CA2103219C - Lithium secondary battery - Google Patents
Lithium secondary batteryInfo
- Publication number
- CA2103219C CA2103219C CA002103219A CA2103219A CA2103219C CA 2103219 C CA2103219 C CA 2103219C CA 002103219 A CA002103219 A CA 002103219A CA 2103219 A CA2103219 A CA 2103219A CA 2103219 C CA2103219 C CA 2103219C
- Authority
- CA
- Canada
- Prior art keywords
- natural graphite
- secondary battery
- lithium secondary
- temperature
- heat treated
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
- H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/058—Construction or manufacture
- H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
- H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
- H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
- H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/621—Binders
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/49—Method of mechanical manufacture
- Y10T29/49002—Electrical device making
- Y10T29/49108—Electric battery cell making
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Inorganic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
- Carbon And Carbon Compounds (AREA)
- Secondary Cells (AREA)
Abstract
A lithium secondary battery comprises a natural graphite as a negative electrode capable of occluding and discharging lithium ion, in which the natural graphite has been heat treated at a temperature of at least 1,800°C. The heat treatment removes impurities from natural graphite. As a result, the electrolyte solution used for the battery hardly decomposes during charge and discharge and self discharge hardly occurs during storage of the battery.
Description
o ~
The present invention relates to a lithium secondary battery and, more specifically to improvement of negative electrode material used therefor to achieve better cycle characteristics and storage capability.
In recent years, lithium secondary batteries utilizing nonaqueous electrolytes have become of interest because of possible high-voltage design without taking decomposition voltage of water into consideration, thus differing from water-based secondary batteries utilizing aqueous electrolyte solutions, such as nickel-cadmium batteries.
Metallic lithium has been used as the negative electrode material of these lithium secondary batteries. In recent years~
however, it has been pointed out that metallic lithium causes bad cycle characteristirs due to growth of dendric deposits of lithium. Carbon materials, that occlude and discharge lithium ion solely during charge and discharge and have no problem of the above, are now studied as replacement of metallic lithium. Among these carbon materials, natural graphite is, having particularly high crystallinity and a large ~ h~rge capacity of 370 mAh/g, one of the most promising negative electrode materials.
However, natural graphite, being a natural product, contains in the crystals thereof impuritles such as bound water and active -~
teL i n~ l groups. These impurities react, during charge or -- 1 -- .
:' ' .
- : ~
,. ~ ~ , -~ 2 ;~
discharge or during storage, with the electrolyte solution used to decompose and degrade it, whereby lithium secondary batteries with a negative electrode of natural graphite have had the problem of poor cycle characteristiGs and storage characteristics.
The present invention provides a lithium second~ry battery with a negative electrode of natural graphite having excellent cycle characteristics and storage characteristics.
The present invention provides a lithium sPcon~Ary battery (hereinafter referred to as "the battery of the present invention") comprising a natural graphite as a negative electrode capable of occluding and discharging lithium ion, said natural graphite having been heat treated at a temperature of at least 1800~C.
A more complete appreciation of the invention and many of the att~n~nt advantages thereof will be readily obtained as the ~ -same become better understood by reference to the following ~; :
detailed description when considered in connection with the accompanying drawings, wherein:
FIGUR~ 1 is a schematic cross-sectional view of the battery of the present invention;
. - 2 -FIGURE 2 is a graph showing the relationship between the cycle characteristics and the heat treatment temperature of '~ ~
natural graphite; and ;;
FIGURE 3 is a graph showing the relationship between the stora~e characteristics and the heat treatment temperature of natural graphite. - '~
In the battery of the present invention, utilizing natural graphite from which impurities have been removed by heat treatment at a high temperature of at least 1,800~C, the electrolyte solution used hardly decomposes even by repeated cycles of charge and discharge. Besides, self discharge caused by impurities during storage is i ni i zed. These facts constitutes the grounds for the battery of the present invention having better cycle characteristics and storage characteristics ~ ~
as - ~-red with lithium secondary batteries utilizing natural ~ -graphite as it is, without heat treatment.
The above heat treatment is carried out by heating natural graphite in a heating oven at a temperature of at least 1,800~C
under an atmosphere of inert gas such as nitrogen or argon. It is particularly desirable, a~ shown in the Examples to be described later herein, to conduct the heat treatment at a -temperature of at least 2,400~C, for the purpose of obtA;ning batteries having excellent cycle characteristics and storage :: ~, . .
