OQ ARAAAA
`
`US005487960A
`
`119
`United States Patent
`5,487,960
`Jan. 30, 1996
`[45] Date of Patent:
`
`
`[11] Patent Number:
`
`Tanaka
`
`[54] NONAQUEOUS SECONDARY BATTERY
`
`{75]
`
`Inventor: Mitsutoshi Tanaka, Kanagawa, Japan
`
`[73] Assignee: Fuji Photo Film Co., Ltd., Kanagawa,
`Japan
`
`[21] Appl. No.: 434,052
`
`[22] Filed:
`
`May3, 1995
`
`........sscsesseceees 429/194
`5/1991 Miyazaki et al.
`5,013,620
`5,273,848 12/1993 Noguchi et al. wu...eeeeee 429/218
`5,366,830
`11/1994 Koksbamg .....ssscsesecssssnerenees 429/218
`
`Primary Examiner—Prince Willis, Jz.
`Assistant Examiner—Richard H.Lilley, Jr.
`Attorney, Agent, or Firm—Sughrue, Mion, Zinn, Macpeak &
`Seas
`
`[30]
`
`Foreign Application Priority Data
`
`May 12, 1994
`
`[JP]
`
`Sapam csscssscscscscsssessssnsecseeeeees 6-098673
`
`Int. C18cece HOIM 4/36; HO1M 4/02
`(51)
`[52] US. CI. eeetssseeseneecees 429/218; 429/193; 429/223;
`429/224
`
`[58] Field of Search 0...esssssssssssesssees 429/218, 223,
`429/224, 193
`
`[57]
`
`ABSTRACT
`
`A nonaqueous secondary battery comprising a positive elec-
`trode and a negative electrode, in which a mixture of the
`positive electrode active material contains an acid contain-
`ing at least one of P, B, Si, Mo, and W ora salt thereof. The
`battery has improved safety in case of abrupt temperature
`rise.
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`4,956,248
`
`9/1990 Furukawaetal...sseeeneee 429/194
`
`12 Claims, 1 Drawing Sheet
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`5,487,960
`
`1
`
`NONAQUEOUS SECONDARY BATTERY
`
`FIELD OF THE INVENTION
`
`This invention relates to a nonaqueous secondary battery
`using a lithium-containing transition metal oxideas a posi-
`tive electrode active matcrial and having improvedsafety.
`
`BACKGROUND OF THE INVENTION
`
`JP-B-4-60302(the term “JP-B” as used herein means an
`“examined published Japancse patent application”) dis-
`closes a technique for preventing an increase of impedance
`in the inside of batteries during storage by adding a borate,
`a silicate, etc. of an alkali metal or an alkaline earth metal to
`a mixture of the positive electrode active material compris-
`ing manganese dioxide.
`In order to improve safety in case of an overcharge,it has
`been suggested to add lithium oxalate to LiCoO, (JP-A-4-
`329269, the term “JP-A” as used herein means an “unex-
`amined published Japanese patent application”) or to add
`lithium carbonate to LiCoO, (JP-A-4-329268 and JP-A-4-
`328278). However,
`these techniques cannot reduce the
`occurrence of rupture in case of rapid temperature rise or
`heating. «
`Nonaqueousbatteries using a lithium-containing transi-
`tion metal oxide, such as LiCoO,, LiNiO. or LiMn,O,, as
`a positive electrode active material and a substance capable
`of intercalating and deintercalating a lithium ion (e.g., an
`Li-containing metal oxide or calcined carbonaceous mate-
`rial) as a negative electrode active material have a higher
`cut-off voltage in charging than conventional alkali batteries,
`usually of from 3.5 to 5 V, and have beenattracting attention
`as high-energy density and high-safety batteries. A wide
`variety of the nonaqueousbatteries have been put to prac-
`tical use (JP-A-55-136131 and JP-B-3-30146).
`
`SUMMARY OF THE INVENTION
`
`BRIEF DESCRIPTION OF THE DRAWING
`
`wherein M represents an element selected from the group
`consisting of Ni, V, Fe, Mn, Ti, and Cu; x is a value varying
`on charging and discharging and is from 0.7 to 1.20 as
`measured immediately after calcination; y,+Y,=1, and Y, is
`from 0.75 to 1.0, with Y, being from 0.25 to 0; and zis a
`value varying depending on Y,, Y>, and the valency of M
`and is preferably from 1.5 to 3.0.
`Examples of suitable compoundsrepresented by formula
`An object of the present invention is to provide a non-
`include
`LiCoO,,
`Ligg,C0O,,
`LiCog,Nip,O,,
`@)
`aqueoussecondary battery having improved safety in case of
`
`LiCog95Vo0sO,—LiCog.9sCoo20,, LiCog75Feo250,,
`abrupt temperature rise, which is capable of intercalating
`LiCo9.75Mntg950,, LiCoggsMin 9.150,, LiCogosMig950,
`and deintercalating a lithium ion and has a charging cut-off
`Li, 92C09.97MNp930,,
`LiC0997Tig930,
`and
`voltage of 3.5 to 5 V.
`LiCog97Cug930,, wherein z is from 1.7 to 2.3.
