Unlted States Patent
`
`[19]
`
`[11] Patent Number:
`
`5 470 357
`9
`9
`
`Schmutz et al.
`
`
`[45] Date of Patent:
`Nov. 28, 1995
`
`l|||||lllllllllllllllllllllIllllllllllllllllllllllllIllllllllllllllllllllll
`USOOS470357A
`
`[54] METHOD OF MAKING A LAMINATED
`LITHIUM-ION RECHARGEABLE BATTERY
`CELL
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`[75]
`
`Inventors: Caroline N. Schmutz, Eatontown;
`Frough K. Shokoohi, Fair Haven;
`Jean-Marie Tarascon Martinsville‘
`’
`.
`’
`Paul C" Warren, Far Hflls’ all Of N'J'
`[73] Assignee: Bell Communications Research, Inc.,
`Livingston, NJ.
`
`[21] APPL NO-i 423,970
`[22]
`Filed'
`A r 26 1995
`'
`p '
`’
`t' D ta
`R l t d U.S. A li
`ea e
`pp ca run
`a
`[63] Continuation—impart 0f Ser. No. 160,018, NOV. 30, 1993,
`Pat. No. 5,450,904, which is a confinuafion-in—part of sex.
`No. 110,262, Aug. 23, 1993, Pat- No. 5,418,091, which is a
`?:?gg%°§‘1'§n'9m 0f Ser. No' 26304, Mar. 5’ 1993’ Pat'
`'
`’
`’
`'
`Int. Cl.6 .............................. H01M 6/00; H01M 6/18
`. 29/6235; 29/6231; 429/192
`
`.................... 29/6235, 623.1;
`429/192
`
`[51]
`[52]
`[58]
`
`1:391:33 1:23; 15:23:11; 81‘ """""""""""""""" 233/3:
`,
`,
`...................................
`.
`.
`Primary Exammer—John S. Maples
`Attorney, Agent, or Firm—Leonard Charles Suchyta; Lionel
`N‘ White
`
`[57]
`
`ABSTRACT
`
`ry
`
`cell electrode and electrolyte/
`Li-ion rechargeable batte
`separator elements formulated as layers of plasticized poly-
`meric matrix compositions are laminated with electrically
`conductive collector elements to form a unitary battery cell
`structure. Adhesion between the electrode and collector
`elements is enhanced by pretreatment of the collector ele-
`ments in which a 0.25% to 3.0% solution of a polymeric
`material compatible with said matrix polymer is applied to
`a collector foil or grid and dried to form a coated film, and
`the resulting coated collector element is heated within the
`range of about 250° to 450° C. for about 5 to 60 seconds.
`
`8 Claims, 4 Drawing Sheets
`
`49
`
`
`
`V/l'l/l/l/I/l/I/l/l/l/I/A
`”figs," ”warms” e .
`t
`'
`,
`‘ “\ » _ —- ‘1
`t
`4;“; .211; 1i?
`‘-
`v
`-
`i
`|
`
`‘\\ 46
`\\ r
`\\§\
` 47
`
`46
`
` _
`
`46
`
`43
`
`:"+\
`in '
`
`é _. _ _l
`
`41
`
`46
`
`46
`
`JLab/Cambridge, Exh. 1017, p. 1
`
`JLab/Cambridge, Exh. 1017, p. 1
`
`

`

`753,07
`
`4.1IsFat
`
`US. Patent
`
`0N
`
`4cm
`
`
`
`
`
`%‘,wwwwwwwwmwwwwwwwwwwwWWWm”wwwwwmwwwwwwww
`
`eAmua‘r////////e...
`
`
`HN“:.m.“
`
`-..?xx///////////////////0
`
`JLab/Cambridge, Exhi 1017, p. 2
`
`JLab/Cambridge, Exh. 1017, p. 2
`
`
`

`

`US. Patent
`
`Nov. 28, 1995
`
`Sheet 2 of 4
`
`5,470,357
`
`5
`8‘
`2
`:15
`
`Z x
`
`0.
`
`GD
`0'
`
`(Q
`0
`
`‘1'.
`O
`
`N O
`
`"
`
`0.
`:—
`
`JLab/Cambridge, Exh. 1017, p. 3
`
`N
`-
`L5
`LL
`
`
`
`O
`Lri
`
`O
`<15
`
`O.
`co
`
`O.
`N
`
`SJJOA
`
`JLab/Cambridge, Exh. 1017, p. 3
`
`

