WO2013146285A1 - リチウムイオン二次電池 - Google Patents
リチウムイオン二次電池 Download PDFInfo
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- WO2013146285A1 WO2013146285A1 PCT/JP2013/057127 JP2013057127W WO2013146285A1 WO 2013146285 A1 WO2013146285 A1 WO 2013146285A1 JP 2013057127 W JP2013057127 W JP 2013057127W WO 2013146285 A1 WO2013146285 A1 WO 2013146285A1
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- 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
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- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
- H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
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- 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
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- 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
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- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/621—Binders
- H01M4/622—Binders being polymers
- H01M4/623—Binders being polymers fluorinated polymers
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- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
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- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
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- H01M2220/00—Batteries for particular applications
- H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
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- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
- H01M4/364—Composites as mixtures
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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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- 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
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/70—Energy storage systems for electromobility, e.g. batteries
Definitions
- the present invention relates to a lithium ion secondary battery.
- a lithium ion secondary battery As a secondary battery for driving a motor, a lithium ion secondary battery having a high theoretical energy is attracting attention, and is currently being developed rapidly.
- a lithium ion secondary battery is generally composed of a positive electrode, a negative electrode, a separator and an electrolyte positioned therebetween, and an exterior body that houses them.
- the positive electrode used in the lithium ion secondary battery for example, lithium cobaltate (LiCoO 2 ) or lithium manganate (LiMn 2 O 4 ) is used as the main application material, and the main application material is used for the negative electrode.
- graphite is used for the negative electrode.
- porous polyolefin is used for the separator used in the lithium ion secondary battery, for example, lithium hexafluorophosphate (LiPF 6 ) is used for the electrolyte, and for example, a laminate film is used for the exterior body. used.
- LiPF 6 lithium hexafluorophosphate
- Li x Mn 2 -y MA y O 4 + z [wherein MA is Mg, Al, Cr, Fe, in order to suppress elution of manganese from the lithium manganese composite oxide as the positive electrode active material] Lithium manganese, which is at least one element selected from the group consisting of Co and Ni, represented by 1 ⁇ x ⁇ 1.2, 0 ⁇ y ⁇ 0.1 and ⁇ 0.3 ⁇ z ⁇ 0.3]
- Non-aqueous secondary batteries using a composite oxide as a positive electrode active material have been proposed.
- a negative electrode comprising a lithium manganese composite oxide partially substituted with magnesium as a positive electrode active material, graphite not subjected to carbon coating treatment, and graphite subjected to carbon coating treatment
- a negative electrode comprising a lithium manganese composite oxide partially substituted with magnesium as a positive electrode active material, graphite not subjected to carbon coating treatment, and graphite subjected to carbon coating treatment
- new technical knowledge that the resistance is increased was obtained.
- the present invention has been made based on such new technical knowledge. And the place made into the objective of this invention is providing the lithium ion secondary battery which can suppress a resistance raise.
- a positive electrode containing a positive electrode active material containing a lithium manganese composite oxide partially substituted with magnesium, graphite coated with amorphous carbon as a negative electrode active material, and a carbon black-based conductive assistant The present invention has been completed by finding that the above-mentioned object can be achieved by employing a constitution comprising a negative electrode containing an agent and a fluororesin-based binder.
- FIG. 3 is a schematic sectional view taken along line III-III of the lithium ion secondary battery shown in FIG.
- the lithium ion secondary battery of the present invention includes a positive electrode and a negative electrode.
- the positive electrode in the lithium ion secondary battery of this invention contains the lithium manganese complex oxide in which a part was substituted by magnesium as a positive electrode active material.
- the negative electrode in the lithium ion secondary battery of the present invention contains graphite coated with amorphous carbon as a negative electrode active material, a carbon black-based conductive additive, and a fluororesin-based binder.
- Such a configuration can suppress an increase in resistance in the lithium ion secondary battery.
- the reason for this is not clear, but by using graphite coated with amorphous carbon as the negative electrode active material, magnesium is trapped (trapped) on the amorphous carbon surface that hardly contributes to the negative electrode capacity. It is presumed that the increase in resistance is suppressed by inhibiting the factor of lithium ion entry / exit (generation of lithium resistance film).
- the fluororesin-based binder contained so that the carbon black-based conductive additive is dispersed is present in the active material in such a content as to cover at least a part between the particles of the negative electrode active material.
- FIG. 1 is a diagram (a) and (b) for explaining how magnesium is captured (adsorbed) in the negative electrode of the lithium ion secondary battery of the present invention.
- downward arrows indicate the flow of electrons.
- the negative electrode current collector 11A As shown in FIG. 1A, on the negative electrode current collector 11A, graphite 11 ⁇ coated with amorphous carbon 11 ⁇ as a negative electrode active material 11a, a carbon black-based conductive additive 11b, and a fluorine-based resin bond are formed.
- a negative electrode active material layer 11B containing an adhesive 11c is formed.
- the fluororesin-based binder 11c includes the carbon black-based conductive auxiliary agent 11b in a dispersed state and covers at least a part between the particles of the negative electrode active material 11a.
- the substance 11a and the negative electrode current collector 11A are bound.
- Magnesium ions (Mg 2+ ) are eluted from a positive electrode (not shown).
- magnesium ions (Mg 2+ ) are trapped on the surface of the amorphous carbon 11 ⁇ that hardly contributes to the negative electrode capacity and the carbon black conductive auxiliary agent 11b.
- magnesium reaching the contact point between the particles of the negative electrode active material is reduced, and the flow of electrons at the contact point becomes difficult to be inhibited. Therefore, it is considered that an increase in resistance can be suppressed.
- FIG. 2 is a perspective view showing an outline of an example of a lithium ion secondary battery according to an embodiment of the present invention.
- FIG. 3 is a schematic cross-sectional view taken along line III-III of the lithium ion secondary battery shown in FIG.
