US 8,236,441 B2
`(10) Patent No.:
`a2) United States Patent
`Gardneret al.
`(45) Date of Patent:
`Aug. 7, 2012
`
`
`US008236441B2
`
`(75)
`
`(54) BATTERY CELL DESIGN AND METHODS OF
`ITS CONSTRUCTION
`Inventors: William H. Gardner, East Freetown,
`MA (US); Grace S. Chang, Watertown,
`MA(US)
`(73) Assignee: A123 Systems, Inc., Waltham, MA (US)
`
`(*) Notice:
`
`Subject to any disclaimer, the term ofthis
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 1049 days.
`
`5,554,459 A
`5,773,164 A
`5,834,133 A
`ae A
`
`9/1996 Gozdz etal.
`6/1998 Venkatesan et al.
`11/1998 Narukawaetal.
`900 mawstont al.
`.
`(Continued)
`FOREIGN PATENT DOCUMENTS
`0771040 A2
`5/1997
`
`EP
`
`(Continued)
`
`OTHER PUBLICATIONS
`
`(21) Appl. No.: 12/178,538
`
`(22)
`
`Filed:
`
`Jul. 23, 2008
`
`(65)
`
`Prior Publication Data
`US 2009/0029240 Al
`Jan. 29, 2009
`.
`oe
`Related U.S. Application Data
`(60) Provisional application No. 60/951,571, filed on Jul.
`24, 2007.
`
`(51)
`
`Int. Cl.
`(2006.01)
`HOIM 2/26
`(2006.01)
`HOIM 2/20
`(2006.01)
`HOIM 4/66
`;
`;
`:
`429/94; 429/161; 429/164; 429/21]
`(52) US. Ch.
`.....-.
`(58) Field of Classification Search ...............settee None
`See applicationfile for complete search history.
`,
`References Cited
`U.S. PATENT DOCUMENTS
`3,823,040 A »
`7/1974 Jagid
`eeees ‘
`alone Beeoe 429/115
`4.400415 A
`8/1983 Kessler et al.
`4,966,822 A
`10/1990 Johnston
`5,464,705 A
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`(56)
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`International
`International Search Report and Written Opinion,
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`pages).
`
`(Continued)
`Primary Examiner — Robert Hodge
`(74) Attorney, Agent, or Firm — Wilmer Cutler Pickering
`Hale & Dorr LLP
`
`ABSTRACT
`(57)
`In some embodiments, a battery cell can include an assembly
`haviaving an anode sheet and a cathode sheet separated by sepa-
`:
`:
`rator membranes, each sheet having an electroactive layer on
`acurrentcollector. At least oneofthe current collectors can be
`.
`.
`Le
`:
`:
`in electrical communication with conducting tabs that extend
`from at least one ofthe anode sheet and the cathode sheet, the
`conducting tabs extends from an end face of the spirally
`woundassembly. In addition, the cell can include a first tab
`insulator having concentrically positioned outer and inner
`members, each ofthe outer and inner members havingat least
`one slot that allows one or moreofthe plurality of conducting
`tabs to pass through. The inner and outer membersare adjust-
`able with respect to relative angular orientation ofthe at least
`one slot on the outer and inner members of the first tab
`insulator.
`
`15 Claims, 13 Drawing Sheets
`
`1402
`
`1400
`
`1406a
`
`oo
`
`ZY 1404
`SS
`1406b
`
`1406c
`
`1442
`
`1416a
`
`1413 1416¢
`
`JLab/Cambridge, Exh. 1014, p. 1
`
`JLab/Cambridge, Exh. 1014, p. 1
`
`

