US007566515B2
`
`(12) United States Patent
`US 7,566,515 B2
`(10) Patent N0.:
`
` Suzuki et a]. (45) Date of Patent: Jul. 28, 2009
`
`
`(54) FLAT NON-AQUEOUS ELECTROLYTE
`SECONDARY CELL
`
`(75)
`
`Inventors: Masami Suzuki, Kawasaki (JP);
`Muneto Hayaml, Takasaki (JP); Kazuo
`Udagawa, Tokyo (JP); Kazuo Iizuka,
`Takasaki (JP); Naomi Ishihara, Annaka
`(JP); Satoshi Hirahara, Annaka (JP);
`Hirotaka Sakai, Usui-gun (JP); Kiyoto
`Yoda, Kawasaki (JP); Masataka
`Shikota, Yokohama (JP)
`
`(73) Assignee: Toshiba Battery Co., Ltd., Tokyo (JP)
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 801 days.
`
`(21) Appl.No.: 11/176,400
`
`(22)
`
`Filed:
`
`Jul. 8, 2005
`
`(65)
`
`Prior Publication Data
`
`US 2005/0271938 A1
`
`Dec. 8, 2005
`
`Related U.S. Application Data
`
`(62) Division of application No. 10/318,177, filed on Dec.
`13, 2002, now Pat. No. 7,378,186, which is a division
`ofapplication No. 09/641 ,267, filed onAug. 17, 2000,
`now Pat. No. 6,521,373.
`
`(30)
`
`Foreign Application Priority Data
`
`Aug. 27, 1999
`Aug. 27, 1999
`Nov. 18, 1999
`Jun. 19, 2000
`Jun. 19,2000
`
`(JP)
`(JP)
`(JP)
`(JP)
`(JP)
`
`................................. 11-240964
`................................. 11-241290
`................................. 11-327679
`..... 2000-183000
`............................. 2000-183001
`
`(51)
`
`Int. Cl.
`H01M 2/02
`H01M 2/08
`H01M 4/58
`H01M 10/40
`
`(2006.01)
`(2006.01)
`(2006.01)
`(2006.01)
`
`......................... 429/162; 429/94; 429/127;
`(52) U.S. Cl.
`429/124; 429/185; 429/128; 429/176; 429/175
`(58) Field of Classification Search ....................... None
`See application file for complete search history.
`References Cited
`U.S. PATENT DOCUMENTS
`
`(56)
`
`2,971,999 A
`
`2/1961 Jacquier
`
`(Continued)
`FOREIGN PATENT DOCUMENTS
`
`EP
`JP
`JP
`JP
`JP
`
`1011 163 Al
`08-031394
`10-255733
`10-289707
`2001-164259
`
`6/2000
`2/1996
`9/1998
`10/1998
`6/2000
`
`Primary ExamineriPatrick Ryan
`Assistant ExamineriAngela Martin
`(74) Attorney, Agent, or FirmgOblon, Spivak, McClelland,
`Maier & Neustadt, PC.
`
`(57)
`
`ABSTRACT
`
`A non-aqueous electrolyte secondary cell containing an elec-
`tricity-generating element with at least a cathode, a separator
`and an anode and a non-aqueous electrolyte inside a cathode
`case, electrode units each consisting of the cathode and the
`anode opposite to each another via the separator laminated to
`form an electrode group, or an electrode unit in a sheet form
`consisting of the cathode and the anode opposite to each
`another via the separator wound to form an electrode group,
`or a sheet-shape cathode wrapped with the separator except
`for a part contacting at inner face of cathode case and a
`sheet-shaped anode set on the sheet-shaped cathode in a right
`angled position each other and bent alternately to form an
`electrode group, and the total sum ofthe areas ofthe opposing
`cathode and anode in the electrode group larger than the area
`ofthe opening of an insulating gasket in a sealed portion in the
`cathode case or than the area of an opening in a sealed plate in
`a sealed portion in the cathode case.
`
`33 Claims, 13 Drawing Sheets
`
`1
`
`5
`
`2
`
`I II 'I I‘m,
`
`unflinnn‘nnlnfnnlulnlmn
`
`JLab/Cambridge, Exh. 1013, p. 1
`
`JLab/Cambridge, Exh. 1013, p. 1
`
`