`

`US. Patent
`
`Nov. 28, 1995
`
`Sheet 3 of 4
`
`5,470,357
`
`0.8
`
`0.6
`
`0.4
`
`0.2
`
`o
`
`0
`
`4O
`
`80
`
`120
`
`160
`
`Cycles
`
`FIG. 3
`
`JLab/Cambridge, Exh. 1017, p. 4
`
`v
`cg
`
`C E_
`
`_><
`_l
`
`.E
`
`g
`é:
`‘5
`(U
`Q.
`(’5
`'0
`
`JLab/Cambridge, Exh. 1017, p. 4
`
`

`

`US. Patent
`
`Nov. 28, 1995
`
`Sheet 4 of 4
`
`5,470,357
`
`mv
`
`mv
`
`mv
`
`V.GE
`
`m».
`
`Voqoé‘o4040494«o4.«¢«¢4¢<¢<¢4¢4¢<¢49¢9<oiii:
`WOOOOOOOODOOOOODODOOO00.0OODOOOOODODODOOOOOOODOOw.
`mv
` Eu
`
`m,
`
`JLab/Cambridge, Exh. 1017, p. 5
`
`JLab/Cambridge, Exh. 1017, p. 5
`
`
`
`
`

`

`1
`METHOD OF MAKING A LANIINATED
`LITHIUM-ION RECHARGEABLE BATTERY
`CELL
`
`RELATED APPLICATIONS
`
`This application is a continuation—in—part of U.S. patent
`application Ser. No. 08/160,018, filed 30 Nov. 1993, which
`is a continuation-in—part of Ser. No. 08/110,262, filed Aug.
`23, 1993, now U.S. Pat. No. 5,418,091, which is a continu-
`ation-in-paxt of Ser. No. 08/026,904, filed Mar. 5, 1993, now
`U.S. Pat. No. 5,296,318.
`
`BACKGROUND OF THE INVENTION
`
`The present invention relates to electrolytic cells com-
`prising polymeric film composition electrodes and separator
`membranes and to a method of economically making such
`cells. In particular, the invention relates to rechargeable
`lithium battery cells comprising an intermediate separator
`element containing an electrolyte solution through which
`lithium ions from a source electrode material move between
`
`cell electrodes during the charge/discharge cycles of the cell.
`The invention is particularly useful for making such cells in
`which the ion source electrode is a lithium compound or
`other material capable of intercalating lithium ions, and
`where the electrode separator membrane comprises a poly-
`meric matrix made ionically conductive by the incorporation
`of an organic solution of a dissociable lithium salt which
`provides ionic mobility.
`These flexible polymeric electrolytic cell separator mem-
`brane materials may be employed as separator elements with
`mechanically assembled battery cell components or in com-
`posite battery cells constructed of successively coated layers
`of electrode and electrolyte compositions. Preferably, how-
`ever, electrolytic cells for use as rechargeable batteries are
`constructed of individual electrode and electrolyte compo-
`sition membranes which are laminated together with outer
`layers of conductive metal foil serving as current collectors,
`typically under heat and pressure.
`The present invention provides, in particular, a means of
`improving the adhesion between polymeric electrode mem-
`brane compositions and the collector elements during the
`lamination operation. Through the use of this improvement,
`the present electrolytic cell yields a more economical and
`reliable battery cell product.
`
`SUMMARY OF THE INVENTION
`
`Electrolytic cell electrode and separator elements utilizing
`polymeric materials according to the present invention pref-
`erably comprise the combination of a poly(vinylidene fluo-
`ride) copolymer matrix and 20% to 70% by weight of a
`compatible organic plasticizer which maintains a homoge—
`neous composition in the form of a flexible, self-supporting
`film. The copolymer comprises about 75 to 92% by weight
`vinylidene fluoride (VdF) and 8 to 25% hexafiuoropropylene
`(HFP), a range in which the latter comonomer limits the
`crystallinity of the final copolymer to a degree which
`ensures good film strength while enabling the retention of
`about 40 to 60% of preferred solvents for lithium electrolyte
`salts. Within this range of solvent content, the 5 to 7.5% salt
`ultimately comprising a hybrid electrolyte membrane yields
`an effective room temperature ionic conductivity of about
`10‘4 to 10‘3 S/cm, yet the membrane exhibits no evidence
`of solvent exudation which might lead to cell leakage or loss
`of conductivity.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`6O
`
`65
`
`5,470,357
`
`2
`
`Electrolytic cells, such as rechargeable battery cells, are
