CA2641152C - Lithium secondary battery using ionic liquid - Google Patents
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- CA2641152C CA2641152C CA2641152A CA2641152A CA2641152C CA 2641152 C CA2641152 C CA 2641152C CA 2641152 A CA2641152 A CA 2641152A CA 2641152 A CA2641152 A CA 2641152A CA 2641152 C CA2641152 C CA 2641152C
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- 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
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- 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
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0566—Liquid materials
- H01M10/0567—Liquid materials characterised by the additives
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- 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
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0566—Liquid materials
- H01M10/0568—Liquid materials characterised by the solutes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M6/00—Primary cells; Manufacture thereof
- H01M6/14—Cells with non-aqueous electrolyte
- H01M6/16—Cells with non-aqueous electrolyte with organic electrolyte
- H01M6/162—Cells with non-aqueous electrolyte with organic electrolyte characterised by the electrolyte
- H01M6/166—Cells with non-aqueous electrolyte with organic electrolyte characterised by the electrolyte by the solute
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M6/00—Primary cells; Manufacture thereof
- H01M6/14—Cells with non-aqueous electrolyte
- H01M6/16—Cells with non-aqueous electrolyte with organic electrolyte
- H01M6/162—Cells with non-aqueous electrolyte with organic electrolyte characterised by the electrolyte
- H01M6/168—Cells with non-aqueous electrolyte with organic electrolyte characterised by the electrolyte by additives
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- 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
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Abstract
The invention provides a lithium secondary battery having high performance even at the time of high-rate charging and discharging, high energy density, high voltage, and a nonaqueous electrolyte excellent in safety. More specifically, the invention provides a lithium secondary battery using an ionic liquid, comprising a positive electrode, a negative electrode, a separator provided between the positive electrode and the negative electrode, and a nonaqueous electrolyte containing a lithium salt, wherein the nonaqueous electrolyte uses an ionic liquid containing bis(fluorosulfonyl)imide anion as an anionic component, as a solvent, voltage at the time of full charging is 3.6V or higher, and average discharge voltage in a discharge rate of 1-hour rate is 2.9V or higher.
Description
Description Lithium secondary battery using ionic liquid Technical Field [0001]
The present invention relates to a lithium secondary battery using an ionic liquid, and more particularly, it relates to a high voltage lithium secondary battery using a nonflammable nonaqueous electrolyte.
Background Art [0002]
A lithium secondary battery has high voltage and high energy density even though it is compact and lightweight.
Therefore, the lithium secondary battery is used in power source of terminals of information and communication devices such as mobile phones, laptop computers and digital cameras, and demand is rapidly expanded. Furthermore, it is noted as power source of electric vehicles from the viewpoint of environmental and resource problems.
The present invention relates to a lithium secondary battery using an ionic liquid, and more particularly, it relates to a high voltage lithium secondary battery using a nonflammable nonaqueous electrolyte.
Background Art [0002]
A lithium secondary battery has high voltage and high energy density even though it is compact and lightweight.
Therefore, the lithium secondary battery is used in power source of terminals of information and communication devices such as mobile phones, laptop computers and digital cameras, and demand is rapidly expanded. Furthermore, it is noted as power source of electric vehicles from the viewpoint of environmental and resource problems.
[0003]
Conventionally, a polar aprotic organic solvent which is liable to dissolve a lithium salt and is difficult to be electrolyzed has been used as a nonaqueous solvent used in a nonaqueous electrolyte of a lithium secondary battery.
Examples of the polar aprotic organic solvent include carbonates such as ethylene carbonate and propylene carbonate;
carbonic esters such as dimethyl carbonate, methyl ethyl carbonate and diethyl carbonate; lactones such as y-butyrolactone and 3-methyl-y-valerolactone; esters such as methyl formate, methyl acetate and methyl propionate; and ethers such as 1,2-dimethoxyethane, tetrahydrofuran and dioxolan. Examples of the lithium salt dissolved include LiPF6, LiBF4, LiN(CF3S02)2, LiC104 and LiCF3S03.
Conventionally, a polar aprotic organic solvent which is liable to dissolve a lithium salt and is difficult to be electrolyzed has been used as a nonaqueous solvent used in a nonaqueous electrolyte of a lithium secondary battery.
Examples of the polar aprotic organic solvent include carbonates such as ethylene carbonate and propylene carbonate;
carbonic esters such as dimethyl carbonate, methyl ethyl carbonate and diethyl carbonate; lactones such as y-butyrolactone and 3-methyl-y-valerolactone; esters such as methyl formate, methyl acetate and methyl propionate; and ethers such as 1,2-dimethoxyethane, tetrahydrofuran and dioxolan. Examples of the lithium salt dissolved include LiPF6, LiBF4, LiN(CF3S02)2, LiC104 and LiCF3S03.
[0004]
Among the above solvents, dimethyl carbonate, 1,2-dimethoxyethane and the like are particularly frequently used. Those solvents have very low flash point, and therefore have great problems on safety of a battery such as flash or explosion due to generation of heat in the case of overcharging or short-circuiting. Particularly, in recent years, development of a high capacity and high output lithium secondary battery is urgently needed, and the problem of safety becomes increasingly an important problem to be solved.
Among the above solvents, dimethyl carbonate, 1,2-dimethoxyethane and the like are particularly frequently used. Those solvents have very low flash point, and therefore have great problems on safety of a battery such as flash or explosion due to generation of heat in the case of overcharging or short-circuiting. Particularly, in recent years, development of a high capacity and high output lithium secondary battery is urgently needed, and the problem of safety becomes increasingly an important problem to be solved.
[0005]
For this reason, various proposals are made to use a nonflammable compound in a nonaqueous electrolyte. For example, using phosphoric esters, esters or specific phosphoric ester compounds (Patent Documents 1 and 2) , an electrolyte containing a specific fluorinated ketone in an aprotic solvent (Patent Document 3) , and the like are disclosed, but those are not yet sufficiently satisfied.
For this reason, various proposals are made to use a nonflammable compound in a nonaqueous electrolyte. For example, using phosphoric esters, esters or specific phosphoric ester compounds (Patent Documents 1 and 2) , an electrolyte containing a specific fluorinated ketone in an aprotic solvent (Patent Document 3) , and the like are disclosed, but those are not yet sufficiently satisfied.
[0006]
Furthermore, in a lithium secondary battery using an ionic liquid in place of a nonaqueous solvent, potential window of the ionic liquid used is narrow, and viscosity after dissolving an ionic compound is relatively high. Therefore, the lithium secondary battery using those has the problem on cycle characteristic, and discharge capacity is not almost obtained during discharging (high-rate discharge) in the state of high current density. As a result, the performance as a secondary battery was insufficient. In particular, irreversible reaction is generated electrochemically at a reducing side, and as a result, only a low voltage lithium secondary battery is merely achieved as compared with the conventional electrolyte.
Furthermore, in a lithium secondary battery using an ionic liquid in place of a nonaqueous solvent, potential window of the ionic liquid used is narrow, and viscosity after dissolving an ionic compound is relatively high. Therefore, the lithium secondary battery using those has the problem on cycle characteristic, and discharge capacity is not almost obtained during discharging (high-rate discharge) in the state of high current density. As a result, the performance as a secondary battery was insufficient. In particular, irreversible reaction is generated electrochemically at a reducing side, and as a result, only a low voltage lithium secondary battery is merely achieved as compared with the conventional electrolyte.
[0007]
For example, using an ionic liquid containing bis(fluorosulfonyl)imide anion as an anion component is known as the embodiment of using an ionic liquid in a nonaqueous electrolyte (Patent Document 4). The lithium secondary battery illustrated in this patent document uses 4V-level active material (LiCo02) in a positive electrode, but uses Li4Ti5012 in a negative electrode. Therefore, the usable voltage region is narrow as 2.8 to 2.0V, and this is disadvantageous in the point of energy density. There is no disclosure to show that 4V-level voltage region is obtained.
Patent Document 1: JP-A-2000-195544 Patent Document 2: JP-A-2001-126726 Patent Document 3: JP-A-2005-276517 Patent Document 4: US Patent No. 6,365,301 Disclosure of the Invention Problems that the Invention is to Solve [0008]
The present invention has been made in view of the above problems, and has an object to provide a lithium secondary battery having high performance even at the time of high-rate charging and discharging, high energy density, high voltage, and excellent safety due to that a nonflammable ionic liquid is used as a solvent of a nonaqueous electrolyte.
Means for Solving the Problems [0009]
As a result of extensive and intensive investigations to solve the above problems, the present inventors have found that high voltage and high energy density are obtained even in the case of using an ionic liquid containing bis(fluorosulfonyl)imide anion as an anionic component, as a solvent for dissolving a lithium salt as a supporting electrolyte in a lithium ion-conductive nonaqueous electrolyte, and have reached the present invention.
For example, using an ionic liquid containing bis(fluorosulfonyl)imide anion as an anion component is known as the embodiment of using an ionic liquid in a nonaqueous electrolyte (Patent Document 4). The lithium secondary battery illustrated in this patent document uses 4V-level active material (LiCo02) in a positive electrode, but uses Li4Ti5012 in a negative electrode. Therefore, the usable voltage region is narrow as 2.8 to 2.0V, and this is disadvantageous in the point of energy density. There is no disclosure to show that 4V-level voltage region is obtained.