`

`US 7,566,515 B2
`
`Page 2
`
`US. PATENT DOCUMENTS
`
`4,356,240 A
`4,830,940 A
`5,707,756 A
`
`10/1982 De? 6t 31~
`5/1989 Kelster et al.
`1/1998 Inoue et a1.
`
`6,312,848 B1 *
`6,617,074 B1*
`6,638,662 B2
`
`................... 429/162
`11/2001 Kilb etal.
`9/2003 Watarai et al.
`......... 429/23195
`10/2003 Kaneda et al.
`
`* cited by examiner
`
`JLab/Cambridge, Exh. 1013, p. 2
`
`JLab/Cambridge, Exh. 1013, p. 2
`
`

`

`US. Patent
`
`Jul. 28, 2009
`
`Sheet 1 of 13
`
`US 7,566,515 B2
`
`20
`
`Lb
`5
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`FIG.
`
`2
`
`JLab/Cambridge, Exh. 1013, p. 3
`
`JLab/Cambridge, Exh. 1013, p. 3
`
`

`

`US. Patent
`
`Jul. 28, 2009
`
`Sheet 2 of 13
`
`US 7,566,515 B2
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`
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`JLab/Cambridge, Exh. 1013, p. 4
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`JLab/Cambridge, Exh. 1013, p. 4
`
`

`

`US. Patent
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`Jul. 28, 2009
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`Sheet 3 of 13
`
`US 7,566,515 B2
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`11
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`JLab/Cambridge, Exh. 1013, p. 5
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`JLab/Cambridge, Exh. 1013, p. 5
`
`

`

`US. Patent
`
`Jul. 28, 2009
`
`Sheet 4 of 13
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`US 7,566,515 B2
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`
`
`JLab/Cambridge, Exh. 1013, p. 6
`
`JLab/Cambridge, Exh. 1013, p. 6
`
`

`

`US. Patent
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`Jul. 28, 2009
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`Sheet 5 of 13
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`US 7,566,515 B2
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`
`
`FIG.
`
`10
`
`JLab/Cambridge, Exh. 1013, p. 7
`
`JLab/Cambridge, Exh. 1013, p. 7
`
`

`

`US. Patent
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`Jul. 28, 2009
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`Sheet 6 of 13
`
`US 7,566,515 B2
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`
`
`FIG.
`
`11
`
`— 1
`
`5
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`1b
`
`FIG.
`
`12
`
`JLab/Cambridge, Exh. 1013, p. 8
`
`JLab/Cambridge, Exh. 1013, p. 8
`
`

`

`US. Patent
`
`Jul. 28, 2009
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`Sheet 7 of 13
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`US 7,566,515 B2
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`
`
`FIG.
`
`13
`
`
`
`JLab/Cambridge, Exh. 1013, p. 9
`
`JLab/Cambridge, Exh. 1013, p. 9
`
`

`

`US. Patent
`
`Jul. 28, 2009
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`Sheet 8 of 13
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`US 7,566,515 B2
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`5e
`
`1
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`5
`
`5f
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`1
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`5
`
`FIG.
`
`15
`
`6
`
`FIG.
`
`16
`
`JLab/Cambridge, Exh. 1013, p. 10
`
`JLab/Cambridge, Exh. 1013, p. 10
`
`

`

`US. Patent
`
`Jul. 28, 2009
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`Sheet 9 of 13
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`US 7,566,515 B2
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`
`
`FIG.
`
`18
`
`JLab/Cambridge, Exh. 1013, p. 11
`
`JLab/Cambridge, Exh. 1013, p. 11
`
`

`

`US. Patent
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`Jul. 28, 2009
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`Sheet 10 of 13
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`US 7,566,515 B2
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`5i
`
`1
`
`5
`
`6
`
`FIG.
`
`19
`
`5
`
`15
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`1
`
`5
`
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`
`FIG. 20
`
`JLab/Cambridge, Exh. 1013, p. 12
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`JLab/Cambridge, Exh. 1013, p. 12
`
`