: - ~
' -' 2 ~ ~ ' characteristics. The heat treatment time varies according to the type o~ natural graphite, but generally, tha usual impurities can be removed by heat treatment for about 24 hours.
It is desirable that the natural graphite to be heat treated have high crystallinity, with a d-value (doo2) in the lattice plane of (002) of not more than 3.37 ~ and a crystal size in the c-axis direction (Lc) of at least 200 ~. Raw natural graphite of this type hardly changes its doo2 and Lc by heat treatment.
As described above, the key feature of the present invention lies in the use, to obtain a lithium secondary battery having excellent cycle characteristics and storage ~;
characteristics, of a natural graphite having little impurities as a negative electrode material. Accordingly, there are no particular restrictions with respect to other materials constituting the battery, such as positive electrode material and electrolyte solution and various materials that have been used or proposed can be used without limitation.
Thu~ les of usable positive electrode materials ;
(active materials) are modified MnO2, ~iCoO2,LiNiO2~LiMnO2, LiMn2O4 and LiFeO2 Examples of usahle electrolyte solutions are those of 3.~
electrolyte solutes such as LiPF6, LiBF4, LiC104, and LiCF3So3 each dissolved in an organic solvent such as ethylene carbonate, vinylene carbonate or propylene carbonate, or in a mixed solvent :
of any one of the above organic solvents with a low-boiling-point solvent such as dimethyl carbonate, diethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane or ethoxymethoxyethane.
Other faatures of the invention will become apparent in the course of the following descriptions of exemplary embodiments which are given for illustration of the invention and are not int~nded to be limiting thereof.
EXAMPLES
Examples 1 through 7 AA-size lithium secondary batteries according to the present invention were prepared as follows.
Positive electrode A slurry was prepared by dispersing a mixture obt~;nP~ by ; ;~-mixing LiCoO2, as a positive electrode active material and artificial graphite as a conductive agent in a ratio by weight of 9~1 in a 5~ by weight solution of polyvinylidene fluoride in N-methylpyrrolidone (NMP). The slurry thus prepared was applied by doctor blade method to both sides of an aluminum *oil as a positive electrode collector, and then vacuum-dried at , , : :
j~ , . .: . . - :
100~C for 2 hours, to obtain a positive electrode.
Neqative electrodes Natural graphite (doo2 = 3.360 A, Lc = 1,500 ~) was heat treated in a heating oven under an atmosphere of nitrog~n (upper limit of heating temperature in the oven: 3,000~C) at a temperature of 1,800, 2,000, 2,200, 2,400, 2,600, 2,800 or 3,000~C for 24 hours. The doo2 and Lc were obta;ne~ after each heat treatment, all of which were the same as those before heat treatment.
Slurries were prepared by dispersing each of the above heat-treated graphite in a 5% by weight polyvinylidene fluoride as a ;
binder in NMP. The slurries thus ob~;ne~ w~re each applied by doctor blade method to both sides of a copper foil as a negative electrode collector, which were then vacuum-dried at lG0~C for 2 hours, to give 7 types of negative electrodes.
ElPctrolyte solution LiPF6 was dissolved in a 1/1 by volume mixed isolvent of ethylene carbonate and dimethyl carbonate in a concentration of l mole/l, to prepare an electrolyte solution.
-Pre~aration of batteries Seven types of AA-size batteries, BAl through BA7 (larger numbers mean higher heat treating temperatures) of the present - ::: :. .:.:: . ~ . .
~ , 19 invention having different negative electrodes were prepared with the above positive electrode and electrolyte solution. A
polypropylene microporous film (trade mark: CELGARD, made by Celanese Corp.) was used as separator, which was impregnated with the above electrolyte solution.
FIGURE 1 is a schematic cross-sec~ional view o~ the battery BAl of the present invention (BA2 through BA7 have similar structure~. In the FIGURE, the battery B~l comprises a positive electrode 1, a negative electrode 2, a separator 3 separating the two electrodes, a positive electrode lead 4, a negative electrode lead 5, a positive electrode external terminal 6 and a negative electrode can 7. The positive and negative electrodes 1 and 2, between which a separator 3 is sandwiched, are spirally wound and housed in the negative electrode can 7. The positive electrode 1 -is connected, via the positive electrode lead 4, to the positive electrode external terminal 6, and the negative electrode 2 to ~ ~
the negative electrode lead 7 via the negative electrode lead 5, ~ :
so that chemical energy that generates inside the battery can be taken out as electric energy.
