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`Certification of Accuracy
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`I, Frank McGee, a translator fluent in the English and Japanese languages, on behalf of
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`Source IP, do solemnly and sincerely declare that the following is, to the best of my
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`knowledge and belief, a true and correct translation of the document(s) listed below in a
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`form that best reflects the intention and meaning of the original text.
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` hereby declare that all statements made herein of my own knowledge are true and that
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`all statements made on information and belief are believed to be true; and further that
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`these statements were made with the knowledge that willful false statements and the like
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`so made are punishable by fine or imprisonment, or both, under Section 1001 of Title 18
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`The document is designated as: #89467_JP2001-167763-Yamaki
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`___________________
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`Frank McGee
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`May 17, 2023
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`244 Fifth Avenue, Suite R269, New York N.Y. 10001 | www.sourceip.com | info@sourceip.com
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`
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`APPLE-1004
`
`1
`
`

`

`(19) [Issuing Country] Japan Patent Office (JP)
`(12) [Publication Name] Gazette of Unexamined Patent Applications (A)
`(11) [Publication Number] 2001-167763 (P2001-167763A)
`(43) [Publication Date] June 22, 2001 (2001.6.22)
`
`(51) [Int.Cl.7]
`[Internal Codes]
`
`
`
`H01M 4/58
`
`
`
`4/02
`
`
`
`4/52
`10/40
`
`
`[Examination Request] Not Yet Received
`[Number of Claims] 4
`[Application Format] Online (OL)
`[Total Number of Pages] 6
`
`
`
`[FI]
`
`H01M 4/58
`
`4/02 C
`
`4/52
`
`
`10/40 Z
`
`[Theme Codes (Reference)]
`5H003
`5H014
`5H029
`
`
`
`
`
`(21) [Application Number] H11-349782
`(22) [Filing Date] December 9, 1999 (1999.12.9)
`(71) [Applicant]
`[Identification Number] 000005108
`[Name] Hitachi, Ltd.
`[Address] 4-6 Kanda Surugadai, Chiyoda-ku, Tokyo
`(71) [Applicant]
`[Identification Number] 000005810
`[Name] Hitachi Maxell, Ltd.
`[Address] 1-1-88 Ushitora, Ibaraki-shi, Osaka
`(72) [Inventor]
`[Name] Takahiro YAMAKI
`[Address] Hitachi, Ltd., Hitachi Research Center, 7-1-1 Omikacho, Hitachi-shi, Ibaraki-ken
`(74) [Agent]
`[Identification Number] 100068504
`[Attorney]
`[Name] Katsuo OGAWA (and 1 other)
`
`Continued on Last Page
`
`
`
`
`
`
`
`2
`
`

`

`JP 2001-167763 A
`
`(54) [Title of the Invention]
`
`Lithium Secondary Battery
`
`(57) [Abstract]
`
`[Problem]
`
`To provide a lithium secondary battery with high energy density and excellent cycle
`characteristics.
`
`[Solution]
`
`A lithium secondary battery having a positive electrode 1 containing a Co-based oxide
`including Li and Co as a positive electrode active material and a conductive material whose
`main component is carbon, a negative electrode 2, and an organic electrolytic solution 4,
`the lithium secondary battery characterized in that the Co-based oxide contains at least one
`element selected from Mg, Al, Mn, Ti, and Sr, and at least the surface layer of the
`conductive material has an amorphous carbonaceous material.
`
`Fig. 2
`
`3
`
`