`

`US. Patent
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`Jul. 28, 2009
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`Sheet 11 of 13
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`US 7,566,515 B2
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`FIG.
`
`21
`
`F I G .
`
`2 2
`
`JLab/Cambridge, Exh. 1013, p. 13
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`JLab/Cambridge, Exh. 1013, p. 13
`
`

`

`US. Patent
`
`Jul. 28, 2009
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`Sheet 12 of 13
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`US 7,566,515 B2
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`5
`
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`
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`
`FIG.
`
`24
`
`JLab/Cambridge, Exh. 1013, p. 14
`
`JLab/Cambridge, Exh. 1013, p. 14
`
`

`

`US. Patent
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`Jul. 28, 2009
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`Sheet 13 of 13
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`US 7,566,515 B2
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`1
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`5
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`2
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`
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`
`25
`
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`
`FIG.
`
`26
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`JLab/Cambridge, Exh. 1013, p. 15
`
`JLab/Cambridge, Exh. 1013, p. 15
`
`

`

`US 7,566,515 B2
`
`1
`FLAT NON-AQUEOUS ELECTROLYTE
`SECONDARY CELL
`
`This application is a Divisional ofUS. application Ser. No.
`10/318,177, filed Dec. 13, 2002 now US. Pat. No. 7,378,186,
`which is a Divisional application of US. application Ser. No.
`09/641 ,267, filed on Aug. 17, 2000 now US. Pat. No. 6,521,
`373.
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`
`The present invention relates to a flat non-aqueous electro-
`lyte secondary cell and in particular to a flat non-aqueous
`electrolyte secondary cell with improvements in heavy load-
`ing discharge characteristics.
`2. Description of the Prior Art
`In recent years, there are commercially available coin— or
`button-shaped flat non-aqueous electrolyte secondary cells
`wherein metal oxides such as MnO2 and V205, inorganic
`compounds such as fluorinated graphite, or organic com-
`pounds such as polyaniline and polyacene structural com-
`pounds are used as the cathode active material, while metal
`lithium or lithium alloys, organic compounds such as poly-
`acene structural compounds, carbon materials capable of
`occluding and releasing lithium, or oxides such as lithium
`titanate or lithium-containing silicon oxides are used in the
`anode, and non-aqueous electrolytes containing a supporting
`electrolyte such as LiClO4, LiPF6, LiBF4, LiCF3SO3, LiN
`(CF3SOZ)2 and LiN(C2F5SOz)2 dissolved in a non-aqueous
`solvent such as propylene carbonate, ethylene carbonate,
`butylene carbonate, diethyl carbonate, dimethyl carbonate,
`methyl ethyl carbonate, dimethoxyethane and y-butyl lactone
`are used as the electrolyte. These cells are used as power
`sources for backing up SRAM and RTC where an electric
`current is discharged for light loading of about several to
`dozens MA, or as main power sources for wristwatches not
`requiring cell exchange.
`In general, these coin- or button-shaped flat non-aqueous
`electrolyte secondary cells have the structure shown in FIG. 4.
`That is, a metallic anode case 5 also serving as an anode
`terminal and a metallic cathode case 1 also serving as a
`cathode terminal are fit to each other via an insulating gasket
`6, and further the cathode case 1 has a sealed opening struc-
`ture caulked by caulking, and in the inside of this structure,
`tablet-shaped cathode 12 and anode 14 having a smaller
`diameter than the opening ofthe insulating gasket 6 are set up
`against each other via a single- or multi-ply separator 13
`impregnated with a non-aqueous electrolyte.
`The coin- or button-shaped flat non-aqueous electrolyte
`secondary cells as described above have the advantage that
`they are easily producible, excellent in mass-productivity,
`and superior in long-term reliability and safety. Further, by
`virtue of their simple structure, the most distinctive feature of
`these cells is that their miniaturization is feasible.
`
`Meanwhile, the miniaturization of devices (mainly com-
`pact information terminals) such as portable telephones and