`constructed according to the invention by means of the
`lamination of electrode and electrolyte cell elements which
`are individually prepared, by coating, extrusion, or other-
`wise,
`from compositions comprising the noted polyvi-
`nylidene fluoride (PVdF) copolymer materials. For example,
`in the construction of a lithium-ion battery, a positive
`electrode film or membrane is separately prepared as a
`coated layer of a dispersion of intercalation electrode com-
`position, e.g., a LiMn204 powder in a copolymer matrix
`solution, which is dried to form the membrane. A positive
`current collector layer of aluminum foil or grid is pretreated,
`or primed, with a polymeric material compatible with the
`matrix copolymer to enhance adhesion to the positive elec~
`trode which is then overlaid upon the collector.
`An electrolyte/separator membrane formed as a dried
`coating of a composition comprising a solution of the
`VdF:HFP copolymer and a plasticizer is then overlaid upon
`the positive electrode film. A negative electrode membrane
`formed as a dried coating of a powdered carbon dispersion
`in a copolymer matrix solution is similarly overlaid upon the
`separator membrane layer, and a negative copper collector
`foil or grid which is pretreated, or primed, in a manner
`similar to that of the positive collector is laid upon the
`negative electrode layer to complete the cell assembly. This
`assembly is then heated under pressure to heat-fused bond—
`ing between the plasticized copolymer matrix components
`and to the collector grids to thereby efiect lamination of the
`cell elements into a unitary flexible battery cell structure.
`At this stage the laminated structure comprises a signifi-
`cant measure of homogeneously distributed organic plasti-
`cizer, particularly in the separator membrane stratum, yet is
`devoid of hygroscopic electrolyte salt. As a result,
`the
`“inactive” battery cell may be stored at ambient conditions,
`either before or after being shaped or further processed,
`without concern for electrolyte deterioration due to reaction
`with atmospheric moisture. Only during a final operation
`when an electrolyte salt solution is introduced to activate the
`battery cell need there be concern for maintaining special
`conditions, such as an atmosphere of dry, inert gas.
`When it is desired to so activate a battery in the final stage
`of manufacture, the laminate cell structure is immersed in or
`otherwise contacted with an electrolyte salt solution which
`will imbibe into the VszHFP copolymer membrane matrix
`to provide
`substantially the
`same ionic conductivity
`enhancement as achieved by a preformed hybrid electrolyte/
`separator film containing such an electrolyte salt solution. In
`order to facilitate the absorption of electrolyte solution, it is
`preferred that a substantial portion of the plasticizer be
`previously removed from the copolymer matrix. This may
`be readily accomplished at any time following the laminat-
`ing operation by immersion of the cell laminate in a copoly-
`mer-inert,
`low-boiling solvent, such as diethyl ether or
`hexane, which will selectively extract the plasticizer without
`significantly affecting the copolymer matrix of the cell
`element strata. The extracting solvent may then be simply
`evaporated to yield a dry, inactive battery cell. The laminate
`structure may be stored in either plasticized or extracted
`form for an extended period of time prior to activation.
`The battery-forming process of the present invention is
`readily adaptable to batch or continuous operation, since the
`electrode and electrolyte/separator membrane elements, as
`well as the collector grid foils, may be shaped or sized prior
`to laminate assembly or they may be laminated from con-
`fluent webs of membrane materials for later shaping or
`manifolding, as desired. The extraordinary advantage of the
`present invention lies in the fact that all such operations may
`
`JLab/Cambridge, Exh. 1017, p. 6
`
`JLab/Cambridge, Exh. 1017, p. 6
`
`