`

`US 8,236,441 B2
`
`Page 2
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`6,673,128
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`6,780,303
`6,875,540
`6,884,541
`7,033,697
`7,927,732
`8,084,158
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`2003/003 5993
`2003/009 1893
`2003/0175587
`2003/0194601
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`Bl
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`2007/0117011 Al
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`2009/0109099 Al
`FOREIGN PATENT DOCUMENTS
`WO-2005076936 A2
`8/2005
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`3/2007
`
`Wo
`Wo
`
`OTHER PUBLICATIONS
`
`International Search Report, International Application No. PCT/
`US2006/34478, mailed Aug. 13, 2007. (1 Page).
`Supplementary European Search Report for European Patent Appli-
`cation No. 06814143.1 mailed May 9, 2011. 11 pages.
`
`* cited by examiner
`
`JLab/Cambridge, Exh. 1014, p. 2
`
`JLab/Cambridge, Exh. 1014, p. 2
`
`

`

`U.S. Patent
`
`Aug.7, 2012
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`Sheet 1 of 13
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`US 8,236,441 B2
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`JLab/Cambridge, Exh. 1014, p. 3
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`JLab/Cambridge, Exh. 1014, p. 3
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`

`

`U.S. Patent
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`Aug.7, 2012
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`Sheet 2 of 13
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`US 8,236,441 B2
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`JLab/Cambridge, Exh. 1014, p. 4
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`JLab/Cambridge, Exh. 1014, p. 4
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`

`

`U.S. Patent
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`Aug.7, 2012
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`Sheet 3 of 13
`
`US 8,236,441 B2
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`JLab/Cambridge, Exh. 1014, p. 5
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`JLab/Cambridge, Exh. 1014, p. 5
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`

`

`U.S. Patent
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`Aug.7, 2012
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`Sheet 4 of 13
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`US 8,236,441 B2
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`64
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`63
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`JLab/Cambridge, Exh. 1014, p. 6
`
`JLab/Cambridge, Exh. 1014, p. 6
`
`

`

`U.S. Patent
`
`Aug.7, 2012
`
`Sheet 5 of 13
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`US 8,236,441 B2
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`JLab/Cambridge, Exh. 1014, p. 7
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`JLab/Cambridge, Exh. 1014, p. 7
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`
`

`

`U.S. Patent
`
`Aug.7, 2012
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`Sheet 6 of 13
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`US 8,236,441 B2
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`JLab/Cambridge, Exh. 1014, p. 8
`
`JLab/Cambridge, Exh. 1014, p. 8
`
`

`

`U.S. Patent
`
`Aug.7, 2012
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`Sheet 7 of 13
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`US 8,236,441 B2
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`JLab/Cambridge, Exh. 1014, p. 9
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`JLab/Cambridge, Exh. 1014, p. 9
`
`
`
`

`

`U.S. Patent
`
`Aug.7, 2012
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`Sheet 8 of 13
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`US 8,236,441 B2
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`JLab/Cambridge, Exh. 1014, p. 10
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`

`

`U.S. Patent
`
`Aug.7, 2012
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`Sheet 9 of 13
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`US 8,236,441 B2
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`JLab/Cambridge, Exh. 1014, p. 11
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`JLab/Cambridge, Exh. 1014, p. 11
`
`

`

`U.S. Patent
`
`Aug.7, 2012
`
`Sheet 10 of 13
`
`US 8,236,441 B2
`
`FIG,15
`
`JLab/Cambridge, Exh. 1014, p. 12
`
`JLab/Cambridge, Exh. 1014, p. 12
`
`

`

`U.S. Patent
`
`US 8,236,441 B2
`
`Aug. 7, 2012
`
`Sheet 11 of 13
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`JLab/Cambridge, Exh. 1014, p. 13
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`

`

`US.
`
`Patent
`
`Aug.7, 2012
`
`Sheet 12 of 13
`
`US 8,236,441 B2
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`JLab/Cambridge, Exh. 1014, p. 14
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`JLab/Cambridge, Exh. 1014, p. 14
`
`

`

`U.S. Patent
`
`Aug.7, 2012
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`Sheet 13 of 13
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`US 8,236,441 B2
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`JLab/Cambridge, Exh. 1014, p. 15
`
`