`PDA is promoted, thus making it essential to miniaturize
`secondary cells as their main power sources. In these power
`sources, there have been used cylindrical or rectangular alkali
`secondary cells such as lithium ion secondary cells wherein
`lithium-containing oxides such as lithium cobaltate is used as
`the cathode active material while a carbon material is used in
`
`the anode, or nickel hydride secondary cells wherein nickel
`oxyhydroxide is used as the cathode active material and a
`hydrogen-occluding alloy is used as the anode active mate-
`rial. These cells have been constructed by coating or filling a
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`2
`
`current-collecting body consisting of a metal foil or metal net
`with an active material layer to form an electrode, then weld-
`ing a tab terminal into the center ofthe electrode, and winding
`or laminating it to form an electrode group, complicatedly
`bending the tab terminal from the center of the electrode
`group and welding the terminal into a safety element, an
`opening-sealed pin or a cell can. However, these cells have
`been constructed in such a complicated process that they are
`inferior in workability and the miniaturization ofparts therein
`is also difficult. Further, these cells shouldbe provided therein
`with a space for preventing the tab terminal from short-cir-
`cuiting or for integrating a large number of parts such as
`safety element into the cells, and thus there is a limit to the
`miniaturization of these cells at present.
`For miniaturization of the cells under these circumstances,
`the present inventors have attempted not at miniaturizing
`cylindrical or rectangular lithium ion secondary cells or
`nickel hydride secondary cells, but at achieving a higher
`output of the flat non-aqueous electrolyte secondary cells
`described above. That is, the present inventors have used
`lithium cobaltate of high capacity and high potential as the
`cathode active material and a graphitized carbon material of
`high capacity excellent in voltage evenness as the anode
`active material, and according to the process and structure of
`the conventional flat non-aqueous electrolyte secondary cell,
`the inventors have processed the cathode and anode into tab-
`lets smaller than a gasket, to prepare a cell.
`However, this cell though attaining superior characteristics
`to the conventional flat non-aqueous electrolyte secondary
`cell is not satisfactory when discharged in a large current
`required of a main power source in compact portable devices,
`thus failing to achieve levels satisfactory as a main power
`source in compact portable devices. Accordingly, the devel-
`opment of techniques for permitting the heavy-loading dis-
`charge characteristics of the compact flat non-aqueous sec-
`ondary cell to reach levels not achieved in the prior art is
`necessary.
`
`SUMMARY OF THE INVENTION
`
`This invention was made in view of the circumstances
`
`described above, and the object ofthis invention is to provide
`a flat non-aqueous electrolyte secondary cell, which is
`remarkably superior in heavy-loading discharge characteris-
`tics.
`
`inventors made extensive study on the
`The present
`improvement of the heavy-loading discharge characteristics
`of the flat non-aqueous electrolyte secondary cell described
`above. As a result, they found that the heavy-loading dis-
`charge characteristics are significantly improved by allowing
`the area of the electrodes to be significantly larger than in the
`conventional flat non-aqueous electrolyte secondary cell, to
`arrive at the present invention.
`That is, the present invention relates to a flat non-aqueous
`electrolyte secondary cell comprising a metallic anode case
`also serving as an anode terminal and a metallic cathode case
`also serving as a cathode terminal fit to each other via an
`insulating gasket, the anode or cathode case having an open-
`ing-sealed structure caulked by caulking and having in the
`inside thereof an electricity-generating element including at
`least a cathode, a separator and an anode and a non-aqueous
`electrolyte, wherein a plurality of electrode units each con-
`sisting of the cathode and the anode opposite to each another
`via the separator are laminated to form an electrode group, or
`a sheet-shaped electrode unit consisting of the cathode and
`the anode opposite to each another via the separator is wound
`to form an electrode group, or a sheet-shape cathode is
`
`JLab/Cambridge, Exh. 1013, p. 16
`
`JLab/Cambridge, Exh. 1013, p. 16
`
`

