United States Patent 11
`Schmutz etal.
`
`0a
`(11] Patent Number:
`5,470,357
`3
`’
`[45] Date of Patent:
`Nov. 28, 1995
`
`
`(54) METHOD OF MAKING A LAMINATED
`LITHIUM-ION RECHARGEABLE BATTERY
`U.S. PATENT DOCUMENTS
`CELL
`S310ceo hoes iegelet Al orverererrnennnne toon
`Inventors: Caroline N. Schmutz, Eatontown;
`{75]
`
`
`Frough K. Shokoohi, Fait Haven.6/1993Fautenx.0......sescesseesssseeseeerees,219,680
`
`Jean-Marie Tarascon, Martinsville;
`.
`.
`vs
`Primary Examiner—iobn S. Maples
`Paul C. Warren,Far Hills, all of NJ.
`Attorney, Agent, or Firm—Leonard Charles Suchyta; Lionel
`[73] Assignee: Beli Communications Research, Inc.,
`N. White
`Livingston, N.J.
`
`[56]
`
`References Cited
`
`[21] Appl. No.: 428,970
`[22]
`Filed:
`Apr. 26. 1995
`°
`Pr.
`20,
`Related U.S. Application Data
`
`[63] Continuation-in-part of Ser. No. 160,018, Nov. 30, 1993,
`Pat. No. 5,460,904, which is a continuation-in-part of Ser.
`No. 110,262, Aug. 23, 1993, Pat. No. 5,418,091, which isa
`continuation-in-part of Ser. No. 26,904, Mar. 5, 1993, Pat.
`No. 5.296.318
`eee
`(51)
`Int. Cloecceseeecee HOIM 6/00; HO1M 6/18
`
`[52]
`. 29/623.5; 29/623.1; 429/192
`[58] Field of Search 2... 29/623.5, 623.1;
`429/192
`
`[57]
`ABSTRACT
`Li-ion rechargeable battery cell electrode andelectrolyte/
`separator elements formulated as layersof 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
`
`
`
`46
`
`43 W\
`
`PO
`
`ToSSSI
`
`——p — —
`
`46
`
`41
`
`46
`
`JLab/Cambridge, Exh. 1017, p. 1
`
`JLab/Cambridge, Exh. 1017, p. 1
`
`

`

`U.S. Patent
`
`Nov. 28, 1995
`
`Sheet 1 of 4
`
`5,470,357
`
`LOld
`
`Zi
`
`
`
`SoERO5050552555505250505
`
`PROCIMIIIOIS0550552252555SCOSOOPG2ET
`
`ooPRKKKKRMRRKKHRMIoooIOI
`
`JLab/Cambridge, Exh. 1017, p. 2
`
`JLab/Cambridge, Exh. 1017, p. 2
`
`
`
`
`

`

`U.S. Patent
`
`Nov. 28, 1995
`
`Sheet 2 of 4
`
`5,470,357
`
`XINLixMnsO,
`
`1.0
`
`0.8
`
`0.6
`
`0.4
`
`0.2
`
`1.0
`
`EzZ=i=
`
`
`
` f
`
`FIG.2
`
`5.0
`
`SLIOA
`
`JLab/Cambridge, Exh. 1017, p. 3
`
`JLab/Cambridge, Exh. 1017, p. 3
`
`

`

`U.S. Patent
`
`Noy. 28, 1995
`
`Sheet 3 of 4
`
`5,470,357
`
`0.8
`
`0.6
`
`0.4
`
`0.2
`
`Capacity-AxinLi,MnjO,4
`
`0
`
`40
`
`80
`
`120
`
`160
`
`Cycles
`
`FIG. 3
`
`JLab/Cambridge, Exh. 1017, p. 4
`
`JLab/Cambridge, Exh. 1017, p. 4
`
`

`

`U.S. Patent
`
`Nov. 28, 1995
`
`Sheet 4 of 4
`
`5,470,357
`
`
`BESTSCIIICIINKIIOYG2OI
`Ev
`
`bola
`
`oF
`
`JLab/Cambridge, Exh. 1017, p. 5
`
`JLab/Cambridge, Exh. 1017, p. 5
`
`
`
`