Comparative Examples 1 through 5 The procedure for Examples 1 through 7 was repeated except that natural graphite without heat treatment, or that heat treated at 1,000~C, 1,200~C, 1,400~C or 1,600~C was used, to prepare comparison batteries, in the above order, BCl through , ~ .. ,~,; .-BC 5.
Relationship between the cYcle characteristics and the heat treatinq temperature The batteries were each subjected to a cycle test to study the relationship between the cycle characteristic and the heat treating temperature for natural graphite. one cycle comprised charging with a charge current of 200 ~A to a charge termination voltage of 4.1 V, followed by discharging with a discharge current of 200 mA to a discharge termination voltage of 2.75 V.
The results are shown in FIGURE 2.
. s,..
FIGURE 2 is a graph showing the relationship between the cycle characteristics and the heat treating temperature of natural graphite, with the ordinate representing the cycle deterioration ratio (%/cycle~ at the 500-th cycle and the abscissa representing the heat treating temperature (~C). Zero (0) on the abscissa means no heat treatment. The cycle deterioration ratio is obtained by dividing the ratio (~) of the discharge capacity at the 500-th cycle to that at the initial stage of cycles by the total number of cycles repeated, i.e. 500.
It is understood from the FIGURE that the batteries of the present invention, BAl through BA7, utilizing a~ their negativ~
electrode natural graphite heat treated at a temperature of at least 1,800~C, have smaller cycle deterioration ratios, i.e.
. .; . , . . ~.
i'i;..;~ , ' '. ~ ~ , ' . .. . ' ,' . ;
.,. ~ . ., better cycle characteristics than those of comparison battery BCl with a negative electrode utilizing natural graphite as it is, without heat treatment, and comparison batteries BC2 through BC5, utilizing natural graphite heat treated at a temperature of not more than 1,600~C. It is also understood from the FIGURE that, in particular, the batteries of the present invention BA4 through BA7, with the heat treating temperature P~cee~7n~ 2400~C have markedly small cycle deteriorakion ratios, i.e; markedly excellent cycle characteristics.
:~
RelationshiP between the storage characteristics and the heat treatin~ temperature -' ,".''.' -Each of the above batteries was, after being stored for l year, charged with a charge current of 200 mA to a charge -~
termination voltage of 4.1 V and then discharged with a discharge --~
current of 200 mA to a discharge termination voltage of 2.75 V, to study the relationship between the storage characteristics and the heat treating temperature for the natural graphite used for their negative electrode. The results are shown in FIGURE 3.
FIGURE 3 shows the relationship between the storage characteristic and the heat treating temperature of natural graphite, with the ordinate representing the capa~ity retention (%) after l-year storage and the abscissa representing the heat treating temperature (~C). Like in _ g _ : - -., -.: ., .. : . :
The present invention relates to a lithium secondary battery and, more specifically to improvement of negative electrode material used therefor to achieve better cycle characteristics and storage capability.
In recent years, lithium secondary batteries utilizing nonaqueous electrolytes have become of interest because of possible high-voltage design without taking decomposition voltage of water into consideration, thus differing from water-based secondary batteries utilizing aqueous electrolyte solutions, such as nickel-cadmium batteries.
Metallic lithium has been used as the negative electrode material of these lithium secondary batteries. In recent years~
however, it has been pointed out that metallic lithium causes bad cycle characteristirs due to growth of dendric deposits of lithium. Carbon materials, that occlude and discharge lithium ion solely during charge and discharge and have no problem of the above, are now studied as replacement of metallic lithium. Among these carbon materials, natural graphite is, having particularly high crystallinity and a large ~ h~rge capacity of 370 mAh/g, one of the most promising negative electrode materials.
However, natural graphite, being a natural product, contains in the crystals thereof impuritles such as bound water and active -~
teL i n~ l groups. These impurities react, during charge or -- 1 -- .
:' ' .
- : ~
,. ~ ~ , -~ 2 ;~
discharge or during storage, with the electrolyte solution used to decompose and degrade it, whereby lithium secondary batteries with a negative electrode of natural graphite have had the problem of poor cycle characteristiGs and storage characteristics.
The present invention provides a lithium second~ry battery with a negative electrode of natural graphite having excellent cycle characteristics and storage characteristics.