`

`JP 2001-167763 A
`
`[Claims]
`
`[Claim 1]
`
`A lithium secondary battery having a positive electrode containing a Co-based oxide
`including Li and Co as a positive electrode active material and a conductive material whose
`main component is carbon, a negative electrode, and an organic electrolytic solution, the
`lithium secondary battery characterized in that the Co-based oxide contains at least one
`element selected from Mg, Al, Mn, Ti, and Sr, and at least the surface layer of the
`conductive material has an amorphous carbonaceous material.
`
`[Claim 2]
`
`The lithium secondary battery according to claim 1, wherein the Co-based oxide is
`represented by the general formula LixCoyAzO2 (where A is at least one element selected
`from Mg, Al, Mn, Ti and Sr, and x, y, and z satisfy (cid:19)(cid:17)(cid:28)(cid:3)(cid:148)(cid:3)(cid:91)(cid:3)(cid:148)(cid:3)(cid:20)(cid:17)(cid:20)(cid:15)(cid:3)(cid:19)(cid:17)(cid:28)(cid:26)(cid:3)(cid:148)(cid:3)(cid:92)(cid:3)(cid:148)(cid:3)(cid:20)(cid:17)(cid:19)(cid:19) , (cid:19)(cid:17)(cid:19)(cid:20)(cid:3)(cid:148)(cid:3)(cid:93)(cid:3)
`(cid:148)(cid:3)(cid:19)(cid:17)(cid:19)(cid:22)(cid:12)(cid:17)
`
`[Claim 3]
`
`The lithium secondary battery according to claim 1 or 2, wherein the conductive material
`has a peak half width of 100 cm-1 or more in the Raman spectrum range of 1,540 cm-1 to
`1,600 cm-1.
`
`[Claim 4]
`
`The lithium secondary battery according to any of claims 1 to 3, wherein the discharge
`capacity of the positive electrode active material is 160 mAh/g or more and the capacity
`retention rate is 80% or more when charging and discharging are repeated 10 times.
`
`[Detailed Description of the Invention]
`
`[0001]
`
`[Technical Field of the Invention]
`
`The present invention relates to a lithium secondary battery, and more specifically to a
`lithium secondary battery with high energy density and excellent cycle characteristics.
`
`[0002]
`
`[Prior Art]
`
`There is increasing demand for lithium secondary batteries using a Co-based oxide including
`lithium (Li) and cobalt (Co) as the active material for the positive electrode due to their high
`voltage and high capacity.
`
`[0003]
`
`In lithium secondary batteries of the prior art using Co-based oxides, lithium cobalt oxide
`(LiCoO2) is used as the positive electrode active material, the negative electrode contains a
`carbon material such as graphite into which Li has been inserted, and a porous film of a
`polymer such as polyethylene used to separate the positive electrode and the negative
`
`4
`
`

`

`JP 2001-167763 A
`
`electrode is impregnated with an organic electrolytic solution obtained by dissolving a
`lithium salt in an organic solvent.
`
`[0004]
`
`In particularly wide use is a high-capacity organic electrolyte obtained by dissolving a
`lithium salt such as LiClO4 or LiPF6 in a mixed solvent of carbonate esters such as ethylene
`carbonate (“EC” below) or dimethyl carbonate (“DMC” below).
`
`[0005]
`
`When a Co-based oxide is used as a positive electrode active material, a conductive material
`is added to the positive electrode in order to reduce the electrical resistance of the positive
`electrode, and highly crystalline carbon materials such as graphite have been used from the
`standpoint of chemical stability and electrical conductivity.
`
`[0006]
`
`However, in lithium secondary batteries of the prior art that use LiCoO2 as the positive
`electrode active material, the maximum potential of the positive electrode during charging is
`set to about 4.3 V in terms of metallic Li, and the discharge capacity of LiCoO2 in the battery
`is limited to 160 mAh/g or less.
`
`[0007]
`
`Theoretically, all of the Li in the LiCoO2 is released and the theoretical capacity reaches
`about 274 mAh/g when charging to about 4.8 V in terms of metallic Li. However, raising the
`charging potential to increase the energy density causes what is called cycle deterioration,
`in which the reversibility of charging and discharging declines markedly as the charging and
`discharging cycles are performed.
`
`[0008]
`
`A factor in cycle deterioration is that when the potential of the positive electrode exceeds
`4.3 V relative to metallic Li, the crystal structure of the LiCoO2 undergoes a rhombohedral-
`to-monoclinic phase transition, impairing the reversibility of Li ion insertion and ejection.
`
`[0009]
`
`Another factor is that oxidative decomposition of the organic solvent and lithium salt
`constituting the organic electrolyte occurs on the surface of the highly crystalline carbon
`material serving as the positive electrode conductive material when it has reached a high
`potential due to charging. This does not impede the practical use of lithium secondary
`batteries of the prior art at a charge potential of 4.3 V in terms of metallic Li, but charge-
`discharge efficiency drops significantly when the charge potential is raised.
`
`[0010]
`
`[Problem to Be Solved by the Invention]
`
`The addition of various elements has been proposed in order to improve the cycle
`characteristics of a Co-based oxide used in a positive electrode (see, for example, JP H08-
`031408 A and JP H06-044973 A).
`
`5
`
`