Patent Document 1: JP-A-2000-195544 Patent Document 2: JP-A-2001-126726 Patent Document 3: JP-A-2005-276517 Patent Document 4: US Patent No. 6,365,301 Disclosure of the Invention Problems that the Invention is to Solve [0008]
The present invention has been made in view of the above problems, and has an object to provide a lithium secondary battery having high performance even at the time of high-rate charging and discharging, high energy density, high voltage, and excellent safety due to that a nonflammable ionic liquid is used as a solvent of a nonaqueous electrolyte.
Means for Solving the Problems [0009]
As a result of extensive and intensive investigations to solve the above problems, the present inventors have found that high voltage and high energy density are obtained even in the case of using an ionic liquid containing bis(fluorosulfonyl)imide anion as an anionic component, as a solvent for dissolving a lithium salt as a supporting electrolyte in a lithium ion-conductive nonaqueous electrolyte, and have reached the present invention.
[0010]
That is, the invention is directed to a lithium CA 02641152 2013-1()-30 secondary battery using an ionic liquid, comprising a positive electrode, a negative electrode, a separator provided between the positive electrode and the negative electrode, and a nonaqueous electrolyte containing a lithium salt, wherein the nonaqueous electrolyte uses an ionic liquid containing bis(fluorosulfonyl)imide anion as an anionic component, as a solvent, voltage at full charge is 3.6V or higher, and average discharge voltage in a discharge rate of 1-hour rate is 2.9V or higher.
In a particular embodiment the negative electrode is one or more of mesocarbon microbead or graphite.
That is, the invention is directed to a lithium CA 02641152 2013-1()-30 secondary battery using an ionic liquid, comprising a positive electrode, a negative electrode, a separator provided between the positive electrode and the negative electrode, and a nonaqueous electrolyte containing a lithium salt, wherein the nonaqueous electrolyte uses an ionic liquid containing bis(fluorosulfonyl)imide anion as an anionic component, as a solvent, voltage at full charge is 3.6V or higher, and average discharge voltage in a discharge rate of 1-hour rate is 2.9V or higher.
In a particular embodiment the negative electrode is one or more of mesocarbon microbead or graphite.
[0011]
The invention is further directed to the lithium secondary battery using an ionic liquid as described above, wherein the ionic liquid contains a cation containing a nitrogen atom as a cationic component.
The invention is further directed to the lithium secondary battery using an ionic liquid as described above, wherein the ionic liquid contains a cation containing a nitrogen atom as a cationic component.
[0012]
The invention is also directed to the lithium secondary battery using an ionic liquid as described above, wherein the cation containing a nitrogen atom is alkyl ammonium, imidazolium, pyrrolidinium or piperidinium.
The invention is also directed to the lithium secondary battery using an ionic liquid as described above, wherein the cation containing a nitrogen atom is alkyl ammonium, imidazolium, pyrrolidinium or piperidinium.
[0013]
The invention is still further directed to the lithium secondary battery using an ionic liquid as described above, wherein the amount of halogen ions contained in the nonaqueous electrolyte is 10 ppm or lower.
Advantage of the Invention [0014]
According to the lithium secondary battery using an ionic liquid of the present invention, there can be provided a lithium secondary battery which has excellent safety, high performance even at the time of high-rate charging and discharging, high energy density and high capacity, and can obtain 4V-level high voltage.
Best Mode for Carrying Out the Invention [0015]
The embodiment of the present invention is described below.
The invention is still further directed to the lithium secondary battery using an ionic liquid as described above, wherein the amount of halogen ions contained in the nonaqueous electrolyte is 10 ppm or lower.
Advantage of the Invention [0014]
According to the lithium secondary battery using an ionic liquid of the present invention, there can be provided a lithium secondary battery which has excellent safety, high performance even at the time of high-rate charging and discharging, high energy density and high capacity, and can obtain 4V-level high voltage.
Best Mode for Carrying Out the Invention [0015]
The embodiment of the present invention is described below.
[0016]
The lithium secondary battery according to the present invention is constituted of a positive electrode, a negative electrode, a separator provided between the positive electrode and the negative electrode for partitioning those, and a nonaqueous electrolyte comprising a solvent for conducting lithium ions, having dissolved therein a lithium salt as a supporting electrolyte.
The lithium secondary battery according to the present invention is constituted of a positive electrode, a negative electrode, a separator provided between the positive electrode and the negative electrode for partitioning those, and a nonaqueous electrolyte comprising a solvent for conducting lithium ions, having dissolved therein a lithium salt as a supporting electrolyte.
[0017]
An active material of the positive electrode used in the present invention is not particularly limited so long as insertion and desorption of lithium ions are possible. For example, examples of the positive electrode active material include metal oxides such as CuO, Cu20, Mn02, Mo03, V205, Cr03, Mo03, Fe203, Ni-O3 and Co03; composite oxides of lithium and a transition metal, such as Li,Co02, Li,Ni02 and Liy_Mn204; metal chalcogenides such as TiS,, MoS2 and NbSe3; and conductive polymer compounds such as polyacene, polyparaphenylene, polypyrrole and polyaniline.
An active material of the positive electrode used in the present invention is not particularly limited so long as insertion and desorption of lithium ions are possible. For example, examples of the positive electrode active material include metal oxides such as CuO, Cu20, Mn02, Mo03, V205, Cr03, Mo03, Fe203, Ni-O3 and Co03; composite oxides of lithium and a transition metal, such as Li,Co02, Li,Ni02 and Liy_Mn204; metal chalcogenides such as TiS,, MoS2 and NbSe3; and conductive polymer compounds such as polyacene, polyparaphenylene, polypyrrole and polyaniline.
[0018]
Particularly, in the present invention, composite oxides of at least one selected from transition metals such as cobalt, nickel and manganese, and lithium, that are generally said to be of high voltage type are preferred in the point that releasability of lithium ions and high voltage are easily obtained. Specific examples of the composite oxide of cobalt, nickel or manganese with lithium include LiCo02, LiMn02, LiMn204, LiNi02, LiNiy.Co(i_x)02 and LiMnaNibCo, (a+b+c=1).
Particularly, in the present invention, composite oxides of at least one selected from transition metals such as cobalt, nickel and manganese, and lithium, that are generally said to be of high voltage type are preferred in the point that releasability of lithium ions and high voltage are easily obtained. Specific examples of the composite oxide of cobalt, nickel or manganese with lithium include LiCo02, LiMn02, LiMn204, LiNi02, LiNiy.Co(i_x)02 and LiMnaNibCo, (a+b+c=1).
[0019]
Furthermore, those lithium composite oxides maybe doped with a small amount of elements such as fluorine, boron, aluminum, chromium, zirconium, molybdenum and iron.
Furthermore, those lithium composite oxides maybe doped with a small amount of elements such as fluorine, boron, aluminum, chromium, zirconium, molybdenum and iron.
[0020]
Furthermore, the surface of particles of lithium composite oxide maybe surface-treated with carbon, MgO, A1203, Si02 or the like.
Furthermore, the surface of particles of lithium composite oxide maybe surface-treated with carbon, MgO, A1203, Si02 or the like.
[0021]
The active material of the positive electrode of the present invention preferably includes lithium iron phosphate represented by Li,FePO4 (0<x1.2, generally 1), in addition to the above-described lithium and transition metal oxide.
The active material of the positive electrode of the present invention preferably includes lithium iron phosphate represented by Li,FePO4 (0<x1.2, generally 1), in addition to the above-described lithium and transition metal oxide.
[0022]
Lithium iron phosphate has flat insertion and desorption potential of lithium in the vicinity of 3.1 to 3.5V/Li, and all of oxygen is bonded to phosphorus by a covalent bond to form a polyanion. Therefore, there is no case that oxygen in a positive electrode is released with the rise of temperature, thereby burning an electrolyte. For this reason, lithium iron phosphate is superior in safety in a high temperature charging state to LiCoO, and the like. Furthermore, lithium iron phosphate has extremely excellent properties in chemical and mechanical stabilities, and is also excellent in long-term storage performance.
Lithium iron phosphate has flat insertion and desorption potential of lithium in the vicinity of 3.1 to 3.5V/Li, and all of oxygen is bonded to phosphorus by a covalent bond to form a polyanion. Therefore, there is no case that oxygen in a positive electrode is released with the rise of temperature, thereby burning an electrolyte. For this reason, lithium iron phosphate is superior in safety in a high temperature charging state to LiCoO, and the like. Furthermore, lithium iron phosphate has extremely excellent properties in chemical and mechanical stabilities, and is also excellent in long-term storage performance.
[0023]
Those positive electrode active materials can be used as mixtures of two kinds or more thereof.
Those positive electrode active materials can be used as mixtures of two kinds or more thereof.
[0024]
An active material that insertion and desorption of lithium ions are possible is used as an active material of the negative electrode. Metal compounds and conductive polymer compounds used in the positive electrode can similarly be used similarly as an active material. In the present invention, metal lithium; lithium alloys such as LiAl; carbon materials such as amorphous carbon, mesocarbon microbead (MOMS), graphite and natural graphite; surface-modified products of those carbon materials; tin oxide; and Si type negative electrode such as Si02 are preferred, and examples of the carbon material include activated carbon, carbon fiber and carbon black. Above all, metal lithium, lithium alloy, carbon material and Si type negative electrode are particularly preferred. Those active materials maybe used as mixtures of two or more thereof.