`The aboveobject of the present invention is accomplished
`Among these, LiCoO,, Lig9,CoO,, LiCog73;Mnp250,,
`by anonaqueous secondary battery in which a mixture of the
`LiC0g95MNp950, and Li, pxC0g97Mnp9390, are particu-
`positive electrode active material contains an acid contain-
`larly preferred.
`ing at least one of P, B, Si, Mo, and W ora salt thereof.
`These positive electrode active materials can be synthe-
`sized by a process comprising mixing a lithium compound
`and a transition metal compound and calcining the mixture,
`FIG. 1 is across section of a cylindrical battery (diameter:
`or a solution reaction. The former calcination process is
`17 mm;height: 50 mm) according to the present invention.
`preferred. The calcining temperature is selected so that a part
`The numerals in FIG. 1 are shown below.
`of the mixture may be decomposed and melted, preferably
`from the range of from 250°to 2000° C., more preferably of
`1 Gasket made of the synthetic resin (polypropylene)
`from 350°to 1500° C. The calcination is conductedin air, an
`2 Battery case having a function as a negative electrode
`terminal
`oxygen-rich air (oxygen content: 30% by weight or more),
`argon or a like atmosphere.
`3 Negative electrode(sheet)
`LiNiO, and LiMn,O,asapositive electrode active mate-
`4 Separator
`5 Positive electrode (sheet)
`rial may also contain a minor proportion of other elements
`similarly to LiCoO,. These materials can be synthesized in
`6 Electrolytic solution
`the
`same manner as described for LiCoO,. Specific
`7 Safety valve
`examples of the positive electrode active materials include
`8 Positive electrode cap having a function as a positive
`electrode terminal
`LiNiO,, LiggsNiO,, LiNig9Cog,;0,,
`LiNig9gVo.o20_,
`LiNig9F€y :O,,
`LiNip9sMNp950,,
`LiNip97Tip039,
`9 Vent hole of safety valve
`LINip.97CUp9309.
`LiMn,0,,
`Lip.gsMn,O,,
`10 Sealing plate
`LiMn, gCo,;0,, LiMnoFeg,0,, LiMngo7Tigg30,, and
`11 Hole of safety valve
`LiMng97Cup930,, wherein z is from 1.7 to 2.3.
`12 Ring-shaped PCT element
`
`13 Ring
`14 Ring
`15 Positive electrode lead
`16 Positive electrode lead (a portion ofinsulating tape to be
`adhered)
`17 Negative electrode lead
`18 Insulating memberfor insulating core and bottom por-
`tions
`19 Top-insulating plate
`For the sake of convenience, the positive electrode, nega-
`tive electrode, and separator are depicted with the thickness
`magnified by 3 (the numberof turns is reduced to /%), and
`the body is depicted with the length (corresponding to the
`length of the negative electrode can) reduced to ¥%.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`The positive electrode active material which can be used
`as the positive electrode in the present invention is not
`particularly limited as long as it achieves a charging cut-off
`voltage of 3.5 to 5 V. Examples of such the active material
`include lithium-containing transition metal oxides contain-
`ing at least one, of Co, Mn and Ni, such as LiCoO,, LiNiO,,
`and LiMn,0,,.
`LiCoO, as a positive electrode active material may con-
`tain a minor proportion of other elements as is represented
`by formula(D):
`
`1i,CO,.M,,0,
`
`a)
`
`10
`
`20
`
`25
`
`35
`
`45
`
`50
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`60
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`65
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`3
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`5,487,960
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`10
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`3
`such as orthophosphoric acid, metaphosphoric acid, pyro-
`The above chemical formulae given to positive electrode
`phosphoric acid,
`triphosphoric acid, and tetraphosphoric
`active materials are thosein the state before charging,i.e., in
`the form of a positive electrode active material precursor.
`acid, with orthophosphoric acid and pyrophosphoric acid
`Therefore, when a battery is in use, the proportion of Li is
`being preferred.
`the
`The term “boric acid” as used herein means all
`reduced by charging as compared with that described above.
`The positive electrode active materials is contained in the
`oxoacids resulting from hydration of diboron trioxide, such
`nonaqueous secondary battery in an amountof 1 to 100 g.
`as orthoboric acid, metaboric acid, and tetraboric acid, with
`The negative electrode active material which can be used
`orthoboric acid and metaboric acid being preferred.
`in the present invention is a substance capable of interca-
`The term “boric acid” as used herein means orthosilicic
`lating and deintercalating a lithium ion. Specific examples of
`acid, metasilicic acid, mesodisilicic acid, mesotrisilicic acid,
`such the substance include Li-containing metal oxides rep-
`mesotetrasilicic acid, and so on, with orthosilicic acid and
`resented in the form of the negative electrode active material
`metasilicic acid being preferred.
`precursors, such as LiNiyos, LiCoVO,, SnO, SiSnO;, and
`The term “molybdic acid” as used herein means ortho-
`SnO,; calcined carbonaceous materials; spinel compounds,
`molybdic acid, paramolybdic acid, metamolybdic acid, etc.,
`such as TiS,, LiTiS,, WO,, and Li,Fe(Fe,0,) wherein x is
`with orthomolybdic acid being preferred.