The present invention provides a lithium sPcon~Ary battery (hereinafter referred to as "the battery of the present invention") comprising a natural graphite as a negative electrode capable of occluding and discharging lithium ion, said natural graphite having been heat treated at a temperature of at least 1800~C.
A more complete appreciation of the invention and many of the att~n~nt advantages thereof will be readily obtained as the ~ -same become better understood by reference to the following ~; :
detailed description when considered in connection with the accompanying drawings, wherein:
FIGUR~ 1 is a schematic cross-sectional view of the battery of the present invention;
. - 2 -FIGURE 2 is a graph showing the relationship between the cycle characteristics and the heat treatment temperature of '~ ~
natural graphite; and ;;
FIGURE 3 is a graph showing the relationship between the stora~e characteristics and the heat treatment temperature of natural graphite. - '~
In the battery of the present invention, utilizing natural graphite from which impurities have been removed by heat treatment at a high temperature of at least 1,800~C, the electrolyte solution used hardly decomposes even by repeated cycles of charge and discharge. Besides, self discharge caused by impurities during storage is i ni i zed. These facts constitutes the grounds for the battery of the present invention having better cycle characteristics and storage characteristics ~ ~
as - ~-red with lithium secondary batteries utilizing natural ~ -graphite as it is, without heat treatment.
The above heat treatment is carried out by heating natural graphite in a heating oven at a temperature of at least 1,800~C
under an atmosphere of inert gas such as nitrogen or argon. It is particularly desirable, a~ shown in the Examples to be described later herein, to conduct the heat treatment at a -temperature of at least 2,400~C, for the purpose of obtA;ning batteries having excellent cycle characteristics and storage :: ~, . .
: - ~
' -' 2 ~ ~ ' characteristics. The heat treatment time varies according to the type o~ natural graphite, but generally, tha usual impurities can be removed by heat treatment for about 24 hours.
It is desirable that the natural graphite to be heat treated have high crystallinity, with a d-value (doo2) in the lattice plane of (002) of not more than 3.37 ~ and a crystal size in the c-axis direction (Lc) of at least 200 ~. Raw natural graphite of this type hardly changes its doo2 and Lc by heat treatment.
As described above, the key feature of the present invention lies in the use, to obtain a lithium secondary battery having excellent cycle characteristics and storage ~;
characteristics, of a natural graphite having little impurities as a negative electrode material. Accordingly, there are no particular restrictions with respect to other materials constituting the battery, such as positive electrode material and electrolyte solution and various materials that have been used or proposed can be used without limitation.
Thu~ les of usable positive electrode materials ;
(active materials) are modified MnO2, ~iCoO2,LiNiO2~LiMnO2, LiMn2O4 and LiFeO2 Examples of usahle electrolyte solutions are those of 3.~
electrolyte solutes such as LiPF6, LiBF4, LiC104, and LiCF3So3 each dissolved in an organic solvent such as ethylene carbonate, vinylene carbonate or propylene carbonate, or in a mixed solvent :
of any one of the above organic solvents with a low-boiling-point solvent such as dimethyl carbonate, diethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane or ethoxymethoxyethane.
Other faatures of the invention will become apparent in the course of the following descriptions of exemplary embodiments which are given for illustration of the invention and are not int~nded to be limiting thereof.
EXAMPLES
Examples 1 through 7 AA-size lithium secondary batteries according to the present invention were prepared as follows.
Positive electrode A slurry was prepared by dispersing a mixture obt~;nP~ by ; ;~-mixing LiCoO2, as a positive electrode active material and artificial graphite as a conductive agent in a ratio by weight of 9~1 in a 5~ by weight solution of polyvinylidene fluoride in N-methylpyrrolidone (NMP). The slurry thus prepared was applied by doctor blade method to both sides of an aluminum *oil as a positive electrode collector, and then vacuum-dried at , , : :
j~ , . .: . . - :
100~C for 2 hours, to obtain a positive electrode.
Neqative electrodes Natural graphite (doo2 = 3.360 A, Lc = 1,500 ~) was heat treated in a heating oven under an atmosphere of nitrog~n (upper limit of heating temperature in the oven: 3,000~C) at a temperature of 1,800, 2,000, 2,200, 2,400, 2,600, 2,800 or 3,000~C for 24 hours. The doo2 and Lc were obta;ne~ after each heat treatment, all of which were the same as those before heat treatment.