`

`3
`wrapped with the separator except for a part contacting at
`inner face of cathode case and a sheet-shaped anode is set on
`the sheet-shaped cathode in a right angled position each other
`and then these cathode and anode are bent alternately to form
`an electrode group, and the total sum of the areas of the
`opposing cathode and anode in this electrode group is larger
`than the area of the opening of said insulating gasket.
`Further, the present invention relates to a flat non-aqueous
`electrolyte secondary cell comprising a metallic cell case also
`serving as an electrode terminal, an opening-sealing plate for
`sealing an opening in said cell case, and another electrode
`terminal arranged Via an insulator in an opening provided in
`a part of the opening-sealing plate, said cell case being pro-
`vided inside with an electricity-generating element including
`at least a cathode, a separator and an anode and a non-aqueous
`electrolyte, wherein an electrode group consisting of an elec-
`trode unit having the cathode and the anode opposite to each
`another Via the separator is formed, and the total sum of the
`areas of the opposing cathode and anode in this electrode
`group is larger than the area of the opening of said opening-
`sealing plate.
`As the forms where the total sum of the areas ofthe oppos-
`ing cathode and anode in the electrode group is larger than the
`area of the opening of the insulating gasket in the present
`invention as described above, there is the form (I) wherein a
`plurality of the above-described electrode units are laminated
`to form an electrode group, and the total sum of the areas of
`the opposing cathodes and anodes in this electrode group is
`larger than the area ofthe opening of the insulating gasket, or
`the form (2) wherein the above electrode units are in the form
`of a sheet, and said sheet-formed electrode units are wound to
`form an electrode group, and the total sum of the areas of the
`opposing cathodes and anodes in this electrode group is larger
`than the area of the opening of the insulating gasket, or the
`form (3) wherein a sheet-shape cathode is wrapped with the
`separator except for a part contacting at inner face of cathode
`case and a sheet-shaped anode is set on the sheet-shaped
`cathode in a right angled position each other and then these
`cathode and anode are bent alternately to form an electrode
`group, and the total sum ofthe areas ofthe opposing cathodes
`and anodes in this electrode group is larger than the area ofthe
`opening of the insulating gasket.
`As described above, the total sum ofthe areas ofthe oppos-
`ing cathodes and anodes in the electrode group is made larger
`than the area of the opening of the insulating gasket or the
`opening-sealed plate, whereby the heavy-loading discharge
`characteristics of the flat non-aqueous electrolyte secondary
`cell can be significantly improved.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1. Non-aqueous electrolyte secondary cell.
`FIG. 2. Non-aqueous electrolyte secondary cell with cath-
`ode and anode in sheet form, sectional view of present inven-
`tion.
`
`FIG. 3. Non-aqueous solvent secondary cell, sectional
`drawing.
`FIG. 4. A coin-shaped or button-shaped flat non-aqueous
`electrolyte secondary cell.
`FIG. 5. Flat non-aqueous electrolyte secondary cell.
`FIG. 6. Sectional drawing of a cell with a metal net.
`FIG. 7. Sectional drawing of cell containing non-metallic
`thermal insulator.
`
`40
`
`45
`
`50
`
`55
`
`60
`
`FIG. 8. Sectional drawing of cell containing non-metallic
`thermal insulator.
`
`65
`
`FIG. 9. Cathode case with cutting.
`FIG. 10. Cathode case with cutting.
`
`US 7,566,515 B2
`
`4
`
`FIG. 11. Sectional drawing of flat non-aqueous electrolyte
`secondary cell with one or two grooves.
`FIG. 12. Opening-sealed portion of cathode case with
`groove.
`FIG. 13. Sectional drawing of cathode case.
`FIG. 14. Anode case with shattering groove.
`FIG. 15. Top view of anode case with shattering groove.
`FIG. 16. Top view of anode case having shattering groove
`of concave shape.
`FIG. 17. Top view ofanode case with shattering groove and
`circular shape.
`FIG. 18. Top view of anode case with half-round shattering
`groove along circumference.
`FIG. 19. Top view of anode case with linear section con-
`cave shaped groove.
`FIG. 20. Top view of anode case with shattering grooves
`gathered at central.
`FIG. 21. Top view of anode case with five lines of shatter-
`ing groove.
`FIG. 22. Top view of anode case, cathode case having no
`shattering groove.
`FIG. 23. Sectional drawing of cell with cathode or anode
`case having protrusions.
`FIG. 24. Top view of cell having cathode and anode cases
`with protrusions.
`FIG. 25. Sectional drawing of cell with bent alternating
`cathode and anode sheet.
`
`FIG. 26. Sectional drawing of cell having alternating cath-
`ode sheet and anode sheet.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`DETAILED DESCRIPTION OF THE INVENTION