`from 0.7 to 1.3; lithium compounds of Fe,0;; Nb,O., iron
`The term “tungstic acid” as used herein means orthotung-
`oxides (e.g., FeO, Fe,O,,and Fe,0,), cobalt oxides ( e.g.,
`stic acid, paratungstic acid, metatungstic acid, etc., with
`CoO, Co,0,, and Co,0,), and other lithium ailoys. Pre-
`orthotungstic acid being preferred.
`ferred of them are Li-containing metal oxides(e.g., LiNiyoa,
`A part or the whole of the hydrogen atomsof these acids
`LiCoVO,, SnO, SiSnO,, and SnO,) and calcined carbon-
`aceous materials.
`may form a salt with ammonium, an alkali metal or an
`alkaline earth metal.
`Suitable combinations of positive electrode active mate-
`If the amountofthe acid orasalt thereof is too small, the
`rial (fepresented in the form of precursor)/negative electrode
`effect of addition is insubstantial. If it is excessive, the
`active material
`(represented in the form of precursor)
`amount of the positive electrode active material is reduced
`include (i) LiCoO,/SnO, LiCoO,/SnSiO,, LiNiO,/SnO,
`to reduce the capacity. From these considerations, the acid or
`LiNiO,/SnSiO,, LiMn,0,/SnO, LiMn,0O,/SnSiO,
`(the
`a salt thereof is preferably added in an amountof from 0.02
`charging cut-off voltage of combinations(i) is preferably 3.9
`to 10% by weight, more preferably from 0.05 Lo 7% by
`to 5.0 V, more preferably 4.0 to 4.6 V, most preferably 4.1
`weight, most preferably from 0.2 to 5% by weight, based on
`to 4.4 V);
`(ii) LiCog,/LiCoVO,, LiNiO,/LiCoVO,, and
`the weight of the positive electrode active material. The acid
`LiMn,0,/LiCoVO, (the charging cut-off voltage of combi-
`is preferably added as such or in the form of an ammonium
`nations (ii) is from 3.5 to 4.2 V, more preferably 4.0 to 4.2
`salt, a lithium salt, a sodium salt or a potassium salt.
`V); Gii) LiCoO,/Sn0,, LiNiO,/SnO,, and LiMn,0,/Sn0,
`The acid or a salt thereof should be added after the
`(the charging cut-off voltage of combinations (iii) is pref-
`preparation of a positive electrode active material. If it is
`erably from 4.0 to 4.6 V, more preferably 4.1 to 4.3 V); (iv)
`added in the course of the preparation ofa positive electrode
`LiCoO,/calcined carbonaceous material, LiNiO,/calcined
`active material, for example, as a part of the raw material to
`carbonaceous material, and LiMn,O,/calcined carbon-
`be calcined, there are unfavorable tendenciesthat the result-
`aceous material (the charging cut-off voltage of combina-
`ing battery fails to fully exhibit its performance andthat the
`tions (iv) is preferably from 4.0 to 4.6 V, more preferably 4.1
`effect of addition is not fully obtained. The acid or a salt
`to 4.3 V); and (v) LiCoO./Liy g—Alp» alloy, LiNiO,/Lipg—
`thereof can be added, for example, by a method in which the
`Alp» alloy, and LiMn,0,/Lip,—Aly. alloy (the charging
`acid or a salt thereof is dissolved in a solvent, e.g., water or
`cut-off voltage of combinations(v) is preferably from 4.0 to
`an alcohol, putting a positive electrode active material into
`4.7 V). More preferred of these combinations are LiCoO,/
`the solution, and, after stirring, the solvent is removed to
`SnO, LiCoO,/SnSiO;, LiNiO,/SnO, LiNiO,/SnSiO,,
`adhere the acid or a salt thereof onto the vicinities of the
`LiMn,0,/SnO,
`LiMn,0,/SnSiO,,
`LiCoO,/LiCoVO,,
`surface of the positive electrode active material; a method in
`LiNiO./LiCoVO,, LiMn,0,/LiCoVO,,
`LiCoO,/SnO,,
`45
`which the acid orasalt thereof is added to a slurry (coating
`LiNiO,/SnO,, LiMn,O,/SnO,, LiCoO,/calcined carbon-
`composition) containinga positive electrode active material,
`aceous material, LiNiO./calcined carbonaceous material,
`and ‘the acid or a salt thereof is adhered to the vicinities of
`and LiMn,0,/calcined carbonaceous material. LiCoO,/
`the surface of the positive electrode active material while the
`SnO, LiCoO,/SnSiO3, LiNiO,/SnO, LiNiO,/SnSiO,,
`applied coating composition is dried; a method in which a
`LiMn,0,/SnO,and LiMn,O,/SnSiO, are most preferred.
`solution of the acid or a salt thereof is applied to a positive
`The terminology “a mixture of the positive electrode
`active material” as used herein refers to a mixture compris-
`electrode after coating or after compressing by spraying or
`impregnation; or a method in which theacid ora salt thereof
`ing a positive electrode active material, a conducting agent,
`is previously added to an electrolytic solution and made to
`a binder, and the like. More concretely, the mixture of the
`migrate and adsorb onto the surface of a positive electrode
`positive electrode active material preferably comprises 50 to
`active material. These methods have their several charac-
`99 parts, more preferably 70 to 98 parts, most preferably 85
`teristics and are selected appropriately according to the
`to 96 parts, by weightofa positive electrode active material;
`situation.