Slurries were prepared by dispersing each of the above heat-treated graphite in a 5% by weight polyvinylidene fluoride as a ;
binder in NMP. The slurries thus ob~;ne~ w~re each applied by doctor blade method to both sides of a copper foil as a negative electrode collector, which were then vacuum-dried at lG0~C for 2 hours, to give 7 types of negative electrodes.
ElPctrolyte solution LiPF6 was dissolved in a 1/1 by volume mixed isolvent of ethylene carbonate and dimethyl carbonate in a concentration of l mole/l, to prepare an electrolyte solution.
-Pre~aration of batteries Seven types of AA-size batteries, BAl through BA7 (larger numbers mean higher heat treating temperatures) of the present - ::: :. .:.:: . ~ . .
~ , 19 invention having different negative electrodes were prepared with the above positive electrode and electrolyte solution. A
polypropylene microporous film (trade mark: CELGARD, made by Celanese Corp.) was used as separator, which was impregnated with the above electrolyte solution.
FIGURE 1 is a schematic cross-sec~ional view o~ the battery BAl of the present invention (BA2 through BA7 have similar structure~. In the FIGURE, the battery B~l comprises a positive electrode 1, a negative electrode 2, a separator 3 separating the two electrodes, a positive electrode lead 4, a negative electrode lead 5, a positive electrode external terminal 6 and a negative electrode can 7. The positive and negative electrodes 1 and 2, between which a separator 3 is sandwiched, are spirally wound and housed in the negative electrode can 7. The positive electrode 1 -is connected, via the positive electrode lead 4, to the positive electrode external terminal 6, and the negative electrode 2 to ~ ~
the negative electrode lead 7 via the negative electrode lead 5, ~ :
so that chemical energy that generates inside the battery can be taken out as electric energy.
Comparative Examples 1 through 5 The procedure for Examples 1 through 7 was repeated except that natural graphite without heat treatment, or that heat treated at 1,000~C, 1,200~C, 1,400~C or 1,600~C was used, to prepare comparison batteries, in the above order, BCl through , ~ .. ,~,; .-BC 5.
Relationship between the cYcle characteristics and the heat treatinq temperature The batteries were each subjected to a cycle test to study the relationship between the cycle characteristic and the heat treating temperature for natural graphite. one cycle comprised charging with a charge current of 200 ~A to a charge termination voltage of 4.1 V, followed by discharging with a discharge current of 200 mA to a discharge termination voltage of 2.75 V.
The results are shown in FIGURE 2.
. s,..
FIGURE 2 is a graph showing the relationship between the cycle characteristics and the heat treating temperature of natural graphite, with the ordinate representing the cycle deterioration ratio (%/cycle~ at the 500-th cycle and the abscissa representing the heat treating temperature (~C). Zero (0) on the abscissa means no heat treatment. The cycle deterioration ratio is obtained by dividing the ratio (~) of the discharge capacity at the 500-th cycle to that at the initial stage of cycles by the total number of cycles repeated, i.e. 500.
It is understood from the FIGURE that the batteries of the present invention, BAl through BA7, utilizing a~ their negativ~
electrode natural graphite heat treated at a temperature of at least 1,800~C, have smaller cycle deterioration ratios, i.e.
. .; . , . . ~.
i'i;..;~ , ' '. ~ ~ , ' . .. . ' ,' . ;
.,. ~ . ., better cycle characteristics than those of comparison battery BCl with a negative electrode utilizing natural graphite as it is, without heat treatment, and comparison batteries BC2 through BC5, utilizing natural graphite heat treated at a temperature of not more than 1,600~C. It is also understood from the FIGURE that, in particular, the batteries of the present invention BA4 through BA7, with the heat treating temperature P~cee~7n~ 2400~C have markedly small cycle deteriorakion ratios, i.e; markedly excellent cycle characteristics.
:~
RelationshiP between the storage characteristics and the heat treatin~ temperature -' ,".''.' -Each of the above batteries was, after being stored for l year, charged with a charge current of 200 mA to a charge -~
termination voltage of 4.1 V and then discharged with a discharge --~
current of 200 mA to a discharge termination voltage of 2.75 V, to study the relationship between the storage characteristics and the heat treating temperature for the natural graphite used for their negative electrode. The results are shown in FIGURE 3.