`
`To improve the heavy-loading discharge characteristics, it
`is considered effective to increase the area of the electrodes.
`
`35
`
`In the conventional flat non-aqueous electrolyte secondary
`cell, however, a cathode and an anode, both in a tablet form,
`are accommodated respectively to contact with an insulating
`gasket in the cell, so that the area of the cathode and anode
`opposing to each other via a separator will inevitably be
`smaller than the area of the opening of the insulating gasket.
`Even if the area of the opposing electrodes can be enlarged to
`some degrees by thinning the gasket, the opposing electrodes
`having a larger area than the area of the opening of the gasket
`can theoretically not be accommodated in the cell.
`Accordingly, the present inventors have solved this prob-
`lem from a different viewpoint from the prior art by laminat-
`ing electrode units each consisting of a cathode, an anode and
`a separator, or by winding an electrode unit, or by bending
`alternately the sheet-shaped cathode and the sheet-shaped
`anode settled in a right angled position each other, in a cell
`case for the very small coin- or button-shaped flat cell, to
`permit the total sum of the areas of the opposing cathode(s)
`and anode(s) in the electrode group to be larger than the area
`of the opening of the insulating gasket.
`In the conventional cylindrical or rectangular large second-
`ary cells described above, there are cases where dozens elec-
`trode layers are accommodated in one cell, but such cells have
`the complicated structure as described above, so it is difficult
`to apply the electrode structure of such cells to the coin- or
`button-shaped, compact flat non-aqueous electrolyte second-
`ary cell. Even if such a structure can be successfully applied,
`the advantages of the flat non-aqueous electrolyte secondary
`cell, for example miniaturizablility and high productivity,
`cannot be maintained. Accordingly, there has been no study
`attempting at permitting an electrode group whose opposing
`cathode and anode have a larger area than the area of the
`
`JLab/Cambridge, Exh. 1013, p. 17
`
`JLab/Cambridge, Exh. 1013, p. 17
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`US 7,566,515 B2
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`opening of an insulating gasket to be accommodated in the
`coin- or button-shaped, compact flat non-aqueous electrolyte
`secondary cell.
`In the coin- or button-shaped, compact flat non-aqueous
`electrolyte secondary cell in the present invention, the elec-
`trode group is constituted as shown above in (l), (2) and (3)
`thereby maximizing the area of the electrodes and minimiz-
`ing the number of parts, thus succeeding in accommodating
`the electrode group and an amount of the non-aqueous elec-
`trolyte necessary for discharge in the space of the compact
`cell. Further, the electrodes can be easily produced according
`to this accommodation method and thus are suitable for mass-
`
`production by Virtue of superiority in productivity and pro-
`duction costs.
`When the electrode units are laminated to form the elec-
`
`trode group in the present invention, the number of faces
`where a cathode is opposite an anode in the electrode unit is
`preferably at least 3. Cathode and anode plates, each provided
`with an electrically connecting portion at a part (terminal)
`thereof, are arranged as the electrodes such that they are
`opposite to each another via a separator, wherein the electri-
`cally connecting portion of each cathode plate is exposed in
`one direction of the separator, while the electrically connect-
`ing portion of each anode plate is exposed in the opposite
`direction of the separator, and thereafter the electrodes are
`laminated such that the electrically connecting portions ofthe
`cathodes are exposed to and electrically connected at the
`same side, while the electrically connecting portions of the
`anodes are exposed to and electrically connected at the oppo-
`site side. By arranging the electrically connecting portions of
`the cathodes opposite the electrically connecting portions of
`the anodes, internal short-circuiting upon contact between the
`cathode and anode electrically connecting portions can be
`prevented even in the coin- or button-shaped, compact flat
`non-aqueous electrolyte secondary cell.
`Now, the method of connecting the electrode group to a
`metal case is described.
`
`In the cylindrical or rectangular, relatively large lithium ion
`secondary cell as described above, a tab terminal is welded for
`current collection into the center ofthe electrode group or into
`a core of the wound electrode group, then bend and welded
`into a safety element or an opening-sealed pin. However, the
`technique of bending processing is complicated and thus
`inferior in productivity, and further the cell should be pro-
`vided therein with a space for preventing internal short-cir-
`cuiting, or an insulating plate should be inserted between the