- Such a lithium ion secondary battery is called a laminate-type secondary battery.
- the lithium ion secondary battery 1 of the present embodiment has a configuration in which a battery element 10 to which a negative electrode terminal 21 and a positive electrode terminal 22 are attached is enclosed in an exterior body 30. ing.
- the negative electrode terminal 21 and the positive electrode terminal 22 are led out in the same direction from the inside of the exterior body 30 to the outside.
- the negative electrode terminal and the positive electrode terminal may be led out in the opposite direction from the inside of the exterior body to the outside.
- such a negative electrode terminal and a positive electrode terminal can be attached to the positive electrode collector and negative electrode collector which are mentioned later by ultrasonic welding, resistance welding, etc., for example.
- the negative electrode terminal 21 and the positive electrode terminal 22 are made of materials such as aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof. However, it is not limited to these, The conventionally well-known material used as a terminal for lithium ion secondary batteries can be used. Note that the negative electrode terminal and the positive electrode terminal may be made of the same material or different materials. In addition, as in the present embodiment, a separately prepared terminal may be connected to a negative electrode current collector and a positive electrode current collector described later, and each negative electrode current collector and each positive electrode current collector described later are extended. Thus, a terminal may be formed.
- the exterior body 30 is preferable from the viewpoint of, for example, reducing the weight by applying a laminate exterior body made of a flexible film made of a laminate of a synthetic resin and a metal foil, and improving the battery energy density.
- the laminate type secondary battery is also excellent in heat dissipation, it can be suitably used as an in-vehicle battery such as an electric vehicle.
- the battery element 10 includes a negative electrode 11 in which a negative electrode active material layer 11B containing a negative electrode active material capable of occluding and releasing lithium ions is formed on the main surface of the negative electrode current collector 11A.
- the lithium ion secondary battery 1 of the present embodiment has a configuration in which a plurality of single battery layers 14 are stacked and electrically connected in parallel.
- an insulating layer (not shown) for insulating between adjacent negative electrode current collectors and positive electrode current collectors may be provided on the outer periphery of the unit cell layer.
- the negative electrode 11 has a structure in which a negative electrode active material layer 11B is formed on both main surfaces of the negative electrode current collector 11A.
- the negative electrode active material layer contains a negative electrode active material, a conductive auxiliary agent, and a binder. Furthermore, since the binder is subjected to a step of mixing and stirring the active material, the conductive assistant and the binder when preparing a slurry as will be described later, the conductive assistant is contained in a dispersed state. it is conceivable that.
- the negative electrode active materials are bound to each other in a state where at least a part between the particles of the negative electrode active material is coated by setting the content of the binder in the negative electrode within a predetermined preferable range.
- Negative electrode current collector for example, copper, stainless steel (SUS), nickel, titanium, or an alloy thereof can be used.
- graphite coated with amorphous carbon As the negative electrode active material, graphite coated with amorphous carbon is used.
- the average particle diameter of graphite coated with such amorphous carbon is preferably several ⁇ m to several tens of ⁇ m, for example.
- the BET specific surface area of the graphite coated with such amorphous carbon is preferably, for example, 10 ⁇ 1 to 10 m 2 / g.
- a carbon black conductive assistant As the conductive assistant, a carbon black conductive assistant is used.
- the carbon black conductive auxiliary agent preferably has a BET specific surface area of, for example, 10 to 10 2 m 2 / g. By setting it as such a range, it is thought that sufficient magnesium capture
- the BET specific surface area of a conductive support agent is larger than the BET specific surface area of a negative electrode active material. Thereby, it is thought that it can exist in a position closer to the contact point between the particles of the negative electrode active material.
- the carbon black-based conductive assistant ketjen black, acetylene black, channel black, lamp black, oil furnace black, thermal black, or a mixture of any combination thereof can be used.
- a fluororesin binder As the binder (binder), a fluororesin binder is used.
- the fluororesin include polyvinylidene fluoride (PVdF) and vinylidene fluoride polymers obtained by copolymerizing vinylidene fluoride and other fluorine monomers.
- the “fluororesin-based binder” is not particularly limited to one containing only a fluororesin, for example, as long as it can penetrate a non-aqueous electrolyte described later.
- the conductive auxiliary agent is covered by forming a film that cannot penetrate the non-aqueous electrolyte. Even if the conductive auxiliary agent is contained in the negative electrode, the intended magnesium capture (adsorption) action by the carbon black conductive auxiliary agent used in the present invention cannot be expressed.
- the positive electrode 12 has a structure in which a positive electrode active material layer 12B is formed on both main surfaces of the positive electrode current collector 12A.
- the positive electrode active material layer contains a positive electrode active material, a conductive additive and a binder that are added as necessary.
- a conductive support agent and a binder what can be conventionally used for a lithium ion secondary battery can be selected suitably, and can be used.
- Positive electrode current collector for example, aluminum, stainless steel (SUS), nickel, titanium, or an alloy thereof can be used.
- the lithium manganese composite oxide as the positive electrode active material used in the present invention is a part of which is substituted with magnesium, for example, a part of the manganese site substituted with magnesium, or magnesium and another element. Has been replaced.
- LiMn 2-xy Mg x MA y O 4 + z (MA is at least one transition metal element and / or Li other than Mn, x, y and z are 0 ⁇ x ⁇ 2,0 ⁇ y ⁇ 2, satisfying the relationship of ⁇ 1 ⁇ z ⁇ 1)
- LiMn 1-xy Mg x MB y O 2 + z (MB is at least one transition metal element other than Mn and / or Li, x, y, and z satisfy the relations of 0 ⁇ x ⁇ 1, 0 ⁇ y ⁇ 1, and ⁇ 0.5 ⁇ z ⁇ 0.5).
- LiMn 2-xy Mg x MA y O 4 + z having a spinel structure because it is more effective.