`

`3
`
`4
`
`5,470,357
`
`be carried out at ambient conditions prior to the introduction
`of any vulnerable electrolyte salts.
`
`BRIEF DESCRIPTION OF THE DRAWING
`
`The present invention will be described with reference to
`the accompanying drawing of which:
`FIG. 1 is a diagrammatic representation of a typical
`laminated lithium-ion battery cell structure of the present
`invention;
`
`FIG. 2 is a graph tracing recycling voltage as a function
`of intercalated lithium for a laminated lithium-ion battery
`cell of FIG. 1;
`
`FIG. 3 is a graph of the capacity of a laminated lithium-
`ion battery cell of FIG. 1 as a function of the number of
`charge/discharge cycles;
`FIG. 4 is a diagrammatic representation of a laminating
`process for preparing a battery cell structure of the present
`invention;
`
`DESCRIPTION OF THE INVENTION
`
`A laminated rechargeable battery cell structure of the
`present invention as depicted in FIG. 1 comprises a copper
`collector foil 11, preferably in the form of a pretreated open
`mesh grid, upon which is laid a negative electrode mem-
`brane 13 comprising an intercalatable material, such as
`carbon or graphite, or a low-voltage lithium insertion com-
`pound, such as W02, M002, or Al, dispersed in a polymeric
`binder matrix. An electrolyte/separator film membrane 15 of
`plasticized VdF2HFP copolymer is positioned upon elec-
`trode element 13 and is covered with a positive electrode
`membrane 17 comprising a composition of a finely-divided
`lithium intercalation compound, such as LiMn204, LiCoOZ,
`or LiNiOz,
`in a polymeric binder matrix. A pretreated
`aluminum collector foil or grid 19 completes the assembly
`which is then pressed between platens (not shown) under
`heat and pressure to soften and bond the polymeric compo-
`nents and laminate the membrane and grid layers.
`Separator membrane element 15 is generally prepared
`from a composition comprising the earlier-noted 75 to 92%
`vinylidene fluoride (VdF): 8 to 25% hexafluoropropylene
`(HFP) copolymer (available commercially from Atochem
`North America as Kynar FLEX) and a compatible organic
`plasticizer. Such a copolymer composition is also preferred
`for the preparation of the electrode membrane elements,
`since subsequent laminate interface compatibility is ensured.
`The plasticizer may be one of the various organic com-
`pounds cornmonly used as solvents for electrolyte salts, e.g.,
`propylene carbonate or ethylene carbonate, as well as mix-
`tures of these compounds. Higher-boiling plasticizer com-
`pounds, such as dibutyl phthalate, dimethyl phthalate,
`diethyl phthalate, and tris butoxyethyl phosphate are par-
`ticularly suitable. Inorganic filler adjuncts, such as fumed
`alumina or silanized fumed silica, may be used to enhance
`the physical strength and melt viscosity of a separator
`membrane and, in some compositions, to increase the sub-
`sequent level of electrolyte solution absorption.
`Any common procedure for casting or forming films or
`membranes of polymer compositions may be employed in
`the preparation of the present membrane materials. Where
`casting or coating of a fluid composition is used, e.g., with
`meter bar or doctor blade apparatus, the viscosity of the
`composition will normally be reduced by the addition of a
`readily evaporated casting solvent, such as tetrahydrofuran
`(TI-IF), acetone, or the like. Such coatings are normally
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`air-dried at moderate temperature to yield self-supporting
`films of homogeneous, plasticized copolymer compositions.
`A membrane material, particularly for use as a separator
`element, may also be formed by allowing the copolymer in
`commercial form, i.e., bead or powder, to swell in a pro—
`portionate amount of plasticizer and then pressing the swol-
`len mass between heated (e.g., about 130° C.) plates or
`rollers, or extruding the mixture.
`In order to provide electrolytic battery cell terminals, the
`respective electrode membranes are maintained in intimate
`contact with conductive current collector elements, usually
`metal foils. While in cells of stacked layer structure a
`constant pressure is relied upon to yield such contact
`between the elements, the lamination of the present cell
`provides both the electrical continuity and the flexible cell
`integrity. In accordance with the present invention, pretreat-
`ment of the collector elements with an electrode—compatible
`polymeric material, preferably by application of a 0.25% to
`2.5% solution of a copolymer similar to that of the electrode
`matrix, typically VdF with 6% to 25% HFP, and heating at
`250° to 450° C. for about 5 to 50 seconds ensures persistent
`adhesion upon lamination. A somewhat heavier layer of the
`copolymer alone, e.g., that obtained by dipping in a 3%
`solution of the pretreatment polymer, provides improved
`adhesion without a post-heating operation.
`As with the membrane—forming operations, lamination of
`assembled cell structures may be accomplished by com-
`monly-used apparatus. Preshaped or sized assemblies may
`be simply pressed for a short while between metal plates
`weighted at about 3X 104 to 5X104 Pa in an oven at a
`temperature of about 120° to 160° C. or in a heated press
`providing similar conditions. Where continuous webs of
`component membranes are employed, the operation may be
`carried out using heated calender rollers.
`Subsequent to lamination, the battery cell material may be
`stored under normal conditions, either with the retained
`plasticizer or as a “dry” sheet after extraction of the plasti-
`cizer with a selective low-boiling solvent, for any length of
`time prior to final battery processing and activation. The
`laminate may be die—punched into coins for use in the
`familiar “button” batteries or elongated sheets of the flexible
`laminated cell material may be rolled with an interposed
`insulator or manifolded to yield a compact, high-density
`structure to be sealed with activating electrolyte solution in
`a protective enclosure.
`Although a plasticized copolymer matrix, particularly that
`of the separator stratum, will readily imbibe an electrolyte
`salt solution which, in eifect, displaces the plasticizer, it is
`preferable to extract the plasticizer to facilitate absorption of
`the fluid electrolyte. While an extracted, “dry” battery cell
`laminate possesses no discernible voids, it appears to exhibit
`a solvent recovery “memory” which prompts the rapid
`absorption of an amount of electrolyte solution substantially
`equal to that of the initial plasticizer. In this manner, the
`desired ion conductivity range of up to about 10‘3 S/cm is
`readily achieved.
`A number of electrolytic cell laminates with compositions
`comprising VszHFP copolymers within the noted mono-
`mer ratio range were prepared and tested for electrolytic and
`physical suitability for use in rechargeable batteries cells.
`The following examples are illustrative of such preparation
`and use.
`
`EXAMPLE 1
`
`A coating composition was prepared by suspending 1.5 g
`of an 85:15 VszHFP copolymer of about 260x103 MW
`
`JLab/Cambridge, Exh. 1017, p. 7
`
`JLab/Cambridge, Exh. 1017, p. 7
`
`

