachings of the above noted safety mechanisms. As a result, typically, protection located in the header for small prismatic cells has been limited to forming a pressure vent (not shown) in cover 8 without interrupting the current path between the terminals comprising a thin membrane received over an aperture in the cover and rupturable at some specified pressure level.
FIGS. 2-5 show a current interrupt device 10 made in accordance with a first embodiment of the invention, especially adapted for use in small prismatic cells, although useable in other applications as well. Current interrupt device 10 comprises a cup-shaped member 12 having a generally flat bottom wall 12a and side wall 12b extending upwardly, i.e., in a direction away from the interior of the cell, as seen in the drawings, to a radially extending flange 12c. Stated in another way, the side wall of the cup-shaped member extends from its mounting location, in a direction toward the interior of the cell. Cup member 12 is formed with side wall 12b and end wall 12a forming an interior angle preferably greater than 90° to facilitate having the force generated by pressure generated in the cell to act on the side wall through a controlled moment arm utilizing end wall 12a to be discussed. Flange 12c is crimped onto a top cap terminal plate 14 by a crimp ring 16 with an electrically insulative sleeve 18 interposed therebetween to electrically isolate terminal plate 14 and cup-shaped member 12 from crimp ring 16 and cover 8 and to provide an electrolyte seal. As shown (see FIG. 5), flange 12c is advantageously formed with an extended, upwardly formed free end portion 12d to be folded over onto the top surface of the outer flange 14a of terminal plate 14 to provide an extended seal path without sharp edges. That is, the possibility of a sharp blanking burr on terminal plate 14 cutting through the polymer seal 18 is obviated. Crimp ring 16 is received in an opening of cover 8 of prismatic cell 4 formed by downwardly extending wall portion 8a and hermetically attached thereto as by laser welding around the perimeter of wall portion 8a. Cover 8 is in turn hermetically attached to side wall 6 of the cell as by laser welding an upper wall portion 8b thereto. An electrically conductive plate 22 is attached to the center portion of bottom wall 12a, as by laser or ultrasonic welding, which in turn is welded to an electrode tab 24 from the core of the cell. An electrical insulator member 26 having an aperture 26a is disposed intermediate to cover 8, crimp ring 16 and plate 22 to maintain electrical isolation between cover 8, crimp ring 16 and plate 22 and to limit translation of plate 22 in the case of actuation of the current interrupt device to be discussed below. If desired, insulator member 26 could be eliminated by extending vertical wall portion 18b of sleeve 18 toward plate 22 and between the outer portion of plate 22 and the cup member surface.
As mentioned above, top cap terminal plate 14, along with crimp ring 16, supports an electrolyte seal in the form of sleeve 18 of suitable material such as polypropylene. Plate 14 serves as a positive or negative electrode of the cell and forms part of the current path. Terminal plate 14 is formed with an offset central portion 14b which provides a cavity for collapse and inversion of cup member 12 while vent holes formed through plate 14 allow air volume displacement during such collapse.