`

`JP 2001-167763 A
`
`[0011]
`
`Also, use of a sulfide-based lithium ion conductive solid electrolyte instead of an organic
`electrolyte has been proposed in order to solve the problem of organic electrolyte
`decomposition at high potentials (see JP H11-021803 A), but deterioration over repeated
`charge-discharge cycles has not yet been studied.
`
`[0012]
`
`It is an object of the present invention to solve this problem by providing a lithium
`secondary battery with high energy density and excellent cycle characteristics by specifying
`a Co-based oxide to be used as the positive electrode active material and a conductive
`material to be used in the positive electrode.
`
`[0013]
`
`[Means for Solving the Problem]
`
`In order to achieve this object, the present invention is a lithium secondary battery having a
`positive electrode containing a Co-based oxide including Li and Co as a positive electrode
`active material and a conductive material whose main component is carbon, a negative
`electrode, and an organic electrolytic solution, the lithium secondary battery characterized
`in that the Co-based oxide contains at least one element selected from Mg, Al, Mn, Ti, and
`Sr, and at least the surface layer of the conductive material has an amorphous
`carbonaceous material.
`
`[0014]
`
`When such a battery configuration is used, the maximum potential of the positive electrode
`during charging can be from 4.4 V to 4.8 V in terms of metallic Li while also suppressing
`deterioration in the reversibility of charging and discharging as more charging and
`discharging cycles are performed.
`
`[0015]
`
`In other words, the discharge capacity of the positive electrode active material can be
`improved by setting the maximum potential of the positive electrode during charging to 4.4
`V or more in terms of metallic Li. As a result, the amount of positive electrode active
`material in the battery can be reduced, and the amount of negative electrode active
`material can be increased. Therefore, a lithium secondary battery with a higher energy
`density can be obtained in a limited battery volume.
`
`[0016]
`
`The energy density increases as the charge potential of the positive electrode increases, and
`a potential of up to 4.8 V is theoretically possible. However, from the standpoint of cycle
`deterioration, the upper limit on the highest potential of the positive electrode in the present
`invention is preferably 4.6 V or less in terms of metallic Li. The positive electrode potential
`is specified in terms of the physical properties of the Co-based oxide serving as the positive
`electrode active material, and therefore is specified independently of the type of negative
`electrode being used in the battery.
`
`6
`
`