`1 to 50 parts, more preferably 2 to 20 parts, most preferably
`The nonaqueouselectrolytic solution which can be used
`3 to 10 parts, by weight of a conducting agent; and 0.1 to 15
`in the nonaqueous secondary battery of the presentinvention
`parts, more preferably 0.2 to 5 parts, most preferably 0.3 to
`is a nonaqueouselectrolyte which is liquid in the form of use
`2 parts, by weight of a binder. The mixture may further
`at normal temperature (an electrolyte which is solid per se
`contain a dispersant and other additives.
`but can be used as liquid as dissolved in a solvent is
`The acid containing at least one of P, B, Si, Mo, and W
`included) and has a molecular weight of less than about
`which is to be contained in the mixture of the positive
`10,000. Suitable nonaqueouselectrolytic solutions consist of
`electrode active material includes phosphoric acid, boric
`at least one aprotic organic solvent anda lithium salt soluble
`acid, silicic acid, molybdic acid, and tungstic acid.
`in the solvent. Examples of the aprotic organic solvent
`The term “phosphoric acid” as used herein meansall the
`includes ethylene carbonate, propylene carbonate, butylene
`acids resulting from hydration of diphosphorus pentoxide,
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`5,487,960
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`6
`mixed powder was added to a solution of 0.4 part of
`carboxymethyl] cellulose in 40 parts of water and dispersed
`in a homogenizer at 15000 rpm for 5 minutes. To the
`dispersion was added 1.5 part of a carboxy-modified SBR
`latex “Lx2570x5”, produced by Nippon Zeon Co., Ltd. (an
`aqueous dispersion having a solid content of 55%). The
`mixture was further kneaded in a homogenizerat 15000 rpm
`for 1 minute, followed by defoaming to prepare a positive
`electrode slurry. The slurry was applied to each side of a 30
`pm thick aluminum foil (1N30-H18) collector to a single
`spread of 500 9/m? on a dry basis, dried in warm air at 40°
`C. (dew point: 10° C.) blowing at a velocity of 5 m/sec,
`compression moldedin a roller press under a Linear pressure
`of 4000 N/cm, and cut to a prescribed size to prepare a
`positive electrode sheet. The sheet was further dried in dry
`air heated to 150° C. by means of an infrared heater (dew
`point: —60° C.).
`Eighty-six parts of SnSiO, as a negative electrode active
`material precursor were mixed with a conducting agent
`consisting of 3 parts of acetylene black and 6 parts of
`graphite, and a binder consisting of 4 parts of polyvinylidene
`fluoride (“Kynar-301F’, produced by Mitsubishi Petro-
`chemical Co., Ltd.), and 1 part of carboxymethyl cellulose
`was added thereto. The mixture was kneaded with 56 parts
`of water, followed by defoaming to prepare a negative
`electrode slurry. The slurry was applied to eachside of a 18
`pm thick copper foil (TCU-H18) collector at a single spread
`of 100 g/m? on a dry basis, dried in warm air having a
`temperature of 40° and a dew point of 10° and blowing at a
`velocity of 5 m/sec, compression molded in a roller press
`undera linear pressure of 4000 N/cm,and cut to a prescribed
`size to prepare a negative electrode sheet. The sheet was
`further dried in dry air heated to 150° C. by an infrared
`heater (dew point: —60° C.).
`Reference is now made to FIG. 1. Porous polypropylene
`film separator “Cell Guard 2400”, the above-preparcd ncega-
`tive electrode sheet, separator, and the above-prepared posi-
`tive electrode sheet were laminated in this order and rolled
`up. The roll was put in cylindrical open-top battery case
`made of nickel-plated iron, which also served as a negative
`electrode terminal. A 1 mol/l solution of LiPF, in a 2:2:6 (by
`volume) mixture of ethylene carbonate, butylene carbonate,
`and diethyl carbonate was poured into the case as an
`electrolytic solution. Battery cap having a safety valve,
`which also served as a positive electrode terminal, was fitted
`into the top opening of battery case via gasket made of
`polypropylene to prepare a cylindrical battery shown in FIG.
`
`ethod 2 for Preparation of Battery:
`The mixture of the positive electrode active material and
`the mixture of the negative electrode active material were
`scraped off from the air-dried positive electrode sheet and
`negative electrode sheet prepared in Method 1, respectively,
`and the powder wastableted to obtain a positive electrode
`pellet weighing 450 mg (for a 2032 type coin battery) or 675
`mg (for a 2332 type coin battery) and a negative electrode
`pellet weighing 90 mg (for a 2032 type coin battery) or 135
`mg (for a 2332 type coin battery), respectively. The positive
`electrode and negative electrode pellets were dried in dry air
`(dew point: —60° C.) heated to 150° C. by an infrared heater
`and put into a 2032 type or 2332 type coin case together with
`a separator and 200 1 ql of an electrolytic solution in dry air
`(dew point: —60° C.) at 25° C,
`Method 3 for Preparation of Battery:
`Lithium nitrate and nickel hydroxide were mixed at an
`Li:Ni atomic ratio of 1:1. The mixture was calcined at 700°
`C. for 10 hours and then at 800° C. for 8 hours to prepare
`
`1 M
`
`5
`ethylmethyl carbonate,
`carbonate, dimethyl carbonate,
`diethyl carbonate, methyl propionate, ethyl propionate,
`y-butyrolactone,
`1,2-dimethoxyethane,
`tetrahydrofuran,
`2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane,
`formamide, dimethylformamide, dioxolane, acetonitrile,
`nitromethane, phosphoric triesters,
`trimethoxymethane,
`dioxolane derivatives, sulfolane, 3-methyl- 2-oxazolidinone,
`propylene carbonate derivatives,
`tetrahydrofuran deriva-
`tives, ethy] ether, 1,3-propanesultone and a mixturethereof.