`

`US 8,236,441 B2
`
`1
`BATTERY CELL DESIGN AND METHODS OF
`ITS CONSTRUCTION
`
`RELATED APPLICATION
`
`This application claims priority from U.S. Provisional
`Patent Application No. 60/951,571, filed on Jul. 24, 2007,
`whichis hereby incorporated by referencein its entirety. This
`application is also related to U.S. patent application Ser. No.
`11/515,597, filed Sep. 5, 2006, U.S. Application No. 60/714,
`171, filed Sep. 2, 2005, and US. patent application Ser. No.
`11/748,286, filed May 14, 2007, all of which are entitled
`“Battery Cell Design and MethodofIts Construction,” which
`are hereby incorporated by reference in their entirety.
`
`15
`
`FIELD OF THE INVENTION
`
`2
`include a first tab insulator having concentrically positioned
`outer and inner members, each of the outer and inner mem-
`bers having at least one slot that allows one or more of the
`plurality of conducting tabs to pass through. The inner and
`outer membersare adjustable with respectto relative angular
`orientation of the at least one slot on the outer and inner
`membersofthe first tab insulator.
`In one or more embodiments,the slots on the outer member
`and/or the inner memberare arc shaped. In one embodiment,
`at least one of the slots has an angular span of about 120-180
`degrees. In another embodiment,at least one of the slots has
`an angular span of about 90 degrees.
`In one or more embodiments, the outer member has a
`cylindrical side wall perpendicular to a face of the outer
`member.
`
`In one or more embodiments, at least one of the outer
`memberand the inner memberhasa rib shapedprotrusion for
`facilitating the bending of at least one of the plurality of
`conducting tabs.
`In one or more embodiments, at least one of the outer
`memberand the inner member has one or moreridges for
`nesting the inner memberwith the outer member
`In one or more embodiments, the conducting tabs include
`4 to 12 tabs.
`In one or more embodiments, the first current collectoris in
`electrical communication with a first plurality of conducting
`tabs that extend from the cathode sheet, and the second cur-
`rent collector is in electrical communication with a second
`plurality of conducting tabs that extend from the anode sheet.
`Thefirst plurality of conducting tabs and the secondplurality
`of conducting tabs extend from opposing end faces of the
`electrode of the opposing polarity, causing a short circuit and
`spirally wound assembly. In one embodiment,the cell further
`a non-functioning product. A short circuit can also be caused
`include a secondtab insulator, and thefirst tab insulator and
`by a tab’s movement dueto cell cycling, mechanical shock,
`the secondtab insulator are disposed on opposingfaces ofthe
`and/or vibration loading during the lifetime of the cell. To
`spirally wound assembly.
`prevent short circuits, a tab insulator with one or more holes
`In one or more embodiments, one of the inner and outer
`that allow one or more tabs to pass through can be used.
`membershasat least two slots that are located on opposites of
`However, becausethe relative positions of the tabs can vary
`the memberwith respect to the center of the member.
`significantly, an insulator that can accommodate multiple
`In one or more embodiments, a method of making an
`tabs and can be easily assembled into a working cell can be
`electrochemical cell is included. The method can include
`difficult to make, especially when there are 4 or more tabs to
`interposing a separator membrane between a positive elec-
`accommodate. It is also possible to cover each tab with adhe-
`trode comprising a first electroactive layer onafirst current
`sive backed polyimide material, and use additional strips of
`collector and a negative electrode comprising a second elec-
`polyimide tape over the battery cell to prevent the tabs from
`troactive layer on a second current collector to form a multi-
`contacting the cell. However, currently knownpolyimide tape
`layer assembly, wherein each of the current collectors has a
`adhesives soften considerably with exposure to heat or
`plurality of conductive tabs in electrical contact with and
`lithium ion cell electrolyte. This would allow the tape to move
`extending outward from the current collectors, wherein the
`from its protective position on the tab during mechanical
`shock and vibration loads.
`tabs of the positive electrode and the tabs of the negative
`electrode are on opposite sides of the multilayer assembly.
`Improvements to address these and other limitations of
`The method further includes spirally winding the multilayer
`conventional cylindrical and prismatic batteries are desired.
`assembly, fitting the tabs of the selected current collector
`throughslots ofa first tab insulator having an outer member
`and an inner member, whereinthe first insulator is adjustable
`In one or more embodiments, an electrochemical cell can
`with respectto relative angular orientation of the outer mem-
`ber and the inner member. In addition, the method includes
`include an assembly, which may be a cylindrical spirally
`folding the tabs of the selected current collector towards the
`wound assembly, having an anode sheet and a cathode sheet
`separated by separator membranes, the cathode sheet having
`center of the spiral wound assembly such that the tabs inter-
`
`a first electroactive layer onafirst current collector, and the sect one another at a central axis, collecting the overlapped
`anode sheet having a secondelectroactive layer on a second
`tabs of the selected current collector at a point beyondthe tab
`current collector, the spirally wound assembly having a cylin-
`intersection, and securing the collected tabs of the selected
`drical side wall and opposing end faces. The cell can also
`current collector to a connecting strap.
`In one or more embodiments, a tab insulator for use in
`include conducting tabs that extend from at least one of the
`anodesheetand the cathode sheet, the tabs extending from an
`battery cells can include concentrically positioned outer
`end face of the spirally wound assembly and in electrical
`member and inner members, each member having one or
`communication with at least one of the first current collector
`more slot that allows one or more conducting tabs of the
`and the second current collector. In addition, the cell can
`battery cell to pass through. The inner and outer members are
`JLab/Cambridge, Exh. 1014, p. 16
`
`The present invention generally relates to an electrochemi-
`cal battery cell. More particularly,
`the present invention
`relates to a compact, robust, multifunctional and highly
`manufacturable rechargeable battery cell.
`
`BACKGROUND
`
`To facilitate manufacturing of electrochemical cells, cur-
`rent collecting tabs are often made longer than what is
`required by the final geometry ofthe cells. Because ofthis, the
`tabs are often formedintotheir final positions through a series
`of deliberate bends. As a result of inherent variation in manu-
`
`facturing processes, the bending of the tabs may impart an
`undesirable force so that tab material makes contact with
`
`30
`
`40
`
`45
`
`SUMMARYOF THE INVENTION
`
`JLab/Cambridge, Exh. 1014, p. 16
`
`