An active material that insertion and desorption of lithium ions are possible is used as an active material of the negative electrode. Metal compounds and conductive polymer compounds used in the positive electrode can similarly be used similarly as an active material. In the present invention, metal lithium; lithium alloys such as LiAl; carbon materials such as amorphous carbon, mesocarbon microbead (MOMS), graphite and natural graphite; surface-modified products of those carbon materials; tin oxide; and Si type negative electrode such as Si02 are preferred, and examples of the carbon material include activated carbon, carbon fiber and carbon black. Above all, metal lithium, lithium alloy, carbon material and Si type negative electrode are particularly preferred. Those active materials maybe used as mixtures of two or more thereof.
[0025]
Those negative electrode active materials select materials having oxidation-reduction potential nearly close to that of metal lithium, thereby high potential andhigh energy density of the present invention are realized. For this, the combination with the above positive electrode is important.
Those negative electrode active materials select materials having oxidation-reduction potential nearly close to that of metal lithium, thereby high potential andhigh energy density of the present invention are realized. For this, the combination with the above positive electrode is important.
[0026]
The positive electrode and the negative electrode use a conductive agent. Any conductive agent can be used so long as it is an electron conductive material which does not adversely affect battery performance. Carbon black such as acetylene black or Kitchen black is generally used, but conductive materials such as natural graphite (scaly graphite, scale graphite or earthy graphite), artificial graphite, carbonwhisker, carbon fiber, metal (copper, nickel, aluminum, silver, gold or the like) powder, metal fiber and conductive ceramic material may be used. Those materials can be contained as mixtures of two or more thereof. The addition amount is preferably 1 to 30% by weight, and particularly preferably 2 to 20% by weight, based on the amount of the active material.
The positive electrode and the negative electrode use a conductive agent. Any conductive agent can be used so long as it is an electron conductive material which does not adversely affect battery performance. Carbon black such as acetylene black or Kitchen black is generally used, but conductive materials such as natural graphite (scaly graphite, scale graphite or earthy graphite), artificial graphite, carbonwhisker, carbon fiber, metal (copper, nickel, aluminum, silver, gold or the like) powder, metal fiber and conductive ceramic material may be used. Those materials can be contained as mixtures of two or more thereof. The addition amount is preferably 1 to 30% by weight, and particularly preferably 2 to 20% by weight, based on the amount of the active material.
[0027]
Any electron conductor may be used as a current collector of an electrode active material so long as it does not adversely affect in a battery constituted. For example, as a current collector for positive electrode, aluminum, titanium, stainless steel, nickel, baked carbon, conductive polymer, conductive glass and the like are used, and in addition to those, products obtained by treating the surface of aluminum, copper or the like with carbon, nickel, titanium, silver or the like for the purpose of improvement of adhesiveness, conductivity and oxidation resistance can also be used.
Any electron conductor may be used as a current collector of an electrode active material so long as it does not adversely affect in a battery constituted. For example, as a current collector for positive electrode, aluminum, titanium, stainless steel, nickel, baked carbon, conductive polymer, conductive glass and the like are used, and in addition to those, products obtained by treating the surface of aluminum, copper or the like with carbon, nickel, titanium, silver or the like for the purpose of improvement of adhesiveness, conductivity and oxidation resistance can also be used.
[0028]
A current collector for the negative electrode can use copper, stainless steel, nickel, aluminum, titanium, baked carbon, conductive polymer, conductive glass, Al-Cd alloy and the like, and in addition to those, products obtained by treating the surface of copper or the like with carbon, nickel, titanium, silver or the like for the purpose of improvement of adhesiveness, conductivity and oxidation resistance can also be used.
A current collector for the negative electrode can use copper, stainless steel, nickel, aluminum, titanium, baked carbon, conductive polymer, conductive glass, Al-Cd alloy and the like, and in addition to those, products obtained by treating the surface of copper or the like with carbon, nickel, titanium, silver or the like for the purpose of improvement of adhesiveness, conductivity and oxidation resistance can also be used.
[0029]
The surface of those current collector materials can be oxidation treated. Regarding the shape of those, moldings of foil-like, film-like, sheet-like, net-like, punched or expanded product, lath type material, porous material, foamed material or the like are used. The thickness is not particularly limited, but a material having a thickness of 1 to 100 m is used.
The surface of those current collector materials can be oxidation treated. Regarding the shape of those, moldings of foil-like, film-like, sheet-like, net-like, punched or expanded product, lath type material, porous material, foamed material or the like are used. The thickness is not particularly limited, but a material having a thickness of 1 to 100 m is used.
[0030]
Examples of a binder which binds the above active material to the positive electrode and the negative electrode include polyvinylidene fluoride (PVDF); PVDF copolymer resins such as copolymers of PVDF with hexafluropropylene (HFP), perfluoromethyl vinyl ether (PFMV) or tetrafluoroethylene (TFE); fluorine resins such as polytetrafluoroethylene (PTFE) and fluorine rubber; styrene-butadiene rubber (SBR);
ethylene-propylene rubber (EPDM); and polymers such as styrene-acrylonitrile copolymer. Polysaccharides such as carboxymethyl cellulose (CMC), thermoplastic resins such as polyimide resin, and the like can be used together. However, the invention is not limited to those embodiments.
Furthermore, those materials may be used as mixtures of two or more thereof. The addition amount is preferably 1 to 30%
byweight, andparticularlypreferably 2 to 20% byweight, based on the amount of the active material.
Examples of a binder which binds the above active material to the positive electrode and the negative electrode include polyvinylidene fluoride (PVDF); PVDF copolymer resins such as copolymers of PVDF with hexafluropropylene (HFP), perfluoromethyl vinyl ether (PFMV) or tetrafluoroethylene (TFE); fluorine resins such as polytetrafluoroethylene (PTFE) and fluorine rubber; styrene-butadiene rubber (SBR);
ethylene-propylene rubber (EPDM); and polymers such as styrene-acrylonitrile copolymer. Polysaccharides such as carboxymethyl cellulose (CMC), thermoplastic resins such as polyimide resin, and the like can be used together. However, the invention is not limited to those embodiments.
Furthermore, those materials may be used as mixtures of two or more thereof. The addition amount is preferably 1 to 30%
byweight, andparticularlypreferably 2 to 20% byweight, based on the amount of the active material.
[0031]
A porous film is used as the separator, and a microporous polymer film or a nonwoven fabric is generally preferably used.
In particular, a porous film comprising a polyolefin polymer is preferred. Specific examples of the porous film include a microporous film of a polyethylene-made or polypropylene-made film, a multilayered film of porous polyethylene film and polypropylene, a nonwoven fabric comprising polyester fiber, aramide fiber, glass fiber or the like, and products of those having adhered on the surface thereof ceramic fine particles of silica, alumina, titania or the like.
A porous film is used as the separator, and a microporous polymer film or a nonwoven fabric is generally preferably used.
In particular, a porous film comprising a polyolefin polymer is preferred. Specific examples of the porous film include a microporous film of a polyethylene-made or polypropylene-made film, a multilayered film of porous polyethylene film and polypropylene, a nonwoven fabric comprising polyester fiber, aramide fiber, glass fiber or the like, and products of those having adhered on the surface thereof ceramic fine particles of silica, alumina, titania or the like.
[0032]
The lithium secondary battery of the present invention uses a nonaqueous electrolyte comprising a nonflammable ionic liquid and a lithium salt, as a lithium ion-conductive electrolyte.
The lithium secondary battery of the present invention uses a nonaqueous electrolyte comprising a nonflammable ionic liquid and a lithium salt, as a lithium ion-conductive electrolyte.
[0033]
A solvent of the nonaqueous electrolyte uses an ionic liquid containing his (fluorosulfonyl)imide anion (FSI anion) represented by the following formula (1) as an anionic component.
0 ¨ 0 ,N, F\ 'F (1) [0034]
A method for preparing the FSI anion is not particularly limited, and the conventional methods such as a reaction between fluorosulfonic acid and urea can be used. FSI
compounds obtained by those methods generally have low purity, and to obtain a preferred ionic liquid containing impurities of 10 ppm or less, the FSI compounds are appropriately purified with water, an organic solvent or the like, and used.
Impurities can be confirmed by the analysis using a plasma emission spectrometer (ICP) .
A solvent of the nonaqueous electrolyte uses an ionic liquid containing his (fluorosulfonyl)imide anion (FSI anion) represented by the following formula (1) as an anionic component.
0 ¨ 0 ,N, F\ 'F (1) [0034]
A method for preparing the FSI anion is not particularly limited, and the conventional methods such as a reaction between fluorosulfonic acid and urea can be used. FSI
compounds obtained by those methods generally have low purity, and to obtain a preferred ionic liquid containing impurities of 10 ppm or less, the FSI compounds are appropriately purified with water, an organic solvent or the like, and used.
Impurities can be confirmed by the analysis using a plasma emission spectrometer (ICP) .
[0035]
The anionic component contained in the ionic liquid may contain, for example, anions such as BF4-, PF6-, SbF6-, NO3-, CF3S03-, (CF3S02) 2W ( called TFSI) , (C,F5S02.-)2N-, (CF3S02) 3C, CF3C0_ , C3F7CO2-, CH3C0z- and (CN)2N-. Two or more of those anions may be contained.
The anionic component contained in the ionic liquid may contain, for example, anions such as BF4-, PF6-, SbF6-, NO3-, CF3S03-, (CF3S02) 2W ( called TFSI) , (C,F5S02.-)2N-, (CF3S02) 3C, CF3C0_ , C3F7CO2-, CH3C0z- and (CN)2N-. Two or more of those anions may be contained.