- a positive electrode active material mixture obtained by mixing a lithium manganese composite oxide powder partially substituted with magnesium and a lithium nickel composite oxide powder so that the former is 50% or more can also be used.
- Nonaqueous electrolyte layer As the nonaqueous electrolyte layer 13, for example, a layered structure formed using a nonaqueous electrolyte solution or a polymer gel electrolyte held in a separator described later can be used. Specifically, a nonaqueous solvent in which a supporting salt (lithium salt) is dissolved can be used as the nonaqueous electrolytic solution.
- a supporting salt lithium salt
- lithium salt examples include lithium imide salt, lithium hexafluorophosphate (LiPF 6 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium aluminum tetrachloride (LiAlCl 4 ), and lithium perchlorate (LiClO 4). ), Lithium tetrafluoroborate (LiBF 4 ), lithium hexafluoroantimonate (LiSbF 6 ), and the like can be used. Among these, it is particularly preferable to use lithium hexafluorophosphate (LiPF 6 ) or lithium tetrafluoroborate (LiBF 4 ).
- lithium imide salt examples include LiN (C k F 2k + 1 SO 2 ) (C m F 2m + 1 SO 2 ) (k and m are each independently 1 or 2). These lithium salts can be used alone or in combination of two or more.
- Non-aqueous solvent examples include at least selected from the group consisting of cyclic carbonates, chain carbonates, aliphatic carboxylic acid esters, ⁇ -lactones, cyclic ethers, chain ethers, and fluorinated derivatives thereof.
- One organic solvent can be used.
- the cyclic carbonates include propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), and fluorinated derivatives thereof.
- Examples of the chain carbonates include dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dipropyl carbonate (DPC), and fluorinated derivatives thereof.
- Examples of the aliphatic carboxylic acid ester include methyl formate, methyl acetate, ethyl propionate, and fluorinated derivatives thereof.
- Examples of ⁇ -lactones include ⁇ -butyrolactone and fluorinated derivatives thereof.
- Examples of cyclic ethers include tetrahydrofuran and 2-methyltetrahydrofuran.
- Examples of chain ethers include 1,2-ethoxyethane (DEE), ethoxymethoxyethane (EME), diethyl ether, and fluorinated derivatives thereof.
- Others include dimethyl sulfoxide, 1,3-dioxolane, formaldehyde, acetamide, dimethylformamide, dioxolane, acetonitrile, propylnitrile, nitromethane, ethyl monoglyme, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane,
- Examples include 1,3-dimethyl-2-yl ether, 1,3-propane sultone, anisole, N-methylpyrrolidone, and fluorinated carboxylic acid ester. These can be used alone or in combination of two or more.
- a microporous film made of a polyolefin such as polyethylene (PE) or polypropylene (PP), or a fluororesin such as polyvinylidene fluoride (PVdF) or polytetrafluoroethylene (PTFE) can be used.
- PE polyethylene
- PP polypropylene
- PVdF polyvinylidene fluoride
- PTFE polytetrafluoroethylene
- a solvent such as N-methyl-2-pyrrolidone (NMP) in a predetermined amount of graphite coated with amorphous carbon as a negative electrode active material, a carbon black-based conductive additive, and a fluororesin-based binder.
- NMP N-methyl-2-pyrrolidone
- the negative electrode is produced by applying the slurry dispersed therein to a negative electrode current collector such as a copper foil and drying to form a negative electrode active material layer. Further, the obtained negative electrode can be compressed to a suitable density by a method such as a roll press.
- a slurry in which a lithium manganese composite oxide substituted with magnesium as a positive electrode active material, a conductive additive, and a binder are dispersed in a solvent such as NMP in a predetermined blending amount is placed on a doctor on a hot plate.
- a positive electrode is produced by applying to a positive electrode current collector such as an aluminum foil using a blade or the like and drying to form a positive electrode active material layer.
- the obtained positive electrode can be compressed to a suitable density by a method such as a roll press.
- the negative electrode terminal is attached to the negative electrode and the positive electrode terminal is attached to the positive electrode.
- the laminated product is sandwiched between polymer-metal composite laminate sheets, and the outer peripheral edge except for one side is heat-sealed to form a bag-like outer package.
- Example 1 ⁇ Production of negative electrode> Spherical natural graphite powder (average particle size: 20 ⁇ m, average aspect ratio: 1.2, BET specific surface area: 1.2 m 2 / g) coated with amorphous carbon as a negative electrode active material, and fluororesin-based bond Polyvinylidene fluoride as an adhesive and first carbon black (average particle diameter: 1 ⁇ m, BET specific surface area: 64 m 2 / g) as a carbon black-based conductive auxiliary agent, in a solid content mass ratio of 96.5: 3 : It was put in N-methyl-2-pyrrolidone (NMP) at a ratio of 0.5, and was uniformly dispersed by stirring to prepare a slurry.
- NMP N-methyl-2-pyrrolidone
- the obtained slurry was applied onto a 15 ⁇ m thick copper foil serving as a negative electrode current collector, and then a negative electrode active material layer was formed by evaporating NMP at 125 ° C. for 10 minutes, followed by pressing on one side.
- a negative electrode was prepared.
- the density of the negative electrode active material layer per unit area after drying was 0.008 g / cm 2 .
- Each of the negative electrode and the positive electrode produced as described above was cut into 5 cm (width) ⁇ 6.0 cm (length). Among these, a side of 5 cm ⁇ 1 cm is an uncoated portion for connecting terminals, and the active material layer is 5 cm ⁇ 5 cm.
- a positive electrode terminal made of aluminum having a width of 5 cm, a length of 3 cm, and a thickness of 0.1 mm was ultrasonically welded to the uncoated portion of the positive electrode at a length of 1 cm.