`

`JP 2001-167763 A
`
`[0017]
`
`The maximum potential of the positive electrode during charging corresponds to the
`potential in constant voltage charging or constant current charging normally required to
`bring the secondary battery to a fully charged state. However, because the voltage of the
`battery is controlled by the charger during charging, the maximum potential of the positive
`electrode during charging may be defined in the present invention based on the set charging
`voltage of the charger.
`
`[0018]
`
`[Embodiment of the Invention]
`
`The Co-based oxide in the present invention contains at least one element selected from
`Mg, Al, Mn, Ti and Sr, because the metal has the effect of suppressing deterioration in the
`reversibility of charging and discharging due to a phase transition occurring in the Co-based
`oxide as charging and discharging cycles continued to be performed.
`
`[0019]
`
`This is because the added element is believed to replace Co or Li or form a solid solution in
`the crystal structure of the Co-based oxide, slightly distorting the ideal layered crystal
`structure of the rhombohedral LiCoO2, and acting as points of inhibition in the phase
`transition. This is not limited to one added element, and a plurality elements may be added.
`
`[0020]
`
`The Co-based oxide serving as the positive electrode active material in the present invention
`can be represented by the general formula LixCoyAzO2 (where A is at least one element
`selected from Mg, Al, Mn, Ti and S(cid:85)(cid:15)(cid:3)(cid:68)(cid:81)(cid:71)(cid:3)(cid:91)(cid:15)(cid:3)(cid:92)(cid:15)(cid:3)(cid:68)(cid:81)(cid:71)(cid:3)(cid:93)(cid:3)(cid:86)(cid:68)(cid:87)(cid:76)(cid:86)(cid:73)(cid:92)(cid:3)(cid:19)(cid:17)(cid:28)(cid:3)(cid:148) (cid:91)(cid:3)(cid:148)(cid:3)(cid:20)(cid:17)(cid:20)(cid:15)(cid:3)(cid:19)(cid:17)(cid:28)(cid:26)(cid:3)(cid:148)(cid:3)(cid:92)(cid:3)(cid:148)(cid:3)(cid:20)(cid:17)(cid:19)(cid:19)(cid:15)(cid:3)
`(cid:19)(cid:17)(cid:19)(cid:20)(cid:3)(cid:148)(cid:3)(cid:93)(cid:3)(cid:148)(cid:3)(cid:19)(cid:17)(cid:19)(cid:22)(cid:12)(cid:17)
`
`[0021]
`
`The value of x indicates the deviation from the stoichiometric composition in the production
`stage of the Co-(cid:69)(cid:68)(cid:86)(cid:72)(cid:71)(cid:3)(cid:82)(cid:91)(cid:76)(cid:71)(cid:72)(cid:15)(cid:3)(cid:68)(cid:81)(cid:71)(cid:3)(cid:86)(cid:75)(cid:82)(cid:88)(cid:79)(cid:71)(cid:3)(cid:81)(cid:82)(cid:85)(cid:80)(cid:68)(cid:79)(cid:79)(cid:92)(cid:3)(cid:69)(cid:72)(cid:3)(cid:76)(cid:81)(cid:3)(cid:87)(cid:75)(cid:72)(cid:3)(cid:85)(cid:68)(cid:81)(cid:74)(cid:72)(cid:3)(cid:82)(cid:73)(cid:3)(cid:19)(cid:17)(cid:28)(cid:3)(cid:148)(cid:3)(cid:91)(cid:3)(cid:148) 1.1.
`
`[0022]
`
`The value of y is y = 1 in conventional LiCoO2. There are no particular restrictions on the
`value of y, but a value closer to y = 1 yields a higher discharge capacity, and the desirable
`(cid:89)(cid:68)(cid:79)(cid:88)(cid:72)(cid:3)(cid:76)(cid:86)(cid:3)(cid:19)(cid:17)(cid:28)(cid:26)(cid:3)(cid:148)(cid:3)(cid:92)(cid:3)(cid:148)(cid:3)(cid:20)(cid:17)(cid:19)(cid:19)(cid:17)
`
`[0023]
`
`Also, the added element indicated by A does not have to be one type of element, and may
`(cid:69)(cid:72)(cid:3)(cid:68)(cid:3)(cid:83)(cid:79)(cid:88)(cid:85)(cid:68)(cid:79)(cid:76)(cid:87)(cid:92)(cid:3)(cid:82)(cid:73)(cid:3)(cid:72)(cid:79)(cid:72)(cid:80)(cid:72)(cid:81)(cid:87)(cid:86)(cid:15)(cid:3)(cid:68)(cid:81)(cid:71)(cid:3)(cid:87)(cid:75)(cid:72)(cid:3)(cid:89)(cid:68)(cid:79)(cid:88)(cid:72)(cid:3)(cid:82)(cid:73)(cid:3)(cid:93)(cid:3)(cid:76)(cid:86)(cid:3)(cid:83)(cid:85)(cid:72)(cid:73)(cid:72)(cid:85)(cid:68)(cid:69)(cid:79)(cid:92)(cid:3)(cid:19)(cid:17)(cid:19)(cid:20)(cid:3)(cid:148)(cid:3)(cid:93)(cid:3)(cid:148)(cid:3)(cid:19)(cid:17)(cid:19)(cid:22)(cid:17) When the value
`(cid:76)(cid:86)(cid:3)(cid:19)(cid:17)(cid:19)(cid:20)(cid:3)(cid:148)(cid:3)(cid:93)(cid:15)(cid:3)(cid:87)(cid:75)(cid:72)(cid:3)(cid:72)(cid:73)(cid:73)(cid:72)(cid:70)(cid:87)(cid:3)(cid:82)(cid:73)(cid:3)(cid:87)(cid:75)(cid:72)(cid:3)(cid:68)(cid:71)(cid:71)(cid:72)(cid:71)(cid:3)(cid:72)(cid:79)(cid:72)(cid:80)(cid:72)(cid:81)(cid:87)(cid:3)(cid:82)(cid:81)(cid:3)(cid:87)(cid:75)(cid:72)(cid:3)(cid:85)(cid:72)(cid:89)(cid:72)(cid:85)(cid:86)(cid:76)(cid:69)(cid:76)(cid:79)(cid:76)(cid:87)(cid:92)(cid:3)(cid:82)(cid:73)(cid:3)(cid:76)(cid:81)(cid:86)(cid:72)(cid:85)(cid:87)(cid:76)(cid:81)(cid:74)(cid:3)(cid:68)(cid:81)(cid:71)(cid:3)(cid:72)(cid:77)(cid:72)(cid:70)(cid:87)(cid:76)(cid:81)(cid:74) Li
`(cid:76)(cid:82)(cid:81)(cid:86)(cid:3)(cid:76)(cid:86)(cid:3)(cid:80)(cid:82)(cid:85)(cid:72)(cid:3)(cid:73)(cid:88)(cid:79)(cid:79)(cid:92)(cid:3)(cid:82)(cid:69)(cid:87)(cid:68)(cid:76)(cid:81)(cid:72)(cid:71)(cid:15)(cid:3)(cid:68)(cid:81)(cid:71)(cid:3)(cid:90)(cid:75)(cid:72)(cid:81)(cid:3)(cid:87)(cid:75)(cid:72)(cid:3)(cid:89)(cid:68)(cid:79)(cid:88)(cid:72)(cid:3)(cid:76)(cid:86)(cid:3)(cid:93)(cid:3)(cid:148)(cid:3)(cid:19)(cid:17)(cid:19)(cid:22)(cid:15)(cid:3)(cid:68)(cid:3)(cid:75)(cid:76)(cid:74)(cid:75)(cid:72)(cid:85)(cid:3)(cid:71)(cid:76)(cid:86)(cid:70)(cid:75)(cid:68)(cid:85)(cid:74)(cid:72)(cid:3)(cid:70)(cid:68)(cid:83)(cid:68)(cid:70)(cid:76)(cid:87)(cid:92)(cid:3)(cid:76)(cid:86)(cid:3)
`obtained.
`
`[0024]
`
`7
`
`