[0036]
The ionic liquid contained in the lithium secondary battery of the present invention does not particularly have limitation in a cation structure to be combined with the FSI
anion. However, the combination with a cation which forms an ionic liquid having a melting point of 50 C or lower is preferred.
Where the melting point exceeds 50 C, viscosity of the nonaqueous electrolyte is increased. As a result, the problem arises in cycle characteristic of a lithium secondary battery, and discharge capacity tends to be decreased, which are not preferred.
The ionic liquid contained in the lithium secondary battery of the present invention does not particularly have limitation in a cation structure to be combined with the FSI
anion. However, the combination with a cation which forms an ionic liquid having a melting point of 50 C or lower is preferred.
Where the melting point exceeds 50 C, viscosity of the nonaqueous electrolyte is increased. As a result, the problem arises in cycle characteristic of a lithium secondary battery, and discharge capacity tends to be decreased, which are not preferred.
[0037]
Examples of the cation include compounds containing-any of N, P, S, 0, C and Si , or at least two elements in the structure, and having a chain structure or a cyclic structure such as five-membered ring or six-membered ring in the skeleton.
Examples of the cation include compounds containing-any of N, P, S, 0, C and Si , or at least two elements in the structure, and having a chain structure or a cyclic structure such as five-membered ring or six-membered ring in the skeleton.
[0038]
Examples of the cyclic structure such as five-membered ring or six-membered ring include heteromonocyclic compounds such as furan, thiophene, pyrrole, pyridine, oxazole, isooxazole, thiazole, isothiazole, furazan, imidazole, pyrazole, pyrazine, pyrimidine, pyridazine, pyrrolidine or piperidine; and condensed heterocyclic compounds such as benzofuran, isobenzofuran, indole, isoindole, indolizine or carbazole.
Examples of the cyclic structure such as five-membered ring or six-membered ring include heteromonocyclic compounds such as furan, thiophene, pyrrole, pyridine, oxazole, isooxazole, thiazole, isothiazole, furazan, imidazole, pyrazole, pyrazine, pyrimidine, pyridazine, pyrrolidine or piperidine; and condensed heterocyclic compounds such as benzofuran, isobenzofuran, indole, isoindole, indolizine or carbazole.
[0039]
Of those cations, chain or cyclic compounds containing a nitrogen element are particularly preferred in the points that those are industrially inexpensive and are chemically and electrochemically stable.
Of those cations, chain or cyclic compounds containing a nitrogen element are particularly preferred in the points that those are industrially inexpensive and are chemically and electrochemically stable.
[0040]
Preferred examples of the cation containing a nitrogen element include alkyl ammonium such as triethylammonium;
imidazolium such as ethyl methyl imidazolium and butyl methyl imidazolium; pyrrolidinium such as 1-methyl-1-propyl pyrrolidinium; and piperidinium such as methyl propyl piperidinium.
Preferred examples of the cation containing a nitrogen element include alkyl ammonium such as triethylammonium;
imidazolium such as ethyl methyl imidazolium and butyl methyl imidazolium; pyrrolidinium such as 1-methyl-1-propyl pyrrolidinium; and piperidinium such as methyl propyl piperidinium.
[0041]
In the present invention, the lithium salt dissolved in the ionic liquid as a supporting electrolyte of the non-aqueous electrolyte can use any lithium salt without particular limitation so long as it is a lithium salt generally used as an electrolyte for nonaqueous electrolyte.
In the present invention, the lithium salt dissolved in the ionic liquid as a supporting electrolyte of the non-aqueous electrolyte can use any lithium salt without particular limitation so long as it is a lithium salt generally used as an electrolyte for nonaqueous electrolyte.
[0042]
Examples of the lithium salt include LiPF6, LiBF4, LiC104, LiAsFr, LiC1, LiBr, LiCF3S03, LiI, LiA1C104, LiC (CF3S02) 3/
LiN(C2F5S02)2, LiBC408, LiFSI and LiTFSI. Those lithium salts can be used by mixing two or more thereof.
Examples of the lithium salt include LiPF6, LiBF4, LiC104, LiAsFr, LiC1, LiBr, LiCF3S03, LiI, LiA1C104, LiC (CF3S02) 3/
LiN(C2F5S02)2, LiBC408, LiFSI and LiTFSI. Those lithium salts can be used by mixing two or more thereof.
[0043]
Above all, LiFSI and LiTFSI are preferred.
Above all, LiFSI and LiTFSI are preferred.
[0044]
It is desired that such a lithium salt is contained in the ionic liquid in a concentration of generally 0.1 to 2.0 mol/liter, and preferably 0.3 to 1.0 mol/liter.
It is desired that such a lithium salt is contained in the ionic liquid in a concentration of generally 0.1 to 2.0 mol/liter, and preferably 0.3 to 1.0 mol/liter.
[0045]
Furthermore, it is desired that the amount of halogen ions contained as an impurity in the nonaqueous electrolyte used in the lithium secondary battery of the present invention is 10 ppm or less. Other impurities include alkali metal ions and alkaline earth metal ions, and it is preferred that the total amount of those impurities is 10 ppm or less. Where those impurities are contained in a large amount, it adversely affects cycle characteristic of a lithium secondary battery, and life as a secondary battery is shortened.
Furthermore, it is desired that the amount of halogen ions contained as an impurity in the nonaqueous electrolyte used in the lithium secondary battery of the present invention is 10 ppm or less. Other impurities include alkali metal ions and alkaline earth metal ions, and it is preferred that the total amount of those impurities is 10 ppm or less. Where those impurities are contained in a large amount, it adversely affects cycle characteristic of a lithium secondary battery, and life as a secondary battery is shortened.
[0046]
The lithium secondary battery of the present invention can be formed into cylindrical form, coin form, square form or other optional form. The basic constitution of a battery is the same, regardless of a form, and design can be changed depending on the purpose.
The lithium secondary battery of the present invention can be formed into cylindrical form, coin form, square form or other optional form. The basic constitution of a battery is the same, regardless of a form, and design can be changed depending on the purpose.
[0047]
The lithium secondary battery according to the present invention can be obtained by, for example, in the case of a cylindrical form, winding a negative electrode obtained by applying a negative electrode active material to a negative electrode current collector, and a positive electrode obtained by applying a positive electrode active material to a positive electrode current collector through a separator, placing the resulting wound body in a battery can, pouring a nonaqueous electrolyte, and sealing in a state of arranging an insulating plate up and down.
The lithium secondary battery according to the present invention can be obtained by, for example, in the case of a cylindrical form, winding a negative electrode obtained by applying a negative electrode active material to a negative electrode current collector, and a positive electrode obtained by applying a positive electrode active material to a positive electrode current collector through a separator, placing the resulting wound body in a battery can, pouring a nonaqueous electrolyte, and sealing in a state of arranging an insulating plate up and down.
[0048]
In the case of applying to a coin-type lithium secondary battery, a disc-shaped negative electrode, a separator, a disc-shaped positive electrode and a stainless steel plate are placed in a coin-like battery can in a laminated state, a nonaqueous electrolyte is poured, and the can is sealed.
Examples [0049]
The present invention is described in more detail by reference to the following Examples and Comparative Examples, but the invention is not limited by those.
In the case of applying to a coin-type lithium secondary battery, a disc-shaped negative electrode, a separator, a disc-shaped positive electrode and a stainless steel plate are placed in a coin-like battery can in a laminated state, a nonaqueous electrolyte is poured, and the can is sealed.
Examples [0049]
The present invention is described in more detail by reference to the following Examples and Comparative Examples, but the invention is not limited by those.
[0050]
A lithium secondary battery of each of Examples and Comparative Examples was prepared. Preparation of a positive electrode and a negative electrode, and preparation method of a battery are described below. Materials used are as follows.
A lithium secondary battery of each of Examples and Comparative Examples was prepared. Preparation of a positive electrode and a negative electrode, and preparation method of a battery are described below. Materials used are as follows.
[0051]
[Material used]
Conductive agent, acetylene black: a product of Denki Kagaku Kogyo Kabushiki Kaisha, DENKA BLACK
Conductive agent, Kitchen black: a product of Kitchen Black International, KITCHEN BLACK EC300J
Negative electrode active material, MCMB: a product of Osaka Gas Chemicals Co., Ltd., MCMB 25-28 Binder, PVDF: a product of Kureha Co., Ltd., KF BINDER
Binder, SBR: a product of Nippon Zeon Co., Ltd., BM-400M
Binder, CMC/3H: a product of Daiichi Kogyo Seiyaku Co., Ltd., CELLOGEN"-3H
Binder, CMC/4H: a product of Daiichi Kogyo Seiyaku Co., Ltd., CELLOGEN-4H
Binder, CMC/WSC: a product of Daiichi Kogyo Seiyaku Co., Ltd., CELLOGEN WS-C
<Example 1>
[Preparation of positive electrode]
100 g of LiMn204 as a positive electrode active material, g of acetylene black as a conductive agent, 6 g of PVIDF as a binder and 97.5 g of N-methyl-2-pyrrolidone (NMP) as a dispersion medium were mixed with a planetary mixer to prepare a positive electrode coating liquid having a solid content (components excluding NMP) of 53.2%. This coating liquid was applied onto an aluminum foil having a thickness of 20 p,m with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a positive electrode active material weight of 16 mg/cm2.