FIGURE 3 shows the relationship between the storage characteristic and the heat treating temperature of natural graphite, with the ordinate representing the capa~ity retention (%) after l-year storage and the abscissa representing the heat treating temperature (~C). Like in _ g _ : - -., -.: ., .. : . :
2~2~ ~
FIGURE 2, zero (0) on the abscissa means no heat treatment. The capacity retention means the ratio (~) of the discharge capacity after 1-year storage to that before storage.
From the FIGURE it is understood that the bàtteries of the present invention BAl through BA7, utilizing as their negative electrode natural graphite heat treated at a temperature cee~ing 1,800~C, have larger capacity retentions, i.e. better storage characteristics compared with comparison batteries BCl .
through BC5. It is also understood from the FIGURE that the batteries of the present invention BA4 through BA7, utilizing natural graphite heat treated at a temperature of, in particular, at least 2,400~C have markedly excellent storage characteristics.
Although the present invention has been described hereinabove by reference to AA-size batteries alone, the invention can apply to batteries of any other shape, such as flat or square, with no particular limitation~
FIGURE 2, zero (0) on the abscissa means no heat treatment. The capacity retention means the ratio (~) of the discharge capacity after 1-year storage to that before storage.
From the FIGURE it is understood that the bàtteries of the present invention BAl through BA7, utilizing as their negative electrode natural graphite heat treated at a temperature cee~ing 1,800~C, have larger capacity retentions, i.e. better storage characteristics compared with comparison batteries BCl .
through BC5. It is also understood from the FIGURE that the batteries of the present invention BA4 through BA7, utilizing natural graphite heat treated at a temperature of, in particular, at least 2,400~C have markedly excellent storage characteristics.
Although the present invention has been described hereinabove by reference to AA-size batteries alone, the invention can apply to batteries of any other shape, such as flat or square, with no particular limitation~
Claims (11)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A lithium secondary battery comprising a natural graphite as a negative electrode capable of occluding and discharging lithium ion, said natural graphite having been heat treated at a temperature of at least 1,800°C.
2. The lithium secondary battery according to claim 1, wherein said natural graphite has been heat treated at a temperature of at least 2,400°C.
3. The lithium secondary battery according to either claim 1 or 2, wherein said natural graphite has a d-value (d002) in the lattice plane of (002) of not more than 3.37.ANG. and a crystallite size in the c-axis direction (Lc) of at least 200.ANG..
4. In a lithium secondary battery comprising a carbon material as a negative electrode capable of occluding and discharging lithium ion, the improvement comprising:
said carbon material consisting of a natural graphite heat treated at a temperature of at least 1,800°C whereby impurities are removed from said natural graphite.
said carbon material consisting of a natural graphite heat treated at a temperature of at least 1,800°C whereby impurities are removed from said natural graphite.
5. The lithium secondary battery according to Claim 4, wherein said natural graphite has been heat treated at a temperature of at least 2,400°C.
6. The lithium secondary battery according to Claim 4, wherein said natural graphite has a d-value (d002) in the lattice plane of (002) of not more than 3.37 .ANG. and a crystallite size in the c-axis direction (Lc) of at least 200 .ANG..
7. A lithium secondary battery comprising a carbon material as a negative electrode capable of occluding and discharging lithium ion, comprising:
a positive electrode;
an electrolyte including an electrolyte solute selected from the group consisting of LiPF6, LiClO4, LiBF4 and LiCF3SO3, and an organic solvent selected from a group consisting of ethylene carbonate, vinylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane and ethoxymethoxyethane; and said negative electrode consisting essentially of a binder and said carbon material, wherein said carbon material is a natural graphite having been heat treated at a temperature of 1,800°C to 3,000°C.
a positive electrode;
an electrolyte including an electrolyte solute selected from the group consisting of LiPF6, LiClO4, LiBF4 and LiCF3SO3, and an organic solvent selected from a group consisting of ethylene carbonate, vinylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane and ethoxymethoxyethane; and said negative electrode consisting essentially of a binder and said carbon material, wherein said carbon material is a natural graphite having been heat treated at a temperature of 1,800°C to 3,000°C.
8. The lithium secondary battery according to Claim 7, wherein said natural graphite has been heat treated at a temperature of 2,400°C to 3,000°C.
9. The lithium secondary battery according to Claim 7, wherein said positive electrode includes a material selected from a group consisting of modified MnO2, LiCoO2, LiMnO2, LiMn2O4 and LiFeO2.