- a nickel negative electrode terminal having the same size as the positive electrode terminal was ultrasonically welded at a length of 1 cm to an uncoated portion of the negative electrode.
- the negative electrode and the positive electrode were placed on both sides of a 6 cm ⁇ 6 cm separator made of polyethylene and polypropylene so that the active material layer overlapped with the separator therebetween to obtain an electrode laminate.
- a bag-shaped laminate outer package was prepared by bonding one side of the two 7 cm ⁇ 10 cm aluminum laminate films except for one of the long sides to a width of 5 mm by thermal fusion.
- the electrode laminate was inserted so as to be a distance of 1 cm from one short side of the laminate outer package. After 0.203 g of the following non-aqueous electrolyte was injected and vacuum impregnated, the opening was sealed with a width of 5 mm by heat sealing under reduced pressure to obtain a laminate type secondary battery of this example. .
- EC ethylene carbonate
- DEC diethyl carbonate
- LiPF 6 lithium dissolved to a concentration of 1.0 mol / L
- a cyclic disulfonic acid ester dissolved to a concentration of 1.5% by mass is used as an additive. It was.
- Example 2 In the production of the negative electrode, the amount of the first carbon black added was changed from 0.5% by mass to 1.0% by mass, and the negative electrode active material, the fluororesin binder, and the carbon black conductive auxiliary agent The same procedure as in Example 1 was repeated except that the slurry was prepared by uniformly dispersing in NMP at a mass ratio of 96: 3: 1 and stirring to make a slurry. A battery was obtained.
- Example 3 In producing the negative electrode, the second carbon black (average particle size: 3 ⁇ m, BET specific surface area: 20 m 2 / g) is added to the first carbon black, the added amount of the second carbon black is 2 mass%, and the negative electrode active material And a fluororesin binder and a carbon black conductive assistant in NMP at a solid content mass ratio of 94.5: 3: 2.5 and stirred to uniformly disperse the slurry. Except for the production, the same operation as in Example 1 was repeated to obtain a laminated secondary battery of this example.
- the second carbon black average particle size: 3 ⁇ m, BET specific surface area: 20 m 2 / g
- Example 4 In producing the negative electrode, the second carbon black (average particle size: 3 ⁇ m, BET specific surface area: 20 m 2 / g) is added to the first carbon black, the added amount of the second carbon black is 4% by mass, and the negative electrode active material And a fluororesin binder and a carbon black conductive assistant in NMP at a solid content mass ratio of 92.5: 3: 4.5 and stirred to uniformly disperse the slurry. Except for the production, the same operation as in Example 1 was repeated to obtain a laminated secondary battery of this example.
- the second carbon black average particle size: 3 ⁇ m, BET specific surface area: 20 m 2 / g
- Example 5 When producing the negative electrode, the second carbon black (average particle size: 3 ⁇ m, BET specific surface area: 20 m 2 / g) is added to the first carbon black, the added amount of the second carbon black is 8% by mass, and the negative electrode active material And a fluororesin binder and a carbon black conductive assistant in NMP at a solid content mass ratio of 88.5: 3: 8.5 and stirred to uniformly disperse the slurry. Except for the production, the same operation as in Example 1 was repeated to obtain a laminated secondary battery of this example.
- the second carbon black average particle size: 3 ⁇ m, BET specific surface area: 20 m 2 / g
- Example 6 In producing the negative electrode, the second carbon black (average particle size: 3 ⁇ m, BET specific surface area: 20 m 2 / g) is added to the first carbon black, the added amount of the second carbon black is 2 mass%, and the negative electrode active material
- the slurry was prepared by uniformly dispersing the fluororesin binder and the carbon black conductive additive into NMP at a solid mass ratio of 94: 3: 3 and stirring the mixture. Except for the above, the same operation as in Example 2 was repeated to obtain a laminated secondary battery of this example.
- Example 7 In producing the negative electrode, the second carbon black (average particle size: 3 ⁇ m, BET specific surface area: 20 m 2 / g) is added to the first carbon black, the added amount of the second carbon black is 4% by mass, and the negative electrode active material And a fluororesin-based binder and a carbon black-based conductive additive in NMP at a solid content mass ratio of 92: 3: 5 and stirred to be uniformly dispersed to prepare a slurry. Except for the above, the same operation as in Example 2 was repeated to obtain a laminated secondary battery of this example.
- the second carbon black average particle size: 3 ⁇ m, BET specific surface area: 20 m 2 / g
- Example 8 When producing the negative electrode, the second carbon black (average particle size: 3 ⁇ m, BET specific surface area: 20 m 2 / g) is added to the first carbon black, the added amount of the second carbon black is 8% by mass, and the negative electrode active material And a fluororesin-based binder and a carbon black-based conductive auxiliary agent were placed in NMP at a solid mass ratio of 88: 3: 9 and stirred to uniformly disperse the slurry. Except for the above, the same operation as in Example 2 was repeated to obtain a laminated secondary battery of this example.
- the second carbon black average particle size: 3 ⁇ m, BET specific surface area: 20 m 2 / g
- Example 9 When producing a positive electrode, Li 1.1 Mn 1.8 Mg 0.1 O 4 powder (average particle size: 10 ⁇ m) having a spinel structure as a positive electrode active material and lithium nickelate (LiNi 0.8 Co 0.15 Al 0.05 O 2 ) powder as a positive electrode active material The amount of lithium nickelate added is 20% by mass, and the positive electrode active material, the binder, and the conductive additive are placed in NMP at a solid content mass ratio of 92: 4: 4 and stirred. Thus, except that the slurry was uniformly dispersed, the same operation as in Example 1 was repeated to obtain a laminate type secondary battery of this example.
- Example 1 Spherical natural graphite powder (average particle size: 20 ⁇ m, average aspect ratio: 1.2, BET specific surface area: 1.2 m 2 / g) coated with amorphous carbon as a negative electrode active material, and fluororesin-based bond The same operation as in Example 1 except that polyvinylidene fluoride as an adhesive was stirred in NMP at a solid mass ratio of 97: 3 to uniformly disperse the slurry.