[Material used]
Conductive agent, acetylene black: a product of Denki Kagaku Kogyo Kabushiki Kaisha, DENKA BLACK
Conductive agent, Kitchen black: a product of Kitchen Black International, KITCHEN BLACK EC300J
Negative electrode active material, MCMB: a product of Osaka Gas Chemicals Co., Ltd., MCMB 25-28 Binder, PVDF: a product of Kureha Co., Ltd., KF BINDER
Binder, SBR: a product of Nippon Zeon Co., Ltd., BM-400M
Binder, CMC/3H: a product of Daiichi Kogyo Seiyaku Co., Ltd., CELLOGEN"-3H
Binder, CMC/4H: a product of Daiichi Kogyo Seiyaku Co., Ltd., CELLOGEN-4H
Binder, CMC/WSC: a product of Daiichi Kogyo Seiyaku Co., Ltd., CELLOGEN WS-C
<Example 1>
[Preparation of positive electrode]
100 g of LiMn204 as a positive electrode active material, g of acetylene black as a conductive agent, 6 g of PVIDF as a binder and 97.5 g of N-methyl-2-pyrrolidone (NMP) as a dispersion medium were mixed with a planetary mixer to prepare a positive electrode coating liquid having a solid content (components excluding NMP) of 53.2%. This coating liquid was applied onto an aluminum foil having a thickness of 20 p,m with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a positive electrode active material weight of 16 mg/cm2.
[0052]
[Preparation of negative electrode]
100 g of MCMB as a negative electrode active material, g of acetylene black as a conductive agent, 5 g of PVDF as a binder and 107.5 g of NMP as a dispersion medium were mixed with a planetary mixer to prepare a negative electrode coating liquid having a solid content (components excluding NMP) of 50 . This coating liquid was applied onto a copper foil having a thickness of 10 i_tm with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a negative electrode active material weight of 7 mg/cm2.
[Preparation of negative electrode]
100 g of MCMB as a negative electrode active material, g of acetylene black as a conductive agent, 5 g of PVDF as a binder and 107.5 g of NMP as a dispersion medium were mixed with a planetary mixer to prepare a negative electrode coating liquid having a solid content (components excluding NMP) of 50 . This coating liquid was applied onto a copper foil having a thickness of 10 i_tm with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a negative electrode active material weight of 7 mg/cm2.
[0053]
[Preparation of lithium secondary battery]
A lithium secondary battery having a positive electrode area of 4 cm2 and a negative electrode area of 4.41 cm2 was prepared using the positive electrode and the negative electrode obtained above, and a polypropylene separator. A
solution prepared by dissolving 0.8 mol of lithium salt LiFSI
in ethyl methyl imidazolium/FSI solvent, as an electrolyte was poured. After pouring, the inlet was sealed to prepare a battery.
[Preparation of lithium secondary battery]
A lithium secondary battery having a positive electrode area of 4 cm2 and a negative electrode area of 4.41 cm2 was prepared using the positive electrode and the negative electrode obtained above, and a polypropylene separator. A
solution prepared by dissolving 0.8 mol of lithium salt LiFSI
in ethyl methyl imidazolium/FSI solvent, as an electrolyte was poured. After pouring, the inlet was sealed to prepare a battery.
[0054]
<Example 2>
[Preparation of positive electrode]
100 g of LiMn123Ni1/3Co1/302 as a positive electrode active material, 7 g of acetylene black as a conductive agent, 4 g of PVDF as a binder and 95 g of NMP as a dispersion medium were mixed with a planetary mixer to prepare a positive electrode coating liquid having a solid content (components excluding NMP) of 53.9%. This coating liquid was applied onto an aluminum foil having a thickness of 20 p.m with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a positive electrode active material weight of 16 mg/cm2.
<Example 2>
[Preparation of positive electrode]
100 g of LiMn123Ni1/3Co1/302 as a positive electrode active material, 7 g of acetylene black as a conductive agent, 4 g of PVDF as a binder and 95 g of NMP as a dispersion medium were mixed with a planetary mixer to prepare a positive electrode coating liquid having a solid content (components excluding NMP) of 53.9%. This coating liquid was applied onto an aluminum foil having a thickness of 20 p.m with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a positive electrode active material weight of 16 mg/cm2.
[0055]
[Preparation of negative electrode]
"
100 g of MCMB as a negative electrode active material, 2 g of acetylene black as a conductive agent, 4 g of PVDF as a binder and 90g of NMP as a dispersion medium were mixed with a planetary mixer to prepare a negative electrode coating liquid having a solid content (components excluding NMP) of 54%. This coating liquid was applied onto a copper foil having a thickness of 10 1.tra with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a negative electrode active material weight of 7.5 mg/cm2.
[Preparation of negative electrode]
"
100 g of MCMB as a negative electrode active material, 2 g of acetylene black as a conductive agent, 4 g of PVDF as a binder and 90g of NMP as a dispersion medium were mixed with a planetary mixer to prepare a negative electrode coating liquid having a solid content (components excluding NMP) of 54%. This coating liquid was applied onto a copper foil having a thickness of 10 1.tra with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a negative electrode active material weight of 7.5 mg/cm2.
[0056]
[Preparation of lithium secondary battery]
According to the method of Example 1, a battery was prepared using a solution obtained by dissolving 0.6 mol of lithium salt LiFSI in butyl methyl imidazolium/FSI solvent, as an electrolyte.
[Preparation of lithium secondary battery]
According to the method of Example 1, a battery was prepared using a solution obtained by dissolving 0.6 mol of lithium salt LiFSI in butyl methyl imidazolium/FSI solvent, as an electrolyte.
[0057]
<Example 3>
[Preparation of positive electrode]
100 g of LiMn1nNi1/202 as a positive electrode active material, 3 g of Kitchen black as a conductive agent, 3 g of PVDF as a binder and 90 g of NMP as a dispersion medium were mixed with a planetary mixer to prepare a positive electrode coating liquid having a solid content (components excluding NMP) of 54.1%. This coating liquid was applied onto an aluminum foil having a thickness of 20 m with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a positive electrode active material weight of 15 mg/cm-.
<Example 3>
[Preparation of positive electrode]
100 g of LiMn1nNi1/202 as a positive electrode active material, 3 g of Kitchen black as a conductive agent, 3 g of PVDF as a binder and 90 g of NMP as a dispersion medium were mixed with a planetary mixer to prepare a positive electrode coating liquid having a solid content (components excluding NMP) of 54.1%. This coating liquid was applied onto an aluminum foil having a thickness of 20 m with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a positive electrode active material weight of 15 mg/cm-.
[0058]
[Preparation of negative electrode]
Amixture of 100 g of MCMB as a negative electrode active material, 1 g of acetylene black as a conductive agent, 2 g of SBR as a binder and 1 g of CMC/4H as a thickener, and 89 g of water as a dispersion medium were mixed with a planetary mixer to prepare a negative electrode coating liquid having a solid content of 53 . 6% . This coating liquid was applied onto a copper foil having a thickness of 10 m with a coater, and dried at 80 C, followed by conducting roll press treatment, thereby obtaining an electrode having a negative electrode active material weight of 6 mg/cm2.
[Preparation of negative electrode]
Amixture of 100 g of MCMB as a negative electrode active material, 1 g of acetylene black as a conductive agent, 2 g of SBR as a binder and 1 g of CMC/4H as a thickener, and 89 g of water as a dispersion medium were mixed with a planetary mixer to prepare a negative electrode coating liquid having a solid content of 53 . 6% . This coating liquid was applied onto a copper foil having a thickness of 10 m with a coater, and dried at 80 C, followed by conducting roll press treatment, thereby obtaining an electrode having a negative electrode active material weight of 6 mg/cm2.
[0059]
[Preparation of lithium secondary battery]
According to the method of Example 1, a battery was prepared using a solution obtained by dissolving 0.5 mol of lithium salt LiFSI in 1-methyl-l-propyl pyrrolidinium/FSI
solvent, as an electrolyte.
[Preparation of lithium secondary battery]
According to the method of Example 1, a battery was prepared using a solution obtained by dissolving 0.5 mol of lithium salt LiFSI in 1-methyl-l-propyl pyrrolidinium/FSI
solvent, as an electrolyte.
[0060]
<Example 4>
[Preparation of positive electrode]
100 g of LiFePO4 (covered with carbon in an amount of 5% based on the weight of LiFePO4) as a positive electrode active material, 3 g of acetylene black as a conductive agent, 5 g of PVDF as a binder and 120 g of NMP as a dispersion medium were mixed with a planetary mixer to prepare a positive electrode coating liquid having a solid content (components excluding NMP) of 47.4%. This coating liquid was applied onto an aluminum foil having a thickness of 20 p,m with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a positive electrode active material weight of 12 mg/cm2.
[ 0061 ]
[Preparation of negative electrode]
A mixture of 100 g of natural graphite as a negative electrode active material, 2 g of acetylene black as a conductive agent, 2 g of SBR as a binder and 2 g of CMC/:3H as a thickener, and 88 g of water as a dispersion medium were mixed with a planetary mixer to prepare a negative electrode coating liquid having a solid content of 53.6%. This coating liquid was applied onto a copper foil having a thickness of 10 tim with a coater, and dried at 80 C, followed by conducting roll press treatment, thereby obtaining an electrode having a negative electrode active material weight of 5 mg/cm2.
[ 0062 ]
[Preparation of lithium secondary battery]
According to the method of Example 1, a battery was prepared using a solution obtained by dissolving 0.6 mol of lithium salt LiTFSI in ethyl methyl imidazolium/FSI solvent, as an electrolyte.