10. The lithium secondary battery according to Claim 7, wherein said natural graphite has a d-value (d002) in the lattice plane of (002) of not more than 3.37 .ANG. and a crystallite size in the c-axis direction of (Lc) of at least 200 .ANG..
11. The lithium secondary battery according to any one of Claims 1 to 10, wherein said natural graphite is heat treated at said temperature for at least about 24 hours.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP96875/1993 | 1993-03-30 | ||
| JP09687593A JP3188032B2 (en) | 1993-03-30 | 1993-03-30 | Lithium secondary battery |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2103219A1 CA2103219A1 (en) | 1994-10-01 |
| CA2103219C true CA2103219C (en) | 1998-08-11 |
Family
ID=14176601
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002103219A Expired - Lifetime CA2103219C (en) | 1993-03-30 | 1993-11-16 | Lithium secondary battery |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US6447955B1 (en) |
| EP (1) | EP0624913B1 (en) |
| JP (1) | JP3188032B2 (en) |
| CA (1) | CA2103219C (en) |
| DE (1) | DE69401160T2 (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20010049059A1 (en) * | 1995-04-10 | 2001-12-06 | Hidetoshi Honbo | Non-aqueous secondary battery having negative electrode including graphite powder |
| JPH0992284A (en) * | 1995-09-26 | 1997-04-04 | Kureha Chem Ind Co Ltd | Graphite material for secondary battery electrode, method for producing the same, and secondary battery |
| JP4075259B2 (en) * | 1999-05-26 | 2008-04-16 | ソニー株式会社 | Solid electrolyte secondary battery |
| US6623889B2 (en) | 1999-12-20 | 2003-09-23 | Kabushiki Kaisha Toshiba | Nonaqueous electrolyte secondary battery, carbon material for negative electrode, and method for manufacturing carbon material for negative electrode |
| JP4557381B2 (en) * | 2000-06-27 | 2010-10-06 | 三井化学株式会社 | Non-aqueous electrolyte and secondary battery using the same |
| JP5082207B2 (en) | 2004-06-30 | 2012-11-28 | 三菱化学株式会社 | Method for producing negative electrode material for lithium secondary battery, and negative electrode for lithium secondary battery and lithium secondary battery using the same |
| JP2006216511A (en) * | 2005-02-07 | 2006-08-17 | Sanyo Electric Co Ltd | Nonaqueous electrolyte secondary battery |
| EP2352192B1 (en) | 2008-10-31 | 2016-06-01 | Mitsubishi Chemical Corporation | Negative electrode material for nonaqueous secondary battery |
Family Cites Families (20)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4388227A (en) * | 1979-03-02 | 1983-06-14 | Celanese Corporation | Intercalation of graphitic carbon fibers |
| JPS5719970A (en) | 1980-07-08 | 1982-02-02 | Matsushita Electric Ind Co Ltd | Primary alkaline battery |
| JPS57208079A (en) | 1981-06-18 | 1982-12-21 | Sanyo Electric Co Ltd | Rechargeable lithium cell |
| US4707423A (en) * | 1982-06-10 | 1987-11-17 | Celanese Corporation | Electric storage battery and process for the manufacture thereof |
| US4423125A (en) | 1982-09-13 | 1983-12-27 | Bell Telephone Laboratories, Incorporated | Ambient temperature rechargeable battery |
| DE3588167T2 (en) | 1984-06-12 | 1998-03-12 | Mitsubishi Chem Corp | Secondary batteries containing pseudo-graphite produced by pyrolysis as the electrode material |
| US4702977A (en) | 1985-04-30 | 1987-10-27 | Toshiba Battery Co., Ltd. | Secondary battery using non-aqueous solvent |
| DE3680249D1 (en) | 1985-05-10 | 1991-08-22 | Asahi Chemical Ind | SECONDARY BATTERY. |
| CA1296766C (en) | 1986-05-13 | 1992-03-03 | Yuzuru Takahashi | Secondary battery |
| US4863818A (en) * | 1986-06-24 | 1989-09-05 | Sharp Kabushiki Kaisha | Graphite intercalation compound electrodes for rechargeable batteries and a method for the manufacture of the same |