`

`5
`
`6
`
`5,470,357
`
`(Atochem Kynar FLEX 2750) in 10 g of acetone and 1.5 g
`of propylene carbonate (PC). The mixture was warmed to
`about 50° C. to facilitate dissolution and with occasional
`
`agitation a solution was obtained which retained its fluidity
`upon standing at room temperature for a number of hours.
`The solution was cast upon a glass plate with a doctor-blade
`device gapped at about 1.5 mm and was allowed to dry in air
`at room temperature for about 10 minutes. The resulting dry,
`clear, tough, flexible film was readily removed from the
`glass substrate and was divided into test samples. A few
`samples were completely extracted with diethyl ether to
`remove the homogeneously dispersed PC plasticizer which
`was then calculated to be present in the original samples at
`a level of about 47.7% by weight. Such a film with retained
`plasticizer (PC) represents the “wet” form of polymeric
`electrolyte/separator membrane material which may be
`stored for later convenient assembly with cell electrode
`elements. The test sample films from which the PC had been
`extracted represents the “dry” form of the membrane mate-
`rial.
`
`EXAMPLE 2
`
`A control film material was prepared as in Example 1 with
`the exception that the PC plasticizer was not added. The
`resulting film was clear, tough, and flexible, although, under-
`standably, not as extensible as the plasticized sample.
`Samples of the “wet”, “dry”, and control
`films were
`immersed for a few minutes in a typical rechargeable lithium
`battery electrolyte solution, viz., a 1M solution of LiPF6 in
`a 1:1 mixture of ethylene carbonate and propylene carbonate
`(EC/PC). The samples were then wiped to remove any
`surface accumulation of electrolyte solution, weighed, and
`extracted with PC and diethyl ether,
`in turn,
`to remove
`imbibed electrolyte solution. It was then calculated that the
`control sample absorbed about 27% electrolyte solution,
`while the preswollen “wet” sample took up about 47%, a
`nearly complete substitution for the original amount of the
`PC plasticizer in the membrane before immersion in elec-
`trolyte. The remaining “dry” sample, that from which the
`original PC plasticizer had been extracted, absorbed about
`37% electrolyte solution, nearly 40% more than the control
`sample. This increase in absorption capacity is indicative of
`the swelling “memory” imparted to the film by the initial
`plasticizer content. The ionic conductivity of the membrane
`samples thus swollen by immersion in electrolyte solution
`were tested for conductivity according to the usual ac
`impedance method on common test equipment, e.g., a
`Hewlett—Packard computer—controlled HP4192A capaci-
`tance bridge operating over the frequency range of 5 Hz to
`10 MHZ. The “wet”, “dry”, and control film samples exhib—
`ited ionic conductivities of about 3X10“: 9X10_5, and 5x
`10‘5 S/cm, respectively.
`EXAMPLE 3
`
`Test samples were prepared in the manner of Example 2
`with substitution of dibutyl phthalate (DBP) for the PC
`plasticizer. The absorption of electrolyte by the “wet” and
`“”dry samples during immersion increased significantly
`over the PC samples, amounting to about 65% and 45%,
`respectively. Ionic conductivity of the samples increased
`accordingly, measuring about 2X10”3 and 3X10_4 S/cm,
`respectively.
`
`EXAMPLE 4
`
`Test samples according to Examples 1—3 were prepared
`with tetrahydrofuran (TI-H3) instead of acetone. The results
`