- the laminate type secondary battery of this example was obtained by repeating the above.
- the DC resistance value was measured by measuring the voltage drop when discharged at a predetermined current value immediately after shipment (initial) and after 1000 cycles, and the rate of increase in internal resistance was determined. Calculated. The obtained results are shown in Tables 1 and 2 together with some of the specifications of the laminated secondary battery.
- the “internal resistance increase rate” is the ratio of the DC resistance value of the battery after 1000 cycles to the DC resistance value of the battery immediately after shipment (initial).
- Table 1 shows that Examples 1 to 8 belonging to the scope of the present invention are compared with Comparative Example 1 outside the present invention, and a positive electrode using a lithium-manganese composite oxide substituted with magnesium as a positive electrode active material, Compared to lithium ion secondary battery using graphite coated with crystalline carbon, predetermined negative electrode containing carbon black conductive aid and fluororesin binder, contains carbon black conductive aid It can be seen that the resistance increase is not suppressed in the comparative example. Moreover, it turns out that resistance rise is suppressed more among the lithium ion secondary batteries of Example 4 and Example 7, especially the lithium ion secondary battery of Example 7, among them.
- the change rate of the internal resistance increase rate when comparing Example 1 and Example 2 and the internal resistance increase when comparing Example 1 and Example 3 or Example 2 and Example 6 are compared.
- the rate of change of the ratio is compared, it can be seen that the higher the BET specific surface area of the carbon black-based conductive additive is, the better the resistance increase suppressing effect is.
- the BET specific surface area of the carbon black conductive auxiliary agent is preferably 10 to 10 2 m 2 / g.
- Example 9 when Example 9 and Example 1 belonging to the scope of the present invention are compared, lithium using a positive electrode using a lithium manganese composite oxide substituted with magnesium and a lithium nickel composite oxide as a positive electrode active material is shown. It can be seen that the resistance increase is further suppressed in the ion secondary battery.
- the configuration described in the above-described examples is not limited to each example, and the configuration details of the positive electrode active material, the negative electrode active material, the carbon black-based conductive additive, and the fluororesin-based binder are changed. Or the configurations of the embodiments can be combined with other than the embodiments described above.
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Abstract
Description
そして、本発明のリチウムイオン二次電池における正極は、正極活物質として一部がマグネシウムによって置換されたリチウムマンガン複合酸化物を含有する。また、本発明のリチウムイオン二次電池における負極は、負極活物質としての非晶質炭素で被覆された黒鉛と、カーボンブラック系導電助剤と、フッ素樹脂系結着剤とを含有する。