`electrode group and the tab terminal. Furthermore, if stress is
`applied to the part where the tab terminal was welded into the
`electrode, the separator may be broken and the electrode may
`be deformed, thus making it necessary to protect the tab
`terminal by an insulating tape or to provide the wound core
`with a space. Accordingly, the method of current collection
`for the cylindrical or rectangular lithium ion secondary cells
`cannot be applied to the coin-shaped or button-shaped, flat
`non-aqueous electrolyte secondary cells having a small inter-
`nal volume.
`
`Accordingly, the present inventors have secured current
`collection for the electrode group and the cell case by expos-
`ing an electrically conductive constituent material ofthe cath-
`ode at one edge face of the laminated electrode group (face
`parallel to the flat plane of the flat cell) while exposing an
`electrically conductive constituent material of the anode at
`the other edge face and then bringing the respective exposed
`electrode constituent materials into contact with the cathode
`
`and anode cell cases, respectively. According to this method,
`the discharge capacity can be increased without providing
`any space or insulating plate between the electrode group and
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`the cell case. In addition, because no short-circuiting occurs
`between the cell case or the electrode and the tab terminal, the
`cell is superior in safety and reliability.
`Further, the area of contact between the electrode consti-
`tutional material and the cell case can be made significantly
`larger than the area of contact between the conventional tab
`terminal and the cell case, to achieve stable current collection,
`and the conventionally inevitable operation ofwelding the tab
`terminal into the electrode case can be omitted.
`
`As a matter of course, the good electrical contact between
`the electrode constitutional material and the cell case,
`achieved in the method of collecting current in the present
`invention, can be further improved by welding the electrode
`constitutional material into the cell case or by fixing these
`members via a conductive adhesive or via a current collecting
`net between the electrode constitutional material and the cell
`case.
`
`When the electrode unit is wound to form the electrode
`
`group in the present invention, the face where the cathode is
`opposite the anode in the electrode unit may be in either the
`parallel or perpendicular direction to the flat plane of the flat
`cell, preferably the parallel direction. This is because the
`structure for securing current collection is made by exposing
`a conductive constituent material of the cathode at one termi-
`
`nal of the electrode group while exposing the conductive
`constituent material of the anode at the other terminal and
`
`then bringing each material into contact with the cell case.
`In the case of the wound electrode group, the method of
`collecting current involves exposing an electrically conduc-
`tive constituent material ofthe cathode at one edge face ofthe
`electrode group (face parallel to the flat plane of the flat cell)
`while exposing an electrically conductive constituent mate-
`rial of the anode at the other edge face and then bringing the
`respective exposed electrode constituent materials into con-
`tact with the cathode and anode cell cases, respectively.
`According to this structure, the discharge capacity can be
`increased without providing any space or insulating plate
`between the electrode group and the cell case. In addition,
`because no short-circuiting occurs between the cell case or
`the electrode and the tab terminal, the cell is superior in safety
`and reliability.
`A large number of systems can be used for winding the
`electrode group. In a preferable system, the cathode and the
`anode, both in a sheet form, are wound to be opposite to each
`other via a separator as shown in FIG. 2. According to this
`winding system, the electrode from the start to the end of
`winding can be efficiently used. Further, there is no space in
`the center of a core of the wound electrodes, so that when a
`spiral form ofthe flat electrodes is used, the electrodes can be
`effectively utilizable because both the electrodes are opposite
`to each other from the start of winding.
`The wound electrode group may be used as such, but after
`being wound, it is preferably compressed to improve adhe-
`sion of the cathode via the separator to the anode. In the coin-
`or button-shaped, flat non-aqueous electrolyte secondary cell
`whose internal volume is small, if there is no space in the
`center of a core ofthe wound electrodes, the electrodes can be
`additionally accommodated therein, and further the adhesion
`ofthe cathode via the separator to the anode can be improved.
`The flat electrodes in a spiral form, constructed by bending
`and winding the opposing electrodes such that the face where