`

`US 8,236,441 B2
`
`3
`adjustable with respect to relative angular orientation of the
`slots of the inner and outer members.
`
`BRIEF DESCRIPTION OF THE DRAWING
`
`The invention is described with reference to the following
`figures, which are provided for the purpose of illustration
`only, the full scope of the invention being set forth in the
`claimsthat follow.
`
`FIG. 1 is an exploded diagram illustrating the internal
`components of an exemplary battery cell that can use one or
`more embodiments of the invention.
`
`FIG. 2 is a cross-sectional illustration of an exemplary
`assembledbattery cell.
`FIG.3 is a view of a positive (cathode) end cap showing a
`pressure release vent and an interface terminal.
`FIG. 4A provides an exploded view of the components
`used in a negative (anode) end cap assembly.
`FIG. 4B showsa cross-sectional view of an assembled
`
`negative end cap.
`FIG. 4C showsa perspective view ofan assembled negative
`end cap afterriveting.
`FIG. 5A depicts a perspective view the sealing of thefill
`hole in the negative end cap with a metal plug anda plastic
`sealafter cell activation.
`
`FIG. 5B depicts a cross-sectional enlarged view of the
`sealing of thefill hole in the negative end cap with a metal
`plug and a plastic seal after cell activation.
`FIG.6A is a plan view of an electrode sheet with tabs.
`FIG.6B is an enlarged plan view of an electrode sheet with
`tabs.
`FIG. 7A showsa top view ofa battery can indicating the
`exemplary location of collector tabs within a 90 degree quad-
`rant.
`
`FIG.7B depicts a series of views ofthe cell design accord-
`ing to one or more embodiments of the invention, andillus-
`trates the location and bending of current collecting tabs.
`FIG.8 depicts the attachment of current extension tabs to
`the respective terminals.
`FIG.9 is a plot of currentvs. time in a motorthat is pulsed
`about 4000 times/sec.
`
`FIG. 10A illustrates the tab position and current flow in an
`exemplary cylindrically woundbattery, as viewed from the
`rolled end face ofthe spirally woundelectrode.
`FIG. 10B is a plan view of an unrolled electrode of the
`cylindrically wound battery shown in FIG. 10A.
`FIG. 11A illustrates the tab position and current flow in
`another exemplary cylindrically wound battery, as viewed
`from the rolled end face of the spirally woundelectrode.
`FIG. 11B is a plan view of an unrolled electrode of the
`cylindrically wound battery shown in FIG. 11A.
`FIG. 12 shows a high-inductance battery’s voltage and
`current waveforms.
`
`FIG. 13 shows a low-inductancebattery’s voltage and cur-
`rent waveforms.
`
`FIG. 14 depicts a tab insulator having two members
`according to one or more embodiments ofthe invention.
`FIG.15 is a top view ofthe insulator shown in FIG.14, in
`which the two membersare concentrically disposed.
`FIG. 16 depicts a tab insulator design according to another
`embodimentof the present invention.
`FIG. 17 is a perspective view of a memberof a tab insulator
`having tab risers and a cylindrical side wall.
`FIG. 18 is a perspective view of two members of a tab
`insulator, one member having a ridge to ensure that the two
`membersstay concentric after assembly.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`4
`DETAILED DESCRIPTION
`
`Embodiments of the present invention provide tab insula-
`tors that can be used on battery cells to prevent current col-
`lecting tabs from contacting electrode of opposite polarity.
`Exemplary embodiments of battery cells are illustrated in
`FIGS. 1-13. FIGS. 14-18 illustrate tab insulators according to
`one or more embodiments of the present invention. Although