`

`JP 2001-167763 A
`
`In the present invention, the conductive material used in the positive electrode is
`amorphous carbon or at least a material whose main component is carbon with amorphous
`carbon in the surface layer. This can suppress the oxidative decomposition of the organic
`electrolyte even at a high charging potential.
`
`[0025]
`
`As for the structure of the conductive material, the conductive material may be formed
`entirely of amorphous carbon, but an amorphous carbon layer on the surface of a highly
`crystalline carbon material with high electrical conductivity such as graphite is preferred
`from the standpoint of conductivity. A preferred conductive material is one in which the half-
`value width of the peak present in the Raman spectrum range of 1,540 cm-1 to 1,600 cm-1 is
`100 cm-1 or more, and in which amorphous carbonaceous material sufficiently covers the
`surface of the highly crystalline carbonaceous material.
`
`[0026]
`
`In the present invention, the half-width of the peak of the Raman spectrum is defined as the
`width of the peak at half the peak height relative to a baseline that is a straight line
`connecting the signal intensities at 1,800 cm-1 and 1,000 cm-1 as shown in Fig. 1.
`
`[0027]
`
`In the present invention, a carbon conductive material having an amorphous carbonaceous
`layer on the surface can be obtained, for example, by immersing a carbon material such as
`artificial graphite in a liquid resin, pitch, or tar, followed by firing. Alternatively, the vapor
`phase method can be used to carbonize a hydrocarbon gas such as propane or acetylene by
`thermal decomposition, and deposit the product on the surface of a carbon material.
`
`[0028]
`
`A characteristic of the lithium secondary battery in the present invention is using a Co-
`based oxide containing at least one element selected from Mg, Al, Mn, Ti and Sr as a
`positive electrode active material and a carbon conductive material having amorphous
`carbon in at least the surface layer, and setting the highest potential of the positive
`electrode during charging to 4.4 V to 4.8 V, preferably 4.4 V to 4.6 V, in terms of metallic Li
`to obtain a battery with an initial discharge capacity for the positive electrode active
`material of 160 mAh/g or more, and a capacity retention rate of 80% or more when
`charging and discharging have been repeated 10 times.
`
`[0029]
`
`The positive electrode used in the battery of the present invention is prepared based on a
`mixture obtained by adding a binder such as polyvinylidene fluoride to a Co-based oxide and
`a conductive material. For example, a molded product with a current collecting material
`such as aluminum foil serving as the core material can be used.
`
`[0030]
`
`The negative electrode used in the battery of the present invention is prepared based on a
`mixture obtained by adding a binder to a carbon material or a material capable of
`intercalating Li or forming a compound. For example, the mixture can be dispersed in a
`
`8
`
`

`

`JP 2001-167763 A
`
`solvent, applied to a collector material such as a copper foil, dried, and finished to obtain a
`molded product.
`
`[0031]
`
`The carbon material can be, for example, natural graphite, artificial graphite, or a carbon
`material obtained by heat-treating heavy oil, coal tar, or pitch-based fibers before being
`carbonized and pulverized. Materials capable of intercalating Li or forming compounds
`include metals such as aluminum, metal oxides including silicon, and composites of these
`materials including carbon materials.
`
`[0032]
`
`A porous film made of an organic polymer material such as polyethylene or polypropylene,
`or a gel organic polymer compound is interposed between the positive electrode and the
`negative electrode to provide insulation and then impregnated with an injected organic
`electrolyte.
`
`[0033]
`
`An organic electrolyte common in the art can be used, for example, such as a lithium salt
`dissolved in an organic solvent. Examples of organic solvents include carbonates such as
`ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl
`carbonate (DMC), methylethyl carbonate (MEC) and diethyl carbonate (DEC), esters such as
`(cid:452)-butyrolactone ((cid:452)-BL) and methyl acetate (EA), and ethers such as 1,3-dioxolane and 1,2-
`dimethoxyethane.
`
`[0034]
`
`Other examples of organic solvents include sulfur compounds such as sulfolane, nitrogen-
`containing compounds, silicon-containing compounds, fluorine-containing compounds, and
`phosphorus-containing compounds. These can be used alone or in combinations of two or
`more.
`
`[0035]
`
`Lithium salts dissolved in the organic solvent include LiClO4, LiCF3SO3, LiPF6, LiBF4, LiAsF6,
`etc., which are dissolved in the solvent at 0.1 to 2 mol/liter. The present invention will now
`be described in greater detail with reference to examples.
`
`[0036]
`
`(Example 1)
`
`The battery of the present invention can assume various forms such as that of a cylindrical,
`button, coin, or square battery. In this example, a button battery was used.
`
`[0037]
`
`First, an organic electrolytic solution was prepared by adding 1.4 mol/liter of LiPF6 to a
`mixed solvent of EC and MEC (EC/MEC = 1/2) and mixing the components together.
`
`[0038]
`
`9
`
`