`of electrolyte absorption and ionic conductivity tests were
`substantially similar.
`
`EXAMPLE 5
`
`Indicative of other film formation techniques which may
`be used, about 50 parts by weight of the 85: 15 copolymer of
`Examples 1 were suspended, without acetone vehicle sol-
`vent, in an equal amount by weight of dibutyl phthalate and
`allowed to swell until substantially homogeneous. The
`resulting swollen mass was then pressed at about 130° C. for
`l min between polished aluminum plates separated by 0.15
`mm shims. After cooling to room temperature, the resulting
`clear, flexible film sheet was readily removed from the
`plates. A sample section of the sheet was then extracted with
`diethyl ether and reswollen in the electrolyte solution of
`Example 2 to yield an electrolyte/separator membrane
`retaining about 40% electrolyte solution and exhibiting an
`ionic conductivity of about lxlO‘4 S/cm.
`
`EXAMPLE 6
`
`An electrolyte/separator membrane coating solution was
`prepared by suspending 2.0 g of an 88:12 Vszl-IFP copoly—
`mer of about 380x103 MW (Atochem Kynar FLEX 2801) in
`about 10 g of acetone and adding to this mixture about 2.0
`g of dibutyl phthalate (DBP). The completed mixture was
`warmed to about 50 ° C. to facilitate dissolution and with
`
`occasional agitation a solution was obtained which retained
`its fluidity after standing at room temperature for a number
`of hours. A portion of the solution was coated on a glass
`plate with a doctor blade device gapped at about 0.5 mm.
`The coated film was allowed to dry within the coating
`enclosure under moderately flowing dry air at room tem-
`perature for about 10 min to yield a clear, tough, elastic
`membrane which was readily stripped from the glass plate.
`The film was about 85 pm thick with a dry basis weight of
`about 0.1 kg/m2 and was easily cut into rectangular separator
`elements of about 175x45 mm which could be stored for
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`4o
`
`days at ambient room conditions without significant weight
`loss.
`
`EXAMPLE 7
`
`45
`
`50
`
`55
`
`60
`
`65
`
`A positive electrode coating composition was prepared by
`homogenizing in a lid-covered stainless steel blender for
`about 10 min at 4000 rpm a mixture of 10.5 g of Li
`1+an204, where 0<x§l (e.g., Lil‘osMnZO4 prepared in a
`manner described in U.S. Pat. No. 5,196,279), sieved
`through 53 mm, 2.8 g of the VszHFP copolymer (FLEX
`2801) of example 6, 4.3 g dibutyl phthalate, 1.125 g Super—P
`conductive carbon, and about 20 g acetone. The resulting
`paste was degassified by briefly applying a reduced pressure
`to the mixing vessel, and a portion was then coated on a
`glass plate with a doctor blade device gapped at about 1.1
`mm. The coated layer was allowed to dry within the coating
`enclosure under moderately flowing dry air at room tem-
`perature for about 10 min to yield a tough, elastic film which
`was readily stripped from the glass plate. The film was about
`0.3 mm thick with a dry basis weight of about 0.6 kg/m2 and
`was easily cut into rectangular electrode elements of about
`165x40 mm. These film elements could be stored for days at
`ambient room conditions without significant weight loss.
`
`EXAMPLE 8
`
`A negative electrode coating composition was prepared
`by homogenizing in a lid-covered stainless steel blender for
`about 10 min at 4000 rpm a mixture of 7.0 g of a commercial
`JLab/Cambridge, Exh. 1017, p. 8
`
`JLab/Cambridge, Exh. 1017, p. 8
`
`