`Among these, ethylene carbonate, diethyl carbonate, ethyl
`propionate, propylene carbonate, butylene carbonate, dim-
`ethyl carbonate and ethylmethyl carbonate are more pre-
`ferred. Further, ethylene carbonate or a mixture of ethylene
`carbonate and diethyl carbonate or dimethyl carbonate is
`most preferred. Examples of the lithium salts soluble in
`these solvents include LiClO,, LiBF,, LiPF,, LiCF,SQ,,
`LiN(CF,SO,), LiCF,CO,, LiAsF,, LiSbF,, LiB,,Cl,,, Li(1,
`2-dimethoxyethane),C1O,, lower fatty acid lithium salts,
`LiAICl,, LiCl, LiBr, Lil, chloroboran lithium,lithium tet-
`raphenylborate and a mixture thereof. Among these, LiBF,
`and LiPF, are particularly preferred.
`Further, the nonaqueouselectrolytic solutions are prefer-
`ably a mixture of diethyl carbonate and LiPF, or a mixture
`of dimethyl carbonate and LiPF,. The water content of the
`electrolytic solution is preferably not higher than 1000 ppm,
`more preferably not higher than 100 ppm, and most prefer-
`ably not higher than 20 ppm.
`The present invention is not limited by the other elements
`constituting the battery or techniques for producing the
`battery. For example, JP-A-6-325767 and JP-A-6-3 46523
`can be referred to for the details of a separator, a volume
`ratio of a positive electrode to a negative electrode, a
`conducting agent, a binder, a support for a mixture of an
`electrode active material, methods of coating, drying, cut-
`ting, dehydration, and compression of a mixture of an
`electrode active material, the surface of a support, charging
`of a sheet battery, a lead tab, an insulating tape, a core,
`winding, web handling, a stopping tape, a battery case, an
`insulating sheet, insertion of an electrode, beading, a sealant,
`measurementof leakage current and insulation, a ratio of an
`electrolytic solution to an active material, a gas phase inside
`the battery, a gasket, a sealing plate or cap, a battery
`container, a safety valve, a safety element, a method of
`sealing, throttling of a battery case, insulation of the periph-
`ery of a cap, washing of members, tolerance of members,
`washingofthe battery, post-treatmentof the battery, exterior
`coating, a set of batteries, charging, and equipment used for
`battery production.
`The present invention will now be illustrated in greater
`detail with reference to Examples, but it should be under-
`stood that the present invention is not construed as being
`limited thereto. Unless otherwise indicated, all the percents
`and parts are by weight.
`Method 1 for Preparation of Battery:
`Lithium carbonate and cobalt oxide (a mixture of Co;0,
`and CoO; average particle size: 4.2 um) were mixed at a
`Li:Co atomic ratio of 1:1. The resulting mixture had a
`density of 0.75 g/cm®. The mixture was calcined in air at
`750° C.for 3 hours and then at 900° C. for 6 hours to prepare
`LiCoO,, which was ground to powder having an average
`particle size of 8.6 um by a high-speed air flow impact
`method. The powder had a specific surface area of 0.45
`m?/g. The proportion of particles having a diameter of from
`3 to 15 um was 87% by weight of the total particles.
`Eighty-five F, arts of the resulting LiCoO, powder as a
`positive electrode active material and 85 parts of acetylene
`black as a conducting agent were mixed in a mortar, and the
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`5,487,960
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`7
`LiNig2, which was ground to powder having an average
`particle size of 11 pm by a high-speed air flow impact
`method. A cylindrical battery was prepared in the same
`manneras in Method 1, except for using resulting LINiO, as
`a positive electrode active material.
`Method 4 for Preparation of Battery:
`Lithium nitrate and chemically synthesized manganese
`dioxide were mixed at an Li:Mn atomic ratio of 1:2. The
`mixture was calcined at 260° C. for 10 hours, at 300° C. for
`3 hours, at 450° C.for 8 hours, andfinally at 750° C. for 36
`hours to prepare LiMn,O,, which was ground to powder
`having an averageparticle size of 9 ym by a high-speed air
`flow impact method. A cylindrical battery was prepared in
`the same manner as in Method 1, except for using the
`resulting LiMn,O, as a positive electrode active material.