`

`5,470,357
`
`1
`METHOD OF MAKING A LAMINATED
`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-part of Ser. No. 08/026,904,filed Mar. 5, 1993, now
`USS. 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 cyclesof the cell.
`The invention is particularly useful for making suchcells 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 employedas 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 inventionpref-
`erably comprise the combination of a poly(vinylidene fiuo-
`tide) copolymer matrix and 20% to 70% by weight of a
`compatible organic plasticizer which maintains a homoge-
`neous compositionin the form of a flexible, self-supporting
`film. The copolymer comprises about 75 to 92% by weight
`vinylidene fluoride (VdF) and 8 to 25% hexafluoropropylene
`(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 membraneyields
`an effective room temperature ionic conductivity of about
`10~ to 10°? S/em, yet the membrane exhibits no evidence
`of solvent exudation which might lead to cell leakage orloss
`of conductivity.
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`2
`Electrolytic cells, such as rechargeable battery cells, are
`constructed according to the invention by means of the
`jamination 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 LiMn,O, powder in a copolymer matrix
`solution, which is dried to form the membrane. A positive
`current collector layer of aluminumfoil 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 effect lamination of the
`cell elements into a unitary flexible battery cell structure.
`Atthis stage the laminated structure comprises a signifi-
`cant measure of homogeneously distributed organic plasti-
`cizer, particularly in the separator membrane stratum, yetis
`devoid of hygroscopic electrolyte salt. As a result,
`the
`“{nactive” 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
`whenan 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.
`Whenit 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 VdF:HFP copolymer membrane matrix
`to provide
`substantially the
`same ionic conductivity
`enhancementas achieved by a preformed hybrid electrolyte/
`separator film containing such an electrolyte salt solution. In
`order to facilitate the absorption ofelectrolyte 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 ofthe 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 oftime priorto 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 orsized 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 inventionlies in the fact that all such operations may
`JLab/Cambridge, Exh. 1017, p. 6
`
`JLab/Cambridge, Exh. 1017, p. 6
`
`

`

`5,470,357
`
`3
`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;
`
`4
`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 amountof plasticizer and then pressing the swol-
`len mass between heated (e.g., about 130° C.) plates or
`tollers, 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 theflexible cell
`integrity. In accordance with the present invention, pretreat-
`ment ofthe collector elements with an electrode-compatible
`polymeric material, preferably by application of a 0.25% to
`2.5% solution of a copolymersimilar 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%
`A laminated rechargeable battery cell structure of the
`solution of the pretreatment polymer, provides improved
`present invention as depicted in FIG. 1 comprises a copper
`adhesion without a post-heating operation.
`collector foil 11, preferably in the form ofa pretreated open
`As with the membrane-forming operations, lamination of
`mesh grid, upon which is laid a negative electrode mem-
`assembled cell structures may be accomplished by com-
`brane 13 comprising an intercalatable material, such as
`monly-used apparatus. Preshaped or sized assemblies may
`carbon or graphite, or a low-voltage lithium insertion com-
`be simply pressed for a short while between metal plates
`pound, such as WO,, MoO,,or Al, dispersed in a polymeric
`weighted at about 3x 10* to 5x10* Pa in an oven at a
`binder matrix. An electrolyte/separator film membrane 15 of
`temperature of about 120° to 160° C. or in a heated press
`plasticized VdF:HFP copolymer is positioned upon elec-
`providing similar conditions. Where continuous webs of
`trode element 13 and is covered with a positive electrode
`component membranes are employed, the operation may be
`membrane 17 comprising a composition of a finely-divided
`carried out using heated calenderrollers.
`lithium intercalation compound, such as LiMn,O,, LiCoO,,
`or LiNiO,,
`in a polymeric binder matrix. A pretreated
`Subsequentto lamination, the battery cell material may be
`aluminum collector foil or grid 19 completes the assembly
`stored under normal conditions, either with the retained
`which is then pressed between platens (not shown) under
`plasticizer or as a “dry” sheet after extraction of the plasti-
`heat and pressure to soften and bond the polymeric compo-
`cizer with a selective low-boiling solvent, for any length of
`nents and laminate the membrane andgrid layers.
`time prior to final battery processing and activation. The
`laminate may be die-punched into coins for use in the
`Separator membrane element 15 is generally prepared
`familiar “button” batteries or elongated sheetsof the flexible
`from a composition comprising the earlier-noted 75 to 92%
`laminated cell material may be rolled with an interposed
`vinylidene fluoride (VdF): 8 to 25% hexafluoropropylene
`insulator or manifolded to yield a compact, high-density
`(HFP) copolymer (available commercially from Atochem
`structure to be sealed with activating electrolyte solution in
`North America as Kynar FLEX) and a compatible organic
`a protective enclosure.
`plasticizer. Such a copolymer composition is also preferred
`for the preparation of the electrode membrane elements,
`Althoughaplasticized copolymer matrix, particularly that
`since subsequent laminate interface compatibility is ensured.
`of the separator stratum, will readily imbibe an electrolyte
`The plasticizer may be one of the various organic com-
`salt solution which, in effect, displaces the plasticizer, it is
`pounds commonly used as solvents for electrolytesalts,e.g.,
`preferable to extract the plasticizerto facilitate absorption of
`propylene carbonate or ethylene carbonate, as well as mix-
`the fluid electrolyte. While an extracted, “dry” battery cell
`laminate possesses no discernible voids, it appears to exhibit
`tures of these compounds. Higher-boiling plasticizer com-
`pounds, such as dibutyl phthalate, dimethyl phthalate,
`a solvent recovery “memory” which prompts the rapid
`diethyl phthalate, and tris butoxyethy] phosphate are par-
`absorption of an amountofelectrolyte solution substantially
`ticularly suitable. Inorganic filler adjuncts, such as fumed
`equal to that of the initial plasticizer. In this manner, the
`desired ion conductivity range of up to about 10~> S/cm is
`aluminaor silanized fumed silica, may be used to enhance
`the physical strength and melt viscosity of a separator
`readily achieved.
`membrane and, in some compositions, to increase the sub-
`A numberofelectrolytic cell laminates with compositions
`sequentlevel of electrolyte solution absorption.
`comprising VdF:HFP copolymers within the noted mono-
`Any commonprocedure for casting or forming films or
`merratio range were prepared andtested for electrolytic and
`membranes of polymer compositions may be employed in
`physical suitability for use in rechargeable batteries cells.
`the preparation of the present membrane materials. Where
`The following examples are illustrative of such preparation
`and use.
`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
`(THF), acetone, or the like. Such coatings are normally
`
`DESCRIPTION OF THE INVENTION
`
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`EXAMPLE1
`
`A coating composition was prepared by suspending 1.5 g
`of an 85:15 VdF:HFP copolymer of about 260x10* MW
`
`JLab/Cambridge, Exh. 1017, p. 7
`
`JLab/Cambridge, Exh. 1017, p. 7
`
`