`tab insulators according to some embodiments are described
`in connection with exemplary battery cells illustrated in
`FIGS. 1-13, it is to be understood that one or more embodi-
`ments of the invention can also be used on any other suitable
`battery cells.
`A battery cell can include upper and lower welded end
`caps. The cell’s primary packaging (can and end caps) can be
`composed of aluminum alloy. The weld seal
`is typically
`obtained by laser welding, or optionally by other metal join-
`ing methodssuch as ultrasonic welding, resistance welding,
`MIG welding, TIG welding. The end caps of the doubly
`(upper and lower ends) welded container maybe thicker than
`the can wall; e.g., the end caps may be upto about 50% thicker
`than the can wall. This differential in thickness is not accom-
`plished by other means, such as deep drawing. The doubly
`welded cell packaging can provide significantly greater cell
`volumethan crimpedseals or singly weldedcells. In addition,
`the thick end caps improve mechanical robustnessof the cell,
`for example, against crushing. The additional cell modifica-
`tions incorporated into the cell design permit the use of a
`doubly welded packaging, which is not otherwise possible or
`convenient with conventional battery cell designs.
`The battery cell package design uses a low weight and
`highly compact aluminum housing, andis typically an alu-
`minum alloy such as Al3003H14. Aluminum and aluminum
`alloys provide high specific modulus and high specific stiff-
`ness in the structure and a high strength to weight ratio.
`Aluminum is also one of the few materials that are stable at
`
`the cathode potential of a Li-ion cell. Several features of the
`battery design are shownin the exploded diagram of FIG. 1.
`The cell design includes a positive end cap (1), a cathode
`extensiontab (2), an insulation disc (3), a cylindrical tube (4),
`a negative end cap (5), anode current collection tabs (6),
`cathode current collection tabs (7), and internal active cath-
`ode and anode materials (electrodes) (8a and 84). Although
`exemplary embodiments discuss cylindrical
`tubes, other
`shapes or outer configurations can be utilized. The positive
`end cap (1) contains both the positive battery terminalfor the
`cell as well as the cell’s vent mechanism. The cathode exten-
`
`sion tab (2) acts as an electrical connection between the
`cathode current collection tabs (7) and the cell’s external
`positive terminal (1). The insulation disk (3) includesslots
`(3a) through which the current collection tabs extend. The
`insulationdisc (3) prevents the cathode current collection tabs
`(7) and the cathode extension tab (2) from shorting to the
`internal active cathode and anode materials (8a and 84). The
`cylindrical tube (4) acts as the main housing for the cell
`package.
`During assembly, weld and crimp joints are used to connect
`both sets of current collector tabs (6) and (7) to both end caps
`(5) and (1), respectively, via the extension tab (2) and the
`integrated extension tab (5a) found in the negative end cap
`(5). Both end caps are welded to tube (4) to make the cylin-
`drical cell. The negative end cap (5) contains both the cell’s
`negative battery terminal as well as the cell’s fill hole (dis-
`cussed in greater detail below), both of which share the same
`internal volume and external space and are symmetrically
`centered in the cell. Negative end cap (5) also has an inte-
`grated extension tab (5a) for making an electrical connection
`JLab/Cambridge, Exh. 1014, p. 17
`
`JLab/Cambridge, Exh. 1014, p. 17
`
`