[0063]
<Example 5>
[Preparation of positive electrode]
A mixture of 100 g of LiFePO4 (covered with carbon in an amount of 3% based on the weight of LiFePO4) as a positive electrode active material, 8 g of acetylene black as a conductive agent, 3 g of SBR as a binder and 2 g of CMC/3H as a thickener, and 114.5 g of water as a dispersion medium were mixed with a planetary mixer to prepare a positive electrode coating liquid having a solid content of 49.2%. This coating liquid was applied onto an aluminum foil having a thickness of 20 p.m with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a positive electrode active material weight of 10 mg/cm2.
[0064]
[Preparation of lithium secondary battery]
The positive electrode obtained and a metal lithium foil having a thickness of 200 jim as a negative electrode were used, and according to the method of Example 1, a battery was prepared using a solution obtained by dissolving 0.8 mol of lithium salt LiFSI in methyl propyl piperidinium/FSI :butyl methyl imidazolium/FSI (-5:5 vol) solvent, as an electrolyte.
[0065]
<Example 6>
[Preparation of positive electrode]
100 g of LiCo02 as a positive electrode active material, g of acetylene black as a conductive agent, 5 g of PVDF as a binder and 93 g of NMP as a dispersion medium were mixed with a planetary mixer to prepare a positive electrode coating liquid having a solid content (components excluding NMP) of 54.2%. This coating liquid was applied onto an aluminum foil having a thickness of 20 j.xm with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a positive electrode active material weight of 16 mg/cm2.
[0066]
[Preparation of negative electrode]
A mixture of 100 g of a surface-covered product of natural graphite as a negative electrode active material, 1 g of acetylene black as a conductive agent, 6 g of SBR as a binder and 4 g of CMC/3H as a thickener, and 90.8 g of water as a dispersion medium were mixed with a planetary mixer to prepare a negative electrode coating liquid having a solid content of 55%. This coating liquid was applied onto a copper foil having a thickness of 10 m with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a negative electrode active material weight of 9 mg/cm.
[0067]
[Preparation of lithium secondary battery]
According to the method of Example 1, a battery was prepared using a solution obtained by dissolving 0.7 mol of lithium salt LiTFSI in ethyl methyl imidazolium/FSI:tetraethyl ammonium/FSI (=9.5:0.5 vol) solvent, as an electrolyte.
[0068]
<Example 7>
[Preparation of positive electrode]
100 g of LiNi02 as a positive electrode active material, g of acetylene black as a conductive agent, 5 g of PVDF as a binder and 85 g of NMP as a dispersion medium were mixed with a planetary mixer to prepare a positive electrode coating liquid having a solid content (components excluding NIP) of 56.4%. This coating liquid was applied onto an aluminum foil having a thickness of 20 pm with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a positive electrode active material weight of 16 mg/cm:.
[0069]
[Preparation of negative electrode]
A mixture of 100 g of MCMB as a negative electrode active material, 3 g of acetylene black as a conductive agent, 7 g of SBR as a binder and 2 g of CMC/WSC as a thickener, and 54.6 g of water as a dispersion medium were mixed with a planetary mixer to prepare a negative electrode coating liquid having a solid content of 54 . 6%. This coating liquid was applied onto a copper foil having a thickness of 10 m with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a negative electrode active material weight of 12 mg/cm2.
[0070]
[Preparation of lithium secondary battery]
According to the method of Example 1, a battery was prepared using a solution obtained by dissolving 0.6 mol of lithium salt LiFSI in ethyl methyl imidazolium/FSI solvent, as an electrolyte.
[0071]
<Example 8>
[Preparation of positive electrode]
100 g of LiCo02 as a positive electrode active material, g of acetylene black as a conductive agent, 5 g of PVDF as a binder and 90 g of NMP as a dispersion medium were mixed with a planetary mixer to prepare a positive electrode coating liquid having a solid content (components excluding NMP) of 55%. This coating liquid was applied onto an aluminum foil having a thickness of 20 im with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a positive electrode active material weight of 15 mg/cm2.
[0072]
[Preparation of negative electrode]
100 g of MCMB as a negative electrode active material, 3 g of acetylene black as a conductive agent, 4 g of PVDF as a binder, and 87.5 g of NMP as a dispersion medium were mixed with a planetary mixer to prepare a negative electrode coating liquid having a solid content (components excluding NM?) of 55%. This coating liquid was applied onto a copper foil having a thickness of 101.1m with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a negative electrode active material weight of 8 mg/cm2.
[0073]
[Preparation of lithium secondary battery]
According to the method of Example 1, a battery was prepared using a solution obtained by dissolving 0.5 mol of lithium salt LiFSI in ethyl methyl imidazolium/FSI solvent, as an electrolyte.
[0074]
<Comparative Example 1>
[Preparation of positive electrode]
100 g of LiCo02as a positive electrode active material, g of acetylene black as a conductive agent, 5 g of PVDF as a binder and 80 g of NMP as a dispersion medium were mixed with a planetary mixer to prepare a positive electrode coating liquid having a solid content (components excluding NMP) of 57.9%. This coating liquid was applied onto an aluminum foil having a thickness of 20 m with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a positive electrode active material weight of 15 mg/cm2.
[0075]
[Preparation of negative electrode]
100 g of MCMB as a negative electrode active material, 2 g of acetylene black as a conductive agent, 8 g of PVDF as a binder, and 95 g of NMP as a dispersion medium were mixed with a planetary mixer to prepare a negative electrode coating liquid having a solid content (components excluding NMP) of 53.7%. This coating liquid was applied onto a copper foil having a thickness of 10 m with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a negative electrode active material weight of 8 mg/cm2.
[0076]
[Preparation of lithium secondary battery]
According to the method of Example 1, a battery was prepared using a solution obtained by dissolving 0.5 mol of lithium salt LiTFSI in 1-methyl-1-propyl pyrrolidinium/TFSI
solvent, as an electrolyte.
[0077]
<Comparative Example 2>
[Preparation of positive electrode]
100 g of LiCo02 as a positive electrode active material, g of acetylene black as a conductive agent, 5 g of PVDF as a binder and 90g of NMP as a dispersion medium were mixed with a planetary mixer to prepare a positive electrode coating liquid having a solid content (components excluding NMP) of 55%. This coating liquid was applied onto an aluminum foil having a thickness of 20 pm with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a positive electrode active material weight of 15 mg/cm2.
[0078]
[Preparation of negative electrode]
100 g of Li4T15012 as a negative electrode active material, g of acetylene black as a conductive agent, 5 g of PVDF as a binder, and 100 g of NMP as a dispersion medium were mixed with a planetary mixer to prepare a negative electrode coating liquid having a solid content (components excluding NMP) of 52.4%. This coating liquid was applied onto a copper foil having a thickness of 10 m with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a negative electrode active material weight of 8 mg/cm.
[0079]
[Preparation of lithium secondary battery]
According to the method of Example 1, a battery was prepared using a solution obtained by dissolving 0.5 mol of lithium salt LiFSI in ethyl methyl imidazolium/FSI solvent, as an electrolyte.
[0080]
<Comparative Example 3>
[Preparation of positive electrode]
100 g of LiCoO, as a positive electrode active material, g of acetylene black as a conductive agent, 5 g of PVDF as a binder and 80 g of NMP as a dispersion medium were mixed with a planetary mixer to prepare a positive electrode coating liquid having a solid content (components excluding NMP) of 57.9%. This coating liquid was applied onto an aluminum foil having a thickness of 20 m with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a positive electrode active material weight of 15 mg/cm2.
[0081]
[Preparation of negative electrode]
100 g of MCMB as a negative electrode active material, 2 g of acetylene black as a conductive agent, 4 g of PVDF as a binder, and 95 g of NMP as a dispersion medium were mixed with a planetary mixer to prepare a negative electrode coating liquid having a solid content (components excluding NM?) of 52.7%. This coating liquid was applied onto a copper foil having a thickness of 10 pm with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a negative electrode active material weight of 8 mg/cm2.
[0082]
[Preparation of lithium secondary battery]
According to the method of Example 1, a battery was prepared using a solution obtained by dissolving 0.5 mol of lithium salt LiTFSI in 1-methyl-1-propyl pyrrolidinium/TFSI
solvent, as an electrolyte.
[0083]
Na ion and Cl ion concentrations in the electrolyte used in Examples and Comparative Examples are shown in Table 1.
[Table 1]
Na ion Cl ion concentration concentration PPm PPm Example 1 5 1 Example 2 2 2 Example 3 3 2 Example 4 2 1 Example 5 2 3 Example 6 5 1 Example 7 2 1 Example 8 2 1 Comparative Example 1 , 2 5 Comparative Example 2 2 4 Comparative Example 3 2 50 [0084]
The lithium secondary batteries prepared were subjected to performance test at 20 C. The evaluation method is as follows. The results are shown in Table 2.
[0085]
[Performance test]
Using a charge and discharge test device, battery performance and discharge average voltage were confirmed under the conditions of 0.5-hour rate charge and 1-hour rate discharge. Furthermore, cycle characteristic test of 200 cycles was conducted under the conditions of 1-hour rate charge and 1-hour rate discharge, and cycle number when capacity is decreased to 80% of the first discharge capacity in the cycle test was confirmed. The cycle test results shown in Table 2 are based on the first discharge capacity per positive electrode active material.