`the cathode is opposite the anode is parallel to the flat plane of
`the flat cell, followed by compressing the electrodes, have the
`advantage that they are firmly wound and excellent in adhe-
`sion. Furthermore the above advantage is obtained by sticking
`any tapes on R part of side of electrode group.
`
`JLab/Cambridge, Exh. 1013, p. 18
`
`JLab/Cambridge, Exh. 1013, p. 18
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`US 7,566,515 B2
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`7
`Furthermore, in the flat cell having such an opening-sealed
`structure as in the present invention, stress was applied in the
`perpendicular direction to the flat plane of the cathode and
`anode cases upon caulking of the cell case, whereby the
`adhesion between the electrode group and the cell case is
`improved, charge/discharge can be conducted smoothly, and
`the characteristics of the cell are improved. The exposed
`portions ofthe electrode constituent materials ofthe electrode
`group may contact the electrode case directly or electrically
`indirectly via a metal foil, a metal net, metal powder, carbon
`fillers or a conductive coating.
`Now, the electrodes are described. Forboth the cathode and
`anode, it is possible to use a conventional method of forming
`a granular depolarizing mix for cell or a method of filling a
`metal substrate such as metal net or foamed nickel with a
`
`depolarizing mix for cell. Preferably, a depolarizing mix for
`cell in a slurry form is applied onto a metal foil, then dried and
`optionally further rolled so that a thin electrode can be easily
`prepared. If the electrodes on which the depolarizing mix for
`cell containing the active material is applied on a metal foil as
`described above are used, it is preferable for volume effi-
`ciency that the inner electrodes in the electrode group are
`those wherein a layer of the active material is formed on both
`sides of the metal foil, while the outermost electrodes in the
`electrode group, that is, the electrodes in contact with the cell
`case, are preferably those wherein particularly the metal foil
`in the electrode materials is exposed in order to reduce contact
`resistance. In this case, the active material layer may be
`formed on only one side of the outermost electrode, or after
`the active material later is formed on both sides of the outer-
`
`most electrode, the active material layer may be removed
`from one side.
`
`Now, the cathode and anode active materials used in the
`cell of the present invention are described.
`In the present invention, special attention is paid to the
`structure of the cell including the electrodes, so there is no
`limit to the cathode active materials. It is possible to use metal
`oxides such as MnOz, V205, NbZOS, LiTi204, Li4Ti5012,
`LiFeZO4,
`lithium cobaltate,
`lithium nickelate and lithium
`manganate, inorganic compounds such as fluorinated graph-
`ite and FeSz, and organic compounds such as polyaniline or
`polyacene structural compounds. Among these materials,
`lithium cobaltate, lithium nickelate, lithium manganate and a
`mixture thereof, or lithium-containing oxides where such
`elements are partially replaced by other metal elements are
`more preferable because ofhigh working potential and excel-
`lent cycle characteristics, and in the flat non-aqueous electro-
`lyte secondary cell which may be used for a prolonged period
`of time, lithium cobaltate is most preferable because of high
`capacity,
`low reactivity with an electrolyte or water, and
`chemical stability.
`The anode active materials are not particularly limited
`
`neither, and it is possible to use metal lithium, lithium alloys
`such as Li Al, Li
`ln, Li
`Sn, Li
`Si, Li Ge, Li Bi and
`Liin, organic compounds such as polyacene structural
`compounds, carbon materials capable of occluding and
`releasing lithium, oxides such as NbZOS, LiTi204, Li4Ti5012,
`Li-containing silicon oxides and Li-containing tin oxides,
`and nitrides such as Li3N. Carbon materials capable of
`occluding and releasing lithium Li are preferable in respect of
`excellent cycle characteristics, low working potential and
`high capacity. Particularly, carbon materials having a devel-
`oped graphite structure wherein the distance of the face d002
`is 0.338 nm or less, for example natural graphite, artificial
`graphite, expanded graphite, calcinated mesophase pitch and
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`calcinated mesophase pitch fiber are preferable in respect of
`less reduction in the working voltage of the cell in the end of
`discharge.
`In the flat non-aqueous electrolyte secondary cell having
`an electrode group in a laminate, wound or bent form as
`described above, the degree of adhesion between the cathode
`and anode cell cases and the electrode group has a significant
`influence on cell
`impedance and cell performance. For
`example, when the cell is stored for a long time in a high-
`temperature atmosphere