`

`US 8,236,441 B2
`
`5
`between the anode current collection tabs (6) and the cell’s
`external negative terminal located on the negative end cap (5).
`An insulation disk (3) with slots (3a) is also used at the anode
`to prevent shorting ofthe anode current collection tabs (6) and
`anode extension tab (5a).
`An assembled cell incorporating the design features of
`FIG. 1 is shown in FIG. 2 in cross-section, where like ele-
`ments are similarly labeled. Also represented are separator
`layers or separator membranes(8') betweenthe electrodes (8a
`and 85). Once assembled, the cell incorporates favorable
`features for both manufacturing and customerinterface in a
`volumetrically efficient package. This allows for the vast
`majority ofthe inside ofthe cell to be used for active material,
`greatly improving the cell’s energy storage capacity to vol-
`umeratio.
`Individual components and features of the cell are
`described.
`
`Thepositive end cap (1) includes an engineered vent score
`(10) and a nickel interface terminal (9), as illustrated in FIG.
`3. The engineered vent score opens under a predetermined
`internal pressure, letting large amounts of gas and material
`exit the cell ifnecessary. The vent is an annular groove located
`near the periphery of the positive end cap, disposed between
`the end cap circumference and the nickel terminal. The
`groove can be located on the innerorouter face ofthe end cap,
`or both. In one or more embodiments, the grooveis located on
`both the inner and outer faces ofthe end cap. The grooves may
`oppose one anotheror be offset from one another. The groove
`provides a thinned radial section in the end cap that is
`designed to rupture at a preselected pressure. The annular
`groove formsan arc on the end cap thatis in the range ofabout
`150 degrees to a full 360 degrees, or about 180 degrees to
`about 300 degrees. The actual arc length will depend on the
`size of the cell. The arc length can be selected so that the end
`cap hinges when ruptured and the ruptured end cap is not
`severed from the battery can, but also can be up to abouta full
`360 degree arch with no apparent hinge. A further advantage
`ofthe annular grooveis that it serves to thermally insulate the
`terminal during welding of the end cap to the battery body.
`The grooveis introduced by conventional methods, such as
`stamping, scoring or scribing andthe like.
`Thenickel interface terminal (9) providesa low resistance,
`corrosion resistant battery terminal, as well as a weldable
`interface for connecting batteries together in packs. The
`nickel plate can range in thickness and typically has a thick-
`ness in the range of about 75 um to about 125 wm. Thicker
`terminal plates are particularly well-suited for high power
`batteries. In one or more embodiments, the body of the cath-
`ode cap is aluminum and, for example, is the same aluminum
`alloy as the battery tube. In one or more embodiments, the
`cathode cap maybeplated with a layer ofnickelonits outside
`surface. The nickel interface terminalis then either resistance
`
`(spot) welded to the cathode cap to give a mechanically robust
`interface, re-flow solderedto the nickel plating layer to give
`an electrically robust interface betweenthe twoparts, or both.
`Other welding and soldering techniques may be used, for
`example, ultrasonic welding or electrically conductive adhe-
`sives. Suitable solder includes solder having a melting tem-
`perature above the maximum use temperature ofthe battery.
`This joining technique between the Ni terminal and the Al
`cathode cap is uniquein the battery industry.
`The pressure vent occupies a peripheral region of the end
`cap face and doesnotinterfere with the location and securing
`of the nickel terminal. The nickel terminal cross-sectional
`
`area can be quite large and can occupya significant portion of
`the end cap face. This serves to reduce cell impedance and to
`provide cell to cell weld-ability during pack assembly.
`
`5
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`6