図2は、本発明の一実施形態に係るリチウムイオン二次電池の一例の概略を示す斜視図である。図3は、図2に示したリチウムイオン二次電池のIII-III線に沿った模式的な断面図である。なお、このようなリチウムイオン二次電池は、ラミネート型二次電池と呼ばれるものである。
負極端子21及び正極端子22は、例えば、アルミニウムや銅、チタン、ニッケル、ステンレス鋼(SUS)、これらの合金などの材料により構成されている。しかしながら、これらに限定されるものではなく、リチウムイオン二次電池用の端子として用いられている従来公知の材料を用いることができる。なお、負極端子及び正極端子は、同一材質のものを用いてもよく、異なる材質のものを用いてもよい。また、本実施形態のように、別途準備した端子を後述する負極集電体及び正極集電体に接続してもよいし、後述する各負極集電体及び各正極集電体をそれぞれ延長することによって端子を形成してもよい。
外装体30は、例えば、合成樹脂と金属箔との積層体からなる可撓性フィルムなどよりなるラミネート外装体を適用することで軽量化が可能であり電池エネルギー密度の向上を図るという観点から好ましい。また、ラミネート型二次電池は、放熱性にも優れるため、電気自動車などの車載用電池として好適に用いることができる。
図3に示すように、電池要素10は、負極集電体11Aの主面上にリチウムイオンを吸蔵及び放出し得る負極活物質を含有する負極活物質層11Bが形成された負極11と、非水電解質層13と、正極集電体12Aの主面上にリチウムイオンを吸蔵及び放出し得る正極活物質を含有する正極活物質層12Bが形成された正極12とを複数積層した構成を有している。このようにして、負極、非水電解質層及び正極が、この順に複数積層されている。
負極11は、負極集電体11Aの両方の主面上に負極活物質層11Bが形成された構造を有する。また、負極活物質層は、負極活物質と導電助剤と結着剤とを含有する。更に結着剤は、後述するようにスラリーを作成する際に、活物質、導電助剤及び結着剤を混合・攪拌する工程を経るため、導電助剤は分散された状態で含まれていると考えられる。また、結着剤は負極におけるその含有率を所定の好ましい範囲とすることで、負極活物質の粒子間の少なくとも一部は被覆した状態で負極活物質同士を結着していると考えられる。
負極集電体としては、例えば、銅、ステンレス鋼(SUS)、ニッケル、チタン、これらの合金などを使用することができる。
負極活物質としては、非晶質炭素で被覆された黒鉛を用いる。このような非晶質炭素で被覆された黒鉛の平均粒子径は、例えば、数μm~数十μmであることが好ましい。また、このような非晶質炭素で被覆された黒鉛のBET比表面積は、例えば、10-1~10m2/gであることが好ましい。
導電助剤としては、カーボンブラック系導電助剤を用いる。このようなカーボンブラック系導電助剤のBET比表面積は、例えば、10~102m2/gであることが好ましい。このような範囲とすることにより、十分なマグネシウム捕捉(吸着)能力を発揮すると考えられる。また、導電助剤のBET比表面積は、負極活物質のBET比表面積より大きいことが好ましい。これにより、負極活物質の粒子間の接触点に、より近い位置で存在することができると考えられる。カーボンブラック系導電助剤としては、ケッチェンブラック、アセチレンブラック、チャンネルブラック、ランプブラック、オイルファーネスブラック若しくはサーマルブラック又はこれらの任意の組み合わせに係る混合物を用いることができる。
結着剤(バインダー)としては、フッ素樹脂系結着剤を用いる。フッ素樹脂としては、例えば、ポリフッ化ビニリデン(PVdF)や、フッ化ビニリデンと他のフッ素系モノマーを共重合させたフッ化ビニリデン系重合体を挙げることができる。なお、本発明において、「フッ素樹脂系結着剤」とは、例えば、後述する非水電解液が浸透しうるものであれば、フッ素樹脂のみを含むものに、特に限定されるものではない。逆に、フッ素樹脂系接着材より密着性が高いアクリル樹脂系結着剤を用いた場合、非水電解液が浸透不可能な膜が形成されることによって、導電助剤が覆われてしまうため、導電助剤を負極に含有させた場合であっても、本発明に用いたカーボンブラック系導電助剤による所期のマグネシウム捕捉(吸着)作用を発現させることができない。
正極12は、正極集電体12Aの両方の主面上に正極活物質層12Bが形成された構造を有する。また、正極活物質層は、正極活物質と、必要に応じて添加される導電助剤と結着剤とを含有する。導電助剤や結着剤としては、従来リチウムイオン二次電池に用いることができるものを適宜選択して用いることができる。
正極集電体としては、例えば、アルミニウム、ステンレス鋼(SUS)、ニッケル、チタン、これらの合金などを使用することができる。
本発明に用いられる正極活物質としてのリチウムマンガン複合酸化物は、一部をマグネシウムで置換したものであり、例えばマンガンサイトの一部がマグネシウムで置換されたもの、あるいはマグネシウム及び更に別の元素で置換されたものである。例としては、LiMn2-x-yMgxMAyO4+z(MAはMn以外の少なくとも1種の遷移金属元素及び/又はLiであり、x、y及びzは0<x<2、0≦y<2、-1<z<1の関係を満たす。)や、LiMn1-x-yMgxMByO2+z(MBはMn以外の少なくとも1種の遷移金属元素及び/又はLiであり、x、y及びzは0<x<1、0≦y<1、-0.5<z<0.5の関係を満たす。)を使用できる。中でも、スピネル構造を持つLiMn2-x-yMgxMAyO4+zを使用するとより効果があるため好ましい。あるいは、一部をマグネシウムで置換したリチウムマンガン複合酸化物粉末と、リチウムニッケル複合酸化物粉末とを、前者を50%以上となるように混合した正極活物質混合物を使用することもできる。
非水電解質層13としては、例えば、後述するセパレータに保持させた非水電解液や高分子ゲル電解質を用いて層構造を形成したものなどを用いることができる。非水電解液としては、具体的には、支持塩(リチウム塩)が溶解された非水溶媒を用いることができる。
リチウム塩としては、例えば、リチウムイミド塩や、六フッ化リン酸リチウム(LiPF6)、六フッ化ヒ酸リチウム(LiAsF6)、四塩化アルミニウムリチウム(LiAlCl4)、過塩素酸リチウム(LiClO4)、四フッ化ホウ素酸リチウム(LiBF4)、六フッ化アンチモン酸リチウム(LiSbF6)などを用いることができる。この中でも、特に、六フッ化リン酸リチウム(LiPF6)、四フッ化ホウ素酸リチウム(LiBF4)を用いることが好ましい。リチウムイミド塩としては、例えばLiN(CkF2k+1SO2)(CmF2m+1SO2)(k、mはそれぞれ独立して1又は2である。)を挙げることができる。これらのリチウム塩は、1種を単独で又は2種以上を組み合わせて用いることができる。