`

`JP 2001-167763 A
`
`The conductive material was a lumpy carbon material (A) with an average particle size of 5
`(cid:459)m that contained graphite and that had an amorphous carbonaceous layer on the surface.
`When the Raman spectrum of this conductive material was measured, the half width of the
`peak at 1,585 cm-1 was 104 cm-1.
`
`[0039]
`
`An Al-containing Co-based oxide (LiCo0.97Al0.03O2) with an average particle size of 7 (cid:459)m was
`used as the positive electrode active material, and 4.5% by weight of the carbon material
`(A) serving as the conductive material was added to 91.5% by weight of the active material.
`After mixing the components together, they were dispersed in a solution prepared
`beforehand by dissolving 4% by weight of the polyvinylidene fluoride serving as the binder
`in N-methylpyrrolidone to obtain a slurry.
`
`[0040]
`
`This positive electrode mixture slurry was evenly applied to one side of the aluminum foil
`(with a thickness of 20 (cid:459)m) serving as the positive electrode current collector in an amount
`of 24.0 mg/cm2, and then dried. This was subjected to compression molding using a roller
`press so that the density of the positive electrode mixture was 3.2 g/cm3, and punched to a
`predetermined size to obtain a disk-shaped positive electrode.
`
`[0041]
`
`Separately, 92% by weight of flaky graphite with an average particle size of 20 (cid:459)m was
`dispersed in a solution obtained beforehand by dissolving 8 parts by weight of
`polyvinylidene fluoride serving as the binder in N-methylpyrrolidone to form a slurry. This
`negative electrode mixture slurry was evenly applied to one side of the copper foil (with a
`thickness of 20 (cid:459)m) serving as the negative electrode current collector in an amount of 16.5
`mg/cm2, and then dried. This was subjected to compression molding using a roller press so
`that the density of the negative electrode mixture was 1.5 g/cm3, and punched to a
`predetermined size to obtain a disk-shaped negative electrode.
`
`[0042]
`
`Next, the positive electrode 1, the negative electrode 2, and the separator 3 were housed in
`order inside a battery case 5. The separator was a microporous polyethylene film with a
`thickness of 25 (cid:459)m and a porosity of 38%.
`
`[0043]
`
`An Al foil sheet 14 was also arranged on the inner surface of the battery case 5. The organic
`electrolytic solution 4 described was injected and sealed with a gasket 7 made of
`polypropylene to produce the button-type lithium secondary battery shown in Fig. 2.
`
`[0044]
`
`Fig. 3 is an enlarged schematic cross-sectional view of the positive electrode 1 observed
`under a SEM microscope. The Co-based oxide 9 and the conductive material 10 with an
`amorphous carbon layer 12 on the surface are bonded to the positive electrode current
`collector 8 by the binder 13. The gaps are permeated with the organic electrolyte injected
`into the battery.
`
`10
`
`

`

`JP 2001-167763 A
`
`[0045]
`
`(Example 2)
`
`A button-type lithium secondary battery was produced in the same manner as in Example 1,
`except that a Co-based oxide (LiCo0.99Al0.01O2) with a different amount of Al than Example 1
`was used as the positive electrode active material.
`
`[0046]
`
`(Example 3-8)
`
`Button-type lithium secondary batteries were produced in the same manner as in Example
`1, except that a Mg-containing Co-based oxide (LiCoMg0.03O2), Mn-containing Co-based
`oxide (LiCo0.97Mn0.03O2), Sr-containing Co-based oxide (LiCo0.99Sr0.01O2), Al and Mn-
`containing Co-based oxide (LiCo0.97Al0.02Mn0.01O2), Ti- and Mg-containing Co-based oxide
`(LiCo0.98Ti0.02Mg0.01O2), and Al-, Ti-, and Mn-containing Co-based oxide
`(LiCo0.97Al0.01Ti0.01Mn0.01O2) were used, respectively, as the positive electrode active material.
`
`[0047]
`
`(Example 9)
`
`A button-type lithium secondary battery was produced in the same manner as in Example 1
`by preparing electrodes in which coating on the positive electrode was 25.5 mg/cm2 and the
`coating on the negative electrode was 15.7 mg/cm2.
`
`[0048]
`
`(Example 10)
`
`A button-type lithium secondary battery was produced in the same manner as in Example 1
`by preparing electrodes in which coating on the positive electrode was 21.7 mg/cm2 and the
`coating on the negative electrode was 17.5 mg/cm2.
`
`[0049]
`
`(Comparative Example 1)
`
`The conductive material was a lumpy carbon material (B) with an average particle size of 5
`(cid:459)m that contained graphite and that had an amorphous carbonaceous layer on the surface.
`When the Raman spectrum of this conductive material was measured, the half width of the
`peak at 1,585 cm-1 was 66 cm-1.
`
`[0050]
`
`A button-type secondary battery was produced using a conventional additional element-free
`Co-based oxide (LiCoO2) with an average particle size of 7 (cid:459)m as the positive electrode
`active material and the carbon material (B) as the conductive material.
`
`[0051]
`
`11
`
`