[Table 2]
Discharge capacity per Voltage when Discharge Battery Cycles when full charge average voltage performance positive electrode active capacity material in 1-hour rate V V mAh retention is 80%
mA1-1/g -Example 1 4.3 3.8 7.3 104 200 or more Example 2 4.3 3.8 7.6 108 200 or more -Example 3 4.2 3.6 6.3 96 200 or more Example 4 4.0 3.0 6.8 Example 5 4.0 3.0 4.7 112 200 or more KJ
M
Example 6 4.2 3.6 7.7 109 178 a, H
H
M
KJ
Example 7 4.2 3.5 10.8 154 200 or more 1.) -Example 8 4.2 3.6 6.3 96 200 or more co , -.I
Comparative 4.2 3.6 5.9 88 49 w Example 1 H
Comparative 2.3 1.7 8.4 128 200 or more Example 2 Comparative 4.2 3.6 3.3 50 Example 3 [0086]
As shown in Table 1 and Table 2, it is seen that the lithium secondary battery according to the present invention is that charge voltage of the positive electrode is high voltage of 4V or higher, and battery performance, discharge capacity and cycle characteristic are all excellent. Contrary to this, Comparative Example 1 using TFSI as an electrolyte is very poor in cycle characteristic. Comparative Example 2 using Li4Ti5012 as a negative electrode active material is that charge voltage and discharge average voltage are low, and high voltage is not obtained. Comparative Example 3 using 1-methyl-1-propyl pyrrolidinium/TFSI as a solvent of an electrolyte is that Cl ion concentration in the electrolyte is 50 ppm and abnormally high, and it is seen that cycle characteristic is not obtained due to impurities.
Industrial Applicability [0087]
The lithium secondary battery using an ionic liquid according to the present invention can form into optional shape of a cylindrical shape, a coin shape, a square shape or the like, and can be used as power source in mobile device terminals of mobile phones, notebook computers, digital cameras, camera integrated VTR, MD players and the like; and portable electronic equipments such as laptop computers. Furthermore, development of use in various fields of power source mounted on transport machines such as electric vehicles, power storage, and the like.
<Example 4>
[Preparation of positive electrode]
100 g of LiFePO4 (covered with carbon in an amount of 5% based on the weight of LiFePO4) as a positive electrode active material, 3 g of acetylene black as a conductive agent, 5 g of PVDF as a binder and 120 g of NMP as a dispersion medium were mixed with a planetary mixer to prepare a positive electrode coating liquid having a solid content (components excluding NMP) of 47.4%. This coating liquid was applied onto an aluminum foil having a thickness of 20 p,m with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a positive electrode active material weight of 12 mg/cm2.
[ 0061 ]
[Preparation of negative electrode]
A mixture of 100 g of natural graphite as a negative electrode active material, 2 g of acetylene black as a conductive agent, 2 g of SBR as a binder and 2 g of CMC/:3H as a thickener, and 88 g of water as a dispersion medium were mixed with a planetary mixer to prepare a negative electrode coating liquid having a solid content of 53.6%. This coating liquid was applied onto a copper foil having a thickness of 10 tim with a coater, and dried at 80 C, followed by conducting roll press treatment, thereby obtaining an electrode having a negative electrode active material weight of 5 mg/cm2.
[ 0062 ]
[Preparation of lithium secondary battery]
According to the method of Example 1, a battery was prepared using a solution obtained by dissolving 0.6 mol of lithium salt LiTFSI in ethyl methyl imidazolium/FSI solvent, as an electrolyte.
[0063]
<Example 5>
[Preparation of positive electrode]
A mixture of 100 g of LiFePO4 (covered with carbon in an amount of 3% based on the weight of LiFePO4) as a positive electrode active material, 8 g of acetylene black as a conductive agent, 3 g of SBR as a binder and 2 g of CMC/3H as a thickener, and 114.5 g of water as a dispersion medium were mixed with a planetary mixer to prepare a positive electrode coating liquid having a solid content of 49.2%. This coating liquid was applied onto an aluminum foil having a thickness of 20 p.m with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a positive electrode active material weight of 10 mg/cm2.
[0064]
[Preparation of lithium secondary battery]
The positive electrode obtained and a metal lithium foil having a thickness of 200 jim as a negative electrode were used, and according to the method of Example 1, a battery was prepared using a solution obtained by dissolving 0.8 mol of lithium salt LiFSI in methyl propyl piperidinium/FSI :butyl methyl imidazolium/FSI (-5:5 vol) solvent, as an electrolyte.
[0065]
<Example 6>
[Preparation of positive electrode]
100 g of LiCo02 as a positive electrode active material, g of acetylene black as a conductive agent, 5 g of PVDF as a binder and 93 g of NMP as a dispersion medium were mixed with a planetary mixer to prepare a positive electrode coating liquid having a solid content (components excluding NMP) of 54.2%. This coating liquid was applied onto an aluminum foil having a thickness of 20 j.xm with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a positive electrode active material weight of 16 mg/cm2.
[0066]
[Preparation of negative electrode]
A mixture of 100 g of a surface-covered product of natural graphite as a negative electrode active material, 1 g of acetylene black as a conductive agent, 6 g of SBR as a binder and 4 g of CMC/3H as a thickener, and 90.8 g of water as a dispersion medium were mixed with a planetary mixer to prepare a negative electrode coating liquid having a solid content of 55%. This coating liquid was applied onto a copper foil having a thickness of 10 m with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a negative electrode active material weight of 9 mg/cm.
[0067]
[Preparation of lithium secondary battery]
According to the method of Example 1, a battery was prepared using a solution obtained by dissolving 0.7 mol of lithium salt LiTFSI in ethyl methyl imidazolium/FSI:tetraethyl ammonium/FSI (=9.5:0.5 vol) solvent, as an electrolyte.
[0068]
<Example 7>
[Preparation of positive electrode]
100 g of LiNi02 as a positive electrode active material, g of acetylene black as a conductive agent, 5 g of PVDF as a binder and 85 g of NMP as a dispersion medium were mixed with a planetary mixer to prepare a positive electrode coating liquid having a solid content (components excluding NIP) of 56.4%. This coating liquid was applied onto an aluminum foil having a thickness of 20 pm with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a positive electrode active material weight of 16 mg/cm:.
[0069]
[Preparation of negative electrode]
A mixture of 100 g of MCMB as a negative electrode active material, 3 g of acetylene black as a conductive agent, 7 g of SBR as a binder and 2 g of CMC/WSC as a thickener, and 54.6 g of water as a dispersion medium were mixed with a planetary mixer to prepare a negative electrode coating liquid having a solid content of 54 . 6%. This coating liquid was applied onto a copper foil having a thickness of 10 m with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a negative electrode active material weight of 12 mg/cm2.
[0070]
[Preparation of lithium secondary battery]
According to the method of Example 1, a battery was prepared using a solution obtained by dissolving 0.6 mol of lithium salt LiFSI in ethyl methyl imidazolium/FSI solvent, as an electrolyte.
[0071]
<Example 8>
[Preparation of positive electrode]
100 g of LiCo02 as a positive electrode active material, g of acetylene black as a conductive agent, 5 g of PVDF as a binder and 90 g of NMP as a dispersion medium were mixed with a planetary mixer to prepare a positive electrode coating liquid having a solid content (components excluding NMP) of 55%. This coating liquid was applied onto an aluminum foil having a thickness of 20 im with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a positive electrode active material weight of 15 mg/cm2.
[0072]
[Preparation of negative electrode]
100 g of MCMB as a negative electrode active material, 3 g of acetylene black as a conductive agent, 4 g of PVDF as a binder, and 87.5 g of NMP as a dispersion medium were mixed with a planetary mixer to prepare a negative electrode coating liquid having a solid content (components excluding NM?) of 55%. This coating liquid was applied onto a copper foil having a thickness of 101.1m with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a negative electrode active material weight of 8 mg/cm2.
[0073]
[Preparation of lithium secondary battery]
According to the method of Example 1, a battery was prepared using a solution obtained by dissolving 0.5 mol of lithium salt LiFSI in ethyl methyl imidazolium/FSI solvent, as an electrolyte.
[0074]
<Comparative Example 1>
[Preparation of positive electrode]
100 g of LiCo02as a positive electrode active material, g of acetylene black as a conductive agent, 5 g of PVDF as a binder and 80 g of NMP as a dispersion medium were mixed with a planetary mixer to prepare a positive electrode coating liquid having a solid content (components excluding NMP) of 57.9%. This coating liquid was applied onto an aluminum foil having a thickness of 20 m with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a positive electrode active material weight of 15 mg/cm2.
[0075]
[Preparation of negative electrode]
100 g of MCMB as a negative electrode active material, 2 g of acetylene black as a conductive agent, 8 g of PVDF as a binder, and 95 g of NMP as a dispersion medium were mixed with a planetary mixer to prepare a negative electrode coating liquid having a solid content (components excluding NMP) of 53.7%. This coating liquid was applied onto a copper foil having a thickness of 10 m with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a negative electrode active material weight of 8 mg/cm2.
[0076]
[Preparation of lithium secondary battery]
According to the method of Example 1, a battery was prepared using a solution obtained by dissolving 0.5 mol of lithium salt LiTFSI in 1-methyl-1-propyl pyrrolidinium/TFSI
solvent, as an electrolyte.
[0077]
<Comparative Example 2>
[Preparation of positive electrode]
100 g of LiCo02 as a positive electrode active material, g of acetylene black as a conductive agent, 5 g of PVDF as a binder and 90g of NMP as a dispersion medium were mixed with a planetary mixer to prepare a positive electrode coating liquid having a solid content (components excluding NMP) of 55%. This coating liquid was applied onto an aluminum foil having a thickness of 20 pm with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a positive electrode active material weight of 15 mg/cm2.