非水溶媒としては、例えば、環状カーボネート類、鎖状カーボネート類、脂肪族カルボン酸エステル類、γ-ラクトン類、環状エーテル類、鎖状エーテル類及びこれらのフッ化誘導体からなる群より選ばれる少なくとも1種の有機溶媒を用いることができる。環状カーボネート類としては、例えば、プロピレンカーボネート(PC)、エチレンカーボネート(EC)、ブチレンカーボネート(BC)、これらのフッ化誘導体等を挙げることができる。また、鎖状カーボネート類としては、例えば、ジメチルカーボネート(DMC)、ジエチルカーボネート(DEC)、エチルメチルカーボネート(EMC)、ジプロピルカーボネート(DPC)、これらのフッ化誘導体等を挙げることができる。脂肪族カルボン酸エステルとしては、例えば、ギ酸メチル、酢酸メチル、プロピオン酸エチル、これらのフッ化誘導体を挙げることができる。γ-ラクトン類としては、例えば、γ-ブチロラクトンやこのフッ化誘導体等を挙げることができる。環状エーテル類としては、例えば、テトラヒドロフラン、2-メチルテトラヒドロフラン等を挙げることができる。鎖状エーテル類としては、例えば、1,2-エトキシエタン(DEE)、エトキシメトキシエタン(EME)、ジエチルエーテル、これらのフッ化誘導体等を挙げることができる。その他としては、ジメチルスルホキシド、1,3-ジオキソラン、ホルムアルデヒド、アセトアミド、ジメチルホルムアミド、ジオキソラン、アセトニトリル、プロピルニトリル、ニトロメタン、エチルモノグライム、リン酸トリエステル、トリメトキシメタン、ジオキソラン誘導体、スルホラン、メチルスルホラン、1,3-ジメチル-2-イルエーテル、1,3-プロパンスルトン、アニソール、N-メチルピロリドン、フッ素化カルボン酸エステル等を挙げることができる。これらは、1種を単独で、2種以上を組み合わせて用いることができる。
セパレータとしては、例えば、ポリエチレン(PE)やポリプロピレン(PP)等のポリオレフィン、ポリフッ化ビニリデン(PVdF)やポリテトラフルオロエチレン(PTFE)等のフッ素樹脂からなる微多孔膜を用いることができる。ポリフッ化ビニリデンは、非水電解質を保持した場合、高分子ゲル電解質を形成することもある。
次に、上述した本実施形態のリチウムイオン二次電池の製造方法の一例について説明する。
に限定されるものではない。
<負極の作製>
負極活物質としての非晶質性炭素で被覆された球状天然黒鉛粉末(平均粒子径:20μm、平均アスペクト比:1.2、BET比表面積:1.2m2/g)と、フッ素樹脂系結着剤としてのポリフッ化ビニリデンと、カーボンブラック系導電助剤としての第1カーボンブラック(平均粒子径:1μm、BET比表面積:64m2/g)とを、固形分質量比で96.5:3:0.5の割合でN-メチル-2-ピロリドン(NMP)中に入れ、攪拌させることで均一に分散させてスラリーを作製した。得られたスラリーを負極集電体となる厚み15μmの銅箔上に塗布し、次いで、125℃にて10分間NMPを蒸発させることにより負極活物質層を形成し、更にプレスすることによって片面塗布した負極を作製した。乾燥後の単位面積当たりの負極活物質層の密度は0.008g/cm2とした。
正極活物質としてのスピネル構造を有するLi1.1Mn1.8Mg0.1O4粉末(平均粒子径:10μm)と、結着剤としてのポリフッ化ビニリデンと、導電助剤としてのカーボンブラック粉末とを、固形分質量比で92:4:4の割合でN-メチル-2-ピロリドン(NMP)中に入れ攪拌させることで均一に分散させてスラリーを作製した。得られたスラリーを正極集電体となる厚み20μmのアルミニウム箔上に塗布し、次いで、125℃にて10分間NMPを蒸発させることにより正極活物質層を形成することによって片面塗布した正極を作製した。乾燥後の単位面積当たりの正極活物質層の密度は0.025g/cm2とした。
上記のように作製した負極と正極とを各々5cm(幅)×6.0cm(長さ)に切り出した。このうち、一辺5cm×1cmは端子を接続するための未塗布部であって、活物質層は5cm×5cmである。幅5cm、長さ3cm、厚み0.1mmのアルミニウム製の正極端子を正極における未塗布部に長さ1cmで超音波溶接した。同様に、正極端子と同サイズのニッケル製の負極端子を負極における未塗布部に長さ1cmで超音波溶接した。
6cm×6cmのポリエチレン及びポリプロピレンからなるセパレータの両面に上記負極と正極とを活物質層がセパレータを隔てて重なるように配置して電極積層体を得た。2枚の7cm×10cmのアルミニウムラミネートフィルムの長辺の一方を除いて三辺を熱融着により幅5mmにて接着して袋状のラミネート外装体を作製した。ラミネート外装体の一方の短辺より1cmの距離となるように上記電極積層体を挿入した。下記非水電解液を0.203g注液して真空含浸させた後、減圧下にて開口部を熱融着により幅5mmで封止することによって、本例のラミネート型二次電池を得た。
非水電解液としては、エチレンカーボネート(EC)とジエチルカーボネート(DEC)とをEC:DEC=30:70(体積比)の割合で混合した非水溶媒に、電解質塩としての六フッ化リン酸リチウム(LiPF6)を濃度が1.0mol/Lとなるように溶解させたものに対して、添加剤として環状ジスルホン酸エステルを濃度が1.5質量%となるように溶解させたものを用いた。
負極の作製に際して、第1カーボンブラックの添加量を0.5質量%から1.0質量%に変更し、負極活物質とフッ素樹脂系結着剤とカーボンブラック系導電助剤とを、固形分質量比で96:3:1の割合でNMP中に入れ攪拌させることで均一に分散させてスラリーを作製したこと以外は、実施例1と同様の操作を繰り返して、本例のラミネート型二次電池を得た。
負極の作製に際して、第1カーボンブラックに第2カーボンブラック(平均粒子径:3μm、BET比表面積:20m2/g)を添加し、第2カーボンブラックの添加量を2質量%とし、負極活物質とフッ素樹脂系結着剤とカーボンブラック系導電助剤とを、固形分質量比で94.5:3:2.5の割合でNMP中に入れ攪拌させることで、均一に分散させてスラリーを作製したこと以外は、実施例1と同様の操作を繰り返して、本例のラミネート型二次電池を得た。
負極の作製に際して、第1カーボンブラックに第2カーボンブラック(平均粒子径:3μm、BET比表面積:20m2/g)を添加し、第2カーボンブラックの添加量を4質量%とし、負極活物質とフッ素樹脂系結着剤とカーボンブラック系導電助剤とを、固形分質量比で92.5:3:4.5の割合でNMP中に入れ攪拌させることで、均一に分散させてスラリーを作製したこと以外は、実施例1と同様の操作を繰り返して、本例のラミネート型二次電池を得た。