`

`JP 2001-167763 A
`
`(Comparative Example 2)
`
`A button-type lithium secondary battery was produced in the same manner as in
`Comparative Example 1 by preparing electrodes in which coating on the positive electrode
`was 26.5 mg/cm2 and the coating on the negative electrode was 15.3 mg/cm2.
`
`[0052]
`
`The button-type lithium secondary batteries in Examples 1 to 8 and Comparative Example 1
`were subjected to a charge/discharge test using a repeated cycle in which the charging
`current was 0.5mA, the charging positive electrode potential was 4.5V in terms of metallic
`Li, the constant voltage was kept at 4.5V for two hours after reaching 4.5 V, and discharging
`was performed to 3.0V at 0.5mA.
`
`[0053]
`
`The button-type lithium secondary batteries in Example 9 was subjected to a
`charge/discharge test identical to the one above except that the charging positive electrode
`potential was 4.4 V in terms of metallic Li.
`
`[0054]
`
`The button-type lithium secondary batteries in Example 10 was subjected to a
`charge/discharge test identical to the one above except that the charging positive electrode
`potential was 4.6 V in terms of metallic Li.
`
`[0055]
`
`The button-type lithium secondary batteries in Comparative Example 2 was subjected to a
`charge/discharge test identical to the one above except that the charging positive electrode
`potential was set to 4.3 V in terms of metallic Li, which is the same as that for conventional
`lithium secondary batteries.
`
`[0056]
`
`Table 1 shows the initial battery capacities, the initial discharge capacities of the positive
`electrode active materials, and the capacity retention of the batteries after 10 cycles of the
`charge-discharge test.
`
`12
`
`

`

`JP 2001-167763 A
`
`[0057]
`
`[Table 1]
`
`Ex. 1
`Ex. 2
`Ex. 3
`Ex. 4
`Ex. 5
`Ex. 6
`Ex. 7
`Ex. 8
`Ex. 9
`Ex. 10
`C. Ex. 1
`C. Ex. 2
`
`[0058]
`
`Positive Electrode Active
`Material
`
`Conductive
`Material
`
`Table 1
`Charged
`Positive
`Electrode
`Potential (V:
`Metal Li
`Reference)
`
`Initial
`Battery
`Capacity
`(mAh)
`
`LiCo0.97Al0.03O2
`LiCo0.99Al0.01O2
`LiCoMg0.03O2
`LiCo0.97Mn0.03O2
`LiCo0.99Sr0.01O2
`LiCo0.97Al0.02Mn0.01O2
`LiCo0.98Ti0.02Mg0.01O2
`LiCo0.97Al0.01Ti0.01Mn0.01O2
`LiCo0.97Al0.03O2
`LiCo0.97Al0.03O2
`LiCoO2
`LiCoO2
`
`(A)
`(A)
`(A)
`(A)
`(A)
`(A)
`(A)
`(A)
`(A)
`(A)
`(B)
`(B)
`
`4.5
`4.5
`4.5
`4.5
`4.5
`4.5
`4.5
`4.5
`4.4
`4.6
`4.5
`4.3
`
`3.99
`4.12
`4.17
`4.05
`4.24
`4.00
`4.07
`4.00
`3.86
`4.19
`4.15
`3.82
`
`Initial
`Discharge
`Capacity of
`Positive
`Electrode
`Material
`(mAh/g)
`182
`188
`190
`184
`193
`182
`184
`182
`165
`211
`189
`157
`
`Capacity
`Retention
`After 10
`Cycles (%)
`
`95
`94
`98
`97
`93
`95
`95
`93
`97
`89
`75
`95
`
`In the configuration of the lithium secondary battery of the prior art shown in Comparative
`Example 1, setting the charge potential to 4.5 V resulted in low capacity retention and poor
`cycle characteristics even though the positive electrode active material had a high initial
`discharge capacity. As shown in Comparative Example 2, the charge potential must be 4.3 V
`and the initial discharge capacity of the positive electrode active material must be kept low
`in order to maintain the cycle characteristics.
`
`[0059]
`
`However, in Examples 1 to 10, the initial discharge capacity of the positive electrode active
`material was 160 mAh/g or more, and the discharge capacity of the battery was high. In
`addition, the cycle characteristics were excellent with a capacity retention rate of 80% or
`higher.
`
`[0060]
`
`[Effects of the Invention]
`
`The present invention is able to provide a lithium secondary battery with high energy
`density and excellent cycle characteristics by using a Co-based oxide containing at least one
`element selected from Mg, Al, Mn, Ti and Sr as the positive electrode active material, and
`using a carbon conductive material having at least a surface layer of amorphous
`carbonaceous material.
`
`[Brief Description of the Drawings]
`
`[Fig. 1]
`
`13
`
`