`Test Method:
`Five to ten batteries for each run were charged at a
`constant current density of 1000 mA/cm”to a cut-off voltage
`of 4.1 V and then inserted into a 300 W solenoid type heater
`and heated up to 350° C. The frequency of rupture of the
`batieries was examined. To make the testing accelerated, the
`diameter of vent hole of the safety valve was narrowed to
`about ‘40 of the ordinary size. Since batteries containing not
`more than 3 g/cell of LiCoO,are less liable to rupture, the
`numberofbatteries tested in each run wasincreased to 50.
`Those containing not more than 1 g/cell of LiCoO,arestill
`less liable to,rupture, 200 batteries were tested in each run,
`and no safety valve was provided.
`
`EXAMPLE1
`
`Cylindrical batteries (diameter: 18 mm; height: 65 mm),
`designated 001 to 040, were prepared in accordance with
`Method 1, except that 100 parts of the LiCoO, powder was
`mixed with 100 parts of water and the compound shown in
`Tables 1
`through 5 below, and water was evaporated to
`prepare a positive electrode active material. The content of
`the positive electrode active material in each battery was
`17.0 g/cell.
`
`TABLE1
`
`Amount of
`Battery
`Compound
`No.
`Compound Added
`(part)
`
`
`1.00
`HPO,
`001
`0.50
`.
`002
`0.20
`"
`003
`0.05
`"
`004
`0.50
`(NH,)3P0,.3H,0
`005
`0.50
`LiH,PO,
`006
`10.00
`Na,PO,.12H,O
`007
`0.50
`"
`008
`0.20
`"
`009
`0.50
`K,HPO,
`010
`0.50
`HPO,
`on
`012
`H,P20,
`0.50
`013
`NasP30j9
`0.50
`
`
`TABLE2
`
`Amount of
`Battery
`Compound
`
` No. Compound Added (part)
`
`
`
`
`014
`os
`016
`O17
`018
`
`H3BO;
`‘
`"
`"
`HBO,
`
`1,00
`0.50
`0.10
`0.05
`0.50
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`65
`
`8
`
`TABLE2-continued
`
`Amount of
`Battery
`Compound
`No.
`Compound Added
`(part)
`
`
`0.50
`H,B,0,
`019
`0.50
`Li,B,0,
`020
`5.00
`Na,B,0,
`021
`022
`(NH,),0.5B,03.8H,0
`0.50
`023
`NaBO,.4H,O0
`0.50
`
`
`TABLE3
`
`Amountof
`Battery
`Compound
`No.
`Compound Added
`(part)
`
`
`0.05
`H,Si0O,
`024
`0.50
`H,Si0,
`025
`0.50
`Na,SiO;
`026
`0.50
`K,Si0,
`027
`028
`Na,Si03.9H,O
`0.50
`029
`LiHSi,0,
`0.50
`
`
`TABLE 4
`
`Amount of
`Battery
`Compound
`No.
`Compound Added
`(part)
`
`
`1.00
`H,Mo0,
`030
`0.05
`H,MoO,
`031
`1.00
`(NH,) Mo0,.4H,O
`032
`1.00
`K,Mo0,
`033
`034
`Na,Mo0,.2H,O
`1.00
`035
`Li,MoO,
`1.00
`
`
`TABLE 5
`
`Amount of
`Battery
`Compound
`No.
`Compound Added
`(part)
`
`
`1.00
`H,WO,
`036
`0.05
`H,WO,
`037
`1.00
`(NE),0W 1202;.5H,O
`038
`1.00
`K,WO,
`039
`
`
`Na,WO,.2H,O040 1.00
`
`COMPARATIVE EXAMPLE1
`
`Batteries, designated 041 to 046, were prepared in the
`same manner as in Example 1, except for using the com-
`pound shownin Table 6 below as the compoundto be added
`to the positive electrode active material.
`
`TABLE 6
`
`Amount of
`Battery
`Compound
`No
`Compound Added
`(part)
`
`041
`none
`—
`042
`HPO,
`0.01
`043
`H,BO3
`0.01
`044
`H,Si0,
`0.01
`045
`lithium carbonate
`0.5
`
`lithium oxalate046 0.5
`
`
`6
`
`

`

`9
`TEST EXAMPLE1
`
`5,487,960
`
`10
`
`Eachofthe batteries 001 to 046 was tested in accordance
`with the above-described test method (the diameter of the
`vent hole was narrowedto 40 as a forced testing condition).
`The results obtained are shown in Table 7.
`
`TABLE7
`Number of
`Number
`of Tested
`Battery
`Ruptured
`
`BatteriesNo.
`Batteries
`001
`002
`003
`004
`00s
`006
`007
`008
`009
`010
`oll
`012
`013
`014
`015
`016
`017
`018
`019
`020
`021
`022
`023
`024
`025
`026
`027
`028
`029
`030
`031
`032
`033
`034
`035
`036
`037
`038
`039
`040
`041
`042
`043
`044
`045
`046
`
`AMAUNAMAMMAAANNNnAaGUETUAAAA
`BRABRAREHENEEERENPEEPRPRPPNRRPBREENNPEEEEeWeeeON
`
`It is clearly seen from the results of Table 7 that the
`batteries according to the present invention have improved
`safety in case of abrupt temperaturerise.