[0078]
[Preparation of negative electrode]
100 g of Li4T15012 as a negative electrode active material, g of acetylene black as a conductive agent, 5 g of PVDF as a binder, and 100 g of NMP as a dispersion medium were mixed with a planetary mixer to prepare a negative electrode coating liquid having a solid content (components excluding NMP) of 52.4%. This coating liquid was applied onto a copper foil having a thickness of 10 m with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a negative electrode active material weight of 8 mg/cm.
[0079]
[Preparation of lithium secondary battery]
According to the method of Example 1, a battery was prepared using a solution obtained by dissolving 0.5 mol of lithium salt LiFSI in ethyl methyl imidazolium/FSI solvent, as an electrolyte.
[0080]
<Comparative Example 3>
[Preparation of positive electrode]
100 g of LiCoO, as a positive electrode active material, g of acetylene black as a conductive agent, 5 g of PVDF as a binder and 80 g of NMP as a dispersion medium were mixed with a planetary mixer to prepare a positive electrode coating liquid having a solid content (components excluding NMP) of 57.9%. This coating liquid was applied onto an aluminum foil having a thickness of 20 m with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a positive electrode active material weight of 15 mg/cm2.
[0081]
[Preparation of negative electrode]
100 g of MCMB as a negative electrode active material, 2 g of acetylene black as a conductive agent, 4 g of PVDF as a binder, and 95 g of NMP as a dispersion medium were mixed with a planetary mixer to prepare a negative electrode coating liquid having a solid content (components excluding NM?) of 52.7%. This coating liquid was applied onto a copper foil having a thickness of 10 pm with a coater, and dried at 130 C, followed by conducting roll press treatment, thereby obtaining an electrode having a negative electrode active material weight of 8 mg/cm2.
[0082]
[Preparation of lithium secondary battery]
According to the method of Example 1, a battery was prepared using a solution obtained by dissolving 0.5 mol of lithium salt LiTFSI in 1-methyl-1-propyl pyrrolidinium/TFSI
solvent, as an electrolyte.
[0083]
Na ion and Cl ion concentrations in the electrolyte used in Examples and Comparative Examples are shown in Table 1.
[Table 1]
Na ion Cl ion concentration concentration PPm PPm Example 1 5 1 Example 2 2 2 Example 3 3 2 Example 4 2 1 Example 5 2 3 Example 6 5 1 Example 7 2 1 Example 8 2 1 Comparative Example 1 , 2 5 Comparative Example 2 2 4 Comparative Example 3 2 50 [0084]
The lithium secondary batteries prepared were subjected to performance test at 20 C. The evaluation method is as follows. The results are shown in Table 2.
[0085]
[Performance test]
Using a charge and discharge test device, battery performance and discharge average voltage were confirmed under the conditions of 0.5-hour rate charge and 1-hour rate discharge. Furthermore, cycle characteristic test of 200 cycles was conducted under the conditions of 1-hour rate charge and 1-hour rate discharge, and cycle number when capacity is decreased to 80% of the first discharge capacity in the cycle test was confirmed. The cycle test results shown in Table 2 are based on the first discharge capacity per positive electrode active material.
[Table 2]
Discharge capacity per Voltage when Discharge Battery Cycles when full charge average voltage performance positive electrode active capacity material in 1-hour rate V V mAh retention is 80%
mA1-1/g -Example 1 4.3 3.8 7.3 104 200 or more Example 2 4.3 3.8 7.6 108 200 or more -Example 3 4.2 3.6 6.3 96 200 or more Example 4 4.0 3.0 6.8 Example 5 4.0 3.0 4.7 112 200 or more KJ
M
Example 6 4.2 3.6 7.7 109 178 a, H
H
M
KJ
Example 7 4.2 3.5 10.8 154 200 or more 1.) -Example 8 4.2 3.6 6.3 96 200 or more co , -.I
Comparative 4.2 3.6 5.9 88 49 w Example 1 H
Comparative 2.3 1.7 8.4 128 200 or more Example 2 Comparative 4.2 3.6 3.3 50 Example 3 [0086]
As shown in Table 1 and Table 2, it is seen that the lithium secondary battery according to the present invention is that charge voltage of the positive electrode is high voltage of 4V or higher, and battery performance, discharge capacity and cycle characteristic are all excellent. Contrary to this, Comparative Example 1 using TFSI as an electrolyte is very poor in cycle characteristic. Comparative Example 2 using Li4Ti5012 as a negative electrode active material is that charge voltage and discharge average voltage are low, and high voltage is not obtained. Comparative Example 3 using 1-methyl-1-propyl pyrrolidinium/TFSI as a solvent of an electrolyte is that Cl ion concentration in the electrolyte is 50 ppm and abnormally high, and it is seen that cycle characteristic is not obtained due to impurities.
Industrial Applicability [0087]
The lithium secondary battery using an ionic liquid according to the present invention can form into optional shape of a cylindrical shape, a coin shape, a square shape or the like, and can be used as power source in mobile device terminals of mobile phones, notebook computers, digital cameras, camera integrated VTR, MD players and the like; and portable electronic equipments such as laptop computers. Furthermore, development of use in various fields of power source mounted on transport machines such as electric vehicles, power storage, and the like.
Claims (4)
1. A lithium secondary battery using an ionic liquid, comprising a positive electrode, a negative electrode, a separator provided between the positive electrode and the negative electrode, and a nonaqueous electrolyte containing a lithium salt, wherein the nonaqueous electrolyte uses an ionic liquid containing bis(fluorosulfonyl)imide anion as an anionic component, as a solvent, voltage at full charge is 3.6V or higher, and average discharge voltage in a discharge rate of 1-hour rate is 2.9V or higher, and wherein the negative electrode is mesocarbon microbead.
2. The lithium secondary battery using an ionic liquid as claimed in claim 1, wherein the ionic liquid contains a cation containing a nitrogen atom as a cationic component.
3. The lithium secondary battery using an ionic liquid as claimed in claim 2, wherein the cation containing a nitrogen atom is alkyl ammonium, imidazolium, pyrrolidinium or piperidinium.
4. The lithium secondary battery using an ionic liquid as claimed in any one of claims 1 to 3, wherein the amount of halogen ions contained in the nonaqueous electrolyte is 10 ppm or lower.
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| JP2006-027368 | 2006-02-03 | ||
| JP2006027368A JP5032773B2 (en) | 2006-02-03 | 2006-02-03 | Lithium secondary battery using ionic liquid |
| PCT/JP2006/324702 WO2007088677A1 (en) | 2006-02-03 | 2006-12-11 | Lithium rechargeable battery using ionic liquid |
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| US (1) | US20090169992A1 (en) |
| EP (1) | EP1995817B1 (en) |
| JP (1) | JP5032773B2 (en) |
| KR (1) | KR101177160B1 (en) |
| CN (1) | CN101379653B (en) |
| CA (1) | CA2641152C (en) |
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| WO (1) | WO2007088677A1 (en) |
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| JP4572602B2 (en) * | 2004-06-30 | 2010-11-04 | パナソニック株式会社 | Non-aqueous electrolyte and non-aqueous electrolyte secondary battery and their production method |
| US20060088767A1 (en) * | 2004-09-01 | 2006-04-27 | Wen Li | Battery with molten salt electrolyte and high voltage positive active material |
| CA2597882C (en) * | 2005-01-12 | 2010-09-14 | Otsuka Chemical Co., Ltd. | Quaternary ammonium salt, electrolyte, electrolyte solution and electrochemical device |
| JP4519685B2 (en) * | 2005-03-14 | 2010-08-04 | 株式会社東芝 | Non-aqueous electrolyte battery |
| JP4955951B2 (en) * | 2005-07-25 | 2012-06-20 | 株式会社豊田中央研究所 | Lithium ion secondary battery |
| CA2517248A1 (en) * | 2005-08-29 | 2007-02-28 | Hydro-Quebec | Process for purifying an electrolyte, the electrolyte thus obtained and its uses |
-
2006
- 2006-02-03 JP JP2006027368A patent/JP5032773B2/en not_active Expired - Lifetime
- 2006-12-11 US US12/223,627 patent/US20090169992A1/en not_active Abandoned
- 2006-12-11 WO PCT/JP2006/324702 patent/WO2007088677A1/en not_active Ceased
- 2006-12-11 CN CN2006800530285A patent/CN101379653B/en not_active Expired - Fee Related
- 2006-12-11 EP EP06834457.1A patent/EP1995817B1/en not_active Ceased
- 2006-12-11 CA CA2641152A patent/CA2641152C/en active Active
- 2006-12-11 KR KR1020087020458A patent/KR101177160B1/en not_active Expired - Fee Related
- 2006-12-13 TW TW095146637A patent/TW200805735A/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| US20090169992A1 (en) | 2009-07-02 |
| TW200805735A (en) | 2008-01-16 |
| EP1995817A1 (en) | 2008-11-26 |
| JP5032773B2 (en) | 2012-09-26 |
| CN101379653B (en) | 2011-08-31 |
| WO2007088677A1 (en) | 2007-08-09 |
| CA2641152A1 (en) | 2007-08-09 |
| CN101379653A (en) | 2009-03-04 |
| EP1995817B1 (en) | 2016-08-10 |
| JP2007207675A (en) | 2007-08-16 |
| EP1995817A4 (en) | 2012-08-08 |
| KR101177160B1 (en) | 2012-08-24 |
| TWI344712B (en) | 2011-07-01 |
| KR20080105045A (en) | 2008-12-03 |
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