`

`JP 2001-167763 A
`
`Fig. 1 is a Raman spectrum graph of a carbon material whose surface layer is amorphous
`carbon.
`
`[Fig. 2]
`
`Fig. 2 is a vertical cross-sectional view of a button-type lithium secondary battery that
`shows an example of the configuration of the lithium secondary battery in the present
`invention.
`
`[Fig. 3]
`
`Fig. 3 is an enlarged schematic cross-sectional view of a positive electrode that shows an
`example of the configuration of the lithium secondary battery in the present invention.
`
`[Key to the Drawings]
`
`1: Positive electrode
`2: Negative electrode
`3: Separator
`4: Organic electrolytic solution
`5: Battery case
`6: Sealing plate
`7: Gasket
`8: Positive electrode current collector
`9: Co-based oxide
`10: Conductive material
`11: Graphite
`12: Amorphous carbon layer
`13: Binder
`14: Al foil sheet
`
`14
`
`

`

`JP 2001-167763 A
`
`[Fig. 1]
`
`[Fig. 2]
`
`1: Positive electrode; 2: Negative electrode; 3: Separator; 4: Organic electrolytic solution;
`5: Battery case; 6: Sealing plate; 7: Packing; 14: Al foil sheet
`
`15
`
`

`

`[Fig. 3]
`
`JP 2001-167763 A
`
`8: Positive electrode current collector; 9: Co-based oxide; 10: Conductive material; 11:
`Graphite;
`12: Amorphous carbon layer; 13: Binder
`
`16
`
`

`

`JP 2001-167763 A
`
`Continued From Front Page
`
`(72) [Inventor]
`[Name] Hidetoshi HONBO
`[Address] Hitachi, Ltd., Hitachi Research Center, 7-1-1 Omikacho, Hitachi-shi, Ibaraki-ken
`(72) [Inventor]
`[Name] Fusaji KITA
`[Address] Hitachi Maxell, Ltd., 1-1-88 Ushitora, Ibaraki-shi, Osaka
`(72) [Inventor]
`[Name] Tetsuo ITSU
`[Address] Hitachi Maxell, Ltd., 1-1-88 Ushitora, Ibaraki-shi, Osaka
`[F Terms (Reference)]
`5H003 AA02 AA04 BB05 BC01 BC06 BD00 BD03
`5H014 AA01 EE10 HH00 HH01 HH04
`5H029 AJ03 AJ05 AK03 AL06 AL07 AM03 AM05 AM07 BJ03 DJ16 DJ17 HJ02 HJ13 HJ19
`
`17
`
`

`

`(19)日本国特許庁（JP）
`
`(51)Int.Cl7
` H 0 1 M 4/58
` 4/02
` 4/52
` 10/40
`
`識別記号
`
`(12) 公 開 特 許 公 報（Ａ） (11)特許出願公開番号
`特開2001−167763
`(P2001−167763A)
`(43)公開日 平成13年6月22日(2001.6.22)
`ﾃｰﾏｺｰﾄﾞ(参考)
` 5 H 0 0 3
` 5 H 0 1 4
` 5 H 0 2 9
`
`FI
` H 0 1 M 4/58
` 4/02
` 4/52
` 10/40
`
`C
`
`Z
`
`審査請求 未請求 請求項の数 4ＯＬ（全 6 数）
`(71)出願人 000005108
`株式会社日立製作所
`東京都千代田区神田駿河台四丁目6番地
`(71)出願人 000005810
`日立マクセル株式会社
`大阪府茨木市丑寅1丁目1番88号
`(72)発明者 山木 孝博
`茨城県日立市大みか町七丁目1番1号 株式
`会社日立製作所日立研究所内
`(74)代理人 100068504
`弁理士 小川 勝男 (外1名)
`
`最終頁に続く
`
`(21)出願番号
`
`特願平11−349782
`
`(22)出願日
`
`平成11年12月9日(1999.12.9)
`
`(54)【発明の名称】 リチウム二次電池
`
`(57)【要約】
`【課題】高エネルギー密度で、かつ、サイクル特性に優
`れたリチウム二次電池の提供。
`【解決手段】正極活物質としてＬｉおよびＣｏを含有す
`るＣｏ系酸化物と、主成分が炭素である導電材