`
`EXAMPLE2
`
`Coin batteries having a varied size, designated 047 and
`048, and cylindrical batteries having a varied size, desig-
`nated 049 to 054, were prepared in accordance with Methods
`2 and 1, respectively, except that 100 parts of the LiCoO,
`powder was mixed with 100 parts of water and 0.5 part of
`H,PO,, and water was evaporated to prepare a positive
`electrode active material. For a forced testing condition, coin
`batteries 047 and 048 had no safety valve, and cylindrical
`batteries 049 to 054 had its vent hole diameter reduced to
`Yo. The size and LiCoO, content of each battery are shown
`in Table8.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`35
`
`60
`
`65
`
`TABLE &
`
`
`LiCoO,,
`Diameter x
`Battery
`Height
`Content
`No.
`(mm)
`(gicell)
`
`047
`20 x 3.2
`0.400
`048
`23 x 3.2
`0.600
`049
`12x 10.5
`14
`050
`12x 30
`2.9
`051
`10 x 44
`3.8
`052
`14 x 50
`7.2
`053
`17 x 50
`11.0
`054
`18 x 65
`17.0
`
`
`COMPARATIVE EXAMPLE 2
`
`Batteries 055 to 062 having a varied size were prepared in
`the same manneras in Example 2, except that no compound
`was addedto the positive electrode active material. The size
`and LiCoO, content of each battery are shown in Table 9.
`
`TABLE 9
`
`
`LiCoO0,
`Diameter x
`Battery
`Height
`Content
`No.
`(mm)
`(g/cell)
`
`055
`20 x 3.2
`0.400
`056
`23 x 3.2
`0.600
`057
`12x 10.5
`1.4
`058
`12 x 30
`2.9
`059
`10x 44
`3.8
`060
`14x 50
`72
`061
`17 x 50
`11.0
`
`18 x 65062 17.0
`
`
`TEST EXAMPLE2
`
`Each ofthe batteries 047 to 062 was tested in accordance
`with the above-described test method. The results obtained
`are shown in Table 10.
`
`TABLE 10
`
`Number
`Number of
`Battery
`of Tested
`Ruptured
`No.
`Batteries
`Batteries
`
`047
`200
`0
`048
`200
`0
`049
`50
`0
`050
`50
`0
`051
`10
`0.
`052
`10
`0
`053
`10
`1
`054
`10
`1
`055
`200
`0
`056
`200
`1
`057
`50
`1
`058
`50
`4
`059
`10
`1
`060
`10
`2
`061
`10
`5
`
`10062 8
`
`
`It is clearly seen that the tendency to rupture in case of
`abrupt temperature rise depends on size andthat the safety
`of batteries can be improved by the present invention.
`While, in Example 2, the effect of the present invention
`obtained by using H;PO, has been demonstrated, the same
`effect was observed when (NH,),P0,.3H,O, LiH,PO,,
`Na,PO,.12H,O,
` K,HPO,, HPO, H,P,0,, Na,P3;0;o,
`H3BOs,
`HBO,,
`H,B,0,,
`Li,B,,
`Na,B,0,,
`
`7
`
`

`

`5,487,960
`
`12
`
`TABLE 11-continued
`
`
`11
`(NH,),0.5B;.8H,O, NaBO,4H,0, H,SiO,, Na,SiO,,
`K,SiO3,
` Na,SiO3.9H,O,
` LiHSi,0,,
` H»MoO,,
`(NH,)Mo0,.4H,0, K,MoO,, Na2MoO,.2H,0, Li,MoO,,
`H,WO,, (NH4) 9W }204,-5H.O, K,WO,, or Na,WO,.2H,0
`was added to the mixture of the positive electrode active
`material.
`
`EXAMPLE3
`
`Cylindrical batteries having a diameter of 18 mm and a
`height of 65 mm, designated 063 to 124, were prepared in
`accordance with Method 1, except that 100 parts of the
`LiCoO, powder was mixed with 100 parts of water and 0.5
`part of H,PO,, and water was evaporated to prepare a
`positive electrode active material, and that the electrolytic
`solution shown in Table 11 was used. The LiCoO, content
`in each battery was 17.0 g.
`
`TABLE 11
`
`Battery
`No.