`

`5,470,357
`
`7
`
`petroleum coke (ball-milled and sieved through 53 pm), 2.0
`g of the VszHFP copolymer (FLEX 2801) of example 6,
`3.12 g dibutyl phthalate, 0.37 g Super-P conductive carbon,
`and about 12 g acetone. The resulting paste was degassified
`by briefly applying a reduced pressure to the mixing vessel,
`and a portion was then coated on a glass plate with a doctor
`blade device gapped at about 0.6 mm. The coated layer was
`allowed to dry within the coating enclosure under moder—
`ately flowing dry air at room temperature for about 10 min
`to yield a tough, elastic film which was readily stripped from
`the glass plate. The film was about 0.2 mm thick with a dry
`basis weight of about 0.3 kg/m2 and was easily cut into
`rectangular electrode elements of about 165x40 mm. These
`film elements could be stored for days at ambient room
`conditions without significant weight loss.
`
`EXAMPLE 9
`
`A 180x40 mm copper negative current collector foil 11,
`preferably in the form of an open mesh grid of about 50 um
`thickness (e.g., a MicroGrid precision expanded foil mar-
`keted by Delker Corporation), was trimmed at one end to
`form a tab 12 which would subsequently serve as a conve-
`nient battery terminal. To enhance the ensuing adherence to
`its associated electrode element, grid 11 was surface-cleaned
`of oils and oxidation by immersing for a few seconds in a
`common “copper bright” solution (mixed dilute HNO3,
`H2804), rinsed in water, air dried, and surface—treated with
`the matrix polymer comprising the negative electrode com-
`position. To examine the eflicacy of the treatment, a number
`of grid samples were respectively dip-coated in 0.25% to
`3.0% acetone solutions of the VszHFP copolymer of
`Example 6, air dried, and oven heated within the range of
`about 250° to 450° C. for periods ranging from 5 to 60
`seconds, depending upon the concentration of the polymer
`solution. Adhesion between the electrode and treated col-
`lector elements upon subsequent lamination according to
`Example 10 was improved in substantially all instances over
`that in which untreated collector foil was used. Comparable
`results were obtained with a 94:6 VszHFP copolymer.
`Based upon economy of time and materials, a preferred
`treatment employed a 0.5% to 1.5% solution of the copoly-
`mer with heating at about 300 ° to 350° C. for about 5 to 30
`seconds. A particularly preferred treatment utilized a solu-
`tion of about 0.5% copolymer with heating at about 340° C.
`for about 5 to 20 seconds. It was observed that a heating
`temperature of not more than 350° C. is generally preferred
`in order to avoid significant copper oxidation and thus
`maintain optimum electrical conductivity at the collector
`surface. It was also noted that the heating step may be
`eliminated by using a dip coating solution comprising about
`3% each of the copolymer and electrode composition plas- -
`ticizer, such as dibutyl phthalate. Aluminum positive current
`collector foils, or grids, were prepared in substantially
`similar manner after a simple cleansing rinse in acetone.
`
`EXAMPLE 10
`
`Rechargeable battery structures were assembled from
`component collector, electrode, and electrolyte elements
`prepared in the manner of the foregoing examples. The
`conditions of electrode preparation may be varied, either in
`coating composition consistency or coated layer thickness,
`to obtain a basis weight ratio of active intercalation com-
`pound in the positive:negative electrode combination
`between about 1.5 and 2.5, preferably about 2.2. A basic
`battery cell structure as depicted in FIG. 1 was assembled in
`the following manner:
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`8
`A negative grid 11 of Example 9 was laid smoothly upon
`a flat rigid base plate (not shown) of a good heat conductive
`material, such as aluminum. A carbon negative electrode
`element 13, as prepared in Example 8, was overlaid upon
`grid 11, and was itself overlaid with electrolyte/separator
`element 15, as prepared in Example 6. The slightly larger
`dimensions of element 15 provide protection from possible
`misalignment and undesirable contact between the electrode
`elements of the assembled battery structure. Positive elec-
`trode element 17, as prepared in Example 7, was then
`positioned upon separator element 16, and a treated alumi-
`num collector foil or grid 19 was positioned upon electrode
`17 so as to provide a transversely situated terminal tab 18.
`It should be noted that at least one of the current collector
`elements has an open grid structure to facilitate the passage
`of extraction and activating fluids during the ensuing battery
`preparation operations.
`The resulting structure was then covered with a second
`similar rigid plate (not shown), and the assembly was placed
`in a 135° C. oven and weighted with about 24 kg to provide
`a pressure of about 3.7)(104 Pa at the element interfaces. The
`assembly remained in the oven for about 30 minutes to
`ensure temperature equilibrium in the plate sinks and effect
`adequate fusion of the battery elements. The laminate struc-
`ture was then remove from the oven, unweighted, and
`cooled between a pair of room temperature metal plates. In
`order to enhance the bonding or embedding of the collector
`grids in a final single cell structure, about 50 um membranes
`of electrolyte/separator composition (not shown) may be
`overlaid upon the grid elements prior to lamination, or,
`preferably, about 20 um coatings of the composition may be
`applied over the surfaces of a laminated structure.
`
`EXAMPLE 11
`
`The battery structure of Example 10 was prepared for
`“dry” film activation, as described in Example 2, by immer-
`sion of the laminate structure in diethyl ether at room
`temperature for about 25 minutes to remove substantially all
`of the DBP plasticizer from the layered elements, notably the
`electrolyte/separator 15. This extraction was carried out with
`a minimum of agitation of the immersion solvent. Extraction
`time for similar structure samples was reduced to about 10
`min with mild agitation, e.g., from stirring or bubbling air,
`and was optimally reduced to about 3 minutes with continu-
`ous countercurrent processing using fresh extraction solvent.
`Other useful solvents include pentane, petroleum ether,
`hexane, and cyclohexane.
`
`EXAMPLE 12
`
`An extracted battery structure from Example 11 was
`activated in preparation for charge/discharge cycling by
`immersion under a substantially moisture-free atmosphere
`in a 1M electrolyte solution of LiPF6 in 50:50 ethylene
`carbonate (EC): dimethyl carbonate (DMC) for about 20
`min during which the laminated battery imbibed about 31%
`of its extracted weight. Following a mild wiping with
`absorbent materials to remove surface electrolyte, the acti-
`vated battery structure was hermetically sealed, but for the
`extending terminal tabs 12, 18, within a polyolefin envelope
`(not shown) to maintain a moisture—free environment. A
`similar battery sample was prepared by enclosing the
`extracted battery structure within the envelope with the
`measured amount of electrolyte solution.
`
`JLab/Cambridge, Exh. 1017, p. 9
`
`JLab/Cambridge, Exh. 1017, p. 9
`
`