`FIGS. 4A-4C depict a negative end cap (5) including a
`centrally locatedfill hole (40). Thefill hole is used to activate
`the cell once assembled andis defined, at least in part, by a
`hollow bore rivet (45) which makes up the powerterminal.
`Dualuse ofthe central location ofthe negative end cap as both
`a fill hole and as a power terminal provides efficient use of
`space and does notinterfere with battery operation. Thefill
`hole (40) is centrally located in the end cap face. The centrally
`located fill hole provides a feed through inlet fittingly dis-
`posed within the hole and connecting to the interior of the
`cell. Electrolyte is introduced throughthis feed through inlet
`during activation.
`The negative end cap is constructed by assembling the
`constituent components as illustrated in the exploded dia-
`gram of FIG. 4A. Upper gasket (44) is placed into end cap
`body (43), which may contain a depression for receiving the
`gasket. The hollow borerivet serving as the power terminal
`(45) is assembled into upper gasket (44). The stem (45a) of
`rivet (45) extends through a central opening ofboth the upper
`gasket (44) and end cap body (43). The assembly is flipped
`over, and seal gasket (47) is inserted onto gasket (44) and
`placed onto body (43). Lower gasket (42), seal gasket (47),
`and rivet backing disc (46) are assembled and positioned as
`illustrated in FIG. 4A. Extension tab (41) is inserted onto the
`stem of rivet (45). The as-assembled components, prior to
`crimping are shownin FIG.4B.
`Rivet (45) may be Niplated steel for both good corrosion
`resistance and good weldability, which serves as the power
`terminalforthe cell. Theflat head ofrivet (45) extends over a
`portion ofthe external face ofthe end cap and the hollow stem
`(45a) extendsinto the interior of the cell. It also includesa fill
`hole through its center with an engineered ledge to help
`sealing, a symmetric shape, and a centralized rivet stem for
`sharing space and symmetry betweenthe battery terminal and
`the fill hole. Extension tab (41) connects the power terminal
`(45) with the cell’s internal active anode material. A lower
`gasket (42) protects the extension tab (41) from contacting the
`end cap body (43), which is at a different voltage potential.
`Body (43) is hermetically sealed to the battery tube (not
`shown) or the main body ofthe cell through any numberof
`methods, including but not limited to the aforementioned
`methods of crimping and welding. Upper gasket (44) insu-
`lates the power terminal (45) from the end cap body (43),
`whichareat different voltage potentials. Rivet backing disc
`(46) helps to create a robust press-rivet clamp force onto body
`(43). Seal gasket (47) helps to achieve a robust seal under-
`neath the press-rivet.
`The entire assembly may be crimped together by pressing
`and deforming the stem ofrivet(45), as illustrated in FIG. 4C,
`squeezingall ofthe parts together to form press-rivet (48) and
`creating a goodelectrical contact between the extension tab
`(41) and the powerterminal (45).
`After the end caps have been weldedto the cell’s tube, the
`cell is activated byfilling electrolyte through the hole in the
`power terminal (45). Turning now to FIGS. 5A and 5B, fill
`hole (40) is hermetically sealed by meansoffill hole plug seal
`(50) (e.g., a high temp plastic seal) andfill hole plug (51), a
`deformable insert; e.g., a deformable metal insert. Fill hole
`plugseal (50) is pressed into the fill hole opening after the end
`cap has been sealed to the tube and thecell has been activated
`with electrolyte. The fill hole plug (51) is then pressed into
`this samefill hole, expanding, clamping and holding the seal
`(50) up against the engineered ledge of the rivet (45) and
`achieving a hermitic seal wherethefill hole usedto be.
`The internally active material ofthe cell includes twoelec-
`trodes, a cathode and an anode. One contributor to the imped-
`ance of a battery cell is the lack of current carrying paths
`JLab/Cambridge, Exh. 1014, p. 18
`
`JLab/Cambridge, Exh. 1014, p. 18
`
`