負極の作製に際して、第1カーボンブラックに第2カーボンブラック(平均粒子径:3μm、BET比表面積:20m2/g)を添加し、第2カーボンブラックの添加量を8質量%とし、負極活物質とフッ素樹脂系結着剤とカーボンブラック系導電助剤とを、固形分質量比で88.5:3:8.5の割合でNMP中に入れ攪拌させることで、均一に分散させてスラリーを作製したこと以外は、実施例1と同様の操作を繰り返して、本例のラミネート型二次電池を得た。
負極の作製に際して、第1カーボンブラックに第2カーボンブラック(平均粒子径:3μm、BET比表面積:20m2/g)を添加し、第2カーボンブラックの添加量を2質量%とし、負極活物質とフッ素樹脂系結着剤とカーボンブラック系導電助剤とを、固形分質量比で94:3:3の割合でNMP中に入れ、攪拌させることで、均一に分散させてスラリーを作製したこと以外は、実施例2と同様の操作を繰り返して、本例のラミネート型二次電池を得た。
負極の作製に際して、第1カーボンブラックに第2カーボンブラック(平均粒子径:3μm、BET比表面積:20m2/g)を添加し、第2カーボンブラックの添加量を4質量%とし、負極活物質とフッ素樹脂系結着剤とカーボンブラック系導電助剤とを、固形分質量比で92:3:5の割合でNMP中に入れ、攪拌させることで、均一に分散させてスラリーを作製したこと以外は、実施例2と同様の操作を繰り返して、本例のラミネート型二次電池を得た。
負極の作製に際して、第1カーボンブラックに第2カーボンブラック(平均粒子径:3μm、BET比表面積:20m2/g)を添加し、第2カーボンブラックの添加量を8質量%とし、負極活物質とフッ素樹脂系結着剤とカーボンブラック系導電助剤とを、固形分質量比で88:3:9の割合でNMP中に入れ、攪拌させることで、均一に分散させてスラリーを作製したこと以外は、実施例2と同様の操作を繰り返して、本例のラミネート型二次電池を得た。
正極の作製に際して、正極活物質としてのスピネル構造を有するLi1.1Mn1.8Mg0.1O4粉末(平均粒子径:10μm)に正極活物質としてのニッケル酸リチウム(LiNi0.8Co0.15Al0.05O2)粉末を添加し、ニッケル酸リチウムの添加量を20質量%とし、正極活物質と結着剤と導電助剤とを、固形分質量比で92:4:4の割合でNMP中に入れ、攪拌させることで、均一に分散させてスラリーを作製したこと以外は、実施例1と同様の操作を繰り返して、本例のラミネート型二次電池を得た。
負極活物質としての非晶質性炭素で被覆された球状天然黒鉛粉末(平均粒子径:20μm、平均アスペクト比:1.2、BET比表面積:1.2m2/g)と、フッ素樹脂系結着剤としてのポリフッ化ビニリデンとを、固形分質量比で97:3の割合でNMP中に入れ攪拌させることで、均一に分散させてスラリーを作製したこと以外は、実施例1と同様の操作を繰り返して、本例のラミネート型二次電池を得た。
負極活物質としての非晶質性炭素で被覆された球状天然黒鉛粉末(平均粒子径:20μm、平均アスペクト比:1.2、BET比表面積:1.2m2/g)と、フッ素樹脂系結着剤としてのポリフッ化ビニリデンとを、固形分質量比で97:3の割合でNMP中に入れ攪拌させることで、均一に分散させてスラリーを作製したこと以外は、実施例9と同様の操作を繰り返して、本例のラミネート型二次電池を得た。
上記各例のラミネート型二次電池について、出荷直後(初期)及び1000サイクル後において所定の電流値で放電させたときの電圧降下を測定することで直流抵抗値を測定し、内部抵抗上昇率を算出した。得られた結果をラミネート型二次電池の仕様の一部と共に表1及び表2に示す。ここで、「内部抵抗上昇率」とは、出荷直後(初期)の電池の直流抵抗値に対する1000サイクル後の電池の直流抵抗値の比のことである。
Claims (5)
- 正極活物質として一部をマグネシウムで置換したリチウムマンガン複合酸化物を含有する正極と、
負極活物質としての非晶質炭素で被覆された黒鉛と、カーボンブラック系導電助剤と、フッ素樹脂系結着剤とを含有する負極と、
を備えたリチウムイオン二次電池。 - 上記カーボンブラック系導電助剤のBET比表面積は10~102m2/gである
請求項1に記載のリチウムイオン二次電池。 - 上記正極は正極活物質としてのリチウムニッケル複合酸化物を更に含有する
請求項1又は2に記載のリチウムイオン二次電池。 - 上記カーボンブラック系導電助剤は比表面積が異なる2種類のカーボンブラックである請求項3に記載のリチウムイオン二次電池。
- 上記カーボンブラック系導電助剤は上記負極活物質の比表面積よりも大きい
請求項2に記載のリチウムイオン二次電池。
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JP6081339B2 (ja) * | 2013-10-11 | 2017-02-15 | オートモーティブエナジーサプライ株式会社 | 非水電解質二次電池 |
CN103730651A (zh) * | 2013-12-16 | 2014-04-16 | 广西科技大学 | 一种电池正极材料及其高温固相合成方法 |
JP6246682B2 (ja) * | 2014-09-01 | 2017-12-13 | 日立オートモティブシステムズ株式会社 | リチウムイオン二次電池 |
JP6308307B2 (ja) * | 2014-11-18 | 2018-04-11 | 株式会社村田製作所 | リチウムイオン二次電池用正極およびそれを用いたリチウムイオン二次電池 |
US11011774B2 (en) | 2014-12-16 | 2021-05-18 | Nec Corporation | Lithium-ion secondary battery |
JP2016219181A (ja) * | 2015-05-18 | 2016-12-22 | オートモーティブエナジーサプライ株式会社 | 非水電解質二次電池 |
WO2017217407A1 (ja) * | 2016-06-13 | 2017-12-21 | 日本電気株式会社 | リチウムイオン二次電池 |
JP6783717B2 (ja) * | 2017-07-31 | 2020-11-11 | トヨタ自動車株式会社 | 非水系二次電池 |
CN108110230B (zh) * | 2017-11-26 | 2020-06-02 | 潘素娇 | 一种锂铬充电电池及其制造方法 |
US20230327125A1 (en) * | 2021-03-16 | 2023-10-12 | Lg Energy Solution, Ltd. | Negative electrode for lithium secondary battery and lithium secondary battery including the same |
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