`

`5,470,357
`
`9
`EXAMPLE 13
`
`The activated battery of Example 11 was tested by cycling
`between 2 and 4.5 V at a rate of 10 mA which was
`
`maintained constant within 1% in a “Mac Pile” cycling
`system from Bio-Logic of Claix, France. Operating in the
`galvanostatic mode, this system calculated from elapsed
`time and current the lithium content, x, in the Lian204
`positive electrode. The multicycle trace of these data are
`shown in FIG. 2 and is indicative of the stability of the
`battery. The trace of cell capacity over extended charging
`cycles is shown in FIG. 3.
`
`EXAMPLE 14
`
`In a preferred variant of the present laminate battery
`assembly method, as depicted in FIG. 4, a copper collector
`grid 41, pretreated as in Example 9 with a 1% copolymer
`solution and heating at about 350° C. for about 25 seconds,
`and a negative electrode element 43, as prepared in Example
`8, were assembled between buffer sheets of abherent poly-
`ethylene terephthalate (not shown) and were passed through
`the rolls 46 of a commercial card-sealing laminator at a
`temperature of about 150° C. A 50 um film of electrolyte/
`separator composition may also be inserted on top of the grid
`prior to lamination. A treated aluminum collector grid 49 of
`Example 9 and a positive electrode element 47, as prepared
`in Example 7, were similarly laminated to provided a pair of
`electrode/collector battery elements. An electrolyte/separa-
`tor element 45 from Example 6 was then inserted between
`the electrode/collector pair and the resulting assembly was