`

`US 8,236,441 B2
`
`7
`betweenthe active cell materials (anode and cathode) and the
`external cell terminals. It has been surprisingly discovered
`that overall cell impedance can be significantly lowered by
`using more current carriers, or “tabs”, than conventional
`cylindrical (wound assembly) cells, whose designs call for
`one or twotabs perelectrode. In one or more embodiments of
`the invention, a plurality of tabs are joinedat a larger current
`collector on either side of the cell called an extension tab,
`which then makes the connection with each of the battery
`terminals of the cell. In one or more embodiments, the elec-
`trode can include about 4 to about 12 tabs, and for example,
`may include four tabs. In other embodiments, the electrode
`includes one tab per 200 cm?areaof electrode. High power
`battery cells will require a higher density of tabs than low
`powercells.
`Electrodes in this cell design uses several, e.g., four to
`twelve, current collecting tabs to conduct current out of each
`of the active material, e.g., cathode and anode, and into the
`battery terminals. FIG. 6A depicts an exemplary electrode
`sheet (60). The electrode sheet (60) includes an integral cur-
`rent collector substrate (66) and a layer of electroactive mate-
`rial (67) in electrical connection to the current collector sub-
`strate. Current collecting tabs (61), (62), (63), (64) extend
`from an edge portion (68) of the electrode.
`The tabbed electrodes are then organized into an electro-
`chemicalcell. A separator sheet, e.g., two separator sheets, is
`interposed between the cathode and anode sheets such that
`the tabs ofthe cathode and anode are located at opposite sides
`ofthe assembly. The multilayer assemblyis spirally wound to
`form a spiral electrochemical assembly, known asa “jelly-
`roll.” A jellyroll with extended tabs (6), (7) is illustrated in
`FIG.1.
`
`The tabs can be of different length, which reflect their
`distances from thejelly role center when wound. The length
`of the tabs may be adjusted before or after windingthejelly-
`roll. In order to form the tabbed electrode, a portion of the
`electroactive material is removed from an edge ofthe elec-
`trode to create a clean surface forelectrical contact as shown
`
`in FIG. 6B (not drawn to scale). The tabs are electrically
`connected, e.g., by welding,riveting, crimping or other simi-
`lar technique, to an exposed portion of the electrode. An
`exemplary method for cleaning the contact surfaces and
`attaching the collector tabs is provided in co-pending U.S.
`Provisional Patent Application No. 60/799,894 entitled “Use
`of a Heated Base to Accelerate Removal of Coated Electrode
`
`in the Presence of a Solvent,” filed on May 12, 2006, the
`contents of which are incorporated by reference. The tabs are
`then covered with a non-reactive tape (65), which covers the
`exposed metal tabs and prevents undesired chemical reac-
`tions with the cell chemicals. Tape (65) covers both sides of
`the electrode in the vicinity of the tabs. The tape covers that
`portion of the tab that lies over the electrode and may cover
`someorall of the underlying electrode that remains exposed,
`i.e., that is not covered by either active electrode layer or a
`current collecting tab. At least a portion ofthe tab that extends
`out from the electrode is not covered by tape.
`In order to maximize the reduction in impedanceofa cell
`through the addition oftabs, these four tabs can be positioned
`at equal intervals along each of the two electrode’s lengths,
`e.g., as close to th, *eth, %th, and 7th of the electrode
`length as possible, to thereby mi