`
`Solvent*
`
`063
`064
`065
`066
`067
`068
`069
`070
`071
`
`072
`
`073
`
`074
`
`075
`
`076
`
`077
`
`078
`079
`080
`081
`082
`083
`
`084
`
`085
`
`086
`
`087
`088
`089
`090
`091
`092
`093
`094
`095
`096
`097
`098
`099
`100
`101
`102
`103
`104
`105
`106
`
`EC/DEC (2/4)**
`EC/DEC(2/8)
`EC/DECIMP(2/2/6)
`EC/DEC/MP(2/6/2)
`EC/DEC/EP (2/2/6)
`ED/DEC/EP(2/6/2)
`EC/DEC/DMC(2/2/6)
`EC/DEC/DMC(2/6/2)
`EC/DMC/EMC/DEC/MP/EP
`(36/3/6/2/24/29)
`EC/DEC (2/8)
`
`ECIDEC (2/8)
`
`EC/DEC(2/8)
`
`EC/DEC (2/8)
`
`EC/DEC(2/8)
`
`ECIDEC (2/8)
`
`EC/DEC (2/2)
`EC/DEC(2/2)
`EC/DEC (2/2)
`EC/DECMP(2/6/1)
`EC/DEC/MP(2/6/4)
`EC/DEC/MP(2/6/2)
`
`EC/DEC/MP(2/6/2)
`
`EC/DEC/MP(2/6/2}
`
`EC/DEC/MP(2/6/2}
`
`EC/DEC/MP(2/8/1)
`EC/DEC/MP(2/8/2)
`EC/DEC/MP(2/8/4)
`PCIDEC (2/2)
`PC/DME(2/2)
`PC/DME(2/2)
`EC/DME (2/2)
`BC/DME(2/8)
`ECI/DEC (2/1)
`BCYDEC (2/1)
`BCIDEC (2/2)
`BC/DEC(1/2)
`EC/DMC(2/2)
`EC/DMC (2/2)
`EC/MP(2/2)
`EC/EP (2/2)
`EC/DEC(2/2)
`EC/DEC (2/2)
`EC/DME (2/2)
`EC/DME (2/2)
`
`Supporting
`Electrolyte
`
`LiPF, (1)***
`LiPF, (1)
`LiPF, (1)
`LiPF, (1)
`LiPF, (1)
`LiPF, (1)
`LiPF, (1)
`LiPF, (1)
`LiPF, (1)
`
`LiPF,/LiBF,
`(0.5/0.5)
`LiPF,/LiBF,
`(0.7/0.3)
`LiPF,/LIBF,
`(0.9/0.1)
`LiPF,/LiCF,SO3
`(0.5/0.5)
`LiPF,/LiCF,SO3
`(0.7/0.3)
`LiPF,/LiCF,5S0,
`(0.9/0.1)
`LiPF, (1)
`LiPF, (0.8)
`LiPF, (0.5)
`LiPF, (1)
`LiPF, (1)
`LiPF,/LiBF,
`(0.8/0.2)
`LiPF,/LiBF,
`(0.9/0.2)
`LiPF,/LiBF,
`(0.9/0.1)
`LiPF,/LiBF,
`(1.0/0.1)
`LiPF, (1.0)
`LiPF, (1)
`LiPF, (1)
`LiBF, (1)
`LiPF, (1)
`LiCF,SO3 (1)
`LiBF,(1)
`LiBF, (1)
`LiPF, (1)
`LiPF, (1)
`LiPF, (1)
`LiPF, (1)
`LiPF, (1)
`LiPF, (1)
`LiPF, (1)
`LiPF, (1)
`LiBF, ()
`LiCF,SO, (1)
`LiPF, (1)
`LiCF,SO, (1)
`
`10
`
`15
`
`20
`
`30
`
`35
`
`45
`
`50
`
`55
`
`60
`
`Battery
`No,
`
`107
`108
`109
`110
`11
`112
`113
`114
`115
`116
`117
`118
`119
`120
`
`121
`
`122
`
`Soivent*
`
`PC/DME(2/2)
`PCIDEC (2/2)
`PCIDEC (2/1)
`PCIDEC(1/2)
`EC/DEC (2/8)
`EC/DEC(2/8)
`EC/DEC(2/8)
`EC/DEC(2/8)
`PC/DME(2/2)
`EC/DECIBC (2/6/2)
`EC/DEC/DME (2/1/2)
`EC/DEC/PC (2/6/2)
`DEC(1)
`EC/DEC (2/8)
`
`EC/DEC (2/8)
`
`EC/DEC (2/8)
`
`Supporting
`Electrolyte
`
`LiPF, (1)
`LiCF,SO, (1)
`LiPF, (1)
`LiPF, (1)
`LiBF, (1)
`LiCF3SO3 (1)
`LiPF, (0.8)
`LiPF, (0.5)
`LiBF, (1)
`LiPF, (1)
`LiBF, (1)
`LiPF, (1)
`LiPF, (1)
`LiPF,/LiN(CF,SO,).
`(0.9/0.1)
`LiPF,/LiN(CF;SO.)>
`(0.7/0.3)
`LiPF,/LiN(CF,SO,).
`(0.5/0.5)
`LiCF,SO, (1)
`LiCF,SO, (1)
`
`ECIDEC (2/2)
`EC/DEC/BC (2/6/2)
`
`123
`124
`Note:
`*The abbreviations for solvents have the following meanings.
`EC: ethylene carbonate
`PC: propylene carbonate
`BC:butylene carbonate
`DMC:dimethyl carbonate
`EMC;ethylmethyl carbonate
`DEC:diethyl carbonate
`MP: methyl propionate
`EP: ethyl propionate
`DME:dimethoxyethane
`**The ratio in parentheses is a mixing ratio of the solvents by volume.
`***The number(s) in parentheses is(are) the concentration(s) of the support-
`ing salt(s) (mol/l). For example, “EC/DEC (2/4).LiPF, (1)” for Battery 063
`means a 1 mol/l solution of LiPF, in a 2:4 by volume mixed solvent of EC
`and DEC.
`
`TEST EXAMPLE3
`
`Each of Batteries 063 to 124 was tested by the abo