| JPS63139012A (en) | 1986-11-29 | 1988-06-10 | Koa Sekiyu Kk | Production of graphitic material for electric cell |
| JP2797390B2 (en) * | 1989-04-03 | 1998-09-17 | ソニー株式会社 | Non-aqueous electrolyte secondary battery |
| US5153082A (en) * | 1990-09-04 | 1992-10-06 | Bridgestone Corporation | Nonaqueous electrolyte secondary battery |
| JPH04184862A (en) | 1990-11-19 | 1992-07-01 | Yuasa Corp | Lithium secondary battery |
| JP3233417B2 (en) | 1991-07-25 | 2001-11-26 | 富士写真フイルム株式会社 | Organic electrolyte secondary battery |
| JP3727666B2 (en) * | 1991-07-29 | 2005-12-14 | 株式会社東芝 | Lithium secondary battery |
| CA2113421A1 (en) * | 1992-05-15 | 1993-11-25 | Kazuya Kuriyama | Secondary battery and its manufacturing method |
| US5340670A (en) * | 1992-06-01 | 1994-08-23 | Kabushiki Kaisha Toshiba | Lithium secondary battery and method of manufacturing carbonaceous material for negative electrode of the battery |
| JPH0684542A (en) | 1992-09-02 | 1994-03-25 | Sanyo Electric Co Ltd | Nonaqueous electrolytic solution secondary battery |
| JPH06239607A (en) | 1993-02-12 | 1994-08-30 | Sanyo Electric Co Ltd | Highly graphitized carbon material manufacturing method and secondary battery |
-
1993
- 1993-03-30 JP JP09687593A patent/JP3188032B2/en not_active Expired - Lifetime
- 1993-11-16 CA CA002103219A patent/CA2103219C/en not_active Expired - Lifetime
-
1994
- 1994-03-03 DE DE69401160T patent/DE69401160T2/en not_active Expired - Lifetime
- 1994-03-03 EP EP94103209A patent/EP0624913B1/en not_active Expired - Lifetime
-
1996
- 1996-06-27 US US08/671,077 patent/US6447955B1/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| EP0624913A2 (en) | 1994-11-17 |
| JPH06290781A (en) | 1994-10-18 |
| JP3188032B2 (en) | 2001-07-16 |
| EP0624913B1 (en) | 1996-12-18 |
| EP0624913A3 (en) | 1995-02-15 |
| CA2103219A1 (en) | 1994-10-01 |
| DE69401160D1 (en) | 1997-01-30 |
| US6447955B1 (en) | 2002-09-10 |
| DE69401160T2 (en) | 1997-04-10 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| EP0688057B1 (en) | Lithium ion secondary battery | |
| JP3978881B2 (en) | Non-aqueous electrolyte and lithium secondary battery using the same | |
| JP3439082B2 (en) | Non-aqueous electrolyte secondary battery | |
| US6156457A (en) | Lithium secondary battery and method for manufacturing a negative electrode | |
| KR100531064B1 (en) | Nonaqueous Electrolyte Secondary Battery | |
| JPH0652887A (en) | Lithium secondary battery | |
| JP3059820B2 (en) | Lithium secondary battery | |
| US6319633B1 (en) | Rechargeable lithium battery | |
| US9136529B2 (en) | Method of charging and discharging a non-aqueous electrolyte secondary battery | |
| JPH09147863A (en) | Nonaqueous electrolyte battery | |
| CA2103219C (en) | Lithium secondary battery | |
| JPH06295725A (en) | Nonaqueous secondary battery | |
| US6482546B1 (en) | Rechargeable lithium battery | |
| JPH07114940A (en) | Non-aqueous electrolyte secondary battery | |
| JPH10189045A (en) | Lithium secondary battery | |
| JPH0684542A (en) | Nonaqueous electrolytic solution secondary battery | |
| JPH11111291A (en) | Positive electrode material for non-aqueous secondary battery and battery using the same | |
| JPH0864246A (en) | Sealed type nonaqueous electrolyte secondary battery | |
| JP3519766B2 (en) | Non-aqueous secondary battery | |
| US20230420751A1 (en) | Secondary battery, and battery module, battery pack, and electrical device comprising the same | |
| JP2000021392A (en) | Nonaqueous secondary battery | |
| JP3268924B2 (en) | Non-aqueous electrolyte battery | |
| US6613476B2 (en) | Positive active material for rechargeable lithium battery and method of preparing same | |
| JPH06275271A (en) | Lithium secondary battery | |
| JPH08171934A (en) | Lithium secondary battery |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKEX | Expiry |
Effective date: 20131118 |