`

`5,470,357
`
`5
`(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 whichretained its fluidity
`upon standing at room temperature for a numberof hours.
`The solution was cast upon a glass plate with a doctor-blade
`device gapped at about 1.5 mm and was allowedto 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.
`
`EXAMPLE2
`
`Acontrol 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 LiPF, 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~°, and 5x
`10> S/em, respectively.
`EXAMPLE3
`
`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 2x107? and 3x10-* S/cm,
`respectively.
`
`EXAMPLE4
`
`Test samples according to Examples 1-3 were prepared
`with tetrahydrofuran (THF) instead of acetone. The results
`
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`of electrolyte absorption and ionic conductivity tests were
`substantially similar.
`
`EXAMPLE5
`
`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
`1 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 reswolien in the electrolyte solution of
`Example 2 to yield an electrolyte/separator membrane
`tetaining about 40% electrolyte solution and exhibiting an
`ionic conductivity of about 1x10 S/cm.
`
`EXAMPLE6
`
`An electrolyte/separator membrane coating solution was
`prepared by suspending 2.0 g of an 88:12 VdF:HFP copoly-
`merof about 380x10° 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 um thick with a dry basis weight of
`about 0.1 kg/m? and waseasily cut into rectangular separator
`elements of about 175x45 mm which could be stored for
`days at ambient room conditions without significant weight
`loss.
`
`EXAMPLE7
`
`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
`1sxMn,0,, where 0<x21 (e.g., Li,9;Mn,O, prepared in a
`manner described in U.S. Pat. No. 5,196,279), sieved
`through 53 pm, 2.8 g of the VdF:HFP 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 minto yield a tough,elastic film which
`wasreadily stripped from theglass plate. The film was about
`0.3 mm thick with a dry basis weight of about 0.6 kg/m? and
`waseasily cut into rectangular electrode elements of about
`165x40 mm. Thesefilm elements could be stored for days at
`ambient room conditions without significant weight loss.
`
`EXAMPLE8
`
`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 acommercial
`JLab/Cambridge, Exh. 1017, p. 8
`
`JLab/Cambridge, Exh. 1017, p. 8
`
`

`

`5,470,357
`
`7
`petroleum coke (ball-milled and sieved through 53 jm), 2.0
`g of the VdF:HFP 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 wasreadily stripped from
`the glass plate. The film was about 0.2 mm thick with a dry
`basis weight of about 0.3 kg/m? 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.
`
`EXAMPLE9
`
`A 180x40 mm copper negative current collector foil 11,
`preferably in the form of an open meshgrid 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 HNO;,
`H,SO,), rinsed in water, air dried, and surface-treated with
`the matrix polymer comprising the negative electrode com-
`position. To examinethe efficacy of the treatment, a number
`of grid samples were respectively dip-coated in 0.25% to
`3.0% acetone solutions of the VdF:HFP 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 VdF:HFP 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.
`
`EXAMPLE10
`
`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:
`
`15
`
`20
`
`25
`
`30
`
`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 3.7x10* 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
`gridsin a final single cell structure, about 50 zm 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.
`
`EXAMPLE11
`
`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 DBPplasticizer from the layered elements, notably the
`electrolyte/separator 15. This extraction wascarried out with
`a minimum ofagitation of the immersion solvent. Extraction
`time for similar structure samples was reduced to about 10
`min with mild agitation, e.g., from stirring or bubblingair,
`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.
`
`EXAMPLE12
`
`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 LiPF, 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 Li,Mn,O,
`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.
`
`EXAMPLE14
`
`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 mayalso be inserted on topof 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
`passed through the laminator deviceat a roll temperature of
`about 120° C. with somewhat less pressure to obtain the
`laminate battery structure. The laminate was then immersed
`under moisture-free conditions in a mildlystirred electrolyte
`solution from Example 12 for about 40 minutes to effect
`substantial replacement of the DBP plasticizer with the
`electrolyte solution. The activated battery, having a thick-
`ness of about 0.5 mm, was then sealed in a protective
`polyolefin envelope enclosure (not shown) a